extend.texi revision 256281
1@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1996, 1998, 1999, 2000, 2@c 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc. 3 4@c This is part of the GCC manual. 5@c For copying conditions, see the file gcc.texi. 6 7@node C Extensions 8@chapter Extensions to the C Language Family 9@cindex extensions, C language 10@cindex C language extensions 11 12@opindex pedantic 13GNU C provides several language features not found in ISO standard C@. 14(The @option{-pedantic} option directs GCC to print a warning message if 15any of these features is used.) To test for the availability of these 16features in conditional compilation, check for a predefined macro 17@code{__GNUC__}, which is always defined under GCC@. 18 19These extensions are available in C. Most of them are also available 20in C++. @xref{C++ Extensions,,Extensions to the C++ Language}, for 21extensions that apply @emph{only} to C++. 22 23Some features that are in ISO C99 but not C89 or C++ are also, as 24extensions, accepted by GCC in C89 mode and in C++. 25 26@menu 27* Statement Exprs:: Putting statements and declarations inside expressions. 28* Local Labels:: Labels local to a block. 29* Labels as Values:: Getting pointers to labels, and computed gotos. 30* Nested Functions:: As in Algol and Pascal, lexical scoping of functions. 31* Constructing Calls:: Dispatching a call to another function. 32* Typeof:: @code{typeof}: referring to the type of an expression. 33* Conditionals:: Omitting the middle operand of a @samp{?:} expression. 34* Long Long:: Double-word integers---@code{long long int}. 35* Complex:: Data types for complex numbers. 36* Decimal Float:: Decimal Floating Types. 37* Hex Floats:: Hexadecimal floating-point constants. 38* Zero Length:: Zero-length arrays. 39* Variable Length:: Arrays whose length is computed at run time. 40* Empty Structures:: Structures with no members. 41* Variadic Macros:: Macros with a variable number of arguments. 42* Escaped Newlines:: Slightly looser rules for escaped newlines. 43* Subscripting:: Any array can be subscripted, even if not an lvalue. 44* Pointer Arith:: Arithmetic on @code{void}-pointers and function pointers. 45* Initializers:: Non-constant initializers. 46* Compound Literals:: Compound literals give structures, unions 47 or arrays as values. 48* Designated Inits:: Labeling elements of initializers. 49* Cast to Union:: Casting to union type from any member of the union. 50* Case Ranges:: `case 1 ... 9' and such. 51* Mixed Declarations:: Mixing declarations and code. 52* Function Attributes:: Declaring that functions have no side effects, 53 or that they can never return. 54* Attribute Syntax:: Formal syntax for attributes. 55* Function Prototypes:: Prototype declarations and old-style definitions. 56* C++ Comments:: C++ comments are recognized. 57* Dollar Signs:: Dollar sign is allowed in identifiers. 58* Character Escapes:: @samp{\e} stands for the character @key{ESC}. 59* Variable Attributes:: Specifying attributes of variables. 60* Type Attributes:: Specifying attributes of types. 61* Alignment:: Inquiring about the alignment of a type or variable. 62* Inline:: Defining inline functions (as fast as macros). 63* Extended Asm:: Assembler instructions with C expressions as operands. 64 (With them you can define ``built-in'' functions.) 65* Constraints:: Constraints for asm operands 66* Asm Labels:: Specifying the assembler name to use for a C symbol. 67* Explicit Reg Vars:: Defining variables residing in specified registers. 68* Alternate Keywords:: @code{__const__}, @code{__asm__}, etc., for header files. 69* Incomplete Enums:: @code{enum foo;}, with details to follow. 70* Function Names:: Printable strings which are the name of the current 71 function. 72* Return Address:: Getting the return or frame address of a function. 73* Vector Extensions:: Using vector instructions through built-in functions. 74* Offsetof:: Special syntax for implementing @code{offsetof}. 75* Atomic Builtins:: Built-in functions for atomic memory access. 76* Object Size Checking:: Built-in functions for limited buffer overflow 77 checking. 78* Other Builtins:: Other built-in functions. 79* Target Builtins:: Built-in functions specific to particular targets. 80* Target Format Checks:: Format checks specific to particular targets. 81* Pragmas:: Pragmas accepted by GCC. 82* Unnamed Fields:: Unnamed struct/union fields within structs/unions. 83* Thread-Local:: Per-thread variables. 84* Binary constants:: Binary constants using the @samp{0b} prefix. 85@end menu 86 87@node Statement Exprs 88@section Statements and Declarations in Expressions 89@cindex statements inside expressions 90@cindex declarations inside expressions 91@cindex expressions containing statements 92@cindex macros, statements in expressions 93 94@c the above section title wrapped and causes an underfull hbox.. i 95@c changed it from "within" to "in". --mew 4feb93 96A compound statement enclosed in parentheses may appear as an expression 97in GNU C@. This allows you to use loops, switches, and local variables 98within an expression. 99 100Recall that a compound statement is a sequence of statements surrounded 101by braces; in this construct, parentheses go around the braces. For 102example: 103 104@smallexample 105(@{ int y = foo (); int z; 106 if (y > 0) z = y; 107 else z = - y; 108 z; @}) 109@end smallexample 110 111@noindent 112is a valid (though slightly more complex than necessary) expression 113for the absolute value of @code{foo ()}. 114 115The last thing in the compound statement should be an expression 116followed by a semicolon; the value of this subexpression serves as the 117value of the entire construct. (If you use some other kind of statement 118last within the braces, the construct has type @code{void}, and thus 119effectively no value.) 120 121This feature is especially useful in making macro definitions ``safe'' (so 122that they evaluate each operand exactly once). For example, the 123``maximum'' function is commonly defined as a macro in standard C as 124follows: 125 126@smallexample 127#define max(a,b) ((a) > (b) ? (a) : (b)) 128@end smallexample 129 130@noindent 131@cindex side effects, macro argument 132But this definition computes either @var{a} or @var{b} twice, with bad 133results if the operand has side effects. In GNU C, if you know the 134type of the operands (here taken as @code{int}), you can define 135the macro safely as follows: 136 137@smallexample 138#define maxint(a,b) \ 139 (@{int _a = (a), _b = (b); _a > _b ? _a : _b; @}) 140@end smallexample 141 142Embedded statements are not allowed in constant expressions, such as 143the value of an enumeration constant, the width of a bit-field, or 144the initial value of a static variable. 145 146If you don't know the type of the operand, you can still do this, but you 147must use @code{typeof} (@pxref{Typeof}). 148 149In G++, the result value of a statement expression undergoes array and 150function pointer decay, and is returned by value to the enclosing 151expression. For instance, if @code{A} is a class, then 152 153@smallexample 154 A a; 155 156 (@{a;@}).Foo () 157@end smallexample 158 159@noindent 160will construct a temporary @code{A} object to hold the result of the 161statement expression, and that will be used to invoke @code{Foo}. 162Therefore the @code{this} pointer observed by @code{Foo} will not be the 163address of @code{a}. 164 165Any temporaries created within a statement within a statement expression 166will be destroyed at the statement's end. This makes statement 167expressions inside macros slightly different from function calls. In 168the latter case temporaries introduced during argument evaluation will 169be destroyed at the end of the statement that includes the function 170call. In the statement expression case they will be destroyed during 171the statement expression. For instance, 172 173@smallexample 174#define macro(a) (@{__typeof__(a) b = (a); b + 3; @}) 175template<typename T> T function(T a) @{ T b = a; return b + 3; @} 176 177void foo () 178@{ 179 macro (X ()); 180 function (X ()); 181@} 182@end smallexample 183 184@noindent 185will have different places where temporaries are destroyed. For the 186@code{macro} case, the temporary @code{X} will be destroyed just after 187the initialization of @code{b}. In the @code{function} case that 188temporary will be destroyed when the function returns. 189 190These considerations mean that it is probably a bad idea to use 191statement-expressions of this form in header files that are designed to 192work with C++. (Note that some versions of the GNU C Library contained 193header files using statement-expression that lead to precisely this 194bug.) 195 196Jumping into a statement expression with @code{goto} or using a 197@code{switch} statement outside the statement expression with a 198@code{case} or @code{default} label inside the statement expression is 199not permitted. Jumping into a statement expression with a computed 200@code{goto} (@pxref{Labels as Values}) yields undefined behavior. 201Jumping out of a statement expression is permitted, but if the 202statement expression is part of a larger expression then it is 203unspecified which other subexpressions of that expression have been 204evaluated except where the language definition requires certain 205subexpressions to be evaluated before or after the statement 206expression. In any case, as with a function call the evaluation of a 207statement expression is not interleaved with the evaluation of other 208parts of the containing expression. For example, 209 210@smallexample 211 foo (), ((@{ bar1 (); goto a; 0; @}) + bar2 ()), baz(); 212@end smallexample 213 214@noindent 215will call @code{foo} and @code{bar1} and will not call @code{baz} but 216may or may not call @code{bar2}. If @code{bar2} is called, it will be 217called after @code{foo} and before @code{bar1} 218 219@node Local Labels 220@section Locally Declared Labels 221@cindex local labels 222@cindex macros, local labels 223 224GCC allows you to declare @dfn{local labels} in any nested block 225scope. A local label is just like an ordinary label, but you can 226only reference it (with a @code{goto} statement, or by taking its 227address) within the block in which it was declared. 228 229A local label declaration looks like this: 230 231@smallexample 232__label__ @var{label}; 233@end smallexample 234 235@noindent 236or 237 238@smallexample 239__label__ @var{label1}, @var{label2}, /* @r{@dots{}} */; 240@end smallexample 241 242Local label declarations must come at the beginning of the block, 243before any ordinary declarations or statements. 244 245The label declaration defines the label @emph{name}, but does not define 246the label itself. You must do this in the usual way, with 247@code{@var{label}:}, within the statements of the statement expression. 248 249The local label feature is useful for complex macros. If a macro 250contains nested loops, a @code{goto} can be useful for breaking out of 251them. However, an ordinary label whose scope is the whole function 252cannot be used: if the macro can be expanded several times in one 253function, the label will be multiply defined in that function. A 254local label avoids this problem. For example: 255 256@smallexample 257#define SEARCH(value, array, target) \ 258do @{ \ 259 __label__ found; \ 260 typeof (target) _SEARCH_target = (target); \ 261 typeof (*(array)) *_SEARCH_array = (array); \ 262 int i, j; \ 263 int value; \ 264 for (i = 0; i < max; i++) \ 265 for (j = 0; j < max; j++) \ 266 if (_SEARCH_array[i][j] == _SEARCH_target) \ 267 @{ (value) = i; goto found; @} \ 268 (value) = -1; \ 269 found:; \ 270@} while (0) 271@end smallexample 272 273This could also be written using a statement-expression: 274 275@smallexample 276#define SEARCH(array, target) \ 277(@{ \ 278 __label__ found; \ 279 typeof (target) _SEARCH_target = (target); \ 280 typeof (*(array)) *_SEARCH_array = (array); \ 281 int i, j; \ 282 int value; \ 283 for (i = 0; i < max; i++) \ 284 for (j = 0; j < max; j++) \ 285 if (_SEARCH_array[i][j] == _SEARCH_target) \ 286 @{ value = i; goto found; @} \ 287 value = -1; \ 288 found: \ 289 value; \ 290@}) 291@end smallexample 292 293Local label declarations also make the labels they declare visible to 294nested functions, if there are any. @xref{Nested Functions}, for details. 295 296@node Labels as Values 297@section Labels as Values 298@cindex labels as values 299@cindex computed gotos 300@cindex goto with computed label 301@cindex address of a label 302 303You can get the address of a label defined in the current function 304(or a containing function) with the unary operator @samp{&&}. The 305value has type @code{void *}. This value is a constant and can be used 306wherever a constant of that type is valid. For example: 307 308@smallexample 309void *ptr; 310/* @r{@dots{}} */ 311ptr = &&foo; 312@end smallexample 313 314To use these values, you need to be able to jump to one. This is done 315with the computed goto statement@footnote{The analogous feature in 316Fortran is called an assigned goto, but that name seems inappropriate in 317C, where one can do more than simply store label addresses in label 318variables.}, @code{goto *@var{exp};}. For example, 319 320@smallexample 321goto *ptr; 322@end smallexample 323 324@noindent 325Any expression of type @code{void *} is allowed. 326 327One way of using these constants is in initializing a static array that 328will serve as a jump table: 329 330@smallexample 331static void *array[] = @{ &&foo, &&bar, &&hack @}; 332@end smallexample 333 334Then you can select a label with indexing, like this: 335 336@smallexample 337goto *array[i]; 338@end smallexample 339 340@noindent 341Note that this does not check whether the subscript is in bounds---array 342indexing in C never does that. 343 344Such an array of label values serves a purpose much like that of the 345@code{switch} statement. The @code{switch} statement is cleaner, so 346use that rather than an array unless the problem does not fit a 347@code{switch} statement very well. 348 349Another use of label values is in an interpreter for threaded code. 350The labels within the interpreter function can be stored in the 351threaded code for super-fast dispatching. 352 353You may not use this mechanism to jump to code in a different function. 354If you do that, totally unpredictable things will happen. The best way to 355avoid this is to store the label address only in automatic variables and 356never pass it as an argument. 357 358An alternate way to write the above example is 359 360@smallexample 361static const int array[] = @{ &&foo - &&foo, &&bar - &&foo, 362 &&hack - &&foo @}; 363goto *(&&foo + array[i]); 364@end smallexample 365 366@noindent 367This is more friendly to code living in shared libraries, as it reduces 368the number of dynamic relocations that are needed, and by consequence, 369allows the data to be read-only. 370 371@node Nested Functions 372@section Nested Functions 373@cindex nested functions 374@cindex downward funargs 375@cindex thunks 376 377A @dfn{nested function} is a function defined inside another function. 378(Nested functions are not supported for GNU C++.) The nested function's 379name is local to the block where it is defined. For example, here we 380define a nested function named @code{square}, and call it twice: 381 382@smallexample 383@group 384foo (double a, double b) 385@{ 386 double square (double z) @{ return z * z; @} 387 388 return square (a) + square (b); 389@} 390@end group 391@end smallexample 392 393The nested function can access all the variables of the containing 394function that are visible at the point of its definition. This is 395called @dfn{lexical scoping}. For example, here we show a nested 396function which uses an inherited variable named @code{offset}: 397 398@smallexample 399@group 400bar (int *array, int offset, int size) 401@{ 402 int access (int *array, int index) 403 @{ return array[index + offset]; @} 404 int i; 405 /* @r{@dots{}} */ 406 for (i = 0; i < size; i++) 407 /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */ 408@} 409@end group 410@end smallexample 411 412Nested function definitions are permitted within functions in the places 413where variable definitions are allowed; that is, in any block, mixed 414with the other declarations and statements in the block. 415 416It is possible to call the nested function from outside the scope of its 417name by storing its address or passing the address to another function: 418 419@smallexample 420hack (int *array, int size) 421@{ 422 void store (int index, int value) 423 @{ array[index] = value; @} 424 425 intermediate (store, size); 426@} 427@end smallexample 428 429Here, the function @code{intermediate} receives the address of 430@code{store} as an argument. If @code{intermediate} calls @code{store}, 431the arguments given to @code{store} are used to store into @code{array}. 432But this technique works only so long as the containing function 433(@code{hack}, in this example) does not exit. 434 435If you try to call the nested function through its address after the 436containing function has exited, all hell will break loose. If you try 437to call it after a containing scope level has exited, and if it refers 438to some of the variables that are no longer in scope, you may be lucky, 439but it's not wise to take the risk. If, however, the nested function 440does not refer to anything that has gone out of scope, you should be 441safe. 442 443GCC implements taking the address of a nested function using a technique 444called @dfn{trampolines}. A paper describing them is available as 445 446@noindent 447@uref{http://people.debian.org/~aaronl/Usenix88-lexic.pdf}. 448 449A nested function can jump to a label inherited from a containing 450function, provided the label was explicitly declared in the containing 451function (@pxref{Local Labels}). Such a jump returns instantly to the 452containing function, exiting the nested function which did the 453@code{goto} and any intermediate functions as well. Here is an example: 454 455@smallexample 456@group 457bar (int *array, int offset, int size) 458@{ 459 __label__ failure; 460 int access (int *array, int index) 461 @{ 462 if (index > size) 463 goto failure; 464 return array[index + offset]; 465 @} 466 int i; 467 /* @r{@dots{}} */ 468 for (i = 0; i < size; i++) 469 /* @r{@dots{}} */ access (array, i) /* @r{@dots{}} */ 470 /* @r{@dots{}} */ 471 return 0; 472 473 /* @r{Control comes here from @code{access} 474 if it detects an error.} */ 475 failure: 476 return -1; 477@} 478@end group 479@end smallexample 480 481A nested function always has no linkage. Declaring one with 482@code{extern} or @code{static} is erroneous. If you need to declare the nested function 483before its definition, use @code{auto} (which is otherwise meaningless 484for function declarations). 485 486@smallexample 487bar (int *array, int offset, int size) 488@{ 489 __label__ failure; 490 auto int access (int *, int); 491 /* @r{@dots{}} */ 492 int access (int *array, int index) 493 @{ 494 if (index > size) 495 goto failure; 496 return array[index + offset]; 497 @} 498 /* @r{@dots{}} */ 499@} 500@end smallexample 501 502@node Constructing Calls 503@section Constructing Function Calls 504@cindex constructing calls 505@cindex forwarding calls 506 507Using the built-in functions described below, you can record 508the arguments a function received, and call another function 509with the same arguments, without knowing the number or types 510of the arguments. 511 512You can also record the return value of that function call, 513and later return that value, without knowing what data type 514the function tried to return (as long as your caller expects 515that data type). 516 517However, these built-in functions may interact badly with some 518sophisticated features or other extensions of the language. It 519is, therefore, not recommended to use them outside very simple 520functions acting as mere forwarders for their arguments. 521 522@deftypefn {Built-in Function} {void *} __builtin_apply_args () 523This built-in function returns a pointer to data 524describing how to perform a call with the same arguments as were passed 525to the current function. 526 527The function saves the arg pointer register, structure value address, 528and all registers that might be used to pass arguments to a function 529into a block of memory allocated on the stack. Then it returns the 530address of that block. 531@end deftypefn 532 533@deftypefn {Built-in Function} {void *} __builtin_apply (void (*@var{function})(), void *@var{arguments}, size_t @var{size}) 534This built-in function invokes @var{function} 535with a copy of the parameters described by @var{arguments} 536and @var{size}. 537 538The value of @var{arguments} should be the value returned by 539@code{__builtin_apply_args}. The argument @var{size} specifies the size 540of the stack argument data, in bytes. 541 542This function returns a pointer to data describing 543how to return whatever value was returned by @var{function}. The data 544is saved in a block of memory allocated on the stack. 545 546It is not always simple to compute the proper value for @var{size}. The 547value is used by @code{__builtin_apply} to compute the amount of data 548that should be pushed on the stack and copied from the incoming argument 549area. 550@end deftypefn 551 552@deftypefn {Built-in Function} {void} __builtin_return (void *@var{result}) 553This built-in function returns the value described by @var{result} from 554the containing function. You should specify, for @var{result}, a value 555returned by @code{__builtin_apply}. 556@end deftypefn 557 558@node Typeof 559@section Referring to a Type with @code{typeof} 560@findex typeof 561@findex sizeof 562@cindex macros, types of arguments 563 564Another way to refer to the type of an expression is with @code{typeof}. 565The syntax of using of this keyword looks like @code{sizeof}, but the 566construct acts semantically like a type name defined with @code{typedef}. 567 568There are two ways of writing the argument to @code{typeof}: with an 569expression or with a type. Here is an example with an expression: 570 571@smallexample 572typeof (x[0](1)) 573@end smallexample 574 575@noindent 576This assumes that @code{x} is an array of pointers to functions; 577the type described is that of the values of the functions. 578 579Here is an example with a typename as the argument: 580 581@smallexample 582typeof (int *) 583@end smallexample 584 585@noindent 586Here the type described is that of pointers to @code{int}. 587 588If you are writing a header file that must work when included in ISO C 589programs, write @code{__typeof__} instead of @code{typeof}. 590@xref{Alternate Keywords}. 591 592A @code{typeof}-construct can be used anywhere a typedef name could be 593used. For example, you can use it in a declaration, in a cast, or inside 594of @code{sizeof} or @code{typeof}. 595 596@code{typeof} is often useful in conjunction with the 597statements-within-expressions feature. Here is how the two together can 598be used to define a safe ``maximum'' macro that operates on any 599arithmetic type and evaluates each of its arguments exactly once: 600 601@smallexample 602#define max(a,b) \ 603 (@{ typeof (a) _a = (a); \ 604 typeof (b) _b = (b); \ 605 _a > _b ? _a : _b; @}) 606@end smallexample 607 608@cindex underscores in variables in macros 609@cindex @samp{_} in variables in macros 610@cindex local variables in macros 611@cindex variables, local, in macros 612@cindex macros, local variables in 613 614The reason for using names that start with underscores for the local 615variables is to avoid conflicts with variable names that occur within the 616expressions that are substituted for @code{a} and @code{b}. Eventually we 617hope to design a new form of declaration syntax that allows you to declare 618variables whose scopes start only after their initializers; this will be a 619more reliable way to prevent such conflicts. 620 621@noindent 622Some more examples of the use of @code{typeof}: 623 624@itemize @bullet 625@item 626This declares @code{y} with the type of what @code{x} points to. 627 628@smallexample 629typeof (*x) y; 630@end smallexample 631 632@item 633This declares @code{y} as an array of such values. 634 635@smallexample 636typeof (*x) y[4]; 637@end smallexample 638 639@item 640This declares @code{y} as an array of pointers to characters: 641 642@smallexample 643typeof (typeof (char *)[4]) y; 644@end smallexample 645 646@noindent 647It is equivalent to the following traditional C declaration: 648 649@smallexample 650char *y[4]; 651@end smallexample 652 653To see the meaning of the declaration using @code{typeof}, and why it 654might be a useful way to write, rewrite it with these macros: 655 656@smallexample 657#define pointer(T) typeof(T *) 658#define array(T, N) typeof(T [N]) 659@end smallexample 660 661@noindent 662Now the declaration can be rewritten this way: 663 664@smallexample 665array (pointer (char), 4) y; 666@end smallexample 667 668@noindent 669Thus, @code{array (pointer (char), 4)} is the type of arrays of 4 670pointers to @code{char}. 671@end itemize 672 673@emph{Compatibility Note:} In addition to @code{typeof}, GCC 2 supported 674a more limited extension which permitted one to write 675 676@smallexample 677typedef @var{T} = @var{expr}; 678@end smallexample 679 680@noindent 681with the effect of declaring @var{T} to have the type of the expression 682@var{expr}. This extension does not work with GCC 3 (versions between 6833.0 and 3.2 will crash; 3.2.1 and later give an error). Code which 684relies on it should be rewritten to use @code{typeof}: 685 686@smallexample 687typedef typeof(@var{expr}) @var{T}; 688@end smallexample 689 690@noindent 691This will work with all versions of GCC@. 692 693@node Conditionals 694@section Conditionals with Omitted Operands 695@cindex conditional expressions, extensions 696@cindex omitted middle-operands 697@cindex middle-operands, omitted 698@cindex extensions, @code{?:} 699@cindex @code{?:} extensions 700 701The middle operand in a conditional expression may be omitted. Then 702if the first operand is nonzero, its value is the value of the conditional 703expression. 704 705Therefore, the expression 706 707@smallexample 708x ? : y 709@end smallexample 710 711@noindent 712has the value of @code{x} if that is nonzero; otherwise, the value of 713@code{y}. 714 715This example is perfectly equivalent to 716 717@smallexample 718x ? x : y 719@end smallexample 720 721@cindex side effect in ?: 722@cindex ?: side effect 723@noindent 724In this simple case, the ability to omit the middle operand is not 725especially useful. When it becomes useful is when the first operand does, 726or may (if it is a macro argument), contain a side effect. Then repeating 727the operand in the middle would perform the side effect twice. Omitting 728the middle operand uses the value already computed without the undesirable 729effects of recomputing it. 730 731@node Long Long 732@section Double-Word Integers 733@cindex @code{long long} data types 734@cindex double-word arithmetic 735@cindex multiprecision arithmetic 736@cindex @code{LL} integer suffix 737@cindex @code{ULL} integer suffix 738 739ISO C99 supports data types for integers that are at least 64 bits wide, 740and as an extension GCC supports them in C89 mode and in C++. 741Simply write @code{long long int} for a signed integer, or 742@code{unsigned long long int} for an unsigned integer. To make an 743integer constant of type @code{long long int}, add the suffix @samp{LL} 744to the integer. To make an integer constant of type @code{unsigned long 745long int}, add the suffix @samp{ULL} to the integer. 746 747You can use these types in arithmetic like any other integer types. 748Addition, subtraction, and bitwise boolean operations on these types 749are open-coded on all types of machines. Multiplication is open-coded 750if the machine supports fullword-to-doubleword a widening multiply 751instruction. Division and shifts are open-coded only on machines that 752provide special support. The operations that are not open-coded use 753special library routines that come with GCC@. 754 755There may be pitfalls when you use @code{long long} types for function 756arguments, unless you declare function prototypes. If a function 757expects type @code{int} for its argument, and you pass a value of type 758@code{long long int}, confusion will result because the caller and the 759subroutine will disagree about the number of bytes for the argument. 760Likewise, if the function expects @code{long long int} and you pass 761@code{int}. The best way to avoid such problems is to use prototypes. 762 763@node Complex 764@section Complex Numbers 765@cindex complex numbers 766@cindex @code{_Complex} keyword 767@cindex @code{__complex__} keyword 768 769ISO C99 supports complex floating data types, and as an extension GCC 770supports them in C89 mode and in C++, and supports complex integer data 771types which are not part of ISO C99. You can declare complex types 772using the keyword @code{_Complex}. As an extension, the older GNU 773keyword @code{__complex__} is also supported. 774 775For example, @samp{_Complex double x;} declares @code{x} as a 776variable whose real part and imaginary part are both of type 777@code{double}. @samp{_Complex short int y;} declares @code{y} to 778have real and imaginary parts of type @code{short int}; this is not 779likely to be useful, but it shows that the set of complex types is 780complete. 781 782To write a constant with a complex data type, use the suffix @samp{i} or 783@samp{j} (either one; they are equivalent). For example, @code{2.5fi} 784has type @code{_Complex float} and @code{3i} has type 785@code{_Complex int}. Such a constant always has a pure imaginary 786value, but you can form any complex value you like by adding one to a 787real constant. This is a GNU extension; if you have an ISO C99 788conforming C library (such as GNU libc), and want to construct complex 789constants of floating type, you should include @code{<complex.h>} and 790use the macros @code{I} or @code{_Complex_I} instead. 791 792@cindex @code{__real__} keyword 793@cindex @code{__imag__} keyword 794To extract the real part of a complex-valued expression @var{exp}, write 795@code{__real__ @var{exp}}. Likewise, use @code{__imag__} to 796extract the imaginary part. This is a GNU extension; for values of 797floating type, you should use the ISO C99 functions @code{crealf}, 798@code{creal}, @code{creall}, @code{cimagf}, @code{cimag} and 799@code{cimagl}, declared in @code{<complex.h>} and also provided as 800built-in functions by GCC@. 801 802@cindex complex conjugation 803The operator @samp{~} performs complex conjugation when used on a value 804with a complex type. This is a GNU extension; for values of 805floating type, you should use the ISO C99 functions @code{conjf}, 806@code{conj} and @code{conjl}, declared in @code{<complex.h>} and also 807provided as built-in functions by GCC@. 808 809GCC can allocate complex automatic variables in a noncontiguous 810fashion; it's even possible for the real part to be in a register while 811the imaginary part is on the stack (or vice-versa). Only the DWARF2 812debug info format can represent this, so use of DWARF2 is recommended. 813If you are using the stabs debug info format, GCC describes a noncontiguous 814complex variable as if it were two separate variables of noncomplex type. 815If the variable's actual name is @code{foo}, the two fictitious 816variables are named @code{foo$real} and @code{foo$imag}. You can 817examine and set these two fictitious variables with your debugger. 818 819@node Decimal Float 820@section Decimal Floating Types 821@cindex decimal floating types 822@cindex @code{_Decimal32} data type 823@cindex @code{_Decimal64} data type 824@cindex @code{_Decimal128} data type 825@cindex @code{df} integer suffix 826@cindex @code{dd} integer suffix 827@cindex @code{dl} integer suffix 828@cindex @code{DF} integer suffix 829@cindex @code{DD} integer suffix 830@cindex @code{DL} integer suffix 831 832As an extension, the GNU C compiler supports decimal floating types as 833defined in the N1176 draft of ISO/IEC WDTR24732. Support for decimal 834floating types in GCC will evolve as the draft technical report changes. 835Calling conventions for any target might also change. Not all targets 836support decimal floating types. 837 838The decimal floating types are @code{_Decimal32}, @code{_Decimal64}, and 839@code{_Decimal128}. They use a radix of ten, unlike the floating types 840@code{float}, @code{double}, and @code{long double} whose radix is not 841specified by the C standard but is usually two. 842 843Support for decimal floating types includes the arithmetic operators 844add, subtract, multiply, divide; unary arithmetic operators; 845relational operators; equality operators; and conversions to and from 846integer and other floating types. Use a suffix @samp{df} or 847@samp{DF} in a literal constant of type @code{_Decimal32}, @samp{dd} 848or @samp{DD} for @code{_Decimal64}, and @samp{dl} or @samp{DL} for 849@code{_Decimal128}. 850 851GCC support of decimal float as specified by the draft technical report 852is incomplete: 853 854@itemize @bullet 855@item 856Translation time data type (TTDT) is not supported. 857 858@item 859Characteristics of decimal floating types are defined in header file 860@file{decfloat.h} rather than @file{float.h}. 861 862@item 863When the value of a decimal floating type cannot be represented in the 864integer type to which it is being converted, the result is undefined 865rather than the result value specified by the draft technical report. 866@end itemize 867 868Types @code{_Decimal32}, @code{_Decimal64}, and @code{_Decimal128} 869are supported by the DWARF2 debug information format. 870 871@node Hex Floats 872@section Hex Floats 873@cindex hex floats 874 875ISO C99 supports floating-point numbers written not only in the usual 876decimal notation, such as @code{1.55e1}, but also numbers such as 877@code{0x1.fp3} written in hexadecimal format. As a GNU extension, GCC 878supports this in C89 mode (except in some cases when strictly 879conforming) and in C++. In that format the 880@samp{0x} hex introducer and the @samp{p} or @samp{P} exponent field are 881mandatory. The exponent is a decimal number that indicates the power of 8822 by which the significant part will be multiplied. Thus @samp{0x1.f} is 883@tex 884$1 {15\over16}$, 885@end tex 886@ifnottex 8871 15/16, 888@end ifnottex 889@samp{p3} multiplies it by 8, and the value of @code{0x1.fp3} 890is the same as @code{1.55e1}. 891 892Unlike for floating-point numbers in the decimal notation the exponent 893is always required in the hexadecimal notation. Otherwise the compiler 894would not be able to resolve the ambiguity of, e.g., @code{0x1.f}. This 895could mean @code{1.0f} or @code{1.9375} since @samp{f} is also the 896extension for floating-point constants of type @code{float}. 897 898@node Zero Length 899@section Arrays of Length Zero 900@cindex arrays of length zero 901@cindex zero-length arrays 902@cindex length-zero arrays 903@cindex flexible array members 904 905Zero-length arrays are allowed in GNU C@. They are very useful as the 906last element of a structure which is really a header for a variable-length 907object: 908 909@smallexample 910struct line @{ 911 int length; 912 char contents[0]; 913@}; 914 915struct line *thisline = (struct line *) 916 malloc (sizeof (struct line) + this_length); 917thisline->length = this_length; 918@end smallexample 919 920In ISO C90, you would have to give @code{contents} a length of 1, which 921means either you waste space or complicate the argument to @code{malloc}. 922 923In ISO C99, you would use a @dfn{flexible array member}, which is 924slightly different in syntax and semantics: 925 926@itemize @bullet 927@item 928Flexible array members are written as @code{contents[]} without 929the @code{0}. 930 931@item 932Flexible array members have incomplete type, and so the @code{sizeof} 933operator may not be applied. As a quirk of the original implementation 934of zero-length arrays, @code{sizeof} evaluates to zero. 935 936@item 937Flexible array members may only appear as the last member of a 938@code{struct} that is otherwise non-empty. 939 940@item 941A structure containing a flexible array member, or a union containing 942such a structure (possibly recursively), may not be a member of a 943structure or an element of an array. (However, these uses are 944permitted by GCC as extensions.) 945@end itemize 946 947GCC versions before 3.0 allowed zero-length arrays to be statically 948initialized, as if they were flexible arrays. In addition to those 949cases that were useful, it also allowed initializations in situations 950that would corrupt later data. Non-empty initialization of zero-length 951arrays is now treated like any case where there are more initializer 952elements than the array holds, in that a suitable warning about "excess 953elements in array" is given, and the excess elements (all of them, in 954this case) are ignored. 955 956Instead GCC allows static initialization of flexible array members. 957This is equivalent to defining a new structure containing the original 958structure followed by an array of sufficient size to contain the data. 959I.e.@: in the following, @code{f1} is constructed as if it were declared 960like @code{f2}. 961 962@smallexample 963struct f1 @{ 964 int x; int y[]; 965@} f1 = @{ 1, @{ 2, 3, 4 @} @}; 966 967struct f2 @{ 968 struct f1 f1; int data[3]; 969@} f2 = @{ @{ 1 @}, @{ 2, 3, 4 @} @}; 970@end smallexample 971 972@noindent 973The convenience of this extension is that @code{f1} has the desired 974type, eliminating the need to consistently refer to @code{f2.f1}. 975 976This has symmetry with normal static arrays, in that an array of 977unknown size is also written with @code{[]}. 978 979Of course, this extension only makes sense if the extra data comes at 980the end of a top-level object, as otherwise we would be overwriting 981data at subsequent offsets. To avoid undue complication and confusion 982with initialization of deeply nested arrays, we simply disallow any 983non-empty initialization except when the structure is the top-level 984object. For example: 985 986@smallexample 987struct foo @{ int x; int y[]; @}; 988struct bar @{ struct foo z; @}; 989 990struct foo a = @{ 1, @{ 2, 3, 4 @} @}; // @r{Valid.} 991struct bar b = @{ @{ 1, @{ 2, 3, 4 @} @} @}; // @r{Invalid.} 992struct bar c = @{ @{ 1, @{ @} @} @}; // @r{Valid.} 993struct foo d[1] = @{ @{ 1 @{ 2, 3, 4 @} @} @}; // @r{Invalid.} 994@end smallexample 995 996@node Empty Structures 997@section Structures With No Members 998@cindex empty structures 999@cindex zero-size structures 1000 1001GCC permits a C structure to have no members: 1002 1003@smallexample 1004struct empty @{ 1005@}; 1006@end smallexample 1007 1008The structure will have size zero. In C++, empty structures are part 1009of the language. G++ treats empty structures as if they had a single 1010member of type @code{char}. 1011 1012@node Variable Length 1013@section Arrays of Variable Length 1014@cindex variable-length arrays 1015@cindex arrays of variable length 1016@cindex VLAs 1017 1018Variable-length automatic arrays are allowed in ISO C99, and as an 1019extension GCC accepts them in C89 mode and in C++. (However, GCC's 1020implementation of variable-length arrays does not yet conform in detail 1021to the ISO C99 standard.) These arrays are 1022declared like any other automatic arrays, but with a length that is not 1023a constant expression. The storage is allocated at the point of 1024declaration and deallocated when the brace-level is exited. For 1025example: 1026 1027@smallexample 1028FILE * 1029concat_fopen (char *s1, char *s2, char *mode) 1030@{ 1031 char str[strlen (s1) + strlen (s2) + 1]; 1032 strcpy (str, s1); 1033 strcat (str, s2); 1034 return fopen (str, mode); 1035@} 1036@end smallexample 1037 1038@cindex scope of a variable length array 1039@cindex variable-length array scope 1040@cindex deallocating variable length arrays 1041Jumping or breaking out of the scope of the array name deallocates the 1042storage. Jumping into the scope is not allowed; you get an error 1043message for it. 1044 1045@cindex @code{alloca} vs variable-length arrays 1046You can use the function @code{alloca} to get an effect much like 1047variable-length arrays. The function @code{alloca} is available in 1048many other C implementations (but not in all). On the other hand, 1049variable-length arrays are more elegant. 1050 1051There are other differences between these two methods. Space allocated 1052with @code{alloca} exists until the containing @emph{function} returns. 1053The space for a variable-length array is deallocated as soon as the array 1054name's scope ends. (If you use both variable-length arrays and 1055@code{alloca} in the same function, deallocation of a variable-length array 1056will also deallocate anything more recently allocated with @code{alloca}.) 1057 1058You can also use variable-length arrays as arguments to functions: 1059 1060@smallexample 1061struct entry 1062tester (int len, char data[len][len]) 1063@{ 1064 /* @r{@dots{}} */ 1065@} 1066@end smallexample 1067 1068The length of an array is computed once when the storage is allocated 1069and is remembered for the scope of the array in case you access it with 1070@code{sizeof}. 1071 1072If you want to pass the array first and the length afterward, you can 1073use a forward declaration in the parameter list---another GNU extension. 1074 1075@smallexample 1076struct entry 1077tester (int len; char data[len][len], int len) 1078@{ 1079 /* @r{@dots{}} */ 1080@} 1081@end smallexample 1082 1083@cindex parameter forward declaration 1084The @samp{int len} before the semicolon is a @dfn{parameter forward 1085declaration}, and it serves the purpose of making the name @code{len} 1086known when the declaration of @code{data} is parsed. 1087 1088You can write any number of such parameter forward declarations in the 1089parameter list. They can be separated by commas or semicolons, but the 1090last one must end with a semicolon, which is followed by the ``real'' 1091parameter declarations. Each forward declaration must match a ``real'' 1092declaration in parameter name and data type. ISO C99 does not support 1093parameter forward declarations. 1094 1095@node Variadic Macros 1096@section Macros with a Variable Number of Arguments. 1097@cindex variable number of arguments 1098@cindex macro with variable arguments 1099@cindex rest argument (in macro) 1100@cindex variadic macros 1101 1102In the ISO C standard of 1999, a macro can be declared to accept a 1103variable number of arguments much as a function can. The syntax for 1104defining the macro is similar to that of a function. Here is an 1105example: 1106 1107@smallexample 1108#define debug(format, ...) fprintf (stderr, format, __VA_ARGS__) 1109@end smallexample 1110 1111Here @samp{@dots{}} is a @dfn{variable argument}. In the invocation of 1112such a macro, it represents the zero or more tokens until the closing 1113parenthesis that ends the invocation, including any commas. This set of 1114tokens replaces the identifier @code{__VA_ARGS__} in the macro body 1115wherever it appears. See the CPP manual for more information. 1116 1117GCC has long supported variadic macros, and used a different syntax that 1118allowed you to give a name to the variable arguments just like any other 1119argument. Here is an example: 1120 1121@smallexample 1122#define debug(format, args...) fprintf (stderr, format, args) 1123@end smallexample 1124 1125This is in all ways equivalent to the ISO C example above, but arguably 1126more readable and descriptive. 1127 1128GNU CPP has two further variadic macro extensions, and permits them to 1129be used with either of the above forms of macro definition. 1130 1131In standard C, you are not allowed to leave the variable argument out 1132entirely; but you are allowed to pass an empty argument. For example, 1133this invocation is invalid in ISO C, because there is no comma after 1134the string: 1135 1136@smallexample 1137debug ("A message") 1138@end smallexample 1139 1140GNU CPP permits you to completely omit the variable arguments in this 1141way. In the above examples, the compiler would complain, though since 1142the expansion of the macro still has the extra comma after the format 1143string. 1144 1145To help solve this problem, CPP behaves specially for variable arguments 1146used with the token paste operator, @samp{##}. If instead you write 1147 1148@smallexample 1149#define debug(format, ...) fprintf (stderr, format, ## __VA_ARGS__) 1150@end smallexample 1151 1152and if the variable arguments are omitted or empty, the @samp{##} 1153operator causes the preprocessor to remove the comma before it. If you 1154do provide some variable arguments in your macro invocation, GNU CPP 1155does not complain about the paste operation and instead places the 1156variable arguments after the comma. Just like any other pasted macro 1157argument, these arguments are not macro expanded. 1158 1159@node Escaped Newlines 1160@section Slightly Looser Rules for Escaped Newlines 1161@cindex escaped newlines 1162@cindex newlines (escaped) 1163 1164Recently, the preprocessor has relaxed its treatment of escaped 1165newlines. Previously, the newline had to immediately follow a 1166backslash. The current implementation allows whitespace in the form 1167of spaces, horizontal and vertical tabs, and form feeds between the 1168backslash and the subsequent newline. The preprocessor issues a 1169warning, but treats it as a valid escaped newline and combines the two 1170lines to form a single logical line. This works within comments and 1171tokens, as well as between tokens. Comments are @emph{not} treated as 1172whitespace for the purposes of this relaxation, since they have not 1173yet been replaced with spaces. 1174 1175@node Subscripting 1176@section Non-Lvalue Arrays May Have Subscripts 1177@cindex subscripting 1178@cindex arrays, non-lvalue 1179 1180@cindex subscripting and function values 1181In ISO C99, arrays that are not lvalues still decay to pointers, and 1182may be subscripted, although they may not be modified or used after 1183the next sequence point and the unary @samp{&} operator may not be 1184applied to them. As an extension, GCC allows such arrays to be 1185subscripted in C89 mode, though otherwise they do not decay to 1186pointers outside C99 mode. For example, 1187this is valid in GNU C though not valid in C89: 1188 1189@smallexample 1190@group 1191struct foo @{int a[4];@}; 1192 1193struct foo f(); 1194 1195bar (int index) 1196@{ 1197 return f().a[index]; 1198@} 1199@end group 1200@end smallexample 1201 1202@node Pointer Arith 1203@section Arithmetic on @code{void}- and Function-Pointers 1204@cindex void pointers, arithmetic 1205@cindex void, size of pointer to 1206@cindex function pointers, arithmetic 1207@cindex function, size of pointer to 1208 1209In GNU C, addition and subtraction operations are supported on pointers to 1210@code{void} and on pointers to functions. This is done by treating the 1211size of a @code{void} or of a function as 1. 1212 1213A consequence of this is that @code{sizeof} is also allowed on @code{void} 1214and on function types, and returns 1. 1215 1216@opindex Wpointer-arith 1217The option @option{-Wpointer-arith} requests a warning if these extensions 1218are used. 1219 1220@node Initializers 1221@section Non-Constant Initializers 1222@cindex initializers, non-constant 1223@cindex non-constant initializers 1224 1225As in standard C++ and ISO C99, the elements of an aggregate initializer for an 1226automatic variable are not required to be constant expressions in GNU C@. 1227Here is an example of an initializer with run-time varying elements: 1228 1229@smallexample 1230foo (float f, float g) 1231@{ 1232 float beat_freqs[2] = @{ f-g, f+g @}; 1233 /* @r{@dots{}} */ 1234@} 1235@end smallexample 1236 1237@node Compound Literals 1238@section Compound Literals 1239@cindex constructor expressions 1240@cindex initializations in expressions 1241@cindex structures, constructor expression 1242@cindex expressions, constructor 1243@cindex compound literals 1244@c The GNU C name for what C99 calls compound literals was "constructor expressions". 1245 1246ISO C99 supports compound literals. A compound literal looks like 1247a cast containing an initializer. Its value is an object of the 1248type specified in the cast, containing the elements specified in 1249the initializer; it is an lvalue. As an extension, GCC supports 1250compound literals in C89 mode and in C++. 1251 1252Usually, the specified type is a structure. Assume that 1253@code{struct foo} and @code{structure} are declared as shown: 1254 1255@smallexample 1256struct foo @{int a; char b[2];@} structure; 1257@end smallexample 1258 1259@noindent 1260Here is an example of constructing a @code{struct foo} with a compound literal: 1261 1262@smallexample 1263structure = ((struct foo) @{x + y, 'a', 0@}); 1264@end smallexample 1265 1266@noindent 1267This is equivalent to writing the following: 1268 1269@smallexample 1270@{ 1271 struct foo temp = @{x + y, 'a', 0@}; 1272 structure = temp; 1273@} 1274@end smallexample 1275 1276You can also construct an array. If all the elements of the compound literal 1277are (made up of) simple constant expressions, suitable for use in 1278initializers of objects of static storage duration, then the compound 1279literal can be coerced to a pointer to its first element and used in 1280such an initializer, as shown here: 1281 1282@smallexample 1283char **foo = (char *[]) @{ "x", "y", "z" @}; 1284@end smallexample 1285 1286Compound literals for scalar types and union types are is 1287also allowed, but then the compound literal is equivalent 1288to a cast. 1289 1290As a GNU extension, GCC allows initialization of objects with static storage 1291duration by compound literals (which is not possible in ISO C99, because 1292the initializer is not a constant). 1293It is handled as if the object was initialized only with the bracket 1294enclosed list if the types of the compound literal and the object match. 1295The initializer list of the compound literal must be constant. 1296If the object being initialized has array type of unknown size, the size is 1297determined by compound literal size. 1298 1299@smallexample 1300static struct foo x = (struct foo) @{1, 'a', 'b'@}; 1301static int y[] = (int []) @{1, 2, 3@}; 1302static int z[] = (int [3]) @{1@}; 1303@end smallexample 1304 1305@noindent 1306The above lines are equivalent to the following: 1307@smallexample 1308static struct foo x = @{1, 'a', 'b'@}; 1309static int y[] = @{1, 2, 3@}; 1310static int z[] = @{1, 0, 0@}; 1311@end smallexample 1312 1313@node Designated Inits 1314@section Designated Initializers 1315@cindex initializers with labeled elements 1316@cindex labeled elements in initializers 1317@cindex case labels in initializers 1318@cindex designated initializers 1319 1320Standard C89 requires the elements of an initializer to appear in a fixed 1321order, the same as the order of the elements in the array or structure 1322being initialized. 1323 1324In ISO C99 you can give the elements in any order, specifying the array 1325indices or structure field names they apply to, and GNU C allows this as 1326an extension in C89 mode as well. This extension is not 1327implemented in GNU C++. 1328 1329To specify an array index, write 1330@samp{[@var{index}] =} before the element value. For example, 1331 1332@smallexample 1333int a[6] = @{ [4] = 29, [2] = 15 @}; 1334@end smallexample 1335 1336@noindent 1337is equivalent to 1338 1339@smallexample 1340int a[6] = @{ 0, 0, 15, 0, 29, 0 @}; 1341@end smallexample 1342 1343@noindent 1344The index values must be constant expressions, even if the array being 1345initialized is automatic. 1346 1347An alternative syntax for this which has been obsolete since GCC 2.5 but 1348GCC still accepts is to write @samp{[@var{index}]} before the element 1349value, with no @samp{=}. 1350 1351To initialize a range of elements to the same value, write 1352@samp{[@var{first} ... @var{last}] = @var{value}}. This is a GNU 1353extension. For example, 1354 1355@smallexample 1356int widths[] = @{ [0 ... 9] = 1, [10 ... 99] = 2, [100] = 3 @}; 1357@end smallexample 1358 1359@noindent 1360If the value in it has side-effects, the side-effects will happen only once, 1361not for each initialized field by the range initializer. 1362 1363@noindent 1364Note that the length of the array is the highest value specified 1365plus one. 1366 1367In a structure initializer, specify the name of a field to initialize 1368with @samp{.@var{fieldname} =} before the element value. For example, 1369given the following structure, 1370 1371@smallexample 1372struct point @{ int x, y; @}; 1373@end smallexample 1374 1375@noindent 1376the following initialization 1377 1378@smallexample 1379struct point p = @{ .y = yvalue, .x = xvalue @}; 1380@end smallexample 1381 1382@noindent 1383is equivalent to 1384 1385@smallexample 1386struct point p = @{ xvalue, yvalue @}; 1387@end smallexample 1388 1389Another syntax which has the same meaning, obsolete since GCC 2.5, is 1390@samp{@var{fieldname}:}, as shown here: 1391 1392@smallexample 1393struct point p = @{ y: yvalue, x: xvalue @}; 1394@end smallexample 1395 1396@cindex designators 1397The @samp{[@var{index}]} or @samp{.@var{fieldname}} is known as a 1398@dfn{designator}. You can also use a designator (or the obsolete colon 1399syntax) when initializing a union, to specify which element of the union 1400should be used. For example, 1401 1402@smallexample 1403union foo @{ int i; double d; @}; 1404 1405union foo f = @{ .d = 4 @}; 1406@end smallexample 1407 1408@noindent 1409will convert 4 to a @code{double} to store it in the union using 1410the second element. By contrast, casting 4 to type @code{union foo} 1411would store it into the union as the integer @code{i}, since it is 1412an integer. (@xref{Cast to Union}.) 1413 1414You can combine this technique of naming elements with ordinary C 1415initialization of successive elements. Each initializer element that 1416does not have a designator applies to the next consecutive element of the 1417array or structure. For example, 1418 1419@smallexample 1420int a[6] = @{ [1] = v1, v2, [4] = v4 @}; 1421@end smallexample 1422 1423@noindent 1424is equivalent to 1425 1426@smallexample 1427int a[6] = @{ 0, v1, v2, 0, v4, 0 @}; 1428@end smallexample 1429 1430Labeling the elements of an array initializer is especially useful 1431when the indices are characters or belong to an @code{enum} type. 1432For example: 1433 1434@smallexample 1435int whitespace[256] 1436 = @{ [' '] = 1, ['\t'] = 1, ['\h'] = 1, 1437 ['\f'] = 1, ['\n'] = 1, ['\r'] = 1 @}; 1438@end smallexample 1439 1440@cindex designator lists 1441You can also write a series of @samp{.@var{fieldname}} and 1442@samp{[@var{index}]} designators before an @samp{=} to specify a 1443nested subobject to initialize; the list is taken relative to the 1444subobject corresponding to the closest surrounding brace pair. For 1445example, with the @samp{struct point} declaration above: 1446 1447@smallexample 1448struct point ptarray[10] = @{ [2].y = yv2, [2].x = xv2, [0].x = xv0 @}; 1449@end smallexample 1450 1451@noindent 1452If the same field is initialized multiple times, it will have value from 1453the last initialization. If any such overridden initialization has 1454side-effect, it is unspecified whether the side-effect happens or not. 1455Currently, GCC will discard them and issue a warning. 1456 1457@node Case Ranges 1458@section Case Ranges 1459@cindex case ranges 1460@cindex ranges in case statements 1461 1462You can specify a range of consecutive values in a single @code{case} label, 1463like this: 1464 1465@smallexample 1466case @var{low} ... @var{high}: 1467@end smallexample 1468 1469@noindent 1470This has the same effect as the proper number of individual @code{case} 1471labels, one for each integer value from @var{low} to @var{high}, inclusive. 1472 1473This feature is especially useful for ranges of ASCII character codes: 1474 1475@smallexample 1476case 'A' ... 'Z': 1477@end smallexample 1478 1479@strong{Be careful:} Write spaces around the @code{...}, for otherwise 1480it may be parsed wrong when you use it with integer values. For example, 1481write this: 1482 1483@smallexample 1484case 1 ... 5: 1485@end smallexample 1486 1487@noindent 1488rather than this: 1489 1490@smallexample 1491case 1...5: 1492@end smallexample 1493 1494@node Cast to Union 1495@section Cast to a Union Type 1496@cindex cast to a union 1497@cindex union, casting to a 1498 1499A cast to union type is similar to other casts, except that the type 1500specified is a union type. You can specify the type either with 1501@code{union @var{tag}} or with a typedef name. A cast to union is actually 1502a constructor though, not a cast, and hence does not yield an lvalue like 1503normal casts. (@xref{Compound Literals}.) 1504 1505The types that may be cast to the union type are those of the members 1506of the union. Thus, given the following union and variables: 1507 1508@smallexample 1509union foo @{ int i; double d; @}; 1510int x; 1511double y; 1512@end smallexample 1513 1514@noindent 1515both @code{x} and @code{y} can be cast to type @code{union foo}. 1516 1517Using the cast as the right-hand side of an assignment to a variable of 1518union type is equivalent to storing in a member of the union: 1519 1520@smallexample 1521union foo u; 1522/* @r{@dots{}} */ 1523u = (union foo) x @equiv{} u.i = x 1524u = (union foo) y @equiv{} u.d = y 1525@end smallexample 1526 1527You can also use the union cast as a function argument: 1528 1529@smallexample 1530void hack (union foo); 1531/* @r{@dots{}} */ 1532hack ((union foo) x); 1533@end smallexample 1534 1535@node Mixed Declarations 1536@section Mixed Declarations and Code 1537@cindex mixed declarations and code 1538@cindex declarations, mixed with code 1539@cindex code, mixed with declarations 1540 1541ISO C99 and ISO C++ allow declarations and code to be freely mixed 1542within compound statements. As an extension, GCC also allows this in 1543C89 mode. For example, you could do: 1544 1545@smallexample 1546int i; 1547/* @r{@dots{}} */ 1548i++; 1549int j = i + 2; 1550@end smallexample 1551 1552Each identifier is visible from where it is declared until the end of 1553the enclosing block. 1554 1555@node Function Attributes 1556@section Declaring Attributes of Functions 1557@cindex function attributes 1558@cindex declaring attributes of functions 1559@cindex functions that never return 1560@cindex functions that return more than once 1561@cindex functions that have no side effects 1562@cindex functions in arbitrary sections 1563@cindex functions that behave like malloc 1564@cindex @code{volatile} applied to function 1565@cindex @code{const} applied to function 1566@cindex functions with @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style arguments 1567@cindex functions with non-null pointer arguments 1568@cindex functions that are passed arguments in registers on the 386 1569@cindex functions that pop the argument stack on the 386 1570@cindex functions that do not pop the argument stack on the 386 1571 1572In GNU C, you declare certain things about functions called in your program 1573which help the compiler optimize function calls and check your code more 1574carefully. 1575 1576The keyword @code{__attribute__} allows you to specify special 1577attributes when making a declaration. This keyword is followed by an 1578attribute specification inside double parentheses. The following 1579attributes are currently defined for functions on all targets: 1580@code{noreturn}, @code{returns_twice}, @code{noinline}, @code{always_inline}, 1581@code{flatten}, @code{pure}, @code{const}, @code{nothrow}, @code{sentinel}, 1582@code{format}, @code{format_arg}, @code{no_instrument_function}, 1583@code{section}, @code{constructor}, @code{destructor}, @code{used}, 1584@code{unused}, @code{deprecated}, @code{weak}, @code{malloc}, 1585@code{alias}, @code{warn_unused_result}, @code{nonnull}, 1586@code{gnu_inline} and @code{externally_visible}. Several other 1587attributes are defined for functions on particular target systems. Other 1588attributes, including @code{section} are supported for variables declarations 1589(@pxref{Variable Attributes}) and for types (@pxref{Type Attributes}). 1590 1591You may also specify attributes with @samp{__} preceding and following 1592each keyword. This allows you to use them in header files without 1593being concerned about a possible macro of the same name. For example, 1594you may use @code{__noreturn__} instead of @code{noreturn}. 1595 1596@xref{Attribute Syntax}, for details of the exact syntax for using 1597attributes. 1598 1599@table @code 1600@c Keep this table alphabetized by attribute name. Treat _ as space. 1601 1602@item alias ("@var{target}") 1603@cindex @code{alias} attribute 1604The @code{alias} attribute causes the declaration to be emitted as an 1605alias for another symbol, which must be specified. For instance, 1606 1607@smallexample 1608void __f () @{ /* @r{Do something.} */; @} 1609void f () __attribute__ ((weak, alias ("__f"))); 1610@end smallexample 1611 1612defines @samp{f} to be a weak alias for @samp{__f}. In C++, the 1613mangled name for the target must be used. It is an error if @samp{__f} 1614is not defined in the same translation unit. 1615 1616Not all target machines support this attribute. 1617 1618@item always_inline 1619@cindex @code{always_inline} function attribute 1620Generally, functions are not inlined unless optimization is specified. 1621For functions declared inline, this attribute inlines the function even 1622if no optimization level was specified. 1623 1624@item gnu_inline 1625@cindex @code{gnu_inline} function attribute 1626This attribute should be used with a function which is also declared 1627with the @code{inline} keyword. It directs GCC to treat the function 1628as if it were defined in gnu89 mode even when compiling in C99 or 1629gnu99 mode. 1630 1631If the function is declared @code{extern}, then this definition of the 1632function is used only for inlining. In no case is the function 1633compiled as a standalone function, not even if you take its address 1634explicitly. Such an address becomes an external reference, as if you 1635had only declared the function, and had not defined it. This has 1636almost the effect of a macro. The way to use this is to put a 1637function definition in a header file with this attribute, and put 1638another copy of the function, without @code{extern}, in a library 1639file. The definition in the header file will cause most calls to the 1640function to be inlined. If any uses of the function remain, they will 1641refer to the single copy in the library. Note that the two 1642definitions of the functions need not be precisely the same, although 1643if they do not have the same effect your program may behave oddly. 1644 1645If the function is neither @code{extern} nor @code{static}, then the 1646function is compiled as a standalone function, as well as being 1647inlined where possible. 1648 1649This is how GCC traditionally handled functions declared 1650@code{inline}. Since ISO C99 specifies a different semantics for 1651@code{inline}, this function attribute is provided as a transition 1652measure and as a useful feature in its own right. This attribute is 1653available in GCC 4.1.3 and later. It is available if either of the 1654preprocessor macros @code{__GNUC_GNU_INLINE__} or 1655@code{__GNUC_STDC_INLINE__} are defined. @xref{Inline,,An Inline 1656Function is As Fast As a Macro}. 1657 1658Note that since the first version of GCC to support C99 inline semantics 1659is 4.3, earlier versions of GCC which accept this attribute effectively 1660assume that it is always present, whether or not it is given explicitly. 1661In versions prior to 4.3, the only effect of explicitly including it is 1662to disable warnings about using inline functions in C99 mode. 1663 1664@cindex @code{flatten} function attribute 1665@item flatten 1666Generally, inlining into a function is limited. For a function marked with 1667this attribute, every call inside this function will be inlined, if possible. 1668Whether the function itself is considered for inlining depends on its size and 1669the current inlining parameters. The @code{flatten} attribute only works 1670reliably in unit-at-a-time mode. 1671 1672@item cdecl 1673@cindex functions that do pop the argument stack on the 386 1674@opindex mrtd 1675On the Intel 386, the @code{cdecl} attribute causes the compiler to 1676assume that the calling function will pop off the stack space used to 1677pass arguments. This is 1678useful to override the effects of the @option{-mrtd} switch. 1679 1680@item const 1681@cindex @code{const} function attribute 1682Many functions do not examine any values except their arguments, and 1683have no effects except the return value. Basically this is just slightly 1684more strict class than the @code{pure} attribute below, since function is not 1685allowed to read global memory. 1686 1687@cindex pointer arguments 1688Note that a function that has pointer arguments and examines the data 1689pointed to must @emph{not} be declared @code{const}. Likewise, a 1690function that calls a non-@code{const} function usually must not be 1691@code{const}. It does not make sense for a @code{const} function to 1692return @code{void}. 1693 1694The attribute @code{const} is not implemented in GCC versions earlier 1695than 2.5. An alternative way to declare that a function has no side 1696effects, which works in the current version and in some older versions, 1697is as follows: 1698 1699@smallexample 1700typedef int intfn (); 1701 1702extern const intfn square; 1703@end smallexample 1704 1705This approach does not work in GNU C++ from 2.6.0 on, since the language 1706specifies that the @samp{const} must be attached to the return value. 1707 1708@item constructor 1709@itemx destructor 1710@cindex @code{constructor} function attribute 1711@cindex @code{destructor} function attribute 1712The @code{constructor} attribute causes the function to be called 1713automatically before execution enters @code{main ()}. Similarly, the 1714@code{destructor} attribute causes the function to be called 1715automatically after @code{main ()} has completed or @code{exit ()} has 1716been called. Functions with these attributes are useful for 1717initializing data that will be used implicitly during the execution of 1718the program. 1719 1720@item deprecated 1721@cindex @code{deprecated} attribute. 1722The @code{deprecated} attribute results in a warning if the function 1723is used anywhere in the source file. This is useful when identifying 1724functions that are expected to be removed in a future version of a 1725program. The warning also includes the location of the declaration 1726of the deprecated function, to enable users to easily find further 1727information about why the function is deprecated, or what they should 1728do instead. Note that the warnings only occurs for uses: 1729 1730@smallexample 1731int old_fn () __attribute__ ((deprecated)); 1732int old_fn (); 1733int (*fn_ptr)() = old_fn; 1734@end smallexample 1735 1736results in a warning on line 3 but not line 2. 1737 1738The @code{deprecated} attribute can also be used for variables and 1739types (@pxref{Variable Attributes}, @pxref{Type Attributes}.) 1740 1741@item dllexport 1742@cindex @code{__declspec(dllexport)} 1743On Microsoft Windows targets and Symbian OS targets the 1744@code{dllexport} attribute causes the compiler to provide a global 1745pointer to a pointer in a DLL, so that it can be referenced with the 1746@code{dllimport} attribute. On Microsoft Windows targets, the pointer 1747name is formed by combining @code{_imp__} and the function or variable 1748name. 1749 1750You can use @code{__declspec(dllexport)} as a synonym for 1751@code{__attribute__ ((dllexport))} for compatibility with other 1752compilers. 1753 1754On systems that support the @code{visibility} attribute, this 1755attribute also implies ``default'' visibility, unless a 1756@code{visibility} attribute is explicitly specified. You should avoid 1757the use of @code{dllexport} with ``hidden'' or ``internal'' 1758visibility; in the future GCC may issue an error for those cases. 1759 1760Currently, the @code{dllexport} attribute is ignored for inlined 1761functions, unless the @option{-fkeep-inline-functions} flag has been 1762used. The attribute is also ignored for undefined symbols. 1763 1764When applied to C++ classes, the attribute marks defined non-inlined 1765member functions and static data members as exports. Static consts 1766initialized in-class are not marked unless they are also defined 1767out-of-class. 1768 1769For Microsoft Windows targets there are alternative methods for 1770including the symbol in the DLL's export table such as using a 1771@file{.def} file with an @code{EXPORTS} section or, with GNU ld, using 1772the @option{--export-all} linker flag. 1773 1774@item dllimport 1775@cindex @code{__declspec(dllimport)} 1776On Microsoft Windows and Symbian OS targets, the @code{dllimport} 1777attribute causes the compiler to reference a function or variable via 1778a global pointer to a pointer that is set up by the DLL exporting the 1779symbol. The attribute implies @code{extern} storage. On Microsoft 1780Windows targets, the pointer name is formed by combining @code{_imp__} 1781and the function or variable name. 1782 1783You can use @code{__declspec(dllimport)} as a synonym for 1784@code{__attribute__ ((dllimport))} for compatibility with other 1785compilers. 1786 1787Currently, the attribute is ignored for inlined functions. If the 1788attribute is applied to a symbol @emph{definition}, an error is reported. 1789If a symbol previously declared @code{dllimport} is later defined, the 1790attribute is ignored in subsequent references, and a warning is emitted. 1791The attribute is also overridden by a subsequent declaration as 1792@code{dllexport}. 1793 1794When applied to C++ classes, the attribute marks non-inlined 1795member functions and static data members as imports. However, the 1796attribute is ignored for virtual methods to allow creation of vtables 1797using thunks. 1798 1799On the SH Symbian OS target the @code{dllimport} attribute also has 1800another affect---it can cause the vtable and run-time type information 1801for a class to be exported. This happens when the class has a 1802dllimport'ed constructor or a non-inline, non-pure virtual function 1803and, for either of those two conditions, the class also has a inline 1804constructor or destructor and has a key function that is defined in 1805the current translation unit. 1806 1807For Microsoft Windows based targets the use of the @code{dllimport} 1808attribute on functions is not necessary, but provides a small 1809performance benefit by eliminating a thunk in the DLL@. The use of the 1810@code{dllimport} attribute on imported variables was required on older 1811versions of the GNU linker, but can now be avoided by passing the 1812@option{--enable-auto-import} switch to the GNU linker. As with 1813functions, using the attribute for a variable eliminates a thunk in 1814the DLL@. 1815 1816One drawback to using this attribute is that a pointer to a function 1817or variable marked as @code{dllimport} cannot be used as a constant 1818address. On Microsoft Windows targets, the attribute can be disabled 1819for functions by setting the @option{-mnop-fun-dllimport} flag. 1820 1821@item eightbit_data 1822@cindex eight bit data on the H8/300, H8/300H, and H8S 1823Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified 1824variable should be placed into the eight bit data section. 1825The compiler will generate more efficient code for certain operations 1826on data in the eight bit data area. Note the eight bit data area is limited to 1827256 bytes of data. 1828 1829You must use GAS and GLD from GNU binutils version 2.7 or later for 1830this attribute to work correctly. 1831 1832@item exception_handler 1833@cindex exception handler functions on the Blackfin processor 1834Use this attribute on the Blackfin to indicate that the specified function 1835is an exception handler. The compiler will generate function entry and 1836exit sequences suitable for use in an exception handler when this 1837attribute is present. 1838 1839@item far 1840@cindex functions which handle memory bank switching 1841On 68HC11 and 68HC12 the @code{far} attribute causes the compiler to 1842use a calling convention that takes care of switching memory banks when 1843entering and leaving a function. This calling convention is also the 1844default when using the @option{-mlong-calls} option. 1845 1846On 68HC12 the compiler will use the @code{call} and @code{rtc} instructions 1847to call and return from a function. 1848 1849On 68HC11 the compiler will generate a sequence of instructions 1850to invoke a board-specific routine to switch the memory bank and call the 1851real function. The board-specific routine simulates a @code{call}. 1852At the end of a function, it will jump to a board-specific routine 1853instead of using @code{rts}. The board-specific return routine simulates 1854the @code{rtc}. 1855 1856@item fastcall 1857@cindex functions that pop the argument stack on the 386 1858On the Intel 386, the @code{fastcall} attribute causes the compiler to 1859pass the first argument (if of integral type) in the register ECX and 1860the second argument (if of integral type) in the register EDX@. Subsequent 1861and other typed arguments are passed on the stack. The called function will 1862pop the arguments off the stack. If the number of arguments is variable all 1863arguments are pushed on the stack. 1864 1865@item format (@var{archetype}, @var{string-index}, @var{first-to-check}) 1866@cindex @code{format} function attribute 1867@opindex Wformat 1868The @code{format} attribute specifies that a function takes @code{printf}, 1869@code{scanf}, @code{strftime} or @code{strfmon} style arguments which 1870should be type-checked against a format string. For example, the 1871declaration: 1872 1873@smallexample 1874extern int 1875my_printf (void *my_object, const char *my_format, ...) 1876 __attribute__ ((format (printf, 2, 3))); 1877@end smallexample 1878 1879@noindent 1880causes the compiler to check the arguments in calls to @code{my_printf} 1881for consistency with the @code{printf} style format string argument 1882@code{my_format}. 1883 1884The parameter @var{archetype} determines how the format string is 1885interpreted, and should be @code{printf}, @code{scanf}, @code{strftime} 1886or @code{strfmon}. (You can also use @code{__printf__}, 1887@code{__scanf__}, @code{__strftime__} or @code{__strfmon__}.) The 1888parameter @var{string-index} specifies which argument is the format 1889string argument (starting from 1), while @var{first-to-check} is the 1890number of the first argument to check against the format string. For 1891functions where the arguments are not available to be checked (such as 1892@code{vprintf}), specify the third parameter as zero. In this case the 1893compiler only checks the format string for consistency. For 1894@code{strftime} formats, the third parameter is required to be zero. 1895Since non-static C++ methods have an implicit @code{this} argument, the 1896arguments of such methods should be counted from two, not one, when 1897giving values for @var{string-index} and @var{first-to-check}. 1898 1899In the example above, the format string (@code{my_format}) is the second 1900argument of the function @code{my_print}, and the arguments to check 1901start with the third argument, so the correct parameters for the format 1902attribute are 2 and 3. 1903 1904@opindex ffreestanding 1905@opindex fno-builtin 1906The @code{format} attribute allows you to identify your own functions 1907which take format strings as arguments, so that GCC can check the 1908calls to these functions for errors. The compiler always (unless 1909@option{-ffreestanding} or @option{-fno-builtin} is used) checks formats 1910for the standard library functions @code{printf}, @code{fprintf}, 1911@code{sprintf}, @code{scanf}, @code{fscanf}, @code{sscanf}, @code{strftime}, 1912@code{vprintf}, @code{vfprintf} and @code{vsprintf} whenever such 1913warnings are requested (using @option{-Wformat}), so there is no need to 1914modify the header file @file{stdio.h}. In C99 mode, the functions 1915@code{snprintf}, @code{vsnprintf}, @code{vscanf}, @code{vfscanf} and 1916@code{vsscanf} are also checked. Except in strictly conforming C 1917standard modes, the X/Open function @code{strfmon} is also checked as 1918are @code{printf_unlocked} and @code{fprintf_unlocked}. 1919@xref{C Dialect Options,,Options Controlling C Dialect}. 1920 1921The target may provide additional types of format checks. 1922@xref{Target Format Checks,,Format Checks Specific to Particular 1923Target Machines}. 1924 1925@item format_arg (@var{string-index}) 1926@cindex @code{format_arg} function attribute 1927@opindex Wformat-nonliteral 1928The @code{format_arg} attribute specifies that a function takes a format 1929string for a @code{printf}, @code{scanf}, @code{strftime} or 1930@code{strfmon} style function and modifies it (for example, to translate 1931it into another language), so the result can be passed to a 1932@code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} style 1933function (with the remaining arguments to the format function the same 1934as they would have been for the unmodified string). For example, the 1935declaration: 1936 1937@smallexample 1938extern char * 1939my_dgettext (char *my_domain, const char *my_format) 1940 __attribute__ ((format_arg (2))); 1941@end smallexample 1942 1943@noindent 1944causes the compiler to check the arguments in calls to a @code{printf}, 1945@code{scanf}, @code{strftime} or @code{strfmon} type function, whose 1946format string argument is a call to the @code{my_dgettext} function, for 1947consistency with the format string argument @code{my_format}. If the 1948@code{format_arg} attribute had not been specified, all the compiler 1949could tell in such calls to format functions would be that the format 1950string argument is not constant; this would generate a warning when 1951@option{-Wformat-nonliteral} is used, but the calls could not be checked 1952without the attribute. 1953 1954The parameter @var{string-index} specifies which argument is the format 1955string argument (starting from one). Since non-static C++ methods have 1956an implicit @code{this} argument, the arguments of such methods should 1957be counted from two. 1958 1959The @code{format-arg} attribute allows you to identify your own 1960functions which modify format strings, so that GCC can check the 1961calls to @code{printf}, @code{scanf}, @code{strftime} or @code{strfmon} 1962type function whose operands are a call to one of your own function. 1963The compiler always treats @code{gettext}, @code{dgettext}, and 1964@code{dcgettext} in this manner except when strict ISO C support is 1965requested by @option{-ansi} or an appropriate @option{-std} option, or 1966@option{-ffreestanding} or @option{-fno-builtin} 1967is used. @xref{C Dialect Options,,Options 1968Controlling C Dialect}. 1969 1970@item function_vector 1971@cindex calling functions through the function vector on the H8/300 processors 1972Use this attribute on the H8/300, H8/300H, and H8S to indicate that the specified 1973function should be called through the function vector. Calling a 1974function through the function vector will reduce code size, however; 1975the function vector has a limited size (maximum 128 entries on the H8/300 1976and 64 entries on the H8/300H and H8S) and shares space with the interrupt vector. 1977 1978You must use GAS and GLD from GNU binutils version 2.7 or later for 1979this attribute to work correctly. 1980 1981@item interrupt 1982@cindex interrupt handler functions 1983Use this attribute on the ARM, AVR, C4x, CRX, M32C, M32R/D, MS1, and Xstormy16 1984ports to indicate that the specified function is an interrupt handler. 1985The compiler will generate function entry and exit sequences suitable 1986for use in an interrupt handler when this attribute is present. 1987 1988Note, interrupt handlers for the Blackfin, m68k, H8/300, H8/300H, H8S, and 1989SH processors can be specified via the @code{interrupt_handler} attribute. 1990 1991Note, on the AVR, interrupts will be enabled inside the function. 1992 1993Note, for the ARM, you can specify the kind of interrupt to be handled by 1994adding an optional parameter to the interrupt attribute like this: 1995 1996@smallexample 1997void f () __attribute__ ((interrupt ("IRQ"))); 1998@end smallexample 1999 2000Permissible values for this parameter are: IRQ, FIQ, SWI, ABORT and UNDEF@. 2001 2002@item interrupt_handler 2003@cindex interrupt handler functions on the Blackfin, m68k, H8/300 and SH processors 2004Use this attribute on the Blackfin, m68k, H8/300, H8/300H, H8S, and SH to 2005indicate that the specified function is an interrupt handler. The compiler 2006will generate function entry and exit sequences suitable for use in an 2007interrupt handler when this attribute is present. 2008 2009@item kspisusp 2010@cindex User stack pointer in interrupts on the Blackfin 2011When used together with @code{interrupt_handler}, @code{exception_handler} 2012or @code{nmi_handler}, code will be generated to load the stack pointer 2013from the USP register in the function prologue. 2014 2015@item long_call/short_call 2016@cindex indirect calls on ARM 2017This attribute specifies how a particular function is called on 2018ARM@. Both attributes override the @option{-mlong-calls} (@pxref{ARM Options}) 2019command line switch and @code{#pragma long_calls} settings. The 2020@code{long_call} attribute indicates that the function might be far 2021away from the call site and require a different (more expensive) 2022calling sequence. The @code{short_call} attribute always places 2023the offset to the function from the call site into the @samp{BL} 2024instruction directly. 2025 2026@item longcall/shortcall 2027@cindex functions called via pointer on the RS/6000 and PowerPC 2028On the Blackfin, RS/6000 and PowerPC, the @code{longcall} attribute 2029indicates that the function might be far away from the call site and 2030require a different (more expensive) calling sequence. The 2031@code{shortcall} attribute indicates that the function is always close 2032enough for the shorter calling sequence to be used. These attributes 2033override both the @option{-mlongcall} switch and, on the RS/6000 and 2034PowerPC, the @code{#pragma longcall} setting. 2035 2036@xref{RS/6000 and PowerPC Options}, for more information on whether long 2037calls are necessary. 2038 2039@item long_call 2040@cindex indirect calls on MIPS 2041This attribute specifies how a particular function is called on MIPS@. 2042The attribute overrides the @option{-mlong-calls} (@pxref{MIPS Options}) 2043command line switch. This attribute causes the compiler to always call 2044the function by first loading its address into a register, and then using 2045the contents of that register. 2046 2047@item malloc 2048@cindex @code{malloc} attribute 2049The @code{malloc} attribute is used to tell the compiler that a function 2050may be treated as if any non-@code{NULL} pointer it returns cannot 2051alias any other pointer valid when the function returns. 2052This will often improve optimization. 2053Standard functions with this property include @code{malloc} and 2054@code{calloc}. @code{realloc}-like functions have this property as 2055long as the old pointer is never referred to (including comparing it 2056to the new pointer) after the function returns a non-@code{NULL} 2057value. 2058 2059@item model (@var{model-name}) 2060@cindex function addressability on the M32R/D 2061@cindex variable addressability on the IA-64 2062 2063On the M32R/D, use this attribute to set the addressability of an 2064object, and of the code generated for a function. The identifier 2065@var{model-name} is one of @code{small}, @code{medium}, or 2066@code{large}, representing each of the code models. 2067 2068Small model objects live in the lower 16MB of memory (so that their 2069addresses can be loaded with the @code{ld24} instruction), and are 2070callable with the @code{bl} instruction. 2071 2072Medium model objects may live anywhere in the 32-bit address space (the 2073compiler will generate @code{seth/add3} instructions to load their addresses), 2074and are callable with the @code{bl} instruction. 2075 2076Large model objects may live anywhere in the 32-bit address space (the 2077compiler will generate @code{seth/add3} instructions to load their addresses), 2078and may not be reachable with the @code{bl} instruction (the compiler will 2079generate the much slower @code{seth/add3/jl} instruction sequence). 2080 2081On IA-64, use this attribute to set the addressability of an object. 2082At present, the only supported identifier for @var{model-name} is 2083@code{small}, indicating addressability via ``small'' (22-bit) 2084addresses (so that their addresses can be loaded with the @code{addl} 2085instruction). Caveat: such addressing is by definition not position 2086independent and hence this attribute must not be used for objects 2087defined by shared libraries. 2088 2089@item naked 2090@cindex function without a prologue/epilogue code 2091Use this attribute on the ARM, AVR, C4x and IP2K ports to indicate that the 2092specified function does not need prologue/epilogue sequences generated by 2093the compiler. It is up to the programmer to provide these sequences. 2094 2095@item near 2096@cindex functions which do not handle memory bank switching on 68HC11/68HC12 2097On 68HC11 and 68HC12 the @code{near} attribute causes the compiler to 2098use the normal calling convention based on @code{jsr} and @code{rts}. 2099This attribute can be used to cancel the effect of the @option{-mlong-calls} 2100option. 2101 2102@item nesting 2103@cindex Allow nesting in an interrupt handler on the Blackfin processor. 2104Use this attribute together with @code{interrupt_handler}, 2105@code{exception_handler} or @code{nmi_handler} to indicate that the function 2106entry code should enable nested interrupts or exceptions. 2107 2108@item nmi_handler 2109@cindex NMI handler functions on the Blackfin processor 2110Use this attribute on the Blackfin to indicate that the specified function 2111is an NMI handler. The compiler will generate function entry and 2112exit sequences suitable for use in an NMI handler when this 2113attribute is present. 2114 2115@item no_instrument_function 2116@cindex @code{no_instrument_function} function attribute 2117@opindex finstrument-functions 2118If @option{-finstrument-functions} is given, profiling function calls will 2119be generated at entry and exit of most user-compiled functions. 2120Functions with this attribute will not be so instrumented. 2121 2122@item noinline 2123@cindex @code{noinline} function attribute 2124This function attribute prevents a function from being considered for 2125inlining. 2126 2127@item nonnull (@var{arg-index}, @dots{}) 2128@cindex @code{nonnull} function attribute 2129The @code{nonnull} attribute specifies that some function parameters should 2130be non-null pointers. For instance, the declaration: 2131 2132@smallexample 2133extern void * 2134my_memcpy (void *dest, const void *src, size_t len) 2135 __attribute__((nonnull (1, 2))); 2136@end smallexample 2137 2138@noindent 2139causes the compiler to check that, in calls to @code{my_memcpy}, 2140arguments @var{dest} and @var{src} are non-null. If the compiler 2141determines that a null pointer is passed in an argument slot marked 2142as non-null, and the @option{-Wnonnull} option is enabled, a warning 2143is issued. The compiler may also choose to make optimizations based 2144on the knowledge that certain function arguments will not be null. 2145 2146If no argument index list is given to the @code{nonnull} attribute, 2147all pointer arguments are marked as non-null. To illustrate, the 2148following declaration is equivalent to the previous example: 2149 2150@smallexample 2151extern void * 2152my_memcpy (void *dest, const void *src, size_t len) 2153 __attribute__((nonnull)); 2154@end smallexample 2155 2156@item noreturn 2157@cindex @code{noreturn} function attribute 2158A few standard library functions, such as @code{abort} and @code{exit}, 2159cannot return. GCC knows this automatically. Some programs define 2160their own functions that never return. You can declare them 2161@code{noreturn} to tell the compiler this fact. For example, 2162 2163@smallexample 2164@group 2165void fatal () __attribute__ ((noreturn)); 2166 2167void 2168fatal (/* @r{@dots{}} */) 2169@{ 2170 /* @r{@dots{}} */ /* @r{Print error message.} */ /* @r{@dots{}} */ 2171 exit (1); 2172@} 2173@end group 2174@end smallexample 2175 2176The @code{noreturn} keyword tells the compiler to assume that 2177@code{fatal} cannot return. It can then optimize without regard to what 2178would happen if @code{fatal} ever did return. This makes slightly 2179better code. More importantly, it helps avoid spurious warnings of 2180uninitialized variables. 2181 2182The @code{noreturn} keyword does not affect the exceptional path when that 2183applies: a @code{noreturn}-marked function may still return to the caller 2184by throwing an exception or calling @code{longjmp}. 2185 2186Do not assume that registers saved by the calling function are 2187restored before calling the @code{noreturn} function. 2188 2189It does not make sense for a @code{noreturn} function to have a return 2190type other than @code{void}. 2191 2192The attribute @code{noreturn} is not implemented in GCC versions 2193earlier than 2.5. An alternative way to declare that a function does 2194not return, which works in the current version and in some older 2195versions, is as follows: 2196 2197@smallexample 2198typedef void voidfn (); 2199 2200volatile voidfn fatal; 2201@end smallexample 2202 2203This approach does not work in GNU C++. 2204 2205@item nothrow 2206@cindex @code{nothrow} function attribute 2207The @code{nothrow} attribute is used to inform the compiler that a 2208function cannot throw an exception. For example, most functions in 2209the standard C library can be guaranteed not to throw an exception 2210with the notable exceptions of @code{qsort} and @code{bsearch} that 2211take function pointer arguments. The @code{nothrow} attribute is not 2212implemented in GCC versions earlier than 3.3. 2213 2214@item pure 2215@cindex @code{pure} function attribute 2216Many functions have no effects except the return value and their 2217return value depends only on the parameters and/or global variables. 2218Such a function can be subject 2219to common subexpression elimination and loop optimization just as an 2220arithmetic operator would be. These functions should be declared 2221with the attribute @code{pure}. For example, 2222 2223@smallexample 2224int square (int) __attribute__ ((pure)); 2225@end smallexample 2226 2227@noindent 2228says that the hypothetical function @code{square} is safe to call 2229fewer times than the program says. 2230 2231Some of common examples of pure functions are @code{strlen} or @code{memcmp}. 2232Interesting non-pure functions are functions with infinite loops or those 2233depending on volatile memory or other system resource, that may change between 2234two consecutive calls (such as @code{feof} in a multithreading environment). 2235 2236The attribute @code{pure} is not implemented in GCC versions earlier 2237than 2.96. 2238 2239@item regparm (@var{number}) 2240@cindex @code{regparm} attribute 2241@cindex functions that are passed arguments in registers on the 386 2242On the Intel 386, the @code{regparm} attribute causes the compiler to 2243pass arguments number one to @var{number} if they are of integral type 2244in registers EAX, EDX, and ECX instead of on the stack. Functions that 2245take a variable number of arguments will continue to be passed all of their 2246arguments on the stack. 2247 2248Beware that on some ELF systems this attribute is unsuitable for 2249global functions in shared libraries with lazy binding (which is the 2250default). Lazy binding will send the first call via resolving code in 2251the loader, which might assume EAX, EDX and ECX can be clobbered, as 2252per the standard calling conventions. Solaris 8 is affected by this. 2253GNU systems with GLIBC 2.1 or higher, and FreeBSD, are believed to be 2254safe since the loaders there save all registers. (Lazy binding can be 2255disabled with the linker or the loader if desired, to avoid the 2256problem.) 2257 2258@item sseregparm 2259@cindex @code{sseregparm} attribute 2260On the Intel 386 with SSE support, the @code{sseregparm} attribute 2261causes the compiler to pass up to 3 floating point arguments in 2262SSE registers instead of on the stack. Functions that take a 2263variable number of arguments will continue to pass all of their 2264floating point arguments on the stack. 2265 2266@item force_align_arg_pointer 2267@cindex @code{force_align_arg_pointer} attribute 2268On the Intel x86, the @code{force_align_arg_pointer} attribute may be 2269applied to individual function definitions, generating an alternate 2270prologue and epilogue that realigns the runtime stack. This supports 2271mixing legacy codes that run with a 4-byte aligned stack with modern 2272codes that keep a 16-byte stack for SSE compatibility. The alternate 2273prologue and epilogue are slower and bigger than the regular ones, and 2274the alternate prologue requires a scratch register; this lowers the 2275number of registers available if used in conjunction with the 2276@code{regparm} attribute. The @code{force_align_arg_pointer} 2277attribute is incompatible with nested functions; this is considered a 2278hard error. 2279 2280@item returns_twice 2281@cindex @code{returns_twice} attribute 2282The @code{returns_twice} attribute tells the compiler that a function may 2283return more than one time. The compiler will ensure that all registers 2284are dead before calling such a function and will emit a warning about 2285the variables that may be clobbered after the second return from the 2286function. Examples of such functions are @code{setjmp} and @code{vfork}. 2287The @code{longjmp}-like counterpart of such function, if any, might need 2288to be marked with the @code{noreturn} attribute. 2289 2290@item saveall 2291@cindex save all registers on the Blackfin, H8/300, H8/300H, and H8S 2292Use this attribute on the Blackfin, H8/300, H8/300H, and H8S to indicate that 2293all registers except the stack pointer should be saved in the prologue 2294regardless of whether they are used or not. 2295 2296@item section ("@var{section-name}") 2297@cindex @code{section} function attribute 2298Normally, the compiler places the code it generates in the @code{text} section. 2299Sometimes, however, you need additional sections, or you need certain 2300particular functions to appear in special sections. The @code{section} 2301attribute specifies that a function lives in a particular section. 2302For example, the declaration: 2303 2304@smallexample 2305extern void foobar (void) __attribute__ ((section ("bar"))); 2306@end smallexample 2307 2308@noindent 2309puts the function @code{foobar} in the @code{bar} section. 2310 2311Some file formats do not support arbitrary sections so the @code{section} 2312attribute is not available on all platforms. 2313If you need to map the entire contents of a module to a particular 2314section, consider using the facilities of the linker instead. 2315 2316@item sentinel 2317@cindex @code{sentinel} function attribute 2318This function attribute ensures that a parameter in a function call is 2319an explicit @code{NULL}. The attribute is only valid on variadic 2320functions. By default, the sentinel is located at position zero, the 2321last parameter of the function call. If an optional integer position 2322argument P is supplied to the attribute, the sentinel must be located at 2323position P counting backwards from the end of the argument list. 2324 2325@smallexample 2326__attribute__ ((sentinel)) 2327is equivalent to 2328__attribute__ ((sentinel(0))) 2329@end smallexample 2330 2331The attribute is automatically set with a position of 0 for the built-in 2332functions @code{execl} and @code{execlp}. The built-in function 2333@code{execle} has the attribute set with a position of 1. 2334 2335A valid @code{NULL} in this context is defined as zero with any pointer 2336type. If your system defines the @code{NULL} macro with an integer type 2337then you need to add an explicit cast. GCC replaces @code{stddef.h} 2338with a copy that redefines NULL appropriately. 2339 2340The warnings for missing or incorrect sentinels are enabled with 2341@option{-Wformat}. 2342 2343@item short_call 2344See long_call/short_call. 2345 2346@item shortcall 2347See longcall/shortcall. 2348 2349@item signal 2350@cindex signal handler functions on the AVR processors 2351Use this attribute on the AVR to indicate that the specified 2352function is a signal handler. The compiler will generate function 2353entry and exit sequences suitable for use in a signal handler when this 2354attribute is present. Interrupts will be disabled inside the function. 2355 2356@item sp_switch 2357Use this attribute on the SH to indicate an @code{interrupt_handler} 2358function should switch to an alternate stack. It expects a string 2359argument that names a global variable holding the address of the 2360alternate stack. 2361 2362@smallexample 2363void *alt_stack; 2364void f () __attribute__ ((interrupt_handler, 2365 sp_switch ("alt_stack"))); 2366@end smallexample 2367 2368@item stdcall 2369@cindex functions that pop the argument stack on the 386 2370On the Intel 386, the @code{stdcall} attribute causes the compiler to 2371assume that the called function will pop off the stack space used to 2372pass arguments, unless it takes a variable number of arguments. 2373 2374@item tiny_data 2375@cindex tiny data section on the H8/300H and H8S 2376Use this attribute on the H8/300H and H8S to indicate that the specified 2377variable should be placed into the tiny data section. 2378The compiler will generate more efficient code for loads and stores 2379on data in the tiny data section. Note the tiny data area is limited to 2380slightly under 32kbytes of data. 2381 2382@item trap_exit 2383Use this attribute on the SH for an @code{interrupt_handler} to return using 2384@code{trapa} instead of @code{rte}. This attribute expects an integer 2385argument specifying the trap number to be used. 2386 2387@item unused 2388@cindex @code{unused} attribute. 2389This attribute, attached to a function, means that the function is meant 2390to be possibly unused. GCC will not produce a warning for this 2391function. 2392 2393@item used 2394@cindex @code{used} attribute. 2395This attribute, attached to a function, means that code must be emitted 2396for the function even if it appears that the function is not referenced. 2397This is useful, for example, when the function is referenced only in 2398inline assembly. 2399 2400@item visibility ("@var{visibility_type}") 2401@cindex @code{visibility} attribute 2402This attribute affects the linkage of the declaration to which it is attached. 2403There are four supported @var{visibility_type} values: default, 2404hidden, protected or internal visibility. 2405 2406@smallexample 2407void __attribute__ ((visibility ("protected"))) 2408f () @{ /* @r{Do something.} */; @} 2409int i __attribute__ ((visibility ("hidden"))); 2410@end smallexample 2411 2412The possible values of @var{visibility_type} correspond to the 2413visibility settings in the ELF gABI. 2414 2415@table @dfn 2416@c keep this list of visibilities in alphabetical order. 2417 2418@item default 2419Default visibility is the normal case for the object file format. 2420This value is available for the visibility attribute to override other 2421options that may change the assumed visibility of entities. 2422 2423On ELF, default visibility means that the declaration is visible to other 2424modules and, in shared libraries, means that the declared entity may be 2425overridden. 2426 2427On Darwin, default visibility means that the declaration is visible to 2428other modules. 2429 2430Default visibility corresponds to ``external linkage'' in the language. 2431 2432@item hidden 2433Hidden visibility indicates that the entity declared will have a new 2434form of linkage, which we'll call ``hidden linkage''. Two 2435declarations of an object with hidden linkage refer to the same object 2436if they are in the same shared object. 2437 2438@item internal 2439Internal visibility is like hidden visibility, but with additional 2440processor specific semantics. Unless otherwise specified by the 2441psABI, GCC defines internal visibility to mean that a function is 2442@emph{never} called from another module. Compare this with hidden 2443functions which, while they cannot be referenced directly by other 2444modules, can be referenced indirectly via function pointers. By 2445indicating that a function cannot be called from outside the module, 2446GCC may for instance omit the load of a PIC register since it is known 2447that the calling function loaded the correct value. 2448 2449@item protected 2450Protected visibility is like default visibility except that it 2451indicates that references within the defining module will bind to the 2452definition in that module. That is, the declared entity cannot be 2453overridden by another module. 2454 2455@end table 2456 2457All visibilities are supported on many, but not all, ELF targets 2458(supported when the assembler supports the @samp{.visibility} 2459pseudo-op). Default visibility is supported everywhere. Hidden 2460visibility is supported on Darwin targets. 2461 2462The visibility attribute should be applied only to declarations which 2463would otherwise have external linkage. The attribute should be applied 2464consistently, so that the same entity should not be declared with 2465different settings of the attribute. 2466 2467In C++, the visibility attribute applies to types as well as functions 2468and objects, because in C++ types have linkage. A class must not have 2469greater visibility than its non-static data member types and bases, 2470and class members default to the visibility of their class. Also, a 2471declaration without explicit visibility is limited to the visibility 2472of its type. 2473 2474In C++, you can mark member functions and static member variables of a 2475class with the visibility attribute. This is useful if if you know a 2476particular method or static member variable should only be used from 2477one shared object; then you can mark it hidden while the rest of the 2478class has default visibility. Care must be taken to avoid breaking 2479the One Definition Rule; for example, it is usually not useful to mark 2480an inline method as hidden without marking the whole class as hidden. 2481 2482A C++ namespace declaration can also have the visibility attribute. 2483This attribute applies only to the particular namespace body, not to 2484other definitions of the same namespace; it is equivalent to using 2485@samp{#pragma GCC visibility} before and after the namespace 2486definition (@pxref{Visibility Pragmas}). 2487 2488In C++, if a template argument has limited visibility, this 2489restriction is implicitly propagated to the template instantiation. 2490Otherwise, template instantiations and specializations default to the 2491visibility of their template. 2492 2493If both the template and enclosing class have explicit visibility, the 2494visibility from the template is used. 2495 2496@item warn_unused_result 2497@cindex @code{warn_unused_result} attribute 2498The @code{warn_unused_result} attribute causes a warning to be emitted 2499if a caller of the function with this attribute does not use its 2500return value. This is useful for functions where not checking 2501the result is either a security problem or always a bug, such as 2502@code{realloc}. 2503 2504@smallexample 2505int fn () __attribute__ ((warn_unused_result)); 2506int foo () 2507@{ 2508 if (fn () < 0) return -1; 2509 fn (); 2510 return 0; 2511@} 2512@end smallexample 2513 2514results in warning on line 5. 2515 2516@item weak 2517@cindex @code{weak} attribute 2518The @code{weak} attribute causes the declaration to be emitted as a weak 2519symbol rather than a global. This is primarily useful in defining 2520library functions which can be overridden in user code, though it can 2521also be used with non-function declarations. Weak symbols are supported 2522for ELF targets, and also for a.out targets when using the GNU assembler 2523and linker. 2524 2525@item weakref 2526@itemx weakref ("@var{target}") 2527@cindex @code{weakref} attribute 2528The @code{weakref} attribute marks a declaration as a weak reference. 2529Without arguments, it should be accompanied by an @code{alias} attribute 2530naming the target symbol. Optionally, the @var{target} may be given as 2531an argument to @code{weakref} itself. In either case, @code{weakref} 2532implicitly marks the declaration as @code{weak}. Without a 2533@var{target}, given as an argument to @code{weakref} or to @code{alias}, 2534@code{weakref} is equivalent to @code{weak}. 2535 2536@smallexample 2537static int x() __attribute__ ((weakref ("y"))); 2538/* is equivalent to... */ 2539static int x() __attribute__ ((weak, weakref, alias ("y"))); 2540/* and to... */ 2541static int x() __attribute__ ((weakref)); 2542static int x() __attribute__ ((alias ("y"))); 2543@end smallexample 2544 2545A weak reference is an alias that does not by itself require a 2546definition to be given for the target symbol. If the target symbol is 2547only referenced through weak references, then the becomes a @code{weak} 2548undefined symbol. If it is directly referenced, however, then such 2549strong references prevail, and a definition will be required for the 2550symbol, not necessarily in the same translation unit. 2551 2552The effect is equivalent to moving all references to the alias to a 2553separate translation unit, renaming the alias to the aliased symbol, 2554declaring it as weak, compiling the two separate translation units and 2555performing a reloadable link on them. 2556 2557At present, a declaration to which @code{weakref} is attached can 2558only be @code{static}. 2559 2560@item externally_visible 2561@cindex @code{externally_visible} attribute. 2562This attribute, attached to a global variable or function nullify 2563effect of @option{-fwhole-program} command line option, so the object 2564remain visible outside the current compilation unit 2565 2566@end table 2567 2568You can specify multiple attributes in a declaration by separating them 2569by commas within the double parentheses or by immediately following an 2570attribute declaration with another attribute declaration. 2571 2572@cindex @code{#pragma}, reason for not using 2573@cindex pragma, reason for not using 2574Some people object to the @code{__attribute__} feature, suggesting that 2575ISO C's @code{#pragma} should be used instead. At the time 2576@code{__attribute__} was designed, there were two reasons for not doing 2577this. 2578 2579@enumerate 2580@item 2581It is impossible to generate @code{#pragma} commands from a macro. 2582 2583@item 2584There is no telling what the same @code{#pragma} might mean in another 2585compiler. 2586@end enumerate 2587 2588These two reasons applied to almost any application that might have been 2589proposed for @code{#pragma}. It was basically a mistake to use 2590@code{#pragma} for @emph{anything}. 2591 2592The ISO C99 standard includes @code{_Pragma}, which now allows pragmas 2593to be generated from macros. In addition, a @code{#pragma GCC} 2594namespace is now in use for GCC-specific pragmas. However, it has been 2595found convenient to use @code{__attribute__} to achieve a natural 2596attachment of attributes to their corresponding declarations, whereas 2597@code{#pragma GCC} is of use for constructs that do not naturally form 2598part of the grammar. @xref{Other Directives,,Miscellaneous 2599Preprocessing Directives, cpp, The GNU C Preprocessor}. 2600 2601@node Attribute Syntax 2602@section Attribute Syntax 2603@cindex attribute syntax 2604 2605This section describes the syntax with which @code{__attribute__} may be 2606used, and the constructs to which attribute specifiers bind, for the C 2607language. Some details may vary for C++. Because of infelicities in 2608the grammar for attributes, some forms described here may not be 2609successfully parsed in all cases. 2610 2611There are some problems with the semantics of attributes in C++. For 2612example, there are no manglings for attributes, although they may affect 2613code generation, so problems may arise when attributed types are used in 2614conjunction with templates or overloading. Similarly, @code{typeid} 2615does not distinguish between types with different attributes. Support 2616for attributes in C++ may be restricted in future to attributes on 2617declarations only, but not on nested declarators. 2618 2619@xref{Function Attributes}, for details of the semantics of attributes 2620applying to functions. @xref{Variable Attributes}, for details of the 2621semantics of attributes applying to variables. @xref{Type Attributes}, 2622for details of the semantics of attributes applying to structure, union 2623and enumerated types. 2624 2625An @dfn{attribute specifier} is of the form 2626@code{__attribute__ ((@var{attribute-list}))}. An @dfn{attribute list} 2627is a possibly empty comma-separated sequence of @dfn{attributes}, where 2628each attribute is one of the following: 2629 2630@itemize @bullet 2631@item 2632Empty. Empty attributes are ignored. 2633 2634@item 2635A word (which may be an identifier such as @code{unused}, or a reserved 2636word such as @code{const}). 2637 2638@item 2639A word, followed by, in parentheses, parameters for the attribute. 2640These parameters take one of the following forms: 2641 2642@itemize @bullet 2643@item 2644An identifier. For example, @code{mode} attributes use this form. 2645 2646@item 2647An identifier followed by a comma and a non-empty comma-separated list 2648of expressions. For example, @code{format} attributes use this form. 2649 2650@item 2651A possibly empty comma-separated list of expressions. For example, 2652@code{format_arg} attributes use this form with the list being a single 2653integer constant expression, and @code{alias} attributes use this form 2654with the list being a single string constant. 2655@end itemize 2656@end itemize 2657 2658An @dfn{attribute specifier list} is a sequence of one or more attribute 2659specifiers, not separated by any other tokens. 2660 2661In GNU C, an attribute specifier list may appear after the colon following a 2662label, other than a @code{case} or @code{default} label. The only 2663attribute it makes sense to use after a label is @code{unused}. This 2664feature is intended for code generated by programs which contains labels 2665that may be unused but which is compiled with @option{-Wall}. It would 2666not normally be appropriate to use in it human-written code, though it 2667could be useful in cases where the code that jumps to the label is 2668contained within an @code{#ifdef} conditional. GNU C++ does not permit 2669such placement of attribute lists, as it is permissible for a 2670declaration, which could begin with an attribute list, to be labelled in 2671C++. Declarations cannot be labelled in C90 or C99, so the ambiguity 2672does not arise there. 2673 2674An attribute specifier list may appear as part of a @code{struct}, 2675@code{union} or @code{enum} specifier. It may go either immediately 2676after the @code{struct}, @code{union} or @code{enum} keyword, or after 2677the closing brace. The former syntax is preferred. 2678Where attribute specifiers follow the closing brace, they are considered 2679to relate to the structure, union or enumerated type defined, not to any 2680enclosing declaration the type specifier appears in, and the type 2681defined is not complete until after the attribute specifiers. 2682@c Otherwise, there would be the following problems: a shift/reduce 2683@c conflict between attributes binding the struct/union/enum and 2684@c binding to the list of specifiers/qualifiers; and "aligned" 2685@c attributes could use sizeof for the structure, but the size could be 2686@c changed later by "packed" attributes. 2687 2688Otherwise, an attribute specifier appears as part of a declaration, 2689counting declarations of unnamed parameters and type names, and relates 2690to that declaration (which may be nested in another declaration, for 2691example in the case of a parameter declaration), or to a particular declarator 2692within a declaration. Where an 2693attribute specifier is applied to a parameter declared as a function or 2694an array, it should apply to the function or array rather than the 2695pointer to which the parameter is implicitly converted, but this is not 2696yet correctly implemented. 2697 2698Any list of specifiers and qualifiers at the start of a declaration may 2699contain attribute specifiers, whether or not such a list may in that 2700context contain storage class specifiers. (Some attributes, however, 2701are essentially in the nature of storage class specifiers, and only make 2702sense where storage class specifiers may be used; for example, 2703@code{section}.) There is one necessary limitation to this syntax: the 2704first old-style parameter declaration in a function definition cannot 2705begin with an attribute specifier, because such an attribute applies to 2706the function instead by syntax described below (which, however, is not 2707yet implemented in this case). In some other cases, attribute 2708specifiers are permitted by this grammar but not yet supported by the 2709compiler. All attribute specifiers in this place relate to the 2710declaration as a whole. In the obsolescent usage where a type of 2711@code{int} is implied by the absence of type specifiers, such a list of 2712specifiers and qualifiers may be an attribute specifier list with no 2713other specifiers or qualifiers. 2714 2715At present, the first parameter in a function prototype must have some 2716type specifier which is not an attribute specifier; this resolves an 2717ambiguity in the interpretation of @code{void f(int 2718(__attribute__((foo)) x))}, but is subject to change. At present, if 2719the parentheses of a function declarator contain only attributes then 2720those attributes are ignored, rather than yielding an error or warning 2721or implying a single parameter of type int, but this is subject to 2722change. 2723 2724An attribute specifier list may appear immediately before a declarator 2725(other than the first) in a comma-separated list of declarators in a 2726declaration of more than one identifier using a single list of 2727specifiers and qualifiers. Such attribute specifiers apply 2728only to the identifier before whose declarator they appear. For 2729example, in 2730 2731@smallexample 2732__attribute__((noreturn)) void d0 (void), 2733 __attribute__((format(printf, 1, 2))) d1 (const char *, ...), 2734 d2 (void) 2735@end smallexample 2736 2737@noindent 2738the @code{noreturn} attribute applies to all the functions 2739declared; the @code{format} attribute only applies to @code{d1}. 2740 2741An attribute specifier list may appear immediately before the comma, 2742@code{=} or semicolon terminating the declaration of an identifier other 2743than a function definition. At present, such attribute specifiers apply 2744to the declared object or function, but in future they may attach to the 2745outermost adjacent declarator. In simple cases there is no difference, 2746but, for example, in 2747 2748@smallexample 2749void (****f)(void) __attribute__((noreturn)); 2750@end smallexample 2751 2752@noindent 2753at present the @code{noreturn} attribute applies to @code{f}, which 2754causes a warning since @code{f} is not a function, but in future it may 2755apply to the function @code{****f}. The precise semantics of what 2756attributes in such cases will apply to are not yet specified. Where an 2757assembler name for an object or function is specified (@pxref{Asm 2758Labels}), at present the attribute must follow the @code{asm} 2759specification; in future, attributes before the @code{asm} specification 2760may apply to the adjacent declarator, and those after it to the declared 2761object or function. 2762 2763An attribute specifier list may, in future, be permitted to appear after 2764the declarator in a function definition (before any old-style parameter 2765declarations or the function body). 2766 2767Attribute specifiers may be mixed with type qualifiers appearing inside 2768the @code{[]} of a parameter array declarator, in the C99 construct by 2769which such qualifiers are applied to the pointer to which the array is 2770implicitly converted. Such attribute specifiers apply to the pointer, 2771not to the array, but at present this is not implemented and they are 2772ignored. 2773 2774An attribute specifier list may appear at the start of a nested 2775declarator. At present, there are some limitations in this usage: the 2776attributes correctly apply to the declarator, but for most individual 2777attributes the semantics this implies are not implemented. 2778When attribute specifiers follow the @code{*} of a pointer 2779declarator, they may be mixed with any type qualifiers present. 2780The following describes the formal semantics of this syntax. It will make the 2781most sense if you are familiar with the formal specification of 2782declarators in the ISO C standard. 2783 2784Consider (as in C99 subclause 6.7.5 paragraph 4) a declaration @code{T 2785D1}, where @code{T} contains declaration specifiers that specify a type 2786@var{Type} (such as @code{int}) and @code{D1} is a declarator that 2787contains an identifier @var{ident}. The type specified for @var{ident} 2788for derived declarators whose type does not include an attribute 2789specifier is as in the ISO C standard. 2790 2791If @code{D1} has the form @code{( @var{attribute-specifier-list} D )}, 2792and the declaration @code{T D} specifies the type 2793``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then 2794@code{T D1} specifies the type ``@var{derived-declarator-type-list} 2795@var{attribute-specifier-list} @var{Type}'' for @var{ident}. 2796 2797If @code{D1} has the form @code{* 2798@var{type-qualifier-and-attribute-specifier-list} D}, and the 2799declaration @code{T D} specifies the type 2800``@var{derived-declarator-type-list} @var{Type}'' for @var{ident}, then 2801@code{T D1} specifies the type ``@var{derived-declarator-type-list} 2802@var{type-qualifier-and-attribute-specifier-list} @var{Type}'' for 2803@var{ident}. 2804 2805For example, 2806 2807@smallexample 2808void (__attribute__((noreturn)) ****f) (void); 2809@end smallexample 2810 2811@noindent 2812specifies the type ``pointer to pointer to pointer to pointer to 2813non-returning function returning @code{void}''. As another example, 2814 2815@smallexample 2816char *__attribute__((aligned(8))) *f; 2817@end smallexample 2818 2819@noindent 2820specifies the type ``pointer to 8-byte-aligned pointer to @code{char}''. 2821Note again that this does not work with most attributes; for example, 2822the usage of @samp{aligned} and @samp{noreturn} attributes given above 2823is not yet supported. 2824 2825For compatibility with existing code written for compiler versions that 2826did not implement attributes on nested declarators, some laxity is 2827allowed in the placing of attributes. If an attribute that only applies 2828to types is applied to a declaration, it will be treated as applying to 2829the type of that declaration. If an attribute that only applies to 2830declarations is applied to the type of a declaration, it will be treated 2831as applying to that declaration; and, for compatibility with code 2832placing the attributes immediately before the identifier declared, such 2833an attribute applied to a function return type will be treated as 2834applying to the function type, and such an attribute applied to an array 2835element type will be treated as applying to the array type. If an 2836attribute that only applies to function types is applied to a 2837pointer-to-function type, it will be treated as applying to the pointer 2838target type; if such an attribute is applied to a function return type 2839that is not a pointer-to-function type, it will be treated as applying 2840to the function type. 2841 2842@node Function Prototypes 2843@section Prototypes and Old-Style Function Definitions 2844@cindex function prototype declarations 2845@cindex old-style function definitions 2846@cindex promotion of formal parameters 2847 2848GNU C extends ISO C to allow a function prototype to override a later 2849old-style non-prototype definition. Consider the following example: 2850 2851@smallexample 2852/* @r{Use prototypes unless the compiler is old-fashioned.} */ 2853#ifdef __STDC__ 2854#define P(x) x 2855#else 2856#define P(x) () 2857#endif 2858 2859/* @r{Prototype function declaration.} */ 2860int isroot P((uid_t)); 2861 2862/* @r{Old-style function definition.} */ 2863int 2864isroot (x) /* @r{??? lossage here ???} */ 2865 uid_t x; 2866@{ 2867 return x == 0; 2868@} 2869@end smallexample 2870 2871Suppose the type @code{uid_t} happens to be @code{short}. ISO C does 2872not allow this example, because subword arguments in old-style 2873non-prototype definitions are promoted. Therefore in this example the 2874function definition's argument is really an @code{int}, which does not 2875match the prototype argument type of @code{short}. 2876 2877This restriction of ISO C makes it hard to write code that is portable 2878to traditional C compilers, because the programmer does not know 2879whether the @code{uid_t} type is @code{short}, @code{int}, or 2880@code{long}. Therefore, in cases like these GNU C allows a prototype 2881to override a later old-style definition. More precisely, in GNU C, a 2882function prototype argument type overrides the argument type specified 2883by a later old-style definition if the former type is the same as the 2884latter type before promotion. Thus in GNU C the above example is 2885equivalent to the following: 2886 2887@smallexample 2888int isroot (uid_t); 2889 2890int 2891isroot (uid_t x) 2892@{ 2893 return x == 0; 2894@} 2895@end smallexample 2896 2897@noindent 2898GNU C++ does not support old-style function definitions, so this 2899extension is irrelevant. 2900 2901@node C++ Comments 2902@section C++ Style Comments 2903@cindex // 2904@cindex C++ comments 2905@cindex comments, C++ style 2906 2907In GNU C, you may use C++ style comments, which start with @samp{//} and 2908continue until the end of the line. Many other C implementations allow 2909such comments, and they are included in the 1999 C standard. However, 2910C++ style comments are not recognized if you specify an @option{-std} 2911option specifying a version of ISO C before C99, or @option{-ansi} 2912(equivalent to @option{-std=c89}). 2913 2914@node Dollar Signs 2915@section Dollar Signs in Identifier Names 2916@cindex $ 2917@cindex dollar signs in identifier names 2918@cindex identifier names, dollar signs in 2919 2920In GNU C, you may normally use dollar signs in identifier names. 2921This is because many traditional C implementations allow such identifiers. 2922However, dollar signs in identifiers are not supported on a few target 2923machines, typically because the target assembler does not allow them. 2924 2925@node Character Escapes 2926@section The Character @key{ESC} in Constants 2927 2928You can use the sequence @samp{\e} in a string or character constant to 2929stand for the ASCII character @key{ESC}. 2930 2931@node Alignment 2932@section Inquiring on Alignment of Types or Variables 2933@cindex alignment 2934@cindex type alignment 2935@cindex variable alignment 2936 2937The keyword @code{__alignof__} allows you to inquire about how an object 2938is aligned, or the minimum alignment usually required by a type. Its 2939syntax is just like @code{sizeof}. 2940 2941For example, if the target machine requires a @code{double} value to be 2942aligned on an 8-byte boundary, then @code{__alignof__ (double)} is 8. 2943This is true on many RISC machines. On more traditional machine 2944designs, @code{__alignof__ (double)} is 4 or even 2. 2945 2946Some machines never actually require alignment; they allow reference to any 2947data type even at an odd address. For these machines, @code{__alignof__} 2948reports the @emph{recommended} alignment of a type. 2949 2950If the operand of @code{__alignof__} is an lvalue rather than a type, 2951its value is the required alignment for its type, taking into account 2952any minimum alignment specified with GCC's @code{__attribute__} 2953extension (@pxref{Variable Attributes}). For example, after this 2954declaration: 2955 2956@smallexample 2957struct foo @{ int x; char y; @} foo1; 2958@end smallexample 2959 2960@noindent 2961the value of @code{__alignof__ (foo1.y)} is 1, even though its actual 2962alignment is probably 2 or 4, the same as @code{__alignof__ (int)}. 2963 2964It is an error to ask for the alignment of an incomplete type. 2965 2966@node Variable Attributes 2967@section Specifying Attributes of Variables 2968@cindex attribute of variables 2969@cindex variable attributes 2970 2971The keyword @code{__attribute__} allows you to specify special 2972attributes of variables or structure fields. This keyword is followed 2973by an attribute specification inside double parentheses. Some 2974attributes are currently defined generically for variables. 2975Other attributes are defined for variables on particular target 2976systems. Other attributes are available for functions 2977(@pxref{Function Attributes}) and for types (@pxref{Type Attributes}). 2978Other front ends might define more attributes 2979(@pxref{C++ Extensions,,Extensions to the C++ Language}). 2980 2981You may also specify attributes with @samp{__} preceding and following 2982each keyword. This allows you to use them in header files without 2983being concerned about a possible macro of the same name. For example, 2984you may use @code{__aligned__} instead of @code{aligned}. 2985 2986@xref{Attribute Syntax}, for details of the exact syntax for using 2987attributes. 2988 2989@table @code 2990@cindex @code{aligned} attribute 2991@item aligned (@var{alignment}) 2992This attribute specifies a minimum alignment for the variable or 2993structure field, measured in bytes. For example, the declaration: 2994 2995@smallexample 2996int x __attribute__ ((aligned (16))) = 0; 2997@end smallexample 2998 2999@noindent 3000causes the compiler to allocate the global variable @code{x} on a 300116-byte boundary. On a 68040, this could be used in conjunction with 3002an @code{asm} expression to access the @code{move16} instruction which 3003requires 16-byte aligned operands. 3004 3005You can also specify the alignment of structure fields. For example, to 3006create a double-word aligned @code{int} pair, you could write: 3007 3008@smallexample 3009struct foo @{ int x[2] __attribute__ ((aligned (8))); @}; 3010@end smallexample 3011 3012@noindent 3013This is an alternative to creating a union with a @code{double} member 3014that forces the union to be double-word aligned. 3015 3016As in the preceding examples, you can explicitly specify the alignment 3017(in bytes) that you wish the compiler to use for a given variable or 3018structure field. Alternatively, you can leave out the alignment factor 3019and just ask the compiler to align a variable or field to the maximum 3020useful alignment for the target machine you are compiling for. For 3021example, you could write: 3022 3023@smallexample 3024short array[3] __attribute__ ((aligned)); 3025@end smallexample 3026 3027Whenever you leave out the alignment factor in an @code{aligned} attribute 3028specification, the compiler automatically sets the alignment for the declared 3029variable or field to the largest alignment which is ever used for any data 3030type on the target machine you are compiling for. Doing this can often make 3031copy operations more efficient, because the compiler can use whatever 3032instructions copy the biggest chunks of memory when performing copies to 3033or from the variables or fields that you have aligned this way. 3034 3035The @code{aligned} attribute can only increase the alignment; but you 3036can decrease it by specifying @code{packed} as well. See below. 3037 3038Note that the effectiveness of @code{aligned} attributes may be limited 3039by inherent limitations in your linker. On many systems, the linker is 3040only able to arrange for variables to be aligned up to a certain maximum 3041alignment. (For some linkers, the maximum supported alignment may 3042be very very small.) If your linker is only able to align variables 3043up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} 3044in an @code{__attribute__} will still only provide you with 8 byte 3045alignment. See your linker documentation for further information. 3046 3047@item cleanup (@var{cleanup_function}) 3048@cindex @code{cleanup} attribute 3049The @code{cleanup} attribute runs a function when the variable goes 3050out of scope. This attribute can only be applied to auto function 3051scope variables; it may not be applied to parameters or variables 3052with static storage duration. The function must take one parameter, 3053a pointer to a type compatible with the variable. The return value 3054of the function (if any) is ignored. 3055 3056If @option{-fexceptions} is enabled, then @var{cleanup_function} 3057will be run during the stack unwinding that happens during the 3058processing of the exception. Note that the @code{cleanup} attribute 3059does not allow the exception to be caught, only to perform an action. 3060It is undefined what happens if @var{cleanup_function} does not 3061return normally. 3062 3063@item common 3064@itemx nocommon 3065@cindex @code{common} attribute 3066@cindex @code{nocommon} attribute 3067@opindex fcommon 3068@opindex fno-common 3069The @code{common} attribute requests GCC to place a variable in 3070``common'' storage. The @code{nocommon} attribute requests the 3071opposite---to allocate space for it directly. 3072 3073These attributes override the default chosen by the 3074@option{-fno-common} and @option{-fcommon} flags respectively. 3075 3076@item deprecated 3077@cindex @code{deprecated} attribute 3078The @code{deprecated} attribute results in a warning if the variable 3079is used anywhere in the source file. This is useful when identifying 3080variables that are expected to be removed in a future version of a 3081program. The warning also includes the location of the declaration 3082of the deprecated variable, to enable users to easily find further 3083information about why the variable is deprecated, or what they should 3084do instead. Note that the warning only occurs for uses: 3085 3086@smallexample 3087extern int old_var __attribute__ ((deprecated)); 3088extern int old_var; 3089int new_fn () @{ return old_var; @} 3090@end smallexample 3091 3092results in a warning on line 3 but not line 2. 3093 3094The @code{deprecated} attribute can also be used for functions and 3095types (@pxref{Function Attributes}, @pxref{Type Attributes}.) 3096 3097@item mode (@var{mode}) 3098@cindex @code{mode} attribute 3099This attribute specifies the data type for the declaration---whichever 3100type corresponds to the mode @var{mode}. This in effect lets you 3101request an integer or floating point type according to its width. 3102 3103You may also specify a mode of @samp{byte} or @samp{__byte__} to 3104indicate the mode corresponding to a one-byte integer, @samp{word} or 3105@samp{__word__} for the mode of a one-word integer, and @samp{pointer} 3106or @samp{__pointer__} for the mode used to represent pointers. 3107 3108@item packed 3109@cindex @code{packed} attribute 3110The @code{packed} attribute specifies that a variable or structure field 3111should have the smallest possible alignment---one byte for a variable, 3112and one bit for a field, unless you specify a larger value with the 3113@code{aligned} attribute. 3114 3115Here is a structure in which the field @code{x} is packed, so that it 3116immediately follows @code{a}: 3117 3118@smallexample 3119struct foo 3120@{ 3121 char a; 3122 int x[2] __attribute__ ((packed)); 3123@}; 3124@end smallexample 3125 3126@item section ("@var{section-name}") 3127@cindex @code{section} variable attribute 3128Normally, the compiler places the objects it generates in sections like 3129@code{data} and @code{bss}. Sometimes, however, you need additional sections, 3130or you need certain particular variables to appear in special sections, 3131for example to map to special hardware. The @code{section} 3132attribute specifies that a variable (or function) lives in a particular 3133section. For example, this small program uses several specific section names: 3134 3135@smallexample 3136struct duart a __attribute__ ((section ("DUART_A"))) = @{ 0 @}; 3137struct duart b __attribute__ ((section ("DUART_B"))) = @{ 0 @}; 3138char stack[10000] __attribute__ ((section ("STACK"))) = @{ 0 @}; 3139int init_data __attribute__ ((section ("INITDATA"))) = 0; 3140 3141main() 3142@{ 3143 /* @r{Initialize stack pointer} */ 3144 init_sp (stack + sizeof (stack)); 3145 3146 /* @r{Initialize initialized data} */ 3147 memcpy (&init_data, &data, &edata - &data); 3148 3149 /* @r{Turn on the serial ports} */ 3150 init_duart (&a); 3151 init_duart (&b); 3152@} 3153@end smallexample 3154 3155@noindent 3156Use the @code{section} attribute with an @emph{initialized} definition 3157of a @emph{global} variable, as shown in the example. GCC issues 3158a warning and otherwise ignores the @code{section} attribute in 3159uninitialized variable declarations. 3160 3161You may only use the @code{section} attribute with a fully initialized 3162global definition because of the way linkers work. The linker requires 3163each object be defined once, with the exception that uninitialized 3164variables tentatively go in the @code{common} (or @code{bss}) section 3165and can be multiply ``defined''. You can force a variable to be 3166initialized with the @option{-fno-common} flag or the @code{nocommon} 3167attribute. 3168 3169Some file formats do not support arbitrary sections so the @code{section} 3170attribute is not available on all platforms. 3171If you need to map the entire contents of a module to a particular 3172section, consider using the facilities of the linker instead. 3173 3174@item shared 3175@cindex @code{shared} variable attribute 3176On Microsoft Windows, in addition to putting variable definitions in a named 3177section, the section can also be shared among all running copies of an 3178executable or DLL@. For example, this small program defines shared data 3179by putting it in a named section @code{shared} and marking the section 3180shareable: 3181 3182@smallexample 3183int foo __attribute__((section ("shared"), shared)) = 0; 3184 3185int 3186main() 3187@{ 3188 /* @r{Read and write foo. All running 3189 copies see the same value.} */ 3190 return 0; 3191@} 3192@end smallexample 3193 3194@noindent 3195You may only use the @code{shared} attribute along with @code{section} 3196attribute with a fully initialized global definition because of the way 3197linkers work. See @code{section} attribute for more information. 3198 3199The @code{shared} attribute is only available on Microsoft Windows@. 3200 3201@item tls_model ("@var{tls_model}") 3202@cindex @code{tls_model} attribute 3203The @code{tls_model} attribute sets thread-local storage model 3204(@pxref{Thread-Local}) of a particular @code{__thread} variable, 3205overriding @option{-ftls-model=} command line switch on a per-variable 3206basis. 3207The @var{tls_model} argument should be one of @code{global-dynamic}, 3208@code{local-dynamic}, @code{initial-exec} or @code{local-exec}. 3209 3210Not all targets support this attribute. 3211 3212@item unused 3213This attribute, attached to a variable, means that the variable is meant 3214to be possibly unused. GCC will not produce a warning for this 3215variable. 3216 3217@item used 3218This attribute, attached to a variable, means that the variable must be 3219emitted even if it appears that the variable is not referenced. 3220 3221@item vector_size (@var{bytes}) 3222This attribute specifies the vector size for the variable, measured in 3223bytes. For example, the declaration: 3224 3225@smallexample 3226int foo __attribute__ ((vector_size (16))); 3227@end smallexample 3228 3229@noindent 3230causes the compiler to set the mode for @code{foo}, to be 16 bytes, 3231divided into @code{int} sized units. Assuming a 32-bit int (a vector of 32324 units of 4 bytes), the corresponding mode of @code{foo} will be V4SI@. 3233 3234This attribute is only applicable to integral and float scalars, 3235although arrays, pointers, and function return values are allowed in 3236conjunction with this construct. 3237 3238Aggregates with this attribute are invalid, even if they are of the same 3239size as a corresponding scalar. For example, the declaration: 3240 3241@smallexample 3242struct S @{ int a; @}; 3243struct S __attribute__ ((vector_size (16))) foo; 3244@end smallexample 3245 3246@noindent 3247is invalid even if the size of the structure is the same as the size of 3248the @code{int}. 3249 3250@item selectany 3251The @code{selectany} attribute causes an initialized global variable to 3252have link-once semantics. When multiple definitions of the variable are 3253encountered by the linker, the first is selected and the remainder are 3254discarded. Following usage by the Microsoft compiler, the linker is told 3255@emph{not} to warn about size or content differences of the multiple 3256definitions. 3257 3258Although the primary usage of this attribute is for POD types, the 3259attribute can also be applied to global C++ objects that are initialized 3260by a constructor. In this case, the static initialization and destruction 3261code for the object is emitted in each translation defining the object, 3262but the calls to the constructor and destructor are protected by a 3263link-once guard variable. 3264 3265The @code{selectany} attribute is only available on Microsoft Windows 3266targets. You can use @code{__declspec (selectany)} as a synonym for 3267@code{__attribute__ ((selectany))} for compatibility with other 3268compilers. 3269 3270@item weak 3271The @code{weak} attribute is described in @xref{Function Attributes}. 3272 3273@item dllimport 3274The @code{dllimport} attribute is described in @xref{Function Attributes}. 3275 3276@item dllexport 3277The @code{dllexport} attribute is described in @xref{Function Attributes}. 3278 3279@end table 3280 3281@subsection M32R/D Variable Attributes 3282 3283One attribute is currently defined for the M32R/D@. 3284 3285@table @code 3286@item model (@var{model-name}) 3287@cindex variable addressability on the M32R/D 3288Use this attribute on the M32R/D to set the addressability of an object. 3289The identifier @var{model-name} is one of @code{small}, @code{medium}, 3290or @code{large}, representing each of the code models. 3291 3292Small model objects live in the lower 16MB of memory (so that their 3293addresses can be loaded with the @code{ld24} instruction). 3294 3295Medium and large model objects may live anywhere in the 32-bit address space 3296(the compiler will generate @code{seth/add3} instructions to load their 3297addresses). 3298@end table 3299 3300@anchor{i386 Variable Attributes} 3301@subsection i386 Variable Attributes 3302 3303Two attributes are currently defined for i386 configurations: 3304@code{ms_struct} and @code{gcc_struct} 3305 3306@table @code 3307@item ms_struct 3308@itemx gcc_struct 3309@cindex @code{ms_struct} attribute 3310@cindex @code{gcc_struct} attribute 3311 3312If @code{packed} is used on a structure, or if bit-fields are used 3313it may be that the Microsoft ABI packs them differently 3314than GCC would normally pack them. Particularly when moving packed 3315data between functions compiled with GCC and the native Microsoft compiler 3316(either via function call or as data in a file), it may be necessary to access 3317either format. 3318 3319Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86 3320compilers to match the native Microsoft compiler. 3321 3322The Microsoft structure layout algorithm is fairly simple with the exception 3323of the bitfield packing: 3324 3325The padding and alignment of members of structures and whether a bit field 3326can straddle a storage-unit boundary 3327 3328@enumerate 3329@item Structure members are stored sequentially in the order in which they are 3330declared: the first member has the lowest memory address and the last member 3331the highest. 3332 3333@item Every data object has an alignment-requirement. The alignment-requirement 3334for all data except structures, unions, and arrays is either the size of the 3335object or the current packing size (specified with either the aligned attribute 3336or the pack pragma), whichever is less. For structures, unions, and arrays, 3337the alignment-requirement is the largest alignment-requirement of its members. 3338Every object is allocated an offset so that: 3339 3340offset % alignment-requirement == 0 3341 3342@item Adjacent bit fields are packed into the same 1-, 2-, or 4-byte allocation 3343unit if the integral types are the same size and if the next bit field fits 3344into the current allocation unit without crossing the boundary imposed by the 3345common alignment requirements of the bit fields. 3346@end enumerate 3347 3348Handling of zero-length bitfields: 3349 3350MSVC interprets zero-length bitfields in the following ways: 3351 3352@enumerate 3353@item If a zero-length bitfield is inserted between two bitfields that would 3354normally be coalesced, the bitfields will not be coalesced. 3355 3356For example: 3357 3358@smallexample 3359struct 3360 @{ 3361 unsigned long bf_1 : 12; 3362 unsigned long : 0; 3363 unsigned long bf_2 : 12; 3364 @} t1; 3365@end smallexample 3366 3367The size of @code{t1} would be 8 bytes with the zero-length bitfield. If the 3368zero-length bitfield were removed, @code{t1}'s size would be 4 bytes. 3369 3370@item If a zero-length bitfield is inserted after a bitfield, @code{foo}, and the 3371alignment of the zero-length bitfield is greater than the member that follows it, 3372@code{bar}, @code{bar} will be aligned as the type of the zero-length bitfield. 3373 3374For example: 3375 3376@smallexample 3377struct 3378 @{ 3379 char foo : 4; 3380 short : 0; 3381 char bar; 3382 @} t2; 3383 3384struct 3385 @{ 3386 char foo : 4; 3387 short : 0; 3388 double bar; 3389 @} t3; 3390@end smallexample 3391 3392For @code{t2}, @code{bar} will be placed at offset 2, rather than offset 1. 3393Accordingly, the size of @code{t2} will be 4. For @code{t3}, the zero-length 3394bitfield will not affect the alignment of @code{bar} or, as a result, the size 3395of the structure. 3396 3397Taking this into account, it is important to note the following: 3398 3399@enumerate 3400@item If a zero-length bitfield follows a normal bitfield, the type of the 3401zero-length bitfield may affect the alignment of the structure as whole. For 3402example, @code{t2} has a size of 4 bytes, since the zero-length bitfield follows a 3403normal bitfield, and is of type short. 3404 3405@item Even if a zero-length bitfield is not followed by a normal bitfield, it may 3406still affect the alignment of the structure: 3407 3408@smallexample 3409struct 3410 @{ 3411 char foo : 6; 3412 long : 0; 3413 @} t4; 3414@end smallexample 3415 3416Here, @code{t4} will take up 4 bytes. 3417@end enumerate 3418 3419@item Zero-length bitfields following non-bitfield members are ignored: 3420 3421@smallexample 3422struct 3423 @{ 3424 char foo; 3425 long : 0; 3426 char bar; 3427 @} t5; 3428@end smallexample 3429 3430Here, @code{t5} will take up 2 bytes. 3431@end enumerate 3432@end table 3433 3434@subsection PowerPC Variable Attributes 3435 3436Three attributes currently are defined for PowerPC configurations: 3437@code{altivec}, @code{ms_struct} and @code{gcc_struct}. 3438 3439For full documentation of the struct attributes please see the 3440documentation in the @xref{i386 Variable Attributes}, section. 3441 3442For documentation of @code{altivec} attribute please see the 3443documentation in the @xref{PowerPC Type Attributes}, section. 3444 3445@subsection Xstormy16 Variable Attributes 3446 3447One attribute is currently defined for xstormy16 configurations: 3448@code{below100} 3449 3450@table @code 3451@item below100 3452@cindex @code{below100} attribute 3453 3454If a variable has the @code{below100} attribute (@code{BELOW100} is 3455allowed also), GCC will place the variable in the first 0x100 bytes of 3456memory and use special opcodes to access it. Such variables will be 3457placed in either the @code{.bss_below100} section or the 3458@code{.data_below100} section. 3459 3460@end table 3461 3462@node Type Attributes 3463@section Specifying Attributes of Types 3464@cindex attribute of types 3465@cindex type attributes 3466 3467The keyword @code{__attribute__} allows you to specify special 3468attributes of @code{struct} and @code{union} types when you define 3469such types. This keyword is followed by an attribute specification 3470inside double parentheses. Seven attributes are currently defined for 3471types: @code{aligned}, @code{packed}, @code{transparent_union}, 3472@code{unused}, @code{deprecated}, @code{visibility}, and 3473@code{may_alias}. Other attributes are defined for functions 3474(@pxref{Function Attributes}) and for variables (@pxref{Variable 3475Attributes}). 3476 3477You may also specify any one of these attributes with @samp{__} 3478preceding and following its keyword. This allows you to use these 3479attributes in header files without being concerned about a possible 3480macro of the same name. For example, you may use @code{__aligned__} 3481instead of @code{aligned}. 3482 3483You may specify type attributes either in a @code{typedef} declaration 3484or in an enum, struct or union type declaration or definition. 3485 3486For an enum, struct or union type, you may specify attributes either 3487between the enum, struct or union tag and the name of the type, or 3488just past the closing curly brace of the @emph{definition}. The 3489former syntax is preferred. 3490 3491@xref{Attribute Syntax}, for details of the exact syntax for using 3492attributes. 3493 3494@table @code 3495@cindex @code{aligned} attribute 3496@item aligned (@var{alignment}) 3497This attribute specifies a minimum alignment (in bytes) for variables 3498of the specified type. For example, the declarations: 3499 3500@smallexample 3501struct S @{ short f[3]; @} __attribute__ ((aligned (8))); 3502typedef int more_aligned_int __attribute__ ((aligned (8))); 3503@end smallexample 3504 3505@noindent 3506force the compiler to insure (as far as it can) that each variable whose 3507type is @code{struct S} or @code{more_aligned_int} will be allocated and 3508aligned @emph{at least} on a 8-byte boundary. On a SPARC, having all 3509variables of type @code{struct S} aligned to 8-byte boundaries allows 3510the compiler to use the @code{ldd} and @code{std} (doubleword load and 3511store) instructions when copying one variable of type @code{struct S} to 3512another, thus improving run-time efficiency. 3513 3514Note that the alignment of any given @code{struct} or @code{union} type 3515is required by the ISO C standard to be at least a perfect multiple of 3516the lowest common multiple of the alignments of all of the members of 3517the @code{struct} or @code{union} in question. This means that you @emph{can} 3518effectively adjust the alignment of a @code{struct} or @code{union} 3519type by attaching an @code{aligned} attribute to any one of the members 3520of such a type, but the notation illustrated in the example above is a 3521more obvious, intuitive, and readable way to request the compiler to 3522adjust the alignment of an entire @code{struct} or @code{union} type. 3523 3524As in the preceding example, you can explicitly specify the alignment 3525(in bytes) that you wish the compiler to use for a given @code{struct} 3526or @code{union} type. Alternatively, you can leave out the alignment factor 3527and just ask the compiler to align a type to the maximum 3528useful alignment for the target machine you are compiling for. For 3529example, you could write: 3530 3531@smallexample 3532struct S @{ short f[3]; @} __attribute__ ((aligned)); 3533@end smallexample 3534 3535Whenever you leave out the alignment factor in an @code{aligned} 3536attribute specification, the compiler automatically sets the alignment 3537for the type to the largest alignment which is ever used for any data 3538type on the target machine you are compiling for. Doing this can often 3539make copy operations more efficient, because the compiler can use 3540whatever instructions copy the biggest chunks of memory when performing 3541copies to or from the variables which have types that you have aligned 3542this way. 3543 3544In the example above, if the size of each @code{short} is 2 bytes, then 3545the size of the entire @code{struct S} type is 6 bytes. The smallest 3546power of two which is greater than or equal to that is 8, so the 3547compiler sets the alignment for the entire @code{struct S} type to 8 3548bytes. 3549 3550Note that although you can ask the compiler to select a time-efficient 3551alignment for a given type and then declare only individual stand-alone 3552objects of that type, the compiler's ability to select a time-efficient 3553alignment is primarily useful only when you plan to create arrays of 3554variables having the relevant (efficiently aligned) type. If you 3555declare or use arrays of variables of an efficiently-aligned type, then 3556it is likely that your program will also be doing pointer arithmetic (or 3557subscripting, which amounts to the same thing) on pointers to the 3558relevant type, and the code that the compiler generates for these 3559pointer arithmetic operations will often be more efficient for 3560efficiently-aligned types than for other types. 3561 3562The @code{aligned} attribute can only increase the alignment; but you 3563can decrease it by specifying @code{packed} as well. See below. 3564 3565Note that the effectiveness of @code{aligned} attributes may be limited 3566by inherent limitations in your linker. On many systems, the linker is 3567only able to arrange for variables to be aligned up to a certain maximum 3568alignment. (For some linkers, the maximum supported alignment may 3569be very very small.) If your linker is only able to align variables 3570up to a maximum of 8 byte alignment, then specifying @code{aligned(16)} 3571in an @code{__attribute__} will still only provide you with 8 byte 3572alignment. See your linker documentation for further information. 3573 3574@item packed 3575This attribute, attached to @code{struct} or @code{union} type 3576definition, specifies that each member (other than zero-width bitfields) 3577of the structure or union is placed to minimize the memory required. When 3578attached to an @code{enum} definition, it indicates that the smallest 3579integral type should be used. 3580 3581@opindex fshort-enums 3582Specifying this attribute for @code{struct} and @code{union} types is 3583equivalent to specifying the @code{packed} attribute on each of the 3584structure or union members. Specifying the @option{-fshort-enums} 3585flag on the line is equivalent to specifying the @code{packed} 3586attribute on all @code{enum} definitions. 3587 3588In the following example @code{struct my_packed_struct}'s members are 3589packed closely together, but the internal layout of its @code{s} member 3590is not packed---to do that, @code{struct my_unpacked_struct} would need to 3591be packed too. 3592 3593@smallexample 3594struct my_unpacked_struct 3595 @{ 3596 char c; 3597 int i; 3598 @}; 3599 3600struct __attribute__ ((__packed__)) my_packed_struct 3601 @{ 3602 char c; 3603 int i; 3604 struct my_unpacked_struct s; 3605 @}; 3606@end smallexample 3607 3608You may only specify this attribute on the definition of a @code{enum}, 3609@code{struct} or @code{union}, not on a @code{typedef} which does not 3610also define the enumerated type, structure or union. 3611 3612@item transparent_union 3613This attribute, attached to a @code{union} type definition, indicates 3614that any function parameter having that union type causes calls to that 3615function to be treated in a special way. 3616 3617First, the argument corresponding to a transparent union type can be of 3618any type in the union; no cast is required. Also, if the union contains 3619a pointer type, the corresponding argument can be a null pointer 3620constant or a void pointer expression; and if the union contains a void 3621pointer type, the corresponding argument can be any pointer expression. 3622If the union member type is a pointer, qualifiers like @code{const} on 3623the referenced type must be respected, just as with normal pointer 3624conversions. 3625 3626Second, the argument is passed to the function using the calling 3627conventions of the first member of the transparent union, not the calling 3628conventions of the union itself. All members of the union must have the 3629same machine representation; this is necessary for this argument passing 3630to work properly. 3631 3632Transparent unions are designed for library functions that have multiple 3633interfaces for compatibility reasons. For example, suppose the 3634@code{wait} function must accept either a value of type @code{int *} to 3635comply with Posix, or a value of type @code{union wait *} to comply with 3636the 4.1BSD interface. If @code{wait}'s parameter were @code{void *}, 3637@code{wait} would accept both kinds of arguments, but it would also 3638accept any other pointer type and this would make argument type checking 3639less useful. Instead, @code{<sys/wait.h>} might define the interface 3640as follows: 3641 3642@smallexample 3643typedef union 3644 @{ 3645 int *__ip; 3646 union wait *__up; 3647 @} wait_status_ptr_t __attribute__ ((__transparent_union__)); 3648 3649pid_t wait (wait_status_ptr_t); 3650@end smallexample 3651 3652This interface allows either @code{int *} or @code{union wait *} 3653arguments to be passed, using the @code{int *} calling convention. 3654The program can call @code{wait} with arguments of either type: 3655 3656@smallexample 3657int w1 () @{ int w; return wait (&w); @} 3658int w2 () @{ union wait w; return wait (&w); @} 3659@end smallexample 3660 3661With this interface, @code{wait}'s implementation might look like this: 3662 3663@smallexample 3664pid_t wait (wait_status_ptr_t p) 3665@{ 3666 return waitpid (-1, p.__ip, 0); 3667@} 3668@end smallexample 3669 3670@item unused 3671When attached to a type (including a @code{union} or a @code{struct}), 3672this attribute means that variables of that type are meant to appear 3673possibly unused. GCC will not produce a warning for any variables of 3674that type, even if the variable appears to do nothing. This is often 3675the case with lock or thread classes, which are usually defined and then 3676not referenced, but contain constructors and destructors that have 3677nontrivial bookkeeping functions. 3678 3679@item deprecated 3680The @code{deprecated} attribute results in a warning if the type 3681is used anywhere in the source file. This is useful when identifying 3682types that are expected to be removed in a future version of a program. 3683If possible, the warning also includes the location of the declaration 3684of the deprecated type, to enable users to easily find further 3685information about why the type is deprecated, or what they should do 3686instead. Note that the warnings only occur for uses and then only 3687if the type is being applied to an identifier that itself is not being 3688declared as deprecated. 3689 3690@smallexample 3691typedef int T1 __attribute__ ((deprecated)); 3692T1 x; 3693typedef T1 T2; 3694T2 y; 3695typedef T1 T3 __attribute__ ((deprecated)); 3696T3 z __attribute__ ((deprecated)); 3697@end smallexample 3698 3699results in a warning on line 2 and 3 but not lines 4, 5, or 6. No 3700warning is issued for line 4 because T2 is not explicitly 3701deprecated. Line 5 has no warning because T3 is explicitly 3702deprecated. Similarly for line 6. 3703 3704The @code{deprecated} attribute can also be used for functions and 3705variables (@pxref{Function Attributes}, @pxref{Variable Attributes}.) 3706 3707@item may_alias 3708Accesses to objects with types with this attribute are not subjected to 3709type-based alias analysis, but are instead assumed to be able to alias 3710any other type of objects, just like the @code{char} type. See 3711@option{-fstrict-aliasing} for more information on aliasing issues. 3712 3713Example of use: 3714 3715@smallexample 3716typedef short __attribute__((__may_alias__)) short_a; 3717 3718int 3719main (void) 3720@{ 3721 int a = 0x12345678; 3722 short_a *b = (short_a *) &a; 3723 3724 b[1] = 0; 3725 3726 if (a == 0x12345678) 3727 abort(); 3728 3729 exit(0); 3730@} 3731@end smallexample 3732 3733If you replaced @code{short_a} with @code{short} in the variable 3734declaration, the above program would abort when compiled with 3735@option{-fstrict-aliasing}, which is on by default at @option{-O2} or 3736above in recent GCC versions. 3737 3738@item visibility 3739In C++, attribute visibility (@pxref{Function Attributes}) can also be 3740applied to class, struct, union and enum types. Unlike other type 3741attributes, the attribute must appear between the initial keyword and 3742the name of the type; it cannot appear after the body of the type. 3743 3744Note that the type visibility is applied to vague linkage entities 3745associated with the class (vtable, typeinfo node, etc.). In 3746particular, if a class is thrown as an exception in one shared object 3747and caught in another, the class must have default visibility. 3748Otherwise the two shared objects will be unable to use the same 3749typeinfo node and exception handling will break. 3750 3751@subsection ARM Type Attributes 3752 3753On those ARM targets that support @code{dllimport} (such as Symbian 3754OS), you can use the @code{notshared} attribute to indicate that the 3755virtual table and other similar data for a class should not be 3756exported from a DLL@. For example: 3757 3758@smallexample 3759class __declspec(notshared) C @{ 3760public: 3761 __declspec(dllimport) C(); 3762 virtual void f(); 3763@} 3764 3765__declspec(dllexport) 3766C::C() @{@} 3767@end smallexample 3768 3769In this code, @code{C::C} is exported from the current DLL, but the 3770virtual table for @code{C} is not exported. (You can use 3771@code{__attribute__} instead of @code{__declspec} if you prefer, but 3772most Symbian OS code uses @code{__declspec}.) 3773 3774@anchor{i386 Type Attributes} 3775@subsection i386 Type Attributes 3776 3777Two attributes are currently defined for i386 configurations: 3778@code{ms_struct} and @code{gcc_struct} 3779 3780@item ms_struct 3781@itemx gcc_struct 3782@cindex @code{ms_struct} 3783@cindex @code{gcc_struct} 3784 3785If @code{packed} is used on a structure, or if bit-fields are used 3786it may be that the Microsoft ABI packs them differently 3787than GCC would normally pack them. Particularly when moving packed 3788data between functions compiled with GCC and the native Microsoft compiler 3789(either via function call or as data in a file), it may be necessary to access 3790either format. 3791 3792Currently @option{-m[no-]ms-bitfields} is provided for the Microsoft Windows X86 3793compilers to match the native Microsoft compiler. 3794@end table 3795 3796To specify multiple attributes, separate them by commas within the 3797double parentheses: for example, @samp{__attribute__ ((aligned (16), 3798packed))}. 3799 3800@anchor{PowerPC Type Attributes} 3801@subsection PowerPC Type Attributes 3802 3803Three attributes currently are defined for PowerPC configurations: 3804@code{altivec}, @code{ms_struct} and @code{gcc_struct}. 3805 3806For full documentation of the struct attributes please see the 3807documentation in the @xref{i386 Type Attributes}, section. 3808 3809The @code{altivec} attribute allows one to declare AltiVec vector data 3810types supported by the AltiVec Programming Interface Manual. The 3811attribute requires an argument to specify one of three vector types: 3812@code{vector__}, @code{pixel__} (always followed by unsigned short), 3813and @code{bool__} (always followed by unsigned). 3814 3815@smallexample 3816__attribute__((altivec(vector__))) 3817__attribute__((altivec(pixel__))) unsigned short 3818__attribute__((altivec(bool__))) unsigned 3819@end smallexample 3820 3821These attributes mainly are intended to support the @code{__vector}, 3822@code{__pixel}, and @code{__bool} AltiVec keywords. 3823 3824@node Inline 3825@section An Inline Function is As Fast As a Macro 3826@cindex inline functions 3827@cindex integrating function code 3828@cindex open coding 3829@cindex macros, inline alternative 3830 3831By declaring a function inline, you can direct GCC to make 3832calls to that function faster. One way GCC can achieve this is to 3833integrate that function's code into the code for its callers. This 3834makes execution faster by eliminating the function-call overhead; in 3835addition, if any of the actual argument values are constant, their 3836known values may permit simplifications at compile time so that not 3837all of the inline function's code needs to be included. The effect on 3838code size is less predictable; object code may be larger or smaller 3839with function inlining, depending on the particular case. You can 3840also direct GCC to try to integrate all ``simple enough'' functions 3841into their callers with the option @option{-finline-functions}. 3842 3843GCC implements three different semantics of declaring a function 3844inline. One is available with @option{-std=gnu89}, another when 3845@option{-std=c99} or @option{-std=gnu99}, and the third is used when 3846compiling C++. 3847 3848To declare a function inline, use the @code{inline} keyword in its 3849declaration, like this: 3850 3851@smallexample 3852static inline int 3853inc (int *a) 3854@{ 3855 (*a)++; 3856@} 3857@end smallexample 3858 3859If you are writing a header file to be included in ISO C89 programs, write 3860@code{__inline__} instead of @code{inline}. @xref{Alternate Keywords}. 3861 3862The three types of inlining behave similarly in two important cases: 3863when the @code{inline} keyword is used on a @code{static} function, 3864like the example above, and when a function is first declared without 3865using the @code{inline} keyword and then is defined with 3866@code{inline}, like this: 3867 3868@smallexample 3869extern int inc (int *a); 3870inline int 3871inc (int *a) 3872@{ 3873 (*a)++; 3874@} 3875@end smallexample 3876 3877In both of these common cases, the program behaves the same as if you 3878had not used the @code{inline} keyword, except for its speed. 3879 3880@cindex inline functions, omission of 3881@opindex fkeep-inline-functions 3882When a function is both inline and @code{static}, if all calls to the 3883function are integrated into the caller, and the function's address is 3884never used, then the function's own assembler code is never referenced. 3885In this case, GCC does not actually output assembler code for the 3886function, unless you specify the option @option{-fkeep-inline-functions}. 3887Some calls cannot be integrated for various reasons (in particular, 3888calls that precede the function's definition cannot be integrated, and 3889neither can recursive calls within the definition). If there is a 3890nonintegrated call, then the function is compiled to assembler code as 3891usual. The function must also be compiled as usual if the program 3892refers to its address, because that can't be inlined. 3893 3894@cindex automatic @code{inline} for C++ member fns 3895@cindex @code{inline} automatic for C++ member fns 3896@cindex member fns, automatically @code{inline} 3897@cindex C++ member fns, automatically @code{inline} 3898@opindex fno-default-inline 3899As required by ISO C++, GCC considers member functions defined within 3900the body of a class to be marked inline even if they are 3901not explicitly declared with the @code{inline} keyword. You can 3902override this with @option{-fno-default-inline}; @pxref{C++ Dialect 3903Options,,Options Controlling C++ Dialect}. 3904 3905GCC does not inline any functions when not optimizing unless you specify 3906the @samp{always_inline} attribute for the function, like this: 3907 3908@smallexample 3909/* @r{Prototype.} */ 3910inline void foo (const char) __attribute__((always_inline)); 3911@end smallexample 3912 3913The remainder of this section is specific to GNU C89 inlining. 3914 3915@cindex non-static inline function 3916When an inline function is not @code{static}, then the compiler must assume 3917that there may be calls from other source files; since a global symbol can 3918be defined only once in any program, the function must not be defined in 3919the other source files, so the calls therein cannot be integrated. 3920Therefore, a non-@code{static} inline function is always compiled on its 3921own in the usual fashion. 3922 3923If you specify both @code{inline} and @code{extern} in the function 3924definition, then the definition is used only for inlining. In no case 3925is the function compiled on its own, not even if you refer to its 3926address explicitly. Such an address becomes an external reference, as 3927if you had only declared the function, and had not defined it. 3928 3929This combination of @code{inline} and @code{extern} has almost the 3930effect of a macro. The way to use it is to put a function definition in 3931a header file with these keywords, and put another copy of the 3932definition (lacking @code{inline} and @code{extern}) in a library file. 3933The definition in the header file will cause most calls to the function 3934to be inlined. If any uses of the function remain, they will refer to 3935the single copy in the library. 3936 3937@node Extended Asm 3938@section Assembler Instructions with C Expression Operands 3939@cindex extended @code{asm} 3940@cindex @code{asm} expressions 3941@cindex assembler instructions 3942@cindex registers 3943 3944In an assembler instruction using @code{asm}, you can specify the 3945operands of the instruction using C expressions. This means you need not 3946guess which registers or memory locations will contain the data you want 3947to use. 3948 3949You must specify an assembler instruction template much like what 3950appears in a machine description, plus an operand constraint string for 3951each operand. 3952 3953For example, here is how to use the 68881's @code{fsinx} instruction: 3954 3955@smallexample 3956asm ("fsinx %1,%0" : "=f" (result) : "f" (angle)); 3957@end smallexample 3958 3959@noindent 3960Here @code{angle} is the C expression for the input operand while 3961@code{result} is that of the output operand. Each has @samp{"f"} as its 3962operand constraint, saying that a floating point register is required. 3963The @samp{=} in @samp{=f} indicates that the operand is an output; all 3964output operands' constraints must use @samp{=}. The constraints use the 3965same language used in the machine description (@pxref{Constraints}). 3966 3967Each operand is described by an operand-constraint string followed by 3968the C expression in parentheses. A colon separates the assembler 3969template from the first output operand and another separates the last 3970output operand from the first input, if any. Commas separate the 3971operands within each group. The total number of operands is currently 3972limited to 30; this limitation may be lifted in some future version of 3973GCC@. 3974 3975If there are no output operands but there are input operands, you must 3976place two consecutive colons surrounding the place where the output 3977operands would go. 3978 3979As of GCC version 3.1, it is also possible to specify input and output 3980operands using symbolic names which can be referenced within the 3981assembler code. These names are specified inside square brackets 3982preceding the constraint string, and can be referenced inside the 3983assembler code using @code{%[@var{name}]} instead of a percentage sign 3984followed by the operand number. Using named operands the above example 3985could look like: 3986 3987@smallexample 3988asm ("fsinx %[angle],%[output]" 3989 : [output] "=f" (result) 3990 : [angle] "f" (angle)); 3991@end smallexample 3992 3993@noindent 3994Note that the symbolic operand names have no relation whatsoever to 3995other C identifiers. You may use any name you like, even those of 3996existing C symbols, but you must ensure that no two operands within the same 3997assembler construct use the same symbolic name. 3998 3999Output operand expressions must be lvalues; the compiler can check this. 4000The input operands need not be lvalues. The compiler cannot check 4001whether the operands have data types that are reasonable for the 4002instruction being executed. It does not parse the assembler instruction 4003template and does not know what it means or even whether it is valid 4004assembler input. The extended @code{asm} feature is most often used for 4005machine instructions the compiler itself does not know exist. If 4006the output expression cannot be directly addressed (for example, it is a 4007bit-field), your constraint must allow a register. In that case, GCC 4008will use the register as the output of the @code{asm}, and then store 4009that register into the output. 4010 4011The ordinary output operands must be write-only; GCC will assume that 4012the values in these operands before the instruction are dead and need 4013not be generated. Extended asm supports input-output or read-write 4014operands. Use the constraint character @samp{+} to indicate such an 4015operand and list it with the output operands. You should only use 4016read-write operands when the constraints for the operand (or the 4017operand in which only some of the bits are to be changed) allow a 4018register. 4019 4020You may, as an alternative, logically split its function into two 4021separate operands, one input operand and one write-only output 4022operand. The connection between them is expressed by constraints 4023which say they need to be in the same location when the instruction 4024executes. You can use the same C expression for both operands, or 4025different expressions. For example, here we write the (fictitious) 4026@samp{combine} instruction with @code{bar} as its read-only source 4027operand and @code{foo} as its read-write destination: 4028 4029@smallexample 4030asm ("combine %2,%0" : "=r" (foo) : "0" (foo), "g" (bar)); 4031@end smallexample 4032 4033@noindent 4034The constraint @samp{"0"} for operand 1 says that it must occupy the 4035same location as operand 0. A number in constraint is allowed only in 4036an input operand and it must refer to an output operand. 4037 4038Only a number in the constraint can guarantee that one operand will be in 4039the same place as another. The mere fact that @code{foo} is the value 4040of both operands is not enough to guarantee that they will be in the 4041same place in the generated assembler code. The following would not 4042work reliably: 4043 4044@smallexample 4045asm ("combine %2,%0" : "=r" (foo) : "r" (foo), "g" (bar)); 4046@end smallexample 4047 4048Various optimizations or reloading could cause operands 0 and 1 to be in 4049different registers; GCC knows no reason not to do so. For example, the 4050compiler might find a copy of the value of @code{foo} in one register and 4051use it for operand 1, but generate the output operand 0 in a different 4052register (copying it afterward to @code{foo}'s own address). Of course, 4053since the register for operand 1 is not even mentioned in the assembler 4054code, the result will not work, but GCC can't tell that. 4055 4056As of GCC version 3.1, one may write @code{[@var{name}]} instead of 4057the operand number for a matching constraint. For example: 4058 4059@smallexample 4060asm ("cmoveq %1,%2,%[result]" 4061 : [result] "=r"(result) 4062 : "r" (test), "r"(new), "[result]"(old)); 4063@end smallexample 4064 4065Sometimes you need to make an @code{asm} operand be a specific register, 4066but there's no matching constraint letter for that register @emph{by 4067itself}. To force the operand into that register, use a local variable 4068for the operand and specify the register in the variable declaration. 4069@xref{Explicit Reg Vars}. Then for the @code{asm} operand, use any 4070register constraint letter that matches the register: 4071 4072@smallexample 4073register int *p1 asm ("r0") = @dots{}; 4074register int *p2 asm ("r1") = @dots{}; 4075register int *result asm ("r0"); 4076asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2)); 4077@end smallexample 4078 4079@anchor{Example of asm with clobbered asm reg} 4080In the above example, beware that a register that is call-clobbered by 4081the target ABI will be overwritten by any function call in the 4082assignment, including library calls for arithmetic operators. 4083Assuming it is a call-clobbered register, this may happen to @code{r0} 4084above by the assignment to @code{p2}. If you have to use such a 4085register, use temporary variables for expressions between the register 4086assignment and use: 4087 4088@smallexample 4089int t1 = @dots{}; 4090register int *p1 asm ("r0") = @dots{}; 4091register int *p2 asm ("r1") = t1; 4092register int *result asm ("r0"); 4093asm ("sysint" : "=r" (result) : "0" (p1), "r" (p2)); 4094@end smallexample 4095 4096Some instructions clobber specific hard registers. To describe this, 4097write a third colon after the input operands, followed by the names of 4098the clobbered hard registers (given as strings). Here is a realistic 4099example for the VAX: 4100 4101@smallexample 4102asm volatile ("movc3 %0,%1,%2" 4103 : /* @r{no outputs} */ 4104 : "g" (from), "g" (to), "g" (count) 4105 : "r0", "r1", "r2", "r3", "r4", "r5"); 4106@end smallexample 4107 4108You may not write a clobber description in a way that overlaps with an 4109input or output operand. For example, you may not have an operand 4110describing a register class with one member if you mention that register 4111in the clobber list. Variables declared to live in specific registers 4112(@pxref{Explicit Reg Vars}), and used as asm input or output operands must 4113have no part mentioned in the clobber description. 4114There is no way for you to specify that an input 4115operand is modified without also specifying it as an output 4116operand. Note that if all the output operands you specify are for this 4117purpose (and hence unused), you will then also need to specify 4118@code{volatile} for the @code{asm} construct, as described below, to 4119prevent GCC from deleting the @code{asm} statement as unused. 4120 4121If you refer to a particular hardware register from the assembler code, 4122you will probably have to list the register after the third colon to 4123tell the compiler the register's value is modified. In some assemblers, 4124the register names begin with @samp{%}; to produce one @samp{%} in the 4125assembler code, you must write @samp{%%} in the input. 4126 4127If your assembler instruction can alter the condition code register, add 4128@samp{cc} to the list of clobbered registers. GCC on some machines 4129represents the condition codes as a specific hardware register; 4130@samp{cc} serves to name this register. On other machines, the 4131condition code is handled differently, and specifying @samp{cc} has no 4132effect. But it is valid no matter what the machine. 4133 4134If your assembler instructions access memory in an unpredictable 4135fashion, add @samp{memory} to the list of clobbered registers. This 4136will cause GCC to not keep memory values cached in registers across the 4137assembler instruction and not optimize stores or loads to that memory. 4138You will also want to add the @code{volatile} keyword if the memory 4139affected is not listed in the inputs or outputs of the @code{asm}, as 4140the @samp{memory} clobber does not count as a side-effect of the 4141@code{asm}. If you know how large the accessed memory is, you can add 4142it as input or output but if this is not known, you should add 4143@samp{memory}. As an example, if you access ten bytes of a string, you 4144can use a memory input like: 4145 4146@smallexample 4147@{"m"( (@{ struct @{ char x[10]; @} *p = (void *)ptr ; *p; @}) )@}. 4148@end smallexample 4149 4150Note that in the following example the memory input is necessary, 4151otherwise GCC might optimize the store to @code{x} away: 4152@smallexample 4153int foo () 4154@{ 4155 int x = 42; 4156 int *y = &x; 4157 int result; 4158 asm ("magic stuff accessing an 'int' pointed to by '%1'" 4159 "=&d" (r) : "a" (y), "m" (*y)); 4160 return result; 4161@} 4162@end smallexample 4163 4164You can put multiple assembler instructions together in a single 4165@code{asm} template, separated by the characters normally used in assembly 4166code for the system. A combination that works in most places is a newline 4167to break the line, plus a tab character to move to the instruction field 4168(written as @samp{\n\t}). Sometimes semicolons can be used, if the 4169assembler allows semicolons as a line-breaking character. Note that some 4170assembler dialects use semicolons to start a comment. 4171The input operands are guaranteed not to use any of the clobbered 4172registers, and neither will the output operands' addresses, so you can 4173read and write the clobbered registers as many times as you like. Here 4174is an example of multiple instructions in a template; it assumes the 4175subroutine @code{_foo} accepts arguments in registers 9 and 10: 4176 4177@smallexample 4178asm ("movl %0,r9\n\tmovl %1,r10\n\tcall _foo" 4179 : /* no outputs */ 4180 : "g" (from), "g" (to) 4181 : "r9", "r10"); 4182@end smallexample 4183 4184Unless an output operand has the @samp{&} constraint modifier, GCC 4185may allocate it in the same register as an unrelated input operand, on 4186the assumption the inputs are consumed before the outputs are produced. 4187This assumption may be false if the assembler code actually consists of 4188more than one instruction. In such a case, use @samp{&} for each output 4189operand that may not overlap an input. @xref{Modifiers}. 4190 4191If you want to test the condition code produced by an assembler 4192instruction, you must include a branch and a label in the @code{asm} 4193construct, as follows: 4194 4195@smallexample 4196asm ("clr %0\n\tfrob %1\n\tbeq 0f\n\tmov #1,%0\n0:" 4197 : "g" (result) 4198 : "g" (input)); 4199@end smallexample 4200 4201@noindent 4202This assumes your assembler supports local labels, as the GNU assembler 4203and most Unix assemblers do. 4204 4205Speaking of labels, jumps from one @code{asm} to another are not 4206supported. The compiler's optimizers do not know about these jumps, and 4207therefore they cannot take account of them when deciding how to 4208optimize. 4209 4210@cindex macros containing @code{asm} 4211Usually the most convenient way to use these @code{asm} instructions is to 4212encapsulate them in macros that look like functions. For example, 4213 4214@smallexample 4215#define sin(x) \ 4216(@{ double __value, __arg = (x); \ 4217 asm ("fsinx %1,%0": "=f" (__value): "f" (__arg)); \ 4218 __value; @}) 4219@end smallexample 4220 4221@noindent 4222Here the variable @code{__arg} is used to make sure that the instruction 4223operates on a proper @code{double} value, and to accept only those 4224arguments @code{x} which can convert automatically to a @code{double}. 4225 4226Another way to make sure the instruction operates on the correct data 4227type is to use a cast in the @code{asm}. This is different from using a 4228variable @code{__arg} in that it converts more different types. For 4229example, if the desired type were @code{int}, casting the argument to 4230@code{int} would accept a pointer with no complaint, while assigning the 4231argument to an @code{int} variable named @code{__arg} would warn about 4232using a pointer unless the caller explicitly casts it. 4233 4234If an @code{asm} has output operands, GCC assumes for optimization 4235purposes the instruction has no side effects except to change the output 4236operands. This does not mean instructions with a side effect cannot be 4237used, but you must be careful, because the compiler may eliminate them 4238if the output operands aren't used, or move them out of loops, or 4239replace two with one if they constitute a common subexpression. Also, 4240if your instruction does have a side effect on a variable that otherwise 4241appears not to change, the old value of the variable may be reused later 4242if it happens to be found in a register. 4243 4244You can prevent an @code{asm} instruction from being deleted 4245by writing the keyword @code{volatile} after 4246the @code{asm}. For example: 4247 4248@smallexample 4249#define get_and_set_priority(new) \ 4250(@{ int __old; \ 4251 asm volatile ("get_and_set_priority %0, %1" \ 4252 : "=g" (__old) : "g" (new)); \ 4253 __old; @}) 4254@end smallexample 4255 4256@noindent 4257The @code{volatile} keyword indicates that the instruction has 4258important side-effects. GCC will not delete a volatile @code{asm} if 4259it is reachable. (The instruction can still be deleted if GCC can 4260prove that control-flow will never reach the location of the 4261instruction.) Note that even a volatile @code{asm} instruction 4262can be moved relative to other code, including across jump 4263instructions. For example, on many targets there is a system 4264register which can be set to control the rounding mode of 4265floating point operations. You might try 4266setting it with a volatile @code{asm}, like this PowerPC example: 4267 4268@smallexample 4269 asm volatile("mtfsf 255,%0" : : "f" (fpenv)); 4270 sum = x + y; 4271@end smallexample 4272 4273@noindent 4274This will not work reliably, as the compiler may move the addition back 4275before the volatile @code{asm}. To make it work you need to add an 4276artificial dependency to the @code{asm} referencing a variable in the code 4277you don't want moved, for example: 4278 4279@smallexample 4280 asm volatile ("mtfsf 255,%1" : "=X"(sum): "f"(fpenv)); 4281 sum = x + y; 4282@end smallexample 4283 4284Similarly, you can't expect a 4285sequence of volatile @code{asm} instructions to remain perfectly 4286consecutive. If you want consecutive output, use a single @code{asm}. 4287Also, GCC will perform some optimizations across a volatile @code{asm} 4288instruction; GCC does not ``forget everything'' when it encounters 4289a volatile @code{asm} instruction the way some other compilers do. 4290 4291An @code{asm} instruction without any output operands will be treated 4292identically to a volatile @code{asm} instruction. 4293 4294It is a natural idea to look for a way to give access to the condition 4295code left by the assembler instruction. However, when we attempted to 4296implement this, we found no way to make it work reliably. The problem 4297is that output operands might need reloading, which would result in 4298additional following ``store'' instructions. On most machines, these 4299instructions would alter the condition code before there was time to 4300test it. This problem doesn't arise for ordinary ``test'' and 4301``compare'' instructions because they don't have any output operands. 4302 4303For reasons similar to those described above, it is not possible to give 4304an assembler instruction access to the condition code left by previous 4305instructions. 4306 4307If you are writing a header file that should be includable in ISO C 4308programs, write @code{__asm__} instead of @code{asm}. @xref{Alternate 4309Keywords}. 4310 4311@subsection Size of an @code{asm} 4312 4313Some targets require that GCC track the size of each instruction used in 4314order to generate correct code. Because the final length of an 4315@code{asm} is only known by the assembler, GCC must make an estimate as 4316to how big it will be. The estimate is formed by counting the number of 4317statements in the pattern of the @code{asm} and multiplying that by the 4318length of the longest instruction on that processor. Statements in the 4319@code{asm} are identified by newline characters and whatever statement 4320separator characters are supported by the assembler; on most processors 4321this is the `@code{;}' character. 4322 4323Normally, GCC's estimate is perfectly adequate to ensure that correct 4324code is generated, but it is possible to confuse the compiler if you use 4325pseudo instructions or assembler macros that expand into multiple real 4326instructions or if you use assembler directives that expand to more 4327space in the object file than would be needed for a single instruction. 4328If this happens then the assembler will produce a diagnostic saying that 4329a label is unreachable. 4330 4331@subsection i386 floating point asm operands 4332 4333There are several rules on the usage of stack-like regs in 4334asm_operands insns. These rules apply only to the operands that are 4335stack-like regs: 4336 4337@enumerate 4338@item 4339Given a set of input regs that die in an asm_operands, it is 4340necessary to know which are implicitly popped by the asm, and 4341which must be explicitly popped by gcc. 4342 4343An input reg that is implicitly popped by the asm must be 4344explicitly clobbered, unless it is constrained to match an 4345output operand. 4346 4347@item 4348For any input reg that is implicitly popped by an asm, it is 4349necessary to know how to adjust the stack to compensate for the pop. 4350If any non-popped input is closer to the top of the reg-stack than 4351the implicitly popped reg, it would not be possible to know what the 4352stack looked like---it's not clear how the rest of the stack ``slides 4353up''. 4354 4355All implicitly popped input regs must be closer to the top of 4356the reg-stack than any input that is not implicitly popped. 4357 4358It is possible that if an input dies in an insn, reload might 4359use the input reg for an output reload. Consider this example: 4360 4361@smallexample 4362asm ("foo" : "=t" (a) : "f" (b)); 4363@end smallexample 4364 4365This asm says that input B is not popped by the asm, and that 4366the asm pushes a result onto the reg-stack, i.e., the stack is one 4367deeper after the asm than it was before. But, it is possible that 4368reload will think that it can use the same reg for both the input and 4369the output, if input B dies in this insn. 4370 4371If any input operand uses the @code{f} constraint, all output reg 4372constraints must use the @code{&} earlyclobber. 4373 4374The asm above would be written as 4375 4376@smallexample 4377asm ("foo" : "=&t" (a) : "f" (b)); 4378@end smallexample 4379 4380@item 4381Some operands need to be in particular places on the stack. All 4382output operands fall in this category---there is no other way to 4383know which regs the outputs appear in unless the user indicates 4384this in the constraints. 4385 4386Output operands must specifically indicate which reg an output 4387appears in after an asm. @code{=f} is not allowed: the operand 4388constraints must select a class with a single reg. 4389 4390@item 4391Output operands may not be ``inserted'' between existing stack regs. 4392Since no 387 opcode uses a read/write operand, all output operands 4393are dead before the asm_operands, and are pushed by the asm_operands. 4394It makes no sense to push anywhere but the top of the reg-stack. 4395 4396Output operands must start at the top of the reg-stack: output 4397operands may not ``skip'' a reg. 4398 4399@item 4400Some asm statements may need extra stack space for internal 4401calculations. This can be guaranteed by clobbering stack registers 4402unrelated to the inputs and outputs. 4403 4404@end enumerate 4405 4406Here are a couple of reasonable asms to want to write. This asm 4407takes one input, which is internally popped, and produces two outputs. 4408 4409@smallexample 4410asm ("fsincos" : "=t" (cos), "=u" (sin) : "0" (inp)); 4411@end smallexample 4412 4413This asm takes two inputs, which are popped by the @code{fyl2xp1} opcode, 4414and replaces them with one output. The user must code the @code{st(1)} 4415clobber for reg-stack.c to know that @code{fyl2xp1} pops both inputs. 4416 4417@smallexample 4418asm ("fyl2xp1" : "=t" (result) : "0" (x), "u" (y) : "st(1)"); 4419@end smallexample 4420 4421@include md.texi 4422 4423@node Asm Labels 4424@section Controlling Names Used in Assembler Code 4425@cindex assembler names for identifiers 4426@cindex names used in assembler code 4427@cindex identifiers, names in assembler code 4428 4429You can specify the name to be used in the assembler code for a C 4430function or variable by writing the @code{asm} (or @code{__asm__}) 4431keyword after the declarator as follows: 4432 4433@smallexample 4434int foo asm ("myfoo") = 2; 4435@end smallexample 4436 4437@noindent 4438This specifies that the name to be used for the variable @code{foo} in 4439the assembler code should be @samp{myfoo} rather than the usual 4440@samp{_foo}. 4441 4442On systems where an underscore is normally prepended to the name of a C 4443function or variable, this feature allows you to define names for the 4444linker that do not start with an underscore. 4445 4446It does not make sense to use this feature with a non-static local 4447variable since such variables do not have assembler names. If you are 4448trying to put the variable in a particular register, see @ref{Explicit 4449Reg Vars}. GCC presently accepts such code with a warning, but will 4450probably be changed to issue an error, rather than a warning, in the 4451future. 4452 4453You cannot use @code{asm} in this way in a function @emph{definition}; but 4454you can get the same effect by writing a declaration for the function 4455before its definition and putting @code{asm} there, like this: 4456 4457@smallexample 4458extern func () asm ("FUNC"); 4459 4460func (x, y) 4461 int x, y; 4462/* @r{@dots{}} */ 4463@end smallexample 4464 4465It is up to you to make sure that the assembler names you choose do not 4466conflict with any other assembler symbols. Also, you must not use a 4467register name; that would produce completely invalid assembler code. GCC 4468does not as yet have the ability to store static variables in registers. 4469Perhaps that will be added. 4470 4471@node Explicit Reg Vars 4472@section Variables in Specified Registers 4473@cindex explicit register variables 4474@cindex variables in specified registers 4475@cindex specified registers 4476@cindex registers, global allocation 4477 4478GNU C allows you to put a few global variables into specified hardware 4479registers. You can also specify the register in which an ordinary 4480register variable should be allocated. 4481 4482@itemize @bullet 4483@item 4484Global register variables reserve registers throughout the program. 4485This may be useful in programs such as programming language 4486interpreters which have a couple of global variables that are accessed 4487very often. 4488 4489@item 4490Local register variables in specific registers do not reserve the 4491registers, except at the point where they are used as input or output 4492operands in an @code{asm} statement and the @code{asm} statement itself is 4493not deleted. The compiler's data flow analysis is capable of determining 4494where the specified registers contain live values, and where they are 4495available for other uses. Stores into local register variables may be deleted 4496when they appear to be dead according to dataflow analysis. References 4497to local register variables may be deleted or moved or simplified. 4498 4499These local variables are sometimes convenient for use with the extended 4500@code{asm} feature (@pxref{Extended Asm}), if you want to write one 4501output of the assembler instruction directly into a particular register. 4502(This will work provided the register you specify fits the constraints 4503specified for that operand in the @code{asm}.) 4504@end itemize 4505 4506@menu 4507* Global Reg Vars:: 4508* Local Reg Vars:: 4509@end menu 4510 4511@node Global Reg Vars 4512@subsection Defining Global Register Variables 4513@cindex global register variables 4514@cindex registers, global variables in 4515 4516You can define a global register variable in GNU C like this: 4517 4518@smallexample 4519register int *foo asm ("a5"); 4520@end smallexample 4521 4522@noindent 4523Here @code{a5} is the name of the register which should be used. Choose a 4524register which is normally saved and restored by function calls on your 4525machine, so that library routines will not clobber it. 4526 4527Naturally the register name is cpu-dependent, so you would need to 4528conditionalize your program according to cpu type. The register 4529@code{a5} would be a good choice on a 68000 for a variable of pointer 4530type. On machines with register windows, be sure to choose a ``global'' 4531register that is not affected magically by the function call mechanism. 4532 4533In addition, operating systems on one type of cpu may differ in how they 4534name the registers; then you would need additional conditionals. For 4535example, some 68000 operating systems call this register @code{%a5}. 4536 4537Eventually there may be a way of asking the compiler to choose a register 4538automatically, but first we need to figure out how it should choose and 4539how to enable you to guide the choice. No solution is evident. 4540 4541Defining a global register variable in a certain register reserves that 4542register entirely for this use, at least within the current compilation. 4543The register will not be allocated for any other purpose in the functions 4544in the current compilation. The register will not be saved and restored by 4545these functions. Stores into this register are never deleted even if they 4546would appear to be dead, but references may be deleted or moved or 4547simplified. 4548 4549It is not safe to access the global register variables from signal 4550handlers, or from more than one thread of control, because the system 4551library routines may temporarily use the register for other things (unless 4552you recompile them specially for the task at hand). 4553 4554@cindex @code{qsort}, and global register variables 4555It is not safe for one function that uses a global register variable to 4556call another such function @code{foo} by way of a third function 4557@code{lose} that was compiled without knowledge of this variable (i.e.@: in a 4558different source file in which the variable wasn't declared). This is 4559because @code{lose} might save the register and put some other value there. 4560For example, you can't expect a global register variable to be available in 4561the comparison-function that you pass to @code{qsort}, since @code{qsort} 4562might have put something else in that register. (If you are prepared to 4563recompile @code{qsort} with the same global register variable, you can 4564solve this problem.) 4565 4566If you want to recompile @code{qsort} or other source files which do not 4567actually use your global register variable, so that they will not use that 4568register for any other purpose, then it suffices to specify the compiler 4569option @option{-ffixed-@var{reg}}. You need not actually add a global 4570register declaration to their source code. 4571 4572A function which can alter the value of a global register variable cannot 4573safely be called from a function compiled without this variable, because it 4574could clobber the value the caller expects to find there on return. 4575Therefore, the function which is the entry point into the part of the 4576program that uses the global register variable must explicitly save and 4577restore the value which belongs to its caller. 4578 4579@cindex register variable after @code{longjmp} 4580@cindex global register after @code{longjmp} 4581@cindex value after @code{longjmp} 4582@findex longjmp 4583@findex setjmp 4584On most machines, @code{longjmp} will restore to each global register 4585variable the value it had at the time of the @code{setjmp}. On some 4586machines, however, @code{longjmp} will not change the value of global 4587register variables. To be portable, the function that called @code{setjmp} 4588should make other arrangements to save the values of the global register 4589variables, and to restore them in a @code{longjmp}. This way, the same 4590thing will happen regardless of what @code{longjmp} does. 4591 4592All global register variable declarations must precede all function 4593definitions. If such a declaration could appear after function 4594definitions, the declaration would be too late to prevent the register from 4595being used for other purposes in the preceding functions. 4596 4597Global register variables may not have initial values, because an 4598executable file has no means to supply initial contents for a register. 4599 4600On the SPARC, there are reports that g3 @dots{} g7 are suitable 4601registers, but certain library functions, such as @code{getwd}, as well 4602as the subroutines for division and remainder, modify g3 and g4. g1 and 4603g2 are local temporaries. 4604 4605On the 68000, a2 @dots{} a5 should be suitable, as should d2 @dots{} d7. 4606Of course, it will not do to use more than a few of those. 4607 4608@node Local Reg Vars 4609@subsection Specifying Registers for Local Variables 4610@cindex local variables, specifying registers 4611@cindex specifying registers for local variables 4612@cindex registers for local variables 4613 4614You can define a local register variable with a specified register 4615like this: 4616 4617@smallexample 4618register int *foo asm ("a5"); 4619@end smallexample 4620 4621@noindent 4622Here @code{a5} is the name of the register which should be used. Note 4623that this is the same syntax used for defining global register 4624variables, but for a local variable it would appear within a function. 4625 4626Naturally the register name is cpu-dependent, but this is not a 4627problem, since specific registers are most often useful with explicit 4628assembler instructions (@pxref{Extended Asm}). Both of these things 4629generally require that you conditionalize your program according to 4630cpu type. 4631 4632In addition, operating systems on one type of cpu may differ in how they 4633name the registers; then you would need additional conditionals. For 4634example, some 68000 operating systems call this register @code{%a5}. 4635 4636Defining such a register variable does not reserve the register; it 4637remains available for other uses in places where flow control determines 4638the variable's value is not live. 4639 4640This option does not guarantee that GCC will generate code that has 4641this variable in the register you specify at all times. You may not 4642code an explicit reference to this register in the @emph{assembler 4643instruction template} part of an @code{asm} statement and assume it will 4644always refer to this variable. However, using the variable as an 4645@code{asm} @emph{operand} guarantees that the specified register is used 4646for the operand. 4647 4648Stores into local register variables may be deleted when they appear to be dead 4649according to dataflow analysis. References to local register variables may 4650be deleted or moved or simplified. 4651 4652As for global register variables, it's recommended that you choose a 4653register which is normally saved and restored by function calls on 4654your machine, so that library routines will not clobber it. A common 4655pitfall is to initialize multiple call-clobbered registers with 4656arbitrary expressions, where a function call or library call for an 4657arithmetic operator will overwrite a register value from a previous 4658assignment, for example @code{r0} below: 4659@smallexample 4660register int *p1 asm ("r0") = @dots{}; 4661register int *p2 asm ("r1") = @dots{}; 4662@end smallexample 4663In those cases, a solution is to use a temporary variable for 4664each arbitrary expression. @xref{Example of asm with clobbered asm reg}. 4665 4666@node Alternate Keywords 4667@section Alternate Keywords 4668@cindex alternate keywords 4669@cindex keywords, alternate 4670 4671@option{-ansi} and the various @option{-std} options disable certain 4672keywords. This causes trouble when you want to use GNU C extensions, or 4673a general-purpose header file that should be usable by all programs, 4674including ISO C programs. The keywords @code{asm}, @code{typeof} and 4675@code{inline} are not available in programs compiled with 4676@option{-ansi} or @option{-std} (although @code{inline} can be used in a 4677program compiled with @option{-std=c99}). The ISO C99 keyword 4678@code{restrict} is only available when @option{-std=gnu99} (which will 4679eventually be the default) or @option{-std=c99} (or the equivalent 4680@option{-std=iso9899:1999}) is used. 4681 4682The way to solve these problems is to put @samp{__} at the beginning and 4683end of each problematical keyword. For example, use @code{__asm__} 4684instead of @code{asm}, and @code{__inline__} instead of @code{inline}. 4685 4686Other C compilers won't accept these alternative keywords; if you want to 4687compile with another compiler, you can define the alternate keywords as 4688macros to replace them with the customary keywords. It looks like this: 4689 4690@smallexample 4691#ifndef __GNUC__ 4692#define __asm__ asm 4693#endif 4694@end smallexample 4695 4696@findex __extension__ 4697@opindex pedantic 4698@option{-pedantic} and other options cause warnings for many GNU C extensions. 4699You can 4700prevent such warnings within one expression by writing 4701@code{__extension__} before the expression. @code{__extension__} has no 4702effect aside from this. 4703 4704@node Incomplete Enums 4705@section Incomplete @code{enum} Types 4706 4707You can define an @code{enum} tag without specifying its possible values. 4708This results in an incomplete type, much like what you get if you write 4709@code{struct foo} without describing the elements. A later declaration 4710which does specify the possible values completes the type. 4711 4712You can't allocate variables or storage using the type while it is 4713incomplete. However, you can work with pointers to that type. 4714 4715This extension may not be very useful, but it makes the handling of 4716@code{enum} more consistent with the way @code{struct} and @code{union} 4717are handled. 4718 4719This extension is not supported by GNU C++. 4720 4721@node Function Names 4722@section Function Names as Strings 4723@cindex @code{__func__} identifier 4724@cindex @code{__FUNCTION__} identifier 4725@cindex @code{__PRETTY_FUNCTION__} identifier 4726 4727GCC provides three magic variables which hold the name of the current 4728function, as a string. The first of these is @code{__func__}, which 4729is part of the C99 standard: 4730 4731@display 4732The identifier @code{__func__} is implicitly declared by the translator 4733as if, immediately following the opening brace of each function 4734definition, the declaration 4735 4736@smallexample 4737static const char __func__[] = "function-name"; 4738@end smallexample 4739 4740appeared, where function-name is the name of the lexically-enclosing 4741function. This name is the unadorned name of the function. 4742@end display 4743 4744@code{__FUNCTION__} is another name for @code{__func__}. Older 4745versions of GCC recognize only this name. However, it is not 4746standardized. For maximum portability, we recommend you use 4747@code{__func__}, but provide a fallback definition with the 4748preprocessor: 4749 4750@smallexample 4751#if __STDC_VERSION__ < 199901L 4752# if __GNUC__ >= 2 4753# define __func__ __FUNCTION__ 4754# else 4755# define __func__ "<unknown>" 4756# endif 4757#endif 4758@end smallexample 4759 4760In C, @code{__PRETTY_FUNCTION__} is yet another name for 4761@code{__func__}. However, in C++, @code{__PRETTY_FUNCTION__} contains 4762the type signature of the function as well as its bare name. For 4763example, this program: 4764 4765@smallexample 4766extern "C" @{ 4767extern int printf (char *, ...); 4768@} 4769 4770class a @{ 4771 public: 4772 void sub (int i) 4773 @{ 4774 printf ("__FUNCTION__ = %s\n", __FUNCTION__); 4775 printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__); 4776 @} 4777@}; 4778 4779int 4780main (void) 4781@{ 4782 a ax; 4783 ax.sub (0); 4784 return 0; 4785@} 4786@end smallexample 4787 4788@noindent 4789gives this output: 4790 4791@smallexample 4792__FUNCTION__ = sub 4793__PRETTY_FUNCTION__ = void a::sub(int) 4794@end smallexample 4795 4796These identifiers are not preprocessor macros. In GCC 3.3 and 4797earlier, in C only, @code{__FUNCTION__} and @code{__PRETTY_FUNCTION__} 4798were treated as string literals; they could be used to initialize 4799@code{char} arrays, and they could be concatenated with other string 4800literals. GCC 3.4 and later treat them as variables, like 4801@code{__func__}. In C++, @code{__FUNCTION__} and 4802@code{__PRETTY_FUNCTION__} have always been variables. 4803 4804@node Return Address 4805@section Getting the Return or Frame Address of a Function 4806 4807These functions may be used to get information about the callers of a 4808function. 4809 4810@deftypefn {Built-in Function} {void *} __builtin_return_address (unsigned int @var{level}) 4811This function returns the return address of the current function, or of 4812one of its callers. The @var{level} argument is number of frames to 4813scan up the call stack. A value of @code{0} yields the return address 4814of the current function, a value of @code{1} yields the return address 4815of the caller of the current function, and so forth. When inlining 4816the expected behavior is that the function will return the address of 4817the function that will be returned to. To work around this behavior use 4818the @code{noinline} function attribute. 4819 4820The @var{level} argument must be a constant integer. 4821 4822On some machines it may be impossible to determine the return address of 4823any function other than the current one; in such cases, or when the top 4824of the stack has been reached, this function will return @code{0} or a 4825random value. In addition, @code{__builtin_frame_address} may be used 4826to determine if the top of the stack has been reached. 4827 4828This function should only be used with a nonzero argument for debugging 4829purposes. 4830@end deftypefn 4831 4832@deftypefn {Built-in Function} {void *} __builtin_frame_address (unsigned int @var{level}) 4833This function is similar to @code{__builtin_return_address}, but it 4834returns the address of the function frame rather than the return address 4835of the function. Calling @code{__builtin_frame_address} with a value of 4836@code{0} yields the frame address of the current function, a value of 4837@code{1} yields the frame address of the caller of the current function, 4838and so forth. 4839 4840The frame is the area on the stack which holds local variables and saved 4841registers. The frame address is normally the address of the first word 4842pushed on to the stack by the function. However, the exact definition 4843depends upon the processor and the calling convention. If the processor 4844has a dedicated frame pointer register, and the function has a frame, 4845then @code{__builtin_frame_address} will return the value of the frame 4846pointer register. 4847 4848On some machines it may be impossible to determine the frame address of 4849any function other than the current one; in such cases, or when the top 4850of the stack has been reached, this function will return @code{0} if 4851the first frame pointer is properly initialized by the startup code. 4852 4853This function should only be used with a nonzero argument for debugging 4854purposes. 4855@end deftypefn 4856 4857@node Vector Extensions 4858@section Using vector instructions through built-in functions 4859 4860On some targets, the instruction set contains SIMD vector instructions that 4861operate on multiple values contained in one large register at the same time. 4862For example, on the i386 the MMX, 3Dnow! and SSE extensions can be used 4863this way. 4864 4865The first step in using these extensions is to provide the necessary data 4866types. This should be done using an appropriate @code{typedef}: 4867 4868@smallexample 4869typedef int v4si __attribute__ ((vector_size (16))); 4870@end smallexample 4871 4872The @code{int} type specifies the base type, while the attribute specifies 4873the vector size for the variable, measured in bytes. For example, the 4874declaration above causes the compiler to set the mode for the @code{v4si} 4875type to be 16 bytes wide and divided into @code{int} sized units. For 4876a 32-bit @code{int} this means a vector of 4 units of 4 bytes, and the 4877corresponding mode of @code{foo} will be @acronym{V4SI}. 4878 4879The @code{vector_size} attribute is only applicable to integral and 4880float scalars, although arrays, pointers, and function return values 4881are allowed in conjunction with this construct. 4882 4883All the basic integer types can be used as base types, both as signed 4884and as unsigned: @code{char}, @code{short}, @code{int}, @code{long}, 4885@code{long long}. In addition, @code{float} and @code{double} can be 4886used to build floating-point vector types. 4887 4888Specifying a combination that is not valid for the current architecture 4889will cause GCC to synthesize the instructions using a narrower mode. 4890For example, if you specify a variable of type @code{V4SI} and your 4891architecture does not allow for this specific SIMD type, GCC will 4892produce code that uses 4 @code{SIs}. 4893 4894The types defined in this manner can be used with a subset of normal C 4895operations. Currently, GCC will allow using the following operators 4896on these types: @code{+, -, *, /, unary minus, ^, |, &, ~}@. 4897 4898The operations behave like C++ @code{valarrays}. Addition is defined as 4899the addition of the corresponding elements of the operands. For 4900example, in the code below, each of the 4 elements in @var{a} will be 4901added to the corresponding 4 elements in @var{b} and the resulting 4902vector will be stored in @var{c}. 4903 4904@smallexample 4905typedef int v4si __attribute__ ((vector_size (16))); 4906 4907v4si a, b, c; 4908 4909c = a + b; 4910@end smallexample 4911 4912Subtraction, multiplication, division, and the logical operations 4913operate in a similar manner. Likewise, the result of using the unary 4914minus or complement operators on a vector type is a vector whose 4915elements are the negative or complemented values of the corresponding 4916elements in the operand. 4917 4918You can declare variables and use them in function calls and returns, as 4919well as in assignments and some casts. You can specify a vector type as 4920a return type for a function. Vector types can also be used as function 4921arguments. It is possible to cast from one vector type to another, 4922provided they are of the same size (in fact, you can also cast vectors 4923to and from other datatypes of the same size). 4924 4925You cannot operate between vectors of different lengths or different 4926signedness without a cast. 4927 4928A port that supports hardware vector operations, usually provides a set 4929of built-in functions that can be used to operate on vectors. For 4930example, a function to add two vectors and multiply the result by a 4931third could look like this: 4932 4933@smallexample 4934v4si f (v4si a, v4si b, v4si c) 4935@{ 4936 v4si tmp = __builtin_addv4si (a, b); 4937 return __builtin_mulv4si (tmp, c); 4938@} 4939 4940@end smallexample 4941 4942@node Offsetof 4943@section Offsetof 4944@findex __builtin_offsetof 4945 4946GCC implements for both C and C++ a syntactic extension to implement 4947the @code{offsetof} macro. 4948 4949@smallexample 4950primary: 4951 "__builtin_offsetof" "(" @code{typename} "," offsetof_member_designator ")" 4952 4953offsetof_member_designator: 4954 @code{identifier} 4955 | offsetof_member_designator "." @code{identifier} 4956 | offsetof_member_designator "[" @code{expr} "]" 4957@end smallexample 4958 4959This extension is sufficient such that 4960 4961@smallexample 4962#define offsetof(@var{type}, @var{member}) __builtin_offsetof (@var{type}, @var{member}) 4963@end smallexample 4964 4965is a suitable definition of the @code{offsetof} macro. In C++, @var{type} 4966may be dependent. In either case, @var{member} may consist of a single 4967identifier, or a sequence of member accesses and array references. 4968 4969@node Atomic Builtins 4970@section Built-in functions for atomic memory access 4971 4972The following builtins are intended to be compatible with those described 4973in the @cite{Intel Itanium Processor-specific Application Binary Interface}, 4974section 7.4. As such, they depart from the normal GCC practice of using 4975the ``__builtin_'' prefix, and further that they are overloaded such that 4976they work on multiple types. 4977 4978The definition given in the Intel documentation allows only for the use of 4979the types @code{int}, @code{long}, @code{long long} as well as their unsigned 4980counterparts. GCC will allow any integral scalar or pointer type that is 49811, 2, 4 or 8 bytes in length. 4982 4983Not all operations are supported by all target processors. If a particular 4984operation cannot be implemented on the target processor, a warning will be 4985generated and a call an external function will be generated. The external 4986function will carry the same name as the builtin, with an additional suffix 4987@samp{_@var{n}} where @var{n} is the size of the data type. 4988 4989@c ??? Should we have a mechanism to suppress this warning? This is almost 4990@c useful for implementing the operation under the control of an external 4991@c mutex. 4992 4993In most cases, these builtins are considered a @dfn{full barrier}. That is, 4994no memory operand will be moved across the operation, either forward or 4995backward. Further, instructions will be issued as necessary to prevent the 4996processor from speculating loads across the operation and from queuing stores 4997after the operation. 4998 4999All of the routines are are described in the Intel documentation to take 5000``an optional list of variables protected by the memory barrier''. It's 5001not clear what is meant by that; it could mean that @emph{only} the 5002following variables are protected, or it could mean that these variables 5003should in addition be protected. At present GCC ignores this list and 5004protects all variables which are globally accessible. If in the future 5005we make some use of this list, an empty list will continue to mean all 5006globally accessible variables. 5007 5008@table @code 5009@item @var{type} __sync_fetch_and_add (@var{type} *ptr, @var{type} value, ...) 5010@itemx @var{type} __sync_fetch_and_sub (@var{type} *ptr, @var{type} value, ...) 5011@itemx @var{type} __sync_fetch_and_or (@var{type} *ptr, @var{type} value, ...) 5012@itemx @var{type} __sync_fetch_and_and (@var{type} *ptr, @var{type} value, ...) 5013@itemx @var{type} __sync_fetch_and_xor (@var{type} *ptr, @var{type} value, ...) 5014@itemx @var{type} __sync_fetch_and_nand (@var{type} *ptr, @var{type} value, ...) 5015@findex __sync_fetch_and_add 5016@findex __sync_fetch_and_sub 5017@findex __sync_fetch_and_or 5018@findex __sync_fetch_and_and 5019@findex __sync_fetch_and_xor 5020@findex __sync_fetch_and_nand 5021These builtins perform the operation suggested by the name, and 5022returns the value that had previously been in memory. That is, 5023 5024@smallexample 5025@{ tmp = *ptr; *ptr @var{op}= value; return tmp; @} 5026@{ tmp = *ptr; *ptr = ~tmp & value; return tmp; @} // nand 5027@end smallexample 5028 5029@item @var{type} __sync_add_and_fetch (@var{type} *ptr, @var{type} value, ...) 5030@itemx @var{type} __sync_sub_and_fetch (@var{type} *ptr, @var{type} value, ...) 5031@itemx @var{type} __sync_or_and_fetch (@var{type} *ptr, @var{type} value, ...) 5032@itemx @var{type} __sync_and_and_fetch (@var{type} *ptr, @var{type} value, ...) 5033@itemx @var{type} __sync_xor_and_fetch (@var{type} *ptr, @var{type} value, ...) 5034@itemx @var{type} __sync_nand_and_fetch (@var{type} *ptr, @var{type} value, ...) 5035@findex __sync_add_and_fetch 5036@findex __sync_sub_and_fetch 5037@findex __sync_or_and_fetch 5038@findex __sync_and_and_fetch 5039@findex __sync_xor_and_fetch 5040@findex __sync_nand_and_fetch 5041These builtins perform the operation suggested by the name, and 5042return the new value. That is, 5043 5044@smallexample 5045@{ *ptr @var{op}= value; return *ptr; @} 5046@{ *ptr = ~*ptr & value; return *ptr; @} // nand 5047@end smallexample 5048 5049@item bool __sync_bool_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...) 5050@itemx @var{type} __sync_val_compare_and_swap (@var{type} *ptr, @var{type} oldval @var{type} newval, ...) 5051@findex __sync_bool_compare_and_swap 5052@findex __sync_val_compare_and_swap 5053These builtins perform an atomic compare and swap. That is, if the current 5054value of @code{*@var{ptr}} is @var{oldval}, then write @var{newval} into 5055@code{*@var{ptr}}. 5056 5057The ``bool'' version returns true if the comparison is successful and 5058@var{newval} was written. The ``val'' version returns the contents 5059of @code{*@var{ptr}} before the operation. 5060 5061@item __sync_synchronize (...) 5062@findex __sync_synchronize 5063This builtin issues a full memory barrier. 5064 5065@item @var{type} __sync_lock_test_and_set (@var{type} *ptr, @var{type} value, ...) 5066@findex __sync_lock_test_and_set 5067This builtin, as described by Intel, is not a traditional test-and-set 5068operation, but rather an atomic exchange operation. It writes @var{value} 5069into @code{*@var{ptr}}, and returns the previous contents of 5070@code{*@var{ptr}}. 5071 5072Many targets have only minimal support for such locks, and do not support 5073a full exchange operation. In this case, a target may support reduced 5074functionality here by which the @emph{only} valid value to store is the 5075immediate constant 1. The exact value actually stored in @code{*@var{ptr}} 5076is implementation defined. 5077 5078This builtin is not a full barrier, but rather an @dfn{acquire barrier}. 5079This means that references after the builtin cannot move to (or be 5080speculated to) before the builtin, but previous memory stores may not 5081be globally visible yet, and previous memory loads may not yet be 5082satisfied. 5083 5084@item void __sync_lock_release (@var{type} *ptr, ...) 5085@findex __sync_lock_release 5086This builtin releases the lock acquired by @code{__sync_lock_test_and_set}. 5087Normally this means writing the constant 0 to @code{*@var{ptr}}. 5088 5089This builtin is not a full barrier, but rather a @dfn{release barrier}. 5090This means that all previous memory stores are globally visible, and all 5091previous memory loads have been satisfied, but following memory reads 5092are not prevented from being speculated to before the barrier. 5093@end table 5094 5095@node Object Size Checking 5096@section Object Size Checking Builtins 5097@findex __builtin_object_size 5098@findex __builtin___memcpy_chk 5099@findex __builtin___mempcpy_chk 5100@findex __builtin___memmove_chk 5101@findex __builtin___memset_chk 5102@findex __builtin___strcpy_chk 5103@findex __builtin___stpcpy_chk 5104@findex __builtin___strncpy_chk 5105@findex __builtin___strcat_chk 5106@findex __builtin___strncat_chk 5107@findex __builtin___sprintf_chk 5108@findex __builtin___snprintf_chk 5109@findex __builtin___vsprintf_chk 5110@findex __builtin___vsnprintf_chk 5111@findex __builtin___printf_chk 5112@findex __builtin___vprintf_chk 5113@findex __builtin___fprintf_chk 5114@findex __builtin___vfprintf_chk 5115 5116GCC implements a limited buffer overflow protection mechanism 5117that can prevent some buffer overflow attacks. 5118 5119@deftypefn {Built-in Function} {size_t} __builtin_object_size (void * @var{ptr}, int @var{type}) 5120is a built-in construct that returns a constant number of bytes from 5121@var{ptr} to the end of the object @var{ptr} pointer points to 5122(if known at compile time). @code{__builtin_object_size} never evaluates 5123its arguments for side-effects. If there are any side-effects in them, it 5124returns @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0} 5125for @var{type} 2 or 3. If there are multiple objects @var{ptr} can 5126point to and all of them are known at compile time, the returned number 5127is the maximum of remaining byte counts in those objects if @var{type} & 2 is 51280 and minimum if nonzero. If it is not possible to determine which objects 5129@var{ptr} points to at compile time, @code{__builtin_object_size} should 5130return @code{(size_t) -1} for @var{type} 0 or 1 and @code{(size_t) 0} 5131for @var{type} 2 or 3. 5132 5133@var{type} is an integer constant from 0 to 3. If the least significant 5134bit is clear, objects are whole variables, if it is set, a closest 5135surrounding subobject is considered the object a pointer points to. 5136The second bit determines if maximum or minimum of remaining bytes 5137is computed. 5138 5139@smallexample 5140struct V @{ char buf1[10]; int b; char buf2[10]; @} var; 5141char *p = &var.buf1[1], *q = &var.b; 5142 5143/* Here the object p points to is var. */ 5144assert (__builtin_object_size (p, 0) == sizeof (var) - 1); 5145/* The subobject p points to is var.buf1. */ 5146assert (__builtin_object_size (p, 1) == sizeof (var.buf1) - 1); 5147/* The object q points to is var. */ 5148assert (__builtin_object_size (q, 0) 5149 == (char *) (&var + 1) - (char *) &var.b); 5150/* The subobject q points to is var.b. */ 5151assert (__builtin_object_size (q, 1) == sizeof (var.b)); 5152@end smallexample 5153@end deftypefn 5154 5155There are built-in functions added for many common string operation 5156functions, e.g. for @code{memcpy} @code{__builtin___memcpy_chk} 5157built-in is provided. This built-in has an additional last argument, 5158which is the number of bytes remaining in object the @var{dest} 5159argument points to or @code{(size_t) -1} if the size is not known. 5160 5161The built-in functions are optimized into the normal string functions 5162like @code{memcpy} if the last argument is @code{(size_t) -1} or if 5163it is known at compile time that the destination object will not 5164be overflown. If the compiler can determine at compile time the 5165object will be always overflown, it issues a warning. 5166 5167The intended use can be e.g. 5168 5169@smallexample 5170#undef memcpy 5171#define bos0(dest) __builtin_object_size (dest, 0) 5172#define memcpy(dest, src, n) \ 5173 __builtin___memcpy_chk (dest, src, n, bos0 (dest)) 5174 5175char *volatile p; 5176char buf[10]; 5177/* It is unknown what object p points to, so this is optimized 5178 into plain memcpy - no checking is possible. */ 5179memcpy (p, "abcde", n); 5180/* Destination is known and length too. It is known at compile 5181 time there will be no overflow. */ 5182memcpy (&buf[5], "abcde", 5); 5183/* Destination is known, but the length is not known at compile time. 5184 This will result in __memcpy_chk call that can check for overflow 5185 at runtime. */ 5186memcpy (&buf[5], "abcde", n); 5187/* Destination is known and it is known at compile time there will 5188 be overflow. There will be a warning and __memcpy_chk call that 5189 will abort the program at runtime. */ 5190memcpy (&buf[6], "abcde", 5); 5191@end smallexample 5192 5193Such built-in functions are provided for @code{memcpy}, @code{mempcpy}, 5194@code{memmove}, @code{memset}, @code{strcpy}, @code{stpcpy}, @code{strncpy}, 5195@code{strcat} and @code{strncat}. 5196 5197There are also checking built-in functions for formatted output functions. 5198@smallexample 5199int __builtin___sprintf_chk (char *s, int flag, size_t os, const char *fmt, ...); 5200int __builtin___snprintf_chk (char *s, size_t maxlen, int flag, size_t os, 5201 const char *fmt, ...); 5202int __builtin___vsprintf_chk (char *s, int flag, size_t os, const char *fmt, 5203 va_list ap); 5204int __builtin___vsnprintf_chk (char *s, size_t maxlen, int flag, size_t os, 5205 const char *fmt, va_list ap); 5206@end smallexample 5207 5208The added @var{flag} argument is passed unchanged to @code{__sprintf_chk} 5209etc. functions and can contain implementation specific flags on what 5210additional security measures the checking function might take, such as 5211handling @code{%n} differently. 5212 5213The @var{os} argument is the object size @var{s} points to, like in the 5214other built-in functions. There is a small difference in the behavior 5215though, if @var{os} is @code{(size_t) -1}, the built-in functions are 5216optimized into the non-checking functions only if @var{flag} is 0, otherwise 5217the checking function is called with @var{os} argument set to 5218@code{(size_t) -1}. 5219 5220In addition to this, there are checking built-in functions 5221@code{__builtin___printf_chk}, @code{__builtin___vprintf_chk}, 5222@code{__builtin___fprintf_chk} and @code{__builtin___vfprintf_chk}. 5223These have just one additional argument, @var{flag}, right before 5224format string @var{fmt}. If the compiler is able to optimize them to 5225@code{fputc} etc. functions, it will, otherwise the checking function 5226should be called and the @var{flag} argument passed to it. 5227 5228@node Other Builtins 5229@section Other built-in functions provided by GCC 5230@cindex built-in functions 5231@findex __builtin_isgreater 5232@findex __builtin_isgreaterequal 5233@findex __builtin_isless 5234@findex __builtin_islessequal 5235@findex __builtin_islessgreater 5236@findex __builtin_isunordered 5237@findex __builtin_powi 5238@findex __builtin_powif 5239@findex __builtin_powil 5240@findex _Exit 5241@findex _exit 5242@findex abort 5243@findex abs 5244@findex acos 5245@findex acosf 5246@findex acosh 5247@findex acoshf 5248@findex acoshl 5249@findex acosl 5250@findex alloca 5251@findex asin 5252@findex asinf 5253@findex asinh 5254@findex asinhf 5255@findex asinhl 5256@findex asinl 5257@findex atan 5258@findex atan2 5259@findex atan2f 5260@findex atan2l 5261@findex atanf 5262@findex atanh 5263@findex atanhf 5264@findex atanhl 5265@findex atanl 5266@findex bcmp 5267@findex bzero 5268@findex cabs 5269@findex cabsf 5270@findex cabsl 5271@findex cacos 5272@findex cacosf 5273@findex cacosh 5274@findex cacoshf 5275@findex cacoshl 5276@findex cacosl 5277@findex calloc 5278@findex carg 5279@findex cargf 5280@findex cargl 5281@findex casin 5282@findex casinf 5283@findex casinh 5284@findex casinhf 5285@findex casinhl 5286@findex casinl 5287@findex catan 5288@findex catanf 5289@findex catanh 5290@findex catanhf 5291@findex catanhl 5292@findex catanl 5293@findex cbrt 5294@findex cbrtf 5295@findex cbrtl 5296@findex ccos 5297@findex ccosf 5298@findex ccosh 5299@findex ccoshf 5300@findex ccoshl 5301@findex ccosl 5302@findex ceil 5303@findex ceilf 5304@findex ceill 5305@findex cexp 5306@findex cexpf 5307@findex cexpl 5308@findex cimag 5309@findex cimagf 5310@findex cimagl 5311@findex clog 5312@findex clogf 5313@findex clogl 5314@findex conj 5315@findex conjf 5316@findex conjl 5317@findex copysign 5318@findex copysignf 5319@findex copysignl 5320@findex cos 5321@findex cosf 5322@findex cosh 5323@findex coshf 5324@findex coshl 5325@findex cosl 5326@findex cpow 5327@findex cpowf 5328@findex cpowl 5329@findex cproj 5330@findex cprojf 5331@findex cprojl 5332@findex creal 5333@findex crealf 5334@findex creall 5335@findex csin 5336@findex csinf 5337@findex csinh 5338@findex csinhf 5339@findex csinhl 5340@findex csinl 5341@findex csqrt 5342@findex csqrtf 5343@findex csqrtl 5344@findex ctan 5345@findex ctanf 5346@findex ctanh 5347@findex ctanhf 5348@findex ctanhl 5349@findex ctanl 5350@findex dcgettext 5351@findex dgettext 5352@findex drem 5353@findex dremf 5354@findex dreml 5355@findex erf 5356@findex erfc 5357@findex erfcf 5358@findex erfcl 5359@findex erff 5360@findex erfl 5361@findex exit 5362@findex exp 5363@findex exp10 5364@findex exp10f 5365@findex exp10l 5366@findex exp2 5367@findex exp2f 5368@findex exp2l 5369@findex expf 5370@findex expl 5371@findex expm1 5372@findex expm1f 5373@findex expm1l 5374@findex fabs 5375@findex fabsf 5376@findex fabsl 5377@findex fdim 5378@findex fdimf 5379@findex fdiml 5380@findex ffs 5381@findex floor 5382@findex floorf 5383@findex floorl 5384@findex fma 5385@findex fmaf 5386@findex fmal 5387@findex fmax 5388@findex fmaxf 5389@findex fmaxl 5390@findex fmin 5391@findex fminf 5392@findex fminl 5393@findex fmod 5394@findex fmodf 5395@findex fmodl 5396@findex fprintf 5397@findex fprintf_unlocked 5398@findex fputs 5399@findex fputs_unlocked 5400@findex frexp 5401@findex frexpf 5402@findex frexpl 5403@findex fscanf 5404@findex gamma 5405@findex gammaf 5406@findex gammal 5407@findex gettext 5408@findex hypot 5409@findex hypotf 5410@findex hypotl 5411@findex ilogb 5412@findex ilogbf 5413@findex ilogbl 5414@findex imaxabs 5415@findex index 5416@findex isalnum 5417@findex isalpha 5418@findex isascii 5419@findex isblank 5420@findex iscntrl 5421@findex isdigit 5422@findex isgraph 5423@findex islower 5424@findex isprint 5425@findex ispunct 5426@findex isspace 5427@findex isupper 5428@findex iswalnum 5429@findex iswalpha 5430@findex iswblank 5431@findex iswcntrl 5432@findex iswdigit 5433@findex iswgraph 5434@findex iswlower 5435@findex iswprint 5436@findex iswpunct 5437@findex iswspace 5438@findex iswupper 5439@findex iswxdigit 5440@findex isxdigit 5441@findex j0 5442@findex j0f 5443@findex j0l 5444@findex j1 5445@findex j1f 5446@findex j1l 5447@findex jn 5448@findex jnf 5449@findex jnl 5450@findex labs 5451@findex ldexp 5452@findex ldexpf 5453@findex ldexpl 5454@findex lgamma 5455@findex lgammaf 5456@findex lgammal 5457@findex llabs 5458@findex llrint 5459@findex llrintf 5460@findex llrintl 5461@findex llround 5462@findex llroundf 5463@findex llroundl 5464@findex log 5465@findex log10 5466@findex log10f 5467@findex log10l 5468@findex log1p 5469@findex log1pf 5470@findex log1pl 5471@findex log2 5472@findex log2f 5473@findex log2l 5474@findex logb 5475@findex logbf 5476@findex logbl 5477@findex logf 5478@findex logl 5479@findex lrint 5480@findex lrintf 5481@findex lrintl 5482@findex lround 5483@findex lroundf 5484@findex lroundl 5485@findex malloc 5486@findex memcmp 5487@findex memcpy 5488@findex mempcpy 5489@findex memset 5490@findex modf 5491@findex modff 5492@findex modfl 5493@findex nearbyint 5494@findex nearbyintf 5495@findex nearbyintl 5496@findex nextafter 5497@findex nextafterf 5498@findex nextafterl 5499@findex nexttoward 5500@findex nexttowardf 5501@findex nexttowardl 5502@findex pow 5503@findex pow10 5504@findex pow10f 5505@findex pow10l 5506@findex powf 5507@findex powl 5508@findex printf 5509@findex printf_unlocked 5510@findex putchar 5511@findex puts 5512@findex remainder 5513@findex remainderf 5514@findex remainderl 5515@findex remquo 5516@findex remquof 5517@findex remquol 5518@findex rindex 5519@findex rint 5520@findex rintf 5521@findex rintl 5522@findex round 5523@findex roundf 5524@findex roundl 5525@findex scalb 5526@findex scalbf 5527@findex scalbl 5528@findex scalbln 5529@findex scalblnf 5530@findex scalblnf 5531@findex scalbn 5532@findex scalbnf 5533@findex scanfnl 5534@findex signbit 5535@findex signbitf 5536@findex signbitl 5537@findex significand 5538@findex significandf 5539@findex significandl 5540@findex sin 5541@findex sincos 5542@findex sincosf 5543@findex sincosl 5544@findex sinf 5545@findex sinh 5546@findex sinhf 5547@findex sinhl 5548@findex sinl 5549@findex snprintf 5550@findex sprintf 5551@findex sqrt 5552@findex sqrtf 5553@findex sqrtl 5554@findex sscanf 5555@findex stpcpy 5556@findex stpncpy 5557@findex strcasecmp 5558@findex strcat 5559@findex strchr 5560@findex strcmp 5561@findex strcpy 5562@findex strcspn 5563@findex strdup 5564@findex strfmon 5565@findex strftime 5566@findex strlen 5567@findex strncasecmp 5568@findex strncat 5569@findex strncmp 5570@findex strncpy 5571@findex strndup 5572@findex strpbrk 5573@findex strrchr 5574@findex strspn 5575@findex strstr 5576@findex tan 5577@findex tanf 5578@findex tanh 5579@findex tanhf 5580@findex tanhl 5581@findex tanl 5582@findex tgamma 5583@findex tgammaf 5584@findex tgammal 5585@findex toascii 5586@findex tolower 5587@findex toupper 5588@findex towlower 5589@findex towupper 5590@findex trunc 5591@findex truncf 5592@findex truncl 5593@findex vfprintf 5594@findex vfscanf 5595@findex vprintf 5596@findex vscanf 5597@findex vsnprintf 5598@findex vsprintf 5599@findex vsscanf 5600@findex y0 5601@findex y0f 5602@findex y0l 5603@findex y1 5604@findex y1f 5605@findex y1l 5606@findex yn 5607@findex ynf 5608@findex ynl 5609 5610GCC provides a large number of built-in functions other than the ones 5611mentioned above. Some of these are for internal use in the processing 5612of exceptions or variable-length argument lists and will not be 5613documented here because they may change from time to time; we do not 5614recommend general use of these functions. 5615 5616The remaining functions are provided for optimization purposes. 5617 5618@opindex fno-builtin 5619GCC includes built-in versions of many of the functions in the standard 5620C library. The versions prefixed with @code{__builtin_} will always be 5621treated as having the same meaning as the C library function even if you 5622specify the @option{-fno-builtin} option. (@pxref{C Dialect Options}) 5623Many of these functions are only optimized in certain cases; if they are 5624not optimized in a particular case, a call to the library function will 5625be emitted. 5626 5627@opindex ansi 5628@opindex std 5629Outside strict ISO C mode (@option{-ansi}, @option{-std=c89} or 5630@option{-std=c99}), the functions 5631@code{_exit}, @code{alloca}, @code{bcmp}, @code{bzero}, 5632@code{dcgettext}, @code{dgettext}, @code{dremf}, @code{dreml}, 5633@code{drem}, @code{exp10f}, @code{exp10l}, @code{exp10}, @code{ffsll}, 5634@code{ffsl}, @code{ffs}, @code{fprintf_unlocked}, @code{fputs_unlocked}, 5635@code{gammaf}, @code{gammal}, @code{gamma}, @code{gettext}, 5636@code{index}, @code{isascii}, @code{j0f}, @code{j0l}, @code{j0}, 5637@code{j1f}, @code{j1l}, @code{j1}, @code{jnf}, @code{jnl}, @code{jn}, 5638@code{mempcpy}, @code{pow10f}, @code{pow10l}, @code{pow10}, 5639@code{printf_unlocked}, @code{rindex}, @code{scalbf}, @code{scalbl}, 5640@code{scalb}, @code{signbit}, @code{signbitf}, @code{signbitl}, 5641@code{significandf}, @code{significandl}, @code{significand}, 5642@code{sincosf}, @code{sincosl}, @code{sincos}, @code{stpcpy}, 5643@code{stpncpy}, @code{strcasecmp}, @code{strdup}, @code{strfmon}, 5644@code{strncasecmp}, @code{strndup}, @code{toascii}, @code{y0f}, 5645@code{y0l}, @code{y0}, @code{y1f}, @code{y1l}, @code{y1}, @code{ynf}, 5646@code{ynl} and @code{yn} 5647may be handled as built-in functions. 5648All these functions have corresponding versions 5649prefixed with @code{__builtin_}, which may be used even in strict C89 5650mode. 5651 5652The ISO C99 functions 5653@code{_Exit}, @code{acoshf}, @code{acoshl}, @code{acosh}, @code{asinhf}, 5654@code{asinhl}, @code{asinh}, @code{atanhf}, @code{atanhl}, @code{atanh}, 5655@code{cabsf}, @code{cabsl}, @code{cabs}, @code{cacosf}, @code{cacoshf}, 5656@code{cacoshl}, @code{cacosh}, @code{cacosl}, @code{cacos}, 5657@code{cargf}, @code{cargl}, @code{carg}, @code{casinf}, @code{casinhf}, 5658@code{casinhl}, @code{casinh}, @code{casinl}, @code{casin}, 5659@code{catanf}, @code{catanhf}, @code{catanhl}, @code{catanh}, 5660@code{catanl}, @code{catan}, @code{cbrtf}, @code{cbrtl}, @code{cbrt}, 5661@code{ccosf}, @code{ccoshf}, @code{ccoshl}, @code{ccosh}, @code{ccosl}, 5662@code{ccos}, @code{cexpf}, @code{cexpl}, @code{cexp}, @code{cimagf}, 5663@code{cimagl}, @code{cimag}, @code{clogf}, @code{clogl}, @code{clog}, 5664@code{conjf}, @code{conjl}, @code{conj}, @code{copysignf}, @code{copysignl}, 5665@code{copysign}, @code{cpowf}, @code{cpowl}, @code{cpow}, @code{cprojf}, 5666@code{cprojl}, @code{cproj}, @code{crealf}, @code{creall}, @code{creal}, 5667@code{csinf}, @code{csinhf}, @code{csinhl}, @code{csinh}, @code{csinl}, 5668@code{csin}, @code{csqrtf}, @code{csqrtl}, @code{csqrt}, @code{ctanf}, 5669@code{ctanhf}, @code{ctanhl}, @code{ctanh}, @code{ctanl}, @code{ctan}, 5670@code{erfcf}, @code{erfcl}, @code{erfc}, @code{erff}, @code{erfl}, 5671@code{erf}, @code{exp2f}, @code{exp2l}, @code{exp2}, @code{expm1f}, 5672@code{expm1l}, @code{expm1}, @code{fdimf}, @code{fdiml}, @code{fdim}, 5673@code{fmaf}, @code{fmal}, @code{fmaxf}, @code{fmaxl}, @code{fmax}, 5674@code{fma}, @code{fminf}, @code{fminl}, @code{fmin}, @code{hypotf}, 5675@code{hypotl}, @code{hypot}, @code{ilogbf}, @code{ilogbl}, @code{ilogb}, 5676@code{imaxabs}, @code{isblank}, @code{iswblank}, @code{lgammaf}, 5677@code{lgammal}, @code{lgamma}, @code{llabs}, @code{llrintf}, @code{llrintl}, 5678@code{llrint}, @code{llroundf}, @code{llroundl}, @code{llround}, 5679@code{log1pf}, @code{log1pl}, @code{log1p}, @code{log2f}, @code{log2l}, 5680@code{log2}, @code{logbf}, @code{logbl}, @code{logb}, @code{lrintf}, 5681@code{lrintl}, @code{lrint}, @code{lroundf}, @code{lroundl}, 5682@code{lround}, @code{nearbyintf}, @code{nearbyintl}, @code{nearbyint}, 5683@code{nextafterf}, @code{nextafterl}, @code{nextafter}, 5684@code{nexttowardf}, @code{nexttowardl}, @code{nexttoward}, 5685@code{remainderf}, @code{remainderl}, @code{remainder}, @code{remquof}, 5686@code{remquol}, @code{remquo}, @code{rintf}, @code{rintl}, @code{rint}, 5687@code{roundf}, @code{roundl}, @code{round}, @code{scalblnf}, 5688@code{scalblnl}, @code{scalbln}, @code{scalbnf}, @code{scalbnl}, 5689@code{scalbn}, @code{snprintf}, @code{tgammaf}, @code{tgammal}, 5690@code{tgamma}, @code{truncf}, @code{truncl}, @code{trunc}, 5691@code{vfscanf}, @code{vscanf}, @code{vsnprintf} and @code{vsscanf} 5692are handled as built-in functions 5693except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}). 5694 5695There are also built-in versions of the ISO C99 functions 5696@code{acosf}, @code{acosl}, @code{asinf}, @code{asinl}, @code{atan2f}, 5697@code{atan2l}, @code{atanf}, @code{atanl}, @code{ceilf}, @code{ceill}, 5698@code{cosf}, @code{coshf}, @code{coshl}, @code{cosl}, @code{expf}, 5699@code{expl}, @code{fabsf}, @code{fabsl}, @code{floorf}, @code{floorl}, 5700@code{fmodf}, @code{fmodl}, @code{frexpf}, @code{frexpl}, @code{ldexpf}, 5701@code{ldexpl}, @code{log10f}, @code{log10l}, @code{logf}, @code{logl}, 5702@code{modfl}, @code{modf}, @code{powf}, @code{powl}, @code{sinf}, 5703@code{sinhf}, @code{sinhl}, @code{sinl}, @code{sqrtf}, @code{sqrtl}, 5704@code{tanf}, @code{tanhf}, @code{tanhl} and @code{tanl} 5705that are recognized in any mode since ISO C90 reserves these names for 5706the purpose to which ISO C99 puts them. All these functions have 5707corresponding versions prefixed with @code{__builtin_}. 5708 5709The ISO C94 functions 5710@code{iswalnum}, @code{iswalpha}, @code{iswcntrl}, @code{iswdigit}, 5711@code{iswgraph}, @code{iswlower}, @code{iswprint}, @code{iswpunct}, 5712@code{iswspace}, @code{iswupper}, @code{iswxdigit}, @code{towlower} and 5713@code{towupper} 5714are handled as built-in functions 5715except in strict ISO C90 mode (@option{-ansi} or @option{-std=c89}). 5716 5717The ISO C90 functions 5718@code{abort}, @code{abs}, @code{acos}, @code{asin}, @code{atan2}, 5719@code{atan}, @code{calloc}, @code{ceil}, @code{cosh}, @code{cos}, 5720@code{exit}, @code{exp}, @code{fabs}, @code{floor}, @code{fmod}, 5721@code{fprintf}, @code{fputs}, @code{frexp}, @code{fscanf}, 5722@code{isalnum}, @code{isalpha}, @code{iscntrl}, @code{isdigit}, 5723@code{isgraph}, @code{islower}, @code{isprint}, @code{ispunct}, 5724@code{isspace}, @code{isupper}, @code{isxdigit}, @code{tolower}, 5725@code{toupper}, @code{labs}, @code{ldexp}, @code{log10}, @code{log}, 5726@code{malloc}, @code{memcmp}, @code{memcpy}, @code{memset}, @code{modf}, 5727@code{pow}, @code{printf}, @code{putchar}, @code{puts}, @code{scanf}, 5728@code{sinh}, @code{sin}, @code{snprintf}, @code{sprintf}, @code{sqrt}, 5729@code{sscanf}, @code{strcat}, @code{strchr}, @code{strcmp}, 5730@code{strcpy}, @code{strcspn}, @code{strlen}, @code{strncat}, 5731@code{strncmp}, @code{strncpy}, @code{strpbrk}, @code{strrchr}, 5732@code{strspn}, @code{strstr}, @code{tanh}, @code{tan}, @code{vfprintf}, 5733@code{vprintf} and @code{vsprintf} 5734are all recognized as built-in functions unless 5735@option{-fno-builtin} is specified (or @option{-fno-builtin-@var{function}} 5736is specified for an individual function). All of these functions have 5737corresponding versions prefixed with @code{__builtin_}. 5738 5739GCC provides built-in versions of the ISO C99 floating point comparison 5740macros that avoid raising exceptions for unordered operands. They have 5741the same names as the standard macros ( @code{isgreater}, 5742@code{isgreaterequal}, @code{isless}, @code{islessequal}, 5743@code{islessgreater}, and @code{isunordered}) , with @code{__builtin_} 5744prefixed. We intend for a library implementor to be able to simply 5745@code{#define} each standard macro to its built-in equivalent. 5746 5747@deftypefn {Built-in Function} int __builtin_types_compatible_p (@var{type1}, @var{type2}) 5748 5749You can use the built-in function @code{__builtin_types_compatible_p} to 5750determine whether two types are the same. 5751 5752This built-in function returns 1 if the unqualified versions of the 5753types @var{type1} and @var{type2} (which are types, not expressions) are 5754compatible, 0 otherwise. The result of this built-in function can be 5755used in integer constant expressions. 5756 5757This built-in function ignores top level qualifiers (e.g., @code{const}, 5758@code{volatile}). For example, @code{int} is equivalent to @code{const 5759int}. 5760 5761The type @code{int[]} and @code{int[5]} are compatible. On the other 5762hand, @code{int} and @code{char *} are not compatible, even if the size 5763of their types, on the particular architecture are the same. Also, the 5764amount of pointer indirection is taken into account when determining 5765similarity. Consequently, @code{short *} is not similar to 5766@code{short **}. Furthermore, two types that are typedefed are 5767considered compatible if their underlying types are compatible. 5768 5769An @code{enum} type is not considered to be compatible with another 5770@code{enum} type even if both are compatible with the same integer 5771type; this is what the C standard specifies. 5772For example, @code{enum @{foo, bar@}} is not similar to 5773@code{enum @{hot, dog@}}. 5774 5775You would typically use this function in code whose execution varies 5776depending on the arguments' types. For example: 5777 5778@smallexample 5779#define foo(x) \ 5780 (@{ \ 5781 typeof (x) tmp = (x); \ 5782 if (__builtin_types_compatible_p (typeof (x), long double)) \ 5783 tmp = foo_long_double (tmp); \ 5784 else if (__builtin_types_compatible_p (typeof (x), double)) \ 5785 tmp = foo_double (tmp); \ 5786 else if (__builtin_types_compatible_p (typeof (x), float)) \ 5787 tmp = foo_float (tmp); \ 5788 else \ 5789 abort (); \ 5790 tmp; \ 5791 @}) 5792@end smallexample 5793 5794@emph{Note:} This construct is only available for C@. 5795 5796@end deftypefn 5797 5798@deftypefn {Built-in Function} @var{type} __builtin_choose_expr (@var{const_exp}, @var{exp1}, @var{exp2}) 5799 5800You can use the built-in function @code{__builtin_choose_expr} to 5801evaluate code depending on the value of a constant expression. This 5802built-in function returns @var{exp1} if @var{const_exp}, which is a 5803constant expression that must be able to be determined at compile time, 5804is nonzero. Otherwise it returns 0. 5805 5806This built-in function is analogous to the @samp{? :} operator in C, 5807except that the expression returned has its type unaltered by promotion 5808rules. Also, the built-in function does not evaluate the expression 5809that was not chosen. For example, if @var{const_exp} evaluates to true, 5810@var{exp2} is not evaluated even if it has side-effects. 5811 5812This built-in function can return an lvalue if the chosen argument is an 5813lvalue. 5814 5815If @var{exp1} is returned, the return type is the same as @var{exp1}'s 5816type. Similarly, if @var{exp2} is returned, its return type is the same 5817as @var{exp2}. 5818 5819Example: 5820 5821@smallexample 5822#define foo(x) \ 5823 __builtin_choose_expr ( \ 5824 __builtin_types_compatible_p (typeof (x), double), \ 5825 foo_double (x), \ 5826 __builtin_choose_expr ( \ 5827 __builtin_types_compatible_p (typeof (x), float), \ 5828 foo_float (x), \ 5829 /* @r{The void expression results in a compile-time error} \ 5830 @r{when assigning the result to something.} */ \ 5831 (void)0)) 5832@end smallexample 5833 5834@emph{Note:} This construct is only available for C@. Furthermore, the 5835unused expression (@var{exp1} or @var{exp2} depending on the value of 5836@var{const_exp}) may still generate syntax errors. This may change in 5837future revisions. 5838 5839@end deftypefn 5840 5841@deftypefn {Built-in Function} int __builtin_constant_p (@var{exp}) 5842You can use the built-in function @code{__builtin_constant_p} to 5843determine if a value is known to be constant at compile-time and hence 5844that GCC can perform constant-folding on expressions involving that 5845value. The argument of the function is the value to test. The function 5846returns the integer 1 if the argument is known to be a compile-time 5847constant and 0 if it is not known to be a compile-time constant. A 5848return of 0 does not indicate that the value is @emph{not} a constant, 5849but merely that GCC cannot prove it is a constant with the specified 5850value of the @option{-O} option. 5851 5852You would typically use this function in an embedded application where 5853memory was a critical resource. If you have some complex calculation, 5854you may want it to be folded if it involves constants, but need to call 5855a function if it does not. For example: 5856 5857@smallexample 5858#define Scale_Value(X) \ 5859 (__builtin_constant_p (X) \ 5860 ? ((X) * SCALE + OFFSET) : Scale (X)) 5861@end smallexample 5862 5863You may use this built-in function in either a macro or an inline 5864function. However, if you use it in an inlined function and pass an 5865argument of the function as the argument to the built-in, GCC will 5866never return 1 when you call the inline function with a string constant 5867or compound literal (@pxref{Compound Literals}) and will not return 1 5868when you pass a constant numeric value to the inline function unless you 5869specify the @option{-O} option. 5870 5871You may also use @code{__builtin_constant_p} in initializers for static 5872data. For instance, you can write 5873 5874@smallexample 5875static const int table[] = @{ 5876 __builtin_constant_p (EXPRESSION) ? (EXPRESSION) : -1, 5877 /* @r{@dots{}} */ 5878@}; 5879@end smallexample 5880 5881@noindent 5882This is an acceptable initializer even if @var{EXPRESSION} is not a 5883constant expression. GCC must be more conservative about evaluating the 5884built-in in this case, because it has no opportunity to perform 5885optimization. 5886 5887Previous versions of GCC did not accept this built-in in data 5888initializers. The earliest version where it is completely safe is 58893.0.1. 5890@end deftypefn 5891 5892@deftypefn {Built-in Function} long __builtin_expect (long @var{exp}, long @var{c}) 5893@opindex fprofile-arcs 5894You may use @code{__builtin_expect} to provide the compiler with 5895branch prediction information. In general, you should prefer to 5896use actual profile feedback for this (@option{-fprofile-arcs}), as 5897programmers are notoriously bad at predicting how their programs 5898actually perform. However, there are applications in which this 5899data is hard to collect. 5900 5901The return value is the value of @var{exp}, which should be an 5902integral expression. The value of @var{c} must be a compile-time 5903constant. The semantics of the built-in are that it is expected 5904that @var{exp} == @var{c}. For example: 5905 5906@smallexample 5907if (__builtin_expect (x, 0)) 5908 foo (); 5909@end smallexample 5910 5911@noindent 5912would indicate that we do not expect to call @code{foo}, since 5913we expect @code{x} to be zero. Since you are limited to integral 5914expressions for @var{exp}, you should use constructions such as 5915 5916@smallexample 5917if (__builtin_expect (ptr != NULL, 1)) 5918 error (); 5919@end smallexample 5920 5921@noindent 5922when testing pointer or floating-point values. 5923@end deftypefn 5924 5925@deftypefn {Built-in Function} void __builtin_prefetch (const void *@var{addr}, ...) 5926This function is used to minimize cache-miss latency by moving data into 5927a cache before it is accessed. 5928You can insert calls to @code{__builtin_prefetch} into code for which 5929you know addresses of data in memory that is likely to be accessed soon. 5930If the target supports them, data prefetch instructions will be generated. 5931If the prefetch is done early enough before the access then the data will 5932be in the cache by the time it is accessed. 5933 5934The value of @var{addr} is the address of the memory to prefetch. 5935There are two optional arguments, @var{rw} and @var{locality}. 5936The value of @var{rw} is a compile-time constant one or zero; one 5937means that the prefetch is preparing for a write to the memory address 5938and zero, the default, means that the prefetch is preparing for a read. 5939The value @var{locality} must be a compile-time constant integer between 5940zero and three. A value of zero means that the data has no temporal 5941locality, so it need not be left in the cache after the access. A value 5942of three means that the data has a high degree of temporal locality and 5943should be left in all levels of cache possible. Values of one and two 5944mean, respectively, a low or moderate degree of temporal locality. The 5945default is three. 5946 5947@smallexample 5948for (i = 0; i < n; i++) 5949 @{ 5950 a[i] = a[i] + b[i]; 5951 __builtin_prefetch (&a[i+j], 1, 1); 5952 __builtin_prefetch (&b[i+j], 0, 1); 5953 /* @r{@dots{}} */ 5954 @} 5955@end smallexample 5956 5957Data prefetch does not generate faults if @var{addr} is invalid, but 5958the address expression itself must be valid. For example, a prefetch 5959of @code{p->next} will not fault if @code{p->next} is not a valid 5960address, but evaluation will fault if @code{p} is not a valid address. 5961 5962If the target does not support data prefetch, the address expression 5963is evaluated if it includes side effects but no other code is generated 5964and GCC does not issue a warning. 5965@end deftypefn 5966 5967@deftypefn {Built-in Function} double __builtin_huge_val (void) 5968Returns a positive infinity, if supported by the floating-point format, 5969else @code{DBL_MAX}. This function is suitable for implementing the 5970ISO C macro @code{HUGE_VAL}. 5971@end deftypefn 5972 5973@deftypefn {Built-in Function} float __builtin_huge_valf (void) 5974Similar to @code{__builtin_huge_val}, except the return type is @code{float}. 5975@end deftypefn 5976 5977@deftypefn {Built-in Function} {long double} __builtin_huge_vall (void) 5978Similar to @code{__builtin_huge_val}, except the return 5979type is @code{long double}. 5980@end deftypefn 5981 5982@deftypefn {Built-in Function} double __builtin_inf (void) 5983Similar to @code{__builtin_huge_val}, except a warning is generated 5984if the target floating-point format does not support infinities. 5985@end deftypefn 5986 5987@deftypefn {Built-in Function} _Decimal32 __builtin_infd32 (void) 5988Similar to @code{__builtin_inf}, except the return type is @code{_Decimal32}. 5989@end deftypefn 5990 5991@deftypefn {Built-in Function} _Decimal64 __builtin_infd64 (void) 5992Similar to @code{__builtin_inf}, except the return type is @code{_Decimal64}. 5993@end deftypefn 5994 5995@deftypefn {Built-in Function} _Decimal128 __builtin_infd128 (void) 5996Similar to @code{__builtin_inf}, except the return type is @code{_Decimal128}. 5997@end deftypefn 5998 5999@deftypefn {Built-in Function} float __builtin_inff (void) 6000Similar to @code{__builtin_inf}, except the return type is @code{float}. 6001This function is suitable for implementing the ISO C99 macro @code{INFINITY}. 6002@end deftypefn 6003 6004@deftypefn {Built-in Function} {long double} __builtin_infl (void) 6005Similar to @code{__builtin_inf}, except the return 6006type is @code{long double}. 6007@end deftypefn 6008 6009@deftypefn {Built-in Function} double __builtin_nan (const char *str) 6010This is an implementation of the ISO C99 function @code{nan}. 6011 6012Since ISO C99 defines this function in terms of @code{strtod}, which we 6013do not implement, a description of the parsing is in order. The string 6014is parsed as by @code{strtol}; that is, the base is recognized by 6015leading @samp{0} or @samp{0x} prefixes. The number parsed is placed 6016in the significand such that the least significant bit of the number 6017is at the least significant bit of the significand. The number is 6018truncated to fit the significand field provided. The significand is 6019forced to be a quiet NaN@. 6020 6021This function, if given a string literal all of which would have been 6022consumed by strtol, is evaluated early enough that it is considered a 6023compile-time constant. 6024@end deftypefn 6025 6026@deftypefn {Built-in Function} _Decimal32 __builtin_nand32 (const char *str) 6027Similar to @code{__builtin_nan}, except the return type is @code{_Decimal32}. 6028@end deftypefn 6029 6030@deftypefn {Built-in Function} _Decimal64 __builtin_nand64 (const char *str) 6031Similar to @code{__builtin_nan}, except the return type is @code{_Decimal64}. 6032@end deftypefn 6033 6034@deftypefn {Built-in Function} _Decimal128 __builtin_nand128 (const char *str) 6035Similar to @code{__builtin_nan}, except the return type is @code{_Decimal128}. 6036@end deftypefn 6037 6038@deftypefn {Built-in Function} float __builtin_nanf (const char *str) 6039Similar to @code{__builtin_nan}, except the return type is @code{float}. 6040@end deftypefn 6041 6042@deftypefn {Built-in Function} {long double} __builtin_nanl (const char *str) 6043Similar to @code{__builtin_nan}, except the return type is @code{long double}. 6044@end deftypefn 6045 6046@deftypefn {Built-in Function} double __builtin_nans (const char *str) 6047Similar to @code{__builtin_nan}, except the significand is forced 6048to be a signaling NaN@. The @code{nans} function is proposed by 6049@uref{http://www.open-std.org/jtc1/sc22/wg14/www/docs/n965.htm,,WG14 N965}. 6050@end deftypefn 6051 6052@deftypefn {Built-in Function} float __builtin_nansf (const char *str) 6053Similar to @code{__builtin_nans}, except the return type is @code{float}. 6054@end deftypefn 6055 6056@deftypefn {Built-in Function} {long double} __builtin_nansl (const char *str) 6057Similar to @code{__builtin_nans}, except the return type is @code{long double}. 6058@end deftypefn 6059 6060@deftypefn {Built-in Function} int __builtin_ffs (unsigned int x) 6061Returns one plus the index of the least significant 1-bit of @var{x}, or 6062if @var{x} is zero, returns zero. 6063@end deftypefn 6064 6065@deftypefn {Built-in Function} int __builtin_clz (unsigned int x) 6066Returns the number of leading 0-bits in @var{x}, starting at the most 6067significant bit position. If @var{x} is 0, the result is undefined. 6068@end deftypefn 6069 6070@deftypefn {Built-in Function} int __builtin_ctz (unsigned int x) 6071Returns the number of trailing 0-bits in @var{x}, starting at the least 6072significant bit position. If @var{x} is 0, the result is undefined. 6073@end deftypefn 6074 6075@deftypefn {Built-in Function} int __builtin_popcount (unsigned int x) 6076Returns the number of 1-bits in @var{x}. 6077@end deftypefn 6078 6079@deftypefn {Built-in Function} int __builtin_parity (unsigned int x) 6080Returns the parity of @var{x}, i.e.@: the number of 1-bits in @var{x} 6081modulo 2. 6082@end deftypefn 6083 6084@deftypefn {Built-in Function} int __builtin_ffsl (unsigned long) 6085Similar to @code{__builtin_ffs}, except the argument type is 6086@code{unsigned long}. 6087@end deftypefn 6088 6089@deftypefn {Built-in Function} int __builtin_clzl (unsigned long) 6090Similar to @code{__builtin_clz}, except the argument type is 6091@code{unsigned long}. 6092@end deftypefn 6093 6094@deftypefn {Built-in Function} int __builtin_ctzl (unsigned long) 6095Similar to @code{__builtin_ctz}, except the argument type is 6096@code{unsigned long}. 6097@end deftypefn 6098 6099@deftypefn {Built-in Function} int __builtin_popcountl (unsigned long) 6100Similar to @code{__builtin_popcount}, except the argument type is 6101@code{unsigned long}. 6102@end deftypefn 6103 6104@deftypefn {Built-in Function} int __builtin_parityl (unsigned long) 6105Similar to @code{__builtin_parity}, except the argument type is 6106@code{unsigned long}. 6107@end deftypefn 6108 6109@deftypefn {Built-in Function} int __builtin_ffsll (unsigned long long) 6110Similar to @code{__builtin_ffs}, except the argument type is 6111@code{unsigned long long}. 6112@end deftypefn 6113 6114@deftypefn {Built-in Function} int __builtin_clzll (unsigned long long) 6115Similar to @code{__builtin_clz}, except the argument type is 6116@code{unsigned long long}. 6117@end deftypefn 6118 6119@deftypefn {Built-in Function} int __builtin_ctzll (unsigned long long) 6120Similar to @code{__builtin_ctz}, except the argument type is 6121@code{unsigned long long}. 6122@end deftypefn 6123 6124@deftypefn {Built-in Function} int __builtin_popcountll (unsigned long long) 6125Similar to @code{__builtin_popcount}, except the argument type is 6126@code{unsigned long long}. 6127@end deftypefn 6128 6129@deftypefn {Built-in Function} int __builtin_parityll (unsigned long long) 6130Similar to @code{__builtin_parity}, except the argument type is 6131@code{unsigned long long}. 6132@end deftypefn 6133 6134@deftypefn {Built-in Function} double __builtin_powi (double, int) 6135Returns the first argument raised to the power of the second. Unlike the 6136@code{pow} function no guarantees about precision and rounding are made. 6137@end deftypefn 6138 6139@deftypefn {Built-in Function} float __builtin_powif (float, int) 6140Similar to @code{__builtin_powi}, except the argument and return types 6141are @code{float}. 6142@end deftypefn 6143 6144@deftypefn {Built-in Function} {long double} __builtin_powil (long double, int) 6145Similar to @code{__builtin_powi}, except the argument and return types 6146are @code{long double}. 6147@end deftypefn 6148 6149 6150@node Target Builtins 6151@section Built-in Functions Specific to Particular Target Machines 6152 6153On some target machines, GCC supports many built-in functions specific 6154to those machines. Generally these generate calls to specific machine 6155instructions, but allow the compiler to schedule those calls. 6156 6157@menu 6158* Alpha Built-in Functions:: 6159* ARM Built-in Functions:: 6160* Blackfin Built-in Functions:: 6161* FR-V Built-in Functions:: 6162* X86 Built-in Functions:: 6163* MIPS DSP Built-in Functions:: 6164* MIPS Paired-Single Support:: 6165* PowerPC AltiVec Built-in Functions:: 6166* SPARC VIS Built-in Functions:: 6167@end menu 6168 6169@node Alpha Built-in Functions 6170@subsection Alpha Built-in Functions 6171 6172These built-in functions are available for the Alpha family of 6173processors, depending on the command-line switches used. 6174 6175The following built-in functions are always available. They 6176all generate the machine instruction that is part of the name. 6177 6178@smallexample 6179long __builtin_alpha_implver (void) 6180long __builtin_alpha_rpcc (void) 6181long __builtin_alpha_amask (long) 6182long __builtin_alpha_cmpbge (long, long) 6183long __builtin_alpha_extbl (long, long) 6184long __builtin_alpha_extwl (long, long) 6185long __builtin_alpha_extll (long, long) 6186long __builtin_alpha_extql (long, long) 6187long __builtin_alpha_extwh (long, long) 6188long __builtin_alpha_extlh (long, long) 6189long __builtin_alpha_extqh (long, long) 6190long __builtin_alpha_insbl (long, long) 6191long __builtin_alpha_inswl (long, long) 6192long __builtin_alpha_insll (long, long) 6193long __builtin_alpha_insql (long, long) 6194long __builtin_alpha_inswh (long, long) 6195long __builtin_alpha_inslh (long, long) 6196long __builtin_alpha_insqh (long, long) 6197long __builtin_alpha_mskbl (long, long) 6198long __builtin_alpha_mskwl (long, long) 6199long __builtin_alpha_mskll (long, long) 6200long __builtin_alpha_mskql (long, long) 6201long __builtin_alpha_mskwh (long, long) 6202long __builtin_alpha_msklh (long, long) 6203long __builtin_alpha_mskqh (long, long) 6204long __builtin_alpha_umulh (long, long) 6205long __builtin_alpha_zap (long, long) 6206long __builtin_alpha_zapnot (long, long) 6207@end smallexample 6208 6209The following built-in functions are always with @option{-mmax} 6210or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{pca56} or 6211later. They all generate the machine instruction that is part 6212of the name. 6213 6214@smallexample 6215long __builtin_alpha_pklb (long) 6216long __builtin_alpha_pkwb (long) 6217long __builtin_alpha_unpkbl (long) 6218long __builtin_alpha_unpkbw (long) 6219long __builtin_alpha_minub8 (long, long) 6220long __builtin_alpha_minsb8 (long, long) 6221long __builtin_alpha_minuw4 (long, long) 6222long __builtin_alpha_minsw4 (long, long) 6223long __builtin_alpha_maxub8 (long, long) 6224long __builtin_alpha_maxsb8 (long, long) 6225long __builtin_alpha_maxuw4 (long, long) 6226long __builtin_alpha_maxsw4 (long, long) 6227long __builtin_alpha_perr (long, long) 6228@end smallexample 6229 6230The following built-in functions are always with @option{-mcix} 6231or @option{-mcpu=@var{cpu}} where @var{cpu} is @code{ev67} or 6232later. They all generate the machine instruction that is part 6233of the name. 6234 6235@smallexample 6236long __builtin_alpha_cttz (long) 6237long __builtin_alpha_ctlz (long) 6238long __builtin_alpha_ctpop (long) 6239@end smallexample 6240 6241The following builtins are available on systems that use the OSF/1 6242PALcode. Normally they invoke the @code{rduniq} and @code{wruniq} 6243PAL calls, but when invoked with @option{-mtls-kernel}, they invoke 6244@code{rdval} and @code{wrval}. 6245 6246@smallexample 6247void *__builtin_thread_pointer (void) 6248void __builtin_set_thread_pointer (void *) 6249@end smallexample 6250 6251@node ARM Built-in Functions 6252@subsection ARM Built-in Functions 6253 6254These built-in functions are available for the ARM family of 6255processors, when the @option{-mcpu=iwmmxt} switch is used: 6256 6257@smallexample 6258typedef int v2si __attribute__ ((vector_size (8))); 6259typedef short v4hi __attribute__ ((vector_size (8))); 6260typedef char v8qi __attribute__ ((vector_size (8))); 6261 6262int __builtin_arm_getwcx (int) 6263void __builtin_arm_setwcx (int, int) 6264int __builtin_arm_textrmsb (v8qi, int) 6265int __builtin_arm_textrmsh (v4hi, int) 6266int __builtin_arm_textrmsw (v2si, int) 6267int __builtin_arm_textrmub (v8qi, int) 6268int __builtin_arm_textrmuh (v4hi, int) 6269int __builtin_arm_textrmuw (v2si, int) 6270v8qi __builtin_arm_tinsrb (v8qi, int) 6271v4hi __builtin_arm_tinsrh (v4hi, int) 6272v2si __builtin_arm_tinsrw (v2si, int) 6273long long __builtin_arm_tmia (long long, int, int) 6274long long __builtin_arm_tmiabb (long long, int, int) 6275long long __builtin_arm_tmiabt (long long, int, int) 6276long long __builtin_arm_tmiaph (long long, int, int) 6277long long __builtin_arm_tmiatb (long long, int, int) 6278long long __builtin_arm_tmiatt (long long, int, int) 6279int __builtin_arm_tmovmskb (v8qi) 6280int __builtin_arm_tmovmskh (v4hi) 6281int __builtin_arm_tmovmskw (v2si) 6282long long __builtin_arm_waccb (v8qi) 6283long long __builtin_arm_wacch (v4hi) 6284long long __builtin_arm_waccw (v2si) 6285v8qi __builtin_arm_waddb (v8qi, v8qi) 6286v8qi __builtin_arm_waddbss (v8qi, v8qi) 6287v8qi __builtin_arm_waddbus (v8qi, v8qi) 6288v4hi __builtin_arm_waddh (v4hi, v4hi) 6289v4hi __builtin_arm_waddhss (v4hi, v4hi) 6290v4hi __builtin_arm_waddhus (v4hi, v4hi) 6291v2si __builtin_arm_waddw (v2si, v2si) 6292v2si __builtin_arm_waddwss (v2si, v2si) 6293v2si __builtin_arm_waddwus (v2si, v2si) 6294v8qi __builtin_arm_walign (v8qi, v8qi, int) 6295long long __builtin_arm_wand(long long, long long) 6296long long __builtin_arm_wandn (long long, long long) 6297v8qi __builtin_arm_wavg2b (v8qi, v8qi) 6298v8qi __builtin_arm_wavg2br (v8qi, v8qi) 6299v4hi __builtin_arm_wavg2h (v4hi, v4hi) 6300v4hi __builtin_arm_wavg2hr (v4hi, v4hi) 6301v8qi __builtin_arm_wcmpeqb (v8qi, v8qi) 6302v4hi __builtin_arm_wcmpeqh (v4hi, v4hi) 6303v2si __builtin_arm_wcmpeqw (v2si, v2si) 6304v8qi __builtin_arm_wcmpgtsb (v8qi, v8qi) 6305v4hi __builtin_arm_wcmpgtsh (v4hi, v4hi) 6306v2si __builtin_arm_wcmpgtsw (v2si, v2si) 6307v8qi __builtin_arm_wcmpgtub (v8qi, v8qi) 6308v4hi __builtin_arm_wcmpgtuh (v4hi, v4hi) 6309v2si __builtin_arm_wcmpgtuw (v2si, v2si) 6310long long __builtin_arm_wmacs (long long, v4hi, v4hi) 6311long long __builtin_arm_wmacsz (v4hi, v4hi) 6312long long __builtin_arm_wmacu (long long, v4hi, v4hi) 6313long long __builtin_arm_wmacuz (v4hi, v4hi) 6314v4hi __builtin_arm_wmadds (v4hi, v4hi) 6315v4hi __builtin_arm_wmaddu (v4hi, v4hi) 6316v8qi __builtin_arm_wmaxsb (v8qi, v8qi) 6317v4hi __builtin_arm_wmaxsh (v4hi, v4hi) 6318v2si __builtin_arm_wmaxsw (v2si, v2si) 6319v8qi __builtin_arm_wmaxub (v8qi, v8qi) 6320v4hi __builtin_arm_wmaxuh (v4hi, v4hi) 6321v2si __builtin_arm_wmaxuw (v2si, v2si) 6322v8qi __builtin_arm_wminsb (v8qi, v8qi) 6323v4hi __builtin_arm_wminsh (v4hi, v4hi) 6324v2si __builtin_arm_wminsw (v2si, v2si) 6325v8qi __builtin_arm_wminub (v8qi, v8qi) 6326v4hi __builtin_arm_wminuh (v4hi, v4hi) 6327v2si __builtin_arm_wminuw (v2si, v2si) 6328v4hi __builtin_arm_wmulsm (v4hi, v4hi) 6329v4hi __builtin_arm_wmulul (v4hi, v4hi) 6330v4hi __builtin_arm_wmulum (v4hi, v4hi) 6331long long __builtin_arm_wor (long long, long long) 6332v2si __builtin_arm_wpackdss (long long, long long) 6333v2si __builtin_arm_wpackdus (long long, long long) 6334v8qi __builtin_arm_wpackhss (v4hi, v4hi) 6335v8qi __builtin_arm_wpackhus (v4hi, v4hi) 6336v4hi __builtin_arm_wpackwss (v2si, v2si) 6337v4hi __builtin_arm_wpackwus (v2si, v2si) 6338long long __builtin_arm_wrord (long long, long long) 6339long long __builtin_arm_wrordi (long long, int) 6340v4hi __builtin_arm_wrorh (v4hi, long long) 6341v4hi __builtin_arm_wrorhi (v4hi, int) 6342v2si __builtin_arm_wrorw (v2si, long long) 6343v2si __builtin_arm_wrorwi (v2si, int) 6344v2si __builtin_arm_wsadb (v8qi, v8qi) 6345v2si __builtin_arm_wsadbz (v8qi, v8qi) 6346v2si __builtin_arm_wsadh (v4hi, v4hi) 6347v2si __builtin_arm_wsadhz (v4hi, v4hi) 6348v4hi __builtin_arm_wshufh (v4hi, int) 6349long long __builtin_arm_wslld (long long, long long) 6350long long __builtin_arm_wslldi (long long, int) 6351v4hi __builtin_arm_wsllh (v4hi, long long) 6352v4hi __builtin_arm_wsllhi (v4hi, int) 6353v2si __builtin_arm_wsllw (v2si, long long) 6354v2si __builtin_arm_wsllwi (v2si, int) 6355long long __builtin_arm_wsrad (long long, long long) 6356long long __builtin_arm_wsradi (long long, int) 6357v4hi __builtin_arm_wsrah (v4hi, long long) 6358v4hi __builtin_arm_wsrahi (v4hi, int) 6359v2si __builtin_arm_wsraw (v2si, long long) 6360v2si __builtin_arm_wsrawi (v2si, int) 6361long long __builtin_arm_wsrld (long long, long long) 6362long long __builtin_arm_wsrldi (long long, int) 6363v4hi __builtin_arm_wsrlh (v4hi, long long) 6364v4hi __builtin_arm_wsrlhi (v4hi, int) 6365v2si __builtin_arm_wsrlw (v2si, long long) 6366v2si __builtin_arm_wsrlwi (v2si, int) 6367v8qi __builtin_arm_wsubb (v8qi, v8qi) 6368v8qi __builtin_arm_wsubbss (v8qi, v8qi) 6369v8qi __builtin_arm_wsubbus (v8qi, v8qi) 6370v4hi __builtin_arm_wsubh (v4hi, v4hi) 6371v4hi __builtin_arm_wsubhss (v4hi, v4hi) 6372v4hi __builtin_arm_wsubhus (v4hi, v4hi) 6373v2si __builtin_arm_wsubw (v2si, v2si) 6374v2si __builtin_arm_wsubwss (v2si, v2si) 6375v2si __builtin_arm_wsubwus (v2si, v2si) 6376v4hi __builtin_arm_wunpckehsb (v8qi) 6377v2si __builtin_arm_wunpckehsh (v4hi) 6378long long __builtin_arm_wunpckehsw (v2si) 6379v4hi __builtin_arm_wunpckehub (v8qi) 6380v2si __builtin_arm_wunpckehuh (v4hi) 6381long long __builtin_arm_wunpckehuw (v2si) 6382v4hi __builtin_arm_wunpckelsb (v8qi) 6383v2si __builtin_arm_wunpckelsh (v4hi) 6384long long __builtin_arm_wunpckelsw (v2si) 6385v4hi __builtin_arm_wunpckelub (v8qi) 6386v2si __builtin_arm_wunpckeluh (v4hi) 6387long long __builtin_arm_wunpckeluw (v2si) 6388v8qi __builtin_arm_wunpckihb (v8qi, v8qi) 6389v4hi __builtin_arm_wunpckihh (v4hi, v4hi) 6390v2si __builtin_arm_wunpckihw (v2si, v2si) 6391v8qi __builtin_arm_wunpckilb (v8qi, v8qi) 6392v4hi __builtin_arm_wunpckilh (v4hi, v4hi) 6393v2si __builtin_arm_wunpckilw (v2si, v2si) 6394long long __builtin_arm_wxor (long long, long long) 6395long long __builtin_arm_wzero () 6396@end smallexample 6397 6398@node Blackfin Built-in Functions 6399@subsection Blackfin Built-in Functions 6400 6401Currently, there are two Blackfin-specific built-in functions. These are 6402used for generating @code{CSYNC} and @code{SSYNC} machine insns without 6403using inline assembly; by using these built-in functions the compiler can 6404automatically add workarounds for hardware errata involving these 6405instructions. These functions are named as follows: 6406 6407@smallexample 6408void __builtin_bfin_csync (void) 6409void __builtin_bfin_ssync (void) 6410@end smallexample 6411 6412@node FR-V Built-in Functions 6413@subsection FR-V Built-in Functions 6414 6415GCC provides many FR-V-specific built-in functions. In general, 6416these functions are intended to be compatible with those described 6417by @cite{FR-V Family, Softune C/C++ Compiler Manual (V6), Fujitsu 6418Semiconductor}. The two exceptions are @code{__MDUNPACKH} and 6419@code{__MBTOHE}, the gcc forms of which pass 128-bit values by 6420pointer rather than by value. 6421 6422Most of the functions are named after specific FR-V instructions. 6423Such functions are said to be ``directly mapped'' and are summarized 6424here in tabular form. 6425 6426@menu 6427* Argument Types:: 6428* Directly-mapped Integer Functions:: 6429* Directly-mapped Media Functions:: 6430* Raw read/write Functions:: 6431* Other Built-in Functions:: 6432@end menu 6433 6434@node Argument Types 6435@subsubsection Argument Types 6436 6437The arguments to the built-in functions can be divided into three groups: 6438register numbers, compile-time constants and run-time values. In order 6439to make this classification clear at a glance, the arguments and return 6440values are given the following pseudo types: 6441 6442@multitable @columnfractions .20 .30 .15 .35 6443@item Pseudo type @tab Real C type @tab Constant? @tab Description 6444@item @code{uh} @tab @code{unsigned short} @tab No @tab an unsigned halfword 6445@item @code{uw1} @tab @code{unsigned int} @tab No @tab an unsigned word 6446@item @code{sw1} @tab @code{int} @tab No @tab a signed word 6447@item @code{uw2} @tab @code{unsigned long long} @tab No 6448@tab an unsigned doubleword 6449@item @code{sw2} @tab @code{long long} @tab No @tab a signed doubleword 6450@item @code{const} @tab @code{int} @tab Yes @tab an integer constant 6451@item @code{acc} @tab @code{int} @tab Yes @tab an ACC register number 6452@item @code{iacc} @tab @code{int} @tab Yes @tab an IACC register number 6453@end multitable 6454 6455These pseudo types are not defined by GCC, they are simply a notational 6456convenience used in this manual. 6457 6458Arguments of type @code{uh}, @code{uw1}, @code{sw1}, @code{uw2} 6459and @code{sw2} are evaluated at run time. They correspond to 6460register operands in the underlying FR-V instructions. 6461 6462@code{const} arguments represent immediate operands in the underlying 6463FR-V instructions. They must be compile-time constants. 6464 6465@code{acc} arguments are evaluated at compile time and specify the number 6466of an accumulator register. For example, an @code{acc} argument of 2 6467will select the ACC2 register. 6468 6469@code{iacc} arguments are similar to @code{acc} arguments but specify the 6470number of an IACC register. See @pxref{Other Built-in Functions} 6471for more details. 6472 6473@node Directly-mapped Integer Functions 6474@subsubsection Directly-mapped Integer Functions 6475 6476The functions listed below map directly to FR-V I-type instructions. 6477 6478@multitable @columnfractions .45 .32 .23 6479@item Function prototype @tab Example usage @tab Assembly output 6480@item @code{sw1 __ADDSS (sw1, sw1)} 6481@tab @code{@var{c} = __ADDSS (@var{a}, @var{b})} 6482@tab @code{ADDSS @var{a},@var{b},@var{c}} 6483@item @code{sw1 __SCAN (sw1, sw1)} 6484@tab @code{@var{c} = __SCAN (@var{a}, @var{b})} 6485@tab @code{SCAN @var{a},@var{b},@var{c}} 6486@item @code{sw1 __SCUTSS (sw1)} 6487@tab @code{@var{b} = __SCUTSS (@var{a})} 6488@tab @code{SCUTSS @var{a},@var{b}} 6489@item @code{sw1 __SLASS (sw1, sw1)} 6490@tab @code{@var{c} = __SLASS (@var{a}, @var{b})} 6491@tab @code{SLASS @var{a},@var{b},@var{c}} 6492@item @code{void __SMASS (sw1, sw1)} 6493@tab @code{__SMASS (@var{a}, @var{b})} 6494@tab @code{SMASS @var{a},@var{b}} 6495@item @code{void __SMSSS (sw1, sw1)} 6496@tab @code{__SMSSS (@var{a}, @var{b})} 6497@tab @code{SMSSS @var{a},@var{b}} 6498@item @code{void __SMU (sw1, sw1)} 6499@tab @code{__SMU (@var{a}, @var{b})} 6500@tab @code{SMU @var{a},@var{b}} 6501@item @code{sw2 __SMUL (sw1, sw1)} 6502@tab @code{@var{c} = __SMUL (@var{a}, @var{b})} 6503@tab @code{SMUL @var{a},@var{b},@var{c}} 6504@item @code{sw1 __SUBSS (sw1, sw1)} 6505@tab @code{@var{c} = __SUBSS (@var{a}, @var{b})} 6506@tab @code{SUBSS @var{a},@var{b},@var{c}} 6507@item @code{uw2 __UMUL (uw1, uw1)} 6508@tab @code{@var{c} = __UMUL (@var{a}, @var{b})} 6509@tab @code{UMUL @var{a},@var{b},@var{c}} 6510@end multitable 6511 6512@node Directly-mapped Media Functions 6513@subsubsection Directly-mapped Media Functions 6514 6515The functions listed below map directly to FR-V M-type instructions. 6516 6517@multitable @columnfractions .45 .32 .23 6518@item Function prototype @tab Example usage @tab Assembly output 6519@item @code{uw1 __MABSHS (sw1)} 6520@tab @code{@var{b} = __MABSHS (@var{a})} 6521@tab @code{MABSHS @var{a},@var{b}} 6522@item @code{void __MADDACCS (acc, acc)} 6523@tab @code{__MADDACCS (@var{b}, @var{a})} 6524@tab @code{MADDACCS @var{a},@var{b}} 6525@item @code{sw1 __MADDHSS (sw1, sw1)} 6526@tab @code{@var{c} = __MADDHSS (@var{a}, @var{b})} 6527@tab @code{MADDHSS @var{a},@var{b},@var{c}} 6528@item @code{uw1 __MADDHUS (uw1, uw1)} 6529@tab @code{@var{c} = __MADDHUS (@var{a}, @var{b})} 6530@tab @code{MADDHUS @var{a},@var{b},@var{c}} 6531@item @code{uw1 __MAND (uw1, uw1)} 6532@tab @code{@var{c} = __MAND (@var{a}, @var{b})} 6533@tab @code{MAND @var{a},@var{b},@var{c}} 6534@item @code{void __MASACCS (acc, acc)} 6535@tab @code{__MASACCS (@var{b}, @var{a})} 6536@tab @code{MASACCS @var{a},@var{b}} 6537@item @code{uw1 __MAVEH (uw1, uw1)} 6538@tab @code{@var{c} = __MAVEH (@var{a}, @var{b})} 6539@tab @code{MAVEH @var{a},@var{b},@var{c}} 6540@item @code{uw2 __MBTOH (uw1)} 6541@tab @code{@var{b} = __MBTOH (@var{a})} 6542@tab @code{MBTOH @var{a},@var{b}} 6543@item @code{void __MBTOHE (uw1 *, uw1)} 6544@tab @code{__MBTOHE (&@var{b}, @var{a})} 6545@tab @code{MBTOHE @var{a},@var{b}} 6546@item @code{void __MCLRACC (acc)} 6547@tab @code{__MCLRACC (@var{a})} 6548@tab @code{MCLRACC @var{a}} 6549@item @code{void __MCLRACCA (void)} 6550@tab @code{__MCLRACCA ()} 6551@tab @code{MCLRACCA} 6552@item @code{uw1 __Mcop1 (uw1, uw1)} 6553@tab @code{@var{c} = __Mcop1 (@var{a}, @var{b})} 6554@tab @code{Mcop1 @var{a},@var{b},@var{c}} 6555@item @code{uw1 __Mcop2 (uw1, uw1)} 6556@tab @code{@var{c} = __Mcop2 (@var{a}, @var{b})} 6557@tab @code{Mcop2 @var{a},@var{b},@var{c}} 6558@item @code{uw1 __MCPLHI (uw2, const)} 6559@tab @code{@var{c} = __MCPLHI (@var{a}, @var{b})} 6560@tab @code{MCPLHI @var{a},#@var{b},@var{c}} 6561@item @code{uw1 __MCPLI (uw2, const)} 6562@tab @code{@var{c} = __MCPLI (@var{a}, @var{b})} 6563@tab @code{MCPLI @var{a},#@var{b},@var{c}} 6564@item @code{void __MCPXIS (acc, sw1, sw1)} 6565@tab @code{__MCPXIS (@var{c}, @var{a}, @var{b})} 6566@tab @code{MCPXIS @var{a},@var{b},@var{c}} 6567@item @code{void __MCPXIU (acc, uw1, uw1)} 6568@tab @code{__MCPXIU (@var{c}, @var{a}, @var{b})} 6569@tab @code{MCPXIU @var{a},@var{b},@var{c}} 6570@item @code{void __MCPXRS (acc, sw1, sw1)} 6571@tab @code{__MCPXRS (@var{c}, @var{a}, @var{b})} 6572@tab @code{MCPXRS @var{a},@var{b},@var{c}} 6573@item @code{void __MCPXRU (acc, uw1, uw1)} 6574@tab @code{__MCPXRU (@var{c}, @var{a}, @var{b})} 6575@tab @code{MCPXRU @var{a},@var{b},@var{c}} 6576@item @code{uw1 __MCUT (acc, uw1)} 6577@tab @code{@var{c} = __MCUT (@var{a}, @var{b})} 6578@tab @code{MCUT @var{a},@var{b},@var{c}} 6579@item @code{uw1 __MCUTSS (acc, sw1)} 6580@tab @code{@var{c} = __MCUTSS (@var{a}, @var{b})} 6581@tab @code{MCUTSS @var{a},@var{b},@var{c}} 6582@item @code{void __MDADDACCS (acc, acc)} 6583@tab @code{__MDADDACCS (@var{b}, @var{a})} 6584@tab @code{MDADDACCS @var{a},@var{b}} 6585@item @code{void __MDASACCS (acc, acc)} 6586@tab @code{__MDASACCS (@var{b}, @var{a})} 6587@tab @code{MDASACCS @var{a},@var{b}} 6588@item @code{uw2 __MDCUTSSI (acc, const)} 6589@tab @code{@var{c} = __MDCUTSSI (@var{a}, @var{b})} 6590@tab @code{MDCUTSSI @var{a},#@var{b},@var{c}} 6591@item @code{uw2 __MDPACKH (uw2, uw2)} 6592@tab @code{@var{c} = __MDPACKH (@var{a}, @var{b})} 6593@tab @code{MDPACKH @var{a},@var{b},@var{c}} 6594@item @code{uw2 __MDROTLI (uw2, const)} 6595@tab @code{@var{c} = __MDROTLI (@var{a}, @var{b})} 6596@tab @code{MDROTLI @var{a},#@var{b},@var{c}} 6597@item @code{void __MDSUBACCS (acc, acc)} 6598@tab @code{__MDSUBACCS (@var{b}, @var{a})} 6599@tab @code{MDSUBACCS @var{a},@var{b}} 6600@item @code{void __MDUNPACKH (uw1 *, uw2)} 6601@tab @code{__MDUNPACKH (&@var{b}, @var{a})} 6602@tab @code{MDUNPACKH @var{a},@var{b}} 6603@item @code{uw2 __MEXPDHD (uw1, const)} 6604@tab @code{@var{c} = __MEXPDHD (@var{a}, @var{b})} 6605@tab @code{MEXPDHD @var{a},#@var{b},@var{c}} 6606@item @code{uw1 __MEXPDHW (uw1, const)} 6607@tab @code{@var{c} = __MEXPDHW (@var{a}, @var{b})} 6608@tab @code{MEXPDHW @var{a},#@var{b},@var{c}} 6609@item @code{uw1 __MHDSETH (uw1, const)} 6610@tab @code{@var{c} = __MHDSETH (@var{a}, @var{b})} 6611@tab @code{MHDSETH @var{a},#@var{b},@var{c}} 6612@item @code{sw1 __MHDSETS (const)} 6613@tab @code{@var{b} = __MHDSETS (@var{a})} 6614@tab @code{MHDSETS #@var{a},@var{b}} 6615@item @code{uw1 __MHSETHIH (uw1, const)} 6616@tab @code{@var{b} = __MHSETHIH (@var{b}, @var{a})} 6617@tab @code{MHSETHIH #@var{a},@var{b}} 6618@item @code{sw1 __MHSETHIS (sw1, const)} 6619@tab @code{@var{b} = __MHSETHIS (@var{b}, @var{a})} 6620@tab @code{MHSETHIS #@var{a},@var{b}} 6621@item @code{uw1 __MHSETLOH (uw1, const)} 6622@tab @code{@var{b} = __MHSETLOH (@var{b}, @var{a})} 6623@tab @code{MHSETLOH #@var{a},@var{b}} 6624@item @code{sw1 __MHSETLOS (sw1, const)} 6625@tab @code{@var{b} = __MHSETLOS (@var{b}, @var{a})} 6626@tab @code{MHSETLOS #@var{a},@var{b}} 6627@item @code{uw1 __MHTOB (uw2)} 6628@tab @code{@var{b} = __MHTOB (@var{a})} 6629@tab @code{MHTOB @var{a},@var{b}} 6630@item @code{void __MMACHS (acc, sw1, sw1)} 6631@tab @code{__MMACHS (@var{c}, @var{a}, @var{b})} 6632@tab @code{MMACHS @var{a},@var{b},@var{c}} 6633@item @code{void __MMACHU (acc, uw1, uw1)} 6634@tab @code{__MMACHU (@var{c}, @var{a}, @var{b})} 6635@tab @code{MMACHU @var{a},@var{b},@var{c}} 6636@item @code{void __MMRDHS (acc, sw1, sw1)} 6637@tab @code{__MMRDHS (@var{c}, @var{a}, @var{b})} 6638@tab @code{MMRDHS @var{a},@var{b},@var{c}} 6639@item @code{void __MMRDHU (acc, uw1, uw1)} 6640@tab @code{__MMRDHU (@var{c}, @var{a}, @var{b})} 6641@tab @code{MMRDHU @var{a},@var{b},@var{c}} 6642@item @code{void __MMULHS (acc, sw1, sw1)} 6643@tab @code{__MMULHS (@var{c}, @var{a}, @var{b})} 6644@tab @code{MMULHS @var{a},@var{b},@var{c}} 6645@item @code{void __MMULHU (acc, uw1, uw1)} 6646@tab @code{__MMULHU (@var{c}, @var{a}, @var{b})} 6647@tab @code{MMULHU @var{a},@var{b},@var{c}} 6648@item @code{void __MMULXHS (acc, sw1, sw1)} 6649@tab @code{__MMULXHS (@var{c}, @var{a}, @var{b})} 6650@tab @code{MMULXHS @var{a},@var{b},@var{c}} 6651@item @code{void __MMULXHU (acc, uw1, uw1)} 6652@tab @code{__MMULXHU (@var{c}, @var{a}, @var{b})} 6653@tab @code{MMULXHU @var{a},@var{b},@var{c}} 6654@item @code{uw1 __MNOT (uw1)} 6655@tab @code{@var{b} = __MNOT (@var{a})} 6656@tab @code{MNOT @var{a},@var{b}} 6657@item @code{uw1 __MOR (uw1, uw1)} 6658@tab @code{@var{c} = __MOR (@var{a}, @var{b})} 6659@tab @code{MOR @var{a},@var{b},@var{c}} 6660@item @code{uw1 __MPACKH (uh, uh)} 6661@tab @code{@var{c} = __MPACKH (@var{a}, @var{b})} 6662@tab @code{MPACKH @var{a},@var{b},@var{c}} 6663@item @code{sw2 __MQADDHSS (sw2, sw2)} 6664@tab @code{@var{c} = __MQADDHSS (@var{a}, @var{b})} 6665@tab @code{MQADDHSS @var{a},@var{b},@var{c}} 6666@item @code{uw2 __MQADDHUS (uw2, uw2)} 6667@tab @code{@var{c} = __MQADDHUS (@var{a}, @var{b})} 6668@tab @code{MQADDHUS @var{a},@var{b},@var{c}} 6669@item @code{void __MQCPXIS (acc, sw2, sw2)} 6670@tab @code{__MQCPXIS (@var{c}, @var{a}, @var{b})} 6671@tab @code{MQCPXIS @var{a},@var{b},@var{c}} 6672@item @code{void __MQCPXIU (acc, uw2, uw2)} 6673@tab @code{__MQCPXIU (@var{c}, @var{a}, @var{b})} 6674@tab @code{MQCPXIU @var{a},@var{b},@var{c}} 6675@item @code{void __MQCPXRS (acc, sw2, sw2)} 6676@tab @code{__MQCPXRS (@var{c}, @var{a}, @var{b})} 6677@tab @code{MQCPXRS @var{a},@var{b},@var{c}} 6678@item @code{void __MQCPXRU (acc, uw2, uw2)} 6679@tab @code{__MQCPXRU (@var{c}, @var{a}, @var{b})} 6680@tab @code{MQCPXRU @var{a},@var{b},@var{c}} 6681@item @code{sw2 __MQLCLRHS (sw2, sw2)} 6682@tab @code{@var{c} = __MQLCLRHS (@var{a}, @var{b})} 6683@tab @code{MQLCLRHS @var{a},@var{b},@var{c}} 6684@item @code{sw2 __MQLMTHS (sw2, sw2)} 6685@tab @code{@var{c} = __MQLMTHS (@var{a}, @var{b})} 6686@tab @code{MQLMTHS @var{a},@var{b},@var{c}} 6687@item @code{void __MQMACHS (acc, sw2, sw2)} 6688@tab @code{__MQMACHS (@var{c}, @var{a}, @var{b})} 6689@tab @code{MQMACHS @var{a},@var{b},@var{c}} 6690@item @code{void __MQMACHU (acc, uw2, uw2)} 6691@tab @code{__MQMACHU (@var{c}, @var{a}, @var{b})} 6692@tab @code{MQMACHU @var{a},@var{b},@var{c}} 6693@item @code{void __MQMACXHS (acc, sw2, sw2)} 6694@tab @code{__MQMACXHS (@var{c}, @var{a}, @var{b})} 6695@tab @code{MQMACXHS @var{a},@var{b},@var{c}} 6696@item @code{void __MQMULHS (acc, sw2, sw2)} 6697@tab @code{__MQMULHS (@var{c}, @var{a}, @var{b})} 6698@tab @code{MQMULHS @var{a},@var{b},@var{c}} 6699@item @code{void __MQMULHU (acc, uw2, uw2)} 6700@tab @code{__MQMULHU (@var{c}, @var{a}, @var{b})} 6701@tab @code{MQMULHU @var{a},@var{b},@var{c}} 6702@item @code{void __MQMULXHS (acc, sw2, sw2)} 6703@tab @code{__MQMULXHS (@var{c}, @var{a}, @var{b})} 6704@tab @code{MQMULXHS @var{a},@var{b},@var{c}} 6705@item @code{void __MQMULXHU (acc, uw2, uw2)} 6706@tab @code{__MQMULXHU (@var{c}, @var{a}, @var{b})} 6707@tab @code{MQMULXHU @var{a},@var{b},@var{c}} 6708@item @code{sw2 __MQSATHS (sw2, sw2)} 6709@tab @code{@var{c} = __MQSATHS (@var{a}, @var{b})} 6710@tab @code{MQSATHS @var{a},@var{b},@var{c}} 6711@item @code{uw2 __MQSLLHI (uw2, int)} 6712@tab @code{@var{c} = __MQSLLHI (@var{a}, @var{b})} 6713@tab @code{MQSLLHI @var{a},@var{b},@var{c}} 6714@item @code{sw2 __MQSRAHI (sw2, int)} 6715@tab @code{@var{c} = __MQSRAHI (@var{a}, @var{b})} 6716@tab @code{MQSRAHI @var{a},@var{b},@var{c}} 6717@item @code{sw2 __MQSUBHSS (sw2, sw2)} 6718@tab @code{@var{c} = __MQSUBHSS (@var{a}, @var{b})} 6719@tab @code{MQSUBHSS @var{a},@var{b},@var{c}} 6720@item @code{uw2 __MQSUBHUS (uw2, uw2)} 6721@tab @code{@var{c} = __MQSUBHUS (@var{a}, @var{b})} 6722@tab @code{MQSUBHUS @var{a},@var{b},@var{c}} 6723@item @code{void __MQXMACHS (acc, sw2, sw2)} 6724@tab @code{__MQXMACHS (@var{c}, @var{a}, @var{b})} 6725@tab @code{MQXMACHS @var{a},@var{b},@var{c}} 6726@item @code{void __MQXMACXHS (acc, sw2, sw2)} 6727@tab @code{__MQXMACXHS (@var{c}, @var{a}, @var{b})} 6728@tab @code{MQXMACXHS @var{a},@var{b},@var{c}} 6729@item @code{uw1 __MRDACC (acc)} 6730@tab @code{@var{b} = __MRDACC (@var{a})} 6731@tab @code{MRDACC @var{a},@var{b}} 6732@item @code{uw1 __MRDACCG (acc)} 6733@tab @code{@var{b} = __MRDACCG (@var{a})} 6734@tab @code{MRDACCG @var{a},@var{b}} 6735@item @code{uw1 __MROTLI (uw1, const)} 6736@tab @code{@var{c} = __MROTLI (@var{a}, @var{b})} 6737@tab @code{MROTLI @var{a},#@var{b},@var{c}} 6738@item @code{uw1 __MROTRI (uw1, const)} 6739@tab @code{@var{c} = __MROTRI (@var{a}, @var{b})} 6740@tab @code{MROTRI @var{a},#@var{b},@var{c}} 6741@item @code{sw1 __MSATHS (sw1, sw1)} 6742@tab @code{@var{c} = __MSATHS (@var{a}, @var{b})} 6743@tab @code{MSATHS @var{a},@var{b},@var{c}} 6744@item @code{uw1 __MSATHU (uw1, uw1)} 6745@tab @code{@var{c} = __MSATHU (@var{a}, @var{b})} 6746@tab @code{MSATHU @var{a},@var{b},@var{c}} 6747@item @code{uw1 __MSLLHI (uw1, const)} 6748@tab @code{@var{c} = __MSLLHI (@var{a}, @var{b})} 6749@tab @code{MSLLHI @var{a},#@var{b},@var{c}} 6750@item @code{sw1 __MSRAHI (sw1, const)} 6751@tab @code{@var{c} = __MSRAHI (@var{a}, @var{b})} 6752@tab @code{MSRAHI @var{a},#@var{b},@var{c}} 6753@item @code{uw1 __MSRLHI (uw1, const)} 6754@tab @code{@var{c} = __MSRLHI (@var{a}, @var{b})} 6755@tab @code{MSRLHI @var{a},#@var{b},@var{c}} 6756@item @code{void __MSUBACCS (acc, acc)} 6757@tab @code{__MSUBACCS (@var{b}, @var{a})} 6758@tab @code{MSUBACCS @var{a},@var{b}} 6759@item @code{sw1 __MSUBHSS (sw1, sw1)} 6760@tab @code{@var{c} = __MSUBHSS (@var{a}, @var{b})} 6761@tab @code{MSUBHSS @var{a},@var{b},@var{c}} 6762@item @code{uw1 __MSUBHUS (uw1, uw1)} 6763@tab @code{@var{c} = __MSUBHUS (@var{a}, @var{b})} 6764@tab @code{MSUBHUS @var{a},@var{b},@var{c}} 6765@item @code{void __MTRAP (void)} 6766@tab @code{__MTRAP ()} 6767@tab @code{MTRAP} 6768@item @code{uw2 __MUNPACKH (uw1)} 6769@tab @code{@var{b} = __MUNPACKH (@var{a})} 6770@tab @code{MUNPACKH @var{a},@var{b}} 6771@item @code{uw1 __MWCUT (uw2, uw1)} 6772@tab @code{@var{c} = __MWCUT (@var{a}, @var{b})} 6773@tab @code{MWCUT @var{a},@var{b},@var{c}} 6774@item @code{void __MWTACC (acc, uw1)} 6775@tab @code{__MWTACC (@var{b}, @var{a})} 6776@tab @code{MWTACC @var{a},@var{b}} 6777@item @code{void __MWTACCG (acc, uw1)} 6778@tab @code{__MWTACCG (@var{b}, @var{a})} 6779@tab @code{MWTACCG @var{a},@var{b}} 6780@item @code{uw1 __MXOR (uw1, uw1)} 6781@tab @code{@var{c} = __MXOR (@var{a}, @var{b})} 6782@tab @code{MXOR @var{a},@var{b},@var{c}} 6783@end multitable 6784 6785@node Raw read/write Functions 6786@subsubsection Raw read/write Functions 6787 6788This sections describes built-in functions related to read and write 6789instructions to access memory. These functions generate 6790@code{membar} instructions to flush the I/O load and stores where 6791appropriate, as described in Fujitsu's manual described above. 6792 6793@table @code 6794 6795@item unsigned char __builtin_read8 (void *@var{data}) 6796@item unsigned short __builtin_read16 (void *@var{data}) 6797@item unsigned long __builtin_read32 (void *@var{data}) 6798@item unsigned long long __builtin_read64 (void *@var{data}) 6799 6800@item void __builtin_write8 (void *@var{data}, unsigned char @var{datum}) 6801@item void __builtin_write16 (void *@var{data}, unsigned short @var{datum}) 6802@item void __builtin_write32 (void *@var{data}, unsigned long @var{datum}) 6803@item void __builtin_write64 (void *@var{data}, unsigned long long @var{datum}) 6804@end table 6805 6806@node Other Built-in Functions 6807@subsubsection Other Built-in Functions 6808 6809This section describes built-in functions that are not named after 6810a specific FR-V instruction. 6811 6812@table @code 6813@item sw2 __IACCreadll (iacc @var{reg}) 6814Return the full 64-bit value of IACC0@. The @var{reg} argument is reserved 6815for future expansion and must be 0. 6816 6817@item sw1 __IACCreadl (iacc @var{reg}) 6818Return the value of IACC0H if @var{reg} is 0 and IACC0L if @var{reg} is 1. 6819Other values of @var{reg} are rejected as invalid. 6820 6821@item void __IACCsetll (iacc @var{reg}, sw2 @var{x}) 6822Set the full 64-bit value of IACC0 to @var{x}. The @var{reg} argument 6823is reserved for future expansion and must be 0. 6824 6825@item void __IACCsetl (iacc @var{reg}, sw1 @var{x}) 6826Set IACC0H to @var{x} if @var{reg} is 0 and IACC0L to @var{x} if @var{reg} 6827is 1. Other values of @var{reg} are rejected as invalid. 6828 6829@item void __data_prefetch0 (const void *@var{x}) 6830Use the @code{dcpl} instruction to load the contents of address @var{x} 6831into the data cache. 6832 6833@item void __data_prefetch (const void *@var{x}) 6834Use the @code{nldub} instruction to load the contents of address @var{x} 6835into the data cache. The instruction will be issued in slot I1@. 6836@end table 6837 6838@node X86 Built-in Functions 6839@subsection X86 Built-in Functions 6840 6841These built-in functions are available for the i386 and x86-64 family 6842of computers, depending on the command-line switches used. 6843 6844Note that, if you specify command-line switches such as @option{-msse}, 6845the compiler could use the extended instruction sets even if the built-ins 6846are not used explicitly in the program. For this reason, applications 6847which perform runtime CPU detection must compile separate files for each 6848supported architecture, using the appropriate flags. In particular, 6849the file containing the CPU detection code should be compiled without 6850these options. 6851 6852The following machine modes are available for use with MMX built-in functions 6853(@pxref{Vector Extensions}): @code{V2SI} for a vector of two 32-bit integers, 6854@code{V4HI} for a vector of four 16-bit integers, and @code{V8QI} for a 6855vector of eight 8-bit integers. Some of the built-in functions operate on 6856MMX registers as a whole 64-bit entity, these use @code{DI} as their mode. 6857 6858If 3Dnow extensions are enabled, @code{V2SF} is used as a mode for a vector 6859of two 32-bit floating point values. 6860 6861If SSE extensions are enabled, @code{V4SF} is used for a vector of four 32-bit 6862floating point values. Some instructions use a vector of four 32-bit 6863integers, these use @code{V4SI}. Finally, some instructions operate on an 6864entire vector register, interpreting it as a 128-bit integer, these use mode 6865@code{TI}. 6866 6867The following built-in functions are made available by @option{-mmmx}. 6868All of them generate the machine instruction that is part of the name. 6869 6870@smallexample 6871v8qi __builtin_ia32_paddb (v8qi, v8qi) 6872v4hi __builtin_ia32_paddw (v4hi, v4hi) 6873v2si __builtin_ia32_paddd (v2si, v2si) 6874v8qi __builtin_ia32_psubb (v8qi, v8qi) 6875v4hi __builtin_ia32_psubw (v4hi, v4hi) 6876v2si __builtin_ia32_psubd (v2si, v2si) 6877v8qi __builtin_ia32_paddsb (v8qi, v8qi) 6878v4hi __builtin_ia32_paddsw (v4hi, v4hi) 6879v8qi __builtin_ia32_psubsb (v8qi, v8qi) 6880v4hi __builtin_ia32_psubsw (v4hi, v4hi) 6881v8qi __builtin_ia32_paddusb (v8qi, v8qi) 6882v4hi __builtin_ia32_paddusw (v4hi, v4hi) 6883v8qi __builtin_ia32_psubusb (v8qi, v8qi) 6884v4hi __builtin_ia32_psubusw (v4hi, v4hi) 6885v4hi __builtin_ia32_pmullw (v4hi, v4hi) 6886v4hi __builtin_ia32_pmulhw (v4hi, v4hi) 6887di __builtin_ia32_pand (di, di) 6888di __builtin_ia32_pandn (di,di) 6889di __builtin_ia32_por (di, di) 6890di __builtin_ia32_pxor (di, di) 6891v8qi __builtin_ia32_pcmpeqb (v8qi, v8qi) 6892v4hi __builtin_ia32_pcmpeqw (v4hi, v4hi) 6893v2si __builtin_ia32_pcmpeqd (v2si, v2si) 6894v8qi __builtin_ia32_pcmpgtb (v8qi, v8qi) 6895v4hi __builtin_ia32_pcmpgtw (v4hi, v4hi) 6896v2si __builtin_ia32_pcmpgtd (v2si, v2si) 6897v8qi __builtin_ia32_punpckhbw (v8qi, v8qi) 6898v4hi __builtin_ia32_punpckhwd (v4hi, v4hi) 6899v2si __builtin_ia32_punpckhdq (v2si, v2si) 6900v8qi __builtin_ia32_punpcklbw (v8qi, v8qi) 6901v4hi __builtin_ia32_punpcklwd (v4hi, v4hi) 6902v2si __builtin_ia32_punpckldq (v2si, v2si) 6903v8qi __builtin_ia32_packsswb (v4hi, v4hi) 6904v4hi __builtin_ia32_packssdw (v2si, v2si) 6905v8qi __builtin_ia32_packuswb (v4hi, v4hi) 6906@end smallexample 6907 6908The following built-in functions are made available either with 6909@option{-msse}, or with a combination of @option{-m3dnow} and 6910@option{-march=athlon}. All of them generate the machine 6911instruction that is part of the name. 6912 6913@smallexample 6914v4hi __builtin_ia32_pmulhuw (v4hi, v4hi) 6915v8qi __builtin_ia32_pavgb (v8qi, v8qi) 6916v4hi __builtin_ia32_pavgw (v4hi, v4hi) 6917v4hi __builtin_ia32_psadbw (v8qi, v8qi) 6918v8qi __builtin_ia32_pmaxub (v8qi, v8qi) 6919v4hi __builtin_ia32_pmaxsw (v4hi, v4hi) 6920v8qi __builtin_ia32_pminub (v8qi, v8qi) 6921v4hi __builtin_ia32_pminsw (v4hi, v4hi) 6922int __builtin_ia32_pextrw (v4hi, int) 6923v4hi __builtin_ia32_pinsrw (v4hi, int, int) 6924int __builtin_ia32_pmovmskb (v8qi) 6925void __builtin_ia32_maskmovq (v8qi, v8qi, char *) 6926void __builtin_ia32_movntq (di *, di) 6927void __builtin_ia32_sfence (void) 6928@end smallexample 6929 6930The following built-in functions are available when @option{-msse} is used. 6931All of them generate the machine instruction that is part of the name. 6932 6933@smallexample 6934int __builtin_ia32_comieq (v4sf, v4sf) 6935int __builtin_ia32_comineq (v4sf, v4sf) 6936int __builtin_ia32_comilt (v4sf, v4sf) 6937int __builtin_ia32_comile (v4sf, v4sf) 6938int __builtin_ia32_comigt (v4sf, v4sf) 6939int __builtin_ia32_comige (v4sf, v4sf) 6940int __builtin_ia32_ucomieq (v4sf, v4sf) 6941int __builtin_ia32_ucomineq (v4sf, v4sf) 6942int __builtin_ia32_ucomilt (v4sf, v4sf) 6943int __builtin_ia32_ucomile (v4sf, v4sf) 6944int __builtin_ia32_ucomigt (v4sf, v4sf) 6945int __builtin_ia32_ucomige (v4sf, v4sf) 6946v4sf __builtin_ia32_addps (v4sf, v4sf) 6947v4sf __builtin_ia32_subps (v4sf, v4sf) 6948v4sf __builtin_ia32_mulps (v4sf, v4sf) 6949v4sf __builtin_ia32_divps (v4sf, v4sf) 6950v4sf __builtin_ia32_addss (v4sf, v4sf) 6951v4sf __builtin_ia32_subss (v4sf, v4sf) 6952v4sf __builtin_ia32_mulss (v4sf, v4sf) 6953v4sf __builtin_ia32_divss (v4sf, v4sf) 6954v4si __builtin_ia32_cmpeqps (v4sf, v4sf) 6955v4si __builtin_ia32_cmpltps (v4sf, v4sf) 6956v4si __builtin_ia32_cmpleps (v4sf, v4sf) 6957v4si __builtin_ia32_cmpgtps (v4sf, v4sf) 6958v4si __builtin_ia32_cmpgeps (v4sf, v4sf) 6959v4si __builtin_ia32_cmpunordps (v4sf, v4sf) 6960v4si __builtin_ia32_cmpneqps (v4sf, v4sf) 6961v4si __builtin_ia32_cmpnltps (v4sf, v4sf) 6962v4si __builtin_ia32_cmpnleps (v4sf, v4sf) 6963v4si __builtin_ia32_cmpngtps (v4sf, v4sf) 6964v4si __builtin_ia32_cmpngeps (v4sf, v4sf) 6965v4si __builtin_ia32_cmpordps (v4sf, v4sf) 6966v4si __builtin_ia32_cmpeqss (v4sf, v4sf) 6967v4si __builtin_ia32_cmpltss (v4sf, v4sf) 6968v4si __builtin_ia32_cmpless (v4sf, v4sf) 6969v4si __builtin_ia32_cmpunordss (v4sf, v4sf) 6970v4si __builtin_ia32_cmpneqss (v4sf, v4sf) 6971v4si __builtin_ia32_cmpnlts (v4sf, v4sf) 6972v4si __builtin_ia32_cmpnless (v4sf, v4sf) 6973v4si __builtin_ia32_cmpordss (v4sf, v4sf) 6974v4sf __builtin_ia32_maxps (v4sf, v4sf) 6975v4sf __builtin_ia32_maxss (v4sf, v4sf) 6976v4sf __builtin_ia32_minps (v4sf, v4sf) 6977v4sf __builtin_ia32_minss (v4sf, v4sf) 6978v4sf __builtin_ia32_andps (v4sf, v4sf) 6979v4sf __builtin_ia32_andnps (v4sf, v4sf) 6980v4sf __builtin_ia32_orps (v4sf, v4sf) 6981v4sf __builtin_ia32_xorps (v4sf, v4sf) 6982v4sf __builtin_ia32_movss (v4sf, v4sf) 6983v4sf __builtin_ia32_movhlps (v4sf, v4sf) 6984v4sf __builtin_ia32_movlhps (v4sf, v4sf) 6985v4sf __builtin_ia32_unpckhps (v4sf, v4sf) 6986v4sf __builtin_ia32_unpcklps (v4sf, v4sf) 6987v4sf __builtin_ia32_cvtpi2ps (v4sf, v2si) 6988v4sf __builtin_ia32_cvtsi2ss (v4sf, int) 6989v2si __builtin_ia32_cvtps2pi (v4sf) 6990int __builtin_ia32_cvtss2si (v4sf) 6991v2si __builtin_ia32_cvttps2pi (v4sf) 6992int __builtin_ia32_cvttss2si (v4sf) 6993v4sf __builtin_ia32_rcpps (v4sf) 6994v4sf __builtin_ia32_rsqrtps (v4sf) 6995v4sf __builtin_ia32_sqrtps (v4sf) 6996v4sf __builtin_ia32_rcpss (v4sf) 6997v4sf __builtin_ia32_rsqrtss (v4sf) 6998v4sf __builtin_ia32_sqrtss (v4sf) 6999v4sf __builtin_ia32_shufps (v4sf, v4sf, int) 7000void __builtin_ia32_movntps (float *, v4sf) 7001int __builtin_ia32_movmskps (v4sf) 7002@end smallexample 7003 7004The following built-in functions are available when @option{-msse} is used. 7005 7006@table @code 7007@item v4sf __builtin_ia32_loadaps (float *) 7008Generates the @code{movaps} machine instruction as a load from memory. 7009@item void __builtin_ia32_storeaps (float *, v4sf) 7010Generates the @code{movaps} machine instruction as a store to memory. 7011@item v4sf __builtin_ia32_loadups (float *) 7012Generates the @code{movups} machine instruction as a load from memory. 7013@item void __builtin_ia32_storeups (float *, v4sf) 7014Generates the @code{movups} machine instruction as a store to memory. 7015@item v4sf __builtin_ia32_loadsss (float *) 7016Generates the @code{movss} machine instruction as a load from memory. 7017@item void __builtin_ia32_storess (float *, v4sf) 7018Generates the @code{movss} machine instruction as a store to memory. 7019@item v4sf __builtin_ia32_loadhps (v4sf, v2si *) 7020Generates the @code{movhps} machine instruction as a load from memory. 7021@item v4sf __builtin_ia32_loadlps (v4sf, v2si *) 7022Generates the @code{movlps} machine instruction as a load from memory 7023@item void __builtin_ia32_storehps (v4sf, v2si *) 7024Generates the @code{movhps} machine instruction as a store to memory. 7025@item void __builtin_ia32_storelps (v4sf, v2si *) 7026Generates the @code{movlps} machine instruction as a store to memory. 7027@end table 7028 7029The following built-in functions are available when @option{-msse2} is used. 7030All of them generate the machine instruction that is part of the name. 7031 7032@smallexample 7033int __builtin_ia32_comisdeq (v2df, v2df) 7034int __builtin_ia32_comisdlt (v2df, v2df) 7035int __builtin_ia32_comisdle (v2df, v2df) 7036int __builtin_ia32_comisdgt (v2df, v2df) 7037int __builtin_ia32_comisdge (v2df, v2df) 7038int __builtin_ia32_comisdneq (v2df, v2df) 7039int __builtin_ia32_ucomisdeq (v2df, v2df) 7040int __builtin_ia32_ucomisdlt (v2df, v2df) 7041int __builtin_ia32_ucomisdle (v2df, v2df) 7042int __builtin_ia32_ucomisdgt (v2df, v2df) 7043int __builtin_ia32_ucomisdge (v2df, v2df) 7044int __builtin_ia32_ucomisdneq (v2df, v2df) 7045v2df __builtin_ia32_cmpeqpd (v2df, v2df) 7046v2df __builtin_ia32_cmpltpd (v2df, v2df) 7047v2df __builtin_ia32_cmplepd (v2df, v2df) 7048v2df __builtin_ia32_cmpgtpd (v2df, v2df) 7049v2df __builtin_ia32_cmpgepd (v2df, v2df) 7050v2df __builtin_ia32_cmpunordpd (v2df, v2df) 7051v2df __builtin_ia32_cmpneqpd (v2df, v2df) 7052v2df __builtin_ia32_cmpnltpd (v2df, v2df) 7053v2df __builtin_ia32_cmpnlepd (v2df, v2df) 7054v2df __builtin_ia32_cmpngtpd (v2df, v2df) 7055v2df __builtin_ia32_cmpngepd (v2df, v2df) 7056v2df __builtin_ia32_cmpordpd (v2df, v2df) 7057v2df __builtin_ia32_cmpeqsd (v2df, v2df) 7058v2df __builtin_ia32_cmpltsd (v2df, v2df) 7059v2df __builtin_ia32_cmplesd (v2df, v2df) 7060v2df __builtin_ia32_cmpunordsd (v2df, v2df) 7061v2df __builtin_ia32_cmpneqsd (v2df, v2df) 7062v2df __builtin_ia32_cmpnltsd (v2df, v2df) 7063v2df __builtin_ia32_cmpnlesd (v2df, v2df) 7064v2df __builtin_ia32_cmpordsd (v2df, v2df) 7065v2di __builtin_ia32_paddq (v2di, v2di) 7066v2di __builtin_ia32_psubq (v2di, v2di) 7067v2df __builtin_ia32_addpd (v2df, v2df) 7068v2df __builtin_ia32_subpd (v2df, v2df) 7069v2df __builtin_ia32_mulpd (v2df, v2df) 7070v2df __builtin_ia32_divpd (v2df, v2df) 7071v2df __builtin_ia32_addsd (v2df, v2df) 7072v2df __builtin_ia32_subsd (v2df, v2df) 7073v2df __builtin_ia32_mulsd (v2df, v2df) 7074v2df __builtin_ia32_divsd (v2df, v2df) 7075v2df __builtin_ia32_minpd (v2df, v2df) 7076v2df __builtin_ia32_maxpd (v2df, v2df) 7077v2df __builtin_ia32_minsd (v2df, v2df) 7078v2df __builtin_ia32_maxsd (v2df, v2df) 7079v2df __builtin_ia32_andpd (v2df, v2df) 7080v2df __builtin_ia32_andnpd (v2df, v2df) 7081v2df __builtin_ia32_orpd (v2df, v2df) 7082v2df __builtin_ia32_xorpd (v2df, v2df) 7083v2df __builtin_ia32_movsd (v2df, v2df) 7084v2df __builtin_ia32_unpckhpd (v2df, v2df) 7085v2df __builtin_ia32_unpcklpd (v2df, v2df) 7086v16qi __builtin_ia32_paddb128 (v16qi, v16qi) 7087v8hi __builtin_ia32_paddw128 (v8hi, v8hi) 7088v4si __builtin_ia32_paddd128 (v4si, v4si) 7089v2di __builtin_ia32_paddq128 (v2di, v2di) 7090v16qi __builtin_ia32_psubb128 (v16qi, v16qi) 7091v8hi __builtin_ia32_psubw128 (v8hi, v8hi) 7092v4si __builtin_ia32_psubd128 (v4si, v4si) 7093v2di __builtin_ia32_psubq128 (v2di, v2di) 7094v8hi __builtin_ia32_pmullw128 (v8hi, v8hi) 7095v8hi __builtin_ia32_pmulhw128 (v8hi, v8hi) 7096v2di __builtin_ia32_pand128 (v2di, v2di) 7097v2di __builtin_ia32_pandn128 (v2di, v2di) 7098v2di __builtin_ia32_por128 (v2di, v2di) 7099v2di __builtin_ia32_pxor128 (v2di, v2di) 7100v16qi __builtin_ia32_pavgb128 (v16qi, v16qi) 7101v8hi __builtin_ia32_pavgw128 (v8hi, v8hi) 7102v16qi __builtin_ia32_pcmpeqb128 (v16qi, v16qi) 7103v8hi __builtin_ia32_pcmpeqw128 (v8hi, v8hi) 7104v4si __builtin_ia32_pcmpeqd128 (v4si, v4si) 7105v16qi __builtin_ia32_pcmpgtb128 (v16qi, v16qi) 7106v8hi __builtin_ia32_pcmpgtw128 (v8hi, v8hi) 7107v4si __builtin_ia32_pcmpgtd128 (v4si, v4si) 7108v16qi __builtin_ia32_pmaxub128 (v16qi, v16qi) 7109v8hi __builtin_ia32_pmaxsw128 (v8hi, v8hi) 7110v16qi __builtin_ia32_pminub128 (v16qi, v16qi) 7111v8hi __builtin_ia32_pminsw128 (v8hi, v8hi) 7112v16qi __builtin_ia32_punpckhbw128 (v16qi, v16qi) 7113v8hi __builtin_ia32_punpckhwd128 (v8hi, v8hi) 7114v4si __builtin_ia32_punpckhdq128 (v4si, v4si) 7115v2di __builtin_ia32_punpckhqdq128 (v2di, v2di) 7116v16qi __builtin_ia32_punpcklbw128 (v16qi, v16qi) 7117v8hi __builtin_ia32_punpcklwd128 (v8hi, v8hi) 7118v4si __builtin_ia32_punpckldq128 (v4si, v4si) 7119v2di __builtin_ia32_punpcklqdq128 (v2di, v2di) 7120v16qi __builtin_ia32_packsswb128 (v16qi, v16qi) 7121v8hi __builtin_ia32_packssdw128 (v8hi, v8hi) 7122v16qi __builtin_ia32_packuswb128 (v16qi, v16qi) 7123v8hi __builtin_ia32_pmulhuw128 (v8hi, v8hi) 7124void __builtin_ia32_maskmovdqu (v16qi, v16qi) 7125v2df __builtin_ia32_loadupd (double *) 7126void __builtin_ia32_storeupd (double *, v2df) 7127v2df __builtin_ia32_loadhpd (v2df, double *) 7128v2df __builtin_ia32_loadlpd (v2df, double *) 7129int __builtin_ia32_movmskpd (v2df) 7130int __builtin_ia32_pmovmskb128 (v16qi) 7131void __builtin_ia32_movnti (int *, int) 7132void __builtin_ia32_movntpd (double *, v2df) 7133void __builtin_ia32_movntdq (v2df *, v2df) 7134v4si __builtin_ia32_pshufd (v4si, int) 7135v8hi __builtin_ia32_pshuflw (v8hi, int) 7136v8hi __builtin_ia32_pshufhw (v8hi, int) 7137v2di __builtin_ia32_psadbw128 (v16qi, v16qi) 7138v2df __builtin_ia32_sqrtpd (v2df) 7139v2df __builtin_ia32_sqrtsd (v2df) 7140v2df __builtin_ia32_shufpd (v2df, v2df, int) 7141v2df __builtin_ia32_cvtdq2pd (v4si) 7142v4sf __builtin_ia32_cvtdq2ps (v4si) 7143v4si __builtin_ia32_cvtpd2dq (v2df) 7144v2si __builtin_ia32_cvtpd2pi (v2df) 7145v4sf __builtin_ia32_cvtpd2ps (v2df) 7146v4si __builtin_ia32_cvttpd2dq (v2df) 7147v2si __builtin_ia32_cvttpd2pi (v2df) 7148v2df __builtin_ia32_cvtpi2pd (v2si) 7149int __builtin_ia32_cvtsd2si (v2df) 7150int __builtin_ia32_cvttsd2si (v2df) 7151long long __builtin_ia32_cvtsd2si64 (v2df) 7152long long __builtin_ia32_cvttsd2si64 (v2df) 7153v4si __builtin_ia32_cvtps2dq (v4sf) 7154v2df __builtin_ia32_cvtps2pd (v4sf) 7155v4si __builtin_ia32_cvttps2dq (v4sf) 7156v2df __builtin_ia32_cvtsi2sd (v2df, int) 7157v2df __builtin_ia32_cvtsi642sd (v2df, long long) 7158v4sf __builtin_ia32_cvtsd2ss (v4sf, v2df) 7159v2df __builtin_ia32_cvtss2sd (v2df, v4sf) 7160void __builtin_ia32_clflush (const void *) 7161void __builtin_ia32_lfence (void) 7162void __builtin_ia32_mfence (void) 7163v16qi __builtin_ia32_loaddqu (const char *) 7164void __builtin_ia32_storedqu (char *, v16qi) 7165unsigned long long __builtin_ia32_pmuludq (v2si, v2si) 7166v2di __builtin_ia32_pmuludq128 (v4si, v4si) 7167v8hi __builtin_ia32_psllw128 (v8hi, v2di) 7168v4si __builtin_ia32_pslld128 (v4si, v2di) 7169v2di __builtin_ia32_psllq128 (v4si, v2di) 7170v8hi __builtin_ia32_psrlw128 (v8hi, v2di) 7171v4si __builtin_ia32_psrld128 (v4si, v2di) 7172v2di __builtin_ia32_psrlq128 (v2di, v2di) 7173v8hi __builtin_ia32_psraw128 (v8hi, v2di) 7174v4si __builtin_ia32_psrad128 (v4si, v2di) 7175v2di __builtin_ia32_pslldqi128 (v2di, int) 7176v8hi __builtin_ia32_psllwi128 (v8hi, int) 7177v4si __builtin_ia32_pslldi128 (v4si, int) 7178v2di __builtin_ia32_psllqi128 (v2di, int) 7179v2di __builtin_ia32_psrldqi128 (v2di, int) 7180v8hi __builtin_ia32_psrlwi128 (v8hi, int) 7181v4si __builtin_ia32_psrldi128 (v4si, int) 7182v2di __builtin_ia32_psrlqi128 (v2di, int) 7183v8hi __builtin_ia32_psrawi128 (v8hi, int) 7184v4si __builtin_ia32_psradi128 (v4si, int) 7185v4si __builtin_ia32_pmaddwd128 (v8hi, v8hi) 7186@end smallexample 7187 7188The following built-in functions are available when @option{-msse3} is used. 7189All of them generate the machine instruction that is part of the name. 7190 7191@smallexample 7192v2df __builtin_ia32_addsubpd (v2df, v2df) 7193v4sf __builtin_ia32_addsubps (v4sf, v4sf) 7194v2df __builtin_ia32_haddpd (v2df, v2df) 7195v4sf __builtin_ia32_haddps (v4sf, v4sf) 7196v2df __builtin_ia32_hsubpd (v2df, v2df) 7197v4sf __builtin_ia32_hsubps (v4sf, v4sf) 7198v16qi __builtin_ia32_lddqu (char const *) 7199void __builtin_ia32_monitor (void *, unsigned int, unsigned int) 7200v2df __builtin_ia32_movddup (v2df) 7201v4sf __builtin_ia32_movshdup (v4sf) 7202v4sf __builtin_ia32_movsldup (v4sf) 7203void __builtin_ia32_mwait (unsigned int, unsigned int) 7204@end smallexample 7205 7206The following built-in functions are available when @option{-msse3} is used. 7207 7208@table @code 7209@item v2df __builtin_ia32_loadddup (double const *) 7210Generates the @code{movddup} machine instruction as a load from memory. 7211@end table 7212 7213The following built-in functions are available when @option{-mssse3} is used. 7214All of them generate the machine instruction that is part of the name 7215with MMX registers. 7216 7217@smallexample 7218v2si __builtin_ia32_phaddd (v2si, v2si) 7219v4hi __builtin_ia32_phaddw (v4hi, v4hi) 7220v4hi __builtin_ia32_phaddsw (v4hi, v4hi) 7221v2si __builtin_ia32_phsubd (v2si, v2si) 7222v4hi __builtin_ia32_phsubw (v4hi, v4hi) 7223v4hi __builtin_ia32_phsubsw (v4hi, v4hi) 7224v8qi __builtin_ia32_pmaddubsw (v8qi, v8qi) 7225v4hi __builtin_ia32_pmulhrsw (v4hi, v4hi) 7226v8qi __builtin_ia32_pshufb (v8qi, v8qi) 7227v8qi __builtin_ia32_psignb (v8qi, v8qi) 7228v2si __builtin_ia32_psignd (v2si, v2si) 7229v4hi __builtin_ia32_psignw (v4hi, v4hi) 7230long long __builtin_ia32_palignr (long long, long long, int) 7231v8qi __builtin_ia32_pabsb (v8qi) 7232v2si __builtin_ia32_pabsd (v2si) 7233v4hi __builtin_ia32_pabsw (v4hi) 7234@end smallexample 7235 7236The following built-in functions are available when @option{-mssse3} is used. 7237All of them generate the machine instruction that is part of the name 7238with SSE registers. 7239 7240@smallexample 7241v4si __builtin_ia32_phaddd128 (v4si, v4si) 7242v8hi __builtin_ia32_phaddw128 (v8hi, v8hi) 7243v8hi __builtin_ia32_phaddsw128 (v8hi, v8hi) 7244v4si __builtin_ia32_phsubd128 (v4si, v4si) 7245v8hi __builtin_ia32_phsubw128 (v8hi, v8hi) 7246v8hi __builtin_ia32_phsubsw128 (v8hi, v8hi) 7247v16qi __builtin_ia32_pmaddubsw128 (v16qi, v16qi) 7248v8hi __builtin_ia32_pmulhrsw128 (v8hi, v8hi) 7249v16qi __builtin_ia32_pshufb128 (v16qi, v16qi) 7250v16qi __builtin_ia32_psignb128 (v16qi, v16qi) 7251v4si __builtin_ia32_psignd128 (v4si, v4si) 7252v8hi __builtin_ia32_psignw128 (v8hi, v8hi) 7253v2di __builtin_ia32_palignr (v2di, v2di, int) 7254v16qi __builtin_ia32_pabsb128 (v16qi) 7255v4si __builtin_ia32_pabsd128 (v4si) 7256v8hi __builtin_ia32_pabsw128 (v8hi) 7257@end smallexample 7258 7259The following built-in functions are available when @option{-msse4a} is used. 7260 7261@smallexample 7262void _mm_stream_sd (double*,__m128d); 7263Generates the @code{movntsd} machine instruction. 7264void _mm_stream_ss (float*,__m128); 7265Generates the @code{movntss} machine instruction. 7266__m128i _mm_extract_si64 (__m128i, __m128i); 7267Generates the @code{extrq} machine instruction with only SSE register operands. 7268__m128i _mm_extracti_si64 (__m128i, int, int); 7269Generates the @code{extrq} machine instruction with SSE register and immediate operands. 7270__m128i _mm_insert_si64 (__m128i, __m128i); 7271Generates the @code{insertq} machine instruction with only SSE register operands. 7272__m128i _mm_inserti_si64 (__m128i, __m128i, int, int); 7273Generates the @code{insertq} machine instruction with SSE register and immediate operands. 7274@end smallexample 7275 7276The following built-in functions are available when @option{-m3dnow} is used. 7277All of them generate the machine instruction that is part of the name. 7278 7279@smallexample 7280void __builtin_ia32_femms (void) 7281v8qi __builtin_ia32_pavgusb (v8qi, v8qi) 7282v2si __builtin_ia32_pf2id (v2sf) 7283v2sf __builtin_ia32_pfacc (v2sf, v2sf) 7284v2sf __builtin_ia32_pfadd (v2sf, v2sf) 7285v2si __builtin_ia32_pfcmpeq (v2sf, v2sf) 7286v2si __builtin_ia32_pfcmpge (v2sf, v2sf) 7287v2si __builtin_ia32_pfcmpgt (v2sf, v2sf) 7288v2sf __builtin_ia32_pfmax (v2sf, v2sf) 7289v2sf __builtin_ia32_pfmin (v2sf, v2sf) 7290v2sf __builtin_ia32_pfmul (v2sf, v2sf) 7291v2sf __builtin_ia32_pfrcp (v2sf) 7292v2sf __builtin_ia32_pfrcpit1 (v2sf, v2sf) 7293v2sf __builtin_ia32_pfrcpit2 (v2sf, v2sf) 7294v2sf __builtin_ia32_pfrsqrt (v2sf) 7295v2sf __builtin_ia32_pfrsqrtit1 (v2sf, v2sf) 7296v2sf __builtin_ia32_pfsub (v2sf, v2sf) 7297v2sf __builtin_ia32_pfsubr (v2sf, v2sf) 7298v2sf __builtin_ia32_pi2fd (v2si) 7299v4hi __builtin_ia32_pmulhrw (v4hi, v4hi) 7300@end smallexample 7301 7302The following built-in functions are available when both @option{-m3dnow} 7303and @option{-march=athlon} are used. All of them generate the machine 7304instruction that is part of the name. 7305 7306@smallexample 7307v2si __builtin_ia32_pf2iw (v2sf) 7308v2sf __builtin_ia32_pfnacc (v2sf, v2sf) 7309v2sf __builtin_ia32_pfpnacc (v2sf, v2sf) 7310v2sf __builtin_ia32_pi2fw (v2si) 7311v2sf __builtin_ia32_pswapdsf (v2sf) 7312v2si __builtin_ia32_pswapdsi (v2si) 7313@end smallexample 7314 7315@node MIPS DSP Built-in Functions 7316@subsection MIPS DSP Built-in Functions 7317 7318The MIPS DSP Application-Specific Extension (ASE) includes new 7319instructions that are designed to improve the performance of DSP and 7320media applications. It provides instructions that operate on packed 73218-bit integer data, Q15 fractional data and Q31 fractional data. 7322 7323GCC supports MIPS DSP operations using both the generic 7324vector extensions (@pxref{Vector Extensions}) and a collection of 7325MIPS-specific built-in functions. Both kinds of support are 7326enabled by the @option{-mdsp} command-line option. 7327 7328At present, GCC only provides support for operations on 32-bit 7329vectors. The vector type associated with 8-bit integer data is 7330usually called @code{v4i8} and the vector type associated with Q15 is 7331usually called @code{v2q15}. They can be defined in C as follows: 7332 7333@smallexample 7334typedef char v4i8 __attribute__ ((vector_size(4))); 7335typedef short v2q15 __attribute__ ((vector_size(4))); 7336@end smallexample 7337 7338@code{v4i8} and @code{v2q15} values are initialized in the same way as 7339aggregates. For example: 7340 7341@smallexample 7342v4i8 a = @{1, 2, 3, 4@}; 7343v4i8 b; 7344b = (v4i8) @{5, 6, 7, 8@}; 7345 7346v2q15 c = @{0x0fcb, 0x3a75@}; 7347v2q15 d; 7348d = (v2q15) @{0.1234 * 0x1.0p15, 0.4567 * 0x1.0p15@}; 7349@end smallexample 7350 7351@emph{Note:} The CPU's endianness determines the order in which values 7352are packed. On little-endian targets, the first value is the least 7353significant and the last value is the most significant. The opposite 7354order applies to big-endian targets. For example, the code above will 7355set the lowest byte of @code{a} to @code{1} on little-endian targets 7356and @code{4} on big-endian targets. 7357 7358@emph{Note:} Q15 and Q31 values must be initialized with their integer 7359representation. As shown in this example, the integer representation 7360of a Q15 value can be obtained by multiplying the fractional value by 7361@code{0x1.0p15}. The equivalent for Q31 values is to multiply by 7362@code{0x1.0p31}. 7363 7364The table below lists the @code{v4i8} and @code{v2q15} operations for which 7365hardware support exists. @code{a} and @code{b} are @code{v4i8} values, 7366and @code{c} and @code{d} are @code{v2q15} values. 7367 7368@multitable @columnfractions .50 .50 7369@item C code @tab MIPS instruction 7370@item @code{a + b} @tab @code{addu.qb} 7371@item @code{c + d} @tab @code{addq.ph} 7372@item @code{a - b} @tab @code{subu.qb} 7373@item @code{c - d} @tab @code{subq.ph} 7374@end multitable 7375 7376It is easier to describe the DSP built-in functions if we first define 7377the following types: 7378 7379@smallexample 7380typedef int q31; 7381typedef int i32; 7382typedef long long a64; 7383@end smallexample 7384 7385@code{q31} and @code{i32} are actually the same as @code{int}, but we 7386use @code{q31} to indicate a Q31 fractional value and @code{i32} to 7387indicate a 32-bit integer value. Similarly, @code{a64} is the same as 7388@code{long long}, but we use @code{a64} to indicate values that will 7389be placed in one of the four DSP accumulators (@code{$ac0}, 7390@code{$ac1}, @code{$ac2} or @code{$ac3}). 7391 7392Also, some built-in functions prefer or require immediate numbers as 7393parameters, because the corresponding DSP instructions accept both immediate 7394numbers and register operands, or accept immediate numbers only. The 7395immediate parameters are listed as follows. 7396 7397@smallexample 7398imm0_7: 0 to 7. 7399imm0_15: 0 to 15. 7400imm0_31: 0 to 31. 7401imm0_63: 0 to 63. 7402imm0_255: 0 to 255. 7403imm_n32_31: -32 to 31. 7404imm_n512_511: -512 to 511. 7405@end smallexample 7406 7407The following built-in functions map directly to a particular MIPS DSP 7408instruction. Please refer to the architecture specification 7409for details on what each instruction does. 7410 7411@smallexample 7412v2q15 __builtin_mips_addq_ph (v2q15, v2q15) 7413v2q15 __builtin_mips_addq_s_ph (v2q15, v2q15) 7414q31 __builtin_mips_addq_s_w (q31, q31) 7415v4i8 __builtin_mips_addu_qb (v4i8, v4i8) 7416v4i8 __builtin_mips_addu_s_qb (v4i8, v4i8) 7417v2q15 __builtin_mips_subq_ph (v2q15, v2q15) 7418v2q15 __builtin_mips_subq_s_ph (v2q15, v2q15) 7419q31 __builtin_mips_subq_s_w (q31, q31) 7420v4i8 __builtin_mips_subu_qb (v4i8, v4i8) 7421v4i8 __builtin_mips_subu_s_qb (v4i8, v4i8) 7422i32 __builtin_mips_addsc (i32, i32) 7423i32 __builtin_mips_addwc (i32, i32) 7424i32 __builtin_mips_modsub (i32, i32) 7425i32 __builtin_mips_raddu_w_qb (v4i8) 7426v2q15 __builtin_mips_absq_s_ph (v2q15) 7427q31 __builtin_mips_absq_s_w (q31) 7428v4i8 __builtin_mips_precrq_qb_ph (v2q15, v2q15) 7429v2q15 __builtin_mips_precrq_ph_w (q31, q31) 7430v2q15 __builtin_mips_precrq_rs_ph_w (q31, q31) 7431v4i8 __builtin_mips_precrqu_s_qb_ph (v2q15, v2q15) 7432q31 __builtin_mips_preceq_w_phl (v2q15) 7433q31 __builtin_mips_preceq_w_phr (v2q15) 7434v2q15 __builtin_mips_precequ_ph_qbl (v4i8) 7435v2q15 __builtin_mips_precequ_ph_qbr (v4i8) 7436v2q15 __builtin_mips_precequ_ph_qbla (v4i8) 7437v2q15 __builtin_mips_precequ_ph_qbra (v4i8) 7438v2q15 __builtin_mips_preceu_ph_qbl (v4i8) 7439v2q15 __builtin_mips_preceu_ph_qbr (v4i8) 7440v2q15 __builtin_mips_preceu_ph_qbla (v4i8) 7441v2q15 __builtin_mips_preceu_ph_qbra (v4i8) 7442v4i8 __builtin_mips_shll_qb (v4i8, imm0_7) 7443v4i8 __builtin_mips_shll_qb (v4i8, i32) 7444v2q15 __builtin_mips_shll_ph (v2q15, imm0_15) 7445v2q15 __builtin_mips_shll_ph (v2q15, i32) 7446v2q15 __builtin_mips_shll_s_ph (v2q15, imm0_15) 7447v2q15 __builtin_mips_shll_s_ph (v2q15, i32) 7448q31 __builtin_mips_shll_s_w (q31, imm0_31) 7449q31 __builtin_mips_shll_s_w (q31, i32) 7450v4i8 __builtin_mips_shrl_qb (v4i8, imm0_7) 7451v4i8 __builtin_mips_shrl_qb (v4i8, i32) 7452v2q15 __builtin_mips_shra_ph (v2q15, imm0_15) 7453v2q15 __builtin_mips_shra_ph (v2q15, i32) 7454v2q15 __builtin_mips_shra_r_ph (v2q15, imm0_15) 7455v2q15 __builtin_mips_shra_r_ph (v2q15, i32) 7456q31 __builtin_mips_shra_r_w (q31, imm0_31) 7457q31 __builtin_mips_shra_r_w (q31, i32) 7458v2q15 __builtin_mips_muleu_s_ph_qbl (v4i8, v2q15) 7459v2q15 __builtin_mips_muleu_s_ph_qbr (v4i8, v2q15) 7460v2q15 __builtin_mips_mulq_rs_ph (v2q15, v2q15) 7461q31 __builtin_mips_muleq_s_w_phl (v2q15, v2q15) 7462q31 __builtin_mips_muleq_s_w_phr (v2q15, v2q15) 7463a64 __builtin_mips_dpau_h_qbl (a64, v4i8, v4i8) 7464a64 __builtin_mips_dpau_h_qbr (a64, v4i8, v4i8) 7465a64 __builtin_mips_dpsu_h_qbl (a64, v4i8, v4i8) 7466a64 __builtin_mips_dpsu_h_qbr (a64, v4i8, v4i8) 7467a64 __builtin_mips_dpaq_s_w_ph (a64, v2q15, v2q15) 7468a64 __builtin_mips_dpaq_sa_l_w (a64, q31, q31) 7469a64 __builtin_mips_dpsq_s_w_ph (a64, v2q15, v2q15) 7470a64 __builtin_mips_dpsq_sa_l_w (a64, q31, q31) 7471a64 __builtin_mips_mulsaq_s_w_ph (a64, v2q15, v2q15) 7472a64 __builtin_mips_maq_s_w_phl (a64, v2q15, v2q15) 7473a64 __builtin_mips_maq_s_w_phr (a64, v2q15, v2q15) 7474a64 __builtin_mips_maq_sa_w_phl (a64, v2q15, v2q15) 7475a64 __builtin_mips_maq_sa_w_phr (a64, v2q15, v2q15) 7476i32 __builtin_mips_bitrev (i32) 7477i32 __builtin_mips_insv (i32, i32) 7478v4i8 __builtin_mips_repl_qb (imm0_255) 7479v4i8 __builtin_mips_repl_qb (i32) 7480v2q15 __builtin_mips_repl_ph (imm_n512_511) 7481v2q15 __builtin_mips_repl_ph (i32) 7482void __builtin_mips_cmpu_eq_qb (v4i8, v4i8) 7483void __builtin_mips_cmpu_lt_qb (v4i8, v4i8) 7484void __builtin_mips_cmpu_le_qb (v4i8, v4i8) 7485i32 __builtin_mips_cmpgu_eq_qb (v4i8, v4i8) 7486i32 __builtin_mips_cmpgu_lt_qb (v4i8, v4i8) 7487i32 __builtin_mips_cmpgu_le_qb (v4i8, v4i8) 7488void __builtin_mips_cmp_eq_ph (v2q15, v2q15) 7489void __builtin_mips_cmp_lt_ph (v2q15, v2q15) 7490void __builtin_mips_cmp_le_ph (v2q15, v2q15) 7491v4i8 __builtin_mips_pick_qb (v4i8, v4i8) 7492v2q15 __builtin_mips_pick_ph (v2q15, v2q15) 7493v2q15 __builtin_mips_packrl_ph (v2q15, v2q15) 7494i32 __builtin_mips_extr_w (a64, imm0_31) 7495i32 __builtin_mips_extr_w (a64, i32) 7496i32 __builtin_mips_extr_r_w (a64, imm0_31) 7497i32 __builtin_mips_extr_s_h (a64, i32) 7498i32 __builtin_mips_extr_rs_w (a64, imm0_31) 7499i32 __builtin_mips_extr_rs_w (a64, i32) 7500i32 __builtin_mips_extr_s_h (a64, imm0_31) 7501i32 __builtin_mips_extr_r_w (a64, i32) 7502i32 __builtin_mips_extp (a64, imm0_31) 7503i32 __builtin_mips_extp (a64, i32) 7504i32 __builtin_mips_extpdp (a64, imm0_31) 7505i32 __builtin_mips_extpdp (a64, i32) 7506a64 __builtin_mips_shilo (a64, imm_n32_31) 7507a64 __builtin_mips_shilo (a64, i32) 7508a64 __builtin_mips_mthlip (a64, i32) 7509void __builtin_mips_wrdsp (i32, imm0_63) 7510i32 __builtin_mips_rddsp (imm0_63) 7511i32 __builtin_mips_lbux (void *, i32) 7512i32 __builtin_mips_lhx (void *, i32) 7513i32 __builtin_mips_lwx (void *, i32) 7514i32 __builtin_mips_bposge32 (void) 7515@end smallexample 7516 7517@node MIPS Paired-Single Support 7518@subsection MIPS Paired-Single Support 7519 7520The MIPS64 architecture includes a number of instructions that 7521operate on pairs of single-precision floating-point values. 7522Each pair is packed into a 64-bit floating-point register, 7523with one element being designated the ``upper half'' and 7524the other being designated the ``lower half''. 7525 7526GCC supports paired-single operations using both the generic 7527vector extensions (@pxref{Vector Extensions}) and a collection of 7528MIPS-specific built-in functions. Both kinds of support are 7529enabled by the @option{-mpaired-single} command-line option. 7530 7531The vector type associated with paired-single values is usually 7532called @code{v2sf}. It can be defined in C as follows: 7533 7534@smallexample 7535typedef float v2sf __attribute__ ((vector_size (8))); 7536@end smallexample 7537 7538@code{v2sf} values are initialized in the same way as aggregates. 7539For example: 7540 7541@smallexample 7542v2sf a = @{1.5, 9.1@}; 7543v2sf b; 7544float e, f; 7545b = (v2sf) @{e, f@}; 7546@end smallexample 7547 7548@emph{Note:} The CPU's endianness determines which value is stored in 7549the upper half of a register and which value is stored in the lower half. 7550On little-endian targets, the first value is the lower one and the second 7551value is the upper one. The opposite order applies to big-endian targets. 7552For example, the code above will set the lower half of @code{a} to 7553@code{1.5} on little-endian targets and @code{9.1} on big-endian targets. 7554 7555@menu 7556* Paired-Single Arithmetic:: 7557* Paired-Single Built-in Functions:: 7558* MIPS-3D Built-in Functions:: 7559@end menu 7560 7561@node Paired-Single Arithmetic 7562@subsubsection Paired-Single Arithmetic 7563 7564The table below lists the @code{v2sf} operations for which hardware 7565support exists. @code{a}, @code{b} and @code{c} are @code{v2sf} 7566values and @code{x} is an integral value. 7567 7568@multitable @columnfractions .50 .50 7569@item C code @tab MIPS instruction 7570@item @code{a + b} @tab @code{add.ps} 7571@item @code{a - b} @tab @code{sub.ps} 7572@item @code{-a} @tab @code{neg.ps} 7573@item @code{a * b} @tab @code{mul.ps} 7574@item @code{a * b + c} @tab @code{madd.ps} 7575@item @code{a * b - c} @tab @code{msub.ps} 7576@item @code{-(a * b + c)} @tab @code{nmadd.ps} 7577@item @code{-(a * b - c)} @tab @code{nmsub.ps} 7578@item @code{x ? a : b} @tab @code{movn.ps}/@code{movz.ps} 7579@end multitable 7580 7581Note that the multiply-accumulate instructions can be disabled 7582using the command-line option @code{-mno-fused-madd}. 7583 7584@node Paired-Single Built-in Functions 7585@subsubsection Paired-Single Built-in Functions 7586 7587The following paired-single functions map directly to a particular 7588MIPS instruction. Please refer to the architecture specification 7589for details on what each instruction does. 7590 7591@table @code 7592@item v2sf __builtin_mips_pll_ps (v2sf, v2sf) 7593Pair lower lower (@code{pll.ps}). 7594 7595@item v2sf __builtin_mips_pul_ps (v2sf, v2sf) 7596Pair upper lower (@code{pul.ps}). 7597 7598@item v2sf __builtin_mips_plu_ps (v2sf, v2sf) 7599Pair lower upper (@code{plu.ps}). 7600 7601@item v2sf __builtin_mips_puu_ps (v2sf, v2sf) 7602Pair upper upper (@code{puu.ps}). 7603 7604@item v2sf __builtin_mips_cvt_ps_s (float, float) 7605Convert pair to paired single (@code{cvt.ps.s}). 7606 7607@item float __builtin_mips_cvt_s_pl (v2sf) 7608Convert pair lower to single (@code{cvt.s.pl}). 7609 7610@item float __builtin_mips_cvt_s_pu (v2sf) 7611Convert pair upper to single (@code{cvt.s.pu}). 7612 7613@item v2sf __builtin_mips_abs_ps (v2sf) 7614Absolute value (@code{abs.ps}). 7615 7616@item v2sf __builtin_mips_alnv_ps (v2sf, v2sf, int) 7617Align variable (@code{alnv.ps}). 7618 7619@emph{Note:} The value of the third parameter must be 0 or 4 7620modulo 8, otherwise the result will be unpredictable. Please read the 7621instruction description for details. 7622@end table 7623 7624The following multi-instruction functions are also available. 7625In each case, @var{cond} can be any of the 16 floating-point conditions: 7626@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult}, 7627@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, @code{ngl}, 7628@code{lt}, @code{nge}, @code{le} or @code{ngt}. 7629 7630@table @code 7631@item v2sf __builtin_mips_movt_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7632@itemx v2sf __builtin_mips_movf_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7633Conditional move based on floating point comparison (@code{c.@var{cond}.ps}, 7634@code{movt.ps}/@code{movf.ps}). 7635 7636The @code{movt} functions return the value @var{x} computed by: 7637 7638@smallexample 7639c.@var{cond}.ps @var{cc},@var{a},@var{b} 7640mov.ps @var{x},@var{c} 7641movt.ps @var{x},@var{d},@var{cc} 7642@end smallexample 7643 7644The @code{movf} functions are similar but use @code{movf.ps} instead 7645of @code{movt.ps}. 7646 7647@item int __builtin_mips_upper_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7648@itemx int __builtin_mips_lower_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7649Comparison of two paired-single values (@code{c.@var{cond}.ps}, 7650@code{bc1t}/@code{bc1f}). 7651 7652These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps} 7653and return either the upper or lower half of the result. For example: 7654 7655@smallexample 7656v2sf a, b; 7657if (__builtin_mips_upper_c_eq_ps (a, b)) 7658 upper_halves_are_equal (); 7659else 7660 upper_halves_are_unequal (); 7661 7662if (__builtin_mips_lower_c_eq_ps (a, b)) 7663 lower_halves_are_equal (); 7664else 7665 lower_halves_are_unequal (); 7666@end smallexample 7667@end table 7668 7669@node MIPS-3D Built-in Functions 7670@subsubsection MIPS-3D Built-in Functions 7671 7672The MIPS-3D Application-Specific Extension (ASE) includes additional 7673paired-single instructions that are designed to improve the performance 7674of 3D graphics operations. Support for these instructions is controlled 7675by the @option{-mips3d} command-line option. 7676 7677The functions listed below map directly to a particular MIPS-3D 7678instruction. Please refer to the architecture specification for 7679more details on what each instruction does. 7680 7681@table @code 7682@item v2sf __builtin_mips_addr_ps (v2sf, v2sf) 7683Reduction add (@code{addr.ps}). 7684 7685@item v2sf __builtin_mips_mulr_ps (v2sf, v2sf) 7686Reduction multiply (@code{mulr.ps}). 7687 7688@item v2sf __builtin_mips_cvt_pw_ps (v2sf) 7689Convert paired single to paired word (@code{cvt.pw.ps}). 7690 7691@item v2sf __builtin_mips_cvt_ps_pw (v2sf) 7692Convert paired word to paired single (@code{cvt.ps.pw}). 7693 7694@item float __builtin_mips_recip1_s (float) 7695@itemx double __builtin_mips_recip1_d (double) 7696@itemx v2sf __builtin_mips_recip1_ps (v2sf) 7697Reduced precision reciprocal (sequence step 1) (@code{recip1.@var{fmt}}). 7698 7699@item float __builtin_mips_recip2_s (float, float) 7700@itemx double __builtin_mips_recip2_d (double, double) 7701@itemx v2sf __builtin_mips_recip2_ps (v2sf, v2sf) 7702Reduced precision reciprocal (sequence step 2) (@code{recip2.@var{fmt}}). 7703 7704@item float __builtin_mips_rsqrt1_s (float) 7705@itemx double __builtin_mips_rsqrt1_d (double) 7706@itemx v2sf __builtin_mips_rsqrt1_ps (v2sf) 7707Reduced precision reciprocal square root (sequence step 1) 7708(@code{rsqrt1.@var{fmt}}). 7709 7710@item float __builtin_mips_rsqrt2_s (float, float) 7711@itemx double __builtin_mips_rsqrt2_d (double, double) 7712@itemx v2sf __builtin_mips_rsqrt2_ps (v2sf, v2sf) 7713Reduced precision reciprocal square root (sequence step 2) 7714(@code{rsqrt2.@var{fmt}}). 7715@end table 7716 7717The following multi-instruction functions are also available. 7718In each case, @var{cond} can be any of the 16 floating-point conditions: 7719@code{f}, @code{un}, @code{eq}, @code{ueq}, @code{olt}, @code{ult}, 7720@code{ole}, @code{ule}, @code{sf}, @code{ngle}, @code{seq}, 7721@code{ngl}, @code{lt}, @code{nge}, @code{le} or @code{ngt}. 7722 7723@table @code 7724@item int __builtin_mips_cabs_@var{cond}_s (float @var{a}, float @var{b}) 7725@itemx int __builtin_mips_cabs_@var{cond}_d (double @var{a}, double @var{b}) 7726Absolute comparison of two scalar values (@code{cabs.@var{cond}.@var{fmt}}, 7727@code{bc1t}/@code{bc1f}). 7728 7729These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.s} 7730or @code{cabs.@var{cond}.d} and return the result as a boolean value. 7731For example: 7732 7733@smallexample 7734float a, b; 7735if (__builtin_mips_cabs_eq_s (a, b)) 7736 true (); 7737else 7738 false (); 7739@end smallexample 7740 7741@item int __builtin_mips_upper_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7742@itemx int __builtin_mips_lower_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7743Absolute comparison of two paired-single values (@code{cabs.@var{cond}.ps}, 7744@code{bc1t}/@code{bc1f}). 7745 7746These functions compare @var{a} and @var{b} using @code{cabs.@var{cond}.ps} 7747and return either the upper or lower half of the result. For example: 7748 7749@smallexample 7750v2sf a, b; 7751if (__builtin_mips_upper_cabs_eq_ps (a, b)) 7752 upper_halves_are_equal (); 7753else 7754 upper_halves_are_unequal (); 7755 7756if (__builtin_mips_lower_cabs_eq_ps (a, b)) 7757 lower_halves_are_equal (); 7758else 7759 lower_halves_are_unequal (); 7760@end smallexample 7761 7762@item v2sf __builtin_mips_movt_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7763@itemx v2sf __builtin_mips_movf_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7764Conditional move based on absolute comparison (@code{cabs.@var{cond}.ps}, 7765@code{movt.ps}/@code{movf.ps}). 7766 7767The @code{movt} functions return the value @var{x} computed by: 7768 7769@smallexample 7770cabs.@var{cond}.ps @var{cc},@var{a},@var{b} 7771mov.ps @var{x},@var{c} 7772movt.ps @var{x},@var{d},@var{cc} 7773@end smallexample 7774 7775The @code{movf} functions are similar but use @code{movf.ps} instead 7776of @code{movt.ps}. 7777 7778@item int __builtin_mips_any_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7779@itemx int __builtin_mips_all_c_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7780@itemx int __builtin_mips_any_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7781@itemx int __builtin_mips_all_cabs_@var{cond}_ps (v2sf @var{a}, v2sf @var{b}) 7782Comparison of two paired-single values 7783(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps}, 7784@code{bc1any2t}/@code{bc1any2f}). 7785 7786These functions compare @var{a} and @var{b} using @code{c.@var{cond}.ps} 7787or @code{cabs.@var{cond}.ps}. The @code{any} forms return true if either 7788result is true and the @code{all} forms return true if both results are true. 7789For example: 7790 7791@smallexample 7792v2sf a, b; 7793if (__builtin_mips_any_c_eq_ps (a, b)) 7794 one_is_true (); 7795else 7796 both_are_false (); 7797 7798if (__builtin_mips_all_c_eq_ps (a, b)) 7799 both_are_true (); 7800else 7801 one_is_false (); 7802@end smallexample 7803 7804@item int __builtin_mips_any_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7805@itemx int __builtin_mips_all_c_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7806@itemx int __builtin_mips_any_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7807@itemx int __builtin_mips_all_cabs_@var{cond}_4s (v2sf @var{a}, v2sf @var{b}, v2sf @var{c}, v2sf @var{d}) 7808Comparison of four paired-single values 7809(@code{c.@var{cond}.ps}/@code{cabs.@var{cond}.ps}, 7810@code{bc1any4t}/@code{bc1any4f}). 7811 7812These functions use @code{c.@var{cond}.ps} or @code{cabs.@var{cond}.ps} 7813to compare @var{a} with @var{b} and to compare @var{c} with @var{d}. 7814The @code{any} forms return true if any of the four results are true 7815and the @code{all} forms return true if all four results are true. 7816For example: 7817 7818@smallexample 7819v2sf a, b, c, d; 7820if (__builtin_mips_any_c_eq_4s (a, b, c, d)) 7821 some_are_true (); 7822else 7823 all_are_false (); 7824 7825if (__builtin_mips_all_c_eq_4s (a, b, c, d)) 7826 all_are_true (); 7827else 7828 some_are_false (); 7829@end smallexample 7830@end table 7831 7832@node PowerPC AltiVec Built-in Functions 7833@subsection PowerPC AltiVec Built-in Functions 7834 7835GCC provides an interface for the PowerPC family of processors to access 7836the AltiVec operations described in Motorola's AltiVec Programming 7837Interface Manual. The interface is made available by including 7838@code{<altivec.h>} and using @option{-maltivec} and 7839@option{-mabi=altivec}. The interface supports the following vector 7840types. 7841 7842@smallexample 7843vector unsigned char 7844vector signed char 7845vector bool char 7846 7847vector unsigned short 7848vector signed short 7849vector bool short 7850vector pixel 7851 7852vector unsigned int 7853vector signed int 7854vector bool int 7855vector float 7856@end smallexample 7857 7858GCC's implementation of the high-level language interface available from 7859C and C++ code differs from Motorola's documentation in several ways. 7860 7861@itemize @bullet 7862 7863@item 7864A vector constant is a list of constant expressions within curly braces. 7865 7866@item 7867A vector initializer requires no cast if the vector constant is of the 7868same type as the variable it is initializing. 7869 7870@item 7871If @code{signed} or @code{unsigned} is omitted, the signedness of the 7872vector type is the default signedness of the base type. The default 7873varies depending on the operating system, so a portable program should 7874always specify the signedness. 7875 7876@item 7877Compiling with @option{-maltivec} adds keywords @code{__vector}, 7878@code{__pixel}, and @code{__bool}. Macros @option{vector}, 7879@code{pixel}, and @code{bool} are defined in @code{<altivec.h>} and can 7880be undefined. 7881 7882@item 7883GCC allows using a @code{typedef} name as the type specifier for a 7884vector type. 7885 7886@item 7887For C, overloaded functions are implemented with macros so the following 7888does not work: 7889 7890@smallexample 7891 vec_add ((vector signed int)@{1, 2, 3, 4@}, foo); 7892@end smallexample 7893 7894Since @code{vec_add} is a macro, the vector constant in the example 7895is treated as four separate arguments. Wrap the entire argument in 7896parentheses for this to work. 7897@end itemize 7898 7899@emph{Note:} Only the @code{<altivec.h>} interface is supported. 7900Internally, GCC uses built-in functions to achieve the functionality in 7901the aforementioned header file, but they are not supported and are 7902subject to change without notice. 7903 7904The following interfaces are supported for the generic and specific 7905AltiVec operations and the AltiVec predicates. In cases where there 7906is a direct mapping between generic and specific operations, only the 7907generic names are shown here, although the specific operations can also 7908be used. 7909 7910Arguments that are documented as @code{const int} require literal 7911integral values within the range required for that operation. 7912 7913@smallexample 7914vector signed char vec_abs (vector signed char); 7915vector signed short vec_abs (vector signed short); 7916vector signed int vec_abs (vector signed int); 7917vector float vec_abs (vector float); 7918 7919vector signed char vec_abss (vector signed char); 7920vector signed short vec_abss (vector signed short); 7921vector signed int vec_abss (vector signed int); 7922 7923vector signed char vec_add (vector bool char, vector signed char); 7924vector signed char vec_add (vector signed char, vector bool char); 7925vector signed char vec_add (vector signed char, vector signed char); 7926vector unsigned char vec_add (vector bool char, vector unsigned char); 7927vector unsigned char vec_add (vector unsigned char, vector bool char); 7928vector unsigned char vec_add (vector unsigned char, 7929 vector unsigned char); 7930vector signed short vec_add (vector bool short, vector signed short); 7931vector signed short vec_add (vector signed short, vector bool short); 7932vector signed short vec_add (vector signed short, vector signed short); 7933vector unsigned short vec_add (vector bool short, 7934 vector unsigned short); 7935vector unsigned short vec_add (vector unsigned short, 7936 vector bool short); 7937vector unsigned short vec_add (vector unsigned short, 7938 vector unsigned short); 7939vector signed int vec_add (vector bool int, vector signed int); 7940vector signed int vec_add (vector signed int, vector bool int); 7941vector signed int vec_add (vector signed int, vector signed int); 7942vector unsigned int vec_add (vector bool int, vector unsigned int); 7943vector unsigned int vec_add (vector unsigned int, vector bool int); 7944vector unsigned int vec_add (vector unsigned int, vector unsigned int); 7945vector float vec_add (vector float, vector float); 7946 7947vector float vec_vaddfp (vector float, vector float); 7948 7949vector signed int vec_vadduwm (vector bool int, vector signed int); 7950vector signed int vec_vadduwm (vector signed int, vector bool int); 7951vector signed int vec_vadduwm (vector signed int, vector signed int); 7952vector unsigned int vec_vadduwm (vector bool int, vector unsigned int); 7953vector unsigned int vec_vadduwm (vector unsigned int, vector bool int); 7954vector unsigned int vec_vadduwm (vector unsigned int, 7955 vector unsigned int); 7956 7957vector signed short vec_vadduhm (vector bool short, 7958 vector signed short); 7959vector signed short vec_vadduhm (vector signed short, 7960 vector bool short); 7961vector signed short vec_vadduhm (vector signed short, 7962 vector signed short); 7963vector unsigned short vec_vadduhm (vector bool short, 7964 vector unsigned short); 7965vector unsigned short vec_vadduhm (vector unsigned short, 7966 vector bool short); 7967vector unsigned short vec_vadduhm (vector unsigned short, 7968 vector unsigned short); 7969 7970vector signed char vec_vaddubm (vector bool char, vector signed char); 7971vector signed char vec_vaddubm (vector signed char, vector bool char); 7972vector signed char vec_vaddubm (vector signed char, vector signed char); 7973vector unsigned char vec_vaddubm (vector bool char, 7974 vector unsigned char); 7975vector unsigned char vec_vaddubm (vector unsigned char, 7976 vector bool char); 7977vector unsigned char vec_vaddubm (vector unsigned char, 7978 vector unsigned char); 7979 7980vector unsigned int vec_addc (vector unsigned int, vector unsigned int); 7981 7982vector unsigned char vec_adds (vector bool char, vector unsigned char); 7983vector unsigned char vec_adds (vector unsigned char, vector bool char); 7984vector unsigned char vec_adds (vector unsigned char, 7985 vector unsigned char); 7986vector signed char vec_adds (vector bool char, vector signed char); 7987vector signed char vec_adds (vector signed char, vector bool char); 7988vector signed char vec_adds (vector signed char, vector signed char); 7989vector unsigned short vec_adds (vector bool short, 7990 vector unsigned short); 7991vector unsigned short vec_adds (vector unsigned short, 7992 vector bool short); 7993vector unsigned short vec_adds (vector unsigned short, 7994 vector unsigned short); 7995vector signed short vec_adds (vector bool short, vector signed short); 7996vector signed short vec_adds (vector signed short, vector bool short); 7997vector signed short vec_adds (vector signed short, vector signed short); 7998vector unsigned int vec_adds (vector bool int, vector unsigned int); 7999vector unsigned int vec_adds (vector unsigned int, vector bool int); 8000vector unsigned int vec_adds (vector unsigned int, vector unsigned int); 8001vector signed int vec_adds (vector bool int, vector signed int); 8002vector signed int vec_adds (vector signed int, vector bool int); 8003vector signed int vec_adds (vector signed int, vector signed int); 8004 8005vector signed int vec_vaddsws (vector bool int, vector signed int); 8006vector signed int vec_vaddsws (vector signed int, vector bool int); 8007vector signed int vec_vaddsws (vector signed int, vector signed int); 8008 8009vector unsigned int vec_vadduws (vector bool int, vector unsigned int); 8010vector unsigned int vec_vadduws (vector unsigned int, vector bool int); 8011vector unsigned int vec_vadduws (vector unsigned int, 8012 vector unsigned int); 8013 8014vector signed short vec_vaddshs (vector bool short, 8015 vector signed short); 8016vector signed short vec_vaddshs (vector signed short, 8017 vector bool short); 8018vector signed short vec_vaddshs (vector signed short, 8019 vector signed short); 8020 8021vector unsigned short vec_vadduhs (vector bool short, 8022 vector unsigned short); 8023vector unsigned short vec_vadduhs (vector unsigned short, 8024 vector bool short); 8025vector unsigned short vec_vadduhs (vector unsigned short, 8026 vector unsigned short); 8027 8028vector signed char vec_vaddsbs (vector bool char, vector signed char); 8029vector signed char vec_vaddsbs (vector signed char, vector bool char); 8030vector signed char vec_vaddsbs (vector signed char, vector signed char); 8031 8032vector unsigned char vec_vaddubs (vector bool char, 8033 vector unsigned char); 8034vector unsigned char vec_vaddubs (vector unsigned char, 8035 vector bool char); 8036vector unsigned char vec_vaddubs (vector unsigned char, 8037 vector unsigned char); 8038 8039vector float vec_and (vector float, vector float); 8040vector float vec_and (vector float, vector bool int); 8041vector float vec_and (vector bool int, vector float); 8042vector bool int vec_and (vector bool int, vector bool int); 8043vector signed int vec_and (vector bool int, vector signed int); 8044vector signed int vec_and (vector signed int, vector bool int); 8045vector signed int vec_and (vector signed int, vector signed int); 8046vector unsigned int vec_and (vector bool int, vector unsigned int); 8047vector unsigned int vec_and (vector unsigned int, vector bool int); 8048vector unsigned int vec_and (vector unsigned int, vector unsigned int); 8049vector bool short vec_and (vector bool short, vector bool short); 8050vector signed short vec_and (vector bool short, vector signed short); 8051vector signed short vec_and (vector signed short, vector bool short); 8052vector signed short vec_and (vector signed short, vector signed short); 8053vector unsigned short vec_and (vector bool short, 8054 vector unsigned short); 8055vector unsigned short vec_and (vector unsigned short, 8056 vector bool short); 8057vector unsigned short vec_and (vector unsigned short, 8058 vector unsigned short); 8059vector signed char vec_and (vector bool char, vector signed char); 8060vector bool char vec_and (vector bool char, vector bool char); 8061vector signed char vec_and (vector signed char, vector bool char); 8062vector signed char vec_and (vector signed char, vector signed char); 8063vector unsigned char vec_and (vector bool char, vector unsigned char); 8064vector unsigned char vec_and (vector unsigned char, vector bool char); 8065vector unsigned char vec_and (vector unsigned char, 8066 vector unsigned char); 8067 8068vector float vec_andc (vector float, vector float); 8069vector float vec_andc (vector float, vector bool int); 8070vector float vec_andc (vector bool int, vector float); 8071vector bool int vec_andc (vector bool int, vector bool int); 8072vector signed int vec_andc (vector bool int, vector signed int); 8073vector signed int vec_andc (vector signed int, vector bool int); 8074vector signed int vec_andc (vector signed int, vector signed int); 8075vector unsigned int vec_andc (vector bool int, vector unsigned int); 8076vector unsigned int vec_andc (vector unsigned int, vector bool int); 8077vector unsigned int vec_andc (vector unsigned int, vector unsigned int); 8078vector bool short vec_andc (vector bool short, vector bool short); 8079vector signed short vec_andc (vector bool short, vector signed short); 8080vector signed short vec_andc (vector signed short, vector bool short); 8081vector signed short vec_andc (vector signed short, vector signed short); 8082vector unsigned short vec_andc (vector bool short, 8083 vector unsigned short); 8084vector unsigned short vec_andc (vector unsigned short, 8085 vector bool short); 8086vector unsigned short vec_andc (vector unsigned short, 8087 vector unsigned short); 8088vector signed char vec_andc (vector bool char, vector signed char); 8089vector bool char vec_andc (vector bool char, vector bool char); 8090vector signed char vec_andc (vector signed char, vector bool char); 8091vector signed char vec_andc (vector signed char, vector signed char); 8092vector unsigned char vec_andc (vector bool char, vector unsigned char); 8093vector unsigned char vec_andc (vector unsigned char, vector bool char); 8094vector unsigned char vec_andc (vector unsigned char, 8095 vector unsigned char); 8096 8097vector unsigned char vec_avg (vector unsigned char, 8098 vector unsigned char); 8099vector signed char vec_avg (vector signed char, vector signed char); 8100vector unsigned short vec_avg (vector unsigned short, 8101 vector unsigned short); 8102vector signed short vec_avg (vector signed short, vector signed short); 8103vector unsigned int vec_avg (vector unsigned int, vector unsigned int); 8104vector signed int vec_avg (vector signed int, vector signed int); 8105 8106vector signed int vec_vavgsw (vector signed int, vector signed int); 8107 8108vector unsigned int vec_vavguw (vector unsigned int, 8109 vector unsigned int); 8110 8111vector signed short vec_vavgsh (vector signed short, 8112 vector signed short); 8113 8114vector unsigned short vec_vavguh (vector unsigned short, 8115 vector unsigned short); 8116 8117vector signed char vec_vavgsb (vector signed char, vector signed char); 8118 8119vector unsigned char vec_vavgub (vector unsigned char, 8120 vector unsigned char); 8121 8122vector float vec_ceil (vector float); 8123 8124vector signed int vec_cmpb (vector float, vector float); 8125 8126vector bool char vec_cmpeq (vector signed char, vector signed char); 8127vector bool char vec_cmpeq (vector unsigned char, vector unsigned char); 8128vector bool short vec_cmpeq (vector signed short, vector signed short); 8129vector bool short vec_cmpeq (vector unsigned short, 8130 vector unsigned short); 8131vector bool int vec_cmpeq (vector signed int, vector signed int); 8132vector bool int vec_cmpeq (vector unsigned int, vector unsigned int); 8133vector bool int vec_cmpeq (vector float, vector float); 8134 8135vector bool int vec_vcmpeqfp (vector float, vector float); 8136 8137vector bool int vec_vcmpequw (vector signed int, vector signed int); 8138vector bool int vec_vcmpequw (vector unsigned int, vector unsigned int); 8139 8140vector bool short vec_vcmpequh (vector signed short, 8141 vector signed short); 8142vector bool short vec_vcmpequh (vector unsigned short, 8143 vector unsigned short); 8144 8145vector bool char vec_vcmpequb (vector signed char, vector signed char); 8146vector bool char vec_vcmpequb (vector unsigned char, 8147 vector unsigned char); 8148 8149vector bool int vec_cmpge (vector float, vector float); 8150 8151vector bool char vec_cmpgt (vector unsigned char, vector unsigned char); 8152vector bool char vec_cmpgt (vector signed char, vector signed char); 8153vector bool short vec_cmpgt (vector unsigned short, 8154 vector unsigned short); 8155vector bool short vec_cmpgt (vector signed short, vector signed short); 8156vector bool int vec_cmpgt (vector unsigned int, vector unsigned int); 8157vector bool int vec_cmpgt (vector signed int, vector signed int); 8158vector bool int vec_cmpgt (vector float, vector float); 8159 8160vector bool int vec_vcmpgtfp (vector float, vector float); 8161 8162vector bool int vec_vcmpgtsw (vector signed int, vector signed int); 8163 8164vector bool int vec_vcmpgtuw (vector unsigned int, vector unsigned int); 8165 8166vector bool short vec_vcmpgtsh (vector signed short, 8167 vector signed short); 8168 8169vector bool short vec_vcmpgtuh (vector unsigned short, 8170 vector unsigned short); 8171 8172vector bool char vec_vcmpgtsb (vector signed char, vector signed char); 8173 8174vector bool char vec_vcmpgtub (vector unsigned char, 8175 vector unsigned char); 8176 8177vector bool int vec_cmple (vector float, vector float); 8178 8179vector bool char vec_cmplt (vector unsigned char, vector unsigned char); 8180vector bool char vec_cmplt (vector signed char, vector signed char); 8181vector bool short vec_cmplt (vector unsigned short, 8182 vector unsigned short); 8183vector bool short vec_cmplt (vector signed short, vector signed short); 8184vector bool int vec_cmplt (vector unsigned int, vector unsigned int); 8185vector bool int vec_cmplt (vector signed int, vector signed int); 8186vector bool int vec_cmplt (vector float, vector float); 8187 8188vector float vec_ctf (vector unsigned int, const int); 8189vector float vec_ctf (vector signed int, const int); 8190 8191vector float vec_vcfsx (vector signed int, const int); 8192 8193vector float vec_vcfux (vector unsigned int, const int); 8194 8195vector signed int vec_cts (vector float, const int); 8196 8197vector unsigned int vec_ctu (vector float, const int); 8198 8199void vec_dss (const int); 8200 8201void vec_dssall (void); 8202 8203void vec_dst (const vector unsigned char *, int, const int); 8204void vec_dst (const vector signed char *, int, const int); 8205void vec_dst (const vector bool char *, int, const int); 8206void vec_dst (const vector unsigned short *, int, const int); 8207void vec_dst (const vector signed short *, int, const int); 8208void vec_dst (const vector bool short *, int, const int); 8209void vec_dst (const vector pixel *, int, const int); 8210void vec_dst (const vector unsigned int *, int, const int); 8211void vec_dst (const vector signed int *, int, const int); 8212void vec_dst (const vector bool int *, int, const int); 8213void vec_dst (const vector float *, int, const int); 8214void vec_dst (const unsigned char *, int, const int); 8215void vec_dst (const signed char *, int, const int); 8216void vec_dst (const unsigned short *, int, const int); 8217void vec_dst (const short *, int, const int); 8218void vec_dst (const unsigned int *, int, const int); 8219void vec_dst (const int *, int, const int); 8220void vec_dst (const unsigned long *, int, const int); 8221void vec_dst (const long *, int, const int); 8222void vec_dst (const float *, int, const int); 8223 8224void vec_dstst (const vector unsigned char *, int, const int); 8225void vec_dstst (const vector signed char *, int, const int); 8226void vec_dstst (const vector bool char *, int, const int); 8227void vec_dstst (const vector unsigned short *, int, const int); 8228void vec_dstst (const vector signed short *, int, const int); 8229void vec_dstst (const vector bool short *, int, const int); 8230void vec_dstst (const vector pixel *, int, const int); 8231void vec_dstst (const vector unsigned int *, int, const int); 8232void vec_dstst (const vector signed int *, int, const int); 8233void vec_dstst (const vector bool int *, int, const int); 8234void vec_dstst (const vector float *, int, const int); 8235void vec_dstst (const unsigned char *, int, const int); 8236void vec_dstst (const signed char *, int, const int); 8237void vec_dstst (const unsigned short *, int, const int); 8238void vec_dstst (const short *, int, const int); 8239void vec_dstst (const unsigned int *, int, const int); 8240void vec_dstst (const int *, int, const int); 8241void vec_dstst (const unsigned long *, int, const int); 8242void vec_dstst (const long *, int, const int); 8243void vec_dstst (const float *, int, const int); 8244 8245void vec_dststt (const vector unsigned char *, int, const int); 8246void vec_dststt (const vector signed char *, int, const int); 8247void vec_dststt (const vector bool char *, int, const int); 8248void vec_dststt (const vector unsigned short *, int, const int); 8249void vec_dststt (const vector signed short *, int, const int); 8250void vec_dststt (const vector bool short *, int, const int); 8251void vec_dststt (const vector pixel *, int, const int); 8252void vec_dststt (const vector unsigned int *, int, const int); 8253void vec_dststt (const vector signed int *, int, const int); 8254void vec_dststt (const vector bool int *, int, const int); 8255void vec_dststt (const vector float *, int, const int); 8256void vec_dststt (const unsigned char *, int, const int); 8257void vec_dststt (const signed char *, int, const int); 8258void vec_dststt (const unsigned short *, int, const int); 8259void vec_dststt (const short *, int, const int); 8260void vec_dststt (const unsigned int *, int, const int); 8261void vec_dststt (const int *, int, const int); 8262void vec_dststt (const unsigned long *, int, const int); 8263void vec_dststt (const long *, int, const int); 8264void vec_dststt (const float *, int, const int); 8265 8266void vec_dstt (const vector unsigned char *, int, const int); 8267void vec_dstt (const vector signed char *, int, const int); 8268void vec_dstt (const vector bool char *, int, const int); 8269void vec_dstt (const vector unsigned short *, int, const int); 8270void vec_dstt (const vector signed short *, int, const int); 8271void vec_dstt (const vector bool short *, int, const int); 8272void vec_dstt (const vector pixel *, int, const int); 8273void vec_dstt (const vector unsigned int *, int, const int); 8274void vec_dstt (const vector signed int *, int, const int); 8275void vec_dstt (const vector bool int *, int, const int); 8276void vec_dstt (const vector float *, int, const int); 8277void vec_dstt (const unsigned char *, int, const int); 8278void vec_dstt (const signed char *, int, const int); 8279void vec_dstt (const unsigned short *, int, const int); 8280void vec_dstt (const short *, int, const int); 8281void vec_dstt (const unsigned int *, int, const int); 8282void vec_dstt (const int *, int, const int); 8283void vec_dstt (const unsigned long *, int, const int); 8284void vec_dstt (const long *, int, const int); 8285void vec_dstt (const float *, int, const int); 8286 8287vector float vec_expte (vector float); 8288 8289vector float vec_floor (vector float); 8290 8291vector float vec_ld (int, const vector float *); 8292vector float vec_ld (int, const float *); 8293vector bool int vec_ld (int, const vector bool int *); 8294vector signed int vec_ld (int, const vector signed int *); 8295vector signed int vec_ld (int, const int *); 8296vector signed int vec_ld (int, const long *); 8297vector unsigned int vec_ld (int, const vector unsigned int *); 8298vector unsigned int vec_ld (int, const unsigned int *); 8299vector unsigned int vec_ld (int, const unsigned long *); 8300vector bool short vec_ld (int, const vector bool short *); 8301vector pixel vec_ld (int, const vector pixel *); 8302vector signed short vec_ld (int, const vector signed short *); 8303vector signed short vec_ld (int, const short *); 8304vector unsigned short vec_ld (int, const vector unsigned short *); 8305vector unsigned short vec_ld (int, const unsigned short *); 8306vector bool char vec_ld (int, const vector bool char *); 8307vector signed char vec_ld (int, const vector signed char *); 8308vector signed char vec_ld (int, const signed char *); 8309vector unsigned char vec_ld (int, const vector unsigned char *); 8310vector unsigned char vec_ld (int, const unsigned char *); 8311 8312vector signed char vec_lde (int, const signed char *); 8313vector unsigned char vec_lde (int, const unsigned char *); 8314vector signed short vec_lde (int, const short *); 8315vector unsigned short vec_lde (int, const unsigned short *); 8316vector float vec_lde (int, const float *); 8317vector signed int vec_lde (int, const int *); 8318vector unsigned int vec_lde (int, const unsigned int *); 8319vector signed int vec_lde (int, const long *); 8320vector unsigned int vec_lde (int, const unsigned long *); 8321 8322vector float vec_lvewx (int, float *); 8323vector signed int vec_lvewx (int, int *); 8324vector unsigned int vec_lvewx (int, unsigned int *); 8325vector signed int vec_lvewx (int, long *); 8326vector unsigned int vec_lvewx (int, unsigned long *); 8327 8328vector signed short vec_lvehx (int, short *); 8329vector unsigned short vec_lvehx (int, unsigned short *); 8330 8331vector signed char vec_lvebx (int, char *); 8332vector unsigned char vec_lvebx (int, unsigned char *); 8333 8334vector float vec_ldl (int, const vector float *); 8335vector float vec_ldl (int, const float *); 8336vector bool int vec_ldl (int, const vector bool int *); 8337vector signed int vec_ldl (int, const vector signed int *); 8338vector signed int vec_ldl (int, const int *); 8339vector signed int vec_ldl (int, const long *); 8340vector unsigned int vec_ldl (int, const vector unsigned int *); 8341vector unsigned int vec_ldl (int, const unsigned int *); 8342vector unsigned int vec_ldl (int, const unsigned long *); 8343vector bool short vec_ldl (int, const vector bool short *); 8344vector pixel vec_ldl (int, const vector pixel *); 8345vector signed short vec_ldl (int, const vector signed short *); 8346vector signed short vec_ldl (int, const short *); 8347vector unsigned short vec_ldl (int, const vector unsigned short *); 8348vector unsigned short vec_ldl (int, const unsigned short *); 8349vector bool char vec_ldl (int, const vector bool char *); 8350vector signed char vec_ldl (int, const vector signed char *); 8351vector signed char vec_ldl (int, const signed char *); 8352vector unsigned char vec_ldl (int, const vector unsigned char *); 8353vector unsigned char vec_ldl (int, const unsigned char *); 8354 8355vector float vec_loge (vector float); 8356 8357vector unsigned char vec_lvsl (int, const volatile unsigned char *); 8358vector unsigned char vec_lvsl (int, const volatile signed char *); 8359vector unsigned char vec_lvsl (int, const volatile unsigned short *); 8360vector unsigned char vec_lvsl (int, const volatile short *); 8361vector unsigned char vec_lvsl (int, const volatile unsigned int *); 8362vector unsigned char vec_lvsl (int, const volatile int *); 8363vector unsigned char vec_lvsl (int, const volatile unsigned long *); 8364vector unsigned char vec_lvsl (int, const volatile long *); 8365vector unsigned char vec_lvsl (int, const volatile float *); 8366 8367vector unsigned char vec_lvsr (int, const volatile unsigned char *); 8368vector unsigned char vec_lvsr (int, const volatile signed char *); 8369vector unsigned char vec_lvsr (int, const volatile unsigned short *); 8370vector unsigned char vec_lvsr (int, const volatile short *); 8371vector unsigned char vec_lvsr (int, const volatile unsigned int *); 8372vector unsigned char vec_lvsr (int, const volatile int *); 8373vector unsigned char vec_lvsr (int, const volatile unsigned long *); 8374vector unsigned char vec_lvsr (int, const volatile long *); 8375vector unsigned char vec_lvsr (int, const volatile float *); 8376 8377vector float vec_madd (vector float, vector float, vector float); 8378 8379vector signed short vec_madds (vector signed short, 8380 vector signed short, 8381 vector signed short); 8382 8383vector unsigned char vec_max (vector bool char, vector unsigned char); 8384vector unsigned char vec_max (vector unsigned char, vector bool char); 8385vector unsigned char vec_max (vector unsigned char, 8386 vector unsigned char); 8387vector signed char vec_max (vector bool char, vector signed char); 8388vector signed char vec_max (vector signed char, vector bool char); 8389vector signed char vec_max (vector signed char, vector signed char); 8390vector unsigned short vec_max (vector bool short, 8391 vector unsigned short); 8392vector unsigned short vec_max (vector unsigned short, 8393 vector bool short); 8394vector unsigned short vec_max (vector unsigned short, 8395 vector unsigned short); 8396vector signed short vec_max (vector bool short, vector signed short); 8397vector signed short vec_max (vector signed short, vector bool short); 8398vector signed short vec_max (vector signed short, vector signed short); 8399vector unsigned int vec_max (vector bool int, vector unsigned int); 8400vector unsigned int vec_max (vector unsigned int, vector bool int); 8401vector unsigned int vec_max (vector unsigned int, vector unsigned int); 8402vector signed int vec_max (vector bool int, vector signed int); 8403vector signed int vec_max (vector signed int, vector bool int); 8404vector signed int vec_max (vector signed int, vector signed int); 8405vector float vec_max (vector float, vector float); 8406 8407vector float vec_vmaxfp (vector float, vector float); 8408 8409vector signed int vec_vmaxsw (vector bool int, vector signed int); 8410vector signed int vec_vmaxsw (vector signed int, vector bool int); 8411vector signed int vec_vmaxsw (vector signed int, vector signed int); 8412 8413vector unsigned int vec_vmaxuw (vector bool int, vector unsigned int); 8414vector unsigned int vec_vmaxuw (vector unsigned int, vector bool int); 8415vector unsigned int vec_vmaxuw (vector unsigned int, 8416 vector unsigned int); 8417 8418vector signed short vec_vmaxsh (vector bool short, vector signed short); 8419vector signed short vec_vmaxsh (vector signed short, vector bool short); 8420vector signed short vec_vmaxsh (vector signed short, 8421 vector signed short); 8422 8423vector unsigned short vec_vmaxuh (vector bool short, 8424 vector unsigned short); 8425vector unsigned short vec_vmaxuh (vector unsigned short, 8426 vector bool short); 8427vector unsigned short vec_vmaxuh (vector unsigned short, 8428 vector unsigned short); 8429 8430vector signed char vec_vmaxsb (vector bool char, vector signed char); 8431vector signed char vec_vmaxsb (vector signed char, vector bool char); 8432vector signed char vec_vmaxsb (vector signed char, vector signed char); 8433 8434vector unsigned char vec_vmaxub (vector bool char, 8435 vector unsigned char); 8436vector unsigned char vec_vmaxub (vector unsigned char, 8437 vector bool char); 8438vector unsigned char vec_vmaxub (vector unsigned char, 8439 vector unsigned char); 8440 8441vector bool char vec_mergeh (vector bool char, vector bool char); 8442vector signed char vec_mergeh (vector signed char, vector signed char); 8443vector unsigned char vec_mergeh (vector unsigned char, 8444 vector unsigned char); 8445vector bool short vec_mergeh (vector bool short, vector bool short); 8446vector pixel vec_mergeh (vector pixel, vector pixel); 8447vector signed short vec_mergeh (vector signed short, 8448 vector signed short); 8449vector unsigned short vec_mergeh (vector unsigned short, 8450 vector unsigned short); 8451vector float vec_mergeh (vector float, vector float); 8452vector bool int vec_mergeh (vector bool int, vector bool int); 8453vector signed int vec_mergeh (vector signed int, vector signed int); 8454vector unsigned int vec_mergeh (vector unsigned int, 8455 vector unsigned int); 8456 8457vector float vec_vmrghw (vector float, vector float); 8458vector bool int vec_vmrghw (vector bool int, vector bool int); 8459vector signed int vec_vmrghw (vector signed int, vector signed int); 8460vector unsigned int vec_vmrghw (vector unsigned int, 8461 vector unsigned int); 8462 8463vector bool short vec_vmrghh (vector bool short, vector bool short); 8464vector signed short vec_vmrghh (vector signed short, 8465 vector signed short); 8466vector unsigned short vec_vmrghh (vector unsigned short, 8467 vector unsigned short); 8468vector pixel vec_vmrghh (vector pixel, vector pixel); 8469 8470vector bool char vec_vmrghb (vector bool char, vector bool char); 8471vector signed char vec_vmrghb (vector signed char, vector signed char); 8472vector unsigned char vec_vmrghb (vector unsigned char, 8473 vector unsigned char); 8474 8475vector bool char vec_mergel (vector bool char, vector bool char); 8476vector signed char vec_mergel (vector signed char, vector signed char); 8477vector unsigned char vec_mergel (vector unsigned char, 8478 vector unsigned char); 8479vector bool short vec_mergel (vector bool short, vector bool short); 8480vector pixel vec_mergel (vector pixel, vector pixel); 8481vector signed short vec_mergel (vector signed short, 8482 vector signed short); 8483vector unsigned short vec_mergel (vector unsigned short, 8484 vector unsigned short); 8485vector float vec_mergel (vector float, vector float); 8486vector bool int vec_mergel (vector bool int, vector bool int); 8487vector signed int vec_mergel (vector signed int, vector signed int); 8488vector unsigned int vec_mergel (vector unsigned int, 8489 vector unsigned int); 8490 8491vector float vec_vmrglw (vector float, vector float); 8492vector signed int vec_vmrglw (vector signed int, vector signed int); 8493vector unsigned int vec_vmrglw (vector unsigned int, 8494 vector unsigned int); 8495vector bool int vec_vmrglw (vector bool int, vector bool int); 8496 8497vector bool short vec_vmrglh (vector bool short, vector bool short); 8498vector signed short vec_vmrglh (vector signed short, 8499 vector signed short); 8500vector unsigned short vec_vmrglh (vector unsigned short, 8501 vector unsigned short); 8502vector pixel vec_vmrglh (vector pixel, vector pixel); 8503 8504vector bool char vec_vmrglb (vector bool char, vector bool char); 8505vector signed char vec_vmrglb (vector signed char, vector signed char); 8506vector unsigned char vec_vmrglb (vector unsigned char, 8507 vector unsigned char); 8508 8509vector unsigned short vec_mfvscr (void); 8510 8511vector unsigned char vec_min (vector bool char, vector unsigned char); 8512vector unsigned char vec_min (vector unsigned char, vector bool char); 8513vector unsigned char vec_min (vector unsigned char, 8514 vector unsigned char); 8515vector signed char vec_min (vector bool char, vector signed char); 8516vector signed char vec_min (vector signed char, vector bool char); 8517vector signed char vec_min (vector signed char, vector signed char); 8518vector unsigned short vec_min (vector bool short, 8519 vector unsigned short); 8520vector unsigned short vec_min (vector unsigned short, 8521 vector bool short); 8522vector unsigned short vec_min (vector unsigned short, 8523 vector unsigned short); 8524vector signed short vec_min (vector bool short, vector signed short); 8525vector signed short vec_min (vector signed short, vector bool short); 8526vector signed short vec_min (vector signed short, vector signed short); 8527vector unsigned int vec_min (vector bool int, vector unsigned int); 8528vector unsigned int vec_min (vector unsigned int, vector bool int); 8529vector unsigned int vec_min (vector unsigned int, vector unsigned int); 8530vector signed int vec_min (vector bool int, vector signed int); 8531vector signed int vec_min (vector signed int, vector bool int); 8532vector signed int vec_min (vector signed int, vector signed int); 8533vector float vec_min (vector float, vector float); 8534 8535vector float vec_vminfp (vector float, vector float); 8536 8537vector signed int vec_vminsw (vector bool int, vector signed int); 8538vector signed int vec_vminsw (vector signed int, vector bool int); 8539vector signed int vec_vminsw (vector signed int, vector signed int); 8540 8541vector unsigned int vec_vminuw (vector bool int, vector unsigned int); 8542vector unsigned int vec_vminuw (vector unsigned int, vector bool int); 8543vector unsigned int vec_vminuw (vector unsigned int, 8544 vector unsigned int); 8545 8546vector signed short vec_vminsh (vector bool short, vector signed short); 8547vector signed short vec_vminsh (vector signed short, vector bool short); 8548vector signed short vec_vminsh (vector signed short, 8549 vector signed short); 8550 8551vector unsigned short vec_vminuh (vector bool short, 8552 vector unsigned short); 8553vector unsigned short vec_vminuh (vector unsigned short, 8554 vector bool short); 8555vector unsigned short vec_vminuh (vector unsigned short, 8556 vector unsigned short); 8557 8558vector signed char vec_vminsb (vector bool char, vector signed char); 8559vector signed char vec_vminsb (vector signed char, vector bool char); 8560vector signed char vec_vminsb (vector signed char, vector signed char); 8561 8562vector unsigned char vec_vminub (vector bool char, 8563 vector unsigned char); 8564vector unsigned char vec_vminub (vector unsigned char, 8565 vector bool char); 8566vector unsigned char vec_vminub (vector unsigned char, 8567 vector unsigned char); 8568 8569vector signed short vec_mladd (vector signed short, 8570 vector signed short, 8571 vector signed short); 8572vector signed short vec_mladd (vector signed short, 8573 vector unsigned short, 8574 vector unsigned short); 8575vector signed short vec_mladd (vector unsigned short, 8576 vector signed short, 8577 vector signed short); 8578vector unsigned short vec_mladd (vector unsigned short, 8579 vector unsigned short, 8580 vector unsigned short); 8581 8582vector signed short vec_mradds (vector signed short, 8583 vector signed short, 8584 vector signed short); 8585 8586vector unsigned int vec_msum (vector unsigned char, 8587 vector unsigned char, 8588 vector unsigned int); 8589vector signed int vec_msum (vector signed char, 8590 vector unsigned char, 8591 vector signed int); 8592vector unsigned int vec_msum (vector unsigned short, 8593 vector unsigned short, 8594 vector unsigned int); 8595vector signed int vec_msum (vector signed short, 8596 vector signed short, 8597 vector signed int); 8598 8599vector signed int vec_vmsumshm (vector signed short, 8600 vector signed short, 8601 vector signed int); 8602 8603vector unsigned int vec_vmsumuhm (vector unsigned short, 8604 vector unsigned short, 8605 vector unsigned int); 8606 8607vector signed int vec_vmsummbm (vector signed char, 8608 vector unsigned char, 8609 vector signed int); 8610 8611vector unsigned int vec_vmsumubm (vector unsigned char, 8612 vector unsigned char, 8613 vector unsigned int); 8614 8615vector unsigned int vec_msums (vector unsigned short, 8616 vector unsigned short, 8617 vector unsigned int); 8618vector signed int vec_msums (vector signed short, 8619 vector signed short, 8620 vector signed int); 8621 8622vector signed int vec_vmsumshs (vector signed short, 8623 vector signed short, 8624 vector signed int); 8625 8626vector unsigned int vec_vmsumuhs (vector unsigned short, 8627 vector unsigned short, 8628 vector unsigned int); 8629 8630void vec_mtvscr (vector signed int); 8631void vec_mtvscr (vector unsigned int); 8632void vec_mtvscr (vector bool int); 8633void vec_mtvscr (vector signed short); 8634void vec_mtvscr (vector unsigned short); 8635void vec_mtvscr (vector bool short); 8636void vec_mtvscr (vector pixel); 8637void vec_mtvscr (vector signed char); 8638void vec_mtvscr (vector unsigned char); 8639void vec_mtvscr (vector bool char); 8640 8641vector unsigned short vec_mule (vector unsigned char, 8642 vector unsigned char); 8643vector signed short vec_mule (vector signed char, 8644 vector signed char); 8645vector unsigned int vec_mule (vector unsigned short, 8646 vector unsigned short); 8647vector signed int vec_mule (vector signed short, vector signed short); 8648 8649vector signed int vec_vmulesh (vector signed short, 8650 vector signed short); 8651 8652vector unsigned int vec_vmuleuh (vector unsigned short, 8653 vector unsigned short); 8654 8655vector signed short vec_vmulesb (vector signed char, 8656 vector signed char); 8657 8658vector unsigned short vec_vmuleub (vector unsigned char, 8659 vector unsigned char); 8660 8661vector unsigned short vec_mulo (vector unsigned char, 8662 vector unsigned char); 8663vector signed short vec_mulo (vector signed char, vector signed char); 8664vector unsigned int vec_mulo (vector unsigned short, 8665 vector unsigned short); 8666vector signed int vec_mulo (vector signed short, vector signed short); 8667 8668vector signed int vec_vmulosh (vector signed short, 8669 vector signed short); 8670 8671vector unsigned int vec_vmulouh (vector unsigned short, 8672 vector unsigned short); 8673 8674vector signed short vec_vmulosb (vector signed char, 8675 vector signed char); 8676 8677vector unsigned short vec_vmuloub (vector unsigned char, 8678 vector unsigned char); 8679 8680vector float vec_nmsub (vector float, vector float, vector float); 8681 8682vector float vec_nor (vector float, vector float); 8683vector signed int vec_nor (vector signed int, vector signed int); 8684vector unsigned int vec_nor (vector unsigned int, vector unsigned int); 8685vector bool int vec_nor (vector bool int, vector bool int); 8686vector signed short vec_nor (vector signed short, vector signed short); 8687vector unsigned short vec_nor (vector unsigned short, 8688 vector unsigned short); 8689vector bool short vec_nor (vector bool short, vector bool short); 8690vector signed char vec_nor (vector signed char, vector signed char); 8691vector unsigned char vec_nor (vector unsigned char, 8692 vector unsigned char); 8693vector bool char vec_nor (vector bool char, vector bool char); 8694 8695vector float vec_or (vector float, vector float); 8696vector float vec_or (vector float, vector bool int); 8697vector float vec_or (vector bool int, vector float); 8698vector bool int vec_or (vector bool int, vector bool int); 8699vector signed int vec_or (vector bool int, vector signed int); 8700vector signed int vec_or (vector signed int, vector bool int); 8701vector signed int vec_or (vector signed int, vector signed int); 8702vector unsigned int vec_or (vector bool int, vector unsigned int); 8703vector unsigned int vec_or (vector unsigned int, vector bool int); 8704vector unsigned int vec_or (vector unsigned int, vector unsigned int); 8705vector bool short vec_or (vector bool short, vector bool short); 8706vector signed short vec_or (vector bool short, vector signed short); 8707vector signed short vec_or (vector signed short, vector bool short); 8708vector signed short vec_or (vector signed short, vector signed short); 8709vector unsigned short vec_or (vector bool short, vector unsigned short); 8710vector unsigned short vec_or (vector unsigned short, vector bool short); 8711vector unsigned short vec_or (vector unsigned short, 8712 vector unsigned short); 8713vector signed char vec_or (vector bool char, vector signed char); 8714vector bool char vec_or (vector bool char, vector bool char); 8715vector signed char vec_or (vector signed char, vector bool char); 8716vector signed char vec_or (vector signed char, vector signed char); 8717vector unsigned char vec_or (vector bool char, vector unsigned char); 8718vector unsigned char vec_or (vector unsigned char, vector bool char); 8719vector unsigned char vec_or (vector unsigned char, 8720 vector unsigned char); 8721 8722vector signed char vec_pack (vector signed short, vector signed short); 8723vector unsigned char vec_pack (vector unsigned short, 8724 vector unsigned short); 8725vector bool char vec_pack (vector bool short, vector bool short); 8726vector signed short vec_pack (vector signed int, vector signed int); 8727vector unsigned short vec_pack (vector unsigned int, 8728 vector unsigned int); 8729vector bool short vec_pack (vector bool int, vector bool int); 8730 8731vector bool short vec_vpkuwum (vector bool int, vector bool int); 8732vector signed short vec_vpkuwum (vector signed int, vector signed int); 8733vector unsigned short vec_vpkuwum (vector unsigned int, 8734 vector unsigned int); 8735 8736vector bool char vec_vpkuhum (vector bool short, vector bool short); 8737vector signed char vec_vpkuhum (vector signed short, 8738 vector signed short); 8739vector unsigned char vec_vpkuhum (vector unsigned short, 8740 vector unsigned short); 8741 8742vector pixel vec_packpx (vector unsigned int, vector unsigned int); 8743 8744vector unsigned char vec_packs (vector unsigned short, 8745 vector unsigned short); 8746vector signed char vec_packs (vector signed short, vector signed short); 8747vector unsigned short vec_packs (vector unsigned int, 8748 vector unsigned int); 8749vector signed short vec_packs (vector signed int, vector signed int); 8750 8751vector signed short vec_vpkswss (vector signed int, vector signed int); 8752 8753vector unsigned short vec_vpkuwus (vector unsigned int, 8754 vector unsigned int); 8755 8756vector signed char vec_vpkshss (vector signed short, 8757 vector signed short); 8758 8759vector unsigned char vec_vpkuhus (vector unsigned short, 8760 vector unsigned short); 8761 8762vector unsigned char vec_packsu (vector unsigned short, 8763 vector unsigned short); 8764vector unsigned char vec_packsu (vector signed short, 8765 vector signed short); 8766vector unsigned short vec_packsu (vector unsigned int, 8767 vector unsigned int); 8768vector unsigned short vec_packsu (vector signed int, vector signed int); 8769 8770vector unsigned short vec_vpkswus (vector signed int, 8771 vector signed int); 8772 8773vector unsigned char vec_vpkshus (vector signed short, 8774 vector signed short); 8775 8776vector float vec_perm (vector float, 8777 vector float, 8778 vector unsigned char); 8779vector signed int vec_perm (vector signed int, 8780 vector signed int, 8781 vector unsigned char); 8782vector unsigned int vec_perm (vector unsigned int, 8783 vector unsigned int, 8784 vector unsigned char); 8785vector bool int vec_perm (vector bool int, 8786 vector bool int, 8787 vector unsigned char); 8788vector signed short vec_perm (vector signed short, 8789 vector signed short, 8790 vector unsigned char); 8791vector unsigned short vec_perm (vector unsigned short, 8792 vector unsigned short, 8793 vector unsigned char); 8794vector bool short vec_perm (vector bool short, 8795 vector bool short, 8796 vector unsigned char); 8797vector pixel vec_perm (vector pixel, 8798 vector pixel, 8799 vector unsigned char); 8800vector signed char vec_perm (vector signed char, 8801 vector signed char, 8802 vector unsigned char); 8803vector unsigned char vec_perm (vector unsigned char, 8804 vector unsigned char, 8805 vector unsigned char); 8806vector bool char vec_perm (vector bool char, 8807 vector bool char, 8808 vector unsigned char); 8809 8810vector float vec_re (vector float); 8811 8812vector signed char vec_rl (vector signed char, 8813 vector unsigned char); 8814vector unsigned char vec_rl (vector unsigned char, 8815 vector unsigned char); 8816vector signed short vec_rl (vector signed short, vector unsigned short); 8817vector unsigned short vec_rl (vector unsigned short, 8818 vector unsigned short); 8819vector signed int vec_rl (vector signed int, vector unsigned int); 8820vector unsigned int vec_rl (vector unsigned int, vector unsigned int); 8821 8822vector signed int vec_vrlw (vector signed int, vector unsigned int); 8823vector unsigned int vec_vrlw (vector unsigned int, vector unsigned int); 8824 8825vector signed short vec_vrlh (vector signed short, 8826 vector unsigned short); 8827vector unsigned short vec_vrlh (vector unsigned short, 8828 vector unsigned short); 8829 8830vector signed char vec_vrlb (vector signed char, vector unsigned char); 8831vector unsigned char vec_vrlb (vector unsigned char, 8832 vector unsigned char); 8833 8834vector float vec_round (vector float); 8835 8836vector float vec_rsqrte (vector float); 8837 8838vector float vec_sel (vector float, vector float, vector bool int); 8839vector float vec_sel (vector float, vector float, vector unsigned int); 8840vector signed int vec_sel (vector signed int, 8841 vector signed int, 8842 vector bool int); 8843vector signed int vec_sel (vector signed int, 8844 vector signed int, 8845 vector unsigned int); 8846vector unsigned int vec_sel (vector unsigned int, 8847 vector unsigned int, 8848 vector bool int); 8849vector unsigned int vec_sel (vector unsigned int, 8850 vector unsigned int, 8851 vector unsigned int); 8852vector bool int vec_sel (vector bool int, 8853 vector bool int, 8854 vector bool int); 8855vector bool int vec_sel (vector bool int, 8856 vector bool int, 8857 vector unsigned int); 8858vector signed short vec_sel (vector signed short, 8859 vector signed short, 8860 vector bool short); 8861vector signed short vec_sel (vector signed short, 8862 vector signed short, 8863 vector unsigned short); 8864vector unsigned short vec_sel (vector unsigned short, 8865 vector unsigned short, 8866 vector bool short); 8867vector unsigned short vec_sel (vector unsigned short, 8868 vector unsigned short, 8869 vector unsigned short); 8870vector bool short vec_sel (vector bool short, 8871 vector bool short, 8872 vector bool short); 8873vector bool short vec_sel (vector bool short, 8874 vector bool short, 8875 vector unsigned short); 8876vector signed char vec_sel (vector signed char, 8877 vector signed char, 8878 vector bool char); 8879vector signed char vec_sel (vector signed char, 8880 vector signed char, 8881 vector unsigned char); 8882vector unsigned char vec_sel (vector unsigned char, 8883 vector unsigned char, 8884 vector bool char); 8885vector unsigned char vec_sel (vector unsigned char, 8886 vector unsigned char, 8887 vector unsigned char); 8888vector bool char vec_sel (vector bool char, 8889 vector bool char, 8890 vector bool char); 8891vector bool char vec_sel (vector bool char, 8892 vector bool char, 8893 vector unsigned char); 8894 8895vector signed char vec_sl (vector signed char, 8896 vector unsigned char); 8897vector unsigned char vec_sl (vector unsigned char, 8898 vector unsigned char); 8899vector signed short vec_sl (vector signed short, vector unsigned short); 8900vector unsigned short vec_sl (vector unsigned short, 8901 vector unsigned short); 8902vector signed int vec_sl (vector signed int, vector unsigned int); 8903vector unsigned int vec_sl (vector unsigned int, vector unsigned int); 8904 8905vector signed int vec_vslw (vector signed int, vector unsigned int); 8906vector unsigned int vec_vslw (vector unsigned int, vector unsigned int); 8907 8908vector signed short vec_vslh (vector signed short, 8909 vector unsigned short); 8910vector unsigned short vec_vslh (vector unsigned short, 8911 vector unsigned short); 8912 8913vector signed char vec_vslb (vector signed char, vector unsigned char); 8914vector unsigned char vec_vslb (vector unsigned char, 8915 vector unsigned char); 8916 8917vector float vec_sld (vector float, vector float, const int); 8918vector signed int vec_sld (vector signed int, 8919 vector signed int, 8920 const int); 8921vector unsigned int vec_sld (vector unsigned int, 8922 vector unsigned int, 8923 const int); 8924vector bool int vec_sld (vector bool int, 8925 vector bool int, 8926 const int); 8927vector signed short vec_sld (vector signed short, 8928 vector signed short, 8929 const int); 8930vector unsigned short vec_sld (vector unsigned short, 8931 vector unsigned short, 8932 const int); 8933vector bool short vec_sld (vector bool short, 8934 vector bool short, 8935 const int); 8936vector pixel vec_sld (vector pixel, 8937 vector pixel, 8938 const int); 8939vector signed char vec_sld (vector signed char, 8940 vector signed char, 8941 const int); 8942vector unsigned char vec_sld (vector unsigned char, 8943 vector unsigned char, 8944 const int); 8945vector bool char vec_sld (vector bool char, 8946 vector bool char, 8947 const int); 8948 8949vector signed int vec_sll (vector signed int, 8950 vector unsigned int); 8951vector signed int vec_sll (vector signed int, 8952 vector unsigned short); 8953vector signed int vec_sll (vector signed int, 8954 vector unsigned char); 8955vector unsigned int vec_sll (vector unsigned int, 8956 vector unsigned int); 8957vector unsigned int vec_sll (vector unsigned int, 8958 vector unsigned short); 8959vector unsigned int vec_sll (vector unsigned int, 8960 vector unsigned char); 8961vector bool int vec_sll (vector bool int, 8962 vector unsigned int); 8963vector bool int vec_sll (vector bool int, 8964 vector unsigned short); 8965vector bool int vec_sll (vector bool int, 8966 vector unsigned char); 8967vector signed short vec_sll (vector signed short, 8968 vector unsigned int); 8969vector signed short vec_sll (vector signed short, 8970 vector unsigned short); 8971vector signed short vec_sll (vector signed short, 8972 vector unsigned char); 8973vector unsigned short vec_sll (vector unsigned short, 8974 vector unsigned int); 8975vector unsigned short vec_sll (vector unsigned short, 8976 vector unsigned short); 8977vector unsigned short vec_sll (vector unsigned short, 8978 vector unsigned char); 8979vector bool short vec_sll (vector bool short, vector unsigned int); 8980vector bool short vec_sll (vector bool short, vector unsigned short); 8981vector bool short vec_sll (vector bool short, vector unsigned char); 8982vector pixel vec_sll (vector pixel, vector unsigned int); 8983vector pixel vec_sll (vector pixel, vector unsigned short); 8984vector pixel vec_sll (vector pixel, vector unsigned char); 8985vector signed char vec_sll (vector signed char, vector unsigned int); 8986vector signed char vec_sll (vector signed char, vector unsigned short); 8987vector signed char vec_sll (vector signed char, vector unsigned char); 8988vector unsigned char vec_sll (vector unsigned char, 8989 vector unsigned int); 8990vector unsigned char vec_sll (vector unsigned char, 8991 vector unsigned short); 8992vector unsigned char vec_sll (vector unsigned char, 8993 vector unsigned char); 8994vector bool char vec_sll (vector bool char, vector unsigned int); 8995vector bool char vec_sll (vector bool char, vector unsigned short); 8996vector bool char vec_sll (vector bool char, vector unsigned char); 8997 8998vector float vec_slo (vector float, vector signed char); 8999vector float vec_slo (vector float, vector unsigned char); 9000vector signed int vec_slo (vector signed int, vector signed char); 9001vector signed int vec_slo (vector signed int, vector unsigned char); 9002vector unsigned int vec_slo (vector unsigned int, vector signed char); 9003vector unsigned int vec_slo (vector unsigned int, vector unsigned char); 9004vector signed short vec_slo (vector signed short, vector signed char); 9005vector signed short vec_slo (vector signed short, vector unsigned char); 9006vector unsigned short vec_slo (vector unsigned short, 9007 vector signed char); 9008vector unsigned short vec_slo (vector unsigned short, 9009 vector unsigned char); 9010vector pixel vec_slo (vector pixel, vector signed char); 9011vector pixel vec_slo (vector pixel, vector unsigned char); 9012vector signed char vec_slo (vector signed char, vector signed char); 9013vector signed char vec_slo (vector signed char, vector unsigned char); 9014vector unsigned char vec_slo (vector unsigned char, vector signed char); 9015vector unsigned char vec_slo (vector unsigned char, 9016 vector unsigned char); 9017 9018vector signed char vec_splat (vector signed char, const int); 9019vector unsigned char vec_splat (vector unsigned char, const int); 9020vector bool char vec_splat (vector bool char, const int); 9021vector signed short vec_splat (vector signed short, const int); 9022vector unsigned short vec_splat (vector unsigned short, const int); 9023vector bool short vec_splat (vector bool short, const int); 9024vector pixel vec_splat (vector pixel, const int); 9025vector float vec_splat (vector float, const int); 9026vector signed int vec_splat (vector signed int, const int); 9027vector unsigned int vec_splat (vector unsigned int, const int); 9028vector bool int vec_splat (vector bool int, const int); 9029 9030vector float vec_vspltw (vector float, const int); 9031vector signed int vec_vspltw (vector signed int, const int); 9032vector unsigned int vec_vspltw (vector unsigned int, const int); 9033vector bool int vec_vspltw (vector bool int, const int); 9034 9035vector bool short vec_vsplth (vector bool short, const int); 9036vector signed short vec_vsplth (vector signed short, const int); 9037vector unsigned short vec_vsplth (vector unsigned short, const int); 9038vector pixel vec_vsplth (vector pixel, const int); 9039 9040vector signed char vec_vspltb (vector signed char, const int); 9041vector unsigned char vec_vspltb (vector unsigned char, const int); 9042vector bool char vec_vspltb (vector bool char, const int); 9043 9044vector signed char vec_splat_s8 (const int); 9045 9046vector signed short vec_splat_s16 (const int); 9047 9048vector signed int vec_splat_s32 (const int); 9049 9050vector unsigned char vec_splat_u8 (const int); 9051 9052vector unsigned short vec_splat_u16 (const int); 9053 9054vector unsigned int vec_splat_u32 (const int); 9055 9056vector signed char vec_sr (vector signed char, vector unsigned char); 9057vector unsigned char vec_sr (vector unsigned char, 9058 vector unsigned char); 9059vector signed short vec_sr (vector signed short, 9060 vector unsigned short); 9061vector unsigned short vec_sr (vector unsigned short, 9062 vector unsigned short); 9063vector signed int vec_sr (vector signed int, vector unsigned int); 9064vector unsigned int vec_sr (vector unsigned int, vector unsigned int); 9065 9066vector signed int vec_vsrw (vector signed int, vector unsigned int); 9067vector unsigned int vec_vsrw (vector unsigned int, vector unsigned int); 9068 9069vector signed short vec_vsrh (vector signed short, 9070 vector unsigned short); 9071vector unsigned short vec_vsrh (vector unsigned short, 9072 vector unsigned short); 9073 9074vector signed char vec_vsrb (vector signed char, vector unsigned char); 9075vector unsigned char vec_vsrb (vector unsigned char, 9076 vector unsigned char); 9077 9078vector signed char vec_sra (vector signed char, vector unsigned char); 9079vector unsigned char vec_sra (vector unsigned char, 9080 vector unsigned char); 9081vector signed short vec_sra (vector signed short, 9082 vector unsigned short); 9083vector unsigned short vec_sra (vector unsigned short, 9084 vector unsigned short); 9085vector signed int vec_sra (vector signed int, vector unsigned int); 9086vector unsigned int vec_sra (vector unsigned int, vector unsigned int); 9087 9088vector signed int vec_vsraw (vector signed int, vector unsigned int); 9089vector unsigned int vec_vsraw (vector unsigned int, 9090 vector unsigned int); 9091 9092vector signed short vec_vsrah (vector signed short, 9093 vector unsigned short); 9094vector unsigned short vec_vsrah (vector unsigned short, 9095 vector unsigned short); 9096 9097vector signed char vec_vsrab (vector signed char, vector unsigned char); 9098vector unsigned char vec_vsrab (vector unsigned char, 9099 vector unsigned char); 9100 9101vector signed int vec_srl (vector signed int, vector unsigned int); 9102vector signed int vec_srl (vector signed int, vector unsigned short); 9103vector signed int vec_srl (vector signed int, vector unsigned char); 9104vector unsigned int vec_srl (vector unsigned int, vector unsigned int); 9105vector unsigned int vec_srl (vector unsigned int, 9106 vector unsigned short); 9107vector unsigned int vec_srl (vector unsigned int, vector unsigned char); 9108vector bool int vec_srl (vector bool int, vector unsigned int); 9109vector bool int vec_srl (vector bool int, vector unsigned short); 9110vector bool int vec_srl (vector bool int, vector unsigned char); 9111vector signed short vec_srl (vector signed short, vector unsigned int); 9112vector signed short vec_srl (vector signed short, 9113 vector unsigned short); 9114vector signed short vec_srl (vector signed short, vector unsigned char); 9115vector unsigned short vec_srl (vector unsigned short, 9116 vector unsigned int); 9117vector unsigned short vec_srl (vector unsigned short, 9118 vector unsigned short); 9119vector unsigned short vec_srl (vector unsigned short, 9120 vector unsigned char); 9121vector bool short vec_srl (vector bool short, vector unsigned int); 9122vector bool short vec_srl (vector bool short, vector unsigned short); 9123vector bool short vec_srl (vector bool short, vector unsigned char); 9124vector pixel vec_srl (vector pixel, vector unsigned int); 9125vector pixel vec_srl (vector pixel, vector unsigned short); 9126vector pixel vec_srl (vector pixel, vector unsigned char); 9127vector signed char vec_srl (vector signed char, vector unsigned int); 9128vector signed char vec_srl (vector signed char, vector unsigned short); 9129vector signed char vec_srl (vector signed char, vector unsigned char); 9130vector unsigned char vec_srl (vector unsigned char, 9131 vector unsigned int); 9132vector unsigned char vec_srl (vector unsigned char, 9133 vector unsigned short); 9134vector unsigned char vec_srl (vector unsigned char, 9135 vector unsigned char); 9136vector bool char vec_srl (vector bool char, vector unsigned int); 9137vector bool char vec_srl (vector bool char, vector unsigned short); 9138vector bool char vec_srl (vector bool char, vector unsigned char); 9139 9140vector float vec_sro (vector float, vector signed char); 9141vector float vec_sro (vector float, vector unsigned char); 9142vector signed int vec_sro (vector signed int, vector signed char); 9143vector signed int vec_sro (vector signed int, vector unsigned char); 9144vector unsigned int vec_sro (vector unsigned int, vector signed char); 9145vector unsigned int vec_sro (vector unsigned int, vector unsigned char); 9146vector signed short vec_sro (vector signed short, vector signed char); 9147vector signed short vec_sro (vector signed short, vector unsigned char); 9148vector unsigned short vec_sro (vector unsigned short, 9149 vector signed char); 9150vector unsigned short vec_sro (vector unsigned short, 9151 vector unsigned char); 9152vector pixel vec_sro (vector pixel, vector signed char); 9153vector pixel vec_sro (vector pixel, vector unsigned char); 9154vector signed char vec_sro (vector signed char, vector signed char); 9155vector signed char vec_sro (vector signed char, vector unsigned char); 9156vector unsigned char vec_sro (vector unsigned char, vector signed char); 9157vector unsigned char vec_sro (vector unsigned char, 9158 vector unsigned char); 9159 9160void vec_st (vector float, int, vector float *); 9161void vec_st (vector float, int, float *); 9162void vec_st (vector signed int, int, vector signed int *); 9163void vec_st (vector signed int, int, int *); 9164void vec_st (vector unsigned int, int, vector unsigned int *); 9165void vec_st (vector unsigned int, int, unsigned int *); 9166void vec_st (vector bool int, int, vector bool int *); 9167void vec_st (vector bool int, int, unsigned int *); 9168void vec_st (vector bool int, int, int *); 9169void vec_st (vector signed short, int, vector signed short *); 9170void vec_st (vector signed short, int, short *); 9171void vec_st (vector unsigned short, int, vector unsigned short *); 9172void vec_st (vector unsigned short, int, unsigned short *); 9173void vec_st (vector bool short, int, vector bool short *); 9174void vec_st (vector bool short, int, unsigned short *); 9175void vec_st (vector pixel, int, vector pixel *); 9176void vec_st (vector pixel, int, unsigned short *); 9177void vec_st (vector pixel, int, short *); 9178void vec_st (vector bool short, int, short *); 9179void vec_st (vector signed char, int, vector signed char *); 9180void vec_st (vector signed char, int, signed char *); 9181void vec_st (vector unsigned char, int, vector unsigned char *); 9182void vec_st (vector unsigned char, int, unsigned char *); 9183void vec_st (vector bool char, int, vector bool char *); 9184void vec_st (vector bool char, int, unsigned char *); 9185void vec_st (vector bool char, int, signed char *); 9186 9187void vec_ste (vector signed char, int, signed char *); 9188void vec_ste (vector unsigned char, int, unsigned char *); 9189void vec_ste (vector bool char, int, signed char *); 9190void vec_ste (vector bool char, int, unsigned char *); 9191void vec_ste (vector signed short, int, short *); 9192void vec_ste (vector unsigned short, int, unsigned short *); 9193void vec_ste (vector bool short, int, short *); 9194void vec_ste (vector bool short, int, unsigned short *); 9195void vec_ste (vector pixel, int, short *); 9196void vec_ste (vector pixel, int, unsigned short *); 9197void vec_ste (vector float, int, float *); 9198void vec_ste (vector signed int, int, int *); 9199void vec_ste (vector unsigned int, int, unsigned int *); 9200void vec_ste (vector bool int, int, int *); 9201void vec_ste (vector bool int, int, unsigned int *); 9202 9203void vec_stvewx (vector float, int, float *); 9204void vec_stvewx (vector signed int, int, int *); 9205void vec_stvewx (vector unsigned int, int, unsigned int *); 9206void vec_stvewx (vector bool int, int, int *); 9207void vec_stvewx (vector bool int, int, unsigned int *); 9208 9209void vec_stvehx (vector signed short, int, short *); 9210void vec_stvehx (vector unsigned short, int, unsigned short *); 9211void vec_stvehx (vector bool short, int, short *); 9212void vec_stvehx (vector bool short, int, unsigned short *); 9213void vec_stvehx (vector pixel, int, short *); 9214void vec_stvehx (vector pixel, int, unsigned short *); 9215 9216void vec_stvebx (vector signed char, int, signed char *); 9217void vec_stvebx (vector unsigned char, int, unsigned char *); 9218void vec_stvebx (vector bool char, int, signed char *); 9219void vec_stvebx (vector bool char, int, unsigned char *); 9220 9221void vec_stl (vector float, int, vector float *); 9222void vec_stl (vector float, int, float *); 9223void vec_stl (vector signed int, int, vector signed int *); 9224void vec_stl (vector signed int, int, int *); 9225void vec_stl (vector unsigned int, int, vector unsigned int *); 9226void vec_stl (vector unsigned int, int, unsigned int *); 9227void vec_stl (vector bool int, int, vector bool int *); 9228void vec_stl (vector bool int, int, unsigned int *); 9229void vec_stl (vector bool int, int, int *); 9230void vec_stl (vector signed short, int, vector signed short *); 9231void vec_stl (vector signed short, int, short *); 9232void vec_stl (vector unsigned short, int, vector unsigned short *); 9233void vec_stl (vector unsigned short, int, unsigned short *); 9234void vec_stl (vector bool short, int, vector bool short *); 9235void vec_stl (vector bool short, int, unsigned short *); 9236void vec_stl (vector bool short, int, short *); 9237void vec_stl (vector pixel, int, vector pixel *); 9238void vec_stl (vector pixel, int, unsigned short *); 9239void vec_stl (vector pixel, int, short *); 9240void vec_stl (vector signed char, int, vector signed char *); 9241void vec_stl (vector signed char, int, signed char *); 9242void vec_stl (vector unsigned char, int, vector unsigned char *); 9243void vec_stl (vector unsigned char, int, unsigned char *); 9244void vec_stl (vector bool char, int, vector bool char *); 9245void vec_stl (vector bool char, int, unsigned char *); 9246void vec_stl (vector bool char, int, signed char *); 9247 9248vector signed char vec_sub (vector bool char, vector signed char); 9249vector signed char vec_sub (vector signed char, vector bool char); 9250vector signed char vec_sub (vector signed char, vector signed char); 9251vector unsigned char vec_sub (vector bool char, vector unsigned char); 9252vector unsigned char vec_sub (vector unsigned char, vector bool char); 9253vector unsigned char vec_sub (vector unsigned char, 9254 vector unsigned char); 9255vector signed short vec_sub (vector bool short, vector signed short); 9256vector signed short vec_sub (vector signed short, vector bool short); 9257vector signed short vec_sub (vector signed short, vector signed short); 9258vector unsigned short vec_sub (vector bool short, 9259 vector unsigned short); 9260vector unsigned short vec_sub (vector unsigned short, 9261 vector bool short); 9262vector unsigned short vec_sub (vector unsigned short, 9263 vector unsigned short); 9264vector signed int vec_sub (vector bool int, vector signed int); 9265vector signed int vec_sub (vector signed int, vector bool int); 9266vector signed int vec_sub (vector signed int, vector signed int); 9267vector unsigned int vec_sub (vector bool int, vector unsigned int); 9268vector unsigned int vec_sub (vector unsigned int, vector bool int); 9269vector unsigned int vec_sub (vector unsigned int, vector unsigned int); 9270vector float vec_sub (vector float, vector float); 9271 9272vector float vec_vsubfp (vector float, vector float); 9273 9274vector signed int vec_vsubuwm (vector bool int, vector signed int); 9275vector signed int vec_vsubuwm (vector signed int, vector bool int); 9276vector signed int vec_vsubuwm (vector signed int, vector signed int); 9277vector unsigned int vec_vsubuwm (vector bool int, vector unsigned int); 9278vector unsigned int vec_vsubuwm (vector unsigned int, vector bool int); 9279vector unsigned int vec_vsubuwm (vector unsigned int, 9280 vector unsigned int); 9281 9282vector signed short vec_vsubuhm (vector bool short, 9283 vector signed short); 9284vector signed short vec_vsubuhm (vector signed short, 9285 vector bool short); 9286vector signed short vec_vsubuhm (vector signed short, 9287 vector signed short); 9288vector unsigned short vec_vsubuhm (vector bool short, 9289 vector unsigned short); 9290vector unsigned short vec_vsubuhm (vector unsigned short, 9291 vector bool short); 9292vector unsigned short vec_vsubuhm (vector unsigned short, 9293 vector unsigned short); 9294 9295vector signed char vec_vsububm (vector bool char, vector signed char); 9296vector signed char vec_vsububm (vector signed char, vector bool char); 9297vector signed char vec_vsububm (vector signed char, vector signed char); 9298vector unsigned char vec_vsububm (vector bool char, 9299 vector unsigned char); 9300vector unsigned char vec_vsububm (vector unsigned char, 9301 vector bool char); 9302vector unsigned char vec_vsububm (vector unsigned char, 9303 vector unsigned char); 9304 9305vector unsigned int vec_subc (vector unsigned int, vector unsigned int); 9306 9307vector unsigned char vec_subs (vector bool char, vector unsigned char); 9308vector unsigned char vec_subs (vector unsigned char, vector bool char); 9309vector unsigned char vec_subs (vector unsigned char, 9310 vector unsigned char); 9311vector signed char vec_subs (vector bool char, vector signed char); 9312vector signed char vec_subs (vector signed char, vector bool char); 9313vector signed char vec_subs (vector signed char, vector signed char); 9314vector unsigned short vec_subs (vector bool short, 9315 vector unsigned short); 9316vector unsigned short vec_subs (vector unsigned short, 9317 vector bool short); 9318vector unsigned short vec_subs (vector unsigned short, 9319 vector unsigned short); 9320vector signed short vec_subs (vector bool short, vector signed short); 9321vector signed short vec_subs (vector signed short, vector bool short); 9322vector signed short vec_subs (vector signed short, vector signed short); 9323vector unsigned int vec_subs (vector bool int, vector unsigned int); 9324vector unsigned int vec_subs (vector unsigned int, vector bool int); 9325vector unsigned int vec_subs (vector unsigned int, vector unsigned int); 9326vector signed int vec_subs (vector bool int, vector signed int); 9327vector signed int vec_subs (vector signed int, vector bool int); 9328vector signed int vec_subs (vector signed int, vector signed int); 9329 9330vector signed int vec_vsubsws (vector bool int, vector signed int); 9331vector signed int vec_vsubsws (vector signed int, vector bool int); 9332vector signed int vec_vsubsws (vector signed int, vector signed int); 9333 9334vector unsigned int vec_vsubuws (vector bool int, vector unsigned int); 9335vector unsigned int vec_vsubuws (vector unsigned int, vector bool int); 9336vector unsigned int vec_vsubuws (vector unsigned int, 9337 vector unsigned int); 9338 9339vector signed short vec_vsubshs (vector bool short, 9340 vector signed short); 9341vector signed short vec_vsubshs (vector signed short, 9342 vector bool short); 9343vector signed short vec_vsubshs (vector signed short, 9344 vector signed short); 9345 9346vector unsigned short vec_vsubuhs (vector bool short, 9347 vector unsigned short); 9348vector unsigned short vec_vsubuhs (vector unsigned short, 9349 vector bool short); 9350vector unsigned short vec_vsubuhs (vector unsigned short, 9351 vector unsigned short); 9352 9353vector signed char vec_vsubsbs (vector bool char, vector signed char); 9354vector signed char vec_vsubsbs (vector signed char, vector bool char); 9355vector signed char vec_vsubsbs (vector signed char, vector signed char); 9356 9357vector unsigned char vec_vsububs (vector bool char, 9358 vector unsigned char); 9359vector unsigned char vec_vsububs (vector unsigned char, 9360 vector bool char); 9361vector unsigned char vec_vsububs (vector unsigned char, 9362 vector unsigned char); 9363 9364vector unsigned int vec_sum4s (vector unsigned char, 9365 vector unsigned int); 9366vector signed int vec_sum4s (vector signed char, vector signed int); 9367vector signed int vec_sum4s (vector signed short, vector signed int); 9368 9369vector signed int vec_vsum4shs (vector signed short, vector signed int); 9370 9371vector signed int vec_vsum4sbs (vector signed char, vector signed int); 9372 9373vector unsigned int vec_vsum4ubs (vector unsigned char, 9374 vector unsigned int); 9375 9376vector signed int vec_sum2s (vector signed int, vector signed int); 9377 9378vector signed int vec_sums (vector signed int, vector signed int); 9379 9380vector float vec_trunc (vector float); 9381 9382vector signed short vec_unpackh (vector signed char); 9383vector bool short vec_unpackh (vector bool char); 9384vector signed int vec_unpackh (vector signed short); 9385vector bool int vec_unpackh (vector bool short); 9386vector unsigned int vec_unpackh (vector pixel); 9387 9388vector bool int vec_vupkhsh (vector bool short); 9389vector signed int vec_vupkhsh (vector signed short); 9390 9391vector unsigned int vec_vupkhpx (vector pixel); 9392 9393vector bool short vec_vupkhsb (vector bool char); 9394vector signed short vec_vupkhsb (vector signed char); 9395 9396vector signed short vec_unpackl (vector signed char); 9397vector bool short vec_unpackl (vector bool char); 9398vector unsigned int vec_unpackl (vector pixel); 9399vector signed int vec_unpackl (vector signed short); 9400vector bool int vec_unpackl (vector bool short); 9401 9402vector unsigned int vec_vupklpx (vector pixel); 9403 9404vector bool int vec_vupklsh (vector bool short); 9405vector signed int vec_vupklsh (vector signed short); 9406 9407vector bool short vec_vupklsb (vector bool char); 9408vector signed short vec_vupklsb (vector signed char); 9409 9410vector float vec_xor (vector float, vector float); 9411vector float vec_xor (vector float, vector bool int); 9412vector float vec_xor (vector bool int, vector float); 9413vector bool int vec_xor (vector bool int, vector bool int); 9414vector signed int vec_xor (vector bool int, vector signed int); 9415vector signed int vec_xor (vector signed int, vector bool int); 9416vector signed int vec_xor (vector signed int, vector signed int); 9417vector unsigned int vec_xor (vector bool int, vector unsigned int); 9418vector unsigned int vec_xor (vector unsigned int, vector bool int); 9419vector unsigned int vec_xor (vector unsigned int, vector unsigned int); 9420vector bool short vec_xor (vector bool short, vector bool short); 9421vector signed short vec_xor (vector bool short, vector signed short); 9422vector signed short vec_xor (vector signed short, vector bool short); 9423vector signed short vec_xor (vector signed short, vector signed short); 9424vector unsigned short vec_xor (vector bool short, 9425 vector unsigned short); 9426vector unsigned short vec_xor (vector unsigned short, 9427 vector bool short); 9428vector unsigned short vec_xor (vector unsigned short, 9429 vector unsigned short); 9430vector signed char vec_xor (vector bool char, vector signed char); 9431vector bool char vec_xor (vector bool char, vector bool char); 9432vector signed char vec_xor (vector signed char, vector bool char); 9433vector signed char vec_xor (vector signed char, vector signed char); 9434vector unsigned char vec_xor (vector bool char, vector unsigned char); 9435vector unsigned char vec_xor (vector unsigned char, vector bool char); 9436vector unsigned char vec_xor (vector unsigned char, 9437 vector unsigned char); 9438 9439int vec_all_eq (vector signed char, vector bool char); 9440int vec_all_eq (vector signed char, vector signed char); 9441int vec_all_eq (vector unsigned char, vector bool char); 9442int vec_all_eq (vector unsigned char, vector unsigned char); 9443int vec_all_eq (vector bool char, vector bool char); 9444int vec_all_eq (vector bool char, vector unsigned char); 9445int vec_all_eq (vector bool char, vector signed char); 9446int vec_all_eq (vector signed short, vector bool short); 9447int vec_all_eq (vector signed short, vector signed short); 9448int vec_all_eq (vector unsigned short, vector bool short); 9449int vec_all_eq (vector unsigned short, vector unsigned short); 9450int vec_all_eq (vector bool short, vector bool short); 9451int vec_all_eq (vector bool short, vector unsigned short); 9452int vec_all_eq (vector bool short, vector signed short); 9453int vec_all_eq (vector pixel, vector pixel); 9454int vec_all_eq (vector signed int, vector bool int); 9455int vec_all_eq (vector signed int, vector signed int); 9456int vec_all_eq (vector unsigned int, vector bool int); 9457int vec_all_eq (vector unsigned int, vector unsigned int); 9458int vec_all_eq (vector bool int, vector bool int); 9459int vec_all_eq (vector bool int, vector unsigned int); 9460int vec_all_eq (vector bool int, vector signed int); 9461int vec_all_eq (vector float, vector float); 9462 9463int vec_all_ge (vector bool char, vector unsigned char); 9464int vec_all_ge (vector unsigned char, vector bool char); 9465int vec_all_ge (vector unsigned char, vector unsigned char); 9466int vec_all_ge (vector bool char, vector signed char); 9467int vec_all_ge (vector signed char, vector bool char); 9468int vec_all_ge (vector signed char, vector signed char); 9469int vec_all_ge (vector bool short, vector unsigned short); 9470int vec_all_ge (vector unsigned short, vector bool short); 9471int vec_all_ge (vector unsigned short, vector unsigned short); 9472int vec_all_ge (vector signed short, vector signed short); 9473int vec_all_ge (vector bool short, vector signed short); 9474int vec_all_ge (vector signed short, vector bool short); 9475int vec_all_ge (vector bool int, vector unsigned int); 9476int vec_all_ge (vector unsigned int, vector bool int); 9477int vec_all_ge (vector unsigned int, vector unsigned int); 9478int vec_all_ge (vector bool int, vector signed int); 9479int vec_all_ge (vector signed int, vector bool int); 9480int vec_all_ge (vector signed int, vector signed int); 9481int vec_all_ge (vector float, vector float); 9482 9483int vec_all_gt (vector bool char, vector unsigned char); 9484int vec_all_gt (vector unsigned char, vector bool char); 9485int vec_all_gt (vector unsigned char, vector unsigned char); 9486int vec_all_gt (vector bool char, vector signed char); 9487int vec_all_gt (vector signed char, vector bool char); 9488int vec_all_gt (vector signed char, vector signed char); 9489int vec_all_gt (vector bool short, vector unsigned short); 9490int vec_all_gt (vector unsigned short, vector bool short); 9491int vec_all_gt (vector unsigned short, vector unsigned short); 9492int vec_all_gt (vector bool short, vector signed short); 9493int vec_all_gt (vector signed short, vector bool short); 9494int vec_all_gt (vector signed short, vector signed short); 9495int vec_all_gt (vector bool int, vector unsigned int); 9496int vec_all_gt (vector unsigned int, vector bool int); 9497int vec_all_gt (vector unsigned int, vector unsigned int); 9498int vec_all_gt (vector bool int, vector signed int); 9499int vec_all_gt (vector signed int, vector bool int); 9500int vec_all_gt (vector signed int, vector signed int); 9501int vec_all_gt (vector float, vector float); 9502 9503int vec_all_in (vector float, vector float); 9504 9505int vec_all_le (vector bool char, vector unsigned char); 9506int vec_all_le (vector unsigned char, vector bool char); 9507int vec_all_le (vector unsigned char, vector unsigned char); 9508int vec_all_le (vector bool char, vector signed char); 9509int vec_all_le (vector signed char, vector bool char); 9510int vec_all_le (vector signed char, vector signed char); 9511int vec_all_le (vector bool short, vector unsigned short); 9512int vec_all_le (vector unsigned short, vector bool short); 9513int vec_all_le (vector unsigned short, vector unsigned short); 9514int vec_all_le (vector bool short, vector signed short); 9515int vec_all_le (vector signed short, vector bool short); 9516int vec_all_le (vector signed short, vector signed short); 9517int vec_all_le (vector bool int, vector unsigned int); 9518int vec_all_le (vector unsigned int, vector bool int); 9519int vec_all_le (vector unsigned int, vector unsigned int); 9520int vec_all_le (vector bool int, vector signed int); 9521int vec_all_le (vector signed int, vector bool int); 9522int vec_all_le (vector signed int, vector signed int); 9523int vec_all_le (vector float, vector float); 9524 9525int vec_all_lt (vector bool char, vector unsigned char); 9526int vec_all_lt (vector unsigned char, vector bool char); 9527int vec_all_lt (vector unsigned char, vector unsigned char); 9528int vec_all_lt (vector bool char, vector signed char); 9529int vec_all_lt (vector signed char, vector bool char); 9530int vec_all_lt (vector signed char, vector signed char); 9531int vec_all_lt (vector bool short, vector unsigned short); 9532int vec_all_lt (vector unsigned short, vector bool short); 9533int vec_all_lt (vector unsigned short, vector unsigned short); 9534int vec_all_lt (vector bool short, vector signed short); 9535int vec_all_lt (vector signed short, vector bool short); 9536int vec_all_lt (vector signed short, vector signed short); 9537int vec_all_lt (vector bool int, vector unsigned int); 9538int vec_all_lt (vector unsigned int, vector bool int); 9539int vec_all_lt (vector unsigned int, vector unsigned int); 9540int vec_all_lt (vector bool int, vector signed int); 9541int vec_all_lt (vector signed int, vector bool int); 9542int vec_all_lt (vector signed int, vector signed int); 9543int vec_all_lt (vector float, vector float); 9544 9545int vec_all_nan (vector float); 9546 9547int vec_all_ne (vector signed char, vector bool char); 9548int vec_all_ne (vector signed char, vector signed char); 9549int vec_all_ne (vector unsigned char, vector bool char); 9550int vec_all_ne (vector unsigned char, vector unsigned char); 9551int vec_all_ne (vector bool char, vector bool char); 9552int vec_all_ne (vector bool char, vector unsigned char); 9553int vec_all_ne (vector bool char, vector signed char); 9554int vec_all_ne (vector signed short, vector bool short); 9555int vec_all_ne (vector signed short, vector signed short); 9556int vec_all_ne (vector unsigned short, vector bool short); 9557int vec_all_ne (vector unsigned short, vector unsigned short); 9558int vec_all_ne (vector bool short, vector bool short); 9559int vec_all_ne (vector bool short, vector unsigned short); 9560int vec_all_ne (vector bool short, vector signed short); 9561int vec_all_ne (vector pixel, vector pixel); 9562int vec_all_ne (vector signed int, vector bool int); 9563int vec_all_ne (vector signed int, vector signed int); 9564int vec_all_ne (vector unsigned int, vector bool int); 9565int vec_all_ne (vector unsigned int, vector unsigned int); 9566int vec_all_ne (vector bool int, vector bool int); 9567int vec_all_ne (vector bool int, vector unsigned int); 9568int vec_all_ne (vector bool int, vector signed int); 9569int vec_all_ne (vector float, vector float); 9570 9571int vec_all_nge (vector float, vector float); 9572 9573int vec_all_ngt (vector float, vector float); 9574 9575int vec_all_nle (vector float, vector float); 9576 9577int vec_all_nlt (vector float, vector float); 9578 9579int vec_all_numeric (vector float); 9580 9581int vec_any_eq (vector signed char, vector bool char); 9582int vec_any_eq (vector signed char, vector signed char); 9583int vec_any_eq (vector unsigned char, vector bool char); 9584int vec_any_eq (vector unsigned char, vector unsigned char); 9585int vec_any_eq (vector bool char, vector bool char); 9586int vec_any_eq (vector bool char, vector unsigned char); 9587int vec_any_eq (vector bool char, vector signed char); 9588int vec_any_eq (vector signed short, vector bool short); 9589int vec_any_eq (vector signed short, vector signed short); 9590int vec_any_eq (vector unsigned short, vector bool short); 9591int vec_any_eq (vector unsigned short, vector unsigned short); 9592int vec_any_eq (vector bool short, vector bool short); 9593int vec_any_eq (vector bool short, vector unsigned short); 9594int vec_any_eq (vector bool short, vector signed short); 9595int vec_any_eq (vector pixel, vector pixel); 9596int vec_any_eq (vector signed int, vector bool int); 9597int vec_any_eq (vector signed int, vector signed int); 9598int vec_any_eq (vector unsigned int, vector bool int); 9599int vec_any_eq (vector unsigned int, vector unsigned int); 9600int vec_any_eq (vector bool int, vector bool int); 9601int vec_any_eq (vector bool int, vector unsigned int); 9602int vec_any_eq (vector bool int, vector signed int); 9603int vec_any_eq (vector float, vector float); 9604 9605int vec_any_ge (vector signed char, vector bool char); 9606int vec_any_ge (vector unsigned char, vector bool char); 9607int vec_any_ge (vector unsigned char, vector unsigned char); 9608int vec_any_ge (vector signed char, vector signed char); 9609int vec_any_ge (vector bool char, vector unsigned char); 9610int vec_any_ge (vector bool char, vector signed char); 9611int vec_any_ge (vector unsigned short, vector bool short); 9612int vec_any_ge (vector unsigned short, vector unsigned short); 9613int vec_any_ge (vector signed short, vector signed short); 9614int vec_any_ge (vector signed short, vector bool short); 9615int vec_any_ge (vector bool short, vector unsigned short); 9616int vec_any_ge (vector bool short, vector signed short); 9617int vec_any_ge (vector signed int, vector bool int); 9618int vec_any_ge (vector unsigned int, vector bool int); 9619int vec_any_ge (vector unsigned int, vector unsigned int); 9620int vec_any_ge (vector signed int, vector signed int); 9621int vec_any_ge (vector bool int, vector unsigned int); 9622int vec_any_ge (vector bool int, vector signed int); 9623int vec_any_ge (vector float, vector float); 9624 9625int vec_any_gt (vector bool char, vector unsigned char); 9626int vec_any_gt (vector unsigned char, vector bool char); 9627int vec_any_gt (vector unsigned char, vector unsigned char); 9628int vec_any_gt (vector bool char, vector signed char); 9629int vec_any_gt (vector signed char, vector bool char); 9630int vec_any_gt (vector signed char, vector signed char); 9631int vec_any_gt (vector bool short, vector unsigned short); 9632int vec_any_gt (vector unsigned short, vector bool short); 9633int vec_any_gt (vector unsigned short, vector unsigned short); 9634int vec_any_gt (vector bool short, vector signed short); 9635int vec_any_gt (vector signed short, vector bool short); 9636int vec_any_gt (vector signed short, vector signed short); 9637int vec_any_gt (vector bool int, vector unsigned int); 9638int vec_any_gt (vector unsigned int, vector bool int); 9639int vec_any_gt (vector unsigned int, vector unsigned int); 9640int vec_any_gt (vector bool int, vector signed int); 9641int vec_any_gt (vector signed int, vector bool int); 9642int vec_any_gt (vector signed int, vector signed int); 9643int vec_any_gt (vector float, vector float); 9644 9645int vec_any_le (vector bool char, vector unsigned char); 9646int vec_any_le (vector unsigned char, vector bool char); 9647int vec_any_le (vector unsigned char, vector unsigned char); 9648int vec_any_le (vector bool char, vector signed char); 9649int vec_any_le (vector signed char, vector bool char); 9650int vec_any_le (vector signed char, vector signed char); 9651int vec_any_le (vector bool short, vector unsigned short); 9652int vec_any_le (vector unsigned short, vector bool short); 9653int vec_any_le (vector unsigned short, vector unsigned short); 9654int vec_any_le (vector bool short, vector signed short); 9655int vec_any_le (vector signed short, vector bool short); 9656int vec_any_le (vector signed short, vector signed short); 9657int vec_any_le (vector bool int, vector unsigned int); 9658int vec_any_le (vector unsigned int, vector bool int); 9659int vec_any_le (vector unsigned int, vector unsigned int); 9660int vec_any_le (vector bool int, vector signed int); 9661int vec_any_le (vector signed int, vector bool int); 9662int vec_any_le (vector signed int, vector signed int); 9663int vec_any_le (vector float, vector float); 9664 9665int vec_any_lt (vector bool char, vector unsigned char); 9666int vec_any_lt (vector unsigned char, vector bool char); 9667int vec_any_lt (vector unsigned char, vector unsigned char); 9668int vec_any_lt (vector bool char, vector signed char); 9669int vec_any_lt (vector signed char, vector bool char); 9670int vec_any_lt (vector signed char, vector signed char); 9671int vec_any_lt (vector bool short, vector unsigned short); 9672int vec_any_lt (vector unsigned short, vector bool short); 9673int vec_any_lt (vector unsigned short, vector unsigned short); 9674int vec_any_lt (vector bool short, vector signed short); 9675int vec_any_lt (vector signed short, vector bool short); 9676int vec_any_lt (vector signed short, vector signed short); 9677int vec_any_lt (vector bool int, vector unsigned int); 9678int vec_any_lt (vector unsigned int, vector bool int); 9679int vec_any_lt (vector unsigned int, vector unsigned int); 9680int vec_any_lt (vector bool int, vector signed int); 9681int vec_any_lt (vector signed int, vector bool int); 9682int vec_any_lt (vector signed int, vector signed int); 9683int vec_any_lt (vector float, vector float); 9684 9685int vec_any_nan (vector float); 9686 9687int vec_any_ne (vector signed char, vector bool char); 9688int vec_any_ne (vector signed char, vector signed char); 9689int vec_any_ne (vector unsigned char, vector bool char); 9690int vec_any_ne (vector unsigned char, vector unsigned char); 9691int vec_any_ne (vector bool char, vector bool char); 9692int vec_any_ne (vector bool char, vector unsigned char); 9693int vec_any_ne (vector bool char, vector signed char); 9694int vec_any_ne (vector signed short, vector bool short); 9695int vec_any_ne (vector signed short, vector signed short); 9696int vec_any_ne (vector unsigned short, vector bool short); 9697int vec_any_ne (vector unsigned short, vector unsigned short); 9698int vec_any_ne (vector bool short, vector bool short); 9699int vec_any_ne (vector bool short, vector unsigned short); 9700int vec_any_ne (vector bool short, vector signed short); 9701int vec_any_ne (vector pixel, vector pixel); 9702int vec_any_ne (vector signed int, vector bool int); 9703int vec_any_ne (vector signed int, vector signed int); 9704int vec_any_ne (vector unsigned int, vector bool int); 9705int vec_any_ne (vector unsigned int, vector unsigned int); 9706int vec_any_ne (vector bool int, vector bool int); 9707int vec_any_ne (vector bool int, vector unsigned int); 9708int vec_any_ne (vector bool int, vector signed int); 9709int vec_any_ne (vector float, vector float); 9710 9711int vec_any_nge (vector float, vector float); 9712 9713int vec_any_ngt (vector float, vector float); 9714 9715int vec_any_nle (vector float, vector float); 9716 9717int vec_any_nlt (vector float, vector float); 9718 9719int vec_any_numeric (vector float); 9720 9721int vec_any_out (vector float, vector float); 9722@end smallexample 9723 9724@node SPARC VIS Built-in Functions 9725@subsection SPARC VIS Built-in Functions 9726 9727GCC supports SIMD operations on the SPARC using both the generic vector 9728extensions (@pxref{Vector Extensions}) as well as built-in functions for 9729the SPARC Visual Instruction Set (VIS). When you use the @option{-mvis} 9730switch, the VIS extension is exposed as the following built-in functions: 9731 9732@smallexample 9733typedef int v2si __attribute__ ((vector_size (8))); 9734typedef short v4hi __attribute__ ((vector_size (8))); 9735typedef short v2hi __attribute__ ((vector_size (4))); 9736typedef char v8qi __attribute__ ((vector_size (8))); 9737typedef char v4qi __attribute__ ((vector_size (4))); 9738 9739void * __builtin_vis_alignaddr (void *, long); 9740int64_t __builtin_vis_faligndatadi (int64_t, int64_t); 9741v2si __builtin_vis_faligndatav2si (v2si, v2si); 9742v4hi __builtin_vis_faligndatav4hi (v4si, v4si); 9743v8qi __builtin_vis_faligndatav8qi (v8qi, v8qi); 9744 9745v4hi __builtin_vis_fexpand (v4qi); 9746 9747v4hi __builtin_vis_fmul8x16 (v4qi, v4hi); 9748v4hi __builtin_vis_fmul8x16au (v4qi, v4hi); 9749v4hi __builtin_vis_fmul8x16al (v4qi, v4hi); 9750v4hi __builtin_vis_fmul8sux16 (v8qi, v4hi); 9751v4hi __builtin_vis_fmul8ulx16 (v8qi, v4hi); 9752v2si __builtin_vis_fmuld8sux16 (v4qi, v2hi); 9753v2si __builtin_vis_fmuld8ulx16 (v4qi, v2hi); 9754 9755v4qi __builtin_vis_fpack16 (v4hi); 9756v8qi __builtin_vis_fpack32 (v2si, v2si); 9757v2hi __builtin_vis_fpackfix (v2si); 9758v8qi __builtin_vis_fpmerge (v4qi, v4qi); 9759 9760int64_t __builtin_vis_pdist (v8qi, v8qi, int64_t); 9761@end smallexample 9762 9763@node Target Format Checks 9764@section Format Checks Specific to Particular Target Machines 9765 9766For some target machines, GCC supports additional options to the 9767format attribute 9768(@pxref{Function Attributes,,Declaring Attributes of Functions}). 9769 9770@menu 9771* Solaris Format Checks:: 9772@end menu 9773 9774@node Solaris Format Checks 9775@subsection Solaris Format Checks 9776 9777Solaris targets support the @code{cmn_err} (or @code{__cmn_err__}) format 9778check. @code{cmn_err} accepts a subset of the standard @code{printf} 9779conversions, and the two-argument @code{%b} conversion for displaying 9780bit-fields. See the Solaris man page for @code{cmn_err} for more information. 9781 9782@node Pragmas 9783@section Pragmas Accepted by GCC 9784@cindex pragmas 9785@cindex #pragma 9786 9787GCC supports several types of pragmas, primarily in order to compile 9788code originally written for other compilers. Note that in general 9789we do not recommend the use of pragmas; @xref{Function Attributes}, 9790for further explanation. 9791 9792@menu 9793* ARM Pragmas:: 9794* M32C Pragmas:: 9795* RS/6000 and PowerPC Pragmas:: 9796* Darwin Pragmas:: 9797* Solaris Pragmas:: 9798* Symbol-Renaming Pragmas:: 9799* Structure-Packing Pragmas:: 9800* Weak Pragmas:: 9801* Diagnostic Pragmas:: 9802* Visibility Pragmas:: 9803@end menu 9804 9805@node ARM Pragmas 9806@subsection ARM Pragmas 9807 9808The ARM target defines pragmas for controlling the default addition of 9809@code{long_call} and @code{short_call} attributes to functions. 9810@xref{Function Attributes}, for information about the effects of these 9811attributes. 9812 9813@table @code 9814@item long_calls 9815@cindex pragma, long_calls 9816Set all subsequent functions to have the @code{long_call} attribute. 9817 9818@item no_long_calls 9819@cindex pragma, no_long_calls 9820Set all subsequent functions to have the @code{short_call} attribute. 9821 9822@item long_calls_off 9823@cindex pragma, long_calls_off 9824Do not affect the @code{long_call} or @code{short_call} attributes of 9825subsequent functions. 9826@end table 9827 9828@node M32C Pragmas 9829@subsection M32C Pragmas 9830 9831@table @code 9832@item memregs @var{number} 9833@cindex pragma, memregs 9834Overrides the command line option @code{-memregs=} for the current 9835file. Use with care! This pragma must be before any function in the 9836file, and mixing different memregs values in different objects may 9837make them incompatible. This pragma is useful when a 9838performance-critical function uses a memreg for temporary values, 9839as it may allow you to reduce the number of memregs used. 9840 9841@end table 9842 9843@node RS/6000 and PowerPC Pragmas 9844@subsection RS/6000 and PowerPC Pragmas 9845 9846The RS/6000 and PowerPC targets define one pragma for controlling 9847whether or not the @code{longcall} attribute is added to function 9848declarations by default. This pragma overrides the @option{-mlongcall} 9849option, but not the @code{longcall} and @code{shortcall} attributes. 9850@xref{RS/6000 and PowerPC Options}, for more information about when long 9851calls are and are not necessary. 9852 9853@table @code 9854@item longcall (1) 9855@cindex pragma, longcall 9856Apply the @code{longcall} attribute to all subsequent function 9857declarations. 9858 9859@item longcall (0) 9860Do not apply the @code{longcall} attribute to subsequent function 9861declarations. 9862@end table 9863 9864@c Describe c4x pragmas here. 9865@c Describe h8300 pragmas here. 9866@c Describe sh pragmas here. 9867@c Describe v850 pragmas here. 9868 9869@node Darwin Pragmas 9870@subsection Darwin Pragmas 9871 9872The following pragmas are available for all architectures running the 9873Darwin operating system. These are useful for compatibility with other 9874Mac OS compilers. 9875 9876@table @code 9877@item mark @var{tokens}@dots{} 9878@cindex pragma, mark 9879This pragma is accepted, but has no effect. 9880 9881@item options align=@var{alignment} 9882@cindex pragma, options align 9883This pragma sets the alignment of fields in structures. The values of 9884@var{alignment} may be @code{mac68k}, to emulate m68k alignment, or 9885@code{power}, to emulate PowerPC alignment. Uses of this pragma nest 9886properly; to restore the previous setting, use @code{reset} for the 9887@var{alignment}. 9888 9889@item segment @var{tokens}@dots{} 9890@cindex pragma, segment 9891This pragma is accepted, but has no effect. 9892 9893@item unused (@var{var} [, @var{var}]@dots{}) 9894@cindex pragma, unused 9895This pragma declares variables to be possibly unused. GCC will not 9896produce warnings for the listed variables. The effect is similar to 9897that of the @code{unused} attribute, except that this pragma may appear 9898anywhere within the variables' scopes. 9899@end table 9900 9901@node Solaris Pragmas 9902@subsection Solaris Pragmas 9903 9904The Solaris target supports @code{#pragma redefine_extname} 9905(@pxref{Symbol-Renaming Pragmas}). It also supports additional 9906@code{#pragma} directives for compatibility with the system compiler. 9907 9908@table @code 9909@item align @var{alignment} (@var{variable} [, @var{variable}]...) 9910@cindex pragma, align 9911 9912Increase the minimum alignment of each @var{variable} to @var{alignment}. 9913This is the same as GCC's @code{aligned} attribute @pxref{Variable 9914Attributes}). Macro expansion occurs on the arguments to this pragma 9915when compiling C. It does not currently occur when compiling C++, but 9916this is a bug which may be fixed in a future release. 9917 9918@item fini (@var{function} [, @var{function}]...) 9919@cindex pragma, fini 9920 9921This pragma causes each listed @var{function} to be called after 9922main, or during shared module unloading, by adding a call to the 9923@code{.fini} section. 9924 9925@item init (@var{function} [, @var{function}]...) 9926@cindex pragma, init 9927 9928This pragma causes each listed @var{function} to be called during 9929initialization (before @code{main}) or during shared module loading, by 9930adding a call to the @code{.init} section. 9931 9932@end table 9933 9934@node Symbol-Renaming Pragmas 9935@subsection Symbol-Renaming Pragmas 9936 9937For compatibility with the Solaris and Tru64 UNIX system headers, GCC 9938supports two @code{#pragma} directives which change the name used in 9939assembly for a given declaration. These pragmas are only available on 9940platforms whose system headers need them. To get this effect on all 9941platforms supported by GCC, use the asm labels extension (@pxref{Asm 9942Labels}). 9943 9944@table @code 9945@item redefine_extname @var{oldname} @var{newname} 9946@cindex pragma, redefine_extname 9947 9948This pragma gives the C function @var{oldname} the assembly symbol 9949@var{newname}. The preprocessor macro @code{__PRAGMA_REDEFINE_EXTNAME} 9950will be defined if this pragma is available (currently only on 9951Solaris). 9952 9953@item extern_prefix @var{string} 9954@cindex pragma, extern_prefix 9955 9956This pragma causes all subsequent external function and variable 9957declarations to have @var{string} prepended to their assembly symbols. 9958This effect may be terminated with another @code{extern_prefix} pragma 9959whose argument is an empty string. The preprocessor macro 9960@code{__PRAGMA_EXTERN_PREFIX} will be defined if this pragma is 9961available (currently only on Tru64 UNIX)@. 9962@end table 9963 9964These pragmas and the asm labels extension interact in a complicated 9965manner. Here are some corner cases you may want to be aware of. 9966 9967@enumerate 9968@item Both pragmas silently apply only to declarations with external 9969linkage. Asm labels do not have this restriction. 9970 9971@item In C++, both pragmas silently apply only to declarations with 9972``C'' linkage. Again, asm labels do not have this restriction. 9973 9974@item If any of the three ways of changing the assembly name of a 9975declaration is applied to a declaration whose assembly name has 9976already been determined (either by a previous use of one of these 9977features, or because the compiler needed the assembly name in order to 9978generate code), and the new name is different, a warning issues and 9979the name does not change. 9980 9981@item The @var{oldname} used by @code{#pragma redefine_extname} is 9982always the C-language name. 9983 9984@item If @code{#pragma extern_prefix} is in effect, and a declaration 9985occurs with an asm label attached, the prefix is silently ignored for 9986that declaration. 9987 9988@item If @code{#pragma extern_prefix} and @code{#pragma redefine_extname} 9989apply to the same declaration, whichever triggered first wins, and a 9990warning issues if they contradict each other. (We would like to have 9991@code{#pragma redefine_extname} always win, for consistency with asm 9992labels, but if @code{#pragma extern_prefix} triggers first we have no 9993way of knowing that that happened.) 9994@end enumerate 9995 9996@node Structure-Packing Pragmas 9997@subsection Structure-Packing Pragmas 9998 9999For compatibility with Win32, GCC supports a set of @code{#pragma} 10000directives which change the maximum alignment of members of structures 10001(other than zero-width bitfields), unions, and classes subsequently 10002defined. The @var{n} value below always is required to be a small power 10003of two and specifies the new alignment in bytes. 10004 10005@enumerate 10006@item @code{#pragma pack(@var{n})} simply sets the new alignment. 10007@item @code{#pragma pack()} sets the alignment to the one that was in 10008effect when compilation started (see also command line option 10009@option{-fpack-struct[=<n>]} @pxref{Code Gen Options}). 10010@item @code{#pragma pack(push[,@var{n}])} pushes the current alignment 10011setting on an internal stack and then optionally sets the new alignment. 10012@item @code{#pragma pack(pop)} restores the alignment setting to the one 10013saved at the top of the internal stack (and removes that stack entry). 10014Note that @code{#pragma pack([@var{n}])} does not influence this internal 10015stack; thus it is possible to have @code{#pragma pack(push)} followed by 10016multiple @code{#pragma pack(@var{n})} instances and finalized by a single 10017@code{#pragma pack(pop)}. 10018@end enumerate 10019 10020Some targets, e.g. i386 and powerpc, support the @code{ms_struct} 10021@code{#pragma} which lays out a structure as the documented 10022@code{__attribute__ ((ms_struct))}. 10023@enumerate 10024@item @code{#pragma ms_struct on} turns on the layout for structures 10025declared. 10026@item @code{#pragma ms_struct off} turns off the layout for structures 10027declared. 10028@item @code{#pragma ms_struct reset} goes back to the default layout. 10029@end enumerate 10030 10031@node Weak Pragmas 10032@subsection Weak Pragmas 10033 10034For compatibility with SVR4, GCC supports a set of @code{#pragma} 10035directives for declaring symbols to be weak, and defining weak 10036aliases. 10037 10038@table @code 10039@item #pragma weak @var{symbol} 10040@cindex pragma, weak 10041This pragma declares @var{symbol} to be weak, as if the declaration 10042had the attribute of the same name. The pragma may appear before 10043or after the declaration of @var{symbol}, but must appear before 10044either its first use or its definition. It is not an error for 10045@var{symbol} to never be defined at all. 10046 10047@item #pragma weak @var{symbol1} = @var{symbol2} 10048This pragma declares @var{symbol1} to be a weak alias of @var{symbol2}. 10049It is an error if @var{symbol2} is not defined in the current 10050translation unit. 10051@end table 10052 10053@node Diagnostic Pragmas 10054@subsection Diagnostic Pragmas 10055 10056GCC allows the user to selectively enable or disable certain types of 10057diagnostics, and change the kind of the diagnostic. For example, a 10058project's policy might require that all sources compile with 10059@option{-Werror} but certain files might have exceptions allowing 10060specific types of warnings. Or, a project might selectively enable 10061diagnostics and treat them as errors depending on which preprocessor 10062macros are defined. 10063 10064@table @code 10065@item #pragma GCC diagnostic @var{kind} @var{option} 10066@cindex pragma, diagnostic 10067 10068Modifies the disposition of a diagnostic. Note that not all 10069diagnostics are modifiable; at the moment only warnings (normally 10070controlled by @samp{-W...}) can be controlled, and not all of them. 10071Use @option{-fdiagnostics-show-option} to determine which diagnostics 10072are controllable and which option controls them. 10073 10074@var{kind} is @samp{error} to treat this diagnostic as an error, 10075@samp{warning} to treat it like a warning (even if @option{-Werror} is 10076in effect), or @samp{ignored} if the diagnostic is to be ignored. 10077@var{option} is a double quoted string which matches the command line 10078option. 10079 10080@example 10081#pragma GCC diagnostic warning "-Wformat" 10082#pragma GCC diagnostic error "-Wformat" 10083#pragma GCC diagnostic ignored "-Wformat" 10084@end example 10085 10086Note that these pragmas override any command line options. Also, 10087while it is syntactically valid to put these pragmas anywhere in your 10088sources, the only supported location for them is before any data or 10089functions are defined. Doing otherwise may result in unpredictable 10090results depending on how the optimizer manages your sources. If the 10091same option is listed multiple times, the last one specified is the 10092one that is in effect. This pragma is not intended to be a general 10093purpose replacement for command line options, but for implementing 10094strict control over project policies. 10095 10096@end table 10097 10098@node Visibility Pragmas 10099@subsection Visibility Pragmas 10100 10101@table @code 10102@item #pragma GCC visibility push(@var{visibility}) 10103@itemx #pragma GCC visibility pop 10104@cindex pragma, visibility 10105 10106This pragma allows the user to set the visibility for multiple 10107declarations without having to give each a visibility attribute 10108@xref{Function Attributes}, for more information about visibility and 10109the attribute syntax. 10110 10111In C++, @samp{#pragma GCC visibility} affects only namespace-scope 10112declarations. Class members and template specializations are not 10113affected; if you want to override the visibility for a particular 10114member or instantiation, you must use an attribute. 10115 10116@end table 10117 10118@node Unnamed Fields 10119@section Unnamed struct/union fields within structs/unions 10120@cindex struct 10121@cindex union 10122 10123For compatibility with other compilers, GCC allows you to define 10124a structure or union that contains, as fields, structures and unions 10125without names. For example: 10126 10127@smallexample 10128struct @{ 10129 int a; 10130 union @{ 10131 int b; 10132 float c; 10133 @}; 10134 int d; 10135@} foo; 10136@end smallexample 10137 10138In this example, the user would be able to access members of the unnamed 10139union with code like @samp{foo.b}. Note that only unnamed structs and 10140unions are allowed, you may not have, for example, an unnamed 10141@code{int}. 10142 10143You must never create such structures that cause ambiguous field definitions. 10144For example, this structure: 10145 10146@smallexample 10147struct @{ 10148 int a; 10149 struct @{ 10150 int a; 10151 @}; 10152@} foo; 10153@end smallexample 10154 10155It is ambiguous which @code{a} is being referred to with @samp{foo.a}. 10156Such constructs are not supported and must be avoided. In the future, 10157such constructs may be detected and treated as compilation errors. 10158 10159@opindex fms-extensions 10160Unless @option{-fms-extensions} is used, the unnamed field must be a 10161structure or union definition without a tag (for example, @samp{struct 10162@{ int a; @};}). If @option{-fms-extensions} is used, the field may 10163also be a definition with a tag such as @samp{struct foo @{ int a; 10164@};}, a reference to a previously defined structure or union such as 10165@samp{struct foo;}, or a reference to a @code{typedef} name for a 10166previously defined structure or union type. 10167 10168@node Thread-Local 10169@section Thread-Local Storage 10170@cindex Thread-Local Storage 10171@cindex @acronym{TLS} 10172@cindex __thread 10173 10174Thread-local storage (@acronym{TLS}) is a mechanism by which variables 10175are allocated such that there is one instance of the variable per extant 10176thread. The run-time model GCC uses to implement this originates 10177in the IA-64 processor-specific ABI, but has since been migrated 10178to other processors as well. It requires significant support from 10179the linker (@command{ld}), dynamic linker (@command{ld.so}), and 10180system libraries (@file{libc.so} and @file{libpthread.so}), so it 10181is not available everywhere. 10182 10183At the user level, the extension is visible with a new storage 10184class keyword: @code{__thread}. For example: 10185 10186@smallexample 10187__thread int i; 10188extern __thread struct state s; 10189static __thread char *p; 10190@end smallexample 10191 10192The @code{__thread} specifier may be used alone, with the @code{extern} 10193or @code{static} specifiers, but with no other storage class specifier. 10194When used with @code{extern} or @code{static}, @code{__thread} must appear 10195immediately after the other storage class specifier. 10196 10197The @code{__thread} specifier may be applied to any global, file-scoped 10198static, function-scoped static, or static data member of a class. It may 10199not be applied to block-scoped automatic or non-static data member. 10200 10201When the address-of operator is applied to a thread-local variable, it is 10202evaluated at run-time and returns the address of the current thread's 10203instance of that variable. An address so obtained may be used by any 10204thread. When a thread terminates, any pointers to thread-local variables 10205in that thread become invalid. 10206 10207No static initialization may refer to the address of a thread-local variable. 10208 10209In C++, if an initializer is present for a thread-local variable, it must 10210be a @var{constant-expression}, as defined in 5.19.2 of the ANSI/ISO C++ 10211standard. 10212 10213See @uref{http://people.redhat.com/drepper/tls.pdf, 10214ELF Handling For Thread-Local Storage} for a detailed explanation of 10215the four thread-local storage addressing models, and how the run-time 10216is expected to function. 10217 10218@menu 10219* C99 Thread-Local Edits:: 10220* C++98 Thread-Local Edits:: 10221@end menu 10222 10223@node C99 Thread-Local Edits 10224@subsection ISO/IEC 9899:1999 Edits for Thread-Local Storage 10225 10226The following are a set of changes to ISO/IEC 9899:1999 (aka C99) 10227that document the exact semantics of the language extension. 10228 10229@itemize @bullet 10230@item 10231@cite{5.1.2 Execution environments} 10232 10233Add new text after paragraph 1 10234 10235@quotation 10236Within either execution environment, a @dfn{thread} is a flow of 10237control within a program. It is implementation defined whether 10238or not there may be more than one thread associated with a program. 10239It is implementation defined how threads beyond the first are 10240created, the name and type of the function called at thread 10241startup, and how threads may be terminated. However, objects 10242with thread storage duration shall be initialized before thread 10243startup. 10244@end quotation 10245 10246@item 10247@cite{6.2.4 Storage durations of objects} 10248 10249Add new text before paragraph 3 10250 10251@quotation 10252An object whose identifier is declared with the storage-class 10253specifier @w{@code{__thread}} has @dfn{thread storage duration}. 10254Its lifetime is the entire execution of the thread, and its 10255stored value is initialized only once, prior to thread startup. 10256@end quotation 10257 10258@item 10259@cite{6.4.1 Keywords} 10260 10261Add @code{__thread}. 10262 10263@item 10264@cite{6.7.1 Storage-class specifiers} 10265 10266Add @code{__thread} to the list of storage class specifiers in 10267paragraph 1. 10268 10269Change paragraph 2 to 10270 10271@quotation 10272With the exception of @code{__thread}, at most one storage-class 10273specifier may be given [@dots{}]. The @code{__thread} specifier may 10274be used alone, or immediately following @code{extern} or 10275@code{static}. 10276@end quotation 10277 10278Add new text after paragraph 6 10279 10280@quotation 10281The declaration of an identifier for a variable that has 10282block scope that specifies @code{__thread} shall also 10283specify either @code{extern} or @code{static}. 10284 10285The @code{__thread} specifier shall be used only with 10286variables. 10287@end quotation 10288@end itemize 10289 10290@node C++98 Thread-Local Edits 10291@subsection ISO/IEC 14882:1998 Edits for Thread-Local Storage 10292 10293The following are a set of changes to ISO/IEC 14882:1998 (aka C++98) 10294that document the exact semantics of the language extension. 10295 10296@itemize @bullet 10297@item 10298@b{[intro.execution]} 10299 10300New text after paragraph 4 10301 10302@quotation 10303A @dfn{thread} is a flow of control within the abstract machine. 10304It is implementation defined whether or not there may be more than 10305one thread. 10306@end quotation 10307 10308New text after paragraph 7 10309 10310@quotation 10311It is unspecified whether additional action must be taken to 10312ensure when and whether side effects are visible to other threads. 10313@end quotation 10314 10315@item 10316@b{[lex.key]} 10317 10318Add @code{__thread}. 10319 10320@item 10321@b{[basic.start.main]} 10322 10323Add after paragraph 5 10324 10325@quotation 10326The thread that begins execution at the @code{main} function is called 10327the @dfn{main thread}. It is implementation defined how functions 10328beginning threads other than the main thread are designated or typed. 10329A function so designated, as well as the @code{main} function, is called 10330a @dfn{thread startup function}. It is implementation defined what 10331happens if a thread startup function returns. It is implementation 10332defined what happens to other threads when any thread calls @code{exit}. 10333@end quotation 10334 10335@item 10336@b{[basic.start.init]} 10337 10338Add after paragraph 4 10339 10340@quotation 10341The storage for an object of thread storage duration shall be 10342statically initialized before the first statement of the thread startup 10343function. An object of thread storage duration shall not require 10344dynamic initialization. 10345@end quotation 10346 10347@item 10348@b{[basic.start.term]} 10349 10350Add after paragraph 3 10351 10352@quotation 10353The type of an object with thread storage duration shall not have a 10354non-trivial destructor, nor shall it be an array type whose elements 10355(directly or indirectly) have non-trivial destructors. 10356@end quotation 10357 10358@item 10359@b{[basic.stc]} 10360 10361Add ``thread storage duration'' to the list in paragraph 1. 10362 10363Change paragraph 2 10364 10365@quotation 10366Thread, static, and automatic storage durations are associated with 10367objects introduced by declarations [@dots{}]. 10368@end quotation 10369 10370Add @code{__thread} to the list of specifiers in paragraph 3. 10371 10372@item 10373@b{[basic.stc.thread]} 10374 10375New section before @b{[basic.stc.static]} 10376 10377@quotation 10378The keyword @code{__thread} applied to a non-local object gives the 10379object thread storage duration. 10380 10381A local variable or class data member declared both @code{static} 10382and @code{__thread} gives the variable or member thread storage 10383duration. 10384@end quotation 10385 10386@item 10387@b{[basic.stc.static]} 10388 10389Change paragraph 1 10390 10391@quotation 10392All objects which have neither thread storage duration, dynamic 10393storage duration nor are local [@dots{}]. 10394@end quotation 10395 10396@item 10397@b{[dcl.stc]} 10398 10399Add @code{__thread} to the list in paragraph 1. 10400 10401Change paragraph 1 10402 10403@quotation 10404With the exception of @code{__thread}, at most one 10405@var{storage-class-specifier} shall appear in a given 10406@var{decl-specifier-seq}. The @code{__thread} specifier may 10407be used alone, or immediately following the @code{extern} or 10408@code{static} specifiers. [@dots{}] 10409@end quotation 10410 10411Add after paragraph 5 10412 10413@quotation 10414The @code{__thread} specifier can be applied only to the names of objects 10415and to anonymous unions. 10416@end quotation 10417 10418@item 10419@b{[class.mem]} 10420 10421Add after paragraph 6 10422 10423@quotation 10424Non-@code{static} members shall not be @code{__thread}. 10425@end quotation 10426@end itemize 10427 10428@node Binary constants 10429@section Binary constants using the @samp{0b} prefix 10430@cindex Binary constants using the @samp{0b} prefix 10431 10432Integer constants can be written as binary constants, consisting of a 10433sequence of @samp{0} and @samp{1} digits, prefixed by @samp{0b} or 10434@samp{0B}. This is particularly useful in environments that operate a 10435lot on the bit-level (like microcontrollers). 10436 10437The following statements are identical: 10438 10439@smallexample 10440i = 42; 10441i = 0x2a; 10442i = 052; 10443i = 0b101010; 10444@end smallexample 10445 10446The type of these constants follows the same rules as for octal or 10447hexadecimal integer constants, so suffixes like @samp{L} or @samp{UL} 10448can be applied. 10449 10450@node C++ Extensions 10451@chapter Extensions to the C++ Language 10452@cindex extensions, C++ language 10453@cindex C++ language extensions 10454 10455The GNU compiler provides these extensions to the C++ language (and you 10456can also use most of the C language extensions in your C++ programs). If you 10457want to write code that checks whether these features are available, you can 10458test for the GNU compiler the same way as for C programs: check for a 10459predefined macro @code{__GNUC__}. You can also use @code{__GNUG__} to 10460test specifically for GNU C++ (@pxref{Common Predefined Macros,, 10461Predefined Macros,cpp,The GNU C Preprocessor}). 10462 10463@menu 10464* Volatiles:: What constitutes an access to a volatile object. 10465* Restricted Pointers:: C99 restricted pointers and references. 10466* Vague Linkage:: Where G++ puts inlines, vtables and such. 10467* C++ Interface:: You can use a single C++ header file for both 10468 declarations and definitions. 10469* Template Instantiation:: Methods for ensuring that exactly one copy of 10470 each needed template instantiation is emitted. 10471* Bound member functions:: You can extract a function pointer to the 10472 method denoted by a @samp{->*} or @samp{.*} expression. 10473* C++ Attributes:: Variable, function, and type attributes for C++ only. 10474* Namespace Association:: Strong using-directives for namespace association. 10475* Java Exceptions:: Tweaking exception handling to work with Java. 10476* Deprecated Features:: Things will disappear from g++. 10477* Backwards Compatibility:: Compatibilities with earlier definitions of C++. 10478@end menu 10479 10480@node Volatiles 10481@section When is a Volatile Object Accessed? 10482@cindex accessing volatiles 10483@cindex volatile read 10484@cindex volatile write 10485@cindex volatile access 10486 10487Both the C and C++ standard have the concept of volatile objects. These 10488are normally accessed by pointers and used for accessing hardware. The 10489standards encourage compilers to refrain from optimizations concerning 10490accesses to volatile objects. The C standard leaves it implementation 10491defined as to what constitutes a volatile access. The C++ standard omits 10492to specify this, except to say that C++ should behave in a similar manner 10493to C with respect to volatiles, where possible. The minimum either 10494standard specifies is that at a sequence point all previous accesses to 10495volatile objects have stabilized and no subsequent accesses have 10496occurred. Thus an implementation is free to reorder and combine 10497volatile accesses which occur between sequence points, but cannot do so 10498for accesses across a sequence point. The use of volatiles does not 10499allow you to violate the restriction on updating objects multiple times 10500within a sequence point. 10501 10502@xref{Qualifiers implementation, , Volatile qualifier and the C compiler}. 10503 10504The behavior differs slightly between C and C++ in the non-obvious cases: 10505 10506@smallexample 10507volatile int *src = @var{somevalue}; 10508*src; 10509@end smallexample 10510 10511With C, such expressions are rvalues, and GCC interprets this either as a 10512read of the volatile object being pointed to or only as request to evaluate 10513the side-effects. The C++ standard specifies that such expressions do not 10514undergo lvalue to rvalue conversion, and that the type of the dereferenced 10515object may be incomplete. The C++ standard does not specify explicitly 10516that it is this lvalue to rvalue conversion which may be responsible for 10517causing an access. However, there is reason to believe that it is, 10518because otherwise certain simple expressions become undefined. However, 10519because it would surprise most programmers, G++ treats dereferencing a 10520pointer to volatile object of complete type when the value is unused as 10521GCC would do for an equivalent type in C. When the object has incomplete 10522type, G++ issues a warning; if you wish to force an error, you must 10523force a conversion to rvalue with, for instance, a static cast. 10524 10525When using a reference to volatile, G++ does not treat equivalent 10526expressions as accesses to volatiles, but instead issues a warning that 10527no volatile is accessed. The rationale for this is that otherwise it 10528becomes difficult to determine where volatile access occur, and not 10529possible to ignore the return value from functions returning volatile 10530references. Again, if you wish to force a read, cast the reference to 10531an rvalue. 10532 10533@node Restricted Pointers 10534@section Restricting Pointer Aliasing 10535@cindex restricted pointers 10536@cindex restricted references 10537@cindex restricted this pointer 10538 10539As with the C front end, G++ understands the C99 feature of restricted pointers, 10540specified with the @code{__restrict__}, or @code{__restrict} type 10541qualifier. Because you cannot compile C++ by specifying the @option{-std=c99} 10542language flag, @code{restrict} is not a keyword in C++. 10543 10544In addition to allowing restricted pointers, you can specify restricted 10545references, which indicate that the reference is not aliased in the local 10546context. 10547 10548@smallexample 10549void fn (int *__restrict__ rptr, int &__restrict__ rref) 10550@{ 10551 /* @r{@dots{}} */ 10552@} 10553@end smallexample 10554 10555@noindent 10556In the body of @code{fn}, @var{rptr} points to an unaliased integer and 10557@var{rref} refers to a (different) unaliased integer. 10558 10559You may also specify whether a member function's @var{this} pointer is 10560unaliased by using @code{__restrict__} as a member function qualifier. 10561 10562@smallexample 10563void T::fn () __restrict__ 10564@{ 10565 /* @r{@dots{}} */ 10566@} 10567@end smallexample 10568 10569@noindent 10570Within the body of @code{T::fn}, @var{this} will have the effective 10571definition @code{T *__restrict__ const this}. Notice that the 10572interpretation of a @code{__restrict__} member function qualifier is 10573different to that of @code{const} or @code{volatile} qualifier, in that it 10574is applied to the pointer rather than the object. This is consistent with 10575other compilers which implement restricted pointers. 10576 10577As with all outermost parameter qualifiers, @code{__restrict__} is 10578ignored in function definition matching. This means you only need to 10579specify @code{__restrict__} in a function definition, rather than 10580in a function prototype as well. 10581 10582@node Vague Linkage 10583@section Vague Linkage 10584@cindex vague linkage 10585 10586There are several constructs in C++ which require space in the object 10587file but are not clearly tied to a single translation unit. We say that 10588these constructs have ``vague linkage''. Typically such constructs are 10589emitted wherever they are needed, though sometimes we can be more 10590clever. 10591 10592@table @asis 10593@item Inline Functions 10594Inline functions are typically defined in a header file which can be 10595included in many different compilations. Hopefully they can usually be 10596inlined, but sometimes an out-of-line copy is necessary, if the address 10597of the function is taken or if inlining fails. In general, we emit an 10598out-of-line copy in all translation units where one is needed. As an 10599exception, we only emit inline virtual functions with the vtable, since 10600it will always require a copy. 10601 10602Local static variables and string constants used in an inline function 10603are also considered to have vague linkage, since they must be shared 10604between all inlined and out-of-line instances of the function. 10605 10606@item VTables 10607@cindex vtable 10608C++ virtual functions are implemented in most compilers using a lookup 10609table, known as a vtable. The vtable contains pointers to the virtual 10610functions provided by a class, and each object of the class contains a 10611pointer to its vtable (or vtables, in some multiple-inheritance 10612situations). If the class declares any non-inline, non-pure virtual 10613functions, the first one is chosen as the ``key method'' for the class, 10614and the vtable is only emitted in the translation unit where the key 10615method is defined. 10616 10617@emph{Note:} If the chosen key method is later defined as inline, the 10618vtable will still be emitted in every translation unit which defines it. 10619Make sure that any inline virtuals are declared inline in the class 10620body, even if they are not defined there. 10621 10622@item type_info objects 10623@cindex type_info 10624@cindex RTTI 10625C++ requires information about types to be written out in order to 10626implement @samp{dynamic_cast}, @samp{typeid} and exception handling. 10627For polymorphic classes (classes with virtual functions), the type_info 10628object is written out along with the vtable so that @samp{dynamic_cast} 10629can determine the dynamic type of a class object at runtime. For all 10630other types, we write out the type_info object when it is used: when 10631applying @samp{typeid} to an expression, throwing an object, or 10632referring to a type in a catch clause or exception specification. 10633 10634@item Template Instantiations 10635Most everything in this section also applies to template instantiations, 10636but there are other options as well. 10637@xref{Template Instantiation,,Where's the Template?}. 10638 10639@end table 10640 10641When used with GNU ld version 2.8 or later on an ELF system such as 10642GNU/Linux or Solaris 2, or on Microsoft Windows, duplicate copies of 10643these constructs will be discarded at link time. This is known as 10644COMDAT support. 10645 10646On targets that don't support COMDAT, but do support weak symbols, GCC 10647will use them. This way one copy will override all the others, but 10648the unused copies will still take up space in the executable. 10649 10650For targets which do not support either COMDAT or weak symbols, 10651most entities with vague linkage will be emitted as local symbols to 10652avoid duplicate definition errors from the linker. This will not happen 10653for local statics in inlines, however, as having multiple copies will 10654almost certainly break things. 10655 10656@xref{C++ Interface,,Declarations and Definitions in One Header}, for 10657another way to control placement of these constructs. 10658 10659@node C++ Interface 10660@section #pragma interface and implementation 10661 10662@cindex interface and implementation headers, C++ 10663@cindex C++ interface and implementation headers 10664@cindex pragmas, interface and implementation 10665 10666@code{#pragma interface} and @code{#pragma implementation} provide the 10667user with a way of explicitly directing the compiler to emit entities 10668with vague linkage (and debugging information) in a particular 10669translation unit. 10670 10671@emph{Note:} As of GCC 2.7.2, these @code{#pragma}s are not useful in 10672most cases, because of COMDAT support and the ``key method'' heuristic 10673mentioned in @ref{Vague Linkage}. Using them can actually cause your 10674program to grow due to unnecessary out-of-line copies of inline 10675functions. Currently (3.4) the only benefit of these 10676@code{#pragma}s is reduced duplication of debugging information, and 10677that should be addressed soon on DWARF 2 targets with the use of 10678COMDAT groups. 10679 10680@table @code 10681@item #pragma interface 10682@itemx #pragma interface "@var{subdir}/@var{objects}.h" 10683@kindex #pragma interface 10684Use this directive in @emph{header files} that define object classes, to save 10685space in most of the object files that use those classes. Normally, 10686local copies of certain information (backup copies of inline member 10687functions, debugging information, and the internal tables that implement 10688virtual functions) must be kept in each object file that includes class 10689definitions. You can use this pragma to avoid such duplication. When a 10690header file containing @samp{#pragma interface} is included in a 10691compilation, this auxiliary information will not be generated (unless 10692the main input source file itself uses @samp{#pragma implementation}). 10693Instead, the object files will contain references to be resolved at link 10694time. 10695 10696The second form of this directive is useful for the case where you have 10697multiple headers with the same name in different directories. If you 10698use this form, you must specify the same string to @samp{#pragma 10699implementation}. 10700 10701@item #pragma implementation 10702@itemx #pragma implementation "@var{objects}.h" 10703@kindex #pragma implementation 10704Use this pragma in a @emph{main input file}, when you want full output from 10705included header files to be generated (and made globally visible). The 10706included header file, in turn, should use @samp{#pragma interface}. 10707Backup copies of inline member functions, debugging information, and the 10708internal tables used to implement virtual functions are all generated in 10709implementation files. 10710 10711@cindex implied @code{#pragma implementation} 10712@cindex @code{#pragma implementation}, implied 10713@cindex naming convention, implementation headers 10714If you use @samp{#pragma implementation} with no argument, it applies to 10715an include file with the same basename@footnote{A file's @dfn{basename} 10716was the name stripped of all leading path information and of trailing 10717suffixes, such as @samp{.h} or @samp{.C} or @samp{.cc}.} as your source 10718file. For example, in @file{allclass.cc}, giving just 10719@samp{#pragma implementation} 10720by itself is equivalent to @samp{#pragma implementation "allclass.h"}. 10721 10722In versions of GNU C++ prior to 2.6.0 @file{allclass.h} was treated as 10723an implementation file whenever you would include it from 10724@file{allclass.cc} even if you never specified @samp{#pragma 10725implementation}. This was deemed to be more trouble than it was worth, 10726however, and disabled. 10727 10728Use the string argument if you want a single implementation file to 10729include code from multiple header files. (You must also use 10730@samp{#include} to include the header file; @samp{#pragma 10731implementation} only specifies how to use the file---it doesn't actually 10732include it.) 10733 10734There is no way to split up the contents of a single header file into 10735multiple implementation files. 10736@end table 10737 10738@cindex inlining and C++ pragmas 10739@cindex C++ pragmas, effect on inlining 10740@cindex pragmas in C++, effect on inlining 10741@samp{#pragma implementation} and @samp{#pragma interface} also have an 10742effect on function inlining. 10743 10744If you define a class in a header file marked with @samp{#pragma 10745interface}, the effect on an inline function defined in that class is 10746similar to an explicit @code{extern} declaration---the compiler emits 10747no code at all to define an independent version of the function. Its 10748definition is used only for inlining with its callers. 10749 10750@opindex fno-implement-inlines 10751Conversely, when you include the same header file in a main source file 10752that declares it as @samp{#pragma implementation}, the compiler emits 10753code for the function itself; this defines a version of the function 10754that can be found via pointers (or by callers compiled without 10755inlining). If all calls to the function can be inlined, you can avoid 10756emitting the function by compiling with @option{-fno-implement-inlines}. 10757If any calls were not inlined, you will get linker errors. 10758 10759@node Template Instantiation 10760@section Where's the Template? 10761@cindex template instantiation 10762 10763C++ templates are the first language feature to require more 10764intelligence from the environment than one usually finds on a UNIX 10765system. Somehow the compiler and linker have to make sure that each 10766template instance occurs exactly once in the executable if it is needed, 10767and not at all otherwise. There are two basic approaches to this 10768problem, which are referred to as the Borland model and the Cfront model. 10769 10770@table @asis 10771@item Borland model 10772Borland C++ solved the template instantiation problem by adding the code 10773equivalent of common blocks to their linker; the compiler emits template 10774instances in each translation unit that uses them, and the linker 10775collapses them together. The advantage of this model is that the linker 10776only has to consider the object files themselves; there is no external 10777complexity to worry about. This disadvantage is that compilation time 10778is increased because the template code is being compiled repeatedly. 10779Code written for this model tends to include definitions of all 10780templates in the header file, since they must be seen to be 10781instantiated. 10782 10783@item Cfront model 10784The AT&T C++ translator, Cfront, solved the template instantiation 10785problem by creating the notion of a template repository, an 10786automatically maintained place where template instances are stored. A 10787more modern version of the repository works as follows: As individual 10788object files are built, the compiler places any template definitions and 10789instantiations encountered in the repository. At link time, the link 10790wrapper adds in the objects in the repository and compiles any needed 10791instances that were not previously emitted. The advantages of this 10792model are more optimal compilation speed and the ability to use the 10793system linker; to implement the Borland model a compiler vendor also 10794needs to replace the linker. The disadvantages are vastly increased 10795complexity, and thus potential for error; for some code this can be 10796just as transparent, but in practice it can been very difficult to build 10797multiple programs in one directory and one program in multiple 10798directories. Code written for this model tends to separate definitions 10799of non-inline member templates into a separate file, which should be 10800compiled separately. 10801@end table 10802 10803When used with GNU ld version 2.8 or later on an ELF system such as 10804GNU/Linux or Solaris 2, or on Microsoft Windows, G++ supports the 10805Borland model. On other systems, G++ implements neither automatic 10806model. 10807 10808A future version of G++ will support a hybrid model whereby the compiler 10809will emit any instantiations for which the template definition is 10810included in the compile, and store template definitions and 10811instantiation context information into the object file for the rest. 10812The link wrapper will extract that information as necessary and invoke 10813the compiler to produce the remaining instantiations. The linker will 10814then combine duplicate instantiations. 10815 10816In the mean time, you have the following options for dealing with 10817template instantiations: 10818 10819@enumerate 10820@item 10821@opindex frepo 10822Compile your template-using code with @option{-frepo}. The compiler will 10823generate files with the extension @samp{.rpo} listing all of the 10824template instantiations used in the corresponding object files which 10825could be instantiated there; the link wrapper, @samp{collect2}, will 10826then update the @samp{.rpo} files to tell the compiler where to place 10827those instantiations and rebuild any affected object files. The 10828link-time overhead is negligible after the first pass, as the compiler 10829will continue to place the instantiations in the same files. 10830 10831This is your best option for application code written for the Borland 10832model, as it will just work. Code written for the Cfront model will 10833need to be modified so that the template definitions are available at 10834one or more points of instantiation; usually this is as simple as adding 10835@code{#include <tmethods.cc>} to the end of each template header. 10836 10837For library code, if you want the library to provide all of the template 10838instantiations it needs, just try to link all of its object files 10839together; the link will fail, but cause the instantiations to be 10840generated as a side effect. Be warned, however, that this may cause 10841conflicts if multiple libraries try to provide the same instantiations. 10842For greater control, use explicit instantiation as described in the next 10843option. 10844 10845@item 10846@opindex fno-implicit-templates 10847Compile your code with @option{-fno-implicit-templates} to disable the 10848implicit generation of template instances, and explicitly instantiate 10849all the ones you use. This approach requires more knowledge of exactly 10850which instances you need than do the others, but it's less 10851mysterious and allows greater control. You can scatter the explicit 10852instantiations throughout your program, perhaps putting them in the 10853translation units where the instances are used or the translation units 10854that define the templates themselves; you can put all of the explicit 10855instantiations you need into one big file; or you can create small files 10856like 10857 10858@smallexample 10859#include "Foo.h" 10860#include "Foo.cc" 10861 10862template class Foo<int>; 10863template ostream& operator << 10864 (ostream&, const Foo<int>&); 10865@end smallexample 10866 10867for each of the instances you need, and create a template instantiation 10868library from those. 10869 10870If you are using Cfront-model code, you can probably get away with not 10871using @option{-fno-implicit-templates} when compiling files that don't 10872@samp{#include} the member template definitions. 10873 10874If you use one big file to do the instantiations, you may want to 10875compile it without @option{-fno-implicit-templates} so you get all of the 10876instances required by your explicit instantiations (but not by any 10877other files) without having to specify them as well. 10878 10879G++ has extended the template instantiation syntax given in the ISO 10880standard to allow forward declaration of explicit instantiations 10881(with @code{extern}), instantiation of the compiler support data for a 10882template class (i.e.@: the vtable) without instantiating any of its 10883members (with @code{inline}), and instantiation of only the static data 10884members of a template class, without the support data or member 10885functions (with (@code{static}): 10886 10887@smallexample 10888extern template int max (int, int); 10889inline template class Foo<int>; 10890static template class Foo<int>; 10891@end smallexample 10892 10893@item 10894Do nothing. Pretend G++ does implement automatic instantiation 10895management. Code written for the Borland model will work fine, but 10896each translation unit will contain instances of each of the templates it 10897uses. In a large program, this can lead to an unacceptable amount of code 10898duplication. 10899@end enumerate 10900 10901@node Bound member functions 10902@section Extracting the function pointer from a bound pointer to member function 10903@cindex pmf 10904@cindex pointer to member function 10905@cindex bound pointer to member function 10906 10907In C++, pointer to member functions (PMFs) are implemented using a wide 10908pointer of sorts to handle all the possible call mechanisms; the PMF 10909needs to store information about how to adjust the @samp{this} pointer, 10910and if the function pointed to is virtual, where to find the vtable, and 10911where in the vtable to look for the member function. If you are using 10912PMFs in an inner loop, you should really reconsider that decision. If 10913that is not an option, you can extract the pointer to the function that 10914would be called for a given object/PMF pair and call it directly inside 10915the inner loop, to save a bit of time. 10916 10917Note that you will still be paying the penalty for the call through a 10918function pointer; on most modern architectures, such a call defeats the 10919branch prediction features of the CPU@. This is also true of normal 10920virtual function calls. 10921 10922The syntax for this extension is 10923 10924@smallexample 10925extern A a; 10926extern int (A::*fp)(); 10927typedef int (*fptr)(A *); 10928 10929fptr p = (fptr)(a.*fp); 10930@end smallexample 10931 10932For PMF constants (i.e.@: expressions of the form @samp{&Klasse::Member}), 10933no object is needed to obtain the address of the function. They can be 10934converted to function pointers directly: 10935 10936@smallexample 10937fptr p1 = (fptr)(&A::foo); 10938@end smallexample 10939 10940@opindex Wno-pmf-conversions 10941You must specify @option{-Wno-pmf-conversions} to use this extension. 10942 10943@node C++ Attributes 10944@section C++-Specific Variable, Function, and Type Attributes 10945 10946Some attributes only make sense for C++ programs. 10947 10948@table @code 10949@item init_priority (@var{priority}) 10950@cindex init_priority attribute 10951 10952 10953In Standard C++, objects defined at namespace scope are guaranteed to be 10954initialized in an order in strict accordance with that of their definitions 10955@emph{in a given translation unit}. No guarantee is made for initializations 10956across translation units. However, GNU C++ allows users to control the 10957order of initialization of objects defined at namespace scope with the 10958@code{init_priority} attribute by specifying a relative @var{priority}, 10959a constant integral expression currently bounded between 101 and 65535 10960inclusive. Lower numbers indicate a higher priority. 10961 10962In the following example, @code{A} would normally be created before 10963@code{B}, but the @code{init_priority} attribute has reversed that order: 10964 10965@smallexample 10966Some_Class A __attribute__ ((init_priority (2000))); 10967Some_Class B __attribute__ ((init_priority (543))); 10968@end smallexample 10969 10970@noindent 10971Note that the particular values of @var{priority} do not matter; only their 10972relative ordering. 10973 10974@item java_interface 10975@cindex java_interface attribute 10976 10977This type attribute informs C++ that the class is a Java interface. It may 10978only be applied to classes declared within an @code{extern "Java"} block. 10979Calls to methods declared in this interface will be dispatched using GCJ's 10980interface table mechanism, instead of regular virtual table dispatch. 10981 10982@end table 10983 10984See also @xref{Namespace Association}. 10985 10986@node Namespace Association 10987@section Namespace Association 10988 10989@strong{Caution:} The semantics of this extension are not fully 10990defined. Users should refrain from using this extension as its 10991semantics may change subtly over time. It is possible that this 10992extension will be removed in future versions of G++. 10993 10994A using-directive with @code{__attribute ((strong))} is stronger 10995than a normal using-directive in two ways: 10996 10997@itemize @bullet 10998@item 10999Templates from the used namespace can be specialized and explicitly 11000instantiated as though they were members of the using namespace. 11001 11002@item 11003The using namespace is considered an associated namespace of all 11004templates in the used namespace for purposes of argument-dependent 11005name lookup. 11006@end itemize 11007 11008The used namespace must be nested within the using namespace so that 11009normal unqualified lookup works properly. 11010 11011This is useful for composing a namespace transparently from 11012implementation namespaces. For example: 11013 11014@smallexample 11015namespace std @{ 11016 namespace debug @{ 11017 template <class T> struct A @{ @}; 11018 @} 11019 using namespace debug __attribute ((__strong__)); 11020 template <> struct A<int> @{ @}; // @r{ok to specialize} 11021 11022 template <class T> void f (A<T>); 11023@} 11024 11025int main() 11026@{ 11027 f (std::A<float>()); // @r{lookup finds} std::f 11028 f (std::A<int>()); 11029@} 11030@end smallexample 11031 11032@node Java Exceptions 11033@section Java Exceptions 11034 11035The Java language uses a slightly different exception handling model 11036from C++. Normally, GNU C++ will automatically detect when you are 11037writing C++ code that uses Java exceptions, and handle them 11038appropriately. However, if C++ code only needs to execute destructors 11039when Java exceptions are thrown through it, GCC will guess incorrectly. 11040Sample problematic code is: 11041 11042@smallexample 11043 struct S @{ ~S(); @}; 11044 extern void bar(); // @r{is written in Java, and may throw exceptions} 11045 void foo() 11046 @{ 11047 S s; 11048 bar(); 11049 @} 11050@end smallexample 11051 11052@noindent 11053The usual effect of an incorrect guess is a link failure, complaining of 11054a missing routine called @samp{__gxx_personality_v0}. 11055 11056You can inform the compiler that Java exceptions are to be used in a 11057translation unit, irrespective of what it might think, by writing 11058@samp{@w{#pragma GCC java_exceptions}} at the head of the file. This 11059@samp{#pragma} must appear before any functions that throw or catch 11060exceptions, or run destructors when exceptions are thrown through them. 11061 11062You cannot mix Java and C++ exceptions in the same translation unit. It 11063is believed to be safe to throw a C++ exception from one file through 11064another file compiled for the Java exception model, or vice versa, but 11065there may be bugs in this area. 11066 11067@node Deprecated Features 11068@section Deprecated Features 11069 11070In the past, the GNU C++ compiler was extended to experiment with new 11071features, at a time when the C++ language was still evolving. Now that 11072the C++ standard is complete, some of those features are superseded by 11073superior alternatives. Using the old features might cause a warning in 11074some cases that the feature will be dropped in the future. In other 11075cases, the feature might be gone already. 11076 11077While the list below is not exhaustive, it documents some of the options 11078that are now deprecated: 11079 11080@table @code 11081@item -fexternal-templates 11082@itemx -falt-external-templates 11083These are two of the many ways for G++ to implement template 11084instantiation. @xref{Template Instantiation}. The C++ standard clearly 11085defines how template definitions have to be organized across 11086implementation units. G++ has an implicit instantiation mechanism that 11087should work just fine for standard-conforming code. 11088 11089@item -fstrict-prototype 11090@itemx -fno-strict-prototype 11091Previously it was possible to use an empty prototype parameter list to 11092indicate an unspecified number of parameters (like C), rather than no 11093parameters, as C++ demands. This feature has been removed, except where 11094it is required for backwards compatibility @xref{Backwards Compatibility}. 11095@end table 11096 11097G++ allows a virtual function returning @samp{void *} to be overridden 11098by one returning a different pointer type. This extension to the 11099covariant return type rules is now deprecated and will be removed from a 11100future version. 11101 11102The G++ minimum and maximum operators (@samp{<?} and @samp{>?}) and 11103their compound forms (@samp{<?=}) and @samp{>?=}) have been deprecated 11104and will be removed in a future version. Code using these operators 11105should be modified to use @code{std::min} and @code{std::max} instead. 11106 11107The named return value extension has been deprecated, and is now 11108removed from G++. 11109 11110The use of initializer lists with new expressions has been deprecated, 11111and is now removed from G++. 11112 11113Floating and complex non-type template parameters have been deprecated, 11114and are now removed from G++. 11115 11116The implicit typename extension has been deprecated and is now 11117removed from G++. 11118 11119The use of default arguments in function pointers, function typedefs 11120and other places where they are not permitted by the standard is 11121deprecated and will be removed from a future version of G++. 11122 11123G++ allows floating-point literals to appear in integral constant expressions, 11124e.g. @samp{ enum E @{ e = int(2.2 * 3.7) @} } 11125This extension is deprecated and will be removed from a future version. 11126 11127G++ allows static data members of const floating-point type to be declared 11128with an initializer in a class definition. The standard only allows 11129initializers for static members of const integral types and const 11130enumeration types so this extension has been deprecated and will be removed 11131from a future version. 11132 11133@node Backwards Compatibility 11134@section Backwards Compatibility 11135@cindex Backwards Compatibility 11136@cindex ARM [Annotated C++ Reference Manual] 11137 11138Now that there is a definitive ISO standard C++, G++ has a specification 11139to adhere to. The C++ language evolved over time, and features that 11140used to be acceptable in previous drafts of the standard, such as the ARM 11141[Annotated C++ Reference Manual], are no longer accepted. In order to allow 11142compilation of C++ written to such drafts, G++ contains some backwards 11143compatibilities. @emph{All such backwards compatibility features are 11144liable to disappear in future versions of G++.} They should be considered 11145deprecated @xref{Deprecated Features}. 11146 11147@table @code 11148@item For scope 11149If a variable is declared at for scope, it used to remain in scope until 11150the end of the scope which contained the for statement (rather than just 11151within the for scope). G++ retains this, but issues a warning, if such a 11152variable is accessed outside the for scope. 11153 11154@item Implicit C language 11155Old C system header files did not contain an @code{extern "C" @{@dots{}@}} 11156scope to set the language. On such systems, all header files are 11157implicitly scoped inside a C language scope. Also, an empty prototype 11158@code{()} will be treated as an unspecified number of arguments, rather 11159than no arguments, as C++ demands. 11160@end table 11161