alias.c revision 90075
1/* Alias analysis for GNU C 2 Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc. 3 Contributed by John Carr (jfc@mit.edu). 4 5This file is part of GCC. 6 7GCC is free software; you can redistribute it and/or modify it under 8the terms of the GNU General Public License as published by the Free 9Software Foundation; either version 2, or (at your option) any later 10version. 11 12GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13WARRANTY; without even the implied warranty of MERCHANTABILITY or 14FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15for more details. 16 17You should have received a copy of the GNU General Public License 18along with GCC; see the file COPYING. If not, write to the Free 19Software Foundation, 59 Temple Place - Suite 330, Boston, MA 2002111-1307, USA. */ 21 22#include "config.h" 23#include "system.h" 24#include "rtl.h" 25#include "tree.h" 26#include "tm_p.h" 27#include "function.h" 28#include "expr.h" 29#include "regs.h" 30#include "hard-reg-set.h" 31#include "basic-block.h" 32#include "flags.h" 33#include "output.h" 34#include "toplev.h" 35#include "cselib.h" 36#include "splay-tree.h" 37#include "ggc.h" 38#include "langhooks.h" 39 40/* The alias sets assigned to MEMs assist the back-end in determining 41 which MEMs can alias which other MEMs. In general, two MEMs in 42 different alias sets cannot alias each other, with one important 43 exception. Consider something like: 44 45 struct S {int i; double d; }; 46 47 a store to an `S' can alias something of either type `int' or type 48 `double'. (However, a store to an `int' cannot alias a `double' 49 and vice versa.) We indicate this via a tree structure that looks 50 like: 51 struct S 52 / \ 53 / \ 54 |/_ _\| 55 int double 56 57 (The arrows are directed and point downwards.) 58 In this situation we say the alias set for `struct S' is the 59 `superset' and that those for `int' and `double' are `subsets'. 60 61 To see whether two alias sets can point to the same memory, we must 62 see if either alias set is a subset of the other. We need not trace 63 past immediate descendents, however, since we propagate all 64 grandchildren up one level. 65 66 Alias set zero is implicitly a superset of all other alias sets. 67 However, this is no actual entry for alias set zero. It is an 68 error to attempt to explicitly construct a subset of zero. */ 69 70typedef struct alias_set_entry 71{ 72 /* The alias set number, as stored in MEM_ALIAS_SET. */ 73 HOST_WIDE_INT alias_set; 74 75 /* The children of the alias set. These are not just the immediate 76 children, but, in fact, all descendents. So, if we have: 77 78 struct T { struct S s; float f; } 79 80 continuing our example above, the children here will be all of 81 `int', `double', `float', and `struct S'. */ 82 splay_tree children; 83 84 /* Nonzero if would have a child of zero: this effectively makes this 85 alias set the same as alias set zero. */ 86 int has_zero_child; 87} *alias_set_entry; 88 89static int rtx_equal_for_memref_p PARAMS ((rtx, rtx)); 90static rtx find_symbolic_term PARAMS ((rtx)); 91rtx get_addr PARAMS ((rtx)); 92static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx, 93 HOST_WIDE_INT)); 94static void record_set PARAMS ((rtx, rtx, void *)); 95static rtx find_base_term PARAMS ((rtx)); 96static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode, 97 enum machine_mode)); 98static rtx find_base_value PARAMS ((rtx)); 99static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx)); 100static int insert_subset_children PARAMS ((splay_tree_node, void*)); 101static tree find_base_decl PARAMS ((tree)); 102static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT)); 103static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx, 104 int (*) (rtx, int))); 105static int aliases_everything_p PARAMS ((rtx)); 106static bool nonoverlapping_component_refs_p PARAMS ((tree, tree)); 107static tree decl_for_component_ref PARAMS ((tree)); 108static rtx adjust_offset_for_component_ref PARAMS ((tree, rtx)); 109static int nonoverlapping_memrefs_p PARAMS ((rtx, rtx)); 110static int write_dependence_p PARAMS ((rtx, rtx, int)); 111static int nonlocal_mentioned_p PARAMS ((rtx)); 112 113/* Set up all info needed to perform alias analysis on memory references. */ 114 115/* Returns the size in bytes of the mode of X. */ 116#define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X))) 117 118/* Returns nonzero if MEM1 and MEM2 do not alias because they are in 119 different alias sets. We ignore alias sets in functions making use 120 of variable arguments because the va_arg macros on some systems are 121 not legal ANSI C. */ 122#define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \ 123 mems_in_disjoint_alias_sets_p (MEM1, MEM2) 124 125/* Cap the number of passes we make over the insns propagating alias 126 information through set chains. 10 is a completely arbitrary choice. */ 127#define MAX_ALIAS_LOOP_PASSES 10 128 129/* reg_base_value[N] gives an address to which register N is related. 130 If all sets after the first add or subtract to the current value 131 or otherwise modify it so it does not point to a different top level 132 object, reg_base_value[N] is equal to the address part of the source 133 of the first set. 134 135 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS 136 expressions represent certain special values: function arguments and 137 the stack, frame, and argument pointers. 138 139 The contents of an ADDRESS is not normally used, the mode of the 140 ADDRESS determines whether the ADDRESS is a function argument or some 141 other special value. Pointer equality, not rtx_equal_p, determines whether 142 two ADDRESS expressions refer to the same base address. 143 144 The only use of the contents of an ADDRESS is for determining if the 145 current function performs nonlocal memory memory references for the 146 purposes of marking the function as a constant function. */ 147 148static rtx *reg_base_value; 149static rtx *new_reg_base_value; 150static unsigned int reg_base_value_size; /* size of reg_base_value array */ 151 152#define REG_BASE_VALUE(X) \ 153 (REGNO (X) < reg_base_value_size \ 154 ? reg_base_value[REGNO (X)] : 0) 155 156/* Vector of known invariant relationships between registers. Set in 157 loop unrolling. Indexed by register number, if nonzero the value 158 is an expression describing this register in terms of another. 159 160 The length of this array is REG_BASE_VALUE_SIZE. 161 162 Because this array contains only pseudo registers it has no effect 163 after reload. */ 164static rtx *alias_invariant; 165 166/* Vector indexed by N giving the initial (unchanging) value known for 167 pseudo-register N. This array is initialized in 168 init_alias_analysis, and does not change until end_alias_analysis 169 is called. */ 170rtx *reg_known_value; 171 172/* Indicates number of valid entries in reg_known_value. */ 173static unsigned int reg_known_value_size; 174 175/* Vector recording for each reg_known_value whether it is due to a 176 REG_EQUIV note. Future passes (viz., reload) may replace the 177 pseudo with the equivalent expression and so we account for the 178 dependences that would be introduced if that happens. 179 180 The REG_EQUIV notes created in assign_parms may mention the arg 181 pointer, and there are explicit insns in the RTL that modify the 182 arg pointer. Thus we must ensure that such insns don't get 183 scheduled across each other because that would invalidate the 184 REG_EQUIV notes. One could argue that the REG_EQUIV notes are 185 wrong, but solving the problem in the scheduler will likely give 186 better code, so we do it here. */ 187char *reg_known_equiv_p; 188 189/* True when scanning insns from the start of the rtl to the 190 NOTE_INSN_FUNCTION_BEG note. */ 191static int copying_arguments; 192 193/* The splay-tree used to store the various alias set entries. */ 194static splay_tree alias_sets; 195 196/* Returns a pointer to the alias set entry for ALIAS_SET, if there is 197 such an entry, or NULL otherwise. */ 198 199static alias_set_entry 200get_alias_set_entry (alias_set) 201 HOST_WIDE_INT alias_set; 202{ 203 splay_tree_node sn 204 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set); 205 206 return sn != 0 ? ((alias_set_entry) sn->value) : 0; 207} 208 209/* Returns nonzero if the alias sets for MEM1 and MEM2 are such that 210 the two MEMs cannot alias each other. */ 211 212static int 213mems_in_disjoint_alias_sets_p (mem1, mem2) 214 rtx mem1; 215 rtx mem2; 216{ 217#ifdef ENABLE_CHECKING 218/* Perform a basic sanity check. Namely, that there are no alias sets 219 if we're not using strict aliasing. This helps to catch bugs 220 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or 221 where a MEM is allocated in some way other than by the use of 222 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to 223 use alias sets to indicate that spilled registers cannot alias each 224 other, we might need to remove this check. */ 225 if (! flag_strict_aliasing 226 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0)) 227 abort (); 228#endif 229 230 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2)); 231} 232 233/* Insert the NODE into the splay tree given by DATA. Used by 234 record_alias_subset via splay_tree_foreach. */ 235 236static int 237insert_subset_children (node, data) 238 splay_tree_node node; 239 void *data; 240{ 241 splay_tree_insert ((splay_tree) data, node->key, node->value); 242 243 return 0; 244} 245 246/* Return 1 if the two specified alias sets may conflict. */ 247 248int 249alias_sets_conflict_p (set1, set2) 250 HOST_WIDE_INT set1, set2; 251{ 252 alias_set_entry ase; 253 254 /* If have no alias set information for one of the operands, we have 255 to assume it can alias anything. */ 256 if (set1 == 0 || set2 == 0 257 /* If the two alias sets are the same, they may alias. */ 258 || set1 == set2) 259 return 1; 260 261 /* See if the first alias set is a subset of the second. */ 262 ase = get_alias_set_entry (set1); 263 if (ase != 0 264 && (ase->has_zero_child 265 || splay_tree_lookup (ase->children, 266 (splay_tree_key) set2))) 267 return 1; 268 269 /* Now do the same, but with the alias sets reversed. */ 270 ase = get_alias_set_entry (set2); 271 if (ase != 0 272 && (ase->has_zero_child 273 || splay_tree_lookup (ase->children, 274 (splay_tree_key) set1))) 275 return 1; 276 277 /* The two alias sets are distinct and neither one is the 278 child of the other. Therefore, they cannot alias. */ 279 return 0; 280} 281 282/* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has 283 has any readonly fields. If any of the fields have types that 284 contain readonly fields, return true as well. */ 285 286int 287readonly_fields_p (type) 288 tree type; 289{ 290 tree field; 291 292 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE 293 && TREE_CODE (type) != QUAL_UNION_TYPE) 294 return 0; 295 296 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field)) 297 if (TREE_CODE (field) == FIELD_DECL 298 && (TREE_READONLY (field) 299 || readonly_fields_p (TREE_TYPE (field)))) 300 return 1; 301 302 return 0; 303} 304 305/* Return 1 if any MEM object of type T1 will always conflict (using the 306 dependency routines in this file) with any MEM object of type T2. 307 This is used when allocating temporary storage. If T1 and/or T2 are 308 NULL_TREE, it means we know nothing about the storage. */ 309 310int 311objects_must_conflict_p (t1, t2) 312 tree t1, t2; 313{ 314 /* If neither has a type specified, we don't know if they'll conflict 315 because we may be using them to store objects of various types, for 316 example the argument and local variables areas of inlined functions. */ 317 if (t1 == 0 && t2 == 0) 318 return 0; 319 320 /* If one or the other has readonly fields or is readonly, 321 then they may not conflict. */ 322 if ((t1 != 0 && readonly_fields_p (t1)) 323 || (t2 != 0 && readonly_fields_p (t2)) 324 || (t1 != 0 && TYPE_READONLY (t1)) 325 || (t2 != 0 && TYPE_READONLY (t2))) 326 return 0; 327 328 /* If they are the same type, they must conflict. */ 329 if (t1 == t2 330 /* Likewise if both are volatile. */ 331 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2))) 332 return 1; 333 334 /* If one is aggregate and the other is scalar then they may not 335 conflict. */ 336 if ((t1 != 0 && AGGREGATE_TYPE_P (t1)) 337 != (t2 != 0 && AGGREGATE_TYPE_P (t2))) 338 return 0; 339 340 /* Otherwise they conflict only if the alias sets conflict. */ 341 return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0, 342 t2 ? get_alias_set (t2) : 0); 343} 344 345/* T is an expression with pointer type. Find the DECL on which this 346 expression is based. (For example, in `a[i]' this would be `a'.) 347 If there is no such DECL, or a unique decl cannot be determined, 348 NULL_TREE is returned. */ 349 350static tree 351find_base_decl (t) 352 tree t; 353{ 354 tree d0, d1, d2; 355 356 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t))) 357 return 0; 358 359 /* If this is a declaration, return it. */ 360 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd') 361 return t; 362 363 /* Handle general expressions. It would be nice to deal with 364 COMPONENT_REFs here. If we could tell that `a' and `b' were the 365 same, then `a->f' and `b->f' are also the same. */ 366 switch (TREE_CODE_CLASS (TREE_CODE (t))) 367 { 368 case '1': 369 return find_base_decl (TREE_OPERAND (t, 0)); 370 371 case '2': 372 /* Return 0 if found in neither or both are the same. */ 373 d0 = find_base_decl (TREE_OPERAND (t, 0)); 374 d1 = find_base_decl (TREE_OPERAND (t, 1)); 375 if (d0 == d1) 376 return d0; 377 else if (d0 == 0) 378 return d1; 379 else if (d1 == 0) 380 return d0; 381 else 382 return 0; 383 384 case '3': 385 d0 = find_base_decl (TREE_OPERAND (t, 0)); 386 d1 = find_base_decl (TREE_OPERAND (t, 1)); 387 d2 = find_base_decl (TREE_OPERAND (t, 2)); 388 389 /* Set any nonzero values from the last, then from the first. */ 390 if (d1 == 0) d1 = d2; 391 if (d0 == 0) d0 = d1; 392 if (d1 == 0) d1 = d0; 393 if (d2 == 0) d2 = d1; 394 395 /* At this point all are nonzero or all are zero. If all three are the 396 same, return it. Otherwise, return zero. */ 397 return (d0 == d1 && d1 == d2) ? d0 : 0; 398 399 default: 400 return 0; 401 } 402} 403 404/* Return 1 if all the nested component references handled by 405 get_inner_reference in T are such that we can address the object in T. */ 406 407int 408can_address_p (t) 409 tree t; 410{ 411 /* If we're at the end, it is vacuously addressable. */ 412 if (! handled_component_p (t)) 413 return 1; 414 415 /* Bitfields are never addressable. */ 416 else if (TREE_CODE (t) == BIT_FIELD_REF) 417 return 0; 418 419 /* Fields are addressable unless they are marked as nonaddressable or 420 the containing type has alias set 0. */ 421 else if (TREE_CODE (t) == COMPONENT_REF 422 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)) 423 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0 424 && can_address_p (TREE_OPERAND (t, 0))) 425 return 1; 426 427 /* Likewise for arrays. */ 428 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF) 429 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))) 430 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0 431 && can_address_p (TREE_OPERAND (t, 0))) 432 return 1; 433 434 return 0; 435} 436 437/* Return the alias set for T, which may be either a type or an 438 expression. Call language-specific routine for help, if needed. */ 439 440HOST_WIDE_INT 441get_alias_set (t) 442 tree t; 443{ 444 HOST_WIDE_INT set; 445 446 /* If we're not doing any alias analysis, just assume everything 447 aliases everything else. Also return 0 if this or its type is 448 an error. */ 449 if (! flag_strict_aliasing || t == error_mark_node 450 || (! TYPE_P (t) 451 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node))) 452 return 0; 453 454 /* We can be passed either an expression or a type. This and the 455 language-specific routine may make mutually-recursive calls to each other 456 to figure out what to do. At each juncture, we see if this is a tree 457 that the language may need to handle specially. First handle things that 458 aren't types. */ 459 if (! TYPE_P (t)) 460 { 461 tree inner = t; 462 tree placeholder_ptr = 0; 463 464 /* Remove any nops, then give the language a chance to do 465 something with this tree before we look at it. */ 466 STRIP_NOPS (t); 467 set = (*lang_hooks.get_alias_set) (t); 468 if (set != -1) 469 return set; 470 471 /* First see if the actual object referenced is an INDIRECT_REF from a 472 restrict-qualified pointer or a "void *". Replace 473 PLACEHOLDER_EXPRs. */ 474 while (TREE_CODE (inner) == PLACEHOLDER_EXPR 475 || handled_component_p (inner)) 476 { 477 if (TREE_CODE (inner) == PLACEHOLDER_EXPR) 478 inner = find_placeholder (inner, &placeholder_ptr); 479 else 480 inner = TREE_OPERAND (inner, 0); 481 482 STRIP_NOPS (inner); 483 } 484 485 /* Check for accesses through restrict-qualified pointers. */ 486 if (TREE_CODE (inner) == INDIRECT_REF) 487 { 488 tree decl = find_base_decl (TREE_OPERAND (inner, 0)); 489 490 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl)) 491 { 492 /* If we haven't computed the actual alias set, do it now. */ 493 if (DECL_POINTER_ALIAS_SET (decl) == -2) 494 { 495 /* No two restricted pointers can point at the same thing. 496 However, a restricted pointer can point at the same thing 497 as an unrestricted pointer, if that unrestricted pointer 498 is based on the restricted pointer. So, we make the 499 alias set for the restricted pointer a subset of the 500 alias set for the type pointed to by the type of the 501 decl. */ 502 HOST_WIDE_INT pointed_to_alias_set 503 = get_alias_set (TREE_TYPE (TREE_TYPE (decl))); 504 505 if (pointed_to_alias_set == 0) 506 /* It's not legal to make a subset of alias set zero. */ 507 ; 508 else 509 { 510 DECL_POINTER_ALIAS_SET (decl) = new_alias_set (); 511 record_alias_subset (pointed_to_alias_set, 512 DECL_POINTER_ALIAS_SET (decl)); 513 } 514 } 515 516 /* We use the alias set indicated in the declaration. */ 517 return DECL_POINTER_ALIAS_SET (decl); 518 } 519 520 /* If we have an INDIRECT_REF via a void pointer, we don't 521 know anything about what that might alias. */ 522 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE) 523 return 0; 524 } 525 526 /* Otherwise, pick up the outermost object that we could have a pointer 527 to, processing conversion and PLACEHOLDER_EXPR as above. */ 528 placeholder_ptr = 0; 529 while (TREE_CODE (t) == PLACEHOLDER_EXPR 530 || (handled_component_p (t) && ! can_address_p (t))) 531 { 532 if (TREE_CODE (t) == PLACEHOLDER_EXPR) 533 t = find_placeholder (t, &placeholder_ptr); 534 else 535 t = TREE_OPERAND (t, 0); 536 537 STRIP_NOPS (t); 538 } 539 540 /* If we've already determined the alias set for a decl, just return 541 it. This is necessary for C++ anonymous unions, whose component 542 variables don't look like union members (boo!). */ 543 if (TREE_CODE (t) == VAR_DECL 544 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM) 545 return MEM_ALIAS_SET (DECL_RTL (t)); 546 547 /* Now all we care about is the type. */ 548 t = TREE_TYPE (t); 549 } 550 551 /* Variant qualifiers don't affect the alias set, so get the main 552 variant. If this is a type with a known alias set, return it. */ 553 t = TYPE_MAIN_VARIANT (t); 554 if (TYPE_ALIAS_SET_KNOWN_P (t)) 555 return TYPE_ALIAS_SET (t); 556 557 /* See if the language has special handling for this type. */ 558 set = (*lang_hooks.get_alias_set) (t); 559 if (set != -1) 560 return set; 561 562 /* There are no objects of FUNCTION_TYPE, so there's no point in 563 using up an alias set for them. (There are, of course, pointers 564 and references to functions, but that's different.) */ 565 else if (TREE_CODE (t) == FUNCTION_TYPE) 566 set = 0; 567 else 568 /* Otherwise make a new alias set for this type. */ 569 set = new_alias_set (); 570 571 TYPE_ALIAS_SET (t) = set; 572 573 /* If this is an aggregate type, we must record any component aliasing 574 information. */ 575 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE) 576 record_component_aliases (t); 577 578 return set; 579} 580 581/* Return a brand-new alias set. */ 582 583HOST_WIDE_INT 584new_alias_set () 585{ 586 static HOST_WIDE_INT last_alias_set; 587 588 if (flag_strict_aliasing) 589 return ++last_alias_set; 590 else 591 return 0; 592} 593 594/* Indicate that things in SUBSET can alias things in SUPERSET, but 595 not vice versa. For example, in C, a store to an `int' can alias a 596 structure containing an `int', but not vice versa. Here, the 597 structure would be the SUPERSET and `int' the SUBSET. This 598 function should be called only once per SUPERSET/SUBSET pair. 599 600 It is illegal for SUPERSET to be zero; everything is implicitly a 601 subset of alias set zero. */ 602 603void 604record_alias_subset (superset, subset) 605 HOST_WIDE_INT superset; 606 HOST_WIDE_INT subset; 607{ 608 alias_set_entry superset_entry; 609 alias_set_entry subset_entry; 610 611 /* It is possible in complex type situations for both sets to be the same, 612 in which case we can ignore this operation. */ 613 if (superset == subset) 614 return; 615 616 if (superset == 0) 617 abort (); 618 619 superset_entry = get_alias_set_entry (superset); 620 if (superset_entry == 0) 621 { 622 /* Create an entry for the SUPERSET, so that we have a place to 623 attach the SUBSET. */ 624 superset_entry 625 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry)); 626 superset_entry->alias_set = superset; 627 superset_entry->children 628 = splay_tree_new (splay_tree_compare_ints, 0, 0); 629 superset_entry->has_zero_child = 0; 630 splay_tree_insert (alias_sets, (splay_tree_key) superset, 631 (splay_tree_value) superset_entry); 632 } 633 634 if (subset == 0) 635 superset_entry->has_zero_child = 1; 636 else 637 { 638 subset_entry = get_alias_set_entry (subset); 639 /* If there is an entry for the subset, enter all of its children 640 (if they are not already present) as children of the SUPERSET. */ 641 if (subset_entry) 642 { 643 if (subset_entry->has_zero_child) 644 superset_entry->has_zero_child = 1; 645 646 splay_tree_foreach (subset_entry->children, insert_subset_children, 647 superset_entry->children); 648 } 649 650 /* Enter the SUBSET itself as a child of the SUPERSET. */ 651 splay_tree_insert (superset_entry->children, 652 (splay_tree_key) subset, 0); 653 } 654} 655 656/* Record that component types of TYPE, if any, are part of that type for 657 aliasing purposes. For record types, we only record component types 658 for fields that are marked addressable. For array types, we always 659 record the component types, so the front end should not call this 660 function if the individual component aren't addressable. */ 661 662void 663record_component_aliases (type) 664 tree type; 665{ 666 HOST_WIDE_INT superset = get_alias_set (type); 667 tree field; 668 669 if (superset == 0) 670 return; 671 672 switch (TREE_CODE (type)) 673 { 674 case ARRAY_TYPE: 675 if (! TYPE_NONALIASED_COMPONENT (type)) 676 record_alias_subset (superset, get_alias_set (TREE_TYPE (type))); 677 break; 678 679 case RECORD_TYPE: 680 case UNION_TYPE: 681 case QUAL_UNION_TYPE: 682 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field)) 683 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field)) 684 record_alias_subset (superset, get_alias_set (TREE_TYPE (field))); 685 break; 686 687 case COMPLEX_TYPE: 688 record_alias_subset (superset, get_alias_set (TREE_TYPE (type))); 689 break; 690 691 default: 692 break; 693 } 694} 695 696/* Allocate an alias set for use in storing and reading from the varargs 697 spill area. */ 698 699HOST_WIDE_INT 700get_varargs_alias_set () 701{ 702 static HOST_WIDE_INT set = -1; 703 704 if (set == -1) 705 set = new_alias_set (); 706 707 return set; 708} 709 710/* Likewise, but used for the fixed portions of the frame, e.g., register 711 save areas. */ 712 713HOST_WIDE_INT 714get_frame_alias_set () 715{ 716 static HOST_WIDE_INT set = -1; 717 718 if (set == -1) 719 set = new_alias_set (); 720 721 return set; 722} 723 724/* Inside SRC, the source of a SET, find a base address. */ 725 726static rtx 727find_base_value (src) 728 rtx src; 729{ 730 unsigned int regno; 731 switch (GET_CODE (src)) 732 { 733 case SYMBOL_REF: 734 case LABEL_REF: 735 return src; 736 737 case REG: 738 regno = REGNO (src); 739 /* At the start of a function, argument registers have known base 740 values which may be lost later. Returning an ADDRESS 741 expression here allows optimization based on argument values 742 even when the argument registers are used for other purposes. */ 743 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments) 744 return new_reg_base_value[regno]; 745 746 /* If a pseudo has a known base value, return it. Do not do this 747 for hard regs since it can result in a circular dependency 748 chain for registers which have values at function entry. 749 750 The test above is not sufficient because the scheduler may move 751 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */ 752 if (regno >= FIRST_PSEUDO_REGISTER 753 && regno < reg_base_value_size 754 && reg_base_value[regno]) 755 return reg_base_value[regno]; 756 757 return src; 758 759 case MEM: 760 /* Check for an argument passed in memory. Only record in the 761 copying-arguments block; it is too hard to track changes 762 otherwise. */ 763 if (copying_arguments 764 && (XEXP (src, 0) == arg_pointer_rtx 765 || (GET_CODE (XEXP (src, 0)) == PLUS 766 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) 767 return gen_rtx_ADDRESS (VOIDmode, src); 768 return 0; 769 770 case CONST: 771 src = XEXP (src, 0); 772 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS) 773 break; 774 775 /* ... fall through ... */ 776 777 case PLUS: 778 case MINUS: 779 { 780 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1); 781 782 /* If either operand is a REG that is a known pointer, then it 783 is the base. */ 784 if (REG_P (src_0) && REG_POINTER (src_0)) 785 return find_base_value (src_0); 786 if (REG_P (src_1) && REG_POINTER (src_1)) 787 return find_base_value (src_1); 788 789 /* If either operand is a REG, then see if we already have 790 a known value for it. */ 791 if (REG_P (src_0)) 792 { 793 temp = find_base_value (src_0); 794 if (temp != 0) 795 src_0 = temp; 796 } 797 798 if (REG_P (src_1)) 799 { 800 temp = find_base_value (src_1); 801 if (temp!= 0) 802 src_1 = temp; 803 } 804 805 /* If either base is named object or a special address 806 (like an argument or stack reference), then use it for the 807 base term. */ 808 if (src_0 != 0 809 && (GET_CODE (src_0) == SYMBOL_REF 810 || GET_CODE (src_0) == LABEL_REF 811 || (GET_CODE (src_0) == ADDRESS 812 && GET_MODE (src_0) != VOIDmode))) 813 return src_0; 814 815 if (src_1 != 0 816 && (GET_CODE (src_1) == SYMBOL_REF 817 || GET_CODE (src_1) == LABEL_REF 818 || (GET_CODE (src_1) == ADDRESS 819 && GET_MODE (src_1) != VOIDmode))) 820 return src_1; 821 822 /* Guess which operand is the base address: 823 If either operand is a symbol, then it is the base. If 824 either operand is a CONST_INT, then the other is the base. */ 825 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0)) 826 return find_base_value (src_0); 827 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1)) 828 return find_base_value (src_1); 829 830 return 0; 831 } 832 833 case LO_SUM: 834 /* The standard form is (lo_sum reg sym) so look only at the 835 second operand. */ 836 return find_base_value (XEXP (src, 1)); 837 838 case AND: 839 /* If the second operand is constant set the base 840 address to the first operand. */ 841 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0) 842 return find_base_value (XEXP (src, 0)); 843 return 0; 844 845 case TRUNCATE: 846 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode)) 847 break; 848 /* Fall through. */ 849 case ZERO_EXTEND: 850 case SIGN_EXTEND: /* used for NT/Alpha pointers */ 851 case HIGH: 852 case PRE_INC: 853 case PRE_DEC: 854 case POST_INC: 855 case POST_DEC: 856 case PRE_MODIFY: 857 case POST_MODIFY: 858 return find_base_value (XEXP (src, 0)); 859 860 default: 861 break; 862 } 863 864 return 0; 865} 866 867/* Called from init_alias_analysis indirectly through note_stores. */ 868 869/* While scanning insns to find base values, reg_seen[N] is nonzero if 870 register N has been set in this function. */ 871static char *reg_seen; 872 873/* Addresses which are known not to alias anything else are identified 874 by a unique integer. */ 875static int unique_id; 876 877static void 878record_set (dest, set, data) 879 rtx dest, set; 880 void *data ATTRIBUTE_UNUSED; 881{ 882 unsigned regno; 883 rtx src; 884 885 if (GET_CODE (dest) != REG) 886 return; 887 888 regno = REGNO (dest); 889 890 if (regno >= reg_base_value_size) 891 abort (); 892 893 if (set) 894 { 895 /* A CLOBBER wipes out any old value but does not prevent a previously 896 unset register from acquiring a base address (i.e. reg_seen is not 897 set). */ 898 if (GET_CODE (set) == CLOBBER) 899 { 900 new_reg_base_value[regno] = 0; 901 return; 902 } 903 src = SET_SRC (set); 904 } 905 else 906 { 907 if (reg_seen[regno]) 908 { 909 new_reg_base_value[regno] = 0; 910 return; 911 } 912 reg_seen[regno] = 1; 913 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode, 914 GEN_INT (unique_id++)); 915 return; 916 } 917 918 /* This is not the first set. If the new value is not related to the 919 old value, forget the base value. Note that the following code is 920 not detected: 921 extern int x, y; int *p = &x; p += (&y-&x); 922 ANSI C does not allow computing the difference of addresses 923 of distinct top level objects. */ 924 if (new_reg_base_value[regno]) 925 switch (GET_CODE (src)) 926 { 927 case LO_SUM: 928 case MINUS: 929 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest) 930 new_reg_base_value[regno] = 0; 931 break; 932 case PLUS: 933 /* If the value we add in the PLUS is also a valid base value, 934 this might be the actual base value, and the original value 935 an index. */ 936 { 937 rtx other = NULL_RTX; 938 939 if (XEXP (src, 0) == dest) 940 other = XEXP (src, 1); 941 else if (XEXP (src, 1) == dest) 942 other = XEXP (src, 0); 943 944 if (! other || find_base_value (other)) 945 new_reg_base_value[regno] = 0; 946 break; 947 } 948 case AND: 949 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT) 950 new_reg_base_value[regno] = 0; 951 break; 952 default: 953 new_reg_base_value[regno] = 0; 954 break; 955 } 956 /* If this is the first set of a register, record the value. */ 957 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno]) 958 && ! reg_seen[regno] && new_reg_base_value[regno] == 0) 959 new_reg_base_value[regno] = find_base_value (src); 960 961 reg_seen[regno] = 1; 962} 963 964/* Called from loop optimization when a new pseudo-register is 965 created. It indicates that REGNO is being set to VAL. f INVARIANT 966 is true then this value also describes an invariant relationship 967 which can be used to deduce that two registers with unknown values 968 are different. */ 969 970void 971record_base_value (regno, val, invariant) 972 unsigned int regno; 973 rtx val; 974 int invariant; 975{ 976 if (regno >= reg_base_value_size) 977 return; 978 979 if (invariant && alias_invariant) 980 alias_invariant[regno] = val; 981 982 if (GET_CODE (val) == REG) 983 { 984 if (REGNO (val) < reg_base_value_size) 985 reg_base_value[regno] = reg_base_value[REGNO (val)]; 986 987 return; 988 } 989 990 reg_base_value[regno] = find_base_value (val); 991} 992 993/* Clear alias info for a register. This is used if an RTL transformation 994 changes the value of a register. This is used in flow by AUTO_INC_DEC 995 optimizations. We don't need to clear reg_base_value, since flow only 996 changes the offset. */ 997 998void 999clear_reg_alias_info (reg) 1000 rtx reg; 1001{ 1002 unsigned int regno = REGNO (reg); 1003 1004 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER) 1005 reg_known_value[regno] = reg; 1006} 1007 1008/* Returns a canonical version of X, from the point of view alias 1009 analysis. (For example, if X is a MEM whose address is a register, 1010 and the register has a known value (say a SYMBOL_REF), then a MEM 1011 whose address is the SYMBOL_REF is returned.) */ 1012 1013rtx 1014canon_rtx (x) 1015 rtx x; 1016{ 1017 /* Recursively look for equivalences. */ 1018 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER 1019 && REGNO (x) < reg_known_value_size) 1020 return reg_known_value[REGNO (x)] == x 1021 ? x : canon_rtx (reg_known_value[REGNO (x)]); 1022 else if (GET_CODE (x) == PLUS) 1023 { 1024 rtx x0 = canon_rtx (XEXP (x, 0)); 1025 rtx x1 = canon_rtx (XEXP (x, 1)); 1026 1027 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1)) 1028 { 1029 if (GET_CODE (x0) == CONST_INT) 1030 return plus_constant (x1, INTVAL (x0)); 1031 else if (GET_CODE (x1) == CONST_INT) 1032 return plus_constant (x0, INTVAL (x1)); 1033 return gen_rtx_PLUS (GET_MODE (x), x0, x1); 1034 } 1035 } 1036 1037 /* This gives us much better alias analysis when called from 1038 the loop optimizer. Note we want to leave the original 1039 MEM alone, but need to return the canonicalized MEM with 1040 all the flags with their original values. */ 1041 else if (GET_CODE (x) == MEM) 1042 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0))); 1043 1044 return x; 1045} 1046 1047/* Return 1 if X and Y are identical-looking rtx's. 1048 1049 We use the data in reg_known_value above to see if two registers with 1050 different numbers are, in fact, equivalent. */ 1051 1052static int 1053rtx_equal_for_memref_p (x, y) 1054 rtx x, y; 1055{ 1056 int i; 1057 int j; 1058 enum rtx_code code; 1059 const char *fmt; 1060 1061 if (x == 0 && y == 0) 1062 return 1; 1063 if (x == 0 || y == 0) 1064 return 0; 1065 1066 x = canon_rtx (x); 1067 y = canon_rtx (y); 1068 1069 if (x == y) 1070 return 1; 1071 1072 code = GET_CODE (x); 1073 /* Rtx's of different codes cannot be equal. */ 1074 if (code != GET_CODE (y)) 1075 return 0; 1076 1077 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. 1078 (REG:SI x) and (REG:HI x) are NOT equivalent. */ 1079 1080 if (GET_MODE (x) != GET_MODE (y)) 1081 return 0; 1082 1083 /* Some RTL can be compared without a recursive examination. */ 1084 switch (code) 1085 { 1086 case VALUE: 1087 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y); 1088 1089 case REG: 1090 return REGNO (x) == REGNO (y); 1091 1092 case LABEL_REF: 1093 return XEXP (x, 0) == XEXP (y, 0); 1094 1095 case SYMBOL_REF: 1096 return XSTR (x, 0) == XSTR (y, 0); 1097 1098 case CONST_INT: 1099 case CONST_DOUBLE: 1100 /* There's no need to compare the contents of CONST_DOUBLEs or 1101 CONST_INTs because pointer equality is a good enough 1102 comparison for these nodes. */ 1103 return 0; 1104 1105 case ADDRESSOF: 1106 return (XINT (x, 1) == XINT (y, 1) 1107 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))); 1108 1109 default: 1110 break; 1111 } 1112 1113 /* For commutative operations, the RTX match if the operand match in any 1114 order. Also handle the simple binary and unary cases without a loop. */ 1115 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c') 1116 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) 1117 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))) 1118 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1)) 1119 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0)))); 1120 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2') 1121 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) 1122 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))); 1123 else if (GET_RTX_CLASS (code) == '1') 1124 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)); 1125 1126 /* Compare the elements. If any pair of corresponding elements 1127 fail to match, return 0 for the whole things. 1128 1129 Limit cases to types which actually appear in addresses. */ 1130 1131 fmt = GET_RTX_FORMAT (code); 1132 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) 1133 { 1134 switch (fmt[i]) 1135 { 1136 case 'i': 1137 if (XINT (x, i) != XINT (y, i)) 1138 return 0; 1139 break; 1140 1141 case 'E': 1142 /* Two vectors must have the same length. */ 1143 if (XVECLEN (x, i) != XVECLEN (y, i)) 1144 return 0; 1145 1146 /* And the corresponding elements must match. */ 1147 for (j = 0; j < XVECLEN (x, i); j++) 1148 if (rtx_equal_for_memref_p (XVECEXP (x, i, j), 1149 XVECEXP (y, i, j)) == 0) 1150 return 0; 1151 break; 1152 1153 case 'e': 1154 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0) 1155 return 0; 1156 break; 1157 1158 /* This can happen for asm operands. */ 1159 case 's': 1160 if (strcmp (XSTR (x, i), XSTR (y, i))) 1161 return 0; 1162 break; 1163 1164 /* This can happen for an asm which clobbers memory. */ 1165 case '0': 1166 break; 1167 1168 /* It is believed that rtx's at this level will never 1169 contain anything but integers and other rtx's, 1170 except for within LABEL_REFs and SYMBOL_REFs. */ 1171 default: 1172 abort (); 1173 } 1174 } 1175 return 1; 1176} 1177 1178/* Given an rtx X, find a SYMBOL_REF or LABEL_REF within 1179 X and return it, or return 0 if none found. */ 1180 1181static rtx 1182find_symbolic_term (x) 1183 rtx x; 1184{ 1185 int i; 1186 enum rtx_code code; 1187 const char *fmt; 1188 1189 code = GET_CODE (x); 1190 if (code == SYMBOL_REF || code == LABEL_REF) 1191 return x; 1192 if (GET_RTX_CLASS (code) == 'o') 1193 return 0; 1194 1195 fmt = GET_RTX_FORMAT (code); 1196 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) 1197 { 1198 rtx t; 1199 1200 if (fmt[i] == 'e') 1201 { 1202 t = find_symbolic_term (XEXP (x, i)); 1203 if (t != 0) 1204 return t; 1205 } 1206 else if (fmt[i] == 'E') 1207 break; 1208 } 1209 return 0; 1210} 1211 1212static rtx 1213find_base_term (x) 1214 rtx x; 1215{ 1216 cselib_val *val; 1217 struct elt_loc_list *l; 1218 1219#if defined (FIND_BASE_TERM) 1220 /* Try machine-dependent ways to find the base term. */ 1221 x = FIND_BASE_TERM (x); 1222#endif 1223 1224 switch (GET_CODE (x)) 1225 { 1226 case REG: 1227 return REG_BASE_VALUE (x); 1228 1229 case TRUNCATE: 1230 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode)) 1231 return 0; 1232 /* Fall through. */ 1233 case ZERO_EXTEND: 1234 case SIGN_EXTEND: /* Used for Alpha/NT pointers */ 1235 case HIGH: 1236 case PRE_INC: 1237 case PRE_DEC: 1238 case POST_INC: 1239 case POST_DEC: 1240 case PRE_MODIFY: 1241 case POST_MODIFY: 1242 return find_base_term (XEXP (x, 0)); 1243 1244 case VALUE: 1245 val = CSELIB_VAL_PTR (x); 1246 for (l = val->locs; l; l = l->next) 1247 if ((x = find_base_term (l->loc)) != 0) 1248 return x; 1249 return 0; 1250 1251 case CONST: 1252 x = XEXP (x, 0); 1253 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS) 1254 return 0; 1255 /* fall through */ 1256 case LO_SUM: 1257 case PLUS: 1258 case MINUS: 1259 { 1260 rtx tmp1 = XEXP (x, 0); 1261 rtx tmp2 = XEXP (x, 1); 1262 1263 /* This is a little bit tricky since we have to determine which of 1264 the two operands represents the real base address. Otherwise this 1265 routine may return the index register instead of the base register. 1266 1267 That may cause us to believe no aliasing was possible, when in 1268 fact aliasing is possible. 1269 1270 We use a few simple tests to guess the base register. Additional 1271 tests can certainly be added. For example, if one of the operands 1272 is a shift or multiply, then it must be the index register and the 1273 other operand is the base register. */ 1274 1275 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2)) 1276 return find_base_term (tmp2); 1277 1278 /* If either operand is known to be a pointer, then use it 1279 to determine the base term. */ 1280 if (REG_P (tmp1) && REG_POINTER (tmp1)) 1281 return find_base_term (tmp1); 1282 1283 if (REG_P (tmp2) && REG_POINTER (tmp2)) 1284 return find_base_term (tmp2); 1285 1286 /* Neither operand was known to be a pointer. Go ahead and find the 1287 base term for both operands. */ 1288 tmp1 = find_base_term (tmp1); 1289 tmp2 = find_base_term (tmp2); 1290 1291 /* If either base term is named object or a special address 1292 (like an argument or stack reference), then use it for the 1293 base term. */ 1294 if (tmp1 != 0 1295 && (GET_CODE (tmp1) == SYMBOL_REF 1296 || GET_CODE (tmp1) == LABEL_REF 1297 || (GET_CODE (tmp1) == ADDRESS 1298 && GET_MODE (tmp1) != VOIDmode))) 1299 return tmp1; 1300 1301 if (tmp2 != 0 1302 && (GET_CODE (tmp2) == SYMBOL_REF 1303 || GET_CODE (tmp2) == LABEL_REF 1304 || (GET_CODE (tmp2) == ADDRESS 1305 && GET_MODE (tmp2) != VOIDmode))) 1306 return tmp2; 1307 1308 /* We could not determine which of the two operands was the 1309 base register and which was the index. So we can determine 1310 nothing from the base alias check. */ 1311 return 0; 1312 } 1313 1314 case AND: 1315 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0) 1316 return find_base_term (XEXP (x, 0)); 1317 return 0; 1318 1319 case SYMBOL_REF: 1320 case LABEL_REF: 1321 return x; 1322 1323 case ADDRESSOF: 1324 return REG_BASE_VALUE (frame_pointer_rtx); 1325 1326 default: 1327 return 0; 1328 } 1329} 1330 1331/* Return 0 if the addresses X and Y are known to point to different 1332 objects, 1 if they might be pointers to the same object. */ 1333 1334static int 1335base_alias_check (x, y, x_mode, y_mode) 1336 rtx x, y; 1337 enum machine_mode x_mode, y_mode; 1338{ 1339 rtx x_base = find_base_term (x); 1340 rtx y_base = find_base_term (y); 1341 1342 /* If the address itself has no known base see if a known equivalent 1343 value has one. If either address still has no known base, nothing 1344 is known about aliasing. */ 1345 if (x_base == 0) 1346 { 1347 rtx x_c; 1348 1349 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x) 1350 return 1; 1351 1352 x_base = find_base_term (x_c); 1353 if (x_base == 0) 1354 return 1; 1355 } 1356 1357 if (y_base == 0) 1358 { 1359 rtx y_c; 1360 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y) 1361 return 1; 1362 1363 y_base = find_base_term (y_c); 1364 if (y_base == 0) 1365 return 1; 1366 } 1367 1368 /* If the base addresses are equal nothing is known about aliasing. */ 1369 if (rtx_equal_p (x_base, y_base)) 1370 return 1; 1371 1372 /* The base addresses of the read and write are different expressions. 1373 If they are both symbols and they are not accessed via AND, there is 1374 no conflict. We can bring knowledge of object alignment into play 1375 here. For example, on alpha, "char a, b;" can alias one another, 1376 though "char a; long b;" cannot. */ 1377 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) 1378 { 1379 if (GET_CODE (x) == AND && GET_CODE (y) == AND) 1380 return 1; 1381 if (GET_CODE (x) == AND 1382 && (GET_CODE (XEXP (x, 1)) != CONST_INT 1383 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1)))) 1384 return 1; 1385 if (GET_CODE (y) == AND 1386 && (GET_CODE (XEXP (y, 1)) != CONST_INT 1387 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1)))) 1388 return 1; 1389 /* Differing symbols never alias. */ 1390 return 0; 1391 } 1392 1393 /* If one address is a stack reference there can be no alias: 1394 stack references using different base registers do not alias, 1395 a stack reference can not alias a parameter, and a stack reference 1396 can not alias a global. */ 1397 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode) 1398 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode)) 1399 return 0; 1400 1401 if (! flag_argument_noalias) 1402 return 1; 1403 1404 if (flag_argument_noalias > 1) 1405 return 0; 1406 1407 /* Weak noalias assertion (arguments are distinct, but may match globals). */ 1408 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode); 1409} 1410 1411/* Convert the address X into something we can use. This is done by returning 1412 it unchanged unless it is a value; in the latter case we call cselib to get 1413 a more useful rtx. */ 1414 1415rtx 1416get_addr (x) 1417 rtx x; 1418{ 1419 cselib_val *v; 1420 struct elt_loc_list *l; 1421 1422 if (GET_CODE (x) != VALUE) 1423 return x; 1424 v = CSELIB_VAL_PTR (x); 1425 for (l = v->locs; l; l = l->next) 1426 if (CONSTANT_P (l->loc)) 1427 return l->loc; 1428 for (l = v->locs; l; l = l->next) 1429 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM) 1430 return l->loc; 1431 if (v->locs) 1432 return v->locs->loc; 1433 return x; 1434} 1435 1436/* Return the address of the (N_REFS + 1)th memory reference to ADDR 1437 where SIZE is the size in bytes of the memory reference. If ADDR 1438 is not modified by the memory reference then ADDR is returned. */ 1439 1440rtx 1441addr_side_effect_eval (addr, size, n_refs) 1442 rtx addr; 1443 int size; 1444 int n_refs; 1445{ 1446 int offset = 0; 1447 1448 switch (GET_CODE (addr)) 1449 { 1450 case PRE_INC: 1451 offset = (n_refs + 1) * size; 1452 break; 1453 case PRE_DEC: 1454 offset = -(n_refs + 1) * size; 1455 break; 1456 case POST_INC: 1457 offset = n_refs * size; 1458 break; 1459 case POST_DEC: 1460 offset = -n_refs * size; 1461 break; 1462 1463 default: 1464 return addr; 1465 } 1466 1467 if (offset) 1468 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset)); 1469 else 1470 addr = XEXP (addr, 0); 1471 1472 return addr; 1473} 1474 1475/* Return nonzero if X and Y (memory addresses) could reference the 1476 same location in memory. C is an offset accumulator. When 1477 C is nonzero, we are testing aliases between X and Y + C. 1478 XSIZE is the size in bytes of the X reference, 1479 similarly YSIZE is the size in bytes for Y. 1480 1481 If XSIZE or YSIZE is zero, we do not know the amount of memory being 1482 referenced (the reference was BLKmode), so make the most pessimistic 1483 assumptions. 1484 1485 If XSIZE or YSIZE is negative, we may access memory outside the object 1486 being referenced as a side effect. This can happen when using AND to 1487 align memory references, as is done on the Alpha. 1488 1489 Nice to notice that varying addresses cannot conflict with fp if no 1490 local variables had their addresses taken, but that's too hard now. */ 1491 1492static int 1493memrefs_conflict_p (xsize, x, ysize, y, c) 1494 rtx x, y; 1495 int xsize, ysize; 1496 HOST_WIDE_INT c; 1497{ 1498 if (GET_CODE (x) == VALUE) 1499 x = get_addr (x); 1500 if (GET_CODE (y) == VALUE) 1501 y = get_addr (y); 1502 if (GET_CODE (x) == HIGH) 1503 x = XEXP (x, 0); 1504 else if (GET_CODE (x) == LO_SUM) 1505 x = XEXP (x, 1); 1506 else 1507 x = canon_rtx (addr_side_effect_eval (x, xsize, 0)); 1508 if (GET_CODE (y) == HIGH) 1509 y = XEXP (y, 0); 1510 else if (GET_CODE (y) == LO_SUM) 1511 y = XEXP (y, 1); 1512 else 1513 y = canon_rtx (addr_side_effect_eval (y, ysize, 0)); 1514 1515 if (rtx_equal_for_memref_p (x, y)) 1516 { 1517 if (xsize <= 0 || ysize <= 0) 1518 return 1; 1519 if (c >= 0 && xsize > c) 1520 return 1; 1521 if (c < 0 && ysize+c > 0) 1522 return 1; 1523 return 0; 1524 } 1525 1526 /* This code used to check for conflicts involving stack references and 1527 globals but the base address alias code now handles these cases. */ 1528 1529 if (GET_CODE (x) == PLUS) 1530 { 1531 /* The fact that X is canonicalized means that this 1532 PLUS rtx is canonicalized. */ 1533 rtx x0 = XEXP (x, 0); 1534 rtx x1 = XEXP (x, 1); 1535 1536 if (GET_CODE (y) == PLUS) 1537 { 1538 /* The fact that Y is canonicalized means that this 1539 PLUS rtx is canonicalized. */ 1540 rtx y0 = XEXP (y, 0); 1541 rtx y1 = XEXP (y, 1); 1542 1543 if (rtx_equal_for_memref_p (x1, y1)) 1544 return memrefs_conflict_p (xsize, x0, ysize, y0, c); 1545 if (rtx_equal_for_memref_p (x0, y0)) 1546 return memrefs_conflict_p (xsize, x1, ysize, y1, c); 1547 if (GET_CODE (x1) == CONST_INT) 1548 { 1549 if (GET_CODE (y1) == CONST_INT) 1550 return memrefs_conflict_p (xsize, x0, ysize, y0, 1551 c - INTVAL (x1) + INTVAL (y1)); 1552 else 1553 return memrefs_conflict_p (xsize, x0, ysize, y, 1554 c - INTVAL (x1)); 1555 } 1556 else if (GET_CODE (y1) == CONST_INT) 1557 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); 1558 1559 return 1; 1560 } 1561 else if (GET_CODE (x1) == CONST_INT) 1562 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1)); 1563 } 1564 else if (GET_CODE (y) == PLUS) 1565 { 1566 /* The fact that Y is canonicalized means that this 1567 PLUS rtx is canonicalized. */ 1568 rtx y0 = XEXP (y, 0); 1569 rtx y1 = XEXP (y, 1); 1570 1571 if (GET_CODE (y1) == CONST_INT) 1572 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1)); 1573 else 1574 return 1; 1575 } 1576 1577 if (GET_CODE (x) == GET_CODE (y)) 1578 switch (GET_CODE (x)) 1579 { 1580 case MULT: 1581 { 1582 /* Handle cases where we expect the second operands to be the 1583 same, and check only whether the first operand would conflict 1584 or not. */ 1585 rtx x0, y0; 1586 rtx x1 = canon_rtx (XEXP (x, 1)); 1587 rtx y1 = canon_rtx (XEXP (y, 1)); 1588 if (! rtx_equal_for_memref_p (x1, y1)) 1589 return 1; 1590 x0 = canon_rtx (XEXP (x, 0)); 1591 y0 = canon_rtx (XEXP (y, 0)); 1592 if (rtx_equal_for_memref_p (x0, y0)) 1593 return (xsize == 0 || ysize == 0 1594 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); 1595 1596 /* Can't properly adjust our sizes. */ 1597 if (GET_CODE (x1) != CONST_INT) 1598 return 1; 1599 xsize /= INTVAL (x1); 1600 ysize /= INTVAL (x1); 1601 c /= INTVAL (x1); 1602 return memrefs_conflict_p (xsize, x0, ysize, y0, c); 1603 } 1604 1605 case REG: 1606 /* Are these registers known not to be equal? */ 1607 if (alias_invariant) 1608 { 1609 unsigned int r_x = REGNO (x), r_y = REGNO (y); 1610 rtx i_x, i_y; /* invariant relationships of X and Y */ 1611 1612 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x]; 1613 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y]; 1614 1615 if (i_x == 0 && i_y == 0) 1616 break; 1617 1618 if (! memrefs_conflict_p (xsize, i_x ? i_x : x, 1619 ysize, i_y ? i_y : y, c)) 1620 return 0; 1621 } 1622 break; 1623 1624 default: 1625 break; 1626 } 1627 1628 /* Treat an access through an AND (e.g. a subword access on an Alpha) 1629 as an access with indeterminate size. Assume that references 1630 besides AND are aligned, so if the size of the other reference is 1631 at least as large as the alignment, assume no other overlap. */ 1632 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT) 1633 { 1634 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1))) 1635 xsize = -1; 1636 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c); 1637 } 1638 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT) 1639 { 1640 /* ??? If we are indexing far enough into the array/structure, we 1641 may yet be able to determine that we can not overlap. But we 1642 also need to that we are far enough from the end not to overlap 1643 a following reference, so we do nothing with that for now. */ 1644 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1))) 1645 ysize = -1; 1646 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c); 1647 } 1648 1649 if (GET_CODE (x) == ADDRESSOF) 1650 { 1651 if (y == frame_pointer_rtx 1652 || GET_CODE (y) == ADDRESSOF) 1653 return xsize <= 0 || ysize <= 0; 1654 } 1655 if (GET_CODE (y) == ADDRESSOF) 1656 { 1657 if (x == frame_pointer_rtx) 1658 return xsize <= 0 || ysize <= 0; 1659 } 1660 1661 if (CONSTANT_P (x)) 1662 { 1663 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT) 1664 { 1665 c += (INTVAL (y) - INTVAL (x)); 1666 return (xsize <= 0 || ysize <= 0 1667 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)); 1668 } 1669 1670 if (GET_CODE (x) == CONST) 1671 { 1672 if (GET_CODE (y) == CONST) 1673 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), 1674 ysize, canon_rtx (XEXP (y, 0)), c); 1675 else 1676 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), 1677 ysize, y, c); 1678 } 1679 if (GET_CODE (y) == CONST) 1680 return memrefs_conflict_p (xsize, x, ysize, 1681 canon_rtx (XEXP (y, 0)), c); 1682 1683 if (CONSTANT_P (y)) 1684 return (xsize <= 0 || ysize <= 0 1685 || (rtx_equal_for_memref_p (x, y) 1686 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0)))); 1687 1688 return 1; 1689 } 1690 return 1; 1691} 1692 1693/* Functions to compute memory dependencies. 1694 1695 Since we process the insns in execution order, we can build tables 1696 to keep track of what registers are fixed (and not aliased), what registers 1697 are varying in known ways, and what registers are varying in unknown 1698 ways. 1699 1700 If both memory references are volatile, then there must always be a 1701 dependence between the two references, since their order can not be 1702 changed. A volatile and non-volatile reference can be interchanged 1703 though. 1704 1705 A MEM_IN_STRUCT reference at a non-AND varying address can never 1706 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We 1707 also must allow AND addresses, because they may generate accesses 1708 outside the object being referenced. This is used to generate 1709 aligned addresses from unaligned addresses, for instance, the alpha 1710 storeqi_unaligned pattern. */ 1711 1712/* Read dependence: X is read after read in MEM takes place. There can 1713 only be a dependence here if both reads are volatile. */ 1714 1715int 1716read_dependence (mem, x) 1717 rtx mem; 1718 rtx x; 1719{ 1720 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem); 1721} 1722 1723/* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and 1724 MEM2 is a reference to a structure at a varying address, or returns 1725 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL 1726 value is returned MEM1 and MEM2 can never alias. VARIES_P is used 1727 to decide whether or not an address may vary; it should return 1728 nonzero whenever variation is possible. 1729 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */ 1730 1731static rtx 1732fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p) 1733 rtx mem1, mem2; 1734 rtx mem1_addr, mem2_addr; 1735 int (*varies_p) PARAMS ((rtx, int)); 1736{ 1737 if (! flag_strict_aliasing) 1738 return NULL_RTX; 1739 1740 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2) 1741 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1)) 1742 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a 1743 varying address. */ 1744 return mem1; 1745 1746 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2) 1747 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1)) 1748 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a 1749 varying address. */ 1750 return mem2; 1751 1752 return NULL_RTX; 1753} 1754 1755/* Returns nonzero if something about the mode or address format MEM1 1756 indicates that it might well alias *anything*. */ 1757 1758static int 1759aliases_everything_p (mem) 1760 rtx mem; 1761{ 1762 if (GET_CODE (XEXP (mem, 0)) == AND) 1763 /* If the address is an AND, its very hard to know at what it is 1764 actually pointing. */ 1765 return 1; 1766 1767 return 0; 1768} 1769 1770/* Return true if we can determine that the fields referenced cannot 1771 overlap for any pair of objects. */ 1772 1773static bool 1774nonoverlapping_component_refs_p (x, y) 1775 tree x, y; 1776{ 1777 tree fieldx, fieldy, typex, typey, orig_y; 1778 1779 do 1780 { 1781 /* The comparison has to be done at a common type, since we don't 1782 know how the inheritance hierarchy works. */ 1783 orig_y = y; 1784 do 1785 { 1786 fieldx = TREE_OPERAND (x, 1); 1787 typex = DECL_FIELD_CONTEXT (fieldx); 1788 1789 y = orig_y; 1790 do 1791 { 1792 fieldy = TREE_OPERAND (y, 1); 1793 typey = DECL_FIELD_CONTEXT (fieldy); 1794 1795 if (typex == typey) 1796 goto found; 1797 1798 y = TREE_OPERAND (y, 0); 1799 } 1800 while (y && TREE_CODE (y) == COMPONENT_REF); 1801 1802 x = TREE_OPERAND (x, 0); 1803 } 1804 while (x && TREE_CODE (x) == COMPONENT_REF); 1805 1806 /* Never found a common type. */ 1807 return false; 1808 1809 found: 1810 /* If we're left with accessing different fields of a structure, 1811 then no overlap. */ 1812 if (TREE_CODE (typex) == RECORD_TYPE 1813 && fieldx != fieldy) 1814 return true; 1815 1816 /* The comparison on the current field failed. If we're accessing 1817 a very nested structure, look at the next outer level. */ 1818 x = TREE_OPERAND (x, 0); 1819 y = TREE_OPERAND (y, 0); 1820 } 1821 while (x && y 1822 && TREE_CODE (x) == COMPONENT_REF 1823 && TREE_CODE (y) == COMPONENT_REF); 1824 1825 return false; 1826} 1827 1828/* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */ 1829 1830static tree 1831decl_for_component_ref (x) 1832 tree x; 1833{ 1834 do 1835 { 1836 x = TREE_OPERAND (x, 0); 1837 } 1838 while (x && TREE_CODE (x) == COMPONENT_REF); 1839 1840 return x && DECL_P (x) ? x : NULL_TREE; 1841} 1842 1843/* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the 1844 offset of the field reference. */ 1845 1846static rtx 1847adjust_offset_for_component_ref (x, offset) 1848 tree x; 1849 rtx offset; 1850{ 1851 HOST_WIDE_INT ioffset; 1852 1853 if (! offset) 1854 return NULL_RTX; 1855 1856 ioffset = INTVAL (offset); 1857 do 1858 { 1859 tree field = TREE_OPERAND (x, 1); 1860 1861 if (! host_integerp (DECL_FIELD_OFFSET (field), 1)) 1862 return NULL_RTX; 1863 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1) 1864 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1) 1865 / BITS_PER_UNIT)); 1866 1867 x = TREE_OPERAND (x, 0); 1868 } 1869 while (x && TREE_CODE (x) == COMPONENT_REF); 1870 1871 return GEN_INT (ioffset); 1872} 1873 1874/* Return nonzero if we can deterimine the exprs corresponding to memrefs 1875 X and Y and they do not overlap. */ 1876 1877static int 1878nonoverlapping_memrefs_p (x, y) 1879 rtx x, y; 1880{ 1881 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y); 1882 rtx rtlx, rtly; 1883 rtx basex, basey; 1884 rtx moffsetx, moffsety; 1885 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem; 1886 1887 /* Unless both have exprs, we can't tell anything. */ 1888 if (exprx == 0 || expry == 0) 1889 return 0; 1890 1891 /* If both are field references, we may be able to determine something. */ 1892 if (TREE_CODE (exprx) == COMPONENT_REF 1893 && TREE_CODE (expry) == COMPONENT_REF 1894 && nonoverlapping_component_refs_p (exprx, expry)) 1895 return 1; 1896 1897 /* If the field reference test failed, look at the DECLs involved. */ 1898 moffsetx = MEM_OFFSET (x); 1899 if (TREE_CODE (exprx) == COMPONENT_REF) 1900 { 1901 tree t = decl_for_component_ref (exprx); 1902 if (! t) 1903 return 0; 1904 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx); 1905 exprx = t; 1906 } 1907 moffsety = MEM_OFFSET (y); 1908 if (TREE_CODE (expry) == COMPONENT_REF) 1909 { 1910 tree t = decl_for_component_ref (expry); 1911 if (! t) 1912 return 0; 1913 moffsety = adjust_offset_for_component_ref (expry, moffsety); 1914 expry = t; 1915 } 1916 1917 if (! DECL_P (exprx) || ! DECL_P (expry)) 1918 return 0; 1919 1920 rtlx = DECL_RTL (exprx); 1921 rtly = DECL_RTL (expry); 1922 1923 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they 1924 can't overlap unless they are the same because we never reuse that part 1925 of the stack frame used for locals for spilled pseudos. */ 1926 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM) 1927 && ! rtx_equal_p (rtlx, rtly)) 1928 return 1; 1929 1930 /* Get the base and offsets of both decls. If either is a register, we 1931 know both are and are the same, so use that as the base. The only 1932 we can avoid overlap is if we can deduce that they are nonoverlapping 1933 pieces of that decl, which is very rare. */ 1934 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx; 1935 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT) 1936 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0); 1937 1938 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly; 1939 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT) 1940 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0); 1941 1942 /* If the bases are different, we know they do not overlap if both 1943 are constants or if one is a constant and the other a pointer into the 1944 stack frame. Otherwise a different base means we can't tell if they 1945 overlap or not. */ 1946 if (! rtx_equal_p (basex, basey)) 1947 return ((CONSTANT_P (basex) && CONSTANT_P (basey)) 1948 || (CONSTANT_P (basex) && REG_P (basey) 1949 && REGNO_PTR_FRAME_P (REGNO (basey))) 1950 || (CONSTANT_P (basey) && REG_P (basex) 1951 && REGNO_PTR_FRAME_P (REGNO (basex)))); 1952 1953 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx)) 1954 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx)) 1955 : -1); 1956 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly)) 1957 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) : 1958 -1); 1959 1960 /* If we have an offset for either memref, it can update the values computed 1961 above. */ 1962 if (moffsetx) 1963 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx); 1964 if (moffsety) 1965 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety); 1966 1967 /* If a memref has both a size and an offset, we can use the smaller size. 1968 We can't do this if the offset isn't known because we must view this 1969 memref as being anywhere inside the DECL's MEM. */ 1970 if (MEM_SIZE (x) && moffsetx) 1971 sizex = INTVAL (MEM_SIZE (x)); 1972 if (MEM_SIZE (y) && moffsety) 1973 sizey = INTVAL (MEM_SIZE (y)); 1974 1975 /* Put the values of the memref with the lower offset in X's values. */ 1976 if (offsetx > offsety) 1977 { 1978 tem = offsetx, offsetx = offsety, offsety = tem; 1979 tem = sizex, sizex = sizey, sizey = tem; 1980 } 1981 1982 /* If we don't know the size of the lower-offset value, we can't tell 1983 if they conflict. Otherwise, we do the test. */ 1984 return sizex >= 0 && offsety > offsetx + sizex; 1985} 1986 1987/* True dependence: X is read after store in MEM takes place. */ 1988 1989int 1990true_dependence (mem, mem_mode, x, varies) 1991 rtx mem; 1992 enum machine_mode mem_mode; 1993 rtx x; 1994 int (*varies) PARAMS ((rtx, int)); 1995{ 1996 rtx x_addr, mem_addr; 1997 rtx base; 1998 1999 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 2000 return 1; 2001 2002 if (DIFFERENT_ALIAS_SETS_P (x, mem)) 2003 return 0; 2004 2005 /* Unchanging memory can't conflict with non-unchanging memory. 2006 A non-unchanging read can conflict with a non-unchanging write. 2007 An unchanging read can conflict with an unchanging write since 2008 there may be a single store to this address to initialize it. 2009 Note that an unchanging store can conflict with a non-unchanging read 2010 since we have to make conservative assumptions when we have a 2011 record with readonly fields and we are copying the whole thing. 2012 Just fall through to the code below to resolve potential conflicts. 2013 This won't handle all cases optimally, but the possible performance 2014 loss should be negligible. */ 2015 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem)) 2016 return 0; 2017 2018 if (nonoverlapping_memrefs_p (mem, x)) 2019 return 0; 2020 2021 if (mem_mode == VOIDmode) 2022 mem_mode = GET_MODE (mem); 2023 2024 x_addr = get_addr (XEXP (x, 0)); 2025 mem_addr = get_addr (XEXP (mem, 0)); 2026 2027 base = find_base_term (x_addr); 2028 if (base && (GET_CODE (base) == LABEL_REF 2029 || (GET_CODE (base) == SYMBOL_REF 2030 && CONSTANT_POOL_ADDRESS_P (base)))) 2031 return 0; 2032 2033 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode)) 2034 return 0; 2035 2036 x_addr = canon_rtx (x_addr); 2037 mem_addr = canon_rtx (mem_addr); 2038 2039 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, 2040 SIZE_FOR_MODE (x), x_addr, 0)) 2041 return 0; 2042 2043 if (aliases_everything_p (x)) 2044 return 1; 2045 2046 /* We cannot use aliases_everything_p to test MEM, since we must look 2047 at MEM_MODE, rather than GET_MODE (MEM). */ 2048 if (mem_mode == QImode || GET_CODE (mem_addr) == AND) 2049 return 1; 2050 2051 /* In true_dependence we also allow BLKmode to alias anything. Why 2052 don't we do this in anti_dependence and output_dependence? */ 2053 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode) 2054 return 1; 2055 2056 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, 2057 varies); 2058} 2059 2060/* Canonical true dependence: X is read after store in MEM takes place. 2061 Variant of true_dependence which assumes MEM has already been 2062 canonicalized (hence we no longer do that here). 2063 The mem_addr argument has been added, since true_dependence computed 2064 this value prior to canonicalizing. */ 2065 2066int 2067canon_true_dependence (mem, mem_mode, mem_addr, x, varies) 2068 rtx mem, mem_addr, x; 2069 enum machine_mode mem_mode; 2070 int (*varies) PARAMS ((rtx, int)); 2071{ 2072 rtx x_addr; 2073 2074 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 2075 return 1; 2076 2077 if (DIFFERENT_ALIAS_SETS_P (x, mem)) 2078 return 0; 2079 2080 /* If X is an unchanging read, then it can't possibly conflict with any 2081 non-unchanging store. It may conflict with an unchanging write though, 2082 because there may be a single store to this address to initialize it. 2083 Just fall through to the code below to resolve the case where we have 2084 both an unchanging read and an unchanging write. This won't handle all 2085 cases optimally, but the possible performance loss should be 2086 negligible. */ 2087 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem)) 2088 return 0; 2089 2090 if (nonoverlapping_memrefs_p (x, mem)) 2091 return 0; 2092 2093 x_addr = get_addr (XEXP (x, 0)); 2094 2095 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode)) 2096 return 0; 2097 2098 x_addr = canon_rtx (x_addr); 2099 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, 2100 SIZE_FOR_MODE (x), x_addr, 0)) 2101 return 0; 2102 2103 if (aliases_everything_p (x)) 2104 return 1; 2105 2106 /* We cannot use aliases_everything_p to test MEM, since we must look 2107 at MEM_MODE, rather than GET_MODE (MEM). */ 2108 if (mem_mode == QImode || GET_CODE (mem_addr) == AND) 2109 return 1; 2110 2111 /* In true_dependence we also allow BLKmode to alias anything. Why 2112 don't we do this in anti_dependence and output_dependence? */ 2113 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode) 2114 return 1; 2115 2116 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, 2117 varies); 2118} 2119 2120/* Returns non-zero if a write to X might alias a previous read from 2121 (or, if WRITEP is non-zero, a write to) MEM. */ 2122 2123static int 2124write_dependence_p (mem, x, writep) 2125 rtx mem; 2126 rtx x; 2127 int writep; 2128{ 2129 rtx x_addr, mem_addr; 2130 rtx fixed_scalar; 2131 rtx base; 2132 2133 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 2134 return 1; 2135 2136 if (DIFFERENT_ALIAS_SETS_P (x, mem)) 2137 return 0; 2138 2139 /* Unchanging memory can't conflict with non-unchanging memory. */ 2140 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem)) 2141 return 0; 2142 2143 /* If MEM is an unchanging read, then it can't possibly conflict with 2144 the store to X, because there is at most one store to MEM, and it must 2145 have occurred somewhere before MEM. */ 2146 if (! writep && RTX_UNCHANGING_P (mem)) 2147 return 0; 2148 2149 if (nonoverlapping_memrefs_p (x, mem)) 2150 return 0; 2151 2152 x_addr = get_addr (XEXP (x, 0)); 2153 mem_addr = get_addr (XEXP (mem, 0)); 2154 2155 if (! writep) 2156 { 2157 base = find_base_term (mem_addr); 2158 if (base && (GET_CODE (base) == LABEL_REF 2159 || (GET_CODE (base) == SYMBOL_REF 2160 && CONSTANT_POOL_ADDRESS_P (base)))) 2161 return 0; 2162 } 2163 2164 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), 2165 GET_MODE (mem))) 2166 return 0; 2167 2168 x_addr = canon_rtx (x_addr); 2169 mem_addr = canon_rtx (mem_addr); 2170 2171 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr, 2172 SIZE_FOR_MODE (x), x_addr, 0)) 2173 return 0; 2174 2175 fixed_scalar 2176 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, 2177 rtx_addr_varies_p); 2178 2179 return (!(fixed_scalar == mem && !aliases_everything_p (x)) 2180 && !(fixed_scalar == x && !aliases_everything_p (mem))); 2181} 2182 2183/* Anti dependence: X is written after read in MEM takes place. */ 2184 2185int 2186anti_dependence (mem, x) 2187 rtx mem; 2188 rtx x; 2189{ 2190 return write_dependence_p (mem, x, /*writep=*/0); 2191} 2192 2193/* Output dependence: X is written after store in MEM takes place. */ 2194 2195int 2196output_dependence (mem, x) 2197 rtx mem; 2198 rtx x; 2199{ 2200 return write_dependence_p (mem, x, /*writep=*/1); 2201} 2202 2203/* Returns non-zero if X mentions something which is not 2204 local to the function and is not constant. */ 2205 2206static int 2207nonlocal_mentioned_p (x) 2208 rtx x; 2209{ 2210 rtx base; 2211 RTX_CODE code; 2212 int regno; 2213 2214 code = GET_CODE (x); 2215 2216 if (GET_RTX_CLASS (code) == 'i') 2217 { 2218 /* Constant functions can be constant if they don't use 2219 scratch memory used to mark function w/o side effects. */ 2220 if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x)) 2221 { 2222 x = CALL_INSN_FUNCTION_USAGE (x); 2223 if (x == 0) 2224 return 0; 2225 } 2226 else 2227 x = PATTERN (x); 2228 code = GET_CODE (x); 2229 } 2230 2231 switch (code) 2232 { 2233 case SUBREG: 2234 if (GET_CODE (SUBREG_REG (x)) == REG) 2235 { 2236 /* Global registers are not local. */ 2237 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER 2238 && global_regs[subreg_regno (x)]) 2239 return 1; 2240 return 0; 2241 } 2242 break; 2243 2244 case REG: 2245 regno = REGNO (x); 2246 /* Global registers are not local. */ 2247 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno]) 2248 return 1; 2249 return 0; 2250 2251 case SCRATCH: 2252 case PC: 2253 case CC0: 2254 case CONST_INT: 2255 case CONST_DOUBLE: 2256 case CONST: 2257 case LABEL_REF: 2258 return 0; 2259 2260 case SYMBOL_REF: 2261 /* Constants in the function's constants pool are constant. */ 2262 if (CONSTANT_POOL_ADDRESS_P (x)) 2263 return 0; 2264 return 1; 2265 2266 case CALL: 2267 /* Non-constant calls and recursion are not local. */ 2268 return 1; 2269 2270 case MEM: 2271 /* Be overly conservative and consider any volatile memory 2272 reference as not local. */ 2273 if (MEM_VOLATILE_P (x)) 2274 return 1; 2275 base = find_base_term (XEXP (x, 0)); 2276 if (base) 2277 { 2278 /* A Pmode ADDRESS could be a reference via the structure value 2279 address or static chain. Such memory references are nonlocal. 2280 2281 Thus, we have to examine the contents of the ADDRESS to find 2282 out if this is a local reference or not. */ 2283 if (GET_CODE (base) == ADDRESS 2284 && GET_MODE (base) == Pmode 2285 && (XEXP (base, 0) == stack_pointer_rtx 2286 || XEXP (base, 0) == arg_pointer_rtx 2287#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM 2288 || XEXP (base, 0) == hard_frame_pointer_rtx 2289#endif 2290 || XEXP (base, 0) == frame_pointer_rtx)) 2291 return 0; 2292 /* Constants in the function's constant pool are constant. */ 2293 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base)) 2294 return 0; 2295 } 2296 return 1; 2297 2298 case UNSPEC_VOLATILE: 2299 case ASM_INPUT: 2300 return 1; 2301 2302 case ASM_OPERANDS: 2303 if (MEM_VOLATILE_P (x)) 2304 return 1; 2305 2306 /* FALLTHROUGH */ 2307 2308 default: 2309 break; 2310 } 2311 2312 /* Recursively scan the operands of this expression. */ 2313 2314 { 2315 const char *fmt = GET_RTX_FORMAT (code); 2316 int i; 2317 2318 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) 2319 { 2320 if (fmt[i] == 'e' && XEXP (x, i)) 2321 { 2322 if (nonlocal_mentioned_p (XEXP (x, i))) 2323 return 1; 2324 } 2325 else if (fmt[i] == 'E') 2326 { 2327 int j; 2328 for (j = 0; j < XVECLEN (x, i); j++) 2329 if (nonlocal_mentioned_p (XVECEXP (x, i, j))) 2330 return 1; 2331 } 2332 } 2333 } 2334 2335 return 0; 2336} 2337 2338/* Mark the function if it is constant. */ 2339 2340void 2341mark_constant_function () 2342{ 2343 rtx insn; 2344 int nonlocal_mentioned; 2345 2346 if (TREE_PUBLIC (current_function_decl) 2347 || TREE_READONLY (current_function_decl) 2348 || DECL_IS_PURE (current_function_decl) 2349 || TREE_THIS_VOLATILE (current_function_decl) 2350 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode) 2351 return; 2352 2353 /* A loop might not return which counts as a side effect. */ 2354 if (mark_dfs_back_edges ()) 2355 return; 2356 2357 nonlocal_mentioned = 0; 2358 2359 init_alias_analysis (); 2360 2361 /* Determine if this is a constant function. */ 2362 2363 for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) 2364 if (INSN_P (insn) && nonlocal_mentioned_p (insn)) 2365 { 2366 nonlocal_mentioned = 1; 2367 break; 2368 } 2369 2370 end_alias_analysis (); 2371 2372 /* Mark the function. */ 2373 2374 if (! nonlocal_mentioned) 2375 TREE_READONLY (current_function_decl) = 1; 2376} 2377 2378 2379static HARD_REG_SET argument_registers; 2380 2381void 2382init_alias_once () 2383{ 2384 int i; 2385 2386#ifndef OUTGOING_REGNO 2387#define OUTGOING_REGNO(N) N 2388#endif 2389 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 2390 /* Check whether this register can hold an incoming pointer 2391 argument. FUNCTION_ARG_REGNO_P tests outgoing register 2392 numbers, so translate if necessary due to register windows. */ 2393 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i)) 2394 && HARD_REGNO_MODE_OK (i, Pmode)) 2395 SET_HARD_REG_BIT (argument_registers, i); 2396 2397 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0); 2398} 2399 2400/* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE 2401 array. */ 2402 2403void 2404init_alias_analysis () 2405{ 2406 int maxreg = max_reg_num (); 2407 int changed, pass; 2408 int i; 2409 unsigned int ui; 2410 rtx insn; 2411 2412 reg_known_value_size = maxreg; 2413 2414 reg_known_value 2415 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx)) 2416 - FIRST_PSEUDO_REGISTER; 2417 reg_known_equiv_p 2418 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char)) 2419 - FIRST_PSEUDO_REGISTER; 2420 2421 /* Overallocate reg_base_value to allow some growth during loop 2422 optimization. Loop unrolling can create a large number of 2423 registers. */ 2424 reg_base_value_size = maxreg * 2; 2425 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx)); 2426 ggc_add_rtx_root (reg_base_value, reg_base_value_size); 2427 2428 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx)); 2429 reg_seen = (char *) xmalloc (reg_base_value_size); 2430 if (! reload_completed && flag_unroll_loops) 2431 { 2432 /* ??? Why are we realloc'ing if we're just going to zero it? */ 2433 alias_invariant = (rtx *)xrealloc (alias_invariant, 2434 reg_base_value_size * sizeof (rtx)); 2435 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx)); 2436 } 2437 2438 /* The basic idea is that each pass through this loop will use the 2439 "constant" information from the previous pass to propagate alias 2440 information through another level of assignments. 2441 2442 This could get expensive if the assignment chains are long. Maybe 2443 we should throttle the number of iterations, possibly based on 2444 the optimization level or flag_expensive_optimizations. 2445 2446 We could propagate more information in the first pass by making use 2447 of REG_N_SETS to determine immediately that the alias information 2448 for a pseudo is "constant". 2449 2450 A program with an uninitialized variable can cause an infinite loop 2451 here. Instead of doing a full dataflow analysis to detect such problems 2452 we just cap the number of iterations for the loop. 2453 2454 The state of the arrays for the set chain in question does not matter 2455 since the program has undefined behavior. */ 2456 2457 pass = 0; 2458 do 2459 { 2460 /* Assume nothing will change this iteration of the loop. */ 2461 changed = 0; 2462 2463 /* We want to assign the same IDs each iteration of this loop, so 2464 start counting from zero each iteration of the loop. */ 2465 unique_id = 0; 2466 2467 /* We're at the start of the function each iteration through the 2468 loop, so we're copying arguments. */ 2469 copying_arguments = 1; 2470 2471 /* Wipe the potential alias information clean for this pass. */ 2472 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx)); 2473 2474 /* Wipe the reg_seen array clean. */ 2475 memset ((char *) reg_seen, 0, reg_base_value_size); 2476 2477 /* Mark all hard registers which may contain an address. 2478 The stack, frame and argument pointers may contain an address. 2479 An argument register which can hold a Pmode value may contain 2480 an address even if it is not in BASE_REGS. 2481 2482 The address expression is VOIDmode for an argument and 2483 Pmode for other registers. */ 2484 2485 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 2486 if (TEST_HARD_REG_BIT (argument_registers, i)) 2487 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode, 2488 gen_rtx_REG (Pmode, i)); 2489 2490 new_reg_base_value[STACK_POINTER_REGNUM] 2491 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx); 2492 new_reg_base_value[ARG_POINTER_REGNUM] 2493 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx); 2494 new_reg_base_value[FRAME_POINTER_REGNUM] 2495 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx); 2496#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM 2497 new_reg_base_value[HARD_FRAME_POINTER_REGNUM] 2498 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx); 2499#endif 2500 2501 /* Walk the insns adding values to the new_reg_base_value array. */ 2502 for (insn = get_insns (); insn; insn = NEXT_INSN (insn)) 2503 { 2504 if (INSN_P (insn)) 2505 { 2506 rtx note, set; 2507 2508#if defined (HAVE_prologue) || defined (HAVE_epilogue) 2509 /* The prologue/epilogue insns are not threaded onto the 2510 insn chain until after reload has completed. Thus, 2511 there is no sense wasting time checking if INSN is in 2512 the prologue/epilogue until after reload has completed. */ 2513 if (reload_completed 2514 && prologue_epilogue_contains (insn)) 2515 continue; 2516#endif 2517 2518 /* If this insn has a noalias note, process it, Otherwise, 2519 scan for sets. A simple set will have no side effects 2520 which could change the base value of any other register. */ 2521 2522 if (GET_CODE (PATTERN (insn)) == SET 2523 && REG_NOTES (insn) != 0 2524 && find_reg_note (insn, REG_NOALIAS, NULL_RTX)) 2525 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL); 2526 else 2527 note_stores (PATTERN (insn), record_set, NULL); 2528 2529 set = single_set (insn); 2530 2531 if (set != 0 2532 && GET_CODE (SET_DEST (set)) == REG 2533 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER) 2534 { 2535 unsigned int regno = REGNO (SET_DEST (set)); 2536 rtx src = SET_SRC (set); 2537 2538 if (REG_NOTES (insn) != 0 2539 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0 2540 && REG_N_SETS (regno) == 1) 2541 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0) 2542 && GET_CODE (XEXP (note, 0)) != EXPR_LIST 2543 && ! rtx_varies_p (XEXP (note, 0), 1) 2544 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0))) 2545 { 2546 reg_known_value[regno] = XEXP (note, 0); 2547 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV; 2548 } 2549 else if (REG_N_SETS (regno) == 1 2550 && GET_CODE (src) == PLUS 2551 && GET_CODE (XEXP (src, 0)) == REG 2552 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER 2553 && (reg_known_value[REGNO (XEXP (src, 0))]) 2554 && GET_CODE (XEXP (src, 1)) == CONST_INT) 2555 { 2556 rtx op0 = XEXP (src, 0); 2557 op0 = reg_known_value[REGNO (op0)]; 2558 reg_known_value[regno] 2559 = plus_constant (op0, INTVAL (XEXP (src, 1))); 2560 reg_known_equiv_p[regno] = 0; 2561 } 2562 else if (REG_N_SETS (regno) == 1 2563 && ! rtx_varies_p (src, 1)) 2564 { 2565 reg_known_value[regno] = src; 2566 reg_known_equiv_p[regno] = 0; 2567 } 2568 } 2569 } 2570 else if (GET_CODE (insn) == NOTE 2571 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG) 2572 copying_arguments = 0; 2573 } 2574 2575 /* Now propagate values from new_reg_base_value to reg_base_value. */ 2576 for (ui = 0; ui < reg_base_value_size; ui++) 2577 { 2578 if (new_reg_base_value[ui] 2579 && new_reg_base_value[ui] != reg_base_value[ui] 2580 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui])) 2581 { 2582 reg_base_value[ui] = new_reg_base_value[ui]; 2583 changed = 1; 2584 } 2585 } 2586 } 2587 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES); 2588 2589 /* Fill in the remaining entries. */ 2590 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++) 2591 if (reg_known_value[i] == 0) 2592 reg_known_value[i] = regno_reg_rtx[i]; 2593 2594 /* Simplify the reg_base_value array so that no register refers to 2595 another register, except to special registers indirectly through 2596 ADDRESS expressions. 2597 2598 In theory this loop can take as long as O(registers^2), but unless 2599 there are very long dependency chains it will run in close to linear 2600 time. 2601 2602 This loop may not be needed any longer now that the main loop does 2603 a better job at propagating alias information. */ 2604 pass = 0; 2605 do 2606 { 2607 changed = 0; 2608 pass++; 2609 for (ui = 0; ui < reg_base_value_size; ui++) 2610 { 2611 rtx base = reg_base_value[ui]; 2612 if (base && GET_CODE (base) == REG) 2613 { 2614 unsigned int base_regno = REGNO (base); 2615 if (base_regno == ui) /* register set from itself */ 2616 reg_base_value[ui] = 0; 2617 else 2618 reg_base_value[ui] = reg_base_value[base_regno]; 2619 changed = 1; 2620 } 2621 } 2622 } 2623 while (changed && pass < MAX_ALIAS_LOOP_PASSES); 2624 2625 /* Clean up. */ 2626 free (new_reg_base_value); 2627 new_reg_base_value = 0; 2628 free (reg_seen); 2629 reg_seen = 0; 2630} 2631 2632void 2633end_alias_analysis () 2634{ 2635 free (reg_known_value + FIRST_PSEUDO_REGISTER); 2636 reg_known_value = 0; 2637 reg_known_value_size = 0; 2638 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER); 2639 reg_known_equiv_p = 0; 2640 if (reg_base_value) 2641 { 2642 ggc_del_root (reg_base_value); 2643 free (reg_base_value); 2644 reg_base_value = 0; 2645 } 2646 reg_base_value_size = 0; 2647 if (alias_invariant) 2648 { 2649 free (alias_invariant); 2650 alias_invariant = 0; 2651 } 2652} 2653