1/* Conditional constant propagation pass for the GNU compiler. 2 Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 3 Free Software Foundation, Inc. 4 Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org> 5 Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com> 6 7This file is part of GCC. 8 9GCC is free software; you can redistribute it and/or modify it 10under the terms of the GNU General Public License as published by the 11Free Software Foundation; either version 2, or (at your option) any 12later version. 13 14GCC is distributed in the hope that it will be useful, but WITHOUT 15ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17for more details. 18 19You should have received a copy of the GNU General Public License 20along with GCC; see the file COPYING. If not, write to the Free 21Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 2202110-1301, USA. */ 23 24/* Conditional constant propagation (CCP) is based on the SSA 25 propagation engine (tree-ssa-propagate.c). Constant assignments of 26 the form VAR = CST are propagated from the assignments into uses of 27 VAR, which in turn may generate new constants. The simulation uses 28 a four level lattice to keep track of constant values associated 29 with SSA names. Given an SSA name V_i, it may take one of the 30 following values: 31 32 UNINITIALIZED -> This is the default starting value. V_i 33 has not been processed yet. 34 35 UNDEFINED -> V_i is a local variable whose definition 36 has not been processed yet. Therefore we 37 don't yet know if its value is a constant 38 or not. 39 40 CONSTANT -> V_i has been found to hold a constant 41 value C. 42 43 VARYING -> V_i cannot take a constant value, or if it 44 does, it is not possible to determine it 45 at compile time. 46 47 The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node: 48 49 1- In ccp_visit_stmt, we are interested in assignments whose RHS 50 evaluates into a constant and conditional jumps whose predicate 51 evaluates into a boolean true or false. When an assignment of 52 the form V_i = CONST is found, V_i's lattice value is set to 53 CONSTANT and CONST is associated with it. This causes the 54 propagation engine to add all the SSA edges coming out the 55 assignment into the worklists, so that statements that use V_i 56 can be visited. 57 58 If the statement is a conditional with a constant predicate, we 59 mark the outgoing edges as executable or not executable 60 depending on the predicate's value. This is then used when 61 visiting PHI nodes to know when a PHI argument can be ignored. 62 63 64 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the 65 same constant C, then the LHS of the PHI is set to C. This 66 evaluation is known as the "meet operation". Since one of the 67 goals of this evaluation is to optimistically return constant 68 values as often as possible, it uses two main short cuts: 69 70 - If an argument is flowing in through a non-executable edge, it 71 is ignored. This is useful in cases like this: 72 73 if (PRED) 74 a_9 = 3; 75 else 76 a_10 = 100; 77 a_11 = PHI (a_9, a_10) 78 79 If PRED is known to always evaluate to false, then we can 80 assume that a_11 will always take its value from a_10, meaning 81 that instead of consider it VARYING (a_9 and a_10 have 82 different values), we can consider it CONSTANT 100. 83 84 - If an argument has an UNDEFINED value, then it does not affect 85 the outcome of the meet operation. If a variable V_i has an 86 UNDEFINED value, it means that either its defining statement 87 hasn't been visited yet or V_i has no defining statement, in 88 which case the original symbol 'V' is being used 89 uninitialized. Since 'V' is a local variable, the compiler 90 may assume any initial value for it. 91 92 93 After propagation, every variable V_i that ends up with a lattice 94 value of CONSTANT will have the associated constant value in the 95 array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for 96 final substitution and folding. 97 98 99 Constant propagation in stores and loads (STORE-CCP) 100 ---------------------------------------------------- 101 102 While CCP has all the logic to propagate constants in GIMPLE 103 registers, it is missing the ability to associate constants with 104 stores and loads (i.e., pointer dereferences, structures and 105 global/aliased variables). We don't keep loads and stores in 106 SSA, but we do build a factored use-def web for them (in the 107 virtual operands). 108 109 For instance, consider the following code fragment: 110 111 struct A a; 112 const int B = 42; 113 114 void foo (int i) 115 { 116 if (i > 10) 117 a.a = 42; 118 else 119 { 120 a.b = 21; 121 a.a = a.b + 21; 122 } 123 124 if (a.a != B) 125 never_executed (); 126 } 127 128 We should be able to deduce that the predicate 'a.a != B' is always 129 false. To achieve this, we associate constant values to the SSA 130 names in the V_MAY_DEF and V_MUST_DEF operands for each store. 131 Additionally, since we also glob partial loads/stores with the base 132 symbol, we also keep track of the memory reference where the 133 constant value was stored (in the MEM_REF field of PROP_VALUE_T). 134 For instance, 135 136 # a_5 = V_MAY_DEF <a_4> 137 a.a = 2; 138 139 # VUSE <a_5> 140 x_3 = a.b; 141 142 In the example above, CCP will associate value '2' with 'a_5', but 143 it would be wrong to replace the load from 'a.b' with '2', because 144 '2' had been stored into a.a. 145 146 To support STORE-CCP, it is necessary to add a new value to the 147 constant propagation lattice. When evaluating a load for a memory 148 reference we can no longer assume a value of UNDEFINED if we 149 haven't seen a preceding store to the same memory location. 150 Consider, for instance global variables: 151 152 int A; 153 154 foo (int i) 155 { 156 if (i_3 > 10) 157 A_4 = 3; 158 # A_5 = PHI (A_4, A_2); 159 160 # VUSE <A_5> 161 A.0_6 = A; 162 163 return A.0_6; 164 } 165 166 The value of A_2 cannot be assumed to be UNDEFINED, as it may have 167 been defined outside of foo. If we were to assume it UNDEFINED, we 168 would erroneously optimize the above into 'return 3;'. Therefore, 169 when doing STORE-CCP, we introduce a fifth lattice value 170 (UNKNOWN_VAL), which overrides any other value when computing the 171 meet operation in PHI nodes. 172 173 Though STORE-CCP is not too expensive, it does have to do more work 174 than regular CCP, so it is only enabled at -O2. Both regular CCP 175 and STORE-CCP use the exact same algorithm. The only distinction 176 is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is 177 set to true. This affects the evaluation of statements and PHI 178 nodes. 179 180 References: 181 182 Constant propagation with conditional branches, 183 Wegman and Zadeck, ACM TOPLAS 13(2):181-210. 184 185 Building an Optimizing Compiler, 186 Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9. 187 188 Advanced Compiler Design and Implementation, 189 Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */ 190 191#include "config.h" 192#include "system.h" 193#include "coretypes.h" 194#include "tm.h" 195#include "tree.h" 196#include "flags.h" 197#include "rtl.h" 198#include "tm_p.h" 199#include "ggc.h" 200#include "basic-block.h" 201#include "output.h" 202#include "expr.h" 203#include "function.h" 204#include "diagnostic.h" 205#include "timevar.h" 206#include "tree-dump.h" 207#include "tree-flow.h" 208#include "tree-pass.h" 209#include "tree-ssa-propagate.h" 210#include "langhooks.h" 211#include "target.h" 212#include "toplev.h" 213 214 215/* Possible lattice values. */ 216typedef enum 217{ 218 UNINITIALIZED = 0, 219 UNDEFINED, 220 UNKNOWN_VAL, 221 CONSTANT, 222 VARYING 223} ccp_lattice_t; 224 225/* Array of propagated constant values. After propagation, 226 CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If 227 the constant is held in an SSA name representing a memory store 228 (i.e., a V_MAY_DEF or V_MUST_DEF), CONST_VAL[I].MEM_REF will 229 contain the actual memory reference used to store (i.e., the LHS of 230 the assignment doing the store). */ 231static prop_value_t *const_val; 232 233/* True if we are also propagating constants in stores and loads. */ 234static bool do_store_ccp; 235 236/* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */ 237 238static void 239dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val) 240{ 241 switch (val.lattice_val) 242 { 243 case UNINITIALIZED: 244 fprintf (outf, "%sUNINITIALIZED", prefix); 245 break; 246 case UNDEFINED: 247 fprintf (outf, "%sUNDEFINED", prefix); 248 break; 249 case VARYING: 250 fprintf (outf, "%sVARYING", prefix); 251 break; 252 case UNKNOWN_VAL: 253 fprintf (outf, "%sUNKNOWN_VAL", prefix); 254 break; 255 case CONSTANT: 256 fprintf (outf, "%sCONSTANT ", prefix); 257 print_generic_expr (outf, val.value, dump_flags); 258 break; 259 default: 260 gcc_unreachable (); 261 } 262} 263 264 265/* Print lattice value VAL to stderr. */ 266 267void debug_lattice_value (prop_value_t val); 268 269void 270debug_lattice_value (prop_value_t val) 271{ 272 dump_lattice_value (stderr, "", val); 273 fprintf (stderr, "\n"); 274} 275 276 277/* The regular is_gimple_min_invariant does a shallow test of the object. 278 It assumes that full gimplification has happened, or will happen on the 279 object. For a value coming from DECL_INITIAL, this is not true, so we 280 have to be more strict ourselves. */ 281 282static bool 283ccp_decl_initial_min_invariant (tree t) 284{ 285 if (!is_gimple_min_invariant (t)) 286 return false; 287 if (TREE_CODE (t) == ADDR_EXPR) 288 { 289 /* Inline and unroll is_gimple_addressable. */ 290 while (1) 291 { 292 t = TREE_OPERAND (t, 0); 293 if (is_gimple_id (t)) 294 return true; 295 if (!handled_component_p (t)) 296 return false; 297 } 298 } 299 return true; 300} 301 302 303/* Compute a default value for variable VAR and store it in the 304 CONST_VAL array. The following rules are used to get default 305 values: 306 307 1- Global and static variables that are declared constant are 308 considered CONSTANT. 309 310 2- Any other value is considered UNDEFINED. This is useful when 311 considering PHI nodes. PHI arguments that are undefined do not 312 change the constant value of the PHI node, which allows for more 313 constants to be propagated. 314 315 3- If SSA_NAME_VALUE is set and it is a constant, its value is 316 used. 317 318 4- Variables defined by statements other than assignments and PHI 319 nodes are considered VARYING. 320 321 5- Variables that are not GIMPLE registers are considered 322 UNKNOWN_VAL, which is really a stronger version of UNDEFINED. 323 It's used to avoid the short circuit evaluation implied by 324 UNDEFINED in ccp_lattice_meet. */ 325 326static prop_value_t 327get_default_value (tree var) 328{ 329 tree sym = SSA_NAME_VAR (var); 330 prop_value_t val = { UNINITIALIZED, NULL_TREE, NULL_TREE }; 331 332 if (!do_store_ccp && !is_gimple_reg (var)) 333 { 334 /* Short circuit for regular CCP. We are not interested in any 335 non-register when DO_STORE_CCP is false. */ 336 val.lattice_val = VARYING; 337 } 338 else if (SSA_NAME_VALUE (var) 339 && is_gimple_min_invariant (SSA_NAME_VALUE (var))) 340 { 341 val.lattice_val = CONSTANT; 342 val.value = SSA_NAME_VALUE (var); 343 } 344 else if (TREE_STATIC (sym) 345 && TREE_READONLY (sym) 346 && !MTAG_P (sym) 347 && DECL_INITIAL (sym) 348 && ccp_decl_initial_min_invariant (DECL_INITIAL (sym))) 349 { 350 /* Globals and static variables declared 'const' take their 351 initial value. */ 352 val.lattice_val = CONSTANT; 353 val.value = DECL_INITIAL (sym); 354 val.mem_ref = sym; 355 } 356 else 357 { 358 tree stmt = SSA_NAME_DEF_STMT (var); 359 360 if (IS_EMPTY_STMT (stmt)) 361 { 362 /* Variables defined by an empty statement are those used 363 before being initialized. If VAR is a local variable, we 364 can assume initially that it is UNDEFINED. If we are 365 doing STORE-CCP, function arguments and non-register 366 variables are initially UNKNOWN_VAL, because we cannot 367 discard the value incoming from outside of this function 368 (see ccp_lattice_meet for details). */ 369 if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL) 370 val.lattice_val = UNDEFINED; 371 else if (do_store_ccp) 372 val.lattice_val = UNKNOWN_VAL; 373 else 374 val.lattice_val = VARYING; 375 } 376 else if (TREE_CODE (stmt) == MODIFY_EXPR 377 || TREE_CODE (stmt) == PHI_NODE) 378 { 379 /* Any other variable defined by an assignment or a PHI node 380 is considered UNDEFINED (or UNKNOWN_VAL if VAR is not a 381 GIMPLE register). */ 382 val.lattice_val = is_gimple_reg (sym) ? UNDEFINED : UNKNOWN_VAL; 383 } 384 else 385 { 386 /* Otherwise, VAR will never take on a constant value. */ 387 val.lattice_val = VARYING; 388 } 389 } 390 391 return val; 392} 393 394 395/* Get the constant value associated with variable VAR. If 396 MAY_USE_DEFAULT_P is true, call get_default_value on variables that 397 have the lattice value UNINITIALIZED. */ 398 399static prop_value_t * 400get_value (tree var, bool may_use_default_p) 401{ 402 prop_value_t *val = &const_val[SSA_NAME_VERSION (var)]; 403 if (may_use_default_p && val->lattice_val == UNINITIALIZED) 404 *val = get_default_value (var); 405 406 return val; 407} 408 409 410/* Set the value for variable VAR to NEW_VAL. Return true if the new 411 value is different from VAR's previous value. */ 412 413static bool 414set_lattice_value (tree var, prop_value_t new_val) 415{ 416 prop_value_t *old_val = get_value (var, false); 417 418 /* Lattice transitions must always be monotonically increasing in 419 value. We allow two exceptions: 420 421 1- If *OLD_VAL and NEW_VAL are the same, return false to 422 inform the caller that this was a non-transition. 423 424 2- If we are doing store-ccp (i.e., DOING_STORE_CCP is true), 425 allow CONSTANT->UNKNOWN_VAL. The UNKNOWN_VAL state is a 426 special type of UNDEFINED state which prevents the short 427 circuit evaluation of PHI arguments (see ccp_visit_phi_node 428 and ccp_lattice_meet). */ 429 gcc_assert (old_val->lattice_val <= new_val.lattice_val 430 || (old_val->lattice_val == new_val.lattice_val 431 && old_val->value == new_val.value 432 && old_val->mem_ref == new_val.mem_ref) 433 || (do_store_ccp 434 && old_val->lattice_val == CONSTANT 435 && new_val.lattice_val == UNKNOWN_VAL)); 436 437 if (old_val->lattice_val != new_val.lattice_val) 438 { 439 if (dump_file && (dump_flags & TDF_DETAILS)) 440 { 441 dump_lattice_value (dump_file, "Lattice value changed to ", new_val); 442 fprintf (dump_file, ". %sdding SSA edges to worklist.\n", 443 new_val.lattice_val != UNDEFINED ? "A" : "Not a"); 444 } 445 446 *old_val = new_val; 447 448 /* Transitions UNINITIALIZED -> UNDEFINED are never interesting 449 for propagation purposes. In these cases return false to 450 avoid doing useless work. */ 451 return (new_val.lattice_val != UNDEFINED); 452 } 453 454 return false; 455} 456 457 458/* Return the likely CCP lattice value for STMT. 459 460 If STMT has no operands, then return CONSTANT. 461 462 Else if any operands of STMT are undefined, then return UNDEFINED. 463 464 Else if any operands of STMT are constants, then return CONSTANT. 465 466 Else return VARYING. */ 467 468static ccp_lattice_t 469likely_value (tree stmt) 470{ 471 bool found_constant; 472 stmt_ann_t ann; 473 tree use; 474 ssa_op_iter iter; 475 476 ann = stmt_ann (stmt); 477 478 /* If the statement has volatile operands, it won't fold to a 479 constant value. */ 480 if (ann->has_volatile_ops) 481 return VARYING; 482 483 /* If we are not doing store-ccp, statements with loads 484 and/or stores will never fold into a constant. */ 485 if (!do_store_ccp 486 && !ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS)) 487 return VARYING; 488 489 490 /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly 491 conservative, in the presence of const and pure calls. */ 492 if (get_call_expr_in (stmt) != NULL_TREE) 493 return VARYING; 494 495 /* Anything other than assignments and conditional jumps are not 496 interesting for CCP. */ 497 if (TREE_CODE (stmt) != MODIFY_EXPR 498 && TREE_CODE (stmt) != COND_EXPR 499 && TREE_CODE (stmt) != SWITCH_EXPR) 500 return VARYING; 501 502 if (is_gimple_min_invariant (get_rhs (stmt))) 503 return CONSTANT; 504 505 found_constant = false; 506 FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE|SSA_OP_VUSE) 507 { 508 prop_value_t *val = get_value (use, true); 509 510 if (val->lattice_val == VARYING) 511 return VARYING; 512 513 if (val->lattice_val == UNKNOWN_VAL) 514 { 515 /* UNKNOWN_VAL is invalid when not doing STORE-CCP. */ 516 gcc_assert (do_store_ccp); 517 return UNKNOWN_VAL; 518 } 519 520 if (val->lattice_val == CONSTANT) 521 found_constant = true; 522 } 523 524 if (found_constant 525 || ZERO_SSA_OPERANDS (stmt, SSA_OP_USE) 526 || ZERO_SSA_OPERANDS (stmt, SSA_OP_VUSE)) 527 return CONSTANT; 528 529 return UNDEFINED; 530} 531 532 533/* Initialize local data structures for CCP. */ 534 535static void 536ccp_initialize (void) 537{ 538 basic_block bb; 539 540 const_val = XNEWVEC (prop_value_t, num_ssa_names); 541 memset (const_val, 0, num_ssa_names * sizeof (*const_val)); 542 543 /* Initialize simulation flags for PHI nodes and statements. */ 544 FOR_EACH_BB (bb) 545 { 546 block_stmt_iterator i; 547 548 for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i)) 549 { 550 bool is_varying = false; 551 tree stmt = bsi_stmt (i); 552 553 if (likely_value (stmt) == VARYING) 554 555 { 556 tree def; 557 ssa_op_iter iter; 558 559 /* If the statement will not produce a constant, mark 560 all its outputs VARYING. */ 561 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) 562 get_value (def, false)->lattice_val = VARYING; 563 564 /* Never mark conditional jumps with DONT_SIMULATE_AGAIN, 565 otherwise the propagator will never add the outgoing 566 control edges. */ 567 if (TREE_CODE (stmt) != COND_EXPR 568 && TREE_CODE (stmt) != SWITCH_EXPR) 569 is_varying = true; 570 } 571 572 DONT_SIMULATE_AGAIN (stmt) = is_varying; 573 } 574 } 575 576 /* Now process PHI nodes. */ 577 FOR_EACH_BB (bb) 578 { 579 tree phi; 580 581 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) 582 { 583 int i; 584 tree arg; 585 prop_value_t *val = get_value (PHI_RESULT (phi), false); 586 587 for (i = 0; i < PHI_NUM_ARGS (phi); i++) 588 { 589 arg = PHI_ARG_DEF (phi, i); 590 591 if (TREE_CODE (arg) == SSA_NAME 592 && get_value (arg, false)->lattice_val == VARYING) 593 { 594 val->lattice_val = VARYING; 595 break; 596 } 597 } 598 599 DONT_SIMULATE_AGAIN (phi) = (val->lattice_val == VARYING); 600 } 601 } 602} 603 604 605/* Do final substitution of propagated values, cleanup the flowgraph and 606 free allocated storage. */ 607 608static void 609ccp_finalize (void) 610{ 611 /* Perform substitutions based on the known constant values. */ 612 substitute_and_fold (const_val, false); 613 614 free (const_val); 615} 616 617 618/* Compute the meet operator between *VAL1 and *VAL2. Store the result 619 in VAL1. 620 621 any M UNDEFINED = any 622 any M UNKNOWN_VAL = UNKNOWN_VAL 623 any M VARYING = VARYING 624 Ci M Cj = Ci if (i == j) 625 Ci M Cj = VARYING if (i != j) 626 627 Lattice values UNKNOWN_VAL and UNDEFINED are similar but have 628 different semantics at PHI nodes. Both values imply that we don't 629 know whether the variable is constant or not. However, UNKNOWN_VAL 630 values override all others. For instance, suppose that A is a 631 global variable: 632 633 +------+ 634 | | 635 | / \ 636 | / \ 637 | | A_1 = 4 638 | \ / 639 | \ / 640 | A_3 = PHI (A_2, A_1) 641 | ... = A_3 642 | | 643 +----+ 644 645 If the edge into A_2 is not executable, the first visit to A_3 will 646 yield the constant 4. But the second visit to A_3 will be with A_2 647 in state UNKNOWN_VAL. We can no longer conclude that A_3 is 4 648 because A_2 may have been set in another function. If we had used 649 the lattice value UNDEFINED, we would have had wrongly concluded 650 that A_3 is 4. */ 651 652 653static void 654ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2) 655{ 656 if (val1->lattice_val == UNDEFINED) 657 { 658 /* UNDEFINED M any = any */ 659 *val1 = *val2; 660 } 661 else if (val2->lattice_val == UNDEFINED) 662 { 663 /* any M UNDEFINED = any 664 Nothing to do. VAL1 already contains the value we want. */ 665 ; 666 } 667 else if (val1->lattice_val == UNKNOWN_VAL 668 || val2->lattice_val == UNKNOWN_VAL) 669 { 670 /* UNKNOWN_VAL values are invalid if we are not doing STORE-CCP. */ 671 gcc_assert (do_store_ccp); 672 673 /* any M UNKNOWN_VAL = UNKNOWN_VAL. */ 674 val1->lattice_val = UNKNOWN_VAL; 675 val1->value = NULL_TREE; 676 val1->mem_ref = NULL_TREE; 677 } 678 else if (val1->lattice_val == VARYING 679 || val2->lattice_val == VARYING) 680 { 681 /* any M VARYING = VARYING. */ 682 val1->lattice_val = VARYING; 683 val1->value = NULL_TREE; 684 val1->mem_ref = NULL_TREE; 685 } 686 else if (val1->lattice_val == CONSTANT 687 && val2->lattice_val == CONSTANT 688 && simple_cst_equal (val1->value, val2->value) == 1 689 && (!do_store_ccp 690 || (val1->mem_ref && val2->mem_ref 691 && operand_equal_p (val1->mem_ref, val2->mem_ref, 0)))) 692 { 693 /* Ci M Cj = Ci if (i == j) 694 Ci M Cj = VARYING if (i != j) 695 696 If these two values come from memory stores, make sure that 697 they come from the same memory reference. */ 698 val1->lattice_val = CONSTANT; 699 val1->value = val1->value; 700 val1->mem_ref = val1->mem_ref; 701 } 702 else 703 { 704 /* Any other combination is VARYING. */ 705 val1->lattice_val = VARYING; 706 val1->value = NULL_TREE; 707 val1->mem_ref = NULL_TREE; 708 } 709} 710 711 712/* Loop through the PHI_NODE's parameters for BLOCK and compare their 713 lattice values to determine PHI_NODE's lattice value. The value of a 714 PHI node is determined calling ccp_lattice_meet with all the arguments 715 of the PHI node that are incoming via executable edges. */ 716 717static enum ssa_prop_result 718ccp_visit_phi_node (tree phi) 719{ 720 int i; 721 prop_value_t *old_val, new_val; 722 723 if (dump_file && (dump_flags & TDF_DETAILS)) 724 { 725 fprintf (dump_file, "\nVisiting PHI node: "); 726 print_generic_expr (dump_file, phi, dump_flags); 727 } 728 729 old_val = get_value (PHI_RESULT (phi), false); 730 switch (old_val->lattice_val) 731 { 732 case VARYING: 733 return SSA_PROP_VARYING; 734 735 case CONSTANT: 736 new_val = *old_val; 737 break; 738 739 case UNKNOWN_VAL: 740 /* To avoid the default value of UNKNOWN_VAL overriding 741 that of its possible constant arguments, temporarily 742 set the PHI node's default lattice value to be 743 UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and 744 the new value is UNDEFINED, then we prevent the invalid 745 transition by not calling set_lattice_value. */ 746 gcc_assert (do_store_ccp); 747 748 /* FALLTHRU */ 749 750 case UNDEFINED: 751 case UNINITIALIZED: 752 new_val.lattice_val = UNDEFINED; 753 new_val.value = NULL_TREE; 754 new_val.mem_ref = NULL_TREE; 755 break; 756 757 default: 758 gcc_unreachable (); 759 } 760 761 for (i = 0; i < PHI_NUM_ARGS (phi); i++) 762 { 763 /* Compute the meet operator over all the PHI arguments flowing 764 through executable edges. */ 765 edge e = PHI_ARG_EDGE (phi, i); 766 767 if (dump_file && (dump_flags & TDF_DETAILS)) 768 { 769 fprintf (dump_file, 770 "\n Argument #%d (%d -> %d %sexecutable)\n", 771 i, e->src->index, e->dest->index, 772 (e->flags & EDGE_EXECUTABLE) ? "" : "not "); 773 } 774 775 /* If the incoming edge is executable, Compute the meet operator for 776 the existing value of the PHI node and the current PHI argument. */ 777 if (e->flags & EDGE_EXECUTABLE) 778 { 779 tree arg = PHI_ARG_DEF (phi, i); 780 prop_value_t arg_val; 781 782 if (is_gimple_min_invariant (arg)) 783 { 784 arg_val.lattice_val = CONSTANT; 785 arg_val.value = arg; 786 arg_val.mem_ref = NULL_TREE; 787 } 788 else 789 arg_val = *(get_value (arg, true)); 790 791 ccp_lattice_meet (&new_val, &arg_val); 792 793 if (dump_file && (dump_flags & TDF_DETAILS)) 794 { 795 fprintf (dump_file, "\t"); 796 print_generic_expr (dump_file, arg, dump_flags); 797 dump_lattice_value (dump_file, "\tValue: ", arg_val); 798 fprintf (dump_file, "\n"); 799 } 800 801 if (new_val.lattice_val == VARYING) 802 break; 803 } 804 } 805 806 if (dump_file && (dump_flags & TDF_DETAILS)) 807 { 808 dump_lattice_value (dump_file, "\n PHI node value: ", new_val); 809 fprintf (dump_file, "\n\n"); 810 } 811 812 /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */ 813 if (do_store_ccp 814 && old_val->lattice_val == UNKNOWN_VAL 815 && new_val.lattice_val == UNDEFINED) 816 return SSA_PROP_NOT_INTERESTING; 817 818 /* Otherwise, make the transition to the new value. */ 819 if (set_lattice_value (PHI_RESULT (phi), new_val)) 820 { 821 if (new_val.lattice_val == VARYING) 822 return SSA_PROP_VARYING; 823 else 824 return SSA_PROP_INTERESTING; 825 } 826 else 827 return SSA_PROP_NOT_INTERESTING; 828} 829 830 831/* CCP specific front-end to the non-destructive constant folding 832 routines. 833 834 Attempt to simplify the RHS of STMT knowing that one or more 835 operands are constants. 836 837 If simplification is possible, return the simplified RHS, 838 otherwise return the original RHS. */ 839 840static tree 841ccp_fold (tree stmt) 842{ 843 tree rhs = get_rhs (stmt); 844 enum tree_code code = TREE_CODE (rhs); 845 enum tree_code_class kind = TREE_CODE_CLASS (code); 846 tree retval = NULL_TREE; 847 848 if (TREE_CODE (rhs) == SSA_NAME) 849 { 850 /* If the RHS is an SSA_NAME, return its known constant value, 851 if any. */ 852 return get_value (rhs, true)->value; 853 } 854 else if (do_store_ccp && stmt_makes_single_load (stmt)) 855 { 856 /* If the RHS is a memory load, see if the VUSEs associated with 857 it are a valid constant for that memory load. */ 858 prop_value_t *val = get_value_loaded_by (stmt, const_val); 859 if (val && val->mem_ref) 860 { 861 if (operand_equal_p (val->mem_ref, rhs, 0)) 862 return val->value; 863 864 /* If RHS is extracting REALPART_EXPR or IMAGPART_EXPR of a 865 complex type with a known constant value, return it. */ 866 if ((TREE_CODE (rhs) == REALPART_EXPR 867 || TREE_CODE (rhs) == IMAGPART_EXPR) 868 && operand_equal_p (val->mem_ref, TREE_OPERAND (rhs, 0), 0)) 869 return fold_build1 (TREE_CODE (rhs), TREE_TYPE (rhs), val->value); 870 } 871 return NULL_TREE; 872 } 873 874 /* Unary operators. Note that we know the single operand must 875 be a constant. So this should almost always return a 876 simplified RHS. */ 877 if (kind == tcc_unary) 878 { 879 /* Handle unary operators which can appear in GIMPLE form. */ 880 tree op0 = TREE_OPERAND (rhs, 0); 881 882 /* Simplify the operand down to a constant. */ 883 if (TREE_CODE (op0) == SSA_NAME) 884 { 885 prop_value_t *val = get_value (op0, true); 886 if (val->lattice_val == CONSTANT) 887 op0 = get_value (op0, true)->value; 888 } 889 890 if ((code == NOP_EXPR || code == CONVERT_EXPR) 891 && tree_ssa_useless_type_conversion_1 (TREE_TYPE (rhs), 892 TREE_TYPE (op0))) 893 return op0; 894 return fold_unary (code, TREE_TYPE (rhs), op0); 895 } 896 897 /* Binary and comparison operators. We know one or both of the 898 operands are constants. */ 899 else if (kind == tcc_binary 900 || kind == tcc_comparison 901 || code == TRUTH_AND_EXPR 902 || code == TRUTH_OR_EXPR 903 || code == TRUTH_XOR_EXPR) 904 { 905 /* Handle binary and comparison operators that can appear in 906 GIMPLE form. */ 907 tree op0 = TREE_OPERAND (rhs, 0); 908 tree op1 = TREE_OPERAND (rhs, 1); 909 910 /* Simplify the operands down to constants when appropriate. */ 911 if (TREE_CODE (op0) == SSA_NAME) 912 { 913 prop_value_t *val = get_value (op0, true); 914 if (val->lattice_val == CONSTANT) 915 op0 = val->value; 916 } 917 918 if (TREE_CODE (op1) == SSA_NAME) 919 { 920 prop_value_t *val = get_value (op1, true); 921 if (val->lattice_val == CONSTANT) 922 op1 = val->value; 923 } 924 925 return fold_binary (code, TREE_TYPE (rhs), op0, op1); 926 } 927 928 /* We may be able to fold away calls to builtin functions if their 929 arguments are constants. */ 930 else if (code == CALL_EXPR 931 && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR 932 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)) 933 == FUNCTION_DECL) 934 && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))) 935 { 936 if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_USE)) 937 { 938 tree *orig, var; 939 tree fndecl, arglist; 940 size_t i = 0; 941 ssa_op_iter iter; 942 use_operand_p var_p; 943 944 /* Preserve the original values of every operand. */ 945 orig = XNEWVEC (tree, NUM_SSA_OPERANDS (stmt, SSA_OP_USE)); 946 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE) 947 orig[i++] = var; 948 949 /* Substitute operands with their values and try to fold. */ 950 replace_uses_in (stmt, NULL, const_val); 951 fndecl = get_callee_fndecl (rhs); 952 arglist = TREE_OPERAND (rhs, 1); 953 retval = fold_builtin (fndecl, arglist, false); 954 955 /* Restore operands to their original form. */ 956 i = 0; 957 FOR_EACH_SSA_USE_OPERAND (var_p, stmt, iter, SSA_OP_USE) 958 SET_USE (var_p, orig[i++]); 959 free (orig); 960 } 961 } 962 else 963 return rhs; 964 965 /* If we got a simplified form, see if we need to convert its type. */ 966 if (retval) 967 return fold_convert (TREE_TYPE (rhs), retval); 968 969 /* No simplification was possible. */ 970 return rhs; 971} 972 973 974/* Return the tree representing the element referenced by T if T is an 975 ARRAY_REF or COMPONENT_REF into constant aggregates. Return 976 NULL_TREE otherwise. */ 977 978static tree 979fold_const_aggregate_ref (tree t) 980{ 981 prop_value_t *value; 982 tree base, ctor, idx, field; 983 unsigned HOST_WIDE_INT cnt; 984 tree cfield, cval; 985 986 switch (TREE_CODE (t)) 987 { 988 case ARRAY_REF: 989 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its 990 DECL_INITIAL. If BASE is a nested reference into another 991 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve 992 the inner reference. */ 993 base = TREE_OPERAND (t, 0); 994 switch (TREE_CODE (base)) 995 { 996 case VAR_DECL: 997 if (!TREE_READONLY (base) 998 || TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE 999 || !targetm.binds_local_p (base)) 1000 return NULL_TREE; 1001 1002 ctor = DECL_INITIAL (base); 1003 break; 1004 1005 case ARRAY_REF: 1006 case COMPONENT_REF: 1007 ctor = fold_const_aggregate_ref (base); 1008 break; 1009 1010 default: 1011 return NULL_TREE; 1012 } 1013 1014 if (ctor == NULL_TREE 1015 || (TREE_CODE (ctor) != CONSTRUCTOR 1016 && TREE_CODE (ctor) != STRING_CST) 1017 || !TREE_STATIC (ctor)) 1018 return NULL_TREE; 1019 1020 /* Get the index. If we have an SSA_NAME, try to resolve it 1021 with the current lattice value for the SSA_NAME. */ 1022 idx = TREE_OPERAND (t, 1); 1023 switch (TREE_CODE (idx)) 1024 { 1025 case SSA_NAME: 1026 if ((value = get_value (idx, true)) 1027 && value->lattice_val == CONSTANT 1028 && TREE_CODE (value->value) == INTEGER_CST) 1029 idx = value->value; 1030 else 1031 return NULL_TREE; 1032 break; 1033 1034 case INTEGER_CST: 1035 break; 1036 1037 default: 1038 return NULL_TREE; 1039 } 1040 1041 /* Fold read from constant string. */ 1042 if (TREE_CODE (ctor) == STRING_CST) 1043 { 1044 if ((TYPE_MODE (TREE_TYPE (t)) 1045 == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) 1046 && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) 1047 == MODE_INT) 1048 && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1 1049 && compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0) 1050 return build_int_cst (TREE_TYPE (t), (TREE_STRING_POINTER (ctor) 1051 [TREE_INT_CST_LOW (idx)])); 1052 return NULL_TREE; 1053 } 1054 1055 /* Whoo-hoo! I'll fold ya baby. Yeah! */ 1056 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval) 1057 if (tree_int_cst_equal (cfield, idx)) 1058 return cval; 1059 break; 1060 1061 case COMPONENT_REF: 1062 /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its 1063 DECL_INITIAL. If BASE is a nested reference into another 1064 ARRAY_REF or COMPONENT_REF, make a recursive call to resolve 1065 the inner reference. */ 1066 base = TREE_OPERAND (t, 0); 1067 switch (TREE_CODE (base)) 1068 { 1069 case VAR_DECL: 1070 if (!TREE_READONLY (base) 1071 || TREE_CODE (TREE_TYPE (base)) != RECORD_TYPE 1072 || !targetm.binds_local_p (base)) 1073 return NULL_TREE; 1074 1075 ctor = DECL_INITIAL (base); 1076 break; 1077 1078 case ARRAY_REF: 1079 case COMPONENT_REF: 1080 ctor = fold_const_aggregate_ref (base); 1081 break; 1082 1083 default: 1084 return NULL_TREE; 1085 } 1086 1087 if (ctor == NULL_TREE 1088 || TREE_CODE (ctor) != CONSTRUCTOR 1089 || !TREE_STATIC (ctor)) 1090 return NULL_TREE; 1091 1092 field = TREE_OPERAND (t, 1); 1093 1094 FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval) 1095 if (cfield == field 1096 /* FIXME: Handle bit-fields. */ 1097 && ! DECL_BIT_FIELD (cfield)) 1098 return cval; 1099 break; 1100 1101 case REALPART_EXPR: 1102 case IMAGPART_EXPR: 1103 { 1104 tree c = fold_const_aggregate_ref (TREE_OPERAND (t, 0)); 1105 if (c && TREE_CODE (c) == COMPLEX_CST) 1106 return fold_build1 (TREE_CODE (t), TREE_TYPE (t), c); 1107 break; 1108 } 1109 1110 default: 1111 break; 1112 } 1113 1114 return NULL_TREE; 1115} 1116 1117/* Evaluate statement STMT. */ 1118 1119static prop_value_t 1120evaluate_stmt (tree stmt) 1121{ 1122 prop_value_t val; 1123 tree simplified = NULL_TREE; 1124 ccp_lattice_t likelyvalue = likely_value (stmt); 1125 bool is_constant; 1126 1127 val.mem_ref = NULL_TREE; 1128 1129 fold_defer_overflow_warnings (); 1130 1131 /* If the statement is likely to have a CONSTANT result, then try 1132 to fold the statement to determine the constant value. */ 1133 if (likelyvalue == CONSTANT) 1134 simplified = ccp_fold (stmt); 1135 /* If the statement is likely to have a VARYING result, then do not 1136 bother folding the statement. */ 1137 if (likelyvalue == VARYING) 1138 simplified = get_rhs (stmt); 1139 /* If the statement is an ARRAY_REF or COMPONENT_REF into constant 1140 aggregates, extract the referenced constant. Otherwise the 1141 statement is likely to have an UNDEFINED value, and there will be 1142 nothing to do. Note that fold_const_aggregate_ref returns 1143 NULL_TREE if the first case does not match. */ 1144 else if (!simplified) 1145 simplified = fold_const_aggregate_ref (get_rhs (stmt)); 1146 1147 is_constant = simplified && is_gimple_min_invariant (simplified); 1148 1149 fold_undefer_overflow_warnings (is_constant, stmt, 0); 1150 1151 if (is_constant) 1152 { 1153 /* The statement produced a constant value. */ 1154 val.lattice_val = CONSTANT; 1155 val.value = simplified; 1156 } 1157 else 1158 { 1159 /* The statement produced a nonconstant value. If the statement 1160 had UNDEFINED operands, then the result of the statement 1161 should be UNDEFINED. Otherwise, the statement is VARYING. */ 1162 if (likelyvalue == UNDEFINED || likelyvalue == UNKNOWN_VAL) 1163 val.lattice_val = likelyvalue; 1164 else 1165 val.lattice_val = VARYING; 1166 1167 val.value = NULL_TREE; 1168 } 1169 1170 return val; 1171} 1172 1173 1174/* Visit the assignment statement STMT. Set the value of its LHS to the 1175 value computed by the RHS and store LHS in *OUTPUT_P. If STMT 1176 creates virtual definitions, set the value of each new name to that 1177 of the RHS (if we can derive a constant out of the RHS). */ 1178 1179static enum ssa_prop_result 1180visit_assignment (tree stmt, tree *output_p) 1181{ 1182 prop_value_t val; 1183 tree lhs, rhs; 1184 enum ssa_prop_result retval; 1185 1186 lhs = TREE_OPERAND (stmt, 0); 1187 rhs = TREE_OPERAND (stmt, 1); 1188 1189 if (TREE_CODE (rhs) == SSA_NAME) 1190 { 1191 /* For a simple copy operation, we copy the lattice values. */ 1192 prop_value_t *nval = get_value (rhs, true); 1193 val = *nval; 1194 } 1195 else if (do_store_ccp && stmt_makes_single_load (stmt)) 1196 { 1197 /* Same as above, but the RHS is not a gimple register and yet 1198 has a known VUSE. If STMT is loading from the same memory 1199 location that created the SSA_NAMEs for the virtual operands, 1200 we can propagate the value on the RHS. */ 1201 prop_value_t *nval = get_value_loaded_by (stmt, const_val); 1202 1203 if (nval && nval->mem_ref 1204 && operand_equal_p (nval->mem_ref, rhs, 0)) 1205 val = *nval; 1206 else 1207 val = evaluate_stmt (stmt); 1208 } 1209 else 1210 /* Evaluate the statement. */ 1211 val = evaluate_stmt (stmt); 1212 1213 /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant 1214 value to be a VIEW_CONVERT_EXPR of the old constant value. 1215 1216 ??? Also, if this was a definition of a bitfield, we need to widen 1217 the constant value into the type of the destination variable. This 1218 should not be necessary if GCC represented bitfields properly. */ 1219 { 1220 tree orig_lhs = TREE_OPERAND (stmt, 0); 1221 1222 if (TREE_CODE (orig_lhs) == VIEW_CONVERT_EXPR 1223 && val.lattice_val == CONSTANT) 1224 { 1225 tree w = fold_unary (VIEW_CONVERT_EXPR, 1226 TREE_TYPE (TREE_OPERAND (orig_lhs, 0)), 1227 val.value); 1228 1229 orig_lhs = TREE_OPERAND (orig_lhs, 0); 1230 if (w && is_gimple_min_invariant (w)) 1231 val.value = w; 1232 else 1233 { 1234 val.lattice_val = VARYING; 1235 val.value = NULL; 1236 } 1237 } 1238 1239 if (val.lattice_val == CONSTANT 1240 && TREE_CODE (orig_lhs) == COMPONENT_REF 1241 && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs, 1))) 1242 { 1243 tree w = widen_bitfield (val.value, TREE_OPERAND (orig_lhs, 1), 1244 orig_lhs); 1245 1246 if (w && is_gimple_min_invariant (w)) 1247 val.value = w; 1248 else 1249 { 1250 val.lattice_val = VARYING; 1251 val.value = NULL_TREE; 1252 val.mem_ref = NULL_TREE; 1253 } 1254 } 1255 } 1256 1257 retval = SSA_PROP_NOT_INTERESTING; 1258 1259 /* Set the lattice value of the statement's output. */ 1260 if (TREE_CODE (lhs) == SSA_NAME) 1261 { 1262 /* If STMT is an assignment to an SSA_NAME, we only have one 1263 value to set. */ 1264 if (set_lattice_value (lhs, val)) 1265 { 1266 *output_p = lhs; 1267 if (val.lattice_val == VARYING) 1268 retval = SSA_PROP_VARYING; 1269 else 1270 retval = SSA_PROP_INTERESTING; 1271 } 1272 } 1273 else if (do_store_ccp && stmt_makes_single_store (stmt)) 1274 { 1275 /* Otherwise, set the names in V_MAY_DEF/V_MUST_DEF operands 1276 to the new constant value and mark the LHS as the memory 1277 reference associated with VAL. */ 1278 ssa_op_iter i; 1279 tree vdef; 1280 bool changed; 1281 1282 /* Stores cannot take on an UNDEFINED value. */ 1283 if (val.lattice_val == UNDEFINED) 1284 val.lattice_val = UNKNOWN_VAL; 1285 1286 /* Mark VAL as stored in the LHS of this assignment. */ 1287 val.mem_ref = lhs; 1288 1289 /* Set the value of every VDEF to VAL. */ 1290 changed = false; 1291 FOR_EACH_SSA_TREE_OPERAND (vdef, stmt, i, SSA_OP_VIRTUAL_DEFS) 1292 changed |= set_lattice_value (vdef, val); 1293 1294 /* Note that for propagation purposes, we are only interested in 1295 visiting statements that load the exact same memory reference 1296 stored here. Those statements will have the exact same list 1297 of virtual uses, so it is enough to set the output of this 1298 statement to be its first virtual definition. */ 1299 *output_p = first_vdef (stmt); 1300 if (changed) 1301 { 1302 if (val.lattice_val == VARYING) 1303 retval = SSA_PROP_VARYING; 1304 else 1305 retval = SSA_PROP_INTERESTING; 1306 } 1307 } 1308 1309 return retval; 1310} 1311 1312 1313/* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING 1314 if it can determine which edge will be taken. Otherwise, return 1315 SSA_PROP_VARYING. */ 1316 1317static enum ssa_prop_result 1318visit_cond_stmt (tree stmt, edge *taken_edge_p) 1319{ 1320 prop_value_t val; 1321 basic_block block; 1322 1323 block = bb_for_stmt (stmt); 1324 val = evaluate_stmt (stmt); 1325 1326 /* Find which edge out of the conditional block will be taken and add it 1327 to the worklist. If no single edge can be determined statically, 1328 return SSA_PROP_VARYING to feed all the outgoing edges to the 1329 propagation engine. */ 1330 *taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0; 1331 if (*taken_edge_p) 1332 return SSA_PROP_INTERESTING; 1333 else 1334 return SSA_PROP_VARYING; 1335} 1336 1337 1338/* Evaluate statement STMT. If the statement produces an output value and 1339 its evaluation changes the lattice value of its output, return 1340 SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the 1341 output value. 1342 1343 If STMT is a conditional branch and we can determine its truth 1344 value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying 1345 value, return SSA_PROP_VARYING. */ 1346 1347static enum ssa_prop_result 1348ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p) 1349{ 1350 tree def; 1351 ssa_op_iter iter; 1352 1353 if (dump_file && (dump_flags & TDF_DETAILS)) 1354 { 1355 fprintf (dump_file, "\nVisiting statement:\n"); 1356 print_generic_stmt (dump_file, stmt, dump_flags); 1357 fprintf (dump_file, "\n"); 1358 } 1359 1360 if (TREE_CODE (stmt) == MODIFY_EXPR) 1361 { 1362 /* If the statement is an assignment that produces a single 1363 output value, evaluate its RHS to see if the lattice value of 1364 its output has changed. */ 1365 return visit_assignment (stmt, output_p); 1366 } 1367 else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR) 1368 { 1369 /* If STMT is a conditional branch, see if we can determine 1370 which branch will be taken. */ 1371 return visit_cond_stmt (stmt, taken_edge_p); 1372 } 1373 1374 /* Any other kind of statement is not interesting for constant 1375 propagation and, therefore, not worth simulating. */ 1376 if (dump_file && (dump_flags & TDF_DETAILS)) 1377 fprintf (dump_file, "No interesting values produced. Marked VARYING.\n"); 1378 1379 /* Definitions made by statements other than assignments to 1380 SSA_NAMEs represent unknown modifications to their outputs. 1381 Mark them VARYING. */ 1382 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) 1383 { 1384 prop_value_t v = { VARYING, NULL_TREE, NULL_TREE }; 1385 set_lattice_value (def, v); 1386 } 1387 1388 return SSA_PROP_VARYING; 1389} 1390 1391 1392/* Main entry point for SSA Conditional Constant Propagation. */ 1393 1394static void 1395execute_ssa_ccp (bool store_ccp) 1396{ 1397 do_store_ccp = store_ccp; 1398 ccp_initialize (); 1399 ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node); 1400 ccp_finalize (); 1401} 1402 1403 1404static unsigned int 1405do_ssa_ccp (void) 1406{ 1407 execute_ssa_ccp (false); 1408 return 0; 1409} 1410 1411 1412static bool 1413gate_ccp (void) 1414{ 1415 return flag_tree_ccp != 0; 1416} 1417 1418 1419struct tree_opt_pass pass_ccp = 1420{ 1421 "ccp", /* name */ 1422 gate_ccp, /* gate */ 1423 do_ssa_ccp, /* execute */ 1424 NULL, /* sub */ 1425 NULL, /* next */ 1426 0, /* static_pass_number */ 1427 TV_TREE_CCP, /* tv_id */ 1428 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ 1429 0, /* properties_provided */ 1430 PROP_smt_usage, /* properties_destroyed */ 1431 0, /* todo_flags_start */ 1432 TODO_cleanup_cfg | TODO_dump_func | TODO_update_ssa 1433 | TODO_ggc_collect | TODO_verify_ssa 1434 | TODO_verify_stmts | TODO_update_smt_usage, /* todo_flags_finish */ 1435 0 /* letter */ 1436}; 1437 1438 1439static unsigned int 1440do_ssa_store_ccp (void) 1441{ 1442 /* If STORE-CCP is not enabled, we just run regular CCP. */ 1443 execute_ssa_ccp (flag_tree_store_ccp != 0); 1444 return 0; 1445} 1446 1447static bool 1448gate_store_ccp (void) 1449{ 1450 /* STORE-CCP is enabled only with -ftree-store-ccp, but when 1451 -fno-tree-store-ccp is specified, we should run regular CCP. 1452 That's why the pass is enabled with either flag. */ 1453 return flag_tree_store_ccp != 0 || flag_tree_ccp != 0; 1454} 1455 1456 1457struct tree_opt_pass pass_store_ccp = 1458{ 1459 "store_ccp", /* name */ 1460 gate_store_ccp, /* gate */ 1461 do_ssa_store_ccp, /* execute */ 1462 NULL, /* sub */ 1463 NULL, /* next */ 1464 0, /* static_pass_number */ 1465 TV_TREE_STORE_CCP, /* tv_id */ 1466 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ 1467 0, /* properties_provided */ 1468 PROP_smt_usage, /* properties_destroyed */ 1469 0, /* todo_flags_start */ 1470 TODO_dump_func | TODO_update_ssa 1471 | TODO_ggc_collect | TODO_verify_ssa 1472 | TODO_cleanup_cfg 1473 | TODO_verify_stmts | TODO_update_smt_usage, /* todo_flags_finish */ 1474 0 /* letter */ 1475}; 1476 1477/* Given a constant value VAL for bitfield FIELD, and a destination 1478 variable VAR, return VAL appropriately widened to fit into VAR. If 1479 FIELD is wider than HOST_WIDE_INT, NULL is returned. */ 1480 1481tree 1482widen_bitfield (tree val, tree field, tree var) 1483{ 1484 unsigned HOST_WIDE_INT var_size, field_size; 1485 tree wide_val; 1486 unsigned HOST_WIDE_INT mask; 1487 unsigned int i; 1488 1489 /* We can only do this if the size of the type and field and VAL are 1490 all constants representable in HOST_WIDE_INT. */ 1491 if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1) 1492 || !host_integerp (DECL_SIZE (field), 1) 1493 || !host_integerp (val, 0)) 1494 return NULL_TREE; 1495 1496 var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1); 1497 field_size = tree_low_cst (DECL_SIZE (field), 1); 1498 1499 /* Give up if either the bitfield or the variable are too wide. */ 1500 if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT) 1501 return NULL_TREE; 1502 1503 gcc_assert (var_size >= field_size); 1504 1505 /* If the sign bit of the value is not set or the field's type is unsigned, 1506 just mask off the high order bits of the value. */ 1507 if (DECL_UNSIGNED (field) 1508 || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1)))) 1509 { 1510 /* Zero extension. Build a mask with the lower 'field_size' bits 1511 set and a BIT_AND_EXPR node to clear the high order bits of 1512 the value. */ 1513 for (i = 0, mask = 0; i < field_size; i++) 1514 mask |= ((HOST_WIDE_INT) 1) << i; 1515 1516 wide_val = fold_build2 (BIT_AND_EXPR, TREE_TYPE (var), val, 1517 build_int_cst (TREE_TYPE (var), mask)); 1518 } 1519 else 1520 { 1521 /* Sign extension. Create a mask with the upper 'field_size' 1522 bits set and a BIT_IOR_EXPR to set the high order bits of the 1523 value. */ 1524 for (i = 0, mask = 0; i < (var_size - field_size); i++) 1525 mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1); 1526 1527 wide_val = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (var), val, 1528 build_int_cst (TREE_TYPE (var), mask)); 1529 } 1530 1531 return wide_val; 1532} 1533 1534 1535/* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X]. 1536 BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE 1537 is the desired result type. */ 1538 1539static tree 1540maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type) 1541{ 1542 tree min_idx, idx, elt_offset = integer_zero_node; 1543 tree array_type, elt_type, elt_size; 1544 1545 /* If BASE is an ARRAY_REF, we can pick up another offset (this time 1546 measured in units of the size of elements type) from that ARRAY_REF). 1547 We can't do anything if either is variable. 1548 1549 The case we handle here is *(&A[N]+O). */ 1550 if (TREE_CODE (base) == ARRAY_REF) 1551 { 1552 tree low_bound = array_ref_low_bound (base); 1553 1554 elt_offset = TREE_OPERAND (base, 1); 1555 if (TREE_CODE (low_bound) != INTEGER_CST 1556 || TREE_CODE (elt_offset) != INTEGER_CST) 1557 return NULL_TREE; 1558 1559 elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0); 1560 base = TREE_OPERAND (base, 0); 1561 } 1562 1563 /* Ignore stupid user tricks of indexing non-array variables. */ 1564 array_type = TREE_TYPE (base); 1565 if (TREE_CODE (array_type) != ARRAY_TYPE) 1566 return NULL_TREE; 1567 elt_type = TREE_TYPE (array_type); 1568 if (!lang_hooks.types_compatible_p (orig_type, elt_type)) 1569 return NULL_TREE; 1570 1571 /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the 1572 element type (so we can use the alignment if it's not constant). 1573 Otherwise, compute the offset as an index by using a division. If the 1574 division isn't exact, then don't do anything. */ 1575 elt_size = TYPE_SIZE_UNIT (elt_type); 1576 if (integer_zerop (offset)) 1577 { 1578 if (TREE_CODE (elt_size) != INTEGER_CST) 1579 elt_size = size_int (TYPE_ALIGN (elt_type)); 1580 1581 idx = integer_zero_node; 1582 } 1583 else 1584 { 1585 unsigned HOST_WIDE_INT lquo, lrem; 1586 HOST_WIDE_INT hquo, hrem; 1587 1588 if (TREE_CODE (elt_size) != INTEGER_CST 1589 || div_and_round_double (TRUNC_DIV_EXPR, 1, 1590 TREE_INT_CST_LOW (offset), 1591 TREE_INT_CST_HIGH (offset), 1592 TREE_INT_CST_LOW (elt_size), 1593 TREE_INT_CST_HIGH (elt_size), 1594 &lquo, &hquo, &lrem, &hrem) 1595 || lrem || hrem) 1596 return NULL_TREE; 1597 1598 idx = build_int_cst_wide (NULL_TREE, lquo, hquo); 1599 } 1600 1601 /* Assume the low bound is zero. If there is a domain type, get the 1602 low bound, if any, convert the index into that type, and add the 1603 low bound. */ 1604 min_idx = integer_zero_node; 1605 if (TYPE_DOMAIN (array_type)) 1606 { 1607 if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type))) 1608 min_idx = TYPE_MIN_VALUE (TYPE_DOMAIN (array_type)); 1609 else 1610 min_idx = fold_convert (TYPE_DOMAIN (array_type), min_idx); 1611 1612 if (TREE_CODE (min_idx) != INTEGER_CST) 1613 return NULL_TREE; 1614 1615 idx = fold_convert (TYPE_DOMAIN (array_type), idx); 1616 elt_offset = fold_convert (TYPE_DOMAIN (array_type), elt_offset); 1617 } 1618 1619 if (!integer_zerop (min_idx)) 1620 idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0); 1621 if (!integer_zerop (elt_offset)) 1622 idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0); 1623 1624 return build4 (ARRAY_REF, orig_type, base, idx, NULL_TREE, NULL_TREE); 1625} 1626 1627 1628/* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X. 1629 BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE 1630 is the desired result type. */ 1631/* ??? This doesn't handle class inheritance. */ 1632 1633static tree 1634maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset, 1635 tree orig_type, bool base_is_ptr) 1636{ 1637 tree f, t, field_type, tail_array_field, field_offset; 1638 1639 if (TREE_CODE (record_type) != RECORD_TYPE 1640 && TREE_CODE (record_type) != UNION_TYPE 1641 && TREE_CODE (record_type) != QUAL_UNION_TYPE) 1642 return NULL_TREE; 1643 1644 /* Short-circuit silly cases. */ 1645 if (lang_hooks.types_compatible_p (record_type, orig_type)) 1646 return NULL_TREE; 1647 1648 tail_array_field = NULL_TREE; 1649 for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f)) 1650 { 1651 int cmp; 1652 1653 if (TREE_CODE (f) != FIELD_DECL) 1654 continue; 1655 if (DECL_BIT_FIELD (f)) 1656 continue; 1657 1658 field_offset = byte_position (f); 1659 if (TREE_CODE (field_offset) != INTEGER_CST) 1660 continue; 1661 1662 /* ??? Java creates "interesting" fields for representing base classes. 1663 They have no name, and have no context. With no context, we get into 1664 trouble with nonoverlapping_component_refs_p. Skip them. */ 1665 if (!DECL_FIELD_CONTEXT (f)) 1666 continue; 1667 1668 /* The previous array field isn't at the end. */ 1669 tail_array_field = NULL_TREE; 1670 1671 /* Check to see if this offset overlaps with the field. */ 1672 cmp = tree_int_cst_compare (field_offset, offset); 1673 if (cmp > 0) 1674 continue; 1675 1676 field_type = TREE_TYPE (f); 1677 1678 /* Here we exactly match the offset being checked. If the types match, 1679 then we can return that field. */ 1680 if (cmp == 0 1681 && lang_hooks.types_compatible_p (orig_type, field_type)) 1682 { 1683 if (base_is_ptr) 1684 base = build1 (INDIRECT_REF, record_type, base); 1685 t = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE); 1686 return t; 1687 } 1688 1689 /* Don't care about offsets into the middle of scalars. */ 1690 if (!AGGREGATE_TYPE_P (field_type)) 1691 continue; 1692 1693 /* Check for array at the end of the struct. This is often 1694 used as for flexible array members. We should be able to 1695 turn this into an array access anyway. */ 1696 if (TREE_CODE (field_type) == ARRAY_TYPE) 1697 tail_array_field = f; 1698 1699 /* Check the end of the field against the offset. */ 1700 if (!DECL_SIZE_UNIT (f) 1701 || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST) 1702 continue; 1703 t = int_const_binop (MINUS_EXPR, offset, field_offset, 1); 1704 if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f))) 1705 continue; 1706 1707 /* If we matched, then set offset to the displacement into 1708 this field. */ 1709 offset = t; 1710 goto found; 1711 } 1712 1713 if (!tail_array_field) 1714 return NULL_TREE; 1715 1716 f = tail_array_field; 1717 field_type = TREE_TYPE (f); 1718 offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1); 1719 1720 found: 1721 /* If we get here, we've got an aggregate field, and a possibly 1722 nonzero offset into them. Recurse and hope for a valid match. */ 1723 if (base_is_ptr) 1724 base = build1 (INDIRECT_REF, record_type, base); 1725 base = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE); 1726 1727 t = maybe_fold_offset_to_array_ref (base, offset, orig_type); 1728 if (t) 1729 return t; 1730 return maybe_fold_offset_to_component_ref (field_type, base, offset, 1731 orig_type, false); 1732} 1733 1734 1735/* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET). 1736 Return the simplified expression, or NULL if nothing could be done. */ 1737 1738static tree 1739maybe_fold_stmt_indirect (tree expr, tree base, tree offset) 1740{ 1741 tree t; 1742 1743 /* We may well have constructed a double-nested PLUS_EXPR via multiple 1744 substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that 1745 are sometimes added. */ 1746 base = fold (base); 1747 STRIP_TYPE_NOPS (base); 1748 TREE_OPERAND (expr, 0) = base; 1749 1750 /* One possibility is that the address reduces to a string constant. */ 1751 t = fold_read_from_constant_string (expr); 1752 if (t) 1753 return t; 1754 1755 /* Add in any offset from a PLUS_EXPR. */ 1756 if (TREE_CODE (base) == PLUS_EXPR) 1757 { 1758 tree offset2; 1759 1760 offset2 = TREE_OPERAND (base, 1); 1761 if (TREE_CODE (offset2) != INTEGER_CST) 1762 return NULL_TREE; 1763 base = TREE_OPERAND (base, 0); 1764 1765 offset = int_const_binop (PLUS_EXPR, offset, offset2, 1); 1766 } 1767 1768 if (TREE_CODE (base) == ADDR_EXPR) 1769 { 1770 /* Strip the ADDR_EXPR. */ 1771 base = TREE_OPERAND (base, 0); 1772 1773 /* Fold away CONST_DECL to its value, if the type is scalar. */ 1774 if (TREE_CODE (base) == CONST_DECL 1775 && ccp_decl_initial_min_invariant (DECL_INITIAL (base))) 1776 return DECL_INITIAL (base); 1777 1778 /* Try folding *(&B+O) to B[X]. */ 1779 t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr)); 1780 if (t) 1781 return t; 1782 1783 /* Try folding *(&B+O) to B.X. */ 1784 t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset, 1785 TREE_TYPE (expr), false); 1786 if (t) 1787 return t; 1788 1789 /* Fold *&B to B. We can only do this if EXPR is the same type 1790 as BASE. We can't do this if EXPR is the element type of an array 1791 and BASE is the array. */ 1792 if (integer_zerop (offset) 1793 && lang_hooks.types_compatible_p (TREE_TYPE (base), 1794 TREE_TYPE (expr))) 1795 return base; 1796 } 1797 else 1798 { 1799 /* We can get here for out-of-range string constant accesses, 1800 such as "_"[3]. Bail out of the entire substitution search 1801 and arrange for the entire statement to be replaced by a 1802 call to __builtin_trap. In all likelihood this will all be 1803 constant-folded away, but in the meantime we can't leave with 1804 something that get_expr_operands can't understand. */ 1805 1806 t = base; 1807 STRIP_NOPS (t); 1808 if (TREE_CODE (t) == ADDR_EXPR 1809 && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST) 1810 { 1811 /* FIXME: Except that this causes problems elsewhere with dead 1812 code not being deleted, and we die in the rtl expanders 1813 because we failed to remove some ssa_name. In the meantime, 1814 just return zero. */ 1815 /* FIXME2: This condition should be signaled by 1816 fold_read_from_constant_string directly, rather than 1817 re-checking for it here. */ 1818 return integer_zero_node; 1819 } 1820 1821 /* Try folding *(B+O) to B->X. Still an improvement. */ 1822 if (POINTER_TYPE_P (TREE_TYPE (base))) 1823 { 1824 t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)), 1825 base, offset, 1826 TREE_TYPE (expr), true); 1827 if (t) 1828 return t; 1829 } 1830 } 1831 1832 /* Otherwise we had an offset that we could not simplify. */ 1833 return NULL_TREE; 1834} 1835 1836 1837/* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR. 1838 1839 A quaint feature extant in our address arithmetic is that there 1840 can be hidden type changes here. The type of the result need 1841 not be the same as the type of the input pointer. 1842 1843 What we're after here is an expression of the form 1844 (T *)(&array + const) 1845 where the cast doesn't actually exist, but is implicit in the 1846 type of the PLUS_EXPR. We'd like to turn this into 1847 &array[x] 1848 which may be able to propagate further. */ 1849 1850static tree 1851maybe_fold_stmt_addition (tree expr) 1852{ 1853 tree op0 = TREE_OPERAND (expr, 0); 1854 tree op1 = TREE_OPERAND (expr, 1); 1855 tree ptr_type = TREE_TYPE (expr); 1856 tree ptd_type; 1857 tree t; 1858 bool subtract = (TREE_CODE (expr) == MINUS_EXPR); 1859 1860 /* We're only interested in pointer arithmetic. */ 1861 if (!POINTER_TYPE_P (ptr_type)) 1862 return NULL_TREE; 1863 /* Canonicalize the integral operand to op1. */ 1864 if (INTEGRAL_TYPE_P (TREE_TYPE (op0))) 1865 { 1866 if (subtract) 1867 return NULL_TREE; 1868 t = op0, op0 = op1, op1 = t; 1869 } 1870 /* It had better be a constant. */ 1871 if (TREE_CODE (op1) != INTEGER_CST) 1872 return NULL_TREE; 1873 /* The first operand should be an ADDR_EXPR. */ 1874 if (TREE_CODE (op0) != ADDR_EXPR) 1875 return NULL_TREE; 1876 op0 = TREE_OPERAND (op0, 0); 1877 1878 /* If the first operand is an ARRAY_REF, expand it so that we can fold 1879 the offset into it. */ 1880 while (TREE_CODE (op0) == ARRAY_REF) 1881 { 1882 tree array_obj = TREE_OPERAND (op0, 0); 1883 tree array_idx = TREE_OPERAND (op0, 1); 1884 tree elt_type = TREE_TYPE (op0); 1885 tree elt_size = TYPE_SIZE_UNIT (elt_type); 1886 tree min_idx; 1887 1888 if (TREE_CODE (array_idx) != INTEGER_CST) 1889 break; 1890 if (TREE_CODE (elt_size) != INTEGER_CST) 1891 break; 1892 1893 /* Un-bias the index by the min index of the array type. */ 1894 min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj)); 1895 if (min_idx) 1896 { 1897 min_idx = TYPE_MIN_VALUE (min_idx); 1898 if (min_idx) 1899 { 1900 if (TREE_CODE (min_idx) != INTEGER_CST) 1901 break; 1902 1903 array_idx = fold_convert (TREE_TYPE (min_idx), array_idx); 1904 if (!integer_zerop (min_idx)) 1905 array_idx = int_const_binop (MINUS_EXPR, array_idx, 1906 min_idx, 0); 1907 } 1908 } 1909 1910 /* Convert the index to a byte offset. */ 1911 array_idx = fold_convert (sizetype, array_idx); 1912 array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0); 1913 1914 /* Update the operands for the next round, or for folding. */ 1915 /* If we're manipulating unsigned types, then folding into negative 1916 values can produce incorrect results. Particularly if the type 1917 is smaller than the width of the pointer. */ 1918 if (subtract 1919 && TYPE_UNSIGNED (TREE_TYPE (op1)) 1920 && tree_int_cst_lt (array_idx, op1)) 1921 return NULL; 1922 op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR, 1923 array_idx, op1, 0); 1924 subtract = false; 1925 op0 = array_obj; 1926 } 1927 1928 /* If we weren't able to fold the subtraction into another array reference, 1929 canonicalize the integer for passing to the array and component ref 1930 simplification functions. */ 1931 if (subtract) 1932 { 1933 if (TYPE_UNSIGNED (TREE_TYPE (op1))) 1934 return NULL; 1935 op1 = fold_unary (NEGATE_EXPR, TREE_TYPE (op1), op1); 1936 /* ??? In theory fold should always produce another integer. */ 1937 if (op1 == NULL || TREE_CODE (op1) != INTEGER_CST) 1938 return NULL; 1939 } 1940 1941 ptd_type = TREE_TYPE (ptr_type); 1942 1943 /* At which point we can try some of the same things as for indirects. */ 1944 t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type); 1945 if (!t) 1946 t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1, 1947 ptd_type, false); 1948 if (t) 1949 t = build1 (ADDR_EXPR, ptr_type, t); 1950 1951 return t; 1952} 1953 1954/* For passing state through walk_tree into fold_stmt_r and its 1955 children. */ 1956 1957struct fold_stmt_r_data 1958{ 1959 tree stmt; 1960 bool *changed_p; 1961 bool *inside_addr_expr_p; 1962}; 1963 1964/* Subroutine of fold_stmt called via walk_tree. We perform several 1965 simplifications of EXPR_P, mostly having to do with pointer arithmetic. */ 1966 1967static tree 1968fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data) 1969{ 1970 struct fold_stmt_r_data *fold_stmt_r_data = (struct fold_stmt_r_data *) data; 1971 bool *inside_addr_expr_p = fold_stmt_r_data->inside_addr_expr_p; 1972 bool *changed_p = fold_stmt_r_data->changed_p; 1973 tree expr = *expr_p, t; 1974 1975 /* ??? It'd be nice if walk_tree had a pre-order option. */ 1976 switch (TREE_CODE (expr)) 1977 { 1978 case INDIRECT_REF: 1979 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); 1980 if (t) 1981 return t; 1982 *walk_subtrees = 0; 1983 1984 t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0), 1985 integer_zero_node); 1986 break; 1987 1988 /* ??? Could handle more ARRAY_REFs here, as a variant of INDIRECT_REF. 1989 We'd only want to bother decomposing an existing ARRAY_REF if 1990 the base array is found to have another offset contained within. 1991 Otherwise we'd be wasting time. */ 1992 case ARRAY_REF: 1993 /* If we are not processing expressions found within an 1994 ADDR_EXPR, then we can fold constant array references. */ 1995 if (!*inside_addr_expr_p) 1996 t = fold_read_from_constant_string (expr); 1997 else 1998 t = NULL; 1999 break; 2000 2001 case ADDR_EXPR: 2002 *inside_addr_expr_p = true; 2003 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); 2004 *inside_addr_expr_p = false; 2005 if (t) 2006 return t; 2007 *walk_subtrees = 0; 2008 2009 /* Set TREE_INVARIANT properly so that the value is properly 2010 considered constant, and so gets propagated as expected. */ 2011 if (*changed_p) 2012 recompute_tree_invariant_for_addr_expr (expr); 2013 return NULL_TREE; 2014 2015 case PLUS_EXPR: 2016 case MINUS_EXPR: 2017 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); 2018 if (t) 2019 return t; 2020 t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL); 2021 if (t) 2022 return t; 2023 *walk_subtrees = 0; 2024 2025 t = maybe_fold_stmt_addition (expr); 2026 break; 2027 2028 case COMPONENT_REF: 2029 t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); 2030 if (t) 2031 return t; 2032 *walk_subtrees = 0; 2033 2034 /* Make sure the FIELD_DECL is actually a field in the type on the lhs. 2035 We've already checked that the records are compatible, so we should 2036 come up with a set of compatible fields. */ 2037 { 2038 tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0)); 2039 tree expr_field = TREE_OPERAND (expr, 1); 2040 2041 if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record)) 2042 { 2043 expr_field = find_compatible_field (expr_record, expr_field); 2044 TREE_OPERAND (expr, 1) = expr_field; 2045 } 2046 } 2047 break; 2048 2049 case TARGET_MEM_REF: 2050 t = maybe_fold_tmr (expr); 2051 break; 2052 2053 case COND_EXPR: 2054 if (COMPARISON_CLASS_P (TREE_OPERAND (expr, 0))) 2055 { 2056 tree op0 = TREE_OPERAND (expr, 0); 2057 tree tem; 2058 bool set; 2059 2060 fold_defer_overflow_warnings (); 2061 tem = fold_binary (TREE_CODE (op0), TREE_TYPE (op0), 2062 TREE_OPERAND (op0, 0), 2063 TREE_OPERAND (op0, 1)); 2064 set = tem && is_gimple_condexpr (tem); 2065 fold_undefer_overflow_warnings (set, fold_stmt_r_data->stmt, 0); 2066 if (set) 2067 TREE_OPERAND (expr, 0) = tem; 2068 t = expr; 2069 break; 2070 } 2071 2072 default: 2073 return NULL_TREE; 2074 } 2075 2076 if (t) 2077 { 2078 *expr_p = t; 2079 *changed_p = true; 2080 } 2081 2082 return NULL_TREE; 2083} 2084 2085 2086/* Return the string length, maximum string length or maximum value of 2087 ARG in LENGTH. 2088 If ARG is an SSA name variable, follow its use-def chains. If LENGTH 2089 is not NULL and, for TYPE == 0, its value is not equal to the length 2090 we determine or if we are unable to determine the length or value, 2091 return false. VISITED is a bitmap of visited variables. 2092 TYPE is 0 if string length should be returned, 1 for maximum string 2093 length and 2 for maximum value ARG can have. */ 2094 2095static bool 2096get_maxval_strlen (tree arg, tree *length, bitmap visited, int type) 2097{ 2098 tree var, def_stmt, val; 2099 2100 if (TREE_CODE (arg) != SSA_NAME) 2101 { 2102 if (type == 2) 2103 { 2104 val = arg; 2105 if (TREE_CODE (val) != INTEGER_CST 2106 || tree_int_cst_sgn (val) < 0) 2107 return false; 2108 } 2109 else 2110 val = c_strlen (arg, 1); 2111 if (!val) 2112 return false; 2113 2114 if (*length) 2115 { 2116 if (type > 0) 2117 { 2118 if (TREE_CODE (*length) != INTEGER_CST 2119 || TREE_CODE (val) != INTEGER_CST) 2120 return false; 2121 2122 if (tree_int_cst_lt (*length, val)) 2123 *length = val; 2124 return true; 2125 } 2126 else if (simple_cst_equal (val, *length) != 1) 2127 return false; 2128 } 2129 2130 *length = val; 2131 return true; 2132 } 2133 2134 /* If we were already here, break the infinite cycle. */ 2135 if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg))) 2136 return true; 2137 bitmap_set_bit (visited, SSA_NAME_VERSION (arg)); 2138 2139 var = arg; 2140 def_stmt = SSA_NAME_DEF_STMT (var); 2141 2142 switch (TREE_CODE (def_stmt)) 2143 { 2144 case MODIFY_EXPR: 2145 { 2146 tree rhs; 2147 2148 /* The RHS of the statement defining VAR must either have a 2149 constant length or come from another SSA_NAME with a constant 2150 length. */ 2151 rhs = TREE_OPERAND (def_stmt, 1); 2152 STRIP_NOPS (rhs); 2153 return get_maxval_strlen (rhs, length, visited, type); 2154 } 2155 2156 case PHI_NODE: 2157 { 2158 /* All the arguments of the PHI node must have the same constant 2159 length. */ 2160 int i; 2161 2162 for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) 2163 { 2164 tree arg = PHI_ARG_DEF (def_stmt, i); 2165 2166 /* If this PHI has itself as an argument, we cannot 2167 determine the string length of this argument. However, 2168 if we can find a constant string length for the other 2169 PHI args then we can still be sure that this is a 2170 constant string length. So be optimistic and just 2171 continue with the next argument. */ 2172 if (arg == PHI_RESULT (def_stmt)) 2173 continue; 2174 2175 if (!get_maxval_strlen (arg, length, visited, type)) 2176 return false; 2177 } 2178 2179 return true; 2180 } 2181 2182 default: 2183 break; 2184 } 2185 2186 2187 return false; 2188} 2189 2190 2191/* Fold builtin call FN in statement STMT. If it cannot be folded into a 2192 constant, return NULL_TREE. Otherwise, return its constant value. */ 2193 2194static tree 2195ccp_fold_builtin (tree stmt, tree fn) 2196{ 2197 tree result, val[3]; 2198 tree callee, arglist, a; 2199 int arg_mask, i, type; 2200 bitmap visited; 2201 bool ignore; 2202 2203 ignore = TREE_CODE (stmt) != MODIFY_EXPR; 2204 2205 /* First try the generic builtin folder. If that succeeds, return the 2206 result directly. */ 2207 callee = get_callee_fndecl (fn); 2208 arglist = TREE_OPERAND (fn, 1); 2209 result = fold_builtin (callee, arglist, ignore); 2210 if (result) 2211 { 2212 if (ignore) 2213 STRIP_NOPS (result); 2214 return result; 2215 } 2216 2217 /* Ignore MD builtins. */ 2218 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD) 2219 return NULL_TREE; 2220 2221 /* If the builtin could not be folded, and it has no argument list, 2222 we're done. */ 2223 if (!arglist) 2224 return NULL_TREE; 2225 2226 /* Limit the work only for builtins we know how to simplify. */ 2227 switch (DECL_FUNCTION_CODE (callee)) 2228 { 2229 case BUILT_IN_STRLEN: 2230 case BUILT_IN_FPUTS: 2231 case BUILT_IN_FPUTS_UNLOCKED: 2232 arg_mask = 1; 2233 type = 0; 2234 break; 2235 case BUILT_IN_STRCPY: 2236 case BUILT_IN_STRNCPY: 2237 arg_mask = 2; 2238 type = 0; 2239 break; 2240 case BUILT_IN_MEMCPY_CHK: 2241 case BUILT_IN_MEMPCPY_CHK: 2242 case BUILT_IN_MEMMOVE_CHK: 2243 case BUILT_IN_MEMSET_CHK: 2244 case BUILT_IN_STRNCPY_CHK: 2245 arg_mask = 4; 2246 type = 2; 2247 break; 2248 case BUILT_IN_STRCPY_CHK: 2249 case BUILT_IN_STPCPY_CHK: 2250 arg_mask = 2; 2251 type = 1; 2252 break; 2253 case BUILT_IN_SNPRINTF_CHK: 2254 case BUILT_IN_VSNPRINTF_CHK: 2255 arg_mask = 2; 2256 type = 2; 2257 break; 2258 default: 2259 return NULL_TREE; 2260 } 2261 2262 /* Try to use the dataflow information gathered by the CCP process. */ 2263 visited = BITMAP_ALLOC (NULL); 2264 2265 memset (val, 0, sizeof (val)); 2266 for (i = 0, a = arglist; 2267 arg_mask; 2268 i++, arg_mask >>= 1, a = TREE_CHAIN (a)) 2269 if (arg_mask & 1) 2270 { 2271 bitmap_clear (visited); 2272 if (!get_maxval_strlen (TREE_VALUE (a), &val[i], visited, type)) 2273 val[i] = NULL_TREE; 2274 } 2275 2276 BITMAP_FREE (visited); 2277 2278 result = NULL_TREE; 2279 switch (DECL_FUNCTION_CODE (callee)) 2280 { 2281 case BUILT_IN_STRLEN: 2282 if (val[0]) 2283 { 2284 tree new = fold_convert (TREE_TYPE (fn), val[0]); 2285 2286 /* If the result is not a valid gimple value, or not a cast 2287 of a valid gimple value, then we can not use the result. */ 2288 if (is_gimple_val (new) 2289 || (is_gimple_cast (new) 2290 && is_gimple_val (TREE_OPERAND (new, 0)))) 2291 return new; 2292 } 2293 break; 2294 2295 case BUILT_IN_STRCPY: 2296 if (val[1] && is_gimple_val (val[1])) 2297 result = fold_builtin_strcpy (callee, arglist, val[1]); 2298 break; 2299 2300 case BUILT_IN_STRNCPY: 2301 if (val[1] && is_gimple_val (val[1])) 2302 result = fold_builtin_strncpy (callee, arglist, val[1]); 2303 break; 2304 2305 case BUILT_IN_FPUTS: 2306 result = fold_builtin_fputs (arglist, 2307 TREE_CODE (stmt) != MODIFY_EXPR, 0, 2308 val[0]); 2309 break; 2310 2311 case BUILT_IN_FPUTS_UNLOCKED: 2312 result = fold_builtin_fputs (arglist, 2313 TREE_CODE (stmt) != MODIFY_EXPR, 1, 2314 val[0]); 2315 break; 2316 2317 case BUILT_IN_MEMCPY_CHK: 2318 case BUILT_IN_MEMPCPY_CHK: 2319 case BUILT_IN_MEMMOVE_CHK: 2320 case BUILT_IN_MEMSET_CHK: 2321 if (val[2] && is_gimple_val (val[2])) 2322 result = fold_builtin_memory_chk (callee, arglist, val[2], ignore, 2323 DECL_FUNCTION_CODE (callee)); 2324 break; 2325 2326 case BUILT_IN_STRCPY_CHK: 2327 case BUILT_IN_STPCPY_CHK: 2328 if (val[1] && is_gimple_val (val[1])) 2329 result = fold_builtin_stxcpy_chk (callee, arglist, val[1], ignore, 2330 DECL_FUNCTION_CODE (callee)); 2331 break; 2332 2333 case BUILT_IN_STRNCPY_CHK: 2334 if (val[2] && is_gimple_val (val[2])) 2335 result = fold_builtin_strncpy_chk (arglist, val[2]); 2336 break; 2337 2338 case BUILT_IN_SNPRINTF_CHK: 2339 case BUILT_IN_VSNPRINTF_CHK: 2340 if (val[1] && is_gimple_val (val[1])) 2341 result = fold_builtin_snprintf_chk (arglist, val[1], 2342 DECL_FUNCTION_CODE (callee)); 2343 break; 2344 2345 default: 2346 gcc_unreachable (); 2347 } 2348 2349 if (result && ignore) 2350 result = fold_ignored_result (result); 2351 return result; 2352} 2353 2354 2355/* Fold the statement pointed to by STMT_P. In some cases, this function may 2356 replace the whole statement with a new one. Returns true iff folding 2357 makes any changes. */ 2358 2359bool 2360fold_stmt (tree *stmt_p) 2361{ 2362 tree rhs, result, stmt; 2363 struct fold_stmt_r_data fold_stmt_r_data; 2364 bool changed = false; 2365 bool inside_addr_expr = false; 2366 2367 stmt = *stmt_p; 2368 2369 fold_stmt_r_data.stmt = stmt; 2370 fold_stmt_r_data.changed_p = &changed; 2371 fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr; 2372 2373 /* If we replaced constants and the statement makes pointer dereferences, 2374 then we may need to fold instances of *&VAR into VAR, etc. */ 2375 if (walk_tree (stmt_p, fold_stmt_r, &fold_stmt_r_data, NULL)) 2376 { 2377 *stmt_p 2378 = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP], 2379 NULL); 2380 return true; 2381 } 2382 2383 rhs = get_rhs (stmt); 2384 if (!rhs) 2385 return changed; 2386 result = NULL_TREE; 2387 2388 if (TREE_CODE (rhs) == CALL_EXPR) 2389 { 2390 tree callee; 2391 2392 /* Check for builtins that CCP can handle using information not 2393 available in the generic fold routines. */ 2394 callee = get_callee_fndecl (rhs); 2395 if (callee && DECL_BUILT_IN (callee)) 2396 result = ccp_fold_builtin (stmt, rhs); 2397 else 2398 { 2399 /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve 2400 here are when we've propagated the address of a decl into the 2401 object slot. */ 2402 /* ??? Should perhaps do this in fold proper. However, doing it 2403 there requires that we create a new CALL_EXPR, and that requires 2404 copying EH region info to the new node. Easier to just do it 2405 here where we can just smash the call operand. Also 2406 CALL_EXPR_RETURN_SLOT_OPT needs to be handled correctly and 2407 copied, fold_ternary does not have not information. */ 2408 callee = TREE_OPERAND (rhs, 0); 2409 if (TREE_CODE (callee) == OBJ_TYPE_REF 2410 && lang_hooks.fold_obj_type_ref 2411 && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR 2412 && DECL_P (TREE_OPERAND 2413 (OBJ_TYPE_REF_OBJECT (callee), 0))) 2414 { 2415 tree t; 2416 2417 /* ??? Caution: Broken ADDR_EXPR semantics means that 2418 looking at the type of the operand of the addr_expr 2419 can yield an array type. See silly exception in 2420 check_pointer_types_r. */ 2421 2422 t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee))); 2423 t = lang_hooks.fold_obj_type_ref (callee, t); 2424 if (t) 2425 { 2426 TREE_OPERAND (rhs, 0) = t; 2427 changed = true; 2428 } 2429 } 2430 } 2431 } 2432 2433 /* If we couldn't fold the RHS, hand over to the generic fold routines. */ 2434 if (result == NULL_TREE) 2435 result = fold (rhs); 2436 2437 /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that 2438 may have been added by fold, and "useless" type conversions that might 2439 now be apparent due to propagation. */ 2440 STRIP_USELESS_TYPE_CONVERSION (result); 2441 2442 if (result != rhs) 2443 changed |= set_rhs (stmt_p, result); 2444 2445 return changed; 2446} 2447 2448/* Perform the minimal folding on statement STMT. Only operations like 2449 *&x created by constant propagation are handled. The statement cannot 2450 be replaced with a new one. */ 2451 2452bool 2453fold_stmt_inplace (tree stmt) 2454{ 2455 tree old_stmt = stmt, rhs, new_rhs; 2456 struct fold_stmt_r_data fold_stmt_r_data; 2457 bool changed = false; 2458 bool inside_addr_expr = false; 2459 2460 fold_stmt_r_data.stmt = stmt; 2461 fold_stmt_r_data.changed_p = &changed; 2462 fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr; 2463 2464 walk_tree (&stmt, fold_stmt_r, &fold_stmt_r_data, NULL); 2465 gcc_assert (stmt == old_stmt); 2466 2467 rhs = get_rhs (stmt); 2468 if (!rhs || rhs == stmt) 2469 return changed; 2470 2471 new_rhs = fold (rhs); 2472 STRIP_USELESS_TYPE_CONVERSION (new_rhs); 2473 if (new_rhs == rhs) 2474 return changed; 2475 2476 changed |= set_rhs (&stmt, new_rhs); 2477 gcc_assert (stmt == old_stmt); 2478 2479 return changed; 2480} 2481 2482/* Convert EXPR into a GIMPLE value suitable for substitution on the 2483 RHS of an assignment. Insert the necessary statements before 2484 iterator *SI_P. */ 2485 2486static tree 2487convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr) 2488{ 2489 tree_stmt_iterator ti; 2490 tree stmt = bsi_stmt (*si_p); 2491 tree tmp, stmts = NULL; 2492 2493 push_gimplify_context (); 2494 tmp = get_initialized_tmp_var (expr, &stmts, NULL); 2495 pop_gimplify_context (NULL); 2496 2497 if (EXPR_HAS_LOCATION (stmt)) 2498 annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt)); 2499 2500 /* The replacement can expose previously unreferenced variables. */ 2501 for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti)) 2502 { 2503 tree new_stmt = tsi_stmt (ti); 2504 find_new_referenced_vars (tsi_stmt_ptr (ti)); 2505 bsi_insert_before (si_p, new_stmt, BSI_NEW_STMT); 2506 mark_new_vars_to_rename (bsi_stmt (*si_p)); 2507 bsi_next (si_p); 2508 } 2509 2510 return tmp; 2511} 2512 2513 2514/* A simple pass that attempts to fold all builtin functions. This pass 2515 is run after we've propagated as many constants as we can. */ 2516 2517static unsigned int 2518execute_fold_all_builtins (void) 2519{ 2520 bool cfg_changed = false; 2521 basic_block bb; 2522 FOR_EACH_BB (bb) 2523 { 2524 block_stmt_iterator i; 2525 for (i = bsi_start (bb); !bsi_end_p (i); ) 2526 { 2527 tree *stmtp = bsi_stmt_ptr (i); 2528 tree old_stmt = *stmtp; 2529 tree call = get_rhs (*stmtp); 2530 tree callee, result; 2531 enum built_in_function fcode; 2532 2533 if (!call || TREE_CODE (call) != CALL_EXPR) 2534 { 2535 bsi_next (&i); 2536 continue; 2537 } 2538 callee = get_callee_fndecl (call); 2539 if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL) 2540 { 2541 bsi_next (&i); 2542 continue; 2543 } 2544 fcode = DECL_FUNCTION_CODE (callee); 2545 2546 result = ccp_fold_builtin (*stmtp, call); 2547 if (!result) 2548 switch (DECL_FUNCTION_CODE (callee)) 2549 { 2550 case BUILT_IN_CONSTANT_P: 2551 /* Resolve __builtin_constant_p. If it hasn't been 2552 folded to integer_one_node by now, it's fairly 2553 certain that the value simply isn't constant. */ 2554 result = integer_zero_node; 2555 break; 2556 2557 default: 2558 bsi_next (&i); 2559 continue; 2560 } 2561 2562 if (dump_file && (dump_flags & TDF_DETAILS)) 2563 { 2564 fprintf (dump_file, "Simplified\n "); 2565 print_generic_stmt (dump_file, *stmtp, dump_flags); 2566 } 2567 2568 if (!set_rhs (stmtp, result)) 2569 { 2570 result = convert_to_gimple_builtin (&i, result); 2571 if (result) 2572 { 2573 bool ok = set_rhs (stmtp, result); 2574 2575 gcc_assert (ok); 2576 } 2577 } 2578 mark_new_vars_to_rename (*stmtp); 2579 if (maybe_clean_or_replace_eh_stmt (old_stmt, *stmtp) 2580 && tree_purge_dead_eh_edges (bb)) 2581 cfg_changed = true; 2582 2583 if (dump_file && (dump_flags & TDF_DETAILS)) 2584 { 2585 fprintf (dump_file, "to\n "); 2586 print_generic_stmt (dump_file, *stmtp, dump_flags); 2587 fprintf (dump_file, "\n"); 2588 } 2589 2590 /* Retry the same statement if it changed into another 2591 builtin, there might be new opportunities now. */ 2592 call = get_rhs (*stmtp); 2593 if (!call || TREE_CODE (call) != CALL_EXPR) 2594 { 2595 bsi_next (&i); 2596 continue; 2597 } 2598 callee = get_callee_fndecl (call); 2599 if (!callee 2600 || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL 2601 || DECL_FUNCTION_CODE (callee) == fcode) 2602 bsi_next (&i); 2603 } 2604 } 2605 2606 /* Delete unreachable blocks. */ 2607 if (cfg_changed) 2608 cleanup_tree_cfg (); 2609 return 0; 2610} 2611 2612 2613struct tree_opt_pass pass_fold_builtins = 2614{ 2615 "fab", /* name */ 2616 NULL, /* gate */ 2617 execute_fold_all_builtins, /* execute */ 2618 NULL, /* sub */ 2619 NULL, /* next */ 2620 0, /* static_pass_number */ 2621 0, /* tv_id */ 2622 PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ 2623 0, /* properties_provided */ 2624 0, /* properties_destroyed */ 2625 0, /* todo_flags_start */ 2626 TODO_dump_func 2627 | TODO_verify_ssa 2628 | TODO_update_ssa, /* todo_flags_finish */ 2629 0 /* letter */ 2630}; 2631