1 /* Alias analysis for trees. 2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 3 Free Software Foundation, Inc. 4 Contributed by Diego Novillo <dnovillo@redhat.com> 5 6 This file is part of GCC. 7 8 GCC is free software; you can redistribute it and/or modify 9 it under the terms of the GNU General Public License as published by 10 the Free Software Foundation; either version 3, or (at your option) 11 any later version. 12 13 GCC is distributed in the hope that it will be useful, 14 but WITHOUT ANY WARRANTY; without even the implied warranty of 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 GNU General Public License for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with GCC; see the file COPYING3. If not see 20 <http://www.gnu.org/licenses/>. */ 21 22 #include "config.h" 23 #include "system.h" 24 #include "coretypes.h" 25 #include "tm.h" 26 #include "tree.h" 27 #include "rtl.h" 28 #include "tm_p.h" 29 #include "hard-reg-set.h" 30 #include "basic-block.h" 31 #include "timevar.h" 32 #include "expr.h" 33 #include "ggc.h" 34 #include "langhooks.h" 35 #include "flags.h" 36 #include "function.h" 37 #include "diagnostic.h" 38 #include "tree-dump.h" 39 #include "gimple.h" 40 #include "tree-flow.h" 41 #include "tree-inline.h" 42 #include "tree-pass.h" 43 #include "convert.h" 44 #include "params.h" 45 #include "ipa-type-escape.h" 46 #include "vec.h" 47 #include "bitmap.h" 48 #include "vecprim.h" 49 #include "pointer-set.h" 50 #include "alloc-pool.h" 51 #include "tree-ssa-alias.h" 52 53 /* Broad overview of how alias analysis on gimple works: 54 55 Statements clobbering or using memory are linked through the 56 virtual operand factored use-def chain. The virtual operand 57 is unique per function, its symbol is accessible via gimple_vop (cfun). 58 Virtual operands are used for efficiently walking memory statements 59 in the gimple IL and are useful for things like value-numbering as 60 a generation count for memory references. 61 62 SSA_NAME pointers may have associated points-to information 63 accessible via the SSA_NAME_PTR_INFO macro. Flow-insensitive 64 points-to information is (re-)computed by the TODO_rebuild_alias 65 pass manager todo. Points-to information is also used for more 66 precise tracking of call-clobbered and call-used variables and 67 related disambiguations. 68 69 This file contains functions for disambiguating memory references, 70 the so called alias-oracle and tools for walking of the gimple IL. 71 72 The main alias-oracle entry-points are 73 74 bool stmt_may_clobber_ref_p (gimple, tree) 75 76 This function queries if a statement may invalidate (parts of) 77 the memory designated by the reference tree argument. 78 79 bool ref_maybe_used_by_stmt_p (gimple, tree) 80 81 This function queries if a statement may need (parts of) the 82 memory designated by the reference tree argument. 83 84 There are variants of these functions that only handle the call 85 part of a statement, call_may_clobber_ref_p and ref_maybe_used_by_call_p. 86 Note that these do not disambiguate against a possible call lhs. 87 88 bool refs_may_alias_p (tree, tree) 89 90 This function tries to disambiguate two reference trees. 91 92 bool ptr_deref_may_alias_global_p (tree) 93 94 This function queries if dereferencing a pointer variable may 95 alias global memory. 96 97 More low-level disambiguators are available and documented in 98 this file. Low-level disambiguators dealing with points-to 99 information are in tree-ssa-structalias.c. */ 100 101 102 /* Query statistics for the different low-level disambiguators. 103 A high-level query may trigger multiple of them. */ 104 105 static struct { 106 unsigned HOST_WIDE_INT refs_may_alias_p_may_alias; 107 unsigned HOST_WIDE_INT refs_may_alias_p_no_alias; 108 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_may_alias; 109 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_no_alias; 110 unsigned HOST_WIDE_INT call_may_clobber_ref_p_may_alias; 111 unsigned HOST_WIDE_INT call_may_clobber_ref_p_no_alias; 112 } alias_stats; 113 114 void 115 dump_alias_stats (FILE *s) 116 { 117 fprintf (s, "\nAlias oracle query stats:\n"); 118 fprintf (s, " refs_may_alias_p: " 119 HOST_WIDE_INT_PRINT_DEC" disambiguations, " 120 HOST_WIDE_INT_PRINT_DEC" queries\n", 121 alias_stats.refs_may_alias_p_no_alias, 122 alias_stats.refs_may_alias_p_no_alias 123 + alias_stats.refs_may_alias_p_may_alias); 124 fprintf (s, " ref_maybe_used_by_call_p: " 125 HOST_WIDE_INT_PRINT_DEC" disambiguations, " 126 HOST_WIDE_INT_PRINT_DEC" queries\n", 127 alias_stats.ref_maybe_used_by_call_p_no_alias, 128 alias_stats.refs_may_alias_p_no_alias 129 + alias_stats.ref_maybe_used_by_call_p_may_alias); 130 fprintf (s, " call_may_clobber_ref_p: " 131 HOST_WIDE_INT_PRINT_DEC" disambiguations, " 132 HOST_WIDE_INT_PRINT_DEC" queries\n", 133 alias_stats.call_may_clobber_ref_p_no_alias, 134 alias_stats.call_may_clobber_ref_p_no_alias 135 + alias_stats.call_may_clobber_ref_p_may_alias); 136 } 137 138 139 /* Return true, if dereferencing PTR may alias with a global variable. */ 140 141 bool 142 ptr_deref_may_alias_global_p (tree ptr) 143 { 144 struct ptr_info_def *pi; 145 146 /* If we end up with a pointer constant here that may point 147 to global memory. */ 148 if (TREE_CODE (ptr) != SSA_NAME) 149 return true; 150 151 pi = SSA_NAME_PTR_INFO (ptr); 152 153 /* If we do not have points-to information for this variable, 154 we have to punt. */ 155 if (!pi) 156 return true; 157 158 /* ??? This does not use TBAA to prune globals ptr may not access. */ 159 return pt_solution_includes_global (&pi->pt); 160 } 161 162 /* Return true if dereferencing PTR may alias DECL. 163 The caller is responsible for applying TBAA to see if PTR 164 may access DECL at all. */ 165 166 static bool 167 ptr_deref_may_alias_decl_p (tree ptr, tree decl) 168 { 169 struct ptr_info_def *pi; 170 171 gcc_assert ((TREE_CODE (ptr) == SSA_NAME 172 || TREE_CODE (ptr) == ADDR_EXPR 173 || TREE_CODE (ptr) == INTEGER_CST) 174 && (TREE_CODE (decl) == VAR_DECL 175 || TREE_CODE (decl) == PARM_DECL 176 || TREE_CODE (decl) == RESULT_DECL)); 177 178 /* Non-aliased variables can not be pointed to. */ 179 if (!may_be_aliased (decl)) 180 return false; 181 182 /* ADDR_EXPR pointers either just offset another pointer or directly 183 specify the pointed-to set. */ 184 if (TREE_CODE (ptr) == ADDR_EXPR) 185 { 186 tree base = get_base_address (TREE_OPERAND (ptr, 0)); 187 if (base 188 && INDIRECT_REF_P (base)) 189 ptr = TREE_OPERAND (base, 0); 190 else if (base 191 && SSA_VAR_P (base)) 192 return operand_equal_p (base, decl, 0); 193 else if (base 194 && CONSTANT_CLASS_P (base)) 195 return false; 196 else 197 return true; 198 } 199 200 /* We can end up with dereferencing constant pointers. 201 Just bail out in this case. */ 202 if (TREE_CODE (ptr) == INTEGER_CST) 203 return true; 204 205 /* If we do not have useful points-to information for this pointer 206 we cannot disambiguate anything else. */ 207 pi = SSA_NAME_PTR_INFO (ptr); 208 if (!pi) 209 return true; 210 211 /* If the decl can be used as a restrict tag and we have a restrict 212 pointer and that pointers points-to set doesn't contain this decl 213 then they can't alias. */ 214 if (DECL_RESTRICTED_P (decl) 215 && TYPE_RESTRICT (TREE_TYPE (ptr)) 216 && pi->pt.vars_contains_restrict) 217 return bitmap_bit_p (pi->pt.vars, DECL_UID (decl)); 218 219 return pt_solution_includes (&pi->pt, decl); 220 } 221 222 /* Return true if dereferenced PTR1 and PTR2 may alias. 223 The caller is responsible for applying TBAA to see if accesses 224 through PTR1 and PTR2 may conflict at all. */ 225 226 static bool 227 ptr_derefs_may_alias_p (tree ptr1, tree ptr2) 228 { 229 struct ptr_info_def *pi1, *pi2; 230 231 gcc_assert ((TREE_CODE (ptr1) == SSA_NAME 232 || TREE_CODE (ptr1) == ADDR_EXPR 233 || TREE_CODE (ptr1) == INTEGER_CST) 234 && (TREE_CODE (ptr2) == SSA_NAME 235 || TREE_CODE (ptr2) == ADDR_EXPR 236 || TREE_CODE (ptr2) == INTEGER_CST)); 237 238 /* ADDR_EXPR pointers either just offset another pointer or directly 239 specify the pointed-to set. */ 240 if (TREE_CODE (ptr1) == ADDR_EXPR) 241 { 242 tree base = get_base_address (TREE_OPERAND (ptr1, 0)); 243 if (base 244 && INDIRECT_REF_P (base)) 245 ptr1 = TREE_OPERAND (base, 0); 246 else if (base 247 && SSA_VAR_P (base)) 248 return ptr_deref_may_alias_decl_p (ptr2, base); 249 else 250 return true; 251 } 252 if (TREE_CODE (ptr2) == ADDR_EXPR) 253 { 254 tree base = get_base_address (TREE_OPERAND (ptr2, 0)); 255 if (base 256 && INDIRECT_REF_P (base)) 257 ptr2 = TREE_OPERAND (base, 0); 258 else if (base 259 && SSA_VAR_P (base)) 260 return ptr_deref_may_alias_decl_p (ptr1, base); 261 else 262 return true; 263 } 264 265 /* We can end up with dereferencing constant pointers. 266 Just bail out in this case. */ 267 if (TREE_CODE (ptr1) == INTEGER_CST 268 || TREE_CODE (ptr2) == INTEGER_CST) 269 return true; 270 271 /* We may end up with two empty points-to solutions for two same pointers. 272 In this case we still want to say both pointers alias, so shortcut 273 that here. */ 274 if (ptr1 == ptr2) 275 return true; 276 277 /* If we do not have useful points-to information for either pointer 278 we cannot disambiguate anything else. */ 279 pi1 = SSA_NAME_PTR_INFO (ptr1); 280 pi2 = SSA_NAME_PTR_INFO (ptr2); 281 if (!pi1 || !pi2) 282 return true; 283 284 /* If both pointers are restrict-qualified try to disambiguate 285 with restrict information. */ 286 if (TYPE_RESTRICT (TREE_TYPE (ptr1)) 287 && TYPE_RESTRICT (TREE_TYPE (ptr2)) 288 && !pt_solutions_same_restrict_base (&pi1->pt, &pi2->pt)) 289 return false; 290 291 /* ??? This does not use TBAA to prune decls from the intersection 292 that not both pointers may access. */ 293 return pt_solutions_intersect (&pi1->pt, &pi2->pt); 294 } 295 296 /* Return true if dereferencing PTR may alias *REF. 297 The caller is responsible for applying TBAA to see if PTR 298 may access *REF at all. */ 299 300 static bool 301 ptr_deref_may_alias_ref_p_1 (tree ptr, ao_ref *ref) 302 { 303 tree base = ao_ref_base (ref); 304 305 if (INDIRECT_REF_P (base)) 306 return ptr_derefs_may_alias_p (ptr, TREE_OPERAND (base, 0)); 307 else if (SSA_VAR_P (base)) 308 return ptr_deref_may_alias_decl_p (ptr, base); 309 310 return true; 311 } 312 313 314 /* Dump alias information on FILE. */ 315 316 void 317 dump_alias_info (FILE *file) 318 { 319 size_t i; 320 const char *funcname 321 = lang_hooks.decl_printable_name (current_function_decl, 2); 322 referenced_var_iterator rvi; 323 tree var; 324 325 fprintf (file, "\n\nAlias information for %s\n\n", funcname); 326 327 fprintf (file, "Aliased symbols\n\n"); 328 329 FOR_EACH_REFERENCED_VAR (var, rvi) 330 { 331 if (may_be_aliased (var)) 332 dump_variable (file, var); 333 } 334 335 fprintf (file, "\nCall clobber information\n"); 336 337 fprintf (file, "\nESCAPED"); 338 dump_points_to_solution (file, &cfun->gimple_df->escaped); 339 fprintf (file, "\nCALLUSED"); 340 dump_points_to_solution (file, &cfun->gimple_df->callused); 341 342 fprintf (file, "\n\nFlow-insensitive points-to information\n\n"); 343 344 for (i = 1; i < num_ssa_names; i++) 345 { 346 tree ptr = ssa_name (i); 347 struct ptr_info_def *pi; 348 349 if (ptr == NULL_TREE 350 || SSA_NAME_IN_FREE_LIST (ptr)) 351 continue; 352 353 pi = SSA_NAME_PTR_INFO (ptr); 354 if (pi) 355 dump_points_to_info_for (file, ptr); 356 } 357 358 fprintf (file, "\n"); 359 } 360 361 362 /* Dump alias information on stderr. */ 363 364 void 365 debug_alias_info (void) 366 { 367 dump_alias_info (stderr); 368 } 369 370 371 /* Return the alias information associated with pointer T. It creates a 372 new instance if none existed. */ 373 374 struct ptr_info_def * 375 get_ptr_info (tree t) 376 { 377 struct ptr_info_def *pi; 378 379 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t))); 380 381 pi = SSA_NAME_PTR_INFO (t); 382 if (pi == NULL) 383 { 384 pi = GGC_CNEW (struct ptr_info_def); 385 pt_solution_reset (&pi->pt); 386 SSA_NAME_PTR_INFO (t) = pi; 387 } 388 389 return pi; 390 } 391 392 /* Dump the points-to set *PT into FILE. */ 393 394 void 395 dump_points_to_solution (FILE *file, struct pt_solution *pt) 396 { 397 if (pt->anything) 398 fprintf (file, ", points-to anything"); 399 400 if (pt->nonlocal) 401 fprintf (file, ", points-to non-local"); 402 403 if (pt->escaped) 404 fprintf (file, ", points-to escaped"); 405 406 if (pt->null) 407 fprintf (file, ", points-to NULL"); 408 409 if (pt->vars) 410 { 411 fprintf (file, ", points-to vars: "); 412 dump_decl_set (file, pt->vars); 413 if (pt->vars_contains_global) 414 fprintf (file, " (includes global vars)"); 415 } 416 } 417 418 /* Dump points-to information for SSA_NAME PTR into FILE. */ 419 420 void 421 dump_points_to_info_for (FILE *file, tree ptr) 422 { 423 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); 424 425 print_generic_expr (file, ptr, dump_flags); 426 427 if (pi) 428 dump_points_to_solution (file, &pi->pt); 429 else 430 fprintf (file, ", points-to anything"); 431 432 fprintf (file, "\n"); 433 } 434 435 436 /* Dump points-to information for VAR into stderr. */ 437 438 void 439 debug_points_to_info_for (tree var) 440 { 441 dump_points_to_info_for (stderr, var); 442 } 443 444 445 /* Initializes the alias-oracle reference representation *R from REF. */ 446 447 void 448 ao_ref_init (ao_ref *r, tree ref) 449 { 450 r->ref = ref; 451 r->base = NULL_TREE; 452 r->offset = 0; 453 r->size = -1; 454 r->max_size = -1; 455 r->ref_alias_set = -1; 456 r->base_alias_set = -1; 457 } 458 459 /* Returns the base object of the memory reference *REF. */ 460 461 tree 462 ao_ref_base (ao_ref *ref) 463 { 464 if (ref->base) 465 return ref->base; 466 ref->base = get_ref_base_and_extent (ref->ref, &ref->offset, &ref->size, 467 &ref->max_size); 468 return ref->base; 469 } 470 471 /* Returns the base object alias set of the memory reference *REF. */ 472 473 static alias_set_type ATTRIBUTE_UNUSED 474 ao_ref_base_alias_set (ao_ref *ref) 475 { 476 if (ref->base_alias_set != -1) 477 return ref->base_alias_set; 478 ref->base_alias_set = get_alias_set (ao_ref_base (ref)); 479 return ref->base_alias_set; 480 } 481 482 /* Returns the reference alias set of the memory reference *REF. */ 483 484 alias_set_type 485 ao_ref_alias_set (ao_ref *ref) 486 { 487 if (ref->ref_alias_set != -1) 488 return ref->ref_alias_set; 489 ref->ref_alias_set = get_alias_set (ref->ref); 490 return ref->ref_alias_set; 491 } 492 493 /* Init an alias-oracle reference representation from a gimple pointer 494 PTR and a gimple size SIZE in bytes. If SIZE is NULL_TREE the the 495 size is assumed to be unknown. The access is assumed to be only 496 to or after of the pointer target, not before it. */ 497 498 void 499 ao_ref_init_from_ptr_and_size (ao_ref *ref, tree ptr, tree size) 500 { 501 HOST_WIDE_INT t1, t2; 502 ref->ref = NULL_TREE; 503 if (TREE_CODE (ptr) == ADDR_EXPR) 504 ref->base = get_ref_base_and_extent (TREE_OPERAND (ptr, 0), 505 &ref->offset, &t1, &t2); 506 else 507 { 508 ref->base = build1 (INDIRECT_REF, char_type_node, ptr); 509 ref->offset = 0; 510 } 511 if (size 512 && host_integerp (size, 0) 513 && TREE_INT_CST_LOW (size) * 8 / 8 == TREE_INT_CST_LOW (size)) 514 ref->max_size = ref->size = TREE_INT_CST_LOW (size) * 8; 515 else 516 ref->max_size = ref->size = -1; 517 ref->ref_alias_set = 0; 518 ref->base_alias_set = 0; 519 } 520 521 /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the 522 purpose of TBAA. Return 0 if they are distinct and -1 if we cannot 523 decide. */ 524 525 static inline int 526 same_type_for_tbaa (tree type1, tree type2) 527 { 528 type1 = TYPE_MAIN_VARIANT (type1); 529 type2 = TYPE_MAIN_VARIANT (type2); 530 531 /* If we would have to do structural comparison bail out. */ 532 if (TYPE_STRUCTURAL_EQUALITY_P (type1) 533 || TYPE_STRUCTURAL_EQUALITY_P (type2)) 534 return -1; 535 536 /* Compare the canonical types. */ 537 if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2)) 538 return 1; 539 540 /* ??? Array types are not properly unified in all cases as we have 541 spurious changes in the index types for example. Removing this 542 causes all sorts of problems with the Fortran frontend. */ 543 if (TREE_CODE (type1) == ARRAY_TYPE 544 && TREE_CODE (type2) == ARRAY_TYPE) 545 return -1; 546 547 /* ??? In Ada, an lvalue of an unconstrained type can be used to access an 548 object of one of its constrained subtypes, e.g. when a function with an 549 unconstrained parameter passed by reference is called on an object and 550 inlined. But, even in the case of a fixed size, type and subtypes are 551 not equivalent enough as to share the same TYPE_CANONICAL, since this 552 would mean that conversions between them are useless, whereas they are 553 not (e.g. type and subtypes can have different modes). So, in the end, 554 they are only guaranteed to have the same alias set. */ 555 if (get_alias_set (type1) == get_alias_set (type2)) 556 return -1; 557 558 /* The types are known to be not equal. */ 559 return 0; 560 } 561 562 /* Determine if the two component references REF1 and REF2 which are 563 based on access types TYPE1 and TYPE2 and of which at least one is based 564 on an indirect reference may alias. REF2 is the only one that can 565 be a decl in which case REF2_IS_DECL is true. 566 REF1_ALIAS_SET, BASE1_ALIAS_SET, REF2_ALIAS_SET and BASE2_ALIAS_SET 567 are the respective alias sets. */ 568 569 static bool 570 aliasing_component_refs_p (tree ref1, tree type1, 571 alias_set_type ref1_alias_set, 572 alias_set_type base1_alias_set, 573 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1, 574 tree ref2, tree type2, 575 alias_set_type ref2_alias_set, 576 alias_set_type base2_alias_set, 577 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2, 578 bool ref2_is_decl) 579 { 580 /* If one reference is a component references through pointers try to find a 581 common base and apply offset based disambiguation. This handles 582 for example 583 struct A { int i; int j; } *q; 584 struct B { struct A a; int k; } *p; 585 disambiguating q->i and p->a.j. */ 586 tree *refp; 587 int same_p; 588 589 /* Now search for the type1 in the access path of ref2. This 590 would be a common base for doing offset based disambiguation on. */ 591 refp = &ref2; 592 while (handled_component_p (*refp) 593 && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0) 594 refp = &TREE_OPERAND (*refp, 0); 595 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1); 596 /* If we couldn't compare types we have to bail out. */ 597 if (same_p == -1) 598 return true; 599 else if (same_p == 1) 600 { 601 HOST_WIDE_INT offadj, sztmp, msztmp; 602 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp); 603 offset2 -= offadj; 604 return ranges_overlap_p (offset1, max_size1, offset2, max_size2); 605 } 606 /* If we didn't find a common base, try the other way around. */ 607 refp = &ref1; 608 while (handled_component_p (*refp) 609 && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0) 610 refp = &TREE_OPERAND (*refp, 0); 611 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2); 612 /* If we couldn't compare types we have to bail out. */ 613 if (same_p == -1) 614 return true; 615 else if (same_p == 1) 616 { 617 HOST_WIDE_INT offadj, sztmp, msztmp; 618 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp); 619 offset1 -= offadj; 620 return ranges_overlap_p (offset1, max_size1, offset2, max_size2); 621 } 622 623 /* If we have two type access paths B1.path1 and B2.path2 they may 624 only alias if either B1 is in B2.path2 or B2 is in B1.path1. 625 But we can still have a path that goes B1.path1...B2.path2 with 626 a part that we do not see. So we can only disambiguate now 627 if there is no B2 in the tail of path1 and no B1 on the 628 tail of path2. */ 629 if (base1_alias_set == ref2_alias_set 630 || alias_set_subset_of (base1_alias_set, ref2_alias_set)) 631 return true; 632 /* If this is ptr vs. decl then we know there is no ptr ... decl path. */ 633 if (!ref2_is_decl) 634 return (base2_alias_set == ref1_alias_set 635 || alias_set_subset_of (base2_alias_set, ref1_alias_set)); 636 return false; 637 } 638 639 /* Return true if two memory references based on the variables BASE1 640 and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1) and 641 [OFFSET2, OFFSET2 + MAX_SIZE2) may alias. */ 642 643 static bool 644 decl_refs_may_alias_p (tree base1, 645 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1, 646 tree base2, 647 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2) 648 { 649 gcc_assert (SSA_VAR_P (base1) && SSA_VAR_P (base2)); 650 651 /* If both references are based on different variables, they cannot alias. */ 652 if (!operand_equal_p (base1, base2, 0)) 653 return false; 654 655 /* If both references are based on the same variable, they cannot alias if 656 the accesses do not overlap. */ 657 return ranges_overlap_p (offset1, max_size1, offset2, max_size2); 658 } 659 660 /* Return true if an indirect reference based on *PTR1 constrained 661 to [OFFSET1, OFFSET1 + MAX_SIZE1) may alias a variable based on BASE2 662 constrained to [OFFSET2, OFFSET2 + MAX_SIZE2). *PTR1 and BASE2 have 663 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1 664 in which case they are computed on-demand. REF1 and REF2 665 if non-NULL are the complete memory reference trees. */ 666 667 static bool 668 indirect_ref_may_alias_decl_p (tree ref1, tree ptr1, 669 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1, 670 alias_set_type ref1_alias_set, 671 alias_set_type base1_alias_set, 672 tree ref2, tree base2, 673 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2, 674 alias_set_type ref2_alias_set, 675 alias_set_type base2_alias_set) 676 { 677 /* If only one reference is based on a variable, they cannot alias if 678 the pointer access is beyond the extent of the variable access. 679 (the pointer base cannot validly point to an offset less than zero 680 of the variable). 681 They also cannot alias if the pointer may not point to the decl. */ 682 if (max_size2 != -1 683 && !ranges_overlap_p (offset1, max_size1, 0, offset2 + max_size2)) 684 return false; 685 if (!ptr_deref_may_alias_decl_p (ptr1, base2)) 686 return false; 687 688 /* Disambiguations that rely on strict aliasing rules follow. */ 689 if (!flag_strict_aliasing) 690 return true; 691 692 /* If the alias set for a pointer access is zero all bets are off. */ 693 if (base1_alias_set == -1) 694 base1_alias_set = get_deref_alias_set (ptr1); 695 if (base1_alias_set == 0) 696 return true; 697 if (base2_alias_set == -1) 698 base2_alias_set = get_alias_set (base2); 699 700 /* If both references are through the same type, they do not alias 701 if the accesses do not overlap. This does extra disambiguation 702 for mixed/pointer accesses but requires strict aliasing. */ 703 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)), 704 TREE_TYPE (base2)) == 1) 705 return ranges_overlap_p (offset1, max_size1, offset2, max_size2); 706 707 /* The only way to access a variable is through a pointer dereference 708 of the same alias set or a subset of it. */ 709 if (base1_alias_set != base2_alias_set 710 && !alias_set_subset_of (base1_alias_set, base2_alias_set)) 711 return false; 712 713 /* Do access-path based disambiguation. */ 714 if (ref1 && ref2 715 && handled_component_p (ref1) 716 && handled_component_p (ref2)) 717 return aliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)), 718 ref1_alias_set, base1_alias_set, 719 offset1, max_size1, 720 ref2, TREE_TYPE (base2), 721 ref2_alias_set, base2_alias_set, 722 offset2, max_size2, true); 723 724 return true; 725 } 726 727 /* Return true if two indirect references based on *PTR1 728 and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1) and 729 [OFFSET2, OFFSET2 + MAX_SIZE2) may alias. *PTR1 and *PTR2 have 730 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1 731 in which case they are computed on-demand. REF1 and REF2 732 if non-NULL are the complete memory reference trees. */ 733 734 static bool 735 indirect_refs_may_alias_p (tree ref1, tree ptr1, 736 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1, 737 alias_set_type ref1_alias_set, 738 alias_set_type base1_alias_set, 739 tree ref2, tree ptr2, 740 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2, 741 alias_set_type ref2_alias_set, 742 alias_set_type base2_alias_set) 743 { 744 /* If both bases are based on pointers they cannot alias if they may not 745 point to the same memory object or if they point to the same object 746 and the accesses do not overlap. */ 747 if (operand_equal_p (ptr1, ptr2, 0)) 748 return ranges_overlap_p (offset1, max_size1, offset2, max_size2); 749 if (!ptr_derefs_may_alias_p (ptr1, ptr2)) 750 return false; 751 752 /* Disambiguations that rely on strict aliasing rules follow. */ 753 if (!flag_strict_aliasing) 754 return true; 755 756 /* If the alias set for a pointer access is zero all bets are off. */ 757 if (base1_alias_set == -1) 758 base1_alias_set = get_deref_alias_set (ptr1); 759 if (base1_alias_set == 0) 760 return true; 761 if (base2_alias_set == -1) 762 base2_alias_set = get_deref_alias_set (ptr2); 763 if (base2_alias_set == 0) 764 return true; 765 766 /* If both references are through the same type, they do not alias 767 if the accesses do not overlap. This does extra disambiguation 768 for mixed/pointer accesses but requires strict aliasing. */ 769 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)), 770 TREE_TYPE (TREE_TYPE (ptr2))) == 1) 771 return ranges_overlap_p (offset1, max_size1, offset2, max_size2); 772 773 /* Do type-based disambiguation. */ 774 if (base1_alias_set != base2_alias_set 775 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set)) 776 return false; 777 778 /* Do access-path based disambiguation. */ 779 if (ref1 && ref2 780 && handled_component_p (ref1) 781 && handled_component_p (ref2)) 782 return aliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)), 783 ref1_alias_set, base1_alias_set, 784 offset1, max_size1, 785 ref2, TREE_TYPE (TREE_TYPE (ptr2)), 786 ref2_alias_set, base2_alias_set, 787 offset2, max_size2, false); 788 789 return true; 790 } 791 792 /* Return true, if the two memory references REF1 and REF2 may alias. */ 793 794 bool 795 refs_may_alias_p_1 (ao_ref *ref1, ao_ref *ref2, bool tbaa_p) 796 { 797 tree base1, base2; 798 HOST_WIDE_INT offset1 = 0, offset2 = 0; 799 HOST_WIDE_INT max_size1 = -1, max_size2 = -1; 800 bool var1_p, var2_p, ind1_p, ind2_p; 801 alias_set_type set; 802 803 #ifdef ENABLE_CHECKING 804 gcc_assert ((!ref1->ref 805 || TREE_CODE (ref1->ref) == SSA_NAME 806 || DECL_P (ref1->ref) 807 || handled_component_p (ref1->ref) 808 || INDIRECT_REF_P (ref1->ref) 809 || TREE_CODE (ref1->ref) == TARGET_MEM_REF) 810 && (!ref2->ref 811 || TREE_CODE (ref2->ref) == SSA_NAME 812 || DECL_P (ref2->ref) 813 || handled_component_p (ref2->ref) 814 || INDIRECT_REF_P (ref2->ref) 815 || TREE_CODE (ref2->ref) == TARGET_MEM_REF)); 816 #endif 817 818 /* Decompose the references into their base objects and the access. */ 819 base1 = ao_ref_base (ref1); 820 offset1 = ref1->offset; 821 max_size1 = ref1->max_size; 822 base2 = ao_ref_base (ref2); 823 offset2 = ref2->offset; 824 max_size2 = ref2->max_size; 825 826 /* We can end up with registers or constants as bases for example from 827 *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59); 828 which is seen as a struct copy. */ 829 if (TREE_CODE (base1) == SSA_NAME 830 || TREE_CODE (base2) == SSA_NAME 831 || TREE_CODE (base1) == CONST_DECL 832 || TREE_CODE (base2) == CONST_DECL 833 || is_gimple_min_invariant (base1) 834 || is_gimple_min_invariant (base2)) 835 return false; 836 837 /* We can end up refering to code via function and label decls. 838 As we likely do not properly track code aliases conservatively 839 bail out. */ 840 if (TREE_CODE (base1) == FUNCTION_DECL 841 || TREE_CODE (base2) == FUNCTION_DECL 842 || TREE_CODE (base1) == LABEL_DECL 843 || TREE_CODE (base2) == LABEL_DECL) 844 return true; 845 846 /* Defer to simple offset based disambiguation if we have 847 references based on two decls. Do this before defering to 848 TBAA to handle must-alias cases in conformance with the 849 GCC extension of allowing type-punning through unions. */ 850 var1_p = SSA_VAR_P (base1); 851 var2_p = SSA_VAR_P (base2); 852 if (var1_p && var2_p) 853 return decl_refs_may_alias_p (base1, offset1, max_size1, 854 base2, offset2, max_size2); 855 856 ind1_p = INDIRECT_REF_P (base1); 857 ind2_p = INDIRECT_REF_P (base2); 858 /* Canonicalize the pointer-vs-decl case. */ 859 if (ind1_p && var2_p) 860 { 861 HOST_WIDE_INT tmp1; 862 tree tmp2; 863 ao_ref *tmp3; 864 tmp1 = offset1; offset1 = offset2; offset2 = tmp1; 865 tmp1 = max_size1; max_size1 = max_size2; max_size2 = tmp1; 866 tmp2 = base1; base1 = base2; base2 = tmp2; 867 tmp3 = ref1; ref1 = ref2; ref2 = tmp3; 868 var1_p = true; 869 ind1_p = false; 870 var2_p = false; 871 ind2_p = true; 872 } 873 874 /* If we are about to disambiguate pointer-vs-decl try harder to 875 see must-aliases and give leeway to some invalid cases. 876 This covers a pretty minimal set of cases only and does not 877 when called from the RTL oracle. It handles cases like 878 879 int i = 1; 880 return *(float *)&i; 881 882 and also fixes gfortran.dg/lto/pr40725. */ 883 if (var1_p && ind2_p 884 && cfun 885 && gimple_in_ssa_p (cfun) 886 && TREE_CODE (TREE_OPERAND (base2, 0)) == SSA_NAME) 887 { 888 gimple def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (base2, 0)); 889 while (is_gimple_assign (def_stmt) 890 && (gimple_assign_rhs_code (def_stmt) == SSA_NAME 891 || CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt)))) 892 { 893 tree rhs = gimple_assign_rhs1 (def_stmt); 894 HOST_WIDE_INT offset, size, max_size; 895 896 /* Look through SSA name copies and pointer conversions. */ 897 if (TREE_CODE (rhs) == SSA_NAME 898 && POINTER_TYPE_P (TREE_TYPE (rhs))) 899 { 900 def_stmt = SSA_NAME_DEF_STMT (rhs); 901 continue; 902 } 903 if (TREE_CODE (rhs) != ADDR_EXPR) 904 break; 905 906 /* If the pointer is defined as an address based on a decl 907 use plain offset disambiguation and ignore TBAA. */ 908 rhs = TREE_OPERAND (rhs, 0); 909 rhs = get_ref_base_and_extent (rhs, &offset, &size, &max_size); 910 if (SSA_VAR_P (rhs)) 911 { 912 base2 = rhs; 913 offset2 += offset; 914 if (size != max_size 915 || max_size == -1) 916 max_size2 = -1; 917 return decl_refs_may_alias_p (base1, offset1, max_size1, 918 base2, offset2, max_size2); 919 } 920 921 /* Do not continue looking through &p->x to limit time 922 complexity. */ 923 break; 924 } 925 } 926 927 /* First defer to TBAA if possible. */ 928 if (tbaa_p 929 && flag_strict_aliasing 930 && !alias_sets_conflict_p (ao_ref_alias_set (ref1), 931 ao_ref_alias_set (ref2))) 932 return false; 933 934 /* If one reference is a TARGET_MEM_REF weird things are allowed. Still 935 TBAA disambiguation based on the access type is possible, so bail 936 out only after that check. */ 937 if ((ref1->ref && TREE_CODE (ref1->ref) == TARGET_MEM_REF) 938 || (ref2->ref && TREE_CODE (ref2->ref) == TARGET_MEM_REF)) 939 return true; 940 941 /* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */ 942 set = tbaa_p ? -1 : 0; 943 if (var1_p && ind2_p) 944 return indirect_ref_may_alias_decl_p (ref2->ref, TREE_OPERAND (base2, 0), 945 offset2, max_size2, 946 ao_ref_alias_set (ref2), set, 947 ref1->ref, base1, 948 offset1, max_size1, 949 ao_ref_alias_set (ref1), set); 950 else if (ind1_p && ind2_p) 951 return indirect_refs_may_alias_p (ref1->ref, TREE_OPERAND (base1, 0), 952 offset1, max_size1, 953 ao_ref_alias_set (ref1), set, 954 ref2->ref, TREE_OPERAND (base2, 0), 955 offset2, max_size2, 956 ao_ref_alias_set (ref2), set); 957 958 gcc_unreachable (); 959 } 960 961 bool 962 refs_may_alias_p (tree ref1, tree ref2) 963 { 964 ao_ref r1, r2; 965 bool res; 966 ao_ref_init (&r1, ref1); 967 ao_ref_init (&r2, ref2); 968 res = refs_may_alias_p_1 (&r1, &r2, true); 969 if (res) 970 ++alias_stats.refs_may_alias_p_may_alias; 971 else 972 ++alias_stats.refs_may_alias_p_no_alias; 973 return res; 974 } 975 976 /* Returns true if there is a anti-dependence for the STORE that 977 executes after the LOAD. */ 978 979 bool 980 refs_anti_dependent_p (tree load, tree store) 981 { 982 ao_ref r1, r2; 983 ao_ref_init (&r1, load); 984 ao_ref_init (&r2, store); 985 return refs_may_alias_p_1 (&r1, &r2, false); 986 } 987 988 /* Returns true if there is a output dependence for the stores 989 STORE1 and STORE2. */ 990 991 bool 992 refs_output_dependent_p (tree store1, tree store2) 993 { 994 ao_ref r1, r2; 995 ao_ref_init (&r1, store1); 996 ao_ref_init (&r2, store2); 997 return refs_may_alias_p_1 (&r1, &r2, false); 998 } 999 1000 /* If the call CALL may use the memory reference REF return true, 1001 otherwise return false. */ 1002 1003 static bool 1004 ref_maybe_used_by_call_p_1 (gimple call, ao_ref *ref) 1005 { 1006 tree base, callee; 1007 unsigned i; 1008 int flags = gimple_call_flags (call); 1009 1010 /* Const functions without a static chain do not implicitly use memory. */ 1011 if (!gimple_call_chain (call) 1012 && (flags & (ECF_CONST|ECF_NOVOPS))) 1013 goto process_args; 1014 1015 base = ao_ref_base (ref); 1016 if (!base) 1017 return true; 1018 1019 /* If the reference is based on a decl that is not aliased the call 1020 cannot possibly use it. */ 1021 if (DECL_P (base) 1022 && !may_be_aliased (base) 1023 /* But local statics can be used through recursion. */ 1024 && !is_global_var (base)) 1025 goto process_args; 1026 1027 callee = gimple_call_fndecl (call); 1028 1029 /* Handle those builtin functions explicitly that do not act as 1030 escape points. See tree-ssa-structalias.c:find_func_aliases 1031 for the list of builtins we might need to handle here. */ 1032 if (callee != NULL_TREE 1033 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL) 1034 switch (DECL_FUNCTION_CODE (callee)) 1035 { 1036 /* All the following functions clobber memory pointed to by 1037 their first argument. */ 1038 case BUILT_IN_STRCPY: 1039 case BUILT_IN_STRNCPY: 1040 case BUILT_IN_MEMCPY: 1041 case BUILT_IN_MEMMOVE: 1042 case BUILT_IN_MEMPCPY: 1043 case BUILT_IN_STPCPY: 1044 case BUILT_IN_STPNCPY: 1045 case BUILT_IN_STRCAT: 1046 case BUILT_IN_STRNCAT: 1047 { 1048 ao_ref dref; 1049 tree size = NULL_TREE; 1050 if (gimple_call_num_args (call) == 3) 1051 size = gimple_call_arg (call, 2); 1052 ao_ref_init_from_ptr_and_size (&dref, 1053 gimple_call_arg (call, 1), 1054 size); 1055 return refs_may_alias_p_1 (&dref, ref, false); 1056 } 1057 case BUILT_IN_BCOPY: 1058 { 1059 ao_ref dref; 1060 tree size = gimple_call_arg (call, 2); 1061 ao_ref_init_from_ptr_and_size (&dref, 1062 gimple_call_arg (call, 0), 1063 size); 1064 return refs_may_alias_p_1 (&dref, ref, false); 1065 } 1066 /* The following builtins do not read from memory. */ 1067 case BUILT_IN_FREE: 1068 case BUILT_IN_MALLOC: 1069 case BUILT_IN_CALLOC: 1070 case BUILT_IN_MEMSET: 1071 case BUILT_IN_FREXP: 1072 case BUILT_IN_FREXPF: 1073 case BUILT_IN_FREXPL: 1074 case BUILT_IN_GAMMA_R: 1075 case BUILT_IN_GAMMAF_R: 1076 case BUILT_IN_GAMMAL_R: 1077 case BUILT_IN_LGAMMA_R: 1078 case BUILT_IN_LGAMMAF_R: 1079 case BUILT_IN_LGAMMAL_R: 1080 case BUILT_IN_MODF: 1081 case BUILT_IN_MODFF: 1082 case BUILT_IN_MODFL: 1083 case BUILT_IN_REMQUO: 1084 case BUILT_IN_REMQUOF: 1085 case BUILT_IN_REMQUOL: 1086 case BUILT_IN_SINCOS: 1087 case BUILT_IN_SINCOSF: 1088 case BUILT_IN_SINCOSL: 1089 return false; 1090 1091 default: 1092 /* Fallthru to general call handling. */; 1093 } 1094 1095 /* Check if base is a global static variable that is not read 1096 by the function. */ 1097 if (TREE_CODE (base) == VAR_DECL 1098 && TREE_STATIC (base) 1099 && !TREE_PUBLIC (base)) 1100 { 1101 bitmap not_read; 1102 1103 if (callee != NULL_TREE 1104 && (not_read 1105 = ipa_reference_get_not_read_global (cgraph_node (callee))) 1106 && bitmap_bit_p (not_read, DECL_UID (base))) 1107 goto process_args; 1108 } 1109 1110 /* If the base variable is call-used or call-clobbered then 1111 it may be used. */ 1112 if (flags & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS)) 1113 { 1114 if (DECL_P (base)) 1115 { 1116 if (is_call_used (base)) 1117 return true; 1118 } 1119 else if (INDIRECT_REF_P (base) 1120 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME) 1121 { 1122 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0)); 1123 if (!pi) 1124 return true; 1125 1126 if (pt_solution_includes_global (&pi->pt) 1127 || pt_solutions_intersect (&cfun->gimple_df->callused, &pi->pt) 1128 || pt_solutions_intersect (&cfun->gimple_df->escaped, &pi->pt)) 1129 return true; 1130 } 1131 else 1132 return true; 1133 } 1134 else 1135 { 1136 if (DECL_P (base)) 1137 { 1138 if (is_call_clobbered (base)) 1139 return true; 1140 } 1141 else if (INDIRECT_REF_P (base) 1142 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME) 1143 { 1144 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0)); 1145 if (!pi) 1146 return true; 1147 1148 if (pt_solution_includes_global (&pi->pt) 1149 || pt_solutions_intersect (&cfun->gimple_df->escaped, &pi->pt)) 1150 return true; 1151 } 1152 else 1153 return true; 1154 } 1155 1156 /* Inspect call arguments for passed-by-value aliases. */ 1157 process_args: 1158 for (i = 0; i < gimple_call_num_args (call); ++i) 1159 { 1160 tree op = gimple_call_arg (call, i); 1161 1162 if (TREE_CODE (op) == WITH_SIZE_EXPR) 1163 op = TREE_OPERAND (op, 0); 1164 1165 if (TREE_CODE (op) != SSA_NAME 1166 && !is_gimple_min_invariant (op)) 1167 { 1168 ao_ref r; 1169 ao_ref_init (&r, op); 1170 if (refs_may_alias_p_1 (&r, ref, true)) 1171 return true; 1172 } 1173 } 1174 1175 return false; 1176 } 1177 1178 static bool 1179 ref_maybe_used_by_call_p (gimple call, tree ref) 1180 { 1181 ao_ref r; 1182 bool res; 1183 ao_ref_init (&r, ref); 1184 res = ref_maybe_used_by_call_p_1 (call, &r); 1185 if (res) 1186 ++alias_stats.ref_maybe_used_by_call_p_may_alias; 1187 else 1188 ++alias_stats.ref_maybe_used_by_call_p_no_alias; 1189 return res; 1190 } 1191 1192 1193 /* If the statement STMT may use the memory reference REF return 1194 true, otherwise return false. */ 1195 1196 bool 1197 ref_maybe_used_by_stmt_p (gimple stmt, tree ref) 1198 { 1199 if (is_gimple_assign (stmt)) 1200 { 1201 tree rhs; 1202 1203 /* All memory assign statements are single. */ 1204 if (!gimple_assign_single_p (stmt)) 1205 return false; 1206 1207 rhs = gimple_assign_rhs1 (stmt); 1208 if (is_gimple_reg (rhs) 1209 || is_gimple_min_invariant (rhs) 1210 || gimple_assign_rhs_code (stmt) == CONSTRUCTOR) 1211 return false; 1212 1213 return refs_may_alias_p (rhs, ref); 1214 } 1215 else if (is_gimple_call (stmt)) 1216 return ref_maybe_used_by_call_p (stmt, ref); 1217 1218 return true; 1219 } 1220 1221 /* If the call in statement CALL may clobber the memory reference REF 1222 return true, otherwise return false. */ 1223 1224 static bool 1225 call_may_clobber_ref_p_1 (gimple call, ao_ref *ref) 1226 { 1227 tree base; 1228 tree callee; 1229 1230 /* If the call is pure or const it cannot clobber anything. */ 1231 if (gimple_call_flags (call) 1232 & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS)) 1233 return false; 1234 1235 base = ao_ref_base (ref); 1236 if (!base) 1237 return true; 1238 1239 if (TREE_CODE (base) == SSA_NAME 1240 || CONSTANT_CLASS_P (base)) 1241 return false; 1242 1243 /* If the reference is based on a decl that is not aliased the call 1244 cannot possibly clobber it. */ 1245 if (DECL_P (base) 1246 && !may_be_aliased (base) 1247 /* But local non-readonly statics can be modified through recursion 1248 or the call may implement a threading barrier which we must 1249 treat as may-def. */ 1250 && (TREE_READONLY (base) 1251 || !is_global_var (base))) 1252 return false; 1253 1254 callee = gimple_call_fndecl (call); 1255 1256 /* Handle those builtin functions explicitly that do not act as 1257 escape points. See tree-ssa-structalias.c:find_func_aliases 1258 for the list of builtins we might need to handle here. */ 1259 if (callee != NULL_TREE 1260 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL) 1261 switch (DECL_FUNCTION_CODE (callee)) 1262 { 1263 /* All the following functions clobber memory pointed to by 1264 their first argument. */ 1265 case BUILT_IN_STRCPY: 1266 case BUILT_IN_STRNCPY: 1267 case BUILT_IN_MEMCPY: 1268 case BUILT_IN_MEMMOVE: 1269 case BUILT_IN_MEMPCPY: 1270 case BUILT_IN_STPCPY: 1271 case BUILT_IN_STPNCPY: 1272 case BUILT_IN_STRCAT: 1273 case BUILT_IN_STRNCAT: 1274 case BUILT_IN_MEMSET: 1275 { 1276 ao_ref dref; 1277 tree size = NULL_TREE; 1278 if (gimple_call_num_args (call) == 3) 1279 size = gimple_call_arg (call, 2); 1280 ao_ref_init_from_ptr_and_size (&dref, 1281 gimple_call_arg (call, 0), 1282 size); 1283 return refs_may_alias_p_1 (&dref, ref, false); 1284 } 1285 case BUILT_IN_BCOPY: 1286 { 1287 ao_ref dref; 1288 tree size = gimple_call_arg (call, 2); 1289 ao_ref_init_from_ptr_and_size (&dref, 1290 gimple_call_arg (call, 1), 1291 size); 1292 return refs_may_alias_p_1 (&dref, ref, false); 1293 } 1294 /* Allocating memory does not have any side-effects apart from 1295 being the definition point for the pointer. */ 1296 case BUILT_IN_MALLOC: 1297 case BUILT_IN_CALLOC: 1298 /* Unix98 specifies that errno is set on allocation failure. 1299 Until we properly can track the errno location assume it 1300 is not a local decl but external or anonymous storage in 1301 a different translation unit. Also assume it is of 1302 type int as required by the standard. */ 1303 if (flag_errno_math 1304 && TREE_TYPE (base) == integer_type_node) 1305 { 1306 struct ptr_info_def *pi; 1307 if (DECL_P (base) 1308 && !TREE_STATIC (base)) 1309 return true; 1310 else if (INDIRECT_REF_P (base) 1311 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME 1312 && (pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0)))) 1313 return pi->pt.anything || pi->pt.nonlocal; 1314 } 1315 return false; 1316 /* Freeing memory kills the pointed-to memory. More importantly 1317 the call has to serve as a barrier for moving loads and stores 1318 across it. */ 1319 case BUILT_IN_FREE: 1320 { 1321 tree ptr = gimple_call_arg (call, 0); 1322 return ptr_deref_may_alias_ref_p_1 (ptr, ref); 1323 } 1324 case BUILT_IN_GAMMA_R: 1325 case BUILT_IN_GAMMAF_R: 1326 case BUILT_IN_GAMMAL_R: 1327 case BUILT_IN_LGAMMA_R: 1328 case BUILT_IN_LGAMMAF_R: 1329 case BUILT_IN_LGAMMAL_R: 1330 { 1331 tree out = gimple_call_arg (call, 1); 1332 if (ptr_deref_may_alias_ref_p_1 (out, ref)) 1333 return true; 1334 if (flag_errno_math) 1335 break; 1336 return false; 1337 } 1338 case BUILT_IN_FREXP: 1339 case BUILT_IN_FREXPF: 1340 case BUILT_IN_FREXPL: 1341 case BUILT_IN_MODF: 1342 case BUILT_IN_MODFF: 1343 case BUILT_IN_MODFL: 1344 { 1345 tree out = gimple_call_arg (call, 1); 1346 return ptr_deref_may_alias_ref_p_1 (out, ref); 1347 } 1348 case BUILT_IN_REMQUO: 1349 case BUILT_IN_REMQUOF: 1350 case BUILT_IN_REMQUOL: 1351 { 1352 tree out = gimple_call_arg (call, 2); 1353 if (ptr_deref_may_alias_ref_p_1 (out, ref)) 1354 return true; 1355 if (flag_errno_math) 1356 break; 1357 return false; 1358 } 1359 case BUILT_IN_SINCOS: 1360 case BUILT_IN_SINCOSF: 1361 case BUILT_IN_SINCOSL: 1362 { 1363 tree sin = gimple_call_arg (call, 1); 1364 tree cos = gimple_call_arg (call, 2); 1365 return (ptr_deref_may_alias_ref_p_1 (sin, ref) 1366 || ptr_deref_may_alias_ref_p_1 (cos, ref)); 1367 } 1368 default: 1369 /* Fallthru to general call handling. */; 1370 } 1371 1372 /* Check if base is a global static variable that is not written 1373 by the function. */ 1374 if (callee != NULL_TREE 1375 && TREE_CODE (base) == VAR_DECL 1376 && TREE_STATIC (base) 1377 && !TREE_PUBLIC (base)) 1378 { 1379 bitmap not_written; 1380 1381 if ((not_written 1382 = ipa_reference_get_not_written_global (cgraph_node (callee))) 1383 && bitmap_bit_p (not_written, DECL_UID (base))) 1384 return false; 1385 } 1386 1387 if (DECL_P (base)) 1388 return is_call_clobbered (base); 1389 else if (INDIRECT_REF_P (base) 1390 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME) 1391 { 1392 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0)); 1393 if (!pi) 1394 return true; 1395 1396 return (pt_solution_includes_global (&pi->pt) 1397 || pt_solutions_intersect (&cfun->gimple_df->escaped, &pi->pt)); 1398 } 1399 1400 return true; 1401 } 1402 1403 static bool ATTRIBUTE_UNUSED 1404 call_may_clobber_ref_p (gimple call, tree ref) 1405 { 1406 bool res; 1407 ao_ref r; 1408 ao_ref_init (&r, ref); 1409 res = call_may_clobber_ref_p_1 (call, &r); 1410 if (res) 1411 ++alias_stats.call_may_clobber_ref_p_may_alias; 1412 else 1413 ++alias_stats.call_may_clobber_ref_p_no_alias; 1414 return res; 1415 } 1416 1417 1418 /* If the statement STMT may clobber the memory reference REF return true, 1419 otherwise return false. */ 1420 1421 bool 1422 stmt_may_clobber_ref_p_1 (gimple stmt, ao_ref *ref) 1423 { 1424 if (is_gimple_call (stmt)) 1425 { 1426 tree lhs = gimple_call_lhs (stmt); 1427 if (lhs 1428 && !is_gimple_reg (lhs)) 1429 { 1430 ao_ref r; 1431 ao_ref_init (&r, lhs); 1432 if (refs_may_alias_p_1 (ref, &r, true)) 1433 return true; 1434 } 1435 1436 return call_may_clobber_ref_p_1 (stmt, ref); 1437 } 1438 else if (gimple_assign_single_p (stmt)) 1439 { 1440 tree lhs = gimple_assign_lhs (stmt); 1441 if (!is_gimple_reg (lhs)) 1442 { 1443 ao_ref r; 1444 ao_ref_init (&r, gimple_assign_lhs (stmt)); 1445 return refs_may_alias_p_1 (ref, &r, true); 1446 } 1447 } 1448 else if (gimple_code (stmt) == GIMPLE_ASM) 1449 return true; 1450 1451 return false; 1452 } 1453 1454 bool 1455 stmt_may_clobber_ref_p (gimple stmt, tree ref) 1456 { 1457 ao_ref r; 1458 ao_ref_init (&r, ref); 1459 return stmt_may_clobber_ref_p_1 (stmt, &r); 1460 } 1461 1462 1463 /* Walk the virtual use-def chain of VUSE until hitting the virtual operand 1464 TARGET or a statement clobbering the memory reference REF in which 1465 case false is returned. The walk starts with VUSE, one argument of PHI. */ 1466 1467 static bool 1468 maybe_skip_until (gimple phi, tree target, ao_ref *ref, 1469 tree vuse, bitmap *visited) 1470 { 1471 if (!*visited) 1472 *visited = BITMAP_ALLOC (NULL); 1473 1474 bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi))); 1475 1476 /* Walk until we hit the target. */ 1477 while (vuse != target) 1478 { 1479 gimple def_stmt = SSA_NAME_DEF_STMT (vuse); 1480 /* Recurse for PHI nodes. */ 1481 if (gimple_code (def_stmt) == GIMPLE_PHI) 1482 { 1483 /* An already visited PHI node ends the walk successfully. */ 1484 if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt)))) 1485 return true; 1486 vuse = get_continuation_for_phi (def_stmt, ref, visited); 1487 if (!vuse) 1488 return false; 1489 continue; 1490 } 1491 /* A clobbering statement or the end of the IL ends it failing. */ 1492 else if (gimple_nop_p (def_stmt) 1493 || stmt_may_clobber_ref_p_1 (def_stmt, ref)) 1494 return false; 1495 vuse = gimple_vuse (def_stmt); 1496 } 1497 return true; 1498 } 1499 1500 /* Starting from a PHI node for the virtual operand of the memory reference 1501 REF find a continuation virtual operand that allows to continue walking 1502 statements dominating PHI skipping only statements that cannot possibly 1503 clobber REF. Returns NULL_TREE if no suitable virtual operand can 1504 be found. */ 1505 1506 tree 1507 get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited) 1508 { 1509 unsigned nargs = gimple_phi_num_args (phi); 1510 1511 /* Through a single-argument PHI we can simply look through. */ 1512 if (nargs == 1) 1513 return PHI_ARG_DEF (phi, 0); 1514 1515 /* For two arguments try to skip non-aliasing code until we hit 1516 the phi argument definition that dominates the other one. */ 1517 if (nargs == 2) 1518 { 1519 tree arg0 = PHI_ARG_DEF (phi, 0); 1520 tree arg1 = PHI_ARG_DEF (phi, 1); 1521 gimple def0 = SSA_NAME_DEF_STMT (arg0); 1522 gimple def1 = SSA_NAME_DEF_STMT (arg1); 1523 tree common_vuse; 1524 1525 if (arg0 == arg1) 1526 return arg0; 1527 else if (gimple_nop_p (def0) 1528 || (!gimple_nop_p (def1) 1529 && dominated_by_p (CDI_DOMINATORS, 1530 gimple_bb (def1), gimple_bb (def0)))) 1531 { 1532 if (maybe_skip_until (phi, arg0, ref, arg1, visited)) 1533 return arg0; 1534 } 1535 else if (gimple_nop_p (def1) 1536 || dominated_by_p (CDI_DOMINATORS, 1537 gimple_bb (def0), gimple_bb (def1))) 1538 { 1539 if (maybe_skip_until (phi, arg1, ref, arg0, visited)) 1540 return arg1; 1541 } 1542 /* Special case of a diamond: 1543 MEM_1 = ... 1544 goto (cond) ? L1 : L2 1545 L1: store1 = ... #MEM_2 = vuse(MEM_1) 1546 goto L3 1547 L2: store2 = ... #MEM_3 = vuse(MEM_1) 1548 L3: MEM_4 = PHI<MEM_2, MEM_3> 1549 We were called with the PHI at L3, MEM_2 and MEM_3 don't 1550 dominate each other, but still we can easily skip this PHI node 1551 if we recognize that the vuse MEM operand is the same for both, 1552 and that we can skip both statements (they don't clobber us). 1553 This is still linear. Don't use maybe_skip_until, that might 1554 potentially be slow. */ 1555 else if ((common_vuse = gimple_vuse (def0)) 1556 && common_vuse == gimple_vuse (def1)) 1557 { 1558 if (!stmt_may_clobber_ref_p_1 (def0, ref) 1559 && !stmt_may_clobber_ref_p_1 (def1, ref)) 1560 return common_vuse; 1561 } 1562 } 1563 1564 return NULL_TREE; 1565 } 1566 1567 /* Based on the memory reference REF and its virtual use VUSE call 1568 WALKER for each virtual use that is equivalent to VUSE, including VUSE 1569 itself. That is, for each virtual use for which its defining statement 1570 does not clobber REF. 1571 1572 WALKER is called with REF, the current virtual use and DATA. If 1573 WALKER returns non-NULL the walk stops and its result is returned. 1574 At the end of a non-successful walk NULL is returned. 1575 1576 TRANSLATE if non-NULL is called with a pointer to REF, the virtual 1577 use which definition is a statement that may clobber REF and DATA. 1578 If TRANSLATE returns (void *)-1 the walk stops and NULL is returned. 1579 If TRANSLATE returns non-NULL the walk stops and its result is returned. 1580 If TRANSLATE returns NULL the walk continues and TRANSLATE is supposed 1581 to adjust REF and *DATA to make that valid. 1582 1583 TODO: Cache the vector of equivalent vuses per ref, vuse pair. */ 1584 1585 void * 1586 walk_non_aliased_vuses (ao_ref *ref, tree vuse, 1587 void *(*walker)(ao_ref *, tree, void *), 1588 void *(*translate)(ao_ref *, tree, void *), void *data) 1589 { 1590 bitmap visited = NULL; 1591 void *res; 1592 1593 timevar_push (TV_ALIAS_STMT_WALK); 1594 1595 do 1596 { 1597 gimple def_stmt; 1598 1599 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */ 1600 res = (*walker) (ref, vuse, data); 1601 if (res) 1602 break; 1603 1604 def_stmt = SSA_NAME_DEF_STMT (vuse); 1605 if (gimple_nop_p (def_stmt)) 1606 break; 1607 else if (gimple_code (def_stmt) == GIMPLE_PHI) 1608 vuse = get_continuation_for_phi (def_stmt, ref, &visited); 1609 else 1610 { 1611 if (stmt_may_clobber_ref_p_1 (def_stmt, ref)) 1612 { 1613 if (!translate) 1614 break; 1615 res = (*translate) (ref, vuse, data); 1616 /* Failed lookup and translation. */ 1617 if (res == (void *)-1) 1618 { 1619 res = NULL; 1620 break; 1621 } 1622 /* Lookup succeeded. */ 1623 else if (res != NULL) 1624 break; 1625 /* Translation succeeded, continue walking. */ 1626 } 1627 vuse = gimple_vuse (def_stmt); 1628 } 1629 } 1630 while (vuse); 1631 1632 if (visited) 1633 BITMAP_FREE (visited); 1634 1635 timevar_pop (TV_ALIAS_STMT_WALK); 1636 1637 return res; 1638 } 1639 1640 1641 /* Based on the memory reference REF call WALKER for each vdef which 1642 defining statement may clobber REF, starting with VDEF. If REF 1643 is NULL_TREE, each defining statement is visited. 1644 1645 WALKER is called with REF, the current vdef and DATA. If WALKER 1646 returns true the walk is stopped, otherwise it continues. 1647 1648 At PHI nodes walk_aliased_vdefs forks into one walk for reach 1649 PHI argument (but only one walk continues on merge points), the 1650 return value is true if any of the walks was successful. 1651 1652 The function returns the number of statements walked. */ 1653 1654 static unsigned int 1655 walk_aliased_vdefs_1 (ao_ref *ref, tree vdef, 1656 bool (*walker)(ao_ref *, tree, void *), void *data, 1657 bitmap *visited, unsigned int cnt) 1658 { 1659 do 1660 { 1661 gimple def_stmt = SSA_NAME_DEF_STMT (vdef); 1662 1663 if (*visited 1664 && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef))) 1665 return cnt; 1666 1667 if (gimple_nop_p (def_stmt)) 1668 return cnt; 1669 else if (gimple_code (def_stmt) == GIMPLE_PHI) 1670 { 1671 unsigned i; 1672 if (!*visited) 1673 *visited = BITMAP_ALLOC (NULL); 1674 for (i = 0; i < gimple_phi_num_args (def_stmt); ++i) 1675 cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i), 1676 walker, data, visited, 0); 1677 return cnt; 1678 } 1679 1680 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */ 1681 cnt++; 1682 if ((!ref 1683 || stmt_may_clobber_ref_p_1 (def_stmt, ref)) 1684 && (*walker) (ref, vdef, data)) 1685 return cnt; 1686 1687 vdef = gimple_vuse (def_stmt); 1688 } 1689 while (1); 1690 } 1691 1692 unsigned int 1693 walk_aliased_vdefs (ao_ref *ref, tree vdef, 1694 bool (*walker)(ao_ref *, tree, void *), void *data, 1695 bitmap *visited) 1696 { 1697 bitmap local_visited = NULL; 1698 unsigned int ret; 1699 1700 timevar_push (TV_ALIAS_STMT_WALK); 1701 1702 ret = walk_aliased_vdefs_1 (ref, vdef, walker, data, 1703 visited ? visited : &local_visited, 0); 1704 if (local_visited) 1705 BITMAP_FREE (local_visited); 1706 1707 timevar_pop (TV_ALIAS_STMT_WALK); 1708 1709 return ret; 1710 } 1711 1712