1/* Alias analysis for trees. 2 Copyright (C) 2004, 2005 Free Software Foundation, Inc. 3 Contributed by Diego Novillo <dnovillo@redhat.com> 4 5This file is part of GCC. 6 7GCC is free software; you can redistribute it and/or modify 8it under the terms of the GNU General Public License as published by 9the Free Software Foundation; either version 2, or (at your option) 10any later version. 11 12GCC is distributed in the hope that it will be useful, 13but WITHOUT ANY WARRANTY; without even the implied warranty of 14MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15GNU General Public License for more details. 16 17You should have received a copy of the GNU General Public License 18along with GCC; see the file COPYING. If not, write to 19the Free Software Foundation, 51 Franklin Street, Fifth Floor, 20Boston, MA 02110-1301, USA. */ 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 "tree-gimple.h" 40#include "tree-flow.h" 41#include "tree-inline.h" 42#include "tree-pass.h" 43#include "tree-ssa-structalias.h" 44#include "convert.h" 45#include "params.h" 46#include "ipa-type-escape.h" 47#include "vec.h" 48#include "bitmap.h" 49#include "pointer-set.h" 50 51/* Obstack used to hold grouping bitmaps and other temporary bitmaps used by 52 aliasing */ 53static bitmap_obstack alias_obstack; 54 55/* 'true' after aliases have been computed (see compute_may_aliases). */ 56bool aliases_computed_p; 57 58/* Structure to map a variable to its alias set and keep track of the 59 virtual operands that will be needed to represent it. */ 60struct alias_map_d 61{ 62 /* Variable and its alias set. */ 63 tree var; 64 HOST_WIDE_INT set; 65 66 /* Total number of virtual operands that will be needed to represent 67 all the aliases of VAR. */ 68 long total_alias_vops; 69 70 /* Nonzero if the aliases for this memory tag have been grouped 71 already. Used in group_aliases. */ 72 unsigned int grouped_p : 1; 73 74 /* Set of variables aliased with VAR. This is the exact same 75 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in 76 bitmap form to speed up alias grouping. */ 77 bitmap may_aliases; 78}; 79 80 81/* Counters used to display statistics on alias analysis. */ 82struct alias_stats_d 83{ 84 unsigned int alias_queries; 85 unsigned int alias_mayalias; 86 unsigned int alias_noalias; 87 unsigned int simple_queries; 88 unsigned int simple_resolved; 89 unsigned int tbaa_queries; 90 unsigned int tbaa_resolved; 91 unsigned int structnoaddress_queries; 92 unsigned int structnoaddress_resolved; 93}; 94 95 96/* Local variables. */ 97static struct alias_stats_d alias_stats; 98 99/* Local functions. */ 100static void compute_flow_insensitive_aliasing (struct alias_info *); 101static void dump_alias_stats (FILE *); 102static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT, bool); 103static tree create_memory_tag (tree type, bool is_type_tag); 104static tree get_tmt_for (tree, struct alias_info *); 105static tree get_nmt_for (tree); 106static void add_may_alias (tree, tree); 107static void replace_may_alias (tree, size_t, tree); 108static struct alias_info *init_alias_info (void); 109static void delete_alias_info (struct alias_info *); 110static void compute_flow_sensitive_aliasing (struct alias_info *); 111static void setup_pointers_and_addressables (struct alias_info *); 112static void create_global_var (void); 113static void maybe_create_global_var (struct alias_info *ai); 114static void group_aliases (struct alias_info *); 115static void set_pt_anything (tree ptr); 116 117/* Global declarations. */ 118 119/* Call clobbered variables in the function. If bit I is set, then 120 REFERENCED_VARS (I) is call-clobbered. */ 121bitmap call_clobbered_vars; 122 123/* Addressable variables in the function. If bit I is set, then 124 REFERENCED_VARS (I) has had its address taken. Note that 125 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An 126 addressable variable is not necessarily call-clobbered (e.g., a 127 local addressable whose address does not escape) and not all 128 call-clobbered variables are addressable (e.g., a local static 129 variable). */ 130bitmap addressable_vars; 131 132/* When the program has too many call-clobbered variables and call-sites, 133 this variable is used to represent the clobbering effects of function 134 calls. In these cases, all the call clobbered variables in the program 135 are forced to alias this variable. This reduces compile times by not 136 having to keep track of too many V_MAY_DEF expressions at call sites. */ 137tree global_var; 138 139 140/* Compute may-alias information for every variable referenced in function 141 FNDECL. 142 143 Alias analysis proceeds in 3 main phases: 144 145 1- Points-to and escape analysis. 146 147 This phase walks the use-def chains in the SSA web looking for three 148 things: 149 150 * Assignments of the form P_i = &VAR 151 * Assignments of the form P_i = malloc() 152 * Pointers and ADDR_EXPR that escape the current function. 153 154 The concept of 'escaping' is the same one used in the Java world. When 155 a pointer or an ADDR_EXPR escapes, it means that it has been exposed 156 outside of the current function. So, assignment to global variables, 157 function arguments and returning a pointer are all escape sites, as are 158 conversions between pointers and integers. 159 160 This is where we are currently limited. Since not everything is renamed 161 into SSA, we lose track of escape properties when a pointer is stashed 162 inside a field in a structure, for instance. In those cases, we are 163 assuming that the pointer does escape. 164 165 We use escape analysis to determine whether a variable is 166 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable 167 is call-clobbered. If a pointer P_i escapes, then all the variables 168 pointed-to by P_i (and its memory tag) also escape. 169 170 2- Compute flow-sensitive aliases 171 172 We have two classes of memory tags. Memory tags associated with the 173 pointed-to data type of the pointers in the program. These tags are 174 called "type memory tag" (TMT). The other class are those associated 175 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that 176 when adding operands for an INDIRECT_REF *P_i, we will first check 177 whether P_i has a name tag, if it does we use it, because that will have 178 more precise aliasing information. Otherwise, we use the standard type 179 tag. 180 181 In this phase, we go through all the pointers we found in points-to 182 analysis and create alias sets for the name memory tags associated with 183 each pointer P_i. If P_i escapes, we mark call-clobbered the variables 184 it points to and its tag. 185 186 187 3- Compute flow-insensitive aliases 188 189 This pass will compare the alias set of every type memory tag and every 190 addressable variable found in the program. Given a type memory tag TMT 191 and an addressable variable V. If the alias sets of TMT and V conflict 192 (as computed by may_alias_p), then V is marked as an alias tag and added 193 to the alias set of TMT. 194 195 For instance, consider the following function: 196 197 foo (int i) 198 { 199 int *p, a, b; 200 201 if (i > 10) 202 p = &a; 203 else 204 p = &b; 205 206 *p = 3; 207 a = b + 2; 208 return *p; 209 } 210 211 After aliasing analysis has finished, the type memory tag for pointer 212 'p' will have two aliases, namely variables 'a' and 'b'. Every time 213 pointer 'p' is dereferenced, we want to mark the operation as a 214 potential reference to 'a' and 'b'. 215 216 foo (int i) 217 { 218 int *p, a, b; 219 220 if (i_2 > 10) 221 p_4 = &a; 222 else 223 p_6 = &b; 224 # p_1 = PHI <p_4(1), p_6(2)>; 225 226 # a_7 = V_MAY_DEF <a_3>; 227 # b_8 = V_MAY_DEF <b_5>; 228 *p_1 = 3; 229 230 # a_9 = V_MAY_DEF <a_7> 231 # VUSE <b_8> 232 a_9 = b_8 + 2; 233 234 # VUSE <a_9>; 235 # VUSE <b_8>; 236 return *p_1; 237 } 238 239 In certain cases, the list of may aliases for a pointer may grow too 240 large. This may cause an explosion in the number of virtual operands 241 inserted in the code. Resulting in increased memory consumption and 242 compilation time. 243 244 When the number of virtual operands needed to represent aliased 245 loads and stores grows too large (configurable with @option{--param 246 max-aliased-vops}), alias sets are grouped to avoid severe 247 compile-time slow downs and memory consumption. See group_aliases. */ 248 249static void 250compute_may_aliases (void) 251{ 252 struct alias_info *ai; 253 254 memset (&alias_stats, 0, sizeof (alias_stats)); 255 256 /* Initialize aliasing information. */ 257 ai = init_alias_info (); 258 259 /* For each pointer P_i, determine the sets of variables that P_i may 260 point-to. For every addressable variable V, determine whether the 261 address of V escapes the current function, making V call-clobbered 262 (i.e., whether &V is stored in a global variable or if its passed as a 263 function call argument). */ 264 compute_points_to_sets (ai); 265 266 /* Collect all pointers and addressable variables, compute alias sets, 267 create memory tags for pointers and promote variables whose address is 268 not needed anymore. */ 269 setup_pointers_and_addressables (ai); 270 271 /* Compute flow-sensitive, points-to based aliasing for all the name 272 memory tags. Note that this pass needs to be done before flow 273 insensitive analysis because it uses the points-to information 274 gathered before to mark call-clobbered type tags. */ 275 compute_flow_sensitive_aliasing (ai); 276 277 /* Compute type-based flow-insensitive aliasing for all the type 278 memory tags. */ 279 compute_flow_insensitive_aliasing (ai); 280 281 /* If the program has too many call-clobbered variables and/or function 282 calls, create .GLOBAL_VAR and use it to model call-clobbering 283 semantics at call sites. This reduces the number of virtual operands 284 considerably, improving compile times at the expense of lost 285 aliasing precision. */ 286 maybe_create_global_var (ai); 287 288 /* Debugging dumps. */ 289 if (dump_file) 290 { 291 dump_referenced_vars (dump_file); 292 if (dump_flags & TDF_STATS) 293 dump_alias_stats (dump_file); 294 dump_points_to_info (dump_file); 295 dump_alias_info (dump_file); 296 } 297 298 /* Deallocate memory used by aliasing data structures. */ 299 delete_alias_info (ai); 300 301 { 302 block_stmt_iterator bsi; 303 basic_block bb; 304 FOR_EACH_BB (bb) 305 { 306 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) 307 { 308 update_stmt_if_modified (bsi_stmt (bsi)); 309 } 310 } 311 } 312 313} 314 315struct tree_opt_pass pass_may_alias = 316{ 317 "alias", /* name */ 318 NULL, /* gate */ 319 compute_may_aliases, /* execute */ 320 NULL, /* sub */ 321 NULL, /* next */ 322 0, /* static_pass_number */ 323 TV_TREE_MAY_ALIAS, /* tv_id */ 324 PROP_cfg | PROP_ssa, /* properties_required */ 325 PROP_alias, /* properties_provided */ 326 0, /* properties_destroyed */ 327 0, /* todo_flags_start */ 328 TODO_dump_func | TODO_update_ssa 329 | TODO_ggc_collect | TODO_verify_ssa 330 | TODO_verify_stmts, /* todo_flags_finish */ 331 0 /* letter */ 332}; 333 334 335/* Data structure used to count the number of dereferences to PTR 336 inside an expression. */ 337struct count_ptr_d 338{ 339 tree ptr; 340 unsigned count; 341}; 342 343 344/* Helper for count_uses_and_derefs. Called by walk_tree to look for 345 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */ 346 347static tree 348count_ptr_derefs (tree *tp, int *walk_subtrees, void *data) 349{ 350 struct count_ptr_d *count_p = (struct count_ptr_d *) data; 351 352 /* Do not walk inside ADDR_EXPR nodes. In the expression &ptr->fld, 353 pointer 'ptr' is *not* dereferenced, it is simply used to compute 354 the address of 'fld' as 'ptr + offsetof(fld)'. */ 355 if (TREE_CODE (*tp) == ADDR_EXPR) 356 { 357 *walk_subtrees = 0; 358 return NULL_TREE; 359 } 360 361 if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr) 362 count_p->count++; 363 364 return NULL_TREE; 365} 366 367 368/* Count the number of direct and indirect uses for pointer PTR in 369 statement STMT. The two counts are stored in *NUM_USES_P and 370 *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at 371 least one of those dereferences is a store operation. */ 372 373void 374count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p, 375 unsigned *num_derefs_p, bool *is_store) 376{ 377 ssa_op_iter i; 378 tree use; 379 380 *num_uses_p = 0; 381 *num_derefs_p = 0; 382 *is_store = false; 383 384 /* Find out the total number of uses of PTR in STMT. */ 385 FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE) 386 if (use == ptr) 387 (*num_uses_p)++; 388 389 /* Now count the number of indirect references to PTR. This is 390 truly awful, but we don't have much choice. There are no parent 391 pointers inside INDIRECT_REFs, so an expression like 392 '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to 393 find all the indirect and direct uses of x_1 inside. The only 394 shortcut we can take is the fact that GIMPLE only allows 395 INDIRECT_REFs inside the expressions below. */ 396 if (TREE_CODE (stmt) == MODIFY_EXPR 397 || (TREE_CODE (stmt) == RETURN_EXPR 398 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR) 399 || TREE_CODE (stmt) == ASM_EXPR 400 || TREE_CODE (stmt) == CALL_EXPR) 401 { 402 tree lhs, rhs; 403 404 if (TREE_CODE (stmt) == MODIFY_EXPR) 405 { 406 lhs = TREE_OPERAND (stmt, 0); 407 rhs = TREE_OPERAND (stmt, 1); 408 } 409 else if (TREE_CODE (stmt) == RETURN_EXPR) 410 { 411 tree e = TREE_OPERAND (stmt, 0); 412 lhs = TREE_OPERAND (e, 0); 413 rhs = TREE_OPERAND (e, 1); 414 } 415 else if (TREE_CODE (stmt) == ASM_EXPR) 416 { 417 lhs = ASM_OUTPUTS (stmt); 418 rhs = ASM_INPUTS (stmt); 419 } 420 else 421 { 422 lhs = NULL_TREE; 423 rhs = stmt; 424 } 425 426 if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs))) 427 { 428 struct count_ptr_d count; 429 count.ptr = ptr; 430 count.count = 0; 431 walk_tree (&lhs, count_ptr_derefs, &count, NULL); 432 *is_store = true; 433 *num_derefs_p = count.count; 434 } 435 436 if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs))) 437 { 438 struct count_ptr_d count; 439 count.ptr = ptr; 440 count.count = 0; 441 walk_tree (&rhs, count_ptr_derefs, &count, NULL); 442 *num_derefs_p += count.count; 443 } 444 } 445 446 gcc_assert (*num_uses_p >= *num_derefs_p); 447} 448 449/* Initialize the data structures used for alias analysis. */ 450 451static struct alias_info * 452init_alias_info (void) 453{ 454 struct alias_info *ai; 455 referenced_var_iterator rvi; 456 tree var; 457 458 bitmap_obstack_initialize (&alias_obstack); 459 ai = xcalloc (1, sizeof (struct alias_info)); 460 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names); 461 sbitmap_zero (ai->ssa_names_visited); 462 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs"); 463 ai->written_vars = BITMAP_ALLOC (&alias_obstack); 464 ai->dereferenced_ptrs_store = BITMAP_ALLOC (&alias_obstack); 465 ai->dereferenced_ptrs_load = BITMAP_ALLOC (&alias_obstack); 466 467 /* If aliases have been computed before, clear existing information. */ 468 if (aliases_computed_p) 469 { 470 unsigned i; 471 472 /* Similarly, clear the set of addressable variables. In this 473 case, we can just clear the set because addressability is 474 only computed here. */ 475 bitmap_clear (addressable_vars); 476 477 /* Clear flow-insensitive alias information from each symbol. */ 478 FOR_EACH_REFERENCED_VAR (var, rvi) 479 { 480 var_ann_t ann = var_ann (var); 481 482 ann->is_alias_tag = 0; 483 ann->may_aliases = NULL; 484 NUM_REFERENCES_CLEAR (ann); 485 486 /* Since we are about to re-discover call-clobbered 487 variables, clear the call-clobbered flag. Variables that 488 are intrinsically call-clobbered (globals, local statics, 489 etc) will not be marked by the aliasing code, so we can't 490 remove them from CALL_CLOBBERED_VARS. 491 492 NB: STRUCT_FIELDS are still call clobbered if they are for 493 a global variable, so we *don't* clear their call clobberedness 494 just because they are tags, though we will clear it if they 495 aren't for global variables. */ 496 if (ann->mem_tag_kind == NAME_TAG 497 || ann->mem_tag_kind == TYPE_TAG 498 || !is_global_var (var)) 499 clear_call_clobbered (var); 500 } 501 502 /* Clear flow-sensitive points-to information from each SSA name. */ 503 for (i = 1; i < num_ssa_names; i++) 504 { 505 tree name = ssa_name (i); 506 507 if (!name || !POINTER_TYPE_P (TREE_TYPE (name))) 508 continue; 509 510 if (SSA_NAME_PTR_INFO (name)) 511 { 512 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name); 513 514 /* Clear all the flags but keep the name tag to 515 avoid creating new temporaries unnecessarily. If 516 this pointer is found to point to a subset or 517 superset of its former points-to set, then a new 518 tag will need to be created in create_name_tags. */ 519 pi->pt_anything = 0; 520 pi->pt_null = 0; 521 pi->value_escapes_p = 0; 522 pi->is_dereferenced = 0; 523 if (pi->pt_vars) 524 bitmap_clear (pi->pt_vars); 525 } 526 } 527 } 528 529 /* Next time, we will need to reset alias information. */ 530 aliases_computed_p = true; 531 532 return ai; 533} 534 535 536/* Deallocate memory used by alias analysis. */ 537 538static void 539delete_alias_info (struct alias_info *ai) 540{ 541 size_t i; 542 referenced_var_iterator rvi; 543 tree var; 544 545 sbitmap_free (ai->ssa_names_visited); 546 ai->processed_ptrs = NULL; 547 548 for (i = 0; i < ai->num_addressable_vars; i++) 549 free (ai->addressable_vars[i]); 550 551 FOR_EACH_REFERENCED_VAR(var, rvi) 552 { 553 var_ann_t ann = var_ann (var); 554 NUM_REFERENCES_CLEAR (ann); 555 } 556 557 free (ai->addressable_vars); 558 559 for (i = 0; i < ai->num_pointers; i++) 560 free (ai->pointers[i]); 561 free (ai->pointers); 562 563 BITMAP_FREE (ai->written_vars); 564 BITMAP_FREE (ai->dereferenced_ptrs_store); 565 BITMAP_FREE (ai->dereferenced_ptrs_load); 566 bitmap_obstack_release (&alias_obstack); 567 free (ai); 568 569 delete_points_to_sets (); 570} 571 572/* Create name tags for all the pointers that have been dereferenced. 573 We only create a name tag for a pointer P if P is found to point to 574 a set of variables (so that we can alias them to *P) or if it is 575 the result of a call to malloc (which means that P cannot point to 576 anything else nor alias any other variable). 577 578 If two pointers P and Q point to the same set of variables, they 579 are assigned the same name tag. */ 580 581static void 582create_name_tags (void) 583{ 584 size_t i; 585 VEC (tree, heap) *with_ptvars = NULL; 586 tree ptr; 587 588 /* Collect the list of pointers with a non-empty points to set. */ 589 for (i = 1; i < num_ssa_names; i++) 590 { 591 tree ptr = ssa_name (i); 592 struct ptr_info_def *pi; 593 594 if (!ptr 595 || !POINTER_TYPE_P (TREE_TYPE (ptr)) 596 || !SSA_NAME_PTR_INFO (ptr)) 597 continue; 598 599 pi = SSA_NAME_PTR_INFO (ptr); 600 601 if (pi->pt_anything || !pi->is_dereferenced) 602 { 603 /* No name tags for pointers that have not been 604 dereferenced or point to an arbitrary location. */ 605 pi->name_mem_tag = NULL_TREE; 606 continue; 607 } 608 609 /* Set pt_anything on the pointers without pt_vars filled in so 610 that they are assigned a type tag. */ 611 612 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars)) 613 VEC_safe_push (tree, heap, with_ptvars, ptr); 614 else 615 set_pt_anything (ptr); 616 } 617 618 /* If we didn't find any pointers with pt_vars set, we're done. */ 619 if (!with_ptvars) 620 return; 621 622 /* Now go through the pointers with pt_vars, and find a name tag 623 with the same pt_vars as this pointer, or create one if one 624 doesn't exist. */ 625 for (i = 0; VEC_iterate (tree, with_ptvars, i, ptr); i++) 626 { 627 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); 628 size_t j; 629 tree ptr2; 630 tree old_name_tag = pi->name_mem_tag; 631 632 /* If PTR points to a set of variables, check if we don't 633 have another pointer Q with the same points-to set before 634 creating a tag. If so, use Q's tag instead of creating a 635 new one. 636 637 This is important for not creating unnecessary symbols 638 and also for copy propagation. If we ever need to 639 propagate PTR into Q or vice-versa, we would run into 640 problems if they both had different name tags because 641 they would have different SSA version numbers (which 642 would force us to take the name tags in and out of SSA). */ 643 for (j = 0; j < i && VEC_iterate (tree, with_ptvars, j, ptr2); j++) 644 { 645 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (ptr2); 646 647 if (bitmap_equal_p (pi->pt_vars, qi->pt_vars)) 648 { 649 pi->name_mem_tag = qi->name_mem_tag; 650 break; 651 } 652 } 653 654 /* If we didn't find a pointer with the same points-to set 655 as PTR, create a new name tag if needed. */ 656 if (pi->name_mem_tag == NULL_TREE) 657 pi->name_mem_tag = get_nmt_for (ptr); 658 659 /* If the new name tag computed for PTR is different than 660 the old name tag that it used to have, then the old tag 661 needs to be removed from the IL, so we mark it for 662 renaming. */ 663 if (old_name_tag && old_name_tag != pi->name_mem_tag) 664 mark_sym_for_renaming (old_name_tag); 665 666 TREE_THIS_VOLATILE (pi->name_mem_tag) 667 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr))); 668 669 /* Mark the new name tag for renaming. */ 670 mark_sym_for_renaming (pi->name_mem_tag); 671 } 672 673 VEC_free (tree, heap, with_ptvars); 674} 675 676 677/* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for 678 the name memory tag (NMT) associated with P_i. If P_i escapes, then its 679 name tag and the variables it points-to are call-clobbered. Finally, if 680 P_i escapes and we could not determine where it points to, then all the 681 variables in the same alias set as *P_i are marked call-clobbered. This 682 is necessary because we must assume that P_i may take the address of any 683 variable in the same alias set. */ 684 685static void 686compute_flow_sensitive_aliasing (struct alias_info *ai) 687{ 688 size_t i; 689 690 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++) 691 { 692 tree ptr = VARRAY_TREE (ai->processed_ptrs, i); 693 if (!find_what_p_points_to (ptr)) 694 set_pt_anything (ptr); 695 } 696 697 create_name_tags (); 698 699 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++) 700 { 701 unsigned j; 702 tree ptr = VARRAY_TREE (ai->processed_ptrs, i); 703 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); 704 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr)); 705 bitmap_iterator bi; 706 707 if (pi->value_escapes_p || pi->pt_anything) 708 { 709 /* If PTR escapes or may point to anything, then its associated 710 memory tags and pointed-to variables are call-clobbered. */ 711 if (pi->name_mem_tag) 712 mark_call_clobbered (pi->name_mem_tag); 713 714 if (v_ann->type_mem_tag) 715 mark_call_clobbered (v_ann->type_mem_tag); 716 717 if (pi->pt_vars) 718 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi) 719 mark_call_clobbered (referenced_var (j)); 720 } 721 722 /* Set up aliasing information for PTR's name memory tag (if it has 723 one). Note that only pointers that have been dereferenced will 724 have a name memory tag. */ 725 if (pi->name_mem_tag && pi->pt_vars) 726 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi) 727 { 728 add_may_alias (pi->name_mem_tag, referenced_var (j)); 729 add_may_alias (v_ann->type_mem_tag, referenced_var (j)); 730 } 731 732 /* If the name tag is call clobbered, so is the type tag 733 associated with the base VAR_DECL. */ 734 if (pi->name_mem_tag 735 && v_ann->type_mem_tag 736 && is_call_clobbered (pi->name_mem_tag)) 737 mark_call_clobbered (v_ann->type_mem_tag); 738 } 739} 740 741 742/* Compute type-based alias sets. Traverse all the pointers and 743 addressable variables found in setup_pointers_and_addressables. 744 745 For every pointer P in AI->POINTERS and addressable variable V in 746 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type 747 memory tag (TMT) if their alias sets conflict. V is then marked as 748 an alias tag so that the operand scanner knows that statements 749 containing V have aliased operands. */ 750 751static void 752compute_flow_insensitive_aliasing (struct alias_info *ai) 753{ 754 size_t i; 755 756 /* Initialize counter for the total number of virtual operands that 757 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the 758 threshold set by --params max-alias-vops, we enable alias 759 grouping. */ 760 ai->total_alias_vops = 0; 761 762 /* For every pointer P, determine which addressable variables may alias 763 with P's type memory tag. */ 764 for (i = 0; i < ai->num_pointers; i++) 765 { 766 size_t j; 767 struct alias_map_d *p_map = ai->pointers[i]; 768 tree tag = var_ann (p_map->var)->type_mem_tag; 769 var_ann_t tag_ann = var_ann (tag); 770 tree var; 771 772 p_map->total_alias_vops = 0; 773 p_map->may_aliases = BITMAP_ALLOC (&alias_obstack); 774 775 /* Add any pre-existing may_aliases to the bitmap used to represent 776 TAG's alias set in case we need to group aliases. */ 777 if (tag_ann->may_aliases) 778 for (j = 0; j < VARRAY_ACTIVE_SIZE (tag_ann->may_aliases); ++j) 779 bitmap_set_bit (p_map->may_aliases, 780 DECL_UID (VARRAY_TREE (tag_ann->may_aliases, j))); 781 782 for (j = 0; j < ai->num_addressable_vars; j++) 783 { 784 struct alias_map_d *v_map; 785 var_ann_t v_ann; 786 bool tag_stored_p, var_stored_p; 787 788 v_map = ai->addressable_vars[j]; 789 var = v_map->var; 790 v_ann = var_ann (var); 791 792 /* Skip memory tags and variables that have never been 793 written to. We also need to check if the variables are 794 call-clobbered because they may be overwritten by 795 function calls. 796 797 Note this is effectively random accessing elements in 798 the sparse bitset, which can be highly inefficient. 799 So we first check the call_clobbered status of the 800 tag and variable before querying the bitmap. */ 801 tag_stored_p = is_call_clobbered (tag) 802 || bitmap_bit_p (ai->written_vars, DECL_UID (tag)); 803 var_stored_p = is_call_clobbered (var) 804 || bitmap_bit_p (ai->written_vars, DECL_UID (var)); 805 if (!tag_stored_p && !var_stored_p) 806 continue; 807 808 if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false)) 809 { 810 size_t num_tag_refs, num_var_refs; 811 812 num_tag_refs = NUM_REFERENCES (tag_ann); 813 num_var_refs = NUM_REFERENCES (v_ann); 814 815 /* Add VAR to TAG's may-aliases set. */ 816 817 /* We should never have a var with subvars here, because 818 they shouldn't get into the set of addressable vars */ 819 gcc_assert (!var_can_have_subvars (var) 820 || get_subvars_for_var (var) == NULL); 821 822 add_may_alias (tag, var); 823 /* Update the bitmap used to represent TAG's alias set 824 in case we need to group aliases. */ 825 bitmap_set_bit (p_map->may_aliases, DECL_UID (var)); 826 827 /* Update the total number of virtual operands due to 828 aliasing. Since we are adding one more alias to TAG's 829 may-aliases set, the total number of virtual operands due 830 to aliasing will be increased by the number of references 831 made to VAR and TAG (every reference to TAG will also 832 count as a reference to VAR). */ 833 ai->total_alias_vops += (num_var_refs + num_tag_refs); 834 p_map->total_alias_vops += (num_var_refs + num_tag_refs); 835 836 837 } 838 } 839 } 840 841 /* Since this analysis is based exclusively on symbols, it fails to 842 handle cases where two pointers P and Q have different memory 843 tags with conflicting alias set numbers but no aliased symbols in 844 common. 845 846 For example, suppose that we have two memory tags TMT.1 and TMT.2 847 such that 848 849 may-aliases (TMT.1) = { a } 850 may-aliases (TMT.2) = { b } 851 852 and the alias set number of TMT.1 conflicts with that of TMT.2. 853 Since they don't have symbols in common, loads and stores from 854 TMT.1 and TMT.2 will seem independent of each other, which will 855 lead to the optimizers making invalid transformations (see 856 testsuite/gcc.c-torture/execute/pr15262-[12].c). 857 858 To avoid this problem, we do a final traversal of AI->POINTERS 859 looking for pairs of pointers that have no aliased symbols in 860 common and yet have conflicting alias set numbers. */ 861 for (i = 0; i < ai->num_pointers; i++) 862 { 863 size_t j; 864 struct alias_map_d *p_map1 = ai->pointers[i]; 865 tree tag1 = var_ann (p_map1->var)->type_mem_tag; 866 bitmap may_aliases1 = p_map1->may_aliases; 867 868 for (j = i + 1; j < ai->num_pointers; j++) 869 { 870 struct alias_map_d *p_map2 = ai->pointers[j]; 871 tree tag2 = var_ann (p_map2->var)->type_mem_tag; 872 bitmap may_aliases2 = p_map2->may_aliases; 873 874 /* If the pointers may not point to each other, do nothing. */ 875 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true)) 876 continue; 877 878 /* The two pointers may alias each other. If they already have 879 symbols in common, do nothing. */ 880 if (bitmap_intersect_p (may_aliases1, may_aliases2)) 881 continue; 882 883 if (!bitmap_empty_p (may_aliases2)) 884 { 885 unsigned int k; 886 bitmap_iterator bi; 887 888 /* Add all the aliases for TAG2 into TAG1's alias set. 889 FIXME, update grouping heuristic counters. */ 890 EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi) 891 add_may_alias (tag1, referenced_var (k)); 892 bitmap_ior_into (may_aliases1, may_aliases2); 893 } 894 else 895 { 896 /* Since TAG2 does not have any aliases of its own, add 897 TAG2 itself to the alias set of TAG1. */ 898 add_may_alias (tag1, tag2); 899 bitmap_set_bit (may_aliases1, DECL_UID (tag2)); 900 } 901 } 902 } 903 904 if (dump_file) 905 fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n", 906 get_name (current_function_decl), 907 ai->total_alias_vops); 908 909 /* Determine if we need to enable alias grouping. */ 910 if (ai->total_alias_vops >= MAX_ALIASED_VOPS) 911 group_aliases (ai); 912} 913 914 915/* Comparison function for qsort used in group_aliases. */ 916 917static int 918total_alias_vops_cmp (const void *p, const void *q) 919{ 920 const struct alias_map_d **p1 = (const struct alias_map_d **)p; 921 const struct alias_map_d **p2 = (const struct alias_map_d **)q; 922 long n1 = (*p1)->total_alias_vops; 923 long n2 = (*p2)->total_alias_vops; 924 925 /* We want to sort in descending order. */ 926 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1); 927} 928 929/* Group all the aliases for TAG to make TAG represent all the 930 variables in its alias set. Update the total number 931 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This 932 function will make TAG be the unique alias tag for all the 933 variables in its may-aliases. So, given: 934 935 may-aliases(TAG) = { V1, V2, V3 } 936 937 This function will group the variables into: 938 939 may-aliases(V1) = { TAG } 940 may-aliases(V2) = { TAG } 941 may-aliases(V2) = { TAG } */ 942 943static void 944group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai) 945{ 946 unsigned int i; 947 var_ann_t tag_ann = var_ann (tag); 948 size_t num_tag_refs = NUM_REFERENCES (tag_ann); 949 bitmap_iterator bi; 950 951 EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi) 952 { 953 tree var = referenced_var (i); 954 var_ann_t ann = var_ann (var); 955 956 /* Make TAG the unique alias of VAR. */ 957 ann->is_alias_tag = 0; 958 ann->may_aliases = NULL; 959 960 /* Note that VAR and TAG may be the same if the function has no 961 addressable variables (see the discussion at the end of 962 setup_pointers_and_addressables). */ 963 if (var != tag) 964 add_may_alias (var, tag); 965 966 /* Reduce total number of virtual operands contributed 967 by TAG on behalf of VAR. Notice that the references to VAR 968 itself won't be removed. We will merely replace them with 969 references to TAG. */ 970 ai->total_alias_vops -= num_tag_refs; 971 } 972 973 /* We have reduced the number of virtual operands that TAG makes on 974 behalf of all the variables formerly aliased with it. However, 975 we have also "removed" all the virtual operands for TAG itself, 976 so we add them back. */ 977 ai->total_alias_vops += num_tag_refs; 978 979 /* TAG no longer has any aliases. */ 980 tag_ann->may_aliases = NULL; 981} 982 983 984/* Group may-aliases sets to reduce the number of virtual operands due 985 to aliasing. 986 987 1- Sort the list of pointers in decreasing number of contributed 988 virtual operands. 989 990 2- Take the first entry in AI->POINTERS and revert the role of 991 the memory tag and its aliases. Usually, whenever an aliased 992 variable Vi is found to alias with a memory tag T, we add Vi 993 to the may-aliases set for T. Meaning that after alias 994 analysis, we will have: 995 996 may-aliases(T) = { V1, V2, V3, ..., Vn } 997 998 This means that every statement that references T, will get 'n' 999 virtual operands for each of the Vi tags. But, when alias 1000 grouping is enabled, we make T an alias tag and add it to the 1001 alias set of all the Vi variables: 1002 1003 may-aliases(V1) = { T } 1004 may-aliases(V2) = { T } 1005 ... 1006 may-aliases(Vn) = { T } 1007 1008 This has two effects: (a) statements referencing T will only get 1009 a single virtual operand, and, (b) all the variables Vi will now 1010 appear to alias each other. So, we lose alias precision to 1011 improve compile time. But, in theory, a program with such a high 1012 level of aliasing should not be very optimizable in the first 1013 place. 1014 1015 3- Since variables may be in the alias set of more than one 1016 memory tag, the grouping done in step (2) needs to be extended 1017 to all the memory tags that have a non-empty intersection with 1018 the may-aliases set of tag T. For instance, if we originally 1019 had these may-aliases sets: 1020 1021 may-aliases(T) = { V1, V2, V3 } 1022 may-aliases(R) = { V2, V4 } 1023 1024 In step (2) we would have reverted the aliases for T as: 1025 1026 may-aliases(V1) = { T } 1027 may-aliases(V2) = { T } 1028 may-aliases(V3) = { T } 1029 1030 But note that now V2 is no longer aliased with R. We could 1031 add R to may-aliases(V2), but we are in the process of 1032 grouping aliases to reduce virtual operands so what we do is 1033 add V4 to the grouping to obtain: 1034 1035 may-aliases(V1) = { T } 1036 may-aliases(V2) = { T } 1037 may-aliases(V3) = { T } 1038 may-aliases(V4) = { T } 1039 1040 4- If the total number of virtual operands due to aliasing is 1041 still above the threshold set by max-alias-vops, go back to (2). */ 1042 1043static void 1044group_aliases (struct alias_info *ai) 1045{ 1046 size_t i; 1047 1048 /* Sort the POINTERS array in descending order of contributed 1049 virtual operands. */ 1050 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *), 1051 total_alias_vops_cmp); 1052 1053 /* For every pointer in AI->POINTERS, reverse the roles of its tag 1054 and the tag's may-aliases set. */ 1055 for (i = 0; i < ai->num_pointers; i++) 1056 { 1057 size_t j; 1058 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag; 1059 bitmap tag1_aliases = ai->pointers[i]->may_aliases; 1060 1061 /* Skip tags that have been grouped already. */ 1062 if (ai->pointers[i]->grouped_p) 1063 continue; 1064 1065 /* See if TAG1 had any aliases in common with other type tags. 1066 If we find a TAG2 with common aliases with TAG1, add TAG2's 1067 aliases into TAG1. */ 1068 for (j = i + 1; j < ai->num_pointers; j++) 1069 { 1070 bitmap tag2_aliases = ai->pointers[j]->may_aliases; 1071 1072 if (bitmap_intersect_p (tag1_aliases, tag2_aliases)) 1073 { 1074 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag; 1075 1076 bitmap_ior_into (tag1_aliases, tag2_aliases); 1077 1078 /* TAG2 does not need its aliases anymore. */ 1079 bitmap_clear (tag2_aliases); 1080 var_ann (tag2)->may_aliases = NULL; 1081 1082 /* TAG1 is the unique alias of TAG2. */ 1083 add_may_alias (tag2, tag1); 1084 1085 ai->pointers[j]->grouped_p = true; 1086 } 1087 } 1088 1089 /* Now group all the aliases we collected into TAG1. */ 1090 group_aliases_into (tag1, tag1_aliases, ai); 1091 1092 /* If we've reduced total number of virtual operands below the 1093 threshold, stop. */ 1094 if (ai->total_alias_vops < MAX_ALIASED_VOPS) 1095 break; 1096 } 1097 1098 /* Finally, all the variables that have been grouped cannot be in 1099 the may-alias set of name memory tags. Suppose that we have 1100 grouped the aliases in this code so that may-aliases(a) = TMT.20 1101 1102 p_5 = &a; 1103 ... 1104 # a_9 = V_MAY_DEF <a_8> 1105 p_5->field = 0 1106 ... Several modifications to TMT.20 ... 1107 # VUSE <a_9> 1108 x_30 = p_5->field 1109 1110 Since p_5 points to 'a', the optimizers will try to propagate 0 1111 into p_5->field, but that is wrong because there have been 1112 modifications to 'TMT.20' in between. To prevent this we have to 1113 replace 'a' with 'TMT.20' in the name tag of p_5. */ 1114 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++) 1115 { 1116 size_t j; 1117 tree ptr = VARRAY_TREE (ai->processed_ptrs, i); 1118 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag; 1119 varray_type aliases; 1120 1121 if (name_tag == NULL_TREE) 1122 continue; 1123 1124 aliases = var_ann (name_tag)->may_aliases; 1125 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++) 1126 { 1127 tree alias = VARRAY_TREE (aliases, j); 1128 var_ann_t ann = var_ann (alias); 1129 1130 if ((ann->mem_tag_kind == NOT_A_TAG 1131 || ann->mem_tag_kind == STRUCT_FIELD) 1132 && ann->may_aliases) 1133 { 1134 tree new_alias; 1135 1136 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1); 1137 1138 new_alias = VARRAY_TREE (ann->may_aliases, 0); 1139 replace_may_alias (name_tag, j, new_alias); 1140 } 1141 } 1142 } 1143 1144 if (dump_file) 1145 fprintf (dump_file, 1146 "%s: Total number of aliased vops after grouping: %ld%s\n", 1147 get_name (current_function_decl), 1148 ai->total_alias_vops, 1149 (ai->total_alias_vops < 0) ? " (negative values are OK)" : ""); 1150} 1151 1152 1153/* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */ 1154 1155static void 1156create_alias_map_for (tree var, struct alias_info *ai) 1157{ 1158 struct alias_map_d *alias_map; 1159 alias_map = xcalloc (1, sizeof (*alias_map)); 1160 alias_map->var = var; 1161 alias_map->set = get_alias_set (var); 1162 ai->addressable_vars[ai->num_addressable_vars++] = alias_map; 1163} 1164 1165 1166/* Create memory tags for all the dereferenced pointers and build the 1167 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias 1168 sets. Based on the address escape and points-to information collected 1169 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those 1170 variables whose address is not needed anymore. */ 1171 1172static void 1173setup_pointers_and_addressables (struct alias_info *ai) 1174{ 1175 size_t n_vars, num_addressable_vars, num_pointers; 1176 referenced_var_iterator rvi; 1177 tree var; 1178 VEC (tree, heap) *varvec = NULL; 1179 safe_referenced_var_iterator srvi; 1180 1181 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */ 1182 num_addressable_vars = num_pointers = 0; 1183 1184 FOR_EACH_REFERENCED_VAR (var, rvi) 1185 { 1186 if (may_be_aliased (var)) 1187 num_addressable_vars++; 1188 1189 if (POINTER_TYPE_P (TREE_TYPE (var))) 1190 { 1191 /* Since we don't keep track of volatile variables, assume that 1192 these pointers are used in indirect store operations. */ 1193 if (TREE_THIS_VOLATILE (var)) 1194 bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var)); 1195 1196 num_pointers++; 1197 } 1198 } 1199 1200 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are 1201 always going to be slightly bigger than we actually need them 1202 because some TREE_ADDRESSABLE variables will be marked 1203 non-addressable below and only pointers with unique type tags are 1204 going to be added to POINTERS. */ 1205 ai->addressable_vars = xcalloc (num_addressable_vars, 1206 sizeof (struct alias_map_d *)); 1207 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *)); 1208 ai->num_addressable_vars = 0; 1209 ai->num_pointers = 0; 1210 1211 /* Since we will be creating type memory tags within this loop, cache the 1212 value of NUM_REFERENCED_VARS to avoid processing the additional tags 1213 unnecessarily. */ 1214 n_vars = num_referenced_vars; 1215 1216 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi) 1217 { 1218 var_ann_t v_ann = var_ann (var); 1219 subvar_t svars; 1220 1221 /* Name memory tags already have flow-sensitive aliasing 1222 information, so they need not be processed by 1223 compute_flow_insensitive_aliasing. Similarly, type memory 1224 tags are already accounted for when we process their 1225 associated pointer. 1226 1227 Structure fields, on the other hand, have to have some of this 1228 information processed for them, but it's pointless to mark them 1229 non-addressable (since they are fake variables anyway). */ 1230 if (v_ann->mem_tag_kind != NOT_A_TAG 1231 && v_ann->mem_tag_kind != STRUCT_FIELD) 1232 continue; 1233 1234 /* Remove the ADDRESSABLE flag from every addressable variable whose 1235 address is not needed anymore. This is caused by the propagation 1236 of ADDR_EXPR constants into INDIRECT_REF expressions and the 1237 removal of dead pointer assignments done by the early scalar 1238 cleanup passes. */ 1239 if (TREE_ADDRESSABLE (var)) 1240 { 1241 if (!bitmap_bit_p (addressable_vars, DECL_UID (var)) 1242 && TREE_CODE (var) != RESULT_DECL 1243 && !is_global_var (var)) 1244 { 1245 bool okay_to_mark = true; 1246 1247 /* Since VAR is now a regular GIMPLE register, we will need 1248 to rename VAR into SSA afterwards. */ 1249 mark_sym_for_renaming (var); 1250 1251 /* If VAR can have sub-variables, and any of its 1252 sub-variables has its address taken, then we cannot 1253 remove the addressable flag from VAR. */ 1254 if (var_can_have_subvars (var) 1255 && (svars = get_subvars_for_var (var))) 1256 { 1257 subvar_t sv; 1258 1259 for (sv = svars; sv; sv = sv->next) 1260 { 1261 if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var))) 1262 okay_to_mark = false; 1263 mark_sym_for_renaming (sv->var); 1264 } 1265 } 1266 1267 /* The address of VAR is not needed, remove the 1268 addressable bit, so that it can be optimized as a 1269 regular variable. */ 1270 if (okay_to_mark) 1271 mark_non_addressable (var); 1272 } 1273 } 1274 1275 /* Global variables and addressable locals may be aliased. Create an 1276 entry in ADDRESSABLE_VARS for VAR. */ 1277 if (may_be_aliased (var) 1278 && (!var_can_have_subvars (var) 1279 || get_subvars_for_var (var) == NULL)) 1280 { 1281 create_alias_map_for (var, ai); 1282 mark_sym_for_renaming (var); 1283 } 1284 1285 /* Add pointer variables that have been dereferenced to the POINTERS 1286 array and create a type memory tag for them. */ 1287 if (POINTER_TYPE_P (TREE_TYPE (var))) 1288 { 1289 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)) 1290 || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var)))) 1291 { 1292 tree tag; 1293 var_ann_t t_ann; 1294 1295 /* If pointer VAR still doesn't have a memory tag 1296 associated with it, create it now or re-use an 1297 existing one. */ 1298 tag = get_tmt_for (var, ai); 1299 t_ann = var_ann (tag); 1300 1301 /* The type tag will need to be renamed into SSA 1302 afterwards. Note that we cannot do this inside 1303 get_tmt_for because aliasing may run multiple times 1304 and we only create type tags the first time. */ 1305 mark_sym_for_renaming (tag); 1306 1307 /* Similarly, if pointer VAR used to have another type 1308 tag, we will need to process it in the renamer to 1309 remove the stale virtual operands. */ 1310 if (v_ann->type_mem_tag) 1311 mark_sym_for_renaming (v_ann->type_mem_tag); 1312 1313 /* Associate the tag with pointer VAR. */ 1314 v_ann->type_mem_tag = tag; 1315 1316 /* If pointer VAR has been used in a store operation, 1317 then its memory tag must be marked as written-to. */ 1318 if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))) 1319 bitmap_set_bit (ai->written_vars, DECL_UID (tag)); 1320 1321 /* If pointer VAR is a global variable or a PARM_DECL, 1322 then its memory tag should be considered a global 1323 variable. */ 1324 if (TREE_CODE (var) == PARM_DECL || is_global_var (var)) 1325 mark_call_clobbered (tag); 1326 1327 /* All the dereferences of pointer VAR count as 1328 references of TAG. Since TAG can be associated with 1329 several pointers, add the dereferences of VAR to the 1330 TAG. */ 1331 NUM_REFERENCES_SET (t_ann, 1332 NUM_REFERENCES (t_ann) 1333 + NUM_REFERENCES (v_ann)); 1334 } 1335 else 1336 { 1337 /* The pointer has not been dereferenced. If it had a 1338 type memory tag, remove it and mark the old tag for 1339 renaming to remove it out of the IL. */ 1340 var_ann_t ann = var_ann (var); 1341 tree tag = ann->type_mem_tag; 1342 if (tag) 1343 { 1344 mark_sym_for_renaming (tag); 1345 ann->type_mem_tag = NULL_TREE; 1346 } 1347 } 1348 } 1349 } 1350 VEC_free (tree, heap, varvec); 1351} 1352 1353 1354/* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At 1355 every call site, we need to emit V_MAY_DEF expressions to represent the 1356 clobbering effects of the call for variables whose address escapes the 1357 current function. 1358 1359 One approach is to group all call-clobbered variables into a single 1360 representative that is used as an alias of every call-clobbered variable 1361 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because 1362 references to any call clobbered variable is a reference to .GLOBAL_VAR. 1363 1364 The second approach is to emit a clobbering V_MAY_DEF for every 1365 call-clobbered variable at call sites. This is the preferred way in terms 1366 of optimization opportunities but it may create too many V_MAY_DEF operands 1367 if there are many call clobbered variables and function calls in the 1368 function. 1369 1370 To decide whether or not to use .GLOBAL_VAR we multiply the number of 1371 function calls found by the number of call-clobbered variables. If that 1372 product is beyond a certain threshold, as determined by the parameterized 1373 values shown below, we use .GLOBAL_VAR. 1374 1375 FIXME. This heuristic should be improved. One idea is to use several 1376 .GLOBAL_VARs of different types instead of a single one. The thresholds 1377 have been derived from a typical bootstrap cycle, including all target 1378 libraries. Compile times were found increase by ~1% compared to using 1379 .GLOBAL_VAR. */ 1380 1381static void 1382maybe_create_global_var (struct alias_info *ai) 1383{ 1384 unsigned i, n_clobbered; 1385 bitmap_iterator bi; 1386 1387 /* No need to create it, if we have one already. */ 1388 if (global_var == NULL_TREE) 1389 { 1390 /* Count all the call-clobbered variables. */ 1391 n_clobbered = 0; 1392 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi) 1393 { 1394 n_clobbered++; 1395 } 1396 1397 /* If the number of virtual operands that would be needed to 1398 model all the call-clobbered variables is larger than 1399 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR. 1400 1401 Also create .GLOBAL_VAR if there are no call-clobbered 1402 variables and the program contains a mixture of pure/const 1403 and regular function calls. This is to avoid the problem 1404 described in PR 20115: 1405 1406 int X; 1407 int func_pure (void) { return X; } 1408 int func_non_pure (int a) { X += a; } 1409 int foo () 1410 { 1411 int a = func_pure (); 1412 func_non_pure (a); 1413 a = func_pure (); 1414 return a; 1415 } 1416 1417 Since foo() has no call-clobbered variables, there is 1418 no relationship between the calls to func_pure and 1419 func_non_pure. Since func_pure has no side-effects, value 1420 numbering optimizations elide the second call to func_pure. 1421 So, if we have some pure/const and some regular calls in the 1422 program we create .GLOBAL_VAR to avoid missing these 1423 relations. */ 1424 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD 1425 || (n_clobbered == 0 1426 && ai->num_calls_found > 0 1427 && ai->num_pure_const_calls_found > 0 1428 && ai->num_calls_found > ai->num_pure_const_calls_found)) 1429 create_global_var (); 1430 } 1431 1432 /* Mark all call-clobbered symbols for renaming. Since the initial 1433 rewrite into SSA ignored all call sites, we may need to rename 1434 .GLOBAL_VAR and the call-clobbered variables. */ 1435 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi) 1436 { 1437 tree var = referenced_var (i); 1438 1439 /* If the function has calls to clobbering functions and 1440 .GLOBAL_VAR has been created, make it an alias for all 1441 call-clobbered variables. */ 1442 if (global_var && var != global_var) 1443 { 1444 subvar_t svars; 1445 add_may_alias (var, global_var); 1446 if (var_can_have_subvars (var) 1447 && (svars = get_subvars_for_var (var))) 1448 { 1449 subvar_t sv; 1450 for (sv = svars; sv; sv = sv->next) 1451 mark_sym_for_renaming (sv->var); 1452 } 1453 } 1454 1455 mark_sym_for_renaming (var); 1456 } 1457} 1458 1459 1460/* Return TRUE if pointer PTR may point to variable VAR. 1461 1462 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR 1463 This is needed because when checking for type conflicts we are 1464 interested in the alias set of the memory location pointed-to by 1465 PTR. The alias set of PTR itself is irrelevant. 1466 1467 VAR_ALIAS_SET is the alias set for VAR. */ 1468 1469static bool 1470may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set, 1471 tree var, HOST_WIDE_INT var_alias_set, 1472 bool alias_set_only) 1473{ 1474 tree mem; 1475 var_ann_t m_ann; 1476 1477 alias_stats.alias_queries++; 1478 alias_stats.simple_queries++; 1479 1480 /* By convention, a variable cannot alias itself. */ 1481 mem = var_ann (ptr)->type_mem_tag; 1482 if (mem == var) 1483 { 1484 alias_stats.alias_noalias++; 1485 alias_stats.simple_resolved++; 1486 return false; 1487 } 1488 1489 /* If -fargument-noalias-global is >1, pointer arguments may 1490 not point to global variables. */ 1491 if (flag_argument_noalias > 1 && is_global_var (var) 1492 && TREE_CODE (ptr) == PARM_DECL) 1493 { 1494 alias_stats.alias_noalias++; 1495 alias_stats.simple_resolved++; 1496 return false; 1497 } 1498 1499 /* If either MEM or VAR is a read-only global and the other one 1500 isn't, then PTR cannot point to VAR. */ 1501 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var)) 1502 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem))) 1503 { 1504 alias_stats.alias_noalias++; 1505 alias_stats.simple_resolved++; 1506 return false; 1507 } 1508 1509 m_ann = var_ann (mem); 1510 1511 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG); 1512 1513 alias_stats.tbaa_queries++; 1514 1515 /* If the alias sets don't conflict then MEM cannot alias VAR. */ 1516 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set)) 1517 { 1518 alias_stats.alias_noalias++; 1519 alias_stats.tbaa_resolved++; 1520 return false; 1521 } 1522 1523 /* If var is a record or union type, ptr cannot point into var 1524 unless there is some operation explicit address operation in the 1525 program that can reference a field of the ptr's dereferenced 1526 type. This also assumes that the types of both var and ptr are 1527 contained within the compilation unit, and that there is no fancy 1528 addressing arithmetic associated with any of the types 1529 involved. */ 1530 1531 if ((mem_alias_set != 0) && (var_alias_set != 0)) 1532 { 1533 tree ptr_type = TREE_TYPE (ptr); 1534 tree var_type = TREE_TYPE (var); 1535 1536 /* The star count is -1 if the type at the end of the pointer_to 1537 chain is not a record or union type. */ 1538 if ((!alias_set_only) && 1539 ipa_type_escape_star_count_of_interesting_type (var_type) >= 0) 1540 { 1541 int ptr_star_count = 0; 1542 1543 /* Ipa_type_escape_star_count_of_interesting_type is a little to 1544 restrictive for the pointer type, need to allow pointers to 1545 primitive types as long as those types cannot be pointers 1546 to everything. */ 1547 while (POINTER_TYPE_P (ptr_type)) 1548 /* Strip the *'s off. */ 1549 { 1550 ptr_type = TREE_TYPE (ptr_type); 1551 ptr_star_count++; 1552 } 1553 1554 /* There does not appear to be a better test to see if the 1555 pointer type was one of the pointer to everything 1556 types. */ 1557 1558 if (ptr_star_count > 0) 1559 { 1560 alias_stats.structnoaddress_queries++; 1561 if (ipa_type_escape_field_does_not_clobber_p (var_type, 1562 TREE_TYPE (ptr))) 1563 { 1564 alias_stats.structnoaddress_resolved++; 1565 alias_stats.alias_noalias++; 1566 return false; 1567 } 1568 } 1569 else if (ptr_star_count == 0) 1570 { 1571 /* If ptr_type was not really a pointer to type, it cannot 1572 alias. */ 1573 alias_stats.structnoaddress_queries++; 1574 alias_stats.structnoaddress_resolved++; 1575 alias_stats.alias_noalias++; 1576 return false; 1577 } 1578 } 1579 } 1580 1581 alias_stats.alias_mayalias++; 1582 return true; 1583} 1584 1585 1586/* Add ALIAS to the set of variables that may alias VAR. */ 1587 1588static void 1589add_may_alias (tree var, tree alias) 1590{ 1591 size_t i; 1592 var_ann_t v_ann = get_var_ann (var); 1593 var_ann_t a_ann = get_var_ann (alias); 1594 1595 /* Don't allow self-referential aliases. */ 1596 gcc_assert (var != alias); 1597 1598 /* ALIAS must be addressable if it's being added to an alias set. */ 1599#if 1 1600 TREE_ADDRESSABLE (alias) = 1; 1601#else 1602 gcc_assert (may_be_aliased (alias)); 1603#endif 1604 1605 if (v_ann->may_aliases == NULL) 1606 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases"); 1607 1608 /* Avoid adding duplicates. */ 1609 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++) 1610 if (alias == VARRAY_TREE (v_ann->may_aliases, i)) 1611 return; 1612 1613 /* If VAR is a call-clobbered variable, so is its new ALIAS. 1614 FIXME, call-clobbering should only depend on whether an address 1615 escapes. It should be independent of aliasing. */ 1616 if (is_call_clobbered (var)) 1617 mark_call_clobbered (alias); 1618 1619 /* Likewise. If ALIAS is call-clobbered, so is VAR. */ 1620 else if (is_call_clobbered (alias)) 1621 mark_call_clobbered (var); 1622 1623 VARRAY_PUSH_TREE (v_ann->may_aliases, alias); 1624 a_ann->is_alias_tag = 1; 1625} 1626 1627 1628/* Replace alias I in the alias sets of VAR with NEW_ALIAS. */ 1629 1630static void 1631replace_may_alias (tree var, size_t i, tree new_alias) 1632{ 1633 var_ann_t v_ann = var_ann (var); 1634 VARRAY_TREE (v_ann->may_aliases, i) = new_alias; 1635 1636 /* If VAR is a call-clobbered variable, so is NEW_ALIAS. 1637 FIXME, call-clobbering should only depend on whether an address 1638 escapes. It should be independent of aliasing. */ 1639 if (is_call_clobbered (var)) 1640 mark_call_clobbered (new_alias); 1641 1642 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */ 1643 else if (is_call_clobbered (new_alias)) 1644 mark_call_clobbered (var); 1645} 1646 1647 1648/* Mark pointer PTR as pointing to an arbitrary memory location. */ 1649 1650static void 1651set_pt_anything (tree ptr) 1652{ 1653 struct ptr_info_def *pi = get_ptr_info (ptr); 1654 1655 pi->pt_anything = 1; 1656 pi->pt_vars = NULL; 1657 1658 /* The pointer used to have a name tag, but we now found it pointing 1659 to an arbitrary location. The name tag needs to be renamed and 1660 disassociated from PTR. */ 1661 if (pi->name_mem_tag) 1662 { 1663 mark_sym_for_renaming (pi->name_mem_tag); 1664 pi->name_mem_tag = NULL_TREE; 1665 } 1666} 1667 1668 1669/* Return true if STMT is an "escape" site from the current function. Escape 1670 sites those statements which might expose the address of a variable 1671 outside the current function. STMT is an escape site iff: 1672 1673 1- STMT is a function call, or 1674 2- STMT is an __asm__ expression, or 1675 3- STMT is an assignment to a non-local variable, or 1676 4- STMT is a return statement. 1677 1678 AI points to the alias information collected so far. */ 1679 1680bool 1681is_escape_site (tree stmt, struct alias_info *ai) 1682{ 1683 tree call = get_call_expr_in (stmt); 1684 if (call != NULL_TREE) 1685 { 1686 ai->num_calls_found++; 1687 1688 if (!TREE_SIDE_EFFECTS (call)) 1689 ai->num_pure_const_calls_found++; 1690 1691 return true; 1692 } 1693 else if (TREE_CODE (stmt) == ASM_EXPR) 1694 return true; 1695 else if (TREE_CODE (stmt) == MODIFY_EXPR) 1696 { 1697 tree lhs = TREE_OPERAND (stmt, 0); 1698 1699 /* Get to the base of _REF nodes. */ 1700 if (TREE_CODE (lhs) != SSA_NAME) 1701 lhs = get_base_address (lhs); 1702 1703 /* If we couldn't recognize the LHS of the assignment, assume that it 1704 is a non-local store. */ 1705 if (lhs == NULL_TREE) 1706 return true; 1707 1708 /* If the RHS is a conversion between a pointer and an integer, the 1709 pointer escapes since we can't track the integer. */ 1710 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR 1711 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR 1712 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR) 1713 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND 1714 (TREE_OPERAND (stmt, 1), 0))) 1715 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1)))) 1716 return true; 1717 1718 /* If the LHS is an SSA name, it can't possibly represent a non-local 1719 memory store. */ 1720 if (TREE_CODE (lhs) == SSA_NAME) 1721 return false; 1722 1723 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a 1724 local variables we cannot be sure if it will escape, because we 1725 don't have information about objects not in SSA form. Need to 1726 implement something along the lines of 1727 1728 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P. 1729 Midkiff, ``Escape analysis for java,'' in Proceedings of the 1730 Conference on Object-Oriented Programming Systems, Languages, and 1731 Applications (OOPSLA), pp. 1-19, 1999. */ 1732 return true; 1733 } 1734 else if (TREE_CODE (stmt) == RETURN_EXPR) 1735 return true; 1736 1737 return false; 1738} 1739 1740 1741/* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag 1742 is considered to represent all the pointers whose pointed-to types are 1743 in the same alias set class. Otherwise, the tag represents a single 1744 SSA_NAME pointer variable. */ 1745 1746static tree 1747create_memory_tag (tree type, bool is_type_tag) 1748{ 1749 var_ann_t ann; 1750 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT"); 1751 1752 /* By default, memory tags are local variables. Alias analysis will 1753 determine whether they should be considered globals. */ 1754 DECL_CONTEXT (tag) = current_function_decl; 1755 1756 /* Memory tags are by definition addressable. */ 1757 TREE_ADDRESSABLE (tag) = 1; 1758 1759 ann = get_var_ann (tag); 1760 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG; 1761 ann->type_mem_tag = NULL_TREE; 1762 1763 /* Add the tag to the symbol table. */ 1764 add_referenced_tmp_var (tag); 1765 1766 return tag; 1767} 1768 1769 1770/* Create a name memory tag to represent a specific SSA_NAME pointer P_i. 1771 This is used if P_i has been found to point to a specific set of 1772 variables or to a non-aliased memory location like the address returned 1773 by malloc functions. */ 1774 1775static tree 1776get_nmt_for (tree ptr) 1777{ 1778 struct ptr_info_def *pi = get_ptr_info (ptr); 1779 tree tag = pi->name_mem_tag; 1780 1781 if (tag == NULL_TREE) 1782 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false); 1783 1784 /* If PTR is a PARM_DECL, it points to a global variable or malloc, 1785 then its name tag should be considered a global variable. */ 1786 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL 1787 || pi->pt_global_mem) 1788 mark_call_clobbered (tag); 1789 1790 return tag; 1791} 1792 1793 1794/* Return the type memory tag associated to pointer PTR. A memory tag is an 1795 artificial variable that represents the memory location pointed-to by 1796 PTR. It is used to model the effects of pointer de-references on 1797 addressable variables. 1798 1799 AI points to the data gathered during alias analysis. This function 1800 populates the array AI->POINTERS. */ 1801 1802static tree 1803get_tmt_for (tree ptr, struct alias_info *ai) 1804{ 1805 size_t i; 1806 tree tag; 1807 tree tag_type = TREE_TYPE (TREE_TYPE (ptr)); 1808 HOST_WIDE_INT tag_set = get_alias_set (tag_type); 1809 1810 /* To avoid creating unnecessary memory tags, only create one memory tag 1811 per alias set class. Note that it may be tempting to group 1812 memory tags based on conflicting alias sets instead of 1813 equivalence. That would be wrong because alias sets are not 1814 necessarily transitive (as demonstrated by the libstdc++ test 1815 23_containers/vector/cons/4.cc). Given three alias sets A, B, C 1816 such that conflicts (A, B) == true and conflicts (A, C) == true, 1817 it does not necessarily follow that conflicts (B, C) == true. */ 1818 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++) 1819 { 1820 struct alias_map_d *curr = ai->pointers[i]; 1821 tree curr_tag = var_ann (curr->var)->type_mem_tag; 1822 if (tag_set == curr->set) 1823 { 1824 tag = curr_tag; 1825 break; 1826 } 1827 } 1828 1829 /* If VAR cannot alias with any of the existing memory tags, create a new 1830 tag for PTR and add it to the POINTERS array. */ 1831 if (tag == NULL_TREE) 1832 { 1833 struct alias_map_d *alias_map; 1834 1835 /* If PTR did not have a type tag already, create a new TMT.* 1836 artificial variable representing the memory location 1837 pointed-to by PTR. */ 1838 if (var_ann (ptr)->type_mem_tag == NULL_TREE) 1839 tag = create_memory_tag (tag_type, true); 1840 else 1841 tag = var_ann (ptr)->type_mem_tag; 1842 1843 /* Add PTR to the POINTERS array. Note that we are not interested in 1844 PTR's alias set. Instead, we cache the alias set for the memory that 1845 PTR points to. */ 1846 alias_map = xcalloc (1, sizeof (*alias_map)); 1847 alias_map->var = ptr; 1848 alias_map->set = tag_set; 1849 ai->pointers[ai->num_pointers++] = alias_map; 1850 } 1851 1852 /* If the pointed-to type is volatile, so is the tag. */ 1853 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type); 1854 1855 /* Make sure that the type tag has the same alias set as the 1856 pointed-to type. */ 1857 gcc_assert (tag_set == get_alias_set (tag)); 1858 1859 return tag; 1860} 1861 1862 1863/* Create GLOBAL_VAR, an artificial global variable to act as a 1864 representative of all the variables that may be clobbered by function 1865 calls. */ 1866 1867static void 1868create_global_var (void) 1869{ 1870 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"), 1871 void_type_node); 1872 DECL_ARTIFICIAL (global_var) = 1; 1873 TREE_READONLY (global_var) = 0; 1874 DECL_EXTERNAL (global_var) = 1; 1875 TREE_STATIC (global_var) = 1; 1876 TREE_USED (global_var) = 1; 1877 DECL_CONTEXT (global_var) = NULL_TREE; 1878 TREE_THIS_VOLATILE (global_var) = 0; 1879 TREE_ADDRESSABLE (global_var) = 0; 1880 1881 add_referenced_tmp_var (global_var); 1882 mark_sym_for_renaming (global_var); 1883} 1884 1885 1886/* Dump alias statistics on FILE. */ 1887 1888static void 1889dump_alias_stats (FILE *file) 1890{ 1891 const char *funcname 1892 = lang_hooks.decl_printable_name (current_function_decl, 2); 1893 fprintf (file, "\nAlias statistics for %s\n\n", funcname); 1894 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries); 1895 fprintf (file, "Total alias mayalias results:\t%u\n", 1896 alias_stats.alias_mayalias); 1897 fprintf (file, "Total alias noalias results:\t%u\n", 1898 alias_stats.alias_noalias); 1899 fprintf (file, "Total simple queries:\t%u\n", 1900 alias_stats.simple_queries); 1901 fprintf (file, "Total simple resolved:\t%u\n", 1902 alias_stats.simple_resolved); 1903 fprintf (file, "Total TBAA queries:\t%u\n", 1904 alias_stats.tbaa_queries); 1905 fprintf (file, "Total TBAA resolved:\t%u\n", 1906 alias_stats.tbaa_resolved); 1907 fprintf (file, "Total non-addressable structure type queries:\t%u\n", 1908 alias_stats.structnoaddress_queries); 1909 fprintf (file, "Total non-addressable structure type resolved:\t%u\n", 1910 alias_stats.structnoaddress_resolved); 1911} 1912 1913 1914/* Dump alias information on FILE. */ 1915 1916void 1917dump_alias_info (FILE *file) 1918{ 1919 size_t i; 1920 const char *funcname 1921 = lang_hooks.decl_printable_name (current_function_decl, 2); 1922 referenced_var_iterator rvi; 1923 tree var; 1924 1925 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname); 1926 1927 fprintf (file, "Aliased symbols\n\n"); 1928 1929 FOR_EACH_REFERENCED_VAR (var, rvi) 1930 { 1931 if (may_be_aliased (var)) 1932 dump_variable (file, var); 1933 } 1934 1935 fprintf (file, "\nDereferenced pointers\n\n"); 1936 1937 FOR_EACH_REFERENCED_VAR (var, rvi) 1938 { 1939 var_ann_t ann = var_ann (var); 1940 if (ann->type_mem_tag) 1941 dump_variable (file, var); 1942 } 1943 1944 fprintf (file, "\nType memory tags\n\n"); 1945 1946 FOR_EACH_REFERENCED_VAR (var, rvi) 1947 { 1948 var_ann_t ann = var_ann (var); 1949 if (ann->mem_tag_kind == TYPE_TAG) 1950 dump_variable (file, var); 1951 } 1952 1953 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname); 1954 1955 fprintf (file, "SSA_NAME pointers\n\n"); 1956 for (i = 1; i < num_ssa_names; i++) 1957 { 1958 tree ptr = ssa_name (i); 1959 struct ptr_info_def *pi; 1960 1961 if (ptr == NULL_TREE) 1962 continue; 1963 1964 pi = SSA_NAME_PTR_INFO (ptr); 1965 if (!SSA_NAME_IN_FREE_LIST (ptr) 1966 && pi 1967 && pi->name_mem_tag) 1968 dump_points_to_info_for (file, ptr); 1969 } 1970 1971 fprintf (file, "\nName memory tags\n\n"); 1972 1973 FOR_EACH_REFERENCED_VAR (var, rvi) 1974 { 1975 var_ann_t ann = var_ann (var); 1976 if (ann->mem_tag_kind == NAME_TAG) 1977 dump_variable (file, var); 1978 } 1979 1980 fprintf (file, "\n"); 1981} 1982 1983 1984/* Dump alias information on stderr. */ 1985 1986void 1987debug_alias_info (void) 1988{ 1989 dump_alias_info (stderr); 1990} 1991 1992 1993/* Return the alias information associated with pointer T. It creates a 1994 new instance if none existed. */ 1995 1996struct ptr_info_def * 1997get_ptr_info (tree t) 1998{ 1999 struct ptr_info_def *pi; 2000 2001 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t))); 2002 2003 pi = SSA_NAME_PTR_INFO (t); 2004 if (pi == NULL) 2005 { 2006 pi = ggc_alloc (sizeof (*pi)); 2007 memset ((void *)pi, 0, sizeof (*pi)); 2008 SSA_NAME_PTR_INFO (t) = pi; 2009 } 2010 2011 return pi; 2012} 2013 2014 2015/* Dump points-to information for SSA_NAME PTR into FILE. */ 2016 2017void 2018dump_points_to_info_for (FILE *file, tree ptr) 2019{ 2020 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr); 2021 2022 print_generic_expr (file, ptr, dump_flags); 2023 2024 if (pi) 2025 { 2026 if (pi->name_mem_tag) 2027 { 2028 fprintf (file, ", name memory tag: "); 2029 print_generic_expr (file, pi->name_mem_tag, dump_flags); 2030 } 2031 2032 if (pi->is_dereferenced) 2033 fprintf (file, ", is dereferenced"); 2034 2035 if (pi->value_escapes_p) 2036 fprintf (file, ", its value escapes"); 2037 2038 if (pi->pt_anything) 2039 fprintf (file, ", points-to anything"); 2040 2041 if (pi->pt_null) 2042 fprintf (file, ", points-to NULL"); 2043 2044 if (pi->pt_vars) 2045 { 2046 unsigned ix; 2047 bitmap_iterator bi; 2048 2049 fprintf (file, ", points-to vars: { "); 2050 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi) 2051 { 2052 print_generic_expr (file, referenced_var (ix), dump_flags); 2053 fprintf (file, " "); 2054 } 2055 fprintf (file, "}"); 2056 } 2057 } 2058 2059 fprintf (file, "\n"); 2060} 2061 2062 2063/* Dump points-to information for VAR into stderr. */ 2064 2065void 2066debug_points_to_info_for (tree var) 2067{ 2068 dump_points_to_info_for (stderr, var); 2069} 2070 2071 2072/* Dump points-to information into FILE. NOTE: This function is slow, as 2073 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */ 2074 2075void 2076dump_points_to_info (FILE *file) 2077{ 2078 basic_block bb; 2079 block_stmt_iterator si; 2080 ssa_op_iter iter; 2081 const char *fname = 2082 lang_hooks.decl_printable_name (current_function_decl, 2); 2083 referenced_var_iterator rvi; 2084 tree var; 2085 2086 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname); 2087 2088 /* First dump points-to information for the default definitions of 2089 pointer variables. This is necessary because default definitions are 2090 not part of the code. */ 2091 FOR_EACH_REFERENCED_VAR (var, rvi) 2092 { 2093 if (POINTER_TYPE_P (TREE_TYPE (var))) 2094 { 2095 tree def = default_def (var); 2096 if (def) 2097 dump_points_to_info_for (file, def); 2098 } 2099 } 2100 2101 /* Dump points-to information for every pointer defined in the program. */ 2102 FOR_EACH_BB (bb) 2103 { 2104 tree phi; 2105 2106 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) 2107 { 2108 tree ptr = PHI_RESULT (phi); 2109 if (POINTER_TYPE_P (TREE_TYPE (ptr))) 2110 dump_points_to_info_for (file, ptr); 2111 } 2112 2113 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si)) 2114 { 2115 tree stmt = bsi_stmt (si); 2116 tree def; 2117 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF) 2118 if (POINTER_TYPE_P (TREE_TYPE (def))) 2119 dump_points_to_info_for (file, def); 2120 } 2121 } 2122 2123 fprintf (file, "\n"); 2124} 2125 2126 2127/* Dump points-to info pointed to by PTO into STDERR. */ 2128 2129void 2130debug_points_to_info (void) 2131{ 2132 dump_points_to_info (stderr); 2133} 2134 2135/* Dump to FILE the list of variables that may be aliasing VAR. */ 2136 2137void 2138dump_may_aliases_for (FILE *file, tree var) 2139{ 2140 varray_type aliases; 2141 2142 if (TREE_CODE (var) == SSA_NAME) 2143 var = SSA_NAME_VAR (var); 2144 2145 aliases = var_ann (var)->may_aliases; 2146 if (aliases) 2147 { 2148 size_t i; 2149 fprintf (file, "{ "); 2150 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) 2151 { 2152 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags); 2153 fprintf (file, " "); 2154 } 2155 fprintf (file, "}"); 2156 } 2157} 2158 2159 2160/* Dump to stderr the list of variables that may be aliasing VAR. */ 2161 2162void 2163debug_may_aliases_for (tree var) 2164{ 2165 dump_may_aliases_for (stderr, var); 2166} 2167 2168/* Return true if VAR may be aliased. */ 2169 2170bool 2171may_be_aliased (tree var) 2172{ 2173 /* Obviously. */ 2174 if (TREE_ADDRESSABLE (var)) 2175 return true; 2176 2177 /* Globally visible variables can have their addresses taken by other 2178 translation units. */ 2179 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var)) 2180 return true; 2181 2182 /* Automatic variables can't have their addresses escape any other way. 2183 This must be after the check for global variables, as extern declarations 2184 do not have TREE_STATIC set. */ 2185 if (!TREE_STATIC (var)) 2186 return false; 2187 2188 /* If we're in unit-at-a-time mode, then we must have seen all occurrences 2189 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise 2190 we can only be sure the variable isn't addressable if it's local to the 2191 current function. */ 2192 if (flag_unit_at_a_time) 2193 return false; 2194 if (decl_function_context (var) == current_function_decl) 2195 return false; 2196 2197 return true; 2198} 2199 2200 2201/* Given two symbols return TRUE if one is in the alias set of the other. */ 2202bool 2203is_aliased_with (tree tag, tree sym) 2204{ 2205 size_t i; 2206 varray_type aliases; 2207 2208 if (var_ann (sym)->is_alias_tag) 2209 { 2210 aliases = var_ann (tag)->may_aliases; 2211 2212 if (aliases == NULL) 2213 return false; 2214 2215 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) 2216 if (VARRAY_TREE (aliases, i) == sym) 2217 return true; 2218 } 2219 else 2220 { 2221 aliases = var_ann (sym)->may_aliases; 2222 2223 if (aliases == NULL) 2224 return false; 2225 2226 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) 2227 if (VARRAY_TREE (aliases, i) == tag) 2228 return true; 2229 } 2230 2231 return false; 2232} 2233 2234 2235/* Given two tags return TRUE if their may-alias sets intersect. */ 2236 2237bool 2238may_aliases_intersect (tree tag1, tree tag2) 2239{ 2240 struct pointer_set_t *set1 = pointer_set_create (); 2241 unsigned i; 2242 varray_type may_aliases1 = var_ann (tag1)->may_aliases; 2243 varray_type may_aliases2 = var_ann (tag2)->may_aliases; 2244 2245 if (may_aliases1 == NULL || may_aliases2 == NULL) 2246 return false; 2247 2248 /* Insert all the symbols from the first may-alias set into the 2249 pointer-set. */ 2250 for (i = 0; i < VARRAY_ACTIVE_SIZE (may_aliases1); i++) 2251 pointer_set_insert (set1, VARRAY_TREE (may_aliases1, i)); 2252 2253 /* Go through the second may-alias set and check if it contains symbols that 2254 are common with the first set. */ 2255 for (i = 0; i < VARRAY_ACTIVE_SIZE (may_aliases2); i++) 2256 if (pointer_set_contains (set1, VARRAY_TREE (may_aliases2, i))) 2257 { 2258 pointer_set_destroy (set1); 2259 return true; 2260 } 2261 2262 pointer_set_destroy (set1); 2263 return false; 2264} 2265 2266 2267/* Add VAR to the list of may-aliases of PTR's type tag. If PTR 2268 doesn't already have a type tag, create one. */ 2269 2270void 2271add_type_alias (tree ptr, tree var) 2272{ 2273 varray_type aliases; 2274 tree tag; 2275 var_ann_t ann = var_ann (ptr); 2276 subvar_t svars; 2277 VEC (tree, heap) *varvec = NULL; 2278 2279 if (ann->type_mem_tag == NULL_TREE) 2280 { 2281 tree q = NULL_TREE; 2282 tree tag_type = TREE_TYPE (TREE_TYPE (ptr)); 2283 HOST_WIDE_INT tag_set = get_alias_set (tag_type); 2284 safe_referenced_var_iterator rvi; 2285 2286 /* PTR doesn't have a type tag, create a new one and add VAR to 2287 the new tag's alias set. 2288 2289 FIXME, This is slower than necessary. We need to determine 2290 whether there is another pointer Q with the same alias set as 2291 PTR. This could be sped up by having type tags associated 2292 with types. */ 2293 FOR_EACH_REFERENCED_VAR_SAFE (q, varvec, rvi) 2294 { 2295 if (POINTER_TYPE_P (TREE_TYPE (q)) 2296 && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q)))) 2297 { 2298 /* Found another pointer Q with the same alias set as 2299 the PTR's pointed-to type. If Q has a type tag, use 2300 it. Otherwise, create a new memory tag for PTR. */ 2301 var_ann_t ann1 = var_ann (q); 2302 if (ann1->type_mem_tag) 2303 ann->type_mem_tag = ann1->type_mem_tag; 2304 else 2305 ann->type_mem_tag = create_memory_tag (tag_type, true); 2306 goto found_tag; 2307 } 2308 } 2309 2310 /* Couldn't find any other pointer with a type tag we could use. 2311 Create a new memory tag for PTR. */ 2312 ann->type_mem_tag = create_memory_tag (tag_type, true); 2313 } 2314 2315found_tag: 2316 /* If VAR is not already PTR's type tag, add it to the may-alias set 2317 for PTR's type tag. */ 2318 gcc_assert (var_ann (var)->type_mem_tag == NOT_A_TAG); 2319 tag = ann->type_mem_tag; 2320 2321 /* If VAR has subvars, add the subvars to the tag instead of the 2322 actual var. */ 2323 if (var_can_have_subvars (var) 2324 && (svars = get_subvars_for_var (var))) 2325 { 2326 subvar_t sv; 2327 for (sv = svars; sv; sv = sv->next) 2328 add_may_alias (tag, sv->var); 2329 } 2330 else 2331 add_may_alias (tag, var); 2332 2333 /* TAG and its set of aliases need to be marked for renaming. */ 2334 mark_sym_for_renaming (tag); 2335 if ((aliases = var_ann (tag)->may_aliases) != NULL) 2336 { 2337 size_t i; 2338 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) 2339 mark_sym_for_renaming (VARRAY_TREE (aliases, i)); 2340 } 2341 2342 /* If we had grouped aliases, VAR may have aliases of its own. Mark 2343 them for renaming as well. Other statements referencing the 2344 aliases of VAR will need to be updated. */ 2345 if ((aliases = var_ann (var)->may_aliases) != NULL) 2346 { 2347 size_t i; 2348 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) 2349 mark_sym_for_renaming (VARRAY_TREE (aliases, i)); 2350 } 2351 VEC_free (tree, heap, varvec); 2352} 2353 2354 2355/* Create a new type tag for PTR. Construct the may-alias list of this type 2356 tag so that it has the aliasing of VAR. 2357 2358 Note, the set of aliases represented by the new type tag are not marked 2359 for renaming. */ 2360 2361void 2362new_type_alias (tree ptr, tree var) 2363{ 2364 var_ann_t p_ann = var_ann (ptr); 2365 tree tag_type = TREE_TYPE (TREE_TYPE (ptr)); 2366 var_ann_t v_ann = var_ann (var); 2367 tree tag; 2368 subvar_t svars; 2369 2370 gcc_assert (p_ann->type_mem_tag == NULL_TREE); 2371 gcc_assert (v_ann->mem_tag_kind == NOT_A_TAG); 2372 2373 /* Add VAR to the may-alias set of PTR's new type tag. If VAR has 2374 subvars, add the subvars to the tag instead of the actual var. */ 2375 if (var_can_have_subvars (var) 2376 && (svars = get_subvars_for_var (var))) 2377 { 2378 subvar_t sv; 2379 2380 tag = create_memory_tag (tag_type, true); 2381 p_ann->type_mem_tag = tag; 2382 2383 for (sv = svars; sv; sv = sv->next) 2384 add_may_alias (tag, sv->var); 2385 } 2386 else 2387 { 2388 /* The following is based on code in add_stmt_operand to ensure that the 2389 same defs/uses/vdefs/vuses will be found after replacing a reference 2390 to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value 2391 is the address of var. */ 2392 varray_type aliases = v_ann->may_aliases; 2393 2394 if ((aliases != NULL) 2395 && (VARRAY_ACTIVE_SIZE (aliases) == 1)) 2396 { 2397 tree ali = VARRAY_TREE (aliases, 0); 2398 2399 if (get_var_ann (ali)->mem_tag_kind == TYPE_TAG) 2400 { 2401 p_ann->type_mem_tag = ali; 2402 return; 2403 } 2404 } 2405 2406 tag = create_memory_tag (tag_type, true); 2407 p_ann->type_mem_tag = tag; 2408 2409 if (aliases == NULL) 2410 add_may_alias (tag, var); 2411 else 2412 { 2413 size_t i; 2414 2415 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++) 2416 add_may_alias (tag, VARRAY_TREE (aliases, i)); 2417 } 2418 } 2419} 2420 2421 2422 2423/* This represents the used range of a variable. */ 2424 2425typedef struct used_part 2426{ 2427 HOST_WIDE_INT minused; 2428 HOST_WIDE_INT maxused; 2429 /* True if we have an explicit use/def of some portion of this variable, 2430 even if it is all of it. i.e. a.b = 5 or temp = a.b. */ 2431 bool explicit_uses; 2432 /* True if we have an implicit use/def of some portion of this 2433 variable. Implicit uses occur when we can't tell what part we 2434 are referencing, and have to make conservative assumptions. */ 2435 bool implicit_uses; 2436} *used_part_t; 2437 2438/* An array of used_part structures, indexed by variable uid. */ 2439 2440static htab_t used_portions; 2441 2442struct used_part_map 2443{ 2444 unsigned int uid; 2445 used_part_t to; 2446}; 2447 2448/* Return true if the uid in the two used part maps are equal. */ 2449 2450static int 2451used_part_map_eq (const void *va, const void *vb) 2452{ 2453 const struct used_part_map *a = va, *b = vb; 2454 return (a->uid == b->uid); 2455} 2456 2457/* Hash a from uid in a used_part_map. */ 2458 2459static unsigned int 2460used_part_map_hash (const void *item) 2461{ 2462 return ((const struct used_part_map *)item)->uid; 2463} 2464 2465/* Free a used part map element. */ 2466 2467static void 2468free_used_part_map (void *item) 2469{ 2470 free (((struct used_part_map *)item)->to); 2471 free (item); 2472} 2473 2474/* Lookup a used_part structure for a UID. */ 2475 2476static used_part_t 2477up_lookup (unsigned int uid) 2478{ 2479 struct used_part_map *h, in; 2480 in.uid = uid; 2481 h = htab_find_with_hash (used_portions, &in, uid); 2482 if (!h) 2483 return NULL; 2484 return h->to; 2485} 2486 2487/* Insert the pair UID, TO into the used part hashtable. */ 2488 2489static void 2490up_insert (unsigned int uid, used_part_t to) 2491{ 2492 struct used_part_map *h; 2493 void **loc; 2494 2495 h = xmalloc (sizeof (struct used_part_map)); 2496 h->uid = uid; 2497 h->to = to; 2498 loc = htab_find_slot_with_hash (used_portions, h, 2499 uid, INSERT); 2500 if (*loc != NULL) 2501 free (*loc); 2502 *(struct used_part_map **) loc = h; 2503} 2504 2505 2506/* Given a variable uid, UID, get or create the entry in the used portions 2507 table for the variable. */ 2508 2509static used_part_t 2510get_or_create_used_part_for (size_t uid) 2511{ 2512 used_part_t up; 2513 if ((up = up_lookup (uid)) == NULL) 2514 { 2515 up = xcalloc (1, sizeof (struct used_part)); 2516 up->minused = INT_MAX; 2517 up->maxused = 0; 2518 up->explicit_uses = false; 2519 up->implicit_uses = false; 2520 } 2521 2522 return up; 2523} 2524 2525 2526/* Create and return a structure sub-variable for field FIELD of 2527 variable VAR. */ 2528 2529static tree 2530create_sft (tree var, tree field) 2531{ 2532 var_ann_t ann; 2533 tree subvar = create_tmp_var_raw (TREE_TYPE (field), "SFT"); 2534 2535 /* We need to copy the various flags from VAR to SUBVAR, so that 2536 they are is_global_var iff the original variable was. */ 2537 DECL_CONTEXT (subvar) = DECL_CONTEXT (var); 2538 DECL_EXTERNAL (subvar) = DECL_EXTERNAL (var); 2539 TREE_PUBLIC (subvar) = TREE_PUBLIC (var); 2540 TREE_STATIC (subvar) = TREE_STATIC (var); 2541 TREE_READONLY (subvar) = TREE_READONLY (var); 2542 TREE_ADDRESSABLE (subvar) = TREE_ADDRESSABLE (var); 2543 2544 /* Add the new variable to REFERENCED_VARS. */ 2545 ann = get_var_ann (subvar); 2546 ann->mem_tag_kind = STRUCT_FIELD; 2547 ann->type_mem_tag = NULL; 2548 add_referenced_tmp_var (subvar); 2549 2550 return subvar; 2551} 2552 2553 2554/* Given an aggregate VAR, create the subvariables that represent its 2555 fields. */ 2556 2557static void 2558create_overlap_variables_for (tree var) 2559{ 2560 VEC(fieldoff_s,heap) *fieldstack = NULL; 2561 used_part_t up; 2562 size_t uid = DECL_UID (var); 2563 2564 if (!up_lookup (uid)) 2565 return; 2566 2567 up = up_lookup (uid); 2568 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL); 2569 if (VEC_length (fieldoff_s, fieldstack) != 0) 2570 { 2571 subvar_t *subvars; 2572 fieldoff_s *fo; 2573 bool notokay = false; 2574 int fieldcount = 0; 2575 int i; 2576 HOST_WIDE_INT lastfooffset = -1; 2577 HOST_WIDE_INT lastfosize = -1; 2578 tree lastfotype = NULL_TREE; 2579 2580 /* Not all fields have DECL_SIZE set, and those that don't, we don't 2581 know their size, and thus, can't handle. 2582 The same is true of fields with DECL_SIZE that is not an integer 2583 constant (such as variable sized fields). 2584 Fields with offsets which are not constant will have an offset < 0 2585 We *could* handle fields that are constant sized arrays, but 2586 currently don't. Doing so would require some extra changes to 2587 tree-ssa-operands.c. */ 2588 2589 for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++) 2590 { 2591 if (!DECL_SIZE (fo->field) 2592 || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST 2593 || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE 2594 || fo->offset < 0) 2595 { 2596 notokay = true; 2597 break; 2598 } 2599 fieldcount++; 2600 } 2601 2602 /* The current heuristic we use is as follows: 2603 If the variable has no used portions in this function, no 2604 structure vars are created for it. 2605 Otherwise, 2606 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS, 2607 we always create structure vars for them. 2608 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and 2609 some explicit uses, we create structure vars for them. 2610 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and 2611 no explicit uses, we do not create structure vars for them. 2612 */ 2613 2614 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS 2615 && !up->explicit_uses) 2616 { 2617 if (dump_file && (dump_flags & TDF_DETAILS)) 2618 { 2619 fprintf (dump_file, "Variable "); 2620 print_generic_expr (dump_file, var, 0); 2621 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n"); 2622 } 2623 notokay = true; 2624 } 2625 2626 /* Bail out, if we can't create overlap variables. */ 2627 if (notokay) 2628 { 2629 VEC_free (fieldoff_s, heap, fieldstack); 2630 return; 2631 } 2632 2633 /* Otherwise, create the variables. */ 2634 subvars = lookup_subvars_for_var (var); 2635 2636 sort_fieldstack (fieldstack); 2637 2638 for (i = VEC_length (fieldoff_s, fieldstack); 2639 VEC_iterate (fieldoff_s, fieldstack, --i, fo);) 2640 { 2641 subvar_t sv; 2642 HOST_WIDE_INT fosize; 2643 tree currfotype; 2644 2645 fosize = TREE_INT_CST_LOW (DECL_SIZE (fo->field)); 2646 currfotype = TREE_TYPE (fo->field); 2647 2648 /* If this field isn't in the used portion, 2649 or it has the exact same offset and size as the last 2650 field, skip it. */ 2651 2652 if (((fo->offset <= up->minused 2653 && fo->offset + fosize <= up->minused) 2654 || fo->offset >= up->maxused) 2655 || (fo->offset == lastfooffset 2656 && fosize == lastfosize 2657 && currfotype == lastfotype)) 2658 continue; 2659 sv = ggc_alloc (sizeof (struct subvar)); 2660 sv->offset = fo->offset; 2661 sv->size = fosize; 2662 sv->next = *subvars; 2663 sv->var = create_sft (var, fo->field); 2664 2665 if (dump_file) 2666 { 2667 fprintf (dump_file, "structure field tag %s created for var %s", 2668 get_name (sv->var), get_name (var)); 2669 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC, 2670 sv->offset); 2671 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC, 2672 sv->size); 2673 fprintf (dump_file, "\n"); 2674 } 2675 2676 lastfotype = currfotype; 2677 lastfooffset = fo->offset; 2678 lastfosize = fosize; 2679 *subvars = sv; 2680 } 2681 2682 /* Once we have created subvars, the original is no longer call 2683 clobbered on its own. Its call clobbered status depends 2684 completely on the call clobbered status of the subvars. 2685 2686 add_referenced_var in the above loop will take care of 2687 marking subvars of global variables as call clobbered for us 2688 to start, since they are global as well. */ 2689 clear_call_clobbered (var); 2690 } 2691 2692 VEC_free (fieldoff_s, heap, fieldstack); 2693} 2694 2695 2696/* Find the conservative answer to the question of what portions of what 2697 structures are used by this statement. We assume that if we have a 2698 component ref with a known size + offset, that we only need that part 2699 of the structure. For unknown cases, or cases where we do something 2700 to the whole structure, we assume we need to create fields for the 2701 entire structure. */ 2702 2703static tree 2704find_used_portions (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED) 2705{ 2706 switch (TREE_CODE (*tp)) 2707 { 2708 case COMPONENT_REF: 2709 { 2710 HOST_WIDE_INT bitsize; 2711 HOST_WIDE_INT bitpos; 2712 tree offset; 2713 enum machine_mode mode; 2714 int unsignedp; 2715 int volatilep; 2716 tree ref; 2717 ref = get_inner_reference (*tp, &bitsize, &bitpos, &offset, &mode, 2718 &unsignedp, &volatilep, false); 2719 if (DECL_P (ref) && offset == NULL && bitsize != -1) 2720 { 2721 size_t uid = DECL_UID (ref); 2722 used_part_t up; 2723 2724 up = get_or_create_used_part_for (uid); 2725 2726 if (bitpos <= up->minused) 2727 up->minused = bitpos; 2728 if ((bitpos + bitsize >= up->maxused)) 2729 up->maxused = bitpos + bitsize; 2730 2731 up->explicit_uses = true; 2732 up_insert (uid, up); 2733 2734 *walk_subtrees = 0; 2735 return NULL_TREE; 2736 } 2737 else if (DECL_P (ref)) 2738 { 2739 if (DECL_SIZE (ref) 2740 && var_can_have_subvars (ref) 2741 && TREE_CODE (DECL_SIZE (ref)) == INTEGER_CST) 2742 { 2743 used_part_t up; 2744 size_t uid = DECL_UID (ref); 2745 2746 up = get_or_create_used_part_for (uid); 2747 2748 up->minused = 0; 2749 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (ref)); 2750 2751 up->implicit_uses = true; 2752 2753 up_insert (uid, up); 2754 2755 *walk_subtrees = 0; 2756 return NULL_TREE; 2757 } 2758 } 2759 } 2760 break; 2761 /* This is here to make sure we mark the entire base variable as used 2762 when you take its address. Because our used portion analysis is 2763 simple, we aren't looking at casts or pointer arithmetic to see what 2764 happens when you take the address. */ 2765 case ADDR_EXPR: 2766 { 2767 tree var = get_base_address (TREE_OPERAND (*tp, 0)); 2768 2769 if (var 2770 && DECL_P (var) 2771 && DECL_SIZE (var) 2772 && var_can_have_subvars (var) 2773 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST) 2774 { 2775 used_part_t up; 2776 size_t uid = DECL_UID (var); 2777 2778 up = get_or_create_used_part_for (uid); 2779 2780 up->minused = 0; 2781 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var)); 2782 up->implicit_uses = true; 2783 2784 up_insert (uid, up); 2785 *walk_subtrees = 0; 2786 return NULL_TREE; 2787 } 2788 } 2789 break; 2790 case VAR_DECL: 2791 case PARM_DECL: 2792 case RESULT_DECL: 2793 { 2794 tree var = *tp; 2795 if (DECL_SIZE (var) 2796 && var_can_have_subvars (var) 2797 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST) 2798 { 2799 used_part_t up; 2800 size_t uid = DECL_UID (var); 2801 2802 up = get_or_create_used_part_for (uid); 2803 2804 up->minused = 0; 2805 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var)); 2806 up->implicit_uses = true; 2807 2808 up_insert (uid, up); 2809 *walk_subtrees = 0; 2810 return NULL_TREE; 2811 } 2812 } 2813 break; 2814 2815 default: 2816 break; 2817 2818 } 2819 return NULL_TREE; 2820} 2821 2822/* Create structure field variables for structures used in this function. */ 2823 2824static void 2825create_structure_vars (void) 2826{ 2827 basic_block bb; 2828 safe_referenced_var_iterator rvi; 2829 VEC (tree, heap) *varvec = NULL; 2830 tree var; 2831 2832 used_portions = htab_create (10, used_part_map_hash, used_part_map_eq, 2833 free_used_part_map); 2834 2835 FOR_EACH_BB (bb) 2836 { 2837 block_stmt_iterator bsi; 2838 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi)) 2839 { 2840 walk_tree_without_duplicates (bsi_stmt_ptr (bsi), 2841 find_used_portions, 2842 NULL); 2843 } 2844 } 2845 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, rvi) 2846 { 2847 /* The C++ FE creates vars without DECL_SIZE set, for some reason. */ 2848 if (var 2849 && DECL_SIZE (var) 2850 && var_can_have_subvars (var) 2851 && var_ann (var)->mem_tag_kind == NOT_A_TAG 2852 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST) 2853 create_overlap_variables_for (var); 2854 } 2855 htab_delete (used_portions); 2856 VEC_free (tree, heap, varvec); 2857 2858} 2859 2860static bool 2861gate_structure_vars (void) 2862{ 2863 return flag_tree_salias != 0; 2864} 2865 2866struct tree_opt_pass pass_create_structure_vars = 2867{ 2868 "salias", /* name */ 2869 gate_structure_vars, /* gate */ 2870 create_structure_vars, /* execute */ 2871 NULL, /* sub */ 2872 NULL, /* next */ 2873 0, /* static_pass_number */ 2874 0, /* tv_id */ 2875 PROP_cfg, /* properties_required */ 2876 0, /* properties_provided */ 2877 0, /* properties_destroyed */ 2878 0, /* todo_flags_start */ 2879 TODO_dump_func, /* todo_flags_finish */ 2880 0 /* letter */ 2881}; 2882