1 /* Alias analysis for trees.
2 Copyright (C) 2004, 2005 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to
19 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
20 Boston, MA 02110-1301, USA. */
24 #include "coretypes.h"
29 #include "hard-reg-set.h"
30 #include "basic-block.h"
34 #include "langhooks.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"
46 #include "ipa-type-escape.h"
50 #include "pointer-set.h"
52 /* Obstack used to hold grouping bitmaps and other temporary bitmaps used by
54 static bitmap_obstack alias_obstack;
56 /* 'true' after aliases have been computed (see compute_may_aliases). */
57 bool aliases_computed_p;
59 /* Structure to map a variable to its alias set and keep track of the
60 virtual operands that will be needed to represent it. */
63 /* Variable and its alias set. */
67 /* Total number of virtual operands that will be needed to represent
68 all the aliases of VAR. */
69 long total_alias_vops;
71 /* Nonzero if the aliases for this memory tag have been grouped
72 already. Used in group_aliases. */
73 unsigned int grouped_p : 1;
75 /* Set of variables aliased with VAR. This is the exact same
76 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
77 bitmap form to speed up alias grouping. */
82 /* Counters used to display statistics on alias analysis. */
85 unsigned int alias_queries;
86 unsigned int alias_mayalias;
87 unsigned int alias_noalias;
88 unsigned int simple_queries;
89 unsigned int simple_resolved;
90 unsigned int tbaa_queries;
91 unsigned int tbaa_resolved;
92 unsigned int structnoaddress_queries;
93 unsigned int structnoaddress_resolved;
97 /* Local variables. */
98 static struct alias_stats_d alias_stats;
100 /* Local functions. */
101 static void compute_flow_insensitive_aliasing (struct alias_info *);
102 static void finalize_ref_all_pointers (struct alias_info *);
103 static void dump_alias_stats (FILE *);
104 static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT, bool);
105 static tree create_memory_tag (tree type, bool is_type_tag);
106 static tree get_tmt_for (tree, struct alias_info *);
107 static tree get_nmt_for (tree);
108 static void add_may_alias (tree, tree);
109 static void replace_may_alias (tree, size_t, tree);
110 static struct alias_info *init_alias_info (void);
111 static void delete_alias_info (struct alias_info *);
112 static void compute_flow_sensitive_aliasing (struct alias_info *);
113 static void setup_pointers_and_addressables (struct alias_info *);
114 static void create_global_var (void);
115 static void maybe_create_global_var (struct alias_info *ai);
116 static void group_aliases (struct alias_info *);
117 static void set_pt_anything (tree ptr);
119 /* Global declarations. */
121 /* Call clobbered variables in the function. If bit I is set, then
122 REFERENCED_VARS (I) is call-clobbered. */
123 bitmap call_clobbered_vars;
125 /* Addressable variables in the function. If bit I is set, then
126 REFERENCED_VARS (I) has had its address taken. Note that
127 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
128 addressable variable is not necessarily call-clobbered (e.g., a
129 local addressable whose address does not escape) and not all
130 call-clobbered variables are addressable (e.g., a local static
132 bitmap addressable_vars;
134 /* When the program has too many call-clobbered variables and call-sites,
135 this variable is used to represent the clobbering effects of function
136 calls. In these cases, all the call clobbered variables in the program
137 are forced to alias this variable. This reduces compile times by not
138 having to keep track of too many V_MAY_DEF expressions at call sites. */
141 /* qsort comparison function to sort type/name tags by DECL_UID. */
144 sort_tags_by_id (const void *pa, const void *pb)
146 tree a = *(tree *)pa;
147 tree b = *(tree *)pb;
149 return DECL_UID (a) - DECL_UID (b);
152 /* Initialize WORKLIST to contain those memory tags that are marked call
153 clobbered. Initialized WORKLIST2 to contain the reasons these
154 memory tags escaped. */
157 init_transitive_clobber_worklist (VEC (tree, heap) **worklist,
158 VEC (int, heap) **worklist2)
160 referenced_var_iterator rvi;
163 FOR_EACH_REFERENCED_VAR (curr, rvi)
165 if (MTAG_P (curr) && is_call_clobbered (curr))
167 VEC_safe_push (tree, heap, *worklist, curr);
168 VEC_safe_push (int, heap, *worklist2, var_ann (curr)->escape_mask);
173 /* Add ALIAS to WORKLIST (and the reason for escaping REASON to WORKLIST2) if
174 ALIAS is not already marked call clobbered, and is a memory
178 add_to_worklist (tree alias, VEC (tree, heap) **worklist,
179 VEC (int, heap) **worklist2,
182 if (MTAG_P (alias) && !is_call_clobbered (alias))
184 VEC_safe_push (tree, heap, *worklist, alias);
185 VEC_safe_push (int, heap, *worklist2, reason);
189 /* Mark aliases of TAG as call clobbered, and place any tags on the
190 alias list that were not already call clobbered on WORKLIST. */
193 mark_aliases_call_clobbered (tree tag, VEC (tree, heap) **worklist,
194 VEC (int, heap) **worklist2)
199 var_ann_t ta = var_ann (tag);
203 ma = may_aliases (tag);
207 for (i = 0; VEC_iterate (tree, ma, i, entry); i++)
209 if (!unmodifiable_var_p (entry))
211 add_to_worklist (entry, worklist, worklist2, ta->escape_mask);
212 mark_call_clobbered (entry, ta->escape_mask);
217 /* Tags containing global vars need to be marked as global.
218 Tags containing call clobbered vars need to be marked as call
222 compute_tag_properties (void)
224 referenced_var_iterator rvi;
227 VEC (tree, heap) *taglist = NULL;
229 FOR_EACH_REFERENCED_VAR (tag, rvi)
231 if (!MTAG_P (tag) || TREE_CODE (tag) == STRUCT_FIELD_TAG)
233 VEC_safe_push (tree, heap, taglist, tag);
236 /* We sort the taglist by DECL_UID, for two reasons.
237 1. To get a sequential ordering to make the bitmap accesses
239 2. Because of the way we compute aliases, it's more likely that
240 an earlier tag is included in a later tag, and this will reduce
241 the number of iterations.
243 If we had a real tag graph, we would just topo-order it and be
245 qsort (VEC_address (tree, taglist),
246 VEC_length (tree, taglist),
250 /* Go through each tag not marked as global, and if it aliases
251 global vars, mark it global.
253 If the tag contains call clobbered vars, mark it call
256 This loop iterates because tags may appear in the may-aliases
257 list of other tags when we group. */
264 for (k = 0; VEC_iterate (tree, taglist, k, tag); k++)
269 bool tagcc = is_call_clobbered (tag);
270 bool tagglobal = MTAG_GLOBAL (tag);
272 if (tagcc && tagglobal)
275 ma = may_aliases (tag);
279 for (i = 0; VEC_iterate (tree, ma, i, entry); i++)
281 /* Call clobbered entries cause the tag to be marked
283 if (!tagcc && is_call_clobbered (entry))
285 mark_call_clobbered (tag, var_ann (entry)->escape_mask);
290 /* Global vars cause the tag to be marked global. */
291 if (!tagglobal && is_global_var (entry))
293 MTAG_GLOBAL (tag) = true;
298 /* Early exit once both global and cc are set, since the
299 loop can't do any more than that. */
300 if (tagcc && tagglobal)
305 VEC_free (tree, heap, taglist);
308 /* Set up the initial variable clobbers and globalness.
309 When this function completes, only tags whose aliases need to be
310 clobbered will be set clobbered. Tags clobbered because they
311 contain call clobbered vars are handled in compute_tag_properties. */
314 set_initial_properties (struct alias_info *ai)
317 referenced_var_iterator rvi;
321 FOR_EACH_REFERENCED_VAR (var, rvi)
323 if (is_global_var (var)
324 && (!var_can_have_subvars (var)
325 || get_subvars_for_var (var) == NULL))
327 if (!unmodifiable_var_p (var))
328 mark_call_clobbered (var, ESCAPE_IS_GLOBAL);
330 else if (TREE_CODE (var) == PARM_DECL
332 && POINTER_TYPE_P (TREE_TYPE (var)))
334 tree def = default_def (var);
335 get_ptr_info (def)->value_escapes_p = 1;
336 get_ptr_info (def)->escape_mask |= ESCAPE_IS_PARM;
340 for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
342 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
343 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
345 if (pi->value_escapes_p)
347 /* If PTR escapes then its associated memory tags and
348 pointed-to variables are call-clobbered. */
349 if (pi->name_mem_tag)
350 mark_call_clobbered (pi->name_mem_tag, pi->escape_mask);
352 if (v_ann->symbol_mem_tag)
353 mark_call_clobbered (v_ann->symbol_mem_tag, pi->escape_mask);
359 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
360 if (!unmodifiable_var_p (referenced_var (j)))
361 mark_call_clobbered (referenced_var (j), pi->escape_mask);
365 /* If the name tag is call clobbered, so is the symbol tag
366 associated with the base VAR_DECL. */
368 && v_ann->symbol_mem_tag
369 && is_call_clobbered (pi->name_mem_tag))
370 mark_call_clobbered (v_ann->symbol_mem_tag, pi->escape_mask);
372 /* Name tags and symbol tags that we don't know where they point
373 to, might point to global memory, and thus, are clobbered.
375 FIXME: This is not quite right. They should only be
376 clobbered if value_escapes_p is true, regardless of whether
377 they point to global memory or not.
378 So removing this code and fixing all the bugs would be nice.
379 It is the cause of a bunch of clobbering. */
380 if ((pi->pt_global_mem || pi->pt_anything)
381 && pi->is_dereferenced && pi->name_mem_tag)
383 mark_call_clobbered (pi->name_mem_tag, ESCAPE_IS_GLOBAL);
384 MTAG_GLOBAL (pi->name_mem_tag) = true;
387 if ((pi->pt_global_mem || pi->pt_anything)
388 && pi->is_dereferenced
389 && v_ann->symbol_mem_tag)
391 mark_call_clobbered (v_ann->symbol_mem_tag, ESCAPE_IS_GLOBAL);
392 MTAG_GLOBAL (v_ann->symbol_mem_tag) = true;
398 /* This variable is set to true if we are updating the used alone
399 information for SMTs, or are in a pass that is going to break it
401 bool updating_used_alone;
403 /* Compute which variables need to be marked call clobbered because
404 their tag is call clobbered, and which tags need to be marked
405 global because they contain global variables. */
408 compute_call_clobbered (struct alias_info *ai)
410 VEC (tree, heap) *worklist = NULL;
411 VEC(int,heap) *worklist2 = NULL;
413 set_initial_properties (ai);
414 init_transitive_clobber_worklist (&worklist, &worklist2);
415 while (VEC_length (tree, worklist) != 0)
417 tree curr = VEC_pop (tree, worklist);
418 int reason = VEC_pop (int, worklist2);
420 mark_call_clobbered (curr, reason);
421 mark_aliases_call_clobbered (curr, &worklist, &worklist2);
423 VEC_free (tree, heap, worklist);
424 VEC_free (int, heap, worklist2);
425 compute_tag_properties ();
429 /* Helper for recalculate_used_alone. Return a conservatively correct
430 answer as to whether STMT may make a store on the LHS to SYM. */
433 lhs_may_store_to (tree stmt, tree sym ATTRIBUTE_UNUSED)
435 tree lhs = TREE_OPERAND (stmt, 0);
437 lhs = get_base_address (lhs);
442 if (TREE_CODE (lhs) == SSA_NAME)
444 /* We could do better here by looking at the type tag of LHS, but it
445 is unclear whether this is worth it. */
449 /* Recalculate the used_alone information for SMTs . */
452 recalculate_used_alone (void)
454 VEC (tree, heap) *calls = NULL;
455 block_stmt_iterator bsi;
459 referenced_var_iterator rvi;
462 /* First, reset all the SMT used alone bits to zero. */
463 updating_used_alone = true;
464 FOR_EACH_REFERENCED_VAR (var, rvi)
465 if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
467 SMT_OLD_USED_ALONE (var) = SMT_USED_ALONE (var);
468 SMT_USED_ALONE (var) = 0;
471 /* Walk all the statements.
472 Calls get put into a list of statements to update, since we will
473 need to update operands on them if we make any changes.
474 If we see a bare use of a SMT anywhere in a real virtual use or virtual
475 def, mark the SMT as used alone, and for renaming. */
478 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
483 stmt = bsi_stmt (bsi);
485 if (TREE_CODE (stmt) == CALL_EXPR
486 || (TREE_CODE (stmt) == MODIFY_EXPR
487 && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR))
490 VEC_safe_push (tree, heap, calls, stmt);
493 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter,
494 SSA_OP_VUSE | SSA_OP_VIRTUAL_DEFS)
498 if (TREE_CODE (var) == SSA_NAME)
499 svar = SSA_NAME_VAR (var);
501 if (TREE_CODE (svar) == SYMBOL_MEMORY_TAG)
503 /* We only care about the LHS on calls. */
504 if (iscall && !lhs_may_store_to (stmt, svar))
507 if (!SMT_USED_ALONE (svar))
509 SMT_USED_ALONE (svar) = true;
511 /* Only need to mark for renaming if it wasn't
512 used alone before. */
513 if (!SMT_OLD_USED_ALONE (svar))
514 mark_sym_for_renaming (svar);
521 /* Update the operands on all the calls we saw. */
524 for (i = 0; VEC_iterate (tree, calls, i, stmt); i++)
528 /* We need to mark SMT's that are no longer used for renaming so the
529 symbols go away, or else verification will be angry with us, even
530 though they are dead. */
531 FOR_EACH_REFERENCED_VAR (var, rvi)
532 if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
534 if (SMT_OLD_USED_ALONE (var) && !SMT_USED_ALONE (var))
535 mark_sym_for_renaming (var);
538 VEC_free (tree, heap, calls);
539 updating_used_alone = false;
542 /* Compute may-alias information for every variable referenced in function
545 Alias analysis proceeds in 3 main phases:
547 1- Points-to and escape analysis.
549 This phase walks the use-def chains in the SSA web looking for three
552 * Assignments of the form P_i = &VAR
553 * Assignments of the form P_i = malloc()
554 * Pointers and ADDR_EXPR that escape the current function.
556 The concept of 'escaping' is the same one used in the Java world. When
557 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
558 outside of the current function. So, assignment to global variables,
559 function arguments and returning a pointer are all escape sites, as are
560 conversions between pointers and integers.
562 This is where we are currently limited. Since not everything is renamed
563 into SSA, we lose track of escape properties when a pointer is stashed
564 inside a field in a structure, for instance. In those cases, we are
565 assuming that the pointer does escape.
567 We use escape analysis to determine whether a variable is
568 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
569 is call-clobbered. If a pointer P_i escapes, then all the variables
570 pointed-to by P_i (and its memory tag) also escape.
572 2- Compute flow-sensitive aliases
574 We have two classes of memory tags. Memory tags associated with the
575 pointed-to data type of the pointers in the program. These tags are
576 called "symbol memory tag" (SMT). The other class are those associated
577 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
578 when adding operands for an INDIRECT_REF *P_i, we will first check
579 whether P_i has a name tag, if it does we use it, because that will have
580 more precise aliasing information. Otherwise, we use the standard symbol
583 In this phase, we go through all the pointers we found in points-to
584 analysis and create alias sets for the name memory tags associated with
585 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
586 it points to and its tag.
589 3- Compute flow-insensitive aliases
591 This pass will compare the alias set of every symbol memory tag and
592 every addressable variable found in the program. Given a symbol
593 memory tag SMT and an addressable variable V. If the alias sets of
594 SMT and V conflict (as computed by may_alias_p), then V is marked
595 as an alias tag and added to the alias set of SMT.
597 For instance, consider the following function:
613 After aliasing analysis has finished, the symbol memory tag for pointer
614 'p' will have two aliases, namely variables 'a' and 'b'. Every time
615 pointer 'p' is dereferenced, we want to mark the operation as a
616 potential reference to 'a' and 'b'.
626 # p_1 = PHI <p_4(1), p_6(2)>;
628 # a_7 = V_MAY_DEF <a_3>;
629 # b_8 = V_MAY_DEF <b_5>;
632 # a_9 = V_MAY_DEF <a_7>
641 In certain cases, the list of may aliases for a pointer may grow too
642 large. This may cause an explosion in the number of virtual operands
643 inserted in the code. Resulting in increased memory consumption and
646 When the number of virtual operands needed to represent aliased
647 loads and stores grows too large (configurable with @option{--param
648 max-aliased-vops}), alias sets are grouped to avoid severe
649 compile-time slow downs and memory consumption. See group_aliases. */
652 compute_may_aliases (void)
654 struct alias_info *ai;
656 memset (&alias_stats, 0, sizeof (alias_stats));
658 /* Initialize aliasing information. */
659 ai = init_alias_info ();
661 /* For each pointer P_i, determine the sets of variables that P_i may
662 point-to. For every addressable variable V, determine whether the
663 address of V escapes the current function, making V call-clobbered
664 (i.e., whether &V is stored in a global variable or if its passed as a
665 function call argument). */
666 compute_points_to_sets (ai);
668 /* Collect all pointers and addressable variables, compute alias sets,
669 create memory tags for pointers and promote variables whose address is
670 not needed anymore. */
671 setup_pointers_and_addressables (ai);
673 /* Compute flow-sensitive, points-to based aliasing for all the name
674 memory tags. Note that this pass needs to be done before flow
675 insensitive analysis because it uses the points-to information
676 gathered before to mark call-clobbered symbol tags. */
677 compute_flow_sensitive_aliasing (ai);
679 /* Compute type-based flow-insensitive aliasing for all the type
681 compute_flow_insensitive_aliasing (ai);
683 /* Compute call clobbering information. */
684 compute_call_clobbered (ai);
686 /* Determine if we need to enable alias grouping. */
687 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
690 /* If the program has too many call-clobbered variables and/or function
691 calls, create .GLOBAL_VAR and use it to model call-clobbering
692 semantics at call sites. This reduces the number of virtual operands
693 considerably, improving compile times at the expense of lost
694 aliasing precision. */
695 maybe_create_global_var (ai);
697 /* If the program contains ref-all pointers, finalize may-alias information
698 for them. This pass needs to be run after call-clobbering information
699 has been computed. */
700 if (ai->ref_all_symbol_mem_tag)
701 finalize_ref_all_pointers (ai);
703 /* Debugging dumps. */
706 dump_referenced_vars (dump_file);
707 if (dump_flags & TDF_STATS)
708 dump_alias_stats (dump_file);
709 dump_points_to_info (dump_file);
710 dump_alias_info (dump_file);
713 /* Report strict aliasing violations. */
714 strict_aliasing_warning_backend ();
716 /* Deallocate memory used by aliasing data structures. */
717 delete_alias_info (ai);
719 updating_used_alone = true;
721 block_stmt_iterator bsi;
725 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
727 update_stmt_if_modified (bsi_stmt (bsi));
731 recalculate_used_alone ();
732 updating_used_alone = false;
737 struct tree_opt_pass pass_may_alias =
741 compute_may_aliases, /* execute */
744 0, /* static_pass_number */
745 TV_TREE_MAY_ALIAS, /* tv_id */
746 PROP_cfg | PROP_ssa, /* properties_required */
747 PROP_alias, /* properties_provided */
748 0, /* properties_destroyed */
749 0, /* todo_flags_start */
750 TODO_dump_func | TODO_update_ssa
751 | TODO_ggc_collect | TODO_verify_ssa
752 | TODO_verify_stmts, /* todo_flags_finish */
757 /* Data structure used to count the number of dereferences to PTR
758 inside an expression. */
766 /* Helper for count_uses_and_derefs. Called by walk_tree to look for
767 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
770 count_ptr_derefs (tree *tp, int *walk_subtrees, void *data)
772 struct count_ptr_d *count_p = (struct count_ptr_d *) data;
774 /* Do not walk inside ADDR_EXPR nodes. In the expression &ptr->fld,
775 pointer 'ptr' is *not* dereferenced, it is simply used to compute
776 the address of 'fld' as 'ptr + offsetof(fld)'. */
777 if (TREE_CODE (*tp) == ADDR_EXPR)
783 if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
790 /* Count the number of direct and indirect uses for pointer PTR in
791 statement STMT. The two counts are stored in *NUM_USES_P and
792 *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
793 least one of those dereferences is a store operation. */
796 count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
797 unsigned *num_derefs_p, bool *is_store)
806 /* Find out the total number of uses of PTR in STMT. */
807 FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
811 /* Now count the number of indirect references to PTR. This is
812 truly awful, but we don't have much choice. There are no parent
813 pointers inside INDIRECT_REFs, so an expression like
814 '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
815 find all the indirect and direct uses of x_1 inside. The only
816 shortcut we can take is the fact that GIMPLE only allows
817 INDIRECT_REFs inside the expressions below. */
818 if (TREE_CODE (stmt) == MODIFY_EXPR
819 || (TREE_CODE (stmt) == RETURN_EXPR
820 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
821 || TREE_CODE (stmt) == ASM_EXPR
822 || TREE_CODE (stmt) == CALL_EXPR)
826 if (TREE_CODE (stmt) == MODIFY_EXPR)
828 lhs = TREE_OPERAND (stmt, 0);
829 rhs = TREE_OPERAND (stmt, 1);
831 else if (TREE_CODE (stmt) == RETURN_EXPR)
833 tree e = TREE_OPERAND (stmt, 0);
834 lhs = TREE_OPERAND (e, 0);
835 rhs = TREE_OPERAND (e, 1);
837 else if (TREE_CODE (stmt) == ASM_EXPR)
839 lhs = ASM_OUTPUTS (stmt);
840 rhs = ASM_INPUTS (stmt);
848 if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs)))
850 struct count_ptr_d count;
853 walk_tree (&lhs, count_ptr_derefs, &count, NULL);
855 *num_derefs_p = count.count;
858 if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs)))
860 struct count_ptr_d count;
863 walk_tree (&rhs, count_ptr_derefs, &count, NULL);
864 *num_derefs_p += count.count;
868 gcc_assert (*num_uses_p >= *num_derefs_p);
871 /* Initialize the data structures used for alias analysis. */
873 static struct alias_info *
874 init_alias_info (void)
876 struct alias_info *ai;
877 referenced_var_iterator rvi;
880 bitmap_obstack_initialize (&alias_obstack);
881 ai = XCNEW (struct alias_info);
882 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
883 sbitmap_zero (ai->ssa_names_visited);
884 ai->processed_ptrs = VEC_alloc (tree, heap, 50);
885 ai->written_vars = BITMAP_ALLOC (&alias_obstack);
886 ai->dereferenced_ptrs_store = BITMAP_ALLOC (&alias_obstack);
887 ai->dereferenced_ptrs_load = BITMAP_ALLOC (&alias_obstack);
889 /* If aliases have been computed before, clear existing information. */
890 if (aliases_computed_p)
894 /* Similarly, clear the set of addressable variables. In this
895 case, we can just clear the set because addressability is
896 only computed here. */
897 bitmap_clear (addressable_vars);
899 /* Clear flow-insensitive alias information from each symbol. */
900 FOR_EACH_REFERENCED_VAR (var, rvi)
902 var_ann_t ann = var_ann (var);
905 ann->may_aliases = NULL;
906 NUM_REFERENCES_CLEAR (ann);
908 /* Since we are about to re-discover call-clobbered
909 variables, clear the call-clobbered flag. Variables that
910 are intrinsically call-clobbered (globals, local statics,
911 etc) will not be marked by the aliasing code, so we can't
912 remove them from CALL_CLOBBERED_VARS.
914 NB: STRUCT_FIELDS are still call clobbered if they are for
915 a global variable, so we *don't* clear their call clobberedness
916 just because they are tags, though we will clear it if they
917 aren't for global variables. */
918 if (TREE_CODE (var) == NAME_MEMORY_TAG
919 || TREE_CODE (var) == SYMBOL_MEMORY_TAG
920 || !is_global_var (var))
921 clear_call_clobbered (var);
924 /* Clear flow-sensitive points-to information from each SSA name. */
925 for (i = 1; i < num_ssa_names; i++)
927 tree name = ssa_name (i);
929 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
932 if (SSA_NAME_PTR_INFO (name))
934 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
936 /* Clear all the flags but keep the name tag to
937 avoid creating new temporaries unnecessarily. If
938 this pointer is found to point to a subset or
939 superset of its former points-to set, then a new
940 tag will need to be created in create_name_tags. */
943 pi->value_escapes_p = 0;
944 pi->is_dereferenced = 0;
946 bitmap_clear (pi->pt_vars);
951 /* Next time, we will need to reset alias information. */
952 aliases_computed_p = true;
958 /* Deallocate memory used by alias analysis. */
961 delete_alias_info (struct alias_info *ai)
964 referenced_var_iterator rvi;
967 sbitmap_free (ai->ssa_names_visited);
968 VEC_free (tree, heap, ai->processed_ptrs);
970 for (i = 0; i < ai->num_addressable_vars; i++)
971 free (ai->addressable_vars[i]);
973 FOR_EACH_REFERENCED_VAR(var, rvi)
975 var_ann_t ann = var_ann (var);
976 NUM_REFERENCES_CLEAR (ann);
979 free (ai->addressable_vars);
981 for (i = 0; i < ai->num_pointers; i++)
982 free (ai->pointers[i]);
985 BITMAP_FREE (ai->written_vars);
986 BITMAP_FREE (ai->dereferenced_ptrs_store);
987 BITMAP_FREE (ai->dereferenced_ptrs_load);
988 bitmap_obstack_release (&alias_obstack);
991 delete_points_to_sets ();
994 /* Used for hashing to identify pointer infos with identical
997 eq_ptr_info (const void *p1, const void *p2)
999 const struct ptr_info_def *n1 = (const struct ptr_info_def *) p1;
1000 const struct ptr_info_def *n2 = (const struct ptr_info_def *) p2;
1001 return bitmap_equal_p (n1->pt_vars, n2->pt_vars);
1005 ptr_info_hash (const void *p)
1007 const struct ptr_info_def *n = (const struct ptr_info_def *) p;
1008 return bitmap_hash (n->pt_vars);
1011 /* Create name tags for all the pointers that have been dereferenced.
1012 We only create a name tag for a pointer P if P is found to point to
1013 a set of variables (so that we can alias them to *P) or if it is
1014 the result of a call to malloc (which means that P cannot point to
1015 anything else nor alias any other variable).
1017 If two pointers P and Q point to the same set of variables, they
1018 are assigned the same name tag. */
1021 create_name_tags (void)
1024 VEC (tree, heap) *with_ptvars = NULL;
1028 /* Collect the list of pointers with a non-empty points to set. */
1029 for (i = 1; i < num_ssa_names; i++)
1031 tree ptr = ssa_name (i);
1032 struct ptr_info_def *pi;
1035 || !POINTER_TYPE_P (TREE_TYPE (ptr))
1036 || !SSA_NAME_PTR_INFO (ptr))
1039 pi = SSA_NAME_PTR_INFO (ptr);
1041 if (pi->pt_anything || !pi->is_dereferenced)
1043 /* No name tags for pointers that have not been
1044 dereferenced or point to an arbitrary location. */
1045 pi->name_mem_tag = NULL_TREE;
1049 /* Set pt_anything on the pointers without pt_vars filled in so
1050 that they are assigned a symbol tag. */
1051 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
1052 VEC_safe_push (tree, heap, with_ptvars, ptr);
1054 set_pt_anything (ptr);
1057 /* If we didn't find any pointers with pt_vars set, we're done. */
1061 ptr_hash = htab_create (10, ptr_info_hash, eq_ptr_info, NULL);
1062 /* Now go through the pointers with pt_vars, and find a name tag
1063 with the same pt_vars as this pointer, or create one if one
1065 for (i = 0; VEC_iterate (tree, with_ptvars, i, ptr); i++)
1067 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1068 tree old_name_tag = pi->name_mem_tag;
1069 struct ptr_info_def **slot;
1071 /* If PTR points to a set of variables, check if we don't
1072 have another pointer Q with the same points-to set before
1073 creating a tag. If so, use Q's tag instead of creating a
1076 This is important for not creating unnecessary symbols
1077 and also for copy propagation. If we ever need to
1078 propagate PTR into Q or vice-versa, we would run into
1079 problems if they both had different name tags because
1080 they would have different SSA version numbers (which
1081 would force us to take the name tags in and out of SSA). */
1083 slot = (struct ptr_info_def **) htab_find_slot (ptr_hash, pi, INSERT);
1085 pi->name_mem_tag = (*slot)->name_mem_tag;
1089 /* If we didn't find a pointer with the same points-to set
1090 as PTR, create a new name tag if needed. */
1091 if (pi->name_mem_tag == NULL_TREE)
1092 pi->name_mem_tag = get_nmt_for (ptr);
1095 /* If the new name tag computed for PTR is different than
1096 the old name tag that it used to have, then the old tag
1097 needs to be removed from the IL, so we mark it for
1099 if (old_name_tag && old_name_tag != pi->name_mem_tag)
1100 mark_sym_for_renaming (old_name_tag);
1102 TREE_THIS_VOLATILE (pi->name_mem_tag)
1103 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
1105 /* Mark the new name tag for renaming. */
1106 mark_sym_for_renaming (pi->name_mem_tag);
1108 htab_delete (ptr_hash);
1110 VEC_free (tree, heap, with_ptvars);
1114 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
1115 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
1116 name tag and the variables it points-to are call-clobbered. Finally, if
1117 P_i escapes and we could not determine where it points to, then all the
1118 variables in the same alias set as *P_i are marked call-clobbered. This
1119 is necessary because we must assume that P_i may take the address of any
1120 variable in the same alias set. */
1123 compute_flow_sensitive_aliasing (struct alias_info *ai)
1128 for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
1130 if (!find_what_p_points_to (ptr))
1131 set_pt_anything (ptr);
1134 create_name_tags ();
1136 for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
1139 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1140 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
1144 /* Set up aliasing information for PTR's name memory tag (if it has
1145 one). Note that only pointers that have been dereferenced will
1146 have a name memory tag. */
1147 if (pi->name_mem_tag && pi->pt_vars)
1148 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
1150 add_may_alias (pi->name_mem_tag, referenced_var (j));
1151 add_may_alias (v_ann->symbol_mem_tag, referenced_var (j));
1157 /* Compute type-based alias sets. Traverse all the pointers and
1158 addressable variables found in setup_pointers_and_addressables.
1160 For every pointer P in AI->POINTERS and addressable variable V in
1161 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's symbol
1162 memory tag (SMT) if their alias sets conflict. V is then marked as
1163 an alias tag so that the operand scanner knows that statements
1164 containing V have aliased operands. */
1167 compute_flow_insensitive_aliasing (struct alias_info *ai)
1171 /* Initialize counter for the total number of virtual operands that
1172 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
1173 threshold set by --params max-alias-vops, we enable alias
1175 ai->total_alias_vops = 0;
1177 /* For every pointer P, determine which addressable variables may alias
1178 with P's symbol memory tag. */
1179 for (i = 0; i < ai->num_pointers; i++)
1182 struct alias_map_d *p_map = ai->pointers[i];
1183 tree tag = var_ann (p_map->var)->symbol_mem_tag;
1184 var_ann_t tag_ann = var_ann (tag);
1187 /* Call-clobbering information is not finalized yet at this point. */
1188 if (PTR_IS_REF_ALL (p_map->var))
1191 p_map->total_alias_vops = 0;
1192 p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
1194 /* Add any pre-existing may_aliases to the bitmap used to represent
1195 TAG's alias set in case we need to group aliases. */
1196 for (j = 0; VEC_iterate (tree, tag_ann->may_aliases, j, var); ++j)
1197 bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
1199 for (j = 0; j < ai->num_addressable_vars; j++)
1201 struct alias_map_d *v_map;
1203 bool tag_stored_p, var_stored_p;
1205 v_map = ai->addressable_vars[j];
1207 v_ann = var_ann (var);
1209 /* Skip memory tags and variables that have never been
1210 written to. We also need to check if the variables are
1211 call-clobbered because they may be overwritten by
1214 Note this is effectively random accessing elements in
1215 the sparse bitset, which can be highly inefficient.
1216 So we first check the call_clobbered status of the
1217 tag and variable before querying the bitmap. */
1218 tag_stored_p = is_call_clobbered (tag)
1219 || bitmap_bit_p (ai->written_vars, DECL_UID (tag));
1220 var_stored_p = is_call_clobbered (var)
1221 || bitmap_bit_p (ai->written_vars, DECL_UID (var));
1222 if (!tag_stored_p && !var_stored_p)
1225 if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false))
1227 size_t num_tag_refs, num_var_refs;
1229 num_tag_refs = NUM_REFERENCES (tag_ann);
1230 num_var_refs = NUM_REFERENCES (v_ann);
1232 /* Add VAR to TAG's may-aliases set. */
1234 /* We should never have a var with subvars here, because
1235 they shouldn't get into the set of addressable vars */
1236 gcc_assert (!var_can_have_subvars (var)
1237 || get_subvars_for_var (var) == NULL);
1239 add_may_alias (tag, var);
1240 /* Update the bitmap used to represent TAG's alias set
1241 in case we need to group aliases. */
1242 bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
1244 /* Update the total number of virtual operands due to
1245 aliasing. Since we are adding one more alias to TAG's
1246 may-aliases set, the total number of virtual operands due
1247 to aliasing will be increased by the number of references
1248 made to VAR and TAG (every reference to TAG will also
1249 count as a reference to VAR). */
1250 ai->total_alias_vops += (num_var_refs + num_tag_refs);
1251 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
1258 /* Since this analysis is based exclusively on symbols, it fails to
1259 handle cases where two pointers P and Q have different memory
1260 tags with conflicting alias set numbers but no aliased symbols in
1263 For example, suppose that we have two memory tags SMT.1 and SMT.2
1266 may-aliases (SMT.1) = { a }
1267 may-aliases (SMT.2) = { b }
1269 and the alias set number of SMT.1 conflicts with that of SMT.2.
1270 Since they don't have symbols in common, loads and stores from
1271 SMT.1 and SMT.2 will seem independent of each other, which will
1272 lead to the optimizers making invalid transformations (see
1273 testsuite/gcc.c-torture/execute/pr15262-[12].c).
1275 To avoid this problem, we do a final traversal of AI->POINTERS
1276 looking for pairs of pointers that have no aliased symbols in
1277 common and yet have conflicting alias set numbers. */
1278 for (i = 0; i < ai->num_pointers; i++)
1281 struct alias_map_d *p_map1 = ai->pointers[i];
1282 tree tag1 = var_ann (p_map1->var)->symbol_mem_tag;
1283 bitmap may_aliases1 = p_map1->may_aliases;
1285 if (PTR_IS_REF_ALL (p_map1->var))
1288 for (j = i + 1; j < ai->num_pointers; j++)
1290 struct alias_map_d *p_map2 = ai->pointers[j];
1291 tree tag2 = var_ann (p_map2->var)->symbol_mem_tag;
1292 bitmap may_aliases2 = p_map2->may_aliases;
1294 if (PTR_IS_REF_ALL (p_map2->var))
1297 /* If the pointers may not point to each other, do nothing. */
1298 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true))
1301 /* The two pointers may alias each other. If they already have
1302 symbols in common, do nothing. */
1303 if (bitmap_intersect_p (may_aliases1, may_aliases2))
1306 if (!bitmap_empty_p (may_aliases2))
1311 /* Add all the aliases for TAG2 into TAG1's alias set.
1312 FIXME, update grouping heuristic counters. */
1313 EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi)
1314 add_may_alias (tag1, referenced_var (k));
1315 bitmap_ior_into (may_aliases1, may_aliases2);
1319 /* Since TAG2 does not have any aliases of its own, add
1320 TAG2 itself to the alias set of TAG1. */
1321 add_may_alias (tag1, tag2);
1322 bitmap_set_bit (may_aliases1, DECL_UID (tag2));
1328 fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n",
1329 get_name (current_function_decl),
1330 ai->total_alias_vops);
1334 /* Finalize may-alias information for ref-all pointers. Traverse all
1335 the addressable variables found in setup_pointers_and_addressables.
1337 If flow-sensitive alias analysis has attached a name memory tag to
1338 a ref-all pointer, we will use it for the dereferences because that
1339 will have more precise aliasing information. But if there is no
1340 name tag, we will use a special symbol tag that aliases all the
1341 call-clobbered addressable variables. */
1344 finalize_ref_all_pointers (struct alias_info *ai)
1349 add_may_alias (ai->ref_all_symbol_mem_tag, global_var);
1352 /* First add the real call-clobbered variables. */
1353 for (i = 0; i < ai->num_addressable_vars; i++)
1355 tree var = ai->addressable_vars[i]->var;
1356 if (is_call_clobbered (var))
1357 add_may_alias (ai->ref_all_symbol_mem_tag, var);
1360 /* Then add the call-clobbered pointer memory tags. See
1361 compute_flow_insensitive_aliasing for the rationale. */
1362 for (i = 0; i < ai->num_pointers; i++)
1364 tree ptr = ai->pointers[i]->var, tag;
1365 if (PTR_IS_REF_ALL (ptr))
1367 tag = var_ann (ptr)->symbol_mem_tag;
1368 if (is_call_clobbered (tag))
1369 add_may_alias (ai->ref_all_symbol_mem_tag, tag);
1375 /* Comparison function for qsort used in group_aliases. */
1378 total_alias_vops_cmp (const void *p, const void *q)
1380 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1381 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1382 long n1 = (*p1)->total_alias_vops;
1383 long n2 = (*p2)->total_alias_vops;
1385 /* We want to sort in descending order. */
1386 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1389 /* Group all the aliases for TAG to make TAG represent all the
1390 variables in its alias set. Update the total number
1391 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1392 function will make TAG be the unique alias tag for all the
1393 variables in its may-aliases. So, given:
1395 may-aliases(TAG) = { V1, V2, V3 }
1397 This function will group the variables into:
1399 may-aliases(V1) = { TAG }
1400 may-aliases(V2) = { TAG }
1401 may-aliases(V2) = { TAG } */
1404 group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai)
1407 var_ann_t tag_ann = var_ann (tag);
1408 size_t num_tag_refs = NUM_REFERENCES (tag_ann);
1411 EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi)
1413 tree var = referenced_var (i);
1414 var_ann_t ann = var_ann (var);
1416 /* Make TAG the unique alias of VAR. */
1417 ann->is_aliased = 0;
1418 ann->may_aliases = NULL;
1420 /* Note that VAR and TAG may be the same if the function has no
1421 addressable variables (see the discussion at the end of
1422 setup_pointers_and_addressables). */
1424 add_may_alias (var, tag);
1426 /* Reduce total number of virtual operands contributed
1427 by TAG on behalf of VAR. Notice that the references to VAR
1428 itself won't be removed. We will merely replace them with
1429 references to TAG. */
1430 ai->total_alias_vops -= num_tag_refs;
1433 /* We have reduced the number of virtual operands that TAG makes on
1434 behalf of all the variables formerly aliased with it. However,
1435 we have also "removed" all the virtual operands for TAG itself,
1436 so we add them back. */
1437 ai->total_alias_vops += num_tag_refs;
1439 /* TAG no longer has any aliases. */
1440 tag_ann->may_aliases = NULL;
1444 /* Group may-aliases sets to reduce the number of virtual operands due
1447 1- Sort the list of pointers in decreasing number of contributed
1450 2- Take the first entry in AI->POINTERS and revert the role of
1451 the memory tag and its aliases. Usually, whenever an aliased
1452 variable Vi is found to alias with a memory tag T, we add Vi
1453 to the may-aliases set for T. Meaning that after alias
1454 analysis, we will have:
1456 may-aliases(T) = { V1, V2, V3, ..., Vn }
1458 This means that every statement that references T, will get 'n'
1459 virtual operands for each of the Vi tags. But, when alias
1460 grouping is enabled, we make T an alias tag and add it to the
1461 alias set of all the Vi variables:
1463 may-aliases(V1) = { T }
1464 may-aliases(V2) = { T }
1466 may-aliases(Vn) = { T }
1468 This has two effects: (a) statements referencing T will only get
1469 a single virtual operand, and, (b) all the variables Vi will now
1470 appear to alias each other. So, we lose alias precision to
1471 improve compile time. But, in theory, a program with such a high
1472 level of aliasing should not be very optimizable in the first
1475 3- Since variables may be in the alias set of more than one
1476 memory tag, the grouping done in step (2) needs to be extended
1477 to all the memory tags that have a non-empty intersection with
1478 the may-aliases set of tag T. For instance, if we originally
1479 had these may-aliases sets:
1481 may-aliases(T) = { V1, V2, V3 }
1482 may-aliases(R) = { V2, V4 }
1484 In step (2) we would have reverted the aliases for T as:
1486 may-aliases(V1) = { T }
1487 may-aliases(V2) = { T }
1488 may-aliases(V3) = { T }
1490 But note that now V2 is no longer aliased with R. We could
1491 add R to may-aliases(V2), but we are in the process of
1492 grouping aliases to reduce virtual operands so what we do is
1493 add V4 to the grouping to obtain:
1495 may-aliases(V1) = { T }
1496 may-aliases(V2) = { T }
1497 may-aliases(V3) = { T }
1498 may-aliases(V4) = { T }
1500 4- If the total number of virtual operands due to aliasing is
1501 still above the threshold set by max-alias-vops, go back to (2). */
1504 group_aliases (struct alias_info *ai)
1509 /* Sort the POINTERS array in descending order of contributed
1510 virtual operands. */
1511 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1512 total_alias_vops_cmp);
1514 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1515 and the tag's may-aliases set. */
1516 for (i = 0; i < ai->num_pointers; i++)
1519 tree tag1 = var_ann (ai->pointers[i]->var)->symbol_mem_tag;
1520 bitmap tag1_aliases = ai->pointers[i]->may_aliases;
1522 /* Skip tags that have been grouped already. */
1523 if (ai->pointers[i]->grouped_p)
1526 /* See if TAG1 had any aliases in common with other symbol tags.
1527 If we find a TAG2 with common aliases with TAG1, add TAG2's
1528 aliases into TAG1. */
1529 for (j = i + 1; j < ai->num_pointers; j++)
1531 bitmap tag2_aliases = ai->pointers[j]->may_aliases;
1533 if (bitmap_intersect_p (tag1_aliases, tag2_aliases))
1535 tree tag2 = var_ann (ai->pointers[j]->var)->symbol_mem_tag;
1537 bitmap_ior_into (tag1_aliases, tag2_aliases);
1539 /* TAG2 does not need its aliases anymore. */
1540 bitmap_clear (tag2_aliases);
1541 var_ann (tag2)->may_aliases = NULL;
1543 /* TAG1 is the unique alias of TAG2. */
1544 add_may_alias (tag2, tag1);
1546 ai->pointers[j]->grouped_p = true;
1550 /* Now group all the aliases we collected into TAG1. */
1551 group_aliases_into (tag1, tag1_aliases, ai);
1553 /* If we've reduced total number of virtual operands below the
1555 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1559 /* Finally, all the variables that have been grouped cannot be in
1560 the may-alias set of name memory tags. Suppose that we have
1561 grouped the aliases in this code so that may-aliases(a) = SMT.20
1565 # a_9 = V_MAY_DEF <a_8>
1567 ... Several modifications to SMT.20 ...
1571 Since p_5 points to 'a', the optimizers will try to propagate 0
1572 into p_5->field, but that is wrong because there have been
1573 modifications to 'SMT.20' in between. To prevent this we have to
1574 replace 'a' with 'SMT.20' in the name tag of p_5. */
1575 for (i = 0; VEC_iterate (tree, ai->processed_ptrs, i, ptr); i++)
1578 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1579 VEC(tree,gc) *aliases;
1582 if (name_tag == NULL_TREE)
1585 aliases = var_ann (name_tag)->may_aliases;
1586 for (j = 0; VEC_iterate (tree, aliases, j, alias); j++)
1588 var_ann_t ann = var_ann (alias);
1590 if ((!MTAG_P (alias)
1591 || TREE_CODE (alias) == STRUCT_FIELD_TAG)
1592 && ann->may_aliases)
1596 gcc_assert (VEC_length (tree, ann->may_aliases) == 1);
1598 new_alias = VEC_index (tree, ann->may_aliases, 0);
1599 replace_may_alias (name_tag, j, new_alias);
1606 "%s: Total number of aliased vops after grouping: %ld%s\n",
1607 get_name (current_function_decl),
1608 ai->total_alias_vops,
1609 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1613 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1616 create_alias_map_for (tree var, struct alias_info *ai)
1618 struct alias_map_d *alias_map;
1619 alias_map = XCNEW (struct alias_map_d);
1620 alias_map->var = var;
1621 alias_map->set = get_alias_set (var);
1622 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1626 /* Create memory tags for all the dereferenced pointers and build the
1627 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1628 sets. Based on the address escape and points-to information collected
1629 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1630 variables whose address is not needed anymore. */
1633 setup_pointers_and_addressables (struct alias_info *ai)
1635 size_t n_vars, num_addressable_vars, num_pointers;
1636 referenced_var_iterator rvi;
1638 VEC (tree, heap) *varvec = NULL;
1639 safe_referenced_var_iterator srvi;
1641 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1642 num_addressable_vars = num_pointers = 0;
1644 FOR_EACH_REFERENCED_VAR (var, rvi)
1646 if (may_be_aliased (var))
1647 num_addressable_vars++;
1649 if (POINTER_TYPE_P (TREE_TYPE (var)))
1651 /* Since we don't keep track of volatile variables, assume that
1652 these pointers are used in indirect store operations. */
1653 if (TREE_THIS_VOLATILE (var))
1654 bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var));
1660 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1661 always going to be slightly bigger than we actually need them
1662 because some TREE_ADDRESSABLE variables will be marked
1663 non-addressable below and only pointers with unique symbol tags are
1664 going to be added to POINTERS. */
1665 ai->addressable_vars = XCNEWVEC (struct alias_map_d *, num_addressable_vars);
1666 ai->pointers = XCNEWVEC (struct alias_map_d *, num_pointers);
1667 ai->num_addressable_vars = 0;
1668 ai->num_pointers = 0;
1670 /* Since we will be creating symbol memory tags within this loop,
1671 cache the value of NUM_REFERENCED_VARS to avoid processing the
1672 additional tags unnecessarily. */
1673 n_vars = num_referenced_vars;
1675 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi)
1677 var_ann_t v_ann = var_ann (var);
1680 /* Name memory tags already have flow-sensitive aliasing
1681 information, so they need not be processed by
1682 compute_flow_insensitive_aliasing. Similarly, symbol memory
1683 tags are already accounted for when we process their
1686 Structure fields, on the other hand, have to have some of this
1687 information processed for them, but it's pointless to mark them
1688 non-addressable (since they are fake variables anyway). */
1689 if (MTAG_P (var) && TREE_CODE (var) != STRUCT_FIELD_TAG)
1692 /* Remove the ADDRESSABLE flag from every addressable variable whose
1693 address is not needed anymore. This is caused by the propagation
1694 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1695 removal of dead pointer assignments done by the early scalar
1697 if (TREE_ADDRESSABLE (var))
1699 if (!bitmap_bit_p (addressable_vars, DECL_UID (var))
1700 && TREE_CODE (var) != RESULT_DECL
1701 && !is_global_var (var))
1703 bool okay_to_mark = true;
1705 /* Since VAR is now a regular GIMPLE register, we will need
1706 to rename VAR into SSA afterwards. */
1707 mark_sym_for_renaming (var);
1709 /* If VAR can have sub-variables, and any of its
1710 sub-variables has its address taken, then we cannot
1711 remove the addressable flag from VAR. */
1712 if (var_can_have_subvars (var)
1713 && (svars = get_subvars_for_var (var)))
1717 for (sv = svars; sv; sv = sv->next)
1719 if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var)))
1720 okay_to_mark = false;
1721 mark_sym_for_renaming (sv->var);
1725 /* The address of VAR is not needed, remove the
1726 addressable bit, so that it can be optimized as a
1727 regular variable. */
1729 mark_non_addressable (var);
1733 /* Global variables and addressable locals may be aliased. Create an
1734 entry in ADDRESSABLE_VARS for VAR. */
1735 if (may_be_aliased (var)
1736 && (!var_can_have_subvars (var)
1737 || get_subvars_for_var (var) == NULL))
1739 create_alias_map_for (var, ai);
1740 mark_sym_for_renaming (var);
1743 /* Add pointer variables that have been dereferenced to the POINTERS
1744 array and create a symbol memory tag for them. */
1745 if (POINTER_TYPE_P (TREE_TYPE (var)))
1747 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))
1748 || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var))))
1753 /* If pointer VAR still doesn't have a memory tag
1754 associated with it, create it now or re-use an
1756 tag = get_tmt_for (var, ai);
1757 t_ann = var_ann (tag);
1759 /* The symbol tag will need to be renamed into SSA
1760 afterwards. Note that we cannot do this inside
1761 get_tmt_for because aliasing may run multiple times
1762 and we only create symbol tags the first time. */
1763 mark_sym_for_renaming (tag);
1765 /* Similarly, if pointer VAR used to have another type
1766 tag, we will need to process it in the renamer to
1767 remove the stale virtual operands. */
1768 if (v_ann->symbol_mem_tag)
1769 mark_sym_for_renaming (v_ann->symbol_mem_tag);
1771 /* Associate the tag with pointer VAR. */
1772 v_ann->symbol_mem_tag = tag;
1774 /* If pointer VAR has been used in a store operation,
1775 then its memory tag must be marked as written-to. */
1776 if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)))
1777 bitmap_set_bit (ai->written_vars, DECL_UID (tag));
1779 /* All the dereferences of pointer VAR count as
1780 references of TAG. Since TAG can be associated with
1781 several pointers, add the dereferences of VAR to the
1783 NUM_REFERENCES_SET (t_ann,
1784 NUM_REFERENCES (t_ann)
1785 + NUM_REFERENCES (v_ann));
1789 /* The pointer has not been dereferenced. If it had a
1790 symbol memory tag, remove it and mark the old tag for
1791 renaming to remove it out of the IL. */
1792 var_ann_t ann = var_ann (var);
1793 tree tag = ann->symbol_mem_tag;
1796 mark_sym_for_renaming (tag);
1797 ann->symbol_mem_tag = NULL_TREE;
1802 VEC_free (tree, heap, varvec);
1806 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1807 every call site, we need to emit V_MAY_DEF expressions to represent the
1808 clobbering effects of the call for variables whose address escapes the
1811 One approach is to group all call-clobbered variables into a single
1812 representative that is used as an alias of every call-clobbered variable
1813 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1814 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1816 The second approach is to emit a clobbering V_MAY_DEF for every
1817 call-clobbered variable at call sites. This is the preferred way in terms
1818 of optimization opportunities but it may create too many V_MAY_DEF operands
1819 if there are many call clobbered variables and function calls in the
1822 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1823 function calls found by the number of call-clobbered variables. If that
1824 product is beyond a certain threshold, as determined by the parameterized
1825 values shown below, we use .GLOBAL_VAR.
1827 FIXME. This heuristic should be improved. One idea is to use several
1828 .GLOBAL_VARs of different types instead of a single one. The thresholds
1829 have been derived from a typical bootstrap cycle, including all target
1830 libraries. Compile times were found increase by ~1% compared to using
1834 maybe_create_global_var (struct alias_info *ai)
1836 unsigned i, n_clobbered;
1839 /* No need to create it, if we have one already. */
1840 if (global_var == NULL_TREE)
1842 /* Count all the call-clobbered variables. */
1844 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1849 /* If the number of virtual operands that would be needed to
1850 model all the call-clobbered variables is larger than
1851 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
1853 Also create .GLOBAL_VAR if there are no call-clobbered
1854 variables and the program contains a mixture of pure/const
1855 and regular function calls. This is to avoid the problem
1856 described in PR 20115:
1859 int func_pure (void) { return X; }
1860 int func_non_pure (int a) { X += a; }
1863 int a = func_pure ();
1869 Since foo() has no call-clobbered variables, there is
1870 no relationship between the calls to func_pure and
1871 func_non_pure. Since func_pure has no side-effects, value
1872 numbering optimizations elide the second call to func_pure.
1873 So, if we have some pure/const and some regular calls in the
1874 program we create .GLOBAL_VAR to avoid missing these
1876 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
1877 || (n_clobbered == 0
1878 && ai->num_calls_found > 0
1879 && ai->num_pure_const_calls_found > 0
1880 && ai->num_calls_found > ai->num_pure_const_calls_found))
1881 create_global_var ();
1884 /* Mark all call-clobbered symbols for renaming. Since the initial
1885 rewrite into SSA ignored all call sites, we may need to rename
1886 .GLOBAL_VAR and the call-clobbered variables. */
1887 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1889 tree var = referenced_var (i);
1891 /* If the function has calls to clobbering functions and
1892 .GLOBAL_VAR has been created, make it an alias for all
1893 call-clobbered variables. */
1894 if (global_var && var != global_var)
1896 add_may_alias (var, global_var);
1897 gcc_assert (!get_subvars_for_var (var));
1900 mark_sym_for_renaming (var);
1905 /* Return TRUE if pointer PTR may point to variable VAR.
1907 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1908 This is needed because when checking for type conflicts we are
1909 interested in the alias set of the memory location pointed-to by
1910 PTR. The alias set of PTR itself is irrelevant.
1912 VAR_ALIAS_SET is the alias set for VAR. */
1915 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1916 tree var, HOST_WIDE_INT var_alias_set,
1917 bool alias_set_only)
1921 alias_stats.alias_queries++;
1922 alias_stats.simple_queries++;
1924 /* By convention, a variable cannot alias itself. */
1925 mem = var_ann (ptr)->symbol_mem_tag;
1928 alias_stats.alias_noalias++;
1929 alias_stats.simple_resolved++;
1933 /* If -fargument-noalias-global is > 2, pointer arguments may
1934 not point to anything else. */
1935 if (flag_argument_noalias > 2 && TREE_CODE (ptr) == PARM_DECL)
1937 alias_stats.alias_noalias++;
1938 alias_stats.simple_resolved++;
1942 /* If -fargument-noalias-global is > 1, pointer arguments may
1943 not point to global variables. */
1944 if (flag_argument_noalias > 1 && is_global_var (var)
1945 && TREE_CODE (ptr) == PARM_DECL)
1947 alias_stats.alias_noalias++;
1948 alias_stats.simple_resolved++;
1952 /* If either MEM or VAR is a read-only global and the other one
1953 isn't, then PTR cannot point to VAR. */
1954 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
1955 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
1957 alias_stats.alias_noalias++;
1958 alias_stats.simple_resolved++;
1962 gcc_assert (TREE_CODE (mem) == SYMBOL_MEMORY_TAG);
1964 alias_stats.tbaa_queries++;
1966 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1967 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1969 alias_stats.alias_noalias++;
1970 alias_stats.tbaa_resolved++;
1974 /* If var is a record or union type, ptr cannot point into var
1975 unless there is some operation explicit address operation in the
1976 program that can reference a field of the ptr's dereferenced
1977 type. This also assumes that the types of both var and ptr are
1978 contained within the compilation unit, and that there is no fancy
1979 addressing arithmetic associated with any of the types
1982 if ((mem_alias_set != 0) && (var_alias_set != 0))
1984 tree ptr_type = TREE_TYPE (ptr);
1985 tree var_type = TREE_TYPE (var);
1987 /* The star count is -1 if the type at the end of the pointer_to
1988 chain is not a record or union type. */
1989 if ((!alias_set_only) &&
1990 ipa_type_escape_star_count_of_interesting_type (var_type) >= 0)
1992 int ptr_star_count = 0;
1994 /* Ipa_type_escape_star_count_of_interesting_type is a little to
1995 restrictive for the pointer type, need to allow pointers to
1996 primitive types as long as those types cannot be pointers
1998 while (POINTER_TYPE_P (ptr_type))
1999 /* Strip the *'s off. */
2001 ptr_type = TREE_TYPE (ptr_type);
2005 /* There does not appear to be a better test to see if the
2006 pointer type was one of the pointer to everything
2009 if (ptr_star_count > 0)
2011 alias_stats.structnoaddress_queries++;
2012 if (ipa_type_escape_field_does_not_clobber_p (var_type,
2015 alias_stats.structnoaddress_resolved++;
2016 alias_stats.alias_noalias++;
2020 else if (ptr_star_count == 0)
2022 /* If ptr_type was not really a pointer to type, it cannot
2024 alias_stats.structnoaddress_queries++;
2025 alias_stats.structnoaddress_resolved++;
2026 alias_stats.alias_noalias++;
2032 alias_stats.alias_mayalias++;
2037 /* Add ALIAS to the set of variables that may alias VAR. */
2040 add_may_alias (tree var, tree alias)
2043 var_ann_t v_ann = get_var_ann (var);
2044 var_ann_t a_ann = get_var_ann (alias);
2047 /* Don't allow self-referential aliases. */
2048 gcc_assert (var != alias);
2050 /* ALIAS must be addressable if it's being added to an alias set. */
2052 TREE_ADDRESSABLE (alias) = 1;
2054 gcc_assert (may_be_aliased (alias));
2057 if (v_ann->may_aliases == NULL)
2058 v_ann->may_aliases = VEC_alloc (tree, gc, 2);
2060 /* Avoid adding duplicates. */
2061 for (i = 0; VEC_iterate (tree, v_ann->may_aliases, i, al); i++)
2065 VEC_safe_push (tree, gc, v_ann->may_aliases, alias);
2066 a_ann->is_aliased = 1;
2070 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
2073 replace_may_alias (tree var, size_t i, tree new_alias)
2075 var_ann_t v_ann = var_ann (var);
2076 VEC_replace (tree, v_ann->may_aliases, i, new_alias);
2080 /* Mark pointer PTR as pointing to an arbitrary memory location. */
2083 set_pt_anything (tree ptr)
2085 struct ptr_info_def *pi = get_ptr_info (ptr);
2087 pi->pt_anything = 1;
2090 /* The pointer used to have a name tag, but we now found it pointing
2091 to an arbitrary location. The name tag needs to be renamed and
2092 disassociated from PTR. */
2093 if (pi->name_mem_tag)
2095 mark_sym_for_renaming (pi->name_mem_tag);
2096 pi->name_mem_tag = NULL_TREE;
2101 /* Return true if STMT is an "escape" site from the current function. Escape
2102 sites those statements which might expose the address of a variable
2103 outside the current function. STMT is an escape site iff:
2105 1- STMT is a function call, or
2106 2- STMT is an __asm__ expression, or
2107 3- STMT is an assignment to a non-local variable, or
2108 4- STMT is a return statement.
2110 Return the type of escape site found, if we found one, or NO_ESCAPE
2114 is_escape_site (tree stmt)
2116 tree call = get_call_expr_in (stmt);
2117 if (call != NULL_TREE)
2119 if (!TREE_SIDE_EFFECTS (call))
2120 return ESCAPE_TO_PURE_CONST;
2122 return ESCAPE_TO_CALL;
2124 else if (TREE_CODE (stmt) == ASM_EXPR)
2125 return ESCAPE_TO_ASM;
2126 else if (TREE_CODE (stmt) == MODIFY_EXPR)
2128 tree lhs = TREE_OPERAND (stmt, 0);
2130 /* Get to the base of _REF nodes. */
2131 if (TREE_CODE (lhs) != SSA_NAME)
2132 lhs = get_base_address (lhs);
2134 /* If we couldn't recognize the LHS of the assignment, assume that it
2135 is a non-local store. */
2136 if (lhs == NULL_TREE)
2137 return ESCAPE_UNKNOWN;
2139 if (TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
2140 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
2141 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
2143 tree from = TREE_TYPE (TREE_OPERAND (TREE_OPERAND (stmt, 1), 0));
2144 tree to = TREE_TYPE (TREE_OPERAND (stmt, 1));
2146 /* If the RHS is a conversion between a pointer and an integer, the
2147 pointer escapes since we can't track the integer. */
2148 if (POINTER_TYPE_P (from) && !POINTER_TYPE_P (to))
2149 return ESCAPE_BAD_CAST;
2151 /* Same if the RHS is a conversion between a regular pointer and a
2152 ref-all pointer since we can't track the SMT of the former. */
2153 if (POINTER_TYPE_P (from) && !TYPE_REF_CAN_ALIAS_ALL (from)
2154 && POINTER_TYPE_P (to) && TYPE_REF_CAN_ALIAS_ALL (to))
2155 return ESCAPE_BAD_CAST;
2158 /* If the LHS is an SSA name, it can't possibly represent a non-local
2160 if (TREE_CODE (lhs) == SSA_NAME)
2163 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2164 local variables we cannot be sure if it will escape, because we
2165 don't have information about objects not in SSA form. Need to
2166 implement something along the lines of
2168 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2169 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2170 Conference on Object-Oriented Programming Systems, Languages, and
2171 Applications (OOPSLA), pp. 1-19, 1999. */
2172 return ESCAPE_STORED_IN_GLOBAL;
2174 else if (TREE_CODE (stmt) == RETURN_EXPR)
2175 return ESCAPE_TO_RETURN;
2180 /* Create a new memory tag of type TYPE.
2181 Does NOT push it into the current binding. */
2184 create_tag_raw (enum tree_code code, tree type, const char *prefix)
2189 /* Make the type of the variable writable. */
2190 new_type = build_type_variant (type, 0, 0);
2191 TYPE_ATTRIBUTES (new_type) = TYPE_ATTRIBUTES (type);
2193 tmp_var = build_decl (code, create_tmp_var_name (prefix),
2195 /* Make the variable writable. */
2196 TREE_READONLY (tmp_var) = 0;
2198 /* It doesn't start out global. */
2199 MTAG_GLOBAL (tmp_var) = 0;
2200 TREE_STATIC (tmp_var) = 0;
2201 TREE_USED (tmp_var) = 1;
2206 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2207 is considered to represent all the pointers whose pointed-to types are
2208 in the same alias set class. Otherwise, the tag represents a single
2209 SSA_NAME pointer variable. */
2212 create_memory_tag (tree type, bool is_type_tag)
2215 tree tag = create_tag_raw (is_type_tag ? SYMBOL_MEMORY_TAG : NAME_MEMORY_TAG,
2216 type, (is_type_tag) ? "SMT" : "NMT");
2218 /* By default, memory tags are local variables. Alias analysis will
2219 determine whether they should be considered globals. */
2220 DECL_CONTEXT (tag) = current_function_decl;
2222 /* Memory tags are by definition addressable. */
2223 TREE_ADDRESSABLE (tag) = 1;
2225 ann = get_var_ann (tag);
2226 ann->symbol_mem_tag = NULL_TREE;
2228 /* Add the tag to the symbol table. */
2229 add_referenced_var (tag);
2235 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2236 This is used if P_i has been found to point to a specific set of
2237 variables or to a non-aliased memory location like the address returned
2238 by malloc functions. */
2241 get_nmt_for (tree ptr)
2243 struct ptr_info_def *pi = get_ptr_info (ptr);
2244 tree tag = pi->name_mem_tag;
2246 if (tag == NULL_TREE)
2247 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2252 /* Return the symbol memory tag associated to pointer PTR. A memory
2253 tag is an artificial variable that represents the memory location
2254 pointed-to by PTR. It is used to model the effects of pointer
2255 de-references on addressable variables.
2257 AI points to the data gathered during alias analysis. This
2258 function populates the array AI->POINTERS. */
2261 get_tmt_for (tree ptr, struct alias_info *ai)
2265 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2266 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2268 /* We use a unique memory tag for all the ref-all pointers. */
2269 if (PTR_IS_REF_ALL (ptr))
2271 if (!ai->ref_all_symbol_mem_tag)
2272 ai->ref_all_symbol_mem_tag = create_memory_tag (void_type_node, true);
2273 return ai->ref_all_symbol_mem_tag;
2276 /* To avoid creating unnecessary memory tags, only create one memory tag
2277 per alias set class. Note that it may be tempting to group
2278 memory tags based on conflicting alias sets instead of
2279 equivalence. That would be wrong because alias sets are not
2280 necessarily transitive (as demonstrated by the libstdc++ test
2281 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2282 such that conflicts (A, B) == true and conflicts (A, C) == true,
2283 it does not necessarily follow that conflicts (B, C) == true. */
2284 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2286 struct alias_map_d *curr = ai->pointers[i];
2287 tree curr_tag = var_ann (curr->var)->symbol_mem_tag;
2288 if (tag_set == curr->set)
2295 /* If VAR cannot alias with any of the existing memory tags, create a new
2296 tag for PTR and add it to the POINTERS array. */
2297 if (tag == NULL_TREE)
2299 struct alias_map_d *alias_map;
2301 /* If PTR did not have a symbol tag already, create a new SMT.*
2302 artificial variable representing the memory location
2303 pointed-to by PTR. */
2304 if (var_ann (ptr)->symbol_mem_tag == NULL_TREE)
2305 tag = create_memory_tag (tag_type, true);
2307 tag = var_ann (ptr)->symbol_mem_tag;
2309 /* Add PTR to the POINTERS array. Note that we are not interested in
2310 PTR's alias set. Instead, we cache the alias set for the memory that
2312 alias_map = XCNEW (struct alias_map_d);
2313 alias_map->var = ptr;
2314 alias_map->set = tag_set;
2315 ai->pointers[ai->num_pointers++] = alias_map;
2318 /* If the pointed-to type is volatile, so is the tag. */
2319 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
2321 /* Make sure that the symbol tag has the same alias set as the
2323 gcc_assert (tag_set == get_alias_set (tag));
2329 /* Create GLOBAL_VAR, an artificial global variable to act as a
2330 representative of all the variables that may be clobbered by function
2334 create_global_var (void)
2336 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2338 DECL_ARTIFICIAL (global_var) = 1;
2339 TREE_READONLY (global_var) = 0;
2340 DECL_EXTERNAL (global_var) = 1;
2341 TREE_STATIC (global_var) = 1;
2342 TREE_USED (global_var) = 1;
2343 DECL_CONTEXT (global_var) = NULL_TREE;
2344 TREE_THIS_VOLATILE (global_var) = 0;
2345 TREE_ADDRESSABLE (global_var) = 0;
2347 create_var_ann (global_var);
2348 mark_call_clobbered (global_var, ESCAPE_UNKNOWN);
2349 add_referenced_var (global_var);
2350 mark_sym_for_renaming (global_var);
2354 /* Dump alias statistics on FILE. */
2357 dump_alias_stats (FILE *file)
2359 const char *funcname
2360 = lang_hooks.decl_printable_name (current_function_decl, 2);
2361 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2362 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2363 fprintf (file, "Total alias mayalias results:\t%u\n",
2364 alias_stats.alias_mayalias);
2365 fprintf (file, "Total alias noalias results:\t%u\n",
2366 alias_stats.alias_noalias);
2367 fprintf (file, "Total simple queries:\t%u\n",
2368 alias_stats.simple_queries);
2369 fprintf (file, "Total simple resolved:\t%u\n",
2370 alias_stats.simple_resolved);
2371 fprintf (file, "Total TBAA queries:\t%u\n",
2372 alias_stats.tbaa_queries);
2373 fprintf (file, "Total TBAA resolved:\t%u\n",
2374 alias_stats.tbaa_resolved);
2375 fprintf (file, "Total non-addressable structure type queries:\t%u\n",
2376 alias_stats.structnoaddress_queries);
2377 fprintf (file, "Total non-addressable structure type resolved:\t%u\n",
2378 alias_stats.structnoaddress_resolved);
2382 /* Dump alias information on FILE. */
2385 dump_alias_info (FILE *file)
2388 const char *funcname
2389 = lang_hooks.decl_printable_name (current_function_decl, 2);
2390 referenced_var_iterator rvi;
2393 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2395 fprintf (file, "Aliased symbols\n\n");
2397 FOR_EACH_REFERENCED_VAR (var, rvi)
2399 if (may_be_aliased (var))
2400 dump_variable (file, var);
2403 fprintf (file, "\nDereferenced pointers\n\n");
2405 FOR_EACH_REFERENCED_VAR (var, rvi)
2407 var_ann_t ann = var_ann (var);
2408 if (ann->symbol_mem_tag)
2409 dump_variable (file, var);
2412 fprintf (file, "\nSymbol memory tags\n\n");
2414 FOR_EACH_REFERENCED_VAR (var, rvi)
2416 if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
2417 dump_variable (file, var);
2420 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2422 fprintf (file, "SSA_NAME pointers\n\n");
2423 for (i = 1; i < num_ssa_names; i++)
2425 tree ptr = ssa_name (i);
2426 struct ptr_info_def *pi;
2428 if (ptr == NULL_TREE)
2431 pi = SSA_NAME_PTR_INFO (ptr);
2432 if (!SSA_NAME_IN_FREE_LIST (ptr)
2434 && pi->name_mem_tag)
2435 dump_points_to_info_for (file, ptr);
2438 fprintf (file, "\nName memory tags\n\n");
2440 FOR_EACH_REFERENCED_VAR (var, rvi)
2442 if (TREE_CODE (var) == NAME_MEMORY_TAG)
2443 dump_variable (file, var);
2446 fprintf (file, "\n");
2450 /* Dump alias information on stderr. */
2453 debug_alias_info (void)
2455 dump_alias_info (stderr);
2459 /* Return the alias information associated with pointer T. It creates a
2460 new instance if none existed. */
2462 struct ptr_info_def *
2463 get_ptr_info (tree t)
2465 struct ptr_info_def *pi;
2467 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2469 pi = SSA_NAME_PTR_INFO (t);
2472 pi = GGC_NEW (struct ptr_info_def);
2473 memset ((void *)pi, 0, sizeof (*pi));
2474 SSA_NAME_PTR_INFO (t) = pi;
2481 /* Dump points-to information for SSA_NAME PTR into FILE. */
2484 dump_points_to_info_for (FILE *file, tree ptr)
2486 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2488 print_generic_expr (file, ptr, dump_flags);
2492 if (pi->name_mem_tag)
2494 fprintf (file, ", name memory tag: ");
2495 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2498 if (pi->is_dereferenced)
2499 fprintf (file, ", is dereferenced");
2501 if (pi->value_escapes_p)
2502 fprintf (file, ", its value escapes");
2504 if (pi->pt_anything)
2505 fprintf (file, ", points-to anything");
2508 fprintf (file, ", points-to NULL");
2515 fprintf (file, ", points-to vars: { ");
2516 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2518 print_generic_expr (file, referenced_var (ix), dump_flags);
2519 fprintf (file, " ");
2521 fprintf (file, "}");
2525 fprintf (file, "\n");
2529 /* Dump points-to information for VAR into stderr. */
2532 debug_points_to_info_for (tree var)
2534 dump_points_to_info_for (stderr, var);
2538 /* Dump points-to information into FILE. NOTE: This function is slow, as
2539 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2542 dump_points_to_info (FILE *file)
2545 block_stmt_iterator si;
2548 lang_hooks.decl_printable_name (current_function_decl, 2);
2549 referenced_var_iterator rvi;
2552 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2554 /* First dump points-to information for the default definitions of
2555 pointer variables. This is necessary because default definitions are
2556 not part of the code. */
2557 FOR_EACH_REFERENCED_VAR (var, rvi)
2559 if (POINTER_TYPE_P (TREE_TYPE (var)))
2561 tree def = default_def (var);
2563 dump_points_to_info_for (file, def);
2567 /* Dump points-to information for every pointer defined in the program. */
2572 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2574 tree ptr = PHI_RESULT (phi);
2575 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2576 dump_points_to_info_for (file, ptr);
2579 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2581 tree stmt = bsi_stmt (si);
2583 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2584 if (POINTER_TYPE_P (TREE_TYPE (def)))
2585 dump_points_to_info_for (file, def);
2589 fprintf (file, "\n");
2593 /* Dump points-to info pointed to by PTO into STDERR. */
2596 debug_points_to_info (void)
2598 dump_points_to_info (stderr);
2601 /* Dump to FILE the list of variables that may be aliasing VAR. */
2604 dump_may_aliases_for (FILE *file, tree var)
2606 VEC(tree, gc) *aliases;
2608 if (TREE_CODE (var) == SSA_NAME)
2609 var = SSA_NAME_VAR (var);
2611 aliases = var_ann (var)->may_aliases;
2616 fprintf (file, "{ ");
2617 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2619 print_generic_expr (file, al, dump_flags);
2620 fprintf (file, " ");
2622 fprintf (file, "}");
2627 /* Dump to stderr the list of variables that may be aliasing VAR. */
2630 debug_may_aliases_for (tree var)
2632 dump_may_aliases_for (stderr, var);
2635 /* Return true if VAR may be aliased. */
2638 may_be_aliased (tree var)
2641 if (TREE_ADDRESSABLE (var))
2644 /* Globally visible variables can have their addresses taken by other
2645 translation units. */
2648 && (MTAG_GLOBAL (var) || TREE_PUBLIC (var)))
2650 else if (!MTAG_P (var)
2651 && (DECL_EXTERNAL (var) || TREE_PUBLIC (var)))
2654 /* Automatic variables can't have their addresses escape any other way.
2655 This must be after the check for global variables, as extern declarations
2656 do not have TREE_STATIC set. */
2657 if (!TREE_STATIC (var))
2660 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2661 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2662 we can only be sure the variable isn't addressable if it's local to the
2663 current function. */
2664 if (flag_unit_at_a_time)
2666 if (decl_function_context (var) == current_function_decl)
2673 /* Given two symbols return TRUE if one is in the alias set of the other. */
2675 is_aliased_with (tree tag, tree sym)
2678 VEC(tree,gc) *aliases;
2681 if (var_ann (sym)->is_aliased)
2683 aliases = var_ann (tag)->may_aliases;
2685 if (aliases == NULL)
2688 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2694 aliases = var_ann (sym)->may_aliases;
2696 if (aliases == NULL)
2699 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2708 /* Given two tags return TRUE if their may-alias sets intersect. */
2711 may_aliases_intersect (tree tag1, tree tag2)
2713 struct pointer_set_t *set1 = pointer_set_create ();
2715 VEC(tree,gc) *may_aliases1 = may_aliases (tag1);
2716 VEC(tree,gc) *may_aliases2 = may_aliases (tag2);
2719 /* Insert all the symbols from the first may-alias set into the
2721 for (i = 0; VEC_iterate (tree, may_aliases1, i, sym); i++)
2722 pointer_set_insert (set1, sym);
2724 /* Go through the second may-alias set and check if it contains symbols that
2725 are common with the first set. */
2726 for (i = 0; VEC_iterate (tree, may_aliases2, i, sym); i++)
2727 if (pointer_set_contains (set1, sym))
2729 pointer_set_destroy (set1);
2733 pointer_set_destroy (set1);
2738 /* The following is based on code in add_stmt_operand to ensure that the
2739 same defs/uses/vdefs/vuses will be found after replacing a reference
2740 to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value
2741 is the address of var. Return a memtag for the ptr, after adding the
2742 proper may_aliases to it (which are the aliases of var, if it has any,
2746 add_may_alias_for_new_tag (tree tag, tree var)
2748 var_ann_t v_ann = var_ann (var);
2749 VEC(tree, gc) *aliases = v_ann->may_aliases;
2751 /* Case 1: |aliases| == 1 */
2752 if ((aliases != NULL)
2753 && (VEC_length (tree, aliases) == 1))
2755 tree ali = VEC_index (tree, aliases, 0);
2757 if (TREE_CODE (ali) == SYMBOL_MEMORY_TAG)
2761 /* Case 2: |aliases| == 0 */
2762 if (aliases == NULL)
2763 add_may_alias (tag, var);
2766 /* Case 3: |aliases| > 1 */
2770 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2771 add_may_alias (tag, al);
2777 /* Create a new symbol tag for PTR. Construct the may-alias list of this type
2778 tag so that it has the aliasing of VAR, or of the relevant subvars of VAR
2779 according to the location accessed by EXPR.
2781 Note, the set of aliases represented by the new symbol tag are not marked
2785 new_type_alias (tree ptr, tree var, tree expr)
2787 var_ann_t p_ann = var_ann (ptr);
2788 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2791 tree ali = NULL_TREE;
2792 HOST_WIDE_INT offset, size, maxsize;
2795 gcc_assert (p_ann->symbol_mem_tag == NULL_TREE);
2796 gcc_assert (!MTAG_P (var));
2798 ref = get_ref_base_and_extent (expr, &offset, &size, &maxsize);
2801 tag = create_memory_tag (tag_type, true);
2802 p_ann->symbol_mem_tag = tag;
2804 /* Add VAR to the may-alias set of PTR's new symbol tag. If VAR has
2805 subvars, add the subvars to the tag instead of the actual var. */
2806 if (var_can_have_subvars (var)
2807 && (svars = get_subvars_for_var (var)))
2810 VEC (tree, heap) *overlaps = NULL;
2813 for (sv = svars; sv; sv = sv->next)
2817 if (overlap_subvar (offset, maxsize, sv->var, &exact))
2818 VEC_safe_push (tree, heap, overlaps, sv->var);
2820 len = VEC_length (tree, overlaps);
2821 if (dump_file && (dump_flags & TDF_DETAILS))
2822 fprintf (dump_file, "\nnumber of overlapping subvars = %u\n", len);
2826 ali = add_may_alias_for_new_tag (tag, VEC_index (tree, overlaps, 0));
2832 for (k = 0; VEC_iterate (tree, overlaps, k, sv_var); k++)
2834 ali = add_may_alias_for_new_tag (tag, sv_var);
2838 /* Can happen only if 'Case 1' of add_may_alias_for_new_tag
2839 took place. Since more than one svar was found, we add
2840 'ali' as one of the may_aliases of the new tag. */
2841 add_may_alias (tag, ali);
2848 ali = add_may_alias_for_new_tag (tag, var);
2850 p_ann->symbol_mem_tag = ali;
2851 TREE_READONLY (tag) = TREE_READONLY (var);
2852 MTAG_GLOBAL (tag) = is_global_var (var);
2855 /* This represents the used range of a variable. */
2857 typedef struct used_part
2859 HOST_WIDE_INT minused;
2860 HOST_WIDE_INT maxused;
2861 /* True if we have an explicit use/def of some portion of this variable,
2862 even if it is all of it. i.e. a.b = 5 or temp = a.b. */
2864 /* True if we have an implicit use/def of some portion of this
2865 variable. Implicit uses occur when we can't tell what part we
2866 are referencing, and have to make conservative assumptions. */
2868 /* True if the structure is only written to or taken its address. */
2872 /* An array of used_part structures, indexed by variable uid. */
2874 static htab_t used_portions;
2876 struct used_part_map
2882 /* Return true if the uid in the two used part maps are equal. */
2885 used_part_map_eq (const void *va, const void *vb)
2887 const struct used_part_map *a = (const struct used_part_map *) va;
2888 const struct used_part_map *b = (const struct used_part_map *) vb;
2889 return (a->uid == b->uid);
2892 /* Hash a from uid in a used_part_map. */
2895 used_part_map_hash (const void *item)
2897 return ((const struct used_part_map *)item)->uid;
2900 /* Free a used part map element. */
2903 free_used_part_map (void *item)
2905 free (((struct used_part_map *)item)->to);
2909 /* Lookup a used_part structure for a UID. */
2912 up_lookup (unsigned int uid)
2914 struct used_part_map *h, in;
2916 h = (struct used_part_map *) htab_find_with_hash (used_portions, &in, uid);
2922 /* Insert the pair UID, TO into the used part hashtable. */
2925 up_insert (unsigned int uid, used_part_t to)
2927 struct used_part_map *h;
2930 h = XNEW (struct used_part_map);
2933 loc = htab_find_slot_with_hash (used_portions, h,
2937 *(struct used_part_map **) loc = h;
2941 /* Given a variable uid, UID, get or create the entry in the used portions
2942 table for the variable. */
2945 get_or_create_used_part_for (size_t uid)
2948 if ((up = up_lookup (uid)) == NULL)
2950 up = XCNEW (struct used_part);
2951 up->minused = INT_MAX;
2953 up->explicit_uses = false;
2954 up->implicit_uses = false;
2955 up->write_only = true;
2962 /* Create and return a structure sub-variable for field type FIELD at
2963 offset OFFSET, with size SIZE, of variable VAR. */
2966 create_sft (tree var, tree field, unsigned HOST_WIDE_INT offset,
2967 unsigned HOST_WIDE_INT size)
2970 tree subvar = create_tag_raw (STRUCT_FIELD_TAG, field, "SFT");
2972 /* We need to copy the various flags from VAR to SUBVAR, so that
2973 they are is_global_var iff the original variable was. */
2974 DECL_CONTEXT (subvar) = DECL_CONTEXT (var);
2975 MTAG_GLOBAL (subvar) = DECL_EXTERNAL (var);
2976 TREE_PUBLIC (subvar) = TREE_PUBLIC (var);
2977 TREE_STATIC (subvar) = TREE_STATIC (var);
2978 TREE_READONLY (subvar) = TREE_READONLY (var);
2979 TREE_ADDRESSABLE (subvar) = TREE_ADDRESSABLE (var);
2981 /* Add the new variable to REFERENCED_VARS. */
2982 ann = get_var_ann (subvar);
2983 ann->symbol_mem_tag = NULL;
2984 add_referenced_var (subvar);
2985 SFT_PARENT_VAR (subvar) = var;
2986 SFT_OFFSET (subvar) = offset;
2987 SFT_SIZE (subvar) = size;
2992 /* Given an aggregate VAR, create the subvariables that represent its
2996 create_overlap_variables_for (tree var)
2998 VEC(fieldoff_s,heap) *fieldstack = NULL;
3000 size_t uid = DECL_UID (var);
3002 up = up_lookup (uid);
3007 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL);
3008 if (VEC_length (fieldoff_s, fieldstack) != 0)
3012 bool notokay = false;
3015 HOST_WIDE_INT lastfooffset = -1;
3016 HOST_WIDE_INT lastfosize = -1;
3017 tree lastfotype = NULL_TREE;
3019 /* Not all fields have DECL_SIZE set, and those that don't, we don't
3020 know their size, and thus, can't handle.
3021 The same is true of fields with DECL_SIZE that is not an integer
3022 constant (such as variable sized fields).
3023 Fields with offsets which are not constant will have an offset < 0
3024 We *could* handle fields that are constant sized arrays, but
3025 currently don't. Doing so would require some extra changes to
3026 tree-ssa-operands.c. */
3028 for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
3031 || TREE_CODE (fo->size) != INTEGER_CST
3040 /* The current heuristic we use is as follows:
3041 If the variable has no used portions in this function, no
3042 structure vars are created for it.
3044 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
3045 we always create structure vars for them.
3046 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
3047 some explicit uses, we create structure vars for them.
3048 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
3049 no explicit uses, we do not create structure vars for them.
3052 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
3053 && !up->explicit_uses)
3055 if (dump_file && (dump_flags & TDF_DETAILS))
3057 fprintf (dump_file, "Variable ");
3058 print_generic_expr (dump_file, var, 0);
3059 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
3064 /* Bail out, if we can't create overlap variables. */
3067 VEC_free (fieldoff_s, heap, fieldstack);
3071 /* Otherwise, create the variables. */
3072 subvars = lookup_subvars_for_var (var);
3074 sort_fieldstack (fieldstack);
3076 for (i = VEC_length (fieldoff_s, fieldstack);
3077 VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
3080 HOST_WIDE_INT fosize;
3083 fosize = TREE_INT_CST_LOW (fo->size);
3084 currfotype = fo->type;
3086 /* If this field isn't in the used portion,
3087 or it has the exact same offset and size as the last
3090 if (((fo->offset <= up->minused
3091 && fo->offset + fosize <= up->minused)
3092 || fo->offset >= up->maxused)
3093 || (fo->offset == lastfooffset
3094 && fosize == lastfosize
3095 && currfotype == lastfotype))
3097 sv = GGC_NEW (struct subvar);
3098 sv->next = *subvars;
3099 sv->var = create_sft (var, fo->type, fo->offset, fosize);
3103 fprintf (dump_file, "structure field tag %s created for var %s",
3104 get_name (sv->var), get_name (var));
3105 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
3106 SFT_OFFSET (sv->var));
3107 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
3108 SFT_SIZE (sv->var));
3109 fprintf (dump_file, "\n");
3112 lastfotype = currfotype;
3113 lastfooffset = fo->offset;
3114 lastfosize = fosize;
3118 /* Once we have created subvars, the original is no longer call
3119 clobbered on its own. Its call clobbered status depends
3120 completely on the call clobbered status of the subvars.
3122 add_referenced_var in the above loop will take care of
3123 marking subvars of global variables as call clobbered for us
3124 to start, since they are global as well. */
3125 clear_call_clobbered (var);
3128 VEC_free (fieldoff_s, heap, fieldstack);
3132 /* Find the conservative answer to the question of what portions of what
3133 structures are used by this statement. We assume that if we have a
3134 component ref with a known size + offset, that we only need that part
3135 of the structure. For unknown cases, or cases where we do something
3136 to the whole structure, we assume we need to create fields for the
3137 entire structure. */
3140 find_used_portions (tree *tp, int *walk_subtrees, void *lhs_p)
3142 switch (TREE_CODE (*tp))
3145 /* Recurse manually here to track whether the use is in the
3146 LHS of an assignment. */
3147 find_used_portions (&TREE_OPERAND (*tp, 0), walk_subtrees, tp);
3148 return find_used_portions (&TREE_OPERAND (*tp, 1), walk_subtrees, NULL);
3154 HOST_WIDE_INT bitsize;
3155 HOST_WIDE_INT bitmaxsize;
3156 HOST_WIDE_INT bitpos;
3158 ref = get_ref_base_and_extent (*tp, &bitpos, &bitsize, &bitmaxsize);
3160 && var_can_have_subvars (ref)
3161 && bitmaxsize != -1)
3163 size_t uid = DECL_UID (ref);
3166 up = get_or_create_used_part_for (uid);
3168 if (bitpos <= up->minused)
3169 up->minused = bitpos;
3170 if ((bitpos + bitmaxsize >= up->maxused))
3171 up->maxused = bitpos + bitmaxsize;
3173 if (bitsize == bitmaxsize)
3174 up->explicit_uses = true;
3176 up->implicit_uses = true;
3178 up->write_only = false;
3179 up_insert (uid, up);
3186 /* This is here to make sure we mark the entire base variable as used
3187 when you take its address. Because our used portion analysis is
3188 simple, we aren't looking at casts or pointer arithmetic to see what
3189 happens when you take the address. */
3192 tree var = get_base_address (TREE_OPERAND (*tp, 0));
3197 && var_can_have_subvars (var)
3198 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3201 size_t uid = DECL_UID (var);
3203 up = get_or_create_used_part_for (uid);
3206 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
3207 up->implicit_uses = true;
3209 up->write_only = false;
3211 up_insert (uid, up);
3220 for (arg = &TREE_OPERAND (*tp, 1); *arg; arg = &TREE_CHAIN (*arg))
3222 if (TREE_CODE (TREE_VALUE (*arg)) != ADDR_EXPR)
3223 find_used_portions (&TREE_VALUE (*arg), walk_subtrees, NULL);
3234 && var_can_have_subvars (var)
3235 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3238 size_t uid = DECL_UID (var);
3240 up = get_or_create_used_part_for (uid);
3243 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
3244 up->implicit_uses = true;
3246 up_insert (uid, up);
3260 /* Create structure field variables for structures used in this function. */
3263 create_structure_vars (void)
3266 safe_referenced_var_iterator rvi;
3267 VEC (tree, heap) *varvec = NULL;
3270 used_portions = htab_create (10, used_part_map_hash, used_part_map_eq,
3271 free_used_part_map);
3275 block_stmt_iterator bsi;
3276 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3278 walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
3283 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, rvi)
3285 /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
3288 && var_can_have_subvars (var)
3290 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3291 create_overlap_variables_for (var);
3293 htab_delete (used_portions);
3294 VEC_free (tree, heap, varvec);
3299 gate_structure_vars (void)
3301 return flag_tree_salias != 0;
3304 struct tree_opt_pass pass_create_structure_vars =
3306 "salias", /* name */
3307 gate_structure_vars, /* gate */
3308 create_structure_vars, /* execute */
3311 0, /* static_pass_number */
3313 PROP_cfg, /* properties_required */
3314 0, /* properties_provided */
3315 0, /* properties_destroyed */
3316 0, /* todo_flags_start */
3317 TODO_dump_func, /* todo_flags_finish */
3321 /* Reset the DECL_CALL_CLOBBERED flags on our referenced vars. In
3322 theory, this only needs to be done for globals. */
3325 reset_cc_flags (void)
3328 referenced_var_iterator rvi;
3330 FOR_EACH_REFERENCED_VAR (var, rvi)
3331 DECL_CALL_CLOBBERED (var) = false;
3335 struct tree_opt_pass pass_reset_cc_flags =
3339 reset_cc_flags, /* execute */
3342 0, /* static_pass_number */
3344 PROP_referenced_vars |PROP_cfg, /* properties_required */
3345 0, /* properties_provided */
3346 0, /* properties_destroyed */
3347 0, /* todo_flags_start */
3348 0, /* todo_flags_finish */