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 /* Obstack used to hold grouping bitmaps and other temporary bitmaps used by
52 static bitmap_obstack alias_obstack;
54 /* 'true' after aliases have been computed (see compute_may_aliases). */
55 bool aliases_computed_p;
57 /* Structure to map a variable to its alias set and keep track of the
58 virtual operands that will be needed to represent it. */
61 /* Variable and its alias set. */
65 /* Total number of virtual operands that will be needed to represent
66 all the aliases of VAR. */
67 long total_alias_vops;
69 /* Nonzero if the aliases for this memory tag have been grouped
70 already. Used in group_aliases. */
71 unsigned int grouped_p : 1;
73 /* Set of variables aliased with VAR. This is the exact same
74 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
75 bitmap form to speed up alias grouping. */
80 /* Counters used to display statistics on alias analysis. */
83 unsigned int alias_queries;
84 unsigned int alias_mayalias;
85 unsigned int alias_noalias;
86 unsigned int simple_queries;
87 unsigned int simple_resolved;
88 unsigned int tbaa_queries;
89 unsigned int tbaa_resolved;
90 unsigned int structnoaddress_queries;
91 unsigned int structnoaddress_resolved;
95 /* Local variables. */
96 static struct alias_stats_d alias_stats;
98 /* Local functions. */
99 static void compute_flow_insensitive_aliasing (struct alias_info *);
100 static void dump_alias_stats (FILE *);
101 static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT, bool);
102 static tree create_memory_tag (tree type, bool is_type_tag);
103 static tree get_tmt_for (tree, struct alias_info *);
104 static tree get_nmt_for (tree);
105 static void add_may_alias (tree, tree);
106 static void replace_may_alias (tree, size_t, tree);
107 static struct alias_info *init_alias_info (void);
108 static void delete_alias_info (struct alias_info *);
109 static void compute_flow_sensitive_aliasing (struct alias_info *);
110 static void setup_pointers_and_addressables (struct alias_info *);
111 static void create_global_var (void);
112 static void maybe_create_global_var (struct alias_info *ai);
113 static void group_aliases (struct alias_info *);
114 static void set_pt_anything (tree ptr);
116 /* Global declarations. */
118 /* Call clobbered variables in the function. If bit I is set, then
119 REFERENCED_VARS (I) is call-clobbered. */
120 bitmap call_clobbered_vars;
122 /* Addressable variables in the function. If bit I is set, then
123 REFERENCED_VARS (I) has had its address taken. Note that
124 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
125 addressable variable is not necessarily call-clobbered (e.g., a
126 local addressable whose address does not escape) and not all
127 call-clobbered variables are addressable (e.g., a local static
129 bitmap addressable_vars;
131 /* When the program has too many call-clobbered variables and call-sites,
132 this variable is used to represent the clobbering effects of function
133 calls. In these cases, all the call clobbered variables in the program
134 are forced to alias this variable. This reduces compile times by not
135 having to keep track of too many V_MAY_DEF expressions at call sites. */
139 DEF_VEC_ALLOC_I(int,heap);
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;
320 FOR_EACH_REFERENCED_VAR (var, rvi)
322 if (is_global_var (var)
323 && (!var_can_have_subvars (var)
324 || get_subvars_for_var (var) == NULL))
326 if (!unmodifiable_var_p (var))
327 mark_call_clobbered (var, ESCAPE_IS_GLOBAL);
329 else if (TREE_CODE (var) == PARM_DECL
331 && POINTER_TYPE_P (TREE_TYPE (var)))
333 tree def = default_def (var);
334 get_ptr_info (def)->value_escapes_p = 1;
335 get_ptr_info (def)->escape_mask |= ESCAPE_IS_PARM;
339 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
341 tree ptr = VARRAY_TREE (ai->processed_ptrs, 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 /* Recalculate the used_alone information for SMTs . */
432 recalculate_used_alone (void)
434 VEC (tree, heap) *calls = NULL;
435 block_stmt_iterator bsi;
439 referenced_var_iterator rvi;
442 /* First, reset all the SMT used alone bits to zero. */
443 updating_used_alone = true;
444 FOR_EACH_REFERENCED_VAR (var, rvi)
445 if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
446 SMT_USED_ALONE (var) = 0;
448 /* Walk all the statements.
449 Calls get put into a list of statements to update, since we will
450 need to update operands on them if we make any changes.
451 If we see a bare use of a SMT anywhere in a real virtual use or virtual
452 def, mark the SMT as used alone, and for renaming. */
455 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
457 stmt = bsi_stmt (bsi);
458 if (TREE_CODE (stmt) == CALL_EXPR
459 || (TREE_CODE (stmt) == MODIFY_EXPR
460 && TREE_CODE (TREE_OPERAND (stmt, 1)) == CALL_EXPR))
461 VEC_safe_push (tree, heap, calls, stmt);
466 FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter,
467 SSA_OP_VUSE | SSA_OP_VIRTUAL_DEFS)
471 if(TREE_CODE (var) == SSA_NAME)
472 svar = SSA_NAME_VAR (var);
474 if (TREE_CODE (svar) == SYMBOL_MEMORY_TAG)
476 if (!SMT_USED_ALONE (svar))
478 SMT_USED_ALONE (svar) = true;
479 mark_sym_for_renaming (svar);
487 /* Update the operands on all the calls we saw. */
490 for (i = 0; VEC_iterate (tree, calls, i, stmt); i++)
493 VEC_free (tree, heap, calls);
494 updating_used_alone = false;
497 /* Compute may-alias information for every variable referenced in function
500 Alias analysis proceeds in 3 main phases:
502 1- Points-to and escape analysis.
504 This phase walks the use-def chains in the SSA web looking for three
507 * Assignments of the form P_i = &VAR
508 * Assignments of the form P_i = malloc()
509 * Pointers and ADDR_EXPR that escape the current function.
511 The concept of 'escaping' is the same one used in the Java world. When
512 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
513 outside of the current function. So, assignment to global variables,
514 function arguments and returning a pointer are all escape sites, as are
515 conversions between pointers and integers.
517 This is where we are currently limited. Since not everything is renamed
518 into SSA, we lose track of escape properties when a pointer is stashed
519 inside a field in a structure, for instance. In those cases, we are
520 assuming that the pointer does escape.
522 We use escape analysis to determine whether a variable is
523 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
524 is call-clobbered. If a pointer P_i escapes, then all the variables
525 pointed-to by P_i (and its memory tag) also escape.
527 2- Compute flow-sensitive aliases
529 We have two classes of memory tags. Memory tags associated with the
530 pointed-to data type of the pointers in the program. These tags are
531 called "symbol memory tag" (SMT). The other class are those associated
532 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
533 when adding operands for an INDIRECT_REF *P_i, we will first check
534 whether P_i has a name tag, if it does we use it, because that will have
535 more precise aliasing information. Otherwise, we use the standard symbol
538 In this phase, we go through all the pointers we found in points-to
539 analysis and create alias sets for the name memory tags associated with
540 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
541 it points to and its tag.
544 3- Compute flow-insensitive aliases
546 This pass will compare the alias set of every symbol memory tag and
547 every addressable variable found in the program. Given a symbol
548 memory tag SMT and an addressable variable V. If the alias sets of
549 SMT and V conflict (as computed by may_alias_p), then V is marked
550 as an alias tag and added to the alias set of SMT.
552 For instance, consider the following function:
568 After aliasing analysis has finished, the symbol memory tag for pointer
569 'p' will have two aliases, namely variables 'a' and 'b'. Every time
570 pointer 'p' is dereferenced, we want to mark the operation as a
571 potential reference to 'a' and 'b'.
581 # p_1 = PHI <p_4(1), p_6(2)>;
583 # a_7 = V_MAY_DEF <a_3>;
584 # b_8 = V_MAY_DEF <b_5>;
587 # a_9 = V_MAY_DEF <a_7>
596 In certain cases, the list of may aliases for a pointer may grow too
597 large. This may cause an explosion in the number of virtual operands
598 inserted in the code. Resulting in increased memory consumption and
601 When the number of virtual operands needed to represent aliased
602 loads and stores grows too large (configurable with @option{--param
603 max-aliased-vops}), alias sets are grouped to avoid severe
604 compile-time slow downs and memory consumption. See group_aliases. */
607 compute_may_aliases (void)
609 struct alias_info *ai;
611 memset (&alias_stats, 0, sizeof (alias_stats));
613 /* Initialize aliasing information. */
614 ai = init_alias_info ();
616 /* For each pointer P_i, determine the sets of variables that P_i may
617 point-to. For every addressable variable V, determine whether the
618 address of V escapes the current function, making V call-clobbered
619 (i.e., whether &V is stored in a global variable or if its passed as a
620 function call argument). */
621 compute_points_to_sets (ai);
623 /* Collect all pointers and addressable variables, compute alias sets,
624 create memory tags for pointers and promote variables whose address is
625 not needed anymore. */
626 setup_pointers_and_addressables (ai);
628 /* Compute flow-sensitive, points-to based aliasing for all the name
629 memory tags. Note that this pass needs to be done before flow
630 insensitive analysis because it uses the points-to information
631 gathered before to mark call-clobbered symbol tags. */
632 compute_flow_sensitive_aliasing (ai);
634 /* Compute type-based flow-insensitive aliasing for all the type
636 compute_flow_insensitive_aliasing (ai);
638 /* Determine if we need to enable alias grouping. */
639 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
642 /* Compute call clobbering information. */
643 compute_call_clobbered (ai);
645 /* If the program has too many call-clobbered variables and/or function
646 calls, create .GLOBAL_VAR and use it to model call-clobbering
647 semantics at call sites. This reduces the number of virtual operands
648 considerably, improving compile times at the expense of lost
649 aliasing precision. */
650 maybe_create_global_var (ai);
652 /* Debugging dumps. */
655 dump_referenced_vars (dump_file);
656 if (dump_flags & TDF_STATS)
657 dump_alias_stats (dump_file);
658 dump_points_to_info (dump_file);
659 dump_alias_info (dump_file);
662 /* Deallocate memory used by aliasing data structures. */
663 delete_alias_info (ai);
665 updating_used_alone = true;
667 block_stmt_iterator bsi;
671 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
673 update_stmt_if_modified (bsi_stmt (bsi));
677 recalculate_used_alone ();
678 updating_used_alone = false;
682 struct tree_opt_pass pass_may_alias =
686 compute_may_aliases, /* execute */
689 0, /* static_pass_number */
690 TV_TREE_MAY_ALIAS, /* tv_id */
691 PROP_cfg | PROP_ssa, /* properties_required */
692 PROP_alias, /* properties_provided */
693 0, /* properties_destroyed */
694 0, /* todo_flags_start */
695 TODO_dump_func | TODO_update_ssa
696 | TODO_ggc_collect | TODO_verify_ssa
697 | TODO_verify_stmts, /* todo_flags_finish */
702 /* Data structure used to count the number of dereferences to PTR
703 inside an expression. */
711 /* Helper for count_uses_and_derefs. Called by walk_tree to look for
712 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
715 count_ptr_derefs (tree *tp, int *walk_subtrees, void *data)
717 struct count_ptr_d *count_p = (struct count_ptr_d *) data;
719 /* Do not walk inside ADDR_EXPR nodes. In the expression &ptr->fld,
720 pointer 'ptr' is *not* dereferenced, it is simply used to compute
721 the address of 'fld' as 'ptr + offsetof(fld)'. */
722 if (TREE_CODE (*tp) == ADDR_EXPR)
728 if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
735 /* Count the number of direct and indirect uses for pointer PTR in
736 statement STMT. The two counts are stored in *NUM_USES_P and
737 *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
738 least one of those dereferences is a store operation. */
741 count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
742 unsigned *num_derefs_p, bool *is_store)
751 /* Find out the total number of uses of PTR in STMT. */
752 FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
756 /* Now count the number of indirect references to PTR. This is
757 truly awful, but we don't have much choice. There are no parent
758 pointers inside INDIRECT_REFs, so an expression like
759 '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
760 find all the indirect and direct uses of x_1 inside. The only
761 shortcut we can take is the fact that GIMPLE only allows
762 INDIRECT_REFs inside the expressions below. */
763 if (TREE_CODE (stmt) == MODIFY_EXPR
764 || (TREE_CODE (stmt) == RETURN_EXPR
765 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
766 || TREE_CODE (stmt) == ASM_EXPR
767 || TREE_CODE (stmt) == CALL_EXPR)
771 if (TREE_CODE (stmt) == MODIFY_EXPR)
773 lhs = TREE_OPERAND (stmt, 0);
774 rhs = TREE_OPERAND (stmt, 1);
776 else if (TREE_CODE (stmt) == RETURN_EXPR)
778 tree e = TREE_OPERAND (stmt, 0);
779 lhs = TREE_OPERAND (e, 0);
780 rhs = TREE_OPERAND (e, 1);
782 else if (TREE_CODE (stmt) == ASM_EXPR)
784 lhs = ASM_OUTPUTS (stmt);
785 rhs = ASM_INPUTS (stmt);
793 if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs)))
795 struct count_ptr_d count;
798 walk_tree (&lhs, count_ptr_derefs, &count, NULL);
800 *num_derefs_p = count.count;
803 if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs)))
805 struct count_ptr_d count;
808 walk_tree (&rhs, count_ptr_derefs, &count, NULL);
809 *num_derefs_p += count.count;
813 gcc_assert (*num_uses_p >= *num_derefs_p);
816 /* Initialize the data structures used for alias analysis. */
818 static struct alias_info *
819 init_alias_info (void)
821 struct alias_info *ai;
822 referenced_var_iterator rvi;
825 bitmap_obstack_initialize (&alias_obstack);
826 ai = XCNEW (struct alias_info);
827 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
828 sbitmap_zero (ai->ssa_names_visited);
829 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
830 ai->written_vars = BITMAP_ALLOC (&alias_obstack);
831 ai->dereferenced_ptrs_store = BITMAP_ALLOC (&alias_obstack);
832 ai->dereferenced_ptrs_load = BITMAP_ALLOC (&alias_obstack);
834 /* If aliases have been computed before, clear existing information. */
835 if (aliases_computed_p)
839 /* Similarly, clear the set of addressable variables. In this
840 case, we can just clear the set because addressability is
841 only computed here. */
842 bitmap_clear (addressable_vars);
844 /* Clear flow-insensitive alias information from each symbol. */
845 FOR_EACH_REFERENCED_VAR (var, rvi)
847 var_ann_t ann = var_ann (var);
850 ann->may_aliases = NULL;
851 NUM_REFERENCES_CLEAR (ann);
853 /* Since we are about to re-discover call-clobbered
854 variables, clear the call-clobbered flag. Variables that
855 are intrinsically call-clobbered (globals, local statics,
856 etc) will not be marked by the aliasing code, so we can't
857 remove them from CALL_CLOBBERED_VARS.
859 NB: STRUCT_FIELDS are still call clobbered if they are for
860 a global variable, so we *don't* clear their call clobberedness
861 just because they are tags, though we will clear it if they
862 aren't for global variables. */
863 if (TREE_CODE (var) == NAME_MEMORY_TAG
864 || TREE_CODE (var) == SYMBOL_MEMORY_TAG
865 || !is_global_var (var))
866 clear_call_clobbered (var);
869 /* Clear flow-sensitive points-to information from each SSA name. */
870 for (i = 1; i < num_ssa_names; i++)
872 tree name = ssa_name (i);
874 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
877 if (SSA_NAME_PTR_INFO (name))
879 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
881 /* Clear all the flags but keep the name tag to
882 avoid creating new temporaries unnecessarily. If
883 this pointer is found to point to a subset or
884 superset of its former points-to set, then a new
885 tag will need to be created in create_name_tags. */
888 pi->value_escapes_p = 0;
889 pi->is_dereferenced = 0;
891 bitmap_clear (pi->pt_vars);
896 /* Next time, we will need to reset alias information. */
897 aliases_computed_p = true;
903 /* Deallocate memory used by alias analysis. */
906 delete_alias_info (struct alias_info *ai)
909 referenced_var_iterator rvi;
912 sbitmap_free (ai->ssa_names_visited);
913 ai->processed_ptrs = NULL;
915 for (i = 0; i < ai->num_addressable_vars; i++)
916 free (ai->addressable_vars[i]);
918 FOR_EACH_REFERENCED_VAR(var, rvi)
920 var_ann_t ann = var_ann (var);
921 NUM_REFERENCES_CLEAR (ann);
924 free (ai->addressable_vars);
926 for (i = 0; i < ai->num_pointers; i++)
927 free (ai->pointers[i]);
930 BITMAP_FREE (ai->written_vars);
931 BITMAP_FREE (ai->dereferenced_ptrs_store);
932 BITMAP_FREE (ai->dereferenced_ptrs_load);
933 bitmap_obstack_release (&alias_obstack);
936 delete_points_to_sets ();
939 /* Create name tags for all the pointers that have been dereferenced.
940 We only create a name tag for a pointer P if P is found to point to
941 a set of variables (so that we can alias them to *P) or if it is
942 the result of a call to malloc (which means that P cannot point to
943 anything else nor alias any other variable).
945 If two pointers P and Q point to the same set of variables, they
946 are assigned the same name tag. */
949 create_name_tags (void)
952 VEC (tree, heap) *with_ptvars = NULL;
955 /* Collect the list of pointers with a non-empty points to set. */
956 for (i = 1; i < num_ssa_names; i++)
958 tree ptr = ssa_name (i);
959 struct ptr_info_def *pi;
962 || !POINTER_TYPE_P (TREE_TYPE (ptr))
963 || !SSA_NAME_PTR_INFO (ptr))
966 pi = SSA_NAME_PTR_INFO (ptr);
968 if (pi->pt_anything || !pi->is_dereferenced)
970 /* No name tags for pointers that have not been
971 dereferenced or point to an arbitrary location. */
972 pi->name_mem_tag = NULL_TREE;
976 /* Set pt_anything on the pointers without pt_vars filled in so
977 that they are assigned a symbol tag. */
978 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
979 VEC_safe_push (tree, heap, with_ptvars, ptr);
981 set_pt_anything (ptr);
984 /* If we didn't find any pointers with pt_vars set, we're done. */
988 /* Now go through the pointers with pt_vars, and find a name tag
989 with the same pt_vars as this pointer, or create one if one
991 for (i = 0; VEC_iterate (tree, with_ptvars, i, ptr); i++)
993 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
996 tree old_name_tag = pi->name_mem_tag;
998 /* If PTR points to a set of variables, check if we don't
999 have another pointer Q with the same points-to set before
1000 creating a tag. If so, use Q's tag instead of creating a
1003 This is important for not creating unnecessary symbols
1004 and also for copy propagation. If we ever need to
1005 propagate PTR into Q or vice-versa, we would run into
1006 problems if they both had different name tags because
1007 they would have different SSA version numbers (which
1008 would force us to take the name tags in and out of SSA). */
1009 for (j = 0; j < i && VEC_iterate (tree, with_ptvars, j, ptr2); j++)
1011 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (ptr2);
1013 if (bitmap_equal_p (pi->pt_vars, qi->pt_vars))
1015 pi->name_mem_tag = qi->name_mem_tag;
1020 /* If we didn't find a pointer with the same points-to set
1021 as PTR, create a new name tag if needed. */
1022 if (pi->name_mem_tag == NULL_TREE)
1023 pi->name_mem_tag = get_nmt_for (ptr);
1025 /* If the new name tag computed for PTR is different than
1026 the old name tag that it used to have, then the old tag
1027 needs to be removed from the IL, so we mark it for
1029 if (old_name_tag && old_name_tag != pi->name_mem_tag)
1030 mark_sym_for_renaming (old_name_tag);
1032 TREE_THIS_VOLATILE (pi->name_mem_tag)
1033 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
1035 /* Mark the new name tag for renaming. */
1036 mark_sym_for_renaming (pi->name_mem_tag);
1039 VEC_free (tree, heap, with_ptvars);
1043 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
1044 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
1045 name tag and the variables it points-to are call-clobbered. Finally, if
1046 P_i escapes and we could not determine where it points to, then all the
1047 variables in the same alias set as *P_i are marked call-clobbered. This
1048 is necessary because we must assume that P_i may take the address of any
1049 variable in the same alias set. */
1052 compute_flow_sensitive_aliasing (struct alias_info *ai)
1056 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1058 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1059 if (!find_what_p_points_to (ptr))
1060 set_pt_anything (ptr);
1063 create_name_tags ();
1065 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1068 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1069 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1070 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
1074 /* Set up aliasing information for PTR's name memory tag (if it has
1075 one). Note that only pointers that have been dereferenced will
1076 have a name memory tag. */
1077 if (pi->name_mem_tag && pi->pt_vars)
1078 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
1080 add_may_alias (pi->name_mem_tag, referenced_var (j));
1081 add_may_alias (v_ann->symbol_mem_tag, referenced_var (j));
1087 /* Compute type-based alias sets. Traverse all the pointers and
1088 addressable variables found in setup_pointers_and_addressables.
1090 For every pointer P in AI->POINTERS and addressable variable V in
1091 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's symbol
1092 memory tag (SMT) if their alias sets conflict. V is then marked as
1093 an alias tag so that the operand scanner knows that statements
1094 containing V have aliased operands. */
1097 compute_flow_insensitive_aliasing (struct alias_info *ai)
1101 /* Initialize counter for the total number of virtual operands that
1102 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
1103 threshold set by --params max-alias-vops, we enable alias
1105 ai->total_alias_vops = 0;
1107 /* For every pointer P, determine which addressable variables may alias
1108 with P's symbol memory tag. */
1109 for (i = 0; i < ai->num_pointers; i++)
1112 struct alias_map_d *p_map = ai->pointers[i];
1113 tree tag = var_ann (p_map->var)->symbol_mem_tag;
1114 var_ann_t tag_ann = var_ann (tag);
1116 p_map->total_alias_vops = 0;
1117 p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
1119 for (j = 0; j < ai->num_addressable_vars; j++)
1121 struct alias_map_d *v_map;
1124 bool tag_stored_p, var_stored_p;
1126 v_map = ai->addressable_vars[j];
1128 v_ann = var_ann (var);
1130 /* Skip memory tags and variables that have never been
1131 written to. We also need to check if the variables are
1132 call-clobbered because they may be overwritten by
1135 Note this is effectively random accessing elements in
1136 the sparse bitset, which can be highly inefficient.
1137 So we first check the call_clobbered status of the
1138 tag and variable before querying the bitmap. */
1139 tag_stored_p = is_call_clobbered (tag)
1140 || bitmap_bit_p (ai->written_vars, DECL_UID (tag));
1141 var_stored_p = is_call_clobbered (var)
1142 || bitmap_bit_p (ai->written_vars, DECL_UID (var));
1143 if (!tag_stored_p && !var_stored_p)
1146 if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false))
1148 size_t num_tag_refs, num_var_refs;
1150 num_tag_refs = NUM_REFERENCES (tag_ann);
1151 num_var_refs = NUM_REFERENCES (v_ann);
1153 /* Add VAR to TAG's may-aliases set. */
1155 /* We should never have a var with subvars here, because
1156 they shouldn't get into the set of addressable vars */
1157 gcc_assert (!var_can_have_subvars (var)
1158 || get_subvars_for_var (var) == NULL);
1160 add_may_alias (tag, var);
1161 /* Update the bitmap used to represent TAG's alias set
1162 in case we need to group aliases. */
1163 bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
1165 /* Update the total number of virtual operands due to
1166 aliasing. Since we are adding one more alias to TAG's
1167 may-aliases set, the total number of virtual operands due
1168 to aliasing will be increased by the number of references
1169 made to VAR and TAG (every reference to TAG will also
1170 count as a reference to VAR). */
1171 ai->total_alias_vops += (num_var_refs + num_tag_refs);
1172 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
1179 /* Since this analysis is based exclusively on symbols, it fails to
1180 handle cases where two pointers P and Q have different memory
1181 tags with conflicting alias set numbers but no aliased symbols in
1184 For example, suppose that we have two memory tags SMT.1 and SMT.2
1187 may-aliases (SMT.1) = { a }
1188 may-aliases (SMT.2) = { b }
1190 and the alias set number of SMT.1 conflicts with that of SMT.2.
1191 Since they don't have symbols in common, loads and stores from
1192 SMT.1 and SMT.2 will seem independent of each other, which will
1193 lead to the optimizers making invalid transformations (see
1194 testsuite/gcc.c-torture/execute/pr15262-[12].c).
1196 To avoid this problem, we do a final traversal of AI->POINTERS
1197 looking for pairs of pointers that have no aliased symbols in
1198 common and yet have conflicting alias set numbers. */
1199 for (i = 0; i < ai->num_pointers; i++)
1202 struct alias_map_d *p_map1 = ai->pointers[i];
1203 tree tag1 = var_ann (p_map1->var)->symbol_mem_tag;
1204 bitmap may_aliases1 = p_map1->may_aliases;
1206 for (j = i + 1; j < ai->num_pointers; j++)
1208 struct alias_map_d *p_map2 = ai->pointers[j];
1209 tree tag2 = var_ann (p_map2->var)->symbol_mem_tag;
1210 bitmap may_aliases2 = p_map2->may_aliases;
1212 /* If the pointers may not point to each other, do nothing. */
1213 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true))
1216 /* The two pointers may alias each other. If they already have
1217 symbols in common, do nothing. */
1218 if (bitmap_intersect_p (may_aliases1, may_aliases2))
1221 if (!bitmap_empty_p (may_aliases2))
1226 /* Add all the aliases for TAG2 into TAG1's alias set.
1227 FIXME, update grouping heuristic counters. */
1228 EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi)
1229 add_may_alias (tag1, referenced_var (k));
1230 bitmap_ior_into (may_aliases1, may_aliases2);
1234 /* Since TAG2 does not have any aliases of its own, add
1235 TAG2 itself to the alias set of TAG1. */
1236 add_may_alias (tag1, tag2);
1237 bitmap_set_bit (may_aliases1, DECL_UID (tag2));
1243 fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n",
1244 get_name (current_function_decl),
1245 ai->total_alias_vops);
1249 /* Comparison function for qsort used in group_aliases. */
1252 total_alias_vops_cmp (const void *p, const void *q)
1254 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1255 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1256 long n1 = (*p1)->total_alias_vops;
1257 long n2 = (*p2)->total_alias_vops;
1259 /* We want to sort in descending order. */
1260 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1263 /* Group all the aliases for TAG to make TAG represent all the
1264 variables in its alias set. Update the total number
1265 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1266 function will make TAG be the unique alias tag for all the
1267 variables in its may-aliases. So, given:
1269 may-aliases(TAG) = { V1, V2, V3 }
1271 This function will group the variables into:
1273 may-aliases(V1) = { TAG }
1274 may-aliases(V2) = { TAG }
1275 may-aliases(V2) = { TAG } */
1278 group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai)
1281 var_ann_t tag_ann = var_ann (tag);
1282 size_t num_tag_refs = NUM_REFERENCES (tag_ann);
1285 EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi)
1287 tree var = referenced_var (i);
1288 var_ann_t ann = var_ann (var);
1290 /* Make TAG the unique alias of VAR. */
1291 ann->is_aliased = 0;
1292 ann->may_aliases = NULL;
1294 /* Note that VAR and TAG may be the same if the function has no
1295 addressable variables (see the discussion at the end of
1296 setup_pointers_and_addressables). */
1298 add_may_alias (var, tag);
1300 /* Reduce total number of virtual operands contributed
1301 by TAG on behalf of VAR. Notice that the references to VAR
1302 itself won't be removed. We will merely replace them with
1303 references to TAG. */
1304 ai->total_alias_vops -= num_tag_refs;
1307 /* We have reduced the number of virtual operands that TAG makes on
1308 behalf of all the variables formerly aliased with it. However,
1309 we have also "removed" all the virtual operands for TAG itself,
1310 so we add them back. */
1311 ai->total_alias_vops += num_tag_refs;
1313 /* TAG no longer has any aliases. */
1314 tag_ann->may_aliases = NULL;
1318 /* Group may-aliases sets to reduce the number of virtual operands due
1321 1- Sort the list of pointers in decreasing number of contributed
1324 2- Take the first entry in AI->POINTERS and revert the role of
1325 the memory tag and its aliases. Usually, whenever an aliased
1326 variable Vi is found to alias with a memory tag T, we add Vi
1327 to the may-aliases set for T. Meaning that after alias
1328 analysis, we will have:
1330 may-aliases(T) = { V1, V2, V3, ..., Vn }
1332 This means that every statement that references T, will get 'n'
1333 virtual operands for each of the Vi tags. But, when alias
1334 grouping is enabled, we make T an alias tag and add it to the
1335 alias set of all the Vi variables:
1337 may-aliases(V1) = { T }
1338 may-aliases(V2) = { T }
1340 may-aliases(Vn) = { T }
1342 This has two effects: (a) statements referencing T will only get
1343 a single virtual operand, and, (b) all the variables Vi will now
1344 appear to alias each other. So, we lose alias precision to
1345 improve compile time. But, in theory, a program with such a high
1346 level of aliasing should not be very optimizable in the first
1349 3- Since variables may be in the alias set of more than one
1350 memory tag, the grouping done in step (2) needs to be extended
1351 to all the memory tags that have a non-empty intersection with
1352 the may-aliases set of tag T. For instance, if we originally
1353 had these may-aliases sets:
1355 may-aliases(T) = { V1, V2, V3 }
1356 may-aliases(R) = { V2, V4 }
1358 In step (2) we would have reverted the aliases for T as:
1360 may-aliases(V1) = { T }
1361 may-aliases(V2) = { T }
1362 may-aliases(V3) = { T }
1364 But note that now V2 is no longer aliased with R. We could
1365 add R to may-aliases(V2), but we are in the process of
1366 grouping aliases to reduce virtual operands so what we do is
1367 add V4 to the grouping to obtain:
1369 may-aliases(V1) = { T }
1370 may-aliases(V2) = { T }
1371 may-aliases(V3) = { T }
1372 may-aliases(V4) = { T }
1374 4- If the total number of virtual operands due to aliasing is
1375 still above the threshold set by max-alias-vops, go back to (2). */
1378 group_aliases (struct alias_info *ai)
1382 /* Sort the POINTERS array in descending order of contributed
1383 virtual operands. */
1384 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1385 total_alias_vops_cmp);
1387 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1388 and the tag's may-aliases set. */
1389 for (i = 0; i < ai->num_pointers; i++)
1392 tree tag1 = var_ann (ai->pointers[i]->var)->symbol_mem_tag;
1393 bitmap tag1_aliases = ai->pointers[i]->may_aliases;
1395 /* Skip tags that have been grouped already. */
1396 if (ai->pointers[i]->grouped_p)
1399 /* See if TAG1 had any aliases in common with other symbol tags.
1400 If we find a TAG2 with common aliases with TAG1, add TAG2's
1401 aliases into TAG1. */
1402 for (j = i + 1; j < ai->num_pointers; j++)
1404 bitmap tag2_aliases = ai->pointers[j]->may_aliases;
1406 if (bitmap_intersect_p (tag1_aliases, tag2_aliases))
1408 tree tag2 = var_ann (ai->pointers[j]->var)->symbol_mem_tag;
1410 bitmap_ior_into (tag1_aliases, tag2_aliases);
1412 /* TAG2 does not need its aliases anymore. */
1413 bitmap_clear (tag2_aliases);
1414 var_ann (tag2)->may_aliases = NULL;
1416 /* TAG1 is the unique alias of TAG2. */
1417 add_may_alias (tag2, tag1);
1419 ai->pointers[j]->grouped_p = true;
1423 /* Now group all the aliases we collected into TAG1. */
1424 group_aliases_into (tag1, tag1_aliases, ai);
1426 /* If we've reduced total number of virtual operands below the
1428 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1432 /* Finally, all the variables that have been grouped cannot be in
1433 the may-alias set of name memory tags. Suppose that we have
1434 grouped the aliases in this code so that may-aliases(a) = SMT.20
1438 # a_9 = V_MAY_DEF <a_8>
1440 ... Several modifications to SMT.20 ...
1444 Since p_5 points to 'a', the optimizers will try to propagate 0
1445 into p_5->field, but that is wrong because there have been
1446 modifications to 'SMT.20' in between. To prevent this we have to
1447 replace 'a' with 'SMT.20' in the name tag of p_5. */
1448 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1451 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1452 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1453 VEC(tree,gc) *aliases;
1456 if (name_tag == NULL_TREE)
1459 aliases = var_ann (name_tag)->may_aliases;
1460 for (j = 0; VEC_iterate (tree, aliases, j, alias); j++)
1462 var_ann_t ann = var_ann (alias);
1464 if ((!MTAG_P (alias)
1465 || TREE_CODE (alias) == STRUCT_FIELD_TAG)
1466 && ann->may_aliases)
1470 gcc_assert (VEC_length (tree, ann->may_aliases) == 1);
1472 new_alias = VEC_index (tree, ann->may_aliases, 0);
1473 replace_may_alias (name_tag, j, new_alias);
1480 "%s: Total number of aliased vops after grouping: %ld%s\n",
1481 get_name (current_function_decl),
1482 ai->total_alias_vops,
1483 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1487 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1490 create_alias_map_for (tree var, struct alias_info *ai)
1492 struct alias_map_d *alias_map;
1493 alias_map = XCNEW (struct alias_map_d);
1494 alias_map->var = var;
1495 alias_map->set = get_alias_set (var);
1496 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1500 /* Create memory tags for all the dereferenced pointers and build the
1501 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1502 sets. Based on the address escape and points-to information collected
1503 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1504 variables whose address is not needed anymore. */
1507 setup_pointers_and_addressables (struct alias_info *ai)
1509 size_t n_vars, num_addressable_vars, num_pointers;
1510 referenced_var_iterator rvi;
1512 VEC (tree, heap) *varvec = NULL;
1513 safe_referenced_var_iterator srvi;
1515 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1516 num_addressable_vars = num_pointers = 0;
1518 FOR_EACH_REFERENCED_VAR (var, rvi)
1520 if (may_be_aliased (var))
1521 num_addressable_vars++;
1523 if (POINTER_TYPE_P (TREE_TYPE (var)))
1525 /* Since we don't keep track of volatile variables, assume that
1526 these pointers are used in indirect store operations. */
1527 if (TREE_THIS_VOLATILE (var))
1528 bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var));
1534 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1535 always going to be slightly bigger than we actually need them
1536 because some TREE_ADDRESSABLE variables will be marked
1537 non-addressable below and only pointers with unique symbol tags are
1538 going to be added to POINTERS. */
1539 ai->addressable_vars = XCNEWVEC (struct alias_map_d *, num_addressable_vars);
1540 ai->pointers = XCNEWVEC (struct alias_map_d *, num_pointers);
1541 ai->num_addressable_vars = 0;
1542 ai->num_pointers = 0;
1544 /* Since we will be creating symbol memory tags within this loop,
1545 cache the value of NUM_REFERENCED_VARS to avoid processing the
1546 additional tags unnecessarily. */
1547 n_vars = num_referenced_vars;
1549 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi)
1551 var_ann_t v_ann = var_ann (var);
1554 /* Name memory tags already have flow-sensitive aliasing
1555 information, so they need not be processed by
1556 compute_flow_insensitive_aliasing. Similarly, symbol memory
1557 tags are already accounted for when we process their
1560 Structure fields, on the other hand, have to have some of this
1561 information processed for them, but it's pointless to mark them
1562 non-addressable (since they are fake variables anyway). */
1563 if (MTAG_P (var) && TREE_CODE (var) != STRUCT_FIELD_TAG)
1566 /* Remove the ADDRESSABLE flag from every addressable variable whose
1567 address is not needed anymore. This is caused by the propagation
1568 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1569 removal of dead pointer assignments done by the early scalar
1571 if (TREE_ADDRESSABLE (var))
1573 if (!bitmap_bit_p (addressable_vars, DECL_UID (var))
1574 && TREE_CODE (var) != RESULT_DECL
1575 && !is_global_var (var))
1577 bool okay_to_mark = true;
1579 /* Since VAR is now a regular GIMPLE register, we will need
1580 to rename VAR into SSA afterwards. */
1581 mark_sym_for_renaming (var);
1583 /* If VAR can have sub-variables, and any of its
1584 sub-variables has its address taken, then we cannot
1585 remove the addressable flag from VAR. */
1586 if (var_can_have_subvars (var)
1587 && (svars = get_subvars_for_var (var)))
1591 for (sv = svars; sv; sv = sv->next)
1593 if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var)))
1594 okay_to_mark = false;
1595 mark_sym_for_renaming (sv->var);
1599 /* The address of VAR is not needed, remove the
1600 addressable bit, so that it can be optimized as a
1601 regular variable. */
1603 mark_non_addressable (var);
1607 /* Global variables and addressable locals may be aliased. Create an
1608 entry in ADDRESSABLE_VARS for VAR. */
1609 if (may_be_aliased (var)
1610 && (!var_can_have_subvars (var)
1611 || get_subvars_for_var (var) == NULL))
1613 create_alias_map_for (var, ai);
1614 mark_sym_for_renaming (var);
1617 /* Add pointer variables that have been dereferenced to the POINTERS
1618 array and create a symbol memory tag for them. */
1619 if (POINTER_TYPE_P (TREE_TYPE (var)))
1621 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))
1622 || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var))))
1627 /* If pointer VAR still doesn't have a memory tag
1628 associated with it, create it now or re-use an
1630 tag = get_tmt_for (var, ai);
1631 t_ann = var_ann (tag);
1633 /* The symbol tag will need to be renamed into SSA
1634 afterwards. Note that we cannot do this inside
1635 get_tmt_for because aliasing may run multiple times
1636 and we only create symbol tags the first time. */
1637 mark_sym_for_renaming (tag);
1639 /* Similarly, if pointer VAR used to have another type
1640 tag, we will need to process it in the renamer to
1641 remove the stale virtual operands. */
1642 if (v_ann->symbol_mem_tag)
1643 mark_sym_for_renaming (v_ann->symbol_mem_tag);
1645 /* Associate the tag with pointer VAR. */
1646 v_ann->symbol_mem_tag = tag;
1648 /* If pointer VAR has been used in a store operation,
1649 then its memory tag must be marked as written-to. */
1650 if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)))
1651 bitmap_set_bit (ai->written_vars, DECL_UID (tag));
1653 /* All the dereferences of pointer VAR count as
1654 references of TAG. Since TAG can be associated with
1655 several pointers, add the dereferences of VAR to the
1657 NUM_REFERENCES_SET (t_ann,
1658 NUM_REFERENCES (t_ann)
1659 + NUM_REFERENCES (v_ann));
1663 /* The pointer has not been dereferenced. If it had a
1664 symbol memory tag, remove it and mark the old tag for
1665 renaming to remove it out of the IL. */
1666 var_ann_t ann = var_ann (var);
1667 tree tag = ann->symbol_mem_tag;
1670 mark_sym_for_renaming (tag);
1671 ann->symbol_mem_tag = NULL_TREE;
1676 VEC_free (tree, heap, varvec);
1680 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1681 every call site, we need to emit V_MAY_DEF expressions to represent the
1682 clobbering effects of the call for variables whose address escapes the
1685 One approach is to group all call-clobbered variables into a single
1686 representative that is used as an alias of every call-clobbered variable
1687 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1688 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1690 The second approach is to emit a clobbering V_MAY_DEF for every
1691 call-clobbered variable at call sites. This is the preferred way in terms
1692 of optimization opportunities but it may create too many V_MAY_DEF operands
1693 if there are many call clobbered variables and function calls in the
1696 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1697 function calls found by the number of call-clobbered variables. If that
1698 product is beyond a certain threshold, as determined by the parameterized
1699 values shown below, we use .GLOBAL_VAR.
1701 FIXME. This heuristic should be improved. One idea is to use several
1702 .GLOBAL_VARs of different types instead of a single one. The thresholds
1703 have been derived from a typical bootstrap cycle, including all target
1704 libraries. Compile times were found increase by ~1% compared to using
1708 maybe_create_global_var (struct alias_info *ai)
1710 unsigned i, n_clobbered;
1713 /* No need to create it, if we have one already. */
1714 if (global_var == NULL_TREE)
1716 /* Count all the call-clobbered variables. */
1718 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1723 /* If the number of virtual operands that would be needed to
1724 model all the call-clobbered variables is larger than
1725 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
1727 Also create .GLOBAL_VAR if there are no call-clobbered
1728 variables and the program contains a mixture of pure/const
1729 and regular function calls. This is to avoid the problem
1730 described in PR 20115:
1733 int func_pure (void) { return X; }
1734 int func_non_pure (int a) { X += a; }
1737 int a = func_pure ();
1743 Since foo() has no call-clobbered variables, there is
1744 no relationship between the calls to func_pure and
1745 func_non_pure. Since func_pure has no side-effects, value
1746 numbering optimizations elide the second call to func_pure.
1747 So, if we have some pure/const and some regular calls in the
1748 program we create .GLOBAL_VAR to avoid missing these
1750 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
1751 || (n_clobbered == 0
1752 && ai->num_calls_found > 0
1753 && ai->num_pure_const_calls_found > 0
1754 && ai->num_calls_found > ai->num_pure_const_calls_found))
1755 create_global_var ();
1758 /* Mark all call-clobbered symbols for renaming. Since the initial
1759 rewrite into SSA ignored all call sites, we may need to rename
1760 .GLOBAL_VAR and the call-clobbered variables. */
1761 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1763 tree var = referenced_var (i);
1765 /* If the function has calls to clobbering functions and
1766 .GLOBAL_VAR has been created, make it an alias for all
1767 call-clobbered variables. */
1768 if (global_var && var != global_var)
1770 add_may_alias (var, global_var);
1771 gcc_assert (!get_subvars_for_var (var));
1774 mark_sym_for_renaming (var);
1779 /* Return TRUE if pointer PTR may point to variable VAR.
1781 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1782 This is needed because when checking for type conflicts we are
1783 interested in the alias set of the memory location pointed-to by
1784 PTR. The alias set of PTR itself is irrelevant.
1786 VAR_ALIAS_SET is the alias set for VAR. */
1789 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1790 tree var, HOST_WIDE_INT var_alias_set,
1791 bool alias_set_only)
1795 alias_stats.alias_queries++;
1796 alias_stats.simple_queries++;
1798 /* By convention, a variable cannot alias itself. */
1799 mem = var_ann (ptr)->symbol_mem_tag;
1802 alias_stats.alias_noalias++;
1803 alias_stats.simple_resolved++;
1807 /* If -fargument-noalias-global is >1, pointer arguments may
1808 not point to global variables. */
1809 if (flag_argument_noalias > 1 && is_global_var (var)
1810 && TREE_CODE (ptr) == PARM_DECL)
1812 alias_stats.alias_noalias++;
1813 alias_stats.simple_resolved++;
1817 /* If either MEM or VAR is a read-only global and the other one
1818 isn't, then PTR cannot point to VAR. */
1819 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
1820 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
1822 alias_stats.alias_noalias++;
1823 alias_stats.simple_resolved++;
1827 gcc_assert (TREE_CODE (mem) == SYMBOL_MEMORY_TAG);
1829 alias_stats.tbaa_queries++;
1831 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1832 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1834 alias_stats.alias_noalias++;
1835 alias_stats.tbaa_resolved++;
1839 /* If var is a record or union type, ptr cannot point into var
1840 unless there is some operation explicit address operation in the
1841 program that can reference a field of the ptr's dereferenced
1842 type. This also assumes that the types of both var and ptr are
1843 contained within the compilation unit, and that there is no fancy
1844 addressing arithmetic associated with any of the types
1847 if ((mem_alias_set != 0) && (var_alias_set != 0))
1849 tree ptr_type = TREE_TYPE (ptr);
1850 tree var_type = TREE_TYPE (var);
1852 /* The star count is -1 if the type at the end of the pointer_to
1853 chain is not a record or union type. */
1854 if ((!alias_set_only) &&
1855 ipa_type_escape_star_count_of_interesting_type (var_type) >= 0)
1857 int ptr_star_count = 0;
1859 /* Ipa_type_escape_star_count_of_interesting_type is a little to
1860 restrictive for the pointer type, need to allow pointers to
1861 primitive types as long as those types cannot be pointers
1863 while (POINTER_TYPE_P (ptr_type))
1864 /* Strip the *'s off. */
1866 ptr_type = TREE_TYPE (ptr_type);
1870 /* There does not appear to be a better test to see if the
1871 pointer type was one of the pointer to everything
1874 if (ptr_star_count > 0)
1876 alias_stats.structnoaddress_queries++;
1877 if (ipa_type_escape_field_does_not_clobber_p (var_type,
1880 alias_stats.structnoaddress_resolved++;
1881 alias_stats.alias_noalias++;
1885 else if (ptr_star_count == 0)
1887 /* If ptr_type was not really a pointer to type, it cannot
1889 alias_stats.structnoaddress_queries++;
1890 alias_stats.structnoaddress_resolved++;
1891 alias_stats.alias_noalias++;
1897 alias_stats.alias_mayalias++;
1902 /* Add ALIAS to the set of variables that may alias VAR. */
1905 add_may_alias (tree var, tree alias)
1908 var_ann_t v_ann = get_var_ann (var);
1909 var_ann_t a_ann = get_var_ann (alias);
1912 /* Don't allow self-referential aliases. */
1913 gcc_assert (var != alias);
1915 /* ALIAS must be addressable if it's being added to an alias set. */
1917 TREE_ADDRESSABLE (alias) = 1;
1919 gcc_assert (may_be_aliased (alias));
1922 if (v_ann->may_aliases == NULL)
1923 v_ann->may_aliases = VEC_alloc (tree, gc, 2);
1925 /* Avoid adding duplicates. */
1926 for (i = 0; VEC_iterate (tree, v_ann->may_aliases, i, al); i++)
1930 VEC_safe_push (tree, gc, v_ann->may_aliases, alias);
1931 a_ann->is_aliased = 1;
1935 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1938 replace_may_alias (tree var, size_t i, tree new_alias)
1940 var_ann_t v_ann = var_ann (var);
1941 VEC_replace (tree, v_ann->may_aliases, i, new_alias);
1945 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1948 set_pt_anything (tree ptr)
1950 struct ptr_info_def *pi = get_ptr_info (ptr);
1952 pi->pt_anything = 1;
1955 /* The pointer used to have a name tag, but we now found it pointing
1956 to an arbitrary location. The name tag needs to be renamed and
1957 disassociated from PTR. */
1958 if (pi->name_mem_tag)
1960 mark_sym_for_renaming (pi->name_mem_tag);
1961 pi->name_mem_tag = NULL_TREE;
1966 /* Return true if STMT is an "escape" site from the current function. Escape
1967 sites those statements which might expose the address of a variable
1968 outside the current function. STMT is an escape site iff:
1970 1- STMT is a function call, or
1971 2- STMT is an __asm__ expression, or
1972 3- STMT is an assignment to a non-local variable, or
1973 4- STMT is a return statement.
1975 AI points to the alias information collected so far.
1977 Return the type of escape site found, if we found one, or NO_ESCAPE
1981 is_escape_site (tree stmt, struct alias_info *ai)
1983 tree call = get_call_expr_in (stmt);
1984 if (call != NULL_TREE)
1986 ai->num_calls_found++;
1988 if (!TREE_SIDE_EFFECTS (call))
1990 ai->num_pure_const_calls_found++;
1991 return ESCAPE_TO_PURE_CONST;
1994 return ESCAPE_TO_CALL;
1996 else if (TREE_CODE (stmt) == ASM_EXPR)
1997 return ESCAPE_TO_ASM;
1998 else if (TREE_CODE (stmt) == MODIFY_EXPR)
2000 tree lhs = TREE_OPERAND (stmt, 0);
2002 /* Get to the base of _REF nodes. */
2003 if (TREE_CODE (lhs) != SSA_NAME)
2004 lhs = get_base_address (lhs);
2006 /* If we couldn't recognize the LHS of the assignment, assume that it
2007 is a non-local store. */
2008 if (lhs == NULL_TREE)
2009 return ESCAPE_UNKNOWN;
2011 /* If the RHS is a conversion between a pointer and an integer, the
2012 pointer escapes since we can't track the integer. */
2013 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
2014 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
2015 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
2016 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
2017 (TREE_OPERAND (stmt, 1), 0)))
2018 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
2019 return ESCAPE_BAD_CAST;
2021 /* If the LHS is an SSA name, it can't possibly represent a non-local
2023 if (TREE_CODE (lhs) == SSA_NAME)
2026 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2027 local variables we cannot be sure if it will escape, because we
2028 don't have information about objects not in SSA form. Need to
2029 implement something along the lines of
2031 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2032 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2033 Conference on Object-Oriented Programming Systems, Languages, and
2034 Applications (OOPSLA), pp. 1-19, 1999. */
2035 return ESCAPE_STORED_IN_GLOBAL;
2037 else if (TREE_CODE (stmt) == RETURN_EXPR)
2038 return ESCAPE_TO_RETURN;
2043 /* Create a new memory tag of type TYPE.
2044 Does NOT push it into the current binding. */
2047 create_tag_raw (enum tree_code code, tree type, const char *prefix)
2052 /* Make the type of the variable writable. */
2053 new_type = build_type_variant (type, 0, 0);
2054 TYPE_ATTRIBUTES (new_type) = TYPE_ATTRIBUTES (type);
2056 tmp_var = build_decl (code, create_tmp_var_name (prefix),
2058 /* Make the variable writable. */
2059 TREE_READONLY (tmp_var) = 0;
2061 /* It doesn't start out global. */
2062 MTAG_GLOBAL (tmp_var) = 0;
2063 TREE_STATIC (tmp_var) = 0;
2064 TREE_USED (tmp_var) = 1;
2069 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2070 is considered to represent all the pointers whose pointed-to types are
2071 in the same alias set class. Otherwise, the tag represents a single
2072 SSA_NAME pointer variable. */
2075 create_memory_tag (tree type, bool is_type_tag)
2078 tree tag = create_tag_raw (is_type_tag ? SYMBOL_MEMORY_TAG : NAME_MEMORY_TAG,
2079 type, (is_type_tag) ? "SMT" : "NMT");
2081 /* By default, memory tags are local variables. Alias analysis will
2082 determine whether they should be considered globals. */
2083 DECL_CONTEXT (tag) = current_function_decl;
2085 /* Memory tags are by definition addressable. */
2086 TREE_ADDRESSABLE (tag) = 1;
2088 ann = get_var_ann (tag);
2089 ann->symbol_mem_tag = NULL_TREE;
2091 /* Add the tag to the symbol table. */
2092 add_referenced_tmp_var (tag);
2098 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2099 This is used if P_i has been found to point to a specific set of
2100 variables or to a non-aliased memory location like the address returned
2101 by malloc functions. */
2104 get_nmt_for (tree ptr)
2106 struct ptr_info_def *pi = get_ptr_info (ptr);
2107 tree tag = pi->name_mem_tag;
2109 if (tag == NULL_TREE)
2110 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2115 /* Return the symbol memory tag associated to pointer PTR. A memory
2116 tag is an artificial variable that represents the memory location
2117 pointed-to by PTR. It is used to model the effects of pointer
2118 de-references on addressable variables.
2120 AI points to the data gathered during alias analysis. This
2121 function populates the array AI->POINTERS. */
2124 get_tmt_for (tree ptr, struct alias_info *ai)
2128 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2129 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2131 /* To avoid creating unnecessary memory tags, only create one memory tag
2132 per alias set class. Note that it may be tempting to group
2133 memory tags based on conflicting alias sets instead of
2134 equivalence. That would be wrong because alias sets are not
2135 necessarily transitive (as demonstrated by the libstdc++ test
2136 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2137 such that conflicts (A, B) == true and conflicts (A, C) == true,
2138 it does not necessarily follow that conflicts (B, C) == true. */
2139 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2141 struct alias_map_d *curr = ai->pointers[i];
2142 tree curr_tag = var_ann (curr->var)->symbol_mem_tag;
2143 if (tag_set == curr->set)
2150 /* If VAR cannot alias with any of the existing memory tags, create a new
2151 tag for PTR and add it to the POINTERS array. */
2152 if (tag == NULL_TREE)
2154 struct alias_map_d *alias_map;
2156 /* If PTR did not have a symbol tag already, create a new SMT.*
2157 artificial variable representing the memory location
2158 pointed-to by PTR. */
2159 if (var_ann (ptr)->symbol_mem_tag == NULL_TREE)
2160 tag = create_memory_tag (tag_type, true);
2162 tag = var_ann (ptr)->symbol_mem_tag;
2164 /* Add PTR to the POINTERS array. Note that we are not interested in
2165 PTR's alias set. Instead, we cache the alias set for the memory that
2167 alias_map = XCNEW (struct alias_map_d);
2168 alias_map->var = ptr;
2169 alias_map->set = tag_set;
2170 ai->pointers[ai->num_pointers++] = alias_map;
2173 /* If the pointed-to type is volatile, so is the tag. */
2174 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
2176 /* Make sure that the symbol tag has the same alias set as the
2178 gcc_assert (tag_set == get_alias_set (tag));
2184 /* Create GLOBAL_VAR, an artificial global variable to act as a
2185 representative of all the variables that may be clobbered by function
2189 create_global_var (void)
2191 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2193 DECL_ARTIFICIAL (global_var) = 1;
2194 TREE_READONLY (global_var) = 0;
2195 DECL_EXTERNAL (global_var) = 1;
2196 TREE_STATIC (global_var) = 1;
2197 TREE_USED (global_var) = 1;
2198 DECL_CONTEXT (global_var) = NULL_TREE;
2199 TREE_THIS_VOLATILE (global_var) = 0;
2200 TREE_ADDRESSABLE (global_var) = 0;
2202 create_var_ann (global_var);
2203 mark_call_clobbered (global_var, ESCAPE_UNKNOWN);
2204 add_referenced_tmp_var (global_var);
2205 mark_sym_for_renaming (global_var);
2209 /* Dump alias statistics on FILE. */
2212 dump_alias_stats (FILE *file)
2214 const char *funcname
2215 = lang_hooks.decl_printable_name (current_function_decl, 2);
2216 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2217 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2218 fprintf (file, "Total alias mayalias results:\t%u\n",
2219 alias_stats.alias_mayalias);
2220 fprintf (file, "Total alias noalias results:\t%u\n",
2221 alias_stats.alias_noalias);
2222 fprintf (file, "Total simple queries:\t%u\n",
2223 alias_stats.simple_queries);
2224 fprintf (file, "Total simple resolved:\t%u\n",
2225 alias_stats.simple_resolved);
2226 fprintf (file, "Total TBAA queries:\t%u\n",
2227 alias_stats.tbaa_queries);
2228 fprintf (file, "Total TBAA resolved:\t%u\n",
2229 alias_stats.tbaa_resolved);
2230 fprintf (file, "Total non-addressable structure type queries:\t%u\n",
2231 alias_stats.structnoaddress_queries);
2232 fprintf (file, "Total non-addressable structure type resolved:\t%u\n",
2233 alias_stats.structnoaddress_resolved);
2237 /* Dump alias information on FILE. */
2240 dump_alias_info (FILE *file)
2243 const char *funcname
2244 = lang_hooks.decl_printable_name (current_function_decl, 2);
2245 referenced_var_iterator rvi;
2248 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2250 fprintf (file, "Aliased symbols\n\n");
2252 FOR_EACH_REFERENCED_VAR (var, rvi)
2254 if (may_be_aliased (var))
2255 dump_variable (file, var);
2258 fprintf (file, "\nDereferenced pointers\n\n");
2260 FOR_EACH_REFERENCED_VAR (var, rvi)
2262 var_ann_t ann = var_ann (var);
2263 if (ann->symbol_mem_tag)
2264 dump_variable (file, var);
2267 fprintf (file, "\nSymbol memory tags\n\n");
2269 FOR_EACH_REFERENCED_VAR (var, rvi)
2271 if (TREE_CODE (var) == SYMBOL_MEMORY_TAG)
2272 dump_variable (file, var);
2275 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2277 fprintf (file, "SSA_NAME pointers\n\n");
2278 for (i = 1; i < num_ssa_names; i++)
2280 tree ptr = ssa_name (i);
2281 struct ptr_info_def *pi;
2283 if (ptr == NULL_TREE)
2286 pi = SSA_NAME_PTR_INFO (ptr);
2287 if (!SSA_NAME_IN_FREE_LIST (ptr)
2289 && pi->name_mem_tag)
2290 dump_points_to_info_for (file, ptr);
2293 fprintf (file, "\nName memory tags\n\n");
2295 FOR_EACH_REFERENCED_VAR (var, rvi)
2297 if (TREE_CODE (var) == NAME_MEMORY_TAG)
2298 dump_variable (file, var);
2301 fprintf (file, "\n");
2305 /* Dump alias information on stderr. */
2308 debug_alias_info (void)
2310 dump_alias_info (stderr);
2314 /* Return the alias information associated with pointer T. It creates a
2315 new instance if none existed. */
2317 struct ptr_info_def *
2318 get_ptr_info (tree t)
2320 struct ptr_info_def *pi;
2322 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2324 pi = SSA_NAME_PTR_INFO (t);
2327 pi = GGC_NEW (struct ptr_info_def);
2328 memset ((void *)pi, 0, sizeof (*pi));
2329 SSA_NAME_PTR_INFO (t) = pi;
2336 /* Dump points-to information for SSA_NAME PTR into FILE. */
2339 dump_points_to_info_for (FILE *file, tree ptr)
2341 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2343 print_generic_expr (file, ptr, dump_flags);
2347 if (pi->name_mem_tag)
2349 fprintf (file, ", name memory tag: ");
2350 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2353 if (pi->is_dereferenced)
2354 fprintf (file, ", is dereferenced");
2356 if (pi->value_escapes_p)
2357 fprintf (file, ", its value escapes");
2359 if (pi->pt_anything)
2360 fprintf (file, ", points-to anything");
2363 fprintf (file, ", points-to NULL");
2370 fprintf (file, ", points-to vars: { ");
2371 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2373 print_generic_expr (file, referenced_var (ix), dump_flags);
2374 fprintf (file, " ");
2376 fprintf (file, "}");
2380 fprintf (file, "\n");
2384 /* Dump points-to information for VAR into stderr. */
2387 debug_points_to_info_for (tree var)
2389 dump_points_to_info_for (stderr, var);
2393 /* Dump points-to information into FILE. NOTE: This function is slow, as
2394 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2397 dump_points_to_info (FILE *file)
2400 block_stmt_iterator si;
2403 lang_hooks.decl_printable_name (current_function_decl, 2);
2404 referenced_var_iterator rvi;
2407 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2409 /* First dump points-to information for the default definitions of
2410 pointer variables. This is necessary because default definitions are
2411 not part of the code. */
2412 FOR_EACH_REFERENCED_VAR (var, rvi)
2414 if (POINTER_TYPE_P (TREE_TYPE (var)))
2416 tree def = default_def (var);
2418 dump_points_to_info_for (file, def);
2422 /* Dump points-to information for every pointer defined in the program. */
2427 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2429 tree ptr = PHI_RESULT (phi);
2430 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2431 dump_points_to_info_for (file, ptr);
2434 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2436 tree stmt = bsi_stmt (si);
2438 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2439 if (POINTER_TYPE_P (TREE_TYPE (def)))
2440 dump_points_to_info_for (file, def);
2444 fprintf (file, "\n");
2448 /* Dump points-to info pointed to by PTO into STDERR. */
2451 debug_points_to_info (void)
2453 dump_points_to_info (stderr);
2456 /* Dump to FILE the list of variables that may be aliasing VAR. */
2459 dump_may_aliases_for (FILE *file, tree var)
2461 VEC(tree, gc) *aliases;
2463 if (TREE_CODE (var) == SSA_NAME)
2464 var = SSA_NAME_VAR (var);
2466 aliases = var_ann (var)->may_aliases;
2471 fprintf (file, "{ ");
2472 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2474 print_generic_expr (file, al, dump_flags);
2475 fprintf (file, " ");
2477 fprintf (file, "}");
2482 /* Dump to stderr the list of variables that may be aliasing VAR. */
2485 debug_may_aliases_for (tree var)
2487 dump_may_aliases_for (stderr, var);
2490 /* Return true if VAR may be aliased. */
2493 may_be_aliased (tree var)
2496 if (TREE_ADDRESSABLE (var))
2499 /* Globally visible variables can have their addresses taken by other
2500 translation units. */
2503 && (MTAG_GLOBAL (var) || TREE_PUBLIC (var)))
2505 else if (!MTAG_P (var)
2506 && (DECL_EXTERNAL (var) || TREE_PUBLIC (var)))
2509 /* Automatic variables can't have their addresses escape any other way.
2510 This must be after the check for global variables, as extern declarations
2511 do not have TREE_STATIC set. */
2512 if (!TREE_STATIC (var))
2515 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2516 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2517 we can only be sure the variable isn't addressable if it's local to the
2518 current function. */
2519 if (flag_unit_at_a_time)
2521 if (decl_function_context (var) == current_function_decl)
2528 /* Given two symbols return TRUE if one is in the alias set of the other. */
2530 is_aliased_with (tree tag, tree sym)
2533 VEC(tree,gc) *aliases;
2536 if (var_ann (sym)->is_aliased)
2538 aliases = var_ann (tag)->may_aliases;
2540 if (aliases == NULL)
2543 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2549 aliases = var_ann (sym)->may_aliases;
2551 if (aliases == NULL)
2554 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2563 /* Add VAR to the list of may-aliases of PTR's symbol tag. If PTR
2564 doesn't already have a symbol tag, create one. */
2567 add_type_alias (tree ptr, tree var)
2569 VEC(tree, gc) *aliases;
2571 var_ann_t ann = var_ann (ptr);
2573 VEC (tree, heap) *varvec = NULL;
2576 if (ann->symbol_mem_tag == NULL_TREE)
2579 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2580 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2581 safe_referenced_var_iterator rvi;
2583 /* PTR doesn't have a symbol tag, create a new one and add VAR to
2584 the new tag's alias set.
2586 FIXME, This is slower than necessary. We need to determine
2587 whether there is another pointer Q with the same alias set as
2588 PTR. This could be sped up by having symbol tags associated
2590 FOR_EACH_REFERENCED_VAR_SAFE (q, varvec, rvi)
2592 if (POINTER_TYPE_P (TREE_TYPE (q))
2593 && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q))))
2595 /* Found another pointer Q with the same alias set as
2596 the PTR's pointed-to type. If Q has a symbol tag, use
2597 it. Otherwise, create a new memory tag for PTR. */
2598 var_ann_t ann1 = var_ann (q);
2599 if (ann1->symbol_mem_tag)
2600 ann->symbol_mem_tag = ann1->symbol_mem_tag;
2602 ann->symbol_mem_tag = create_memory_tag (tag_type, true);
2607 /* Couldn't find any other pointer with a symbol tag we could use.
2608 Create a new memory tag for PTR. */
2609 ann->symbol_mem_tag = create_memory_tag (tag_type, true);
2613 /* If VAR is not already PTR's symbol tag, add it to the may-alias set
2614 for PTR's symbol tag. */
2615 gcc_assert (!MTAG_P (var));
2616 tag = ann->symbol_mem_tag;
2618 /* If VAR has subvars, add the subvars to the tag instead of the
2620 if (var_can_have_subvars (var)
2621 && (svars = get_subvars_for_var (var)))
2624 for (sv = svars; sv; sv = sv->next)
2625 add_may_alias (tag, sv->var);
2628 add_may_alias (tag, var);
2630 /* TAG and its set of aliases need to be marked for renaming. */
2631 mark_sym_for_renaming (tag);
2632 if ((aliases = var_ann (tag)->may_aliases) != NULL)
2634 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2635 mark_sym_for_renaming (al);
2638 /* If we had grouped aliases, VAR may have aliases of its own. Mark
2639 them for renaming as well. Other statements referencing the
2640 aliases of VAR will need to be updated. */
2641 if ((aliases = var_ann (var)->may_aliases) != NULL)
2643 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2644 mark_sym_for_renaming (al);
2646 VEC_free (tree, heap, varvec);
2650 /* Create a new symbol tag for PTR. Construct the may-alias list of this type
2651 tag so that it has the aliasing of VAR.
2653 Note, the set of aliases represented by the new symbol tag are not marked
2657 new_type_alias (tree ptr, tree var)
2659 var_ann_t p_ann = var_ann (ptr);
2660 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2661 var_ann_t v_ann = var_ann (var);
2665 gcc_assert (p_ann->symbol_mem_tag == NULL_TREE);
2666 gcc_assert (!MTAG_P (var));
2668 /* Add VAR to the may-alias set of PTR's new symbol tag. If VAR has
2669 subvars, add the subvars to the tag instead of the actual var. */
2670 if (var_can_have_subvars (var)
2671 && (svars = get_subvars_for_var (var)))
2675 tag = create_memory_tag (tag_type, true);
2676 p_ann->symbol_mem_tag = tag;
2678 for (sv = svars; sv; sv = sv->next)
2679 add_may_alias (tag, sv->var);
2683 /* The following is based on code in add_stmt_operand to ensure that the
2684 same defs/uses/vdefs/vuses will be found after replacing a reference
2685 to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value
2686 is the address of var. */
2687 VEC(tree, gc) *aliases = v_ann->may_aliases;
2689 if ((aliases != NULL)
2690 && (VEC_length (tree, aliases) == 1))
2692 tree ali = VEC_index (tree, aliases, 0);
2694 if (TREE_CODE (ali) == SYMBOL_MEMORY_TAG)
2696 p_ann->symbol_mem_tag = ali;
2701 tag = create_memory_tag (tag_type, true);
2702 p_ann->symbol_mem_tag = tag;
2704 if (aliases == NULL)
2705 add_may_alias (tag, var);
2711 for (i = 0; VEC_iterate (tree, aliases, i, al); i++)
2712 add_may_alias (tag, al);
2716 TREE_READONLY (tag) = TREE_READONLY (var);
2717 MTAG_GLOBAL (tag) = is_global_var (var);
2722 /* This represents the used range of a variable. */
2724 typedef struct used_part
2726 HOST_WIDE_INT minused;
2727 HOST_WIDE_INT maxused;
2728 /* True if we have an explicit use/def of some portion of this variable,
2729 even if it is all of it. i.e. a.b = 5 or temp = a.b. */
2731 /* True if we have an implicit use/def of some portion of this
2732 variable. Implicit uses occur when we can't tell what part we
2733 are referencing, and have to make conservative assumptions. */
2735 /* True if the structure is only written to or taken its address. */
2739 /* An array of used_part structures, indexed by variable uid. */
2741 static htab_t used_portions;
2743 struct used_part_map
2749 /* Return true if the uid in the two used part maps are equal. */
2752 used_part_map_eq (const void *va, const void *vb)
2754 const struct used_part_map *a = (const struct used_part_map *) va;
2755 const struct used_part_map *b = (const struct used_part_map *) vb;
2756 return (a->uid == b->uid);
2759 /* Hash a from uid in a used_part_map. */
2762 used_part_map_hash (const void *item)
2764 return ((const struct used_part_map *)item)->uid;
2767 /* Free a used part map element. */
2770 free_used_part_map (void *item)
2772 free (((struct used_part_map *)item)->to);
2776 /* Lookup a used_part structure for a UID. */
2779 up_lookup (unsigned int uid)
2781 struct used_part_map *h, in;
2783 h = (struct used_part_map *) htab_find_with_hash (used_portions, &in, uid);
2789 /* Insert the pair UID, TO into the used part hashtable. */
2792 up_insert (unsigned int uid, used_part_t to)
2794 struct used_part_map *h;
2797 h = XNEW (struct used_part_map);
2800 loc = htab_find_slot_with_hash (used_portions, h,
2804 *(struct used_part_map **) loc = h;
2808 /* Given a variable uid, UID, get or create the entry in the used portions
2809 table for the variable. */
2812 get_or_create_used_part_for (size_t uid)
2815 if ((up = up_lookup (uid)) == NULL)
2817 up = XCNEW (struct used_part);
2818 up->minused = INT_MAX;
2820 up->explicit_uses = false;
2821 up->implicit_uses = false;
2822 up->write_only = true;
2829 /* Create and return a structure sub-variable for field type FIELD at
2830 offset OFFSET, with size SIZE, of variable VAR. */
2833 create_sft (tree var, tree field, unsigned HOST_WIDE_INT offset,
2834 unsigned HOST_WIDE_INT size)
2837 tree subvar = create_tag_raw (STRUCT_FIELD_TAG, field, "SFT");
2839 /* We need to copy the various flags from VAR to SUBVAR, so that
2840 they are is_global_var iff the original variable was. */
2841 DECL_CONTEXT (subvar) = DECL_CONTEXT (var);
2842 MTAG_GLOBAL (subvar) = DECL_EXTERNAL (var);
2843 TREE_PUBLIC (subvar) = TREE_PUBLIC (var);
2844 TREE_STATIC (subvar) = TREE_STATIC (var);
2845 TREE_READONLY (subvar) = TREE_READONLY (var);
2847 /* Add the new variable to REFERENCED_VARS. */
2848 ann = get_var_ann (subvar);
2849 ann->symbol_mem_tag = NULL;
2850 add_referenced_tmp_var (subvar);
2851 SFT_PARENT_VAR (subvar) = var;
2852 SFT_OFFSET (subvar) = offset;
2853 SFT_SIZE (subvar) = size;
2858 /* Given an aggregate VAR, create the subvariables that represent its
2862 create_overlap_variables_for (tree var)
2864 VEC(fieldoff_s,heap) *fieldstack = NULL;
2866 size_t uid = DECL_UID (var);
2868 up = up_lookup (uid);
2873 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL);
2874 if (VEC_length (fieldoff_s, fieldstack) != 0)
2878 bool notokay = false;
2881 HOST_WIDE_INT lastfooffset = -1;
2882 HOST_WIDE_INT lastfosize = -1;
2883 tree lastfotype = NULL_TREE;
2885 /* Not all fields have DECL_SIZE set, and those that don't, we don't
2886 know their size, and thus, can't handle.
2887 The same is true of fields with DECL_SIZE that is not an integer
2888 constant (such as variable sized fields).
2889 Fields with offsets which are not constant will have an offset < 0
2890 We *could* handle fields that are constant sized arrays, but
2891 currently don't. Doing so would require some extra changes to
2892 tree-ssa-operands.c. */
2894 for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
2897 || TREE_CODE (fo->size) != INTEGER_CST
2906 /* The current heuristic we use is as follows:
2907 If the variable has no used portions in this function, no
2908 structure vars are created for it.
2910 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
2911 we always create structure vars for them.
2912 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2913 some explicit uses, we create structure vars for them.
2914 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2915 no explicit uses, we do not create structure vars for them.
2918 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
2919 && !up->explicit_uses)
2921 if (dump_file && (dump_flags & TDF_DETAILS))
2923 fprintf (dump_file, "Variable ");
2924 print_generic_expr (dump_file, var, 0);
2925 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
2930 /* Bail out, if we can't create overlap variables. */
2933 VEC_free (fieldoff_s, heap, fieldstack);
2937 /* Otherwise, create the variables. */
2938 subvars = lookup_subvars_for_var (var);
2940 sort_fieldstack (fieldstack);
2942 for (i = VEC_length (fieldoff_s, fieldstack);
2943 VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
2946 HOST_WIDE_INT fosize;
2949 fosize = TREE_INT_CST_LOW (fo->size);
2950 currfotype = fo->type;
2952 /* If this field isn't in the used portion,
2953 or it has the exact same offset and size as the last
2956 if (((fo->offset <= up->minused
2957 && fo->offset + fosize <= up->minused)
2958 || fo->offset >= up->maxused)
2959 || (fo->offset == lastfooffset
2960 && fosize == lastfosize
2961 && currfotype == lastfotype))
2963 sv = GGC_NEW (struct subvar);
2964 sv->next = *subvars;
2965 sv->var = create_sft (var, fo->type, fo->offset, fosize);
2969 fprintf (dump_file, "structure field tag %s created for var %s",
2970 get_name (sv->var), get_name (var));
2971 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
2972 SFT_OFFSET (sv->var));
2973 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
2974 SFT_SIZE (sv->var));
2975 fprintf (dump_file, "\n");
2978 lastfotype = currfotype;
2979 lastfooffset = fo->offset;
2980 lastfosize = fosize;
2984 /* Once we have created subvars, the original is no longer call
2985 clobbered on its own. Its call clobbered status depends
2986 completely on the call clobbered status of the subvars.
2988 add_referenced_var in the above loop will take care of
2989 marking subvars of global variables as call clobbered for us
2990 to start, since they are global as well. */
2991 clear_call_clobbered (var);
2994 VEC_free (fieldoff_s, heap, fieldstack);
2998 /* Find the conservative answer to the question of what portions of what
2999 structures are used by this statement. We assume that if we have a
3000 component ref with a known size + offset, that we only need that part
3001 of the structure. For unknown cases, or cases where we do something
3002 to the whole structure, we assume we need to create fields for the
3003 entire structure. */
3006 find_used_portions (tree *tp, int *walk_subtrees, void *lhs_p)
3008 switch (TREE_CODE (*tp))
3011 /* Recurse manually here to track whether the use is in the
3012 LHS of an assignment. */
3013 find_used_portions (&TREE_OPERAND (*tp, 0), walk_subtrees, tp);
3014 return find_used_portions (&TREE_OPERAND (*tp, 1), walk_subtrees, NULL);
3020 HOST_WIDE_INT bitsize;
3021 HOST_WIDE_INT bitmaxsize;
3022 HOST_WIDE_INT bitpos;
3024 ref = get_ref_base_and_extent (*tp, &bitpos, &bitsize, &bitmaxsize);
3026 && var_can_have_subvars (ref)
3027 && bitmaxsize != -1)
3029 size_t uid = DECL_UID (ref);
3032 up = get_or_create_used_part_for (uid);
3034 if (bitpos <= up->minused)
3035 up->minused = bitpos;
3036 if ((bitpos + bitmaxsize >= up->maxused))
3037 up->maxused = bitpos + bitmaxsize;
3039 if (bitsize == bitmaxsize)
3040 up->explicit_uses = true;
3042 up->implicit_uses = true;
3044 up->write_only = false;
3045 up_insert (uid, up);
3052 /* This is here to make sure we mark the entire base variable as used
3053 when you take its address. Because our used portion analysis is
3054 simple, we aren't looking at casts or pointer arithmetic to see what
3055 happens when you take the address. */
3058 tree var = get_base_address (TREE_OPERAND (*tp, 0));
3063 && var_can_have_subvars (var)
3064 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3067 size_t uid = DECL_UID (var);
3069 up = get_or_create_used_part_for (uid);
3072 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
3073 up->implicit_uses = true;
3075 up_insert (uid, up);
3084 for (arg = &TREE_OPERAND (*tp, 1); *arg; arg = &TREE_CHAIN (*arg))
3086 if (TREE_CODE (TREE_VALUE (*arg)) != ADDR_EXPR)
3087 find_used_portions (&TREE_VALUE (*arg), walk_subtrees, NULL);
3098 && var_can_have_subvars (var)
3099 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3102 size_t uid = DECL_UID (var);
3104 up = get_or_create_used_part_for (uid);
3107 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
3108 up->implicit_uses = true;
3110 up_insert (uid, up);
3124 /* Create structure field variables for structures used in this function. */
3127 create_structure_vars (void)
3130 safe_referenced_var_iterator rvi;
3131 VEC (tree, heap) *varvec = NULL;
3134 used_portions = htab_create (10, used_part_map_hash, used_part_map_eq,
3135 free_used_part_map);
3139 block_stmt_iterator bsi;
3140 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3142 walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
3147 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, rvi)
3149 /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
3152 && var_can_have_subvars (var)
3154 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3155 create_overlap_variables_for (var);
3157 htab_delete (used_portions);
3158 VEC_free (tree, heap, varvec);
3163 gate_structure_vars (void)
3165 return flag_tree_salias != 0;
3168 struct tree_opt_pass pass_create_structure_vars =
3170 "salias", /* name */
3171 gate_structure_vars, /* gate */
3172 create_structure_vars, /* execute */
3175 0, /* static_pass_number */
3177 PROP_cfg, /* properties_required */
3178 0, /* properties_provided */
3179 0, /* properties_destroyed */
3180 0, /* todo_flags_start */
3181 TODO_dump_func, /* todo_flags_finish */