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 /* Compute may-alias information for every variable referenced in function
142 Alias analysis proceeds in 3 main phases:
144 1- Points-to and escape analysis.
146 This phase walks the use-def chains in the SSA web looking for three
149 * Assignments of the form P_i = &VAR
150 * Assignments of the form P_i = malloc()
151 * Pointers and ADDR_EXPR that escape the current function.
153 The concept of 'escaping' is the same one used in the Java world. When
154 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
155 outside of the current function. So, assignment to global variables,
156 function arguments and returning a pointer are all escape sites, as are
157 conversions between pointers and integers.
159 This is where we are currently limited. Since not everything is renamed
160 into SSA, we lose track of escape properties when a pointer is stashed
161 inside a field in a structure, for instance. In those cases, we are
162 assuming that the pointer does escape.
164 We use escape analysis to determine whether a variable is
165 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
166 is call-clobbered. If a pointer P_i escapes, then all the variables
167 pointed-to by P_i (and its memory tag) also escape.
169 2- Compute flow-sensitive aliases
171 We have two classes of memory tags. Memory tags associated with the
172 pointed-to data type of the pointers in the program. These tags are
173 called "type memory tag" (TMT). The other class are those associated
174 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
175 when adding operands for an INDIRECT_REF *P_i, we will first check
176 whether P_i has a name tag, if it does we use it, because that will have
177 more precise aliasing information. Otherwise, we use the standard type
180 In this phase, we go through all the pointers we found in points-to
181 analysis and create alias sets for the name memory tags associated with
182 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
183 it points to and its tag.
186 3- Compute flow-insensitive aliases
188 This pass will compare the alias set of every type memory tag and every
189 addressable variable found in the program. Given a type memory tag TMT
190 and an addressable variable V. If the alias sets of TMT and V conflict
191 (as computed by may_alias_p), then V is marked as an alias tag and added
192 to the alias set of TMT.
194 For instance, consider the following function:
210 After aliasing analysis has finished, the type memory tag for pointer
211 'p' will have two aliases, namely variables 'a' and 'b'. Every time
212 pointer 'p' is dereferenced, we want to mark the operation as a
213 potential reference to 'a' and 'b'.
223 # p_1 = PHI <p_4(1), p_6(2)>;
225 # a_7 = V_MAY_DEF <a_3>;
226 # b_8 = V_MAY_DEF <b_5>;
229 # a_9 = V_MAY_DEF <a_7>
238 In certain cases, the list of may aliases for a pointer may grow too
239 large. This may cause an explosion in the number of virtual operands
240 inserted in the code. Resulting in increased memory consumption and
243 When the number of virtual operands needed to represent aliased
244 loads and stores grows too large (configurable with @option{--param
245 max-aliased-vops}), alias sets are grouped to avoid severe
246 compile-time slow downs and memory consumption. See group_aliases. */
249 compute_may_aliases (void)
251 struct alias_info *ai;
253 memset (&alias_stats, 0, sizeof (alias_stats));
255 /* Initialize aliasing information. */
256 ai = init_alias_info ();
258 /* For each pointer P_i, determine the sets of variables that P_i may
259 point-to. For every addressable variable V, determine whether the
260 address of V escapes the current function, making V call-clobbered
261 (i.e., whether &V is stored in a global variable or if its passed as a
262 function call argument). */
263 compute_points_to_sets (ai);
265 /* Collect all pointers and addressable variables, compute alias sets,
266 create memory tags for pointers and promote variables whose address is
267 not needed anymore. */
268 setup_pointers_and_addressables (ai);
270 /* Compute flow-sensitive, points-to based aliasing for all the name
271 memory tags. Note that this pass needs to be done before flow
272 insensitive analysis because it uses the points-to information
273 gathered before to mark call-clobbered type tags. */
274 compute_flow_sensitive_aliasing (ai);
276 /* Compute type-based flow-insensitive aliasing for all the type
278 compute_flow_insensitive_aliasing (ai);
280 /* If the program has too many call-clobbered variables and/or function
281 calls, create .GLOBAL_VAR and use it to model call-clobbering
282 semantics at call sites. This reduces the number of virtual operands
283 considerably, improving compile times at the expense of lost
284 aliasing precision. */
285 maybe_create_global_var (ai);
287 /* Debugging dumps. */
290 dump_referenced_vars (dump_file);
291 if (dump_flags & TDF_STATS)
292 dump_alias_stats (dump_file);
293 dump_points_to_info (dump_file);
294 dump_alias_info (dump_file);
297 /* Deallocate memory used by aliasing data structures. */
298 delete_alias_info (ai);
301 block_stmt_iterator bsi;
305 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
307 update_stmt_if_modified (bsi_stmt (bsi));
314 struct tree_opt_pass pass_may_alias =
318 compute_may_aliases, /* execute */
321 0, /* static_pass_number */
322 TV_TREE_MAY_ALIAS, /* tv_id */
323 PROP_cfg | PROP_ssa, /* properties_required */
324 PROP_alias, /* properties_provided */
325 0, /* properties_destroyed */
326 0, /* todo_flags_start */
327 TODO_dump_func | TODO_update_ssa
328 | TODO_ggc_collect | TODO_verify_ssa
329 | TODO_verify_stmts, /* todo_flags_finish */
334 /* Data structure used to count the number of dereferences to PTR
335 inside an expression. */
343 /* Helper for count_uses_and_derefs. Called by walk_tree to look for
344 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
347 count_ptr_derefs (tree *tp, int *walk_subtrees, void *data)
349 struct count_ptr_d *count_p = (struct count_ptr_d *) data;
351 /* Do not walk inside ADDR_EXPR nodes. In the expression &ptr->fld,
352 pointer 'ptr' is *not* dereferenced, it is simply used to compute
353 the address of 'fld' as 'ptr + offsetof(fld)'. */
354 if (TREE_CODE (*tp) == ADDR_EXPR)
360 if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
367 /* Count the number of direct and indirect uses for pointer PTR in
368 statement STMT. The two counts are stored in *NUM_USES_P and
369 *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
370 least one of those dereferences is a store operation. */
373 count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
374 unsigned *num_derefs_p, bool *is_store)
383 /* Find out the total number of uses of PTR in STMT. */
384 FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
388 /* Now count the number of indirect references to PTR. This is
389 truly awful, but we don't have much choice. There are no parent
390 pointers inside INDIRECT_REFs, so an expression like
391 '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
392 find all the indirect and direct uses of x_1 inside. The only
393 shortcut we can take is the fact that GIMPLE only allows
394 INDIRECT_REFs inside the expressions below. */
395 if (TREE_CODE (stmt) == MODIFY_EXPR
396 || (TREE_CODE (stmt) == RETURN_EXPR
397 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
398 || TREE_CODE (stmt) == ASM_EXPR
399 || TREE_CODE (stmt) == CALL_EXPR)
403 if (TREE_CODE (stmt) == MODIFY_EXPR)
405 lhs = TREE_OPERAND (stmt, 0);
406 rhs = TREE_OPERAND (stmt, 1);
408 else if (TREE_CODE (stmt) == RETURN_EXPR)
410 tree e = TREE_OPERAND (stmt, 0);
411 lhs = TREE_OPERAND (e, 0);
412 rhs = TREE_OPERAND (e, 1);
414 else if (TREE_CODE (stmt) == ASM_EXPR)
416 lhs = ASM_OUTPUTS (stmt);
417 rhs = ASM_INPUTS (stmt);
425 if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs)))
427 struct count_ptr_d count;
430 walk_tree (&lhs, count_ptr_derefs, &count, NULL);
432 *num_derefs_p = count.count;
435 if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs)))
437 struct count_ptr_d count;
440 walk_tree (&rhs, count_ptr_derefs, &count, NULL);
441 *num_derefs_p += count.count;
445 gcc_assert (*num_uses_p >= *num_derefs_p);
448 /* Initialize the data structures used for alias analysis. */
450 static struct alias_info *
451 init_alias_info (void)
453 struct alias_info *ai;
454 referenced_var_iterator rvi;
457 bitmap_obstack_initialize (&alias_obstack);
458 ai = xcalloc (1, sizeof (struct alias_info));
459 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
460 sbitmap_zero (ai->ssa_names_visited);
461 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
462 ai->written_vars = BITMAP_ALLOC (&alias_obstack);
463 ai->dereferenced_ptrs_store = BITMAP_ALLOC (&alias_obstack);
464 ai->dereferenced_ptrs_load = BITMAP_ALLOC (&alias_obstack);
466 /* If aliases have been computed before, clear existing information. */
467 if (aliases_computed_p)
471 /* Similarly, clear the set of addressable variables. In this
472 case, we can just clear the set because addressability is
473 only computed here. */
474 bitmap_clear (addressable_vars);
476 /* Clear flow-insensitive alias information from each symbol. */
477 FOR_EACH_REFERENCED_VAR (var, rvi)
479 var_ann_t ann = var_ann (var);
481 ann->is_alias_tag = 0;
482 ann->may_aliases = NULL;
483 NUM_REFERENCES_CLEAR (ann);
485 /* Since we are about to re-discover call-clobbered
486 variables, clear the call-clobbered flag. Variables that
487 are intrinsically call-clobbered (globals, local statics,
488 etc) will not be marked by the aliasing code, so we can't
489 remove them from CALL_CLOBBERED_VARS.
491 NB: STRUCT_FIELDS are still call clobbered if they are for
492 a global variable, so we *don't* clear their call clobberedness
493 just because they are tags, though we will clear it if they
494 aren't for global variables. */
495 if (ann->mem_tag_kind == NAME_TAG
496 || ann->mem_tag_kind == TYPE_TAG
497 || !is_global_var (var))
498 clear_call_clobbered (var);
501 /* Clear flow-sensitive points-to information from each SSA name. */
502 for (i = 1; i < num_ssa_names; i++)
504 tree name = ssa_name (i);
506 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
509 if (SSA_NAME_PTR_INFO (name))
511 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
513 /* Clear all the flags but keep the name tag to
514 avoid creating new temporaries unnecessarily. If
515 this pointer is found to point to a subset or
516 superset of its former points-to set, then a new
517 tag will need to be created in create_name_tags. */
520 pi->value_escapes_p = 0;
521 pi->is_dereferenced = 0;
523 bitmap_clear (pi->pt_vars);
528 /* Next time, we will need to reset alias information. */
529 aliases_computed_p = true;
535 /* Deallocate memory used by alias analysis. */
538 delete_alias_info (struct alias_info *ai)
541 referenced_var_iterator rvi;
544 sbitmap_free (ai->ssa_names_visited);
545 ai->processed_ptrs = NULL;
547 for (i = 0; i < ai->num_addressable_vars; i++)
548 free (ai->addressable_vars[i]);
550 FOR_EACH_REFERENCED_VAR(var, rvi)
552 var_ann_t ann = var_ann (var);
553 NUM_REFERENCES_CLEAR (ann);
556 free (ai->addressable_vars);
558 for (i = 0; i < ai->num_pointers; i++)
559 free (ai->pointers[i]);
562 BITMAP_FREE (ai->written_vars);
563 BITMAP_FREE (ai->dereferenced_ptrs_store);
564 BITMAP_FREE (ai->dereferenced_ptrs_load);
565 bitmap_obstack_release (&alias_obstack);
568 delete_points_to_sets ();
572 /* Create name tags for all the pointers that have been dereferenced.
573 We only create a name tag for a pointer P if P is found to point to
574 a set of variables (so that we can alias them to *P) or if it is
575 the result of a call to malloc (which means that P cannot point to
576 anything else nor alias any other variable).
578 If two pointers P and Q point to the same set of variables, they
579 are assigned the same name tag. */
582 create_name_tags (void)
586 for (i = 1; i < num_ssa_names; i++)
588 tree ptr = ssa_name (i);
589 struct ptr_info_def *pi;
592 || !POINTER_TYPE_P (TREE_TYPE (ptr))
593 || !SSA_NAME_PTR_INFO (ptr))
596 pi = SSA_NAME_PTR_INFO (ptr);
598 if (pi->pt_anything || !pi->is_dereferenced)
600 /* No name tags for pointers that have not been
601 dereferenced or point to an arbitrary location. */
602 pi->name_mem_tag = NULL_TREE;
606 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
609 tree old_name_tag = pi->name_mem_tag;
611 /* If PTR points to a set of variables, check if we don't
612 have another pointer Q with the same points-to set before
613 creating a tag. If so, use Q's tag instead of creating a
616 This is important for not creating unnecessary symbols
617 and also for copy propagation. If we ever need to
618 propagate PTR into Q or vice-versa, we would run into
619 problems if they both had different name tags because
620 they would have different SSA version numbers (which
621 would force us to take the name tags in and out of SSA). */
622 for (j = 1; j < i; j++)
624 tree q = ssa_name (j);
625 struct ptr_info_def *qi;
627 if (!q || !POINTER_TYPE_P (TREE_TYPE (q)))
630 qi = SSA_NAME_PTR_INFO (q);
635 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
637 pi->name_mem_tag = qi->name_mem_tag;
642 /* If we didn't find a pointer with the same points-to set
643 as PTR, create a new name tag if needed. */
644 if (pi->name_mem_tag == NULL_TREE)
645 pi->name_mem_tag = get_nmt_for (ptr);
647 /* If the new name tag computed for PTR is different than
648 the old name tag that it used to have, then the old tag
649 needs to be removed from the IL, so we mark it for
651 if (old_name_tag && old_name_tag != pi->name_mem_tag)
652 mark_sym_for_renaming (old_name_tag);
656 /* If the pointer does not point to a known spot, we should
658 set_pt_anything (ptr);
662 TREE_THIS_VOLATILE (pi->name_mem_tag)
663 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
665 /* Mark the new name tag for renaming. */
666 mark_sym_for_renaming (pi->name_mem_tag);
671 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
672 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
673 name tag and the variables it points-to are call-clobbered. Finally, if
674 P_i escapes and we could not determine where it points to, then all the
675 variables in the same alias set as *P_i are marked call-clobbered. This
676 is necessary because we must assume that P_i may take the address of any
677 variable in the same alias set. */
680 compute_flow_sensitive_aliasing (struct alias_info *ai)
684 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
686 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
687 if (!find_what_p_points_to (ptr))
688 set_pt_anything (ptr);
693 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
696 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
697 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
698 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
701 if (pi->value_escapes_p || pi->pt_anything)
703 /* If PTR escapes or may point to anything, then its associated
704 memory tags and pointed-to variables are call-clobbered. */
705 if (pi->name_mem_tag)
706 mark_call_clobbered (pi->name_mem_tag);
708 if (v_ann->type_mem_tag)
709 mark_call_clobbered (v_ann->type_mem_tag);
712 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
713 mark_call_clobbered (referenced_var (j));
716 /* Set up aliasing information for PTR's name memory tag (if it has
717 one). Note that only pointers that have been dereferenced will
718 have a name memory tag. */
719 if (pi->name_mem_tag && pi->pt_vars)
720 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
722 add_may_alias (pi->name_mem_tag, referenced_var (j));
723 add_may_alias (v_ann->type_mem_tag, referenced_var (j));
726 /* If the name tag is call clobbered, so is the type tag
727 associated with the base VAR_DECL. */
729 && v_ann->type_mem_tag
730 && is_call_clobbered (pi->name_mem_tag))
731 mark_call_clobbered (v_ann->type_mem_tag);
736 /* Compute type-based alias sets. Traverse all the pointers and
737 addressable variables found in setup_pointers_and_addressables.
739 For every pointer P in AI->POINTERS and addressable variable V in
740 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
741 memory tag (TMT) if their alias sets conflict. V is then marked as
742 an alias tag so that the operand scanner knows that statements
743 containing V have aliased operands. */
746 compute_flow_insensitive_aliasing (struct alias_info *ai)
750 /* Initialize counter for the total number of virtual operands that
751 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
752 threshold set by --params max-alias-vops, we enable alias
754 ai->total_alias_vops = 0;
756 /* For every pointer P, determine which addressable variables may alias
757 with P's type memory tag. */
758 for (i = 0; i < ai->num_pointers; i++)
761 struct alias_map_d *p_map = ai->pointers[i];
762 tree tag = var_ann (p_map->var)->type_mem_tag;
763 var_ann_t tag_ann = var_ann (tag);
765 p_map->total_alias_vops = 0;
766 p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
768 for (j = 0; j < ai->num_addressable_vars; j++)
770 struct alias_map_d *v_map;
773 bool tag_stored_p, var_stored_p;
775 v_map = ai->addressable_vars[j];
777 v_ann = var_ann (var);
779 /* Skip memory tags and variables that have never been
780 written to. We also need to check if the variables are
781 call-clobbered because they may be overwritten by
784 Note this is effectively random accessing elements in
785 the sparse bitset, which can be highly inefficient.
786 So we first check the call_clobbered status of the
787 tag and variable before querying the bitmap. */
788 tag_stored_p = is_call_clobbered (tag)
789 || bitmap_bit_p (ai->written_vars, DECL_UID (tag));
790 var_stored_p = is_call_clobbered (var)
791 || bitmap_bit_p (ai->written_vars, DECL_UID (var));
792 if (!tag_stored_p && !var_stored_p)
795 if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false))
798 size_t num_tag_refs, num_var_refs;
800 num_tag_refs = NUM_REFERENCES (tag_ann);
801 num_var_refs = NUM_REFERENCES (v_ann);
803 /* Add VAR to TAG's may-aliases set. */
805 /* If this is an aggregate, we may have subvariables for it
806 that need to be pointed to. */
807 if (var_can_have_subvars (var)
808 && (svars = get_subvars_for_var (var)))
812 for (sv = svars; sv; sv = sv->next)
814 add_may_alias (tag, sv->var);
815 /* Update the bitmap used to represent TAG's alias set
816 in case we need to group aliases. */
817 bitmap_set_bit (p_map->may_aliases, DECL_UID (sv->var));
822 add_may_alias (tag, var);
823 /* Update the bitmap used to represent TAG's alias set
824 in case we need to group aliases. */
825 bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
828 /* Update the total number of virtual operands due to
829 aliasing. Since we are adding one more alias to TAG's
830 may-aliases set, the total number of virtual operands due
831 to aliasing will be increased by the number of references
832 made to VAR and TAG (every reference to TAG will also
833 count as a reference to VAR). */
834 ai->total_alias_vops += (num_var_refs + num_tag_refs);
835 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
842 /* Since this analysis is based exclusively on symbols, it fails to
843 handle cases where two pointers P and Q have different memory
844 tags with conflicting alias set numbers but no aliased symbols in
847 For example, suppose that we have two memory tags TMT.1 and TMT.2
850 may-aliases (TMT.1) = { a }
851 may-aliases (TMT.2) = { b }
853 and the alias set number of TMT.1 conflicts with that of TMT.2.
854 Since they don't have symbols in common, loads and stores from
855 TMT.1 and TMT.2 will seem independent of each other, which will
856 lead to the optimizers making invalid transformations (see
857 testsuite/gcc.c-torture/execute/pr15262-[12].c).
859 To avoid this problem, we do a final traversal of AI->POINTERS
860 looking for pairs of pointers that have no aliased symbols in
861 common and yet have conflicting alias set numbers. */
862 for (i = 0; i < ai->num_pointers; i++)
865 struct alias_map_d *p_map1 = ai->pointers[i];
866 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
867 bitmap may_aliases1 = p_map1->may_aliases;
869 for (j = i + 1; j < ai->num_pointers; j++)
871 struct alias_map_d *p_map2 = ai->pointers[j];
872 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
873 bitmap may_aliases2 = p_map2->may_aliases;
875 /* If the pointers may not point to each other, do nothing. */
876 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true))
879 /* The two pointers may alias each other. If they already have
880 symbols in common, do nothing. */
881 if (bitmap_intersect_p (may_aliases1, may_aliases2))
884 if (!bitmap_empty_p (may_aliases2))
889 /* Add all the aliases for TAG2 into TAG1's alias set.
890 FIXME, update grouping heuristic counters. */
891 EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi)
892 add_may_alias (tag1, referenced_var (k));
893 bitmap_ior_into (may_aliases1, may_aliases2);
897 /* Since TAG2 does not have any aliases of its own, add
898 TAG2 itself to the alias set of TAG1. */
899 add_may_alias (tag1, tag2);
900 bitmap_set_bit (may_aliases1, DECL_UID (tag2));
906 fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n",
907 get_name (current_function_decl),
908 ai->total_alias_vops);
910 /* Determine if we need to enable alias grouping. */
911 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
916 /* Comparison function for qsort used in group_aliases. */
919 total_alias_vops_cmp (const void *p, const void *q)
921 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
922 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
923 long n1 = (*p1)->total_alias_vops;
924 long n2 = (*p2)->total_alias_vops;
926 /* We want to sort in descending order. */
927 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
930 /* Group all the aliases for TAG to make TAG represent all the
931 variables in its alias set. Update the total number
932 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
933 function will make TAG be the unique alias tag for all the
934 variables in its may-aliases. So, given:
936 may-aliases(TAG) = { V1, V2, V3 }
938 This function will group the variables into:
940 may-aliases(V1) = { TAG }
941 may-aliases(V2) = { TAG }
942 may-aliases(V2) = { TAG } */
945 group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai)
948 var_ann_t tag_ann = var_ann (tag);
949 size_t num_tag_refs = NUM_REFERENCES (tag_ann);
952 EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi)
954 tree var = referenced_var (i);
955 var_ann_t ann = var_ann (var);
957 /* Make TAG the unique alias of VAR. */
958 ann->is_alias_tag = 0;
959 ann->may_aliases = NULL;
961 /* Note that VAR and TAG may be the same if the function has no
962 addressable variables (see the discussion at the end of
963 setup_pointers_and_addressables). */
965 add_may_alias (var, tag);
967 /* Reduce total number of virtual operands contributed
968 by TAG on behalf of VAR. Notice that the references to VAR
969 itself won't be removed. We will merely replace them with
970 references to TAG. */
971 ai->total_alias_vops -= num_tag_refs;
974 /* We have reduced the number of virtual operands that TAG makes on
975 behalf of all the variables formerly aliased with it. However,
976 we have also "removed" all the virtual operands for TAG itself,
977 so we add them back. */
978 ai->total_alias_vops += num_tag_refs;
980 /* TAG no longer has any aliases. */
981 tag_ann->may_aliases = NULL;
985 /* Group may-aliases sets to reduce the number of virtual operands due
988 1- Sort the list of pointers in decreasing number of contributed
991 2- Take the first entry in AI->POINTERS and revert the role of
992 the memory tag and its aliases. Usually, whenever an aliased
993 variable Vi is found to alias with a memory tag T, we add Vi
994 to the may-aliases set for T. Meaning that after alias
995 analysis, we will have:
997 may-aliases(T) = { V1, V2, V3, ..., Vn }
999 This means that every statement that references T, will get 'n'
1000 virtual operands for each of the Vi tags. But, when alias
1001 grouping is enabled, we make T an alias tag and add it to the
1002 alias set of all the Vi variables:
1004 may-aliases(V1) = { T }
1005 may-aliases(V2) = { T }
1007 may-aliases(Vn) = { T }
1009 This has two effects: (a) statements referencing T will only get
1010 a single virtual operand, and, (b) all the variables Vi will now
1011 appear to alias each other. So, we lose alias precision to
1012 improve compile time. But, in theory, a program with such a high
1013 level of aliasing should not be very optimizable in the first
1016 3- Since variables may be in the alias set of more than one
1017 memory tag, the grouping done in step (2) needs to be extended
1018 to all the memory tags that have a non-empty intersection with
1019 the may-aliases set of tag T. For instance, if we originally
1020 had these may-aliases sets:
1022 may-aliases(T) = { V1, V2, V3 }
1023 may-aliases(R) = { V2, V4 }
1025 In step (2) we would have reverted the aliases for T as:
1027 may-aliases(V1) = { T }
1028 may-aliases(V2) = { T }
1029 may-aliases(V3) = { T }
1031 But note that now V2 is no longer aliased with R. We could
1032 add R to may-aliases(V2), but we are in the process of
1033 grouping aliases to reduce virtual operands so what we do is
1034 add V4 to the grouping to obtain:
1036 may-aliases(V1) = { T }
1037 may-aliases(V2) = { T }
1038 may-aliases(V3) = { T }
1039 may-aliases(V4) = { T }
1041 4- If the total number of virtual operands due to aliasing is
1042 still above the threshold set by max-alias-vops, go back to (2). */
1045 group_aliases (struct alias_info *ai)
1049 /* Sort the POINTERS array in descending order of contributed
1050 virtual operands. */
1051 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1052 total_alias_vops_cmp);
1054 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1055 and the tag's may-aliases set. */
1056 for (i = 0; i < ai->num_pointers; i++)
1059 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1060 bitmap tag1_aliases = ai->pointers[i]->may_aliases;
1062 /* Skip tags that have been grouped already. */
1063 if (ai->pointers[i]->grouped_p)
1066 /* See if TAG1 had any aliases in common with other type tags.
1067 If we find a TAG2 with common aliases with TAG1, add TAG2's
1068 aliases into TAG1. */
1069 for (j = i + 1; j < ai->num_pointers; j++)
1071 bitmap tag2_aliases = ai->pointers[j]->may_aliases;
1073 if (bitmap_intersect_p (tag1_aliases, tag2_aliases))
1075 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1077 bitmap_ior_into (tag1_aliases, tag2_aliases);
1079 /* TAG2 does not need its aliases anymore. */
1080 bitmap_clear (tag2_aliases);
1081 var_ann (tag2)->may_aliases = NULL;
1083 /* TAG1 is the unique alias of TAG2. */
1084 add_may_alias (tag2, tag1);
1086 ai->pointers[j]->grouped_p = true;
1090 /* Now group all the aliases we collected into TAG1. */
1091 group_aliases_into (tag1, tag1_aliases, ai);
1093 /* If we've reduced total number of virtual operands below the
1095 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1099 /* Finally, all the variables that have been grouped cannot be in
1100 the may-alias set of name memory tags. Suppose that we have
1101 grouped the aliases in this code so that may-aliases(a) = TMT.20
1105 # a_9 = V_MAY_DEF <a_8>
1107 ... Several modifications to TMT.20 ...
1111 Since p_5 points to 'a', the optimizers will try to propagate 0
1112 into p_5->field, but that is wrong because there have been
1113 modifications to 'TMT.20' in between. To prevent this we have to
1114 replace 'a' with 'TMT.20' in the name tag of p_5. */
1115 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1118 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1119 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1120 varray_type aliases;
1122 if (name_tag == NULL_TREE)
1125 aliases = var_ann (name_tag)->may_aliases;
1126 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1128 tree alias = VARRAY_TREE (aliases, j);
1129 var_ann_t ann = var_ann (alias);
1131 if ((ann->mem_tag_kind == NOT_A_TAG
1132 || ann->mem_tag_kind == STRUCT_FIELD)
1133 && ann->may_aliases)
1137 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1139 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1140 replace_may_alias (name_tag, j, new_alias);
1147 "%s: Total number of aliased vops after grouping: %ld%s\n",
1148 get_name (current_function_decl),
1149 ai->total_alias_vops,
1150 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1154 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1157 create_alias_map_for (tree var, struct alias_info *ai)
1159 struct alias_map_d *alias_map;
1160 alias_map = xcalloc (1, sizeof (*alias_map));
1161 alias_map->var = var;
1162 alias_map->set = get_alias_set (var);
1163 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1167 /* Create memory tags for all the dereferenced pointers and build the
1168 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1169 sets. Based on the address escape and points-to information collected
1170 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1171 variables whose address is not needed anymore. */
1174 setup_pointers_and_addressables (struct alias_info *ai)
1176 size_t n_vars, num_addressable_vars, num_pointers;
1177 referenced_var_iterator rvi;
1179 VEC (tree, heap) *varvec = NULL;
1180 safe_referenced_var_iterator srvi;
1182 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1183 num_addressable_vars = num_pointers = 0;
1185 FOR_EACH_REFERENCED_VAR (var, rvi)
1187 if (may_be_aliased (var))
1188 num_addressable_vars++;
1190 if (POINTER_TYPE_P (TREE_TYPE (var)))
1192 /* Since we don't keep track of volatile variables, assume that
1193 these pointers are used in indirect store operations. */
1194 if (TREE_THIS_VOLATILE (var))
1195 bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var));
1201 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1202 always going to be slightly bigger than we actually need them
1203 because some TREE_ADDRESSABLE variables will be marked
1204 non-addressable below and only pointers with unique type tags are
1205 going to be added to POINTERS. */
1206 ai->addressable_vars = xcalloc (num_addressable_vars,
1207 sizeof (struct alias_map_d *));
1208 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1209 ai->num_addressable_vars = 0;
1210 ai->num_pointers = 0;
1212 /* Since we will be creating type memory tags within this loop, cache the
1213 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1215 n_vars = num_referenced_vars;
1217 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi)
1219 var_ann_t v_ann = var_ann (var);
1222 /* Name memory tags already have flow-sensitive aliasing
1223 information, so they need not be processed by
1224 compute_flow_insensitive_aliasing. Similarly, type memory
1225 tags are already accounted for when we process their
1228 Structure fields, on the other hand, have to have some of this
1229 information processed for them, but it's pointless to mark them
1230 non-addressable (since they are fake variables anyway). */
1231 if (v_ann->mem_tag_kind != NOT_A_TAG
1232 && v_ann->mem_tag_kind != STRUCT_FIELD)
1235 /* Remove the ADDRESSABLE flag from every addressable variable whose
1236 address is not needed anymore. This is caused by the propagation
1237 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1238 removal of dead pointer assignments done by the early scalar
1240 if (TREE_ADDRESSABLE (var))
1242 if (!bitmap_bit_p (addressable_vars, DECL_UID (var))
1243 && TREE_CODE (var) != RESULT_DECL
1244 && !is_global_var (var))
1246 bool okay_to_mark = true;
1248 /* Since VAR is now a regular GIMPLE register, we will need
1249 to rename VAR into SSA afterwards. */
1250 mark_sym_for_renaming (var);
1252 /* If VAR can have sub-variables, and any of its
1253 sub-variables has its address taken, then we cannot
1254 remove the addressable flag from VAR. */
1255 if (var_can_have_subvars (var)
1256 && (svars = get_subvars_for_var (var)))
1260 for (sv = svars; sv; sv = sv->next)
1262 if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var)))
1263 okay_to_mark = false;
1264 mark_sym_for_renaming (sv->var);
1268 /* The address of VAR is not needed, remove the
1269 addressable bit, so that it can be optimized as a
1270 regular variable. */
1272 mark_non_addressable (var);
1276 /* Global variables and addressable locals may be aliased. Create an
1277 entry in ADDRESSABLE_VARS for VAR. */
1278 if (may_be_aliased (var))
1280 create_alias_map_for (var, ai);
1281 mark_sym_for_renaming (var);
1284 /* Add pointer variables that have been dereferenced to the POINTERS
1285 array and create a type memory tag for them. */
1286 if (POINTER_TYPE_P (TREE_TYPE (var)))
1288 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))
1289 || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var))))
1294 /* If pointer VAR still doesn't have a memory tag
1295 associated with it, create it now or re-use an
1297 tag = get_tmt_for (var, ai);
1298 t_ann = var_ann (tag);
1300 /* The type tag will need to be renamed into SSA
1301 afterwards. Note that we cannot do this inside
1302 get_tmt_for because aliasing may run multiple times
1303 and we only create type tags the first time. */
1304 mark_sym_for_renaming (tag);
1306 /* Similarly, if pointer VAR used to have another type
1307 tag, we will need to process it in the renamer to
1308 remove the stale virtual operands. */
1309 if (v_ann->type_mem_tag)
1310 mark_sym_for_renaming (v_ann->type_mem_tag);
1312 /* Associate the tag with pointer VAR. */
1313 v_ann->type_mem_tag = tag;
1315 /* If pointer VAR has been used in a store operation,
1316 then its memory tag must be marked as written-to. */
1317 if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)))
1318 bitmap_set_bit (ai->written_vars, DECL_UID (tag));
1320 /* If pointer VAR is a global variable or a PARM_DECL,
1321 then its memory tag should be considered a global
1323 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1324 mark_call_clobbered (tag);
1326 /* All the dereferences of pointer VAR count as
1327 references of TAG. Since TAG can be associated with
1328 several pointers, add the dereferences of VAR to the
1330 NUM_REFERENCES_SET (t_ann,
1331 NUM_REFERENCES (t_ann)
1332 + NUM_REFERENCES (v_ann));
1336 /* The pointer has not been dereferenced. If it had a
1337 type memory tag, remove it and mark the old tag for
1338 renaming to remove it out of the IL. */
1339 var_ann_t ann = var_ann (var);
1340 tree tag = ann->type_mem_tag;
1343 mark_sym_for_renaming (tag);
1344 ann->type_mem_tag = NULL_TREE;
1349 VEC_free (tree, heap, varvec);
1353 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1354 every call site, we need to emit V_MAY_DEF expressions to represent the
1355 clobbering effects of the call for variables whose address escapes the
1358 One approach is to group all call-clobbered variables into a single
1359 representative that is used as an alias of every call-clobbered variable
1360 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1361 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1363 The second approach is to emit a clobbering V_MAY_DEF for every
1364 call-clobbered variable at call sites. This is the preferred way in terms
1365 of optimization opportunities but it may create too many V_MAY_DEF operands
1366 if there are many call clobbered variables and function calls in the
1369 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1370 function calls found by the number of call-clobbered variables. If that
1371 product is beyond a certain threshold, as determined by the parameterized
1372 values shown below, we use .GLOBAL_VAR.
1374 FIXME. This heuristic should be improved. One idea is to use several
1375 .GLOBAL_VARs of different types instead of a single one. The thresholds
1376 have been derived from a typical bootstrap cycle, including all target
1377 libraries. Compile times were found increase by ~1% compared to using
1381 maybe_create_global_var (struct alias_info *ai)
1383 unsigned i, n_clobbered;
1386 /* No need to create it, if we have one already. */
1387 if (global_var == NULL_TREE)
1389 /* Count all the call-clobbered variables. */
1391 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1396 /* If the number of virtual operands that would be needed to
1397 model all the call-clobbered variables is larger than
1398 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
1400 Also create .GLOBAL_VAR if there are no call-clobbered
1401 variables and the program contains a mixture of pure/const
1402 and regular function calls. This is to avoid the problem
1403 described in PR 20115:
1406 int func_pure (void) { return X; }
1407 int func_non_pure (int a) { X += a; }
1410 int a = func_pure ();
1416 Since foo() has no call-clobbered variables, there is
1417 no relationship between the calls to func_pure and
1418 func_non_pure. Since func_pure has no side-effects, value
1419 numbering optimizations elide the second call to func_pure.
1420 So, if we have some pure/const and some regular calls in the
1421 program we create .GLOBAL_VAR to avoid missing these
1423 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
1424 || (n_clobbered == 0
1425 && ai->num_calls_found > 0
1426 && ai->num_pure_const_calls_found > 0
1427 && ai->num_calls_found > ai->num_pure_const_calls_found))
1428 create_global_var ();
1431 /* Mark all call-clobbered symbols for renaming. Since the initial
1432 rewrite into SSA ignored all call sites, we may need to rename
1433 .GLOBAL_VAR and the call-clobbered variables. */
1434 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1436 tree var = referenced_var (i);
1438 /* If the function has calls to clobbering functions and
1439 .GLOBAL_VAR has been created, make it an alias for all
1440 call-clobbered variables. */
1441 if (global_var && var != global_var)
1444 add_may_alias (var, global_var);
1445 if (var_can_have_subvars (var)
1446 && (svars = get_subvars_for_var (var)))
1449 for (sv = svars; sv; sv = sv->next)
1450 mark_sym_for_renaming (sv->var);
1454 mark_sym_for_renaming (var);
1459 /* Return TRUE if pointer PTR may point to variable VAR.
1461 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1462 This is needed because when checking for type conflicts we are
1463 interested in the alias set of the memory location pointed-to by
1464 PTR. The alias set of PTR itself is irrelevant.
1466 VAR_ALIAS_SET is the alias set for VAR. */
1469 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1470 tree var, HOST_WIDE_INT var_alias_set,
1471 bool alias_set_only)
1476 alias_stats.alias_queries++;
1477 alias_stats.simple_queries++;
1479 /* By convention, a variable cannot alias itself. */
1480 mem = var_ann (ptr)->type_mem_tag;
1483 alias_stats.alias_noalias++;
1484 alias_stats.simple_resolved++;
1488 /* If -fargument-noalias-global is >1, pointer arguments may
1489 not point to global variables. */
1490 if (flag_argument_noalias > 1 && is_global_var (var)
1491 && TREE_CODE (ptr) == PARM_DECL)
1493 alias_stats.alias_noalias++;
1494 alias_stats.simple_resolved++;
1498 /* If either MEM or VAR is a read-only global and the other one
1499 isn't, then PTR cannot point to VAR. */
1500 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
1501 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
1503 alias_stats.alias_noalias++;
1504 alias_stats.simple_resolved++;
1508 m_ann = var_ann (mem);
1510 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1512 alias_stats.tbaa_queries++;
1514 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1515 PTR can't possibly affect VAR. Note, that we are specifically testing
1516 for PTR's alias set here, not its pointed-to type. We also can't
1517 do this check with relaxed aliasing enabled. */
1518 if (POINTER_TYPE_P (TREE_TYPE (var))
1519 && var_alias_set != 0
1520 && mem_alias_set != 0)
1522 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1523 if (ptr_alias_set == var_alias_set)
1525 alias_stats.alias_noalias++;
1526 alias_stats.tbaa_resolved++;
1531 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1532 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1534 alias_stats.alias_noalias++;
1535 alias_stats.tbaa_resolved++;
1539 /* If var is a record or union type, ptr cannot point into var
1540 unless there is some operation explicit address operation in the
1541 program that can reference a field of the ptr's dereferenced
1542 type. This also assumes that the types of both var and ptr are
1543 contained within the compilation unit, and that there is no fancy
1544 addressing arithmetic associated with any of the types
1547 if ((mem_alias_set != 0) && (var_alias_set != 0))
1549 tree ptr_type = TREE_TYPE (ptr);
1550 tree var_type = TREE_TYPE (var);
1552 /* The star count is -1 if the type at the end of the pointer_to
1553 chain is not a record or union type. */
1554 if ((!alias_set_only) &&
1555 ipa_type_escape_star_count_of_interesting_type (var_type) >= 0)
1557 int ptr_star_count = 0;
1559 /* Ipa_type_escape_star_count_of_interesting_type is a little to
1560 restrictive for the pointer type, need to allow pointers to
1561 primitive types as long as those types cannot be pointers
1563 while (POINTER_TYPE_P (ptr_type))
1564 /* Strip the *'s off. */
1566 ptr_type = TREE_TYPE (ptr_type);
1570 /* There does not appear to be a better test to see if the
1571 pointer type was one of the pointer to everything
1574 if (ptr_star_count > 0)
1576 alias_stats.structnoaddress_queries++;
1577 if (ipa_type_escape_field_does_not_clobber_p (var_type,
1580 alias_stats.structnoaddress_resolved++;
1581 alias_stats.alias_noalias++;
1585 else if (ptr_star_count == 0)
1587 /* If ptr_type was not really a pointer to type, it cannot
1589 alias_stats.structnoaddress_queries++;
1590 alias_stats.structnoaddress_resolved++;
1591 alias_stats.alias_noalias++;
1597 alias_stats.alias_mayalias++;
1602 /* Add ALIAS to the set of variables that may alias VAR. */
1605 add_may_alias (tree var, tree alias)
1608 var_ann_t v_ann = get_var_ann (var);
1609 var_ann_t a_ann = get_var_ann (alias);
1611 /* Don't allow self-referential aliases. */
1612 gcc_assert (var != alias);
1614 /* ALIAS must be addressable if it's being added to an alias set. */
1616 TREE_ADDRESSABLE (alias) = 1;
1618 gcc_assert (may_be_aliased (alias));
1621 if (v_ann->may_aliases == NULL)
1622 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1624 /* Avoid adding duplicates. */
1625 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1626 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1629 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1630 FIXME, call-clobbering should only depend on whether an address
1631 escapes. It should be independent of aliasing. */
1632 if (is_call_clobbered (var))
1633 mark_call_clobbered (alias);
1635 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1636 else if (is_call_clobbered (alias))
1637 mark_call_clobbered (var);
1639 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1640 a_ann->is_alias_tag = 1;
1644 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1647 replace_may_alias (tree var, size_t i, tree new_alias)
1649 var_ann_t v_ann = var_ann (var);
1650 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1652 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1653 FIXME, call-clobbering should only depend on whether an address
1654 escapes. It should be independent of aliasing. */
1655 if (is_call_clobbered (var))
1656 mark_call_clobbered (new_alias);
1658 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1659 else if (is_call_clobbered (new_alias))
1660 mark_call_clobbered (var);
1664 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1667 set_pt_anything (tree ptr)
1669 struct ptr_info_def *pi = get_ptr_info (ptr);
1671 pi->pt_anything = 1;
1674 /* The pointer used to have a name tag, but we now found it pointing
1675 to an arbitrary location. The name tag needs to be renamed and
1676 disassociated from PTR. */
1677 if (pi->name_mem_tag)
1679 mark_sym_for_renaming (pi->name_mem_tag);
1680 pi->name_mem_tag = NULL_TREE;
1685 /* Return true if STMT is an "escape" site from the current function. Escape
1686 sites those statements which might expose the address of a variable
1687 outside the current function. STMT is an escape site iff:
1689 1- STMT is a function call, or
1690 2- STMT is an __asm__ expression, or
1691 3- STMT is an assignment to a non-local variable, or
1692 4- STMT is a return statement.
1694 AI points to the alias information collected so far. */
1697 is_escape_site (tree stmt, struct alias_info *ai)
1699 tree call = get_call_expr_in (stmt);
1700 if (call != NULL_TREE)
1702 ai->num_calls_found++;
1704 if (!TREE_SIDE_EFFECTS (call))
1705 ai->num_pure_const_calls_found++;
1709 else if (TREE_CODE (stmt) == ASM_EXPR)
1711 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1713 tree lhs = TREE_OPERAND (stmt, 0);
1715 /* Get to the base of _REF nodes. */
1716 if (TREE_CODE (lhs) != SSA_NAME)
1717 lhs = get_base_address (lhs);
1719 /* If we couldn't recognize the LHS of the assignment, assume that it
1720 is a non-local store. */
1721 if (lhs == NULL_TREE)
1724 /* If the RHS is a conversion between a pointer and an integer, the
1725 pointer escapes since we can't track the integer. */
1726 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
1727 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
1728 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
1729 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
1730 (TREE_OPERAND (stmt, 1), 0)))
1731 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
1734 /* If the LHS is an SSA name, it can't possibly represent a non-local
1736 if (TREE_CODE (lhs) == SSA_NAME)
1739 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
1740 local variables we cannot be sure if it will escape, because we
1741 don't have information about objects not in SSA form. Need to
1742 implement something along the lines of
1744 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
1745 Midkiff, ``Escape analysis for java,'' in Proceedings of the
1746 Conference on Object-Oriented Programming Systems, Languages, and
1747 Applications (OOPSLA), pp. 1-19, 1999. */
1750 else if (TREE_CODE (stmt) == RETURN_EXPR)
1757 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
1758 is considered to represent all the pointers whose pointed-to types are
1759 in the same alias set class. Otherwise, the tag represents a single
1760 SSA_NAME pointer variable. */
1763 create_memory_tag (tree type, bool is_type_tag)
1766 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
1768 /* By default, memory tags are local variables. Alias analysis will
1769 determine whether they should be considered globals. */
1770 DECL_CONTEXT (tag) = current_function_decl;
1772 /* Memory tags are by definition addressable. */
1773 TREE_ADDRESSABLE (tag) = 1;
1775 ann = get_var_ann (tag);
1776 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
1777 ann->type_mem_tag = NULL_TREE;
1779 /* Add the tag to the symbol table. */
1780 add_referenced_tmp_var (tag);
1786 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
1787 This is used if P_i has been found to point to a specific set of
1788 variables or to a non-aliased memory location like the address returned
1789 by malloc functions. */
1792 get_nmt_for (tree ptr)
1794 struct ptr_info_def *pi = get_ptr_info (ptr);
1795 tree tag = pi->name_mem_tag;
1797 if (tag == NULL_TREE)
1798 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
1800 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
1801 then its name tag should be considered a global variable. */
1802 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
1803 || pi->pt_global_mem)
1804 mark_call_clobbered (tag);
1810 /* Return the type memory tag associated to pointer PTR. A memory tag is an
1811 artificial variable that represents the memory location pointed-to by
1812 PTR. It is used to model the effects of pointer de-references on
1813 addressable variables.
1815 AI points to the data gathered during alias analysis. This function
1816 populates the array AI->POINTERS. */
1819 get_tmt_for (tree ptr, struct alias_info *ai)
1823 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
1824 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
1826 /* To avoid creating unnecessary memory tags, only create one memory tag
1827 per alias set class. Note that it may be tempting to group
1828 memory tags based on conflicting alias sets instead of
1829 equivalence. That would be wrong because alias sets are not
1830 necessarily transitive (as demonstrated by the libstdc++ test
1831 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
1832 such that conflicts (A, B) == true and conflicts (A, C) == true,
1833 it does not necessarily follow that conflicts (B, C) == true. */
1834 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
1836 struct alias_map_d *curr = ai->pointers[i];
1837 tree curr_tag = var_ann (curr->var)->type_mem_tag;
1838 if (tag_set == curr->set
1839 && TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (curr_tag)))
1846 /* If VAR cannot alias with any of the existing memory tags, create a new
1847 tag for PTR and add it to the POINTERS array. */
1848 if (tag == NULL_TREE)
1850 struct alias_map_d *alias_map;
1852 /* If PTR did not have a type tag already, create a new TMT.*
1853 artificial variable representing the memory location
1854 pointed-to by PTR. */
1855 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
1856 tag = create_memory_tag (tag_type, true);
1858 tag = var_ann (ptr)->type_mem_tag;
1860 /* Add PTR to the POINTERS array. Note that we are not interested in
1861 PTR's alias set. Instead, we cache the alias set for the memory that
1863 alias_map = xcalloc (1, sizeof (*alias_map));
1864 alias_map->var = ptr;
1865 alias_map->set = tag_set;
1866 ai->pointers[ai->num_pointers++] = alias_map;
1869 /* If the pointed-to type is volatile, so is the tag. */
1870 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
1872 /* Make sure that the type tag has the same alias set as the
1874 gcc_assert (tag_set == get_alias_set (tag));
1876 /* If PTR's pointed-to type is read-only, then TAG's type must also
1878 gcc_assert (TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (tag)));
1884 /* Create GLOBAL_VAR, an artificial global variable to act as a
1885 representative of all the variables that may be clobbered by function
1889 create_global_var (void)
1891 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
1893 DECL_ARTIFICIAL (global_var) = 1;
1894 TREE_READONLY (global_var) = 0;
1895 DECL_EXTERNAL (global_var) = 1;
1896 TREE_STATIC (global_var) = 1;
1897 TREE_USED (global_var) = 1;
1898 DECL_CONTEXT (global_var) = NULL_TREE;
1899 TREE_THIS_VOLATILE (global_var) = 0;
1900 TREE_ADDRESSABLE (global_var) = 0;
1902 add_referenced_tmp_var (global_var);
1903 mark_sym_for_renaming (global_var);
1907 /* Dump alias statistics on FILE. */
1910 dump_alias_stats (FILE *file)
1912 const char *funcname
1913 = lang_hooks.decl_printable_name (current_function_decl, 2);
1914 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
1915 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
1916 fprintf (file, "Total alias mayalias results:\t%u\n",
1917 alias_stats.alias_mayalias);
1918 fprintf (file, "Total alias noalias results:\t%u\n",
1919 alias_stats.alias_noalias);
1920 fprintf (file, "Total simple queries:\t%u\n",
1921 alias_stats.simple_queries);
1922 fprintf (file, "Total simple resolved:\t%u\n",
1923 alias_stats.simple_resolved);
1924 fprintf (file, "Total TBAA queries:\t%u\n",
1925 alias_stats.tbaa_queries);
1926 fprintf (file, "Total TBAA resolved:\t%u\n",
1927 alias_stats.tbaa_resolved);
1928 fprintf (file, "Total non-addressable structure type queries:\t%u\n",
1929 alias_stats.structnoaddress_queries);
1930 fprintf (file, "Total non-addressable structure type resolved:\t%u\n",
1931 alias_stats.structnoaddress_resolved);
1935 /* Dump alias information on FILE. */
1938 dump_alias_info (FILE *file)
1941 const char *funcname
1942 = lang_hooks.decl_printable_name (current_function_decl, 2);
1943 referenced_var_iterator rvi;
1946 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
1948 fprintf (file, "Aliased symbols\n\n");
1950 FOR_EACH_REFERENCED_VAR (var, rvi)
1952 if (may_be_aliased (var))
1953 dump_variable (file, var);
1956 fprintf (file, "\nDereferenced pointers\n\n");
1958 FOR_EACH_REFERENCED_VAR (var, rvi)
1960 var_ann_t ann = var_ann (var);
1961 if (ann->type_mem_tag)
1962 dump_variable (file, var);
1965 fprintf (file, "\nType memory tags\n\n");
1967 FOR_EACH_REFERENCED_VAR (var, rvi)
1969 var_ann_t ann = var_ann (var);
1970 if (ann->mem_tag_kind == TYPE_TAG)
1971 dump_variable (file, var);
1974 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
1976 fprintf (file, "SSA_NAME pointers\n\n");
1977 for (i = 1; i < num_ssa_names; i++)
1979 tree ptr = ssa_name (i);
1980 struct ptr_info_def *pi;
1982 if (ptr == NULL_TREE)
1985 pi = SSA_NAME_PTR_INFO (ptr);
1986 if (!SSA_NAME_IN_FREE_LIST (ptr)
1988 && pi->name_mem_tag)
1989 dump_points_to_info_for (file, ptr);
1992 fprintf (file, "\nName memory tags\n\n");
1994 FOR_EACH_REFERENCED_VAR (var, rvi)
1996 var_ann_t ann = var_ann (var);
1997 if (ann->mem_tag_kind == NAME_TAG)
1998 dump_variable (file, var);
2001 fprintf (file, "\n");
2005 /* Dump alias information on stderr. */
2008 debug_alias_info (void)
2010 dump_alias_info (stderr);
2014 /* Return the alias information associated with pointer T. It creates a
2015 new instance if none existed. */
2017 struct ptr_info_def *
2018 get_ptr_info (tree t)
2020 struct ptr_info_def *pi;
2022 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2024 pi = SSA_NAME_PTR_INFO (t);
2027 pi = ggc_alloc (sizeof (*pi));
2028 memset ((void *)pi, 0, sizeof (*pi));
2029 SSA_NAME_PTR_INFO (t) = pi;
2036 /* Dump points-to information for SSA_NAME PTR into FILE. */
2039 dump_points_to_info_for (FILE *file, tree ptr)
2041 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2043 print_generic_expr (file, ptr, dump_flags);
2047 if (pi->name_mem_tag)
2049 fprintf (file, ", name memory tag: ");
2050 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2053 if (pi->is_dereferenced)
2054 fprintf (file, ", is dereferenced");
2056 if (pi->value_escapes_p)
2057 fprintf (file, ", its value escapes");
2059 if (pi->pt_anything)
2060 fprintf (file, ", points-to anything");
2063 fprintf (file, ", points-to NULL");
2070 fprintf (file, ", points-to vars: { ");
2071 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2073 print_generic_expr (file, referenced_var (ix), dump_flags);
2074 fprintf (file, " ");
2076 fprintf (file, "}");
2080 fprintf (file, "\n");
2084 /* Dump points-to information for VAR into stderr. */
2087 debug_points_to_info_for (tree var)
2089 dump_points_to_info_for (stderr, var);
2093 /* Dump points-to information into FILE. NOTE: This function is slow, as
2094 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2097 dump_points_to_info (FILE *file)
2100 block_stmt_iterator si;
2103 lang_hooks.decl_printable_name (current_function_decl, 2);
2104 referenced_var_iterator rvi;
2107 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2109 /* First dump points-to information for the default definitions of
2110 pointer variables. This is necessary because default definitions are
2111 not part of the code. */
2112 FOR_EACH_REFERENCED_VAR (var, rvi)
2114 if (POINTER_TYPE_P (TREE_TYPE (var)))
2116 tree def = default_def (var);
2118 dump_points_to_info_for (file, def);
2122 /* Dump points-to information for every pointer defined in the program. */
2127 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2129 tree ptr = PHI_RESULT (phi);
2130 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2131 dump_points_to_info_for (file, ptr);
2134 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2136 tree stmt = bsi_stmt (si);
2138 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2139 if (POINTER_TYPE_P (TREE_TYPE (def)))
2140 dump_points_to_info_for (file, def);
2144 fprintf (file, "\n");
2148 /* Dump points-to info pointed by PTO into STDERR. */
2151 debug_points_to_info (void)
2153 dump_points_to_info (stderr);
2156 /* Dump to FILE the list of variables that may be aliasing VAR. */
2159 dump_may_aliases_for (FILE *file, tree var)
2161 varray_type aliases;
2163 if (TREE_CODE (var) == SSA_NAME)
2164 var = SSA_NAME_VAR (var);
2166 aliases = var_ann (var)->may_aliases;
2170 fprintf (file, "{ ");
2171 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2173 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2174 fprintf (file, " ");
2176 fprintf (file, "}");
2181 /* Dump to stderr the list of variables that may be aliasing VAR. */
2184 debug_may_aliases_for (tree var)
2186 dump_may_aliases_for (stderr, var);
2189 /* Return true if VAR may be aliased. */
2192 may_be_aliased (tree var)
2195 if (TREE_ADDRESSABLE (var))
2198 /* Globally visible variables can have their addresses taken by other
2199 translation units. */
2200 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2203 /* Automatic variables can't have their addresses escape any other way.
2204 This must be after the check for global variables, as extern declarations
2205 do not have TREE_STATIC set. */
2206 if (!TREE_STATIC (var))
2209 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2210 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2211 we can only be sure the variable isn't addressable if it's local to the
2212 current function. */
2213 if (flag_unit_at_a_time)
2215 if (decl_function_context (var) == current_function_decl)
2222 /* Add VAR to the list of may-aliases of PTR's type tag. If PTR
2223 doesn't already have a type tag, create one. */
2226 add_type_alias (tree ptr, tree var)
2228 varray_type aliases;
2230 var_ann_t ann = var_ann (ptr);
2232 VEC (tree, heap) *varvec = NULL;
2234 if (ann->type_mem_tag == NULL_TREE)
2237 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2238 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2239 safe_referenced_var_iterator rvi;
2241 /* PTR doesn't have a type tag, create a new one and add VAR to
2242 the new tag's alias set.
2244 FIXME, This is slower than necessary. We need to determine
2245 whether there is another pointer Q with the same alias set as
2246 PTR. This could be sped up by having type tags associated
2248 FOR_EACH_REFERENCED_VAR_SAFE (q, varvec, rvi)
2250 if (POINTER_TYPE_P (TREE_TYPE (q))
2251 && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q))))
2253 /* Found another pointer Q with the same alias set as
2254 the PTR's pointed-to type. If Q has a type tag, use
2255 it. Otherwise, create a new memory tag for PTR. */
2256 var_ann_t ann1 = var_ann (q);
2257 if (ann1->type_mem_tag)
2258 ann->type_mem_tag = ann1->type_mem_tag;
2260 ann->type_mem_tag = create_memory_tag (tag_type, true);
2265 /* Couldn't find any other pointer with a type tag we could use.
2266 Create a new memory tag for PTR. */
2267 ann->type_mem_tag = create_memory_tag (tag_type, true);
2271 /* If VAR is not already PTR's type tag, add it to the may-alias set
2272 for PTR's type tag. */
2273 gcc_assert (var_ann (var)->type_mem_tag == NOT_A_TAG);
2274 tag = ann->type_mem_tag;
2276 /* If VAR has subvars, add the subvars to the tag instead of the
2278 if (var_can_have_subvars (var)
2279 && (svars = get_subvars_for_var (var)))
2282 for (sv = svars; sv; sv = sv->next)
2283 add_may_alias (tag, sv->var);
2286 add_may_alias (tag, var);
2288 /* TAG and its set of aliases need to be marked for renaming. */
2289 mark_sym_for_renaming (tag);
2290 if ((aliases = var_ann (tag)->may_aliases) != NULL)
2293 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2294 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2297 /* If we had grouped aliases, VAR may have aliases of its own. Mark
2298 them for renaming as well. Other statements referencing the
2299 aliases of VAR will need to be updated. */
2300 if ((aliases = var_ann (var)->may_aliases) != NULL)
2303 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2304 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2306 VEC_free (tree, heap, varvec);
2310 /* Create a new type tag for PTR. Construct the may-alias list of this type
2311 tag so that it has the aliasing of VAR.
2313 Note, the set of aliases represented by the new type tag are not marked
2317 new_type_alias (tree ptr, tree var)
2319 var_ann_t p_ann = var_ann (ptr);
2320 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2321 var_ann_t v_ann = var_ann (var);
2325 gcc_assert (p_ann->type_mem_tag == NULL_TREE);
2326 gcc_assert (v_ann->mem_tag_kind == NOT_A_TAG);
2328 /* Add VAR to the may-alias set of PTR's new type tag. If VAR has
2329 subvars, add the subvars to the tag instead of the actual var. */
2330 if (var_can_have_subvars (var)
2331 && (svars = get_subvars_for_var (var)))
2335 tag = create_memory_tag (tag_type, true);
2336 p_ann->type_mem_tag = tag;
2338 for (sv = svars; sv; sv = sv->next)
2339 add_may_alias (tag, sv->var);
2343 /* The following is based on code in add_stmt_operand to ensure that the
2344 same defs/uses/vdefs/vuses will be found after replacing a reference
2345 to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value
2346 is the address of var. */
2347 varray_type aliases = v_ann->may_aliases;
2349 if ((aliases != NULL)
2350 && (VARRAY_ACTIVE_SIZE (aliases) == 1))
2352 tree ali = VARRAY_TREE (aliases, 0);
2354 if (get_var_ann (ali)->mem_tag_kind == TYPE_TAG)
2356 p_ann->type_mem_tag = ali;
2361 tag = create_memory_tag (tag_type, true);
2362 p_ann->type_mem_tag = tag;
2364 if (aliases == NULL)
2365 add_may_alias (tag, var);
2370 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2371 add_may_alias (tag, VARRAY_TREE (aliases, i));
2378 /* This represents the used range of a variable. */
2380 typedef struct used_part
2382 HOST_WIDE_INT minused;
2383 HOST_WIDE_INT maxused;
2384 /* True if we have an explicit use/def of some portion of this variable,
2385 even if it is all of it. i.e. a.b = 5 or temp = a.b. */
2387 /* True if we have an implicit use/def of some portion of this
2388 variable. Implicit uses occur when we can't tell what part we
2389 are referencing, and have to make conservative assumptions. */
2393 /* An array of used_part structures, indexed by variable uid. */
2395 static htab_t used_portions;
2397 struct used_part_map
2403 /* Return true if the uid in the two used part maps are equal. */
2406 used_part_map_eq (const void *va, const void *vb)
2408 const struct used_part_map *a = va, *b = vb;
2409 return (a->uid == b->uid);
2412 /* Hash a from uid in a used_part_map. */
2415 used_part_map_hash (const void *item)
2417 return ((const struct used_part_map *)item)->uid;
2420 /* Free a used part map element. */
2423 free_used_part_map (void *item)
2425 free (((struct used_part_map *)item)->to);
2429 /* Lookup a used_part structure for a UID. */
2432 up_lookup (unsigned int uid)
2434 struct used_part_map *h, in;
2436 h = htab_find_with_hash (used_portions, &in, uid);
2442 /* Insert the pair UID, TO into the used part hashtable. */
2445 up_insert (unsigned int uid, used_part_t to)
2447 struct used_part_map *h;
2450 h = xmalloc (sizeof (struct used_part_map));
2453 loc = htab_find_slot_with_hash (used_portions, h,
2457 *(struct used_part_map **) loc = h;
2461 /* Given a variable uid, UID, get or create the entry in the used portions
2462 table for the variable. */
2465 get_or_create_used_part_for (size_t uid)
2468 if ((up = up_lookup (uid)) == NULL)
2470 up = xcalloc (1, sizeof (struct used_part));
2471 up->minused = INT_MAX;
2473 up->explicit_uses = false;
2474 up->implicit_uses = false;
2481 /* Create and return a structure sub-variable for field FIELD of
2485 create_sft (tree var, tree field)
2488 tree subvar = create_tmp_var_raw (TREE_TYPE (field), "SFT");
2490 /* We need to copy the various flags from VAR to SUBVAR, so that
2491 they are is_global_var iff the original variable was. */
2492 DECL_CONTEXT (subvar) = DECL_CONTEXT (var);
2493 DECL_EXTERNAL (subvar) = DECL_EXTERNAL (var);
2494 TREE_PUBLIC (subvar) = TREE_PUBLIC (var);
2495 TREE_STATIC (subvar) = TREE_STATIC (var);
2496 TREE_READONLY (subvar) = TREE_READONLY (var);
2498 /* Add the new variable to REFERENCED_VARS. */
2499 ann = get_var_ann (subvar);
2500 ann->mem_tag_kind = STRUCT_FIELD;
2501 ann->type_mem_tag = NULL;
2502 add_referenced_tmp_var (subvar);
2508 /* Given an aggregate VAR, create the subvariables that represent its
2512 create_overlap_variables_for (tree var)
2514 VEC(fieldoff_s,heap) *fieldstack = NULL;
2516 size_t uid = DECL_UID (var);
2518 if (!up_lookup (uid))
2521 up = up_lookup (uid);
2522 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL);
2523 if (VEC_length (fieldoff_s, fieldstack) != 0)
2527 bool notokay = false;
2530 HOST_WIDE_INT lastfooffset = -1;
2531 HOST_WIDE_INT lastfosize = -1;
2532 tree lastfotype = NULL_TREE;
2534 /* Not all fields have DECL_SIZE set, and those that don't, we don't
2535 know their size, and thus, can't handle.
2536 The same is true of fields with DECL_SIZE that is not an integer
2537 constant (such as variable sized fields).
2538 Fields with offsets which are not constant will have an offset < 0
2539 We *could* handle fields that are constant sized arrays, but
2540 currently don't. Doing so would require some extra changes to
2541 tree-ssa-operands.c. */
2543 for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
2545 if (!DECL_SIZE (fo->field)
2546 || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
2547 || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
2556 /* The current heuristic we use is as follows:
2557 If the variable has no used portions in this function, no
2558 structure vars are created for it.
2560 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
2561 we always create structure vars for them.
2562 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2563 some explicit uses, we create structure vars for them.
2564 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2565 no explicit uses, we do not create structure vars for them.
2568 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
2569 && !up->explicit_uses)
2571 if (dump_file && (dump_flags & TDF_DETAILS))
2573 fprintf (dump_file, "Variable ");
2574 print_generic_expr (dump_file, var, 0);
2575 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
2580 /* Bail out, if we can't create overlap variables. */
2583 VEC_free (fieldoff_s, heap, fieldstack);
2587 /* Otherwise, create the variables. */
2588 subvars = lookup_subvars_for_var (var);
2590 sort_fieldstack (fieldstack);
2592 for (i = VEC_length (fieldoff_s, fieldstack);
2593 VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
2596 HOST_WIDE_INT fosize;
2599 fosize = TREE_INT_CST_LOW (DECL_SIZE (fo->field));
2600 currfotype = TREE_TYPE (fo->field);
2602 /* If this field isn't in the used portion,
2603 or it has the exact same offset and size as the last
2606 if (((fo->offset <= up->minused
2607 && fo->offset + fosize <= up->minused)
2608 || fo->offset >= up->maxused)
2609 || (fo->offset == lastfooffset
2610 && fosize == lastfosize
2611 && currfotype == lastfotype))
2613 sv = ggc_alloc (sizeof (struct subvar));
2614 sv->offset = fo->offset;
2616 sv->next = *subvars;
2617 sv->var = create_sft (var, fo->field);
2621 fprintf (dump_file, "structure field tag %s created for var %s",
2622 get_name (sv->var), get_name (var));
2623 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
2625 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
2627 fprintf (dump_file, "\n");
2630 lastfotype = currfotype;
2631 lastfooffset = fo->offset;
2632 lastfosize = fosize;
2636 /* Once we have created subvars, the original is no longer call
2637 clobbered on its own. Its call clobbered status depends
2638 completely on the call clobbered status of the subvars.
2640 add_referenced_var in the above loop will take care of
2641 marking subvars of global variables as call clobbered for us
2642 to start, since they are global as well. */
2643 clear_call_clobbered (var);
2646 VEC_free (fieldoff_s, heap, fieldstack);
2650 /* Find the conservative answer to the question of what portions of what
2651 structures are used by this statement. We assume that if we have a
2652 component ref with a known size + offset, that we only need that part
2653 of the structure. For unknown cases, or cases where we do something
2654 to the whole structure, we assume we need to create fields for the
2655 entire structure. */
2658 find_used_portions (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
2660 switch (TREE_CODE (*tp))
2664 HOST_WIDE_INT bitsize;
2665 HOST_WIDE_INT bitpos;
2667 enum machine_mode mode;
2671 ref = get_inner_reference (*tp, &bitsize, &bitpos, &offset, &mode,
2672 &unsignedp, &volatilep, false);
2673 if (DECL_P (ref) && offset == NULL && bitsize != -1)
2675 size_t uid = DECL_UID (ref);
2678 up = get_or_create_used_part_for (uid);
2680 if (bitpos <= up->minused)
2681 up->minused = bitpos;
2682 if ((bitpos + bitsize >= up->maxused))
2683 up->maxused = bitpos + bitsize;
2685 up->explicit_uses = true;
2686 up_insert (uid, up);
2691 else if (DECL_P (ref))
2694 && var_can_have_subvars (ref)
2695 && TREE_CODE (DECL_SIZE (ref)) == INTEGER_CST)
2698 size_t uid = DECL_UID (ref);
2700 up = get_or_create_used_part_for (uid);
2703 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (ref));
2705 up->implicit_uses = true;
2707 up_insert (uid, up);
2715 /* This is here to make sure we mark the entire base variable as used
2716 when you take its address. Because our used portion analysis is
2717 simple, we aren't looking at casts or pointer arithmetic to see what
2718 happens when you take the address. */
2721 tree var = get_base_address (TREE_OPERAND (*tp, 0));
2726 && var_can_have_subvars (var)
2727 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
2730 size_t uid = DECL_UID (var);
2732 up = get_or_create_used_part_for (uid);
2735 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
2736 up->implicit_uses = true;
2738 up_insert (uid, up);
2749 && var_can_have_subvars (var)
2750 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
2753 size_t uid = DECL_UID (var);
2755 up = get_or_create_used_part_for (uid);
2758 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
2759 up->implicit_uses = true;
2761 up_insert (uid, up);
2775 /* Create structure field variables for structures used in this function. */
2778 create_structure_vars (void)
2781 safe_referenced_var_iterator rvi;
2782 VEC (tree, heap) *varvec = NULL;
2785 used_portions = htab_create (10, used_part_map_hash, used_part_map_eq,
2786 free_used_part_map);
2790 block_stmt_iterator bsi;
2791 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
2793 walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
2798 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, rvi)
2800 /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
2803 && var_can_have_subvars (var)
2804 && var_ann (var)->mem_tag_kind == NOT_A_TAG
2805 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
2806 create_overlap_variables_for (var);
2808 htab_delete (used_portions);
2809 VEC_free (tree, heap, varvec);
2814 gate_structure_vars (void)
2816 return flag_tree_salias != 0;
2819 struct tree_opt_pass pass_create_structure_vars =
2821 "salias", /* name */
2822 gate_structure_vars, /* gate */
2823 create_structure_vars, /* execute */
2826 0, /* static_pass_number */
2828 PROP_cfg, /* properties_required */
2829 0, /* properties_provided */
2830 0, /* properties_destroyed */
2831 0, /* todo_flags_start */
2832 TODO_dump_func, /* todo_flags_finish */