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 delete_old_heap_vars ();
257 /* Initialize aliasing information. */
258 ai = init_alias_info ();
260 /* For each pointer P_i, determine the sets of variables that P_i may
261 point-to. For every addressable variable V, determine whether the
262 address of V escapes the current function, making V call-clobbered
263 (i.e., whether &V is stored in a global variable or if its passed as a
264 function call argument). */
265 compute_points_to_sets (ai);
267 /* Collect all pointers and addressable variables, compute alias sets,
268 create memory tags for pointers and promote variables whose address is
269 not needed anymore. */
270 setup_pointers_and_addressables (ai);
272 /* Compute flow-sensitive, points-to based aliasing for all the name
273 memory tags. Note that this pass needs to be done before flow
274 insensitive analysis because it uses the points-to information
275 gathered before to mark call-clobbered type tags. */
276 compute_flow_sensitive_aliasing (ai);
278 /* Compute type-based flow-insensitive aliasing for all the type
280 compute_flow_insensitive_aliasing (ai);
282 /* If the program has too many call-clobbered variables and/or function
283 calls, create .GLOBAL_VAR and use it to model call-clobbering
284 semantics at call sites. This reduces the number of virtual operands
285 considerably, improving compile times at the expense of lost
286 aliasing precision. */
287 maybe_create_global_var (ai);
289 /* Debugging dumps. */
292 dump_referenced_vars (dump_file);
293 if (dump_flags & TDF_STATS)
294 dump_alias_stats (dump_file);
295 dump_points_to_info (dump_file);
296 dump_alias_info (dump_file);
299 /* Deallocate memory used by aliasing data structures. */
300 delete_alias_info (ai);
303 block_stmt_iterator bsi;
307 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
309 update_stmt_if_modified (bsi_stmt (bsi));
316 struct tree_opt_pass pass_may_alias =
320 compute_may_aliases, /* execute */
323 0, /* static_pass_number */
324 TV_TREE_MAY_ALIAS, /* tv_id */
325 PROP_cfg | PROP_ssa, /* properties_required */
326 PROP_alias, /* properties_provided */
327 0, /* properties_destroyed */
328 0, /* todo_flags_start */
329 TODO_dump_func | TODO_update_ssa
330 | TODO_ggc_collect | TODO_verify_ssa
331 | TODO_verify_stmts, /* todo_flags_finish */
336 /* Data structure used to count the number of dereferences to PTR
337 inside an expression. */
345 /* Helper for count_uses_and_derefs. Called by walk_tree to look for
346 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
349 count_ptr_derefs (tree *tp, int *walk_subtrees, void *data)
351 struct count_ptr_d *count_p = (struct count_ptr_d *) data;
353 /* Do not walk inside ADDR_EXPR nodes. In the expression &ptr->fld,
354 pointer 'ptr' is *not* dereferenced, it is simply used to compute
355 the address of 'fld' as 'ptr + offsetof(fld)'. */
356 if (TREE_CODE (*tp) == ADDR_EXPR)
362 if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
369 /* Count the number of direct and indirect uses for pointer PTR in
370 statement STMT. The two counts are stored in *NUM_USES_P and
371 *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
372 least one of those dereferences is a store operation. */
375 count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
376 unsigned *num_derefs_p, bool *is_store)
385 /* Find out the total number of uses of PTR in STMT. */
386 FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
390 /* Now count the number of indirect references to PTR. This is
391 truly awful, but we don't have much choice. There are no parent
392 pointers inside INDIRECT_REFs, so an expression like
393 '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
394 find all the indirect and direct uses of x_1 inside. The only
395 shortcut we can take is the fact that GIMPLE only allows
396 INDIRECT_REFs inside the expressions below. */
397 if (TREE_CODE (stmt) == MODIFY_EXPR
398 || (TREE_CODE (stmt) == RETURN_EXPR
399 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
400 || TREE_CODE (stmt) == ASM_EXPR
401 || TREE_CODE (stmt) == CALL_EXPR)
405 if (TREE_CODE (stmt) == MODIFY_EXPR)
407 lhs = TREE_OPERAND (stmt, 0);
408 rhs = TREE_OPERAND (stmt, 1);
410 else if (TREE_CODE (stmt) == RETURN_EXPR)
412 tree e = TREE_OPERAND (stmt, 0);
413 lhs = TREE_OPERAND (e, 0);
414 rhs = TREE_OPERAND (e, 1);
416 else if (TREE_CODE (stmt) == ASM_EXPR)
418 lhs = ASM_OUTPUTS (stmt);
419 rhs = ASM_INPUTS (stmt);
427 if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs)))
429 struct count_ptr_d count;
432 walk_tree (&lhs, count_ptr_derefs, &count, NULL);
434 *num_derefs_p = count.count;
437 if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs)))
439 struct count_ptr_d count;
442 walk_tree (&rhs, count_ptr_derefs, &count, NULL);
443 *num_derefs_p += count.count;
447 gcc_assert (*num_uses_p >= *num_derefs_p);
450 /* Initialize the data structures used for alias analysis. */
452 static struct alias_info *
453 init_alias_info (void)
455 struct alias_info *ai;
456 referenced_var_iterator rvi;
459 bitmap_obstack_initialize (&alias_obstack);
460 ai = xcalloc (1, sizeof (struct alias_info));
461 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
462 sbitmap_zero (ai->ssa_names_visited);
463 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
464 ai->written_vars = BITMAP_ALLOC (&alias_obstack);
465 ai->dereferenced_ptrs_store = BITMAP_ALLOC (&alias_obstack);
466 ai->dereferenced_ptrs_load = BITMAP_ALLOC (&alias_obstack);
468 /* If aliases have been computed before, clear existing information. */
469 if (aliases_computed_p)
473 /* Similarly, clear the set of addressable variables. In this
474 case, we can just clear the set because addressability is
475 only computed here. */
476 bitmap_clear (addressable_vars);
478 /* Clear flow-insensitive alias information from each symbol. */
479 FOR_EACH_REFERENCED_VAR (var, rvi)
481 var_ann_t ann = var_ann (var);
483 ann->is_alias_tag = 0;
484 ann->may_aliases = NULL;
485 NUM_REFERENCES_CLEAR (ann);
487 /* Since we are about to re-discover call-clobbered
488 variables, clear the call-clobbered flag. Variables that
489 are intrinsically call-clobbered (globals, local statics,
490 etc) will not be marked by the aliasing code, so we can't
491 remove them from CALL_CLOBBERED_VARS.
493 NB: STRUCT_FIELDS are still call clobbered if they are for
494 a global variable, so we *don't* clear their call clobberedness
495 just because they are tags, though we will clear it if they
496 aren't for global variables. */
497 if (ann->mem_tag_kind == NAME_TAG
498 || ann->mem_tag_kind == TYPE_TAG
499 || !is_global_var (var))
500 clear_call_clobbered (var);
503 /* Clear flow-sensitive points-to information from each SSA name. */
504 for (i = 1; i < num_ssa_names; i++)
506 tree name = ssa_name (i);
508 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
511 if (SSA_NAME_PTR_INFO (name))
513 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
515 /* Clear all the flags but keep the name tag to
516 avoid creating new temporaries unnecessarily. If
517 this pointer is found to point to a subset or
518 superset of its former points-to set, then a new
519 tag will need to be created in create_name_tags. */
522 pi->value_escapes_p = 0;
523 pi->is_dereferenced = 0;
525 bitmap_clear (pi->pt_vars);
530 /* Next time, we will need to reset alias information. */
531 aliases_computed_p = true;
537 /* Deallocate memory used by alias analysis. */
540 delete_alias_info (struct alias_info *ai)
543 referenced_var_iterator rvi;
546 sbitmap_free (ai->ssa_names_visited);
547 ai->processed_ptrs = NULL;
549 for (i = 0; i < ai->num_addressable_vars; i++)
550 free (ai->addressable_vars[i]);
552 FOR_EACH_REFERENCED_VAR(var, rvi)
554 var_ann_t ann = var_ann (var);
555 NUM_REFERENCES_CLEAR (ann);
558 free (ai->addressable_vars);
560 for (i = 0; i < ai->num_pointers; i++)
561 free (ai->pointers[i]);
564 BITMAP_FREE (ai->written_vars);
565 BITMAP_FREE (ai->dereferenced_ptrs_store);
566 BITMAP_FREE (ai->dereferenced_ptrs_load);
567 bitmap_obstack_release (&alias_obstack);
570 delete_points_to_sets ();
573 /* Create name tags for all the pointers that have been dereferenced.
574 We only create a name tag for a pointer P if P is found to point to
575 a set of variables (so that we can alias them to *P) or if it is
576 the result of a call to malloc (which means that P cannot point to
577 anything else nor alias any other variable).
579 If two pointers P and Q point to the same set of variables, they
580 are assigned the same name tag. */
583 create_name_tags (void)
586 VEC (tree, heap) *with_ptvars = NULL;
589 /* Collect the list of pointers with a non-empty points to set. */
590 for (i = 1; i < num_ssa_names; i++)
592 tree ptr = ssa_name (i);
593 struct ptr_info_def *pi;
596 || !POINTER_TYPE_P (TREE_TYPE (ptr))
597 || !SSA_NAME_PTR_INFO (ptr))
600 pi = SSA_NAME_PTR_INFO (ptr);
602 if (pi->pt_anything || !pi->is_dereferenced)
604 /* No name tags for pointers that have not been
605 dereferenced or point to an arbitrary location. */
606 pi->name_mem_tag = NULL_TREE;
610 /* Set pt_anything on the pointers without pt_vars filled in so
611 that they are assigned a type tag. */
613 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
614 VEC_safe_push (tree, heap, with_ptvars, ptr);
616 set_pt_anything (ptr);
619 /* If we didn't find any pointers with pt_vars set, we're done. */
623 /* Now go through the pointers with pt_vars, and find a name tag
624 with the same pt_vars as this pointer, or create one if one
626 for (i = 0; VEC_iterate (tree, with_ptvars, i, ptr); i++)
628 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
631 tree old_name_tag = pi->name_mem_tag;
633 /* If PTR points to a set of variables, check if we don't
634 have another pointer Q with the same points-to set before
635 creating a tag. If so, use Q's tag instead of creating a
638 This is important for not creating unnecessary symbols
639 and also for copy propagation. If we ever need to
640 propagate PTR into Q or vice-versa, we would run into
641 problems if they both had different name tags because
642 they would have different SSA version numbers (which
643 would force us to take the name tags in and out of SSA). */
644 for (j = 0; j < i && VEC_iterate (tree, with_ptvars, j, ptr2); j++)
646 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (ptr2);
648 if (bitmap_equal_p (pi->pt_vars, qi->pt_vars))
650 pi->name_mem_tag = qi->name_mem_tag;
655 /* If we didn't find a pointer with the same points-to set
656 as PTR, create a new name tag if needed. */
657 if (pi->name_mem_tag == NULL_TREE)
658 pi->name_mem_tag = get_nmt_for (ptr);
660 /* If the new name tag computed for PTR is different than
661 the old name tag that it used to have, then the old tag
662 needs to be removed from the IL, so we mark it for
664 if (old_name_tag && old_name_tag != pi->name_mem_tag)
665 mark_sym_for_renaming (old_name_tag);
667 TREE_THIS_VOLATILE (pi->name_mem_tag)
668 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
670 /* Mark the new name tag for renaming. */
671 mark_sym_for_renaming (pi->name_mem_tag);
674 VEC_free (tree, heap, with_ptvars);
678 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
679 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
680 name tag and the variables it points-to are call-clobbered. Finally, if
681 P_i escapes and we could not determine where it points to, then all the
682 variables in the same alias set as *P_i are marked call-clobbered. This
683 is necessary because we must assume that P_i may take the address of any
684 variable in the same alias set. */
687 compute_flow_sensitive_aliasing (struct alias_info *ai)
691 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
693 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
694 if (!find_what_p_points_to (ptr))
695 set_pt_anything (ptr);
700 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
703 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
704 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
705 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
708 if (pi->value_escapes_p || pi->pt_anything)
710 /* If PTR escapes or may point to anything, then its associated
711 memory tags and pointed-to variables are call-clobbered. */
712 if (pi->name_mem_tag)
713 mark_call_clobbered (pi->name_mem_tag);
715 if (v_ann->type_mem_tag)
716 mark_call_clobbered (v_ann->type_mem_tag);
719 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
720 mark_call_clobbered (referenced_var (j));
723 /* Set up aliasing information for PTR's name memory tag (if it has
724 one). Note that only pointers that have been dereferenced will
725 have a name memory tag. */
726 if (pi->name_mem_tag && pi->pt_vars)
727 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
729 add_may_alias (pi->name_mem_tag, referenced_var (j));
730 add_may_alias (v_ann->type_mem_tag, referenced_var (j));
733 /* If the name tag is call clobbered, so is the type tag
734 associated with the base VAR_DECL. */
736 && v_ann->type_mem_tag
737 && is_call_clobbered (pi->name_mem_tag))
738 mark_call_clobbered (v_ann->type_mem_tag);
743 /* Compute type-based alias sets. Traverse all the pointers and
744 addressable variables found in setup_pointers_and_addressables.
746 For every pointer P in AI->POINTERS and addressable variable V in
747 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
748 memory tag (TMT) if their alias sets conflict. V is then marked as
749 an alias tag so that the operand scanner knows that statements
750 containing V have aliased operands. */
753 compute_flow_insensitive_aliasing (struct alias_info *ai)
757 /* Initialize counter for the total number of virtual operands that
758 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
759 threshold set by --params max-alias-vops, we enable alias
761 ai->total_alias_vops = 0;
763 /* For every pointer P, determine which addressable variables may alias
764 with P's type memory tag. */
765 for (i = 0; i < ai->num_pointers; i++)
768 struct alias_map_d *p_map = ai->pointers[i];
769 tree tag = var_ann (p_map->var)->type_mem_tag;
770 var_ann_t tag_ann = var_ann (tag);
772 p_map->total_alias_vops = 0;
773 p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
775 for (j = 0; j < ai->num_addressable_vars; j++)
777 struct alias_map_d *v_map;
780 bool tag_stored_p, var_stored_p;
782 v_map = ai->addressable_vars[j];
784 v_ann = var_ann (var);
786 /* Skip memory tags and variables that have never been
787 written to. We also need to check if the variables are
788 call-clobbered because they may be overwritten by
791 Note this is effectively random accessing elements in
792 the sparse bitset, which can be highly inefficient.
793 So we first check the call_clobbered status of the
794 tag and variable before querying the bitmap. */
795 tag_stored_p = is_call_clobbered (tag)
796 || bitmap_bit_p (ai->written_vars, DECL_UID (tag));
797 var_stored_p = is_call_clobbered (var)
798 || bitmap_bit_p (ai->written_vars, DECL_UID (var));
799 if (!tag_stored_p && !var_stored_p)
802 if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false))
804 size_t num_tag_refs, num_var_refs;
806 num_tag_refs = NUM_REFERENCES (tag_ann);
807 num_var_refs = NUM_REFERENCES (v_ann);
809 /* Add VAR to TAG's may-aliases set. */
811 /* We should never have a var with subvars here, because
812 they shouldn't get into the set of addressable vars */
813 gcc_assert (!var_can_have_subvars (var)
814 || get_subvars_for_var (var) == NULL);
816 add_may_alias (tag, var);
817 /* Update the bitmap used to represent TAG's alias set
818 in case we need to group aliases. */
819 bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
821 /* Update the total number of virtual operands due to
822 aliasing. Since we are adding one more alias to TAG's
823 may-aliases set, the total number of virtual operands due
824 to aliasing will be increased by the number of references
825 made to VAR and TAG (every reference to TAG will also
826 count as a reference to VAR). */
827 ai->total_alias_vops += (num_var_refs + num_tag_refs);
828 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
835 /* Since this analysis is based exclusively on symbols, it fails to
836 handle cases where two pointers P and Q have different memory
837 tags with conflicting alias set numbers but no aliased symbols in
840 For example, suppose that we have two memory tags TMT.1 and TMT.2
843 may-aliases (TMT.1) = { a }
844 may-aliases (TMT.2) = { b }
846 and the alias set number of TMT.1 conflicts with that of TMT.2.
847 Since they don't have symbols in common, loads and stores from
848 TMT.1 and TMT.2 will seem independent of each other, which will
849 lead to the optimizers making invalid transformations (see
850 testsuite/gcc.c-torture/execute/pr15262-[12].c).
852 To avoid this problem, we do a final traversal of AI->POINTERS
853 looking for pairs of pointers that have no aliased symbols in
854 common and yet have conflicting alias set numbers. */
855 for (i = 0; i < ai->num_pointers; i++)
858 struct alias_map_d *p_map1 = ai->pointers[i];
859 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
860 bitmap may_aliases1 = p_map1->may_aliases;
862 for (j = i + 1; j < ai->num_pointers; j++)
864 struct alias_map_d *p_map2 = ai->pointers[j];
865 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
866 bitmap may_aliases2 = p_map2->may_aliases;
868 /* If the pointers may not point to each other, do nothing. */
869 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true))
872 /* The two pointers may alias each other. If they already have
873 symbols in common, do nothing. */
874 if (bitmap_intersect_p (may_aliases1, may_aliases2))
877 if (!bitmap_empty_p (may_aliases2))
882 /* Add all the aliases for TAG2 into TAG1's alias set.
883 FIXME, update grouping heuristic counters. */
884 EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi)
885 add_may_alias (tag1, referenced_var (k));
886 bitmap_ior_into (may_aliases1, may_aliases2);
890 /* Since TAG2 does not have any aliases of its own, add
891 TAG2 itself to the alias set of TAG1. */
892 add_may_alias (tag1, tag2);
893 bitmap_set_bit (may_aliases1, DECL_UID (tag2));
899 fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n",
900 get_name (current_function_decl),
901 ai->total_alias_vops);
903 /* Determine if we need to enable alias grouping. */
904 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
909 /* Comparison function for qsort used in group_aliases. */
912 total_alias_vops_cmp (const void *p, const void *q)
914 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
915 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
916 long n1 = (*p1)->total_alias_vops;
917 long n2 = (*p2)->total_alias_vops;
919 /* We want to sort in descending order. */
920 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
923 /* Group all the aliases for TAG to make TAG represent all the
924 variables in its alias set. Update the total number
925 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
926 function will make TAG be the unique alias tag for all the
927 variables in its may-aliases. So, given:
929 may-aliases(TAG) = { V1, V2, V3 }
931 This function will group the variables into:
933 may-aliases(V1) = { TAG }
934 may-aliases(V2) = { TAG }
935 may-aliases(V2) = { TAG } */
938 group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai)
941 var_ann_t tag_ann = var_ann (tag);
942 size_t num_tag_refs = NUM_REFERENCES (tag_ann);
945 EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi)
947 tree var = referenced_var (i);
948 var_ann_t ann = var_ann (var);
950 /* Make TAG the unique alias of VAR. */
951 ann->is_alias_tag = 0;
952 ann->may_aliases = NULL;
954 /* Note that VAR and TAG may be the same if the function has no
955 addressable variables (see the discussion at the end of
956 setup_pointers_and_addressables). */
958 add_may_alias (var, tag);
960 /* Reduce total number of virtual operands contributed
961 by TAG on behalf of VAR. Notice that the references to VAR
962 itself won't be removed. We will merely replace them with
963 references to TAG. */
964 ai->total_alias_vops -= num_tag_refs;
967 /* We have reduced the number of virtual operands that TAG makes on
968 behalf of all the variables formerly aliased with it. However,
969 we have also "removed" all the virtual operands for TAG itself,
970 so we add them back. */
971 ai->total_alias_vops += num_tag_refs;
973 /* TAG no longer has any aliases. */
974 tag_ann->may_aliases = NULL;
978 /* Group may-aliases sets to reduce the number of virtual operands due
981 1- Sort the list of pointers in decreasing number of contributed
984 2- Take the first entry in AI->POINTERS and revert the role of
985 the memory tag and its aliases. Usually, whenever an aliased
986 variable Vi is found to alias with a memory tag T, we add Vi
987 to the may-aliases set for T. Meaning that after alias
988 analysis, we will have:
990 may-aliases(T) = { V1, V2, V3, ..., Vn }
992 This means that every statement that references T, will get 'n'
993 virtual operands for each of the Vi tags. But, when alias
994 grouping is enabled, we make T an alias tag and add it to the
995 alias set of all the Vi variables:
997 may-aliases(V1) = { T }
998 may-aliases(V2) = { T }
1000 may-aliases(Vn) = { T }
1002 This has two effects: (a) statements referencing T will only get
1003 a single virtual operand, and, (b) all the variables Vi will now
1004 appear to alias each other. So, we lose alias precision to
1005 improve compile time. But, in theory, a program with such a high
1006 level of aliasing should not be very optimizable in the first
1009 3- Since variables may be in the alias set of more than one
1010 memory tag, the grouping done in step (2) needs to be extended
1011 to all the memory tags that have a non-empty intersection with
1012 the may-aliases set of tag T. For instance, if we originally
1013 had these may-aliases sets:
1015 may-aliases(T) = { V1, V2, V3 }
1016 may-aliases(R) = { V2, V4 }
1018 In step (2) we would have reverted the aliases for T as:
1020 may-aliases(V1) = { T }
1021 may-aliases(V2) = { T }
1022 may-aliases(V3) = { T }
1024 But note that now V2 is no longer aliased with R. We could
1025 add R to may-aliases(V2), but we are in the process of
1026 grouping aliases to reduce virtual operands so what we do is
1027 add V4 to the grouping to obtain:
1029 may-aliases(V1) = { T }
1030 may-aliases(V2) = { T }
1031 may-aliases(V3) = { T }
1032 may-aliases(V4) = { T }
1034 4- If the total number of virtual operands due to aliasing is
1035 still above the threshold set by max-alias-vops, go back to (2). */
1038 group_aliases (struct alias_info *ai)
1042 /* Sort the POINTERS array in descending order of contributed
1043 virtual operands. */
1044 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1045 total_alias_vops_cmp);
1047 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1048 and the tag's may-aliases set. */
1049 for (i = 0; i < ai->num_pointers; i++)
1052 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1053 bitmap tag1_aliases = ai->pointers[i]->may_aliases;
1055 /* Skip tags that have been grouped already. */
1056 if (ai->pointers[i]->grouped_p)
1059 /* See if TAG1 had any aliases in common with other type tags.
1060 If we find a TAG2 with common aliases with TAG1, add TAG2's
1061 aliases into TAG1. */
1062 for (j = i + 1; j < ai->num_pointers; j++)
1064 bitmap tag2_aliases = ai->pointers[j]->may_aliases;
1066 if (bitmap_intersect_p (tag1_aliases, tag2_aliases))
1068 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1070 bitmap_ior_into (tag1_aliases, tag2_aliases);
1072 /* TAG2 does not need its aliases anymore. */
1073 bitmap_clear (tag2_aliases);
1074 var_ann (tag2)->may_aliases = NULL;
1076 /* TAG1 is the unique alias of TAG2. */
1077 add_may_alias (tag2, tag1);
1079 ai->pointers[j]->grouped_p = true;
1083 /* Now group all the aliases we collected into TAG1. */
1084 group_aliases_into (tag1, tag1_aliases, ai);
1086 /* If we've reduced total number of virtual operands below the
1088 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1092 /* Finally, all the variables that have been grouped cannot be in
1093 the may-alias set of name memory tags. Suppose that we have
1094 grouped the aliases in this code so that may-aliases(a) = TMT.20
1098 # a_9 = V_MAY_DEF <a_8>
1100 ... Several modifications to TMT.20 ...
1104 Since p_5 points to 'a', the optimizers will try to propagate 0
1105 into p_5->field, but that is wrong because there have been
1106 modifications to 'TMT.20' in between. To prevent this we have to
1107 replace 'a' with 'TMT.20' in the name tag of p_5. */
1108 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1111 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1112 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1113 varray_type aliases;
1115 if (name_tag == NULL_TREE)
1118 aliases = var_ann (name_tag)->may_aliases;
1119 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1121 tree alias = VARRAY_TREE (aliases, j);
1122 var_ann_t ann = var_ann (alias);
1124 if ((ann->mem_tag_kind == NOT_A_TAG
1125 || ann->mem_tag_kind == STRUCT_FIELD)
1126 && ann->may_aliases)
1130 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1132 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1133 replace_may_alias (name_tag, j, new_alias);
1140 "%s: Total number of aliased vops after grouping: %ld%s\n",
1141 get_name (current_function_decl),
1142 ai->total_alias_vops,
1143 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1147 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1150 create_alias_map_for (tree var, struct alias_info *ai)
1152 struct alias_map_d *alias_map;
1153 alias_map = xcalloc (1, sizeof (*alias_map));
1154 alias_map->var = var;
1155 alias_map->set = get_alias_set (var);
1156 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1160 /* Create memory tags for all the dereferenced pointers and build the
1161 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1162 sets. Based on the address escape and points-to information collected
1163 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1164 variables whose address is not needed anymore. */
1167 setup_pointers_and_addressables (struct alias_info *ai)
1169 size_t n_vars, num_addressable_vars, num_pointers;
1170 referenced_var_iterator rvi;
1172 VEC (tree, heap) *varvec = NULL;
1173 safe_referenced_var_iterator srvi;
1175 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1176 num_addressable_vars = num_pointers = 0;
1178 FOR_EACH_REFERENCED_VAR (var, rvi)
1180 if (may_be_aliased (var))
1181 num_addressable_vars++;
1183 if (POINTER_TYPE_P (TREE_TYPE (var)))
1185 /* Since we don't keep track of volatile variables, assume that
1186 these pointers are used in indirect store operations. */
1187 if (TREE_THIS_VOLATILE (var))
1188 bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var));
1194 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1195 always going to be slightly bigger than we actually need them
1196 because some TREE_ADDRESSABLE variables will be marked
1197 non-addressable below and only pointers with unique type tags are
1198 going to be added to POINTERS. */
1199 ai->addressable_vars = xcalloc (num_addressable_vars,
1200 sizeof (struct alias_map_d *));
1201 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1202 ai->num_addressable_vars = 0;
1203 ai->num_pointers = 0;
1205 /* Since we will be creating type memory tags within this loop, cache the
1206 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1208 n_vars = num_referenced_vars;
1210 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi)
1212 var_ann_t v_ann = var_ann (var);
1215 /* Name memory tags already have flow-sensitive aliasing
1216 information, so they need not be processed by
1217 compute_flow_insensitive_aliasing. Similarly, type memory
1218 tags are already accounted for when we process their
1221 Structure fields, on the other hand, have to have some of this
1222 information processed for them, but it's pointless to mark them
1223 non-addressable (since they are fake variables anyway). */
1224 if (v_ann->mem_tag_kind != NOT_A_TAG
1225 && v_ann->mem_tag_kind != STRUCT_FIELD)
1228 /* Remove the ADDRESSABLE flag from every addressable variable whose
1229 address is not needed anymore. This is caused by the propagation
1230 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1231 removal of dead pointer assignments done by the early scalar
1233 if (TREE_ADDRESSABLE (var))
1235 if (!bitmap_bit_p (addressable_vars, DECL_UID (var))
1236 && TREE_CODE (var) != RESULT_DECL
1237 && !is_global_var (var))
1239 bool okay_to_mark = true;
1241 /* Since VAR is now a regular GIMPLE register, we will need
1242 to rename VAR into SSA afterwards. */
1243 mark_sym_for_renaming (var);
1245 /* If VAR can have sub-variables, and any of its
1246 sub-variables has its address taken, then we cannot
1247 remove the addressable flag from VAR. */
1248 if (var_can_have_subvars (var)
1249 && (svars = get_subvars_for_var (var)))
1253 for (sv = svars; sv; sv = sv->next)
1255 if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var)))
1256 okay_to_mark = false;
1257 mark_sym_for_renaming (sv->var);
1261 /* The address of VAR is not needed, remove the
1262 addressable bit, so that it can be optimized as a
1263 regular variable. */
1265 mark_non_addressable (var);
1269 /* Global variables and addressable locals may be aliased. Create an
1270 entry in ADDRESSABLE_VARS for VAR. */
1271 if (may_be_aliased (var)
1272 && (!var_can_have_subvars (var)
1273 || get_subvars_for_var (var) == NULL))
1275 create_alias_map_for (var, ai);
1276 mark_sym_for_renaming (var);
1279 /* Add pointer variables that have been dereferenced to the POINTERS
1280 array and create a type memory tag for them. */
1281 if (POINTER_TYPE_P (TREE_TYPE (var)))
1283 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))
1284 || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var))))
1289 /* If pointer VAR still doesn't have a memory tag
1290 associated with it, create it now or re-use an
1292 tag = get_tmt_for (var, ai);
1293 t_ann = var_ann (tag);
1295 /* The type tag will need to be renamed into SSA
1296 afterwards. Note that we cannot do this inside
1297 get_tmt_for because aliasing may run multiple times
1298 and we only create type tags the first time. */
1299 mark_sym_for_renaming (tag);
1301 /* Similarly, if pointer VAR used to have another type
1302 tag, we will need to process it in the renamer to
1303 remove the stale virtual operands. */
1304 if (v_ann->type_mem_tag)
1305 mark_sym_for_renaming (v_ann->type_mem_tag);
1307 /* Associate the tag with pointer VAR. */
1308 v_ann->type_mem_tag = tag;
1310 /* If pointer VAR has been used in a store operation,
1311 then its memory tag must be marked as written-to. */
1312 if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)))
1313 bitmap_set_bit (ai->written_vars, DECL_UID (tag));
1315 /* If pointer VAR is a global variable or a PARM_DECL,
1316 then its memory tag should be considered a global
1318 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1319 mark_call_clobbered (tag);
1321 /* All the dereferences of pointer VAR count as
1322 references of TAG. Since TAG can be associated with
1323 several pointers, add the dereferences of VAR to the
1325 NUM_REFERENCES_SET (t_ann,
1326 NUM_REFERENCES (t_ann)
1327 + NUM_REFERENCES (v_ann));
1331 /* The pointer has not been dereferenced. If it had a
1332 type memory tag, remove it and mark the old tag for
1333 renaming to remove it out of the IL. */
1334 var_ann_t ann = var_ann (var);
1335 tree tag = ann->type_mem_tag;
1338 mark_sym_for_renaming (tag);
1339 ann->type_mem_tag = NULL_TREE;
1344 VEC_free (tree, heap, varvec);
1348 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1349 every call site, we need to emit V_MAY_DEF expressions to represent the
1350 clobbering effects of the call for variables whose address escapes the
1353 One approach is to group all call-clobbered variables into a single
1354 representative that is used as an alias of every call-clobbered variable
1355 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1356 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1358 The second approach is to emit a clobbering V_MAY_DEF for every
1359 call-clobbered variable at call sites. This is the preferred way in terms
1360 of optimization opportunities but it may create too many V_MAY_DEF operands
1361 if there are many call clobbered variables and function calls in the
1364 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1365 function calls found by the number of call-clobbered variables. If that
1366 product is beyond a certain threshold, as determined by the parameterized
1367 values shown below, we use .GLOBAL_VAR.
1369 FIXME. This heuristic should be improved. One idea is to use several
1370 .GLOBAL_VARs of different types instead of a single one. The thresholds
1371 have been derived from a typical bootstrap cycle, including all target
1372 libraries. Compile times were found increase by ~1% compared to using
1376 maybe_create_global_var (struct alias_info *ai)
1378 unsigned i, n_clobbered;
1381 /* No need to create it, if we have one already. */
1382 if (global_var == NULL_TREE)
1384 /* Count all the call-clobbered variables. */
1386 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1391 /* If the number of virtual operands that would be needed to
1392 model all the call-clobbered variables is larger than
1393 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
1395 Also create .GLOBAL_VAR if there are no call-clobbered
1396 variables and the program contains a mixture of pure/const
1397 and regular function calls. This is to avoid the problem
1398 described in PR 20115:
1401 int func_pure (void) { return X; }
1402 int func_non_pure (int a) { X += a; }
1405 int a = func_pure ();
1411 Since foo() has no call-clobbered variables, there is
1412 no relationship between the calls to func_pure and
1413 func_non_pure. Since func_pure has no side-effects, value
1414 numbering optimizations elide the second call to func_pure.
1415 So, if we have some pure/const and some regular calls in the
1416 program we create .GLOBAL_VAR to avoid missing these
1418 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
1419 || (n_clobbered == 0
1420 && ai->num_calls_found > 0
1421 && ai->num_pure_const_calls_found > 0
1422 && ai->num_calls_found > ai->num_pure_const_calls_found))
1423 create_global_var ();
1426 /* Mark all call-clobbered symbols for renaming. Since the initial
1427 rewrite into SSA ignored all call sites, we may need to rename
1428 .GLOBAL_VAR and the call-clobbered variables. */
1429 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1431 tree var = referenced_var (i);
1433 /* If the function has calls to clobbering functions and
1434 .GLOBAL_VAR has been created, make it an alias for all
1435 call-clobbered variables. */
1436 if (global_var && var != global_var)
1439 add_may_alias (var, global_var);
1440 if (var_can_have_subvars (var)
1441 && (svars = get_subvars_for_var (var)))
1444 for (sv = svars; sv; sv = sv->next)
1445 mark_sym_for_renaming (sv->var);
1449 mark_sym_for_renaming (var);
1454 /* Return TRUE if pointer PTR may point to variable VAR.
1456 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1457 This is needed because when checking for type conflicts we are
1458 interested in the alias set of the memory location pointed-to by
1459 PTR. The alias set of PTR itself is irrelevant.
1461 VAR_ALIAS_SET is the alias set for VAR. */
1464 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1465 tree var, HOST_WIDE_INT var_alias_set,
1466 bool alias_set_only)
1471 alias_stats.alias_queries++;
1472 alias_stats.simple_queries++;
1474 /* By convention, a variable cannot alias itself. */
1475 mem = var_ann (ptr)->type_mem_tag;
1478 alias_stats.alias_noalias++;
1479 alias_stats.simple_resolved++;
1483 /* If -fargument-noalias-global is >1, pointer arguments may
1484 not point to global variables. */
1485 if (flag_argument_noalias > 1 && is_global_var (var)
1486 && TREE_CODE (ptr) == PARM_DECL)
1488 alias_stats.alias_noalias++;
1489 alias_stats.simple_resolved++;
1493 /* If either MEM or VAR is a read-only global and the other one
1494 isn't, then PTR cannot point to VAR. */
1495 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
1496 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
1498 alias_stats.alias_noalias++;
1499 alias_stats.simple_resolved++;
1503 m_ann = var_ann (mem);
1505 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1507 alias_stats.tbaa_queries++;
1509 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1510 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1512 alias_stats.alias_noalias++;
1513 alias_stats.tbaa_resolved++;
1517 /* If var is a record or union type, ptr cannot point into var
1518 unless there is some operation explicit address operation in the
1519 program that can reference a field of the ptr's dereferenced
1520 type. This also assumes that the types of both var and ptr are
1521 contained within the compilation unit, and that there is no fancy
1522 addressing arithmetic associated with any of the types
1525 if ((mem_alias_set != 0) && (var_alias_set != 0))
1527 tree ptr_type = TREE_TYPE (ptr);
1528 tree var_type = TREE_TYPE (var);
1530 /* The star count is -1 if the type at the end of the pointer_to
1531 chain is not a record or union type. */
1532 if ((!alias_set_only) &&
1533 ipa_type_escape_star_count_of_interesting_type (var_type) >= 0)
1535 int ptr_star_count = 0;
1537 /* Ipa_type_escape_star_count_of_interesting_type is a little to
1538 restrictive for the pointer type, need to allow pointers to
1539 primitive types as long as those types cannot be pointers
1541 while (POINTER_TYPE_P (ptr_type))
1542 /* Strip the *'s off. */
1544 ptr_type = TREE_TYPE (ptr_type);
1548 /* There does not appear to be a better test to see if the
1549 pointer type was one of the pointer to everything
1552 if (ptr_star_count > 0)
1554 alias_stats.structnoaddress_queries++;
1555 if (ipa_type_escape_field_does_not_clobber_p (var_type,
1558 alias_stats.structnoaddress_resolved++;
1559 alias_stats.alias_noalias++;
1563 else if (ptr_star_count == 0)
1565 /* If ptr_type was not really a pointer to type, it cannot
1567 alias_stats.structnoaddress_queries++;
1568 alias_stats.structnoaddress_resolved++;
1569 alias_stats.alias_noalias++;
1575 alias_stats.alias_mayalias++;
1580 /* Add ALIAS to the set of variables that may alias VAR. */
1583 add_may_alias (tree var, tree alias)
1586 var_ann_t v_ann = get_var_ann (var);
1587 var_ann_t a_ann = get_var_ann (alias);
1589 /* Don't allow self-referential aliases. */
1590 gcc_assert (var != alias);
1592 /* ALIAS must be addressable if it's being added to an alias set. */
1594 TREE_ADDRESSABLE (alias) = 1;
1596 gcc_assert (may_be_aliased (alias));
1599 if (v_ann->may_aliases == NULL)
1600 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1602 /* Avoid adding duplicates. */
1603 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1604 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1607 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1608 FIXME, call-clobbering should only depend on whether an address
1609 escapes. It should be independent of aliasing. */
1610 if (is_call_clobbered (var))
1611 mark_call_clobbered (alias);
1613 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1614 else if (is_call_clobbered (alias))
1615 mark_call_clobbered (var);
1617 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1618 a_ann->is_alias_tag = 1;
1622 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1625 replace_may_alias (tree var, size_t i, tree new_alias)
1627 var_ann_t v_ann = var_ann (var);
1628 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1630 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1631 FIXME, call-clobbering should only depend on whether an address
1632 escapes. It should be independent of aliasing. */
1633 if (is_call_clobbered (var))
1634 mark_call_clobbered (new_alias);
1636 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1637 else if (is_call_clobbered (new_alias))
1638 mark_call_clobbered (var);
1642 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1645 set_pt_anything (tree ptr)
1647 struct ptr_info_def *pi = get_ptr_info (ptr);
1649 pi->pt_anything = 1;
1652 /* The pointer used to have a name tag, but we now found it pointing
1653 to an arbitrary location. The name tag needs to be renamed and
1654 disassociated from PTR. */
1655 if (pi->name_mem_tag)
1657 mark_sym_for_renaming (pi->name_mem_tag);
1658 pi->name_mem_tag = NULL_TREE;
1663 /* Return true if STMT is an "escape" site from the current function. Escape
1664 sites those statements which might expose the address of a variable
1665 outside the current function. STMT is an escape site iff:
1667 1- STMT is a function call, or
1668 2- STMT is an __asm__ expression, or
1669 3- STMT is an assignment to a non-local variable, or
1670 4- STMT is a return statement.
1672 AI points to the alias information collected so far. */
1675 is_escape_site (tree stmt, struct alias_info *ai)
1677 tree call = get_call_expr_in (stmt);
1678 if (call != NULL_TREE)
1680 ai->num_calls_found++;
1682 if (!TREE_SIDE_EFFECTS (call))
1683 ai->num_pure_const_calls_found++;
1687 else if (TREE_CODE (stmt) == ASM_EXPR)
1689 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1691 tree lhs = TREE_OPERAND (stmt, 0);
1693 /* Get to the base of _REF nodes. */
1694 if (TREE_CODE (lhs) != SSA_NAME)
1695 lhs = get_base_address (lhs);
1697 /* If we couldn't recognize the LHS of the assignment, assume that it
1698 is a non-local store. */
1699 if (lhs == NULL_TREE)
1702 /* If the RHS is a conversion between a pointer and an integer, the
1703 pointer escapes since we can't track the integer. */
1704 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
1705 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
1706 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
1707 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
1708 (TREE_OPERAND (stmt, 1), 0)))
1709 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
1712 /* If the LHS is an SSA name, it can't possibly represent a non-local
1714 if (TREE_CODE (lhs) == SSA_NAME)
1717 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
1718 local variables we cannot be sure if it will escape, because we
1719 don't have information about objects not in SSA form. Need to
1720 implement something along the lines of
1722 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
1723 Midkiff, ``Escape analysis for java,'' in Proceedings of the
1724 Conference on Object-Oriented Programming Systems, Languages, and
1725 Applications (OOPSLA), pp. 1-19, 1999. */
1728 else if (TREE_CODE (stmt) == RETURN_EXPR)
1735 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
1736 is considered to represent all the pointers whose pointed-to types are
1737 in the same alias set class. Otherwise, the tag represents a single
1738 SSA_NAME pointer variable. */
1741 create_memory_tag (tree type, bool is_type_tag)
1744 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
1746 /* By default, memory tags are local variables. Alias analysis will
1747 determine whether they should be considered globals. */
1748 DECL_CONTEXT (tag) = current_function_decl;
1750 /* Memory tags are by definition addressable. */
1751 TREE_ADDRESSABLE (tag) = 1;
1753 ann = get_var_ann (tag);
1754 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
1755 ann->type_mem_tag = NULL_TREE;
1757 /* Add the tag to the symbol table. */
1758 add_referenced_tmp_var (tag);
1764 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
1765 This is used if P_i has been found to point to a specific set of
1766 variables or to a non-aliased memory location like the address returned
1767 by malloc functions. */
1770 get_nmt_for (tree ptr)
1772 struct ptr_info_def *pi = get_ptr_info (ptr);
1773 tree tag = pi->name_mem_tag;
1775 if (tag == NULL_TREE)
1776 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
1778 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
1779 then its name tag should be considered a global variable. */
1780 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
1781 || pi->pt_global_mem)
1782 mark_call_clobbered (tag);
1788 /* Return the type memory tag associated to pointer PTR. A memory tag is an
1789 artificial variable that represents the memory location pointed-to by
1790 PTR. It is used to model the effects of pointer de-references on
1791 addressable variables.
1793 AI points to the data gathered during alias analysis. This function
1794 populates the array AI->POINTERS. */
1797 get_tmt_for (tree ptr, struct alias_info *ai)
1801 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
1802 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
1804 /* To avoid creating unnecessary memory tags, only create one memory tag
1805 per alias set class. Note that it may be tempting to group
1806 memory tags based on conflicting alias sets instead of
1807 equivalence. That would be wrong because alias sets are not
1808 necessarily transitive (as demonstrated by the libstdc++ test
1809 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
1810 such that conflicts (A, B) == true and conflicts (A, C) == true,
1811 it does not necessarily follow that conflicts (B, C) == true. */
1812 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
1814 struct alias_map_d *curr = ai->pointers[i];
1815 tree curr_tag = var_ann (curr->var)->type_mem_tag;
1816 if (tag_set == curr->set
1817 && TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (curr_tag)))
1824 /* If VAR cannot alias with any of the existing memory tags, create a new
1825 tag for PTR and add it to the POINTERS array. */
1826 if (tag == NULL_TREE)
1828 struct alias_map_d *alias_map;
1830 /* If PTR did not have a type tag already, create a new TMT.*
1831 artificial variable representing the memory location
1832 pointed-to by PTR. */
1833 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
1834 tag = create_memory_tag (tag_type, true);
1836 tag = var_ann (ptr)->type_mem_tag;
1838 /* Add PTR to the POINTERS array. Note that we are not interested in
1839 PTR's alias set. Instead, we cache the alias set for the memory that
1841 alias_map = xcalloc (1, sizeof (*alias_map));
1842 alias_map->var = ptr;
1843 alias_map->set = tag_set;
1844 ai->pointers[ai->num_pointers++] = alias_map;
1847 /* If the pointed-to type is volatile, so is the tag. */
1848 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
1850 /* Make sure that the type tag has the same alias set as the
1852 gcc_assert (tag_set == get_alias_set (tag));
1854 /* If PTR's pointed-to type is read-only, then TAG's type must also
1856 gcc_assert (TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (tag)));
1862 /* Create GLOBAL_VAR, an artificial global variable to act as a
1863 representative of all the variables that may be clobbered by function
1867 create_global_var (void)
1869 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
1871 DECL_ARTIFICIAL (global_var) = 1;
1872 TREE_READONLY (global_var) = 0;
1873 DECL_EXTERNAL (global_var) = 1;
1874 TREE_STATIC (global_var) = 1;
1875 TREE_USED (global_var) = 1;
1876 DECL_CONTEXT (global_var) = NULL_TREE;
1877 TREE_THIS_VOLATILE (global_var) = 0;
1878 TREE_ADDRESSABLE (global_var) = 0;
1880 add_referenced_tmp_var (global_var);
1881 mark_sym_for_renaming (global_var);
1885 /* Dump alias statistics on FILE. */
1888 dump_alias_stats (FILE *file)
1890 const char *funcname
1891 = lang_hooks.decl_printable_name (current_function_decl, 2);
1892 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
1893 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
1894 fprintf (file, "Total alias mayalias results:\t%u\n",
1895 alias_stats.alias_mayalias);
1896 fprintf (file, "Total alias noalias results:\t%u\n",
1897 alias_stats.alias_noalias);
1898 fprintf (file, "Total simple queries:\t%u\n",
1899 alias_stats.simple_queries);
1900 fprintf (file, "Total simple resolved:\t%u\n",
1901 alias_stats.simple_resolved);
1902 fprintf (file, "Total TBAA queries:\t%u\n",
1903 alias_stats.tbaa_queries);
1904 fprintf (file, "Total TBAA resolved:\t%u\n",
1905 alias_stats.tbaa_resolved);
1906 fprintf (file, "Total non-addressable structure type queries:\t%u\n",
1907 alias_stats.structnoaddress_queries);
1908 fprintf (file, "Total non-addressable structure type resolved:\t%u\n",
1909 alias_stats.structnoaddress_resolved);
1913 /* Dump alias information on FILE. */
1916 dump_alias_info (FILE *file)
1919 const char *funcname
1920 = lang_hooks.decl_printable_name (current_function_decl, 2);
1921 referenced_var_iterator rvi;
1924 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
1926 fprintf (file, "Aliased symbols\n\n");
1928 FOR_EACH_REFERENCED_VAR (var, rvi)
1930 if (may_be_aliased (var))
1931 dump_variable (file, var);
1934 fprintf (file, "\nDereferenced pointers\n\n");
1936 FOR_EACH_REFERENCED_VAR (var, rvi)
1938 var_ann_t ann = var_ann (var);
1939 if (ann->type_mem_tag)
1940 dump_variable (file, var);
1943 fprintf (file, "\nType memory tags\n\n");
1945 FOR_EACH_REFERENCED_VAR (var, rvi)
1947 var_ann_t ann = var_ann (var);
1948 if (ann->mem_tag_kind == TYPE_TAG)
1949 dump_variable (file, var);
1952 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
1954 fprintf (file, "SSA_NAME pointers\n\n");
1955 for (i = 1; i < num_ssa_names; i++)
1957 tree ptr = ssa_name (i);
1958 struct ptr_info_def *pi;
1960 if (ptr == NULL_TREE)
1963 pi = SSA_NAME_PTR_INFO (ptr);
1964 if (!SSA_NAME_IN_FREE_LIST (ptr)
1966 && pi->name_mem_tag)
1967 dump_points_to_info_for (file, ptr);
1970 fprintf (file, "\nName memory tags\n\n");
1972 FOR_EACH_REFERENCED_VAR (var, rvi)
1974 var_ann_t ann = var_ann (var);
1975 if (ann->mem_tag_kind == NAME_TAG)
1976 dump_variable (file, var);
1979 fprintf (file, "\n");
1983 /* Dump alias information on stderr. */
1986 debug_alias_info (void)
1988 dump_alias_info (stderr);
1992 /* Return the alias information associated with pointer T. It creates a
1993 new instance if none existed. */
1995 struct ptr_info_def *
1996 get_ptr_info (tree t)
1998 struct ptr_info_def *pi;
2000 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2002 pi = SSA_NAME_PTR_INFO (t);
2005 pi = ggc_alloc (sizeof (*pi));
2006 memset ((void *)pi, 0, sizeof (*pi));
2007 SSA_NAME_PTR_INFO (t) = pi;
2014 /* Dump points-to information for SSA_NAME PTR into FILE. */
2017 dump_points_to_info_for (FILE *file, tree ptr)
2019 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2021 print_generic_expr (file, ptr, dump_flags);
2025 if (pi->name_mem_tag)
2027 fprintf (file, ", name memory tag: ");
2028 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2031 if (pi->is_dereferenced)
2032 fprintf (file, ", is dereferenced");
2034 if (pi->value_escapes_p)
2035 fprintf (file, ", its value escapes");
2037 if (pi->pt_anything)
2038 fprintf (file, ", points-to anything");
2041 fprintf (file, ", points-to NULL");
2048 fprintf (file, ", points-to vars: { ");
2049 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2051 print_generic_expr (file, referenced_var (ix), dump_flags);
2052 fprintf (file, " ");
2054 fprintf (file, "}");
2058 fprintf (file, "\n");
2062 /* Dump points-to information for VAR into stderr. */
2065 debug_points_to_info_for (tree var)
2067 dump_points_to_info_for (stderr, var);
2071 /* Dump points-to information into FILE. NOTE: This function is slow, as
2072 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2075 dump_points_to_info (FILE *file)
2078 block_stmt_iterator si;
2081 lang_hooks.decl_printable_name (current_function_decl, 2);
2082 referenced_var_iterator rvi;
2085 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2087 /* First dump points-to information for the default definitions of
2088 pointer variables. This is necessary because default definitions are
2089 not part of the code. */
2090 FOR_EACH_REFERENCED_VAR (var, rvi)
2092 if (POINTER_TYPE_P (TREE_TYPE (var)))
2094 tree def = default_def (var);
2096 dump_points_to_info_for (file, def);
2100 /* Dump points-to information for every pointer defined in the program. */
2105 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2107 tree ptr = PHI_RESULT (phi);
2108 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2109 dump_points_to_info_for (file, ptr);
2112 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2114 tree stmt = bsi_stmt (si);
2116 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2117 if (POINTER_TYPE_P (TREE_TYPE (def)))
2118 dump_points_to_info_for (file, def);
2122 fprintf (file, "\n");
2126 /* Dump points-to info pointed to by PTO into STDERR. */
2129 debug_points_to_info (void)
2131 dump_points_to_info (stderr);
2134 /* Dump to FILE the list of variables that may be aliasing VAR. */
2137 dump_may_aliases_for (FILE *file, tree var)
2139 varray_type aliases;
2141 if (TREE_CODE (var) == SSA_NAME)
2142 var = SSA_NAME_VAR (var);
2144 aliases = var_ann (var)->may_aliases;
2148 fprintf (file, "{ ");
2149 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2151 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2152 fprintf (file, " ");
2154 fprintf (file, "}");
2159 /* Dump to stderr the list of variables that may be aliasing VAR. */
2162 debug_may_aliases_for (tree var)
2164 dump_may_aliases_for (stderr, var);
2167 /* Return true if VAR may be aliased. */
2170 may_be_aliased (tree var)
2173 if (TREE_ADDRESSABLE (var))
2176 /* Globally visible variables can have their addresses taken by other
2177 translation units. */
2178 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2181 /* Automatic variables can't have their addresses escape any other way.
2182 This must be after the check for global variables, as extern declarations
2183 do not have TREE_STATIC set. */
2184 if (!TREE_STATIC (var))
2187 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2188 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2189 we can only be sure the variable isn't addressable if it's local to the
2190 current function. */
2191 if (flag_unit_at_a_time)
2193 if (decl_function_context (var) == current_function_decl)
2200 /* Given two symbols return TRUE if one is in the alias set of the other. */
2202 is_aliased_with (tree tag, tree sym)
2205 varray_type aliases;
2207 if (var_ann (sym)->is_alias_tag)
2209 aliases = var_ann (tag)->may_aliases;
2211 if (aliases == NULL)
2214 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2215 if (VARRAY_TREE (aliases, i) == sym)
2220 aliases = var_ann (sym)->may_aliases;
2222 if (aliases == NULL)
2225 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2226 if (VARRAY_TREE (aliases, i) == tag)
2234 /* Add VAR to the list of may-aliases of PTR's type tag. If PTR
2235 doesn't already have a type tag, create one. */
2238 add_type_alias (tree ptr, tree var)
2240 varray_type aliases;
2242 var_ann_t ann = var_ann (ptr);
2244 VEC (tree, heap) *varvec = NULL;
2246 if (ann->type_mem_tag == NULL_TREE)
2249 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2250 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2251 safe_referenced_var_iterator rvi;
2253 /* PTR doesn't have a type tag, create a new one and add VAR to
2254 the new tag's alias set.
2256 FIXME, This is slower than necessary. We need to determine
2257 whether there is another pointer Q with the same alias set as
2258 PTR. This could be sped up by having type tags associated
2260 FOR_EACH_REFERENCED_VAR_SAFE (q, varvec, rvi)
2262 if (POINTER_TYPE_P (TREE_TYPE (q))
2263 && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q))))
2265 /* Found another pointer Q with the same alias set as
2266 the PTR's pointed-to type. If Q has a type tag, use
2267 it. Otherwise, create a new memory tag for PTR. */
2268 var_ann_t ann1 = var_ann (q);
2269 if (ann1->type_mem_tag)
2270 ann->type_mem_tag = ann1->type_mem_tag;
2272 ann->type_mem_tag = create_memory_tag (tag_type, true);
2277 /* Couldn't find any other pointer with a type tag we could use.
2278 Create a new memory tag for PTR. */
2279 ann->type_mem_tag = create_memory_tag (tag_type, true);
2283 /* If VAR is not already PTR's type tag, add it to the may-alias set
2284 for PTR's type tag. */
2285 gcc_assert (var_ann (var)->type_mem_tag == NOT_A_TAG);
2286 tag = ann->type_mem_tag;
2288 /* If VAR has subvars, add the subvars to the tag instead of the
2290 if (var_can_have_subvars (var)
2291 && (svars = get_subvars_for_var (var)))
2294 for (sv = svars; sv; sv = sv->next)
2295 add_may_alias (tag, sv->var);
2298 add_may_alias (tag, var);
2300 /* TAG and its set of aliases need to be marked for renaming. */
2301 mark_sym_for_renaming (tag);
2302 if ((aliases = var_ann (tag)->may_aliases) != NULL)
2305 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2306 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2309 /* If we had grouped aliases, VAR may have aliases of its own. Mark
2310 them for renaming as well. Other statements referencing the
2311 aliases of VAR will need to be updated. */
2312 if ((aliases = var_ann (var)->may_aliases) != NULL)
2315 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2316 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2318 VEC_free (tree, heap, varvec);
2322 /* Create a new type tag for PTR. Construct the may-alias list of this type
2323 tag so that it has the aliasing of VAR.
2325 Note, the set of aliases represented by the new type tag are not marked
2329 new_type_alias (tree ptr, tree var)
2331 var_ann_t p_ann = var_ann (ptr);
2332 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2333 var_ann_t v_ann = var_ann (var);
2337 gcc_assert (p_ann->type_mem_tag == NULL_TREE);
2338 gcc_assert (v_ann->mem_tag_kind == NOT_A_TAG);
2340 /* Add VAR to the may-alias set of PTR's new type tag. If VAR has
2341 subvars, add the subvars to the tag instead of the actual var. */
2342 if (var_can_have_subvars (var)
2343 && (svars = get_subvars_for_var (var)))
2347 tag = create_memory_tag (tag_type, true);
2348 p_ann->type_mem_tag = tag;
2350 for (sv = svars; sv; sv = sv->next)
2351 add_may_alias (tag, sv->var);
2355 /* The following is based on code in add_stmt_operand to ensure that the
2356 same defs/uses/vdefs/vuses will be found after replacing a reference
2357 to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value
2358 is the address of var. */
2359 varray_type aliases = v_ann->may_aliases;
2361 if ((aliases != NULL)
2362 && (VARRAY_ACTIVE_SIZE (aliases) == 1))
2364 tree ali = VARRAY_TREE (aliases, 0);
2366 if (get_var_ann (ali)->mem_tag_kind == TYPE_TAG)
2368 p_ann->type_mem_tag = ali;
2373 tag = create_memory_tag (tag_type, true);
2374 p_ann->type_mem_tag = tag;
2376 if (aliases == NULL)
2377 add_may_alias (tag, var);
2382 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2383 add_may_alias (tag, VARRAY_TREE (aliases, i));
2390 /* This represents the used range of a variable. */
2392 typedef struct used_part
2394 HOST_WIDE_INT minused;
2395 HOST_WIDE_INT maxused;
2396 /* True if we have an explicit use/def of some portion of this variable,
2397 even if it is all of it. i.e. a.b = 5 or temp = a.b. */
2399 /* True if we have an implicit use/def of some portion of this
2400 variable. Implicit uses occur when we can't tell what part we
2401 are referencing, and have to make conservative assumptions. */
2405 /* An array of used_part structures, indexed by variable uid. */
2407 static htab_t used_portions;
2409 struct used_part_map
2415 /* Return true if the uid in the two used part maps are equal. */
2418 used_part_map_eq (const void *va, const void *vb)
2420 const struct used_part_map *a = va, *b = vb;
2421 return (a->uid == b->uid);
2424 /* Hash a from uid in a used_part_map. */
2427 used_part_map_hash (const void *item)
2429 return ((const struct used_part_map *)item)->uid;
2432 /* Free a used part map element. */
2435 free_used_part_map (void *item)
2437 free (((struct used_part_map *)item)->to);
2441 /* Lookup a used_part structure for a UID. */
2444 up_lookup (unsigned int uid)
2446 struct used_part_map *h, in;
2448 h = htab_find_with_hash (used_portions, &in, uid);
2454 /* Insert the pair UID, TO into the used part hashtable. */
2457 up_insert (unsigned int uid, used_part_t to)
2459 struct used_part_map *h;
2462 h = xmalloc (sizeof (struct used_part_map));
2465 loc = htab_find_slot_with_hash (used_portions, h,
2469 *(struct used_part_map **) loc = h;
2473 /* Given a variable uid, UID, get or create the entry in the used portions
2474 table for the variable. */
2477 get_or_create_used_part_for (size_t uid)
2480 if ((up = up_lookup (uid)) == NULL)
2482 up = xcalloc (1, sizeof (struct used_part));
2483 up->minused = INT_MAX;
2485 up->explicit_uses = false;
2486 up->implicit_uses = false;
2493 /* Create and return a structure sub-variable for field FIELD of
2497 create_sft (tree var, tree field)
2500 tree subvar = create_tmp_var_raw (TREE_TYPE (field), "SFT");
2502 /* We need to copy the various flags from VAR to SUBVAR, so that
2503 they are is_global_var iff the original variable was. */
2504 DECL_CONTEXT (subvar) = DECL_CONTEXT (var);
2505 DECL_EXTERNAL (subvar) = DECL_EXTERNAL (var);
2506 TREE_PUBLIC (subvar) = TREE_PUBLIC (var);
2507 TREE_STATIC (subvar) = TREE_STATIC (var);
2508 TREE_READONLY (subvar) = TREE_READONLY (var);
2510 /* Add the new variable to REFERENCED_VARS. */
2511 ann = get_var_ann (subvar);
2512 ann->mem_tag_kind = STRUCT_FIELD;
2513 ann->type_mem_tag = NULL;
2514 add_referenced_tmp_var (subvar);
2520 /* Given an aggregate VAR, create the subvariables that represent its
2524 create_overlap_variables_for (tree var)
2526 VEC(fieldoff_s,heap) *fieldstack = NULL;
2528 size_t uid = DECL_UID (var);
2530 if (!up_lookup (uid))
2533 up = up_lookup (uid);
2534 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL);
2535 if (VEC_length (fieldoff_s, fieldstack) != 0)
2539 bool notokay = false;
2542 HOST_WIDE_INT lastfooffset = -1;
2543 HOST_WIDE_INT lastfosize = -1;
2544 tree lastfotype = NULL_TREE;
2546 /* Not all fields have DECL_SIZE set, and those that don't, we don't
2547 know their size, and thus, can't handle.
2548 The same is true of fields with DECL_SIZE that is not an integer
2549 constant (such as variable sized fields).
2550 Fields with offsets which are not constant will have an offset < 0
2551 We *could* handle fields that are constant sized arrays, but
2552 currently don't. Doing so would require some extra changes to
2553 tree-ssa-operands.c. */
2555 for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
2557 if (!DECL_SIZE (fo->field)
2558 || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
2559 || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
2568 /* The current heuristic we use is as follows:
2569 If the variable has no used portions in this function, no
2570 structure vars are created for it.
2572 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
2573 we always create structure vars for them.
2574 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2575 some explicit uses, we create structure vars for them.
2576 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2577 no explicit uses, we do not create structure vars for them.
2580 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
2581 && !up->explicit_uses)
2583 if (dump_file && (dump_flags & TDF_DETAILS))
2585 fprintf (dump_file, "Variable ");
2586 print_generic_expr (dump_file, var, 0);
2587 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
2592 /* Bail out, if we can't create overlap variables. */
2595 VEC_free (fieldoff_s, heap, fieldstack);
2599 /* Otherwise, create the variables. */
2600 subvars = lookup_subvars_for_var (var);
2602 sort_fieldstack (fieldstack);
2604 for (i = VEC_length (fieldoff_s, fieldstack);
2605 VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
2608 HOST_WIDE_INT fosize;
2611 fosize = TREE_INT_CST_LOW (DECL_SIZE (fo->field));
2612 currfotype = TREE_TYPE (fo->field);
2614 /* If this field isn't in the used portion,
2615 or it has the exact same offset and size as the last
2618 if (((fo->offset <= up->minused
2619 && fo->offset + fosize <= up->minused)
2620 || fo->offset >= up->maxused)
2621 || (fo->offset == lastfooffset
2622 && fosize == lastfosize
2623 && currfotype == lastfotype))
2625 sv = ggc_alloc (sizeof (struct subvar));
2626 sv->offset = fo->offset;
2628 sv->next = *subvars;
2629 sv->var = create_sft (var, fo->field);
2633 fprintf (dump_file, "structure field tag %s created for var %s",
2634 get_name (sv->var), get_name (var));
2635 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
2637 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
2639 fprintf (dump_file, "\n");
2642 lastfotype = currfotype;
2643 lastfooffset = fo->offset;
2644 lastfosize = fosize;
2648 /* Once we have created subvars, the original is no longer call
2649 clobbered on its own. Its call clobbered status depends
2650 completely on the call clobbered status of the subvars.
2652 add_referenced_var in the above loop will take care of
2653 marking subvars of global variables as call clobbered for us
2654 to start, since they are global as well. */
2655 clear_call_clobbered (var);
2658 VEC_free (fieldoff_s, heap, fieldstack);
2662 /* Find the conservative answer to the question of what portions of what
2663 structures are used by this statement. We assume that if we have a
2664 component ref with a known size + offset, that we only need that part
2665 of the structure. For unknown cases, or cases where we do something
2666 to the whole structure, we assume we need to create fields for the
2667 entire structure. */
2670 find_used_portions (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
2672 switch (TREE_CODE (*tp))
2676 HOST_WIDE_INT bitsize;
2677 HOST_WIDE_INT bitpos;
2679 enum machine_mode mode;
2683 ref = get_inner_reference (*tp, &bitsize, &bitpos, &offset, &mode,
2684 &unsignedp, &volatilep, false);
2685 if (DECL_P (ref) && offset == NULL && bitsize != -1)
2687 size_t uid = DECL_UID (ref);
2690 up = get_or_create_used_part_for (uid);
2692 if (bitpos <= up->minused)
2693 up->minused = bitpos;
2694 if ((bitpos + bitsize >= up->maxused))
2695 up->maxused = bitpos + bitsize;
2697 up->explicit_uses = true;
2698 up_insert (uid, up);
2703 else if (DECL_P (ref))
2706 && var_can_have_subvars (ref)
2707 && TREE_CODE (DECL_SIZE (ref)) == INTEGER_CST)
2710 size_t uid = DECL_UID (ref);
2712 up = get_or_create_used_part_for (uid);
2715 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (ref));
2717 up->implicit_uses = true;
2719 up_insert (uid, up);
2727 /* This is here to make sure we mark the entire base variable as used
2728 when you take its address. Because our used portion analysis is
2729 simple, we aren't looking at casts or pointer arithmetic to see what
2730 happens when you take the address. */
2733 tree var = get_base_address (TREE_OPERAND (*tp, 0));
2738 && var_can_have_subvars (var)
2739 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
2742 size_t uid = DECL_UID (var);
2744 up = get_or_create_used_part_for (uid);
2747 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
2748 up->implicit_uses = true;
2750 up_insert (uid, up);
2762 && var_can_have_subvars (var)
2763 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
2766 size_t uid = DECL_UID (var);
2768 up = get_or_create_used_part_for (uid);
2771 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
2772 up->implicit_uses = true;
2774 up_insert (uid, up);
2788 /* Create structure field variables for structures used in this function. */
2791 create_structure_vars (void)
2794 safe_referenced_var_iterator rvi;
2795 VEC (tree, heap) *varvec = NULL;
2798 used_portions = htab_create (10, used_part_map_hash, used_part_map_eq,
2799 free_used_part_map);
2803 block_stmt_iterator bsi;
2804 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
2806 walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
2811 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, rvi)
2813 /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
2816 && var_can_have_subvars (var)
2817 && var_ann (var)->mem_tag_kind == NOT_A_TAG
2818 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
2819 create_overlap_variables_for (var);
2821 htab_delete (used_portions);
2822 VEC_free (tree, heap, varvec);
2827 gate_structure_vars (void)
2829 return flag_tree_salias != 0;
2832 struct tree_opt_pass pass_create_structure_vars =
2834 "salias", /* name */
2835 gate_structure_vars, /* gate */
2836 create_structure_vars, /* execute */
2839 0, /* static_pass_number */
2841 PROP_cfg, /* properties_required */
2842 0, /* properties_provided */
2843 0, /* properties_destroyed */
2844 0, /* todo_flags_start */
2845 TODO_dump_func, /* todo_flags_finish */