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 = XCNEW (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 (TREE_CODE (var) == NAME_MEMORY_TAG
496 || TREE_CODE (var) == TYPE_MEMORY_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 ();
571 /* Create name tags for all the pointers that have been dereferenced.
572 We only create a name tag for a pointer P if P is found to point to
573 a set of variables (so that we can alias them to *P) or if it is
574 the result of a call to malloc (which means that P cannot point to
575 anything else nor alias any other variable).
577 If two pointers P and Q point to the same set of variables, they
578 are assigned the same name tag. */
581 create_name_tags (void)
584 VEC (tree, heap) *with_ptvars = NULL;
587 /* Collect the list of pointers with a non-empty points to set. */
588 for (i = 1; i < num_ssa_names; i++)
590 tree ptr = ssa_name (i);
591 struct ptr_info_def *pi;
594 || !POINTER_TYPE_P (TREE_TYPE (ptr))
595 || !SSA_NAME_PTR_INFO (ptr))
598 pi = SSA_NAME_PTR_INFO (ptr);
600 if (pi->pt_anything || !pi->is_dereferenced)
602 /* No name tags for pointers that have not been
603 dereferenced or point to an arbitrary location. */
604 pi->name_mem_tag = NULL_TREE;
608 /* Set pt_anything on the pointers without pt_vars filled in so
609 that they are assigned a type tag. */
611 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
612 VEC_safe_push (tree, heap, with_ptvars, ptr);
614 set_pt_anything (ptr);
617 /* If we didn't find any pointers with pt_vars set, we're done. */
621 /* Now go through the pointers with pt_vars, and find a name tag
622 with the same pt_vars as this pointer, or create one if one
624 for (i = 0; VEC_iterate (tree, with_ptvars, i, ptr); i++)
626 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
629 tree old_name_tag = pi->name_mem_tag;
631 /* If PTR points to a set of variables, check if we don't
632 have another pointer Q with the same points-to set before
633 creating a tag. If so, use Q's tag instead of creating a
636 This is important for not creating unnecessary symbols
637 and also for copy propagation. If we ever need to
638 propagate PTR into Q or vice-versa, we would run into
639 problems if they both had different name tags because
640 they would have different SSA version numbers (which
641 would force us to take the name tags in and out of SSA). */
642 for (j = 0; j < i && VEC_iterate (tree, with_ptvars, j, ptr2); j++)
644 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (ptr2);
646 if (bitmap_equal_p (pi->pt_vars, qi->pt_vars))
648 pi->name_mem_tag = qi->name_mem_tag;
653 /* If we didn't find a pointer with the same points-to set
654 as PTR, create a new name tag if needed. */
655 if (pi->name_mem_tag == NULL_TREE)
656 pi->name_mem_tag = get_nmt_for (ptr);
658 /* If the new name tag computed for PTR is different than
659 the old name tag that it used to have, then the old tag
660 needs to be removed from the IL, so we mark it for
662 if (old_name_tag && old_name_tag != pi->name_mem_tag)
663 mark_sym_for_renaming (old_name_tag);
665 TREE_THIS_VOLATILE (pi->name_mem_tag)
666 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
668 /* Mark the new name tag for renaming. */
669 mark_sym_for_renaming (pi->name_mem_tag);
672 VEC_free (tree, heap, with_ptvars);
676 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
677 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
678 name tag and the variables it points-to are call-clobbered. Finally, if
679 P_i escapes and we could not determine where it points to, then all the
680 variables in the same alias set as *P_i are marked call-clobbered. This
681 is necessary because we must assume that P_i may take the address of any
682 variable in the same alias set. */
685 compute_flow_sensitive_aliasing (struct alias_info *ai)
689 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
691 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
692 if (!find_what_p_points_to (ptr))
693 set_pt_anything (ptr);
698 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
701 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
702 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
703 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
706 if (pi->value_escapes_p || pi->pt_anything)
708 /* If PTR escapes or may point to anything, then its associated
709 memory tags and pointed-to variables are call-clobbered. */
710 if (pi->name_mem_tag)
711 mark_call_clobbered (pi->name_mem_tag);
713 if (v_ann->type_mem_tag)
714 mark_call_clobbered (v_ann->type_mem_tag);
717 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
718 mark_call_clobbered (referenced_var (j));
721 /* Set up aliasing information for PTR's name memory tag (if it has
722 one). Note that only pointers that have been dereferenced will
723 have a name memory tag. */
724 if (pi->name_mem_tag && pi->pt_vars)
725 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
727 add_may_alias (pi->name_mem_tag, referenced_var (j));
728 add_may_alias (v_ann->type_mem_tag, referenced_var (j));
731 /* If the name tag is call clobbered, so is the type tag
732 associated with the base VAR_DECL. */
734 && v_ann->type_mem_tag
735 && is_call_clobbered (pi->name_mem_tag))
736 mark_call_clobbered (v_ann->type_mem_tag);
741 /* Compute type-based alias sets. Traverse all the pointers and
742 addressable variables found in setup_pointers_and_addressables.
744 For every pointer P in AI->POINTERS and addressable variable V in
745 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
746 memory tag (TMT) if their alias sets conflict. V is then marked as
747 an alias tag so that the operand scanner knows that statements
748 containing V have aliased operands. */
751 compute_flow_insensitive_aliasing (struct alias_info *ai)
755 /* Initialize counter for the total number of virtual operands that
756 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
757 threshold set by --params max-alias-vops, we enable alias
759 ai->total_alias_vops = 0;
761 /* For every pointer P, determine which addressable variables may alias
762 with P's type memory tag. */
763 for (i = 0; i < ai->num_pointers; i++)
766 struct alias_map_d *p_map = ai->pointers[i];
767 tree tag = var_ann (p_map->var)->type_mem_tag;
768 var_ann_t tag_ann = var_ann (tag);
770 p_map->total_alias_vops = 0;
771 p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
773 for (j = 0; j < ai->num_addressable_vars; j++)
775 struct alias_map_d *v_map;
778 bool tag_stored_p, var_stored_p;
780 v_map = ai->addressable_vars[j];
782 v_ann = var_ann (var);
784 /* Skip memory tags and variables that have never been
785 written to. We also need to check if the variables are
786 call-clobbered because they may be overwritten by
789 Note this is effectively random accessing elements in
790 the sparse bitset, which can be highly inefficient.
791 So we first check the call_clobbered status of the
792 tag and variable before querying the bitmap. */
793 tag_stored_p = is_call_clobbered (tag)
794 || bitmap_bit_p (ai->written_vars, DECL_UID (tag));
795 var_stored_p = is_call_clobbered (var)
796 || bitmap_bit_p (ai->written_vars, DECL_UID (var));
797 if (!tag_stored_p && !var_stored_p)
800 if (may_alias_p (p_map->var, p_map->set, var, v_map->set, false))
802 size_t num_tag_refs, num_var_refs;
804 num_tag_refs = NUM_REFERENCES (tag_ann);
805 num_var_refs = NUM_REFERENCES (v_ann);
807 /* Add VAR to TAG's may-aliases set. */
809 /* We should never have a var with subvars here, because
810 they shouldn't get into the set of addressable vars */
811 gcc_assert (!var_can_have_subvars (var)
812 || get_subvars_for_var (var) == NULL);
814 add_may_alias (tag, 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 (var));
819 /* Update the total number of virtual operands due to
820 aliasing. Since we are adding one more alias to TAG's
821 may-aliases set, the total number of virtual operands due
822 to aliasing will be increased by the number of references
823 made to VAR and TAG (every reference to TAG will also
824 count as a reference to VAR). */
825 ai->total_alias_vops += (num_var_refs + num_tag_refs);
826 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
833 /* Since this analysis is based exclusively on symbols, it fails to
834 handle cases where two pointers P and Q have different memory
835 tags with conflicting alias set numbers but no aliased symbols in
838 For example, suppose that we have two memory tags TMT.1 and TMT.2
841 may-aliases (TMT.1) = { a }
842 may-aliases (TMT.2) = { b }
844 and the alias set number of TMT.1 conflicts with that of TMT.2.
845 Since they don't have symbols in common, loads and stores from
846 TMT.1 and TMT.2 will seem independent of each other, which will
847 lead to the optimizers making invalid transformations (see
848 testsuite/gcc.c-torture/execute/pr15262-[12].c).
850 To avoid this problem, we do a final traversal of AI->POINTERS
851 looking for pairs of pointers that have no aliased symbols in
852 common and yet have conflicting alias set numbers. */
853 for (i = 0; i < ai->num_pointers; i++)
856 struct alias_map_d *p_map1 = ai->pointers[i];
857 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
858 bitmap may_aliases1 = p_map1->may_aliases;
860 for (j = i + 1; j < ai->num_pointers; j++)
862 struct alias_map_d *p_map2 = ai->pointers[j];
863 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
864 bitmap may_aliases2 = p_map2->may_aliases;
866 /* If the pointers may not point to each other, do nothing. */
867 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set, true))
870 /* The two pointers may alias each other. If they already have
871 symbols in common, do nothing. */
872 if (bitmap_intersect_p (may_aliases1, may_aliases2))
875 if (!bitmap_empty_p (may_aliases2))
880 /* Add all the aliases for TAG2 into TAG1's alias set.
881 FIXME, update grouping heuristic counters. */
882 EXECUTE_IF_SET_IN_BITMAP (may_aliases2, 0, k, bi)
883 add_may_alias (tag1, referenced_var (k));
884 bitmap_ior_into (may_aliases1, may_aliases2);
888 /* Since TAG2 does not have any aliases of its own, add
889 TAG2 itself to the alias set of TAG1. */
890 add_may_alias (tag1, tag2);
891 bitmap_set_bit (may_aliases1, DECL_UID (tag2));
897 fprintf (dump_file, "\n%s: Total number of aliased vops: %ld\n",
898 get_name (current_function_decl),
899 ai->total_alias_vops);
901 /* Determine if we need to enable alias grouping. */
902 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
907 /* Comparison function for qsort used in group_aliases. */
910 total_alias_vops_cmp (const void *p, const void *q)
912 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
913 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
914 long n1 = (*p1)->total_alias_vops;
915 long n2 = (*p2)->total_alias_vops;
917 /* We want to sort in descending order. */
918 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
921 /* Group all the aliases for TAG to make TAG represent all the
922 variables in its alias set. Update the total number
923 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
924 function will make TAG be the unique alias tag for all the
925 variables in its may-aliases. So, given:
927 may-aliases(TAG) = { V1, V2, V3 }
929 This function will group the variables into:
931 may-aliases(V1) = { TAG }
932 may-aliases(V2) = { TAG }
933 may-aliases(V2) = { TAG } */
936 group_aliases_into (tree tag, bitmap tag_aliases, struct alias_info *ai)
939 var_ann_t tag_ann = var_ann (tag);
940 size_t num_tag_refs = NUM_REFERENCES (tag_ann);
943 EXECUTE_IF_SET_IN_BITMAP (tag_aliases, 0, i, bi)
945 tree var = referenced_var (i);
946 var_ann_t ann = var_ann (var);
948 /* Make TAG the unique alias of VAR. */
949 ann->is_alias_tag = 0;
950 ann->may_aliases = NULL;
952 /* Note that VAR and TAG may be the same if the function has no
953 addressable variables (see the discussion at the end of
954 setup_pointers_and_addressables). */
956 add_may_alias (var, tag);
958 /* Reduce total number of virtual operands contributed
959 by TAG on behalf of VAR. Notice that the references to VAR
960 itself won't be removed. We will merely replace them with
961 references to TAG. */
962 ai->total_alias_vops -= num_tag_refs;
965 /* We have reduced the number of virtual operands that TAG makes on
966 behalf of all the variables formerly aliased with it. However,
967 we have also "removed" all the virtual operands for TAG itself,
968 so we add them back. */
969 ai->total_alias_vops += num_tag_refs;
971 /* TAG no longer has any aliases. */
972 tag_ann->may_aliases = NULL;
976 /* Group may-aliases sets to reduce the number of virtual operands due
979 1- Sort the list of pointers in decreasing number of contributed
982 2- Take the first entry in AI->POINTERS and revert the role of
983 the memory tag and its aliases. Usually, whenever an aliased
984 variable Vi is found to alias with a memory tag T, we add Vi
985 to the may-aliases set for T. Meaning that after alias
986 analysis, we will have:
988 may-aliases(T) = { V1, V2, V3, ..., Vn }
990 This means that every statement that references T, will get 'n'
991 virtual operands for each of the Vi tags. But, when alias
992 grouping is enabled, we make T an alias tag and add it to the
993 alias set of all the Vi variables:
995 may-aliases(V1) = { T }
996 may-aliases(V2) = { T }
998 may-aliases(Vn) = { T }
1000 This has two effects: (a) statements referencing T will only get
1001 a single virtual operand, and, (b) all the variables Vi will now
1002 appear to alias each other. So, we lose alias precision to
1003 improve compile time. But, in theory, a program with such a high
1004 level of aliasing should not be very optimizable in the first
1007 3- Since variables may be in the alias set of more than one
1008 memory tag, the grouping done in step (2) needs to be extended
1009 to all the memory tags that have a non-empty intersection with
1010 the may-aliases set of tag T. For instance, if we originally
1011 had these may-aliases sets:
1013 may-aliases(T) = { V1, V2, V3 }
1014 may-aliases(R) = { V2, V4 }
1016 In step (2) we would have reverted the aliases for T as:
1018 may-aliases(V1) = { T }
1019 may-aliases(V2) = { T }
1020 may-aliases(V3) = { T }
1022 But note that now V2 is no longer aliased with R. We could
1023 add R to may-aliases(V2), but we are in the process of
1024 grouping aliases to reduce virtual operands so what we do is
1025 add V4 to the grouping to obtain:
1027 may-aliases(V1) = { T }
1028 may-aliases(V2) = { T }
1029 may-aliases(V3) = { T }
1030 may-aliases(V4) = { T }
1032 4- If the total number of virtual operands due to aliasing is
1033 still above the threshold set by max-alias-vops, go back to (2). */
1036 group_aliases (struct alias_info *ai)
1040 /* Sort the POINTERS array in descending order of contributed
1041 virtual operands. */
1042 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1043 total_alias_vops_cmp);
1045 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1046 and the tag's may-aliases set. */
1047 for (i = 0; i < ai->num_pointers; i++)
1050 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1051 bitmap tag1_aliases = ai->pointers[i]->may_aliases;
1053 /* Skip tags that have been grouped already. */
1054 if (ai->pointers[i]->grouped_p)
1057 /* See if TAG1 had any aliases in common with other type tags.
1058 If we find a TAG2 with common aliases with TAG1, add TAG2's
1059 aliases into TAG1. */
1060 for (j = i + 1; j < ai->num_pointers; j++)
1062 bitmap tag2_aliases = ai->pointers[j]->may_aliases;
1064 if (bitmap_intersect_p (tag1_aliases, tag2_aliases))
1066 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1068 bitmap_ior_into (tag1_aliases, tag2_aliases);
1070 /* TAG2 does not need its aliases anymore. */
1071 bitmap_clear (tag2_aliases);
1072 var_ann (tag2)->may_aliases = NULL;
1074 /* TAG1 is the unique alias of TAG2. */
1075 add_may_alias (tag2, tag1);
1077 ai->pointers[j]->grouped_p = true;
1081 /* Now group all the aliases we collected into TAG1. */
1082 group_aliases_into (tag1, tag1_aliases, ai);
1084 /* If we've reduced total number of virtual operands below the
1086 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1090 /* Finally, all the variables that have been grouped cannot be in
1091 the may-alias set of name memory tags. Suppose that we have
1092 grouped the aliases in this code so that may-aliases(a) = TMT.20
1096 # a_9 = V_MAY_DEF <a_8>
1098 ... Several modifications to TMT.20 ...
1102 Since p_5 points to 'a', the optimizers will try to propagate 0
1103 into p_5->field, but that is wrong because there have been
1104 modifications to 'TMT.20' in between. To prevent this we have to
1105 replace 'a' with 'TMT.20' in the name tag of p_5. */
1106 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1109 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1110 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1111 varray_type aliases;
1113 if (name_tag == NULL_TREE)
1116 aliases = var_ann (name_tag)->may_aliases;
1117 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1119 tree alias = VARRAY_TREE (aliases, j);
1120 var_ann_t ann = var_ann (alias);
1122 if ((!MTAG_P (alias)
1123 || TREE_CODE (alias) == STRUCT_FIELD_TAG)
1124 && ann->may_aliases)
1128 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1130 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1131 replace_may_alias (name_tag, j, new_alias);
1138 "%s: Total number of aliased vops after grouping: %ld%s\n",
1139 get_name (current_function_decl),
1140 ai->total_alias_vops,
1141 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1145 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1148 create_alias_map_for (tree var, struct alias_info *ai)
1150 struct alias_map_d *alias_map;
1151 alias_map = XCNEW (struct alias_map_d);
1152 alias_map->var = var;
1153 alias_map->set = get_alias_set (var);
1154 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1158 /* Create memory tags for all the dereferenced pointers and build the
1159 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1160 sets. Based on the address escape and points-to information collected
1161 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1162 variables whose address is not needed anymore. */
1165 setup_pointers_and_addressables (struct alias_info *ai)
1167 size_t n_vars, num_addressable_vars, num_pointers;
1168 referenced_var_iterator rvi;
1170 VEC (tree, heap) *varvec = NULL;
1171 safe_referenced_var_iterator srvi;
1173 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1174 num_addressable_vars = num_pointers = 0;
1176 FOR_EACH_REFERENCED_VAR (var, rvi)
1178 if (may_be_aliased (var))
1179 num_addressable_vars++;
1181 if (POINTER_TYPE_P (TREE_TYPE (var)))
1183 /* Since we don't keep track of volatile variables, assume that
1184 these pointers are used in indirect store operations. */
1185 if (TREE_THIS_VOLATILE (var))
1186 bitmap_set_bit (ai->dereferenced_ptrs_store, DECL_UID (var));
1192 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1193 always going to be slightly bigger than we actually need them
1194 because some TREE_ADDRESSABLE variables will be marked
1195 non-addressable below and only pointers with unique type tags are
1196 going to be added to POINTERS. */
1197 ai->addressable_vars = XCNEWVEC (struct alias_map_d *, num_addressable_vars);
1198 ai->pointers = XCNEWVEC (struct alias_map_d *, num_pointers);
1199 ai->num_addressable_vars = 0;
1200 ai->num_pointers = 0;
1202 /* Since we will be creating type memory tags within this loop, cache the
1203 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1205 n_vars = num_referenced_vars;
1207 FOR_EACH_REFERENCED_VAR_SAFE (var, varvec, srvi)
1209 var_ann_t v_ann = var_ann (var);
1212 /* Name memory tags already have flow-sensitive aliasing
1213 information, so they need not be processed by
1214 compute_flow_insensitive_aliasing. Similarly, type memory
1215 tags are already accounted for when we process their
1218 Structure fields, on the other hand, have to have some of this
1219 information processed for them, but it's pointless to mark them
1220 non-addressable (since they are fake variables anyway). */
1221 if (MTAG_P (var) && TREE_CODE (var) != STRUCT_FIELD_TAG)
1224 /* Remove the ADDRESSABLE flag from every addressable variable whose
1225 address is not needed anymore. This is caused by the propagation
1226 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1227 removal of dead pointer assignments done by the early scalar
1229 if (TREE_ADDRESSABLE (var))
1231 if (!bitmap_bit_p (addressable_vars, DECL_UID (var))
1232 && TREE_CODE (var) != RESULT_DECL
1233 && !is_global_var (var))
1235 bool okay_to_mark = true;
1237 /* Since VAR is now a regular GIMPLE register, we will need
1238 to rename VAR into SSA afterwards. */
1239 mark_sym_for_renaming (var);
1241 /* If VAR can have sub-variables, and any of its
1242 sub-variables has its address taken, then we cannot
1243 remove the addressable flag from VAR. */
1244 if (var_can_have_subvars (var)
1245 && (svars = get_subvars_for_var (var)))
1249 for (sv = svars; sv; sv = sv->next)
1251 if (bitmap_bit_p (addressable_vars, DECL_UID (sv->var)))
1252 okay_to_mark = false;
1253 mark_sym_for_renaming (sv->var);
1257 /* The address of VAR is not needed, remove the
1258 addressable bit, so that it can be optimized as a
1259 regular variable. */
1261 mark_non_addressable (var);
1265 /* Global variables and addressable locals may be aliased. Create an
1266 entry in ADDRESSABLE_VARS for VAR. */
1267 if (may_be_aliased (var)
1268 && (!var_can_have_subvars (var)
1269 || get_subvars_for_var (var) == NULL))
1271 create_alias_map_for (var, ai);
1272 mark_sym_for_renaming (var);
1275 /* Add pointer variables that have been dereferenced to the POINTERS
1276 array and create a type memory tag for them. */
1277 if (POINTER_TYPE_P (TREE_TYPE (var)))
1279 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var))
1280 || bitmap_bit_p (ai->dereferenced_ptrs_load, DECL_UID (var))))
1285 /* If pointer VAR still doesn't have a memory tag
1286 associated with it, create it now or re-use an
1288 tag = get_tmt_for (var, ai);
1289 t_ann = var_ann (tag);
1291 /* The type tag will need to be renamed into SSA
1292 afterwards. Note that we cannot do this inside
1293 get_tmt_for because aliasing may run multiple times
1294 and we only create type tags the first time. */
1295 mark_sym_for_renaming (tag);
1297 /* Similarly, if pointer VAR used to have another type
1298 tag, we will need to process it in the renamer to
1299 remove the stale virtual operands. */
1300 if (v_ann->type_mem_tag)
1301 mark_sym_for_renaming (v_ann->type_mem_tag);
1303 /* Associate the tag with pointer VAR. */
1304 v_ann->type_mem_tag = tag;
1306 /* If pointer VAR has been used in a store operation,
1307 then its memory tag must be marked as written-to. */
1308 if (bitmap_bit_p (ai->dereferenced_ptrs_store, DECL_UID (var)))
1309 bitmap_set_bit (ai->written_vars, DECL_UID (tag));
1311 /* If pointer VAR is a global variable or a PARM_DECL,
1312 then its memory tag should be considered a global
1314 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1315 mark_call_clobbered (tag);
1317 /* All the dereferences of pointer VAR count as
1318 references of TAG. Since TAG can be associated with
1319 several pointers, add the dereferences of VAR to the
1321 NUM_REFERENCES_SET (t_ann,
1322 NUM_REFERENCES (t_ann)
1323 + NUM_REFERENCES (v_ann));
1327 /* The pointer has not been dereferenced. If it had a
1328 type memory tag, remove it and mark the old tag for
1329 renaming to remove it out of the IL. */
1330 var_ann_t ann = var_ann (var);
1331 tree tag = ann->type_mem_tag;
1334 mark_sym_for_renaming (tag);
1335 ann->type_mem_tag = NULL_TREE;
1340 VEC_free (tree, heap, varvec);
1344 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1345 every call site, we need to emit V_MAY_DEF expressions to represent the
1346 clobbering effects of the call for variables whose address escapes the
1349 One approach is to group all call-clobbered variables into a single
1350 representative that is used as an alias of every call-clobbered variable
1351 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1352 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1354 The second approach is to emit a clobbering V_MAY_DEF for every
1355 call-clobbered variable at call sites. This is the preferred way in terms
1356 of optimization opportunities but it may create too many V_MAY_DEF operands
1357 if there are many call clobbered variables and function calls in the
1360 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1361 function calls found by the number of call-clobbered variables. If that
1362 product is beyond a certain threshold, as determined by the parameterized
1363 values shown below, we use .GLOBAL_VAR.
1365 FIXME. This heuristic should be improved. One idea is to use several
1366 .GLOBAL_VARs of different types instead of a single one. The thresholds
1367 have been derived from a typical bootstrap cycle, including all target
1368 libraries. Compile times were found increase by ~1% compared to using
1372 maybe_create_global_var (struct alias_info *ai)
1374 unsigned i, n_clobbered;
1377 /* No need to create it, if we have one already. */
1378 if (global_var == NULL_TREE)
1380 /* Count all the call-clobbered variables. */
1382 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1387 /* If the number of virtual operands that would be needed to
1388 model all the call-clobbered variables is larger than
1389 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
1391 Also create .GLOBAL_VAR if there are no call-clobbered
1392 variables and the program contains a mixture of pure/const
1393 and regular function calls. This is to avoid the problem
1394 described in PR 20115:
1397 int func_pure (void) { return X; }
1398 int func_non_pure (int a) { X += a; }
1401 int a = func_pure ();
1407 Since foo() has no call-clobbered variables, there is
1408 no relationship between the calls to func_pure and
1409 func_non_pure. Since func_pure has no side-effects, value
1410 numbering optimizations elide the second call to func_pure.
1411 So, if we have some pure/const and some regular calls in the
1412 program we create .GLOBAL_VAR to avoid missing these
1414 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
1415 || (n_clobbered == 0
1416 && ai->num_calls_found > 0
1417 && ai->num_pure_const_calls_found > 0
1418 && ai->num_calls_found > ai->num_pure_const_calls_found))
1419 create_global_var ();
1422 /* Mark all call-clobbered symbols for renaming. Since the initial
1423 rewrite into SSA ignored all call sites, we may need to rename
1424 .GLOBAL_VAR and the call-clobbered variables. */
1425 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1427 tree var = referenced_var (i);
1429 /* If the function has calls to clobbering functions and
1430 .GLOBAL_VAR has been created, make it an alias for all
1431 call-clobbered variables. */
1432 if (global_var && var != global_var)
1435 add_may_alias (var, global_var);
1436 if (var_can_have_subvars (var)
1437 && (svars = get_subvars_for_var (var)))
1440 for (sv = svars; sv; sv = sv->next)
1441 mark_sym_for_renaming (sv->var);
1445 mark_sym_for_renaming (var);
1450 /* Return TRUE if pointer PTR may point to variable VAR.
1452 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1453 This is needed because when checking for type conflicts we are
1454 interested in the alias set of the memory location pointed-to by
1455 PTR. The alias set of PTR itself is irrelevant.
1457 VAR_ALIAS_SET is the alias set for VAR. */
1460 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1461 tree var, HOST_WIDE_INT var_alias_set,
1462 bool alias_set_only)
1466 alias_stats.alias_queries++;
1467 alias_stats.simple_queries++;
1469 /* By convention, a variable cannot alias itself. */
1470 mem = var_ann (ptr)->type_mem_tag;
1473 alias_stats.alias_noalias++;
1474 alias_stats.simple_resolved++;
1478 /* If -fargument-noalias-global is >1, pointer arguments may
1479 not point to global variables. */
1480 if (flag_argument_noalias > 1 && is_global_var (var)
1481 && TREE_CODE (ptr) == PARM_DECL)
1483 alias_stats.alias_noalias++;
1484 alias_stats.simple_resolved++;
1488 /* If either MEM or VAR is a read-only global and the other one
1489 isn't, then PTR cannot point to VAR. */
1490 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
1491 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
1493 alias_stats.alias_noalias++;
1494 alias_stats.simple_resolved++;
1498 gcc_assert (TREE_CODE (mem) == TYPE_MEMORY_TAG);
1500 alias_stats.tbaa_queries++;
1502 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1503 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1505 alias_stats.alias_noalias++;
1506 alias_stats.tbaa_resolved++;
1510 /* If var is a record or union type, ptr cannot point into var
1511 unless there is some operation explicit address operation in the
1512 program that can reference a field of the ptr's dereferenced
1513 type. This also assumes that the types of both var and ptr are
1514 contained within the compilation unit, and that there is no fancy
1515 addressing arithmetic associated with any of the types
1518 if ((mem_alias_set != 0) && (var_alias_set != 0))
1520 tree ptr_type = TREE_TYPE (ptr);
1521 tree var_type = TREE_TYPE (var);
1523 /* The star count is -1 if the type at the end of the pointer_to
1524 chain is not a record or union type. */
1525 if ((!alias_set_only) &&
1526 ipa_type_escape_star_count_of_interesting_type (var_type) >= 0)
1528 int ptr_star_count = 0;
1530 /* Ipa_type_escape_star_count_of_interesting_type is a little to
1531 restrictive for the pointer type, need to allow pointers to
1532 primitive types as long as those types cannot be pointers
1534 while (POINTER_TYPE_P (ptr_type))
1535 /* Strip the *'s off. */
1537 ptr_type = TREE_TYPE (ptr_type);
1541 /* There does not appear to be a better test to see if the
1542 pointer type was one of the pointer to everything
1545 if (ptr_star_count > 0)
1547 alias_stats.structnoaddress_queries++;
1548 if (ipa_type_escape_field_does_not_clobber_p (var_type,
1551 alias_stats.structnoaddress_resolved++;
1552 alias_stats.alias_noalias++;
1556 else if (ptr_star_count == 0)
1558 /* If ptr_type was not really a pointer to type, it cannot
1560 alias_stats.structnoaddress_queries++;
1561 alias_stats.structnoaddress_resolved++;
1562 alias_stats.alias_noalias++;
1568 alias_stats.alias_mayalias++;
1573 /* Add ALIAS to the set of variables that may alias VAR. */
1576 add_may_alias (tree var, tree alias)
1579 var_ann_t v_ann = get_var_ann (var);
1580 var_ann_t a_ann = get_var_ann (alias);
1582 /* Don't allow self-referential aliases. */
1583 gcc_assert (var != alias);
1585 /* ALIAS must be addressable if it's being added to an alias set. */
1587 TREE_ADDRESSABLE (alias) = 1;
1589 gcc_assert (may_be_aliased (alias));
1592 if (v_ann->may_aliases == NULL)
1593 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1595 /* Avoid adding duplicates. */
1596 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1597 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1600 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1601 FIXME, call-clobbering should only depend on whether an address
1602 escapes. It should be independent of aliasing. */
1603 if (is_call_clobbered (var))
1604 mark_call_clobbered (alias);
1606 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1607 else if (is_call_clobbered (alias))
1608 mark_call_clobbered (var);
1610 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1611 a_ann->is_alias_tag = 1;
1615 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1618 replace_may_alias (tree var, size_t i, tree new_alias)
1620 var_ann_t v_ann = var_ann (var);
1621 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1623 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1624 FIXME, call-clobbering should only depend on whether an address
1625 escapes. It should be independent of aliasing. */
1626 if (is_call_clobbered (var))
1627 mark_call_clobbered (new_alias);
1629 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1630 else if (is_call_clobbered (new_alias))
1631 mark_call_clobbered (var);
1635 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1638 set_pt_anything (tree ptr)
1640 struct ptr_info_def *pi = get_ptr_info (ptr);
1642 pi->pt_anything = 1;
1645 /* The pointer used to have a name tag, but we now found it pointing
1646 to an arbitrary location. The name tag needs to be renamed and
1647 disassociated from PTR. */
1648 if (pi->name_mem_tag)
1650 mark_sym_for_renaming (pi->name_mem_tag);
1651 pi->name_mem_tag = NULL_TREE;
1656 /* Return true if STMT is an "escape" site from the current function. Escape
1657 sites those statements which might expose the address of a variable
1658 outside the current function. STMT is an escape site iff:
1660 1- STMT is a function call, or
1661 2- STMT is an __asm__ expression, or
1662 3- STMT is an assignment to a non-local variable, or
1663 4- STMT is a return statement.
1665 AI points to the alias information collected so far. */
1668 is_escape_site (tree stmt, struct alias_info *ai)
1670 tree call = get_call_expr_in (stmt);
1671 if (call != NULL_TREE)
1673 ai->num_calls_found++;
1675 if (!TREE_SIDE_EFFECTS (call))
1676 ai->num_pure_const_calls_found++;
1680 else if (TREE_CODE (stmt) == ASM_EXPR)
1682 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1684 tree lhs = TREE_OPERAND (stmt, 0);
1686 /* Get to the base of _REF nodes. */
1687 if (TREE_CODE (lhs) != SSA_NAME)
1688 lhs = get_base_address (lhs);
1690 /* If we couldn't recognize the LHS of the assignment, assume that it
1691 is a non-local store. */
1692 if (lhs == NULL_TREE)
1695 /* If the RHS is a conversion between a pointer and an integer, the
1696 pointer escapes since we can't track the integer. */
1697 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
1698 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
1699 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
1700 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
1701 (TREE_OPERAND (stmt, 1), 0)))
1702 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
1705 /* If the LHS is an SSA name, it can't possibly represent a non-local
1707 if (TREE_CODE (lhs) == SSA_NAME)
1710 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
1711 local variables we cannot be sure if it will escape, because we
1712 don't have information about objects not in SSA form. Need to
1713 implement something along the lines of
1715 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
1716 Midkiff, ``Escape analysis for java,'' in Proceedings of the
1717 Conference on Object-Oriented Programming Systems, Languages, and
1718 Applications (OOPSLA), pp. 1-19, 1999. */
1721 else if (TREE_CODE (stmt) == RETURN_EXPR)
1727 /* Create a new memory tag of type TYPE.
1728 Does NOT push it into the current binding. */
1731 create_tag_raw (enum tree_code code, tree type, const char *prefix)
1736 /* Make the type of the variable writable. */
1737 new_type = build_type_variant (type, 0, 0);
1738 TYPE_ATTRIBUTES (new_type) = TYPE_ATTRIBUTES (type);
1740 tmp_var = build_decl (code, create_tmp_var_name (prefix),
1742 /* Make the variable writable. */
1743 TREE_READONLY (tmp_var) = 0;
1745 /* It doesn't start out global. */
1746 MTAG_GLOBAL (tmp_var) = 0;
1747 TREE_STATIC (tmp_var) = 0;
1748 TREE_USED (tmp_var) = 1;
1753 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
1754 is considered to represent all the pointers whose pointed-to types are
1755 in the same alias set class. Otherwise, the tag represents a single
1756 SSA_NAME pointer variable. */
1759 create_memory_tag (tree type, bool is_type_tag)
1762 tree tag = create_tag_raw (is_type_tag ? TYPE_MEMORY_TAG : NAME_MEMORY_TAG,
1763 type, (is_type_tag) ? "TMT" : "NMT");
1765 /* By default, memory tags are local variables. Alias analysis will
1766 determine whether they should be considered globals. */
1767 DECL_CONTEXT (tag) = current_function_decl;
1769 /* Memory tags are by definition addressable. */
1770 TREE_ADDRESSABLE (tag) = 1;
1772 ann = get_var_ann (tag);
1773 ann->type_mem_tag = NULL_TREE;
1775 /* Add the tag to the symbol table. */
1776 add_referenced_tmp_var (tag);
1782 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
1783 This is used if P_i has been found to point to a specific set of
1784 variables or to a non-aliased memory location like the address returned
1785 by malloc functions. */
1788 get_nmt_for (tree ptr)
1790 struct ptr_info_def *pi = get_ptr_info (ptr);
1791 tree tag = pi->name_mem_tag;
1793 if (tag == NULL_TREE)
1794 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
1796 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
1797 then its name tag should be considered a global variable. */
1798 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
1799 || pi->pt_global_mem)
1800 mark_call_clobbered (tag);
1806 /* Return the type memory tag associated to pointer PTR. A memory tag is an
1807 artificial variable that represents the memory location pointed-to by
1808 PTR. It is used to model the effects of pointer de-references on
1809 addressable variables.
1811 AI points to the data gathered during alias analysis. This function
1812 populates the array AI->POINTERS. */
1815 get_tmt_for (tree ptr, struct alias_info *ai)
1819 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
1820 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
1822 /* To avoid creating unnecessary memory tags, only create one memory tag
1823 per alias set class. Note that it may be tempting to group
1824 memory tags based on conflicting alias sets instead of
1825 equivalence. That would be wrong because alias sets are not
1826 necessarily transitive (as demonstrated by the libstdc++ test
1827 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
1828 such that conflicts (A, B) == true and conflicts (A, C) == true,
1829 it does not necessarily follow that conflicts (B, C) == true. */
1830 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
1832 struct alias_map_d *curr = ai->pointers[i];
1833 tree curr_tag = var_ann (curr->var)->type_mem_tag;
1834 if (tag_set == curr->set
1835 && TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (curr_tag)))
1842 /* If VAR cannot alias with any of the existing memory tags, create a new
1843 tag for PTR and add it to the POINTERS array. */
1844 if (tag == NULL_TREE)
1846 struct alias_map_d *alias_map;
1848 /* If PTR did not have a type tag already, create a new TMT.*
1849 artificial variable representing the memory location
1850 pointed-to by PTR. */
1851 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
1852 tag = create_memory_tag (tag_type, true);
1854 tag = var_ann (ptr)->type_mem_tag;
1856 /* Add PTR to the POINTERS array. Note that we are not interested in
1857 PTR's alias set. Instead, we cache the alias set for the memory that
1859 alias_map = XCNEW (struct alias_map_d);
1860 alias_map->var = ptr;
1861 alias_map->set = tag_set;
1862 ai->pointers[ai->num_pointers++] = alias_map;
1865 /* If the pointed-to type is volatile, so is the tag. */
1866 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
1868 /* Make sure that the type tag has the same alias set as the
1870 gcc_assert (tag_set == get_alias_set (tag));
1872 /* If PTR's pointed-to type is read-only, then TAG's type must also
1874 gcc_assert (TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (tag)));
1880 /* Create GLOBAL_VAR, an artificial global variable to act as a
1881 representative of all the variables that may be clobbered by function
1885 create_global_var (void)
1887 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
1889 DECL_ARTIFICIAL (global_var) = 1;
1890 TREE_READONLY (global_var) = 0;
1891 DECL_EXTERNAL (global_var) = 1;
1892 TREE_STATIC (global_var) = 1;
1893 TREE_USED (global_var) = 1;
1894 DECL_CONTEXT (global_var) = NULL_TREE;
1895 TREE_THIS_VOLATILE (global_var) = 0;
1896 TREE_ADDRESSABLE (global_var) = 0;
1898 add_referenced_tmp_var (global_var);
1899 mark_sym_for_renaming (global_var);
1903 /* Dump alias statistics on FILE. */
1906 dump_alias_stats (FILE *file)
1908 const char *funcname
1909 = lang_hooks.decl_printable_name (current_function_decl, 2);
1910 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
1911 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
1912 fprintf (file, "Total alias mayalias results:\t%u\n",
1913 alias_stats.alias_mayalias);
1914 fprintf (file, "Total alias noalias results:\t%u\n",
1915 alias_stats.alias_noalias);
1916 fprintf (file, "Total simple queries:\t%u\n",
1917 alias_stats.simple_queries);
1918 fprintf (file, "Total simple resolved:\t%u\n",
1919 alias_stats.simple_resolved);
1920 fprintf (file, "Total TBAA queries:\t%u\n",
1921 alias_stats.tbaa_queries);
1922 fprintf (file, "Total TBAA resolved:\t%u\n",
1923 alias_stats.tbaa_resolved);
1924 fprintf (file, "Total non-addressable structure type queries:\t%u\n",
1925 alias_stats.structnoaddress_queries);
1926 fprintf (file, "Total non-addressable structure type resolved:\t%u\n",
1927 alias_stats.structnoaddress_resolved);
1931 /* Dump alias information on FILE. */
1934 dump_alias_info (FILE *file)
1937 const char *funcname
1938 = lang_hooks.decl_printable_name (current_function_decl, 2);
1939 referenced_var_iterator rvi;
1942 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
1944 fprintf (file, "Aliased symbols\n\n");
1946 FOR_EACH_REFERENCED_VAR (var, rvi)
1948 if (may_be_aliased (var))
1949 dump_variable (file, var);
1952 fprintf (file, "\nDereferenced pointers\n\n");
1954 FOR_EACH_REFERENCED_VAR (var, rvi)
1956 var_ann_t ann = var_ann (var);
1957 if (ann->type_mem_tag)
1958 dump_variable (file, var);
1961 fprintf (file, "\nType memory tags\n\n");
1963 FOR_EACH_REFERENCED_VAR (var, rvi)
1965 if (TREE_CODE (var) == TYPE_MEMORY_TAG)
1966 dump_variable (file, var);
1969 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
1971 fprintf (file, "SSA_NAME pointers\n\n");
1972 for (i = 1; i < num_ssa_names; i++)
1974 tree ptr = ssa_name (i);
1975 struct ptr_info_def *pi;
1977 if (ptr == NULL_TREE)
1980 pi = SSA_NAME_PTR_INFO (ptr);
1981 if (!SSA_NAME_IN_FREE_LIST (ptr)
1983 && pi->name_mem_tag)
1984 dump_points_to_info_for (file, ptr);
1987 fprintf (file, "\nName memory tags\n\n");
1989 FOR_EACH_REFERENCED_VAR (var, rvi)
1991 if (TREE_CODE (var) == NAME_MEMORY_TAG)
1992 dump_variable (file, var);
1995 fprintf (file, "\n");
1999 /* Dump alias information on stderr. */
2002 debug_alias_info (void)
2004 dump_alias_info (stderr);
2008 /* Return the alias information associated with pointer T. It creates a
2009 new instance if none existed. */
2011 struct ptr_info_def *
2012 get_ptr_info (tree t)
2014 struct ptr_info_def *pi;
2016 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2018 pi = SSA_NAME_PTR_INFO (t);
2021 pi = GGC_NEW (struct ptr_info_def);
2022 memset ((void *)pi, 0, sizeof (*pi));
2023 SSA_NAME_PTR_INFO (t) = pi;
2030 /* Dump points-to information for SSA_NAME PTR into FILE. */
2033 dump_points_to_info_for (FILE *file, tree ptr)
2035 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2037 print_generic_expr (file, ptr, dump_flags);
2041 if (pi->name_mem_tag)
2043 fprintf (file, ", name memory tag: ");
2044 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2047 if (pi->is_dereferenced)
2048 fprintf (file, ", is dereferenced");
2050 if (pi->value_escapes_p)
2051 fprintf (file, ", its value escapes");
2053 if (pi->pt_anything)
2054 fprintf (file, ", points-to anything");
2057 fprintf (file, ", points-to NULL");
2064 fprintf (file, ", points-to vars: { ");
2065 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2067 print_generic_expr (file, referenced_var (ix), dump_flags);
2068 fprintf (file, " ");
2070 fprintf (file, "}");
2074 fprintf (file, "\n");
2078 /* Dump points-to information for VAR into stderr. */
2081 debug_points_to_info_for (tree var)
2083 dump_points_to_info_for (stderr, var);
2087 /* Dump points-to information into FILE. NOTE: This function is slow, as
2088 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2091 dump_points_to_info (FILE *file)
2094 block_stmt_iterator si;
2097 lang_hooks.decl_printable_name (current_function_decl, 2);
2098 referenced_var_iterator rvi;
2101 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2103 /* First dump points-to information for the default definitions of
2104 pointer variables. This is necessary because default definitions are
2105 not part of the code. */
2106 FOR_EACH_REFERENCED_VAR (var, rvi)
2108 if (POINTER_TYPE_P (TREE_TYPE (var)))
2110 tree def = default_def (var);
2112 dump_points_to_info_for (file, def);
2116 /* Dump points-to information for every pointer defined in the program. */
2121 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2123 tree ptr = PHI_RESULT (phi);
2124 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2125 dump_points_to_info_for (file, ptr);
2128 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2130 tree stmt = bsi_stmt (si);
2132 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2133 if (POINTER_TYPE_P (TREE_TYPE (def)))
2134 dump_points_to_info_for (file, def);
2138 fprintf (file, "\n");
2142 /* Dump points-to info pointed to by PTO into STDERR. */
2145 debug_points_to_info (void)
2147 dump_points_to_info (stderr);
2150 /* Dump to FILE the list of variables that may be aliasing VAR. */
2153 dump_may_aliases_for (FILE *file, tree var)
2155 varray_type aliases;
2157 if (TREE_CODE (var) == SSA_NAME)
2158 var = SSA_NAME_VAR (var);
2160 aliases = var_ann (var)->may_aliases;
2164 fprintf (file, "{ ");
2165 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2167 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2168 fprintf (file, " ");
2170 fprintf (file, "}");
2175 /* Dump to stderr the list of variables that may be aliasing VAR. */
2178 debug_may_aliases_for (tree var)
2180 dump_may_aliases_for (stderr, var);
2183 /* Return true if VAR may be aliased. */
2186 may_be_aliased (tree var)
2189 if (TREE_ADDRESSABLE (var))
2192 /* Globally visible variables can have their addresses taken by other
2193 translation units. */
2196 && (MTAG_GLOBAL (var) || TREE_PUBLIC (var)))
2198 else if (!MTAG_P (var)
2199 && (DECL_EXTERNAL (var) || TREE_PUBLIC (var)))
2202 /* Automatic variables can't have their addresses escape any other way.
2203 This must be after the check for global variables, as extern declarations
2204 do not have TREE_STATIC set. */
2205 if (!TREE_STATIC (var))
2208 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2209 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2210 we can only be sure the variable isn't addressable if it's local to the
2211 current function. */
2212 if (flag_unit_at_a_time)
2214 if (decl_function_context (var) == current_function_decl)
2221 /* Given two symbols return TRUE if one is in the alias set of the other. */
2223 is_aliased_with (tree tag, tree sym)
2226 varray_type aliases;
2228 if (var_ann (sym)->is_alias_tag)
2230 aliases = var_ann (tag)->may_aliases;
2232 if (aliases == NULL)
2235 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2236 if (VARRAY_TREE (aliases, i) == sym)
2241 aliases = var_ann (sym)->may_aliases;
2243 if (aliases == NULL)
2246 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2247 if (VARRAY_TREE (aliases, i) == tag)
2255 /* Add VAR to the list of may-aliases of PTR's type tag. If PTR
2256 doesn't already have a type tag, create one. */
2259 add_type_alias (tree ptr, tree var)
2261 varray_type aliases;
2263 var_ann_t ann = var_ann (ptr);
2265 VEC (tree, heap) *varvec = NULL;
2267 if (ann->type_mem_tag == NULL_TREE)
2270 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2271 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2272 safe_referenced_var_iterator rvi;
2274 /* PTR doesn't have a type tag, create a new one and add VAR to
2275 the new tag's alias set.
2277 FIXME, This is slower than necessary. We need to determine
2278 whether there is another pointer Q with the same alias set as
2279 PTR. This could be sped up by having type tags associated
2281 FOR_EACH_REFERENCED_VAR_SAFE (q, varvec, rvi)
2283 if (POINTER_TYPE_P (TREE_TYPE (q))
2284 && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q))))
2286 /* Found another pointer Q with the same alias set as
2287 the PTR's pointed-to type. If Q has a type tag, use
2288 it. Otherwise, create a new memory tag for PTR. */
2289 var_ann_t ann1 = var_ann (q);
2290 if (ann1->type_mem_tag)
2291 ann->type_mem_tag = ann1->type_mem_tag;
2293 ann->type_mem_tag = create_memory_tag (tag_type, true);
2298 /* Couldn't find any other pointer with a type tag we could use.
2299 Create a new memory tag for PTR. */
2300 ann->type_mem_tag = create_memory_tag (tag_type, true);
2304 /* If VAR is not already PTR's type tag, add it to the may-alias set
2305 for PTR's type tag. */
2306 gcc_assert (!MTAG_P (var_ann (var)->type_mem_tag));
2307 tag = ann->type_mem_tag;
2309 /* If VAR has subvars, add the subvars to the tag instead of the
2311 if (var_can_have_subvars (var)
2312 && (svars = get_subvars_for_var (var)))
2315 for (sv = svars; sv; sv = sv->next)
2316 add_may_alias (tag, sv->var);
2319 add_may_alias (tag, var);
2321 /* TAG and its set of aliases need to be marked for renaming. */
2322 mark_sym_for_renaming (tag);
2323 if ((aliases = var_ann (tag)->may_aliases) != NULL)
2326 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2327 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2330 /* If we had grouped aliases, VAR may have aliases of its own. Mark
2331 them for renaming as well. Other statements referencing the
2332 aliases of VAR will need to be updated. */
2333 if ((aliases = var_ann (var)->may_aliases) != NULL)
2336 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2337 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2339 VEC_free (tree, heap, varvec);
2343 /* Create a new type tag for PTR. Construct the may-alias list of this type
2344 tag so that it has the aliasing of VAR.
2346 Note, the set of aliases represented by the new type tag are not marked
2350 new_type_alias (tree ptr, tree var)
2352 var_ann_t p_ann = var_ann (ptr);
2353 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2354 var_ann_t v_ann = var_ann (var);
2358 gcc_assert (p_ann->type_mem_tag == NULL_TREE);
2359 gcc_assert (!MTAG_P (var));
2361 /* Add VAR to the may-alias set of PTR's new type tag. If VAR has
2362 subvars, add the subvars to the tag instead of the actual var. */
2363 if (var_can_have_subvars (var)
2364 && (svars = get_subvars_for_var (var)))
2368 tag = create_memory_tag (tag_type, true);
2369 p_ann->type_mem_tag = tag;
2371 for (sv = svars; sv; sv = sv->next)
2372 add_may_alias (tag, sv->var);
2376 /* The following is based on code in add_stmt_operand to ensure that the
2377 same defs/uses/vdefs/vuses will be found after replacing a reference
2378 to var (or ARRAY_REF to var) with an INDIRECT_REF to ptr whose value
2379 is the address of var. */
2380 varray_type aliases = v_ann->may_aliases;
2382 if ((aliases != NULL)
2383 && (VARRAY_ACTIVE_SIZE (aliases) == 1))
2385 tree ali = VARRAY_TREE (aliases, 0);
2387 if (TREE_CODE (ali) == TYPE_MEMORY_TAG)
2389 p_ann->type_mem_tag = ali;
2394 tag = create_memory_tag (tag_type, true);
2395 p_ann->type_mem_tag = tag;
2397 if (aliases == NULL)
2398 add_may_alias (tag, var);
2403 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2404 add_may_alias (tag, VARRAY_TREE (aliases, i));
2411 /* This represents the used range of a variable. */
2413 typedef struct used_part
2415 HOST_WIDE_INT minused;
2416 HOST_WIDE_INT maxused;
2417 /* True if we have an explicit use/def of some portion of this variable,
2418 even if it is all of it. i.e. a.b = 5 or temp = a.b. */
2420 /* True if we have an implicit use/def of some portion of this
2421 variable. Implicit uses occur when we can't tell what part we
2422 are referencing, and have to make conservative assumptions. */
2426 /* An array of used_part structures, indexed by variable uid. */
2428 static htab_t used_portions;
2430 struct used_part_map
2436 /* Return true if the uid in the two used part maps are equal. */
2439 used_part_map_eq (const void *va, const void *vb)
2441 const struct used_part_map *a = (const struct used_part_map *) va;
2442 const struct used_part_map *b = (const struct used_part_map *) vb;
2443 return (a->uid == b->uid);
2446 /* Hash a from uid in a used_part_map. */
2449 used_part_map_hash (const void *item)
2451 return ((const struct used_part_map *)item)->uid;
2454 /* Free a used part map element. */
2457 free_used_part_map (void *item)
2459 free (((struct used_part_map *)item)->to);
2463 /* Lookup a used_part structure for a UID. */
2466 up_lookup (unsigned int uid)
2468 struct used_part_map *h, in;
2470 h = (struct used_part_map *) htab_find_with_hash (used_portions, &in, uid);
2476 /* Insert the pair UID, TO into the used part hashtable. */
2479 up_insert (unsigned int uid, used_part_t to)
2481 struct used_part_map *h;
2484 h = XNEW (struct used_part_map);
2487 loc = htab_find_slot_with_hash (used_portions, h,
2491 *(struct used_part_map **) loc = h;
2495 /* Given a variable uid, UID, get or create the entry in the used portions
2496 table for the variable. */
2499 get_or_create_used_part_for (size_t uid)
2502 if ((up = up_lookup (uid)) == NULL)
2504 up = XCNEW (struct used_part);
2505 up->minused = INT_MAX;
2507 up->explicit_uses = false;
2508 up->implicit_uses = false;
2515 /* Create and return a structure sub-variable for field FIELD of
2519 create_sft (tree var, tree field)
2522 tree subvar = create_tag_raw (STRUCT_FIELD_TAG, TREE_TYPE (field), "SFT");
2524 /* We need to copy the various flags from VAR to SUBVAR, so that
2525 they are is_global_var iff the original variable was. */
2526 DECL_CONTEXT (subvar) = DECL_CONTEXT (var);
2527 MTAG_GLOBAL (subvar) = DECL_EXTERNAL (var);
2528 TREE_PUBLIC (subvar) = TREE_PUBLIC (var);
2529 TREE_STATIC (subvar) = TREE_STATIC (var);
2530 TREE_READONLY (subvar) = TREE_READONLY (var);
2532 /* Add the new variable to REFERENCED_VARS. */
2533 ann = get_var_ann (subvar);
2534 ann->type_mem_tag = NULL;
2535 add_referenced_tmp_var (subvar);
2541 /* Given an aggregate VAR, create the subvariables that represent its
2545 create_overlap_variables_for (tree var)
2547 VEC(fieldoff_s,heap) *fieldstack = NULL;
2549 size_t uid = DECL_UID (var);
2551 if (!up_lookup (uid))
2554 up = up_lookup (uid);
2555 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0, NULL);
2556 if (VEC_length (fieldoff_s, fieldstack) != 0)
2560 bool notokay = false;
2563 HOST_WIDE_INT lastfooffset = -1;
2564 HOST_WIDE_INT lastfosize = -1;
2565 tree lastfotype = NULL_TREE;
2567 /* Not all fields have DECL_SIZE set, and those that don't, we don't
2568 know their size, and thus, can't handle.
2569 The same is true of fields with DECL_SIZE that is not an integer
2570 constant (such as variable sized fields).
2571 Fields with offsets which are not constant will have an offset < 0
2572 We *could* handle fields that are constant sized arrays, but
2573 currently don't. Doing so would require some extra changes to
2574 tree-ssa-operands.c. */
2576 for (i = 0; VEC_iterate (fieldoff_s, fieldstack, i, fo); i++)
2578 if (!DECL_SIZE (fo->field)
2579 || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
2580 || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
2589 /* The current heuristic we use is as follows:
2590 If the variable has no used portions in this function, no
2591 structure vars are created for it.
2593 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
2594 we always create structure vars for them.
2595 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2596 some explicit uses, we create structure vars for them.
2597 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
2598 no explicit uses, we do not create structure vars for them.
2601 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
2602 && !up->explicit_uses)
2604 if (dump_file && (dump_flags & TDF_DETAILS))
2606 fprintf (dump_file, "Variable ");
2607 print_generic_expr (dump_file, var, 0);
2608 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
2613 /* Bail out, if we can't create overlap variables. */
2616 VEC_free (fieldoff_s, heap, fieldstack);
2620 /* Otherwise, create the variables. */
2621 subvars = lookup_subvars_for_var (var);
2623 sort_fieldstack (fieldstack);
2625 for (i = VEC_length (fieldoff_s, fieldstack);
2626 VEC_iterate (fieldoff_s, fieldstack, --i, fo);)
2629 HOST_WIDE_INT fosize;
2632 fosize = TREE_INT_CST_LOW (DECL_SIZE (fo->field));
2633 currfotype = TREE_TYPE (fo->field);
2635 /* If this field isn't in the used portion,
2636 or it has the exact same offset and size as the last
2639 if (((fo->offset <= up->minused
2640 && fo->offset + fosize <= up->minused)
2641 || fo->offset >= up->maxused)
2642 || (fo->offset == lastfooffset
2643 && fosize == lastfosize
2644 && currfotype == lastfotype))
2646 sv = GGC_NEW (struct subvar);
2647 sv->offset = fo->offset;
2649 sv->next = *subvars;
2650 sv->var = create_sft (var, fo->field);
2654 fprintf (dump_file, "structure field tag %s created for var %s",
2655 get_name (sv->var), get_name (var));
2656 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
2658 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
2660 fprintf (dump_file, "\n");
2663 lastfotype = currfotype;
2664 lastfooffset = fo->offset;
2665 lastfosize = fosize;
2669 /* Once we have created subvars, the original is no longer call
2670 clobbered on its own. Its call clobbered status depends
2671 completely on the call clobbered status of the subvars.
2673 add_referenced_var in the above loop will take care of
2674 marking subvars of global variables as call clobbered for us
2675 to start, since they are global as well. */
2676 clear_call_clobbered (var);
2679 VEC_free (fieldoff_s, heap, fieldstack);
2683 /* Find the conservative answer to the question of what portions of what
2684 structures are used by this statement. We assume that if we have a
2685 component ref with a known size + offset, that we only need that part
2686 of the structure. For unknown cases, or cases where we do something
2687 to the whole structure, we assume we need to create fields for the
2688 entire structure. */
2691 find_used_portions (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
2693 switch (TREE_CODE (*tp))
2697 HOST_WIDE_INT bitsize;
2698 HOST_WIDE_INT bitmaxsize;
2699 HOST_WIDE_INT bitpos;
2701 ref = get_ref_base_and_extent (*tp, &bitpos, &bitsize, &bitmaxsize);
2703 && var_can_have_subvars (ref)
2704 && bitmaxsize != -1)
2706 size_t uid = DECL_UID (ref);
2709 up = get_or_create_used_part_for (uid);
2711 if (bitpos <= up->minused)
2712 up->minused = bitpos;
2713 if ((bitpos + bitmaxsize >= up->maxused))
2714 up->maxused = bitpos + bitmaxsize;
2716 if (bitsize == bitmaxsize)
2717 up->explicit_uses = true;
2719 up->implicit_uses = true;
2720 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)
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 */