1 /* Alias analysis for trees.
2 Copyright (C) 2004 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, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, 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"
47 /* Structure to map a variable to its alias set and keep track of the
48 virtual operands that will be needed to represent it. */
51 /* Variable and its alias set. */
55 /* Total number of virtual operands that will be needed to represent
56 all the aliases of VAR. */
57 long total_alias_vops;
59 /* Nonzero if the aliases for this memory tag have been grouped
60 already. Used in group_aliases. */
61 unsigned int grouped_p : 1;
63 /* Set of variables aliased with VAR. This is the exact same
64 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
65 bitmap form to speed up alias grouping. */
70 /* Alias information used by compute_may_aliases and its helpers. */
73 /* SSA names visited while collecting points-to information. If bit I
74 is set, it means that SSA variable with version I has already been
76 bitmap ssa_names_visited;
78 /* Array of SSA_NAME pointers processed by the points-to collector. */
79 varray_type processed_ptrs;
81 /* Variables whose address is still needed. */
82 bitmap addresses_needed;
84 /* ADDRESSABLE_VARS contains all the global variables and locals that
85 have had their address taken. */
86 struct alias_map_d **addressable_vars;
87 size_t num_addressable_vars;
89 /* POINTERS contains all the _DECL pointers with unique memory tags
90 that have been referenced in the program. */
91 struct alias_map_d **pointers;
94 /* Number of function calls found in the program. */
95 size_t num_calls_found;
97 /* Array of counters to keep track of how many times each pointer has
98 been dereferenced in the program. This is used by the alias grouping
99 heuristic in compute_flow_insensitive_aliasing. */
100 varray_type num_references;
102 /* Total number of virtual operands that will be needed to represent
103 all the aliases of all the pointers found in the program. */
104 long total_alias_vops;
106 /* Variables that have been written to. */
109 /* Pointers that have been used in an indirect store operation. */
110 bitmap dereferenced_ptrs_store;
112 /* Pointers that have been used in an indirect load operation. */
113 bitmap dereferenced_ptrs_load;
117 /* Counters used to display statistics on alias analysis. */
120 unsigned int alias_queries;
121 unsigned int alias_mayalias;
122 unsigned int alias_noalias;
123 unsigned int simple_queries;
124 unsigned int simple_resolved;
125 unsigned int tbaa_queries;
126 unsigned int tbaa_resolved;
130 /* Local variables. */
131 static struct alias_stats_d alias_stats;
133 /* Local functions. */
134 static void compute_flow_insensitive_aliasing (struct alias_info *);
135 static void dump_alias_stats (FILE *);
136 static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT);
137 static tree create_memory_tag (tree type, bool is_type_tag);
138 static tree get_tmt_for (tree, struct alias_info *);
139 static tree get_nmt_for (tree);
140 static void add_may_alias (tree, tree);
141 static void replace_may_alias (tree, size_t, tree);
142 static struct alias_info *init_alias_info (void);
143 static void delete_alias_info (struct alias_info *);
144 static void compute_points_to_and_addr_escape (struct alias_info *);
145 static void compute_flow_sensitive_aliasing (struct alias_info *);
146 static void setup_pointers_and_addressables (struct alias_info *);
147 static bool collect_points_to_info_r (tree, tree, void *);
148 static bool is_escape_site (tree, size_t *);
149 static void add_pointed_to_var (struct alias_info *, tree, tree);
150 static void add_pointed_to_expr (tree, tree);
151 static void create_global_var (void);
152 static void collect_points_to_info_for (struct alias_info *, tree);
153 static bool ptr_is_dereferenced_by (tree, tree, bool *);
154 static void maybe_create_global_var (struct alias_info *ai);
155 static void group_aliases (struct alias_info *);
156 static struct ptr_info_def *get_ptr_info (tree t);
157 static void set_pt_anything (tree ptr);
158 static void set_pt_malloc (tree ptr);
160 /* Global declarations. */
162 /* Call clobbered variables in the function. If bit I is set, then
163 REFERENCED_VARS (I) is call-clobbered. */
164 bitmap call_clobbered_vars;
166 /* Addressable variables in the function. If bit I is set, then
167 REFERENCED_VARS (I) has had its address taken. Note that
168 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
169 addressable variable is not necessarily call-clobbered (e.g., a
170 local addressable whose address does not escape) and not all
171 call-clobbered variables are addressable (e.g., a local static
173 bitmap addressable_vars;
175 /* When the program has too many call-clobbered variables and call-sites,
176 this variable is used to represent the clobbering effects of function
177 calls. In these cases, all the call clobbered variables in the program
178 are forced to alias this variable. This reduces compile times by not
179 having to keep track of too many V_MAY_DEF expressions at call sites. */
183 /* Compute may-alias information for every variable referenced in function
186 Alias analysis proceeds in 3 main phases:
188 1- Points-to and escape analysis.
190 This phase walks the use-def chains in the SSA web looking for three
193 * Assignments of the form P_i = &VAR
194 * Assignments of the form P_i = malloc()
195 * Pointers and ADDR_EXPR that escape the current function.
197 The concept of 'escaping' is the same one used in the Java world. When
198 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
199 outside of the current function. So, assignment to global variables,
200 function arguments and returning a pointer are all escape sites.
202 This is where we are currently limited. Since not everything is renamed
203 into SSA, we lose track of escape properties when a pointer is stashed
204 inside a field in a structure, for instance. In those cases, we are
205 assuming that the pointer does escape.
207 We use escape analysis to determine whether a variable is
208 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
209 is call-clobbered. If a pointer P_i escapes, then all the variables
210 pointed-to by P_i (and its memory tag) also escape.
212 2- Compute flow-sensitive aliases
214 We have two classes of memory tags. Memory tags associated with the
215 pointed-to data type of the pointers in the program. These tags are
216 called "type memory tag" (TMT). The other class are those associated
217 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
218 when adding operands for an INDIRECT_REF *P_i, we will first check
219 whether P_i has a name tag, if it does we use it, because that will have
220 more precise aliasing information. Otherwise, we use the standard type
223 In this phase, we go through all the pointers we found in points-to
224 analysis and create alias sets for the name memory tags associated with
225 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
226 it points to and its tag.
229 3- Compute flow-insensitive aliases
231 This pass will compare the alias set of every type memory tag and every
232 addressable variable found in the program. Given a type memory tag TMT
233 and an addressable variable V. If the alias sets of TMT and V conflict
234 (as computed by may_alias_p), then V is marked as an alias tag and added
235 to the alias set of TMT.
237 For instance, consider the following function:
254 After aliasing analysis has finished, the type memory tag for pointer
255 'p' will have two aliases, namely variables 'a' and 'b'. Every time
256 pointer 'p' is dereferenced, we want to mark the operation as a
257 potential reference to 'a' and 'b'.
267 # p_1 = PHI <p_4(1), p_6(2)>;
269 # a_7 = V_MAY_DEF <a_3>;
270 # b_8 = V_MAY_DEF <b_5>;
273 # a_9 = V_MAY_DEF <a_7>
282 In certain cases, the list of may aliases for a pointer may grow too
283 large. This may cause an explosion in the number of virtual operands
284 inserted in the code. Resulting in increased memory consumption and
287 When the number of virtual operands needed to represent aliased
288 loads and stores grows too large (configurable with @option{--param
289 max-aliased-vops}), alias sets are grouped to avoid severe
290 compile-time slow downs and memory consumption. See group_aliases. */
293 compute_may_aliases (void)
295 struct alias_info *ai;
297 memset (&alias_stats, 0, sizeof (alias_stats));
299 /* Initialize aliasing information. */
300 ai = init_alias_info ();
302 /* For each pointer P_i, determine the sets of variables that P_i may
303 point-to. For every addressable variable V, determine whether the
304 address of V escapes the current function, making V call-clobbered
305 (i.e., whether &V is stored in a global variable or if its passed as a
306 function call argument). */
307 compute_points_to_and_addr_escape (ai);
309 /* Collect all pointers and addressable variables, compute alias sets,
310 create memory tags for pointers and promote variables whose address is
311 not needed anymore. */
312 setup_pointers_and_addressables (ai);
314 /* Compute flow-sensitive, points-to based aliasing for all the name
315 memory tags. Note that this pass needs to be done before flow
316 insensitive analysis because it uses the points-to information
317 gathered before to mark call-clobbered type tags. */
318 compute_flow_sensitive_aliasing (ai);
320 /* Compute type-based flow-insensitive aliasing for all the type
322 compute_flow_insensitive_aliasing (ai);
324 /* If the program has too many call-clobbered variables and/or function
325 calls, create .GLOBAL_VAR and use it to model call-clobbering
326 semantics at call sites. This reduces the number of virtual operands
327 considerably, improving compile times at the expense of lost
328 aliasing precision. */
329 maybe_create_global_var (ai);
331 /* Debugging dumps. */
334 dump_referenced_vars (dump_file);
335 if (dump_flags & TDF_STATS)
336 dump_alias_stats (dump_file);
337 dump_points_to_info (dump_file);
338 dump_alias_info (dump_file);
341 /* Deallocate memory used by aliasing data structures. */
342 delete_alias_info (ai);
345 struct tree_opt_pass pass_may_alias =
349 compute_may_aliases, /* execute */
352 0, /* static_pass_number */
353 TV_TREE_MAY_ALIAS, /* tv_id */
354 PROP_cfg | PROP_ssa, /* properties_required */
355 PROP_alias, /* properties_provided */
356 0, /* properties_destroyed */
357 0, /* todo_flags_start */
358 TODO_dump_func | TODO_rename_vars
359 | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
364 /* Initialize the data structures used for alias analysis. */
366 static struct alias_info *
367 init_alias_info (void)
369 struct alias_info *ai;
370 static bool aliases_computed_p = false;
372 ai = xcalloc (1, sizeof (struct alias_info));
373 ai->ssa_names_visited = BITMAP_XMALLOC ();
374 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
375 ai->addresses_needed = BITMAP_XMALLOC ();
376 VARRAY_UINT_INIT (ai->num_references, num_referenced_vars, "num_references");
377 ai->written_vars = BITMAP_XMALLOC ();
378 ai->dereferenced_ptrs_store = BITMAP_XMALLOC ();
379 ai->dereferenced_ptrs_load = BITMAP_XMALLOC ();
381 /* If aliases have been computed before, clear existing information. */
382 if (aliases_computed_p)
386 /* Clear the call-clobbered set. We are going to re-discover
387 call-clobbered variables. */
388 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i,
390 tree var = referenced_var (i);
392 /* Variables that are intrinsically call-clobbered (globals,
393 local statics, etc) will not be marked by the aliasing
394 code, so we can't remove them from CALL_CLOBBERED_VARS. */
395 if (!is_call_clobbered (var))
396 bitmap_clear_bit (call_clobbered_vars, var_ann (var)->uid);
399 /* Similarly, clear the set of addressable variables. In this
400 case, we can just clear the set because addressability is
401 only computed here. */
402 bitmap_clear (addressable_vars);
404 /* Clear flow-insensitive alias information from each symbol. */
405 for (i = 0; i < num_referenced_vars; i++)
407 var_ann_t ann = var_ann (referenced_var (i));
408 ann->is_alias_tag = 0;
409 ann->may_aliases = NULL;
412 /* Clear flow-sensitive points-to information from each SSA name. */
413 for (i = 1; i < num_ssa_names; i++)
415 tree name = ssa_name (i);
417 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
420 if (SSA_NAME_PTR_INFO (name))
422 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
424 /* Clear all the flags but keep the name tag to
425 avoid creating new temporaries unnecessarily. If
426 this pointer is found to point to a subset or
427 superset of its former points-to set, then a new
428 tag will need to be created in create_name_tags. */
431 pi->value_escapes_p = 0;
432 pi->is_dereferenced = 0;
434 bitmap_clear (pi->pt_vars);
439 /* Next time, we will need to reset alias information. */
440 aliases_computed_p = true;
446 /* Deallocate memory used by alias analysis. */
449 delete_alias_info (struct alias_info *ai)
453 BITMAP_XFREE (ai->ssa_names_visited);
454 ai->processed_ptrs = NULL;
455 BITMAP_XFREE (ai->addresses_needed);
457 for (i = 0; i < ai->num_addressable_vars; i++)
459 sbitmap_free (ai->addressable_vars[i]->may_aliases);
460 free (ai->addressable_vars[i]);
462 free (ai->addressable_vars);
464 for (i = 0; i < ai->num_pointers; i++)
466 sbitmap_free (ai->pointers[i]->may_aliases);
467 free (ai->pointers[i]);
471 ai->num_references = NULL;
472 BITMAP_XFREE (ai->written_vars);
473 BITMAP_XFREE (ai->dereferenced_ptrs_store);
474 BITMAP_XFREE (ai->dereferenced_ptrs_load);
480 /* Walk use-def chains for pointer PTR to determine what variables is PTR
484 collect_points_to_info_for (struct alias_info *ai, tree ptr)
486 gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr)));
488 if (!bitmap_bit_p (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)))
490 bitmap_set_bit (ai->ssa_names_visited, SSA_NAME_VERSION (ptr));
491 walk_use_def_chains (ptr, collect_points_to_info_r, ai, true);
492 VARRAY_PUSH_TREE (ai->processed_ptrs, ptr);
497 /* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
498 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
501 find_ptr_dereference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
503 tree ptr = (tree) data;
505 if ((TREE_CODE (*tp) == INDIRECT_REF
506 || TREE_CODE (*tp) == ALIGN_INDIRECT_REF
507 || TREE_CODE (*tp) == MISALIGNED_INDIRECT_REF)
508 && TREE_OPERAND (*tp, 0) == ptr)
515 /* Return true if STMT contains (ALIGN/MISALIGNED_)INDIRECT_REF <PTR>.
516 *IS_STORE is set to 'true' if the dereference is on the LHS of an
520 ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
524 if (TREE_CODE (stmt) == MODIFY_EXPR
525 || (TREE_CODE (stmt) == RETURN_EXPR
526 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
530 e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
531 lhs = TREE_OPERAND (e, 0);
532 rhs = TREE_OPERAND (e, 1);
535 && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
540 else if (EXPR_P (rhs)
541 && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
546 else if (TREE_CODE (stmt) == ASM_EXPR)
548 if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
549 || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
554 else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
564 /* Traverse use-def links for all the pointers in the program to collect
565 address escape and points-to information.
567 This is loosely based on the same idea described in R. Hasti and S.
568 Horwitz, ``Using static single assignment form to improve
569 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
570 Programming Language Design and Implementation, pp. 97-105, 1998. */
573 compute_points_to_and_addr_escape (struct alias_info *ai)
580 timevar_push (TV_TREE_PTA);
584 bb_ann_t block_ann = bb_ann (bb);
585 block_stmt_iterator si;
587 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
590 tree stmt = bsi_stmt (si);
591 bool stmt_escapes_p = is_escape_site (stmt, &ai->num_calls_found);
593 /* Mark all the variables whose address are taken by the
594 statement. Note that this will miss all the addresses taken
595 in PHI nodes (those are discovered while following the use-def
597 get_stmt_operands (stmt);
598 addr_taken = addresses_taken (stmt);
600 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i,
602 tree var = referenced_var (i);
603 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
605 mark_call_clobbered (var);
609 block_ann->has_escape_site = 1;
611 /* Special case for silly ADDR_EXPR tricks
612 (gcc.c-torture/unsorted/pass.c). If this statement is an
613 assignment to a non-pointer variable and the RHS takes the
614 address of a variable, assume that the variable on the RHS is
615 call-clobbered. We could add the LHS to the list of
616 "pointers" and follow it to see if it really escapes, but it's
617 not worth the pain. */
619 && TREE_CODE (stmt) == MODIFY_EXPR
620 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 0))))
621 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i,
623 tree var = referenced_var (i);
624 mark_call_clobbered (var);
627 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
629 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
630 struct ptr_info_def *pi;
633 /* If the operand's variable may be aliased, keep track
634 of how many times we've referenced it. This is used
635 for alias grouping in compute_flow_sensitive_aliasing.
636 Note that we don't need to grow AI->NUM_REFERENCES
637 because we are processing regular variables, not
638 memory tags (the array's initial size is set to
639 NUM_REFERENCED_VARS). */
640 if (may_be_aliased (SSA_NAME_VAR (op)))
641 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
643 if (!POINTER_TYPE_P (TREE_TYPE (op)))
646 collect_points_to_info_for (ai, op);
648 pi = SSA_NAME_PTR_INFO (op);
649 if (ptr_is_dereferenced_by (op, stmt, &is_store))
651 /* Mark OP as dereferenced. In a subsequent pass,
652 dereferenced pointers that point to a set of
653 variables will be assigned a name tag to alias
654 all the variables OP points to. */
655 pi->is_dereferenced = 1;
657 /* Keep track of how many time we've dereferenced each
658 pointer. Again, we don't need to grow
659 AI->NUM_REFERENCES because we're processing
660 existing program variables. */
661 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
663 /* If this is a store operation, mark OP as being
664 dereferenced to store, otherwise mark it as being
665 dereferenced to load. */
667 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
669 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
671 else if (stmt_escapes_p)
673 /* Note that even if STMT is an escape point, pointer OP
674 will not escape if it is being dereferenced. That's
675 why we only check for escape points if OP is not
676 dereferenced by STMT. */
677 pi->value_escapes_p = 1;
679 /* If the statement makes a function call, assume
680 that pointer OP will be dereferenced in a store
681 operation inside the called function. */
682 if (get_call_expr_in (stmt))
684 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
685 pi->is_dereferenced = 1;
690 /* Update reference counter for definitions to any
691 potentially aliased variable. This is used in the alias
692 grouping heuristics. */
693 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
695 tree var = SSA_NAME_VAR (op);
696 var_ann_t ann = var_ann (var);
697 bitmap_set_bit (ai->written_vars, ann->uid);
698 if (may_be_aliased (var))
699 (VARRAY_UINT (ai->num_references, ann->uid))++;
701 if (POINTER_TYPE_P (TREE_TYPE (op)))
702 collect_points_to_info_for (ai, op);
705 /* Mark variables in V_MAY_DEF operands as being written to. */
706 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
708 tree var = SSA_NAME_VAR (op);
709 var_ann_t ann = var_ann (var);
710 bitmap_set_bit (ai->written_vars, ann->uid);
713 /* After promoting variables and computing aliasing we will
714 need to re-scan most statements. FIXME: Try to minimize the
715 number of statements re-scanned. It's not really necessary to
716 re-scan *all* statements. */
721 timevar_pop (TV_TREE_PTA);
725 /* Create name tags for all the pointers that have been dereferenced.
726 We only create a name tag for a pointer P if P is found to point to
727 a set of variables (so that we can alias them to *P) or if it is
728 the result of a call to malloc (which means that P cannot point to
729 anything else nor alias any other variable).
731 If two pointers P and Q point to the same set of variables, they
732 are assigned the same name tag. */
735 create_name_tags (struct alias_info *ai)
739 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
741 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
742 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
744 if (pi->pt_anything || !pi->is_dereferenced)
746 /* No name tags for pointers that have not been
747 dereferenced or point to an arbitrary location. */
748 pi->name_mem_tag = NULL_TREE;
753 && bitmap_first_set_bit (pi->pt_vars) >= 0)
756 tree old_name_tag = pi->name_mem_tag;
758 /* If PTR points to a set of variables, check if we don't
759 have another pointer Q with the same points-to set before
760 creating a tag. If so, use Q's tag instead of creating a
763 This is important for not creating unnecessary symbols
764 and also for copy propagation. If we ever need to
765 propagate PTR into Q or vice-versa, we would run into
766 problems if they both had different name tags because
767 they would have different SSA version numbers (which
768 would force us to take the name tags in and out of SSA). */
769 for (j = 0; j < i; j++)
771 tree q = VARRAY_TREE (ai->processed_ptrs, j);
772 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
777 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
779 pi->name_mem_tag = qi->name_mem_tag;
784 /* If we didn't find a pointer with the same points-to set
785 as PTR, create a new name tag if needed. */
786 if (pi->name_mem_tag == NULL_TREE)
787 pi->name_mem_tag = get_nmt_for (ptr);
789 /* If the new name tag computed for PTR is different than
790 the old name tag that it used to have, then the old tag
791 needs to be removed from the IL, so we mark it for
793 if (old_name_tag && old_name_tag != pi->name_mem_tag)
794 bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid);
796 else if (pi->pt_malloc)
798 /* Otherwise, create a unique name tag for this pointer. */
799 pi->name_mem_tag = get_nmt_for (ptr);
803 /* Only pointers that may point to malloc or other variables
804 may receive a name tag. If the pointer does not point to
805 a known spot, we should use type tags. */
806 set_pt_anything (ptr);
810 /* Mark the new name tag for renaming. */
811 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
817 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
818 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
819 name tag and the variables it points-to are call-clobbered. Finally, if
820 P_i escapes and we could not determine where it points to, then all the
821 variables in the same alias set as *P_i are marked call-clobbered. This
822 is necessary because we must assume that P_i may take the address of any
823 variable in the same alias set. */
826 compute_flow_sensitive_aliasing (struct alias_info *ai)
830 create_name_tags (ai);
832 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
835 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
836 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
837 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
839 if (pi->value_escapes_p || pi->pt_anything)
841 /* If PTR escapes or may point to anything, then its associated
842 memory tags and pointed-to variables are call-clobbered. */
843 if (pi->name_mem_tag)
844 mark_call_clobbered (pi->name_mem_tag);
846 if (v_ann->type_mem_tag)
847 mark_call_clobbered (v_ann->type_mem_tag);
850 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j,
851 mark_call_clobbered (referenced_var (j)));
854 /* Set up aliasing information for PTR's name memory tag (if it has
855 one). Note that only pointers that have been dereferenced will
856 have a name memory tag. */
857 if (pi->name_mem_tag && pi->pt_vars)
858 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j,
859 add_may_alias (pi->name_mem_tag, referenced_var (j)));
861 /* If the name tag is call clobbered, so is the type tag
862 associated with the base VAR_DECL. */
864 && v_ann->type_mem_tag
865 && is_call_clobbered (pi->name_mem_tag))
866 mark_call_clobbered (v_ann->type_mem_tag);
871 /* Compute type-based alias sets. Traverse all the pointers and
872 addressable variables found in setup_pointers_and_addressables.
874 For every pointer P in AI->POINTERS and addressable variable V in
875 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
876 memory tag (TMT) if their alias sets conflict. V is then marked as
877 an alias tag so that the operand scanner knows that statements
878 containing V have aliased operands. */
881 compute_flow_insensitive_aliasing (struct alias_info *ai)
886 /* Initialize counter for the total number of virtual operands that
887 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
888 threshold set by --params max-alias-vops, we enable alias
890 ai->total_alias_vops = 0;
892 /* For every pointer P, determine which addressable variables may alias
893 with P's type memory tag. */
894 for (i = 0; i < ai->num_pointers; i++)
897 struct alias_map_d *p_map = ai->pointers[i];
898 tree tag = var_ann (p_map->var)->type_mem_tag;
899 var_ann_t tag_ann = var_ann (tag);
901 p_map->total_alias_vops = 0;
902 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
903 sbitmap_zero (p_map->may_aliases);
905 for (j = 0; j < ai->num_addressable_vars; j++)
907 struct alias_map_d *v_map;
910 bool tag_stored_p, var_stored_p;
912 v_map = ai->addressable_vars[j];
914 v_ann = var_ann (var);
916 /* Skip memory tags and variables that have never been
917 written to. We also need to check if the variables are
918 call-clobbered because they may be overwritten by
920 tag_stored_p = bitmap_bit_p (ai->written_vars, tag_ann->uid)
921 || is_call_clobbered (tag);
922 var_stored_p = bitmap_bit_p (ai->written_vars, v_ann->uid)
923 || is_call_clobbered (var);
924 if (!tag_stored_p && !var_stored_p)
927 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
929 size_t num_tag_refs, num_var_refs;
931 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
932 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
934 /* Add VAR to TAG's may-aliases set. */
935 add_may_alias (tag, var);
937 /* Update the total number of virtual operands due to
938 aliasing. Since we are adding one more alias to TAG's
939 may-aliases set, the total number of virtual operands due
940 to aliasing will be increased by the number of references
941 made to VAR and TAG (every reference to TAG will also
942 count as a reference to VAR). */
943 ai->total_alias_vops += (num_var_refs + num_tag_refs);
944 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
946 /* Update the bitmap used to represent TAG's alias set
947 in case we need to group aliases. */
948 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
953 /* Since this analysis is based exclusively on symbols, it fails to
954 handle cases where two pointers P and Q have different memory
955 tags with conflicting alias set numbers but no aliased symbols in
958 For example, suppose that we have two memory tags TMT.1 and TMT.2
961 may-aliases (TMT.1) = { a }
962 may-aliases (TMT.2) = { b }
964 and the alias set number of TMT.1 conflicts with that of TMT.2.
965 Since they don't have symbols in common, loads and stores from
966 TMT.1 and TMT.2 will seem independent of each other, which will
967 lead to the optimizers making invalid transformations (see
968 testsuite/gcc.c-torture/execute/pr15262-[12].c).
970 To avoid this problem, we do a final traversal of AI->POINTERS
971 looking for pairs of pointers that have no aliased symbols in
972 common and yet have conflicting alias set numbers. */
973 res = sbitmap_alloc (num_referenced_vars);
975 for (i = 0; i < ai->num_pointers; i++)
978 struct alias_map_d *p_map1 = ai->pointers[i];
979 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
980 sbitmap may_aliases1 = p_map1->may_aliases;
982 for (j = i + 1; j < ai->num_pointers; j++)
984 struct alias_map_d *p_map2 = ai->pointers[j];
985 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
986 sbitmap may_aliases2 = p_map2->may_aliases;
988 /* If the pointers may not point to each other, do nothing. */
989 if (!may_alias_p (p_map1->var, p_map1->set, p_map2->var, p_map2->set))
992 /* The two pointers may alias each other. If they already have
993 symbols in common, do nothing. */
994 sbitmap_a_and_b (res, may_aliases1, may_aliases2);
995 if (sbitmap_first_set_bit (res) >= 0)
998 if (sbitmap_first_set_bit (may_aliases2) >= 0)
1002 /* Add all the aliases for TAG2 into TAG1's alias set.
1003 FIXME, update grouping heuristic counters. */
1004 EXECUTE_IF_SET_IN_SBITMAP (may_aliases2, 0, k,
1005 add_may_alias (tag1, referenced_var (k)));
1006 sbitmap_a_or_b (may_aliases1, may_aliases1, may_aliases2);
1010 /* Since TAG2 does not have any aliases of its own, add
1011 TAG2 itself to the alias set of TAG1. */
1012 add_may_alias (tag1, tag2);
1020 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
1021 get_name (current_function_decl),
1022 ai->total_alias_vops);
1024 /* Determine if we need to enable alias grouping. */
1025 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
1030 /* Comparison function for qsort used in group_aliases. */
1033 total_alias_vops_cmp (const void *p, const void *q)
1035 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1036 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1037 long n1 = (*p1)->total_alias_vops;
1038 long n2 = (*p2)->total_alias_vops;
1040 /* We want to sort in descending order. */
1041 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1044 /* Group all the aliases for TAG to make TAG represent all the
1045 variables in its alias set. Update the total number
1046 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1047 function will make TAG be the unique alias tag for all the
1048 variables in its may-aliases. So, given:
1050 may-aliases(TAG) = { V1, V2, V3 }
1052 This function will group the variables into:
1054 may-aliases(V1) = { TAG }
1055 may-aliases(V2) = { TAG }
1056 may-aliases(V2) = { TAG } */
1059 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
1062 var_ann_t tag_ann = var_ann (tag);
1063 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1065 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
1067 tree var = referenced_var (i);
1068 var_ann_t ann = var_ann (var);
1070 /* Make TAG the unique alias of VAR. */
1071 ann->is_alias_tag = 0;
1072 ann->may_aliases = NULL;
1074 /* Note that VAR and TAG may be the same if the function has no
1075 addressable variables (see the discussion at the end of
1076 setup_pointers_and_addressables). */
1078 add_may_alias (var, tag);
1080 /* Reduce total number of virtual operands contributed
1081 by TAG on behalf of VAR. Notice that the references to VAR
1082 itself won't be removed. We will merely replace them with
1083 references to TAG. */
1084 ai->total_alias_vops -= num_tag_refs;
1087 /* We have reduced the number of virtual operands that TAG makes on
1088 behalf of all the variables formerly aliased with it. However,
1089 we have also "removed" all the virtual operands for TAG itself,
1090 so we add them back. */
1091 ai->total_alias_vops += num_tag_refs;
1093 /* TAG no longer has any aliases. */
1094 tag_ann->may_aliases = NULL;
1098 /* Group may-aliases sets to reduce the number of virtual operands due
1101 1- Sort the list of pointers in decreasing number of contributed
1104 2- Take the first entry in AI->POINTERS and revert the role of
1105 the memory tag and its aliases. Usually, whenever an aliased
1106 variable Vi is found to alias with a memory tag T, we add Vi
1107 to the may-aliases set for T. Meaning that after alias
1108 analysis, we will have:
1110 may-aliases(T) = { V1, V2, V3, ..., Vn }
1112 This means that every statement that references T, will get 'n'
1113 virtual operands for each of the Vi tags. But, when alias
1114 grouping is enabled, we make T an alias tag and add it to the
1115 alias set of all the Vi variables:
1117 may-aliases(V1) = { T }
1118 may-aliases(V2) = { T }
1120 may-aliases(Vn) = { T }
1122 This has two effects: (a) statements referencing T will only get
1123 a single virtual operand, and, (b) all the variables Vi will now
1124 appear to alias each other. So, we lose alias precision to
1125 improve compile time. But, in theory, a program with such a high
1126 level of aliasing should not be very optimizable in the first
1129 3- Since variables may be in the alias set of more than one
1130 memory tag, the grouping done in step (2) needs to be extended
1131 to all the memory tags that have a non-empty intersection with
1132 the may-aliases set of tag T. For instance, if we originally
1133 had these may-aliases sets:
1135 may-aliases(T) = { V1, V2, V3 }
1136 may-aliases(R) = { V2, V4 }
1138 In step (2) we would have reverted the aliases for T as:
1140 may-aliases(V1) = { T }
1141 may-aliases(V2) = { T }
1142 may-aliases(V3) = { T }
1144 But note that now V2 is no longer aliased with R. We could
1145 add R to may-aliases(V2), but we are in the process of
1146 grouping aliases to reduce virtual operands so what we do is
1147 add V4 to the grouping to obtain:
1149 may-aliases(V1) = { T }
1150 may-aliases(V2) = { T }
1151 may-aliases(V3) = { T }
1152 may-aliases(V4) = { T }
1154 4- If the total number of virtual operands due to aliasing is
1155 still above the threshold set by max-alias-vops, go back to (2). */
1158 group_aliases (struct alias_info *ai)
1163 /* Sort the POINTERS array in descending order of contributed
1164 virtual operands. */
1165 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1166 total_alias_vops_cmp);
1168 res = sbitmap_alloc (num_referenced_vars);
1170 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1171 and the tag's may-aliases set. */
1172 for (i = 0; i < ai->num_pointers; i++)
1175 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1176 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1178 /* Skip tags that have been grouped already. */
1179 if (ai->pointers[i]->grouped_p)
1182 /* See if TAG1 had any aliases in common with other type tags.
1183 If we find a TAG2 with common aliases with TAG1, add TAG2's
1184 aliases into TAG1. */
1185 for (j = i + 1; j < ai->num_pointers; j++)
1187 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1189 sbitmap_a_and_b (res, tag1_aliases, tag2_aliases);
1190 if (sbitmap_first_set_bit (res) >= 0)
1192 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1194 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1196 /* TAG2 does not need its aliases anymore. */
1197 sbitmap_zero (tag2_aliases);
1198 var_ann (tag2)->may_aliases = NULL;
1200 /* TAG1 is the unique alias of TAG2. */
1201 add_may_alias (tag2, tag1);
1203 ai->pointers[j]->grouped_p = true;
1207 /* Now group all the aliases we collected into TAG1. */
1208 group_aliases_into (tag1, tag1_aliases, ai);
1210 /* If we've reduced total number of virtual operands below the
1212 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1216 /* Finally, all the variables that have been grouped cannot be in
1217 the may-alias set of name memory tags. Suppose that we have
1218 grouped the aliases in this code so that may-aliases(a) = TMT.20
1222 # a_9 = V_MAY_DEF <a_8>
1224 ... Several modifications to TMT.20 ...
1228 Since p_5 points to 'a', the optimizers will try to propagate 0
1229 into p_5->field, but that is wrong because there have been
1230 modifications to 'TMT.20' in between. To prevent this we have to
1231 replace 'a' with 'TMT.20' in the name tag of p_5. */
1232 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1235 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1236 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1237 varray_type aliases;
1239 if (name_tag == NULL_TREE)
1242 aliases = var_ann (name_tag)->may_aliases;
1243 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1245 tree alias = VARRAY_TREE (aliases, j);
1246 var_ann_t ann = var_ann (alias);
1248 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1252 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1254 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1255 replace_may_alias (name_tag, j, new_alias);
1264 "%s: Total number of aliased vops after grouping: %ld%s\n",
1265 get_name (current_function_decl),
1266 ai->total_alias_vops,
1267 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1271 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1274 create_alias_map_for (tree var, struct alias_info *ai)
1276 struct alias_map_d *alias_map;
1277 alias_map = xcalloc (1, sizeof (*alias_map));
1278 alias_map->var = var;
1279 alias_map->set = get_alias_set (var);
1280 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1284 /* Create memory tags for all the dereferenced pointers and build the
1285 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1286 sets. Based on the address escape and points-to information collected
1287 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1288 variables whose address is not needed anymore. */
1291 setup_pointers_and_addressables (struct alias_info *ai)
1293 size_t i, n_vars, num_addressable_vars, num_pointers;
1295 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1296 num_addressable_vars = num_pointers = 0;
1297 for (i = 0; i < num_referenced_vars; i++)
1299 tree var = referenced_var (i);
1301 if (may_be_aliased (var))
1302 num_addressable_vars++;
1304 if (POINTER_TYPE_P (TREE_TYPE (var)))
1306 /* Since we don't keep track of volatile variables, assume that
1307 these pointers are used in indirect store operations. */
1308 if (TREE_THIS_VOLATILE (var))
1309 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1315 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1316 always going to be slightly bigger than we actually need them
1317 because some TREE_ADDRESSABLE variables will be marked
1318 non-addressable below and only pointers with unique type tags are
1319 going to be added to POINTERS. */
1320 ai->addressable_vars = xcalloc (num_addressable_vars,
1321 sizeof (struct alias_map_d *));
1322 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1323 ai->num_addressable_vars = 0;
1324 ai->num_pointers = 0;
1326 /* Since we will be creating type memory tags within this loop, cache the
1327 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1329 n_vars = num_referenced_vars;
1331 for (i = 0; i < n_vars; i++)
1333 tree var = referenced_var (i);
1334 var_ann_t v_ann = var_ann (var);
1336 /* Name memory tags already have flow-sensitive aliasing
1337 information, so they need not be processed by
1338 compute_flow_insensitive_aliasing. Similarly, type memory
1339 tags are already accounted for when we process their
1340 associated pointer. */
1341 if (v_ann->mem_tag_kind != NOT_A_TAG)
1344 /* Remove the ADDRESSABLE flag from every addressable variable whose
1345 address is not needed anymore. This is caused by the propagation
1346 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1347 removal of dead pointer assignments done by the early scalar
1349 if (TREE_ADDRESSABLE (var))
1351 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1352 && v_ann->mem_tag_kind == NOT_A_TAG
1353 && TREE_CODE (var) != RESULT_DECL
1354 && !is_global_var (var))
1356 /* The address of VAR is not needed, remove the
1357 addressable bit, so that it can be optimized as a
1358 regular variable. */
1359 mark_non_addressable (var);
1361 /* Since VAR is now a regular GIMPLE register, we will need
1362 to rename VAR into SSA afterwards. */
1363 bitmap_set_bit (vars_to_rename, v_ann->uid);
1367 /* Add the variable to the set of addressables. Mostly
1368 used when scanning operands for ASM_EXPRs that
1369 clobber memory. In those cases, we need to clobber
1370 all call-clobbered variables and all addressables. */
1371 bitmap_set_bit (addressable_vars, v_ann->uid);
1375 /* Global variables and addressable locals may be aliased. Create an
1376 entry in ADDRESSABLE_VARS for VAR. */
1377 if (may_be_aliased (var))
1379 create_alias_map_for (var, ai);
1380 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1383 /* Add pointer variables that have been dereferenced to the POINTERS
1384 array and create a type memory tag for them. */
1385 if (POINTER_TYPE_P (TREE_TYPE (var)))
1387 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1388 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1393 /* If pointer VAR still doesn't have a memory tag
1394 associated with it, create it now or re-use an
1396 tag = get_tmt_for (var, ai);
1397 t_ann = var_ann (tag);
1399 /* The type tag will need to be renamed into SSA
1400 afterwards. Note that we cannot do this inside
1401 get_tmt_for because aliasing may run multiple times
1402 and we only create type tags the first time. */
1403 bitmap_set_bit (vars_to_rename, t_ann->uid);
1405 /* Associate the tag with pointer VAR. */
1406 v_ann->type_mem_tag = tag;
1408 /* If pointer VAR has been used in a store operation,
1409 then its memory tag must be marked as written-to. */
1410 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1411 bitmap_set_bit (ai->written_vars, t_ann->uid);
1413 /* If pointer VAR is a global variable or a PARM_DECL,
1414 then its memory tag should be considered a global
1416 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1417 mark_call_clobbered (tag);
1419 /* All the dereferences of pointer VAR count as
1420 references of TAG. Since TAG can be associated with
1421 several pointers, add the dereferences of VAR to the
1422 TAG. We may need to grow AI->NUM_REFERENCES because
1423 we have been adding name and type tags. */
1424 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1425 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1427 VARRAY_UINT (ai->num_references, t_ann->uid)
1428 += VARRAY_UINT (ai->num_references, v_ann->uid);
1432 /* The pointer has not been dereferenced. If it had a
1433 type memory tag, remove it and mark the old tag for
1434 renaming to remove it out of the IL. */
1435 var_ann_t ann = var_ann (var);
1436 tree tag = ann->type_mem_tag;
1439 bitmap_set_bit (vars_to_rename, var_ann (tag)->uid);
1440 ann->type_mem_tag = NULL_TREE;
1448 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1449 every call site, we need to emit V_MAY_DEF expressions to represent the
1450 clobbering effects of the call for variables whose address escapes the
1453 One approach is to group all call-clobbered variables into a single
1454 representative that is used as an alias of every call-clobbered variable
1455 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1456 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1458 The second approach is to emit a clobbering V_MAY_DEF for every
1459 call-clobbered variable at call sites. This is the preferred way in terms
1460 of optimization opportunities but it may create too many V_MAY_DEF operands
1461 if there are many call clobbered variables and function calls in the
1464 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1465 function calls found by the number of call-clobbered variables. If that
1466 product is beyond a certain threshold, as determined by the parameterized
1467 values shown below, we use .GLOBAL_VAR.
1469 FIXME. This heuristic should be improved. One idea is to use several
1470 .GLOBAL_VARs of different types instead of a single one. The thresholds
1471 have been derived from a typical bootstrap cycle, including all target
1472 libraries. Compile times were found increase by ~1% compared to using
1476 maybe_create_global_var (struct alias_info *ai)
1478 size_t i, n_clobbered;
1480 /* No need to create it, if we have one already. */
1481 if (global_var == NULL_TREE)
1483 /* Count all the call-clobbered variables. */
1485 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, n_clobbered++);
1487 /* Create .GLOBAL_VAR if we have too many call-clobbered
1488 variables. We also create .GLOBAL_VAR when there no
1489 call-clobbered variables to prevent code motion
1490 transformations from re-arranging function calls that may
1491 have side effects. For instance,
1500 There are no call-clobbered variables in foo(), so it would
1501 be entirely possible for a pass to want to move the call to
1502 f() after the call to g(). If f() has side effects, that
1503 would be wrong. Creating .GLOBAL_VAR in this case will
1504 insert VDEFs for it and prevent such transformations. */
1505 if (n_clobbered == 0
1506 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1507 create_global_var ();
1510 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1511 been created, make it an alias for all call-clobbered variables. */
1513 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i,
1515 tree var = referenced_var (i);
1516 if (var != global_var)
1518 add_may_alias (var, global_var);
1519 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1525 /* Return TRUE if pointer PTR may point to variable VAR.
1527 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1528 This is needed because when checking for type conflicts we are
1529 interested in the alias set of the memory location pointed-to by
1530 PTR. The alias set of PTR itself is irrelevant.
1532 VAR_ALIAS_SET is the alias set for VAR. */
1535 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1536 tree var, HOST_WIDE_INT var_alias_set)
1539 var_ann_t v_ann, m_ann;
1541 alias_stats.alias_queries++;
1542 alias_stats.simple_queries++;
1544 /* By convention, a variable cannot alias itself. */
1545 mem = var_ann (ptr)->type_mem_tag;
1548 alias_stats.alias_noalias++;
1549 alias_stats.simple_resolved++;
1553 v_ann = var_ann (var);
1554 m_ann = var_ann (mem);
1556 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1558 alias_stats.tbaa_queries++;
1560 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1561 PTR can't possibly affect VAR. Note, that we are specifically testing
1562 for PTR's alias set here, not its pointed-to type. We also can't
1563 do this check with relaxed aliasing enabled. */
1564 if (POINTER_TYPE_P (TREE_TYPE (var))
1565 && var_alias_set != 0
1566 && mem_alias_set != 0)
1568 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1569 if (ptr_alias_set == var_alias_set)
1571 alias_stats.alias_noalias++;
1572 alias_stats.tbaa_resolved++;
1577 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1578 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1580 alias_stats.alias_noalias++;
1581 alias_stats.tbaa_resolved++;
1585 alias_stats.alias_mayalias++;
1590 /* Add ALIAS to the set of variables that may alias VAR. */
1593 add_may_alias (tree var, tree alias)
1596 var_ann_t v_ann = get_var_ann (var);
1597 var_ann_t a_ann = get_var_ann (alias);
1599 gcc_assert (var != alias);
1601 if (v_ann->may_aliases == NULL)
1602 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1604 /* Avoid adding duplicates. */
1605 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1606 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1609 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1610 FIXME, call-clobbering should only depend on whether an address
1611 escapes. It should be independent of aliasing. */
1612 if (is_call_clobbered (var))
1613 mark_call_clobbered (alias);
1615 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1616 else if (is_call_clobbered (alias))
1617 mark_call_clobbered (var);
1619 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1620 a_ann->is_alias_tag = 1;
1624 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1627 replace_may_alias (tree var, size_t i, tree new_alias)
1629 var_ann_t v_ann = var_ann (var);
1630 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1632 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1633 FIXME, call-clobbering should only depend on whether an address
1634 escapes. It should be independent of aliasing. */
1635 if (is_call_clobbered (var))
1636 mark_call_clobbered (new_alias);
1638 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1639 else if (is_call_clobbered (new_alias))
1640 mark_call_clobbered (var);
1644 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1647 set_pt_anything (tree ptr)
1649 struct ptr_info_def *pi = get_ptr_info (ptr);
1651 pi->pt_anything = 1;
1654 /* The pointer used to have a name tag, but we now found it pointing
1655 to an arbitrary location. The name tag needs to be renamed and
1656 disassociated from PTR. */
1657 if (pi->name_mem_tag)
1659 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1660 pi->name_mem_tag = NULL_TREE;
1665 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1668 set_pt_malloc (tree ptr)
1670 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1672 /* If the pointer has already been found to point to arbitrary
1673 memory locations, it is unsafe to mark it as pointing to malloc. */
1674 if (pi->pt_anything)
1681 /* Given two pointers DEST and ORIG. Merge the points-to information in
1682 ORIG into DEST. AI is as in collect_points_to_info. */
1685 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1687 struct ptr_info_def *dest_pi, *orig_pi;
1689 /* Make sure we have points-to information for ORIG. */
1690 collect_points_to_info_for (ai, orig);
1692 dest_pi = get_ptr_info (dest);
1693 orig_pi = SSA_NAME_PTR_INFO (orig);
1697 /* Notice that we never merge PT_MALLOC. This attribute is only
1698 true if the pointer is the result of a malloc() call.
1699 Otherwise, we can end up in this situation:
1705 P_j would be marked as PT_MALLOC, which is wrong because
1706 PT_MALLOC implies that the pointer may not point to another
1709 FIXME 1: Subsequent analysis may determine that P_j
1710 cannot alias anything else, but we are being conservative
1713 FIXME 2: If the merging comes from a copy assignment, we
1714 ought to merge PT_MALLOC, but then both pointers would end up
1715 getting different name tags because create_name_tags is not
1716 smart enough to determine that the two come from the same
1717 malloc call. Copy propagation before aliasing should cure
1719 dest_pi->pt_malloc = 0;
1721 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1722 set_pt_anything (dest);
1724 if (!dest_pi->pt_anything
1726 && bitmap_first_set_bit (orig_pi->pt_vars) >= 0)
1728 if (dest_pi->pt_vars == NULL)
1730 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1731 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1734 bitmap_a_or_b (dest_pi->pt_vars,
1740 set_pt_anything (dest);
1744 /* Add VALUE to the list of expressions pointed-to by PTR. */
1747 add_pointed_to_expr (tree ptr, tree value)
1749 if (TREE_CODE (value) == WITH_SIZE_EXPR)
1750 value = TREE_OPERAND (value, 0);
1752 /* Pointer variables should have been handled by merge_pointed_to_info. */
1753 gcc_assert (TREE_CODE (value) != SSA_NAME
1754 || !POINTER_TYPE_P (TREE_TYPE (value)));
1758 /* If VALUE is the result of a malloc-like call, then the area pointed to
1759 PTR is guaranteed to not alias with anything else. */
1760 if (TREE_CODE (value) == CALL_EXPR
1761 && (call_expr_flags (value) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1762 set_pt_malloc (ptr);
1764 set_pt_anything (ptr);
1768 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1770 fprintf (dump_file, "Pointer ");
1771 print_generic_expr (dump_file, ptr, dump_flags);
1772 fprintf (dump_file, " points to ");
1774 fprintf (dump_file, "malloc space: ");
1776 fprintf (dump_file, "an arbitrary address: ");
1777 print_generic_expr (dump_file, value, dump_flags);
1778 fprintf (dump_file, "\n");
1783 /* If VALUE is of the form &DECL, add DECL to the set of variables
1784 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1785 PTR. AI is as in collect_points_to_info. */
1788 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1790 struct ptr_info_def *pi = get_ptr_info (ptr);
1794 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
1796 pt_var = TREE_OPERAND (value, 0);
1797 if (REFERENCE_CLASS_P (pt_var))
1798 pt_var = get_base_address (pt_var);
1800 if (pt_var && SSA_VAR_P (pt_var))
1802 uid = var_ann (pt_var)->uid;
1803 bitmap_set_bit (ai->addresses_needed, uid);
1805 if (pi->pt_vars == NULL)
1806 pi->pt_vars = BITMAP_GGC_ALLOC ();
1807 bitmap_set_bit (pi->pt_vars, uid);
1809 /* If the variable is a global, mark the pointer as pointing to
1810 global memory (which will make its tag a global variable). */
1811 if (is_global_var (pt_var))
1812 pi->pt_global_mem = 1;
1817 /* Callback for walk_use_def_chains to gather points-to information from the
1820 VAR is an SSA variable or a GIMPLE expression.
1822 STMT is the statement that generates the SSA variable or, if STMT is a
1823 PHI_NODE, VAR is one of the PHI arguments.
1825 DATA is a pointer to a structure of type ALIAS_INFO. */
1828 collect_points_to_info_r (tree var, tree stmt, void *data)
1830 struct alias_info *ai = (struct alias_info *) data;
1832 if (dump_file && (dump_flags & TDF_DETAILS))
1834 fprintf (dump_file, "Visiting use-def links for ");
1835 print_generic_expr (dump_file, var, dump_flags);
1836 fprintf (dump_file, "\n");
1839 switch (TREE_CODE (stmt))
1842 if (TREE_CODE (TREE_OPERAND (stmt, 0)) != MODIFY_EXPR)
1844 stmt = TREE_OPERAND (stmt, 0);
1849 tree rhs = TREE_OPERAND (stmt, 1);
1852 /* Found P_i = ADDR_EXPR */
1853 if (TREE_CODE (rhs) == ADDR_EXPR)
1854 add_pointed_to_var (ai, var, rhs);
1856 /* Found P_i = Q_j. */
1857 else if (TREE_CODE (rhs) == SSA_NAME
1858 && POINTER_TYPE_P (TREE_TYPE (rhs)))
1859 merge_pointed_to_info (ai, var, rhs);
1861 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1862 else if (TREE_CODE (rhs) == PLUS_EXPR
1863 || TREE_CODE (rhs) == MINUS_EXPR)
1865 tree op0 = TREE_OPERAND (rhs, 0);
1866 tree op1 = TREE_OPERAND (rhs, 1);
1868 /* Both operands may be of pointer type. FIXME: Shouldn't
1869 we just expect PTR + OFFSET always? */
1870 if (POINTER_TYPE_P (TREE_TYPE (op0))
1871 && TREE_CODE (op0) != INTEGER_CST)
1873 if (TREE_CODE (op0) == SSA_NAME)
1874 merge_pointed_to_info (ai, var, op0);
1875 else if (TREE_CODE (op0) == ADDR_EXPR)
1876 add_pointed_to_var (ai, var, op0);
1878 add_pointed_to_expr (var, op0);
1881 if (POINTER_TYPE_P (TREE_TYPE (op1))
1882 && TREE_CODE (op1) != INTEGER_CST)
1884 if (TREE_CODE (op1) == SSA_NAME)
1885 merge_pointed_to_info (ai, var, op1);
1886 else if (TREE_CODE (op1) == ADDR_EXPR)
1887 add_pointed_to_var (ai, var, op1);
1889 add_pointed_to_expr (var, op1);
1892 /* Neither operand is a pointer? VAR can be pointing
1893 anywhere. FIXME: Is this right? If we get here, we
1894 found PTR = INT_CST + INT_CST. */
1895 if (!(POINTER_TYPE_P (TREE_TYPE (op0))
1896 && TREE_CODE (op0) != INTEGER_CST)
1897 && !(POINTER_TYPE_P (TREE_TYPE (op1))
1898 && TREE_CODE (op1) != INTEGER_CST))
1899 add_pointed_to_expr (var, rhs);
1902 /* Something else. */
1904 add_pointed_to_expr (var, rhs);
1908 /* Pointers defined by __asm__ statements can point anywhere. */
1909 set_pt_anything (var);
1913 if (IS_EMPTY_STMT (stmt))
1915 tree decl = SSA_NAME_VAR (var);
1917 if (TREE_CODE (decl) == PARM_DECL)
1918 add_pointed_to_expr (var, decl);
1919 else if (DECL_INITIAL (decl))
1920 add_pointed_to_var (ai, var, DECL_INITIAL (decl));
1922 add_pointed_to_expr (var, decl);
1927 /* It STMT is a PHI node, then VAR is one of its arguments. The
1928 variable that we are analyzing is the LHS of the PHI node. */
1929 tree lhs = PHI_RESULT (stmt);
1931 switch (TREE_CODE (var))
1934 add_pointed_to_var (ai, lhs, var);
1938 merge_pointed_to_info (ai, lhs, var);
1942 gcc_assert (is_gimple_min_invariant (var));
1943 add_pointed_to_expr (lhs, var);
1956 /* Return true if STMT is an "escape" site from the current function. Escape
1957 sites those statements which might expose the address of a variable
1958 outside the current function. STMT is an escape site iff:
1960 1- STMT is a function call, or
1961 2- STMT is an __asm__ expression, or
1962 3- STMT is an assignment to a non-local variable, or
1963 4- STMT is a return statement.
1965 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
1969 is_escape_site (tree stmt, size_t *num_calls_p)
1971 if (get_call_expr_in (stmt) != NULL_TREE)
1978 else if (TREE_CODE (stmt) == ASM_EXPR)
1980 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1982 tree lhs = TREE_OPERAND (stmt, 0);
1984 /* Get to the base of _REF nodes. */
1985 if (TREE_CODE (lhs) != SSA_NAME)
1986 lhs = get_base_address (lhs);
1988 /* If we couldn't recognize the LHS of the assignment, assume that it
1989 is a non-local store. */
1990 if (lhs == NULL_TREE)
1993 /* If the LHS is an SSA name, it can't possibly represent a non-local
1995 if (TREE_CODE (lhs) == SSA_NAME)
1998 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
1999 local variables we cannot be sure if it will escape, because we
2000 don't have information about objects not in SSA form. Need to
2001 implement something along the lines of
2003 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2004 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2005 Conference on Object-Oriented Programming Systems, Languages, and
2006 Applications (OOPSLA), pp. 1-19, 1999. */
2009 else if (TREE_CODE (stmt) == RETURN_EXPR)
2016 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2017 is considered to represent all the pointers whose pointed-to types are
2018 in the same alias set class. Otherwise, the tag represents a single
2019 SSA_NAME pointer variable. */
2022 create_memory_tag (tree type, bool is_type_tag)
2025 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2027 /* By default, memory tags are local variables. Alias analysis will
2028 determine whether they should be considered globals. */
2029 DECL_CONTEXT (tag) = current_function_decl;
2031 /* Memory tags are by definition addressable. This also prevents
2032 is_gimple_ref frome confusing memory tags with optimizable
2034 TREE_ADDRESSABLE (tag) = 1;
2036 ann = get_var_ann (tag);
2037 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2038 ann->type_mem_tag = NULL_TREE;
2040 /* Add the tag to the symbol table. */
2041 add_referenced_tmp_var (tag);
2047 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2048 This is used if P_i has been found to point to a specific set of
2049 variables or to a non-aliased memory location like the address returned
2050 by malloc functions. */
2053 get_nmt_for (tree ptr)
2055 struct ptr_info_def *pi = get_ptr_info (ptr);
2056 tree tag = pi->name_mem_tag;
2058 if (tag == NULL_TREE)
2059 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2061 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2062 then its name tag should be considered a global variable. */
2063 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2065 || pi->pt_global_mem)
2066 mark_call_clobbered (tag);
2072 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2073 artificial variable that represents the memory location pointed-to by
2074 PTR. It is used to model the effects of pointer de-references on
2075 addressable variables.
2077 AI points to the data gathered during alias analysis. This function
2078 populates the array AI->POINTERS. */
2081 get_tmt_for (tree ptr, struct alias_info *ai)
2085 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2086 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2088 /* To avoid creating unnecessary memory tags, only create one memory tag
2089 per alias set class. Note that it may be tempting to group
2090 memory tags based on conflicting alias sets instead of
2091 equivalence. That would be wrong because alias sets are not
2092 necessarily transitive (as demonstrated by the libstdc++ test
2093 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2094 such that conflicts (A, B) == true and conflicts (A, C) == true,
2095 it does not necessarily follow that conflicts (B, C) == true. */
2096 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2098 struct alias_map_d *curr = ai->pointers[i];
2099 if (tag_set == curr->set)
2101 tag = var_ann (curr->var)->type_mem_tag;
2106 /* If VAR cannot alias with any of the existing memory tags, create a new
2107 tag for PTR and add it to the POINTERS array. */
2108 if (tag == NULL_TREE)
2110 struct alias_map_d *alias_map;
2112 /* If PTR did not have a type tag already, create a new TMT.*
2113 artificial variable representing the memory location
2114 pointed-to by PTR. */
2115 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2116 tag = create_memory_tag (tag_type, true);
2118 tag = var_ann (ptr)->type_mem_tag;
2120 /* Add PTR to the POINTERS array. Note that we are not interested in
2121 PTR's alias set. Instead, we cache the alias set for the memory that
2123 alias_map = xcalloc (1, sizeof (*alias_map));
2124 alias_map->var = ptr;
2125 alias_map->set = tag_set;
2126 ai->pointers[ai->num_pointers++] = alias_map;
2129 /* If the pointed-to type is volatile, so is the tag. */
2130 TREE_THIS_VOLATILE (tag) = TREE_THIS_VOLATILE (tag_type);
2132 /* Make sure that the type tag has the same alias set as the
2134 gcc_assert (tag_set == get_alias_set (tag));
2140 /* Create GLOBAL_VAR, an artificial global variable to act as a
2141 representative of all the variables that may be clobbered by function
2145 create_global_var (void)
2147 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2149 DECL_ARTIFICIAL (global_var) = 1;
2150 TREE_READONLY (global_var) = 0;
2151 DECL_EXTERNAL (global_var) = 1;
2152 TREE_STATIC (global_var) = 1;
2153 TREE_USED (global_var) = 1;
2154 DECL_CONTEXT (global_var) = NULL_TREE;
2155 TREE_THIS_VOLATILE (global_var) = 0;
2156 TREE_ADDRESSABLE (global_var) = 0;
2158 add_referenced_tmp_var (global_var);
2159 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2163 /* Dump alias statistics on FILE. */
2166 dump_alias_stats (FILE *file)
2168 const char *funcname
2169 = lang_hooks.decl_printable_name (current_function_decl, 2);
2170 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2171 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2172 fprintf (file, "Total alias mayalias results:\t%u\n",
2173 alias_stats.alias_mayalias);
2174 fprintf (file, "Total alias noalias results:\t%u\n",
2175 alias_stats.alias_noalias);
2176 fprintf (file, "Total simple queries:\t%u\n",
2177 alias_stats.simple_queries);
2178 fprintf (file, "Total simple resolved:\t%u\n",
2179 alias_stats.simple_resolved);
2180 fprintf (file, "Total TBAA queries:\t%u\n",
2181 alias_stats.tbaa_queries);
2182 fprintf (file, "Total TBAA resolved:\t%u\n",
2183 alias_stats.tbaa_resolved);
2187 /* Dump alias information on FILE. */
2190 dump_alias_info (FILE *file)
2193 const char *funcname
2194 = lang_hooks.decl_printable_name (current_function_decl, 2);
2196 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2198 fprintf (file, "Aliased symbols\n\n");
2199 for (i = 0; i < num_referenced_vars; i++)
2201 tree var = referenced_var (i);
2202 if (may_be_aliased (var))
2203 dump_variable (file, var);
2206 fprintf (file, "\nDereferenced pointers\n\n");
2207 for (i = 0; i < num_referenced_vars; i++)
2209 tree var = referenced_var (i);
2210 var_ann_t ann = var_ann (var);
2211 if (ann->type_mem_tag)
2212 dump_variable (file, var);
2215 fprintf (file, "\nType memory tags\n\n");
2216 for (i = 0; i < num_referenced_vars; i++)
2218 tree var = referenced_var (i);
2219 var_ann_t ann = var_ann (var);
2220 if (ann->mem_tag_kind == TYPE_TAG)
2221 dump_variable (file, var);
2224 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2226 fprintf (file, "SSA_NAME pointers\n\n");
2227 for (i = 1; i < num_ssa_names; i++)
2229 tree ptr = ssa_name (i);
2230 struct ptr_info_def *pi;
2232 if (ptr == NULL_TREE)
2235 pi = SSA_NAME_PTR_INFO (ptr);
2236 if (!SSA_NAME_IN_FREE_LIST (ptr)
2238 && pi->name_mem_tag)
2239 dump_points_to_info_for (file, ptr);
2242 fprintf (file, "\nName memory tags\n\n");
2243 for (i = 0; i < num_referenced_vars; i++)
2245 tree var = referenced_var (i);
2246 var_ann_t ann = var_ann (var);
2247 if (ann->mem_tag_kind == NAME_TAG)
2248 dump_variable (file, var);
2251 fprintf (file, "\n");
2255 /* Dump alias information on stderr. */
2258 debug_alias_info (void)
2260 dump_alias_info (stderr);
2264 /* Return the alias information associated with pointer T. It creates a
2265 new instance if none existed. */
2267 static struct ptr_info_def *
2268 get_ptr_info (tree t)
2270 struct ptr_info_def *pi;
2272 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2274 pi = SSA_NAME_PTR_INFO (t);
2277 pi = ggc_alloc (sizeof (*pi));
2278 memset ((void *)pi, 0, sizeof (*pi));
2279 SSA_NAME_PTR_INFO (t) = pi;
2286 /* Dump points-to information for SSA_NAME PTR into FILE. */
2289 dump_points_to_info_for (FILE *file, tree ptr)
2291 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2293 print_generic_expr (file, ptr, dump_flags);
2297 if (pi->name_mem_tag)
2299 fprintf (file, ", name memory tag: ");
2300 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2303 if (pi->is_dereferenced)
2304 fprintf (file, ", is dereferenced");
2306 if (pi->value_escapes_p)
2307 fprintf (file, ", its value escapes");
2309 if (pi->pt_anything)
2310 fprintf (file, ", points-to anything");
2313 fprintf (file, ", points-to malloc");
2319 fprintf (file, ", points-to vars: { ");
2320 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix,
2322 print_generic_expr (file, referenced_var (ix), dump_flags);
2323 fprintf (file, " ");
2325 fprintf (file, "}");
2329 fprintf (file, "\n");
2333 /* Dump points-to information for VAR into stderr. */
2336 debug_points_to_info_for (tree var)
2338 dump_points_to_info_for (stderr, var);
2342 /* Dump points-to information into FILE. NOTE: This function is slow, as
2343 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2346 dump_points_to_info (FILE *file)
2349 block_stmt_iterator si;
2353 lang_hooks.decl_printable_name (current_function_decl, 2);
2355 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2357 /* First dump points-to information for the default definitions of
2358 pointer variables. This is necessary because default definitions are
2359 not part of the code. */
2360 for (i = 0; i < num_referenced_vars; i++)
2362 tree var = referenced_var (i);
2363 if (POINTER_TYPE_P (TREE_TYPE (var)))
2365 var_ann_t ann = var_ann (var);
2366 if (ann->default_def)
2367 dump_points_to_info_for (file, ann->default_def);
2371 /* Dump points-to information for every pointer defined in the program. */
2376 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2378 tree ptr = PHI_RESULT (phi);
2379 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2380 dump_points_to_info_for (file, ptr);
2383 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2385 tree stmt = bsi_stmt (si);
2387 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2388 if (POINTER_TYPE_P (TREE_TYPE (def)))
2389 dump_points_to_info_for (file, def);
2393 fprintf (file, "\n");
2397 /* Dump points-to info pointed by PTO into STDERR. */
2400 debug_points_to_info (void)
2402 dump_points_to_info (stderr);
2405 /* Dump to FILE the list of variables that may be aliasing VAR. */
2408 dump_may_aliases_for (FILE *file, tree var)
2410 varray_type aliases;
2412 if (TREE_CODE (var) == SSA_NAME)
2413 var = SSA_NAME_VAR (var);
2415 aliases = var_ann (var)->may_aliases;
2419 fprintf (file, "{ ");
2420 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2422 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2423 fprintf (file, " ");
2425 fprintf (file, "}");
2430 /* Dump to stderr the list of variables that may be aliasing VAR. */
2433 debug_may_aliases_for (tree var)
2435 dump_may_aliases_for (stderr, var);
2438 /* Return true if VAR may be aliased. */
2441 may_be_aliased (tree var)
2444 if (TREE_ADDRESSABLE (var))
2447 /* Globally visible variables can have their addresses taken by other
2448 translation units. */
2449 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2452 /* Automatic variables can't have their addresses escape any other way.
2453 This must be after the check for global variables, as extern declarations
2454 do not have TREE_STATIC set. */
2455 if (!TREE_STATIC (var))
2458 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2459 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2460 we can only be sure the variable isn't addressable if it's local to the
2461 current function. */
2462 if (flag_unit_at_a_time)
2464 if (decl_function_context (var) == current_function_decl)