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 (!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 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_OPERAND (*tp, 0) == ptr)
513 /* Return true if STMT contains INDIRECT_REF <PTR>. *IS_STORE is set
514 to 'true' if the dereference is on the LHS of an assignment. */
517 ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
521 if (TREE_CODE (stmt) == MODIFY_EXPR
522 || (TREE_CODE (stmt) == RETURN_EXPR
523 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
527 e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
528 lhs = TREE_OPERAND (e, 0);
529 rhs = TREE_OPERAND (e, 1);
532 && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
537 else if (EXPR_P (rhs)
538 && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
543 else if (TREE_CODE (stmt) == ASM_EXPR)
545 if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
546 || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
551 else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
561 /* Traverse use-def links for all the pointers in the program to collect
562 address escape and points-to information.
564 This is loosely based on the same idea described in R. Hasti and S.
565 Horwitz, ``Using static single assignment form to improve
566 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
567 Programming Language Design and Implementation, pp. 97-105, 1998. */
570 compute_points_to_and_addr_escape (struct alias_info *ai)
577 timevar_push (TV_TREE_PTA);
581 bb_ann_t block_ann = bb_ann (bb);
582 block_stmt_iterator si;
584 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
587 tree stmt = bsi_stmt (si);
588 bool stmt_escapes_p = is_escape_site (stmt, &ai->num_calls_found);
590 /* Mark all the variables whose address are taken by the
591 statement. Note that this will miss all the addresses taken
592 in PHI nodes (those are discovered while following the use-def
594 get_stmt_operands (stmt);
595 addr_taken = addresses_taken (stmt);
597 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i,
599 tree var = referenced_var (i);
600 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
602 mark_call_clobbered (var);
606 block_ann->has_escape_site = 1;
608 /* Special case for silly ADDR_EXPR tricks
609 (gcc.c-torture/unsorted/pass.c). If this statement is an
610 assignment to a non-pointer variable and the RHS takes the
611 address of a variable, assume that the variable on the RHS is
612 call-clobbered. We could add the LHS to the list of
613 "pointers" and follow it to see if it really escapes, but it's
614 not worth the pain. */
616 && TREE_CODE (stmt) == MODIFY_EXPR
617 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 0))))
618 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i,
620 tree var = referenced_var (i);
621 mark_call_clobbered (var);
624 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
626 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
627 struct ptr_info_def *pi;
630 /* If the operand's variable may be aliased, keep track
631 of how many times we've referenced it. This is used
632 for alias grouping in compute_flow_sensitive_aliasing.
633 Note that we don't need to grow AI->NUM_REFERENCES
634 because we are processing regular variables, not
635 memory tags (the array's initial size is set to
636 NUM_REFERENCED_VARS). */
637 if (may_be_aliased (SSA_NAME_VAR (op)))
638 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
640 if (!POINTER_TYPE_P (TREE_TYPE (op)))
643 collect_points_to_info_for (ai, op);
645 pi = SSA_NAME_PTR_INFO (op);
646 if (ptr_is_dereferenced_by (op, stmt, &is_store))
648 /* Mark OP as dereferenced. In a subsequent pass,
649 dereferenced pointers that point to a set of
650 variables will be assigned a name tag to alias
651 all the variables OP points to. */
652 pi->is_dereferenced = 1;
654 /* Keep track of how many time we've dereferenced each
655 pointer. Again, we don't need to grow
656 AI->NUM_REFERENCES because we're processing
657 existing program variables. */
658 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
660 /* If this is a store operation, mark OP as being
661 dereferenced to store, otherwise mark it as being
662 dereferenced to load. */
664 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
666 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
668 else if (stmt_escapes_p)
670 /* Note that even if STMT is an escape point, pointer OP
671 will not escape if it is being dereferenced. That's
672 why we only check for escape points if OP is not
673 dereferenced by STMT. */
674 pi->value_escapes_p = 1;
676 /* If the statement makes a function call, assume
677 that pointer OP will be dereferenced in a store
678 operation inside the called function. */
679 if (get_call_expr_in (stmt))
681 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
682 pi->is_dereferenced = 1;
687 /* Update reference counter for definitions to any
688 potentially aliased variable. This is used in the alias
689 grouping heuristics. */
690 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
692 tree var = SSA_NAME_VAR (op);
693 var_ann_t ann = var_ann (var);
694 bitmap_set_bit (ai->written_vars, ann->uid);
695 if (may_be_aliased (var))
696 (VARRAY_UINT (ai->num_references, ann->uid))++;
699 /* Mark variables in V_MAY_DEF operands as being written to. */
700 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
702 tree var = SSA_NAME_VAR (op);
703 var_ann_t ann = var_ann (var);
704 bitmap_set_bit (ai->written_vars, ann->uid);
707 /* After promoting variables and computing aliasing we will
708 need to re-scan most statements. FIXME: Try to minimize the
709 number of statements re-scanned. It's not really necessary to
710 re-scan *all* statements. */
715 timevar_pop (TV_TREE_PTA);
719 /* Create name tags for all the pointers that have been dereferenced.
720 We only create a name tag for a pointer P if P is found to point to
721 a set of variables (so that we can alias them to *P) or if it is
722 the result of a call to malloc (which means that P cannot point to
723 anything else nor alias any other variable).
725 If two pointers P and Q point to the same set of variables, they
726 are assigned the same name tag. */
729 create_name_tags (struct alias_info *ai)
733 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
735 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
736 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
738 if (pi->pt_anything || !pi->is_dereferenced)
740 /* No name tags for pointers that have not been
741 dereferenced or point to an arbitrary location. */
742 pi->name_mem_tag = NULL_TREE;
747 && bitmap_first_set_bit (pi->pt_vars) >= 0)
750 tree old_name_tag = pi->name_mem_tag;
752 /* If PTR points to a set of variables, check if we don't
753 have another pointer Q with the same points-to set before
754 creating a tag. If so, use Q's tag instead of creating a
757 This is important for not creating unnecessary symbols
758 and also for copy propagation. If we ever need to
759 propagate PTR into Q or vice-versa, we would run into
760 problems if they both had different name tags because
761 they would have different SSA version numbers (which
762 would force us to take the name tags in and out of SSA). */
763 for (j = 0; j < i; j++)
765 tree q = VARRAY_TREE (ai->processed_ptrs, j);
766 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
771 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
773 pi->name_mem_tag = qi->name_mem_tag;
778 /* If we didn't find a pointer with the same points-to set
779 as PTR, create a new name tag if needed. */
780 if (pi->name_mem_tag == NULL_TREE)
781 pi->name_mem_tag = get_nmt_for (ptr);
783 /* If the new name tag computed for PTR is different than
784 the old name tag that it used to have, then the old tag
785 needs to be removed from the IL, so we mark it for
787 if (old_name_tag && old_name_tag != pi->name_mem_tag)
788 bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid);
790 else if (pi->pt_malloc)
792 /* Otherwise, create a unique name tag for this pointer. */
793 pi->name_mem_tag = get_nmt_for (ptr);
797 /* Only pointers that may point to malloc or other variables
798 may receive a name tag. If the pointer does not point to
799 a known spot, we should use type tags. */
800 set_pt_anything (ptr);
804 /* Mark the new name tag for renaming. */
805 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
811 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
812 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
813 name tag and the variables it points-to are call-clobbered. Finally, if
814 P_i escapes and we could not determine where it points to, then all the
815 variables in the same alias set as *P_i are marked call-clobbered. This
816 is necessary because we must assume that P_i may take the address of any
817 variable in the same alias set. */
820 compute_flow_sensitive_aliasing (struct alias_info *ai)
824 create_name_tags (ai);
826 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
829 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
830 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
831 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
833 if (pi->value_escapes_p || pi->pt_anything)
835 /* If PTR escapes or may point to anything, then its associated
836 memory tags and pointed-to variables are call-clobbered. */
837 if (pi->name_mem_tag)
838 mark_call_clobbered (pi->name_mem_tag);
840 if (v_ann->type_mem_tag)
841 mark_call_clobbered (v_ann->type_mem_tag);
844 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j,
845 mark_call_clobbered (referenced_var (j)));
848 /* Set up aliasing information for PTR's name memory tag (if it has
849 one). Note that only pointers that have been dereferenced will
850 have a name memory tag. */
851 if (pi->name_mem_tag && pi->pt_vars)
852 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j,
853 add_may_alias (pi->name_mem_tag, referenced_var (j)));
855 /* If the name tag is call clobbered, so is the type tag
856 associated with the base VAR_DECL. */
858 && v_ann->type_mem_tag
859 && is_call_clobbered (pi->name_mem_tag))
860 mark_call_clobbered (v_ann->type_mem_tag);
865 /* Compute type-based alias sets. Traverse all the pointers and
866 addressable variables found in setup_pointers_and_addressables.
868 For every pointer P in AI->POINTERS and addressable variable V in
869 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
870 memory tag (TMT) if their alias sets conflict. V is then marked as
871 an alias tag so that the operand scanner knows that statements
872 containing V have aliased operands. */
875 compute_flow_insensitive_aliasing (struct alias_info *ai)
879 /* Initialize counter for the total number of virtual operands that
880 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
881 threshold set by --params max-alias-vops, we enable alias
883 ai->total_alias_vops = 0;
885 /* For every pointer P, determine which addressable variables may alias
886 with P's type memory tag. */
887 for (i = 0; i < ai->num_pointers; i++)
890 struct alias_map_d *p_map = ai->pointers[i];
891 tree tag = var_ann (p_map->var)->type_mem_tag;
892 var_ann_t tag_ann = var_ann (tag);
894 p_map->total_alias_vops = 0;
895 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
896 sbitmap_zero (p_map->may_aliases);
898 for (j = 0; j < ai->num_addressable_vars; j++)
900 struct alias_map_d *v_map;
903 bool tag_stored_p, var_stored_p;
905 v_map = ai->addressable_vars[j];
907 v_ann = var_ann (var);
909 /* Skip memory tags and variables that have never been
910 written to. We also need to check if the variables are
911 call-clobbered because they may be overwritten by
913 tag_stored_p = bitmap_bit_p (ai->written_vars, tag_ann->uid)
914 || is_call_clobbered (tag);
915 var_stored_p = bitmap_bit_p (ai->written_vars, v_ann->uid)
916 || is_call_clobbered (var);
917 if (!tag_stored_p && !var_stored_p)
920 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
922 size_t num_tag_refs, num_var_refs;
924 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
925 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
927 /* If TAG is call clobbered, so is VAR. */
928 if (is_call_clobbered (tag))
929 mark_call_clobbered (var);
931 /* Add VAR to TAG's may-aliases set. */
932 add_may_alias (tag, var);
934 /* Update the total number of virtual operands due to
935 aliasing. Since we are adding one more alias to TAG's
936 may-aliases set, the total number of virtual operands due
937 to aliasing will be increased by the number of references
938 made to VAR and TAG (every reference to TAG will also
939 count as a reference to VAR). */
940 ai->total_alias_vops += (num_var_refs + num_tag_refs);
941 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
943 /* Update the bitmap used to represent TAG's alias set
944 in case we need to group aliases. */
945 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
951 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
952 get_name (current_function_decl),
953 ai->total_alias_vops);
955 /* Determine if we need to enable alias grouping. */
956 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
961 /* Comparison function for qsort used in group_aliases. */
964 total_alias_vops_cmp (const void *p, const void *q)
966 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
967 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
968 long n1 = (*p1)->total_alias_vops;
969 long n2 = (*p2)->total_alias_vops;
971 /* We want to sort in descending order. */
972 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
975 /* Group all the aliases for TAG to make TAG represent all the
976 variables in its alias set. Update the total number
977 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
978 function will make TAG be the unique alias tag for all the
979 variables in its may-aliases. So, given:
981 may-aliases(TAG) = { V1, V2, V3 }
983 This function will group the variables into:
985 may-aliases(V1) = { TAG }
986 may-aliases(V2) = { TAG }
987 may-aliases(V2) = { TAG } */
990 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
993 var_ann_t tag_ann = var_ann (tag);
994 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
996 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
998 tree var = referenced_var (i);
999 var_ann_t ann = var_ann (var);
1001 /* Make TAG the unique alias of VAR. */
1002 ann->is_alias_tag = 0;
1003 ann->may_aliases = NULL;
1005 /* Note that VAR and TAG may be the same if the function has no
1006 addressable variables (see the discussion at the end of
1007 setup_pointers_and_addressables). */
1009 add_may_alias (var, tag);
1011 /* Reduce total number of virtual operands contributed
1012 by TAG on behalf of VAR. Notice that the references to VAR
1013 itself won't be removed. We will merely replace them with
1014 references to TAG. */
1015 ai->total_alias_vops -= num_tag_refs;
1018 /* We have reduced the number of virtual operands that TAG makes on
1019 behalf of all the variables formerly aliased with it. However,
1020 we have also "removed" all the virtual operands for TAG itself,
1021 so we add them back. */
1022 ai->total_alias_vops += num_tag_refs;
1024 /* TAG no longer has any aliases. */
1025 tag_ann->may_aliases = NULL;
1029 /* Group may-aliases sets to reduce the number of virtual operands due
1032 1- Sort the list of pointers in decreasing number of contributed
1035 2- Take the first entry in AI->POINTERS and revert the role of
1036 the memory tag and its aliases. Usually, whenever an aliased
1037 variable Vi is found to alias with a memory tag T, we add Vi
1038 to the may-aliases set for T. Meaning that after alias
1039 analysis, we will have:
1041 may-aliases(T) = { V1, V2, V3, ..., Vn }
1043 This means that every statement that references T, will get 'n'
1044 virtual operands for each of the Vi tags. But, when alias
1045 grouping is enabled, we make T an alias tag and add it to the
1046 alias set of all the Vi variables:
1048 may-aliases(V1) = { T }
1049 may-aliases(V2) = { T }
1051 may-aliases(Vn) = { T }
1053 This has two effects: (a) statements referencing T will only get
1054 a single virtual operand, and, (b) all the variables Vi will now
1055 appear to alias each other. So, we lose alias precision to
1056 improve compile time. But, in theory, a program with such a high
1057 level of aliasing should not be very optimizable in the first
1060 3- Since variables may be in the alias set of more than one
1061 memory tag, the grouping done in step (2) needs to be extended
1062 to all the memory tags that have a non-empty intersection with
1063 the may-aliases set of tag T. For instance, if we originally
1064 had these may-aliases sets:
1066 may-aliases(T) = { V1, V2, V3 }
1067 may-aliases(R) = { V2, V4 }
1069 In step (2) we would have reverted the aliases for T as:
1071 may-aliases(V1) = { T }
1072 may-aliases(V2) = { T }
1073 may-aliases(V3) = { T }
1075 But note that now V2 is no longer aliased with R. We could
1076 add R to may-aliases(V2), but we are in the process of
1077 grouping aliases to reduce virtual operands so what we do is
1078 add V4 to the grouping to obtain:
1080 may-aliases(V1) = { T }
1081 may-aliases(V2) = { T }
1082 may-aliases(V3) = { T }
1083 may-aliases(V4) = { T }
1085 4- If the total number of virtual operands due to aliasing is
1086 still above the threshold set by max-alias-vops, go back to (2). */
1089 group_aliases (struct alias_info *ai)
1094 /* Sort the POINTERS array in descending order of contributed
1095 virtual operands. */
1096 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1097 total_alias_vops_cmp);
1099 res = sbitmap_alloc (num_referenced_vars);
1101 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1102 and the tag's may-aliases set. */
1103 for (i = 0; i < ai->num_pointers; i++)
1106 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1107 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1109 /* Skip tags that have been grouped already. */
1110 if (ai->pointers[i]->grouped_p)
1113 /* See if TAG1 had any aliases in common with other type tags.
1114 If we find a TAG2 with common aliases with TAG1, add TAG2's
1115 aliases into TAG1. */
1116 for (j = i + 1; j < ai->num_pointers; j++)
1118 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1120 sbitmap_a_and_b (res, tag1_aliases, tag2_aliases);
1121 if (sbitmap_first_set_bit (res) >= 0)
1125 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1127 if (!is_call_clobbered (tag1) && is_call_clobbered (tag2))
1129 mark_call_clobbered (tag1);
1130 EXECUTE_IF_SET_IN_SBITMAP (tag1_aliases, 0, k,
1132 tree var = referenced_var (k);
1133 mark_call_clobbered (var);
1136 else if (is_call_clobbered (tag1) && !is_call_clobbered (tag2))
1138 mark_call_clobbered (tag2);
1139 EXECUTE_IF_SET_IN_SBITMAP (tag2_aliases, 0, k,
1141 tree var = referenced_var (k);
1142 mark_call_clobbered (var);
1146 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1148 /* TAG2 does not need its aliases anymore. */
1149 sbitmap_zero (tag2_aliases);
1150 var_ann (tag2)->may_aliases = NULL;
1152 /* TAG1 is the unique alias of TAG2. */
1153 add_may_alias (tag2, tag1);
1155 ai->pointers[j]->grouped_p = true;
1159 /* Now group all the aliases we collected into TAG1. */
1160 group_aliases_into (tag1, tag1_aliases, ai);
1162 /* If we've reduced total number of virtual operands below the
1164 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1168 /* Finally, all the variables that have been grouped cannot be in
1169 the may-alias set of name memory tags. Suppose that we have
1170 grouped the aliases in this code so that may-aliases(a) = TMT.20
1174 # a_9 = V_MAY_DEF <a_8>
1176 ... Several modifications to TMT.20 ...
1180 Since p_5 points to 'a', the optimizers will try to propagate 0
1181 into p_5->field, but that is wrong because there have been
1182 modifications to 'TMT.20' in between. To prevent this we have to
1183 replace 'a' with 'TMT.20' in the name tag of p_5. */
1184 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1187 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1188 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1189 varray_type aliases;
1191 if (name_tag == NULL_TREE)
1194 aliases = var_ann (name_tag)->may_aliases;
1195 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1197 tree alias = VARRAY_TREE (aliases, j);
1198 var_ann_t ann = var_ann (alias);
1200 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1204 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1206 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1207 replace_may_alias (name_tag, j, new_alias);
1216 "%s: Total number of aliased vops after grouping: %ld%s\n",
1217 get_name (current_function_decl),
1218 ai->total_alias_vops,
1219 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1223 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1226 create_alias_map_for (tree var, struct alias_info *ai)
1228 struct alias_map_d *alias_map;
1229 alias_map = xcalloc (1, sizeof (*alias_map));
1230 alias_map->var = var;
1231 alias_map->set = get_alias_set (var);
1232 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1236 /* Create memory tags for all the dereferenced pointers and build the
1237 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1238 sets. Based on the address escape and points-to information collected
1239 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1240 variables whose address is not needed anymore. */
1243 setup_pointers_and_addressables (struct alias_info *ai)
1245 size_t i, n_vars, num_addressable_vars, num_pointers;
1247 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1248 num_addressable_vars = num_pointers = 0;
1249 for (i = 0; i < num_referenced_vars; i++)
1251 tree var = referenced_var (i);
1253 if (may_be_aliased (var))
1254 num_addressable_vars++;
1256 if (POINTER_TYPE_P (TREE_TYPE (var)))
1258 /* Since we don't keep track of volatile variables, assume that
1259 these pointers are used in indirect store operations. */
1260 if (TREE_THIS_VOLATILE (var))
1261 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1267 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1268 always going to be slightly bigger than we actually need them
1269 because some TREE_ADDRESSABLE variables will be marked
1270 non-addressable below and only pointers with unique type tags are
1271 going to be added to POINTERS. */
1272 ai->addressable_vars = xcalloc (num_addressable_vars,
1273 sizeof (struct alias_map_d *));
1274 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1275 ai->num_addressable_vars = 0;
1276 ai->num_pointers = 0;
1278 /* Since we will be creating type memory tags within this loop, cache the
1279 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1281 n_vars = num_referenced_vars;
1283 for (i = 0; i < n_vars; i++)
1285 tree var = referenced_var (i);
1286 var_ann_t v_ann = var_ann (var);
1288 /* Name memory tags already have flow-sensitive aliasing
1289 information, so they need not be processed by
1290 compute_may_aliases. Similarly, type memory tags are already
1291 accounted for when we process their associated pointer. */
1292 if (v_ann->mem_tag_kind != NOT_A_TAG)
1295 /* Remove the ADDRESSABLE flag from every addressable variable whose
1296 address is not needed anymore. This is caused by the propagation
1297 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1298 removal of dead pointer assignments done by the early scalar
1300 if (TREE_ADDRESSABLE (var))
1302 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1303 && v_ann->mem_tag_kind == NOT_A_TAG
1304 && !is_global_var (var))
1306 /* The address of VAR is not needed, remove the
1307 addressable bit, so that it can be optimized as a
1308 regular variable. */
1309 mark_non_addressable (var);
1311 /* Since VAR is now a regular GIMPLE register, we will need
1312 to rename VAR into SSA afterwards. */
1313 bitmap_set_bit (vars_to_rename, v_ann->uid);
1317 /* Add the variable to the set of addressables. Mostly
1318 used when scanning operands for ASM_EXPRs that
1319 clobber memory. In those cases, we need to clobber
1320 all call-clobbered variables and all addressables. */
1321 bitmap_set_bit (addressable_vars, v_ann->uid);
1325 /* Global variables and addressable locals may be aliased. Create an
1326 entry in ADDRESSABLE_VARS for VAR. */
1327 if (may_be_aliased (var))
1329 create_alias_map_for (var, ai);
1330 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1333 /* Add pointer variables that have been dereferenced to the POINTERS
1334 array and create a type memory tag for them. */
1335 if (POINTER_TYPE_P (TREE_TYPE (var)))
1337 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1338 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1343 /* If pointer VAR still doesn't have a memory tag
1344 associated with it, create it now or re-use an
1346 tag = get_tmt_for (var, ai);
1347 t_ann = var_ann (tag);
1349 /* The type tag will need to be renamed into SSA
1350 afterwards. Note that we cannot do this inside
1351 get_tmt_for because aliasing may run multiple times
1352 and we only create type tags the first time. */
1353 bitmap_set_bit (vars_to_rename, t_ann->uid);
1355 /* Associate the tag with pointer VAR. */
1356 v_ann->type_mem_tag = tag;
1358 /* If pointer VAR has been used in a store operation,
1359 then its memory tag must be marked as written-to. */
1360 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1361 bitmap_set_bit (ai->written_vars, t_ann->uid);
1363 /* If pointer VAR is a global variable or a PARM_DECL,
1364 then its memory tag should be considered a global
1366 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1367 mark_call_clobbered (tag);
1369 /* All the dereferences of pointer VAR count as
1370 references of TAG. Since TAG can be associated with
1371 several pointers, add the dereferences of VAR to the
1372 TAG. We may need to grow AI->NUM_REFERENCES because
1373 we have been adding name and type tags. */
1374 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1375 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1377 VARRAY_UINT (ai->num_references, t_ann->uid)
1378 += VARRAY_UINT (ai->num_references, v_ann->uid);
1382 /* The pointer has not been dereferenced. If it had a
1383 type memory tag, remove it and mark the old tag for
1384 renaming to remove it out of the IL. */
1385 var_ann_t ann = var_ann (var);
1386 tree tag = ann->type_mem_tag;
1389 bitmap_set_bit (vars_to_rename, var_ann (tag)->uid);
1390 ann->type_mem_tag = NULL_TREE;
1396 /* If we found no addressable variables, but we have more than one
1397 pointer, we will need to check for conflicts between the
1398 pointers. Otherwise, we would miss alias relations as in
1399 testsuite/gcc.dg/tree-ssa/20040319-1.c:
1401 struct bar { int count; int *arr;};
1403 void foo (struct bar *b)
1411 b->count and *(b->arr) could be aliased if b->arr == &b->count.
1412 To do this, we add all the memory tags for the pointers in
1413 AI->POINTERS to AI->ADDRESSABLE_VARS, so that
1414 compute_flow_insensitive_aliasing will naturally compare every
1415 pointer to every type tag. */
1416 if (ai->num_addressable_vars == 0
1417 && ai->num_pointers > 1)
1419 free (ai->addressable_vars);
1420 ai->addressable_vars = xcalloc (ai->num_pointers,
1421 sizeof (struct alias_map_d *));
1422 ai->num_addressable_vars = 0;
1423 for (i = 0; i < ai->num_pointers; i++)
1425 struct alias_map_d *p = ai->pointers[i];
1426 tree tag = var_ann (p->var)->type_mem_tag;
1427 create_alias_map_for (tag, ai);
1433 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1434 every call site, we need to emit V_MAY_DEF expressions to represent the
1435 clobbering effects of the call for variables whose address escapes the
1438 One approach is to group all call-clobbered variables into a single
1439 representative that is used as an alias of every call-clobbered variable
1440 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1441 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1443 The second approach is to emit a clobbering V_MAY_DEF for every
1444 call-clobbered variable at call sites. This is the preferred way in terms
1445 of optimization opportunities but it may create too many V_MAY_DEF operands
1446 if there are many call clobbered variables and function calls in the
1449 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1450 function calls found by the number of call-clobbered variables. If that
1451 product is beyond a certain threshold, as determined by the parameterized
1452 values shown below, we use .GLOBAL_VAR.
1454 FIXME. This heuristic should be improved. One idea is to use several
1455 .GLOBAL_VARs of different types instead of a single one. The thresholds
1456 have been derived from a typical bootstrap cycle, including all target
1457 libraries. Compile times were found increase by ~1% compared to using
1461 maybe_create_global_var (struct alias_info *ai)
1463 size_t i, n_clobbered;
1465 /* No need to create it, if we have one already. */
1466 if (global_var == NULL_TREE)
1468 /* Count all the call-clobbered variables. */
1470 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, n_clobbered++);
1472 /* Create .GLOBAL_VAR if we have too many call-clobbered
1473 variables. We also create .GLOBAL_VAR when there no
1474 call-clobbered variables to prevent code motion
1475 transformations from re-arranging function calls that may
1476 have side effects. For instance,
1485 There are no call-clobbered variables in foo(), so it would
1486 be entirely possible for a pass to want to move the call to
1487 f() after the call to g(). If f() has side effects, that
1488 would be wrong. Creating .GLOBAL_VAR in this case will
1489 insert VDEFs for it and prevent such transformations. */
1490 if (n_clobbered == 0
1491 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1492 create_global_var ();
1495 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1496 been created, make it an alias for all call-clobbered variables. */
1498 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i,
1500 tree var = referenced_var (i);
1501 if (var != global_var)
1503 add_may_alias (var, global_var);
1504 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1510 /* Return TRUE if pointer PTR may point to variable VAR.
1512 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1513 This is needed because when checking for type conflicts we are
1514 interested in the alias set of the memory location pointed-to by
1515 PTR. The alias set of PTR itself is irrelevant.
1517 VAR_ALIAS_SET is the alias set for VAR. */
1520 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1521 tree var, HOST_WIDE_INT var_alias_set)
1524 var_ann_t v_ann, m_ann;
1526 alias_stats.alias_queries++;
1527 alias_stats.simple_queries++;
1529 /* By convention, a variable cannot alias itself. */
1530 mem = var_ann (ptr)->type_mem_tag;
1533 alias_stats.alias_noalias++;
1534 alias_stats.simple_resolved++;
1538 v_ann = var_ann (var);
1539 m_ann = var_ann (mem);
1541 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1543 alias_stats.tbaa_queries++;
1545 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1546 PTR can't possibly affect VAR. Note, that we are specifically testing
1547 for PTR's alias set here, not its pointed-to type. We also can't
1548 do this check with relaxed aliasing enabled. */
1549 if (POINTER_TYPE_P (TREE_TYPE (var))
1550 && var_alias_set != 0)
1552 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1553 if (ptr_alias_set == var_alias_set)
1555 alias_stats.alias_noalias++;
1556 alias_stats.tbaa_resolved++;
1561 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1562 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1564 /* Handle aliases to structure fields. If either VAR or MEM are
1565 aggregate types, they may not have conflicting types, but one of
1566 the structures could contain a pointer to the other one.
1573 It may happen that '*p' and '*q' can't alias because 'struct P'
1574 and 'struct Q' have non-conflicting alias sets. However, it could
1575 happen that one of the fields in 'struct P' is a 'struct Q *' or
1578 Therefore, we also need to check if 'struct P' aliases 'struct Q *'
1579 or 'struct Q' aliases 'struct P *'. Notice, that since GIMPLE
1580 does not have more than one-level pointers, we don't need to
1581 recurse into the structures. */
1582 if (AGGREGATE_TYPE_P (TREE_TYPE (mem))
1583 || AGGREGATE_TYPE_P (TREE_TYPE (var)))
1587 if (TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE)
1588 ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (TREE_TYPE (var)));
1590 ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (var));
1592 /* If no pointer-to VAR exists, then MEM can't alias VAR. */
1593 if (ptr_to_var == NULL_TREE)
1595 alias_stats.alias_noalias++;
1596 alias_stats.tbaa_resolved++;
1600 /* If MEM doesn't alias a pointer to VAR and VAR doesn't alias
1601 PTR, then PTR can't alias VAR. */
1602 if (!alias_sets_conflict_p (mem_alias_set, get_alias_set (ptr_to_var))
1603 && !alias_sets_conflict_p (var_alias_set, get_alias_set (ptr)))
1605 alias_stats.alias_noalias++;
1606 alias_stats.tbaa_resolved++;
1612 alias_stats.alias_noalias++;
1613 alias_stats.tbaa_resolved++;
1618 alias_stats.alias_mayalias++;
1623 /* Add ALIAS to the set of variables that may alias VAR. */
1626 add_may_alias (tree var, tree alias)
1629 var_ann_t v_ann = get_var_ann (var);
1630 var_ann_t a_ann = get_var_ann (alias);
1632 gcc_assert (var != alias);
1634 if (v_ann->may_aliases == NULL)
1635 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1637 /* Avoid adding duplicates. */
1638 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1639 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1642 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1643 a_ann->is_alias_tag = 1;
1647 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1650 replace_may_alias (tree var, size_t i, tree new_alias)
1652 var_ann_t v_ann = var_ann (var);
1653 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1657 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1660 set_pt_anything (tree ptr)
1662 struct ptr_info_def *pi = get_ptr_info (ptr);
1664 pi->pt_anything = 1;
1667 /* The pointer used to have a name tag, but we now found it pointing
1668 to an arbitrary location. The name tag needs to be renamed and
1669 disassociated from PTR. */
1670 if (pi->name_mem_tag)
1672 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1673 pi->name_mem_tag = NULL_TREE;
1678 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1681 set_pt_malloc (tree ptr)
1683 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1685 /* If the pointer has already been found to point to arbitrary
1686 memory locations, it is unsafe to mark it as pointing to malloc. */
1687 if (pi->pt_anything)
1694 /* Given two pointers DEST and ORIG. Merge the points-to information in
1695 ORIG into DEST. AI is as in collect_points_to_info. */
1698 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1700 struct ptr_info_def *dest_pi, *orig_pi;
1702 /* Make sure we have points-to information for ORIG. */
1703 collect_points_to_info_for (ai, orig);
1705 dest_pi = get_ptr_info (dest);
1706 orig_pi = SSA_NAME_PTR_INFO (orig);
1710 dest_pi->pt_global_mem |= orig_pi->pt_global_mem;
1712 /* Notice that we never merge PT_MALLOC. This attribute is only
1713 true if the pointer is the result of a malloc() call.
1714 Otherwise, we can end up in this situation:
1720 P_j would be marked as PT_MALLOC, which is wrong because
1721 PT_MALLOC implies that the pointer may not point to another
1724 FIXME 1: Subsequent analysis may determine that P_j
1725 cannot alias anything else, but we are being conservative
1728 FIXME 2: If the merging comes from a copy assignment, we
1729 ought to merge PT_MALLOC, but then both pointers would end up
1730 getting different name tags because create_name_tags is not
1731 smart enough to determine that the two come from the same
1732 malloc call. Copy propagation before aliasing should cure
1734 dest_pi->pt_malloc = 0;
1736 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1737 set_pt_anything (dest);
1739 if (!dest_pi->pt_anything
1741 && bitmap_first_set_bit (orig_pi->pt_vars) >= 0)
1743 if (dest_pi->pt_vars == NULL)
1745 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1746 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1749 bitmap_a_or_b (dest_pi->pt_vars,
1755 set_pt_anything (dest);
1759 /* Add VALUE to the list of expressions pointed-to by PTR. */
1762 add_pointed_to_expr (tree ptr, tree value)
1764 if (TREE_CODE (value) == WITH_SIZE_EXPR)
1765 value = TREE_OPERAND (value, 0);
1767 /* Pointer variables should have been handled by merge_pointed_to_info. */
1768 gcc_assert (TREE_CODE (value) != SSA_NAME
1769 || !POINTER_TYPE_P (TREE_TYPE (value)));
1773 /* If VALUE is the result of a malloc-like call, then the area pointed to
1774 PTR is guaranteed to not alias with anything else. */
1775 if (TREE_CODE (value) == CALL_EXPR
1776 && (call_expr_flags (value) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1777 set_pt_malloc (ptr);
1779 set_pt_anything (ptr);
1783 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1785 fprintf (dump_file, "Pointer ");
1786 print_generic_expr (dump_file, ptr, dump_flags);
1787 fprintf (dump_file, " points to ");
1789 fprintf (dump_file, "malloc space: ");
1791 fprintf (dump_file, "an arbitrary address: ");
1792 print_generic_expr (dump_file, value, dump_flags);
1793 fprintf (dump_file, "\n");
1798 /* If VALUE is of the form &DECL, add DECL to the set of variables
1799 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1800 PTR. AI is as in collect_points_to_info. */
1803 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1805 struct ptr_info_def *pi = get_ptr_info (ptr);
1809 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
1811 pt_var = TREE_OPERAND (value, 0);
1812 if (TREE_CODE_CLASS (TREE_CODE (pt_var)) == 'r')
1813 pt_var = get_base_address (pt_var);
1815 if (pt_var && SSA_VAR_P (pt_var))
1817 uid = var_ann (pt_var)->uid;
1818 bitmap_set_bit (ai->addresses_needed, uid);
1820 if (pi->pt_vars == NULL)
1821 pi->pt_vars = BITMAP_GGC_ALLOC ();
1822 bitmap_set_bit (pi->pt_vars, uid);
1824 /* If the variable is a global, mark the pointer as pointing to
1825 global memory (which will make its tag a global variable). */
1826 if (is_global_var (pt_var))
1827 pi->pt_global_mem = 1;
1832 /* Callback for walk_use_def_chains to gather points-to information from the
1835 VAR is an SSA variable or a GIMPLE expression.
1837 STMT is the statement that generates the SSA variable or, if STMT is a
1838 PHI_NODE, VAR is one of the PHI arguments.
1840 DATA is a pointer to a structure of type ALIAS_INFO. */
1843 collect_points_to_info_r (tree var, tree stmt, void *data)
1845 struct alias_info *ai = (struct alias_info *) data;
1847 if (dump_file && (dump_flags & TDF_DETAILS))
1849 fprintf (dump_file, "Visiting use-def links for ");
1850 print_generic_expr (dump_file, var, dump_flags);
1851 fprintf (dump_file, "\n");
1854 switch (TREE_CODE (stmt))
1858 tree rhs = TREE_OPERAND (stmt, 1);
1861 /* Found P_i = ADDR_EXPR */
1862 if (TREE_CODE (rhs) == ADDR_EXPR)
1863 add_pointed_to_var (ai, var, rhs);
1865 /* Found P_i = Q_j. */
1866 else if (TREE_CODE (rhs) == SSA_NAME
1867 && POINTER_TYPE_P (TREE_TYPE (rhs)))
1868 merge_pointed_to_info (ai, var, rhs);
1870 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1871 else if (TREE_CODE (rhs) == PLUS_EXPR
1872 || TREE_CODE (rhs) == MINUS_EXPR)
1874 tree op0 = TREE_OPERAND (rhs, 0);
1875 tree op1 = TREE_OPERAND (rhs, 1);
1877 /* Both operands may be of pointer type. FIXME: Shouldn't
1878 we just expect PTR + OFFSET always? */
1879 if (POINTER_TYPE_P (TREE_TYPE (op0)))
1881 if (TREE_CODE (op0) == SSA_NAME)
1882 merge_pointed_to_info (ai, var, op0);
1883 else if (TREE_CODE (op0) == ADDR_EXPR)
1884 add_pointed_to_var (ai, var, op0);
1886 add_pointed_to_expr (var, op0);
1889 if (POINTER_TYPE_P (TREE_TYPE (op1)))
1891 if (TREE_CODE (op1) == SSA_NAME)
1892 merge_pointed_to_info (ai, var, op1);
1893 else if (TREE_CODE (op1) == ADDR_EXPR)
1894 add_pointed_to_var (ai, var, op1);
1896 add_pointed_to_expr (var, op1);
1899 /* Neither operand is a pointer? VAR can be pointing
1900 anywhere. FIXME: Is this right? If we get here, we
1901 found PTR = INT_CST + INT_CST. */
1902 if (!POINTER_TYPE_P (TREE_TYPE (op0))
1903 && !POINTER_TYPE_P (TREE_TYPE (op1)))
1904 add_pointed_to_expr (var, rhs);
1907 /* Something else. */
1909 add_pointed_to_expr (var, rhs);
1913 /* Pointers defined by __asm__ statements can point anywhere. */
1914 set_pt_anything (var);
1918 if (IS_EMPTY_STMT (stmt))
1920 tree decl = SSA_NAME_VAR (var);
1922 if (TREE_CODE (decl) == PARM_DECL)
1923 add_pointed_to_expr (var, decl);
1924 else if (DECL_INITIAL (decl))
1925 add_pointed_to_var (ai, var, DECL_INITIAL (decl));
1927 add_pointed_to_expr (var, decl);
1932 /* It STMT is a PHI node, then VAR is one of its arguments. The
1933 variable that we are analyzing is the LHS of the PHI node. */
1934 tree lhs = PHI_RESULT (stmt);
1936 switch (TREE_CODE (var))
1939 add_pointed_to_var (ai, lhs, var);
1943 merge_pointed_to_info (ai, lhs, var);
1947 gcc_assert (is_gimple_min_invariant (var));
1948 add_pointed_to_expr (lhs, var);
1961 /* Return true if STMT is an "escape" site from the current function. Escape
1962 sites those statements which might expose the address of a variable
1963 outside the current function. STMT is an escape site iff:
1965 1- STMT is a function call, or
1966 2- STMT is an __asm__ expression, or
1967 3- STMT is an assignment to a non-local variable, or
1968 4- STMT is a return statement.
1970 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
1974 is_escape_site (tree stmt, size_t *num_calls_p)
1976 if (get_call_expr_in (stmt) != NULL_TREE)
1983 else if (TREE_CODE (stmt) == ASM_EXPR)
1985 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1987 tree lhs = TREE_OPERAND (stmt, 0);
1989 /* Get to the base of _REF nodes. */
1990 if (TREE_CODE (lhs) != SSA_NAME)
1991 lhs = get_base_address (lhs);
1993 /* If we couldn't recognize the LHS of the assignment, assume that it
1994 is a non-local store. */
1995 if (lhs == NULL_TREE)
1998 /* If the LHS is an SSA name, it can't possibly represent a non-local
2000 if (TREE_CODE (lhs) == SSA_NAME)
2003 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2004 local variables we cannot be sure if it will escape, because we
2005 don't have information about objects not in SSA form. Need to
2006 implement something along the lines of
2008 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2009 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2010 Conference on Object-Oriented Programming Systems, Languages, and
2011 Applications (OOPSLA), pp. 1-19, 1999. */
2014 else if (TREE_CODE (stmt) == RETURN_EXPR)
2021 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2022 is considered to represent all the pointers whose pointed-to types are
2023 in the same alias set class. Otherwise, the tag represents a single
2024 SSA_NAME pointer variable. */
2027 create_memory_tag (tree type, bool is_type_tag)
2030 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2032 /* By default, memory tags are local variables. Alias analysis will
2033 determine whether they should be considered globals. */
2034 DECL_CONTEXT (tag) = current_function_decl;
2036 /* If the pointed-to type is volatile, so is the tag. */
2037 TREE_THIS_VOLATILE (tag) = TREE_THIS_VOLATILE (type);
2039 /* Memory tags are by definition addressable. This also prevents
2040 is_gimple_ref frome confusing memory tags with optimizable
2042 TREE_ADDRESSABLE (tag) = 1;
2044 ann = get_var_ann (tag);
2045 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2046 ann->type_mem_tag = NULL_TREE;
2048 /* Add the tag to the symbol table. */
2049 add_referenced_tmp_var (tag);
2055 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2056 This is used if P_i has been found to point to a specific set of
2057 variables or to a non-aliased memory location like the address returned
2058 by malloc functions. */
2061 get_nmt_for (tree ptr)
2063 struct ptr_info_def *pi = get_ptr_info (ptr);
2064 tree tag = pi->name_mem_tag;
2066 if (tag == NULL_TREE)
2067 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2069 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2070 then its name tag should be considered a global variable. */
2071 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2073 || pi->pt_global_mem)
2074 mark_call_clobbered (tag);
2080 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2081 artificial variable that represents the memory location pointed-to by
2082 PTR. It is used to model the effects of pointer de-references on
2083 addressable variables.
2085 AI points to the data gathered during alias analysis. This function
2086 populates the array AI->POINTERS. */
2089 get_tmt_for (tree ptr, struct alias_info *ai)
2093 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2094 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2096 /* To avoid creating unnecessary memory tags, only create one memory tag
2097 per alias set class. Note that it may be tempting to group
2098 memory tags based on conflicting alias sets instead of
2099 equivalence. That would be wrong because alias sets are not
2100 necessarily transitive (as demonstrated by the libstdc++ test
2101 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2102 such that conflicts (A, B) == true and conflicts (A, C) == true,
2103 it does not necessarily follow that conflicts (B, C) == true. */
2104 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2106 struct alias_map_d *curr = ai->pointers[i];
2107 if (tag_set == curr->set)
2109 tag = var_ann (curr->var)->type_mem_tag;
2114 /* If VAR cannot alias with any of the existing memory tags, create a new
2115 tag for PTR and add it to the POINTERS array. */
2116 if (tag == NULL_TREE)
2118 struct alias_map_d *alias_map;
2120 /* If PTR did not have a type tag already, create a new TMT.*
2121 artificial variable representing the memory location
2122 pointed-to by PTR. */
2123 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2124 tag = create_memory_tag (tag_type, true);
2126 tag = var_ann (ptr)->type_mem_tag;
2128 /* Add PTR to the POINTERS array. Note that we are not interested in
2129 PTR's alias set. Instead, we cache the alias set for the memory that
2131 alias_map = xcalloc (1, sizeof (*alias_map));
2132 alias_map->var = ptr;
2133 alias_map->set = tag_set;
2134 ai->pointers[ai->num_pointers++] = alias_map;
2137 /* Make sure that the type tag has the same alias set as the
2139 gcc_assert (tag_set == get_alias_set (tag));
2145 /* Create GLOBAL_VAR, an artificial global variable to act as a
2146 representative of all the variables that may be clobbered by function
2150 create_global_var (void)
2152 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2154 DECL_ARTIFICIAL (global_var) = 1;
2155 TREE_READONLY (global_var) = 0;
2156 DECL_EXTERNAL (global_var) = 1;
2157 TREE_STATIC (global_var) = 1;
2158 TREE_USED (global_var) = 1;
2159 DECL_CONTEXT (global_var) = NULL_TREE;
2160 TREE_THIS_VOLATILE (global_var) = 0;
2161 TREE_ADDRESSABLE (global_var) = 0;
2163 add_referenced_tmp_var (global_var);
2164 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2168 /* Dump alias statistics on FILE. */
2171 dump_alias_stats (FILE *file)
2173 const char *funcname
2174 = lang_hooks.decl_printable_name (current_function_decl, 2);
2175 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2176 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2177 fprintf (file, "Total alias mayalias results:\t%u\n",
2178 alias_stats.alias_mayalias);
2179 fprintf (file, "Total alias noalias results:\t%u\n",
2180 alias_stats.alias_noalias);
2181 fprintf (file, "Total simple queries:\t%u\n",
2182 alias_stats.simple_queries);
2183 fprintf (file, "Total simple resolved:\t%u\n",
2184 alias_stats.simple_resolved);
2185 fprintf (file, "Total TBAA queries:\t%u\n",
2186 alias_stats.tbaa_queries);
2187 fprintf (file, "Total TBAA resolved:\t%u\n",
2188 alias_stats.tbaa_resolved);
2192 /* Dump alias information on FILE. */
2195 dump_alias_info (FILE *file)
2198 const char *funcname
2199 = lang_hooks.decl_printable_name (current_function_decl, 2);
2201 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2203 fprintf (file, "Aliased symbols\n\n");
2204 for (i = 0; i < num_referenced_vars; i++)
2206 tree var = referenced_var (i);
2207 if (may_be_aliased (var))
2208 dump_variable (file, var);
2211 fprintf (file, "\nDereferenced pointers\n\n");
2212 for (i = 0; i < num_referenced_vars; i++)
2214 tree var = referenced_var (i);
2215 var_ann_t ann = var_ann (var);
2216 if (ann->type_mem_tag)
2217 dump_variable (file, var);
2220 fprintf (file, "\nType memory tags\n\n");
2221 for (i = 0; i < num_referenced_vars; i++)
2223 tree var = referenced_var (i);
2224 var_ann_t ann = var_ann (var);
2225 if (ann->mem_tag_kind == TYPE_TAG)
2226 dump_variable (file, var);
2229 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2231 fprintf (file, "SSA_NAME pointers\n\n");
2232 for (i = 1; i < num_ssa_names; i++)
2234 tree ptr = ssa_name (i);
2235 struct ptr_info_def *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)