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 /* Add VAR to TAG's may-aliases set. */
928 add_may_alias (tag, var);
930 /* Update the total number of virtual operands due to
931 aliasing. Since we are adding one more alias to TAG's
932 may-aliases set, the total number of virtual operands due
933 to aliasing will be increased by the number of references
934 made to VAR and TAG (every reference to TAG will also
935 count as a reference to VAR). */
936 ai->total_alias_vops += (num_var_refs + num_tag_refs);
937 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
939 /* Update the bitmap used to represent TAG's alias set
940 in case we need to group aliases. */
941 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
947 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
948 get_name (current_function_decl),
949 ai->total_alias_vops);
951 /* Determine if we need to enable alias grouping. */
952 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
957 /* Comparison function for qsort used in group_aliases. */
960 total_alias_vops_cmp (const void *p, const void *q)
962 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
963 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
964 long n1 = (*p1)->total_alias_vops;
965 long n2 = (*p2)->total_alias_vops;
967 /* We want to sort in descending order. */
968 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
971 /* Group all the aliases for TAG to make TAG represent all the
972 variables in its alias set. Update the total number
973 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
974 function will make TAG be the unique alias tag for all the
975 variables in its may-aliases. So, given:
977 may-aliases(TAG) = { V1, V2, V3 }
979 This function will group the variables into:
981 may-aliases(V1) = { TAG }
982 may-aliases(V2) = { TAG }
983 may-aliases(V2) = { TAG } */
986 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
989 var_ann_t tag_ann = var_ann (tag);
990 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
992 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
994 tree var = referenced_var (i);
995 var_ann_t ann = var_ann (var);
997 /* Make TAG the unique alias of VAR. */
998 ann->is_alias_tag = 0;
999 ann->may_aliases = NULL;
1001 /* Note that VAR and TAG may be the same if the function has no
1002 addressable variables (see the discussion at the end of
1003 setup_pointers_and_addressables). */
1005 add_may_alias (var, tag);
1007 /* Reduce total number of virtual operands contributed
1008 by TAG on behalf of VAR. Notice that the references to VAR
1009 itself won't be removed. We will merely replace them with
1010 references to TAG. */
1011 ai->total_alias_vops -= num_tag_refs;
1014 /* We have reduced the number of virtual operands that TAG makes on
1015 behalf of all the variables formerly aliased with it. However,
1016 we have also "removed" all the virtual operands for TAG itself,
1017 so we add them back. */
1018 ai->total_alias_vops += num_tag_refs;
1020 /* TAG no longer has any aliases. */
1021 tag_ann->may_aliases = NULL;
1025 /* Group may-aliases sets to reduce the number of virtual operands due
1028 1- Sort the list of pointers in decreasing number of contributed
1031 2- Take the first entry in AI->POINTERS and revert the role of
1032 the memory tag and its aliases. Usually, whenever an aliased
1033 variable Vi is found to alias with a memory tag T, we add Vi
1034 to the may-aliases set for T. Meaning that after alias
1035 analysis, we will have:
1037 may-aliases(T) = { V1, V2, V3, ..., Vn }
1039 This means that every statement that references T, will get 'n'
1040 virtual operands for each of the Vi tags. But, when alias
1041 grouping is enabled, we make T an alias tag and add it to the
1042 alias set of all the Vi variables:
1044 may-aliases(V1) = { T }
1045 may-aliases(V2) = { T }
1047 may-aliases(Vn) = { T }
1049 This has two effects: (a) statements referencing T will only get
1050 a single virtual operand, and, (b) all the variables Vi will now
1051 appear to alias each other. So, we lose alias precision to
1052 improve compile time. But, in theory, a program with such a high
1053 level of aliasing should not be very optimizable in the first
1056 3- Since variables may be in the alias set of more than one
1057 memory tag, the grouping done in step (2) needs to be extended
1058 to all the memory tags that have a non-empty intersection with
1059 the may-aliases set of tag T. For instance, if we originally
1060 had these may-aliases sets:
1062 may-aliases(T) = { V1, V2, V3 }
1063 may-aliases(R) = { V2, V4 }
1065 In step (2) we would have reverted the aliases for T as:
1067 may-aliases(V1) = { T }
1068 may-aliases(V2) = { T }
1069 may-aliases(V3) = { T }
1071 But note that now V2 is no longer aliased with R. We could
1072 add R to may-aliases(V2), but we are in the process of
1073 grouping aliases to reduce virtual operands so what we do is
1074 add V4 to the grouping to obtain:
1076 may-aliases(V1) = { T }
1077 may-aliases(V2) = { T }
1078 may-aliases(V3) = { T }
1079 may-aliases(V4) = { T }
1081 4- If the total number of virtual operands due to aliasing is
1082 still above the threshold set by max-alias-vops, go back to (2). */
1085 group_aliases (struct alias_info *ai)
1090 /* Sort the POINTERS array in descending order of contributed
1091 virtual operands. */
1092 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1093 total_alias_vops_cmp);
1095 res = sbitmap_alloc (num_referenced_vars);
1097 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1098 and the tag's may-aliases set. */
1099 for (i = 0; i < ai->num_pointers; i++)
1102 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1103 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1105 /* Skip tags that have been grouped already. */
1106 if (ai->pointers[i]->grouped_p)
1109 /* See if TAG1 had any aliases in common with other type tags.
1110 If we find a TAG2 with common aliases with TAG1, add TAG2's
1111 aliases into TAG1. */
1112 for (j = i + 1; j < ai->num_pointers; j++)
1114 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1116 sbitmap_a_and_b (res, tag1_aliases, tag2_aliases);
1117 if (sbitmap_first_set_bit (res) >= 0)
1119 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1121 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1123 /* TAG2 does not need its aliases anymore. */
1124 sbitmap_zero (tag2_aliases);
1125 var_ann (tag2)->may_aliases = NULL;
1127 /* TAG1 is the unique alias of TAG2. */
1128 add_may_alias (tag2, tag1);
1130 ai->pointers[j]->grouped_p = true;
1134 /* Now group all the aliases we collected into TAG1. */
1135 group_aliases_into (tag1, tag1_aliases, ai);
1137 /* If we've reduced total number of virtual operands below the
1139 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1143 /* Finally, all the variables that have been grouped cannot be in
1144 the may-alias set of name memory tags. Suppose that we have
1145 grouped the aliases in this code so that may-aliases(a) = TMT.20
1149 # a_9 = V_MAY_DEF <a_8>
1151 ... Several modifications to TMT.20 ...
1155 Since p_5 points to 'a', the optimizers will try to propagate 0
1156 into p_5->field, but that is wrong because there have been
1157 modifications to 'TMT.20' in between. To prevent this we have to
1158 replace 'a' with 'TMT.20' in the name tag of p_5. */
1159 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1162 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1163 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1164 varray_type aliases;
1166 if (name_tag == NULL_TREE)
1169 aliases = var_ann (name_tag)->may_aliases;
1170 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1172 tree alias = VARRAY_TREE (aliases, j);
1173 var_ann_t ann = var_ann (alias);
1175 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1179 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1181 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1182 replace_may_alias (name_tag, j, new_alias);
1191 "%s: Total number of aliased vops after grouping: %ld%s\n",
1192 get_name (current_function_decl),
1193 ai->total_alias_vops,
1194 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1198 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1201 create_alias_map_for (tree var, struct alias_info *ai)
1203 struct alias_map_d *alias_map;
1204 alias_map = xcalloc (1, sizeof (*alias_map));
1205 alias_map->var = var;
1206 alias_map->set = get_alias_set (var);
1207 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1211 /* Create memory tags for all the dereferenced pointers and build the
1212 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1213 sets. Based on the address escape and points-to information collected
1214 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1215 variables whose address is not needed anymore. */
1218 setup_pointers_and_addressables (struct alias_info *ai)
1220 size_t i, n_vars, num_addressable_vars, num_pointers;
1222 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1223 num_addressable_vars = num_pointers = 0;
1224 for (i = 0; i < num_referenced_vars; i++)
1226 tree var = referenced_var (i);
1228 if (may_be_aliased (var))
1229 num_addressable_vars++;
1231 if (POINTER_TYPE_P (TREE_TYPE (var)))
1233 /* Since we don't keep track of volatile variables, assume that
1234 these pointers are used in indirect store operations. */
1235 if (TREE_THIS_VOLATILE (var))
1236 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1242 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1243 always going to be slightly bigger than we actually need them
1244 because some TREE_ADDRESSABLE variables will be marked
1245 non-addressable below and only pointers with unique type tags are
1246 going to be added to POINTERS. */
1247 ai->addressable_vars = xcalloc (num_addressable_vars,
1248 sizeof (struct alias_map_d *));
1249 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1250 ai->num_addressable_vars = 0;
1251 ai->num_pointers = 0;
1253 /* Since we will be creating type memory tags within this loop, cache the
1254 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1256 n_vars = num_referenced_vars;
1258 for (i = 0; i < n_vars; i++)
1260 tree var = referenced_var (i);
1261 var_ann_t v_ann = var_ann (var);
1263 /* Name memory tags already have flow-sensitive aliasing
1264 information, so they need not be processed by
1265 compute_may_aliases. Similarly, type memory tags are already
1266 accounted for when we process their associated pointer. */
1267 if (v_ann->mem_tag_kind != NOT_A_TAG)
1270 /* Remove the ADDRESSABLE flag from every addressable variable whose
1271 address is not needed anymore. This is caused by the propagation
1272 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1273 removal of dead pointer assignments done by the early scalar
1275 if (TREE_ADDRESSABLE (var))
1277 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1278 && v_ann->mem_tag_kind == NOT_A_TAG
1279 && !is_global_var (var))
1281 /* The address of VAR is not needed, remove the
1282 addressable bit, so that it can be optimized as a
1283 regular variable. */
1284 mark_non_addressable (var);
1286 /* Since VAR is now a regular GIMPLE register, we will need
1287 to rename VAR into SSA afterwards. */
1288 bitmap_set_bit (vars_to_rename, v_ann->uid);
1292 /* Add the variable to the set of addressables. Mostly
1293 used when scanning operands for ASM_EXPRs that
1294 clobber memory. In those cases, we need to clobber
1295 all call-clobbered variables and all addressables. */
1296 bitmap_set_bit (addressable_vars, v_ann->uid);
1300 /* Global variables and addressable locals may be aliased. Create an
1301 entry in ADDRESSABLE_VARS for VAR. */
1302 if (may_be_aliased (var))
1304 create_alias_map_for (var, ai);
1305 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1308 /* Add pointer variables that have been dereferenced to the POINTERS
1309 array and create a type memory tag for them. */
1310 if (POINTER_TYPE_P (TREE_TYPE (var)))
1312 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1313 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1318 /* If pointer VAR still doesn't have a memory tag
1319 associated with it, create it now or re-use an
1321 tag = get_tmt_for (var, ai);
1322 t_ann = var_ann (tag);
1324 /* The type tag will need to be renamed into SSA
1325 afterwards. Note that we cannot do this inside
1326 get_tmt_for because aliasing may run multiple times
1327 and we only create type tags the first time. */
1328 bitmap_set_bit (vars_to_rename, t_ann->uid);
1330 /* Associate the tag with pointer VAR. */
1331 v_ann->type_mem_tag = tag;
1333 /* If pointer VAR has been used in a store operation,
1334 then its memory tag must be marked as written-to. */
1335 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1336 bitmap_set_bit (ai->written_vars, t_ann->uid);
1338 /* If pointer VAR is a global variable or a PARM_DECL,
1339 then its memory tag should be considered a global
1341 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1342 mark_call_clobbered (tag);
1344 /* All the dereferences of pointer VAR count as
1345 references of TAG. Since TAG can be associated with
1346 several pointers, add the dereferences of VAR to the
1347 TAG. We may need to grow AI->NUM_REFERENCES because
1348 we have been adding name and type tags. */
1349 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1350 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1352 VARRAY_UINT (ai->num_references, t_ann->uid)
1353 += VARRAY_UINT (ai->num_references, v_ann->uid);
1357 /* The pointer has not been dereferenced. If it had a
1358 type memory tag, remove it and mark the old tag for
1359 renaming to remove it out of the IL. */
1360 var_ann_t ann = var_ann (var);
1361 tree tag = ann->type_mem_tag;
1364 bitmap_set_bit (vars_to_rename, var_ann (tag)->uid);
1365 ann->type_mem_tag = NULL_TREE;
1371 /* If we found no addressable variables, but we have more than one
1372 pointer, we will need to check for conflicts between the
1373 pointers. Otherwise, we would miss alias relations as in
1374 testsuite/gcc.dg/tree-ssa/20040319-1.c:
1376 struct bar { int count; int *arr;};
1378 void foo (struct bar *b)
1386 b->count and *(b->arr) could be aliased if b->arr == &b->count.
1387 To do this, we add all the memory tags for the pointers in
1388 AI->POINTERS to AI->ADDRESSABLE_VARS, so that
1389 compute_flow_insensitive_aliasing will naturally compare every
1390 pointer to every type tag. */
1391 if (ai->num_addressable_vars == 0
1392 && ai->num_pointers > 1)
1394 free (ai->addressable_vars);
1395 ai->addressable_vars = xcalloc (ai->num_pointers,
1396 sizeof (struct alias_map_d *));
1397 ai->num_addressable_vars = 0;
1398 for (i = 0; i < ai->num_pointers; i++)
1400 struct alias_map_d *p = ai->pointers[i];
1401 tree tag = var_ann (p->var)->type_mem_tag;
1402 create_alias_map_for (tag, ai);
1408 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1409 every call site, we need to emit V_MAY_DEF expressions to represent the
1410 clobbering effects of the call for variables whose address escapes the
1413 One approach is to group all call-clobbered variables into a single
1414 representative that is used as an alias of every call-clobbered variable
1415 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1416 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1418 The second approach is to emit a clobbering V_MAY_DEF for every
1419 call-clobbered variable at call sites. This is the preferred way in terms
1420 of optimization opportunities but it may create too many V_MAY_DEF operands
1421 if there are many call clobbered variables and function calls in the
1424 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1425 function calls found by the number of call-clobbered variables. If that
1426 product is beyond a certain threshold, as determined by the parameterized
1427 values shown below, we use .GLOBAL_VAR.
1429 FIXME. This heuristic should be improved. One idea is to use several
1430 .GLOBAL_VARs of different types instead of a single one. The thresholds
1431 have been derived from a typical bootstrap cycle, including all target
1432 libraries. Compile times were found increase by ~1% compared to using
1436 maybe_create_global_var (struct alias_info *ai)
1438 size_t i, n_clobbered;
1440 /* No need to create it, if we have one already. */
1441 if (global_var == NULL_TREE)
1443 /* Count all the call-clobbered variables. */
1445 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, n_clobbered++);
1447 /* Create .GLOBAL_VAR if we have too many call-clobbered
1448 variables. We also create .GLOBAL_VAR when there no
1449 call-clobbered variables to prevent code motion
1450 transformations from re-arranging function calls that may
1451 have side effects. For instance,
1460 There are no call-clobbered variables in foo(), so it would
1461 be entirely possible for a pass to want to move the call to
1462 f() after the call to g(). If f() has side effects, that
1463 would be wrong. Creating .GLOBAL_VAR in this case will
1464 insert VDEFs for it and prevent such transformations. */
1465 if (n_clobbered == 0
1466 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1467 create_global_var ();
1470 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1471 been created, make it an alias for all call-clobbered variables. */
1473 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i,
1475 tree var = referenced_var (i);
1476 if (var != global_var)
1478 add_may_alias (var, global_var);
1479 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1485 /* Return TRUE if pointer PTR may point to variable VAR.
1487 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1488 This is needed because when checking for type conflicts we are
1489 interested in the alias set of the memory location pointed-to by
1490 PTR. The alias set of PTR itself is irrelevant.
1492 VAR_ALIAS_SET is the alias set for VAR. */
1495 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1496 tree var, HOST_WIDE_INT var_alias_set)
1499 var_ann_t v_ann, m_ann;
1501 alias_stats.alias_queries++;
1502 alias_stats.simple_queries++;
1504 /* By convention, a variable cannot alias itself. */
1505 mem = var_ann (ptr)->type_mem_tag;
1508 alias_stats.alias_noalias++;
1509 alias_stats.simple_resolved++;
1513 v_ann = var_ann (var);
1514 m_ann = var_ann (mem);
1516 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1518 alias_stats.tbaa_queries++;
1520 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1521 PTR can't possibly affect VAR. Note, that we are specifically testing
1522 for PTR's alias set here, not its pointed-to type. We also can't
1523 do this check with relaxed aliasing enabled. */
1524 if (POINTER_TYPE_P (TREE_TYPE (var))
1525 && var_alias_set != 0)
1527 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1528 if (ptr_alias_set == var_alias_set)
1530 alias_stats.alias_noalias++;
1531 alias_stats.tbaa_resolved++;
1536 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1537 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1539 /* Handle aliases to structure fields. If either VAR or MEM are
1540 aggregate types, they may not have conflicting types, but one of
1541 the structures could contain a pointer to the other one.
1548 It may happen that '*p' and '*q' can't alias because 'struct P'
1549 and 'struct Q' have non-conflicting alias sets. However, it could
1550 happen that one of the fields in 'struct P' is a 'struct Q *' or
1553 Therefore, we also need to check if 'struct P' aliases 'struct Q *'
1554 or 'struct Q' aliases 'struct P *'. Notice, that since GIMPLE
1555 does not have more than one-level pointers, we don't need to
1556 recurse into the structures. */
1557 if (AGGREGATE_TYPE_P (TREE_TYPE (mem))
1558 || AGGREGATE_TYPE_P (TREE_TYPE (var)))
1562 if (TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE)
1563 ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (TREE_TYPE (var)));
1565 ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (var));
1567 /* If no pointer-to VAR exists, then MEM can't alias VAR. */
1568 if (ptr_to_var == NULL_TREE)
1570 alias_stats.alias_noalias++;
1571 alias_stats.tbaa_resolved++;
1575 /* If MEM doesn't alias a pointer to VAR and VAR doesn't alias
1576 PTR, then PTR can't alias VAR. */
1577 if (!alias_sets_conflict_p (mem_alias_set, get_alias_set (ptr_to_var))
1578 && !alias_sets_conflict_p (var_alias_set, get_alias_set (ptr)))
1580 alias_stats.alias_noalias++;
1581 alias_stats.tbaa_resolved++;
1587 alias_stats.alias_noalias++;
1588 alias_stats.tbaa_resolved++;
1593 alias_stats.alias_mayalias++;
1598 /* Add ALIAS to the set of variables that may alias VAR. */
1601 add_may_alias (tree var, tree alias)
1604 var_ann_t v_ann = get_var_ann (var);
1605 var_ann_t a_ann = get_var_ann (alias);
1607 gcc_assert (var != alias);
1609 if (v_ann->may_aliases == NULL)
1610 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1612 /* Avoid adding duplicates. */
1613 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1614 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1617 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1618 FIXME, call-clobbering should only depend on whether an address
1619 escapes. It should be independent of aliasing. */
1620 if (is_call_clobbered (var))
1621 mark_call_clobbered (alias);
1623 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1624 else if (is_call_clobbered (alias))
1625 mark_call_clobbered (var);
1627 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1628 a_ann->is_alias_tag = 1;
1632 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1635 replace_may_alias (tree var, size_t i, tree new_alias)
1637 var_ann_t v_ann = var_ann (var);
1638 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1640 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1641 FIXME, call-clobbering should only depend on whether an address
1642 escapes. It should be independent of aliasing. */
1643 if (is_call_clobbered (var))
1644 mark_call_clobbered (new_alias);
1646 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1647 else if (is_call_clobbered (new_alias))
1648 mark_call_clobbered (var);
1652 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1655 set_pt_anything (tree ptr)
1657 struct ptr_info_def *pi = get_ptr_info (ptr);
1659 pi->pt_anything = 1;
1662 /* The pointer used to have a name tag, but we now found it pointing
1663 to an arbitrary location. The name tag needs to be renamed and
1664 disassociated from PTR. */
1665 if (pi->name_mem_tag)
1667 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1668 pi->name_mem_tag = NULL_TREE;
1673 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1676 set_pt_malloc (tree ptr)
1678 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1680 /* If the pointer has already been found to point to arbitrary
1681 memory locations, it is unsafe to mark it as pointing to malloc. */
1682 if (pi->pt_anything)
1689 /* Given two pointers DEST and ORIG. Merge the points-to information in
1690 ORIG into DEST. AI is as in collect_points_to_info. */
1693 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1695 struct ptr_info_def *dest_pi, *orig_pi;
1697 /* Make sure we have points-to information for ORIG. */
1698 collect_points_to_info_for (ai, orig);
1700 dest_pi = get_ptr_info (dest);
1701 orig_pi = SSA_NAME_PTR_INFO (orig);
1705 /* Notice that we never merge PT_MALLOC. This attribute is only
1706 true if the pointer is the result of a malloc() call.
1707 Otherwise, we can end up in this situation:
1713 P_j would be marked as PT_MALLOC, which is wrong because
1714 PT_MALLOC implies that the pointer may not point to another
1717 FIXME 1: Subsequent analysis may determine that P_j
1718 cannot alias anything else, but we are being conservative
1721 FIXME 2: If the merging comes from a copy assignment, we
1722 ought to merge PT_MALLOC, but then both pointers would end up
1723 getting different name tags because create_name_tags is not
1724 smart enough to determine that the two come from the same
1725 malloc call. Copy propagation before aliasing should cure
1727 dest_pi->pt_malloc = 0;
1729 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1730 set_pt_anything (dest);
1732 if (!dest_pi->pt_anything
1734 && bitmap_first_set_bit (orig_pi->pt_vars) >= 0)
1736 if (dest_pi->pt_vars == NULL)
1738 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1739 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1742 bitmap_a_or_b (dest_pi->pt_vars,
1748 set_pt_anything (dest);
1752 /* Add VALUE to the list of expressions pointed-to by PTR. */
1755 add_pointed_to_expr (tree ptr, tree value)
1757 if (TREE_CODE (value) == WITH_SIZE_EXPR)
1758 value = TREE_OPERAND (value, 0);
1760 /* Pointer variables should have been handled by merge_pointed_to_info. */
1761 gcc_assert (TREE_CODE (value) != SSA_NAME
1762 || !POINTER_TYPE_P (TREE_TYPE (value)));
1766 /* If VALUE is the result of a malloc-like call, then the area pointed to
1767 PTR is guaranteed to not alias with anything else. */
1768 if (TREE_CODE (value) == CALL_EXPR
1769 && (call_expr_flags (value) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1770 set_pt_malloc (ptr);
1772 set_pt_anything (ptr);
1776 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1778 fprintf (dump_file, "Pointer ");
1779 print_generic_expr (dump_file, ptr, dump_flags);
1780 fprintf (dump_file, " points to ");
1782 fprintf (dump_file, "malloc space: ");
1784 fprintf (dump_file, "an arbitrary address: ");
1785 print_generic_expr (dump_file, value, dump_flags);
1786 fprintf (dump_file, "\n");
1791 /* If VALUE is of the form &DECL, add DECL to the set of variables
1792 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1793 PTR. AI is as in collect_points_to_info. */
1796 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1798 struct ptr_info_def *pi = get_ptr_info (ptr);
1802 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
1804 pt_var = TREE_OPERAND (value, 0);
1805 if (TREE_CODE_CLASS (TREE_CODE (pt_var)) == 'r')
1806 pt_var = get_base_address (pt_var);
1808 if (pt_var && SSA_VAR_P (pt_var))
1810 uid = var_ann (pt_var)->uid;
1811 bitmap_set_bit (ai->addresses_needed, uid);
1813 if (pi->pt_vars == NULL)
1814 pi->pt_vars = BITMAP_GGC_ALLOC ();
1815 bitmap_set_bit (pi->pt_vars, uid);
1817 /* If the variable is a global, mark the pointer as pointing to
1818 global memory (which will make its tag a global variable). */
1819 if (is_global_var (pt_var))
1820 pi->pt_global_mem = 1;
1825 /* Callback for walk_use_def_chains to gather points-to information from the
1828 VAR is an SSA variable or a GIMPLE expression.
1830 STMT is the statement that generates the SSA variable or, if STMT is a
1831 PHI_NODE, VAR is one of the PHI arguments.
1833 DATA is a pointer to a structure of type ALIAS_INFO. */
1836 collect_points_to_info_r (tree var, tree stmt, void *data)
1838 struct alias_info *ai = (struct alias_info *) data;
1840 if (dump_file && (dump_flags & TDF_DETAILS))
1842 fprintf (dump_file, "Visiting use-def links for ");
1843 print_generic_expr (dump_file, var, dump_flags);
1844 fprintf (dump_file, "\n");
1847 switch (TREE_CODE (stmt))
1851 tree rhs = TREE_OPERAND (stmt, 1);
1854 /* Found P_i = ADDR_EXPR */
1855 if (TREE_CODE (rhs) == ADDR_EXPR)
1856 add_pointed_to_var (ai, var, rhs);
1858 /* Found P_i = Q_j. */
1859 else if (TREE_CODE (rhs) == SSA_NAME
1860 && POINTER_TYPE_P (TREE_TYPE (rhs)))
1861 merge_pointed_to_info (ai, var, rhs);
1863 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1864 else if (TREE_CODE (rhs) == PLUS_EXPR
1865 || TREE_CODE (rhs) == MINUS_EXPR)
1867 tree op0 = TREE_OPERAND (rhs, 0);
1868 tree op1 = TREE_OPERAND (rhs, 1);
1870 /* Both operands may be of pointer type. FIXME: Shouldn't
1871 we just expect PTR + OFFSET always? */
1872 if (POINTER_TYPE_P (TREE_TYPE (op0))
1873 && TREE_CODE (op0) != INTEGER_CST)
1875 if (TREE_CODE (op0) == SSA_NAME)
1876 merge_pointed_to_info (ai, var, op0);
1877 else if (TREE_CODE (op0) == ADDR_EXPR)
1878 add_pointed_to_var (ai, var, op0);
1880 add_pointed_to_expr (var, op0);
1883 if (POINTER_TYPE_P (TREE_TYPE (op1))
1884 && TREE_CODE (op1) != INTEGER_CST)
1886 if (TREE_CODE (op1) == SSA_NAME)
1887 merge_pointed_to_info (ai, var, op1);
1888 else if (TREE_CODE (op1) == ADDR_EXPR)
1889 add_pointed_to_var (ai, var, op1);
1891 add_pointed_to_expr (var, op1);
1894 /* Neither operand is a pointer? VAR can be pointing
1895 anywhere. FIXME: Is this right? If we get here, we
1896 found PTR = INT_CST + INT_CST. */
1897 if (!(POINTER_TYPE_P (TREE_TYPE (op0))
1898 && TREE_CODE (op0) != INTEGER_CST)
1899 && !(POINTER_TYPE_P (TREE_TYPE (op1))
1900 && TREE_CODE (op1) != INTEGER_CST))
1901 add_pointed_to_expr (var, rhs);
1904 /* Something else. */
1906 add_pointed_to_expr (var, rhs);
1910 /* Pointers defined by __asm__ statements can point anywhere. */
1911 set_pt_anything (var);
1915 if (IS_EMPTY_STMT (stmt))
1917 tree decl = SSA_NAME_VAR (var);
1919 if (TREE_CODE (decl) == PARM_DECL)
1920 add_pointed_to_expr (var, decl);
1921 else if (DECL_INITIAL (decl))
1922 add_pointed_to_var (ai, var, DECL_INITIAL (decl));
1924 add_pointed_to_expr (var, decl);
1929 /* It STMT is a PHI node, then VAR is one of its arguments. The
1930 variable that we are analyzing is the LHS of the PHI node. */
1931 tree lhs = PHI_RESULT (stmt);
1933 switch (TREE_CODE (var))
1936 add_pointed_to_var (ai, lhs, var);
1940 merge_pointed_to_info (ai, lhs, var);
1944 gcc_assert (is_gimple_min_invariant (var));
1945 add_pointed_to_expr (lhs, var);
1958 /* Return true if STMT is an "escape" site from the current function. Escape
1959 sites those statements which might expose the address of a variable
1960 outside the current function. STMT is an escape site iff:
1962 1- STMT is a function call, or
1963 2- STMT is an __asm__ expression, or
1964 3- STMT is an assignment to a non-local variable, or
1965 4- STMT is a return statement.
1967 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
1971 is_escape_site (tree stmt, size_t *num_calls_p)
1973 if (get_call_expr_in (stmt) != NULL_TREE)
1980 else if (TREE_CODE (stmt) == ASM_EXPR)
1982 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1984 tree lhs = TREE_OPERAND (stmt, 0);
1986 /* Get to the base of _REF nodes. */
1987 if (TREE_CODE (lhs) != SSA_NAME)
1988 lhs = get_base_address (lhs);
1990 /* If we couldn't recognize the LHS of the assignment, assume that it
1991 is a non-local store. */
1992 if (lhs == NULL_TREE)
1995 /* If the LHS is an SSA name, it can't possibly represent a non-local
1997 if (TREE_CODE (lhs) == SSA_NAME)
2000 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2001 local variables we cannot be sure if it will escape, because we
2002 don't have information about objects not in SSA form. Need to
2003 implement something along the lines of
2005 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2006 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2007 Conference on Object-Oriented Programming Systems, Languages, and
2008 Applications (OOPSLA), pp. 1-19, 1999. */
2011 else if (TREE_CODE (stmt) == RETURN_EXPR)
2018 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2019 is considered to represent all the pointers whose pointed-to types are
2020 in the same alias set class. Otherwise, the tag represents a single
2021 SSA_NAME pointer variable. */
2024 create_memory_tag (tree type, bool is_type_tag)
2027 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2029 /* By default, memory tags are local variables. Alias analysis will
2030 determine whether they should be considered globals. */
2031 DECL_CONTEXT (tag) = current_function_decl;
2033 /* If the pointed-to type is volatile, so is the tag. */
2034 TREE_THIS_VOLATILE (tag) = TREE_THIS_VOLATILE (type);
2036 /* Memory tags are by definition addressable. This also prevents
2037 is_gimple_ref frome confusing memory tags with optimizable
2039 TREE_ADDRESSABLE (tag) = 1;
2041 ann = get_var_ann (tag);
2042 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2043 ann->type_mem_tag = NULL_TREE;
2045 /* Add the tag to the symbol table. */
2046 add_referenced_tmp_var (tag);
2052 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2053 This is used if P_i has been found to point to a specific set of
2054 variables or to a non-aliased memory location like the address returned
2055 by malloc functions. */
2058 get_nmt_for (tree ptr)
2060 struct ptr_info_def *pi = get_ptr_info (ptr);
2061 tree tag = pi->name_mem_tag;
2063 if (tag == NULL_TREE)
2064 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2066 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2067 then its name tag should be considered a global variable. */
2068 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2070 || pi->pt_global_mem)
2071 mark_call_clobbered (tag);
2077 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2078 artificial variable that represents the memory location pointed-to by
2079 PTR. It is used to model the effects of pointer de-references on
2080 addressable variables.
2082 AI points to the data gathered during alias analysis. This function
2083 populates the array AI->POINTERS. */
2086 get_tmt_for (tree ptr, struct alias_info *ai)
2090 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2091 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2093 /* To avoid creating unnecessary memory tags, only create one memory tag
2094 per alias set class. Note that it may be tempting to group
2095 memory tags based on conflicting alias sets instead of
2096 equivalence. That would be wrong because alias sets are not
2097 necessarily transitive (as demonstrated by the libstdc++ test
2098 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2099 such that conflicts (A, B) == true and conflicts (A, C) == true,
2100 it does not necessarily follow that conflicts (B, C) == true. */
2101 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2103 struct alias_map_d *curr = ai->pointers[i];
2104 if (tag_set == curr->set)
2106 tag = var_ann (curr->var)->type_mem_tag;
2111 /* If VAR cannot alias with any of the existing memory tags, create a new
2112 tag for PTR and add it to the POINTERS array. */
2113 if (tag == NULL_TREE)
2115 struct alias_map_d *alias_map;
2117 /* If PTR did not have a type tag already, create a new TMT.*
2118 artificial variable representing the memory location
2119 pointed-to by PTR. */
2120 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2121 tag = create_memory_tag (tag_type, true);
2123 tag = var_ann (ptr)->type_mem_tag;
2125 /* Add PTR to the POINTERS array. Note that we are not interested in
2126 PTR's alias set. Instead, we cache the alias set for the memory that
2128 alias_map = xcalloc (1, sizeof (*alias_map));
2129 alias_map->var = ptr;
2130 alias_map->set = tag_set;
2131 ai->pointers[ai->num_pointers++] = alias_map;
2134 /* Make sure that the type tag has the same alias set as the
2136 gcc_assert (tag_set == get_alias_set (tag));
2142 /* Create GLOBAL_VAR, an artificial global variable to act as a
2143 representative of all the variables that may be clobbered by function
2147 create_global_var (void)
2149 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2151 DECL_ARTIFICIAL (global_var) = 1;
2152 TREE_READONLY (global_var) = 0;
2153 DECL_EXTERNAL (global_var) = 1;
2154 TREE_STATIC (global_var) = 1;
2155 TREE_USED (global_var) = 1;
2156 DECL_CONTEXT (global_var) = NULL_TREE;
2157 TREE_THIS_VOLATILE (global_var) = 0;
2158 TREE_ADDRESSABLE (global_var) = 0;
2160 add_referenced_tmp_var (global_var);
2161 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2165 /* Dump alias statistics on FILE. */
2168 dump_alias_stats (FILE *file)
2170 const char *funcname
2171 = lang_hooks.decl_printable_name (current_function_decl, 2);
2172 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2173 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2174 fprintf (file, "Total alias mayalias results:\t%u\n",
2175 alias_stats.alias_mayalias);
2176 fprintf (file, "Total alias noalias results:\t%u\n",
2177 alias_stats.alias_noalias);
2178 fprintf (file, "Total simple queries:\t%u\n",
2179 alias_stats.simple_queries);
2180 fprintf (file, "Total simple resolved:\t%u\n",
2181 alias_stats.simple_resolved);
2182 fprintf (file, "Total TBAA queries:\t%u\n",
2183 alias_stats.tbaa_queries);
2184 fprintf (file, "Total TBAA resolved:\t%u\n",
2185 alias_stats.tbaa_resolved);
2189 /* Dump alias information on FILE. */
2192 dump_alias_info (FILE *file)
2195 const char *funcname
2196 = lang_hooks.decl_printable_name (current_function_decl, 2);
2198 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2200 fprintf (file, "Aliased symbols\n\n");
2201 for (i = 0; i < num_referenced_vars; i++)
2203 tree var = referenced_var (i);
2204 if (may_be_aliased (var))
2205 dump_variable (file, var);
2208 fprintf (file, "\nDereferenced pointers\n\n");
2209 for (i = 0; i < num_referenced_vars; i++)
2211 tree var = referenced_var (i);
2212 var_ann_t ann = var_ann (var);
2213 if (ann->type_mem_tag)
2214 dump_variable (file, var);
2217 fprintf (file, "\nType memory tags\n\n");
2218 for (i = 0; i < num_referenced_vars; i++)
2220 tree var = referenced_var (i);
2221 var_ann_t ann = var_ann (var);
2222 if (ann->mem_tag_kind == TYPE_TAG)
2223 dump_variable (file, var);
2226 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2228 fprintf (file, "SSA_NAME pointers\n\n");
2229 for (i = 1; i < num_ssa_names; i++)
2231 tree ptr = ssa_name (i);
2232 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2233 if (!SSA_NAME_IN_FREE_LIST (ptr)
2235 && pi->name_mem_tag)
2236 dump_points_to_info_for (file, ptr);
2239 fprintf (file, "\nName memory tags\n\n");
2240 for (i = 0; i < num_referenced_vars; i++)
2242 tree var = referenced_var (i);
2243 var_ann_t ann = var_ann (var);
2244 if (ann->mem_tag_kind == NAME_TAG)
2245 dump_variable (file, var);
2248 fprintf (file, "\n");
2252 /* Dump alias information on stderr. */
2255 debug_alias_info (void)
2257 dump_alias_info (stderr);
2261 /* Return the alias information associated with pointer T. It creates a
2262 new instance if none existed. */
2264 static struct ptr_info_def *
2265 get_ptr_info (tree t)
2267 struct ptr_info_def *pi;
2269 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2271 pi = SSA_NAME_PTR_INFO (t);
2274 pi = ggc_alloc (sizeof (*pi));
2275 memset ((void *)pi, 0, sizeof (*pi));
2276 SSA_NAME_PTR_INFO (t) = pi;
2283 /* Dump points-to information for SSA_NAME PTR into FILE. */
2286 dump_points_to_info_for (FILE *file, tree ptr)
2288 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2290 print_generic_expr (file, ptr, dump_flags);
2294 if (pi->name_mem_tag)
2296 fprintf (file, ", name memory tag: ");
2297 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2300 if (pi->is_dereferenced)
2301 fprintf (file, ", is dereferenced");
2303 if (pi->value_escapes_p)
2304 fprintf (file, ", its value escapes");
2306 if (pi->pt_anything)
2307 fprintf (file, ", points-to anything");
2310 fprintf (file, ", points-to malloc");
2316 fprintf (file, ", points-to vars: { ");
2317 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix,
2319 print_generic_expr (file, referenced_var (ix), dump_flags);
2320 fprintf (file, " ");
2322 fprintf (file, "}");
2326 fprintf (file, "\n");
2330 /* Dump points-to information for VAR into stderr. */
2333 debug_points_to_info_for (tree var)
2335 dump_points_to_info_for (stderr, var);
2339 /* Dump points-to information into FILE. NOTE: This function is slow, as
2340 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2343 dump_points_to_info (FILE *file)
2346 block_stmt_iterator si;
2350 lang_hooks.decl_printable_name (current_function_decl, 2);
2352 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2354 /* First dump points-to information for the default definitions of
2355 pointer variables. This is necessary because default definitions are
2356 not part of the code. */
2357 for (i = 0; i < num_referenced_vars; i++)
2359 tree var = referenced_var (i);
2360 if (POINTER_TYPE_P (TREE_TYPE (var)))
2362 var_ann_t ann = var_ann (var);
2363 if (ann->default_def)
2364 dump_points_to_info_for (file, ann->default_def);
2368 /* Dump points-to information for every pointer defined in the program. */
2373 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2375 tree ptr = PHI_RESULT (phi);
2376 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2377 dump_points_to_info_for (file, ptr);
2380 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2382 tree stmt = bsi_stmt (si);
2384 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2385 if (POINTER_TYPE_P (TREE_TYPE (def)))
2386 dump_points_to_info_for (file, def);
2390 fprintf (file, "\n");
2394 /* Dump points-to info pointed by PTO into STDERR. */
2397 debug_points_to_info (void)
2399 dump_points_to_info (stderr);
2402 /* Dump to FILE the list of variables that may be aliasing VAR. */
2405 dump_may_aliases_for (FILE *file, tree var)
2407 varray_type aliases;
2409 if (TREE_CODE (var) == SSA_NAME)
2410 var = SSA_NAME_VAR (var);
2412 aliases = var_ann (var)->may_aliases;
2416 fprintf (file, "{ ");
2417 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2419 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2420 fprintf (file, " ");
2422 fprintf (file, "}");
2427 /* Dump to stderr the list of variables that may be aliasing VAR. */
2430 debug_may_aliases_for (tree var)
2432 dump_may_aliases_for (stderr, var);
2435 /* Return true if VAR may be aliased. */
2438 may_be_aliased (tree var)
2441 if (TREE_ADDRESSABLE (var))
2444 /* Globally visible variables can have their addresses taken by other
2445 translation units. */
2446 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2449 /* Automatic variables can't have their addresses escape any other way.
2450 This must be after the check for global variables, as extern declarations
2451 do not have TREE_STATIC set. */
2452 if (!TREE_STATIC (var))
2455 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2456 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2457 we can only be sure the variable isn't addressable if it's local to the
2458 current function. */
2459 if (flag_unit_at_a_time)
2461 if (decl_function_context (var) == current_function_decl)