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-alias-common.h"
43 #include "tree-pass.h"
48 /* Structure to map a variable to its alias set and keep track of the
49 virtual operands that will be needed to represent it. */
52 /* Variable and its alias set. */
56 /* Total number of virtual operands that will be needed to represent
57 all the aliases of VAR. */
58 long total_alias_vops;
60 /* Nonzero if the aliases for this memory tag have been grouped
61 already. Used in group_aliases. */
62 unsigned int grouped_p : 1;
64 /* Set of variables aliased with VAR. This is the exact same
65 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
66 bitmap form to speed up alias grouping. */
71 /* Alias information used by compute_may_aliases and its helpers. */
74 /* SSA names visited while collecting points-to information. If bit I
75 is set, it means that SSA variable with version I has already been
77 bitmap ssa_names_visited;
79 /* Array of SSA_NAME pointers processed by the points-to collector. */
80 varray_type processed_ptrs;
82 /* Variables whose address is still needed. */
83 bitmap addresses_needed;
85 /* ADDRESSABLE_VARS contains all the global variables and locals that
86 have had their address taken. */
87 struct alias_map_d **addressable_vars;
88 size_t num_addressable_vars;
90 /* POINTERS contains all the _DECL pointers with unique memory tags
91 that have been referenced in the program. */
92 struct alias_map_d **pointers;
95 /* Number of function calls found in the program. */
96 size_t num_calls_found;
98 /* Array of counters to keep track of how many times each pointer has
99 been dereferenced in the program. This is used by the alias grouping
100 heuristic in compute_flow_insensitive_aliasing. */
101 varray_type num_references;
103 /* Total number of virtual operands that will be needed to represent
104 all the aliases of all the pointers found in the program. */
105 long total_alias_vops;
107 /* Variables that have been written to. */
110 /* Pointers that have been used in an indirect store operation. */
111 bitmap dereferenced_ptrs_store;
113 /* Pointers that have been used in an indirect load operation. */
114 bitmap dereferenced_ptrs_load;
118 /* Counters used to display statistics on alias analysis. */
121 unsigned int alias_queries;
122 unsigned int alias_mayalias;
123 unsigned int alias_noalias;
124 unsigned int simple_queries;
125 unsigned int simple_resolved;
126 unsigned int tbaa_queries;
127 unsigned int tbaa_resolved;
128 unsigned int pta_queries;
129 unsigned int pta_resolved;
133 /* Local variables. */
134 static struct alias_stats_d alias_stats;
136 /* Local functions. */
137 static void compute_flow_insensitive_aliasing (struct alias_info *);
138 static void dump_alias_stats (FILE *);
139 static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT);
140 static tree create_memory_tag (tree type, bool is_type_tag);
141 static tree get_tmt_for (tree, struct alias_info *);
142 static tree get_nmt_for (tree);
143 static void add_may_alias (tree, tree);
144 static void replace_may_alias (tree, size_t, tree);
145 static struct alias_info *init_alias_info (void);
146 static void delete_alias_info (struct alias_info *);
147 static void compute_points_to_and_addr_escape (struct alias_info *);
148 static void compute_flow_sensitive_aliasing (struct alias_info *);
149 static void setup_pointers_and_addressables (struct alias_info *);
150 static bool collect_points_to_info_r (tree, tree, void *);
151 static bool is_escape_site (tree, size_t *);
152 static void add_pointed_to_var (struct alias_info *, tree, tree);
153 static void add_pointed_to_expr (tree, tree);
154 static void create_global_var (void);
155 static void collect_points_to_info_for (struct alias_info *, tree);
156 static bool ptr_is_dereferenced_by (tree, tree, bool *);
157 static void maybe_create_global_var (struct alias_info *ai);
158 static void group_aliases (struct alias_info *);
159 static struct ptr_info_def *get_ptr_info (tree t);
161 /* Global declarations. */
163 /* Call clobbered variables in the function. If bit I is set, then
164 REFERENCED_VARS (I) is call-clobbered. */
165 bitmap call_clobbered_vars;
167 /* Addressable variables in the function. If bit I is set, then
168 REFERENCED_VARS (I) has had its address taken. Note that
169 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
170 addressable variable is not necessarily call-clobbered (e.g., a
171 local addressable whose address does not escape) and not all
172 call-clobbered variables are addressable (e.g., a local static
174 bitmap addressable_vars;
176 /* 'true' after aliases have been computed (see compute_may_aliases). This
177 is used by get_stmt_operands and its helpers to determine what to do
178 when scanning an operand for a variable that may be aliased. If
179 may-alias information is still not available, the statement is marked as
180 having volatile operands. */
181 bool aliases_computed_p;
183 /* When the program has too many call-clobbered variables and call-sites,
184 this variable is used to represent the clobbering effects of function
185 calls. In these cases, all the call clobbered variables in the program
186 are forced to alias this variable. This reduces compile times by not
187 having to keep track of too many V_MAY_DEF expressions at call sites. */
191 /* Compute may-alias information for every variable referenced in function
194 Alias analysis proceeds in 3 main phases:
196 1- Points-to and escape analysis.
198 This phase walks the use-def chains in the SSA web looking for three
201 * Assignments of the form P_i = &VAR
202 * Assignments of the form P_i = malloc()
203 * Pointers and ADDR_EXPR that escape the current function.
205 The concept of 'escaping' is the same one used in the Java world. When
206 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
207 outside of the current function. So, assignment to global variables,
208 function arguments and returning a pointer are all escape sites.
210 This is where we are currently limited. Since not everything is renamed
211 into SSA, we lose track of escape properties when a pointer is stashed
212 inside a field in a structure, for instance. In those cases, we are
213 assuming that the pointer does escape.
215 We use escape analysis to determine whether a variable is
216 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
217 is call-clobbered. If a pointer P_i escapes, then all the variables
218 pointed-to by P_i (and its memory tag) also escape.
220 2- Compute flow-sensitive aliases
222 We have two classes of memory tags. Memory tags associated with the
223 pointed-to data type of the pointers in the program. These tags are
224 called "type memory tag" (TMT). The other class are those associated
225 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
226 when adding operands for an INDIRECT_REF *P_i, we will first check
227 whether P_i has a name tag, if it does we use it, because that will have
228 more precise aliasing information. Otherwise, we use the standard type
231 In this phase, we go through all the pointers we found in points-to
232 analysis and create alias sets for the name memory tags associated with
233 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
234 it points to and its tag.
237 3- Compute flow-insensitive aliases
239 This pass will compare the alias set of every type memory tag and every
240 addressable variable found in the program. Given a type memory tag TMT
241 and an addressable variable V. If the alias sets of TMT and V conflict
242 (as computed by may_alias_p), then V is marked as an alias tag and added
243 to the alias set of TMT.
245 For instance, consider the following function:
262 After aliasing analysis has finished, the type memory tag for pointer
263 'p' will have two aliases, namely variables 'a' and 'b'. Every time
264 pointer 'p' is dereferenced, we want to mark the operation as a
265 potential reference to 'a' and 'b'.
275 # p_1 = PHI <p_4(1), p_6(2)>;
277 # a_7 = V_MAY_DEF <a_3>;
278 # b_8 = V_MAY_DEF <b_5>;
281 # a_9 = V_MAY_DEF <a_7>
290 In certain cases, the list of may aliases for a pointer may grow too
291 large. This may cause an explosion in the number of virtual operands
292 inserted in the code. Resulting in increased memory consumption and
295 When the number of virtual operands needed to represent aliased
296 loads and stores grows too large (configurable with @option{--param
297 max-aliased-vops}), alias sets are grouped to avoid severe
298 compile-time slow downs and memory consumption. See group_aliases. */
301 compute_may_aliases (void)
303 struct alias_info *ai;
305 memset (&alias_stats, 0, sizeof (alias_stats));
307 /* Initialize aliasing information. */
308 ai = init_alias_info ();
310 /* For each pointer P_i, determine the sets of variables that P_i may
311 point-to. For every addressable variable V, determine whether the
312 address of V escapes the current function, making V call-clobbered
313 (i.e., whether &V is stored in a global variable or if its passed as a
314 function call argument). */
315 compute_points_to_and_addr_escape (ai);
317 /* Collect all pointers and addressable variables, compute alias sets,
318 create memory tags for pointers and promote variables whose address is
319 not needed anymore. */
320 setup_pointers_and_addressables (ai);
322 /* Compute flow-sensitive, points-to based aliasing for all the name
323 memory tags. Note that this pass needs to be done before flow
324 insensitive analysis because it uses the points-to information
325 gathered before to mark call-clobbered type tags. */
326 compute_flow_sensitive_aliasing (ai);
328 /* Compute type-based flow-insensitive aliasing for all the type
330 compute_flow_insensitive_aliasing (ai);
332 /* If the program has too many call-clobbered variables and/or function
333 calls, create .GLOBAL_VAR and use it to model call-clobbering
334 semantics at call sites. This reduces the number of virtual operands
335 considerably, improving compile times at the expense of lost
336 aliasing precision. */
337 maybe_create_global_var (ai);
339 /* Debugging dumps. */
342 dump_referenced_vars (dump_file);
343 if (dump_flags & TDF_STATS)
344 dump_alias_stats (dump_file);
345 dump_points_to_info (dump_file);
346 dump_alias_info (dump_file);
349 /* Deallocate memory used by aliasing data structures. */
350 delete_alias_info (ai);
352 /* Indicate that may-alias information is now available. */
353 aliases_computed_p = true;
356 struct tree_opt_pass pass_may_alias =
360 compute_may_aliases, /* execute */
363 0, /* static_pass_number */
364 TV_TREE_MAY_ALIAS, /* tv_id */
365 PROP_cfg | PROP_ssa | PROP_pta, /* properties_required */
366 0, /* properties_provided */
367 0, /* properties_destroyed */
368 0, /* todo_flags_start */
369 TODO_dump_func | TODO_rename_vars
370 | TODO_ggc_collect | TODO_verify_ssa /* todo_flags_finish */
374 /* Initialize the data structures used for alias analysis. */
376 static struct alias_info *
377 init_alias_info (void)
379 struct alias_info *ai;
381 ai = xcalloc (1, sizeof (struct alias_info));
382 ai->ssa_names_visited = BITMAP_XMALLOC ();
383 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
384 ai->addresses_needed = BITMAP_XMALLOC ();
385 VARRAY_UINT_INIT (ai->num_references, num_referenced_vars, "num_references");
386 ai->written_vars = BITMAP_XMALLOC ();
387 ai->dereferenced_ptrs_store = BITMAP_XMALLOC ();
388 ai->dereferenced_ptrs_load = BITMAP_XMALLOC ();
390 /* If aliases have been computed before, clear existing information. */
391 if (aliases_computed_p)
395 /* Clear the call-clobbered set. We are going to re-discover
396 call-clobbered variables. */
397 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i,
399 tree var = referenced_var (i);
400 DECL_NEEDS_TO_LIVE_IN_MEMORY_INTERNAL (var) = 0;
402 /* Variables that are intrinsically call-clobbered (globals,
403 local statics, etc) will not be marked by the aliasing
404 code, so we can't remove them from CALL_CLOBBERED_VARS. */
405 if (!is_call_clobbered (var))
406 bitmap_clear_bit (call_clobbered_vars, var_ann (var)->uid);
409 /* Similarly, clear the set of addressable variables. In this
410 case, we can just clear the set because addressability is
411 only computed here. */
412 bitmap_clear (addressable_vars);
414 /* Clear flow-insensitive alias information from each symbol. */
415 for (i = 0; i < num_referenced_vars; i++)
417 var_ann_t ann = var_ann (referenced_var (i));
419 ann->is_alias_tag = 0;
420 if (ann->type_mem_tag)
422 var_ann_t tag_ann = var_ann (ann->type_mem_tag);
423 tag_ann->may_aliases = NULL;
424 bitmap_set_bit (vars_to_rename, tag_ann->uid);
428 /* Clear flow-sensitive points-to information from each SSA name. */
429 for (i = 1; i < num_ssa_names; i++)
431 tree name = ssa_name (i);
433 if (!POINTER_TYPE_P (TREE_TYPE (name)))
436 if (SSA_NAME_PTR_INFO (name))
438 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
440 /* Clear all the flags but keep the name tag to
441 avoid creating new temporaries unnecessarily. If
442 this pointer is found to point to a subset or
443 superset of its former points-to set, then a new
444 tag will need to be created in create_name_tags. */
447 pi->value_escapes_p = 0;
448 pi->is_dereferenced = 0;
450 bitmap_clear (pi->pt_vars);
451 if (pi->name_mem_tag)
452 var_ann (pi->name_mem_tag)->may_aliases = NULL;
461 /* Deallocate memory used by alias analysis. */
464 delete_alias_info (struct alias_info *ai)
468 BITMAP_XFREE (ai->ssa_names_visited);
469 ai->processed_ptrs = NULL;
470 BITMAP_XFREE (ai->addresses_needed);
472 for (i = 0; i < ai->num_addressable_vars; i++)
474 sbitmap_free (ai->addressable_vars[i]->may_aliases);
475 free (ai->addressable_vars[i]);
477 free (ai->addressable_vars);
479 for (i = 0; i < ai->num_pointers; i++)
481 sbitmap_free (ai->pointers[i]->may_aliases);
482 free (ai->pointers[i]);
486 ai->num_references = NULL;
487 BITMAP_XFREE (ai->written_vars);
488 BITMAP_XFREE (ai->dereferenced_ptrs_store);
489 BITMAP_XFREE (ai->dereferenced_ptrs_load);
495 /* Walk use-def chains for pointer PTR to determine what variables is PTR
499 collect_points_to_info_for (struct alias_info *ai, tree ptr)
501 #if defined ENABLE_CHECKING
502 if (!POINTER_TYPE_P (TREE_TYPE (ptr)))
506 if (!bitmap_bit_p (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)))
508 bitmap_set_bit (ai->ssa_names_visited, SSA_NAME_VERSION (ptr));
509 walk_use_def_chains (ptr, collect_points_to_info_r, ai, true);
510 VARRAY_PUSH_TREE (ai->processed_ptrs, ptr);
515 /* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
516 INDIRECT_REF nodes for the pointer passed in DATA. */
519 find_ptr_dereference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
521 tree ptr = (tree) data;
523 if (TREE_CODE (*tp) == INDIRECT_REF
524 && TREE_OPERAND (*tp, 0) == ptr)
531 /* Return true if STMT contains INDIRECT_REF <PTR>. *IS_STORE is set
532 to 'true' if the dereference is on the LHS of an assignment. */
535 ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
539 if (TREE_CODE (stmt) == MODIFY_EXPR
540 || (TREE_CODE (stmt) == RETURN_EXPR
541 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
545 e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
546 lhs = TREE_OPERAND (e, 0);
547 rhs = TREE_OPERAND (e, 1);
550 && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
555 else if (EXPR_P (rhs)
556 && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
561 else if (TREE_CODE (stmt) == ASM_EXPR)
563 if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
564 || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
569 else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
579 /* Traverse use-def links for all the pointers in the program to collect
580 address escape and points-to information.
582 This is loosely based on the same idea described in R. Hasti and S.
583 Horwitz, ``Using static single assignment form to improve
584 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
585 Programming Language Design and Implementation, pp. 97-105, 1998. */
588 compute_points_to_and_addr_escape (struct alias_info *ai)
593 timevar_push (TV_TREE_PTA);
597 bb_ann_t block_ann = bb_ann (bb);
598 block_stmt_iterator si;
600 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
604 v_may_def_optype v_may_defs;
605 v_must_def_optype v_must_defs;
608 tree stmt = bsi_stmt (si);
609 bool stmt_escapes_p = is_escape_site (stmt, &ai->num_calls_found);
611 /* Mark all the variables whose address are taken by the
612 statement. Note that this will miss all the addresses taken
613 in PHI nodes (those are discovered while following the use-def
615 get_stmt_operands (stmt);
616 addr_taken = addresses_taken (stmt);
618 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i,
620 tree var = referenced_var (i);
621 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
623 mark_call_clobbered (var);
627 block_ann->has_escape_site = 1;
629 /* Special case for silly ADDR_EXPR tricks
630 (gcc.c-torture/unsorted/pass.c). If this statement is an
631 assignment to a non-pointer variable and the RHS takes the
632 address of a variable, assume that the variable on the RHS is
633 call-clobbered. We could add the LHS to the list of
634 "pointers" and follow it to see if it really escapes, but it's
635 not worth the pain. */
637 && TREE_CODE (stmt) == MODIFY_EXPR
638 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 0))))
639 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i,
641 tree var = referenced_var (i);
642 mark_call_clobbered (var);
645 ann = stmt_ann (stmt);
646 uses = USE_OPS (ann);
647 for (i = 0; i < NUM_USES (uses); i++)
649 tree op = USE_OP (uses, i);
650 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
651 struct ptr_info_def *pi;
654 /* If the operand's variable may be aliased, keep track
655 of how many times we've referenced it. This is used
656 for alias grouping in compute_flow_sensitive_aliasing.
657 Note that we don't need to grow AI->NUM_REFERENCES
658 because we are processing regular variables, not
659 memory tags (the array's initial size is set to
660 NUM_REFERENCED_VARS). */
661 if (may_be_aliased (SSA_NAME_VAR (op)))
662 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
664 if (!POINTER_TYPE_P (TREE_TYPE (op)))
667 collect_points_to_info_for (ai, op);
669 pi = SSA_NAME_PTR_INFO (op);
670 if (ptr_is_dereferenced_by (op, stmt, &is_store))
672 /* If we found OP to point to a set of variables or
673 malloc, then mark it as being dereferenced. In a
674 subsequent pass, dereferenced pointers that point
675 to a set of variables will be assigned a name tag
676 to alias all the variables OP points to. */
677 if (pi->pt_malloc || pi->pt_vars)
678 pi->is_dereferenced = 1;
680 /* Keep track of how many time we've dereferenced each
681 pointer. Again, we don't need to grow
682 AI->NUM_REFERENCES because we're processing
683 existing program variables. */
684 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
686 /* If this is a store operation, mark OP as being
687 dereferenced to store, otherwise mark it as being
688 dereferenced to load. */
690 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
692 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
694 else if (stmt_escapes_p)
696 /* Note that even if STMT is an escape point, pointer OP
697 will not escape if it is being dereferenced. That's
698 why we only check for escape points if OP is not
699 dereferenced by STMT. */
700 pi->value_escapes_p = 1;
702 /* If the statement makes a function call, assume
703 that pointer OP will be dereferenced in a store
704 operation inside the called function. */
705 if (get_call_expr_in (stmt))
706 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
710 /* Update reference counter for definitions to any
711 potentially aliased variable. This is used in the alias
712 grouping heuristics. */
713 defs = DEF_OPS (ann);
714 for (i = 0; i < NUM_DEFS (defs); i++)
716 tree op = DEF_OP (defs, i);
717 tree var = SSA_NAME_VAR (op);
718 var_ann_t ann = var_ann (var);
719 bitmap_set_bit (ai->written_vars, ann->uid);
720 if (may_be_aliased (var))
721 (VARRAY_UINT (ai->num_references, ann->uid))++;
724 /* Mark variables in V_MAY_DEF operands as being written to. */
725 v_may_defs = V_MAY_DEF_OPS (ann);
726 for (i = 0; i < NUM_V_MAY_DEFS (v_may_defs); i++)
728 tree op = V_MAY_DEF_OP (v_may_defs, i);
729 tree var = SSA_NAME_VAR (op);
730 var_ann_t ann = var_ann (var);
731 bitmap_set_bit (ai->written_vars, ann->uid);
734 /* Mark variables in V_MUST_DEF operands as being written to. */
735 v_must_defs = V_MUST_DEF_OPS (ann);
736 for (i = 0; i < NUM_V_MUST_DEFS (v_must_defs); i++)
738 tree op = V_MUST_DEF_OP (v_must_defs, i);
739 tree var = SSA_NAME_VAR (op);
740 var_ann_t ann = var_ann (var);
741 bitmap_set_bit (ai->written_vars, ann->uid);
744 /* After promoting variables and computing aliasing we will
745 need to re-scan most statements. FIXME: Try to minimize the
746 number of statements re-scanned. It's not really necessary to
747 re-scan *all* statements. */
752 timevar_pop (TV_TREE_PTA);
756 /* Create name tags for all the pointers that have been dereferenced.
757 We only create a name tag for a pointer P if P is found to point to
758 a set of variables (so that we can alias them to *P) or if it is
759 the result of a call to malloc (which means that P cannot point to
760 anything else nor alias any other variable).
762 If two pointers P and Q point to the same set of variables, they
763 are assigned the same name tag. */
766 create_name_tags (struct alias_info *ai)
770 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
772 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
773 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
775 if (!pi->is_dereferenced)
781 tree old_name_tag = pi->name_mem_tag;
783 /* If PTR points to a set of variables, check if we don't
784 have another pointer Q with the same points-to set before
785 creating a tag. If so, use Q's tag instead of creating a
788 This is important for not creating unnecessary symbols
789 and also for copy propagation. If we ever need to
790 propagate PTR into Q or vice-versa, we would run into
791 problems if they both had different name tags because
792 they would have different SSA version numbers (which
793 would force us to take the name tags in and out of SSA). */
794 for (j = 0; j < i; j++)
796 tree q = VARRAY_TREE (ai->processed_ptrs, j);
797 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
802 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
804 pi->name_mem_tag = qi->name_mem_tag;
809 /* If we didn't find a pointer with the same points-to set
810 as PTR, create a new name tag if needed. */
811 if (pi->name_mem_tag == NULL_TREE)
812 pi->name_mem_tag = get_nmt_for (ptr);
814 /* If the new name tag computed for PTR is different than
815 the old name tag that it used to have, then the old tag
816 needs to be removed from the IL, so we mark it for
818 if (old_name_tag && old_name_tag != pi->name_mem_tag)
819 bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid);
821 else if (pi->pt_malloc)
823 /* Otherwise, create a unique name tag for this pointer. */
824 pi->name_mem_tag = get_nmt_for (ptr);
828 /* Only pointers that may point to malloc or other variables
829 may receive a name tag. If the pointer does not point to
830 a known spot, we should use type tags. */
834 /* Mark the new name tag for renaming. */
835 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
841 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
842 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
843 name tag and the variables it points-to are call-clobbered. Finally, if
844 P_i escapes and we could not determine where it points to, then all the
845 variables in the same alias set as *P_i are marked call-clobbered. This
846 is necessary because we must assume that P_i may take the address of any
847 variable in the same alias set. */
850 compute_flow_sensitive_aliasing (struct alias_info *ai)
854 create_name_tags (ai);
856 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
859 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
860 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
861 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
863 if (pi->value_escapes_p || pi->pt_anything)
865 /* If PTR escapes or may point to anything, then its associated
866 memory tags are call-clobbered. */
867 if (pi->name_mem_tag)
868 mark_call_clobbered (pi->name_mem_tag);
870 if (v_ann->type_mem_tag)
871 mark_call_clobbered (v_ann->type_mem_tag);
873 /* If PTR may point to anything, mark call-clobbered all the
874 addressables with the same alias set as the type pointed-to by
878 HOST_WIDE_INT ptr_set;
879 ptr_set = get_alias_set (TREE_TYPE (TREE_TYPE (ptr)));
880 for (j = 0; j < ai->num_addressable_vars; j++)
882 struct alias_map_d *alias_map = ai->addressable_vars[j];
883 if (alias_map->set == ptr_set)
884 mark_call_clobbered (alias_map->var);
888 /* If PTR's value may escape and PTR is never dereferenced, we
889 need to mark all the variables PTR points-to as
890 call-clobbered. Note that we only need do this it PTR is
891 never dereferenced. If PTR is dereferenced, it will have a
892 name memory tag, which will have been marked call-clobbered.
893 This will in turn mark the pointed-to variables as
894 call-clobbered when we call add_may_alias below. */
895 if (pi->value_escapes_p
896 && pi->name_mem_tag == NULL_TREE
898 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j,
899 mark_call_clobbered (referenced_var (j)));
902 /* Set up aliasing information for PTR's name memory tag (if it has
903 one). Note that only pointers that have been dereferenced will
904 have a name memory tag. */
905 if (pi->name_mem_tag && pi->pt_vars)
906 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j,
907 add_may_alias (pi->name_mem_tag, referenced_var (j)));
909 /* If the name tag is call clobbered, so is the type tag
910 associated with the base VAR_DECL. */
912 && v_ann->type_mem_tag
913 && is_call_clobbered (pi->name_mem_tag))
914 mark_call_clobbered (v_ann->type_mem_tag);
919 /* Compute type-based alias sets. Traverse all the pointers and
920 addressable variables found in setup_pointers_and_addressables.
922 For every pointer P in AI->POINTERS and addressable variable V in
923 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
924 memory tag (TMT) if their alias sets conflict. V is then marked as
925 an alias tag so that the operand scanner knows that statements
926 containing V have aliased operands. */
929 compute_flow_insensitive_aliasing (struct alias_info *ai)
933 /* Initialize counter for the total number of virtual operands that
934 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
935 threshold set by --params max-alias-vops, we enable alias
937 ai->total_alias_vops = 0;
939 /* For every pointer P, determine which addressable variables may alias
940 with P's type memory tag. */
941 for (i = 0; i < ai->num_pointers; i++)
944 struct alias_map_d *p_map = ai->pointers[i];
945 tree tag = var_ann (p_map->var)->type_mem_tag;
946 var_ann_t tag_ann = var_ann (tag);
948 p_map->total_alias_vops = 0;
949 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
950 sbitmap_zero (p_map->may_aliases);
952 for (j = 0; j < ai->num_addressable_vars; j++)
954 struct alias_map_d *v_map;
957 bool tag_stored_p, var_stored_p;
959 v_map = ai->addressable_vars[j];
961 v_ann = var_ann (var);
963 /* Skip memory tags and variables that have never been
964 written to. We also need to check if the variables are
965 call-clobbered because they may be overwritten by
967 tag_stored_p = bitmap_bit_p (ai->written_vars, tag_ann->uid)
968 || is_call_clobbered (tag);
969 var_stored_p = bitmap_bit_p (ai->written_vars, v_ann->uid)
970 || is_call_clobbered (var);
971 if (!tag_stored_p && !var_stored_p)
974 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
976 size_t num_tag_refs, num_var_refs;
978 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
979 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
981 /* Add VAR to TAG's may-aliases set. */
982 add_may_alias (tag, var);
984 /* Update the total number of virtual operands due to
985 aliasing. Since we are adding one more alias to TAG's
986 may-aliases set, the total number of virtual operands due
987 to aliasing will be increased by the number of references
988 made to VAR and TAG (every reference to TAG will also
989 count as a reference to VAR). */
990 ai->total_alias_vops += (num_var_refs + num_tag_refs);
991 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
993 /* Update the bitmap used to represent TAG's alias set
994 in case we need to group aliases. */
995 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
1001 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
1002 get_name (current_function_decl),
1003 ai->total_alias_vops);
1005 /* Determine if we need to enable alias grouping. */
1006 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
1011 /* Comparison function for qsort used in group_aliases. */
1014 total_alias_vops_cmp (const void *p, const void *q)
1016 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1017 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1018 long n1 = (*p1)->total_alias_vops;
1019 long n2 = (*p2)->total_alias_vops;
1021 /* We want to sort in descending order. */
1022 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1025 /* Group all the aliases for TAG to make TAG represent all the
1026 variables in its alias set. Update the total number
1027 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1028 function will make TAG be the unique alias tag for all the
1029 variables in its may-aliases. So, given:
1031 may-aliases(TAG) = { V1, V2, V3 }
1033 This function will group the variables into:
1035 may-aliases(V1) = { TAG }
1036 may-aliases(V2) = { TAG }
1037 may-aliases(V2) = { TAG } */
1040 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
1043 var_ann_t tag_ann = var_ann (tag);
1044 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1046 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
1048 tree var = referenced_var (i);
1049 var_ann_t ann = var_ann (var);
1051 /* Make TAG the unique alias of VAR. */
1052 ann->is_alias_tag = 0;
1053 ann->may_aliases = NULL;
1055 /* Note that VAR and TAG may be the same if the function has no
1056 addressable variables (see the discussion at the end of
1057 setup_pointers_and_addressables). */
1059 add_may_alias (var, tag);
1061 /* Reduce total number of virtual operands contributed
1062 by TAG on behalf of VAR. Notice that the references to VAR
1063 itself won't be removed. We will merely replace them with
1064 references to TAG. */
1065 ai->total_alias_vops -= num_tag_refs;
1068 /* We have reduced the number of virtual operands that TAG makes on
1069 behalf of all the variables formerly aliased with it. However,
1070 we have also "removed" all the virtual operands for TAG itself,
1071 so we add them back. */
1072 ai->total_alias_vops += num_tag_refs;
1074 /* TAG no longer has any aliases. */
1075 tag_ann->may_aliases = NULL;
1079 /* Group may-aliases sets to reduce the number of virtual operands due
1082 1- Sort the list of pointers in decreasing number of contributed
1085 2- Take the first entry in AI->POINTERS and revert the role of
1086 the memory tag and its aliases. Usually, whenever an aliased
1087 variable Vi is found to alias with a memory tag T, we add Vi
1088 to the may-aliases set for T. Meaning that after alias
1089 analysis, we will have:
1091 may-aliases(T) = { V1, V2, V3, ..., Vn }
1093 This means that every statement that references T, will get 'n'
1094 virtual operands for each of the Vi tags. But, when alias
1095 grouping is enabled, we make T an alias tag and add it to the
1096 alias set of all the Vi variables:
1098 may-aliases(V1) = { T }
1099 may-aliases(V2) = { T }
1101 may-aliases(Vn) = { T }
1103 This has two effects: (a) statements referencing T will only get
1104 a single virtual operand, and, (b) all the variables Vi will now
1105 appear to alias each other. So, we lose alias precision to
1106 improve compile time. But, in theory, a program with such a high
1107 level of aliasing should not be very optimizable in the first
1110 3- Since variables may be in the alias set of more than one
1111 memory tag, the grouping done in step (2) needs to be extended
1112 to all the memory tags that have a non-empty intersection with
1113 the may-aliases set of tag T. For instance, if we originally
1114 had these may-aliases sets:
1116 may-aliases(T) = { V1, V2, V3 }
1117 may-aliases(R) = { V2, V4 }
1119 In step (2) we would have reverted the aliases for T as:
1121 may-aliases(V1) = { T }
1122 may-aliases(V2) = { T }
1123 may-aliases(V3) = { T }
1125 But note that now V2 is no longer aliased with R. We could
1126 add R to may-aliases(V2), but we are in the process of
1127 grouping aliases to reduce virtual operands so what we do is
1128 add V4 to the grouping to obtain:
1130 may-aliases(V1) = { T }
1131 may-aliases(V2) = { T }
1132 may-aliases(V3) = { T }
1133 may-aliases(V4) = { T }
1135 4- If the total number of virtual operands due to aliasing is
1136 still above the threshold set by max-alias-vops, go back to (2). */
1139 group_aliases (struct alias_info *ai)
1144 /* Sort the POINTERS array in descending order of contributed
1145 virtual operands. */
1146 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1147 total_alias_vops_cmp);
1149 res = sbitmap_alloc (num_referenced_vars);
1151 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1152 and the tag's may-aliases set. */
1153 for (i = 0; i < ai->num_pointers; i++)
1156 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1157 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1159 /* Skip tags that have been grouped already. */
1160 if (ai->pointers[i]->grouped_p)
1163 /* See if TAG1 had any aliases in common with other type tags.
1164 If we find a TAG2 with common aliases with TAG1, add TAG2's
1165 aliases into TAG1. */
1166 for (j = i + 1; j < ai->num_pointers; j++)
1168 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1170 sbitmap_a_and_b (res, tag1_aliases, tag2_aliases);
1171 if (sbitmap_first_set_bit (res) >= 0)
1173 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1175 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1177 /* TAG2 does not need its aliases anymore. */
1178 sbitmap_zero (tag2_aliases);
1179 var_ann (tag2)->may_aliases = NULL;
1181 /* TAG1 is the unique alias of TAG2. */
1182 add_may_alias (tag2, tag1);
1184 ai->pointers[j]->grouped_p = true;
1188 /* Now group all the aliases we collected into TAG1. */
1189 group_aliases_into (tag1, tag1_aliases, ai);
1191 /* If we've reduced total number of virtual operands below the
1193 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1197 /* Finally, all the variables that have been grouped cannot be in
1198 the may-alias set of name memory tags. Suppose that we have
1199 grouped the aliases in this code so that may-aliases(a) = TMT.20
1203 # a_9 = V_MAY_DEF <a_8>
1205 ... Several modifications to TMT.20 ...
1209 Since p_5 points to 'a', the optimizers will try to propagate 0
1210 into p_5->field, but that is wrong because there have been
1211 modifications to 'TMT.20' in between. To prevent this we have to
1212 replace 'a' with 'TMT.20' in the name tag of p_5. */
1213 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1216 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1217 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1218 varray_type aliases;
1220 if (name_tag == NULL_TREE)
1223 aliases = var_ann (name_tag)->may_aliases;
1224 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1226 tree alias = VARRAY_TREE (aliases, j);
1227 var_ann_t ann = var_ann (alias);
1229 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1233 #if defined ENABLE_CHECKING
1234 if (VARRAY_ACTIVE_SIZE (ann->may_aliases) != 1)
1237 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1238 replace_may_alias (name_tag, j, new_alias);
1247 "%s: Total number of aliased vops after grouping: %ld%s\n",
1248 get_name (current_function_decl),
1249 ai->total_alias_vops,
1250 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1254 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1257 create_alias_map_for (tree var, struct alias_info *ai)
1259 struct alias_map_d *alias_map;
1260 alias_map = xcalloc (1, sizeof (*alias_map));
1261 alias_map->var = var;
1263 if (TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE)
1264 alias_map->set = get_alias_set (TREE_TYPE (TREE_TYPE (var)));
1266 alias_map->set = get_alias_set (var);
1267 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1271 /* Create memory tags for all the dereferenced pointers and build the
1272 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1273 sets. Based on the address escape and points-to information collected
1274 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1275 variables whose address is not needed anymore. */
1278 setup_pointers_and_addressables (struct alias_info *ai)
1280 size_t i, n_vars, num_addressable_vars, num_pointers;
1282 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1283 num_addressable_vars = num_pointers = 0;
1284 for (i = 0; i < num_referenced_vars; i++)
1286 tree var = referenced_var (i);
1288 if (may_be_aliased (var))
1289 num_addressable_vars++;
1291 if (POINTER_TYPE_P (TREE_TYPE (var)))
1293 /* Since we don't keep track of volatile variables, assume that
1294 these pointers are used in indirect store operations. */
1295 if (TREE_THIS_VOLATILE (var))
1296 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1302 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1303 always going to be slightly bigger than we actually need them
1304 because some TREE_ADDRESSABLE variables will be marked
1305 non-addressable below and only pointers with unique type tags are
1306 going to be added to POINTERS. */
1307 ai->addressable_vars = xcalloc (num_addressable_vars,
1308 sizeof (struct alias_map_d *));
1309 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1310 ai->num_addressable_vars = 0;
1311 ai->num_pointers = 0;
1313 /* Since we will be creating type memory tags within this loop, cache the
1314 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1316 n_vars = num_referenced_vars;
1318 for (i = 0; i < n_vars; i++)
1320 tree var = referenced_var (i);
1321 var_ann_t v_ann = var_ann (var);
1323 /* Name memory tags already have flow-sensitive aliasing
1324 information, so they need not be processed by
1325 compute_may_aliases. Similarly, type memory tags are already
1326 accounted for when we process their associated pointer. */
1327 if (v_ann->mem_tag_kind != NOT_A_TAG)
1330 /* Remove the ADDRESSABLE flag from every addressable variable whose
1331 address is not needed anymore. This is caused by the propagation
1332 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1333 removal of dead pointer assignments done by the early scalar
1335 if (TREE_ADDRESSABLE (var))
1337 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1338 && v_ann->mem_tag_kind == NOT_A_TAG
1339 && !needs_to_live_in_memory (var))
1341 /* The address of VAR is not needed, remove the
1342 addressable bit, so that it can be optimized as a
1343 regular variable. */
1344 mark_non_addressable (var);
1346 /* Since VAR is now a regular GIMPLE register, we will need
1347 to rename VAR into SSA afterwards. */
1348 bitmap_set_bit (vars_to_rename, v_ann->uid);
1352 /* Add the variable to the set of addressables. Mostly
1353 used when scanning operands for ASM_EXPRs that
1354 clobber memory. In those cases, we need to clobber
1355 all call-clobbered variables and all addressables. */
1356 bitmap_set_bit (addressable_vars, v_ann->uid);
1360 /* Global variables and addressable locals may be aliased. Create an
1361 entry in ADDRESSABLE_VARS for VAR. */
1362 if (may_be_aliased (var))
1364 create_alias_map_for (var, ai);
1365 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1368 /* Add pointer variables that have been dereferenced to the POINTERS
1369 array and create a type memory tag for them. */
1370 if (POINTER_TYPE_P (TREE_TYPE (var))
1371 && (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1372 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1377 /* If pointer VAR still doesn't have a memory tag associated
1378 with it, create it now or re-use an existing one. */
1379 tag = get_tmt_for (var, ai);
1380 t_ann = var_ann (tag);
1382 /* The type tag will need to be renamed into SSA afterwards.
1383 Note that we cannot do this inside get_tmt_for because
1384 aliasing may run multiple times and we only create type
1385 tags the first time. */
1386 bitmap_set_bit (vars_to_rename, t_ann->uid);
1388 /* Associate the tag with pointer VAR. */
1389 v_ann->type_mem_tag = tag;
1391 /* If pointer VAR has been used in a store operation, then its
1392 memory tag must be marked as written-to. */
1393 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1394 bitmap_set_bit (ai->written_vars, t_ann->uid);
1396 /* If pointer VAR is a global variable or a PARM_DECL, then its
1397 memory tag should be considered a global variable. */
1398 if (TREE_CODE (var) == PARM_DECL || needs_to_live_in_memory (var))
1399 mark_call_clobbered (tag);
1401 /* All the dereferences of pointer VAR count as references of
1402 TAG. Since TAG can be associated with several pointers, add
1403 the dereferences of VAR to the TAG. We may need to grow
1404 AI->NUM_REFERENCES because we have been adding name and
1406 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1407 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1409 VARRAY_UINT (ai->num_references, t_ann->uid)
1410 += VARRAY_UINT (ai->num_references, v_ann->uid);
1414 /* If we found no addressable variables, but we have more than one
1415 pointer, we will need to check for conflicts between the
1416 pointers. Otherwise, we would miss alias relations as in
1417 testsuite/gcc.dg/tree-ssa/20040319-1.c:
1419 struct bar { int count; int *arr;};
1421 void foo (struct bar *b)
1429 b->count and *(b->arr) could be aliased if b->arr == &b->count.
1430 To do this, we add all the memory tags for the pointers in
1431 AI->POINTERS to AI->ADDRESSABLE_VARS, so that
1432 compute_flow_insensitive_aliasing will naturally compare every
1433 pointer to every type tag. */
1434 if (ai->num_addressable_vars == 0
1435 && ai->num_pointers > 1)
1437 free (ai->addressable_vars);
1438 ai->addressable_vars = xcalloc (ai->num_pointers,
1439 sizeof (struct alias_map_d *));
1440 ai->num_addressable_vars = 0;
1441 for (i = 0; i < ai->num_pointers; i++)
1443 struct alias_map_d *p = ai->pointers[i];
1444 tree tag = var_ann (p->var)->type_mem_tag;
1445 create_alias_map_for (tag, ai);
1451 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1452 every call site, we need to emit V_MAY_DEF expressions to represent the
1453 clobbering effects of the call for variables whose address escapes the
1456 One approach is to group all call-clobbered variables into a single
1457 representative that is used as an alias of every call-clobbered variable
1458 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1459 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1461 The second approach is to emit a clobbering V_MAY_DEF for every
1462 call-clobbered variable at call sites. This is the preferred way in terms
1463 of optimization opportunities but it may create too many V_MAY_DEF operands
1464 if there are many call clobbered variables and function calls in the
1467 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1468 function calls found by the number of call-clobbered variables. If that
1469 product is beyond a certain threshold, as determined by the parameterized
1470 values shown below, we use .GLOBAL_VAR.
1472 FIXME. This heuristic should be improved. One idea is to use several
1473 .GLOBAL_VARs of different types instead of a single one. The thresholds
1474 have been derived from a typical bootstrap cycle, including all target
1475 libraries. Compile times were found increase by ~1% compared to using
1479 maybe_create_global_var (struct alias_info *ai)
1481 size_t i, n_clobbered;
1483 /* No need to create it, if we have one already. */
1487 /* Count all the call-clobbered variables. */
1489 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, n_clobbered++);
1491 /* Create .GLOBAL_VAR if we have too many call-clobbered variables.
1492 We also create .GLOBAL_VAR when there no call-clobbered variables
1493 to prevent code motion transformations from re-arranging function
1494 calls that may have side effects. For instance,
1503 There are no call-clobbered variables in foo(), so it would be
1504 entirely possible for a pass to want to move the call to f()
1505 after the call to g(). If f() has side effects, that would be
1506 wrong. Creating .GLOBAL_VAR in this case will insert VDEFs for
1507 it and prevent such transformations. */
1508 if (n_clobbered == 0
1509 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1510 create_global_var ();
1512 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1513 been created, make it an alias for all call-clobbered variables. */
1515 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i,
1517 tree var = referenced_var (i);
1518 if (var != global_var)
1520 add_may_alias (var, global_var);
1521 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1527 /* Return TRUE if pointer PTR may point to variable VAR.
1529 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1530 This is needed because when checking for type conflicts we are
1531 interested in the alias set of the memory location pointed-to by
1532 PTR. The alias set of PTR itself is irrelevant.
1534 VAR_ALIAS_SET is the alias set for VAR. */
1537 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1538 tree var, HOST_WIDE_INT var_alias_set)
1541 var_ann_t v_ann, m_ann;
1543 alias_stats.alias_queries++;
1544 alias_stats.simple_queries++;
1546 /* By convention, a variable cannot alias itself. */
1547 mem = var_ann (ptr)->type_mem_tag;
1550 alias_stats.alias_noalias++;
1551 alias_stats.simple_resolved++;
1555 v_ann = var_ann (var);
1556 m_ann = var_ann (mem);
1558 #if defined ENABLE_CHECKING
1559 if (m_ann->mem_tag_kind != TYPE_TAG)
1563 alias_stats.tbaa_queries++;
1565 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1566 PTR can't possibly affect VAR. Note, that we are specifically testing
1567 for PTR's alias set here, not its pointed-to type. We also can't
1568 do this check with relaxed aliasing enabled. */
1569 if (POINTER_TYPE_P (TREE_TYPE (var))
1570 && var_alias_set != 0)
1572 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1573 if (ptr_alias_set == var_alias_set)
1575 alias_stats.alias_noalias++;
1576 alias_stats.tbaa_resolved++;
1581 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1582 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1584 /* Handle aliases to structure fields. If either VAR or MEM are
1585 aggregate types, they may not have conflicting types, but one of
1586 the structures could contain a pointer to the other one.
1593 It may happen that '*p' and '*q' can't alias because 'struct P'
1594 and 'struct Q' have non-conflicting alias sets. However, it could
1595 happen that one of the fields in 'struct P' is a 'struct Q *' or
1598 Therefore, we also need to check if 'struct P' aliases 'struct Q *'
1599 or 'struct Q' aliases 'struct P *'. Notice, that since GIMPLE
1600 does not have more than one-level pointers, we don't need to
1601 recurse into the structures. */
1602 if (AGGREGATE_TYPE_P (TREE_TYPE (mem))
1603 || AGGREGATE_TYPE_P (TREE_TYPE (var)))
1607 if (TREE_CODE (TREE_TYPE (var)) == ARRAY_TYPE)
1608 ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (TREE_TYPE (var)));
1610 ptr_to_var = TYPE_POINTER_TO (TREE_TYPE (var));
1612 /* If no pointer-to VAR exists, then MEM can't alias VAR. */
1613 if (ptr_to_var == NULL_TREE)
1615 alias_stats.alias_noalias++;
1616 alias_stats.tbaa_resolved++;
1620 /* If MEM doesn't alias a pointer to VAR and VAR doesn't alias
1621 PTR, then PTR can't alias VAR. */
1622 if (!alias_sets_conflict_p (mem_alias_set, get_alias_set (ptr_to_var))
1623 && !alias_sets_conflict_p (var_alias_set, get_alias_set (ptr)))
1625 alias_stats.alias_noalias++;
1626 alias_stats.tbaa_resolved++;
1632 alias_stats.alias_noalias++;
1633 alias_stats.tbaa_resolved++;
1638 if (flag_tree_points_to != PTA_NONE)
1639 alias_stats.pta_queries++;
1641 /* If -ftree-points-to is given, check if PTR may point to VAR. */
1642 if (flag_tree_points_to == PTA_ANDERSEN
1643 && !ptr_may_alias_var (ptr, var))
1645 alias_stats.alias_noalias++;
1646 alias_stats.pta_resolved++;
1650 alias_stats.alias_mayalias++;
1655 /* Add ALIAS to the set of variables that may alias VAR. */
1658 add_may_alias (tree var, tree alias)
1661 var_ann_t v_ann = get_var_ann (var);
1662 var_ann_t a_ann = get_var_ann (alias);
1664 #if defined ENABLE_CHECKING
1669 if (v_ann->may_aliases == NULL)
1670 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1672 /* Avoid adding duplicates. */
1673 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1674 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1677 /* If VAR is a call-clobbered variable, so is its new ALIAS. */
1678 if (is_call_clobbered (var))
1679 mark_call_clobbered (alias);
1681 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1682 else if (is_call_clobbered (alias))
1683 mark_call_clobbered (var);
1685 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1686 a_ann->is_alias_tag = 1;
1690 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1693 replace_may_alias (tree var, size_t i, tree new_alias)
1695 var_ann_t v_ann = var_ann (var);
1696 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1698 /* If VAR is a call-clobbered variable, so is NEW_ALIAS. */
1699 if (is_call_clobbered (var))
1700 mark_call_clobbered (new_alias);
1702 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1703 else if (is_call_clobbered (new_alias))
1704 mark_call_clobbered (var);
1708 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1711 set_pt_anything (tree ptr)
1713 struct ptr_info_def *pi = get_ptr_info (ptr);
1715 pi->pt_anything = 1;
1718 pi->is_dereferenced = 0;
1720 /* The pointer used to have a name tag, but we now found it pointing
1721 to an arbitrary location. The name tag needs to be renamed and
1722 disassociated from PTR. */
1723 if (pi->name_mem_tag)
1725 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1726 pi->name_mem_tag = NULL_TREE;
1731 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1734 set_pt_malloc (tree ptr)
1736 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1738 /* If the pointer has already been found to point to arbitrary
1739 memory locations, it is unsafe to mark it as pointing to malloc. */
1740 if (pi->pt_anything)
1747 /* Given two pointers DEST and ORIG. Merge the points-to information in
1748 ORIG into DEST. AI is as in collect_points_to_info. */
1751 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1753 struct ptr_info_def *dest_pi, *orig_pi;
1755 /* Make sure we have points-to information for ORIG. */
1756 collect_points_to_info_for (ai, orig);
1758 dest_pi = get_ptr_info (dest);
1759 orig_pi = SSA_NAME_PTR_INFO (orig);
1763 /* Notice that we never merge PT_MALLOC. This attribute is only
1764 true if the pointer is the result of a malloc() call.
1765 Otherwise, we can end up in this situation:
1771 P_j would be marked as PT_MALLOC, which is wrong because
1772 PT_MALLOC implies that the pointer may not point to another
1775 FIXME 1: Subsequent analysis may determine that P_j
1776 cannot alias anything else, but we are being conservative
1779 FIXME 2: If the merging comes from a copy assignment, we
1780 ought to merge PT_MALLOC, but then both pointers would end up
1781 getting different name tags because create_name_tags is not
1782 smart enough to determine that the two come from the same
1783 malloc call. Copy propagation before aliasing should cure
1785 dest_pi->pt_malloc = 0;
1787 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1788 set_pt_anything (dest);
1790 if (!dest_pi->pt_anything
1792 && bitmap_first_set_bit (orig_pi->pt_vars) >= 0)
1794 if (dest_pi->pt_vars == NULL)
1796 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1797 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1800 bitmap_a_or_b (dest_pi->pt_vars,
1808 /* Add VALUE to the list of expressions pointed-to by PTR. */
1811 add_pointed_to_expr (tree ptr, tree value)
1813 if (TREE_CODE (value) == WITH_SIZE_EXPR)
1814 value = TREE_OPERAND (value, 0);
1816 #if defined ENABLE_CHECKING
1817 /* Pointer variables should have been handled by merge_pointed_to_info. */
1818 if (TREE_CODE (value) == SSA_NAME
1819 && POINTER_TYPE_P (TREE_TYPE (value)))
1825 /* If VALUE is the result of a malloc-like call, then the area pointed to
1826 PTR is guaranteed to not alias with anything else. */
1827 if (TREE_CODE (value) == CALL_EXPR
1828 && (call_expr_flags (value) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1829 set_pt_malloc (ptr);
1831 set_pt_anything (ptr);
1835 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1837 fprintf (dump_file, "Pointer ");
1838 print_generic_expr (dump_file, ptr, dump_flags);
1839 fprintf (dump_file, " points to ");
1841 fprintf (dump_file, "malloc space: ");
1843 fprintf (dump_file, "an arbitrary address: ");
1844 print_generic_expr (dump_file, value, dump_flags);
1845 fprintf (dump_file, "\n");
1850 /* If VALUE is of the form &DECL, add DECL to the set of variables
1851 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1852 PTR. AI is as in collect_points_to_info. */
1855 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1857 struct ptr_info_def *pi = get_ptr_info (ptr);
1859 if (TREE_CODE (value) == ADDR_EXPR)
1864 pt_var = TREE_OPERAND (value, 0);
1865 if (TREE_CODE_CLASS (TREE_CODE (pt_var)) == 'r')
1866 pt_var = get_base_address (pt_var);
1868 if (pt_var && SSA_VAR_P (pt_var))
1870 uid = var_ann (pt_var)->uid;
1871 bitmap_set_bit (ai->addresses_needed, uid);
1873 /* If PTR has already been found to point anywhere, don't
1874 add the variable to PTR's points-to set. */
1875 if (!pi->pt_anything)
1877 if (pi->pt_vars == NULL)
1878 pi->pt_vars = BITMAP_GGC_ALLOC ();
1879 bitmap_set_bit (pi->pt_vars, uid);
1883 add_pointed_to_expr (ptr, value);
1886 add_pointed_to_expr (ptr, value);
1890 /* Callback for walk_use_def_chains to gather points-to information from the
1893 VAR is an SSA variable or a GIMPLE expression.
1895 STMT is the statement that generates the SSA variable or, if STMT is a
1896 PHI_NODE, VAR is one of the PHI arguments.
1898 DATA is a pointer to a structure of type ALIAS_INFO. */
1901 collect_points_to_info_r (tree var, tree stmt, void *data)
1903 struct alias_info *ai = (struct alias_info *) data;
1905 if (dump_file && (dump_flags & TDF_DETAILS))
1907 fprintf (dump_file, "Visiting use-def links for ");
1908 print_generic_expr (dump_file, var, dump_flags);
1909 fprintf (dump_file, "\n");
1912 if (TREE_CODE (stmt) == MODIFY_EXPR)
1914 tree rhs = TREE_OPERAND (stmt, 1);
1917 /* Found P_i = CONST. */
1918 if (is_gimple_min_invariant (rhs))
1919 add_pointed_to_var (ai, var, rhs);
1921 /* Found P_i = Q_j. */
1922 else if (TREE_CODE (rhs) == SSA_NAME
1923 && POINTER_TYPE_P (TREE_TYPE (rhs)))
1924 merge_pointed_to_info (ai, var, rhs);
1926 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1927 else if (TREE_CODE (rhs) == PLUS_EXPR
1928 || TREE_CODE (rhs) == MINUS_EXPR)
1930 tree op0 = TREE_OPERAND (rhs, 0);
1931 tree op1 = TREE_OPERAND (rhs, 1);
1933 if (TREE_CODE (op0) == SSA_NAME
1934 && POINTER_TYPE_P (TREE_TYPE (op0)))
1935 merge_pointed_to_info (ai, var, op0);
1936 else if (TREE_CODE (op1) == SSA_NAME
1937 && POINTER_TYPE_P (TREE_TYPE (op1)))
1938 merge_pointed_to_info (ai, var, op1);
1939 else if (is_gimple_min_invariant (op0))
1940 add_pointed_to_var (ai, var, op0);
1941 else if (is_gimple_min_invariant (op1))
1942 add_pointed_to_var (ai, var, op1);
1944 add_pointed_to_expr (var, rhs);
1947 /* Something else. */
1949 add_pointed_to_expr (var, rhs);
1951 else if (TREE_CODE (stmt) == ASM_EXPR)
1953 /* Pointers defined by __asm__ statements can point anywhere. */
1954 set_pt_anything (var);
1956 else if (IS_EMPTY_STMT (stmt))
1958 tree decl = SSA_NAME_VAR (var);
1960 if (TREE_CODE (decl) == PARM_DECL)
1961 add_pointed_to_expr (var, decl);
1962 else if (DECL_INITIAL (decl))
1963 add_pointed_to_var (ai, var, DECL_INITIAL (decl));
1965 add_pointed_to_expr (var, decl);
1967 else if (TREE_CODE (stmt) == PHI_NODE)
1969 /* It STMT is a PHI node, then VAR is one of its arguments. The
1970 variable that we are analyzing is the LHS of the PHI node. */
1971 tree lhs = PHI_RESULT (stmt);
1973 if (is_gimple_min_invariant (var))
1974 add_pointed_to_var (ai, lhs, var);
1975 else if (TREE_CODE (var) == SSA_NAME)
1977 if (bitmap_bit_p (ai->ssa_names_visited, SSA_NAME_VERSION (var)))
1978 merge_pointed_to_info (ai, lhs, var);
1980 set_pt_anything (lhs);
1992 /* Return true if STMT is an "escape" site from the current function. Escape
1993 sites those statements which might expose the address of a variable
1994 outside the current function. STMT is an escape site iff:
1996 1- STMT is a function call, or
1997 2- STMT is an __asm__ expression, or
1998 3- STMT is an assignment to a non-local variable, or
1999 4- STMT is a return statement.
2001 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
2005 is_escape_site (tree stmt, size_t *num_calls_p)
2007 if (get_call_expr_in (stmt) != NULL_TREE)
2014 else if (TREE_CODE (stmt) == ASM_EXPR)
2016 else if (TREE_CODE (stmt) == MODIFY_EXPR)
2018 tree lhs = TREE_OPERAND (stmt, 0);
2020 /* Get to the base of _REF nodes. */
2021 if (TREE_CODE (lhs) != SSA_NAME)
2022 lhs = get_base_address (lhs);
2024 /* If we couldn't recognize the LHS of the assignment, assume that it
2025 is a non-local store. */
2026 if (lhs == NULL_TREE)
2029 /* If the LHS is an SSA name, it can't possibly represent a non-local
2031 if (TREE_CODE (lhs) == SSA_NAME)
2034 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2035 local variables we cannot be sure if it will escape, because we
2036 don't have information about objects not in SSA form. Need to
2037 implement something along the lines of
2039 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2040 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2041 Conference on Object-Oriented Programming Systems, Languages, and
2042 Applications (OOPSLA), pp. 1-19, 1999. */
2045 else if (TREE_CODE (stmt) == RETURN_EXPR)
2052 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2053 is considered to represent all the pointers whose pointed-to types are
2054 in the same alias set class. Otherwise, the tag represents a single
2055 SSA_NAME pointer variable. */
2058 create_memory_tag (tree type, bool is_type_tag)
2061 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2063 /* By default, memory tags are local variables. Alias analysis will
2064 determine whether they should be considered globals. */
2065 DECL_CONTEXT (tag) = current_function_decl;
2067 /* If the pointed-to type is volatile, so is the tag. */
2068 TREE_THIS_VOLATILE (tag) = TREE_THIS_VOLATILE (type);
2070 /* Memory tags are by definition addressable. This also prevents
2071 is_gimple_ref frome confusing memory tags with optimizable
2073 TREE_ADDRESSABLE (tag) = 1;
2075 ann = get_var_ann (tag);
2076 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2077 ann->type_mem_tag = NULL_TREE;
2079 /* Add the tag to the symbol table. */
2080 add_referenced_tmp_var (tag);
2086 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2087 This is used if P_i has been found to point to a specific set of
2088 variables or to a non-aliased memory location like the address returned
2089 by malloc functions. */
2092 get_nmt_for (tree ptr)
2094 struct ptr_info_def *pi = get_ptr_info (ptr);
2095 tree tag = pi->name_mem_tag;
2097 if (tag == NULL_TREE)
2099 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2101 /* If PTR is a PARM_DECL, its memory tag should be considered a
2103 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL)
2104 mark_call_clobbered (tag);
2106 /* Similarly, if PTR points to malloc, then TAG is a global. */
2108 mark_call_clobbered (tag);
2115 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2116 artificial variable that represents the memory location pointed-to by
2117 PTR. It is used to model the effects of pointer de-references on
2118 addressable variables.
2120 AI points to the data gathered during alias analysis. This function
2121 populates the array AI->POINTERS. */
2124 get_tmt_for (tree ptr, struct alias_info *ai)
2128 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2129 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2131 /* To avoid creating unnecessary memory tags, only create one memory tag
2132 per alias set class. Note that it may be tempting to group
2133 memory tags based on conflicting alias sets instead of
2134 equivalence. That would be wrong because alias sets are not
2135 necessarily transitive (as demonstrated by the libstdc++ test
2136 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2137 such that conflicts (A, B) == true and conflicts (A, C) == true,
2138 it does not necessarily follow that conflicts (B, C) == true. */
2139 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2141 struct alias_map_d *curr = ai->pointers[i];
2142 if (tag_set == curr->set
2143 && (flag_tree_points_to == PTA_NONE
2144 || same_points_to_set (curr->var, ptr)))
2146 tag = var_ann (curr->var)->type_mem_tag;
2151 /* If VAR cannot alias with any of the existing memory tags, create a new
2152 tag for PTR and add it to the POINTERS array. */
2153 if (tag == NULL_TREE)
2155 struct alias_map_d *alias_map;
2157 /* If PTR did not have a type tag already, create a new TMT.*
2158 artificial variable representing the memory location
2159 pointed-to by PTR. */
2160 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2161 tag = create_memory_tag (tag_type, true);
2163 tag = var_ann (ptr)->type_mem_tag;
2165 /* Add PTR to the POINTERS array. Note that we are not interested in
2166 PTR's alias set. Instead, we cache the alias set for the memory that
2168 alias_map = xcalloc (1, sizeof (*alias_map));
2169 alias_map->var = ptr;
2170 alias_map->set = tag_set;
2171 ai->pointers[ai->num_pointers++] = alias_map;
2174 #if defined ENABLE_CHECKING
2175 /* Make sure that the type tag has the same alias set as the
2177 if (tag_set != get_alias_set (tag))
2186 /* Create GLOBAL_VAR, an artificial global variable to act as a
2187 representative of all the variables that may be clobbered by function
2191 create_global_var (void)
2193 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2195 DECL_ARTIFICIAL (global_var) = 1;
2196 TREE_READONLY (global_var) = 0;
2197 DECL_EXTERNAL (global_var) = 0;
2198 TREE_STATIC (global_var) = 1;
2199 TREE_USED (global_var) = 1;
2200 DECL_CONTEXT (global_var) = NULL_TREE;
2201 TREE_THIS_VOLATILE (global_var) = 0;
2202 TREE_ADDRESSABLE (global_var) = 0;
2204 add_referenced_tmp_var (global_var);
2205 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2209 /* Dump alias statistics on FILE. */
2212 dump_alias_stats (FILE *file)
2214 const char *funcname
2215 = lang_hooks.decl_printable_name (current_function_decl, 2);
2216 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2217 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2218 fprintf (file, "Total alias mayalias results:\t%u\n",
2219 alias_stats.alias_mayalias);
2220 fprintf (file, "Total alias noalias results:\t%u\n",
2221 alias_stats.alias_noalias);
2222 fprintf (file, "Total simple queries:\t%u\n",
2223 alias_stats.simple_queries);
2224 fprintf (file, "Total simple resolved:\t%u\n",
2225 alias_stats.simple_resolved);
2226 fprintf (file, "Total TBAA queries:\t%u\n",
2227 alias_stats.tbaa_queries);
2228 fprintf (file, "Total TBAA resolved:\t%u\n",
2229 alias_stats.tbaa_resolved);
2230 fprintf (file, "Total PTA queries:\t%u\n",
2231 alias_stats.pta_queries);
2232 fprintf (file, "Total PTA resolved:\t%u\n",
2233 alias_stats.pta_resolved);
2237 /* Dump alias information on FILE. */
2240 dump_alias_info (FILE *file)
2243 const char *funcname
2244 = lang_hooks.decl_printable_name (current_function_decl, 2);
2246 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2248 fprintf (file, "Aliased symbols\n\n");
2249 for (i = 0; i < num_referenced_vars; i++)
2251 tree var = referenced_var (i);
2252 if (may_be_aliased (var))
2253 dump_variable (file, var);
2256 fprintf (file, "\nDereferenced pointers\n\n");
2257 for (i = 0; i < num_referenced_vars; i++)
2259 tree var = referenced_var (i);
2260 var_ann_t ann = var_ann (var);
2261 if (ann->type_mem_tag)
2262 dump_variable (file, var);
2265 fprintf (file, "\nType memory tags\n\n");
2266 for (i = 0; i < num_referenced_vars; i++)
2268 tree var = referenced_var (i);
2269 var_ann_t ann = var_ann (var);
2270 if (ann->mem_tag_kind == TYPE_TAG)
2271 dump_variable (file, var);
2274 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2276 fprintf (file, "SSA_NAME pointers\n\n");
2277 for (i = 1; i < num_ssa_names; i++)
2279 tree ptr = ssa_name (i);
2280 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2281 if (!SSA_NAME_IN_FREE_LIST (ptr)
2283 && pi->name_mem_tag)
2284 dump_points_to_info_for (file, ptr);
2287 fprintf (file, "\nName memory tags\n\n");
2288 for (i = 0; i < num_referenced_vars; i++)
2290 tree var = referenced_var (i);
2291 var_ann_t ann = var_ann (var);
2292 if (ann->mem_tag_kind == NAME_TAG)
2293 dump_variable (file, var);
2296 fprintf (file, "\n");
2300 /* Dump alias information on stderr. */
2303 debug_alias_info (void)
2305 dump_alias_info (stderr);
2309 /* Return the alias information associated with pointer T. It creates a
2310 new instance if none existed. */
2312 static struct ptr_info_def *
2313 get_ptr_info (tree t)
2315 struct ptr_info_def *pi;
2317 #if defined ENABLE_CHECKING
2318 if (!POINTER_TYPE_P (TREE_TYPE (t)))
2322 pi = SSA_NAME_PTR_INFO (t);
2325 pi = ggc_alloc (sizeof (*pi));
2326 memset ((void *)pi, 0, sizeof (*pi));
2327 SSA_NAME_PTR_INFO (t) = pi;
2334 /* Dump points-to information for SSA_NAME PTR into FILE. */
2337 dump_points_to_info_for (FILE *file, tree ptr)
2339 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2341 print_generic_expr (file, ptr, dump_flags);
2345 if (pi->name_mem_tag)
2347 fprintf (file, ", name memory tag: ");
2348 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2351 if (pi->is_dereferenced)
2352 fprintf (file, ", is dereferenced");
2354 if (pi->value_escapes_p)
2355 fprintf (file, ", its value escapes");
2357 if (pi->pt_anything)
2358 fprintf (file, ", points-to anything");
2361 fprintf (file, ", points-to malloc");
2367 fprintf (file, ", points-to vars: { ");
2368 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix,
2370 print_generic_expr (file, referenced_var (ix), dump_flags);
2371 fprintf (file, " ");
2373 fprintf (file, "}");
2377 fprintf (file, "\n");
2381 /* Dump points-to information for VAR into stderr. */
2384 debug_points_to_info_for (tree var)
2386 dump_points_to_info_for (stderr, var);
2390 /* Dump points-to information into FILE. NOTE: This function is slow, as
2391 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2394 dump_points_to_info (FILE *file)
2397 block_stmt_iterator si;
2400 lang_hooks.decl_printable_name (current_function_decl, 2);
2402 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2404 /* First dump points-to information for the default definitions of
2405 pointer variables. This is necessary because default definitions are
2406 not part of the code. */
2407 for (i = 0; i < num_referenced_vars; i++)
2409 tree var = referenced_var (i);
2410 if (POINTER_TYPE_P (TREE_TYPE (var)))
2412 var_ann_t ann = var_ann (var);
2413 if (ann->default_def)
2414 dump_points_to_info_for (file, ann->default_def);
2418 /* Dump points-to information for every pointer defined in the program. */
2423 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2425 tree ptr = PHI_RESULT (phi);
2426 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2427 dump_points_to_info_for (file, ptr);
2430 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2432 stmt_ann_t ann = stmt_ann (bsi_stmt (si));
2433 def_optype defs = DEF_OPS (ann);
2435 for (i = 0; i < NUM_DEFS (defs); i++)
2436 if (POINTER_TYPE_P (TREE_TYPE (DEF_OP (defs, i))))
2437 dump_points_to_info_for (file, DEF_OP (defs, i));
2441 fprintf (file, "\n");
2445 /* Dump points-to info pointed by PTO into STDERR. */
2448 debug_points_to_info (void)
2450 dump_points_to_info (stderr);
2453 /* Dump to FILE the list of variables that may be aliasing VAR. */
2456 dump_may_aliases_for (FILE *file, tree var)
2458 varray_type aliases;
2460 if (TREE_CODE (var) == SSA_NAME)
2461 var = SSA_NAME_VAR (var);
2463 aliases = var_ann (var)->may_aliases;
2467 fprintf (file, "{ ");
2468 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2470 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2471 fprintf (file, " ");
2473 fprintf (file, "}");
2478 /* Dump to stderr the list of variables that may be aliasing VAR. */
2481 debug_may_aliases_for (tree var)
2483 dump_may_aliases_for (stderr, var);
2486 /* Return true if VAR may be aliased. */
2489 may_be_aliased (tree var)
2492 if (TREE_ADDRESSABLE (var))
2495 /* Automatic variables can't have their addresses escape any other way. */
2496 if (!TREE_STATIC (var))
2499 /* Globally visible variables can have their addresses taken by other
2500 translation units. */
2501 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2504 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2505 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2506 we can only be sure the variable isn't addressable if it's local to the
2507 current function. */
2508 if (flag_unit_at_a_time)
2510 if (decl_function_context (var) == current_function_decl)