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 sbitmap 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 create_global_var (void);
151 static void collect_points_to_info_for (struct alias_info *, tree);
152 static bool ptr_is_dereferenced_by (tree, tree, bool *);
153 static void maybe_create_global_var (struct alias_info *ai);
154 static void group_aliases (struct alias_info *);
155 static void set_pt_anything (tree ptr);
156 static void set_pt_malloc (tree ptr);
158 /* Global declarations. */
160 /* Call clobbered variables in the function. If bit I is set, then
161 REFERENCED_VARS (I) is call-clobbered. */
162 bitmap call_clobbered_vars;
164 /* Addressable variables in the function. If bit I is set, then
165 REFERENCED_VARS (I) has had its address taken. Note that
166 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
167 addressable variable is not necessarily call-clobbered (e.g., a
168 local addressable whose address does not escape) and not all
169 call-clobbered variables are addressable (e.g., a local static
171 bitmap addressable_vars;
173 /* When the program has too many call-clobbered variables and call-sites,
174 this variable is used to represent the clobbering effects of function
175 calls. In these cases, all the call clobbered variables in the program
176 are forced to alias this variable. This reduces compile times by not
177 having to keep track of too many V_MAY_DEF expressions at call sites. */
181 /* Compute may-alias information for every variable referenced in function
184 Alias analysis proceeds in 3 main phases:
186 1- Points-to and escape analysis.
188 This phase walks the use-def chains in the SSA web looking for three
191 * Assignments of the form P_i = &VAR
192 * Assignments of the form P_i = malloc()
193 * Pointers and ADDR_EXPR that escape the current function.
195 The concept of 'escaping' is the same one used in the Java world. When
196 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
197 outside of the current function. So, assignment to global variables,
198 function arguments and returning a pointer are all escape sites, as are
199 conversions between pointers and integers.
201 This is where we are currently limited. Since not everything is renamed
202 into SSA, we lose track of escape properties when a pointer is stashed
203 inside a field in a structure, for instance. In those cases, we are
204 assuming that the pointer does escape.
206 We use escape analysis to determine whether a variable is
207 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
208 is call-clobbered. If a pointer P_i escapes, then all the variables
209 pointed-to by P_i (and its memory tag) also escape.
211 2- Compute flow-sensitive aliases
213 We have two classes of memory tags. Memory tags associated with the
214 pointed-to data type of the pointers in the program. These tags are
215 called "type memory tag" (TMT). The other class are those associated
216 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
217 when adding operands for an INDIRECT_REF *P_i, we will first check
218 whether P_i has a name tag, if it does we use it, because that will have
219 more precise aliasing information. Otherwise, we use the standard type
222 In this phase, we go through all the pointers we found in points-to
223 analysis and create alias sets for the name memory tags associated with
224 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
225 it points to and its tag.
228 3- Compute flow-insensitive aliases
230 This pass will compare the alias set of every type memory tag and every
231 addressable variable found in the program. Given a type memory tag TMT
232 and an addressable variable V. If the alias sets of TMT and V conflict
233 (as computed by may_alias_p), then V is marked as an alias tag and added
234 to the alias set of TMT.
236 For instance, consider the following function:
252 After aliasing analysis has finished, the type memory tag for pointer
253 'p' will have two aliases, namely variables 'a' and 'b'. Every time
254 pointer 'p' is dereferenced, we want to mark the operation as a
255 potential reference to 'a' and 'b'.
265 # p_1 = PHI <p_4(1), p_6(2)>;
267 # a_7 = V_MAY_DEF <a_3>;
268 # b_8 = V_MAY_DEF <b_5>;
271 # a_9 = V_MAY_DEF <a_7>
280 In certain cases, the list of may aliases for a pointer may grow too
281 large. This may cause an explosion in the number of virtual operands
282 inserted in the code. Resulting in increased memory consumption and
285 When the number of virtual operands needed to represent aliased
286 loads and stores grows too large (configurable with @option{--param
287 max-aliased-vops}), alias sets are grouped to avoid severe
288 compile-time slow downs and memory consumption. See group_aliases. */
291 compute_may_aliases (void)
293 struct alias_info *ai;
295 memset (&alias_stats, 0, sizeof (alias_stats));
297 /* Initialize aliasing information. */
298 ai = init_alias_info ();
300 /* For each pointer P_i, determine the sets of variables that P_i may
301 point-to. For every addressable variable V, determine whether the
302 address of V escapes the current function, making V call-clobbered
303 (i.e., whether &V is stored in a global variable or if its passed as a
304 function call argument). */
305 compute_points_to_and_addr_escape (ai);
307 /* Collect all pointers and addressable variables, compute alias sets,
308 create memory tags for pointers and promote variables whose address is
309 not needed anymore. */
310 setup_pointers_and_addressables (ai);
312 /* Compute flow-sensitive, points-to based aliasing for all the name
313 memory tags. Note that this pass needs to be done before flow
314 insensitive analysis because it uses the points-to information
315 gathered before to mark call-clobbered type tags. */
316 compute_flow_sensitive_aliasing (ai);
318 /* Compute type-based flow-insensitive aliasing for all the type
320 compute_flow_insensitive_aliasing (ai);
322 /* If the program has too many call-clobbered variables and/or function
323 calls, create .GLOBAL_VAR and use it to model call-clobbering
324 semantics at call sites. This reduces the number of virtual operands
325 considerably, improving compile times at the expense of lost
326 aliasing precision. */
327 maybe_create_global_var (ai);
329 /* Debugging dumps. */
332 dump_referenced_vars (dump_file);
333 if (dump_flags & TDF_STATS)
334 dump_alias_stats (dump_file);
335 dump_points_to_info (dump_file);
336 dump_alias_info (dump_file);
339 /* Deallocate memory used by aliasing data structures. */
340 delete_alias_info (ai);
343 struct tree_opt_pass pass_may_alias =
347 compute_may_aliases, /* execute */
350 0, /* static_pass_number */
351 TV_TREE_MAY_ALIAS, /* tv_id */
352 PROP_cfg | PROP_ssa, /* properties_required */
353 PROP_alias, /* properties_provided */
354 0, /* properties_destroyed */
355 0, /* todo_flags_start */
356 TODO_dump_func | TODO_rename_vars
357 | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
361 /* Count the number of calls in the function and conditionally
362 create GLOBAL_VAR. This is performed before translation
363 into SSA (and thus before alias analysis) to avoid compile time
364 and memory utilization explosions in functions with many
365 of calls and call clobbered variables. */
368 count_calls_and_maybe_create_global_var (void)
370 struct alias_info ai;
374 memset (&ai, 0, sizeof (struct alias_info));
376 /* First count the number of calls in the IL. */
379 block_stmt_iterator si;
381 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
383 tree stmt = bsi_stmt (si);
385 if (get_call_expr_in (stmt) != NULL_TREE)
386 ai.num_calls_found++;
390 /* If there are no call clobbered variables, then maybe_create_global_var
391 will always create a GLOBAL_VAR. At this point we do not want that
392 behavior. So we turn on one bit in CALL_CLOBBERED_VARs, call
393 maybe_create_global_var, then reset the bit to its original state. */
394 temp = bitmap_bit_p (call_clobbered_vars, 0);
395 bitmap_set_bit (call_clobbered_vars, 0);
396 maybe_create_global_var (&ai);
398 bitmap_clear_bit (call_clobbered_vars, 0);
401 struct tree_opt_pass pass_maybe_create_global_var =
403 "maybe_create_global_var", /* name */
405 count_calls_and_maybe_create_global_var, /* execute */
408 0, /* static_pass_number */
409 TV_TREE_MAY_ALIAS, /* tv_id */
410 PROP_cfg, /* properties_required */
411 0, /* properties_provided */
412 0, /* properties_destroyed */
413 0, /* todo_flags_start */
414 0, /* todo_flags_finish */
418 /* Initialize the data structures used for alias analysis. */
420 static struct alias_info *
421 init_alias_info (void)
423 struct alias_info *ai;
424 static bool aliases_computed_p = false;
426 ai = xcalloc (1, sizeof (struct alias_info));
427 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
428 sbitmap_zero (ai->ssa_names_visited);
429 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
430 ai->addresses_needed = BITMAP_XMALLOC ();
431 VARRAY_UINT_INIT (ai->num_references, num_referenced_vars, "num_references");
432 ai->written_vars = BITMAP_XMALLOC ();
433 ai->dereferenced_ptrs_store = BITMAP_XMALLOC ();
434 ai->dereferenced_ptrs_load = BITMAP_XMALLOC ();
436 /* If aliases have been computed before, clear existing information. */
437 if (aliases_computed_p)
443 /* Make sure that every statement has a valid set of operands.
444 If a statement needs to be scanned for operands while we
445 compute aliases, it may get erroneous operands because all
446 the alias relations are not built at that point.
447 FIXME: This code will become obsolete when operands are not
451 block_stmt_iterator si;
452 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
453 get_stmt_operands (bsi_stmt (si));
456 /* Clear the call-clobbered set. We are going to re-discover
457 call-clobbered variables. */
458 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
460 tree var = referenced_var (i);
462 /* Variables that are intrinsically call-clobbered (globals,
463 local statics, etc) will not be marked by the aliasing
464 code, so we can't remove them from CALL_CLOBBERED_VARS. */
465 if (!is_call_clobbered (var))
466 bitmap_clear_bit (call_clobbered_vars, var_ann (var)->uid);
469 /* Similarly, clear the set of addressable variables. In this
470 case, we can just clear the set because addressability is
471 only computed here. */
472 bitmap_clear (addressable_vars);
474 /* Clear flow-insensitive alias information from each symbol. */
475 for (i = 0; i < num_referenced_vars; i++)
477 var_ann_t ann = var_ann (referenced_var (i));
478 ann->is_alias_tag = 0;
479 ann->may_aliases = NULL;
482 /* Clear flow-sensitive points-to information from each SSA name. */
483 for (i = 1; i < num_ssa_names; i++)
485 tree name = ssa_name (i);
487 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
490 if (SSA_NAME_PTR_INFO (name))
492 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
494 /* Clear all the flags but keep the name tag to
495 avoid creating new temporaries unnecessarily. If
496 this pointer is found to point to a subset or
497 superset of its former points-to set, then a new
498 tag will need to be created in create_name_tags. */
501 pi->value_escapes_p = 0;
502 pi->is_dereferenced = 0;
504 bitmap_clear (pi->pt_vars);
509 /* Next time, we will need to reset alias information. */
510 aliases_computed_p = true;
516 /* Deallocate memory used by alias analysis. */
519 delete_alias_info (struct alias_info *ai)
523 sbitmap_free (ai->ssa_names_visited);
524 ai->processed_ptrs = NULL;
525 BITMAP_XFREE (ai->addresses_needed);
527 for (i = 0; i < ai->num_addressable_vars; i++)
529 sbitmap_free (ai->addressable_vars[i]->may_aliases);
530 free (ai->addressable_vars[i]);
532 free (ai->addressable_vars);
534 for (i = 0; i < ai->num_pointers; i++)
536 sbitmap_free (ai->pointers[i]->may_aliases);
537 free (ai->pointers[i]);
541 ai->num_references = NULL;
542 BITMAP_XFREE (ai->written_vars);
543 BITMAP_XFREE (ai->dereferenced_ptrs_store);
544 BITMAP_XFREE (ai->dereferenced_ptrs_load);
550 /* Walk use-def chains for pointer PTR to determine what variables is PTR
554 collect_points_to_info_for (struct alias_info *ai, tree ptr)
556 gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr)));
558 if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)))
560 SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr));
561 walk_use_def_chains (ptr, collect_points_to_info_r, ai, true);
562 VARRAY_PUSH_TREE (ai->processed_ptrs, ptr);
567 /* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
568 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
571 find_ptr_dereference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
573 tree ptr = (tree) data;
575 if (INDIRECT_REF_P (*tp)
576 && TREE_OPERAND (*tp, 0) == ptr)
583 /* Return true if STMT contains (ALIGN/MISALIGNED_)INDIRECT_REF <PTR>.
584 *IS_STORE is set to 'true' if the dereference is on the LHS of an
588 ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
592 if (TREE_CODE (stmt) == MODIFY_EXPR
593 || (TREE_CODE (stmt) == RETURN_EXPR
594 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
598 e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
599 lhs = TREE_OPERAND (e, 0);
600 rhs = TREE_OPERAND (e, 1);
603 && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
608 else if (EXPR_P (rhs)
609 && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
614 else if (TREE_CODE (stmt) == ASM_EXPR)
616 if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
617 || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
622 else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
632 /* Traverse use-def links for all the pointers in the program to collect
633 address escape and points-to information.
635 This is loosely based on the same idea described in R. Hasti and S.
636 Horwitz, ``Using static single assignment form to improve
637 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
638 Programming Language Design and Implementation, pp. 97-105, 1998. */
641 compute_points_to_and_addr_escape (struct alias_info *ai)
648 timevar_push (TV_TREE_PTA);
652 bb_ann_t block_ann = bb_ann (bb);
653 block_stmt_iterator si;
655 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
658 tree stmt = bsi_stmt (si);
659 bool stmt_escapes_p = is_escape_site (stmt, &ai->num_calls_found);
662 /* Mark all the variables whose address are taken by the
663 statement. Note that this will miss all the addresses taken
664 in PHI nodes (those are discovered while following the use-def
666 get_stmt_operands (stmt);
667 addr_taken = addresses_taken (stmt);
669 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
671 tree var = referenced_var (i);
672 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
674 mark_call_clobbered (var);
678 block_ann->has_escape_site = 1;
680 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
682 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
683 struct ptr_info_def *pi;
686 /* If the operand's variable may be aliased, keep track
687 of how many times we've referenced it. This is used
688 for alias grouping in compute_flow_sensitive_aliasing.
689 Note that we don't need to grow AI->NUM_REFERENCES
690 because we are processing regular variables, not
691 memory tags (the array's initial size is set to
692 NUM_REFERENCED_VARS). */
693 if (may_be_aliased (SSA_NAME_VAR (op)))
694 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
696 if (!POINTER_TYPE_P (TREE_TYPE (op)))
699 collect_points_to_info_for (ai, op);
701 pi = SSA_NAME_PTR_INFO (op);
702 if (ptr_is_dereferenced_by (op, stmt, &is_store))
704 /* Mark OP as dereferenced. In a subsequent pass,
705 dereferenced pointers that point to a set of
706 variables will be assigned a name tag to alias
707 all the variables OP points to. */
708 pi->is_dereferenced = 1;
710 /* Keep track of how many time we've dereferenced each
711 pointer. Again, we don't need to grow
712 AI->NUM_REFERENCES because we're processing
713 existing program variables. */
714 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
716 /* If this is a store operation, mark OP as being
717 dereferenced to store, otherwise mark it as being
718 dereferenced to load. */
720 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
722 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
724 else if (stmt_escapes_p)
726 /* Note that even if STMT is an escape point, pointer OP
727 will not escape if it is being dereferenced. That's
728 why we only check for escape points if OP is not
729 dereferenced by STMT. */
730 pi->value_escapes_p = 1;
732 /* If the statement makes a function call, assume
733 that pointer OP will be dereferenced in a store
734 operation inside the called function. */
735 if (get_call_expr_in (stmt))
737 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
738 pi->is_dereferenced = 1;
743 /* Update reference counter for definitions to any
744 potentially aliased variable. This is used in the alias
745 grouping heuristics. */
746 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
748 tree var = SSA_NAME_VAR (op);
749 var_ann_t ann = var_ann (var);
750 bitmap_set_bit (ai->written_vars, ann->uid);
751 if (may_be_aliased (var))
752 (VARRAY_UINT (ai->num_references, ann->uid))++;
754 if (POINTER_TYPE_P (TREE_TYPE (op)))
755 collect_points_to_info_for (ai, op);
758 /* Mark variables in V_MAY_DEF operands as being written to. */
759 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
761 tree var = SSA_NAME_VAR (op);
762 var_ann_t ann = var_ann (var);
763 bitmap_set_bit (ai->written_vars, ann->uid);
766 /* After promoting variables and computing aliasing we will
767 need to re-scan most statements. FIXME: Try to minimize the
768 number of statements re-scanned. It's not really necessary to
769 re-scan *all* statements. */
774 timevar_pop (TV_TREE_PTA);
778 /* Create name tags for all the pointers that have been dereferenced.
779 We only create a name tag for a pointer P if P is found to point to
780 a set of variables (so that we can alias them to *P) or if it is
781 the result of a call to malloc (which means that P cannot point to
782 anything else nor alias any other variable).
784 If two pointers P and Q point to the same set of variables, they
785 are assigned the same name tag. */
788 create_name_tags (struct alias_info *ai)
792 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
794 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
795 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
797 if (pi->pt_anything || !pi->is_dereferenced)
799 /* No name tags for pointers that have not been
800 dereferenced or point to an arbitrary location. */
801 pi->name_mem_tag = NULL_TREE;
805 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
808 tree old_name_tag = pi->name_mem_tag;
810 /* If PTR points to a set of variables, check if we don't
811 have another pointer Q with the same points-to set before
812 creating a tag. If so, use Q's tag instead of creating a
815 This is important for not creating unnecessary symbols
816 and also for copy propagation. If we ever need to
817 propagate PTR into Q or vice-versa, we would run into
818 problems if they both had different name tags because
819 they would have different SSA version numbers (which
820 would force us to take the name tags in and out of SSA). */
821 for (j = 0; j < i; j++)
823 tree q = VARRAY_TREE (ai->processed_ptrs, j);
824 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
829 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
831 pi->name_mem_tag = qi->name_mem_tag;
836 /* If we didn't find a pointer with the same points-to set
837 as PTR, create a new name tag if needed. */
838 if (pi->name_mem_tag == NULL_TREE)
839 pi->name_mem_tag = get_nmt_for (ptr);
841 /* If the new name tag computed for PTR is different than
842 the old name tag that it used to have, then the old tag
843 needs to be removed from the IL, so we mark it for
845 if (old_name_tag && old_name_tag != pi->name_mem_tag)
846 bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid);
848 else if (pi->pt_malloc)
850 /* Otherwise, create a unique name tag for this pointer. */
851 pi->name_mem_tag = get_nmt_for (ptr);
855 /* Only pointers that may point to malloc or other variables
856 may receive a name tag. If the pointer does not point to
857 a known spot, we should use type tags. */
858 set_pt_anything (ptr);
862 TREE_THIS_VOLATILE (pi->name_mem_tag)
863 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
865 /* Mark the new name tag for renaming. */
866 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
872 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
873 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
874 name tag and the variables it points-to are call-clobbered. Finally, if
875 P_i escapes and we could not determine where it points to, then all the
876 variables in the same alias set as *P_i are marked call-clobbered. This
877 is necessary because we must assume that P_i may take the address of any
878 variable in the same alias set. */
881 compute_flow_sensitive_aliasing (struct alias_info *ai)
885 create_name_tags (ai);
887 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
890 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
891 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
892 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
895 if (pi->value_escapes_p || pi->pt_anything)
897 /* If PTR escapes or may point to anything, then its associated
898 memory tags and pointed-to variables are call-clobbered. */
899 if (pi->name_mem_tag)
900 mark_call_clobbered (pi->name_mem_tag);
902 if (v_ann->type_mem_tag)
903 mark_call_clobbered (v_ann->type_mem_tag);
906 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
908 mark_call_clobbered (referenced_var (j));
912 /* Set up aliasing information for PTR's name memory tag (if it has
913 one). Note that only pointers that have been dereferenced will
914 have a name memory tag. */
915 if (pi->name_mem_tag && pi->pt_vars)
916 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
918 add_may_alias (pi->name_mem_tag, referenced_var (j));
921 /* If the name tag is call clobbered, so is the type tag
922 associated with the base VAR_DECL. */
924 && v_ann->type_mem_tag
925 && is_call_clobbered (pi->name_mem_tag))
926 mark_call_clobbered (v_ann->type_mem_tag);
931 /* Compute type-based alias sets. Traverse all the pointers and
932 addressable variables found in setup_pointers_and_addressables.
934 For every pointer P in AI->POINTERS and addressable variable V in
935 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
936 memory tag (TMT) if their alias sets conflict. V is then marked as
937 an alias tag so that the operand scanner knows that statements
938 containing V have aliased operands. */
941 compute_flow_insensitive_aliasing (struct alias_info *ai)
945 /* Initialize counter for the total number of virtual operands that
946 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
947 threshold set by --params max-alias-vops, we enable alias
949 ai->total_alias_vops = 0;
951 /* For every pointer P, determine which addressable variables may alias
952 with P's type memory tag. */
953 for (i = 0; i < ai->num_pointers; i++)
956 struct alias_map_d *p_map = ai->pointers[i];
957 tree tag = var_ann (p_map->var)->type_mem_tag;
958 var_ann_t tag_ann = var_ann (tag);
960 p_map->total_alias_vops = 0;
961 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
962 sbitmap_zero (p_map->may_aliases);
964 for (j = 0; j < ai->num_addressable_vars; j++)
966 struct alias_map_d *v_map;
969 bool tag_stored_p, var_stored_p;
971 v_map = ai->addressable_vars[j];
973 v_ann = var_ann (var);
975 /* Skip memory tags and variables that have never been
976 written to. We also need to check if the variables are
977 call-clobbered because they may be overwritten by
980 Note this is effectively random accessing elements in
981 the sparse bitset, which can be highly inefficient.
982 So we first check the call_clobbered status of the
983 tag and variable before querying the bitmap. */
984 tag_stored_p = is_call_clobbered (tag)
985 || bitmap_bit_p (ai->written_vars, tag_ann->uid);
986 var_stored_p = is_call_clobbered (var)
987 || bitmap_bit_p (ai->written_vars, v_ann->uid);
988 if (!tag_stored_p && !var_stored_p)
991 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
993 size_t num_tag_refs, num_var_refs;
995 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
996 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
998 /* Add VAR to TAG's may-aliases set. */
999 add_may_alias (tag, var);
1001 /* Update the total number of virtual operands due to
1002 aliasing. Since we are adding one more alias to TAG's
1003 may-aliases set, the total number of virtual operands due
1004 to aliasing will be increased by the number of references
1005 made to VAR and TAG (every reference to TAG will also
1006 count as a reference to VAR). */
1007 ai->total_alias_vops += (num_var_refs + num_tag_refs);
1008 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
1010 /* Update the bitmap used to represent TAG's alias set
1011 in case we need to group aliases. */
1012 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
1017 /* Since this analysis is based exclusively on symbols, it fails to
1018 handle cases where two pointers P and Q have different memory
1019 tags with conflicting alias set numbers but no aliased symbols in
1022 For example, suppose that we have two memory tags TMT.1 and TMT.2
1025 may-aliases (TMT.1) = { a }
1026 may-aliases (TMT.2) = { b }
1028 and the alias set number of TMT.1 conflicts with that of TMT.2.
1029 Since they don't have symbols in common, loads and stores from
1030 TMT.1 and TMT.2 will seem independent of each other, which will
1031 lead to the optimizers making invalid transformations (see
1032 testsuite/gcc.c-torture/execute/pr15262-[12].c).
1034 To avoid this problem, we do a final traversal of AI->POINTERS
1035 looking for pairs of pointers that have no aliased symbols in
1036 common and yet have conflicting alias set numbers. */
1037 for (i = 0; i < ai->num_pointers; i++)
1040 struct alias_map_d *p_map1 = ai->pointers[i];
1041 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
1042 sbitmap may_aliases1 = p_map1->may_aliases;
1044 for (j = i + 1; j < ai->num_pointers; j++)
1046 struct alias_map_d *p_map2 = ai->pointers[j];
1047 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
1048 sbitmap may_aliases2 = p_map2->may_aliases;
1050 /* If the pointers may not point to each other, do nothing. */
1051 if (!may_alias_p (p_map1->var, p_map1->set, p_map2->var, p_map2->set))
1054 /* The two pointers may alias each other. If they already have
1055 symbols in common, do nothing. */
1056 if (sbitmap_any_common_bits (may_aliases1, may_aliases2))
1059 if (sbitmap_first_set_bit (may_aliases2) >= 0)
1063 /* Add all the aliases for TAG2 into TAG1's alias set.
1064 FIXME, update grouping heuristic counters. */
1065 EXECUTE_IF_SET_IN_SBITMAP (may_aliases2, 0, k,
1066 add_may_alias (tag1, referenced_var (k)));
1067 sbitmap_a_or_b (may_aliases1, may_aliases1, may_aliases2);
1071 /* Since TAG2 does not have any aliases of its own, add
1072 TAG2 itself to the alias set of TAG1. */
1073 add_may_alias (tag1, tag2);
1079 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
1080 get_name (current_function_decl),
1081 ai->total_alias_vops);
1083 /* Determine if we need to enable alias grouping. */
1084 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
1089 /* Comparison function for qsort used in group_aliases. */
1092 total_alias_vops_cmp (const void *p, const void *q)
1094 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1095 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1096 long n1 = (*p1)->total_alias_vops;
1097 long n2 = (*p2)->total_alias_vops;
1099 /* We want to sort in descending order. */
1100 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1103 /* Group all the aliases for TAG to make TAG represent all the
1104 variables in its alias set. Update the total number
1105 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1106 function will make TAG be the unique alias tag for all the
1107 variables in its may-aliases. So, given:
1109 may-aliases(TAG) = { V1, V2, V3 }
1111 This function will group the variables into:
1113 may-aliases(V1) = { TAG }
1114 may-aliases(V2) = { TAG }
1115 may-aliases(V2) = { TAG } */
1118 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
1121 var_ann_t tag_ann = var_ann (tag);
1122 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1124 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
1126 tree var = referenced_var (i);
1127 var_ann_t ann = var_ann (var);
1129 /* Make TAG the unique alias of VAR. */
1130 ann->is_alias_tag = 0;
1131 ann->may_aliases = NULL;
1133 /* Note that VAR and TAG may be the same if the function has no
1134 addressable variables (see the discussion at the end of
1135 setup_pointers_and_addressables). */
1137 add_may_alias (var, tag);
1139 /* Reduce total number of virtual operands contributed
1140 by TAG on behalf of VAR. Notice that the references to VAR
1141 itself won't be removed. We will merely replace them with
1142 references to TAG. */
1143 ai->total_alias_vops -= num_tag_refs;
1146 /* We have reduced the number of virtual operands that TAG makes on
1147 behalf of all the variables formerly aliased with it. However,
1148 we have also "removed" all the virtual operands for TAG itself,
1149 so we add them back. */
1150 ai->total_alias_vops += num_tag_refs;
1152 /* TAG no longer has any aliases. */
1153 tag_ann->may_aliases = NULL;
1157 /* Group may-aliases sets to reduce the number of virtual operands due
1160 1- Sort the list of pointers in decreasing number of contributed
1163 2- Take the first entry in AI->POINTERS and revert the role of
1164 the memory tag and its aliases. Usually, whenever an aliased
1165 variable Vi is found to alias with a memory tag T, we add Vi
1166 to the may-aliases set for T. Meaning that after alias
1167 analysis, we will have:
1169 may-aliases(T) = { V1, V2, V3, ..., Vn }
1171 This means that every statement that references T, will get 'n'
1172 virtual operands for each of the Vi tags. But, when alias
1173 grouping is enabled, we make T an alias tag and add it to the
1174 alias set of all the Vi variables:
1176 may-aliases(V1) = { T }
1177 may-aliases(V2) = { T }
1179 may-aliases(Vn) = { T }
1181 This has two effects: (a) statements referencing T will only get
1182 a single virtual operand, and, (b) all the variables Vi will now
1183 appear to alias each other. So, we lose alias precision to
1184 improve compile time. But, in theory, a program with such a high
1185 level of aliasing should not be very optimizable in the first
1188 3- Since variables may be in the alias set of more than one
1189 memory tag, the grouping done in step (2) needs to be extended
1190 to all the memory tags that have a non-empty intersection with
1191 the may-aliases set of tag T. For instance, if we originally
1192 had these may-aliases sets:
1194 may-aliases(T) = { V1, V2, V3 }
1195 may-aliases(R) = { V2, V4 }
1197 In step (2) we would have reverted the aliases for T as:
1199 may-aliases(V1) = { T }
1200 may-aliases(V2) = { T }
1201 may-aliases(V3) = { T }
1203 But note that now V2 is no longer aliased with R. We could
1204 add R to may-aliases(V2), but we are in the process of
1205 grouping aliases to reduce virtual operands so what we do is
1206 add V4 to the grouping to obtain:
1208 may-aliases(V1) = { T }
1209 may-aliases(V2) = { T }
1210 may-aliases(V3) = { T }
1211 may-aliases(V4) = { T }
1213 4- If the total number of virtual operands due to aliasing is
1214 still above the threshold set by max-alias-vops, go back to (2). */
1217 group_aliases (struct alias_info *ai)
1221 /* Sort the POINTERS array in descending order of contributed
1222 virtual operands. */
1223 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1224 total_alias_vops_cmp);
1226 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1227 and the tag's may-aliases set. */
1228 for (i = 0; i < ai->num_pointers; i++)
1231 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1232 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1234 /* Skip tags that have been grouped already. */
1235 if (ai->pointers[i]->grouped_p)
1238 /* See if TAG1 had any aliases in common with other type tags.
1239 If we find a TAG2 with common aliases with TAG1, add TAG2's
1240 aliases into TAG1. */
1241 for (j = i + 1; j < ai->num_pointers; j++)
1243 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1245 if (sbitmap_any_common_bits (tag1_aliases, tag2_aliases))
1247 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1249 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1251 /* TAG2 does not need its aliases anymore. */
1252 sbitmap_zero (tag2_aliases);
1253 var_ann (tag2)->may_aliases = NULL;
1255 /* TAG1 is the unique alias of TAG2. */
1256 add_may_alias (tag2, tag1);
1258 ai->pointers[j]->grouped_p = true;
1262 /* Now group all the aliases we collected into TAG1. */
1263 group_aliases_into (tag1, tag1_aliases, ai);
1265 /* If we've reduced total number of virtual operands below the
1267 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1271 /* Finally, all the variables that have been grouped cannot be in
1272 the may-alias set of name memory tags. Suppose that we have
1273 grouped the aliases in this code so that may-aliases(a) = TMT.20
1277 # a_9 = V_MAY_DEF <a_8>
1279 ... Several modifications to TMT.20 ...
1283 Since p_5 points to 'a', the optimizers will try to propagate 0
1284 into p_5->field, but that is wrong because there have been
1285 modifications to 'TMT.20' in between. To prevent this we have to
1286 replace 'a' with 'TMT.20' in the name tag of p_5. */
1287 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1290 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1291 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1292 varray_type aliases;
1294 if (name_tag == NULL_TREE)
1297 aliases = var_ann (name_tag)->may_aliases;
1298 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1300 tree alias = VARRAY_TREE (aliases, j);
1301 var_ann_t ann = var_ann (alias);
1303 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1307 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1309 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1310 replace_may_alias (name_tag, j, new_alias);
1317 "%s: Total number of aliased vops after grouping: %ld%s\n",
1318 get_name (current_function_decl),
1319 ai->total_alias_vops,
1320 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1324 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1327 create_alias_map_for (tree var, struct alias_info *ai)
1329 struct alias_map_d *alias_map;
1330 alias_map = xcalloc (1, sizeof (*alias_map));
1331 alias_map->var = var;
1332 alias_map->set = get_alias_set (var);
1333 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1337 /* Create memory tags for all the dereferenced pointers and build the
1338 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1339 sets. Based on the address escape and points-to information collected
1340 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1341 variables whose address is not needed anymore. */
1344 setup_pointers_and_addressables (struct alias_info *ai)
1346 size_t i, n_vars, num_addressable_vars, num_pointers;
1348 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1349 num_addressable_vars = num_pointers = 0;
1350 for (i = 0; i < num_referenced_vars; i++)
1352 tree var = referenced_var (i);
1354 if (may_be_aliased (var))
1355 num_addressable_vars++;
1357 if (POINTER_TYPE_P (TREE_TYPE (var)))
1359 /* Since we don't keep track of volatile variables, assume that
1360 these pointers are used in indirect store operations. */
1361 if (TREE_THIS_VOLATILE (var))
1362 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1368 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1369 always going to be slightly bigger than we actually need them
1370 because some TREE_ADDRESSABLE variables will be marked
1371 non-addressable below and only pointers with unique type tags are
1372 going to be added to POINTERS. */
1373 ai->addressable_vars = xcalloc (num_addressable_vars,
1374 sizeof (struct alias_map_d *));
1375 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1376 ai->num_addressable_vars = 0;
1377 ai->num_pointers = 0;
1379 /* Since we will be creating type memory tags within this loop, cache the
1380 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1382 n_vars = num_referenced_vars;
1384 for (i = 0; i < n_vars; i++)
1386 tree var = referenced_var (i);
1387 var_ann_t v_ann = var_ann (var);
1389 /* Name memory tags already have flow-sensitive aliasing
1390 information, so they need not be processed by
1391 compute_flow_insensitive_aliasing. Similarly, type memory
1392 tags are already accounted for when we process their
1393 associated pointer. */
1394 if (v_ann->mem_tag_kind != NOT_A_TAG)
1397 /* Remove the ADDRESSABLE flag from every addressable variable whose
1398 address is not needed anymore. This is caused by the propagation
1399 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1400 removal of dead pointer assignments done by the early scalar
1402 if (TREE_ADDRESSABLE (var))
1404 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1405 && v_ann->mem_tag_kind == NOT_A_TAG
1406 && TREE_CODE (var) != RESULT_DECL
1407 && !is_global_var (var))
1409 /* The address of VAR is not needed, remove the
1410 addressable bit, so that it can be optimized as a
1411 regular variable. */
1412 mark_non_addressable (var);
1414 /* Since VAR is now a regular GIMPLE register, we will need
1415 to rename VAR into SSA afterwards. */
1416 bitmap_set_bit (vars_to_rename, v_ann->uid);
1420 /* Add the variable to the set of addressables. Mostly
1421 used when scanning operands for ASM_EXPRs that
1422 clobber memory. In those cases, we need to clobber
1423 all call-clobbered variables and all addressables. */
1424 bitmap_set_bit (addressable_vars, v_ann->uid);
1428 /* Global variables and addressable locals may be aliased. Create an
1429 entry in ADDRESSABLE_VARS for VAR. */
1430 if (may_be_aliased (var))
1432 create_alias_map_for (var, ai);
1433 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1436 /* Add pointer variables that have been dereferenced to the POINTERS
1437 array and create a type memory tag for them. */
1438 if (POINTER_TYPE_P (TREE_TYPE (var)))
1440 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1441 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1446 /* If pointer VAR still doesn't have a memory tag
1447 associated with it, create it now or re-use an
1449 tag = get_tmt_for (var, ai);
1450 t_ann = var_ann (tag);
1452 /* The type tag will need to be renamed into SSA
1453 afterwards. Note that we cannot do this inside
1454 get_tmt_for because aliasing may run multiple times
1455 and we only create type tags the first time. */
1456 bitmap_set_bit (vars_to_rename, t_ann->uid);
1458 /* Associate the tag with pointer VAR. */
1459 v_ann->type_mem_tag = tag;
1461 /* If pointer VAR has been used in a store operation,
1462 then its memory tag must be marked as written-to. */
1463 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1464 bitmap_set_bit (ai->written_vars, t_ann->uid);
1466 /* If pointer VAR is a global variable or a PARM_DECL,
1467 then its memory tag should be considered a global
1469 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1470 mark_call_clobbered (tag);
1472 /* All the dereferences of pointer VAR count as
1473 references of TAG. Since TAG can be associated with
1474 several pointers, add the dereferences of VAR to the
1475 TAG. We may need to grow AI->NUM_REFERENCES because
1476 we have been adding name and type tags. */
1477 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1478 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1480 VARRAY_UINT (ai->num_references, t_ann->uid)
1481 += VARRAY_UINT (ai->num_references, v_ann->uid);
1485 /* The pointer has not been dereferenced. If it had a
1486 type memory tag, remove it and mark the old tag for
1487 renaming to remove it out of the IL. */
1488 var_ann_t ann = var_ann (var);
1489 tree tag = ann->type_mem_tag;
1492 bitmap_set_bit (vars_to_rename, var_ann (tag)->uid);
1493 ann->type_mem_tag = NULL_TREE;
1501 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1502 every call site, we need to emit V_MAY_DEF expressions to represent the
1503 clobbering effects of the call for variables whose address escapes the
1506 One approach is to group all call-clobbered variables into a single
1507 representative that is used as an alias of every call-clobbered variable
1508 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1509 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1511 The second approach is to emit a clobbering V_MAY_DEF for every
1512 call-clobbered variable at call sites. This is the preferred way in terms
1513 of optimization opportunities but it may create too many V_MAY_DEF operands
1514 if there are many call clobbered variables and function calls in the
1517 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1518 function calls found by the number of call-clobbered variables. If that
1519 product is beyond a certain threshold, as determined by the parameterized
1520 values shown below, we use .GLOBAL_VAR.
1522 FIXME. This heuristic should be improved. One idea is to use several
1523 .GLOBAL_VARs of different types instead of a single one. The thresholds
1524 have been derived from a typical bootstrap cycle, including all target
1525 libraries. Compile times were found increase by ~1% compared to using
1529 maybe_create_global_var (struct alias_info *ai)
1531 unsigned i, n_clobbered;
1534 /* No need to create it, if we have one already. */
1535 if (global_var == NULL_TREE)
1537 /* Count all the call-clobbered variables. */
1539 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1544 /* Create .GLOBAL_VAR if we have too many call-clobbered
1545 variables. We also create .GLOBAL_VAR when there no
1546 call-clobbered variables to prevent code motion
1547 transformations from re-arranging function calls that may
1548 have side effects. For instance,
1557 There are no call-clobbered variables in foo(), so it would
1558 be entirely possible for a pass to want to move the call to
1559 f() after the call to g(). If f() has side effects, that
1560 would be wrong. Creating .GLOBAL_VAR in this case will
1561 insert VDEFs for it and prevent such transformations. */
1562 if (n_clobbered == 0
1563 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1564 create_global_var ();
1567 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1568 been created, make it an alias for all call-clobbered variables. */
1570 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1572 tree var = referenced_var (i);
1573 if (var != global_var)
1575 add_may_alias (var, global_var);
1576 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1582 /* Return TRUE if pointer PTR may point to variable VAR.
1584 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1585 This is needed because when checking for type conflicts we are
1586 interested in the alias set of the memory location pointed-to by
1587 PTR. The alias set of PTR itself is irrelevant.
1589 VAR_ALIAS_SET is the alias set for VAR. */
1592 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1593 tree var, HOST_WIDE_INT var_alias_set)
1596 var_ann_t v_ann, m_ann;
1598 alias_stats.alias_queries++;
1599 alias_stats.simple_queries++;
1601 /* By convention, a variable cannot alias itself. */
1602 mem = var_ann (ptr)->type_mem_tag;
1605 alias_stats.alias_noalias++;
1606 alias_stats.simple_resolved++;
1610 v_ann = var_ann (var);
1611 m_ann = var_ann (mem);
1613 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1615 alias_stats.tbaa_queries++;
1617 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1618 PTR can't possibly affect VAR. Note, that we are specifically testing
1619 for PTR's alias set here, not its pointed-to type. We also can't
1620 do this check with relaxed aliasing enabled. */
1621 if (POINTER_TYPE_P (TREE_TYPE (var))
1622 && var_alias_set != 0
1623 && mem_alias_set != 0)
1625 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1626 if (ptr_alias_set == var_alias_set)
1628 alias_stats.alias_noalias++;
1629 alias_stats.tbaa_resolved++;
1634 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1635 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1637 alias_stats.alias_noalias++;
1638 alias_stats.tbaa_resolved++;
1642 alias_stats.alias_mayalias++;
1647 /* Add ALIAS to the set of variables that may alias VAR. */
1650 add_may_alias (tree var, tree alias)
1653 var_ann_t v_ann = get_var_ann (var);
1654 var_ann_t a_ann = get_var_ann (alias);
1656 gcc_assert (var != alias);
1658 if (v_ann->may_aliases == NULL)
1659 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1661 /* Avoid adding duplicates. */
1662 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1663 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1666 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1667 FIXME, call-clobbering should only depend on whether an address
1668 escapes. It should be independent of aliasing. */
1669 if (is_call_clobbered (var))
1670 mark_call_clobbered (alias);
1672 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1673 else if (is_call_clobbered (alias))
1674 mark_call_clobbered (var);
1676 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1677 a_ann->is_alias_tag = 1;
1681 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1684 replace_may_alias (tree var, size_t i, tree new_alias)
1686 var_ann_t v_ann = var_ann (var);
1687 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1689 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1690 FIXME, call-clobbering should only depend on whether an address
1691 escapes. It should be independent of aliasing. */
1692 if (is_call_clobbered (var))
1693 mark_call_clobbered (new_alias);
1695 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1696 else if (is_call_clobbered (new_alias))
1697 mark_call_clobbered (var);
1701 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1704 set_pt_anything (tree ptr)
1706 struct ptr_info_def *pi = get_ptr_info (ptr);
1708 pi->pt_anything = 1;
1711 /* The pointer used to have a name tag, but we now found it pointing
1712 to an arbitrary location. The name tag needs to be renamed and
1713 disassociated from PTR. */
1714 if (pi->name_mem_tag)
1716 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1717 pi->name_mem_tag = NULL_TREE;
1722 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1725 set_pt_malloc (tree ptr)
1727 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1729 /* If the pointer has already been found to point to arbitrary
1730 memory locations, it is unsafe to mark it as pointing to malloc. */
1731 if (pi->pt_anything)
1738 /* Given two different pointers DEST and ORIG. Merge the points-to
1739 information in ORIG into DEST. AI is as in
1740 collect_points_to_info. */
1743 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1745 struct ptr_info_def *dest_pi, *orig_pi;
1747 gcc_assert (dest != orig);
1749 /* Make sure we have points-to information for ORIG. */
1750 collect_points_to_info_for (ai, orig);
1752 dest_pi = get_ptr_info (dest);
1753 orig_pi = SSA_NAME_PTR_INFO (orig);
1757 /* Notice that we never merge PT_MALLOC. This attribute is only
1758 true if the pointer is the result of a malloc() call.
1759 Otherwise, we can end up in this situation:
1765 P_j would be marked as PT_MALLOC, however we currently do not
1766 handle cases of more than one pointer pointing to the same
1769 FIXME: If the merging comes from an expression that preserves
1770 the PT_MALLOC attribute (copy assignment, address
1771 arithmetic), we ought to merge PT_MALLOC, but then both
1772 pointers would end up getting different name tags because
1773 create_name_tags is not smart enough to determine that the
1774 two come from the same malloc call. Copy propagation before
1775 aliasing should cure this. */
1776 gcc_assert (orig_pi != dest_pi);
1778 dest_pi->pt_malloc = 0;
1780 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1781 set_pt_anything (dest);
1783 if (!dest_pi->pt_anything
1785 && !bitmap_empty_p (orig_pi->pt_vars))
1787 if (dest_pi->pt_vars == NULL)
1789 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1790 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1793 bitmap_ior_into (dest_pi->pt_vars, orig_pi->pt_vars);
1797 set_pt_anything (dest);
1801 /* Add EXPR to the list of expressions pointed-to by PTR. */
1804 add_pointed_to_expr (struct alias_info *ai, tree ptr, tree expr)
1806 if (TREE_CODE (expr) == WITH_SIZE_EXPR)
1807 expr = TREE_OPERAND (expr, 0);
1811 if (TREE_CODE (expr) == CALL_EXPR
1812 && (call_expr_flags (expr) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1814 /* If EXPR is a malloc-like call, then the area pointed to PTR
1815 is guaranteed to not alias with anything else. */
1816 set_pt_malloc (ptr);
1818 else if (TREE_CODE (expr) == ADDR_EXPR)
1820 /* Found P_i = ADDR_EXPR */
1821 add_pointed_to_var (ai, ptr, expr);
1823 else if (TREE_CODE (expr) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (expr)))
1825 /* Found P_i = Q_j. */
1826 merge_pointed_to_info (ai, ptr, expr);
1828 else if (TREE_CODE (expr) == PLUS_EXPR || TREE_CODE (expr) == MINUS_EXPR)
1830 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1831 tree op0 = TREE_OPERAND (expr, 0);
1832 tree op1 = TREE_OPERAND (expr, 1);
1834 /* Both operands may be of pointer type. FIXME: Shouldn't
1835 we just expect PTR + OFFSET always? */
1836 if (POINTER_TYPE_P (TREE_TYPE (op0))
1837 && TREE_CODE (op0) != INTEGER_CST)
1839 if (TREE_CODE (op0) == SSA_NAME)
1840 merge_pointed_to_info (ai, ptr, op0);
1841 else if (TREE_CODE (op0) == ADDR_EXPR)
1842 add_pointed_to_var (ai, ptr, op0);
1844 set_pt_anything (ptr);
1847 if (POINTER_TYPE_P (TREE_TYPE (op1))
1848 && TREE_CODE (op1) != INTEGER_CST)
1850 if (TREE_CODE (op1) == SSA_NAME)
1851 merge_pointed_to_info (ai, ptr, op1);
1852 else if (TREE_CODE (op1) == ADDR_EXPR)
1853 add_pointed_to_var (ai, ptr, op1);
1855 set_pt_anything (ptr);
1858 /* Neither operand is a pointer? VAR can be pointing anywhere.
1859 FIXME: Shouldn't we abort here? If we get here, we found
1860 PTR = INT_CST + INT_CST, which should not be a valid pointer
1862 if (!(POINTER_TYPE_P (TREE_TYPE (op0))
1863 && TREE_CODE (op0) != INTEGER_CST)
1864 && !(POINTER_TYPE_P (TREE_TYPE (op1))
1865 && TREE_CODE (op1) != INTEGER_CST))
1866 set_pt_anything (ptr);
1870 /* If we can't recognize the expression, assume that PTR may
1872 set_pt_anything (ptr);
1877 /* If VALUE is of the form &DECL, add DECL to the set of variables
1878 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1879 PTR. AI is as in collect_points_to_info. */
1882 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1884 struct ptr_info_def *pi = get_ptr_info (ptr);
1888 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
1890 pt_var = TREE_OPERAND (value, 0);
1891 if (REFERENCE_CLASS_P (pt_var))
1892 pt_var = get_base_address (pt_var);
1894 if (pt_var && SSA_VAR_P (pt_var))
1896 uid = var_ann (pt_var)->uid;
1897 bitmap_set_bit (ai->addresses_needed, uid);
1899 if (pi->pt_vars == NULL)
1900 pi->pt_vars = BITMAP_GGC_ALLOC ();
1901 bitmap_set_bit (pi->pt_vars, uid);
1903 /* If the variable is a global, mark the pointer as pointing to
1904 global memory (which will make its tag a global variable). */
1905 if (is_global_var (pt_var))
1906 pi->pt_global_mem = 1;
1911 /* Callback for walk_use_def_chains to gather points-to information from the
1914 VAR is an SSA variable or a GIMPLE expression.
1916 STMT is the statement that generates the SSA variable or, if STMT is a
1917 PHI_NODE, VAR is one of the PHI arguments.
1919 DATA is a pointer to a structure of type ALIAS_INFO. */
1922 collect_points_to_info_r (tree var, tree stmt, void *data)
1924 struct alias_info *ai = (struct alias_info *) data;
1926 if (dump_file && (dump_flags & TDF_DETAILS))
1928 fprintf (dump_file, "Visiting use-def links for ");
1929 print_generic_expr (dump_file, var, dump_flags);
1930 fprintf (dump_file, "\n");
1933 switch (TREE_CODE (stmt))
1936 if (TREE_CODE (TREE_OPERAND (stmt, 0)) != MODIFY_EXPR)
1938 stmt = TREE_OPERAND (stmt, 0);
1943 tree rhs = TREE_OPERAND (stmt, 1);
1945 add_pointed_to_expr (ai, var, rhs);
1950 /* Pointers defined by __asm__ statements can point anywhere. */
1951 set_pt_anything (var);
1955 if (IS_EMPTY_STMT (stmt))
1957 tree decl = SSA_NAME_VAR (var);
1959 if (TREE_CODE (decl) == PARM_DECL)
1960 add_pointed_to_expr (ai, var, decl);
1961 else if (DECL_INITIAL (decl))
1962 add_pointed_to_expr (ai, var, DECL_INITIAL (decl));
1964 add_pointed_to_expr (ai, var, decl);
1970 /* It STMT is a PHI node, then VAR is one of its arguments. The
1971 variable that we are analyzing is the LHS of the PHI node. */
1972 tree lhs = PHI_RESULT (stmt);
1974 switch (TREE_CODE (var))
1977 add_pointed_to_var (ai, lhs, var);
1981 /* Avoid unnecessary merges. */
1983 merge_pointed_to_info (ai, lhs, var);
1987 gcc_assert (is_gimple_min_invariant (var));
1988 add_pointed_to_expr (ai, lhs, var);
2002 /* Return true if STMT is an "escape" site from the current function. Escape
2003 sites those statements which might expose the address of a variable
2004 outside the current function. STMT is an escape site iff:
2006 1- STMT is a function call, or
2007 2- STMT is an __asm__ expression, or
2008 3- STMT is an assignment to a non-local variable, or
2009 4- STMT is a return statement.
2011 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
2015 is_escape_site (tree stmt, size_t *num_calls_p)
2017 if (get_call_expr_in (stmt) != NULL_TREE)
2024 else if (TREE_CODE (stmt) == ASM_EXPR)
2026 else if (TREE_CODE (stmt) == MODIFY_EXPR)
2028 tree lhs = TREE_OPERAND (stmt, 0);
2030 /* Get to the base of _REF nodes. */
2031 if (TREE_CODE (lhs) != SSA_NAME)
2032 lhs = get_base_address (lhs);
2034 /* If we couldn't recognize the LHS of the assignment, assume that it
2035 is a non-local store. */
2036 if (lhs == NULL_TREE)
2039 /* If the RHS is a conversion between a pointer and an integer, the
2040 pointer escapes since we can't track the integer. */
2041 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
2042 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
2043 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
2044 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
2045 (TREE_OPERAND (stmt, 1), 0)))
2046 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
2049 /* If the LHS is an SSA name, it can't possibly represent a non-local
2051 if (TREE_CODE (lhs) == SSA_NAME)
2054 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2055 local variables we cannot be sure if it will escape, because we
2056 don't have information about objects not in SSA form. Need to
2057 implement something along the lines of
2059 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2060 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2061 Conference on Object-Oriented Programming Systems, Languages, and
2062 Applications (OOPSLA), pp. 1-19, 1999. */
2065 else if (TREE_CODE (stmt) == RETURN_EXPR)
2072 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2073 is considered to represent all the pointers whose pointed-to types are
2074 in the same alias set class. Otherwise, the tag represents a single
2075 SSA_NAME pointer variable. */
2078 create_memory_tag (tree type, bool is_type_tag)
2081 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2083 /* By default, memory tags are local variables. Alias analysis will
2084 determine whether they should be considered globals. */
2085 DECL_CONTEXT (tag) = current_function_decl;
2087 /* Memory tags are by definition addressable. This also prevents
2088 is_gimple_ref frome confusing memory tags with optimizable
2090 TREE_ADDRESSABLE (tag) = 1;
2092 ann = get_var_ann (tag);
2093 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2094 ann->type_mem_tag = NULL_TREE;
2096 /* Add the tag to the symbol table. */
2097 add_referenced_tmp_var (tag);
2103 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2104 This is used if P_i has been found to point to a specific set of
2105 variables or to a non-aliased memory location like the address returned
2106 by malloc functions. */
2109 get_nmt_for (tree ptr)
2111 struct ptr_info_def *pi = get_ptr_info (ptr);
2112 tree tag = pi->name_mem_tag;
2114 if (tag == NULL_TREE)
2115 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2117 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2118 then its name tag should be considered a global variable. */
2119 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2121 || pi->pt_global_mem)
2122 mark_call_clobbered (tag);
2128 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2129 artificial variable that represents the memory location pointed-to by
2130 PTR. It is used to model the effects of pointer de-references on
2131 addressable variables.
2133 AI points to the data gathered during alias analysis. This function
2134 populates the array AI->POINTERS. */
2137 get_tmt_for (tree ptr, struct alias_info *ai)
2141 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2142 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2144 /* To avoid creating unnecessary memory tags, only create one memory tag
2145 per alias set class. Note that it may be tempting to group
2146 memory tags based on conflicting alias sets instead of
2147 equivalence. That would be wrong because alias sets are not
2148 necessarily transitive (as demonstrated by the libstdc++ test
2149 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2150 such that conflicts (A, B) == true and conflicts (A, C) == true,
2151 it does not necessarily follow that conflicts (B, C) == true. */
2152 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2154 struct alias_map_d *curr = ai->pointers[i];
2155 if (tag_set == curr->set)
2157 tag = var_ann (curr->var)->type_mem_tag;
2162 /* If VAR cannot alias with any of the existing memory tags, create a new
2163 tag for PTR and add it to the POINTERS array. */
2164 if (tag == NULL_TREE)
2166 struct alias_map_d *alias_map;
2168 /* If PTR did not have a type tag already, create a new TMT.*
2169 artificial variable representing the memory location
2170 pointed-to by PTR. */
2171 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2172 tag = create_memory_tag (tag_type, true);
2174 tag = var_ann (ptr)->type_mem_tag;
2176 /* Add PTR to the POINTERS array. Note that we are not interested in
2177 PTR's alias set. Instead, we cache the alias set for the memory that
2179 alias_map = xcalloc (1, sizeof (*alias_map));
2180 alias_map->var = ptr;
2181 alias_map->set = tag_set;
2182 ai->pointers[ai->num_pointers++] = alias_map;
2185 /* If the pointed-to type is volatile, so is the tag. */
2186 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
2188 /* Make sure that the type tag has the same alias set as the
2190 gcc_assert (tag_set == get_alias_set (tag));
2196 /* Create GLOBAL_VAR, an artificial global variable to act as a
2197 representative of all the variables that may be clobbered by function
2201 create_global_var (void)
2203 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2205 DECL_ARTIFICIAL (global_var) = 1;
2206 TREE_READONLY (global_var) = 0;
2207 DECL_EXTERNAL (global_var) = 1;
2208 TREE_STATIC (global_var) = 1;
2209 TREE_USED (global_var) = 1;
2210 DECL_CONTEXT (global_var) = NULL_TREE;
2211 TREE_THIS_VOLATILE (global_var) = 0;
2212 TREE_ADDRESSABLE (global_var) = 0;
2214 add_referenced_tmp_var (global_var);
2215 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2219 /* Dump alias statistics on FILE. */
2222 dump_alias_stats (FILE *file)
2224 const char *funcname
2225 = lang_hooks.decl_printable_name (current_function_decl, 2);
2226 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2227 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2228 fprintf (file, "Total alias mayalias results:\t%u\n",
2229 alias_stats.alias_mayalias);
2230 fprintf (file, "Total alias noalias results:\t%u\n",
2231 alias_stats.alias_noalias);
2232 fprintf (file, "Total simple queries:\t%u\n",
2233 alias_stats.simple_queries);
2234 fprintf (file, "Total simple resolved:\t%u\n",
2235 alias_stats.simple_resolved);
2236 fprintf (file, "Total TBAA queries:\t%u\n",
2237 alias_stats.tbaa_queries);
2238 fprintf (file, "Total TBAA resolved:\t%u\n",
2239 alias_stats.tbaa_resolved);
2243 /* Dump alias information on FILE. */
2246 dump_alias_info (FILE *file)
2249 const char *funcname
2250 = lang_hooks.decl_printable_name (current_function_decl, 2);
2252 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2254 fprintf (file, "Aliased symbols\n\n");
2255 for (i = 0; i < num_referenced_vars; i++)
2257 tree var = referenced_var (i);
2258 if (may_be_aliased (var))
2259 dump_variable (file, var);
2262 fprintf (file, "\nDereferenced pointers\n\n");
2263 for (i = 0; i < num_referenced_vars; i++)
2265 tree var = referenced_var (i);
2266 var_ann_t ann = var_ann (var);
2267 if (ann->type_mem_tag)
2268 dump_variable (file, var);
2271 fprintf (file, "\nType memory tags\n\n");
2272 for (i = 0; i < num_referenced_vars; i++)
2274 tree var = referenced_var (i);
2275 var_ann_t ann = var_ann (var);
2276 if (ann->mem_tag_kind == TYPE_TAG)
2277 dump_variable (file, var);
2280 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2282 fprintf (file, "SSA_NAME pointers\n\n");
2283 for (i = 1; i < num_ssa_names; i++)
2285 tree ptr = ssa_name (i);
2286 struct ptr_info_def *pi;
2288 if (ptr == NULL_TREE)
2291 pi = SSA_NAME_PTR_INFO (ptr);
2292 if (!SSA_NAME_IN_FREE_LIST (ptr)
2294 && pi->name_mem_tag)
2295 dump_points_to_info_for (file, ptr);
2298 fprintf (file, "\nName memory tags\n\n");
2299 for (i = 0; i < num_referenced_vars; i++)
2301 tree var = referenced_var (i);
2302 var_ann_t ann = var_ann (var);
2303 if (ann->mem_tag_kind == NAME_TAG)
2304 dump_variable (file, var);
2307 fprintf (file, "\n");
2311 /* Dump alias information on stderr. */
2314 debug_alias_info (void)
2316 dump_alias_info (stderr);
2320 /* Return the alias information associated with pointer T. It creates a
2321 new instance if none existed. */
2323 struct ptr_info_def *
2324 get_ptr_info (tree t)
2326 struct ptr_info_def *pi;
2328 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2330 pi = SSA_NAME_PTR_INFO (t);
2333 pi = ggc_alloc (sizeof (*pi));
2334 memset ((void *)pi, 0, sizeof (*pi));
2335 SSA_NAME_PTR_INFO (t) = pi;
2342 /* Dump points-to information for SSA_NAME PTR into FILE. */
2345 dump_points_to_info_for (FILE *file, tree ptr)
2347 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2349 print_generic_expr (file, ptr, dump_flags);
2353 if (pi->name_mem_tag)
2355 fprintf (file, ", name memory tag: ");
2356 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2359 if (pi->is_dereferenced)
2360 fprintf (file, ", is dereferenced");
2362 if (pi->value_escapes_p)
2363 fprintf (file, ", its value escapes");
2365 if (pi->pt_anything)
2366 fprintf (file, ", points-to anything");
2369 fprintf (file, ", points-to malloc");
2376 fprintf (file, ", points-to vars: { ");
2377 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2379 print_generic_expr (file, referenced_var (ix), dump_flags);
2380 fprintf (file, " ");
2382 fprintf (file, "}");
2386 fprintf (file, "\n");
2390 /* Dump points-to information for VAR into stderr. */
2393 debug_points_to_info_for (tree var)
2395 dump_points_to_info_for (stderr, var);
2399 /* Dump points-to information into FILE. NOTE: This function is slow, as
2400 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2403 dump_points_to_info (FILE *file)
2406 block_stmt_iterator si;
2410 lang_hooks.decl_printable_name (current_function_decl, 2);
2412 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2414 /* First dump points-to information for the default definitions of
2415 pointer variables. This is necessary because default definitions are
2416 not part of the code. */
2417 for (i = 0; i < num_referenced_vars; i++)
2419 tree var = referenced_var (i);
2420 if (POINTER_TYPE_P (TREE_TYPE (var)))
2422 var_ann_t ann = var_ann (var);
2423 if (ann->default_def)
2424 dump_points_to_info_for (file, ann->default_def);
2428 /* Dump points-to information for every pointer defined in the program. */
2433 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2435 tree ptr = PHI_RESULT (phi);
2436 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2437 dump_points_to_info_for (file, ptr);
2440 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2442 tree stmt = bsi_stmt (si);
2444 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2445 if (POINTER_TYPE_P (TREE_TYPE (def)))
2446 dump_points_to_info_for (file, def);
2450 fprintf (file, "\n");
2454 /* Dump points-to info pointed by PTO into STDERR. */
2457 debug_points_to_info (void)
2459 dump_points_to_info (stderr);
2462 /* Dump to FILE the list of variables that may be aliasing VAR. */
2465 dump_may_aliases_for (FILE *file, tree var)
2467 varray_type aliases;
2469 if (TREE_CODE (var) == SSA_NAME)
2470 var = SSA_NAME_VAR (var);
2472 aliases = var_ann (var)->may_aliases;
2476 fprintf (file, "{ ");
2477 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2479 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2480 fprintf (file, " ");
2482 fprintf (file, "}");
2487 /* Dump to stderr the list of variables that may be aliasing VAR. */
2490 debug_may_aliases_for (tree var)
2492 dump_may_aliases_for (stderr, var);
2495 /* Return true if VAR may be aliased. */
2498 may_be_aliased (tree var)
2501 if (TREE_ADDRESSABLE (var))
2504 /* Globally visible variables can have their addresses taken by other
2505 translation units. */
2506 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2509 /* Automatic variables can't have their addresses escape any other way.
2510 This must be after the check for global variables, as extern declarations
2511 do not have TREE_STATIC set. */
2512 if (!TREE_STATIC (var))
2515 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2516 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2517 we can only be sure the variable isn't addressable if it's local to the
2518 current function. */
2519 if (flag_unit_at_a_time)
2521 if (decl_function_context (var) == current_function_decl)