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.
200 This is where we are currently limited. Since not everything is renamed
201 into SSA, we lose track of escape properties when a pointer is stashed
202 inside a field in a structure, for instance. In those cases, we are
203 assuming that the pointer does escape.
205 We use escape analysis to determine whether a variable is
206 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
207 is call-clobbered. If a pointer P_i escapes, then all the variables
208 pointed-to by P_i (and its memory tag) also escape.
210 2- Compute flow-sensitive aliases
212 We have two classes of memory tags. Memory tags associated with the
213 pointed-to data type of the pointers in the program. These tags are
214 called "type memory tag" (TMT). The other class are those associated
215 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
216 when adding operands for an INDIRECT_REF *P_i, we will first check
217 whether P_i has a name tag, if it does we use it, because that will have
218 more precise aliasing information. Otherwise, we use the standard type
221 In this phase, we go through all the pointers we found in points-to
222 analysis and create alias sets for the name memory tags associated with
223 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
224 it points to and its tag.
227 3- Compute flow-insensitive aliases
229 This pass will compare the alias set of every type memory tag and every
230 addressable variable found in the program. Given a type memory tag TMT
231 and an addressable variable V. If the alias sets of TMT and V conflict
232 (as computed by may_alias_p), then V is marked as an alias tag and added
233 to the alias set of TMT.
235 For instance, consider the following function:
251 After aliasing analysis has finished, the type memory tag for pointer
252 'p' will have two aliases, namely variables 'a' and 'b'. Every time
253 pointer 'p' is dereferenced, we want to mark the operation as a
254 potential reference to 'a' and 'b'.
264 # p_1 = PHI <p_4(1), p_6(2)>;
266 # a_7 = V_MAY_DEF <a_3>;
267 # b_8 = V_MAY_DEF <b_5>;
270 # a_9 = V_MAY_DEF <a_7>
279 In certain cases, the list of may aliases for a pointer may grow too
280 large. This may cause an explosion in the number of virtual operands
281 inserted in the code. Resulting in increased memory consumption and
284 When the number of virtual operands needed to represent aliased
285 loads and stores grows too large (configurable with @option{--param
286 max-aliased-vops}), alias sets are grouped to avoid severe
287 compile-time slow downs and memory consumption. See group_aliases. */
290 compute_may_aliases (void)
292 struct alias_info *ai;
294 memset (&alias_stats, 0, sizeof (alias_stats));
296 /* Initialize aliasing information. */
297 ai = init_alias_info ();
299 /* For each pointer P_i, determine the sets of variables that P_i may
300 point-to. For every addressable variable V, determine whether the
301 address of V escapes the current function, making V call-clobbered
302 (i.e., whether &V is stored in a global variable or if its passed as a
303 function call argument). */
304 compute_points_to_and_addr_escape (ai);
306 /* Collect all pointers and addressable variables, compute alias sets,
307 create memory tags for pointers and promote variables whose address is
308 not needed anymore. */
309 setup_pointers_and_addressables (ai);
311 /* Compute flow-sensitive, points-to based aliasing for all the name
312 memory tags. Note that this pass needs to be done before flow
313 insensitive analysis because it uses the points-to information
314 gathered before to mark call-clobbered type tags. */
315 compute_flow_sensitive_aliasing (ai);
317 /* Compute type-based flow-insensitive aliasing for all the type
319 compute_flow_insensitive_aliasing (ai);
321 /* If the program has too many call-clobbered variables and/or function
322 calls, create .GLOBAL_VAR and use it to model call-clobbering
323 semantics at call sites. This reduces the number of virtual operands
324 considerably, improving compile times at the expense of lost
325 aliasing precision. */
326 maybe_create_global_var (ai);
328 /* Debugging dumps. */
331 dump_referenced_vars (dump_file);
332 if (dump_flags & TDF_STATS)
333 dump_alias_stats (dump_file);
334 dump_points_to_info (dump_file);
335 dump_alias_info (dump_file);
338 /* Deallocate memory used by aliasing data structures. */
339 delete_alias_info (ai);
342 struct tree_opt_pass pass_may_alias =
346 compute_may_aliases, /* execute */
349 0, /* static_pass_number */
350 TV_TREE_MAY_ALIAS, /* tv_id */
351 PROP_cfg | PROP_ssa, /* properties_required */
352 PROP_alias, /* properties_provided */
353 0, /* properties_destroyed */
354 0, /* todo_flags_start */
355 TODO_dump_func | TODO_rename_vars
356 | TODO_ggc_collect | TODO_verify_ssa, /* todo_flags_finish */
361 /* Initialize the data structures used for alias analysis. */
363 static struct alias_info *
364 init_alias_info (void)
366 struct alias_info *ai;
367 static bool aliases_computed_p = false;
369 ai = xcalloc (1, sizeof (struct alias_info));
370 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
371 sbitmap_zero (ai->ssa_names_visited);
372 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
373 ai->addresses_needed = BITMAP_XMALLOC ();
374 VARRAY_UINT_INIT (ai->num_references, num_referenced_vars, "num_references");
375 ai->written_vars = BITMAP_XMALLOC ();
376 ai->dereferenced_ptrs_store = BITMAP_XMALLOC ();
377 ai->dereferenced_ptrs_load = BITMAP_XMALLOC ();
379 /* If aliases have been computed before, clear existing information. */
380 if (aliases_computed_p)
385 /* Clear the call-clobbered set. We are going to re-discover
386 call-clobbered variables. */
387 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
389 tree var = referenced_var (i);
391 /* Variables that are intrinsically call-clobbered (globals,
392 local statics, etc) will not be marked by the aliasing
393 code, so we can't remove them from CALL_CLOBBERED_VARS. */
394 if (!is_call_clobbered (var))
395 bitmap_clear_bit (call_clobbered_vars, var_ann (var)->uid);
398 /* Similarly, clear the set of addressable variables. In this
399 case, we can just clear the set because addressability is
400 only computed here. */
401 bitmap_clear (addressable_vars);
403 /* Clear flow-insensitive alias information from each symbol. */
404 for (i = 0; i < num_referenced_vars; i++)
406 var_ann_t ann = var_ann (referenced_var (i));
407 ann->is_alias_tag = 0;
408 ann->may_aliases = NULL;
411 /* Clear flow-sensitive points-to information from each SSA name. */
412 for (i = 1; i < num_ssa_names; i++)
414 tree name = ssa_name (i);
416 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
419 if (SSA_NAME_PTR_INFO (name))
421 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
423 /* Clear all the flags but keep the name tag to
424 avoid creating new temporaries unnecessarily. If
425 this pointer is found to point to a subset or
426 superset of its former points-to set, then a new
427 tag will need to be created in create_name_tags. */
430 pi->value_escapes_p = 0;
431 pi->is_dereferenced = 0;
433 bitmap_clear (pi->pt_vars);
438 /* Next time, we will need to reset alias information. */
439 aliases_computed_p = true;
445 /* Deallocate memory used by alias analysis. */
448 delete_alias_info (struct alias_info *ai)
452 sbitmap_free (ai->ssa_names_visited);
453 ai->processed_ptrs = NULL;
454 BITMAP_XFREE (ai->addresses_needed);
456 for (i = 0; i < ai->num_addressable_vars; i++)
458 sbitmap_free (ai->addressable_vars[i]->may_aliases);
459 free (ai->addressable_vars[i]);
461 free (ai->addressable_vars);
463 for (i = 0; i < ai->num_pointers; i++)
465 sbitmap_free (ai->pointers[i]->may_aliases);
466 free (ai->pointers[i]);
470 ai->num_references = NULL;
471 BITMAP_XFREE (ai->written_vars);
472 BITMAP_XFREE (ai->dereferenced_ptrs_store);
473 BITMAP_XFREE (ai->dereferenced_ptrs_load);
479 /* Walk use-def chains for pointer PTR to determine what variables is PTR
483 collect_points_to_info_for (struct alias_info *ai, tree ptr)
485 gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr)));
487 if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)))
489 SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr));
490 walk_use_def_chains (ptr, collect_points_to_info_r, ai, true);
491 VARRAY_PUSH_TREE (ai->processed_ptrs, ptr);
496 /* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
497 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
500 find_ptr_dereference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
502 tree ptr = (tree) data;
504 if (INDIRECT_REF_P (*tp)
505 && TREE_OPERAND (*tp, 0) == ptr)
512 /* Return true if STMT contains (ALIGN/MISALIGNED_)INDIRECT_REF <PTR>.
513 *IS_STORE is set to 'true' if the dereference is on the LHS of an
517 ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
521 if (TREE_CODE (stmt) == MODIFY_EXPR
522 || (TREE_CODE (stmt) == RETURN_EXPR
523 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
527 e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
528 lhs = TREE_OPERAND (e, 0);
529 rhs = TREE_OPERAND (e, 1);
532 && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
537 else if (EXPR_P (rhs)
538 && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
543 else if (TREE_CODE (stmt) == ASM_EXPR)
545 if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
546 || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
551 else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
561 /* Traverse use-def links for all the pointers in the program to collect
562 address escape and points-to information.
564 This is loosely based on the same idea described in R. Hasti and S.
565 Horwitz, ``Using static single assignment form to improve
566 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
567 Programming Language Design and Implementation, pp. 97-105, 1998. */
570 compute_points_to_and_addr_escape (struct alias_info *ai)
577 timevar_push (TV_TREE_PTA);
581 bb_ann_t block_ann = bb_ann (bb);
582 block_stmt_iterator si;
584 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
587 tree stmt = bsi_stmt (si);
588 bool stmt_escapes_p = is_escape_site (stmt, &ai->num_calls_found);
591 /* Mark all the variables whose address are taken by the
592 statement. Note that this will miss all the addresses taken
593 in PHI nodes (those are discovered while following the use-def
595 get_stmt_operands (stmt);
596 addr_taken = addresses_taken (stmt);
598 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
600 tree var = referenced_var (i);
601 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
603 mark_call_clobbered (var);
607 block_ann->has_escape_site = 1;
609 /* Special case for silly ADDR_EXPR tricks
610 (gcc.c-torture/unsorted/pass.c). If this statement is an
611 assignment to a non-pointer variable and the RHS takes the
612 address of a variable, assume that the variable on the RHS is
613 call-clobbered. We could add the LHS to the list of
614 "pointers" and follow it to see if it really escapes, but it's
615 not worth the pain. */
617 && TREE_CODE (stmt) == MODIFY_EXPR
618 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 0))))
619 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
621 tree var = referenced_var (i);
622 mark_call_clobbered (var);
625 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
627 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
628 struct ptr_info_def *pi;
631 /* If the operand's variable may be aliased, keep track
632 of how many times we've referenced it. This is used
633 for alias grouping in compute_flow_sensitive_aliasing.
634 Note that we don't need to grow AI->NUM_REFERENCES
635 because we are processing regular variables, not
636 memory tags (the array's initial size is set to
637 NUM_REFERENCED_VARS). */
638 if (may_be_aliased (SSA_NAME_VAR (op)))
639 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
641 if (!POINTER_TYPE_P (TREE_TYPE (op)))
644 collect_points_to_info_for (ai, op);
646 pi = SSA_NAME_PTR_INFO (op);
647 if (ptr_is_dereferenced_by (op, stmt, &is_store))
649 /* Mark OP as dereferenced. In a subsequent pass,
650 dereferenced pointers that point to a set of
651 variables will be assigned a name tag to alias
652 all the variables OP points to. */
653 pi->is_dereferenced = 1;
655 /* Keep track of how many time we've dereferenced each
656 pointer. Again, we don't need to grow
657 AI->NUM_REFERENCES because we're processing
658 existing program variables. */
659 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
661 /* If this is a store operation, mark OP as being
662 dereferenced to store, otherwise mark it as being
663 dereferenced to load. */
665 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
667 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
669 else if (stmt_escapes_p)
671 /* Note that even if STMT is an escape point, pointer OP
672 will not escape if it is being dereferenced. That's
673 why we only check for escape points if OP is not
674 dereferenced by STMT. */
675 pi->value_escapes_p = 1;
677 /* If the statement makes a function call, assume
678 that pointer OP will be dereferenced in a store
679 operation inside the called function. */
680 if (get_call_expr_in (stmt))
682 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
683 pi->is_dereferenced = 1;
688 /* Update reference counter for definitions to any
689 potentially aliased variable. This is used in the alias
690 grouping heuristics. */
691 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
693 tree var = SSA_NAME_VAR (op);
694 var_ann_t ann = var_ann (var);
695 bitmap_set_bit (ai->written_vars, ann->uid);
696 if (may_be_aliased (var))
697 (VARRAY_UINT (ai->num_references, ann->uid))++;
699 if (POINTER_TYPE_P (TREE_TYPE (op)))
700 collect_points_to_info_for (ai, op);
703 /* Mark variables in V_MAY_DEF operands as being written to. */
704 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
706 tree var = SSA_NAME_VAR (op);
707 var_ann_t ann = var_ann (var);
708 bitmap_set_bit (ai->written_vars, ann->uid);
711 /* After promoting variables and computing aliasing we will
712 need to re-scan most statements. FIXME: Try to minimize the
713 number of statements re-scanned. It's not really necessary to
714 re-scan *all* statements. */
719 timevar_pop (TV_TREE_PTA);
723 /* Create name tags for all the pointers that have been dereferenced.
724 We only create a name tag for a pointer P if P is found to point to
725 a set of variables (so that we can alias them to *P) or if it is
726 the result of a call to malloc (which means that P cannot point to
727 anything else nor alias any other variable).
729 If two pointers P and Q point to the same set of variables, they
730 are assigned the same name tag. */
733 create_name_tags (struct alias_info *ai)
737 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
739 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
740 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
742 if (pi->pt_anything || !pi->is_dereferenced)
744 /* No name tags for pointers that have not been
745 dereferenced or point to an arbitrary location. */
746 pi->name_mem_tag = NULL_TREE;
750 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
753 tree old_name_tag = pi->name_mem_tag;
755 /* If PTR points to a set of variables, check if we don't
756 have another pointer Q with the same points-to set before
757 creating a tag. If so, use Q's tag instead of creating a
760 This is important for not creating unnecessary symbols
761 and also for copy propagation. If we ever need to
762 propagate PTR into Q or vice-versa, we would run into
763 problems if they both had different name tags because
764 they would have different SSA version numbers (which
765 would force us to take the name tags in and out of SSA). */
766 for (j = 0; j < i; j++)
768 tree q = VARRAY_TREE (ai->processed_ptrs, j);
769 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
774 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
776 pi->name_mem_tag = qi->name_mem_tag;
781 /* If we didn't find a pointer with the same points-to set
782 as PTR, create a new name tag if needed. */
783 if (pi->name_mem_tag == NULL_TREE)
784 pi->name_mem_tag = get_nmt_for (ptr);
786 /* If the new name tag computed for PTR is different than
787 the old name tag that it used to have, then the old tag
788 needs to be removed from the IL, so we mark it for
790 if (old_name_tag && old_name_tag != pi->name_mem_tag)
791 bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid);
793 else if (pi->pt_malloc)
795 /* Otherwise, create a unique name tag for this pointer. */
796 pi->name_mem_tag = get_nmt_for (ptr);
800 /* Only pointers that may point to malloc or other variables
801 may receive a name tag. If the pointer does not point to
802 a known spot, we should use type tags. */
803 set_pt_anything (ptr);
807 TREE_THIS_VOLATILE (pi->name_mem_tag)
808 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
810 /* Mark the new name tag for renaming. */
811 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
817 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
818 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
819 name tag and the variables it points-to are call-clobbered. Finally, if
820 P_i escapes and we could not determine where it points to, then all the
821 variables in the same alias set as *P_i are marked call-clobbered. This
822 is necessary because we must assume that P_i may take the address of any
823 variable in the same alias set. */
826 compute_flow_sensitive_aliasing (struct alias_info *ai)
830 create_name_tags (ai);
832 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
835 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
836 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
837 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
840 if (pi->value_escapes_p || pi->pt_anything)
842 /* If PTR escapes or may point to anything, then its associated
843 memory tags and pointed-to variables are call-clobbered. */
844 if (pi->name_mem_tag)
845 mark_call_clobbered (pi->name_mem_tag);
847 if (v_ann->type_mem_tag)
848 mark_call_clobbered (v_ann->type_mem_tag);
851 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
853 mark_call_clobbered (referenced_var (j));
857 /* Set up aliasing information for PTR's name memory tag (if it has
858 one). Note that only pointers that have been dereferenced will
859 have a name memory tag. */
860 if (pi->name_mem_tag && pi->pt_vars)
861 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
863 add_may_alias (pi->name_mem_tag, referenced_var (j));
866 /* If the name tag is call clobbered, so is the type tag
867 associated with the base VAR_DECL. */
869 && v_ann->type_mem_tag
870 && is_call_clobbered (pi->name_mem_tag))
871 mark_call_clobbered (v_ann->type_mem_tag);
876 /* Compute type-based alias sets. Traverse all the pointers and
877 addressable variables found in setup_pointers_and_addressables.
879 For every pointer P in AI->POINTERS and addressable variable V in
880 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
881 memory tag (TMT) if their alias sets conflict. V is then marked as
882 an alias tag so that the operand scanner knows that statements
883 containing V have aliased operands. */
886 compute_flow_insensitive_aliasing (struct alias_info *ai)
891 /* Initialize counter for the total number of virtual operands that
892 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
893 threshold set by --params max-alias-vops, we enable alias
895 ai->total_alias_vops = 0;
897 /* For every pointer P, determine which addressable variables may alias
898 with P's type memory tag. */
899 for (i = 0; i < ai->num_pointers; i++)
902 struct alias_map_d *p_map = ai->pointers[i];
903 tree tag = var_ann (p_map->var)->type_mem_tag;
904 var_ann_t tag_ann = var_ann (tag);
906 p_map->total_alias_vops = 0;
907 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
908 sbitmap_zero (p_map->may_aliases);
910 for (j = 0; j < ai->num_addressable_vars; j++)
912 struct alias_map_d *v_map;
915 bool tag_stored_p, var_stored_p;
917 v_map = ai->addressable_vars[j];
919 v_ann = var_ann (var);
921 /* Skip memory tags and variables that have never been
922 written to. We also need to check if the variables are
923 call-clobbered because they may be overwritten by
926 Note this is effectively random accessing elements in
927 the sparse bitset, which can be highly inefficient.
928 So we first check the call_clobbered status of the
929 tag and variable before querying the bitmap. */
930 tag_stored_p = is_call_clobbered (tag)
931 || bitmap_bit_p (ai->written_vars, tag_ann->uid);
932 var_stored_p = is_call_clobbered (var)
933 || bitmap_bit_p (ai->written_vars, v_ann->uid);
934 if (!tag_stored_p && !var_stored_p)
937 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
939 size_t num_tag_refs, num_var_refs;
941 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
942 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
944 /* Add VAR to TAG's may-aliases set. */
945 add_may_alias (tag, var);
947 /* Update the total number of virtual operands due to
948 aliasing. Since we are adding one more alias to TAG's
949 may-aliases set, the total number of virtual operands due
950 to aliasing will be increased by the number of references
951 made to VAR and TAG (every reference to TAG will also
952 count as a reference to VAR). */
953 ai->total_alias_vops += (num_var_refs + num_tag_refs);
954 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
956 /* Update the bitmap used to represent TAG's alias set
957 in case we need to group aliases. */
958 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
963 /* Since this analysis is based exclusively on symbols, it fails to
964 handle cases where two pointers P and Q have different memory
965 tags with conflicting alias set numbers but no aliased symbols in
968 For example, suppose that we have two memory tags TMT.1 and TMT.2
971 may-aliases (TMT.1) = { a }
972 may-aliases (TMT.2) = { b }
974 and the alias set number of TMT.1 conflicts with that of TMT.2.
975 Since they don't have symbols in common, loads and stores from
976 TMT.1 and TMT.2 will seem independent of each other, which will
977 lead to the optimizers making invalid transformations (see
978 testsuite/gcc.c-torture/execute/pr15262-[12].c).
980 To avoid this problem, we do a final traversal of AI->POINTERS
981 looking for pairs of pointers that have no aliased symbols in
982 common and yet have conflicting alias set numbers. */
983 res = sbitmap_alloc (num_referenced_vars);
985 for (i = 0; i < ai->num_pointers; i++)
988 struct alias_map_d *p_map1 = ai->pointers[i];
989 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
990 sbitmap may_aliases1 = p_map1->may_aliases;
992 for (j = i + 1; j < ai->num_pointers; j++)
994 struct alias_map_d *p_map2 = ai->pointers[j];
995 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
996 sbitmap may_aliases2 = p_map2->may_aliases;
998 /* If the pointers may not point to each other, do nothing. */
999 if (!may_alias_p (p_map1->var, p_map1->set, p_map2->var, p_map2->set))
1002 /* The two pointers may alias each other. If they already have
1003 symbols in common, do nothing. */
1004 sbitmap_a_and_b (res, may_aliases1, may_aliases2);
1005 if (sbitmap_first_set_bit (res) >= 0)
1008 if (sbitmap_first_set_bit (may_aliases2) >= 0)
1012 /* Add all the aliases for TAG2 into TAG1's alias set.
1013 FIXME, update grouping heuristic counters. */
1014 EXECUTE_IF_SET_IN_SBITMAP (may_aliases2, 0, k,
1015 add_may_alias (tag1, referenced_var (k)));
1016 sbitmap_a_or_b (may_aliases1, may_aliases1, may_aliases2);
1020 /* Since TAG2 does not have any aliases of its own, add
1021 TAG2 itself to the alias set of TAG1. */
1022 add_may_alias (tag1, tag2);
1030 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
1031 get_name (current_function_decl),
1032 ai->total_alias_vops);
1034 /* Determine if we need to enable alias grouping. */
1035 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
1040 /* Comparison function for qsort used in group_aliases. */
1043 total_alias_vops_cmp (const void *p, const void *q)
1045 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1046 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1047 long n1 = (*p1)->total_alias_vops;
1048 long n2 = (*p2)->total_alias_vops;
1050 /* We want to sort in descending order. */
1051 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1054 /* Group all the aliases for TAG to make TAG represent all the
1055 variables in its alias set. Update the total number
1056 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1057 function will make TAG be the unique alias tag for all the
1058 variables in its may-aliases. So, given:
1060 may-aliases(TAG) = { V1, V2, V3 }
1062 This function will group the variables into:
1064 may-aliases(V1) = { TAG }
1065 may-aliases(V2) = { TAG }
1066 may-aliases(V2) = { TAG } */
1069 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
1072 var_ann_t tag_ann = var_ann (tag);
1073 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1075 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
1077 tree var = referenced_var (i);
1078 var_ann_t ann = var_ann (var);
1080 /* Make TAG the unique alias of VAR. */
1081 ann->is_alias_tag = 0;
1082 ann->may_aliases = NULL;
1084 /* Note that VAR and TAG may be the same if the function has no
1085 addressable variables (see the discussion at the end of
1086 setup_pointers_and_addressables). */
1088 add_may_alias (var, tag);
1090 /* Reduce total number of virtual operands contributed
1091 by TAG on behalf of VAR. Notice that the references to VAR
1092 itself won't be removed. We will merely replace them with
1093 references to TAG. */
1094 ai->total_alias_vops -= num_tag_refs;
1097 /* We have reduced the number of virtual operands that TAG makes on
1098 behalf of all the variables formerly aliased with it. However,
1099 we have also "removed" all the virtual operands for TAG itself,
1100 so we add them back. */
1101 ai->total_alias_vops += num_tag_refs;
1103 /* TAG no longer has any aliases. */
1104 tag_ann->may_aliases = NULL;
1108 /* Group may-aliases sets to reduce the number of virtual operands due
1111 1- Sort the list of pointers in decreasing number of contributed
1114 2- Take the first entry in AI->POINTERS and revert the role of
1115 the memory tag and its aliases. Usually, whenever an aliased
1116 variable Vi is found to alias with a memory tag T, we add Vi
1117 to the may-aliases set for T. Meaning that after alias
1118 analysis, we will have:
1120 may-aliases(T) = { V1, V2, V3, ..., Vn }
1122 This means that every statement that references T, will get 'n'
1123 virtual operands for each of the Vi tags. But, when alias
1124 grouping is enabled, we make T an alias tag and add it to the
1125 alias set of all the Vi variables:
1127 may-aliases(V1) = { T }
1128 may-aliases(V2) = { T }
1130 may-aliases(Vn) = { T }
1132 This has two effects: (a) statements referencing T will only get
1133 a single virtual operand, and, (b) all the variables Vi will now
1134 appear to alias each other. So, we lose alias precision to
1135 improve compile time. But, in theory, a program with such a high
1136 level of aliasing should not be very optimizable in the first
1139 3- Since variables may be in the alias set of more than one
1140 memory tag, the grouping done in step (2) needs to be extended
1141 to all the memory tags that have a non-empty intersection with
1142 the may-aliases set of tag T. For instance, if we originally
1143 had these may-aliases sets:
1145 may-aliases(T) = { V1, V2, V3 }
1146 may-aliases(R) = { V2, V4 }
1148 In step (2) we would have reverted the aliases for T as:
1150 may-aliases(V1) = { T }
1151 may-aliases(V2) = { T }
1152 may-aliases(V3) = { T }
1154 But note that now V2 is no longer aliased with R. We could
1155 add R to may-aliases(V2), but we are in the process of
1156 grouping aliases to reduce virtual operands so what we do is
1157 add V4 to the grouping to obtain:
1159 may-aliases(V1) = { T }
1160 may-aliases(V2) = { T }
1161 may-aliases(V3) = { T }
1162 may-aliases(V4) = { T }
1164 4- If the total number of virtual operands due to aliasing is
1165 still above the threshold set by max-alias-vops, go back to (2). */
1168 group_aliases (struct alias_info *ai)
1173 /* Sort the POINTERS array in descending order of contributed
1174 virtual operands. */
1175 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1176 total_alias_vops_cmp);
1178 res = sbitmap_alloc (num_referenced_vars);
1180 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1181 and the tag's may-aliases set. */
1182 for (i = 0; i < ai->num_pointers; i++)
1185 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1186 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1188 /* Skip tags that have been grouped already. */
1189 if (ai->pointers[i]->grouped_p)
1192 /* See if TAG1 had any aliases in common with other type tags.
1193 If we find a TAG2 with common aliases with TAG1, add TAG2's
1194 aliases into TAG1. */
1195 for (j = i + 1; j < ai->num_pointers; j++)
1197 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1199 sbitmap_a_and_b (res, tag1_aliases, tag2_aliases);
1200 if (sbitmap_first_set_bit (res) >= 0)
1202 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1204 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1206 /* TAG2 does not need its aliases anymore. */
1207 sbitmap_zero (tag2_aliases);
1208 var_ann (tag2)->may_aliases = NULL;
1210 /* TAG1 is the unique alias of TAG2. */
1211 add_may_alias (tag2, tag1);
1213 ai->pointers[j]->grouped_p = true;
1217 /* Now group all the aliases we collected into TAG1. */
1218 group_aliases_into (tag1, tag1_aliases, ai);
1220 /* If we've reduced total number of virtual operands below the
1222 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1226 /* Finally, all the variables that have been grouped cannot be in
1227 the may-alias set of name memory tags. Suppose that we have
1228 grouped the aliases in this code so that may-aliases(a) = TMT.20
1232 # a_9 = V_MAY_DEF <a_8>
1234 ... Several modifications to TMT.20 ...
1238 Since p_5 points to 'a', the optimizers will try to propagate 0
1239 into p_5->field, but that is wrong because there have been
1240 modifications to 'TMT.20' in between. To prevent this we have to
1241 replace 'a' with 'TMT.20' in the name tag of p_5. */
1242 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1245 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1246 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1247 varray_type aliases;
1249 if (name_tag == NULL_TREE)
1252 aliases = var_ann (name_tag)->may_aliases;
1253 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1255 tree alias = VARRAY_TREE (aliases, j);
1256 var_ann_t ann = var_ann (alias);
1258 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1262 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1264 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1265 replace_may_alias (name_tag, j, new_alias);
1274 "%s: Total number of aliased vops after grouping: %ld%s\n",
1275 get_name (current_function_decl),
1276 ai->total_alias_vops,
1277 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1281 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1284 create_alias_map_for (tree var, struct alias_info *ai)
1286 struct alias_map_d *alias_map;
1287 alias_map = xcalloc (1, sizeof (*alias_map));
1288 alias_map->var = var;
1289 alias_map->set = get_alias_set (var);
1290 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1294 /* Create memory tags for all the dereferenced pointers and build the
1295 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1296 sets. Based on the address escape and points-to information collected
1297 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1298 variables whose address is not needed anymore. */
1301 setup_pointers_and_addressables (struct alias_info *ai)
1303 size_t i, n_vars, num_addressable_vars, num_pointers;
1305 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1306 num_addressable_vars = num_pointers = 0;
1307 for (i = 0; i < num_referenced_vars; i++)
1309 tree var = referenced_var (i);
1311 if (may_be_aliased (var))
1312 num_addressable_vars++;
1314 if (POINTER_TYPE_P (TREE_TYPE (var)))
1316 /* Since we don't keep track of volatile variables, assume that
1317 these pointers are used in indirect store operations. */
1318 if (TREE_THIS_VOLATILE (var))
1319 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1325 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1326 always going to be slightly bigger than we actually need them
1327 because some TREE_ADDRESSABLE variables will be marked
1328 non-addressable below and only pointers with unique type tags are
1329 going to be added to POINTERS. */
1330 ai->addressable_vars = xcalloc (num_addressable_vars,
1331 sizeof (struct alias_map_d *));
1332 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1333 ai->num_addressable_vars = 0;
1334 ai->num_pointers = 0;
1336 /* Since we will be creating type memory tags within this loop, cache the
1337 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1339 n_vars = num_referenced_vars;
1341 for (i = 0; i < n_vars; i++)
1343 tree var = referenced_var (i);
1344 var_ann_t v_ann = var_ann (var);
1346 /* Name memory tags already have flow-sensitive aliasing
1347 information, so they need not be processed by
1348 compute_flow_insensitive_aliasing. Similarly, type memory
1349 tags are already accounted for when we process their
1350 associated pointer. */
1351 if (v_ann->mem_tag_kind != NOT_A_TAG)
1354 /* Remove the ADDRESSABLE flag from every addressable variable whose
1355 address is not needed anymore. This is caused by the propagation
1356 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1357 removal of dead pointer assignments done by the early scalar
1359 if (TREE_ADDRESSABLE (var))
1361 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1362 && v_ann->mem_tag_kind == NOT_A_TAG
1363 && TREE_CODE (var) != RESULT_DECL
1364 && !is_global_var (var))
1366 /* The address of VAR is not needed, remove the
1367 addressable bit, so that it can be optimized as a
1368 regular variable. */
1369 mark_non_addressable (var);
1371 /* Since VAR is now a regular GIMPLE register, we will need
1372 to rename VAR into SSA afterwards. */
1373 bitmap_set_bit (vars_to_rename, v_ann->uid);
1377 /* Add the variable to the set of addressables. Mostly
1378 used when scanning operands for ASM_EXPRs that
1379 clobber memory. In those cases, we need to clobber
1380 all call-clobbered variables and all addressables. */
1381 bitmap_set_bit (addressable_vars, v_ann->uid);
1385 /* Global variables and addressable locals may be aliased. Create an
1386 entry in ADDRESSABLE_VARS for VAR. */
1387 if (may_be_aliased (var))
1389 create_alias_map_for (var, ai);
1390 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1393 /* Add pointer variables that have been dereferenced to the POINTERS
1394 array and create a type memory tag for them. */
1395 if (POINTER_TYPE_P (TREE_TYPE (var)))
1397 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1398 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1403 /* If pointer VAR still doesn't have a memory tag
1404 associated with it, create it now or re-use an
1406 tag = get_tmt_for (var, ai);
1407 t_ann = var_ann (tag);
1409 /* The type tag will need to be renamed into SSA
1410 afterwards. Note that we cannot do this inside
1411 get_tmt_for because aliasing may run multiple times
1412 and we only create type tags the first time. */
1413 bitmap_set_bit (vars_to_rename, t_ann->uid);
1415 /* Associate the tag with pointer VAR. */
1416 v_ann->type_mem_tag = tag;
1418 /* If pointer VAR has been used in a store operation,
1419 then its memory tag must be marked as written-to. */
1420 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1421 bitmap_set_bit (ai->written_vars, t_ann->uid);
1423 /* If pointer VAR is a global variable or a PARM_DECL,
1424 then its memory tag should be considered a global
1426 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1427 mark_call_clobbered (tag);
1429 /* All the dereferences of pointer VAR count as
1430 references of TAG. Since TAG can be associated with
1431 several pointers, add the dereferences of VAR to the
1432 TAG. We may need to grow AI->NUM_REFERENCES because
1433 we have been adding name and type tags. */
1434 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1435 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1437 VARRAY_UINT (ai->num_references, t_ann->uid)
1438 += VARRAY_UINT (ai->num_references, v_ann->uid);
1442 /* The pointer has not been dereferenced. If it had a
1443 type memory tag, remove it and mark the old tag for
1444 renaming to remove it out of the IL. */
1445 var_ann_t ann = var_ann (var);
1446 tree tag = ann->type_mem_tag;
1449 bitmap_set_bit (vars_to_rename, var_ann (tag)->uid);
1450 ann->type_mem_tag = NULL_TREE;
1458 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1459 every call site, we need to emit V_MAY_DEF expressions to represent the
1460 clobbering effects of the call for variables whose address escapes the
1463 One approach is to group all call-clobbered variables into a single
1464 representative that is used as an alias of every call-clobbered variable
1465 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1466 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1468 The second approach is to emit a clobbering V_MAY_DEF for every
1469 call-clobbered variable at call sites. This is the preferred way in terms
1470 of optimization opportunities but it may create too many V_MAY_DEF operands
1471 if there are many call clobbered variables and function calls in the
1474 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1475 function calls found by the number of call-clobbered variables. If that
1476 product is beyond a certain threshold, as determined by the parameterized
1477 values shown below, we use .GLOBAL_VAR.
1479 FIXME. This heuristic should be improved. One idea is to use several
1480 .GLOBAL_VARs of different types instead of a single one. The thresholds
1481 have been derived from a typical bootstrap cycle, including all target
1482 libraries. Compile times were found increase by ~1% compared to using
1486 maybe_create_global_var (struct alias_info *ai)
1488 unsigned i, n_clobbered;
1491 /* No need to create it, if we have one already. */
1492 if (global_var == NULL_TREE)
1494 /* Count all the call-clobbered variables. */
1496 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1501 /* Create .GLOBAL_VAR if we have too many call-clobbered
1502 variables. We also create .GLOBAL_VAR when there no
1503 call-clobbered variables to prevent code motion
1504 transformations from re-arranging function calls that may
1505 have side effects. For instance,
1514 There are no call-clobbered variables in foo(), so it would
1515 be entirely possible for a pass to want to move the call to
1516 f() after the call to g(). If f() has side effects, that
1517 would be wrong. Creating .GLOBAL_VAR in this case will
1518 insert VDEFs for it and prevent such transformations. */
1519 if (n_clobbered == 0
1520 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1521 create_global_var ();
1524 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1525 been created, make it an alias for all call-clobbered variables. */
1527 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1529 tree var = referenced_var (i);
1530 if (var != global_var)
1532 add_may_alias (var, global_var);
1533 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1539 /* Return TRUE if pointer PTR may point to variable VAR.
1541 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1542 This is needed because when checking for type conflicts we are
1543 interested in the alias set of the memory location pointed-to by
1544 PTR. The alias set of PTR itself is irrelevant.
1546 VAR_ALIAS_SET is the alias set for VAR. */
1549 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1550 tree var, HOST_WIDE_INT var_alias_set)
1553 var_ann_t v_ann, m_ann;
1555 alias_stats.alias_queries++;
1556 alias_stats.simple_queries++;
1558 /* By convention, a variable cannot alias itself. */
1559 mem = var_ann (ptr)->type_mem_tag;
1562 alias_stats.alias_noalias++;
1563 alias_stats.simple_resolved++;
1567 v_ann = var_ann (var);
1568 m_ann = var_ann (mem);
1570 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1572 alias_stats.tbaa_queries++;
1574 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1575 PTR can't possibly affect VAR. Note, that we are specifically testing
1576 for PTR's alias set here, not its pointed-to type. We also can't
1577 do this check with relaxed aliasing enabled. */
1578 if (POINTER_TYPE_P (TREE_TYPE (var))
1579 && var_alias_set != 0
1580 && mem_alias_set != 0)
1582 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1583 if (ptr_alias_set == var_alias_set)
1585 alias_stats.alias_noalias++;
1586 alias_stats.tbaa_resolved++;
1591 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1592 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1594 alias_stats.alias_noalias++;
1595 alias_stats.tbaa_resolved++;
1599 alias_stats.alias_mayalias++;
1604 /* Add ALIAS to the set of variables that may alias VAR. */
1607 add_may_alias (tree var, tree alias)
1610 var_ann_t v_ann = get_var_ann (var);
1611 var_ann_t a_ann = get_var_ann (alias);
1613 gcc_assert (var != alias);
1615 if (v_ann->may_aliases == NULL)
1616 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1618 /* Avoid adding duplicates. */
1619 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1620 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1623 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1624 FIXME, call-clobbering should only depend on whether an address
1625 escapes. It should be independent of aliasing. */
1626 if (is_call_clobbered (var))
1627 mark_call_clobbered (alias);
1629 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1630 else if (is_call_clobbered (alias))
1631 mark_call_clobbered (var);
1633 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1634 a_ann->is_alias_tag = 1;
1638 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1641 replace_may_alias (tree var, size_t i, tree new_alias)
1643 var_ann_t v_ann = var_ann (var);
1644 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1646 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1647 FIXME, call-clobbering should only depend on whether an address
1648 escapes. It should be independent of aliasing. */
1649 if (is_call_clobbered (var))
1650 mark_call_clobbered (new_alias);
1652 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1653 else if (is_call_clobbered (new_alias))
1654 mark_call_clobbered (var);
1658 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1661 set_pt_anything (tree ptr)
1663 struct ptr_info_def *pi = get_ptr_info (ptr);
1665 pi->pt_anything = 1;
1668 /* The pointer used to have a name tag, but we now found it pointing
1669 to an arbitrary location. The name tag needs to be renamed and
1670 disassociated from PTR. */
1671 if (pi->name_mem_tag)
1673 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1674 pi->name_mem_tag = NULL_TREE;
1679 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1682 set_pt_malloc (tree ptr)
1684 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1686 /* If the pointer has already been found to point to arbitrary
1687 memory locations, it is unsafe to mark it as pointing to malloc. */
1688 if (pi->pt_anything)
1695 /* Given two different pointers DEST and ORIG. Merge the points-to
1696 information in ORIG into DEST. AI is as in
1697 collect_points_to_info. */
1700 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1702 struct ptr_info_def *dest_pi, *orig_pi;
1704 gcc_assert (dest != orig);
1706 /* Make sure we have points-to information for ORIG. */
1707 collect_points_to_info_for (ai, orig);
1709 dest_pi = get_ptr_info (dest);
1710 orig_pi = SSA_NAME_PTR_INFO (orig);
1714 /* Notice that we never merge PT_MALLOC. This attribute is only
1715 true if the pointer is the result of a malloc() call.
1716 Otherwise, we can end up in this situation:
1722 P_j would be marked as PT_MALLOC, however we currently do not
1723 handle cases of more than one pointer pointing to the same
1726 FIXME: If the merging comes from an expression that preserves
1727 the PT_MALLOC attribute (copy assignment, address
1728 arithmetic), we ought to merge PT_MALLOC, but then both
1729 pointers would end up getting different name tags because
1730 create_name_tags is not smart enough to determine that the
1731 two come from the same malloc call. Copy propagation before
1732 aliasing should cure this. */
1733 gcc_assert (orig_pi != dest_pi);
1735 dest_pi->pt_malloc = 0;
1737 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1738 set_pt_anything (dest);
1740 if (!dest_pi->pt_anything
1742 && !bitmap_empty_p (orig_pi->pt_vars))
1744 if (dest_pi->pt_vars == NULL)
1746 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1747 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1750 bitmap_ior_into (dest_pi->pt_vars, orig_pi->pt_vars);
1754 set_pt_anything (dest);
1758 /* Add EXPR to the list of expressions pointed-to by PTR. */
1761 add_pointed_to_expr (struct alias_info *ai, tree ptr, tree expr)
1763 if (TREE_CODE (expr) == WITH_SIZE_EXPR)
1764 expr = TREE_OPERAND (expr, 0);
1768 if (TREE_CODE (expr) == CALL_EXPR
1769 && (call_expr_flags (expr) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1771 /* If EXPR is a malloc-like call, then the area pointed to PTR
1772 is guaranteed to not alias with anything else. */
1773 set_pt_malloc (ptr);
1775 else if (TREE_CODE (expr) == ADDR_EXPR)
1777 /* Found P_i = ADDR_EXPR */
1778 add_pointed_to_var (ai, ptr, expr);
1780 else if (TREE_CODE (expr) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (expr)))
1782 /* Found P_i = Q_j. */
1783 merge_pointed_to_info (ai, ptr, expr);
1785 else if (TREE_CODE (expr) == PLUS_EXPR || TREE_CODE (expr) == MINUS_EXPR)
1787 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1788 tree op0 = TREE_OPERAND (expr, 0);
1789 tree op1 = TREE_OPERAND (expr, 1);
1791 /* Both operands may be of pointer type. FIXME: Shouldn't
1792 we just expect PTR + OFFSET always? */
1793 if (POINTER_TYPE_P (TREE_TYPE (op0))
1794 && TREE_CODE (op0) != INTEGER_CST)
1796 if (TREE_CODE (op0) == SSA_NAME)
1797 merge_pointed_to_info (ai, ptr, op0);
1798 else if (TREE_CODE (op0) == ADDR_EXPR)
1799 add_pointed_to_var (ai, ptr, op0);
1801 set_pt_anything (ptr);
1804 if (POINTER_TYPE_P (TREE_TYPE (op1))
1805 && TREE_CODE (op1) != INTEGER_CST)
1807 if (TREE_CODE (op1) == SSA_NAME)
1808 merge_pointed_to_info (ai, ptr, op1);
1809 else if (TREE_CODE (op1) == ADDR_EXPR)
1810 add_pointed_to_var (ai, ptr, op1);
1812 set_pt_anything (ptr);
1815 /* Neither operand is a pointer? VAR can be pointing anywhere.
1816 FIXME: Shouldn't we abort here? If we get here, we found
1817 PTR = INT_CST + INT_CST, which should not be a valid pointer
1819 if (!(POINTER_TYPE_P (TREE_TYPE (op0))
1820 && TREE_CODE (op0) != INTEGER_CST)
1821 && !(POINTER_TYPE_P (TREE_TYPE (op1))
1822 && TREE_CODE (op1) != INTEGER_CST))
1823 set_pt_anything (ptr);
1827 /* If we can't recognize the expression, assume that PTR may
1829 set_pt_anything (ptr);
1834 /* If VALUE is of the form &DECL, add DECL to the set of variables
1835 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1836 PTR. AI is as in collect_points_to_info. */
1839 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1841 struct ptr_info_def *pi = get_ptr_info (ptr);
1845 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
1847 pt_var = TREE_OPERAND (value, 0);
1848 if (REFERENCE_CLASS_P (pt_var))
1849 pt_var = get_base_address (pt_var);
1851 if (pt_var && SSA_VAR_P (pt_var))
1853 uid = var_ann (pt_var)->uid;
1854 bitmap_set_bit (ai->addresses_needed, uid);
1856 if (pi->pt_vars == NULL)
1857 pi->pt_vars = BITMAP_GGC_ALLOC ();
1858 bitmap_set_bit (pi->pt_vars, uid);
1860 /* If the variable is a global, mark the pointer as pointing to
1861 global memory (which will make its tag a global variable). */
1862 if (is_global_var (pt_var))
1863 pi->pt_global_mem = 1;
1868 /* Callback for walk_use_def_chains to gather points-to information from the
1871 VAR is an SSA variable or a GIMPLE expression.
1873 STMT is the statement that generates the SSA variable or, if STMT is a
1874 PHI_NODE, VAR is one of the PHI arguments.
1876 DATA is a pointer to a structure of type ALIAS_INFO. */
1879 collect_points_to_info_r (tree var, tree stmt, void *data)
1881 struct alias_info *ai = (struct alias_info *) data;
1883 if (dump_file && (dump_flags & TDF_DETAILS))
1885 fprintf (dump_file, "Visiting use-def links for ");
1886 print_generic_expr (dump_file, var, dump_flags);
1887 fprintf (dump_file, "\n");
1890 switch (TREE_CODE (stmt))
1893 if (TREE_CODE (TREE_OPERAND (stmt, 0)) != MODIFY_EXPR)
1895 stmt = TREE_OPERAND (stmt, 0);
1900 tree rhs = TREE_OPERAND (stmt, 1);
1902 add_pointed_to_expr (ai, var, rhs);
1907 /* Pointers defined by __asm__ statements can point anywhere. */
1908 set_pt_anything (var);
1912 if (IS_EMPTY_STMT (stmt))
1914 tree decl = SSA_NAME_VAR (var);
1916 if (TREE_CODE (decl) == PARM_DECL)
1917 add_pointed_to_expr (ai, var, decl);
1918 else if (DECL_INITIAL (decl))
1919 add_pointed_to_expr (ai, var, DECL_INITIAL (decl));
1921 add_pointed_to_expr (ai, var, decl);
1927 /* It STMT is a PHI node, then VAR is one of its arguments. The
1928 variable that we are analyzing is the LHS of the PHI node. */
1929 tree lhs = PHI_RESULT (stmt);
1931 switch (TREE_CODE (var))
1934 add_pointed_to_var (ai, lhs, var);
1938 /* Avoid unnecessary merges. */
1940 merge_pointed_to_info (ai, lhs, var);
1944 gcc_assert (is_gimple_min_invariant (var));
1945 add_pointed_to_expr (ai, lhs, var);
1959 /* Return true if STMT is an "escape" site from the current function. Escape
1960 sites those statements which might expose the address of a variable
1961 outside the current function. STMT is an escape site iff:
1963 1- STMT is a function call, or
1964 2- STMT is an __asm__ expression, or
1965 3- STMT is an assignment to a non-local variable, or
1966 4- STMT is a return statement.
1968 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
1972 is_escape_site (tree stmt, size_t *num_calls_p)
1974 if (get_call_expr_in (stmt) != NULL_TREE)
1981 else if (TREE_CODE (stmt) == ASM_EXPR)
1983 else if (TREE_CODE (stmt) == MODIFY_EXPR)
1985 tree lhs = TREE_OPERAND (stmt, 0);
1987 /* Get to the base of _REF nodes. */
1988 if (TREE_CODE (lhs) != SSA_NAME)
1989 lhs = get_base_address (lhs);
1991 /* If we couldn't recognize the LHS of the assignment, assume that it
1992 is a non-local store. */
1993 if (lhs == NULL_TREE)
1996 /* If the LHS is an SSA name, it can't possibly represent a non-local
1998 if (TREE_CODE (lhs) == SSA_NAME)
2001 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2002 local variables we cannot be sure if it will escape, because we
2003 don't have information about objects not in SSA form. Need to
2004 implement something along the lines of
2006 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2007 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2008 Conference on Object-Oriented Programming Systems, Languages, and
2009 Applications (OOPSLA), pp. 1-19, 1999. */
2012 else if (TREE_CODE (stmt) == RETURN_EXPR)
2019 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2020 is considered to represent all the pointers whose pointed-to types are
2021 in the same alias set class. Otherwise, the tag represents a single
2022 SSA_NAME pointer variable. */
2025 create_memory_tag (tree type, bool is_type_tag)
2028 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2030 /* By default, memory tags are local variables. Alias analysis will
2031 determine whether they should be considered globals. */
2032 DECL_CONTEXT (tag) = current_function_decl;
2034 /* Memory tags are by definition addressable. This also prevents
2035 is_gimple_ref frome confusing memory tags with optimizable
2037 TREE_ADDRESSABLE (tag) = 1;
2039 ann = get_var_ann (tag);
2040 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2041 ann->type_mem_tag = NULL_TREE;
2043 /* Add the tag to the symbol table. */
2044 add_referenced_tmp_var (tag);
2050 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2051 This is used if P_i has been found to point to a specific set of
2052 variables or to a non-aliased memory location like the address returned
2053 by malloc functions. */
2056 get_nmt_for (tree ptr)
2058 struct ptr_info_def *pi = get_ptr_info (ptr);
2059 tree tag = pi->name_mem_tag;
2061 if (tag == NULL_TREE)
2062 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2064 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2065 then its name tag should be considered a global variable. */
2066 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2068 || pi->pt_global_mem)
2069 mark_call_clobbered (tag);
2075 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2076 artificial variable that represents the memory location pointed-to by
2077 PTR. It is used to model the effects of pointer de-references on
2078 addressable variables.
2080 AI points to the data gathered during alias analysis. This function
2081 populates the array AI->POINTERS. */
2084 get_tmt_for (tree ptr, struct alias_info *ai)
2088 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2089 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2091 /* To avoid creating unnecessary memory tags, only create one memory tag
2092 per alias set class. Note that it may be tempting to group
2093 memory tags based on conflicting alias sets instead of
2094 equivalence. That would be wrong because alias sets are not
2095 necessarily transitive (as demonstrated by the libstdc++ test
2096 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2097 such that conflicts (A, B) == true and conflicts (A, C) == true,
2098 it does not necessarily follow that conflicts (B, C) == true. */
2099 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2101 struct alias_map_d *curr = ai->pointers[i];
2102 if (tag_set == curr->set)
2104 tag = var_ann (curr->var)->type_mem_tag;
2109 /* If VAR cannot alias with any of the existing memory tags, create a new
2110 tag for PTR and add it to the POINTERS array. */
2111 if (tag == NULL_TREE)
2113 struct alias_map_d *alias_map;
2115 /* If PTR did not have a type tag already, create a new TMT.*
2116 artificial variable representing the memory location
2117 pointed-to by PTR. */
2118 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2119 tag = create_memory_tag (tag_type, true);
2121 tag = var_ann (ptr)->type_mem_tag;
2123 /* Add PTR to the POINTERS array. Note that we are not interested in
2124 PTR's alias set. Instead, we cache the alias set for the memory that
2126 alias_map = xcalloc (1, sizeof (*alias_map));
2127 alias_map->var = ptr;
2128 alias_map->set = tag_set;
2129 ai->pointers[ai->num_pointers++] = alias_map;
2132 /* If the pointed-to type is volatile, so is the tag. */
2133 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
2135 /* Make sure that the type tag has the same alias set as the
2137 gcc_assert (tag_set == get_alias_set (tag));
2143 /* Create GLOBAL_VAR, an artificial global variable to act as a
2144 representative of all the variables that may be clobbered by function
2148 create_global_var (void)
2150 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2152 DECL_ARTIFICIAL (global_var) = 1;
2153 TREE_READONLY (global_var) = 0;
2154 DECL_EXTERNAL (global_var) = 1;
2155 TREE_STATIC (global_var) = 1;
2156 TREE_USED (global_var) = 1;
2157 DECL_CONTEXT (global_var) = NULL_TREE;
2158 TREE_THIS_VOLATILE (global_var) = 0;
2159 TREE_ADDRESSABLE (global_var) = 0;
2161 add_referenced_tmp_var (global_var);
2162 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2166 /* Dump alias statistics on FILE. */
2169 dump_alias_stats (FILE *file)
2171 const char *funcname
2172 = lang_hooks.decl_printable_name (current_function_decl, 2);
2173 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2174 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2175 fprintf (file, "Total alias mayalias results:\t%u\n",
2176 alias_stats.alias_mayalias);
2177 fprintf (file, "Total alias noalias results:\t%u\n",
2178 alias_stats.alias_noalias);
2179 fprintf (file, "Total simple queries:\t%u\n",
2180 alias_stats.simple_queries);
2181 fprintf (file, "Total simple resolved:\t%u\n",
2182 alias_stats.simple_resolved);
2183 fprintf (file, "Total TBAA queries:\t%u\n",
2184 alias_stats.tbaa_queries);
2185 fprintf (file, "Total TBAA resolved:\t%u\n",
2186 alias_stats.tbaa_resolved);
2190 /* Dump alias information on FILE. */
2193 dump_alias_info (FILE *file)
2196 const char *funcname
2197 = lang_hooks.decl_printable_name (current_function_decl, 2);
2199 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2201 fprintf (file, "Aliased symbols\n\n");
2202 for (i = 0; i < num_referenced_vars; i++)
2204 tree var = referenced_var (i);
2205 if (may_be_aliased (var))
2206 dump_variable (file, var);
2209 fprintf (file, "\nDereferenced pointers\n\n");
2210 for (i = 0; i < num_referenced_vars; i++)
2212 tree var = referenced_var (i);
2213 var_ann_t ann = var_ann (var);
2214 if (ann->type_mem_tag)
2215 dump_variable (file, var);
2218 fprintf (file, "\nType memory tags\n\n");
2219 for (i = 0; i < num_referenced_vars; i++)
2221 tree var = referenced_var (i);
2222 var_ann_t ann = var_ann (var);
2223 if (ann->mem_tag_kind == TYPE_TAG)
2224 dump_variable (file, var);
2227 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2229 fprintf (file, "SSA_NAME pointers\n\n");
2230 for (i = 1; i < num_ssa_names; i++)
2232 tree ptr = ssa_name (i);
2233 struct ptr_info_def *pi;
2235 if (ptr == NULL_TREE)
2238 pi = SSA_NAME_PTR_INFO (ptr);
2239 if (!SSA_NAME_IN_FREE_LIST (ptr)
2241 && pi->name_mem_tag)
2242 dump_points_to_info_for (file, ptr);
2245 fprintf (file, "\nName memory tags\n\n");
2246 for (i = 0; i < num_referenced_vars; i++)
2248 tree var = referenced_var (i);
2249 var_ann_t ann = var_ann (var);
2250 if (ann->mem_tag_kind == NAME_TAG)
2251 dump_variable (file, var);
2254 fprintf (file, "\n");
2258 /* Dump alias information on stderr. */
2261 debug_alias_info (void)
2263 dump_alias_info (stderr);
2267 /* Return the alias information associated with pointer T. It creates a
2268 new instance if none existed. */
2270 struct ptr_info_def *
2271 get_ptr_info (tree t)
2273 struct ptr_info_def *pi;
2275 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2277 pi = SSA_NAME_PTR_INFO (t);
2280 pi = ggc_alloc (sizeof (*pi));
2281 memset ((void *)pi, 0, sizeof (*pi));
2282 SSA_NAME_PTR_INFO (t) = pi;
2289 /* Dump points-to information for SSA_NAME PTR into FILE. */
2292 dump_points_to_info_for (FILE *file, tree ptr)
2294 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2296 print_generic_expr (file, ptr, dump_flags);
2300 if (pi->name_mem_tag)
2302 fprintf (file, ", name memory tag: ");
2303 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2306 if (pi->is_dereferenced)
2307 fprintf (file, ", is dereferenced");
2309 if (pi->value_escapes_p)
2310 fprintf (file, ", its value escapes");
2312 if (pi->pt_anything)
2313 fprintf (file, ", points-to anything");
2316 fprintf (file, ", points-to malloc");
2323 fprintf (file, ", points-to vars: { ");
2324 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2326 print_generic_expr (file, referenced_var (ix), dump_flags);
2327 fprintf (file, " ");
2329 fprintf (file, "}");
2333 fprintf (file, "\n");
2337 /* Dump points-to information for VAR into stderr. */
2340 debug_points_to_info_for (tree var)
2342 dump_points_to_info_for (stderr, var);
2346 /* Dump points-to information into FILE. NOTE: This function is slow, as
2347 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2350 dump_points_to_info (FILE *file)
2353 block_stmt_iterator si;
2357 lang_hooks.decl_printable_name (current_function_decl, 2);
2359 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2361 /* First dump points-to information for the default definitions of
2362 pointer variables. This is necessary because default definitions are
2363 not part of the code. */
2364 for (i = 0; i < num_referenced_vars; i++)
2366 tree var = referenced_var (i);
2367 if (POINTER_TYPE_P (TREE_TYPE (var)))
2369 var_ann_t ann = var_ann (var);
2370 if (ann->default_def)
2371 dump_points_to_info_for (file, ann->default_def);
2375 /* Dump points-to information for every pointer defined in the program. */
2380 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2382 tree ptr = PHI_RESULT (phi);
2383 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2384 dump_points_to_info_for (file, ptr);
2387 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2389 tree stmt = bsi_stmt (si);
2391 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2392 if (POINTER_TYPE_P (TREE_TYPE (def)))
2393 dump_points_to_info_for (file, def);
2397 fprintf (file, "\n");
2401 /* Dump points-to info pointed by PTO into STDERR. */
2404 debug_points_to_info (void)
2406 dump_points_to_info (stderr);
2409 /* Dump to FILE the list of variables that may be aliasing VAR. */
2412 dump_may_aliases_for (FILE *file, tree var)
2414 varray_type aliases;
2416 if (TREE_CODE (var) == SSA_NAME)
2417 var = SSA_NAME_VAR (var);
2419 aliases = var_ann (var)->may_aliases;
2423 fprintf (file, "{ ");
2424 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2426 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2427 fprintf (file, " ");
2429 fprintf (file, "}");
2434 /* Dump to stderr the list of variables that may be aliasing VAR. */
2437 debug_may_aliases_for (tree var)
2439 dump_may_aliases_for (stderr, var);
2442 /* Return true if VAR may be aliased. */
2445 may_be_aliased (tree var)
2448 if (TREE_ADDRESSABLE (var))
2451 /* Globally visible variables can have their addresses taken by other
2452 translation units. */
2453 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2456 /* Automatic variables can't have their addresses escape any other way.
2457 This must be after the check for global variables, as extern declarations
2458 do not have TREE_STATIC set. */
2459 if (!TREE_STATIC (var))
2462 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2463 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2464 we can only be sure the variable isn't addressable if it's local to the
2465 current function. */
2466 if (flag_unit_at_a_time)
2468 if (decl_function_context (var) == current_function_decl)