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)
442 /* Clear the call-clobbered set. We are going to re-discover
443 call-clobbered variables. */
444 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
446 tree var = referenced_var (i);
448 /* Variables that are intrinsically call-clobbered (globals,
449 local statics, etc) will not be marked by the aliasing
450 code, so we can't remove them from CALL_CLOBBERED_VARS. */
451 if (!is_call_clobbered (var))
452 bitmap_clear_bit (call_clobbered_vars, var_ann (var)->uid);
455 /* Similarly, clear the set of addressable variables. In this
456 case, we can just clear the set because addressability is
457 only computed here. */
458 bitmap_clear (addressable_vars);
460 /* Clear flow-insensitive alias information from each symbol. */
461 for (i = 0; i < num_referenced_vars; i++)
463 var_ann_t ann = var_ann (referenced_var (i));
464 ann->is_alias_tag = 0;
465 ann->may_aliases = NULL;
468 /* Clear flow-sensitive points-to information from each SSA name. */
469 for (i = 1; i < num_ssa_names; i++)
471 tree name = ssa_name (i);
473 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
476 if (SSA_NAME_PTR_INFO (name))
478 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
480 /* Clear all the flags but keep the name tag to
481 avoid creating new temporaries unnecessarily. If
482 this pointer is found to point to a subset or
483 superset of its former points-to set, then a new
484 tag will need to be created in create_name_tags. */
487 pi->value_escapes_p = 0;
488 pi->is_dereferenced = 0;
490 bitmap_clear (pi->pt_vars);
495 /* Next time, we will need to reset alias information. */
496 aliases_computed_p = true;
502 /* Deallocate memory used by alias analysis. */
505 delete_alias_info (struct alias_info *ai)
509 sbitmap_free (ai->ssa_names_visited);
510 ai->processed_ptrs = NULL;
511 BITMAP_XFREE (ai->addresses_needed);
513 for (i = 0; i < ai->num_addressable_vars; i++)
515 sbitmap_free (ai->addressable_vars[i]->may_aliases);
516 free (ai->addressable_vars[i]);
518 free (ai->addressable_vars);
520 for (i = 0; i < ai->num_pointers; i++)
522 sbitmap_free (ai->pointers[i]->may_aliases);
523 free (ai->pointers[i]);
527 ai->num_references = NULL;
528 BITMAP_XFREE (ai->written_vars);
529 BITMAP_XFREE (ai->dereferenced_ptrs_store);
530 BITMAP_XFREE (ai->dereferenced_ptrs_load);
536 /* Walk use-def chains for pointer PTR to determine what variables is PTR
540 collect_points_to_info_for (struct alias_info *ai, tree ptr)
542 gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr)));
544 if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)))
546 SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr));
547 walk_use_def_chains (ptr, collect_points_to_info_r, ai, true);
548 VARRAY_PUSH_TREE (ai->processed_ptrs, ptr);
553 /* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
554 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
557 find_ptr_dereference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
559 tree ptr = (tree) data;
561 if (INDIRECT_REF_P (*tp)
562 && TREE_OPERAND (*tp, 0) == ptr)
569 /* Return true if STMT contains (ALIGN/MISALIGNED_)INDIRECT_REF <PTR>.
570 *IS_STORE is set to 'true' if the dereference is on the LHS of an
574 ptr_is_dereferenced_by (tree ptr, tree stmt, bool *is_store)
578 if (TREE_CODE (stmt) == MODIFY_EXPR
579 || (TREE_CODE (stmt) == RETURN_EXPR
580 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR))
584 e = (TREE_CODE (stmt) == RETURN_EXPR) ? TREE_OPERAND (stmt, 0) : stmt;
585 lhs = TREE_OPERAND (e, 0);
586 rhs = TREE_OPERAND (e, 1);
589 && walk_tree (&lhs, find_ptr_dereference, ptr, NULL))
594 else if (EXPR_P (rhs)
595 && walk_tree (&rhs, find_ptr_dereference, ptr, NULL))
600 else if (TREE_CODE (stmt) == ASM_EXPR)
602 if (walk_tree (&ASM_OUTPUTS (stmt), find_ptr_dereference, ptr, NULL)
603 || walk_tree (&ASM_CLOBBERS (stmt), find_ptr_dereference, ptr, NULL))
608 else if (walk_tree (&ASM_INPUTS (stmt), find_ptr_dereference, ptr, NULL))
618 /* Traverse use-def links for all the pointers in the program to collect
619 address escape and points-to information.
621 This is loosely based on the same idea described in R. Hasti and S.
622 Horwitz, ``Using static single assignment form to improve
623 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
624 Programming Language Design and Implementation, pp. 97-105, 1998. */
627 compute_points_to_and_addr_escape (struct alias_info *ai)
634 timevar_push (TV_TREE_PTA);
638 bb_ann_t block_ann = bb_ann (bb);
639 block_stmt_iterator si;
641 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
644 tree stmt = bsi_stmt (si);
645 bool stmt_escapes_p = is_escape_site (stmt, &ai->num_calls_found);
648 /* Mark all the variables whose address are taken by the
649 statement. Note that this will miss all the addresses taken
650 in PHI nodes (those are discovered while following the use-def
652 get_stmt_operands (stmt);
653 addr_taken = addresses_taken (stmt);
655 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
657 tree var = referenced_var (i);
658 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
660 mark_call_clobbered (var);
664 block_ann->has_escape_site = 1;
666 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
668 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
669 struct ptr_info_def *pi;
672 /* If the operand's variable may be aliased, keep track
673 of how many times we've referenced it. This is used
674 for alias grouping in compute_flow_sensitive_aliasing.
675 Note that we don't need to grow AI->NUM_REFERENCES
676 because we are processing regular variables, not
677 memory tags (the array's initial size is set to
678 NUM_REFERENCED_VARS). */
679 if (may_be_aliased (SSA_NAME_VAR (op)))
680 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
682 if (!POINTER_TYPE_P (TREE_TYPE (op)))
685 collect_points_to_info_for (ai, op);
687 pi = SSA_NAME_PTR_INFO (op);
688 if (ptr_is_dereferenced_by (op, stmt, &is_store))
690 /* Mark OP as dereferenced. In a subsequent pass,
691 dereferenced pointers that point to a set of
692 variables will be assigned a name tag to alias
693 all the variables OP points to. */
694 pi->is_dereferenced = 1;
696 /* Keep track of how many time we've dereferenced each
697 pointer. Again, we don't need to grow
698 AI->NUM_REFERENCES because we're processing
699 existing program variables. */
700 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
702 /* If this is a store operation, mark OP as being
703 dereferenced to store, otherwise mark it as being
704 dereferenced to load. */
706 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
708 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
710 else if (stmt_escapes_p)
712 /* Note that even if STMT is an escape point, pointer OP
713 will not escape if it is being dereferenced. That's
714 why we only check for escape points if OP is not
715 dereferenced by STMT. */
716 pi->value_escapes_p = 1;
718 /* If the statement makes a function call, assume
719 that pointer OP will be dereferenced in a store
720 operation inside the called function. */
721 if (get_call_expr_in (stmt))
723 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
724 pi->is_dereferenced = 1;
729 /* Update reference counter for definitions to any
730 potentially aliased variable. This is used in the alias
731 grouping heuristics. */
732 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
734 tree var = SSA_NAME_VAR (op);
735 var_ann_t ann = var_ann (var);
736 bitmap_set_bit (ai->written_vars, ann->uid);
737 if (may_be_aliased (var))
738 (VARRAY_UINT (ai->num_references, ann->uid))++;
740 if (POINTER_TYPE_P (TREE_TYPE (op)))
741 collect_points_to_info_for (ai, op);
744 /* Mark variables in V_MAY_DEF operands as being written to. */
745 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
747 tree var = SSA_NAME_VAR (op);
748 var_ann_t ann = var_ann (var);
749 bitmap_set_bit (ai->written_vars, ann->uid);
752 /* After promoting variables and computing aliasing we will
753 need to re-scan most statements. FIXME: Try to minimize the
754 number of statements re-scanned. It's not really necessary to
755 re-scan *all* statements. */
760 timevar_pop (TV_TREE_PTA);
764 /* Create name tags for all the pointers that have been dereferenced.
765 We only create a name tag for a pointer P if P is found to point to
766 a set of variables (so that we can alias them to *P) or if it is
767 the result of a call to malloc (which means that P cannot point to
768 anything else nor alias any other variable).
770 If two pointers P and Q point to the same set of variables, they
771 are assigned the same name tag. */
774 create_name_tags (struct alias_info *ai)
778 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
780 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
781 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
783 if (pi->pt_anything || !pi->is_dereferenced)
785 /* No name tags for pointers that have not been
786 dereferenced or point to an arbitrary location. */
787 pi->name_mem_tag = NULL_TREE;
791 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
794 tree old_name_tag = pi->name_mem_tag;
796 /* If PTR points to a set of variables, check if we don't
797 have another pointer Q with the same points-to set before
798 creating a tag. If so, use Q's tag instead of creating a
801 This is important for not creating unnecessary symbols
802 and also for copy propagation. If we ever need to
803 propagate PTR into Q or vice-versa, we would run into
804 problems if they both had different name tags because
805 they would have different SSA version numbers (which
806 would force us to take the name tags in and out of SSA). */
807 for (j = 0; j < i; j++)
809 tree q = VARRAY_TREE (ai->processed_ptrs, j);
810 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
815 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
817 pi->name_mem_tag = qi->name_mem_tag;
822 /* If we didn't find a pointer with the same points-to set
823 as PTR, create a new name tag if needed. */
824 if (pi->name_mem_tag == NULL_TREE)
825 pi->name_mem_tag = get_nmt_for (ptr);
827 /* If the new name tag computed for PTR is different than
828 the old name tag that it used to have, then the old tag
829 needs to be removed from the IL, so we mark it for
831 if (old_name_tag && old_name_tag != pi->name_mem_tag)
832 bitmap_set_bit (vars_to_rename, var_ann (old_name_tag)->uid);
834 else if (pi->pt_malloc)
836 /* Otherwise, create a unique name tag for this pointer. */
837 pi->name_mem_tag = get_nmt_for (ptr);
841 /* Only pointers that may point to malloc or other variables
842 may receive a name tag. If the pointer does not point to
843 a known spot, we should use type tags. */
844 set_pt_anything (ptr);
848 TREE_THIS_VOLATILE (pi->name_mem_tag)
849 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
851 /* Mark the new name tag for renaming. */
852 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
858 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
859 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
860 name tag and the variables it points-to are call-clobbered. Finally, if
861 P_i escapes and we could not determine where it points to, then all the
862 variables in the same alias set as *P_i are marked call-clobbered. This
863 is necessary because we must assume that P_i may take the address of any
864 variable in the same alias set. */
867 compute_flow_sensitive_aliasing (struct alias_info *ai)
871 create_name_tags (ai);
873 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
876 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
877 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
878 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
881 if (pi->value_escapes_p || pi->pt_anything)
883 /* If PTR escapes or may point to anything, then its associated
884 memory tags and pointed-to variables are call-clobbered. */
885 if (pi->name_mem_tag)
886 mark_call_clobbered (pi->name_mem_tag);
888 if (v_ann->type_mem_tag)
889 mark_call_clobbered (v_ann->type_mem_tag);
892 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
894 mark_call_clobbered (referenced_var (j));
898 /* Set up aliasing information for PTR's name memory tag (if it has
899 one). Note that only pointers that have been dereferenced will
900 have a name memory tag. */
901 if (pi->name_mem_tag && pi->pt_vars)
902 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
904 add_may_alias (pi->name_mem_tag, referenced_var (j));
907 /* If the name tag is call clobbered, so is the type tag
908 associated with the base VAR_DECL. */
910 && v_ann->type_mem_tag
911 && is_call_clobbered (pi->name_mem_tag))
912 mark_call_clobbered (v_ann->type_mem_tag);
917 /* Compute type-based alias sets. Traverse all the pointers and
918 addressable variables found in setup_pointers_and_addressables.
920 For every pointer P in AI->POINTERS and addressable variable V in
921 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
922 memory tag (TMT) if their alias sets conflict. V is then marked as
923 an alias tag so that the operand scanner knows that statements
924 containing V have aliased operands. */
927 compute_flow_insensitive_aliasing (struct alias_info *ai)
932 /* Initialize counter for the total number of virtual operands that
933 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
934 threshold set by --params max-alias-vops, we enable alias
936 ai->total_alias_vops = 0;
938 /* For every pointer P, determine which addressable variables may alias
939 with P's type memory tag. */
940 for (i = 0; i < ai->num_pointers; i++)
943 struct alias_map_d *p_map = ai->pointers[i];
944 tree tag = var_ann (p_map->var)->type_mem_tag;
945 var_ann_t tag_ann = var_ann (tag);
947 p_map->total_alias_vops = 0;
948 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
949 sbitmap_zero (p_map->may_aliases);
951 for (j = 0; j < ai->num_addressable_vars; j++)
953 struct alias_map_d *v_map;
956 bool tag_stored_p, var_stored_p;
958 v_map = ai->addressable_vars[j];
960 v_ann = var_ann (var);
962 /* Skip memory tags and variables that have never been
963 written to. We also need to check if the variables are
964 call-clobbered because they may be overwritten by
967 Note this is effectively random accessing elements in
968 the sparse bitset, which can be highly inefficient.
969 So we first check the call_clobbered status of the
970 tag and variable before querying the bitmap. */
971 tag_stored_p = is_call_clobbered (tag)
972 || bitmap_bit_p (ai->written_vars, tag_ann->uid);
973 var_stored_p = is_call_clobbered (var)
974 || bitmap_bit_p (ai->written_vars, v_ann->uid);
975 if (!tag_stored_p && !var_stored_p)
978 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
980 size_t num_tag_refs, num_var_refs;
982 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
983 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
985 /* Add VAR to TAG's may-aliases set. */
986 add_may_alias (tag, var);
988 /* Update the total number of virtual operands due to
989 aliasing. Since we are adding one more alias to TAG's
990 may-aliases set, the total number of virtual operands due
991 to aliasing will be increased by the number of references
992 made to VAR and TAG (every reference to TAG will also
993 count as a reference to VAR). */
994 ai->total_alias_vops += (num_var_refs + num_tag_refs);
995 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
997 /* Update the bitmap used to represent TAG's alias set
998 in case we need to group aliases. */
999 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
1004 /* Since this analysis is based exclusively on symbols, it fails to
1005 handle cases where two pointers P and Q have different memory
1006 tags with conflicting alias set numbers but no aliased symbols in
1009 For example, suppose that we have two memory tags TMT.1 and TMT.2
1012 may-aliases (TMT.1) = { a }
1013 may-aliases (TMT.2) = { b }
1015 and the alias set number of TMT.1 conflicts with that of TMT.2.
1016 Since they don't have symbols in common, loads and stores from
1017 TMT.1 and TMT.2 will seem independent of each other, which will
1018 lead to the optimizers making invalid transformations (see
1019 testsuite/gcc.c-torture/execute/pr15262-[12].c).
1021 To avoid this problem, we do a final traversal of AI->POINTERS
1022 looking for pairs of pointers that have no aliased symbols in
1023 common and yet have conflicting alias set numbers. */
1024 res = sbitmap_alloc (num_referenced_vars);
1026 for (i = 0; i < ai->num_pointers; i++)
1029 struct alias_map_d *p_map1 = ai->pointers[i];
1030 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
1031 sbitmap may_aliases1 = p_map1->may_aliases;
1033 for (j = i + 1; j < ai->num_pointers; j++)
1035 struct alias_map_d *p_map2 = ai->pointers[j];
1036 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
1037 sbitmap may_aliases2 = p_map2->may_aliases;
1039 /* If the pointers may not point to each other, do nothing. */
1040 if (!may_alias_p (p_map1->var, p_map1->set, p_map2->var, p_map2->set))
1043 /* The two pointers may alias each other. If they already have
1044 symbols in common, do nothing. */
1045 sbitmap_a_and_b (res, may_aliases1, may_aliases2);
1046 if (sbitmap_first_set_bit (res) >= 0)
1049 if (sbitmap_first_set_bit (may_aliases2) >= 0)
1053 /* Add all the aliases for TAG2 into TAG1's alias set.
1054 FIXME, update grouping heuristic counters. */
1055 EXECUTE_IF_SET_IN_SBITMAP (may_aliases2, 0, k,
1056 add_may_alias (tag1, referenced_var (k)));
1057 sbitmap_a_or_b (may_aliases1, may_aliases1, may_aliases2);
1061 /* Since TAG2 does not have any aliases of its own, add
1062 TAG2 itself to the alias set of TAG1. */
1063 add_may_alias (tag1, tag2);
1071 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
1072 get_name (current_function_decl),
1073 ai->total_alias_vops);
1075 /* Determine if we need to enable alias grouping. */
1076 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
1081 /* Comparison function for qsort used in group_aliases. */
1084 total_alias_vops_cmp (const void *p, const void *q)
1086 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1087 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1088 long n1 = (*p1)->total_alias_vops;
1089 long n2 = (*p2)->total_alias_vops;
1091 /* We want to sort in descending order. */
1092 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1095 /* Group all the aliases for TAG to make TAG represent all the
1096 variables in its alias set. Update the total number
1097 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1098 function will make TAG be the unique alias tag for all the
1099 variables in its may-aliases. So, given:
1101 may-aliases(TAG) = { V1, V2, V3 }
1103 This function will group the variables into:
1105 may-aliases(V1) = { TAG }
1106 may-aliases(V2) = { TAG }
1107 may-aliases(V2) = { TAG } */
1110 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
1113 var_ann_t tag_ann = var_ann (tag);
1114 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1116 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
1118 tree var = referenced_var (i);
1119 var_ann_t ann = var_ann (var);
1121 /* Make TAG the unique alias of VAR. */
1122 ann->is_alias_tag = 0;
1123 ann->may_aliases = NULL;
1125 /* Note that VAR and TAG may be the same if the function has no
1126 addressable variables (see the discussion at the end of
1127 setup_pointers_and_addressables). */
1129 add_may_alias (var, tag);
1131 /* Reduce total number of virtual operands contributed
1132 by TAG on behalf of VAR. Notice that the references to VAR
1133 itself won't be removed. We will merely replace them with
1134 references to TAG. */
1135 ai->total_alias_vops -= num_tag_refs;
1138 /* We have reduced the number of virtual operands that TAG makes on
1139 behalf of all the variables formerly aliased with it. However,
1140 we have also "removed" all the virtual operands for TAG itself,
1141 so we add them back. */
1142 ai->total_alias_vops += num_tag_refs;
1144 /* TAG no longer has any aliases. */
1145 tag_ann->may_aliases = NULL;
1149 /* Group may-aliases sets to reduce the number of virtual operands due
1152 1- Sort the list of pointers in decreasing number of contributed
1155 2- Take the first entry in AI->POINTERS and revert the role of
1156 the memory tag and its aliases. Usually, whenever an aliased
1157 variable Vi is found to alias with a memory tag T, we add Vi
1158 to the may-aliases set for T. Meaning that after alias
1159 analysis, we will have:
1161 may-aliases(T) = { V1, V2, V3, ..., Vn }
1163 This means that every statement that references T, will get 'n'
1164 virtual operands for each of the Vi tags. But, when alias
1165 grouping is enabled, we make T an alias tag and add it to the
1166 alias set of all the Vi variables:
1168 may-aliases(V1) = { T }
1169 may-aliases(V2) = { T }
1171 may-aliases(Vn) = { T }
1173 This has two effects: (a) statements referencing T will only get
1174 a single virtual operand, and, (b) all the variables Vi will now
1175 appear to alias each other. So, we lose alias precision to
1176 improve compile time. But, in theory, a program with such a high
1177 level of aliasing should not be very optimizable in the first
1180 3- Since variables may be in the alias set of more than one
1181 memory tag, the grouping done in step (2) needs to be extended
1182 to all the memory tags that have a non-empty intersection with
1183 the may-aliases set of tag T. For instance, if we originally
1184 had these may-aliases sets:
1186 may-aliases(T) = { V1, V2, V3 }
1187 may-aliases(R) = { V2, V4 }
1189 In step (2) we would have reverted the aliases for T as:
1191 may-aliases(V1) = { T }
1192 may-aliases(V2) = { T }
1193 may-aliases(V3) = { T }
1195 But note that now V2 is no longer aliased with R. We could
1196 add R to may-aliases(V2), but we are in the process of
1197 grouping aliases to reduce virtual operands so what we do is
1198 add V4 to the grouping to obtain:
1200 may-aliases(V1) = { T }
1201 may-aliases(V2) = { T }
1202 may-aliases(V3) = { T }
1203 may-aliases(V4) = { T }
1205 4- If the total number of virtual operands due to aliasing is
1206 still above the threshold set by max-alias-vops, go back to (2). */
1209 group_aliases (struct alias_info *ai)
1214 /* Sort the POINTERS array in descending order of contributed
1215 virtual operands. */
1216 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1217 total_alias_vops_cmp);
1219 res = sbitmap_alloc (num_referenced_vars);
1221 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1222 and the tag's may-aliases set. */
1223 for (i = 0; i < ai->num_pointers; i++)
1226 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1227 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1229 /* Skip tags that have been grouped already. */
1230 if (ai->pointers[i]->grouped_p)
1233 /* See if TAG1 had any aliases in common with other type tags.
1234 If we find a TAG2 with common aliases with TAG1, add TAG2's
1235 aliases into TAG1. */
1236 for (j = i + 1; j < ai->num_pointers; j++)
1238 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1240 sbitmap_a_and_b (res, tag1_aliases, tag2_aliases);
1241 if (sbitmap_first_set_bit (res) >= 0)
1243 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1245 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1247 /* TAG2 does not need its aliases anymore. */
1248 sbitmap_zero (tag2_aliases);
1249 var_ann (tag2)->may_aliases = NULL;
1251 /* TAG1 is the unique alias of TAG2. */
1252 add_may_alias (tag2, tag1);
1254 ai->pointers[j]->grouped_p = true;
1258 /* Now group all the aliases we collected into TAG1. */
1259 group_aliases_into (tag1, tag1_aliases, ai);
1261 /* If we've reduced total number of virtual operands below the
1263 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1267 /* Finally, all the variables that have been grouped cannot be in
1268 the may-alias set of name memory tags. Suppose that we have
1269 grouped the aliases in this code so that may-aliases(a) = TMT.20
1273 # a_9 = V_MAY_DEF <a_8>
1275 ... Several modifications to TMT.20 ...
1279 Since p_5 points to 'a', the optimizers will try to propagate 0
1280 into p_5->field, but that is wrong because there have been
1281 modifications to 'TMT.20' in between. To prevent this we have to
1282 replace 'a' with 'TMT.20' in the name tag of p_5. */
1283 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1286 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1287 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1288 varray_type aliases;
1290 if (name_tag == NULL_TREE)
1293 aliases = var_ann (name_tag)->may_aliases;
1294 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1296 tree alias = VARRAY_TREE (aliases, j);
1297 var_ann_t ann = var_ann (alias);
1299 if (ann->mem_tag_kind == NOT_A_TAG && ann->may_aliases)
1303 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1305 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1306 replace_may_alias (name_tag, j, new_alias);
1315 "%s: Total number of aliased vops after grouping: %ld%s\n",
1316 get_name (current_function_decl),
1317 ai->total_alias_vops,
1318 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1322 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1325 create_alias_map_for (tree var, struct alias_info *ai)
1327 struct alias_map_d *alias_map;
1328 alias_map = xcalloc (1, sizeof (*alias_map));
1329 alias_map->var = var;
1330 alias_map->set = get_alias_set (var);
1331 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1335 /* Create memory tags for all the dereferenced pointers and build the
1336 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1337 sets. Based on the address escape and points-to information collected
1338 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1339 variables whose address is not needed anymore. */
1342 setup_pointers_and_addressables (struct alias_info *ai)
1344 size_t i, n_vars, num_addressable_vars, num_pointers;
1346 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1347 num_addressable_vars = num_pointers = 0;
1348 for (i = 0; i < num_referenced_vars; i++)
1350 tree var = referenced_var (i);
1352 if (may_be_aliased (var))
1353 num_addressable_vars++;
1355 if (POINTER_TYPE_P (TREE_TYPE (var)))
1357 /* Since we don't keep track of volatile variables, assume that
1358 these pointers are used in indirect store operations. */
1359 if (TREE_THIS_VOLATILE (var))
1360 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1366 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1367 always going to be slightly bigger than we actually need them
1368 because some TREE_ADDRESSABLE variables will be marked
1369 non-addressable below and only pointers with unique type tags are
1370 going to be added to POINTERS. */
1371 ai->addressable_vars = xcalloc (num_addressable_vars,
1372 sizeof (struct alias_map_d *));
1373 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1374 ai->num_addressable_vars = 0;
1375 ai->num_pointers = 0;
1377 /* Since we will be creating type memory tags within this loop, cache the
1378 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1380 n_vars = num_referenced_vars;
1382 for (i = 0; i < n_vars; i++)
1384 tree var = referenced_var (i);
1385 var_ann_t v_ann = var_ann (var);
1387 /* Name memory tags already have flow-sensitive aliasing
1388 information, so they need not be processed by
1389 compute_flow_insensitive_aliasing. Similarly, type memory
1390 tags are already accounted for when we process their
1391 associated pointer. */
1392 if (v_ann->mem_tag_kind != NOT_A_TAG)
1395 /* Remove the ADDRESSABLE flag from every addressable variable whose
1396 address is not needed anymore. This is caused by the propagation
1397 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1398 removal of dead pointer assignments done by the early scalar
1400 if (TREE_ADDRESSABLE (var))
1402 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1403 && v_ann->mem_tag_kind == NOT_A_TAG
1404 && TREE_CODE (var) != RESULT_DECL
1405 && !is_global_var (var))
1407 /* The address of VAR is not needed, remove the
1408 addressable bit, so that it can be optimized as a
1409 regular variable. */
1410 mark_non_addressable (var);
1412 /* Since VAR is now a regular GIMPLE register, we will need
1413 to rename VAR into SSA afterwards. */
1414 bitmap_set_bit (vars_to_rename, v_ann->uid);
1418 /* Add the variable to the set of addressables. Mostly
1419 used when scanning operands for ASM_EXPRs that
1420 clobber memory. In those cases, we need to clobber
1421 all call-clobbered variables and all addressables. */
1422 bitmap_set_bit (addressable_vars, v_ann->uid);
1426 /* Global variables and addressable locals may be aliased. Create an
1427 entry in ADDRESSABLE_VARS for VAR. */
1428 if (may_be_aliased (var))
1430 create_alias_map_for (var, ai);
1431 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1434 /* Add pointer variables that have been dereferenced to the POINTERS
1435 array and create a type memory tag for them. */
1436 if (POINTER_TYPE_P (TREE_TYPE (var)))
1438 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1439 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1444 /* If pointer VAR still doesn't have a memory tag
1445 associated with it, create it now or re-use an
1447 tag = get_tmt_for (var, ai);
1448 t_ann = var_ann (tag);
1450 /* The type tag will need to be renamed into SSA
1451 afterwards. Note that we cannot do this inside
1452 get_tmt_for because aliasing may run multiple times
1453 and we only create type tags the first time. */
1454 bitmap_set_bit (vars_to_rename, t_ann->uid);
1456 /* Associate the tag with pointer VAR. */
1457 v_ann->type_mem_tag = tag;
1459 /* If pointer VAR has been used in a store operation,
1460 then its memory tag must be marked as written-to. */
1461 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1462 bitmap_set_bit (ai->written_vars, t_ann->uid);
1464 /* If pointer VAR is a global variable or a PARM_DECL,
1465 then its memory tag should be considered a global
1467 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1468 mark_call_clobbered (tag);
1470 /* All the dereferences of pointer VAR count as
1471 references of TAG. Since TAG can be associated with
1472 several pointers, add the dereferences of VAR to the
1473 TAG. We may need to grow AI->NUM_REFERENCES because
1474 we have been adding name and type tags. */
1475 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1476 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1478 VARRAY_UINT (ai->num_references, t_ann->uid)
1479 += VARRAY_UINT (ai->num_references, v_ann->uid);
1483 /* The pointer has not been dereferenced. If it had a
1484 type memory tag, remove it and mark the old tag for
1485 renaming to remove it out of the IL. */
1486 var_ann_t ann = var_ann (var);
1487 tree tag = ann->type_mem_tag;
1490 bitmap_set_bit (vars_to_rename, var_ann (tag)->uid);
1491 ann->type_mem_tag = NULL_TREE;
1499 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1500 every call site, we need to emit V_MAY_DEF expressions to represent the
1501 clobbering effects of the call for variables whose address escapes the
1504 One approach is to group all call-clobbered variables into a single
1505 representative that is used as an alias of every call-clobbered variable
1506 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1507 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1509 The second approach is to emit a clobbering V_MAY_DEF for every
1510 call-clobbered variable at call sites. This is the preferred way in terms
1511 of optimization opportunities but it may create too many V_MAY_DEF operands
1512 if there are many call clobbered variables and function calls in the
1515 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1516 function calls found by the number of call-clobbered variables. If that
1517 product is beyond a certain threshold, as determined by the parameterized
1518 values shown below, we use .GLOBAL_VAR.
1520 FIXME. This heuristic should be improved. One idea is to use several
1521 .GLOBAL_VARs of different types instead of a single one. The thresholds
1522 have been derived from a typical bootstrap cycle, including all target
1523 libraries. Compile times were found increase by ~1% compared to using
1527 maybe_create_global_var (struct alias_info *ai)
1529 unsigned i, n_clobbered;
1532 /* No need to create it, if we have one already. */
1533 if (global_var == NULL_TREE)
1535 /* Count all the call-clobbered variables. */
1537 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1542 /* Create .GLOBAL_VAR if we have too many call-clobbered
1543 variables. We also create .GLOBAL_VAR when there no
1544 call-clobbered variables to prevent code motion
1545 transformations from re-arranging function calls that may
1546 have side effects. For instance,
1555 There are no call-clobbered variables in foo(), so it would
1556 be entirely possible for a pass to want to move the call to
1557 f() after the call to g(). If f() has side effects, that
1558 would be wrong. Creating .GLOBAL_VAR in this case will
1559 insert VDEFs for it and prevent such transformations. */
1560 if (n_clobbered == 0
1561 || ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD)
1562 create_global_var ();
1565 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1566 been created, make it an alias for all call-clobbered variables. */
1568 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1570 tree var = referenced_var (i);
1571 if (var != global_var)
1573 add_may_alias (var, global_var);
1574 bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
1580 /* Return TRUE if pointer PTR may point to variable VAR.
1582 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1583 This is needed because when checking for type conflicts we are
1584 interested in the alias set of the memory location pointed-to by
1585 PTR. The alias set of PTR itself is irrelevant.
1587 VAR_ALIAS_SET is the alias set for VAR. */
1590 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1591 tree var, HOST_WIDE_INT var_alias_set)
1594 var_ann_t v_ann, m_ann;
1596 alias_stats.alias_queries++;
1597 alias_stats.simple_queries++;
1599 /* By convention, a variable cannot alias itself. */
1600 mem = var_ann (ptr)->type_mem_tag;
1603 alias_stats.alias_noalias++;
1604 alias_stats.simple_resolved++;
1608 v_ann = var_ann (var);
1609 m_ann = var_ann (mem);
1611 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1613 alias_stats.tbaa_queries++;
1615 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1616 PTR can't possibly affect VAR. Note, that we are specifically testing
1617 for PTR's alias set here, not its pointed-to type. We also can't
1618 do this check with relaxed aliasing enabled. */
1619 if (POINTER_TYPE_P (TREE_TYPE (var))
1620 && var_alias_set != 0
1621 && mem_alias_set != 0)
1623 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1624 if (ptr_alias_set == var_alias_set)
1626 alias_stats.alias_noalias++;
1627 alias_stats.tbaa_resolved++;
1632 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1633 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1635 alias_stats.alias_noalias++;
1636 alias_stats.tbaa_resolved++;
1640 alias_stats.alias_mayalias++;
1645 /* Add ALIAS to the set of variables that may alias VAR. */
1648 add_may_alias (tree var, tree alias)
1651 var_ann_t v_ann = get_var_ann (var);
1652 var_ann_t a_ann = get_var_ann (alias);
1654 gcc_assert (var != alias);
1656 if (v_ann->may_aliases == NULL)
1657 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1659 /* Avoid adding duplicates. */
1660 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1661 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1664 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1665 FIXME, call-clobbering should only depend on whether an address
1666 escapes. It should be independent of aliasing. */
1667 if (is_call_clobbered (var))
1668 mark_call_clobbered (alias);
1670 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1671 else if (is_call_clobbered (alias))
1672 mark_call_clobbered (var);
1674 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1675 a_ann->is_alias_tag = 1;
1679 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1682 replace_may_alias (tree var, size_t i, tree new_alias)
1684 var_ann_t v_ann = var_ann (var);
1685 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1687 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1688 FIXME, call-clobbering should only depend on whether an address
1689 escapes. It should be independent of aliasing. */
1690 if (is_call_clobbered (var))
1691 mark_call_clobbered (new_alias);
1693 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1694 else if (is_call_clobbered (new_alias))
1695 mark_call_clobbered (var);
1699 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1702 set_pt_anything (tree ptr)
1704 struct ptr_info_def *pi = get_ptr_info (ptr);
1706 pi->pt_anything = 1;
1709 /* The pointer used to have a name tag, but we now found it pointing
1710 to an arbitrary location. The name tag needs to be renamed and
1711 disassociated from PTR. */
1712 if (pi->name_mem_tag)
1714 bitmap_set_bit (vars_to_rename, var_ann (pi->name_mem_tag)->uid);
1715 pi->name_mem_tag = NULL_TREE;
1720 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1723 set_pt_malloc (tree ptr)
1725 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1727 /* If the pointer has already been found to point to arbitrary
1728 memory locations, it is unsafe to mark it as pointing to malloc. */
1729 if (pi->pt_anything)
1736 /* Given two different pointers DEST and ORIG. Merge the points-to
1737 information in ORIG into DEST. AI is as in
1738 collect_points_to_info. */
1741 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1743 struct ptr_info_def *dest_pi, *orig_pi;
1745 gcc_assert (dest != orig);
1747 /* Make sure we have points-to information for ORIG. */
1748 collect_points_to_info_for (ai, orig);
1750 dest_pi = get_ptr_info (dest);
1751 orig_pi = SSA_NAME_PTR_INFO (orig);
1755 /* Notice that we never merge PT_MALLOC. This attribute is only
1756 true if the pointer is the result of a malloc() call.
1757 Otherwise, we can end up in this situation:
1763 P_j would be marked as PT_MALLOC, however we currently do not
1764 handle cases of more than one pointer pointing to the same
1767 FIXME: If the merging comes from an expression that preserves
1768 the PT_MALLOC attribute (copy assignment, address
1769 arithmetic), we ought to merge PT_MALLOC, but then both
1770 pointers would end up getting different name tags because
1771 create_name_tags is not smart enough to determine that the
1772 two come from the same malloc call. Copy propagation before
1773 aliasing should cure this. */
1774 gcc_assert (orig_pi != dest_pi);
1776 dest_pi->pt_malloc = 0;
1778 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1779 set_pt_anything (dest);
1781 if (!dest_pi->pt_anything
1783 && !bitmap_empty_p (orig_pi->pt_vars))
1785 if (dest_pi->pt_vars == NULL)
1787 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1788 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1791 bitmap_ior_into (dest_pi->pt_vars, orig_pi->pt_vars);
1795 set_pt_anything (dest);
1799 /* Add EXPR to the list of expressions pointed-to by PTR. */
1802 add_pointed_to_expr (struct alias_info *ai, tree ptr, tree expr)
1804 if (TREE_CODE (expr) == WITH_SIZE_EXPR)
1805 expr = TREE_OPERAND (expr, 0);
1809 if (TREE_CODE (expr) == CALL_EXPR
1810 && (call_expr_flags (expr) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1812 /* If EXPR is a malloc-like call, then the area pointed to PTR
1813 is guaranteed to not alias with anything else. */
1814 set_pt_malloc (ptr);
1816 else if (TREE_CODE (expr) == ADDR_EXPR)
1818 /* Found P_i = ADDR_EXPR */
1819 add_pointed_to_var (ai, ptr, expr);
1821 else if (TREE_CODE (expr) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (expr)))
1823 /* Found P_i = Q_j. */
1824 merge_pointed_to_info (ai, ptr, expr);
1826 else if (TREE_CODE (expr) == PLUS_EXPR || TREE_CODE (expr) == MINUS_EXPR)
1828 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1829 tree op0 = TREE_OPERAND (expr, 0);
1830 tree op1 = TREE_OPERAND (expr, 1);
1832 /* Both operands may be of pointer type. FIXME: Shouldn't
1833 we just expect PTR + OFFSET always? */
1834 if (POINTER_TYPE_P (TREE_TYPE (op0))
1835 && TREE_CODE (op0) != INTEGER_CST)
1837 if (TREE_CODE (op0) == SSA_NAME)
1838 merge_pointed_to_info (ai, ptr, op0);
1839 else if (TREE_CODE (op0) == ADDR_EXPR)
1840 add_pointed_to_var (ai, ptr, op0);
1842 set_pt_anything (ptr);
1845 if (POINTER_TYPE_P (TREE_TYPE (op1))
1846 && TREE_CODE (op1) != INTEGER_CST)
1848 if (TREE_CODE (op1) == SSA_NAME)
1849 merge_pointed_to_info (ai, ptr, op1);
1850 else if (TREE_CODE (op1) == ADDR_EXPR)
1851 add_pointed_to_var (ai, ptr, op1);
1853 set_pt_anything (ptr);
1856 /* Neither operand is a pointer? VAR can be pointing anywhere.
1857 FIXME: Shouldn't we abort here? If we get here, we found
1858 PTR = INT_CST + INT_CST, which should not be a valid pointer
1860 if (!(POINTER_TYPE_P (TREE_TYPE (op0))
1861 && TREE_CODE (op0) != INTEGER_CST)
1862 && !(POINTER_TYPE_P (TREE_TYPE (op1))
1863 && TREE_CODE (op1) != INTEGER_CST))
1864 set_pt_anything (ptr);
1868 /* If we can't recognize the expression, assume that PTR may
1870 set_pt_anything (ptr);
1875 /* If VALUE is of the form &DECL, add DECL to the set of variables
1876 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1877 PTR. AI is as in collect_points_to_info. */
1880 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
1882 struct ptr_info_def *pi = get_ptr_info (ptr);
1886 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
1888 pt_var = TREE_OPERAND (value, 0);
1889 if (REFERENCE_CLASS_P (pt_var))
1890 pt_var = get_base_address (pt_var);
1892 if (pt_var && SSA_VAR_P (pt_var))
1894 uid = var_ann (pt_var)->uid;
1895 bitmap_set_bit (ai->addresses_needed, uid);
1897 if (pi->pt_vars == NULL)
1898 pi->pt_vars = BITMAP_GGC_ALLOC ();
1899 bitmap_set_bit (pi->pt_vars, uid);
1901 /* If the variable is a global, mark the pointer as pointing to
1902 global memory (which will make its tag a global variable). */
1903 if (is_global_var (pt_var))
1904 pi->pt_global_mem = 1;
1909 /* Callback for walk_use_def_chains to gather points-to information from the
1912 VAR is an SSA variable or a GIMPLE expression.
1914 STMT is the statement that generates the SSA variable or, if STMT is a
1915 PHI_NODE, VAR is one of the PHI arguments.
1917 DATA is a pointer to a structure of type ALIAS_INFO. */
1920 collect_points_to_info_r (tree var, tree stmt, void *data)
1922 struct alias_info *ai = (struct alias_info *) data;
1924 if (dump_file && (dump_flags & TDF_DETAILS))
1926 fprintf (dump_file, "Visiting use-def links for ");
1927 print_generic_expr (dump_file, var, dump_flags);
1928 fprintf (dump_file, "\n");
1931 switch (TREE_CODE (stmt))
1934 if (TREE_CODE (TREE_OPERAND (stmt, 0)) != MODIFY_EXPR)
1936 stmt = TREE_OPERAND (stmt, 0);
1941 tree rhs = TREE_OPERAND (stmt, 1);
1943 add_pointed_to_expr (ai, var, rhs);
1948 /* Pointers defined by __asm__ statements can point anywhere. */
1949 set_pt_anything (var);
1953 if (IS_EMPTY_STMT (stmt))
1955 tree decl = SSA_NAME_VAR (var);
1957 if (TREE_CODE (decl) == PARM_DECL)
1958 add_pointed_to_expr (ai, var, decl);
1959 else if (DECL_INITIAL (decl))
1960 add_pointed_to_expr (ai, var, DECL_INITIAL (decl));
1962 add_pointed_to_expr (ai, var, decl);
1968 /* It STMT is a PHI node, then VAR is one of its arguments. The
1969 variable that we are analyzing is the LHS of the PHI node. */
1970 tree lhs = PHI_RESULT (stmt);
1972 switch (TREE_CODE (var))
1975 add_pointed_to_var (ai, lhs, var);
1979 /* Avoid unnecessary merges. */
1981 merge_pointed_to_info (ai, lhs, var);
1985 gcc_assert (is_gimple_min_invariant (var));
1986 add_pointed_to_expr (ai, lhs, var);
2000 /* Return true if STMT is an "escape" site from the current function. Escape
2001 sites those statements which might expose the address of a variable
2002 outside the current function. STMT is an escape site iff:
2004 1- STMT is a function call, or
2005 2- STMT is an __asm__ expression, or
2006 3- STMT is an assignment to a non-local variable, or
2007 4- STMT is a return statement.
2009 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
2013 is_escape_site (tree stmt, size_t *num_calls_p)
2015 if (get_call_expr_in (stmt) != NULL_TREE)
2022 else if (TREE_CODE (stmt) == ASM_EXPR)
2024 else if (TREE_CODE (stmt) == MODIFY_EXPR)
2026 tree lhs = TREE_OPERAND (stmt, 0);
2028 /* Get to the base of _REF nodes. */
2029 if (TREE_CODE (lhs) != SSA_NAME)
2030 lhs = get_base_address (lhs);
2032 /* If we couldn't recognize the LHS of the assignment, assume that it
2033 is a non-local store. */
2034 if (lhs == NULL_TREE)
2037 /* If the RHS is a conversion between a pointer and an integer, the
2038 pointer escapes since we can't track the integer. */
2039 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
2040 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
2041 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
2042 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
2043 (TREE_OPERAND (stmt, 1), 0)))
2044 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
2047 /* If the LHS is an SSA name, it can't possibly represent a non-local
2049 if (TREE_CODE (lhs) == SSA_NAME)
2052 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2053 local variables we cannot be sure if it will escape, because we
2054 don't have information about objects not in SSA form. Need to
2055 implement something along the lines of
2057 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2058 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2059 Conference on Object-Oriented Programming Systems, Languages, and
2060 Applications (OOPSLA), pp. 1-19, 1999. */
2063 else if (TREE_CODE (stmt) == RETURN_EXPR)
2070 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2071 is considered to represent all the pointers whose pointed-to types are
2072 in the same alias set class. Otherwise, the tag represents a single
2073 SSA_NAME pointer variable. */
2076 create_memory_tag (tree type, bool is_type_tag)
2079 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2081 /* By default, memory tags are local variables. Alias analysis will
2082 determine whether they should be considered globals. */
2083 DECL_CONTEXT (tag) = current_function_decl;
2085 /* Memory tags are by definition addressable. This also prevents
2086 is_gimple_ref frome confusing memory tags with optimizable
2088 TREE_ADDRESSABLE (tag) = 1;
2090 ann = get_var_ann (tag);
2091 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2092 ann->type_mem_tag = NULL_TREE;
2094 /* Add the tag to the symbol table. */
2095 add_referenced_tmp_var (tag);
2101 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2102 This is used if P_i has been found to point to a specific set of
2103 variables or to a non-aliased memory location like the address returned
2104 by malloc functions. */
2107 get_nmt_for (tree ptr)
2109 struct ptr_info_def *pi = get_ptr_info (ptr);
2110 tree tag = pi->name_mem_tag;
2112 if (tag == NULL_TREE)
2113 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2115 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2116 then its name tag should be considered a global variable. */
2117 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2119 || pi->pt_global_mem)
2120 mark_call_clobbered (tag);
2126 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2127 artificial variable that represents the memory location pointed-to by
2128 PTR. It is used to model the effects of pointer de-references on
2129 addressable variables.
2131 AI points to the data gathered during alias analysis. This function
2132 populates the array AI->POINTERS. */
2135 get_tmt_for (tree ptr, struct alias_info *ai)
2139 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2140 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2142 /* To avoid creating unnecessary memory tags, only create one memory tag
2143 per alias set class. Note that it may be tempting to group
2144 memory tags based on conflicting alias sets instead of
2145 equivalence. That would be wrong because alias sets are not
2146 necessarily transitive (as demonstrated by the libstdc++ test
2147 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2148 such that conflicts (A, B) == true and conflicts (A, C) == true,
2149 it does not necessarily follow that conflicts (B, C) == true. */
2150 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2152 struct alias_map_d *curr = ai->pointers[i];
2153 if (tag_set == curr->set)
2155 tag = var_ann (curr->var)->type_mem_tag;
2160 /* If VAR cannot alias with any of the existing memory tags, create a new
2161 tag for PTR and add it to the POINTERS array. */
2162 if (tag == NULL_TREE)
2164 struct alias_map_d *alias_map;
2166 /* If PTR did not have a type tag already, create a new TMT.*
2167 artificial variable representing the memory location
2168 pointed-to by PTR. */
2169 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2170 tag = create_memory_tag (tag_type, true);
2172 tag = var_ann (ptr)->type_mem_tag;
2174 /* Add PTR to the POINTERS array. Note that we are not interested in
2175 PTR's alias set. Instead, we cache the alias set for the memory that
2177 alias_map = xcalloc (1, sizeof (*alias_map));
2178 alias_map->var = ptr;
2179 alias_map->set = tag_set;
2180 ai->pointers[ai->num_pointers++] = alias_map;
2183 /* If the pointed-to type is volatile, so is the tag. */
2184 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
2186 /* Make sure that the type tag has the same alias set as the
2188 gcc_assert (tag_set == get_alias_set (tag));
2194 /* Create GLOBAL_VAR, an artificial global variable to act as a
2195 representative of all the variables that may be clobbered by function
2199 create_global_var (void)
2201 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2203 DECL_ARTIFICIAL (global_var) = 1;
2204 TREE_READONLY (global_var) = 0;
2205 DECL_EXTERNAL (global_var) = 1;
2206 TREE_STATIC (global_var) = 1;
2207 TREE_USED (global_var) = 1;
2208 DECL_CONTEXT (global_var) = NULL_TREE;
2209 TREE_THIS_VOLATILE (global_var) = 0;
2210 TREE_ADDRESSABLE (global_var) = 0;
2212 add_referenced_tmp_var (global_var);
2213 bitmap_set_bit (vars_to_rename, var_ann (global_var)->uid);
2217 /* Dump alias statistics on FILE. */
2220 dump_alias_stats (FILE *file)
2222 const char *funcname
2223 = lang_hooks.decl_printable_name (current_function_decl, 2);
2224 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2225 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2226 fprintf (file, "Total alias mayalias results:\t%u\n",
2227 alias_stats.alias_mayalias);
2228 fprintf (file, "Total alias noalias results:\t%u\n",
2229 alias_stats.alias_noalias);
2230 fprintf (file, "Total simple queries:\t%u\n",
2231 alias_stats.simple_queries);
2232 fprintf (file, "Total simple resolved:\t%u\n",
2233 alias_stats.simple_resolved);
2234 fprintf (file, "Total TBAA queries:\t%u\n",
2235 alias_stats.tbaa_queries);
2236 fprintf (file, "Total TBAA resolved:\t%u\n",
2237 alias_stats.tbaa_resolved);
2241 /* Dump alias information on FILE. */
2244 dump_alias_info (FILE *file)
2247 const char *funcname
2248 = lang_hooks.decl_printable_name (current_function_decl, 2);
2250 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2252 fprintf (file, "Aliased symbols\n\n");
2253 for (i = 0; i < num_referenced_vars; i++)
2255 tree var = referenced_var (i);
2256 if (may_be_aliased (var))
2257 dump_variable (file, var);
2260 fprintf (file, "\nDereferenced pointers\n\n");
2261 for (i = 0; i < num_referenced_vars; i++)
2263 tree var = referenced_var (i);
2264 var_ann_t ann = var_ann (var);
2265 if (ann->type_mem_tag)
2266 dump_variable (file, var);
2269 fprintf (file, "\nType memory tags\n\n");
2270 for (i = 0; i < num_referenced_vars; i++)
2272 tree var = referenced_var (i);
2273 var_ann_t ann = var_ann (var);
2274 if (ann->mem_tag_kind == TYPE_TAG)
2275 dump_variable (file, var);
2278 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2280 fprintf (file, "SSA_NAME pointers\n\n");
2281 for (i = 1; i < num_ssa_names; i++)
2283 tree ptr = ssa_name (i);
2284 struct ptr_info_def *pi;
2286 if (ptr == NULL_TREE)
2289 pi = SSA_NAME_PTR_INFO (ptr);
2290 if (!SSA_NAME_IN_FREE_LIST (ptr)
2292 && pi->name_mem_tag)
2293 dump_points_to_info_for (file, ptr);
2296 fprintf (file, "\nName memory tags\n\n");
2297 for (i = 0; i < num_referenced_vars; i++)
2299 tree var = referenced_var (i);
2300 var_ann_t ann = var_ann (var);
2301 if (ann->mem_tag_kind == NAME_TAG)
2302 dump_variable (file, var);
2305 fprintf (file, "\n");
2309 /* Dump alias information on stderr. */
2312 debug_alias_info (void)
2314 dump_alias_info (stderr);
2318 /* Return the alias information associated with pointer T. It creates a
2319 new instance if none existed. */
2321 struct ptr_info_def *
2322 get_ptr_info (tree t)
2324 struct ptr_info_def *pi;
2326 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2328 pi = SSA_NAME_PTR_INFO (t);
2331 pi = ggc_alloc (sizeof (*pi));
2332 memset ((void *)pi, 0, sizeof (*pi));
2333 SSA_NAME_PTR_INFO (t) = pi;
2340 /* Dump points-to information for SSA_NAME PTR into FILE. */
2343 dump_points_to_info_for (FILE *file, tree ptr)
2345 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2347 print_generic_expr (file, ptr, dump_flags);
2351 if (pi->name_mem_tag)
2353 fprintf (file, ", name memory tag: ");
2354 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2357 if (pi->is_dereferenced)
2358 fprintf (file, ", is dereferenced");
2360 if (pi->value_escapes_p)
2361 fprintf (file, ", its value escapes");
2363 if (pi->pt_anything)
2364 fprintf (file, ", points-to anything");
2367 fprintf (file, ", points-to malloc");
2374 fprintf (file, ", points-to vars: { ");
2375 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2377 print_generic_expr (file, referenced_var (ix), dump_flags);
2378 fprintf (file, " ");
2380 fprintf (file, "}");
2384 fprintf (file, "\n");
2388 /* Dump points-to information for VAR into stderr. */
2391 debug_points_to_info_for (tree var)
2393 dump_points_to_info_for (stderr, var);
2397 /* Dump points-to information into FILE. NOTE: This function is slow, as
2398 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2401 dump_points_to_info (FILE *file)
2404 block_stmt_iterator si;
2408 lang_hooks.decl_printable_name (current_function_decl, 2);
2410 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2412 /* First dump points-to information for the default definitions of
2413 pointer variables. This is necessary because default definitions are
2414 not part of the code. */
2415 for (i = 0; i < num_referenced_vars; i++)
2417 tree var = referenced_var (i);
2418 if (POINTER_TYPE_P (TREE_TYPE (var)))
2420 var_ann_t ann = var_ann (var);
2421 if (ann->default_def)
2422 dump_points_to_info_for (file, ann->default_def);
2426 /* Dump points-to information for every pointer defined in the program. */
2431 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2433 tree ptr = PHI_RESULT (phi);
2434 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2435 dump_points_to_info_for (file, ptr);
2438 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2440 tree stmt = bsi_stmt (si);
2442 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2443 if (POINTER_TYPE_P (TREE_TYPE (def)))
2444 dump_points_to_info_for (file, def);
2448 fprintf (file, "\n");
2452 /* Dump points-to info pointed by PTO into STDERR. */
2455 debug_points_to_info (void)
2457 dump_points_to_info (stderr);
2460 /* Dump to FILE the list of variables that may be aliasing VAR. */
2463 dump_may_aliases_for (FILE *file, tree var)
2465 varray_type aliases;
2467 if (TREE_CODE (var) == SSA_NAME)
2468 var = SSA_NAME_VAR (var);
2470 aliases = var_ann (var)->may_aliases;
2474 fprintf (file, "{ ");
2475 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2477 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2478 fprintf (file, " ");
2480 fprintf (file, "}");
2485 /* Dump to stderr the list of variables that may be aliasing VAR. */
2488 debug_may_aliases_for (tree var)
2490 dump_may_aliases_for (stderr, var);
2493 /* Return true if VAR may be aliased. */
2496 may_be_aliased (tree var)
2499 if (TREE_ADDRESSABLE (var))
2502 /* Globally visible variables can have their addresses taken by other
2503 translation units. */
2504 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2507 /* Automatic variables can't have their addresses escape any other way.
2508 This must be after the check for global variables, as extern declarations
2509 do not have TREE_STATIC set. */
2510 if (!TREE_STATIC (var))
2513 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2514 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2515 we can only be sure the variable isn't addressable if it's local to the
2516 current function. */
2517 if (flag_unit_at_a_time)
2519 if (decl_function_context (var) == current_function_decl)