1 /* Alias analysis for trees.
2 Copyright (C) 2004 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
24 #include "coretypes.h"
29 #include "hard-reg-set.h"
30 #include "basic-block.h"
34 #include "langhooks.h"
37 #include "diagnostic.h"
38 #include "tree-dump.h"
39 #include "tree-gimple.h"
40 #include "tree-flow.h"
41 #include "tree-inline.h"
42 #include "tree-pass.h"
47 /* Structure to map a variable to its alias set and keep track of the
48 virtual operands that will be needed to represent it. */
51 /* Variable and its alias set. */
55 /* Total number of virtual operands that will be needed to represent
56 all the aliases of VAR. */
57 long total_alias_vops
;
59 /* Nonzero if the aliases for this memory tag have been grouped
60 already. Used in group_aliases. */
61 unsigned int grouped_p
: 1;
63 /* Set of variables aliased with VAR. This is the exact same
64 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
65 bitmap form to speed up alias grouping. */
70 /* Alias information used by compute_may_aliases and its helpers. */
73 /* SSA names visited while collecting points-to information. If bit I
74 is set, it means that SSA variable with version I has already been
76 bitmap ssa_names_visited
;
78 /* Array of SSA_NAME pointers processed by the points-to collector. */
79 varray_type processed_ptrs
;
81 /* Variables whose address is still needed. */
82 bitmap addresses_needed
;
84 /* ADDRESSABLE_VARS contains all the global variables and locals that
85 have had their address taken. */
86 struct alias_map_d
**addressable_vars
;
87 size_t num_addressable_vars
;
89 /* POINTERS contains all the _DECL pointers with unique memory tags
90 that have been referenced in the program. */
91 struct alias_map_d
**pointers
;
94 /* Number of function calls found in the program. */
95 size_t num_calls_found
;
97 /* Array of counters to keep track of how many times each pointer has
98 been dereferenced in the program. This is used by the alias grouping
99 heuristic in compute_flow_insensitive_aliasing. */
100 varray_type num_references
;
102 /* Total number of virtual operands that will be needed to represent
103 all the aliases of all the pointers found in the program. */
104 long total_alias_vops
;
106 /* Variables that have been written to. */
109 /* Pointers that have been used in an indirect store operation. */
110 bitmap dereferenced_ptrs_store
;
112 /* Pointers that have been used in an indirect load operation. */
113 bitmap dereferenced_ptrs_load
;
117 /* Counters used to display statistics on alias analysis. */
120 unsigned int alias_queries
;
121 unsigned int alias_mayalias
;
122 unsigned int alias_noalias
;
123 unsigned int simple_queries
;
124 unsigned int simple_resolved
;
125 unsigned int tbaa_queries
;
126 unsigned int tbaa_resolved
;
130 /* Local variables. */
131 static struct alias_stats_d alias_stats
;
133 /* Local functions. */
134 static void compute_flow_insensitive_aliasing (struct alias_info
*);
135 static void dump_alias_stats (FILE *);
136 static bool may_alias_p (tree
, HOST_WIDE_INT
, tree
, HOST_WIDE_INT
);
137 static tree
create_memory_tag (tree type
, bool is_type_tag
);
138 static tree
get_tmt_for (tree
, struct alias_info
*);
139 static tree
get_nmt_for (tree
);
140 static void add_may_alias (tree
, tree
);
141 static void replace_may_alias (tree
, size_t, tree
);
142 static struct alias_info
*init_alias_info (void);
143 static void delete_alias_info (struct alias_info
*);
144 static void compute_points_to_and_addr_escape (struct alias_info
*);
145 static void compute_flow_sensitive_aliasing (struct alias_info
*);
146 static void setup_pointers_and_addressables (struct alias_info
*);
147 static bool collect_points_to_info_r (tree
, tree
, void *);
148 static bool is_escape_site (tree
, size_t *);
149 static void add_pointed_to_var (struct alias_info
*, tree
, tree
);
150 static void add_pointed_to_expr (tree
, tree
);
151 static void create_global_var (void);
152 static void collect_points_to_info_for (struct alias_info
*, tree
);
153 static bool ptr_is_dereferenced_by (tree
, tree
, bool *);
154 static void maybe_create_global_var (struct alias_info
*ai
);
155 static void group_aliases (struct alias_info
*);
156 static struct ptr_info_def
*get_ptr_info (tree t
);
157 static void set_pt_anything (tree ptr
);
158 static void set_pt_malloc (tree ptr
);
160 /* Global declarations. */
162 /* Call clobbered variables in the function. If bit I is set, then
163 REFERENCED_VARS (I) is call-clobbered. */
164 bitmap call_clobbered_vars
;
166 /* Addressable variables in the function. If bit I is set, then
167 REFERENCED_VARS (I) has had its address taken. Note that
168 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
169 addressable variable is not necessarily call-clobbered (e.g., a
170 local addressable whose address does not escape) and not all
171 call-clobbered variables are addressable (e.g., a local static
173 bitmap addressable_vars
;
175 /* When the program has too many call-clobbered variables and call-sites,
176 this variable is used to represent the clobbering effects of function
177 calls. In these cases, all the call clobbered variables in the program
178 are forced to alias this variable. This reduces compile times by not
179 having to keep track of too many V_MAY_DEF expressions at call sites. */
183 /* Compute may-alias information for every variable referenced in function
186 Alias analysis proceeds in 3 main phases:
188 1- Points-to and escape analysis.
190 This phase walks the use-def chains in the SSA web looking for three
193 * Assignments of the form P_i = &VAR
194 * Assignments of the form P_i = malloc()
195 * Pointers and ADDR_EXPR that escape the current function.
197 The concept of 'escaping' is the same one used in the Java world. When
198 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
199 outside of the current function. So, assignment to global variables,
200 function arguments and returning a pointer are all escape sites.
202 This is where we are currently limited. Since not everything is renamed
203 into SSA, we lose track of escape properties when a pointer is stashed
204 inside a field in a structure, for instance. In those cases, we are
205 assuming that the pointer does escape.
207 We use escape analysis to determine whether a variable is
208 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
209 is call-clobbered. If a pointer P_i escapes, then all the variables
210 pointed-to by P_i (and its memory tag) also escape.
212 2- Compute flow-sensitive aliases
214 We have two classes of memory tags. Memory tags associated with the
215 pointed-to data type of the pointers in the program. These tags are
216 called "type memory tag" (TMT). The other class are those associated
217 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
218 when adding operands for an INDIRECT_REF *P_i, we will first check
219 whether P_i has a name tag, if it does we use it, because that will have
220 more precise aliasing information. Otherwise, we use the standard type
223 In this phase, we go through all the pointers we found in points-to
224 analysis and create alias sets for the name memory tags associated with
225 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
226 it points to and its tag.
229 3- Compute flow-insensitive aliases
231 This pass will compare the alias set of every type memory tag and every
232 addressable variable found in the program. Given a type memory tag TMT
233 and an addressable variable V. If the alias sets of TMT and V conflict
234 (as computed by may_alias_p), then V is marked as an alias tag and added
235 to the alias set of TMT.
237 For instance, consider the following function:
254 After aliasing analysis has finished, the type memory tag for pointer
255 'p' will have two aliases, namely variables 'a' and 'b'. Every time
256 pointer 'p' is dereferenced, we want to mark the operation as a
257 potential reference to 'a' and 'b'.
267 # p_1 = PHI <p_4(1), p_6(2)>;
269 # a_7 = V_MAY_DEF <a_3>;
270 # b_8 = V_MAY_DEF <b_5>;
273 # a_9 = V_MAY_DEF <a_7>
282 In certain cases, the list of may aliases for a pointer may grow too
283 large. This may cause an explosion in the number of virtual operands
284 inserted in the code. Resulting in increased memory consumption and
287 When the number of virtual operands needed to represent aliased
288 loads and stores grows too large (configurable with @option{--param
289 max-aliased-vops}), alias sets are grouped to avoid severe
290 compile-time slow downs and memory consumption. See group_aliases. */
293 compute_may_aliases (void)
295 struct alias_info
*ai
;
297 memset (&alias_stats
, 0, sizeof (alias_stats
));
299 /* Initialize aliasing information. */
300 ai
= init_alias_info ();
302 /* For each pointer P_i, determine the sets of variables that P_i may
303 point-to. For every addressable variable V, determine whether the
304 address of V escapes the current function, making V call-clobbered
305 (i.e., whether &V is stored in a global variable or if its passed as a
306 function call argument). */
307 compute_points_to_and_addr_escape (ai
);
309 /* Collect all pointers and addressable variables, compute alias sets,
310 create memory tags for pointers and promote variables whose address is
311 not needed anymore. */
312 setup_pointers_and_addressables (ai
);
314 /* Compute flow-sensitive, points-to based aliasing for all the name
315 memory tags. Note that this pass needs to be done before flow
316 insensitive analysis because it uses the points-to information
317 gathered before to mark call-clobbered type tags. */
318 compute_flow_sensitive_aliasing (ai
);
320 /* Compute type-based flow-insensitive aliasing for all the type
322 compute_flow_insensitive_aliasing (ai
);
324 /* If the program has too many call-clobbered variables and/or function
325 calls, create .GLOBAL_VAR and use it to model call-clobbering
326 semantics at call sites. This reduces the number of virtual operands
327 considerably, improving compile times at the expense of lost
328 aliasing precision. */
329 maybe_create_global_var (ai
);
331 /* Debugging dumps. */
334 dump_referenced_vars (dump_file
);
335 if (dump_flags
& TDF_STATS
)
336 dump_alias_stats (dump_file
);
337 dump_points_to_info (dump_file
);
338 dump_alias_info (dump_file
);
341 /* Deallocate memory used by aliasing data structures. */
342 delete_alias_info (ai
);
345 struct tree_opt_pass pass_may_alias
=
349 compute_may_aliases
, /* execute */
352 0, /* static_pass_number */
353 TV_TREE_MAY_ALIAS
, /* tv_id */
354 PROP_cfg
| PROP_ssa
, /* properties_required */
355 PROP_alias
, /* properties_provided */
356 0, /* properties_destroyed */
357 0, /* todo_flags_start */
358 TODO_dump_func
| TODO_rename_vars
359 | TODO_ggc_collect
| TODO_verify_ssa
, /* todo_flags_finish */
364 /* Initialize the data structures used for alias analysis. */
366 static struct alias_info
*
367 init_alias_info (void)
369 struct alias_info
*ai
;
370 static bool aliases_computed_p
= false;
372 ai
= xcalloc (1, sizeof (struct alias_info
));
373 ai
->ssa_names_visited
= BITMAP_XMALLOC ();
374 VARRAY_TREE_INIT (ai
->processed_ptrs
, 50, "processed_ptrs");
375 ai
->addresses_needed
= BITMAP_XMALLOC ();
376 VARRAY_UINT_INIT (ai
->num_references
, num_referenced_vars
, "num_references");
377 ai
->written_vars
= BITMAP_XMALLOC ();
378 ai
->dereferenced_ptrs_store
= BITMAP_XMALLOC ();
379 ai
->dereferenced_ptrs_load
= BITMAP_XMALLOC ();
381 /* If aliases have been computed before, clear existing information. */
382 if (aliases_computed_p
)
386 /* Clear the call-clobbered set. We are going to re-discover
387 call-clobbered variables. */
388 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars
, 0, i
,
390 tree var
= referenced_var (i
);
392 /* Variables that are intrinsically call-clobbered (globals,
393 local statics, etc) will not be marked by the aliasing
394 code, so we can't remove them from CALL_CLOBBERED_VARS. */
395 if (!is_call_clobbered (var
))
396 bitmap_clear_bit (call_clobbered_vars
, var_ann (var
)->uid
);
399 /* Similarly, clear the set of addressable variables. In this
400 case, we can just clear the set because addressability is
401 only computed here. */
402 bitmap_clear (addressable_vars
);
404 /* Clear flow-insensitive alias information from each symbol. */
405 for (i
= 0; i
< num_referenced_vars
; i
++)
407 var_ann_t ann
= var_ann (referenced_var (i
));
408 ann
->is_alias_tag
= 0;
409 ann
->may_aliases
= NULL
;
412 /* Clear flow-sensitive points-to information from each SSA name. */
413 for (i
= 1; i
< num_ssa_names
; i
++)
415 tree name
= ssa_name (i
);
417 if (!name
|| !POINTER_TYPE_P (TREE_TYPE (name
)))
420 if (SSA_NAME_PTR_INFO (name
))
422 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (name
);
424 /* Clear all the flags but keep the name tag to
425 avoid creating new temporaries unnecessarily. If
426 this pointer is found to point to a subset or
427 superset of its former points-to set, then a new
428 tag will need to be created in create_name_tags. */
431 pi
->value_escapes_p
= 0;
432 pi
->is_dereferenced
= 0;
434 bitmap_clear (pi
->pt_vars
);
439 /* Next time, we will need to reset alias information. */
440 aliases_computed_p
= true;
446 /* Deallocate memory used by alias analysis. */
449 delete_alias_info (struct alias_info
*ai
)
453 BITMAP_XFREE (ai
->ssa_names_visited
);
454 ai
->processed_ptrs
= NULL
;
455 BITMAP_XFREE (ai
->addresses_needed
);
457 for (i
= 0; i
< ai
->num_addressable_vars
; i
++)
459 sbitmap_free (ai
->addressable_vars
[i
]->may_aliases
);
460 free (ai
->addressable_vars
[i
]);
462 free (ai
->addressable_vars
);
464 for (i
= 0; i
< ai
->num_pointers
; i
++)
466 sbitmap_free (ai
->pointers
[i
]->may_aliases
);
467 free (ai
->pointers
[i
]);
471 ai
->num_references
= NULL
;
472 BITMAP_XFREE (ai
->written_vars
);
473 BITMAP_XFREE (ai
->dereferenced_ptrs_store
);
474 BITMAP_XFREE (ai
->dereferenced_ptrs_load
);
480 /* Walk use-def chains for pointer PTR to determine what variables is PTR
484 collect_points_to_info_for (struct alias_info
*ai
, tree ptr
)
486 gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr
)));
488 if (!bitmap_bit_p (ai
->ssa_names_visited
, SSA_NAME_VERSION (ptr
)))
490 bitmap_set_bit (ai
->ssa_names_visited
, SSA_NAME_VERSION (ptr
));
491 walk_use_def_chains (ptr
, collect_points_to_info_r
, ai
, true);
492 VARRAY_PUSH_TREE (ai
->processed_ptrs
, ptr
);
497 /* Helper for ptr_is_dereferenced_by. Called by walk_tree to look for
498 INDIRECT_REF nodes for the pointer passed in DATA. */
501 find_ptr_dereference (tree
*tp
, int *walk_subtrees ATTRIBUTE_UNUSED
, void *data
)
503 tree ptr
= (tree
) data
;
505 if (TREE_CODE (*tp
) == INDIRECT_REF
506 && TREE_OPERAND (*tp
, 0) == ptr
)
513 /* Return true if STMT contains INDIRECT_REF <PTR>. *IS_STORE is set
514 to 'true' if the dereference is on the LHS of an assignment. */
517 ptr_is_dereferenced_by (tree ptr
, tree stmt
, bool *is_store
)
521 if (TREE_CODE (stmt
) == MODIFY_EXPR
522 || (TREE_CODE (stmt
) == RETURN_EXPR
523 && TREE_CODE (TREE_OPERAND (stmt
, 0)) == MODIFY_EXPR
))
527 e
= (TREE_CODE (stmt
) == RETURN_EXPR
) ? TREE_OPERAND (stmt
, 0) : stmt
;
528 lhs
= TREE_OPERAND (e
, 0);
529 rhs
= TREE_OPERAND (e
, 1);
532 && walk_tree (&lhs
, find_ptr_dereference
, ptr
, NULL
))
537 else if (EXPR_P (rhs
)
538 && walk_tree (&rhs
, find_ptr_dereference
, ptr
, NULL
))
543 else if (TREE_CODE (stmt
) == ASM_EXPR
)
545 if (walk_tree (&ASM_OUTPUTS (stmt
), find_ptr_dereference
, ptr
, NULL
)
546 || walk_tree (&ASM_CLOBBERS (stmt
), find_ptr_dereference
, ptr
, NULL
))
551 else if (walk_tree (&ASM_INPUTS (stmt
), find_ptr_dereference
, ptr
, NULL
))
561 /* Traverse use-def links for all the pointers in the program to collect
562 address escape and points-to information.
564 This is loosely based on the same idea described in R. Hasti and S.
565 Horwitz, ``Using static single assignment form to improve
566 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
567 Programming Language Design and Implementation, pp. 97-105, 1998. */
570 compute_points_to_and_addr_escape (struct alias_info
*ai
)
577 timevar_push (TV_TREE_PTA
);
581 bb_ann_t block_ann
= bb_ann (bb
);
582 block_stmt_iterator si
;
584 for (si
= bsi_start (bb
); !bsi_end_p (si
); bsi_next (&si
))
587 tree stmt
= bsi_stmt (si
);
588 bool stmt_escapes_p
= is_escape_site (stmt
, &ai
->num_calls_found
);
590 /* Mark all the variables whose address are taken by the
591 statement. Note that this will miss all the addresses taken
592 in PHI nodes (those are discovered while following the use-def
594 get_stmt_operands (stmt
);
595 addr_taken
= addresses_taken (stmt
);
597 EXECUTE_IF_SET_IN_BITMAP (addr_taken
, 0, i
,
599 tree var
= referenced_var (i
);
600 bitmap_set_bit (ai
->addresses_needed
, var_ann (var
)->uid
);
602 mark_call_clobbered (var
);
606 block_ann
->has_escape_site
= 1;
608 /* Special case for silly ADDR_EXPR tricks
609 (gcc.c-torture/unsorted/pass.c). If this statement is an
610 assignment to a non-pointer variable and the RHS takes the
611 address of a variable, assume that the variable on the RHS is
612 call-clobbered. We could add the LHS to the list of
613 "pointers" and follow it to see if it really escapes, but it's
614 not worth the pain. */
616 && TREE_CODE (stmt
) == MODIFY_EXPR
617 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt
, 0))))
618 EXECUTE_IF_SET_IN_BITMAP (addr_taken
, 0, i
,
620 tree var
= referenced_var (i
);
621 mark_call_clobbered (var
);
624 FOR_EACH_SSA_TREE_OPERAND (op
, stmt
, iter
, SSA_OP_USE
)
626 var_ann_t v_ann
= var_ann (SSA_NAME_VAR (op
));
627 struct ptr_info_def
*pi
;
630 /* If the operand's variable may be aliased, keep track
631 of how many times we've referenced it. This is used
632 for alias grouping in compute_flow_sensitive_aliasing.
633 Note that we don't need to grow AI->NUM_REFERENCES
634 because we are processing regular variables, not
635 memory tags (the array's initial size is set to
636 NUM_REFERENCED_VARS). */
637 if (may_be_aliased (SSA_NAME_VAR (op
)))
638 (VARRAY_UINT (ai
->num_references
, v_ann
->uid
))++;
640 if (!POINTER_TYPE_P (TREE_TYPE (op
)))
643 collect_points_to_info_for (ai
, op
);
645 pi
= SSA_NAME_PTR_INFO (op
);
646 if (ptr_is_dereferenced_by (op
, stmt
, &is_store
))
648 /* Mark OP as dereferenced. In a subsequent pass,
649 dereferenced pointers that point to a set of
650 variables will be assigned a name tag to alias
651 all the variables OP points to. */
652 pi
->is_dereferenced
= 1;
654 /* Keep track of how many time we've dereferenced each
655 pointer. Again, we don't need to grow
656 AI->NUM_REFERENCES because we're processing
657 existing program variables. */
658 (VARRAY_UINT (ai
->num_references
, v_ann
->uid
))++;
660 /* If this is a store operation, mark OP as being
661 dereferenced to store, otherwise mark it as being
662 dereferenced to load. */
664 bitmap_set_bit (ai
->dereferenced_ptrs_store
, v_ann
->uid
);
666 bitmap_set_bit (ai
->dereferenced_ptrs_load
, v_ann
->uid
);
668 else if (stmt_escapes_p
)
670 /* Note that even if STMT is an escape point, pointer OP
671 will not escape if it is being dereferenced. That's
672 why we only check for escape points if OP is not
673 dereferenced by STMT. */
674 pi
->value_escapes_p
= 1;
676 /* If the statement makes a function call, assume
677 that pointer OP will be dereferenced in a store
678 operation inside the called function. */
679 if (get_call_expr_in (stmt
))
681 bitmap_set_bit (ai
->dereferenced_ptrs_store
, v_ann
->uid
);
682 pi
->is_dereferenced
= 1;
687 /* Update reference counter for definitions to any
688 potentially aliased variable. This is used in the alias
689 grouping heuristics. */
690 FOR_EACH_SSA_TREE_OPERAND (op
, stmt
, iter
, SSA_OP_DEF
)
692 tree var
= SSA_NAME_VAR (op
);
693 var_ann_t ann
= var_ann (var
);
694 bitmap_set_bit (ai
->written_vars
, ann
->uid
);
695 if (may_be_aliased (var
))
696 (VARRAY_UINT (ai
->num_references
, ann
->uid
))++;
698 if (POINTER_TYPE_P (TREE_TYPE (op
)))
699 collect_points_to_info_for (ai
, op
);
702 /* Mark variables in V_MAY_DEF operands as being written to. */
703 FOR_EACH_SSA_TREE_OPERAND (op
, stmt
, iter
, SSA_OP_VIRTUAL_DEFS
)
705 tree var
= SSA_NAME_VAR (op
);
706 var_ann_t ann
= var_ann (var
);
707 bitmap_set_bit (ai
->written_vars
, ann
->uid
);
710 /* After promoting variables and computing aliasing we will
711 need to re-scan most statements. FIXME: Try to minimize the
712 number of statements re-scanned. It's not really necessary to
713 re-scan *all* statements. */
718 timevar_pop (TV_TREE_PTA
);
722 /* Create name tags for all the pointers that have been dereferenced.
723 We only create a name tag for a pointer P if P is found to point to
724 a set of variables (so that we can alias them to *P) or if it is
725 the result of a call to malloc (which means that P cannot point to
726 anything else nor alias any other variable).
728 If two pointers P and Q point to the same set of variables, they
729 are assigned the same name tag. */
732 create_name_tags (struct alias_info
*ai
)
736 for (i
= 0; i
< VARRAY_ACTIVE_SIZE (ai
->processed_ptrs
); i
++)
738 tree ptr
= VARRAY_TREE (ai
->processed_ptrs
, i
);
739 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (ptr
);
741 if (pi
->pt_anything
|| !pi
->is_dereferenced
)
743 /* No name tags for pointers that have not been
744 dereferenced or point to an arbitrary location. */
745 pi
->name_mem_tag
= NULL_TREE
;
750 && bitmap_first_set_bit (pi
->pt_vars
) >= 0)
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 /* Mark the new name tag for renaming. */
808 bitmap_set_bit (vars_to_rename
, var_ann (pi
->name_mem_tag
)->uid
);
814 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
815 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
816 name tag and the variables it points-to are call-clobbered. Finally, if
817 P_i escapes and we could not determine where it points to, then all the
818 variables in the same alias set as *P_i are marked call-clobbered. This
819 is necessary because we must assume that P_i may take the address of any
820 variable in the same alias set. */
823 compute_flow_sensitive_aliasing (struct alias_info
*ai
)
827 create_name_tags (ai
);
829 for (i
= 0; i
< VARRAY_ACTIVE_SIZE (ai
->processed_ptrs
); i
++)
832 tree ptr
= VARRAY_TREE (ai
->processed_ptrs
, i
);
833 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (ptr
);
834 var_ann_t v_ann
= var_ann (SSA_NAME_VAR (ptr
));
836 if (pi
->value_escapes_p
|| pi
->pt_anything
)
838 /* If PTR escapes or may point to anything, then its associated
839 memory tags and pointed-to variables are call-clobbered. */
840 if (pi
->name_mem_tag
)
841 mark_call_clobbered (pi
->name_mem_tag
);
843 if (v_ann
->type_mem_tag
)
844 mark_call_clobbered (v_ann
->type_mem_tag
);
847 EXECUTE_IF_SET_IN_BITMAP (pi
->pt_vars
, 0, j
,
848 mark_call_clobbered (referenced_var (j
)));
851 /* Set up aliasing information for PTR's name memory tag (if it has
852 one). Note that only pointers that have been dereferenced will
853 have a name memory tag. */
854 if (pi
->name_mem_tag
&& pi
->pt_vars
)
855 EXECUTE_IF_SET_IN_BITMAP (pi
->pt_vars
, 0, j
,
856 add_may_alias (pi
->name_mem_tag
, referenced_var (j
)));
858 /* If the name tag is call clobbered, so is the type tag
859 associated with the base VAR_DECL. */
861 && v_ann
->type_mem_tag
862 && is_call_clobbered (pi
->name_mem_tag
))
863 mark_call_clobbered (v_ann
->type_mem_tag
);
868 /* Compute type-based alias sets. Traverse all the pointers and
869 addressable variables found in setup_pointers_and_addressables.
871 For every pointer P in AI->POINTERS and addressable variable V in
872 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
873 memory tag (TMT) if their alias sets conflict. V is then marked as
874 an alias tag so that the operand scanner knows that statements
875 containing V have aliased operands. */
878 compute_flow_insensitive_aliasing (struct alias_info
*ai
)
883 /* Initialize counter for the total number of virtual operands that
884 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
885 threshold set by --params max-alias-vops, we enable alias
887 ai
->total_alias_vops
= 0;
889 /* For every pointer P, determine which addressable variables may alias
890 with P's type memory tag. */
891 for (i
= 0; i
< ai
->num_pointers
; i
++)
894 struct alias_map_d
*p_map
= ai
->pointers
[i
];
895 tree tag
= var_ann (p_map
->var
)->type_mem_tag
;
896 var_ann_t tag_ann
= var_ann (tag
);
898 p_map
->total_alias_vops
= 0;
899 p_map
->may_aliases
= sbitmap_alloc (num_referenced_vars
);
900 sbitmap_zero (p_map
->may_aliases
);
902 for (j
= 0; j
< ai
->num_addressable_vars
; j
++)
904 struct alias_map_d
*v_map
;
907 bool tag_stored_p
, var_stored_p
;
909 v_map
= ai
->addressable_vars
[j
];
911 v_ann
= var_ann (var
);
913 /* Skip memory tags and variables that have never been
914 written to. We also need to check if the variables are
915 call-clobbered because they may be overwritten by
917 tag_stored_p
= bitmap_bit_p (ai
->written_vars
, tag_ann
->uid
)
918 || is_call_clobbered (tag
);
919 var_stored_p
= bitmap_bit_p (ai
->written_vars
, v_ann
->uid
)
920 || is_call_clobbered (var
);
921 if (!tag_stored_p
&& !var_stored_p
)
924 if (may_alias_p (p_map
->var
, p_map
->set
, var
, v_map
->set
))
926 size_t num_tag_refs
, num_var_refs
;
928 num_tag_refs
= VARRAY_UINT (ai
->num_references
, tag_ann
->uid
);
929 num_var_refs
= VARRAY_UINT (ai
->num_references
, v_ann
->uid
);
931 /* Add VAR to TAG's may-aliases set. */
932 add_may_alias (tag
, var
);
934 /* Update the total number of virtual operands due to
935 aliasing. Since we are adding one more alias to TAG's
936 may-aliases set, the total number of virtual operands due
937 to aliasing will be increased by the number of references
938 made to VAR and TAG (every reference to TAG will also
939 count as a reference to VAR). */
940 ai
->total_alias_vops
+= (num_var_refs
+ num_tag_refs
);
941 p_map
->total_alias_vops
+= (num_var_refs
+ num_tag_refs
);
943 /* Update the bitmap used to represent TAG's alias set
944 in case we need to group aliases. */
945 SET_BIT (p_map
->may_aliases
, var_ann (var
)->uid
);
950 /* Since this analysis is based exclusively on symbols, it fails to
951 handle cases where two pointers P and Q have different memory
952 tags with conflicting alias set numbers but no aliased symbols in
955 For example, suppose that we have two memory tags TMT.1 and TMT.2
958 may-aliases (TMT.1) = { a }
959 may-aliases (TMT.2) = { b }
961 and the alias set number of TMT.1 conflicts with that of TMT.2.
962 Since they don't have symbols in common, loads and stores from
963 TMT.1 and TMT.2 will seem independent of each other, which will
964 lead to the optimizers making invalid transformations (see
965 testsuite/gcc.c-torture/execute/pr15262-[12].c).
967 To avoid this problem, we do a final traversal of AI->POINTERS
968 looking for pairs of pointers that have no aliased symbols in
969 common and yet have conflicting alias set numbers. */
970 res
= sbitmap_alloc (num_referenced_vars
);
972 for (i
= 0; i
< ai
->num_pointers
; i
++)
975 struct alias_map_d
*p_map1
= ai
->pointers
[i
];
976 tree tag1
= var_ann (p_map1
->var
)->type_mem_tag
;
977 sbitmap may_aliases1
= p_map1
->may_aliases
;
979 for (j
= i
+ 1; j
< ai
->num_pointers
; j
++)
981 struct alias_map_d
*p_map2
= ai
->pointers
[j
];
982 tree tag2
= var_ann (p_map2
->var
)->type_mem_tag
;
983 sbitmap may_aliases2
= p_map2
->may_aliases
;
985 /* If the pointers may not point to each other, do nothing. */
986 if (!may_alias_p (p_map1
->var
, p_map1
->set
, p_map2
->var
, p_map2
->set
))
989 /* The two pointers may alias each other. If they already have
990 symbols in common, do nothing. */
991 sbitmap_a_and_b (res
, may_aliases1
, may_aliases2
);
992 if (sbitmap_first_set_bit (res
) >= 0)
995 if (sbitmap_first_set_bit (may_aliases2
) >= 0)
999 /* Add all the aliases for TAG2 into TAG1's alias set.
1000 FIXME, update grouping heuristic counters. */
1001 EXECUTE_IF_SET_IN_SBITMAP (may_aliases2
, 0, k
,
1002 add_may_alias (tag1
, referenced_var (k
)));
1003 sbitmap_a_or_b (may_aliases1
, may_aliases1
, may_aliases2
);
1007 /* Since TAG2 does not have any aliases of its own, add
1008 TAG2 itself to the alias set of TAG1. */
1009 add_may_alias (tag1
, tag2
);
1017 fprintf (dump_file
, "%s: Total number of aliased vops: %ld\n",
1018 get_name (current_function_decl
),
1019 ai
->total_alias_vops
);
1021 /* Determine if we need to enable alias grouping. */
1022 if (ai
->total_alias_vops
>= MAX_ALIASED_VOPS
)
1027 /* Comparison function for qsort used in group_aliases. */
1030 total_alias_vops_cmp (const void *p
, const void *q
)
1032 const struct alias_map_d
**p1
= (const struct alias_map_d
**)p
;
1033 const struct alias_map_d
**p2
= (const struct alias_map_d
**)q
;
1034 long n1
= (*p1
)->total_alias_vops
;
1035 long n2
= (*p2
)->total_alias_vops
;
1037 /* We want to sort in descending order. */
1038 return (n1
> n2
? -1 : (n1
== n2
) ? 0 : 1);
1041 /* Group all the aliases for TAG to make TAG represent all the
1042 variables in its alias set. Update the total number
1043 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1044 function will make TAG be the unique alias tag for all the
1045 variables in its may-aliases. So, given:
1047 may-aliases(TAG) = { V1, V2, V3 }
1049 This function will group the variables into:
1051 may-aliases(V1) = { TAG }
1052 may-aliases(V2) = { TAG }
1053 may-aliases(V2) = { TAG } */
1056 group_aliases_into (tree tag
, sbitmap tag_aliases
, struct alias_info
*ai
)
1059 var_ann_t tag_ann
= var_ann (tag
);
1060 size_t num_tag_refs
= VARRAY_UINT (ai
->num_references
, tag_ann
->uid
);
1062 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases
, 0, i
,
1064 tree var
= referenced_var (i
);
1065 var_ann_t ann
= var_ann (var
);
1067 /* Make TAG the unique alias of VAR. */
1068 ann
->is_alias_tag
= 0;
1069 ann
->may_aliases
= NULL
;
1071 /* Note that VAR and TAG may be the same if the function has no
1072 addressable variables (see the discussion at the end of
1073 setup_pointers_and_addressables). */
1075 add_may_alias (var
, tag
);
1077 /* Reduce total number of virtual operands contributed
1078 by TAG on behalf of VAR. Notice that the references to VAR
1079 itself won't be removed. We will merely replace them with
1080 references to TAG. */
1081 ai
->total_alias_vops
-= num_tag_refs
;
1084 /* We have reduced the number of virtual operands that TAG makes on
1085 behalf of all the variables formerly aliased with it. However,
1086 we have also "removed" all the virtual operands for TAG itself,
1087 so we add them back. */
1088 ai
->total_alias_vops
+= num_tag_refs
;
1090 /* TAG no longer has any aliases. */
1091 tag_ann
->may_aliases
= NULL
;
1095 /* Group may-aliases sets to reduce the number of virtual operands due
1098 1- Sort the list of pointers in decreasing number of contributed
1101 2- Take the first entry in AI->POINTERS and revert the role of
1102 the memory tag and its aliases. Usually, whenever an aliased
1103 variable Vi is found to alias with a memory tag T, we add Vi
1104 to the may-aliases set for T. Meaning that after alias
1105 analysis, we will have:
1107 may-aliases(T) = { V1, V2, V3, ..., Vn }
1109 This means that every statement that references T, will get 'n'
1110 virtual operands for each of the Vi tags. But, when alias
1111 grouping is enabled, we make T an alias tag and add it to the
1112 alias set of all the Vi variables:
1114 may-aliases(V1) = { T }
1115 may-aliases(V2) = { T }
1117 may-aliases(Vn) = { T }
1119 This has two effects: (a) statements referencing T will only get
1120 a single virtual operand, and, (b) all the variables Vi will now
1121 appear to alias each other. So, we lose alias precision to
1122 improve compile time. But, in theory, a program with such a high
1123 level of aliasing should not be very optimizable in the first
1126 3- Since variables may be in the alias set of more than one
1127 memory tag, the grouping done in step (2) needs to be extended
1128 to all the memory tags that have a non-empty intersection with
1129 the may-aliases set of tag T. For instance, if we originally
1130 had these may-aliases sets:
1132 may-aliases(T) = { V1, V2, V3 }
1133 may-aliases(R) = { V2, V4 }
1135 In step (2) we would have reverted the aliases for T as:
1137 may-aliases(V1) = { T }
1138 may-aliases(V2) = { T }
1139 may-aliases(V3) = { T }
1141 But note that now V2 is no longer aliased with R. We could
1142 add R to may-aliases(V2), but we are in the process of
1143 grouping aliases to reduce virtual operands so what we do is
1144 add V4 to the grouping to obtain:
1146 may-aliases(V1) = { T }
1147 may-aliases(V2) = { T }
1148 may-aliases(V3) = { T }
1149 may-aliases(V4) = { T }
1151 4- If the total number of virtual operands due to aliasing is
1152 still above the threshold set by max-alias-vops, go back to (2). */
1155 group_aliases (struct alias_info
*ai
)
1160 /* Sort the POINTERS array in descending order of contributed
1161 virtual operands. */
1162 qsort (ai
->pointers
, ai
->num_pointers
, sizeof (struct alias_map_d
*),
1163 total_alias_vops_cmp
);
1165 res
= sbitmap_alloc (num_referenced_vars
);
1167 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1168 and the tag's may-aliases set. */
1169 for (i
= 0; i
< ai
->num_pointers
; i
++)
1172 tree tag1
= var_ann (ai
->pointers
[i
]->var
)->type_mem_tag
;
1173 sbitmap tag1_aliases
= ai
->pointers
[i
]->may_aliases
;
1175 /* Skip tags that have been grouped already. */
1176 if (ai
->pointers
[i
]->grouped_p
)
1179 /* See if TAG1 had any aliases in common with other type tags.
1180 If we find a TAG2 with common aliases with TAG1, add TAG2's
1181 aliases into TAG1. */
1182 for (j
= i
+ 1; j
< ai
->num_pointers
; j
++)
1184 sbitmap tag2_aliases
= ai
->pointers
[j
]->may_aliases
;
1186 sbitmap_a_and_b (res
, tag1_aliases
, tag2_aliases
);
1187 if (sbitmap_first_set_bit (res
) >= 0)
1189 tree tag2
= var_ann (ai
->pointers
[j
]->var
)->type_mem_tag
;
1191 sbitmap_a_or_b (tag1_aliases
, tag1_aliases
, tag2_aliases
);
1193 /* TAG2 does not need its aliases anymore. */
1194 sbitmap_zero (tag2_aliases
);
1195 var_ann (tag2
)->may_aliases
= NULL
;
1197 /* TAG1 is the unique alias of TAG2. */
1198 add_may_alias (tag2
, tag1
);
1200 ai
->pointers
[j
]->grouped_p
= true;
1204 /* Now group all the aliases we collected into TAG1. */
1205 group_aliases_into (tag1
, tag1_aliases
, ai
);
1207 /* If we've reduced total number of virtual operands below the
1209 if (ai
->total_alias_vops
< MAX_ALIASED_VOPS
)
1213 /* Finally, all the variables that have been grouped cannot be in
1214 the may-alias set of name memory tags. Suppose that we have
1215 grouped the aliases in this code so that may-aliases(a) = TMT.20
1219 # a_9 = V_MAY_DEF <a_8>
1221 ... Several modifications to TMT.20 ...
1225 Since p_5 points to 'a', the optimizers will try to propagate 0
1226 into p_5->field, but that is wrong because there have been
1227 modifications to 'TMT.20' in between. To prevent this we have to
1228 replace 'a' with 'TMT.20' in the name tag of p_5. */
1229 for (i
= 0; i
< VARRAY_ACTIVE_SIZE (ai
->processed_ptrs
); i
++)
1232 tree ptr
= VARRAY_TREE (ai
->processed_ptrs
, i
);
1233 tree name_tag
= SSA_NAME_PTR_INFO (ptr
)->name_mem_tag
;
1234 varray_type aliases
;
1236 if (name_tag
== NULL_TREE
)
1239 aliases
= var_ann (name_tag
)->may_aliases
;
1240 for (j
= 0; aliases
&& j
< VARRAY_ACTIVE_SIZE (aliases
); j
++)
1242 tree alias
= VARRAY_TREE (aliases
, j
);
1243 var_ann_t ann
= var_ann (alias
);
1245 if (ann
->mem_tag_kind
== NOT_A_TAG
&& ann
->may_aliases
)
1249 gcc_assert (VARRAY_ACTIVE_SIZE (ann
->may_aliases
) == 1);
1251 new_alias
= VARRAY_TREE (ann
->may_aliases
, 0);
1252 replace_may_alias (name_tag
, j
, new_alias
);
1261 "%s: Total number of aliased vops after grouping: %ld%s\n",
1262 get_name (current_function_decl
),
1263 ai
->total_alias_vops
,
1264 (ai
->total_alias_vops
< 0) ? " (negative values are OK)" : "");
1268 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1271 create_alias_map_for (tree var
, struct alias_info
*ai
)
1273 struct alias_map_d
*alias_map
;
1274 alias_map
= xcalloc (1, sizeof (*alias_map
));
1275 alias_map
->var
= var
;
1276 alias_map
->set
= get_alias_set (var
);
1277 ai
->addressable_vars
[ai
->num_addressable_vars
++] = alias_map
;
1281 /* Create memory tags for all the dereferenced pointers and build the
1282 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1283 sets. Based on the address escape and points-to information collected
1284 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1285 variables whose address is not needed anymore. */
1288 setup_pointers_and_addressables (struct alias_info
*ai
)
1290 size_t i
, n_vars
, num_addressable_vars
, num_pointers
;
1292 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1293 num_addressable_vars
= num_pointers
= 0;
1294 for (i
= 0; i
< num_referenced_vars
; i
++)
1296 tree var
= referenced_var (i
);
1298 if (may_be_aliased (var
))
1299 num_addressable_vars
++;
1301 if (POINTER_TYPE_P (TREE_TYPE (var
)))
1303 /* Since we don't keep track of volatile variables, assume that
1304 these pointers are used in indirect store operations. */
1305 if (TREE_THIS_VOLATILE (var
))
1306 bitmap_set_bit (ai
->dereferenced_ptrs_store
, var_ann (var
)->uid
);
1312 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1313 always going to be slightly bigger than we actually need them
1314 because some TREE_ADDRESSABLE variables will be marked
1315 non-addressable below and only pointers with unique type tags are
1316 going to be added to POINTERS. */
1317 ai
->addressable_vars
= xcalloc (num_addressable_vars
,
1318 sizeof (struct alias_map_d
*));
1319 ai
->pointers
= xcalloc (num_pointers
, sizeof (struct alias_map_d
*));
1320 ai
->num_addressable_vars
= 0;
1321 ai
->num_pointers
= 0;
1323 /* Since we will be creating type memory tags within this loop, cache the
1324 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1326 n_vars
= num_referenced_vars
;
1328 for (i
= 0; i
< n_vars
; i
++)
1330 tree var
= referenced_var (i
);
1331 var_ann_t v_ann
= var_ann (var
);
1333 /* Name memory tags already have flow-sensitive aliasing
1334 information, so they need not be processed by
1335 compute_flow_insensitive_aliasing. Similarly, type memory
1336 tags are already accounted for when we process their
1337 associated pointer. */
1338 if (v_ann
->mem_tag_kind
!= NOT_A_TAG
)
1341 /* Remove the ADDRESSABLE flag from every addressable variable whose
1342 address is not needed anymore. This is caused by the propagation
1343 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1344 removal of dead pointer assignments done by the early scalar
1346 if (TREE_ADDRESSABLE (var
))
1348 if (!bitmap_bit_p (ai
->addresses_needed
, v_ann
->uid
)
1349 && v_ann
->mem_tag_kind
== NOT_A_TAG
1350 && !is_global_var (var
))
1352 /* The address of VAR is not needed, remove the
1353 addressable bit, so that it can be optimized as a
1354 regular variable. */
1355 mark_non_addressable (var
);
1357 /* Since VAR is now a regular GIMPLE register, we will need
1358 to rename VAR into SSA afterwards. */
1359 bitmap_set_bit (vars_to_rename
, v_ann
->uid
);
1363 /* Add the variable to the set of addressables. Mostly
1364 used when scanning operands for ASM_EXPRs that
1365 clobber memory. In those cases, we need to clobber
1366 all call-clobbered variables and all addressables. */
1367 bitmap_set_bit (addressable_vars
, v_ann
->uid
);
1371 /* Global variables and addressable locals may be aliased. Create an
1372 entry in ADDRESSABLE_VARS for VAR. */
1373 if (may_be_aliased (var
))
1375 create_alias_map_for (var
, ai
);
1376 bitmap_set_bit (vars_to_rename
, var_ann (var
)->uid
);
1379 /* Add pointer variables that have been dereferenced to the POINTERS
1380 array and create a type memory tag for them. */
1381 if (POINTER_TYPE_P (TREE_TYPE (var
)))
1383 if ((bitmap_bit_p (ai
->dereferenced_ptrs_store
, v_ann
->uid
)
1384 || bitmap_bit_p (ai
->dereferenced_ptrs_load
, v_ann
->uid
)))
1389 /* If pointer VAR still doesn't have a memory tag
1390 associated with it, create it now or re-use an
1392 tag
= get_tmt_for (var
, ai
);
1393 t_ann
= var_ann (tag
);
1395 /* The type tag will need to be renamed into SSA
1396 afterwards. Note that we cannot do this inside
1397 get_tmt_for because aliasing may run multiple times
1398 and we only create type tags the first time. */
1399 bitmap_set_bit (vars_to_rename
, t_ann
->uid
);
1401 /* Associate the tag with pointer VAR. */
1402 v_ann
->type_mem_tag
= tag
;
1404 /* If pointer VAR has been used in a store operation,
1405 then its memory tag must be marked as written-to. */
1406 if (bitmap_bit_p (ai
->dereferenced_ptrs_store
, v_ann
->uid
))
1407 bitmap_set_bit (ai
->written_vars
, t_ann
->uid
);
1409 /* If pointer VAR is a global variable or a PARM_DECL,
1410 then its memory tag should be considered a global
1412 if (TREE_CODE (var
) == PARM_DECL
|| is_global_var (var
))
1413 mark_call_clobbered (tag
);
1415 /* All the dereferences of pointer VAR count as
1416 references of TAG. Since TAG can be associated with
1417 several pointers, add the dereferences of VAR to the
1418 TAG. We may need to grow AI->NUM_REFERENCES because
1419 we have been adding name and type tags. */
1420 if (t_ann
->uid
>= VARRAY_SIZE (ai
->num_references
))
1421 VARRAY_GROW (ai
->num_references
, t_ann
->uid
+ 10);
1423 VARRAY_UINT (ai
->num_references
, t_ann
->uid
)
1424 += VARRAY_UINT (ai
->num_references
, v_ann
->uid
);
1428 /* The pointer has not been dereferenced. If it had a
1429 type memory tag, remove it and mark the old tag for
1430 renaming to remove it out of the IL. */
1431 var_ann_t ann
= var_ann (var
);
1432 tree tag
= ann
->type_mem_tag
;
1435 bitmap_set_bit (vars_to_rename
, var_ann (tag
)->uid
);
1436 ann
->type_mem_tag
= NULL_TREE
;
1444 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1445 every call site, we need to emit V_MAY_DEF expressions to represent the
1446 clobbering effects of the call for variables whose address escapes the
1449 One approach is to group all call-clobbered variables into a single
1450 representative that is used as an alias of every call-clobbered variable
1451 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1452 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1454 The second approach is to emit a clobbering V_MAY_DEF for every
1455 call-clobbered variable at call sites. This is the preferred way in terms
1456 of optimization opportunities but it may create too many V_MAY_DEF operands
1457 if there are many call clobbered variables and function calls in the
1460 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1461 function calls found by the number of call-clobbered variables. If that
1462 product is beyond a certain threshold, as determined by the parameterized
1463 values shown below, we use .GLOBAL_VAR.
1465 FIXME. This heuristic should be improved. One idea is to use several
1466 .GLOBAL_VARs of different types instead of a single one. The thresholds
1467 have been derived from a typical bootstrap cycle, including all target
1468 libraries. Compile times were found increase by ~1% compared to using
1472 maybe_create_global_var (struct alias_info
*ai
)
1474 size_t i
, n_clobbered
;
1476 /* No need to create it, if we have one already. */
1477 if (global_var
== NULL_TREE
)
1479 /* Count all the call-clobbered variables. */
1481 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars
, 0, i
, n_clobbered
++);
1483 /* Create .GLOBAL_VAR if we have too many call-clobbered
1484 variables. We also create .GLOBAL_VAR when there no
1485 call-clobbered variables to prevent code motion
1486 transformations from re-arranging function calls that may
1487 have side effects. For instance,
1496 There are no call-clobbered variables in foo(), so it would
1497 be entirely possible for a pass to want to move the call to
1498 f() after the call to g(). If f() has side effects, that
1499 would be wrong. Creating .GLOBAL_VAR in this case will
1500 insert VDEFs for it and prevent such transformations. */
1501 if (n_clobbered
== 0
1502 || ai
->num_calls_found
* n_clobbered
>= (size_t) GLOBAL_VAR_THRESHOLD
)
1503 create_global_var ();
1506 /* If the function has calls to clobbering functions and .GLOBAL_VAR has
1507 been created, make it an alias for all call-clobbered variables. */
1509 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars
, 0, i
,
1511 tree var
= referenced_var (i
);
1512 if (var
!= global_var
)
1514 add_may_alias (var
, global_var
);
1515 bitmap_set_bit (vars_to_rename
, var_ann (var
)->uid
);
1521 /* Return TRUE if pointer PTR may point to variable VAR.
1523 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1524 This is needed because when checking for type conflicts we are
1525 interested in the alias set of the memory location pointed-to by
1526 PTR. The alias set of PTR itself is irrelevant.
1528 VAR_ALIAS_SET is the alias set for VAR. */
1531 may_alias_p (tree ptr
, HOST_WIDE_INT mem_alias_set
,
1532 tree var
, HOST_WIDE_INT var_alias_set
)
1535 var_ann_t v_ann
, m_ann
;
1537 alias_stats
.alias_queries
++;
1538 alias_stats
.simple_queries
++;
1540 /* By convention, a variable cannot alias itself. */
1541 mem
= var_ann (ptr
)->type_mem_tag
;
1544 alias_stats
.alias_noalias
++;
1545 alias_stats
.simple_resolved
++;
1549 v_ann
= var_ann (var
);
1550 m_ann
= var_ann (mem
);
1552 gcc_assert (m_ann
->mem_tag_kind
== TYPE_TAG
);
1554 alias_stats
.tbaa_queries
++;
1556 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1557 PTR can't possibly affect VAR. Note, that we are specifically testing
1558 for PTR's alias set here, not its pointed-to type. We also can't
1559 do this check with relaxed aliasing enabled. */
1560 if (POINTER_TYPE_P (TREE_TYPE (var
))
1561 && var_alias_set
!= 0
1562 && mem_alias_set
!= 0)
1564 HOST_WIDE_INT ptr_alias_set
= get_alias_set (ptr
);
1565 if (ptr_alias_set
== var_alias_set
)
1567 alias_stats
.alias_noalias
++;
1568 alias_stats
.tbaa_resolved
++;
1573 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1574 if (!alias_sets_conflict_p (mem_alias_set
, var_alias_set
))
1576 alias_stats
.alias_noalias
++;
1577 alias_stats
.tbaa_resolved
++;
1581 alias_stats
.alias_mayalias
++;
1586 /* Add ALIAS to the set of variables that may alias VAR. */
1589 add_may_alias (tree var
, tree alias
)
1592 var_ann_t v_ann
= get_var_ann (var
);
1593 var_ann_t a_ann
= get_var_ann (alias
);
1595 gcc_assert (var
!= alias
);
1597 if (v_ann
->may_aliases
== NULL
)
1598 VARRAY_TREE_INIT (v_ann
->may_aliases
, 2, "aliases");
1600 /* Avoid adding duplicates. */
1601 for (i
= 0; i
< VARRAY_ACTIVE_SIZE (v_ann
->may_aliases
); i
++)
1602 if (alias
== VARRAY_TREE (v_ann
->may_aliases
, i
))
1605 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1606 FIXME, call-clobbering should only depend on whether an address
1607 escapes. It should be independent of aliasing. */
1608 if (is_call_clobbered (var
))
1609 mark_call_clobbered (alias
);
1611 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1612 else if (is_call_clobbered (alias
))
1613 mark_call_clobbered (var
);
1615 VARRAY_PUSH_TREE (v_ann
->may_aliases
, alias
);
1616 a_ann
->is_alias_tag
= 1;
1620 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1623 replace_may_alias (tree var
, size_t i
, tree new_alias
)
1625 var_ann_t v_ann
= var_ann (var
);
1626 VARRAY_TREE (v_ann
->may_aliases
, i
) = new_alias
;
1628 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1629 FIXME, call-clobbering should only depend on whether an address
1630 escapes. It should be independent of aliasing. */
1631 if (is_call_clobbered (var
))
1632 mark_call_clobbered (new_alias
);
1634 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1635 else if (is_call_clobbered (new_alias
))
1636 mark_call_clobbered (var
);
1640 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1643 set_pt_anything (tree ptr
)
1645 struct ptr_info_def
*pi
= get_ptr_info (ptr
);
1647 pi
->pt_anything
= 1;
1650 /* The pointer used to have a name tag, but we now found it pointing
1651 to an arbitrary location. The name tag needs to be renamed and
1652 disassociated from PTR. */
1653 if (pi
->name_mem_tag
)
1655 bitmap_set_bit (vars_to_rename
, var_ann (pi
->name_mem_tag
)->uid
);
1656 pi
->name_mem_tag
= NULL_TREE
;
1661 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1664 set_pt_malloc (tree ptr
)
1666 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (ptr
);
1668 /* If the pointer has already been found to point to arbitrary
1669 memory locations, it is unsafe to mark it as pointing to malloc. */
1670 if (pi
->pt_anything
)
1677 /* Given two pointers DEST and ORIG. Merge the points-to information in
1678 ORIG into DEST. AI is as in collect_points_to_info. */
1681 merge_pointed_to_info (struct alias_info
*ai
, tree dest
, tree orig
)
1683 struct ptr_info_def
*dest_pi
, *orig_pi
;
1685 /* Make sure we have points-to information for ORIG. */
1686 collect_points_to_info_for (ai
, orig
);
1688 dest_pi
= get_ptr_info (dest
);
1689 orig_pi
= SSA_NAME_PTR_INFO (orig
);
1693 /* Notice that we never merge PT_MALLOC. This attribute is only
1694 true if the pointer is the result of a malloc() call.
1695 Otherwise, we can end up in this situation:
1701 P_j would be marked as PT_MALLOC, which is wrong because
1702 PT_MALLOC implies that the pointer may not point to another
1705 FIXME 1: Subsequent analysis may determine that P_j
1706 cannot alias anything else, but we are being conservative
1709 FIXME 2: If the merging comes from a copy assignment, we
1710 ought to merge PT_MALLOC, but then both pointers would end up
1711 getting different name tags because create_name_tags is not
1712 smart enough to determine that the two come from the same
1713 malloc call. Copy propagation before aliasing should cure
1715 dest_pi
->pt_malloc
= 0;
1717 if (orig_pi
->pt_malloc
|| orig_pi
->pt_anything
)
1718 set_pt_anything (dest
);
1720 if (!dest_pi
->pt_anything
1722 && bitmap_first_set_bit (orig_pi
->pt_vars
) >= 0)
1724 if (dest_pi
->pt_vars
== NULL
)
1726 dest_pi
->pt_vars
= BITMAP_GGC_ALLOC ();
1727 bitmap_copy (dest_pi
->pt_vars
, orig_pi
->pt_vars
);
1730 bitmap_a_or_b (dest_pi
->pt_vars
,
1736 set_pt_anything (dest
);
1740 /* Add VALUE to the list of expressions pointed-to by PTR. */
1743 add_pointed_to_expr (tree ptr
, tree value
)
1745 if (TREE_CODE (value
) == WITH_SIZE_EXPR
)
1746 value
= TREE_OPERAND (value
, 0);
1748 /* Pointer variables should have been handled by merge_pointed_to_info. */
1749 gcc_assert (TREE_CODE (value
) != SSA_NAME
1750 || !POINTER_TYPE_P (TREE_TYPE (value
)));
1754 /* If VALUE is the result of a malloc-like call, then the area pointed to
1755 PTR is guaranteed to not alias with anything else. */
1756 if (TREE_CODE (value
) == CALL_EXPR
1757 && (call_expr_flags (value
) & (ECF_MALLOC
| ECF_MAY_BE_ALLOCA
)))
1758 set_pt_malloc (ptr
);
1760 set_pt_anything (ptr
);
1764 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (ptr
);
1766 fprintf (dump_file
, "Pointer ");
1767 print_generic_expr (dump_file
, ptr
, dump_flags
);
1768 fprintf (dump_file
, " points to ");
1770 fprintf (dump_file
, "malloc space: ");
1772 fprintf (dump_file
, "an arbitrary address: ");
1773 print_generic_expr (dump_file
, value
, dump_flags
);
1774 fprintf (dump_file
, "\n");
1779 /* If VALUE is of the form &DECL, add DECL to the set of variables
1780 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
1781 PTR. AI is as in collect_points_to_info. */
1784 add_pointed_to_var (struct alias_info
*ai
, tree ptr
, tree value
)
1786 struct ptr_info_def
*pi
= get_ptr_info (ptr
);
1790 gcc_assert (TREE_CODE (value
) == ADDR_EXPR
);
1792 pt_var
= TREE_OPERAND (value
, 0);
1793 if (REFERENCE_CLASS_P (pt_var
))
1794 pt_var
= get_base_address (pt_var
);
1796 if (pt_var
&& SSA_VAR_P (pt_var
))
1798 uid
= var_ann (pt_var
)->uid
;
1799 bitmap_set_bit (ai
->addresses_needed
, uid
);
1801 if (pi
->pt_vars
== NULL
)
1802 pi
->pt_vars
= BITMAP_GGC_ALLOC ();
1803 bitmap_set_bit (pi
->pt_vars
, uid
);
1805 /* If the variable is a global, mark the pointer as pointing to
1806 global memory (which will make its tag a global variable). */
1807 if (is_global_var (pt_var
))
1808 pi
->pt_global_mem
= 1;
1813 /* Callback for walk_use_def_chains to gather points-to information from the
1816 VAR is an SSA variable or a GIMPLE expression.
1818 STMT is the statement that generates the SSA variable or, if STMT is a
1819 PHI_NODE, VAR is one of the PHI arguments.
1821 DATA is a pointer to a structure of type ALIAS_INFO. */
1824 collect_points_to_info_r (tree var
, tree stmt
, void *data
)
1826 struct alias_info
*ai
= (struct alias_info
*) data
;
1828 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1830 fprintf (dump_file
, "Visiting use-def links for ");
1831 print_generic_expr (dump_file
, var
, dump_flags
);
1832 fprintf (dump_file
, "\n");
1835 switch (TREE_CODE (stmt
))
1838 if (TREE_CODE (TREE_OPERAND (stmt
, 0)) != MODIFY_EXPR
)
1840 stmt
= TREE_OPERAND (stmt
, 0);
1845 tree rhs
= TREE_OPERAND (stmt
, 1);
1848 /* Found P_i = ADDR_EXPR */
1849 if (TREE_CODE (rhs
) == ADDR_EXPR
)
1850 add_pointed_to_var (ai
, var
, rhs
);
1852 /* Found P_i = Q_j. */
1853 else if (TREE_CODE (rhs
) == SSA_NAME
1854 && POINTER_TYPE_P (TREE_TYPE (rhs
)))
1855 merge_pointed_to_info (ai
, var
, rhs
);
1857 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1858 else if (TREE_CODE (rhs
) == PLUS_EXPR
1859 || TREE_CODE (rhs
) == MINUS_EXPR
)
1861 tree op0
= TREE_OPERAND (rhs
, 0);
1862 tree op1
= TREE_OPERAND (rhs
, 1);
1864 /* Both operands may be of pointer type. FIXME: Shouldn't
1865 we just expect PTR + OFFSET always? */
1866 if (POINTER_TYPE_P (TREE_TYPE (op0
))
1867 && TREE_CODE (op0
) != INTEGER_CST
)
1869 if (TREE_CODE (op0
) == SSA_NAME
)
1870 merge_pointed_to_info (ai
, var
, op0
);
1871 else if (TREE_CODE (op0
) == ADDR_EXPR
)
1872 add_pointed_to_var (ai
, var
, op0
);
1874 add_pointed_to_expr (var
, op0
);
1877 if (POINTER_TYPE_P (TREE_TYPE (op1
))
1878 && TREE_CODE (op1
) != INTEGER_CST
)
1880 if (TREE_CODE (op1
) == SSA_NAME
)
1881 merge_pointed_to_info (ai
, var
, op1
);
1882 else if (TREE_CODE (op1
) == ADDR_EXPR
)
1883 add_pointed_to_var (ai
, var
, op1
);
1885 add_pointed_to_expr (var
, op1
);
1888 /* Neither operand is a pointer? VAR can be pointing
1889 anywhere. FIXME: Is this right? If we get here, we
1890 found PTR = INT_CST + INT_CST. */
1891 if (!(POINTER_TYPE_P (TREE_TYPE (op0
))
1892 && TREE_CODE (op0
) != INTEGER_CST
)
1893 && !(POINTER_TYPE_P (TREE_TYPE (op1
))
1894 && TREE_CODE (op1
) != INTEGER_CST
))
1895 add_pointed_to_expr (var
, rhs
);
1898 /* Something else. */
1900 add_pointed_to_expr (var
, rhs
);
1904 /* Pointers defined by __asm__ statements can point anywhere. */
1905 set_pt_anything (var
);
1909 if (IS_EMPTY_STMT (stmt
))
1911 tree decl
= SSA_NAME_VAR (var
);
1913 if (TREE_CODE (decl
) == PARM_DECL
)
1914 add_pointed_to_expr (var
, decl
);
1915 else if (DECL_INITIAL (decl
))
1916 add_pointed_to_var (ai
, var
, DECL_INITIAL (decl
));
1918 add_pointed_to_expr (var
, decl
);
1923 /* It STMT is a PHI node, then VAR is one of its arguments. The
1924 variable that we are analyzing is the LHS of the PHI node. */
1925 tree lhs
= PHI_RESULT (stmt
);
1927 switch (TREE_CODE (var
))
1930 add_pointed_to_var (ai
, lhs
, var
);
1934 merge_pointed_to_info (ai
, lhs
, var
);
1938 gcc_assert (is_gimple_min_invariant (var
));
1939 add_pointed_to_expr (lhs
, var
);
1952 /* Return true if STMT is an "escape" site from the current function. Escape
1953 sites those statements which might expose the address of a variable
1954 outside the current function. STMT is an escape site iff:
1956 1- STMT is a function call, or
1957 2- STMT is an __asm__ expression, or
1958 3- STMT is an assignment to a non-local variable, or
1959 4- STMT is a return statement.
1961 If NUM_CALLS_P is not NULL, the counter is incremented if STMT contains
1965 is_escape_site (tree stmt
, size_t *num_calls_p
)
1967 if (get_call_expr_in (stmt
) != NULL_TREE
)
1974 else if (TREE_CODE (stmt
) == ASM_EXPR
)
1976 else if (TREE_CODE (stmt
) == MODIFY_EXPR
)
1978 tree lhs
= TREE_OPERAND (stmt
, 0);
1980 /* Get to the base of _REF nodes. */
1981 if (TREE_CODE (lhs
) != SSA_NAME
)
1982 lhs
= get_base_address (lhs
);
1984 /* If we couldn't recognize the LHS of the assignment, assume that it
1985 is a non-local store. */
1986 if (lhs
== NULL_TREE
)
1989 /* If the LHS is an SSA name, it can't possibly represent a non-local
1991 if (TREE_CODE (lhs
) == SSA_NAME
)
1994 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
1995 local variables we cannot be sure if it will escape, because we
1996 don't have information about objects not in SSA form. Need to
1997 implement something along the lines of
1999 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2000 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2001 Conference on Object-Oriented Programming Systems, Languages, and
2002 Applications (OOPSLA), pp. 1-19, 1999. */
2005 else if (TREE_CODE (stmt
) == RETURN_EXPR
)
2012 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2013 is considered to represent all the pointers whose pointed-to types are
2014 in the same alias set class. Otherwise, the tag represents a single
2015 SSA_NAME pointer variable. */
2018 create_memory_tag (tree type
, bool is_type_tag
)
2021 tree tag
= create_tmp_var_raw (type
, (is_type_tag
) ? "TMT" : "NMT");
2023 /* By default, memory tags are local variables. Alias analysis will
2024 determine whether they should be considered globals. */
2025 DECL_CONTEXT (tag
) = current_function_decl
;
2027 /* If the pointed-to type is volatile, so is the tag. */
2028 TREE_THIS_VOLATILE (tag
) = TREE_THIS_VOLATILE (type
);
2030 /* Memory tags are by definition addressable. This also prevents
2031 is_gimple_ref frome confusing memory tags with optimizable
2033 TREE_ADDRESSABLE (tag
) = 1;
2035 ann
= get_var_ann (tag
);
2036 ann
->mem_tag_kind
= (is_type_tag
) ? TYPE_TAG
: NAME_TAG
;
2037 ann
->type_mem_tag
= NULL_TREE
;
2039 /* Add the tag to the symbol table. */
2040 add_referenced_tmp_var (tag
);
2046 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2047 This is used if P_i has been found to point to a specific set of
2048 variables or to a non-aliased memory location like the address returned
2049 by malloc functions. */
2052 get_nmt_for (tree ptr
)
2054 struct ptr_info_def
*pi
= get_ptr_info (ptr
);
2055 tree tag
= pi
->name_mem_tag
;
2057 if (tag
== NULL_TREE
)
2058 tag
= create_memory_tag (TREE_TYPE (TREE_TYPE (ptr
)), false);
2060 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2061 then its name tag should be considered a global variable. */
2062 if (TREE_CODE (SSA_NAME_VAR (ptr
)) == PARM_DECL
2064 || pi
->pt_global_mem
)
2065 mark_call_clobbered (tag
);
2071 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2072 artificial variable that represents the memory location pointed-to by
2073 PTR. It is used to model the effects of pointer de-references on
2074 addressable variables.
2076 AI points to the data gathered during alias analysis. This function
2077 populates the array AI->POINTERS. */
2080 get_tmt_for (tree ptr
, struct alias_info
*ai
)
2084 tree tag_type
= TREE_TYPE (TREE_TYPE (ptr
));
2085 HOST_WIDE_INT tag_set
= get_alias_set (tag_type
);
2087 /* To avoid creating unnecessary memory tags, only create one memory tag
2088 per alias set class. Note that it may be tempting to group
2089 memory tags based on conflicting alias sets instead of
2090 equivalence. That would be wrong because alias sets are not
2091 necessarily transitive (as demonstrated by the libstdc++ test
2092 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2093 such that conflicts (A, B) == true and conflicts (A, C) == true,
2094 it does not necessarily follow that conflicts (B, C) == true. */
2095 for (i
= 0, tag
= NULL_TREE
; i
< ai
->num_pointers
; i
++)
2097 struct alias_map_d
*curr
= ai
->pointers
[i
];
2098 if (tag_set
== curr
->set
)
2100 tag
= var_ann (curr
->var
)->type_mem_tag
;
2105 /* If VAR cannot alias with any of the existing memory tags, create a new
2106 tag for PTR and add it to the POINTERS array. */
2107 if (tag
== NULL_TREE
)
2109 struct alias_map_d
*alias_map
;
2111 /* If PTR did not have a type tag already, create a new TMT.*
2112 artificial variable representing the memory location
2113 pointed-to by PTR. */
2114 if (var_ann (ptr
)->type_mem_tag
== NULL_TREE
)
2115 tag
= create_memory_tag (tag_type
, true);
2117 tag
= var_ann (ptr
)->type_mem_tag
;
2119 /* Add PTR to the POINTERS array. Note that we are not interested in
2120 PTR's alias set. Instead, we cache the alias set for the memory that
2122 alias_map
= xcalloc (1, sizeof (*alias_map
));
2123 alias_map
->var
= ptr
;
2124 alias_map
->set
= tag_set
;
2125 ai
->pointers
[ai
->num_pointers
++] = alias_map
;
2128 /* Make sure that the type tag has the same alias set as the
2130 gcc_assert (tag_set
== get_alias_set (tag
));
2136 /* Create GLOBAL_VAR, an artificial global variable to act as a
2137 representative of all the variables that may be clobbered by function
2141 create_global_var (void)
2143 global_var
= build_decl (VAR_DECL
, get_identifier (".GLOBAL_VAR"),
2145 DECL_ARTIFICIAL (global_var
) = 1;
2146 TREE_READONLY (global_var
) = 0;
2147 DECL_EXTERNAL (global_var
) = 1;
2148 TREE_STATIC (global_var
) = 1;
2149 TREE_USED (global_var
) = 1;
2150 DECL_CONTEXT (global_var
) = NULL_TREE
;
2151 TREE_THIS_VOLATILE (global_var
) = 0;
2152 TREE_ADDRESSABLE (global_var
) = 0;
2154 add_referenced_tmp_var (global_var
);
2155 bitmap_set_bit (vars_to_rename
, var_ann (global_var
)->uid
);
2159 /* Dump alias statistics on FILE. */
2162 dump_alias_stats (FILE *file
)
2164 const char *funcname
2165 = lang_hooks
.decl_printable_name (current_function_decl
, 2);
2166 fprintf (file
, "\nAlias statistics for %s\n\n", funcname
);
2167 fprintf (file
, "Total alias queries:\t%u\n", alias_stats
.alias_queries
);
2168 fprintf (file
, "Total alias mayalias results:\t%u\n",
2169 alias_stats
.alias_mayalias
);
2170 fprintf (file
, "Total alias noalias results:\t%u\n",
2171 alias_stats
.alias_noalias
);
2172 fprintf (file
, "Total simple queries:\t%u\n",
2173 alias_stats
.simple_queries
);
2174 fprintf (file
, "Total simple resolved:\t%u\n",
2175 alias_stats
.simple_resolved
);
2176 fprintf (file
, "Total TBAA queries:\t%u\n",
2177 alias_stats
.tbaa_queries
);
2178 fprintf (file
, "Total TBAA resolved:\t%u\n",
2179 alias_stats
.tbaa_resolved
);
2183 /* Dump alias information on FILE. */
2186 dump_alias_info (FILE *file
)
2189 const char *funcname
2190 = lang_hooks
.decl_printable_name (current_function_decl
, 2);
2192 fprintf (file
, "\nFlow-insensitive alias information for %s\n\n", funcname
);
2194 fprintf (file
, "Aliased symbols\n\n");
2195 for (i
= 0; i
< num_referenced_vars
; i
++)
2197 tree var
= referenced_var (i
);
2198 if (may_be_aliased (var
))
2199 dump_variable (file
, var
);
2202 fprintf (file
, "\nDereferenced pointers\n\n");
2203 for (i
= 0; i
< num_referenced_vars
; i
++)
2205 tree var
= referenced_var (i
);
2206 var_ann_t ann
= var_ann (var
);
2207 if (ann
->type_mem_tag
)
2208 dump_variable (file
, var
);
2211 fprintf (file
, "\nType memory tags\n\n");
2212 for (i
= 0; i
< num_referenced_vars
; i
++)
2214 tree var
= referenced_var (i
);
2215 var_ann_t ann
= var_ann (var
);
2216 if (ann
->mem_tag_kind
== TYPE_TAG
)
2217 dump_variable (file
, var
);
2220 fprintf (file
, "\n\nFlow-sensitive alias information for %s\n\n", funcname
);
2222 fprintf (file
, "SSA_NAME pointers\n\n");
2223 for (i
= 1; i
< num_ssa_names
; i
++)
2225 tree ptr
= ssa_name (i
);
2226 struct ptr_info_def
*pi
;
2228 if (ptr
== NULL_TREE
)
2231 pi
= SSA_NAME_PTR_INFO (ptr
);
2232 if (!SSA_NAME_IN_FREE_LIST (ptr
)
2234 && pi
->name_mem_tag
)
2235 dump_points_to_info_for (file
, ptr
);
2238 fprintf (file
, "\nName memory tags\n\n");
2239 for (i
= 0; i
< num_referenced_vars
; i
++)
2241 tree var
= referenced_var (i
);
2242 var_ann_t ann
= var_ann (var
);
2243 if (ann
->mem_tag_kind
== NAME_TAG
)
2244 dump_variable (file
, var
);
2247 fprintf (file
, "\n");
2251 /* Dump alias information on stderr. */
2254 debug_alias_info (void)
2256 dump_alias_info (stderr
);
2260 /* Return the alias information associated with pointer T. It creates a
2261 new instance if none existed. */
2263 static struct ptr_info_def
*
2264 get_ptr_info (tree t
)
2266 struct ptr_info_def
*pi
;
2268 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t
)));
2270 pi
= SSA_NAME_PTR_INFO (t
);
2273 pi
= ggc_alloc (sizeof (*pi
));
2274 memset ((void *)pi
, 0, sizeof (*pi
));
2275 SSA_NAME_PTR_INFO (t
) = pi
;
2282 /* Dump points-to information for SSA_NAME PTR into FILE. */
2285 dump_points_to_info_for (FILE *file
, tree ptr
)
2287 struct ptr_info_def
*pi
= SSA_NAME_PTR_INFO (ptr
);
2289 print_generic_expr (file
, ptr
, dump_flags
);
2293 if (pi
->name_mem_tag
)
2295 fprintf (file
, ", name memory tag: ");
2296 print_generic_expr (file
, pi
->name_mem_tag
, dump_flags
);
2299 if (pi
->is_dereferenced
)
2300 fprintf (file
, ", is dereferenced");
2302 if (pi
->value_escapes_p
)
2303 fprintf (file
, ", its value escapes");
2305 if (pi
->pt_anything
)
2306 fprintf (file
, ", points-to anything");
2309 fprintf (file
, ", points-to malloc");
2315 fprintf (file
, ", points-to vars: { ");
2316 EXECUTE_IF_SET_IN_BITMAP (pi
->pt_vars
, 0, ix
,
2318 print_generic_expr (file
, referenced_var (ix
), dump_flags
);
2319 fprintf (file
, " ");
2321 fprintf (file
, "}");
2325 fprintf (file
, "\n");
2329 /* Dump points-to information for VAR into stderr. */
2332 debug_points_to_info_for (tree var
)
2334 dump_points_to_info_for (stderr
, var
);
2338 /* Dump points-to information into FILE. NOTE: This function is slow, as
2339 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2342 dump_points_to_info (FILE *file
)
2345 block_stmt_iterator si
;
2349 lang_hooks
.decl_printable_name (current_function_decl
, 2);
2351 fprintf (file
, "\n\nPointed-to sets for pointers in %s\n\n", fname
);
2353 /* First dump points-to information for the default definitions of
2354 pointer variables. This is necessary because default definitions are
2355 not part of the code. */
2356 for (i
= 0; i
< num_referenced_vars
; i
++)
2358 tree var
= referenced_var (i
);
2359 if (POINTER_TYPE_P (TREE_TYPE (var
)))
2361 var_ann_t ann
= var_ann (var
);
2362 if (ann
->default_def
)
2363 dump_points_to_info_for (file
, ann
->default_def
);
2367 /* Dump points-to information for every pointer defined in the program. */
2372 for (phi
= phi_nodes (bb
); phi
; phi
= PHI_CHAIN (phi
))
2374 tree ptr
= PHI_RESULT (phi
);
2375 if (POINTER_TYPE_P (TREE_TYPE (ptr
)))
2376 dump_points_to_info_for (file
, ptr
);
2379 for (si
= bsi_start (bb
); !bsi_end_p (si
); bsi_next (&si
))
2381 tree stmt
= bsi_stmt (si
);
2383 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_DEF
)
2384 if (POINTER_TYPE_P (TREE_TYPE (def
)))
2385 dump_points_to_info_for (file
, def
);
2389 fprintf (file
, "\n");
2393 /* Dump points-to info pointed by PTO into STDERR. */
2396 debug_points_to_info (void)
2398 dump_points_to_info (stderr
);
2401 /* Dump to FILE the list of variables that may be aliasing VAR. */
2404 dump_may_aliases_for (FILE *file
, tree var
)
2406 varray_type aliases
;
2408 if (TREE_CODE (var
) == SSA_NAME
)
2409 var
= SSA_NAME_VAR (var
);
2411 aliases
= var_ann (var
)->may_aliases
;
2415 fprintf (file
, "{ ");
2416 for (i
= 0; i
< VARRAY_ACTIVE_SIZE (aliases
); i
++)
2418 print_generic_expr (file
, VARRAY_TREE (aliases
, i
), dump_flags
);
2419 fprintf (file
, " ");
2421 fprintf (file
, "}");
2426 /* Dump to stderr the list of variables that may be aliasing VAR. */
2429 debug_may_aliases_for (tree var
)
2431 dump_may_aliases_for (stderr
, var
);
2434 /* Return true if VAR may be aliased. */
2437 may_be_aliased (tree var
)
2440 if (TREE_ADDRESSABLE (var
))
2443 /* Globally visible variables can have their addresses taken by other
2444 translation units. */
2445 if (DECL_EXTERNAL (var
) || TREE_PUBLIC (var
))
2448 /* Automatic variables can't have their addresses escape any other way.
2449 This must be after the check for global variables, as extern declarations
2450 do not have TREE_STATIC set. */
2451 if (!TREE_STATIC (var
))
2454 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2455 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2456 we can only be sure the variable isn't addressable if it's local to the
2457 current function. */
2458 if (flag_unit_at_a_time
)
2460 if (decl_function_context (var
) == current_function_decl
)