1 /* Alias analysis for trees.
2 Copyright (C) 2004, 2005 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 /* 'true' after aliases have been computed (see compute_may_aliases). */
48 bool aliases_computed_p;
50 /* Structure to map a variable to its alias set and keep track of the
51 virtual operands that will be needed to represent it. */
54 /* Variable and its alias set. */
58 /* Total number of virtual operands that will be needed to represent
59 all the aliases of VAR. */
60 long total_alias_vops;
62 /* Nonzero if the aliases for this memory tag have been grouped
63 already. Used in group_aliases. */
64 unsigned int grouped_p : 1;
66 /* Set of variables aliased with VAR. This is the exact same
67 information contained in VAR_ANN (VAR)->MAY_ALIASES, but in
68 bitmap form to speed up alias grouping. */
73 /* Alias information used by compute_may_aliases and its helpers. */
76 /* SSA names visited while collecting points-to information. If bit I
77 is set, it means that SSA variable with version I has already been
79 sbitmap ssa_names_visited;
81 /* Array of SSA_NAME pointers processed by the points-to collector. */
82 varray_type processed_ptrs;
84 /* Variables whose address is still needed. */
85 bitmap addresses_needed;
87 /* ADDRESSABLE_VARS contains all the global variables and locals that
88 have had their address taken. */
89 struct alias_map_d **addressable_vars;
90 size_t num_addressable_vars;
92 /* POINTERS contains all the _DECL pointers with unique memory tags
93 that have been referenced in the program. */
94 struct alias_map_d **pointers;
97 /* Number of function calls found in the program. */
98 size_t num_calls_found;
100 /* Number of const/pure function calls found in the program. */
101 size_t num_pure_const_calls_found;
103 /* Array of counters to keep track of how many times each pointer has
104 been dereferenced in the program. This is used by the alias grouping
105 heuristic in compute_flow_insensitive_aliasing. */
106 varray_type num_references;
108 /* Total number of virtual operands that will be needed to represent
109 all the aliases of all the pointers found in the program. */
110 long total_alias_vops;
112 /* Variables that have been written to. */
115 /* Pointers that have been used in an indirect store operation. */
116 bitmap dereferenced_ptrs_store;
118 /* Pointers that have been used in an indirect load operation. */
119 bitmap dereferenced_ptrs_load;
123 /* Counters used to display statistics on alias analysis. */
126 unsigned int alias_queries;
127 unsigned int alias_mayalias;
128 unsigned int alias_noalias;
129 unsigned int simple_queries;
130 unsigned int simple_resolved;
131 unsigned int tbaa_queries;
132 unsigned int tbaa_resolved;
136 /* Local variables. */
137 static struct alias_stats_d alias_stats;
139 /* Local functions. */
140 static void compute_flow_insensitive_aliasing (struct alias_info *);
141 static void dump_alias_stats (FILE *);
142 static bool may_alias_p (tree, HOST_WIDE_INT, tree, HOST_WIDE_INT);
143 static tree create_memory_tag (tree type, bool is_type_tag);
144 static tree get_tmt_for (tree, struct alias_info *);
145 static tree get_nmt_for (tree);
146 static void add_may_alias (tree, tree);
147 static void replace_may_alias (tree, size_t, tree);
148 static struct alias_info *init_alias_info (void);
149 static void delete_alias_info (struct alias_info *);
150 static void compute_points_to_and_addr_escape (struct alias_info *);
151 static void compute_flow_sensitive_aliasing (struct alias_info *);
152 static void setup_pointers_and_addressables (struct alias_info *);
153 static bool collect_points_to_info_r (tree, tree, void *);
154 static bool is_escape_site (tree, struct alias_info *);
155 static void add_pointed_to_var (struct alias_info *, tree, tree);
156 static void create_global_var (void);
157 static void collect_points_to_info_for (struct alias_info *, tree);
158 static void maybe_create_global_var (struct alias_info *ai);
159 static void group_aliases (struct alias_info *);
160 static void set_pt_anything (tree ptr);
161 static void set_pt_malloc (tree ptr);
163 /* Global declarations. */
165 /* Call clobbered variables in the function. If bit I is set, then
166 REFERENCED_VARS (I) is call-clobbered. */
167 bitmap call_clobbered_vars;
169 /* Addressable variables in the function. If bit I is set, then
170 REFERENCED_VARS (I) has had its address taken. Note that
171 CALL_CLOBBERED_VARS and ADDRESSABLE_VARS are not related. An
172 addressable variable is not necessarily call-clobbered (e.g., a
173 local addressable whose address does not escape) and not all
174 call-clobbered variables are addressable (e.g., a local static
176 bitmap addressable_vars;
178 /* When the program has too many call-clobbered variables and call-sites,
179 this variable is used to represent the clobbering effects of function
180 calls. In these cases, all the call clobbered variables in the program
181 are forced to alias this variable. This reduces compile times by not
182 having to keep track of too many V_MAY_DEF expressions at call sites. */
186 /* Compute may-alias information for every variable referenced in function
189 Alias analysis proceeds in 3 main phases:
191 1- Points-to and escape analysis.
193 This phase walks the use-def chains in the SSA web looking for three
196 * Assignments of the form P_i = &VAR
197 * Assignments of the form P_i = malloc()
198 * Pointers and ADDR_EXPR that escape the current function.
200 The concept of 'escaping' is the same one used in the Java world. When
201 a pointer or an ADDR_EXPR escapes, it means that it has been exposed
202 outside of the current function. So, assignment to global variables,
203 function arguments and returning a pointer are all escape sites, as are
204 conversions between pointers and integers.
206 This is where we are currently limited. Since not everything is renamed
207 into SSA, we lose track of escape properties when a pointer is stashed
208 inside a field in a structure, for instance. In those cases, we are
209 assuming that the pointer does escape.
211 We use escape analysis to determine whether a variable is
212 call-clobbered. Simply put, if an ADDR_EXPR escapes, then the variable
213 is call-clobbered. If a pointer P_i escapes, then all the variables
214 pointed-to by P_i (and its memory tag) also escape.
216 2- Compute flow-sensitive aliases
218 We have two classes of memory tags. Memory tags associated with the
219 pointed-to data type of the pointers in the program. These tags are
220 called "type memory tag" (TMT). The other class are those associated
221 with SSA_NAMEs, called "name memory tag" (NMT). The basic idea is that
222 when adding operands for an INDIRECT_REF *P_i, we will first check
223 whether P_i has a name tag, if it does we use it, because that will have
224 more precise aliasing information. Otherwise, we use the standard type
227 In this phase, we go through all the pointers we found in points-to
228 analysis and create alias sets for the name memory tags associated with
229 each pointer P_i. If P_i escapes, we mark call-clobbered the variables
230 it points to and its tag.
233 3- Compute flow-insensitive aliases
235 This pass will compare the alias set of every type memory tag and every
236 addressable variable found in the program. Given a type memory tag TMT
237 and an addressable variable V. If the alias sets of TMT and V conflict
238 (as computed by may_alias_p), then V is marked as an alias tag and added
239 to the alias set of TMT.
241 For instance, consider the following function:
257 After aliasing analysis has finished, the type memory tag for pointer
258 'p' will have two aliases, namely variables 'a' and 'b'. Every time
259 pointer 'p' is dereferenced, we want to mark the operation as a
260 potential reference to 'a' and 'b'.
270 # p_1 = PHI <p_4(1), p_6(2)>;
272 # a_7 = V_MAY_DEF <a_3>;
273 # b_8 = V_MAY_DEF <b_5>;
276 # a_9 = V_MAY_DEF <a_7>
285 In certain cases, the list of may aliases for a pointer may grow too
286 large. This may cause an explosion in the number of virtual operands
287 inserted in the code. Resulting in increased memory consumption and
290 When the number of virtual operands needed to represent aliased
291 loads and stores grows too large (configurable with @option{--param
292 max-aliased-vops}), alias sets are grouped to avoid severe
293 compile-time slow downs and memory consumption. See group_aliases. */
296 compute_may_aliases (void)
298 struct alias_info *ai;
300 memset (&alias_stats, 0, sizeof (alias_stats));
302 /* Initialize aliasing information. */
303 ai = init_alias_info ();
305 /* For each pointer P_i, determine the sets of variables that P_i may
306 point-to. For every addressable variable V, determine whether the
307 address of V escapes the current function, making V call-clobbered
308 (i.e., whether &V is stored in a global variable or if its passed as a
309 function call argument). */
310 compute_points_to_and_addr_escape (ai);
312 /* Collect all pointers and addressable variables, compute alias sets,
313 create memory tags for pointers and promote variables whose address is
314 not needed anymore. */
315 setup_pointers_and_addressables (ai);
317 /* Compute flow-sensitive, points-to based aliasing for all the name
318 memory tags. Note that this pass needs to be done before flow
319 insensitive analysis because it uses the points-to information
320 gathered before to mark call-clobbered type tags. */
321 compute_flow_sensitive_aliasing (ai);
323 /* Compute type-based flow-insensitive aliasing for all the type
325 compute_flow_insensitive_aliasing (ai);
327 /* If the program has too many call-clobbered variables and/or function
328 calls, create .GLOBAL_VAR and use it to model call-clobbering
329 semantics at call sites. This reduces the number of virtual operands
330 considerably, improving compile times at the expense of lost
331 aliasing precision. */
332 maybe_create_global_var (ai);
334 /* Debugging dumps. */
337 dump_referenced_vars (dump_file);
338 if (dump_flags & TDF_STATS)
339 dump_alias_stats (dump_file);
340 dump_points_to_info (dump_file);
341 dump_alias_info (dump_file);
344 /* Deallocate memory used by aliasing data structures. */
345 delete_alias_info (ai);
348 block_stmt_iterator bsi;
352 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
354 update_stmt_if_modified (bsi_stmt (bsi));
361 struct tree_opt_pass pass_may_alias =
365 compute_may_aliases, /* execute */
368 0, /* static_pass_number */
369 TV_TREE_MAY_ALIAS, /* tv_id */
370 PROP_cfg | PROP_ssa, /* properties_required */
371 PROP_alias, /* properties_provided */
372 0, /* properties_destroyed */
373 0, /* todo_flags_start */
374 TODO_dump_func | TODO_update_ssa
375 | TODO_ggc_collect | TODO_verify_ssa
376 | TODO_verify_stmts, /* todo_flags_finish */
381 /* Data structure used to count the number of dereferences to PTR
382 inside an expression. */
390 /* Helper for count_uses_and_derefs. Called by walk_tree to look for
391 (ALIGN/MISALIGNED_)INDIRECT_REF nodes for the pointer passed in DATA. */
394 count_ptr_derefs (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED, void *data)
396 struct count_ptr_d *count_p = (struct count_ptr_d *) data;
398 if (INDIRECT_REF_P (*tp) && TREE_OPERAND (*tp, 0) == count_p->ptr)
405 /* Count the number of direct and indirect uses for pointer PTR in
406 statement STMT. The two counts are stored in *NUM_USES_P and
407 *NUM_DEREFS_P respectively. *IS_STORE_P is set to 'true' if at
408 least one of those dereferences is a store operation. */
411 count_uses_and_derefs (tree ptr, tree stmt, unsigned *num_uses_p,
412 unsigned *num_derefs_p, bool *is_store)
421 /* Find out the total number of uses of PTR in STMT. */
422 FOR_EACH_SSA_TREE_OPERAND (use, stmt, i, SSA_OP_USE)
426 /* Now count the number of indirect references to PTR. This is
427 truly awful, but we don't have much choice. There are no parent
428 pointers inside INDIRECT_REFs, so an expression like
429 '*x_1 = foo (x_1, *x_1)' needs to be traversed piece by piece to
430 find all the indirect and direct uses of x_1 inside. The only
431 shortcut we can take is the fact that GIMPLE only allows
432 INDIRECT_REFs inside the expressions below. */
433 if (TREE_CODE (stmt) == MODIFY_EXPR
434 || (TREE_CODE (stmt) == RETURN_EXPR
435 && TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR)
436 || TREE_CODE (stmt) == ASM_EXPR
437 || TREE_CODE (stmt) == CALL_EXPR)
441 if (TREE_CODE (stmt) == MODIFY_EXPR)
443 lhs = TREE_OPERAND (stmt, 0);
444 rhs = TREE_OPERAND (stmt, 1);
446 else if (TREE_CODE (stmt) == RETURN_EXPR)
448 tree e = TREE_OPERAND (stmt, 0);
449 lhs = TREE_OPERAND (e, 0);
450 rhs = TREE_OPERAND (e, 1);
452 else if (TREE_CODE (stmt) == ASM_EXPR)
454 lhs = ASM_OUTPUTS (stmt);
455 rhs = ASM_INPUTS (stmt);
463 if (lhs && (TREE_CODE (lhs) == TREE_LIST || EXPR_P (lhs)))
465 struct count_ptr_d count;
468 walk_tree (&lhs, count_ptr_derefs, &count, NULL);
470 *num_derefs_p = count.count;
473 if (rhs && (TREE_CODE (rhs) == TREE_LIST || EXPR_P (rhs)))
475 struct count_ptr_d count;
478 walk_tree (&rhs, count_ptr_derefs, &count, NULL);
479 *num_derefs_p += count.count;
483 gcc_assert (*num_uses_p >= *num_derefs_p);
487 /* Initialize the data structures used for alias analysis. */
489 static struct alias_info *
490 init_alias_info (void)
492 struct alias_info *ai;
494 ai = xcalloc (1, sizeof (struct alias_info));
495 ai->ssa_names_visited = sbitmap_alloc (num_ssa_names);
496 sbitmap_zero (ai->ssa_names_visited);
497 VARRAY_TREE_INIT (ai->processed_ptrs, 50, "processed_ptrs");
498 ai->addresses_needed = BITMAP_ALLOC (NULL);
499 VARRAY_UINT_INIT (ai->num_references, num_referenced_vars, "num_references");
500 ai->written_vars = BITMAP_ALLOC (NULL);
501 ai->dereferenced_ptrs_store = BITMAP_ALLOC (NULL);
502 ai->dereferenced_ptrs_load = BITMAP_ALLOC (NULL);
504 /* If aliases have been computed before, clear existing information. */
505 if (aliases_computed_p)
510 /* Make sure that every statement has a valid set of operands.
511 If a statement needs to be scanned for operands while we
512 compute aliases, it may get erroneous operands because all
513 the alias relations are not built at that point.
514 FIXME: This code will become obsolete when operands are not
518 block_stmt_iterator si;
519 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
520 get_stmt_operands (bsi_stmt (si));
523 /* Similarly, clear the set of addressable variables. In this
524 case, we can just clear the set because addressability is
525 only computed here. */
526 bitmap_clear (addressable_vars);
528 /* Clear flow-insensitive alias information from each symbol. */
529 for (i = 0; i < num_referenced_vars; i++)
531 tree var = referenced_var (i);
532 var_ann_t ann = var_ann (var);
534 ann->is_alias_tag = 0;
535 ann->may_aliases = NULL;
537 /* Since we are about to re-discover call-clobbered
538 variables, clear the call-clobbered flag. Variables that
539 are intrinsically call-clobbered (globals, local statics,
540 etc) will not be marked by the aliasing code, so we can't
541 remove them from CALL_CLOBBERED_VARS.
543 NB: STRUCT_FIELDS are still call clobbered if they are for
544 a global variable, so we *don't* clear their call clobberedness
545 just because they are tags, though we will clear it if they
546 aren't for global variables. */
547 if (ann->mem_tag_kind == NAME_TAG
548 || ann->mem_tag_kind == TYPE_TAG
549 || !is_global_var (var))
550 clear_call_clobbered (var);
553 /* Clear flow-sensitive points-to information from each SSA name. */
554 for (i = 1; i < num_ssa_names; i++)
556 tree name = ssa_name (i);
558 if (!name || !POINTER_TYPE_P (TREE_TYPE (name)))
561 if (SSA_NAME_PTR_INFO (name))
563 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (name);
565 /* Clear all the flags but keep the name tag to
566 avoid creating new temporaries unnecessarily. If
567 this pointer is found to point to a subset or
568 superset of its former points-to set, then a new
569 tag will need to be created in create_name_tags. */
573 pi->value_escapes_p = 0;
574 pi->is_dereferenced = 0;
576 bitmap_clear (pi->pt_vars);
581 /* Next time, we will need to reset alias information. */
582 aliases_computed_p = true;
588 /* Deallocate memory used by alias analysis. */
591 delete_alias_info (struct alias_info *ai)
595 sbitmap_free (ai->ssa_names_visited);
596 ai->processed_ptrs = NULL;
597 BITMAP_FREE (ai->addresses_needed);
599 for (i = 0; i < ai->num_addressable_vars; i++)
601 sbitmap_free (ai->addressable_vars[i]->may_aliases);
602 free (ai->addressable_vars[i]);
604 free (ai->addressable_vars);
606 for (i = 0; i < ai->num_pointers; i++)
608 sbitmap_free (ai->pointers[i]->may_aliases);
609 free (ai->pointers[i]);
613 ai->num_references = NULL;
614 BITMAP_FREE (ai->written_vars);
615 BITMAP_FREE (ai->dereferenced_ptrs_store);
616 BITMAP_FREE (ai->dereferenced_ptrs_load);
622 /* Walk use-def chains for pointer PTR to determine what variables is PTR
626 collect_points_to_info_for (struct alias_info *ai, tree ptr)
628 gcc_assert (POINTER_TYPE_P (TREE_TYPE (ptr)));
630 if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr)))
632 SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (ptr));
633 walk_use_def_chains (ptr, collect_points_to_info_r, ai, true);
634 VARRAY_PUSH_TREE (ai->processed_ptrs, ptr);
639 /* Traverse use-def links for all the pointers in the program to collect
640 address escape and points-to information.
642 This is loosely based on the same idea described in R. Hasti and S.
643 Horwitz, ``Using static single assignment form to improve
644 flow-insensitive pointer analysis,'' in SIGPLAN Conference on
645 Programming Language Design and Implementation, pp. 97-105, 1998. */
648 compute_points_to_and_addr_escape (struct alias_info *ai)
655 timevar_push (TV_TREE_PTA);
659 bb_ann_t block_ann = bb_ann (bb);
660 block_stmt_iterator si;
662 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
665 tree stmt = bsi_stmt (si);
666 bool stmt_escapes_p = is_escape_site (stmt, ai);
669 /* Mark all the variables whose address are taken by the
670 statement. Note that this will miss all the addresses taken
671 in PHI nodes (those are discovered while following the use-def
673 get_stmt_operands (stmt);
674 addr_taken = addresses_taken (stmt);
676 EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
678 tree var = referenced_var (i);
679 bitmap_set_bit (ai->addresses_needed, var_ann (var)->uid);
681 mark_call_clobbered (var);
685 block_ann->has_escape_site = 1;
687 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_USE)
689 var_ann_t v_ann = var_ann (SSA_NAME_VAR (op));
690 struct ptr_info_def *pi;
692 unsigned num_uses, num_derefs;
694 /* If the operand's variable may be aliased, keep track
695 of how many times we've referenced it. This is used
696 for alias grouping in compute_flow_sensitive_aliasing.
697 Note that we don't need to grow AI->NUM_REFERENCES
698 because we are processing regular variables, not
699 memory tags (the array's initial size is set to
700 NUM_REFERENCED_VARS). */
701 if (may_be_aliased (SSA_NAME_VAR (op)))
702 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
704 if (!POINTER_TYPE_P (TREE_TYPE (op)))
707 collect_points_to_info_for (ai, op);
709 pi = SSA_NAME_PTR_INFO (op);
710 count_uses_and_derefs (op, stmt, &num_uses, &num_derefs,
715 /* Mark OP as dereferenced. In a subsequent pass,
716 dereferenced pointers that point to a set of
717 variables will be assigned a name tag to alias
718 all the variables OP points to. */
719 pi->is_dereferenced = 1;
721 /* Keep track of how many time we've dereferenced each
722 pointer. Again, we don't need to grow
723 AI->NUM_REFERENCES because we're processing
724 existing program variables. */
725 (VARRAY_UINT (ai->num_references, v_ann->uid))++;
727 /* If this is a store operation, mark OP as being
728 dereferenced to store, otherwise mark it as being
729 dereferenced to load. */
731 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
733 bitmap_set_bit (ai->dereferenced_ptrs_load, v_ann->uid);
736 if (stmt_escapes_p && num_derefs < num_uses)
738 /* If STMT is an escape point and STMT contains at
739 least one direct use of OP, then the value of OP
740 escapes and so the pointed-to variables need to
741 be marked call-clobbered. */
742 pi->value_escapes_p = 1;
744 /* If the statement makes a function call, assume
745 that pointer OP will be dereferenced in a store
746 operation inside the called function. */
747 if (get_call_expr_in (stmt))
749 bitmap_set_bit (ai->dereferenced_ptrs_store, v_ann->uid);
750 pi->is_dereferenced = 1;
755 /* Update reference counter for definitions to any
756 potentially aliased variable. This is used in the alias
757 grouping heuristics. */
758 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_DEF)
760 tree var = SSA_NAME_VAR (op);
761 var_ann_t ann = var_ann (var);
762 bitmap_set_bit (ai->written_vars, ann->uid);
763 if (may_be_aliased (var))
764 (VARRAY_UINT (ai->num_references, ann->uid))++;
766 if (POINTER_TYPE_P (TREE_TYPE (op)))
767 collect_points_to_info_for (ai, op);
770 /* Mark variables in V_MAY_DEF operands as being written to. */
771 FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_VIRTUAL_DEFS)
773 tree var = DECL_P (op) ? op : SSA_NAME_VAR (op);
774 var_ann_t ann = var_ann (var);
775 bitmap_set_bit (ai->written_vars, ann->uid);
778 /* After promoting variables and computing aliasing we will
779 need to re-scan most statements. FIXME: Try to minimize the
780 number of statements re-scanned. It's not really necessary to
781 re-scan *all* statements. */
782 mark_stmt_modified (stmt);
786 timevar_pop (TV_TREE_PTA);
790 /* Create name tags for all the pointers that have been dereferenced.
791 We only create a name tag for a pointer P if P is found to point to
792 a set of variables (so that we can alias them to *P) or if it is
793 the result of a call to malloc (which means that P cannot point to
794 anything else nor alias any other variable).
796 If two pointers P and Q point to the same set of variables, they
797 are assigned the same name tag. */
800 create_name_tags (struct alias_info *ai)
804 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
806 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
807 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
809 if (pi->pt_anything || !pi->is_dereferenced)
811 /* No name tags for pointers that have not been
812 dereferenced or point to an arbitrary location. */
813 pi->name_mem_tag = NULL_TREE;
817 if (pi->pt_vars && !bitmap_empty_p (pi->pt_vars))
820 tree old_name_tag = pi->name_mem_tag;
822 /* If PTR points to a set of variables, check if we don't
823 have another pointer Q with the same points-to set before
824 creating a tag. If so, use Q's tag instead of creating a
827 This is important for not creating unnecessary symbols
828 and also for copy propagation. If we ever need to
829 propagate PTR into Q or vice-versa, we would run into
830 problems if they both had different name tags because
831 they would have different SSA version numbers (which
832 would force us to take the name tags in and out of SSA). */
833 for (j = 0; j < i; j++)
835 tree q = VARRAY_TREE (ai->processed_ptrs, j);
836 struct ptr_info_def *qi = SSA_NAME_PTR_INFO (q);
841 && bitmap_equal_p (pi->pt_vars, qi->pt_vars))
843 pi->name_mem_tag = qi->name_mem_tag;
848 /* If we didn't find a pointer with the same points-to set
849 as PTR, create a new name tag if needed. */
850 if (pi->name_mem_tag == NULL_TREE)
851 pi->name_mem_tag = get_nmt_for (ptr);
853 /* If the new name tag computed for PTR is different than
854 the old name tag that it used to have, then the old tag
855 needs to be removed from the IL, so we mark it for
857 if (old_name_tag && old_name_tag != pi->name_mem_tag)
858 mark_sym_for_renaming (old_name_tag);
860 else if (pi->pt_malloc)
862 /* Otherwise, create a unique name tag for this pointer. */
863 pi->name_mem_tag = get_nmt_for (ptr);
867 /* Only pointers that may point to malloc or other variables
868 may receive a name tag. If the pointer does not point to
869 a known spot, we should use type tags. */
870 set_pt_anything (ptr);
874 TREE_THIS_VOLATILE (pi->name_mem_tag)
875 |= TREE_THIS_VOLATILE (TREE_TYPE (TREE_TYPE (ptr)));
877 /* Mark the new name tag for renaming. */
878 mark_sym_for_renaming (pi->name_mem_tag);
884 /* For every pointer P_i in AI->PROCESSED_PTRS, create may-alias sets for
885 the name memory tag (NMT) associated with P_i. If P_i escapes, then its
886 name tag and the variables it points-to are call-clobbered. Finally, if
887 P_i escapes and we could not determine where it points to, then all the
888 variables in the same alias set as *P_i are marked call-clobbered. This
889 is necessary because we must assume that P_i may take the address of any
890 variable in the same alias set. */
893 compute_flow_sensitive_aliasing (struct alias_info *ai)
897 create_name_tags (ai);
899 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
902 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
903 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
904 var_ann_t v_ann = var_ann (SSA_NAME_VAR (ptr));
907 if (pi->value_escapes_p || pi->pt_anything)
909 /* If PTR escapes or may point to anything, then its associated
910 memory tags and pointed-to variables are call-clobbered. */
911 if (pi->name_mem_tag)
912 mark_call_clobbered (pi->name_mem_tag);
914 if (v_ann->type_mem_tag)
915 mark_call_clobbered (v_ann->type_mem_tag);
918 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
920 mark_call_clobbered (referenced_var (j));
924 /* Set up aliasing information for PTR's name memory tag (if it has
925 one). Note that only pointers that have been dereferenced will
926 have a name memory tag. */
927 if (pi->name_mem_tag && pi->pt_vars)
928 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, j, bi)
930 add_may_alias (pi->name_mem_tag, referenced_var (j));
931 add_may_alias (v_ann->type_mem_tag, referenced_var (j));
934 /* If the name tag is call clobbered, so is the type tag
935 associated with the base VAR_DECL. */
937 && v_ann->type_mem_tag
938 && is_call_clobbered (pi->name_mem_tag))
939 mark_call_clobbered (v_ann->type_mem_tag);
944 /* Compute type-based alias sets. Traverse all the pointers and
945 addressable variables found in setup_pointers_and_addressables.
947 For every pointer P in AI->POINTERS and addressable variable V in
948 AI->ADDRESSABLE_VARS, add V to the may-alias sets of P's type
949 memory tag (TMT) if their alias sets conflict. V is then marked as
950 an alias tag so that the operand scanner knows that statements
951 containing V have aliased operands. */
954 compute_flow_insensitive_aliasing (struct alias_info *ai)
958 /* Initialize counter for the total number of virtual operands that
959 aliasing will introduce. When AI->TOTAL_ALIAS_VOPS goes beyond the
960 threshold set by --params max-alias-vops, we enable alias
962 ai->total_alias_vops = 0;
964 /* For every pointer P, determine which addressable variables may alias
965 with P's type memory tag. */
966 for (i = 0; i < ai->num_pointers; i++)
969 struct alias_map_d *p_map = ai->pointers[i];
970 tree tag = var_ann (p_map->var)->type_mem_tag;
971 var_ann_t tag_ann = var_ann (tag);
973 p_map->total_alias_vops = 0;
974 p_map->may_aliases = sbitmap_alloc (num_referenced_vars);
975 sbitmap_zero (p_map->may_aliases);
977 for (j = 0; j < ai->num_addressable_vars; j++)
979 struct alias_map_d *v_map;
982 bool tag_stored_p, var_stored_p;
984 v_map = ai->addressable_vars[j];
986 v_ann = var_ann (var);
988 /* Skip memory tags and variables that have never been
989 written to. We also need to check if the variables are
990 call-clobbered because they may be overwritten by
993 Note this is effectively random accessing elements in
994 the sparse bitset, which can be highly inefficient.
995 So we first check the call_clobbered status of the
996 tag and variable before querying the bitmap. */
997 tag_stored_p = is_call_clobbered (tag)
998 || bitmap_bit_p (ai->written_vars, tag_ann->uid);
999 var_stored_p = is_call_clobbered (var)
1000 || bitmap_bit_p (ai->written_vars, v_ann->uid);
1001 if (!tag_stored_p && !var_stored_p)
1004 if (may_alias_p (p_map->var, p_map->set, var, v_map->set))
1007 size_t num_tag_refs, num_var_refs;
1009 num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1010 num_var_refs = VARRAY_UINT (ai->num_references, v_ann->uid);
1012 /* Add VAR to TAG's may-aliases set. */
1014 /* If this is an aggregate, we may have subvariables for it
1015 that need to be pointed to. */
1016 if (var_can_have_subvars (var)
1017 && (svars = get_subvars_for_var (var)))
1021 for (sv = svars; sv; sv = sv->next)
1023 add_may_alias (tag, sv->var);
1024 /* Update the bitmap used to represent TAG's alias set
1025 in case we need to group aliases. */
1026 SET_BIT (p_map->may_aliases, var_ann (sv->var)->uid);
1031 add_may_alias (tag, var);
1032 /* Update the bitmap used to represent TAG's alias set
1033 in case we need to group aliases. */
1034 SET_BIT (p_map->may_aliases, var_ann (var)->uid);
1037 /* Update the total number of virtual operands due to
1038 aliasing. Since we are adding one more alias to TAG's
1039 may-aliases set, the total number of virtual operands due
1040 to aliasing will be increased by the number of references
1041 made to VAR and TAG (every reference to TAG will also
1042 count as a reference to VAR). */
1043 ai->total_alias_vops += (num_var_refs + num_tag_refs);
1044 p_map->total_alias_vops += (num_var_refs + num_tag_refs);
1051 /* Since this analysis is based exclusively on symbols, it fails to
1052 handle cases where two pointers P and Q have different memory
1053 tags with conflicting alias set numbers but no aliased symbols in
1056 For example, suppose that we have two memory tags TMT.1 and TMT.2
1059 may-aliases (TMT.1) = { a }
1060 may-aliases (TMT.2) = { b }
1062 and the alias set number of TMT.1 conflicts with that of TMT.2.
1063 Since they don't have symbols in common, loads and stores from
1064 TMT.1 and TMT.2 will seem independent of each other, which will
1065 lead to the optimizers making invalid transformations (see
1066 testsuite/gcc.c-torture/execute/pr15262-[12].c).
1068 To avoid this problem, we do a final traversal of AI->POINTERS
1069 looking for pairs of pointers that have no aliased symbols in
1070 common and yet have conflicting alias set numbers. */
1071 for (i = 0; i < ai->num_pointers; i++)
1074 struct alias_map_d *p_map1 = ai->pointers[i];
1075 tree tag1 = var_ann (p_map1->var)->type_mem_tag;
1076 sbitmap may_aliases1 = p_map1->may_aliases;
1078 for (j = i + 1; j < ai->num_pointers; j++)
1080 struct alias_map_d *p_map2 = ai->pointers[j];
1081 tree tag2 = var_ann (p_map2->var)->type_mem_tag;
1082 sbitmap may_aliases2 = p_map2->may_aliases;
1084 /* If the pointers may not point to each other, do nothing. */
1085 if (!may_alias_p (p_map1->var, p_map1->set, tag2, p_map2->set))
1088 /* The two pointers may alias each other. If they already have
1089 symbols in common, do nothing. */
1090 if (sbitmap_any_common_bits (may_aliases1, may_aliases2))
1093 if (sbitmap_first_set_bit (may_aliases2) >= 0)
1097 /* Add all the aliases for TAG2 into TAG1's alias set.
1098 FIXME, update grouping heuristic counters. */
1099 EXECUTE_IF_SET_IN_SBITMAP (may_aliases2, 0, k,
1100 add_may_alias (tag1, referenced_var (k)));
1101 sbitmap_a_or_b (may_aliases1, may_aliases1, may_aliases2);
1105 /* Since TAG2 does not have any aliases of its own, add
1106 TAG2 itself to the alias set of TAG1. */
1107 add_may_alias (tag1, tag2);
1108 SET_BIT (may_aliases1, var_ann (tag2)->uid);
1114 fprintf (dump_file, "%s: Total number of aliased vops: %ld\n",
1115 get_name (current_function_decl),
1116 ai->total_alias_vops);
1118 /* Determine if we need to enable alias grouping. */
1119 if (ai->total_alias_vops >= MAX_ALIASED_VOPS)
1124 /* Comparison function for qsort used in group_aliases. */
1127 total_alias_vops_cmp (const void *p, const void *q)
1129 const struct alias_map_d **p1 = (const struct alias_map_d **)p;
1130 const struct alias_map_d **p2 = (const struct alias_map_d **)q;
1131 long n1 = (*p1)->total_alias_vops;
1132 long n2 = (*p2)->total_alias_vops;
1134 /* We want to sort in descending order. */
1135 return (n1 > n2 ? -1 : (n1 == n2) ? 0 : 1);
1138 /* Group all the aliases for TAG to make TAG represent all the
1139 variables in its alias set. Update the total number
1140 of virtual operands due to aliasing (AI->TOTAL_ALIAS_VOPS). This
1141 function will make TAG be the unique alias tag for all the
1142 variables in its may-aliases. So, given:
1144 may-aliases(TAG) = { V1, V2, V3 }
1146 This function will group the variables into:
1148 may-aliases(V1) = { TAG }
1149 may-aliases(V2) = { TAG }
1150 may-aliases(V2) = { TAG } */
1153 group_aliases_into (tree tag, sbitmap tag_aliases, struct alias_info *ai)
1156 var_ann_t tag_ann = var_ann (tag);
1157 size_t num_tag_refs = VARRAY_UINT (ai->num_references, tag_ann->uid);
1159 EXECUTE_IF_SET_IN_SBITMAP (tag_aliases, 0, i,
1161 tree var = referenced_var (i);
1162 var_ann_t ann = var_ann (var);
1164 /* Make TAG the unique alias of VAR. */
1165 ann->is_alias_tag = 0;
1166 ann->may_aliases = NULL;
1168 /* Note that VAR and TAG may be the same if the function has no
1169 addressable variables (see the discussion at the end of
1170 setup_pointers_and_addressables). */
1172 add_may_alias (var, tag);
1174 /* Reduce total number of virtual operands contributed
1175 by TAG on behalf of VAR. Notice that the references to VAR
1176 itself won't be removed. We will merely replace them with
1177 references to TAG. */
1178 ai->total_alias_vops -= num_tag_refs;
1181 /* We have reduced the number of virtual operands that TAG makes on
1182 behalf of all the variables formerly aliased with it. However,
1183 we have also "removed" all the virtual operands for TAG itself,
1184 so we add them back. */
1185 ai->total_alias_vops += num_tag_refs;
1187 /* TAG no longer has any aliases. */
1188 tag_ann->may_aliases = NULL;
1192 /* Group may-aliases sets to reduce the number of virtual operands due
1195 1- Sort the list of pointers in decreasing number of contributed
1198 2- Take the first entry in AI->POINTERS and revert the role of
1199 the memory tag and its aliases. Usually, whenever an aliased
1200 variable Vi is found to alias with a memory tag T, we add Vi
1201 to the may-aliases set for T. Meaning that after alias
1202 analysis, we will have:
1204 may-aliases(T) = { V1, V2, V3, ..., Vn }
1206 This means that every statement that references T, will get 'n'
1207 virtual operands for each of the Vi tags. But, when alias
1208 grouping is enabled, we make T an alias tag and add it to the
1209 alias set of all the Vi variables:
1211 may-aliases(V1) = { T }
1212 may-aliases(V2) = { T }
1214 may-aliases(Vn) = { T }
1216 This has two effects: (a) statements referencing T will only get
1217 a single virtual operand, and, (b) all the variables Vi will now
1218 appear to alias each other. So, we lose alias precision to
1219 improve compile time. But, in theory, a program with such a high
1220 level of aliasing should not be very optimizable in the first
1223 3- Since variables may be in the alias set of more than one
1224 memory tag, the grouping done in step (2) needs to be extended
1225 to all the memory tags that have a non-empty intersection with
1226 the may-aliases set of tag T. For instance, if we originally
1227 had these may-aliases sets:
1229 may-aliases(T) = { V1, V2, V3 }
1230 may-aliases(R) = { V2, V4 }
1232 In step (2) we would have reverted the aliases for T as:
1234 may-aliases(V1) = { T }
1235 may-aliases(V2) = { T }
1236 may-aliases(V3) = { T }
1238 But note that now V2 is no longer aliased with R. We could
1239 add R to may-aliases(V2), but we are in the process of
1240 grouping aliases to reduce virtual operands so what we do is
1241 add V4 to the grouping to obtain:
1243 may-aliases(V1) = { T }
1244 may-aliases(V2) = { T }
1245 may-aliases(V3) = { T }
1246 may-aliases(V4) = { T }
1248 4- If the total number of virtual operands due to aliasing is
1249 still above the threshold set by max-alias-vops, go back to (2). */
1252 group_aliases (struct alias_info *ai)
1256 /* Sort the POINTERS array in descending order of contributed
1257 virtual operands. */
1258 qsort (ai->pointers, ai->num_pointers, sizeof (struct alias_map_d *),
1259 total_alias_vops_cmp);
1261 /* For every pointer in AI->POINTERS, reverse the roles of its tag
1262 and the tag's may-aliases set. */
1263 for (i = 0; i < ai->num_pointers; i++)
1266 tree tag1 = var_ann (ai->pointers[i]->var)->type_mem_tag;
1267 sbitmap tag1_aliases = ai->pointers[i]->may_aliases;
1269 /* Skip tags that have been grouped already. */
1270 if (ai->pointers[i]->grouped_p)
1273 /* See if TAG1 had any aliases in common with other type tags.
1274 If we find a TAG2 with common aliases with TAG1, add TAG2's
1275 aliases into TAG1. */
1276 for (j = i + 1; j < ai->num_pointers; j++)
1278 sbitmap tag2_aliases = ai->pointers[j]->may_aliases;
1280 if (sbitmap_any_common_bits (tag1_aliases, tag2_aliases))
1282 tree tag2 = var_ann (ai->pointers[j]->var)->type_mem_tag;
1284 sbitmap_a_or_b (tag1_aliases, tag1_aliases, tag2_aliases);
1286 /* TAG2 does not need its aliases anymore. */
1287 sbitmap_zero (tag2_aliases);
1288 var_ann (tag2)->may_aliases = NULL;
1290 /* TAG1 is the unique alias of TAG2. */
1291 add_may_alias (tag2, tag1);
1293 ai->pointers[j]->grouped_p = true;
1297 /* Now group all the aliases we collected into TAG1. */
1298 group_aliases_into (tag1, tag1_aliases, ai);
1300 /* If we've reduced total number of virtual operands below the
1302 if (ai->total_alias_vops < MAX_ALIASED_VOPS)
1306 /* Finally, all the variables that have been grouped cannot be in
1307 the may-alias set of name memory tags. Suppose that we have
1308 grouped the aliases in this code so that may-aliases(a) = TMT.20
1312 # a_9 = V_MAY_DEF <a_8>
1314 ... Several modifications to TMT.20 ...
1318 Since p_5 points to 'a', the optimizers will try to propagate 0
1319 into p_5->field, but that is wrong because there have been
1320 modifications to 'TMT.20' in between. To prevent this we have to
1321 replace 'a' with 'TMT.20' in the name tag of p_5. */
1322 for (i = 0; i < VARRAY_ACTIVE_SIZE (ai->processed_ptrs); i++)
1325 tree ptr = VARRAY_TREE (ai->processed_ptrs, i);
1326 tree name_tag = SSA_NAME_PTR_INFO (ptr)->name_mem_tag;
1327 varray_type aliases;
1329 if (name_tag == NULL_TREE)
1332 aliases = var_ann (name_tag)->may_aliases;
1333 for (j = 0; aliases && j < VARRAY_ACTIVE_SIZE (aliases); j++)
1335 tree alias = VARRAY_TREE (aliases, j);
1336 var_ann_t ann = var_ann (alias);
1338 if ((ann->mem_tag_kind == NOT_A_TAG
1339 || ann->mem_tag_kind == STRUCT_FIELD)
1340 && ann->may_aliases)
1344 gcc_assert (VARRAY_ACTIVE_SIZE (ann->may_aliases) == 1);
1346 new_alias = VARRAY_TREE (ann->may_aliases, 0);
1347 replace_may_alias (name_tag, j, new_alias);
1354 "%s: Total number of aliased vops after grouping: %ld%s\n",
1355 get_name (current_function_decl),
1356 ai->total_alias_vops,
1357 (ai->total_alias_vops < 0) ? " (negative values are OK)" : "");
1361 /* Create a new alias set entry for VAR in AI->ADDRESSABLE_VARS. */
1364 create_alias_map_for (tree var, struct alias_info *ai)
1366 struct alias_map_d *alias_map;
1367 alias_map = xcalloc (1, sizeof (*alias_map));
1368 alias_map->var = var;
1369 alias_map->set = get_alias_set (var);
1370 ai->addressable_vars[ai->num_addressable_vars++] = alias_map;
1374 /* Create memory tags for all the dereferenced pointers and build the
1375 ADDRESSABLE_VARS and POINTERS arrays used for building the may-alias
1376 sets. Based on the address escape and points-to information collected
1377 earlier, this pass will also clear the TREE_ADDRESSABLE flag from those
1378 variables whose address is not needed anymore. */
1381 setup_pointers_and_addressables (struct alias_info *ai)
1383 size_t i, n_vars, num_addressable_vars, num_pointers;
1385 /* Size up the arrays ADDRESSABLE_VARS and POINTERS. */
1386 num_addressable_vars = num_pointers = 0;
1387 for (i = 0; i < num_referenced_vars; i++)
1389 tree var = referenced_var (i);
1391 if (may_be_aliased (var))
1392 num_addressable_vars++;
1394 if (POINTER_TYPE_P (TREE_TYPE (var)))
1396 /* Since we don't keep track of volatile variables, assume that
1397 these pointers are used in indirect store operations. */
1398 if (TREE_THIS_VOLATILE (var))
1399 bitmap_set_bit (ai->dereferenced_ptrs_store, var_ann (var)->uid);
1405 /* Create ADDRESSABLE_VARS and POINTERS. Note that these arrays are
1406 always going to be slightly bigger than we actually need them
1407 because some TREE_ADDRESSABLE variables will be marked
1408 non-addressable below and only pointers with unique type tags are
1409 going to be added to POINTERS. */
1410 ai->addressable_vars = xcalloc (num_addressable_vars,
1411 sizeof (struct alias_map_d *));
1412 ai->pointers = xcalloc (num_pointers, sizeof (struct alias_map_d *));
1413 ai->num_addressable_vars = 0;
1414 ai->num_pointers = 0;
1416 /* Since we will be creating type memory tags within this loop, cache the
1417 value of NUM_REFERENCED_VARS to avoid processing the additional tags
1419 n_vars = num_referenced_vars;
1421 for (i = 0; i < n_vars; i++)
1423 tree var = referenced_var (i);
1424 var_ann_t v_ann = var_ann (var);
1427 /* Name memory tags already have flow-sensitive aliasing
1428 information, so they need not be processed by
1429 compute_flow_insensitive_aliasing. Similarly, type memory
1430 tags are already accounted for when we process their
1433 Structure fields, on the other hand, have to have some of this
1434 information processed for them, but it's pointless to mark them
1435 non-addressable (since they are fake variables anyway). */
1436 if (v_ann->mem_tag_kind != NOT_A_TAG
1437 && v_ann->mem_tag_kind != STRUCT_FIELD)
1440 /* Remove the ADDRESSABLE flag from every addressable variable whose
1441 address is not needed anymore. This is caused by the propagation
1442 of ADDR_EXPR constants into INDIRECT_REF expressions and the
1443 removal of dead pointer assignments done by the early scalar
1445 if (TREE_ADDRESSABLE (var) && v_ann->mem_tag_kind != STRUCT_FIELD)
1447 if (!bitmap_bit_p (ai->addresses_needed, v_ann->uid)
1448 && TREE_CODE (var) != RESULT_DECL
1449 && !is_global_var (var))
1451 bool okay_to_mark = true;
1453 /* Since VAR is now a regular GIMPLE register, we will need
1454 to rename VAR into SSA afterwards. */
1455 mark_sym_for_renaming (var);
1457 if (var_can_have_subvars (var)
1458 && (svars = get_subvars_for_var (var)))
1462 for (sv = svars; sv; sv = sv->next)
1464 var_ann_t svann = var_ann (sv->var);
1465 if (bitmap_bit_p (ai->addresses_needed, svann->uid))
1466 okay_to_mark = false;
1467 mark_sym_for_renaming (sv->var);
1471 /* The address of VAR is not needed, remove the
1472 addressable bit, so that it can be optimized as a
1473 regular variable. */
1475 mark_non_addressable (var);
1479 /* Add the variable to the set of addressables. Mostly
1480 used when scanning operands for ASM_EXPRs that
1481 clobber memory. In those cases, we need to clobber
1482 all call-clobbered variables and all addressables. */
1483 bitmap_set_bit (addressable_vars, v_ann->uid);
1484 if (var_can_have_subvars (var)
1485 && (svars = get_subvars_for_var (var)))
1488 for (sv = svars; sv; sv = sv->next)
1489 bitmap_set_bit (addressable_vars, var_ann (sv->var)->uid);
1495 /* Global variables and addressable locals may be aliased. Create an
1496 entry in ADDRESSABLE_VARS for VAR. */
1497 if (may_be_aliased (var))
1499 create_alias_map_for (var, ai);
1500 mark_sym_for_renaming (var);
1503 /* Add pointer variables that have been dereferenced to the POINTERS
1504 array and create a type memory tag for them. */
1505 if (POINTER_TYPE_P (TREE_TYPE (var)))
1507 if ((bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid)
1508 || bitmap_bit_p (ai->dereferenced_ptrs_load, v_ann->uid)))
1513 /* If pointer VAR still doesn't have a memory tag
1514 associated with it, create it now or re-use an
1516 tag = get_tmt_for (var, ai);
1517 t_ann = var_ann (tag);
1519 /* The type tag will need to be renamed into SSA
1520 afterwards. Note that we cannot do this inside
1521 get_tmt_for because aliasing may run multiple times
1522 and we only create type tags the first time. */
1523 mark_sym_for_renaming (tag);
1525 /* Similarly, if pointer VAR used to have another type
1526 tag, we will need to process it in the renamer to
1527 remove the stale virtual operands. */
1528 if (v_ann->type_mem_tag)
1529 mark_sym_for_renaming (v_ann->type_mem_tag);
1531 /* Associate the tag with pointer VAR. */
1532 v_ann->type_mem_tag = tag;
1534 /* If pointer VAR has been used in a store operation,
1535 then its memory tag must be marked as written-to. */
1536 if (bitmap_bit_p (ai->dereferenced_ptrs_store, v_ann->uid))
1537 bitmap_set_bit (ai->written_vars, t_ann->uid);
1539 /* If pointer VAR is a global variable or a PARM_DECL,
1540 then its memory tag should be considered a global
1542 if (TREE_CODE (var) == PARM_DECL || is_global_var (var))
1543 mark_call_clobbered (tag);
1545 /* All the dereferences of pointer VAR count as
1546 references of TAG. Since TAG can be associated with
1547 several pointers, add the dereferences of VAR to the
1548 TAG. We may need to grow AI->NUM_REFERENCES because
1549 we have been adding name and type tags. */
1550 if (t_ann->uid >= VARRAY_SIZE (ai->num_references))
1551 VARRAY_GROW (ai->num_references, t_ann->uid + 10);
1553 VARRAY_UINT (ai->num_references, t_ann->uid)
1554 += VARRAY_UINT (ai->num_references, v_ann->uid);
1558 /* The pointer has not been dereferenced. If it had a
1559 type memory tag, remove it and mark the old tag for
1560 renaming to remove it out of the IL. */
1561 var_ann_t ann = var_ann (var);
1562 tree tag = ann->type_mem_tag;
1565 mark_sym_for_renaming (tag);
1566 ann->type_mem_tag = NULL_TREE;
1574 /* Determine whether to use .GLOBAL_VAR to model call clobbering semantics. At
1575 every call site, we need to emit V_MAY_DEF expressions to represent the
1576 clobbering effects of the call for variables whose address escapes the
1579 One approach is to group all call-clobbered variables into a single
1580 representative that is used as an alias of every call-clobbered variable
1581 (.GLOBAL_VAR). This works well, but it ties the optimizer hands because
1582 references to any call clobbered variable is a reference to .GLOBAL_VAR.
1584 The second approach is to emit a clobbering V_MAY_DEF for every
1585 call-clobbered variable at call sites. This is the preferred way in terms
1586 of optimization opportunities but it may create too many V_MAY_DEF operands
1587 if there are many call clobbered variables and function calls in the
1590 To decide whether or not to use .GLOBAL_VAR we multiply the number of
1591 function calls found by the number of call-clobbered variables. If that
1592 product is beyond a certain threshold, as determined by the parameterized
1593 values shown below, we use .GLOBAL_VAR.
1595 FIXME. This heuristic should be improved. One idea is to use several
1596 .GLOBAL_VARs of different types instead of a single one. The thresholds
1597 have been derived from a typical bootstrap cycle, including all target
1598 libraries. Compile times were found increase by ~1% compared to using
1602 maybe_create_global_var (struct alias_info *ai)
1604 unsigned i, n_clobbered;
1607 /* No need to create it, if we have one already. */
1608 if (global_var == NULL_TREE)
1610 /* Count all the call-clobbered variables. */
1612 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1617 /* If the number of virtual operands that would be needed to
1618 model all the call-clobbered variables is larger than
1619 GLOBAL_VAR_THRESHOLD, create .GLOBAL_VAR.
1621 Also create .GLOBAL_VAR if there are no call-clobbered
1622 variables and the program contains a mixture of pure/const
1623 and regular function calls. This is to avoid the problem
1624 described in PR 20115:
1627 int func_pure (void) { return X; }
1628 int func_non_pure (int a) { X += a; }
1631 int a = func_pure ();
1637 Since foo() has no call-clobbered variables, there is
1638 no relationship between the calls to func_pure and
1639 func_non_pure. Since func_pure has no side-effects, value
1640 numbering optimizations elide the second call to func_pure.
1641 So, if we have some pure/const and some regular calls in the
1642 program we create .GLOBAL_VAR to avoid missing these
1644 if (ai->num_calls_found * n_clobbered >= (size_t) GLOBAL_VAR_THRESHOLD
1645 || (n_clobbered == 0
1646 && ai->num_calls_found > 0
1647 && ai->num_pure_const_calls_found > 0
1648 && ai->num_calls_found > ai->num_pure_const_calls_found))
1649 create_global_var ();
1652 /* Mark all call-clobbered symbols for renaming. Since the initial
1653 rewrite into SSA ignored all call sites, we may need to rename
1654 .GLOBAL_VAR and the call-clobbered variables. */
1655 EXECUTE_IF_SET_IN_BITMAP (call_clobbered_vars, 0, i, bi)
1657 tree var = referenced_var (i);
1659 /* If the function has calls to clobbering functions and
1660 .GLOBAL_VAR has been created, make it an alias for all
1661 call-clobbered variables. */
1662 if (global_var && var != global_var)
1665 add_may_alias (var, global_var);
1666 if (var_can_have_subvars (var)
1667 && (svars = get_subvars_for_var (var)))
1670 for (sv = svars; sv; sv = sv->next)
1671 mark_sym_for_renaming (sv->var);
1675 mark_sym_for_renaming (var);
1680 /* Return TRUE if pointer PTR may point to variable VAR.
1682 MEM_ALIAS_SET is the alias set for the memory location pointed-to by PTR
1683 This is needed because when checking for type conflicts we are
1684 interested in the alias set of the memory location pointed-to by
1685 PTR. The alias set of PTR itself is irrelevant.
1687 VAR_ALIAS_SET is the alias set for VAR. */
1690 may_alias_p (tree ptr, HOST_WIDE_INT mem_alias_set,
1691 tree var, HOST_WIDE_INT var_alias_set)
1696 alias_stats.alias_queries++;
1697 alias_stats.simple_queries++;
1699 /* By convention, a variable cannot alias itself. */
1700 mem = var_ann (ptr)->type_mem_tag;
1703 alias_stats.alias_noalias++;
1704 alias_stats.simple_resolved++;
1708 /* If -fargument-noalias-global is >1, pointer arguments may
1709 not point to global variables. */
1710 if (flag_argument_noalias > 1 && is_global_var (var)
1711 && TREE_CODE (ptr) == PARM_DECL)
1713 alias_stats.alias_noalias++;
1714 alias_stats.simple_resolved++;
1718 /* If either MEM or VAR is a read-only global and the other one
1719 isn't, then PTR cannot point to VAR. */
1720 if ((unmodifiable_var_p (mem) && !unmodifiable_var_p (var))
1721 || (unmodifiable_var_p (var) && !unmodifiable_var_p (mem)))
1723 alias_stats.alias_noalias++;
1724 alias_stats.simple_resolved++;
1728 m_ann = var_ann (mem);
1730 gcc_assert (m_ann->mem_tag_kind == TYPE_TAG);
1732 alias_stats.tbaa_queries++;
1734 /* If VAR is a pointer with the same alias set as PTR, then dereferencing
1735 PTR can't possibly affect VAR. Note, that we are specifically testing
1736 for PTR's alias set here, not its pointed-to type. We also can't
1737 do this check with relaxed aliasing enabled. */
1738 if (POINTER_TYPE_P (TREE_TYPE (var))
1739 && var_alias_set != 0
1740 && mem_alias_set != 0)
1742 HOST_WIDE_INT ptr_alias_set = get_alias_set (ptr);
1743 if (ptr_alias_set == var_alias_set)
1745 alias_stats.alias_noalias++;
1746 alias_stats.tbaa_resolved++;
1751 /* If the alias sets don't conflict then MEM cannot alias VAR. */
1752 if (!alias_sets_conflict_p (mem_alias_set, var_alias_set))
1754 alias_stats.alias_noalias++;
1755 alias_stats.tbaa_resolved++;
1758 alias_stats.alias_mayalias++;
1763 /* Add ALIAS to the set of variables that may alias VAR. */
1766 add_may_alias (tree var, tree alias)
1769 var_ann_t v_ann = get_var_ann (var);
1770 var_ann_t a_ann = get_var_ann (alias);
1772 gcc_assert (var != alias);
1774 if (v_ann->may_aliases == NULL)
1775 VARRAY_TREE_INIT (v_ann->may_aliases, 2, "aliases");
1777 /* Avoid adding duplicates. */
1778 for (i = 0; i < VARRAY_ACTIVE_SIZE (v_ann->may_aliases); i++)
1779 if (alias == VARRAY_TREE (v_ann->may_aliases, i))
1782 /* If VAR is a call-clobbered variable, so is its new ALIAS.
1783 FIXME, call-clobbering should only depend on whether an address
1784 escapes. It should be independent of aliasing. */
1785 if (is_call_clobbered (var))
1786 mark_call_clobbered (alias);
1788 /* Likewise. If ALIAS is call-clobbered, so is VAR. */
1789 else if (is_call_clobbered (alias))
1790 mark_call_clobbered (var);
1792 VARRAY_PUSH_TREE (v_ann->may_aliases, alias);
1793 a_ann->is_alias_tag = 1;
1797 /* Replace alias I in the alias sets of VAR with NEW_ALIAS. */
1800 replace_may_alias (tree var, size_t i, tree new_alias)
1802 var_ann_t v_ann = var_ann (var);
1803 VARRAY_TREE (v_ann->may_aliases, i) = new_alias;
1805 /* If VAR is a call-clobbered variable, so is NEW_ALIAS.
1806 FIXME, call-clobbering should only depend on whether an address
1807 escapes. It should be independent of aliasing. */
1808 if (is_call_clobbered (var))
1809 mark_call_clobbered (new_alias);
1811 /* Likewise. If NEW_ALIAS is call-clobbered, so is VAR. */
1812 else if (is_call_clobbered (new_alias))
1813 mark_call_clobbered (var);
1817 /* Mark pointer PTR as pointing to an arbitrary memory location. */
1820 set_pt_anything (tree ptr)
1822 struct ptr_info_def *pi = get_ptr_info (ptr);
1824 pi->pt_anything = 1;
1827 /* The pointer used to have a name tag, but we now found it pointing
1828 to an arbitrary location. The name tag needs to be renamed and
1829 disassociated from PTR. */
1830 if (pi->name_mem_tag)
1832 mark_sym_for_renaming (pi->name_mem_tag);
1833 pi->name_mem_tag = NULL_TREE;
1838 /* Mark pointer PTR as pointing to a malloc'd memory area. */
1841 set_pt_malloc (tree ptr)
1843 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
1845 /* If the pointer has already been found to point to arbitrary
1846 memory locations, it is unsafe to mark it as pointing to malloc. */
1847 if (pi->pt_anything)
1854 /* Given two different pointers DEST and ORIG. Merge the points-to
1855 information in ORIG into DEST. AI contains all the alias
1856 information collected up to this point. */
1859 merge_pointed_to_info (struct alias_info *ai, tree dest, tree orig)
1861 struct ptr_info_def *dest_pi, *orig_pi;
1863 gcc_assert (dest != orig);
1865 /* Make sure we have points-to information for ORIG. */
1866 collect_points_to_info_for (ai, orig);
1868 dest_pi = get_ptr_info (dest);
1869 orig_pi = SSA_NAME_PTR_INFO (orig);
1873 gcc_assert (orig_pi != dest_pi);
1875 /* Notice that we never merge PT_MALLOC. This attribute is only
1876 true if the pointer is the result of a malloc() call.
1877 Otherwise, we can end up in this situation:
1883 P_j would be marked as PT_MALLOC, however we currently do not
1884 handle cases of more than one pointer pointing to the same
1887 FIXME: If the merging comes from an expression that preserves
1888 the PT_MALLOC attribute (copy assignment, address
1889 arithmetic), we ought to merge PT_MALLOC, but then both
1890 pointers would end up getting different name tags because
1891 create_name_tags is not smart enough to determine that the
1892 two come from the same malloc call. Copy propagation before
1893 aliasing should cure this. */
1894 dest_pi->pt_malloc = 0;
1895 if (orig_pi->pt_malloc || orig_pi->pt_anything)
1896 set_pt_anything (dest);
1898 dest_pi->pt_null |= orig_pi->pt_null;
1900 if (!dest_pi->pt_anything
1902 && !bitmap_empty_p (orig_pi->pt_vars))
1904 if (dest_pi->pt_vars == NULL)
1906 dest_pi->pt_vars = BITMAP_GGC_ALLOC ();
1907 bitmap_copy (dest_pi->pt_vars, orig_pi->pt_vars);
1910 bitmap_ior_into (dest_pi->pt_vars, orig_pi->pt_vars);
1914 set_pt_anything (dest);
1918 /* Add EXPR to the list of expressions pointed-to by PTR. */
1921 add_pointed_to_expr (struct alias_info *ai, tree ptr, tree expr)
1923 if (TREE_CODE (expr) == WITH_SIZE_EXPR)
1924 expr = TREE_OPERAND (expr, 0);
1928 if (TREE_CODE (expr) == CALL_EXPR
1929 && (call_expr_flags (expr) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
1931 /* If EXPR is a malloc-like call, then the area pointed to PTR
1932 is guaranteed to not alias with anything else. */
1933 set_pt_malloc (ptr);
1935 else if (TREE_CODE (expr) == ADDR_EXPR)
1937 /* Found P_i = ADDR_EXPR */
1938 add_pointed_to_var (ai, ptr, expr);
1940 else if (TREE_CODE (expr) == SSA_NAME && POINTER_TYPE_P (TREE_TYPE (expr)))
1942 /* Found P_i = Q_j. */
1943 merge_pointed_to_info (ai, ptr, expr);
1945 else if (TREE_CODE (expr) == PLUS_EXPR || TREE_CODE (expr) == MINUS_EXPR)
1947 /* Found P_i = PLUS_EXPR or P_i = MINUS_EXPR */
1948 tree op0 = TREE_OPERAND (expr, 0);
1949 tree op1 = TREE_OPERAND (expr, 1);
1951 /* Both operands may be of pointer type. FIXME: Shouldn't
1952 we just expect PTR + OFFSET always? */
1953 if (POINTER_TYPE_P (TREE_TYPE (op0))
1954 && TREE_CODE (op0) != INTEGER_CST)
1956 if (TREE_CODE (op0) == SSA_NAME)
1957 merge_pointed_to_info (ai, ptr, op0);
1958 else if (TREE_CODE (op0) == ADDR_EXPR)
1959 add_pointed_to_var (ai, ptr, op0);
1961 set_pt_anything (ptr);
1964 if (POINTER_TYPE_P (TREE_TYPE (op1))
1965 && TREE_CODE (op1) != INTEGER_CST)
1967 if (TREE_CODE (op1) == SSA_NAME)
1968 merge_pointed_to_info (ai, ptr, op1);
1969 else if (TREE_CODE (op1) == ADDR_EXPR)
1970 add_pointed_to_var (ai, ptr, op1);
1972 set_pt_anything (ptr);
1975 /* Neither operand is a pointer? VAR can be pointing anywhere.
1976 FIXME: Shouldn't we abort here? If we get here, we found
1977 PTR = INT_CST + INT_CST, which should not be a valid pointer
1979 if (!(POINTER_TYPE_P (TREE_TYPE (op0))
1980 && TREE_CODE (op0) != INTEGER_CST)
1981 && !(POINTER_TYPE_P (TREE_TYPE (op1))
1982 && TREE_CODE (op1) != INTEGER_CST))
1983 set_pt_anything (ptr);
1985 else if (integer_zerop (expr))
1987 /* EXPR is the NULL pointer. Mark PTR as pointing to NULL. */
1988 SSA_NAME_PTR_INFO (ptr)->pt_null = 1;
1992 /* If we can't recognize the expression, assume that PTR may
1994 set_pt_anything (ptr);
1999 /* If VALUE is of the form &DECL, add DECL to the set of variables
2000 pointed-to by PTR. Otherwise, add VALUE as a pointed-to expression by
2001 PTR. AI points to the collected alias information. */
2004 add_pointed_to_var (struct alias_info *ai, tree ptr, tree value)
2006 struct ptr_info_def *pi = get_ptr_info (ptr);
2007 tree pt_var = NULL_TREE;
2008 HOST_WIDE_INT offset, size;
2014 gcc_assert (TREE_CODE (value) == ADDR_EXPR);
2016 addrop = TREE_OPERAND (value, 0);
2017 if (REFERENCE_CLASS_P (addrop))
2018 pt_var = get_base_address (addrop);
2022 /* If this is a component_ref, see if we can get a smaller number of
2023 variables to take the address of. */
2024 if (TREE_CODE (addrop) == COMPONENT_REF
2025 && (ref = okay_component_ref_for_subvars (addrop, &offset ,&size)))
2028 svars = get_subvars_for_var (ref);
2030 uid = var_ann (pt_var)->uid;
2032 if (pi->pt_vars == NULL)
2033 pi->pt_vars = BITMAP_GGC_ALLOC ();
2034 /* If the variable is a global, mark the pointer as pointing to
2035 global memory (which will make its tag a global variable). */
2036 if (is_global_var (pt_var))
2037 pi->pt_global_mem = 1;
2039 for (sv = svars; sv; sv = sv->next)
2041 if (overlap_subvar (offset, size, sv, NULL))
2043 bitmap_set_bit (pi->pt_vars, var_ann (sv->var)->uid);
2044 bitmap_set_bit (ai->addresses_needed, var_ann (sv->var)->uid);
2048 else if (pt_var && SSA_VAR_P (pt_var))
2051 uid = var_ann (pt_var)->uid;
2053 if (pi->pt_vars == NULL)
2054 pi->pt_vars = BITMAP_GGC_ALLOC ();
2056 /* If this is an aggregate, we may have subvariables for it that need
2057 to be pointed to. */
2058 if (var_can_have_subvars (pt_var)
2059 && (svars = get_subvars_for_var (pt_var)))
2062 for (sv = svars; sv; sv = sv->next)
2064 uid = var_ann (sv->var)->uid;
2065 bitmap_set_bit (ai->addresses_needed, uid);
2066 bitmap_set_bit (pi->pt_vars, uid);
2071 bitmap_set_bit (ai->addresses_needed, uid);
2072 bitmap_set_bit (pi->pt_vars, uid);
2075 /* If the variable is a global, mark the pointer as pointing to
2076 global memory (which will make its tag a global variable). */
2077 if (is_global_var (pt_var))
2078 pi->pt_global_mem = 1;
2083 /* Callback for walk_use_def_chains to gather points-to information from the
2086 VAR is an SSA variable or a GIMPLE expression.
2088 STMT is the statement that generates the SSA variable or, if STMT is a
2089 PHI_NODE, VAR is one of the PHI arguments.
2091 DATA is a pointer to a structure of type ALIAS_INFO. */
2094 collect_points_to_info_r (tree var, tree stmt, void *data)
2096 struct alias_info *ai = (struct alias_info *) data;
2098 if (dump_file && (dump_flags & TDF_DETAILS))
2100 fprintf (dump_file, "Visiting use-def links for ");
2101 print_generic_expr (dump_file, var, dump_flags);
2102 fprintf (dump_file, "\n");
2105 switch (TREE_CODE (stmt))
2108 gcc_assert (TREE_CODE (TREE_OPERAND (stmt, 0)) == MODIFY_EXPR);
2109 stmt = TREE_OPERAND (stmt, 0);
2114 tree rhs = TREE_OPERAND (stmt, 1);
2116 add_pointed_to_expr (ai, var, rhs);
2121 /* Pointers defined by __asm__ statements can point anywhere. */
2122 set_pt_anything (var);
2126 if (IS_EMPTY_STMT (stmt))
2128 tree decl = SSA_NAME_VAR (var);
2130 if (TREE_CODE (decl) == PARM_DECL)
2131 add_pointed_to_expr (ai, var, decl);
2132 else if (DECL_INITIAL (decl))
2133 add_pointed_to_expr (ai, var, DECL_INITIAL (decl));
2135 add_pointed_to_expr (ai, var, decl);
2141 /* It STMT is a PHI node, then VAR is one of its arguments. The
2142 variable that we are analyzing is the LHS of the PHI node. */
2143 tree lhs = PHI_RESULT (stmt);
2145 switch (TREE_CODE (var))
2148 add_pointed_to_var (ai, lhs, var);
2152 /* Avoid unnecessary merges. */
2154 merge_pointed_to_info (ai, lhs, var);
2158 gcc_assert (is_gimple_min_invariant (var));
2159 add_pointed_to_expr (ai, lhs, var);
2173 /* Return true if STMT is an "escape" site from the current function. Escape
2174 sites those statements which might expose the address of a variable
2175 outside the current function. STMT is an escape site iff:
2177 1- STMT is a function call, or
2178 2- STMT is an __asm__ expression, or
2179 3- STMT is an assignment to a non-local variable, or
2180 4- STMT is a return statement.
2182 AI points to the alias information collected so far. */
2185 is_escape_site (tree stmt, struct alias_info *ai)
2187 tree call = get_call_expr_in (stmt);
2188 if (call != NULL_TREE)
2190 ai->num_calls_found++;
2192 if (!TREE_SIDE_EFFECTS (call))
2193 ai->num_pure_const_calls_found++;
2197 else if (TREE_CODE (stmt) == ASM_EXPR)
2199 else if (TREE_CODE (stmt) == MODIFY_EXPR)
2201 tree lhs = TREE_OPERAND (stmt, 0);
2203 /* Get to the base of _REF nodes. */
2204 if (TREE_CODE (lhs) != SSA_NAME)
2205 lhs = get_base_address (lhs);
2207 /* If we couldn't recognize the LHS of the assignment, assume that it
2208 is a non-local store. */
2209 if (lhs == NULL_TREE)
2212 /* If the RHS is a conversion between a pointer and an integer, the
2213 pointer escapes since we can't track the integer. */
2214 if ((TREE_CODE (TREE_OPERAND (stmt, 1)) == NOP_EXPR
2215 || TREE_CODE (TREE_OPERAND (stmt, 1)) == CONVERT_EXPR
2216 || TREE_CODE (TREE_OPERAND (stmt, 1)) == VIEW_CONVERT_EXPR)
2217 && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND
2218 (TREE_OPERAND (stmt, 1), 0)))
2219 && !POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (stmt, 1))))
2222 /* If the LHS is an SSA name, it can't possibly represent a non-local
2224 if (TREE_CODE (lhs) == SSA_NAME)
2227 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
2228 local variables we cannot be sure if it will escape, because we
2229 don't have information about objects not in SSA form. Need to
2230 implement something along the lines of
2232 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
2233 Midkiff, ``Escape analysis for java,'' in Proceedings of the
2234 Conference on Object-Oriented Programming Systems, Languages, and
2235 Applications (OOPSLA), pp. 1-19, 1999. */
2238 else if (TREE_CODE (stmt) == RETURN_EXPR)
2245 /* Create a new memory tag of type TYPE. If IS_TYPE_TAG is true, the tag
2246 is considered to represent all the pointers whose pointed-to types are
2247 in the same alias set class. Otherwise, the tag represents a single
2248 SSA_NAME pointer variable. */
2251 create_memory_tag (tree type, bool is_type_tag)
2254 tree tag = create_tmp_var_raw (type, (is_type_tag) ? "TMT" : "NMT");
2256 /* By default, memory tags are local variables. Alias analysis will
2257 determine whether they should be considered globals. */
2258 DECL_CONTEXT (tag) = current_function_decl;
2260 /* Memory tags are by definition addressable. This also prevents
2261 is_gimple_ref frome confusing memory tags with optimizable
2263 TREE_ADDRESSABLE (tag) = 1;
2265 ann = get_var_ann (tag);
2266 ann->mem_tag_kind = (is_type_tag) ? TYPE_TAG : NAME_TAG;
2267 ann->type_mem_tag = NULL_TREE;
2269 /* Add the tag to the symbol table. */
2270 add_referenced_tmp_var (tag);
2276 /* Create a name memory tag to represent a specific SSA_NAME pointer P_i.
2277 This is used if P_i has been found to point to a specific set of
2278 variables or to a non-aliased memory location like the address returned
2279 by malloc functions. */
2282 get_nmt_for (tree ptr)
2284 struct ptr_info_def *pi = get_ptr_info (ptr);
2285 tree tag = pi->name_mem_tag;
2287 if (tag == NULL_TREE)
2288 tag = create_memory_tag (TREE_TYPE (TREE_TYPE (ptr)), false);
2290 /* If PTR is a PARM_DECL, it points to a global variable or malloc,
2291 then its name tag should be considered a global variable. */
2292 if (TREE_CODE (SSA_NAME_VAR (ptr)) == PARM_DECL
2294 || pi->pt_global_mem)
2295 mark_call_clobbered (tag);
2301 /* Return the type memory tag associated to pointer PTR. A memory tag is an
2302 artificial variable that represents the memory location pointed-to by
2303 PTR. It is used to model the effects of pointer de-references on
2304 addressable variables.
2306 AI points to the data gathered during alias analysis. This function
2307 populates the array AI->POINTERS. */
2310 get_tmt_for (tree ptr, struct alias_info *ai)
2314 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2315 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2317 /* To avoid creating unnecessary memory tags, only create one memory tag
2318 per alias set class. Note that it may be tempting to group
2319 memory tags based on conflicting alias sets instead of
2320 equivalence. That would be wrong because alias sets are not
2321 necessarily transitive (as demonstrated by the libstdc++ test
2322 23_containers/vector/cons/4.cc). Given three alias sets A, B, C
2323 such that conflicts (A, B) == true and conflicts (A, C) == true,
2324 it does not necessarily follow that conflicts (B, C) == true. */
2325 for (i = 0, tag = NULL_TREE; i < ai->num_pointers; i++)
2327 struct alias_map_d *curr = ai->pointers[i];
2328 tree curr_tag = var_ann (curr->var)->type_mem_tag;
2329 if (tag_set == curr->set
2330 && TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (curr_tag)))
2337 /* If VAR cannot alias with any of the existing memory tags, create a new
2338 tag for PTR and add it to the POINTERS array. */
2339 if (tag == NULL_TREE)
2341 struct alias_map_d *alias_map;
2343 /* If PTR did not have a type tag already, create a new TMT.*
2344 artificial variable representing the memory location
2345 pointed-to by PTR. */
2346 if (var_ann (ptr)->type_mem_tag == NULL_TREE)
2347 tag = create_memory_tag (tag_type, true);
2349 tag = var_ann (ptr)->type_mem_tag;
2351 /* Add PTR to the POINTERS array. Note that we are not interested in
2352 PTR's alias set. Instead, we cache the alias set for the memory that
2354 alias_map = xcalloc (1, sizeof (*alias_map));
2355 alias_map->var = ptr;
2356 alias_map->set = tag_set;
2357 ai->pointers[ai->num_pointers++] = alias_map;
2360 /* If the pointed-to type is volatile, so is the tag. */
2361 TREE_THIS_VOLATILE (tag) |= TREE_THIS_VOLATILE (tag_type);
2363 /* Make sure that the type tag has the same alias set as the
2365 gcc_assert (tag_set == get_alias_set (tag));
2367 /* If PTR's pointed-to type is read-only, then TAG's type must also
2369 gcc_assert (TYPE_READONLY (tag_type) == TYPE_READONLY (TREE_TYPE (tag)));
2375 /* Create GLOBAL_VAR, an artificial global variable to act as a
2376 representative of all the variables that may be clobbered by function
2380 create_global_var (void)
2382 global_var = build_decl (VAR_DECL, get_identifier (".GLOBAL_VAR"),
2384 DECL_ARTIFICIAL (global_var) = 1;
2385 TREE_READONLY (global_var) = 0;
2386 DECL_EXTERNAL (global_var) = 1;
2387 TREE_STATIC (global_var) = 1;
2388 TREE_USED (global_var) = 1;
2389 DECL_CONTEXT (global_var) = NULL_TREE;
2390 TREE_THIS_VOLATILE (global_var) = 0;
2391 TREE_ADDRESSABLE (global_var) = 0;
2393 add_referenced_tmp_var (global_var);
2394 mark_sym_for_renaming (global_var);
2398 /* Dump alias statistics on FILE. */
2401 dump_alias_stats (FILE *file)
2403 const char *funcname
2404 = lang_hooks.decl_printable_name (current_function_decl, 2);
2405 fprintf (file, "\nAlias statistics for %s\n\n", funcname);
2406 fprintf (file, "Total alias queries:\t%u\n", alias_stats.alias_queries);
2407 fprintf (file, "Total alias mayalias results:\t%u\n",
2408 alias_stats.alias_mayalias);
2409 fprintf (file, "Total alias noalias results:\t%u\n",
2410 alias_stats.alias_noalias);
2411 fprintf (file, "Total simple queries:\t%u\n",
2412 alias_stats.simple_queries);
2413 fprintf (file, "Total simple resolved:\t%u\n",
2414 alias_stats.simple_resolved);
2415 fprintf (file, "Total TBAA queries:\t%u\n",
2416 alias_stats.tbaa_queries);
2417 fprintf (file, "Total TBAA resolved:\t%u\n",
2418 alias_stats.tbaa_resolved);
2422 /* Dump alias information on FILE. */
2425 dump_alias_info (FILE *file)
2428 const char *funcname
2429 = lang_hooks.decl_printable_name (current_function_decl, 2);
2431 fprintf (file, "\nFlow-insensitive alias information for %s\n\n", funcname);
2433 fprintf (file, "Aliased symbols\n\n");
2434 for (i = 0; i < num_referenced_vars; i++)
2436 tree var = referenced_var (i);
2437 if (may_be_aliased (var))
2438 dump_variable (file, var);
2441 fprintf (file, "\nDereferenced pointers\n\n");
2442 for (i = 0; i < num_referenced_vars; i++)
2444 tree var = referenced_var (i);
2445 var_ann_t ann = var_ann (var);
2446 if (ann->type_mem_tag)
2447 dump_variable (file, var);
2450 fprintf (file, "\nType memory tags\n\n");
2451 for (i = 0; i < num_referenced_vars; i++)
2453 tree var = referenced_var (i);
2454 var_ann_t ann = var_ann (var);
2455 if (ann->mem_tag_kind == TYPE_TAG)
2456 dump_variable (file, var);
2459 fprintf (file, "\n\nFlow-sensitive alias information for %s\n\n", funcname);
2461 fprintf (file, "SSA_NAME pointers\n\n");
2462 for (i = 1; i < num_ssa_names; i++)
2464 tree ptr = ssa_name (i);
2465 struct ptr_info_def *pi;
2467 if (ptr == NULL_TREE)
2470 pi = SSA_NAME_PTR_INFO (ptr);
2471 if (!SSA_NAME_IN_FREE_LIST (ptr)
2473 && pi->name_mem_tag)
2474 dump_points_to_info_for (file, ptr);
2477 fprintf (file, "\nName memory tags\n\n");
2478 for (i = 0; i < num_referenced_vars; i++)
2480 tree var = referenced_var (i);
2481 var_ann_t ann = var_ann (var);
2482 if (ann->mem_tag_kind == NAME_TAG)
2483 dump_variable (file, var);
2486 fprintf (file, "\n");
2490 /* Dump alias information on stderr. */
2493 debug_alias_info (void)
2495 dump_alias_info (stderr);
2499 /* Return the alias information associated with pointer T. It creates a
2500 new instance if none existed. */
2502 struct ptr_info_def *
2503 get_ptr_info (tree t)
2505 struct ptr_info_def *pi;
2507 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
2509 pi = SSA_NAME_PTR_INFO (t);
2512 pi = ggc_alloc (sizeof (*pi));
2513 memset ((void *)pi, 0, sizeof (*pi));
2514 SSA_NAME_PTR_INFO (t) = pi;
2521 /* Dump points-to information for SSA_NAME PTR into FILE. */
2524 dump_points_to_info_for (FILE *file, tree ptr)
2526 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
2528 print_generic_expr (file, ptr, dump_flags);
2532 if (pi->name_mem_tag)
2534 fprintf (file, ", name memory tag: ");
2535 print_generic_expr (file, pi->name_mem_tag, dump_flags);
2538 if (pi->is_dereferenced)
2539 fprintf (file, ", is dereferenced");
2541 if (pi->value_escapes_p)
2542 fprintf (file, ", its value escapes");
2544 if (pi->pt_anything)
2545 fprintf (file, ", points-to anything");
2548 fprintf (file, ", points-to malloc");
2551 fprintf (file, ", points-to NULL");
2558 fprintf (file, ", points-to vars: { ");
2559 EXECUTE_IF_SET_IN_BITMAP (pi->pt_vars, 0, ix, bi)
2561 print_generic_expr (file, referenced_var (ix), dump_flags);
2562 fprintf (file, " ");
2564 fprintf (file, "}");
2568 fprintf (file, "\n");
2572 /* Dump points-to information for VAR into stderr. */
2575 debug_points_to_info_for (tree var)
2577 dump_points_to_info_for (stderr, var);
2581 /* Dump points-to information into FILE. NOTE: This function is slow, as
2582 it needs to traverse the whole CFG looking for pointer SSA_NAMEs. */
2585 dump_points_to_info (FILE *file)
2588 block_stmt_iterator si;
2592 lang_hooks.decl_printable_name (current_function_decl, 2);
2594 fprintf (file, "\n\nPointed-to sets for pointers in %s\n\n", fname);
2596 /* First dump points-to information for the default definitions of
2597 pointer variables. This is necessary because default definitions are
2598 not part of the code. */
2599 for (i = 0; i < num_referenced_vars; i++)
2601 tree var = referenced_var (i);
2602 if (POINTER_TYPE_P (TREE_TYPE (var)))
2604 var_ann_t ann = var_ann (var);
2605 if (ann->default_def)
2606 dump_points_to_info_for (file, ann->default_def);
2610 /* Dump points-to information for every pointer defined in the program. */
2615 for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
2617 tree ptr = PHI_RESULT (phi);
2618 if (POINTER_TYPE_P (TREE_TYPE (ptr)))
2619 dump_points_to_info_for (file, ptr);
2622 for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
2624 tree stmt = bsi_stmt (si);
2626 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
2627 if (POINTER_TYPE_P (TREE_TYPE (def)))
2628 dump_points_to_info_for (file, def);
2632 fprintf (file, "\n");
2636 /* Dump points-to info pointed by PTO into STDERR. */
2639 debug_points_to_info (void)
2641 dump_points_to_info (stderr);
2644 /* Dump to FILE the list of variables that may be aliasing VAR. */
2647 dump_may_aliases_for (FILE *file, tree var)
2649 varray_type aliases;
2651 if (TREE_CODE (var) == SSA_NAME)
2652 var = SSA_NAME_VAR (var);
2654 aliases = var_ann (var)->may_aliases;
2658 fprintf (file, "{ ");
2659 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2661 print_generic_expr (file, VARRAY_TREE (aliases, i), dump_flags);
2662 fprintf (file, " ");
2664 fprintf (file, "}");
2669 /* Dump to stderr the list of variables that may be aliasing VAR. */
2672 debug_may_aliases_for (tree var)
2674 dump_may_aliases_for (stderr, var);
2677 /* Return true if VAR may be aliased. */
2680 may_be_aliased (tree var)
2683 if (TREE_ADDRESSABLE (var))
2686 /* Globally visible variables can have their addresses taken by other
2687 translation units. */
2688 if (DECL_EXTERNAL (var) || TREE_PUBLIC (var))
2691 /* Automatic variables can't have their addresses escape any other way.
2692 This must be after the check for global variables, as extern declarations
2693 do not have TREE_STATIC set. */
2694 if (!TREE_STATIC (var))
2697 /* If we're in unit-at-a-time mode, then we must have seen all occurrences
2698 of address-of operators, and so we can trust TREE_ADDRESSABLE. Otherwise
2699 we can only be sure the variable isn't addressable if it's local to the
2700 current function. */
2701 if (flag_unit_at_a_time)
2703 if (decl_function_context (var) == current_function_decl)
2710 /* Add VAR to the list of may-aliases of PTR's type tag. If PTR
2711 doesn't already have a type tag, create one. */
2714 add_type_alias (tree ptr, tree var)
2716 varray_type aliases;
2718 var_ann_t ann = var_ann (ptr);
2721 if (ann->type_mem_tag == NULL_TREE)
2725 tree tag_type = TREE_TYPE (TREE_TYPE (ptr));
2726 HOST_WIDE_INT tag_set = get_alias_set (tag_type);
2728 /* PTR doesn't have a type tag, create a new one and add VAR to
2729 the new tag's alias set.
2731 FIXME, This is slower than necessary. We need to determine
2732 whether there is another pointer Q with the same alias set as
2733 PTR. This could be sped up by having type tags associated
2735 for (i = 0; i < num_referenced_vars; i++)
2737 q = referenced_var (i);
2739 if (POINTER_TYPE_P (TREE_TYPE (q))
2740 && tag_set == get_alias_set (TREE_TYPE (TREE_TYPE (q))))
2742 /* Found another pointer Q with the same alias set as
2743 the PTR's pointed-to type. If Q has a type tag, use
2744 it. Otherwise, create a new memory tag for PTR. */
2745 var_ann_t ann1 = var_ann (q);
2746 if (ann1->type_mem_tag)
2747 ann->type_mem_tag = ann1->type_mem_tag;
2749 ann->type_mem_tag = create_memory_tag (tag_type, true);
2754 /* Couldn't find any other pointer with a type tag we could use.
2755 Create a new memory tag for PTR. */
2756 ann->type_mem_tag = create_memory_tag (tag_type, true);
2760 /* If VAR is not already PTR's type tag, add it to the may-alias set
2761 for PTR's type tag. */
2762 gcc_assert (var_ann (var)->type_mem_tag == NOT_A_TAG);
2763 tag = ann->type_mem_tag;
2765 /* If VAR has subvars, add the subvars to the tag instead of the
2767 if (var_can_have_subvars (var)
2768 && (svars = get_subvars_for_var (var)))
2771 for (sv = svars; sv; sv = sv->next)
2772 add_may_alias (tag, sv->var);
2775 add_may_alias (tag, var);
2777 /* TAG and its set of aliases need to be marked for renaming. */
2778 mark_sym_for_renaming (tag);
2779 if ((aliases = var_ann (tag)->may_aliases) != NULL)
2782 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2783 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2786 /* If we had grouped aliases, VAR may have aliases of its own. Mark
2787 them for renaming as well. Other statements referencing the
2788 aliases of VAR will need to be updated. */
2789 if ((aliases = var_ann (var)->may_aliases) != NULL)
2792 for (i = 0; i < VARRAY_ACTIVE_SIZE (aliases); i++)
2793 mark_sym_for_renaming (VARRAY_TREE (aliases, i));
2798 /* This structure is simply used during pushing fields onto the fieldstack
2799 to track the offset of the field, since bitpos_of_field gives it relative
2800 to its immediate containing type, and we want it relative to the ultimate
2801 containing object. */
2803 typedef struct fieldoff
2806 HOST_WIDE_INT offset;
2809 DEF_VEC_MALLOC_P(fieldoff_t);
2811 /* Return the position, in bits, of FIELD_DECL from the beginning of its
2813 Return -1 if the position is conditional or otherwise non-constant
2816 static HOST_WIDE_INT
2817 bitpos_of_field (const tree fdecl)
2820 if (TREE_CODE (DECL_FIELD_OFFSET (fdecl)) != INTEGER_CST
2821 || TREE_CODE (DECL_FIELD_BIT_OFFSET (fdecl)) != INTEGER_CST)
2824 return (tree_low_cst (DECL_FIELD_OFFSET (fdecl), 1) * 8)
2825 + tree_low_cst (DECL_FIELD_BIT_OFFSET (fdecl), 1);
2828 /* Given a TYPE, and a vector of field offsets FIELDSTACK, push all the fields
2829 of TYPE onto fieldstack, recording their offsets along the way.
2830 OFFSET is used to keep track of the offset in this entire structure, rather
2831 than just the immediately containing structure. */
2834 push_fields_onto_fieldstack (tree type, VEC(fieldoff_t) **fieldstack,
2835 HOST_WIDE_INT offset)
2838 tree field = TYPE_FIELDS (type);
2841 if (var_can_have_subvars (field)
2842 && TREE_CODE (field) == FIELD_DECL)
2844 size_t before = VEC_length (fieldoff_t, *fieldstack);
2845 /* Empty structures may have actual size, like in C++. So see if we
2846 actually end up pushing a field, and if not, if the size is nonzero,
2847 push the field onto the stack */
2848 push_fields_onto_fieldstack (TREE_TYPE (field), fieldstack, offset);
2849 if (before == VEC_length (fieldoff_t, *fieldstack)
2850 && DECL_SIZE (field)
2851 && !integer_zerop (DECL_SIZE (field)))
2853 pair = xmalloc (sizeof (struct fieldoff));
2854 pair->field = field;
2855 pair->offset = offset;
2856 VEC_safe_push (fieldoff_t, *fieldstack, pair);
2859 else if (TREE_CODE (field) == FIELD_DECL)
2861 pair = xmalloc (sizeof (struct fieldoff));
2862 pair->field = field;
2863 pair->offset = offset + bitpos_of_field (field);
2864 VEC_safe_push (fieldoff_t, *fieldstack, pair);
2866 for (field = TREE_CHAIN (field); field; field = TREE_CHAIN (field))
2868 if (TREE_CODE (field) != FIELD_DECL)
2870 if (var_can_have_subvars (field))
2872 size_t before = VEC_length (fieldoff_t, *fieldstack);
2873 push_fields_onto_fieldstack (TREE_TYPE (field), fieldstack,
2874 offset + bitpos_of_field (field));
2875 /* Empty structures may have actual size, like in C++. So see if we
2876 actually end up pushing a field, and if not, if the size is nonzero,
2877 push the field onto the stack */
2878 if (before == VEC_length (fieldoff_t, *fieldstack)
2879 && DECL_SIZE (field)
2880 && !integer_zerop (DECL_SIZE (field)))
2882 pair = xmalloc (sizeof (struct fieldoff));
2883 pair->field = field;
2884 pair->offset = offset + bitpos_of_field (field);
2885 VEC_safe_push (fieldoff_t, *fieldstack, pair);
2890 pair = xmalloc (sizeof (struct fieldoff));
2891 pair->field = field;
2892 pair->offset = offset + bitpos_of_field (field);
2893 VEC_safe_push (fieldoff_t, *fieldstack, pair);
2899 /* This represents the used range of a variable. */
2901 typedef struct used_part
2903 HOST_WIDE_INT minused;
2904 HOST_WIDE_INT maxused;
2905 /* True if we have an explicit use/def of some portion of this variable,
2906 even if it is all of it. i.e. a.b = 5 or temp = a.b. */
2908 /* True if we have an implicit use/def of some portion of this
2909 variable. Implicit uses occur when we can't tell what part we
2910 are referencing, and have to make conservative assumptions. */
2914 /* An array of used_part structures, indexed by variable uid. */
2916 static used_part_t *used_portions;
2918 /* Given a variable uid, UID, get or create the entry in the used portions
2919 table for the variable. */
2922 get_or_create_used_part_for (size_t uid)
2925 if (used_portions[uid] == NULL)
2927 up = xcalloc (1, sizeof (struct used_part));
2928 up->minused = INT_MAX;
2930 up->explicit_uses = false;
2931 up->implicit_uses = false;
2934 up = used_portions[uid];
2938 /* qsort comparison function for two fieldoff_t's PA and PB */
2941 fieldoff_compare (const void *pa, const void *pb)
2943 const fieldoff_t foa = *(fieldoff_t *)pa;
2944 const fieldoff_t fob = *(fieldoff_t *)pb;
2945 HOST_WIDE_INT foasize, fobsize;
2946 if (foa->offset != fob->offset)
2947 return foa->offset - fob->offset;
2949 foasize = TREE_INT_CST_LOW (DECL_SIZE (foa->field));
2950 fobsize = TREE_INT_CST_LOW (DECL_SIZE (fob->field));
2951 if (foasize != fobsize)
2952 return foasize - fobsize;
2956 /* Given an aggregate VAR, create the subvariables that represent its
2960 create_overlap_variables_for (tree var)
2962 VEC(fieldoff_t) *fieldstack = NULL;
2964 size_t uid = var_ann (var)->uid;
2966 if (used_portions[uid] == NULL)
2969 up = used_portions[uid];
2970 push_fields_onto_fieldstack (TREE_TYPE (var), &fieldstack, 0);
2971 if (VEC_length (fieldoff_t, fieldstack) != 0)
2975 bool notokay = false;
2978 HOST_WIDE_INT lastfooffset = -1;
2979 HOST_WIDE_INT lastfosize = -1;
2980 tree lastfotype = NULL_TREE;
2982 /* Not all fields have DECL_SIZE set, and those that don't, we don't
2983 know their size, and thus, can't handle.
2984 The same is true of fields with DECL_SIZE that is not an integer
2985 constant (such as variable sized fields).
2986 Fields with offsets which are not constant will have an offset < 0
2987 We *could* handle fields that are constant sized arrays, but
2988 currently don't. Doing so would require some extra changes to
2989 tree-ssa-operands.c. */
2991 for (i = 0; VEC_iterate (fieldoff_t, fieldstack, i, fo); i++)
2993 if (!DECL_SIZE (fo->field)
2994 || TREE_CODE (DECL_SIZE (fo->field)) != INTEGER_CST
2995 || TREE_CODE (TREE_TYPE (fo->field)) == ARRAY_TYPE
3004 /* The current heuristic we use is as follows:
3005 If the variable has no used portions in this function, no
3006 structure vars are created for it.
3008 If the variable has less than SALIAS_MAX_IMPLICIT_FIELDS,
3009 we always create structure vars for them.
3010 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
3011 some explicit uses, we create structure vars for them.
3012 If the variable has more than SALIAS_MAX_IMPLICIT_FIELDS, and
3013 no explicit uses, we do not create structure vars for them.
3016 if (fieldcount >= SALIAS_MAX_IMPLICIT_FIELDS
3017 && !up->explicit_uses)
3019 if (dump_file && (dump_flags & TDF_DETAILS))
3021 fprintf (dump_file, "Variable ");
3022 print_generic_expr (dump_file, var, 0);
3023 fprintf (dump_file, " has no explicit uses in this function, and is > SALIAS_MAX_IMPLICIT_FIELDS, so skipping\n");
3029 /* Cleanup after ourselves if we can't create overlap variables. */
3032 while (VEC_length (fieldoff_t, fieldstack) != 0)
3034 fo = VEC_pop (fieldoff_t, fieldstack);
3037 VEC_free (fieldoff_t, fieldstack);
3040 /* Otherwise, create the variables. */
3041 subvars = lookup_subvars_for_var (var);
3043 qsort (VEC_address (fieldoff_t, fieldstack),
3044 VEC_length (fieldoff_t, fieldstack),
3045 sizeof (fieldoff_t),
3048 while (VEC_length (fieldoff_t, fieldstack) != 0)
3051 HOST_WIDE_INT fosize;
3055 fo = VEC_pop (fieldoff_t, fieldstack);
3056 fosize = TREE_INT_CST_LOW (DECL_SIZE (fo->field));
3057 currfotype = TREE_TYPE (fo->field);
3059 /* If this field isn't in the used portion,
3060 or it has the exact same offset and size as the last
3063 if (((fo->offset <= up->minused
3064 && fo->offset + fosize <= up->minused)
3065 || fo->offset >= up->maxused)
3066 || (fo->offset == lastfooffset
3067 && fosize == lastfosize
3068 && currfotype == lastfotype))
3073 sv = ggc_alloc (sizeof (struct subvar));
3074 sv->offset = fo->offset;
3076 sv->next = *subvars;
3077 sv->var = create_tmp_var_raw (TREE_TYPE (fo->field), "SFT");
3080 fprintf (dump_file, "structure field tag %s created for var %s",
3081 get_name (sv->var), get_name (var));
3082 fprintf (dump_file, " offset " HOST_WIDE_INT_PRINT_DEC,
3084 fprintf (dump_file, " size " HOST_WIDE_INT_PRINT_DEC,
3086 fprintf (dump_file, "\n");
3090 /* We need to copy the various flags from var to sv->var, so that
3091 they are is_global_var iff the original variable was. */
3093 DECL_EXTERNAL (sv->var) = DECL_EXTERNAL (var);
3094 TREE_PUBLIC (sv->var) = TREE_PUBLIC (var);
3095 TREE_STATIC (sv->var) = TREE_STATIC (var);
3096 TREE_READONLY (sv->var) = TREE_READONLY (var);
3098 /* Like other memory tags, these need to be marked addressable to
3099 keep is_gimple_reg from thinking they are real. */
3100 TREE_ADDRESSABLE (sv->var) = 1;
3102 DECL_CONTEXT (sv->var) = DECL_CONTEXT (var);
3104 ann = get_var_ann (sv->var);
3105 ann->mem_tag_kind = STRUCT_FIELD;
3106 ann->type_mem_tag = NULL;
3107 add_referenced_tmp_var (sv->var);
3109 lastfotype = currfotype;
3110 lastfooffset = fo->offset;
3111 lastfosize = fosize;
3116 /* Once we have created subvars, the original is no longer call
3117 clobbered on its own. Its call clobbered status depends
3118 completely on the call clobbered status of the subvars.
3120 add_referenced_var in the above loop will take care of
3121 marking subvars of global variables as call clobbered for us
3122 to start, since they are global as well. */
3123 clear_call_clobbered (var);
3127 VEC_free (fieldoff_t, fieldstack);
3131 /* Find the conservative answer to the question of what portions of what
3132 structures are used by this statement. We assume that if we have a
3133 component ref with a known size + offset, that we only need that part
3134 of the structure. For unknown cases, or cases where we do something
3135 to the whole structure, we assume we need to create fields for the
3136 entire structure. */
3139 find_used_portions (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
3141 switch (TREE_CODE (*tp))
3145 HOST_WIDE_INT bitsize;
3146 HOST_WIDE_INT bitpos;
3148 enum machine_mode mode;
3152 ref = get_inner_reference (*tp, &bitsize, &bitpos, &offset, &mode,
3153 &unsignedp, &volatilep, false);
3154 if (DECL_P (ref) && offset == NULL && bitsize != -1)
3156 size_t uid = var_ann (ref)->uid;
3159 up = get_or_create_used_part_for (uid);
3161 if (bitpos <= up->minused)
3162 up->minused = bitpos;
3163 if ((bitpos + bitsize >= up->maxused))
3164 up->maxused = bitpos + bitsize;
3166 up->explicit_uses = true;
3167 used_portions[uid] = up;
3172 else if (DECL_P (ref))
3175 && var_can_have_subvars (ref)
3176 && TREE_CODE (DECL_SIZE (ref)) == INTEGER_CST)
3179 size_t uid = var_ann (ref)->uid;
3181 up = get_or_create_used_part_for (uid);
3184 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (ref));
3186 up->implicit_uses = true;
3188 used_portions[uid] = up;
3201 && var_can_have_subvars (var)
3202 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3205 size_t uid = var_ann (var)->uid;
3207 up = get_or_create_used_part_for (uid);
3210 up->maxused = TREE_INT_CST_LOW (DECL_SIZE (var));
3211 up->implicit_uses = true;
3213 used_portions[uid] = up;
3227 /* We are about to create some new referenced variables, and we need the
3230 static size_t old_referenced_vars;
3233 /* Create structure field variables for structures used in this function. */
3236 create_structure_vars (void)
3241 old_referenced_vars = num_referenced_vars;
3242 used_portions = xcalloc (num_referenced_vars, sizeof (used_part_t));
3246 block_stmt_iterator bsi;
3247 for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
3249 walk_tree_without_duplicates (bsi_stmt_ptr (bsi),
3254 for (i = 0; i < old_referenced_vars; i++)
3256 tree var = referenced_var (i);
3257 /* The C++ FE creates vars without DECL_SIZE set, for some reason. */
3260 && var_can_have_subvars (var)
3261 && var_ann (var)->mem_tag_kind == NOT_A_TAG
3262 && TREE_CODE (DECL_SIZE (var)) == INTEGER_CST)
3263 create_overlap_variables_for (var);
3265 for (i = 0; i < old_referenced_vars; i++)
3266 free (used_portions[i]);
3268 free (used_portions);
3272 gate_structure_vars (void)
3274 return flag_tree_salias != 0;
3277 struct tree_opt_pass pass_create_structure_vars =
3279 "salias", /* name */
3280 gate_structure_vars, /* gate */
3281 create_structure_vars, /* execute */
3284 0, /* static_pass_number */
3286 PROP_cfg, /* properties_required */
3287 0, /* properties_provided */
3288 0, /* properties_destroyed */
3289 0, /* todo_flags_start */
3290 TODO_dump_func, /* todo_flags_finish */