1 /* Alias analysis for trees.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
3 Free Software Foundation, Inc.
4 Contributed by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
13 GCC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
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"
40 #include "tree-flow.h"
41 #include "tree-inline.h"
42 #include "tree-pass.h"
45 #include "ipa-type-escape.h"
49 #include "pointer-set.h"
50 #include "alloc-pool.h"
51 #include "tree-ssa-alias.h"
53 /* Broad overview of how alias analysis on gimple works:
55 Statements clobbering or using memory are linked through the
56 virtual operand factored use-def chain. The virtual operand
57 is unique per function, its symbol is accessible via gimple_vop (cfun).
58 Virtual operands are used for efficiently walking memory statements
59 in the gimple IL and are useful for things like value-numbering as
60 a generation count for memory references.
62 SSA_NAME pointers may have associated points-to information
63 accessible via the SSA_NAME_PTR_INFO macro. Flow-insensitive
64 points-to information is (re-)computed by the TODO_rebuild_alias
65 pass manager todo. Points-to information is also used for more
66 precise tracking of call-clobbered and call-used variables and
67 related disambiguations.
69 This file contains functions for disambiguating memory references,
70 the so called alias-oracle and tools for walking of the gimple IL.
72 The main alias-oracle entry-points are
74 bool stmt_may_clobber_ref_p (gimple, tree)
76 This function queries if a statement may invalidate (parts of)
77 the memory designated by the reference tree argument.
79 bool ref_maybe_used_by_stmt_p (gimple, tree)
81 This function queries if a statement may need (parts of) the
82 memory designated by the reference tree argument.
84 There are variants of these functions that only handle the call
85 part of a statement, call_may_clobber_ref_p and ref_maybe_used_by_call_p.
86 Note that these do not disambiguate against a possible call lhs.
88 bool refs_may_alias_p (tree, tree)
90 This function tries to disambiguate two reference trees.
92 bool ptr_deref_may_alias_global_p (tree)
94 This function queries if dereferencing a pointer variable may
97 More low-level disambiguators are available and documented in
98 this file. Low-level disambiguators dealing with points-to
99 information are in tree-ssa-structalias.c. */
102 /* Query statistics for the different low-level disambiguators.
103 A high-level query may trigger multiple of them. */
106 unsigned HOST_WIDE_INT refs_may_alias_p_may_alias;
107 unsigned HOST_WIDE_INT refs_may_alias_p_no_alias;
108 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_may_alias;
109 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_no_alias;
110 unsigned HOST_WIDE_INT call_may_clobber_ref_p_may_alias;
111 unsigned HOST_WIDE_INT call_may_clobber_ref_p_no_alias;
115 dump_alias_stats (FILE *s)
117 fprintf (s, "\nAlias oracle query stats:\n");
118 fprintf (s, " refs_may_alias_p: "
119 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
120 HOST_WIDE_INT_PRINT_DEC" queries\n",
121 alias_stats.refs_may_alias_p_no_alias,
122 alias_stats.refs_may_alias_p_no_alias
123 + alias_stats.refs_may_alias_p_may_alias);
124 fprintf (s, " ref_maybe_used_by_call_p: "
125 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
126 HOST_WIDE_INT_PRINT_DEC" queries\n",
127 alias_stats.ref_maybe_used_by_call_p_no_alias,
128 alias_stats.refs_may_alias_p_no_alias
129 + alias_stats.ref_maybe_used_by_call_p_may_alias);
130 fprintf (s, " call_may_clobber_ref_p: "
131 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
132 HOST_WIDE_INT_PRINT_DEC" queries\n",
133 alias_stats.call_may_clobber_ref_p_no_alias,
134 alias_stats.call_may_clobber_ref_p_no_alias
135 + alias_stats.call_may_clobber_ref_p_may_alias);
139 /* Return true, if dereferencing PTR may alias with a global variable. */
142 ptr_deref_may_alias_global_p (tree ptr)
144 struct ptr_info_def *pi;
146 /* If we end up with a pointer constant here that may point
148 if (TREE_CODE (ptr) != SSA_NAME)
151 pi = SSA_NAME_PTR_INFO (ptr);
153 /* If we do not have points-to information for this variable,
158 /* ??? This does not use TBAA to prune globals ptr may not access. */
159 return pt_solution_includes_global (&pi->pt);
162 /* Return true if dereferencing PTR may alias DECL.
163 The caller is responsible for applying TBAA to see if PTR
164 may access DECL at all. */
167 ptr_deref_may_alias_decl_p (tree ptr, tree decl)
169 struct ptr_info_def *pi;
171 gcc_assert ((TREE_CODE (ptr) == SSA_NAME
172 || TREE_CODE (ptr) == ADDR_EXPR
173 || TREE_CODE (ptr) == INTEGER_CST)
174 && (TREE_CODE (decl) == VAR_DECL
175 || TREE_CODE (decl) == PARM_DECL
176 || TREE_CODE (decl) == RESULT_DECL));
178 /* Non-aliased variables can not be pointed to. */
179 if (!may_be_aliased (decl))
182 /* ADDR_EXPR pointers either just offset another pointer or directly
183 specify the pointed-to set. */
184 if (TREE_CODE (ptr) == ADDR_EXPR)
186 tree base = get_base_address (TREE_OPERAND (ptr, 0));
188 && INDIRECT_REF_P (base))
189 ptr = TREE_OPERAND (base, 0);
192 return operand_equal_p (base, decl, 0);
194 && CONSTANT_CLASS_P (base))
200 /* We can end up with dereferencing constant pointers.
201 Just bail out in this case. */
202 if (TREE_CODE (ptr) == INTEGER_CST)
205 /* If we do not have useful points-to information for this pointer
206 we cannot disambiguate anything else. */
207 pi = SSA_NAME_PTR_INFO (ptr);
211 return pt_solution_includes (&pi->pt, decl);
214 /* Return true if dereferenced PTR1 and PTR2 may alias.
215 The caller is responsible for applying TBAA to see if accesses
216 through PTR1 and PTR2 may conflict at all. */
219 ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
221 struct ptr_info_def *pi1, *pi2;
223 gcc_assert ((TREE_CODE (ptr1) == SSA_NAME
224 || TREE_CODE (ptr1) == ADDR_EXPR
225 || TREE_CODE (ptr1) == INTEGER_CST)
226 && (TREE_CODE (ptr2) == SSA_NAME
227 || TREE_CODE (ptr2) == ADDR_EXPR
228 || TREE_CODE (ptr2) == INTEGER_CST));
230 /* ADDR_EXPR pointers either just offset another pointer or directly
231 specify the pointed-to set. */
232 if (TREE_CODE (ptr1) == ADDR_EXPR)
234 tree base = get_base_address (TREE_OPERAND (ptr1, 0));
236 && INDIRECT_REF_P (base))
237 ptr1 = TREE_OPERAND (base, 0);
240 return ptr_deref_may_alias_decl_p (ptr2, base);
244 if (TREE_CODE (ptr2) == ADDR_EXPR)
246 tree base = get_base_address (TREE_OPERAND (ptr2, 0));
248 && INDIRECT_REF_P (base))
249 ptr2 = TREE_OPERAND (base, 0);
252 return ptr_deref_may_alias_decl_p (ptr1, base);
257 /* We can end up with dereferencing constant pointers.
258 Just bail out in this case. */
259 if (TREE_CODE (ptr1) == INTEGER_CST
260 || TREE_CODE (ptr2) == INTEGER_CST)
263 /* We may end up with two empty points-to solutions for two same pointers.
264 In this case we still want to say both pointers alias, so shortcut
269 /* If we do not have useful points-to information for either pointer
270 we cannot disambiguate anything else. */
271 pi1 = SSA_NAME_PTR_INFO (ptr1);
272 pi2 = SSA_NAME_PTR_INFO (ptr2);
276 /* If both pointers are restrict-qualified try to disambiguate
277 with restrict information. */
278 if (TYPE_RESTRICT (TREE_TYPE (ptr1))
279 && TYPE_RESTRICT (TREE_TYPE (ptr2))
280 && !pt_solutions_same_restrict_base (&pi1->pt, &pi2->pt))
283 /* ??? This does not use TBAA to prune decls from the intersection
284 that not both pointers may access. */
285 return pt_solutions_intersect (&pi1->pt, &pi2->pt);
288 /* Return true if dereferencing PTR may alias *REF.
289 The caller is responsible for applying TBAA to see if PTR
290 may access *REF at all. */
293 ptr_deref_may_alias_ref_p_1 (tree ptr, ao_ref *ref)
295 tree base = ao_ref_base (ref);
297 if (INDIRECT_REF_P (base))
298 return ptr_derefs_may_alias_p (ptr, TREE_OPERAND (base, 0));
299 else if (SSA_VAR_P (base))
300 return ptr_deref_may_alias_decl_p (ptr, base);
306 /* Dump alias information on FILE. */
309 dump_alias_info (FILE *file)
313 = lang_hooks.decl_printable_name (current_function_decl, 2);
314 referenced_var_iterator rvi;
317 fprintf (file, "\n\nAlias information for %s\n\n", funcname);
319 fprintf (file, "Aliased symbols\n\n");
321 FOR_EACH_REFERENCED_VAR (var, rvi)
323 if (may_be_aliased (var))
324 dump_variable (file, var);
327 fprintf (file, "\nCall clobber information\n");
329 fprintf (file, "\nESCAPED");
330 dump_points_to_solution (file, &cfun->gimple_df->escaped);
331 fprintf (file, "\nCALLUSED");
332 dump_points_to_solution (file, &cfun->gimple_df->callused);
334 fprintf (file, "\n\nFlow-insensitive points-to information\n\n");
336 for (i = 1; i < num_ssa_names; i++)
338 tree ptr = ssa_name (i);
339 struct ptr_info_def *pi;
342 || SSA_NAME_IN_FREE_LIST (ptr))
345 pi = SSA_NAME_PTR_INFO (ptr);
347 dump_points_to_info_for (file, ptr);
350 fprintf (file, "\n");
354 /* Dump alias information on stderr. */
357 debug_alias_info (void)
359 dump_alias_info (stderr);
363 /* Return the alias information associated with pointer T. It creates a
364 new instance if none existed. */
366 struct ptr_info_def *
367 get_ptr_info (tree t)
369 struct ptr_info_def *pi;
371 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
373 pi = SSA_NAME_PTR_INFO (t);
376 pi = GGC_CNEW (struct ptr_info_def);
377 pt_solution_reset (&pi->pt);
378 SSA_NAME_PTR_INFO (t) = pi;
384 /* Dump the points-to set *PT into FILE. */
387 dump_points_to_solution (FILE *file, struct pt_solution *pt)
390 fprintf (file, ", points-to anything");
393 fprintf (file, ", points-to non-local");
396 fprintf (file, ", points-to escaped");
399 fprintf (file, ", points-to NULL");
403 fprintf (file, ", points-to vars: ");
404 dump_decl_set (file, pt->vars);
405 if (pt->vars_contains_global)
406 fprintf (file, " (includes global vars)");
410 /* Dump points-to information for SSA_NAME PTR into FILE. */
413 dump_points_to_info_for (FILE *file, tree ptr)
415 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
417 print_generic_expr (file, ptr, dump_flags);
420 dump_points_to_solution (file, &pi->pt);
422 fprintf (file, ", points-to anything");
424 fprintf (file, "\n");
428 /* Dump points-to information for VAR into stderr. */
431 debug_points_to_info_for (tree var)
433 dump_points_to_info_for (stderr, var);
437 /* Initializes the alias-oracle reference representation *R from REF. */
440 ao_ref_init (ao_ref *r, tree ref)
447 r->ref_alias_set = -1;
448 r->base_alias_set = -1;
451 /* Returns the base object of the memory reference *REF. */
454 ao_ref_base (ao_ref *ref)
458 ref->base = get_ref_base_and_extent (ref->ref, &ref->offset, &ref->size,
463 /* Returns the base object alias set of the memory reference *REF. */
465 static alias_set_type ATTRIBUTE_UNUSED
466 ao_ref_base_alias_set (ao_ref *ref)
468 if (ref->base_alias_set != -1)
469 return ref->base_alias_set;
470 ref->base_alias_set = get_alias_set (ao_ref_base (ref));
471 return ref->base_alias_set;
474 /* Returns the reference alias set of the memory reference *REF. */
477 ao_ref_alias_set (ao_ref *ref)
479 if (ref->ref_alias_set != -1)
480 return ref->ref_alias_set;
481 ref->ref_alias_set = get_alias_set (ref->ref);
482 return ref->ref_alias_set;
485 /* Init an alias-oracle reference representation from a gimple pointer
486 PTR and a gimple size SIZE in bytes. If SIZE is NULL_TREE the the
487 size is assumed to be unknown. The access is assumed to be only
488 to or after of the pointer target, not before it. */
491 ao_ref_init_from_ptr_and_size (ao_ref *ref, tree ptr, tree size)
493 HOST_WIDE_INT t1, t2;
494 ref->ref = NULL_TREE;
495 if (TREE_CODE (ptr) == ADDR_EXPR)
496 ref->base = get_ref_base_and_extent (TREE_OPERAND (ptr, 0),
497 &ref->offset, &t1, &t2);
500 ref->base = build1 (INDIRECT_REF, char_type_node, ptr);
504 && host_integerp (size, 0)
505 && TREE_INT_CST_LOW (size) * 8 / 8 == TREE_INT_CST_LOW (size))
506 ref->max_size = ref->size = TREE_INT_CST_LOW (size) * 8;
508 ref->max_size = ref->size = -1;
509 ref->ref_alias_set = 0;
510 ref->base_alias_set = 0;
513 /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the
514 purpose of TBAA. Return 0 if they are distinct and -1 if we cannot
518 same_type_for_tbaa (tree type1, tree type2)
520 type1 = TYPE_MAIN_VARIANT (type1);
521 type2 = TYPE_MAIN_VARIANT (type2);
523 /* If we would have to do structural comparison bail out. */
524 if (TYPE_STRUCTURAL_EQUALITY_P (type1)
525 || TYPE_STRUCTURAL_EQUALITY_P (type2))
528 /* Compare the canonical types. */
529 if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
532 /* ??? Array types are not properly unified in all cases as we have
533 spurious changes in the index types for example. Removing this
534 causes all sorts of problems with the Fortran frontend. */
535 if (TREE_CODE (type1) == ARRAY_TYPE
536 && TREE_CODE (type2) == ARRAY_TYPE)
539 /* The types are known to be not equal. */
543 /* Determine if the two component references REF1 and REF2 which are
544 based on access types TYPE1 and TYPE2 and of which at least one is based
545 on an indirect reference may alias. */
548 nonaliasing_component_refs_p (tree ref1, tree type1,
549 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
550 tree ref2, tree type2,
551 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
553 /* If one reference is a component references through pointers try to find a
554 common base and apply offset based disambiguation. This handles
556 struct A { int i; int j; } *q;
557 struct B { struct A a; int k; } *p;
558 disambiguating q->i and p->a.j. */
562 /* Now search for the type1 in the access path of ref2. This
563 would be a common base for doing offset based disambiguation on. */
565 while (handled_component_p (*refp)
566 && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
567 refp = &TREE_OPERAND (*refp, 0);
568 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
569 /* If we couldn't compare types we have to bail out. */
572 else if (same_p == 1)
574 HOST_WIDE_INT offadj, sztmp, msztmp;
575 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
577 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
579 /* If we didn't find a common base, try the other way around. */
581 while (handled_component_p (*refp)
582 && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
583 refp = &TREE_OPERAND (*refp, 0);
584 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2);
585 /* If we couldn't compare types we have to bail out. */
588 else if (same_p == 1)
590 HOST_WIDE_INT offadj, sztmp, msztmp;
591 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
593 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
595 /* If we have two type access paths B1.path1 and B2.path2 they may
596 only alias if either B1 is in B2.path2 or B2 is in B1.path1. */
600 /* Return true if two memory references based on the variables BASE1
601 and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1) and
602 [OFFSET2, OFFSET2 + MAX_SIZE2) may alias. */
605 decl_refs_may_alias_p (tree base1,
606 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
608 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
610 gcc_assert (SSA_VAR_P (base1) && SSA_VAR_P (base2));
612 /* If both references are based on different variables, they cannot alias. */
613 if (!operand_equal_p (base1, base2, 0))
616 /* If both references are based on the same variable, they cannot alias if
617 the accesses do not overlap. */
618 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
621 /* Return true if an indirect reference based on *PTR1 constrained
622 to [OFFSET1, OFFSET1 + MAX_SIZE1) may alias a variable based on BASE2
623 constrained to [OFFSET2, OFFSET2 + MAX_SIZE2). *PTR1 and BASE2 have
624 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
625 in which case they are computed on-demand. REF1 and REF2
626 if non-NULL are the complete memory reference trees. */
629 indirect_ref_may_alias_decl_p (tree ref1, tree ptr1,
630 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
631 alias_set_type base1_alias_set,
632 tree ref2, tree base2,
633 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
634 alias_set_type base2_alias_set)
636 /* If only one reference is based on a variable, they cannot alias if
637 the pointer access is beyond the extent of the variable access.
638 (the pointer base cannot validly point to an offset less than zero
640 They also cannot alias if the pointer may not point to the decl. */
642 && !ranges_overlap_p (offset1, max_size1, 0, offset2 + max_size2))
644 if (!ptr_deref_may_alias_decl_p (ptr1, base2))
647 /* Disambiguations that rely on strict aliasing rules follow. */
648 if (!flag_strict_aliasing)
651 /* If the alias set for a pointer access is zero all bets are off. */
652 if (base1_alias_set == -1)
653 base1_alias_set = get_deref_alias_set (ptr1);
654 if (base1_alias_set == 0)
656 if (base2_alias_set == -1)
657 base2_alias_set = get_alias_set (base2);
659 /* If both references are through the same type, they do not alias
660 if the accesses do not overlap. This does extra disambiguation
661 for mixed/pointer accesses but requires strict aliasing. */
662 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
663 TREE_TYPE (base2)) == 1)
664 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
666 /* The only way to access a variable is through a pointer dereference
667 of the same alias set or a subset of it. */
668 if (base1_alias_set != base2_alias_set
669 && !alias_set_subset_of (base1_alias_set, base2_alias_set))
672 /* Do access-path based disambiguation. */
674 && handled_component_p (ref1)
675 && handled_component_p (ref2))
676 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
678 ref2, TREE_TYPE (base2),
684 /* Return true if two indirect references based on *PTR1
685 and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1) and
686 [OFFSET2, OFFSET2 + MAX_SIZE2) may alias. *PTR1 and *PTR2 have
687 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
688 in which case they are computed on-demand. REF1 and REF2
689 if non-NULL are the complete memory reference trees. */
692 indirect_refs_may_alias_p (tree ref1, tree ptr1,
693 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
694 alias_set_type base1_alias_set,
695 tree ref2, tree ptr2,
696 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
697 alias_set_type base2_alias_set)
699 /* If both bases are based on pointers they cannot alias if they may not
700 point to the same memory object or if they point to the same object
701 and the accesses do not overlap. */
702 if (operand_equal_p (ptr1, ptr2, 0))
703 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
704 if (!ptr_derefs_may_alias_p (ptr1, ptr2))
707 /* Disambiguations that rely on strict aliasing rules follow. */
708 if (!flag_strict_aliasing)
711 /* If the alias set for a pointer access is zero all bets are off. */
712 if (base1_alias_set == -1)
713 base1_alias_set = get_deref_alias_set (ptr1);
714 if (base1_alias_set == 0)
716 if (base2_alias_set == -1)
717 base2_alias_set = get_deref_alias_set (ptr2);
718 if (base2_alias_set == 0)
721 /* If both references are through the same type, they do not alias
722 if the accesses do not overlap. This does extra disambiguation
723 for mixed/pointer accesses but requires strict aliasing. */
724 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
725 TREE_TYPE (TREE_TYPE (ptr2))) == 1)
726 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
728 /* Do type-based disambiguation. */
729 if (base1_alias_set != base2_alias_set
730 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
733 /* Do access-path based disambiguation. */
735 && handled_component_p (ref1)
736 && handled_component_p (ref2))
737 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
739 ref2, TREE_TYPE (TREE_TYPE (ptr2)),
745 /* Return true, if the two memory references REF1 and REF2 may alias. */
748 refs_may_alias_p_1 (ao_ref *ref1, ao_ref *ref2, bool tbaa_p)
751 HOST_WIDE_INT offset1 = 0, offset2 = 0;
752 HOST_WIDE_INT size1 = -1, size2 = -1;
753 HOST_WIDE_INT max_size1 = -1, max_size2 = -1;
754 bool var1_p, var2_p, ind1_p, ind2_p;
757 gcc_assert ((!ref1->ref
758 || SSA_VAR_P (ref1->ref)
759 || handled_component_p (ref1->ref)
760 || INDIRECT_REF_P (ref1->ref)
761 || TREE_CODE (ref1->ref) == TARGET_MEM_REF)
763 || SSA_VAR_P (ref2->ref)
764 || handled_component_p (ref2->ref)
765 || INDIRECT_REF_P (ref2->ref)
766 || TREE_CODE (ref2->ref) == TARGET_MEM_REF));
768 /* Decompose the references into their base objects and the access. */
769 base1 = ao_ref_base (ref1);
770 offset1 = ref1->offset;
772 max_size1 = ref1->max_size;
773 base2 = ao_ref_base (ref2);
774 offset2 = ref2->offset;
776 max_size2 = ref2->max_size;
778 /* We can end up with registers or constants as bases for example from
779 *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59);
780 which is seen as a struct copy. */
781 if (TREE_CODE (base1) == SSA_NAME
782 || TREE_CODE (base2) == SSA_NAME
783 || is_gimple_min_invariant (base1)
784 || is_gimple_min_invariant (base2))
787 /* We can end up refering to code via function decls. As we likely
788 do not properly track code aliases conservatively bail out. */
789 if (TREE_CODE (base1) == FUNCTION_DECL
790 || TREE_CODE (base2) == FUNCTION_DECL)
793 /* Defer to simple offset based disambiguation if we have
794 references based on two decls. Do this before defering to
795 TBAA to handle must-alias cases in conformance with the
796 GCC extension of allowing type-punning through unions. */
797 var1_p = SSA_VAR_P (base1);
798 var2_p = SSA_VAR_P (base2);
799 if (var1_p && var2_p)
800 return decl_refs_may_alias_p (base1, offset1, max_size1,
801 base2, offset2, max_size2);
803 /* First defer to TBAA if possible. */
805 && flag_strict_aliasing
806 && !alias_sets_conflict_p (ao_ref_alias_set (ref1),
807 ao_ref_alias_set (ref2)))
810 /* If one reference is a TARGET_MEM_REF weird things are allowed. Still
811 TBAA disambiguation based on the access type is possible, so bail
812 out only after that check. */
813 if ((ref1->ref && TREE_CODE (ref1->ref) == TARGET_MEM_REF)
814 || (ref2->ref && TREE_CODE (ref2->ref) == TARGET_MEM_REF))
817 /* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */
818 ind1_p = INDIRECT_REF_P (base1);
819 ind2_p = INDIRECT_REF_P (base2);
820 set = tbaa_p ? -1 : 0;
821 if (var1_p && ind2_p)
822 return indirect_ref_may_alias_decl_p (ref2->ref, TREE_OPERAND (base2, 0),
823 offset2, max_size2, set,
825 offset1, max_size1, set);
826 else if (ind1_p && var2_p)
827 return indirect_ref_may_alias_decl_p (ref1->ref, TREE_OPERAND (base1, 0),
828 offset1, max_size1, set,
830 offset2, max_size2, set);
831 else if (ind1_p && ind2_p)
832 return indirect_refs_may_alias_p (ref1->ref, TREE_OPERAND (base1, 0),
833 offset1, max_size1, set,
834 ref2->ref, TREE_OPERAND (base2, 0),
835 offset2, max_size2, set);
841 refs_may_alias_p (tree ref1, tree ref2)
845 ao_ref_init (&r1, ref1);
846 ao_ref_init (&r2, ref2);
847 res = refs_may_alias_p_1 (&r1, &r2, true);
849 ++alias_stats.refs_may_alias_p_may_alias;
851 ++alias_stats.refs_may_alias_p_no_alias;
855 /* Returns true if there is a anti-dependence for the STORE that
856 executes after the LOAD. */
859 refs_anti_dependent_p (tree load, tree store)
862 ao_ref_init (&r1, load);
863 ao_ref_init (&r2, store);
864 return refs_may_alias_p_1 (&r1, &r2, false);
867 /* Returns true if there is a output dependence for the stores
868 STORE1 and STORE2. */
871 refs_output_dependent_p (tree store1, tree store2)
874 ao_ref_init (&r1, store1);
875 ao_ref_init (&r2, store2);
876 return refs_may_alias_p_1 (&r1, &r2, false);
879 /* If the call CALL may use the memory reference REF return true,
880 otherwise return false. */
883 ref_maybe_used_by_call_p_1 (gimple call, ao_ref *ref)
887 int flags = gimple_call_flags (call);
889 /* Const functions without a static chain do not implicitly use memory. */
890 if (!gimple_call_chain (call)
891 && (flags & (ECF_CONST|ECF_NOVOPS)))
894 base = ao_ref_base (ref);
898 /* If the reference is based on a decl that is not aliased the call
899 cannot possibly use it. */
901 && !may_be_aliased (base)
902 /* But local statics can be used through recursion. */
903 && !is_global_var (base))
906 callee = gimple_call_fndecl (call);
908 /* Handle those builtin functions explicitly that do not act as
909 escape points. See tree-ssa-structalias.c:find_func_aliases
910 for the list of builtins we might need to handle here. */
911 if (callee != NULL_TREE
912 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
913 switch (DECL_FUNCTION_CODE (callee))
915 /* All the following functions clobber memory pointed to by
916 their first argument. */
917 case BUILT_IN_STRCPY:
918 case BUILT_IN_STRNCPY:
920 case BUILT_IN_MEMCPY:
921 case BUILT_IN_MEMMOVE:
922 case BUILT_IN_MEMPCPY:
923 case BUILT_IN_STPCPY:
924 case BUILT_IN_STPNCPY:
925 case BUILT_IN_STRCAT:
926 case BUILT_IN_STRNCAT:
929 tree size = NULL_TREE;
930 if (gimple_call_num_args (call) == 3)
931 size = gimple_call_arg (call, 2);
932 ao_ref_init_from_ptr_and_size (&dref,
933 gimple_call_arg (call, 1),
935 return refs_may_alias_p_1 (&dref, ref, false);
937 /* The following builtins do not read from memory. */
939 case BUILT_IN_MEMSET:
941 case BUILT_IN_FREXPF:
942 case BUILT_IN_FREXPL:
943 case BUILT_IN_GAMMA_R:
944 case BUILT_IN_GAMMAF_R:
945 case BUILT_IN_GAMMAL_R:
946 case BUILT_IN_LGAMMA_R:
947 case BUILT_IN_LGAMMAF_R:
948 case BUILT_IN_LGAMMAL_R:
952 case BUILT_IN_REMQUO:
953 case BUILT_IN_REMQUOF:
954 case BUILT_IN_REMQUOL:
955 case BUILT_IN_SINCOS:
956 case BUILT_IN_SINCOSF:
957 case BUILT_IN_SINCOSL:
961 /* Fallthru to general call handling. */;
964 /* Check if base is a global static variable that is not read
966 if (TREE_CODE (base) == VAR_DECL
967 && TREE_STATIC (base)
968 && !TREE_PUBLIC (base))
972 if (callee != NULL_TREE
974 = ipa_reference_get_not_read_global (cgraph_node (callee)))
975 && bitmap_bit_p (not_read, DECL_UID (base)))
979 /* If the base variable is call-used or call-clobbered then
981 if (flags & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
985 if (is_call_used (base))
988 else if (INDIRECT_REF_P (base)
989 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
991 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0));
995 if (pt_solution_includes_global (&pi->pt)
996 || pt_solutions_intersect (&cfun->gimple_df->callused, &pi->pt)
997 || pt_solutions_intersect (&cfun->gimple_df->escaped, &pi->pt))
1007 if (is_call_clobbered (base))
1010 else if (INDIRECT_REF_P (base)
1011 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
1013 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0));
1017 if (pt_solution_includes_global (&pi->pt)
1018 || pt_solutions_intersect (&cfun->gimple_df->escaped, &pi->pt))
1025 /* Inspect call arguments for passed-by-value aliases. */
1027 for (i = 0; i < gimple_call_num_args (call); ++i)
1029 tree op = gimple_call_arg (call, i);
1031 if (TREE_CODE (op) == EXC_PTR_EXPR
1032 || TREE_CODE (op) == FILTER_EXPR)
1035 if (TREE_CODE (op) == WITH_SIZE_EXPR)
1036 op = TREE_OPERAND (op, 0);
1038 if (TREE_CODE (op) != SSA_NAME
1039 && !is_gimple_min_invariant (op))
1042 ao_ref_init (&r, op);
1043 if (refs_may_alias_p_1 (&r, ref, true))
1052 ref_maybe_used_by_call_p (gimple call, tree ref)
1056 ao_ref_init (&r, ref);
1057 res = ref_maybe_used_by_call_p_1 (call, &r);
1059 ++alias_stats.ref_maybe_used_by_call_p_may_alias;
1061 ++alias_stats.ref_maybe_used_by_call_p_no_alias;
1066 /* If the statement STMT may use the memory reference REF return
1067 true, otherwise return false. */
1070 ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
1072 if (is_gimple_assign (stmt))
1076 /* All memory assign statements are single. */
1077 if (!gimple_assign_single_p (stmt))
1080 rhs = gimple_assign_rhs1 (stmt);
1081 if (is_gimple_reg (rhs)
1082 || is_gimple_min_invariant (rhs)
1083 || gimple_assign_rhs_code (stmt) == CONSTRUCTOR)
1086 return refs_may_alias_p (rhs, ref);
1088 else if (is_gimple_call (stmt))
1089 return ref_maybe_used_by_call_p (stmt, ref);
1094 /* If the call in statement CALL may clobber the memory reference REF
1095 return true, otherwise return false. */
1098 call_may_clobber_ref_p_1 (gimple call, ao_ref *ref)
1103 /* If the call is pure or const it cannot clobber anything. */
1104 if (gimple_call_flags (call)
1105 & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
1108 base = ao_ref_base (ref);
1112 if (TREE_CODE (base) == SSA_NAME
1113 || CONSTANT_CLASS_P (base))
1116 /* If the reference is based on a decl that is not aliased the call
1117 cannot possibly clobber it. */
1119 && !may_be_aliased (base)
1120 /* But local non-readonly statics can be modified through recursion
1121 or the call may implement a threading barrier which we must
1122 treat as may-def. */
1123 && (TREE_READONLY (base)
1124 || !is_global_var (base)))
1127 callee = gimple_call_fndecl (call);
1129 /* Handle those builtin functions explicitly that do not act as
1130 escape points. See tree-ssa-structalias.c:find_func_aliases
1131 for the list of builtins we might need to handle here. */
1132 if (callee != NULL_TREE
1133 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
1134 switch (DECL_FUNCTION_CODE (callee))
1136 /* All the following functions clobber memory pointed to by
1137 their first argument. */
1138 case BUILT_IN_STRCPY:
1139 case BUILT_IN_STRNCPY:
1140 case BUILT_IN_BCOPY:
1141 case BUILT_IN_MEMCPY:
1142 case BUILT_IN_MEMMOVE:
1143 case BUILT_IN_MEMPCPY:
1144 case BUILT_IN_STPCPY:
1145 case BUILT_IN_STPNCPY:
1146 case BUILT_IN_STRCAT:
1147 case BUILT_IN_STRNCAT:
1148 case BUILT_IN_MEMSET:
1151 tree size = NULL_TREE;
1152 if (gimple_call_num_args (call) == 3)
1153 size = gimple_call_arg (call, 2);
1154 ao_ref_init_from_ptr_and_size (&dref,
1155 gimple_call_arg (call, 0),
1157 return refs_may_alias_p_1 (&dref, ref, false);
1159 /* Freeing memory kills the pointed-to memory. More importantly
1160 the call has to serve as a barrier for moving loads and stores
1164 tree ptr = gimple_call_arg (call, 0);
1165 return ptr_deref_may_alias_ref_p_1 (ptr, ref);
1167 case BUILT_IN_GAMMA_R:
1168 case BUILT_IN_GAMMAF_R:
1169 case BUILT_IN_GAMMAL_R:
1170 case BUILT_IN_LGAMMA_R:
1171 case BUILT_IN_LGAMMAF_R:
1172 case BUILT_IN_LGAMMAL_R:
1174 tree out = gimple_call_arg (call, 1);
1175 if (ptr_deref_may_alias_ref_p_1 (out, ref))
1177 if (flag_errno_math)
1181 case BUILT_IN_FREXP:
1182 case BUILT_IN_FREXPF:
1183 case BUILT_IN_FREXPL:
1185 case BUILT_IN_MODFF:
1186 case BUILT_IN_MODFL:
1188 tree out = gimple_call_arg (call, 1);
1189 return ptr_deref_may_alias_ref_p_1 (out, ref);
1191 case BUILT_IN_REMQUO:
1192 case BUILT_IN_REMQUOF:
1193 case BUILT_IN_REMQUOL:
1195 tree out = gimple_call_arg (call, 2);
1196 if (ptr_deref_may_alias_ref_p_1 (out, ref))
1198 if (flag_errno_math)
1202 case BUILT_IN_SINCOS:
1203 case BUILT_IN_SINCOSF:
1204 case BUILT_IN_SINCOSL:
1206 tree sin = gimple_call_arg (call, 1);
1207 tree cos = gimple_call_arg (call, 2);
1208 return (ptr_deref_may_alias_ref_p_1 (sin, ref)
1209 || ptr_deref_may_alias_ref_p_1 (cos, ref));
1212 /* Fallthru to general call handling. */;
1215 /* Check if base is a global static variable that is not written
1217 if (callee != NULL_TREE
1218 && TREE_CODE (base) == VAR_DECL
1219 && TREE_STATIC (base)
1220 && !TREE_PUBLIC (base))
1225 = ipa_reference_get_not_written_global (cgraph_node (callee)))
1226 && bitmap_bit_p (not_written, DECL_UID (base)))
1231 return is_call_clobbered (base);
1232 else if (INDIRECT_REF_P (base)
1233 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
1235 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0));
1239 return (pt_solution_includes_global (&pi->pt)
1240 || pt_solutions_intersect (&cfun->gimple_df->escaped, &pi->pt));
1246 static bool ATTRIBUTE_UNUSED
1247 call_may_clobber_ref_p (gimple call, tree ref)
1251 ao_ref_init (&r, ref);
1252 res = call_may_clobber_ref_p_1 (call, &r);
1254 ++alias_stats.call_may_clobber_ref_p_may_alias;
1256 ++alias_stats.call_may_clobber_ref_p_no_alias;
1261 /* If the statement STMT may clobber the memory reference REF return true,
1262 otherwise return false. */
1265 stmt_may_clobber_ref_p_1 (gimple stmt, ao_ref *ref)
1267 if (is_gimple_call (stmt))
1269 tree lhs = gimple_call_lhs (stmt);
1271 && !is_gimple_reg (lhs))
1274 ao_ref_init (&r, lhs);
1275 if (refs_may_alias_p_1 (ref, &r, true))
1279 return call_may_clobber_ref_p_1 (stmt, ref);
1281 else if (is_gimple_assign (stmt))
1284 ao_ref_init (&r, gimple_assign_lhs (stmt));
1285 return refs_may_alias_p_1 (ref, &r, true);
1287 else if (gimple_code (stmt) == GIMPLE_ASM)
1294 stmt_may_clobber_ref_p (gimple stmt, tree ref)
1297 ao_ref_init (&r, ref);
1298 return stmt_may_clobber_ref_p_1 (stmt, &r);
1302 static tree get_continuation_for_phi (gimple, ao_ref *, bitmap *);
1304 /* Walk the virtual use-def chain of VUSE until hitting the virtual operand
1305 TARGET or a statement clobbering the memory reference REF in which
1306 case false is returned. The walk starts with VUSE, one argument of PHI. */
1309 maybe_skip_until (gimple phi, tree target, ao_ref *ref,
1310 tree vuse, bitmap *visited)
1313 *visited = BITMAP_ALLOC (NULL);
1315 bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
1317 /* Walk until we hit the target. */
1318 while (vuse != target)
1320 gimple def_stmt = SSA_NAME_DEF_STMT (vuse);
1321 /* Recurse for PHI nodes. */
1322 if (gimple_code (def_stmt) == GIMPLE_PHI)
1324 /* An already visited PHI node ends the walk successfully. */
1325 if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt))))
1327 vuse = get_continuation_for_phi (def_stmt, ref, visited);
1332 /* A clobbering statement or the end of the IL ends it failing. */
1333 else if (gimple_nop_p (def_stmt)
1334 || stmt_may_clobber_ref_p_1 (def_stmt, ref))
1336 vuse = gimple_vuse (def_stmt);
1341 /* Starting from a PHI node for the virtual operand of the memory reference
1342 REF find a continuation virtual operand that allows to continue walking
1343 statements dominating PHI skipping only statements that cannot possibly
1344 clobber REF. Returns NULL_TREE if no suitable virtual operand can
1348 get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited)
1350 unsigned nargs = gimple_phi_num_args (phi);
1352 /* Through a single-argument PHI we can simply look through. */
1354 return PHI_ARG_DEF (phi, 0);
1356 /* For two arguments try to skip non-aliasing code until we hit
1357 the phi argument definition that dominates the other one. */
1360 tree arg0 = PHI_ARG_DEF (phi, 0);
1361 tree arg1 = PHI_ARG_DEF (phi, 1);
1362 gimple def0 = SSA_NAME_DEF_STMT (arg0);
1363 gimple def1 = SSA_NAME_DEF_STMT (arg1);
1367 else if (gimple_nop_p (def0)
1368 || (!gimple_nop_p (def1)
1369 && dominated_by_p (CDI_DOMINATORS,
1370 gimple_bb (def1), gimple_bb (def0))))
1372 if (maybe_skip_until (phi, arg0, ref, arg1, visited))
1375 else if (gimple_nop_p (def1)
1376 || dominated_by_p (CDI_DOMINATORS,
1377 gimple_bb (def0), gimple_bb (def1)))
1379 if (maybe_skip_until (phi, arg1, ref, arg0, visited))
1387 /* Based on the memory reference REF and its virtual use VUSE call
1388 WALKER for each virtual use that is equivalent to VUSE, including VUSE
1389 itself. That is, for each virtual use for which its defining statement
1390 does not clobber REF.
1392 WALKER is called with REF, the current virtual use and DATA. If
1393 WALKER returns non-NULL the walk stops and its result is returned.
1394 At the end of a non-successful walk NULL is returned.
1396 TRANSLATE if non-NULL is called with a pointer to REF, the virtual
1397 use which definition is a statement that may clobber REF and DATA.
1398 If TRANSLATE returns (void *)-1 the walk stops and NULL is returned.
1399 If TRANSLATE returns non-NULL the walk stops and its result is returned.
1400 If TRANSLATE returns NULL the walk continues and TRANSLATE is supposed
1401 to adjust REF and *DATA to make that valid.
1403 TODO: Cache the vector of equivalent vuses per ref, vuse pair. */
1406 walk_non_aliased_vuses (ao_ref *ref, tree vuse,
1407 void *(*walker)(ao_ref *, tree, void *),
1408 void *(*translate)(ao_ref *, tree, void *), void *data)
1410 bitmap visited = NULL;
1413 timevar_push (TV_ALIAS_STMT_WALK);
1419 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1420 res = (*walker) (ref, vuse, data);
1424 def_stmt = SSA_NAME_DEF_STMT (vuse);
1425 if (gimple_nop_p (def_stmt))
1427 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1428 vuse = get_continuation_for_phi (def_stmt, ref, &visited);
1431 if (stmt_may_clobber_ref_p_1 (def_stmt, ref))
1435 res = (*translate) (ref, vuse, data);
1436 /* Failed lookup and translation. */
1437 if (res == (void *)-1)
1442 /* Lookup succeeded. */
1443 else if (res != NULL)
1445 /* Translation succeeded, continue walking. */
1447 vuse = gimple_vuse (def_stmt);
1453 BITMAP_FREE (visited);
1455 timevar_pop (TV_ALIAS_STMT_WALK);
1461 /* Based on the memory reference REF call WALKER for each vdef which
1462 defining statement may clobber REF, starting with VDEF. If REF
1463 is NULL_TREE, each defining statement is visited.
1465 WALKER is called with REF, the current vdef and DATA. If WALKER
1466 returns true the walk is stopped, otherwise it continues.
1468 At PHI nodes walk_aliased_vdefs forks into one walk for reach
1469 PHI argument (but only one walk continues on merge points), the
1470 return value is true if any of the walks was successful.
1472 The function returns the number of statements walked. */
1475 walk_aliased_vdefs_1 (ao_ref *ref, tree vdef,
1476 bool (*walker)(ao_ref *, tree, void *), void *data,
1477 bitmap *visited, unsigned int cnt)
1481 gimple def_stmt = SSA_NAME_DEF_STMT (vdef);
1484 && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef)))
1487 if (gimple_nop_p (def_stmt))
1489 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1493 *visited = BITMAP_ALLOC (NULL);
1494 for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
1495 cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i),
1496 walker, data, visited, 0);
1500 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1503 || stmt_may_clobber_ref_p_1 (def_stmt, ref))
1504 && (*walker) (ref, vdef, data))
1507 vdef = gimple_vuse (def_stmt);
1513 walk_aliased_vdefs (ao_ref *ref, tree vdef,
1514 bool (*walker)(ao_ref *, tree, void *), void *data,
1517 bitmap local_visited = NULL;
1520 timevar_push (TV_ALIAS_STMT_WALK);
1522 ret = walk_aliased_vdefs_1 (ref, vdef, walker, data,
1523 visited ? visited : &local_visited, 0);
1525 BITMAP_FREE (local_visited);
1527 timevar_pop (TV_ALIAS_STMT_WALK);