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 /* ??? During SCCVN/PRE we can end up with *&x during valueizing
172 operands. Likewise we can end up with dereferencing constant
173 pointers. Just bail out in these cases for now. */
174 if (TREE_CODE (ptr) == ADDR_EXPR
175 || TREE_CODE (ptr) == INTEGER_CST)
178 gcc_assert (TREE_CODE (ptr) == SSA_NAME
179 && (TREE_CODE (decl) == VAR_DECL
180 || TREE_CODE (decl) == PARM_DECL
181 || TREE_CODE (decl) == RESULT_DECL));
183 /* Non-aliased variables can not be pointed to. */
184 if (!may_be_aliased (decl))
187 /* If we do not have useful points-to information for this pointer
188 we cannot disambiguate anything else. */
189 pi = SSA_NAME_PTR_INFO (ptr);
193 return pt_solution_includes (&pi->pt, decl);
196 /* Return true if dereferenced PTR1 and PTR2 may alias.
197 The caller is responsible for applying TBAA to see if accesses
198 through PTR1 and PTR2 may conflict at all. */
201 ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
203 struct ptr_info_def *pi1, *pi2;
205 /* ??? During SCCVN/PRE we can end up with *&x during valueizing
206 operands. Likewise we can end up with dereferencing constant
207 pointers. Just bail out in these cases for now. */
208 if (TREE_CODE (ptr1) == ADDR_EXPR
209 || TREE_CODE (ptr1) == INTEGER_CST
210 || TREE_CODE (ptr2) == ADDR_EXPR
211 || TREE_CODE (ptr2) == INTEGER_CST)
214 gcc_assert (TREE_CODE (ptr1) == SSA_NAME
215 && TREE_CODE (ptr2) == SSA_NAME);
217 /* We may end up with two empty points-to solutions for two same pointers.
218 In this case we still want to say both pointers alias, so shortcut
223 /* If we do not have useful points-to information for either pointer
224 we cannot disambiguate anything else. */
225 pi1 = SSA_NAME_PTR_INFO (ptr1);
226 pi2 = SSA_NAME_PTR_INFO (ptr2);
230 /* ??? This does not use TBAA to prune decls from the intersection
231 that not both pointers may access. */
232 return pt_solutions_intersect (&pi1->pt, &pi2->pt);
235 /* Return true if STMT is an "escape" site from the current function. Escape
236 sites those statements which might expose the address of a variable
237 outside the current function. STMT is an escape site iff:
239 1- STMT is a function call, or
240 2- STMT is an __asm__ expression, or
241 3- STMT is an assignment to a non-local variable, or
242 4- STMT is a return statement.
244 Return the type of escape site found, if we found one, or NO_ESCAPE
248 is_escape_site (gimple stmt)
250 if (is_gimple_call (stmt))
252 if (gimple_call_flags (stmt) & (ECF_PURE | ECF_CONST))
253 return ESCAPE_TO_PURE_CONST;
255 return ESCAPE_TO_CALL;
257 else if (gimple_code (stmt) == GIMPLE_ASM)
258 return ESCAPE_TO_ASM;
259 else if (is_gimple_assign (stmt))
261 tree lhs = gimple_assign_lhs (stmt);
263 /* Get to the base of _REF nodes. */
264 if (TREE_CODE (lhs) != SSA_NAME)
265 lhs = get_base_address (lhs);
267 /* If we couldn't recognize the LHS of the assignment, assume that it
268 is a non-local store. */
269 if (lhs == NULL_TREE)
270 return ESCAPE_UNKNOWN;
272 if (gimple_assign_cast_p (stmt))
274 tree from = TREE_TYPE (gimple_assign_rhs1 (stmt));
275 tree to = TREE_TYPE (lhs);
277 /* If the RHS is a conversion between a pointer and an integer, the
278 pointer escapes since we can't track the integer. */
279 if (POINTER_TYPE_P (from) && !POINTER_TYPE_P (to))
280 return ESCAPE_BAD_CAST;
283 /* If the LHS is an SSA name, it can't possibly represent a non-local
285 if (TREE_CODE (lhs) == SSA_NAME)
288 /* If the LHS is a non-global decl, it isn't a non-local memory store.
289 If the LHS escapes, the RHS escape is dealt with in the PTA solver. */
291 && !is_global_var (lhs))
294 /* FIXME: LHS is not an SSA_NAME. Even if it's an assignment to a
295 local variables we cannot be sure if it will escape, because we
296 don't have information about objects not in SSA form. Need to
297 implement something along the lines of
299 J.-D. Choi, M. Gupta, M. J. Serrano, V. C. Sreedhar, and S. P.
300 Midkiff, ``Escape analysis for java,'' in Proceedings of the
301 Conference on Object-Oriented Programming Systems, Languages, and
302 Applications (OOPSLA), pp. 1-19, 1999. */
303 return ESCAPE_STORED_IN_GLOBAL;
305 else if (gimple_code (stmt) == GIMPLE_RETURN)
306 return ESCAPE_TO_RETURN;
312 /* Dump alias information on FILE. */
315 dump_alias_info (FILE *file)
319 = lang_hooks.decl_printable_name (current_function_decl, 2);
320 referenced_var_iterator rvi;
323 fprintf (file, "\n\nAlias information for %s\n\n", funcname);
325 fprintf (file, "Aliased symbols\n\n");
327 FOR_EACH_REFERENCED_VAR (var, rvi)
329 if (may_be_aliased (var))
330 dump_variable (file, var);
333 fprintf (file, "\nCall clobber information\n");
335 fprintf (file, "\nESCAPED");
336 dump_points_to_solution (file, &cfun->gimple_df->escaped);
337 fprintf (file, "\nCALLUSED");
338 dump_points_to_solution (file, &cfun->gimple_df->callused);
340 fprintf (file, "\n\nFlow-insensitive points-to information\n\n");
342 for (i = 1; i < num_ssa_names; i++)
344 tree ptr = ssa_name (i);
345 struct ptr_info_def *pi;
348 || SSA_NAME_IN_FREE_LIST (ptr))
351 pi = SSA_NAME_PTR_INFO (ptr);
353 dump_points_to_info_for (file, ptr);
356 fprintf (file, "\n");
360 /* Dump alias information on stderr. */
363 debug_alias_info (void)
365 dump_alias_info (stderr);
369 /* Return the alias information associated with pointer T. It creates a
370 new instance if none existed. */
372 struct ptr_info_def *
373 get_ptr_info (tree t)
375 struct ptr_info_def *pi;
377 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
379 pi = SSA_NAME_PTR_INFO (t);
382 pi = GGC_CNEW (struct ptr_info_def);
383 pt_solution_reset (&pi->pt);
384 SSA_NAME_PTR_INFO (t) = pi;
390 /* Dump the points-to set *PT into FILE. */
393 dump_points_to_solution (FILE *file, struct pt_solution *pt)
396 fprintf (file, ", points-to anything");
399 fprintf (file, ", points-to non-local");
402 fprintf (file, ", points-to escaped");
405 fprintf (file, ", points-to NULL");
409 fprintf (file, ", points-to vars: ");
410 dump_decl_set (file, pt->vars);
411 if (pt->vars_contains_global)
412 fprintf (file, " (includes global vars)");
416 /* Dump points-to information for SSA_NAME PTR into FILE. */
419 dump_points_to_info_for (FILE *file, tree ptr)
421 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
423 print_generic_expr (file, ptr, dump_flags);
426 dump_points_to_solution (file, &pi->pt);
428 fprintf (file, ", points-to anything");
430 fprintf (file, "\n");
434 /* Dump points-to information for VAR into stderr. */
437 debug_points_to_info_for (tree var)
439 dump_points_to_info_for (stderr, var);
443 /* Initializes the alias-oracle reference representation *R from REF. */
446 ao_ref_init (ao_ref *r, tree ref)
453 r->ref_alias_set = -1;
454 r->base_alias_set = -1;
457 /* Returns the base object of the memory reference *REF. */
460 ao_ref_base (ao_ref *ref)
464 ref->base = get_ref_base_and_extent (ref->ref, &ref->offset, &ref->size,
469 /* Returns the base object alias set of the memory reference *REF. */
471 static alias_set_type ATTRIBUTE_UNUSED
472 ao_ref_base_alias_set (ao_ref *ref)
474 if (ref->base_alias_set != -1)
475 return ref->base_alias_set;
476 ref->base_alias_set = get_alias_set (ao_ref_base (ref));
477 return ref->base_alias_set;
480 /* Returns the reference alias set of the memory reference *REF. */
483 ao_ref_alias_set (ao_ref *ref)
485 if (ref->ref_alias_set != -1)
486 return ref->ref_alias_set;
487 ref->ref_alias_set = get_alias_set (ref->ref);
488 return ref->ref_alias_set;
491 /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the
492 purpose of TBAA. Return 0 if they are distinct and -1 if we cannot
496 same_type_for_tbaa (tree type1, tree type2)
498 type1 = TYPE_MAIN_VARIANT (type1);
499 type2 = TYPE_MAIN_VARIANT (type2);
501 /* If we would have to do structural comparison bail out. */
502 if (TYPE_STRUCTURAL_EQUALITY_P (type1)
503 || TYPE_STRUCTURAL_EQUALITY_P (type2))
506 /* Compare the canonical types. */
507 if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
510 /* ??? Array types are not properly unified in all cases as we have
511 spurious changes in the index types for example. Removing this
512 causes all sorts of problems with the Fortran frontend. */
513 if (TREE_CODE (type1) == ARRAY_TYPE
514 && TREE_CODE (type2) == ARRAY_TYPE)
517 /* The types are known to be not equal. */
521 /* Determine if the two component references REF1 and REF2 which are
522 based on access types TYPE1 and TYPE2 and of which at least one is based
523 on an indirect reference may alias. */
526 nonaliasing_component_refs_p (tree ref1, tree type1,
527 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
528 tree ref2, tree type2,
529 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
531 /* If one reference is a component references through pointers try to find a
532 common base and apply offset based disambiguation. This handles
534 struct A { int i; int j; } *q;
535 struct B { struct A a; int k; } *p;
536 disambiguating q->i and p->a.j. */
540 /* Now search for the type1 in the access path of ref2. This
541 would be a common base for doing offset based disambiguation on. */
543 while (handled_component_p (*refp)
544 && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
545 refp = &TREE_OPERAND (*refp, 0);
546 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
547 /* If we couldn't compare types we have to bail out. */
550 else if (same_p == 1)
552 HOST_WIDE_INT offadj, sztmp, msztmp;
553 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
555 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
557 /* If we didn't find a common base, try the other way around. */
559 while (handled_component_p (*refp)
560 && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
561 refp = &TREE_OPERAND (*refp, 0);
562 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2);
563 /* If we couldn't compare types we have to bail out. */
566 else if (same_p == 1)
568 HOST_WIDE_INT offadj, sztmp, msztmp;
569 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
571 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
573 /* If we have two type access paths B1.path1 and B2.path2 they may
574 only alias if either B1 is in B2.path2 or B2 is in B1.path1. */
578 /* Return true if two memory references based on the variables BASE1
579 and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
580 [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. */
583 decl_refs_may_alias_p (tree base1,
584 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
586 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
588 gcc_assert (SSA_VAR_P (base1) && SSA_VAR_P (base2));
590 /* If both references are based on different variables, they cannot alias. */
591 if (!operand_equal_p (base1, base2, 0))
594 /* If both references are based on the same variable, they cannot alias if
595 the accesses do not overlap. */
596 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
599 /* Return true if an indirect reference based on *PTR1 constrained
600 to [OFFSET1, OFFSET1 + MAX_SIZE1[ may alias a variable based on BASE2
601 constrained to [OFFSET2, OFFSET2 + MAX_SIZE2[. *PTR1 and BASE2 have
602 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
603 in which case they are computed on-demand. REF1 and REF2
604 if non-NULL are the complete memory reference trees. */
607 indirect_ref_may_alias_decl_p (tree ref1, tree ptr1,
608 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
609 alias_set_type base1_alias_set,
610 tree ref2, tree base2,
611 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
612 alias_set_type base2_alias_set)
614 /* If only one reference is based on a variable, they cannot alias if
615 the pointer access is beyond the extent of the variable access.
616 (the pointer base cannot validly point to an offset less than zero
618 They also cannot alias if the pointer may not point to the decl. */
620 && !ranges_overlap_p (offset1, max_size1, 0, offset2 + max_size2))
622 if (!ptr_deref_may_alias_decl_p (ptr1, base2))
625 /* Disambiguations that rely on strict aliasing rules follow. */
626 if (!flag_strict_aliasing)
629 /* If the alias set for a pointer access is zero all bets are off. */
630 if (base1_alias_set == -1)
631 base1_alias_set = get_deref_alias_set (ptr1);
632 if (base1_alias_set == 0)
634 if (base2_alias_set == -1)
635 base2_alias_set = get_alias_set (base2);
637 /* If both references are through the same type, they do not alias
638 if the accesses do not overlap. This does extra disambiguation
639 for mixed/pointer accesses but requires strict aliasing. */
640 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
641 TREE_TYPE (base2)) == 1)
642 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
644 /* The only way to access a variable is through a pointer dereference
645 of the same alias set or a subset of it. */
646 if (base1_alias_set != base2_alias_set
647 && !alias_set_subset_of (base1_alias_set, base2_alias_set))
650 /* Do access-path based disambiguation. */
652 && handled_component_p (ref1)
653 && handled_component_p (ref2))
654 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
656 ref2, TREE_TYPE (base2),
662 /* Return true if two indirect references based on *PTR1
663 and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
664 [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. *PTR1 and *PTR2 have
665 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
666 in which case they are computed on-demand. REF1 and REF2
667 if non-NULL are the complete memory reference trees. */
670 indirect_refs_may_alias_p (tree ref1, tree ptr1,
671 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
672 alias_set_type base1_alias_set,
673 tree ref2, tree ptr2,
674 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
675 alias_set_type base2_alias_set)
677 /* If both bases are based on pointers they cannot alias if they may not
678 point to the same memory object or if they point to the same object
679 and the accesses do not overlap. */
680 if (operand_equal_p (ptr1, ptr2, 0))
681 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
682 if (!ptr_derefs_may_alias_p (ptr1, ptr2))
685 /* Disambiguations that rely on strict aliasing rules follow. */
686 if (!flag_strict_aliasing)
689 /* If the alias set for a pointer access is zero all bets are off. */
690 if (base1_alias_set == -1)
691 base1_alias_set = get_deref_alias_set (ptr1);
692 if (base1_alias_set == 0)
694 if (base2_alias_set == -1)
695 base2_alias_set = get_deref_alias_set (ptr2);
696 if (base2_alias_set == 0)
699 /* If both references are through the same type, they do not alias
700 if the accesses do not overlap. This does extra disambiguation
701 for mixed/pointer accesses but requires strict aliasing. */
702 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
703 TREE_TYPE (TREE_TYPE (ptr2))) == 1)
704 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
706 /* Do type-based disambiguation. */
707 if (base1_alias_set != base2_alias_set
708 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
711 /* Do access-path based disambiguation. */
713 && handled_component_p (ref1)
714 && handled_component_p (ref2))
715 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
717 ref2, TREE_TYPE (TREE_TYPE (ptr2)),
723 /* Return true, if the two memory references REF1 and REF2 may alias. */
726 refs_may_alias_p_1 (ao_ref *ref1, ao_ref *ref2, bool tbaa_p)
729 HOST_WIDE_INT offset1 = 0, offset2 = 0;
730 HOST_WIDE_INT size1 = -1, size2 = -1;
731 HOST_WIDE_INT max_size1 = -1, max_size2 = -1;
732 bool var1_p, var2_p, ind1_p, ind2_p;
735 gcc_assert ((!ref1->ref
736 || SSA_VAR_P (ref1->ref)
737 || handled_component_p (ref1->ref)
738 || INDIRECT_REF_P (ref1->ref)
739 || TREE_CODE (ref1->ref) == TARGET_MEM_REF)
741 || SSA_VAR_P (ref2->ref)
742 || handled_component_p (ref2->ref)
743 || INDIRECT_REF_P (ref2->ref)
744 || TREE_CODE (ref2->ref) == TARGET_MEM_REF));
746 /* Decompose the references into their base objects and the access. */
747 base1 = ao_ref_base (ref1);
748 offset1 = ref1->offset;
750 max_size1 = ref1->max_size;
751 base2 = ao_ref_base (ref2);
752 offset2 = ref2->offset;
754 max_size2 = ref2->max_size;
756 /* We can end up with registers or constants as bases for example from
757 *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59);
758 which is seen as a struct copy. */
759 if (TREE_CODE (base1) == SSA_NAME
760 || TREE_CODE (base2) == SSA_NAME
761 || is_gimple_min_invariant (base1)
762 || is_gimple_min_invariant (base2))
765 /* Defer to simple offset based disambiguation if we have
766 references based on two decls. Do this before defering to
767 TBAA to handle must-alias cases in conformance with the
768 GCC extension of allowing type-punning through unions. */
769 var1_p = SSA_VAR_P (base1);
770 var2_p = SSA_VAR_P (base2);
771 if (var1_p && var2_p)
772 return decl_refs_may_alias_p (base1, offset1, max_size1,
773 base2, offset2, max_size2);
775 /* First defer to TBAA if possible. */
777 && flag_strict_aliasing
778 && !alias_sets_conflict_p (ao_ref_alias_set (ref1),
779 ao_ref_alias_set (ref2)))
782 /* If one reference is a TARGET_MEM_REF weird things are allowed. Still
783 TBAA disambiguation based on the access type is possible, so bail
784 out only after that check. */
785 if ((ref1->ref && TREE_CODE (ref1->ref) == TARGET_MEM_REF)
786 || (ref2->ref && TREE_CODE (ref2->ref) == TARGET_MEM_REF))
789 /* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */
790 ind1_p = INDIRECT_REF_P (base1);
791 ind2_p = INDIRECT_REF_P (base2);
792 set = tbaa_p ? -1 : 0;
793 if (var1_p && ind2_p)
794 return indirect_ref_may_alias_decl_p (ref2->ref, TREE_OPERAND (base2, 0),
795 offset2, max_size2, set,
797 offset1, max_size1, set);
798 else if (ind1_p && var2_p)
799 return indirect_ref_may_alias_decl_p (ref1->ref, TREE_OPERAND (base1, 0),
800 offset1, max_size1, set,
802 offset2, max_size2, set);
803 else if (ind1_p && ind2_p)
804 return indirect_refs_may_alias_p (ref1->ref, TREE_OPERAND (base1, 0),
805 offset1, max_size1, set,
806 ref2->ref, TREE_OPERAND (base2, 0),
807 offset2, max_size2, set);
813 refs_may_alias_p (tree ref1, tree ref2)
817 ao_ref_init (&r1, ref1);
818 ao_ref_init (&r2, ref2);
819 res = refs_may_alias_p_1 (&r1, &r2, true);
821 ++alias_stats.refs_may_alias_p_may_alias;
823 ++alias_stats.refs_may_alias_p_no_alias;
827 /* Returns true if there is a anti-dependence for the STORE that
828 executes after the LOAD. */
831 refs_anti_dependent_p (tree load, tree store)
834 ao_ref_init (&r1, load);
835 ao_ref_init (&r2, store);
836 return refs_may_alias_p_1 (&r1, &r2, false);
839 /* Returns true if there is a output dependence for the stores
840 STORE1 and STORE2. */
843 refs_output_dependent_p (tree store1, tree store2)
846 ao_ref_init (&r1, store1);
847 ao_ref_init (&r2, store2);
848 return refs_may_alias_p_1 (&r1, &r2, false);
851 /* If the call CALL may use the memory reference REF return true,
852 otherwise return false. */
855 ref_maybe_used_by_call_p_1 (gimple call, tree ref)
859 int flags = gimple_call_flags (call);
861 /* Const functions without a static chain do not implicitly use memory. */
862 if (!gimple_call_chain (call)
863 && (flags & (ECF_CONST|ECF_NOVOPS)))
866 /* If the reference is not based on a decl give up.
867 ??? Handle indirect references by intersecting the call-used
868 solution with that of the pointer. */
869 base = get_base_address (ref);
874 /* If the reference is based on a decl that is not aliased the call
875 cannot possibly use it. */
877 && !may_be_aliased (base)
878 /* But local statics can be used through recursion. */
879 && !is_global_var (base))
882 /* Check if base is a global static variable that is not read
884 if (TREE_CODE (base) == VAR_DECL
885 && TREE_STATIC (base)
886 && !TREE_PUBLIC (base))
888 tree callee = gimple_call_fndecl (call);
891 if (callee != NULL_TREE
893 = ipa_reference_get_not_read_global (cgraph_node (callee)))
894 && bitmap_bit_p (not_read, DECL_UID (base)))
898 /* If the base variable is call-used or call-clobbered then
900 if (flags & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
902 if (is_call_used (base))
907 if (is_call_clobbered (base))
911 /* Inspect call arguments for passed-by-value aliases. */
913 for (i = 0; i < gimple_call_num_args (call); ++i)
915 tree op = gimple_call_arg (call, i);
917 if (TREE_CODE (op) == EXC_PTR_EXPR
918 || TREE_CODE (op) == FILTER_EXPR)
921 if (TREE_CODE (op) == WITH_SIZE_EXPR)
922 op = TREE_OPERAND (op, 0);
924 if (TREE_CODE (op) != SSA_NAME
925 && !is_gimple_min_invariant (op)
926 && refs_may_alias_p (op, ref))
934 ref_maybe_used_by_call_p (gimple call, tree ref)
936 bool res = ref_maybe_used_by_call_p_1 (call, ref);
938 ++alias_stats.ref_maybe_used_by_call_p_may_alias;
940 ++alias_stats.ref_maybe_used_by_call_p_no_alias;
945 /* If the statement STMT may use the memory reference REF return
946 true, otherwise return false. */
949 ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
951 if (is_gimple_assign (stmt))
955 /* All memory assign statements are single. */
956 if (!gimple_assign_single_p (stmt))
959 rhs = gimple_assign_rhs1 (stmt);
960 if (is_gimple_reg (rhs)
961 || is_gimple_min_invariant (rhs)
962 || gimple_assign_rhs_code (stmt) == CONSTRUCTOR)
965 return refs_may_alias_p (rhs, ref);
967 else if (is_gimple_call (stmt))
968 return ref_maybe_used_by_call_p (stmt, ref);
973 /* If the call in statement CALL may clobber the memory reference REF
974 return true, otherwise return false. */
977 call_may_clobber_ref_p_1 (gimple call, ao_ref *ref)
981 /* If the call is pure or const it cannot clobber anything. */
982 if (gimple_call_flags (call)
983 & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
986 base = ao_ref_base (ref);
990 if (TREE_CODE (base) == SSA_NAME
991 || CONSTANT_CLASS_P (base))
994 /* If the reference is based on a decl that is not aliased the call
995 cannot possibly clobber it. */
997 && !may_be_aliased (base)
998 /* But local non-readonly statics can be modified through recursion
999 or the call may implement a threading barrier which we must
1000 treat as may-def. */
1001 && (TREE_READONLY (base)
1002 || !is_global_var (base)))
1005 /* Check if base is a global static variable that is not written
1007 if (TREE_CODE (base) == VAR_DECL
1008 && TREE_STATIC (base)
1009 && !TREE_PUBLIC (base))
1011 tree callee = gimple_call_fndecl (call);
1014 if (callee != NULL_TREE
1016 = ipa_reference_get_not_written_global (cgraph_node (callee)))
1017 && bitmap_bit_p (not_written, DECL_UID (base)))
1022 return is_call_clobbered (base);
1027 static bool ATTRIBUTE_UNUSED
1028 call_may_clobber_ref_p (gimple call, tree ref)
1032 ao_ref_init (&r, ref);
1033 res = call_may_clobber_ref_p_1 (call, &r);
1035 ++alias_stats.call_may_clobber_ref_p_may_alias;
1037 ++alias_stats.call_may_clobber_ref_p_no_alias;
1042 /* If the statement STMT may clobber the memory reference REF return true,
1043 otherwise return false. */
1046 stmt_may_clobber_ref_p_1 (gimple stmt, ao_ref *ref)
1048 if (is_gimple_call (stmt))
1050 tree lhs = gimple_call_lhs (stmt);
1052 && !is_gimple_reg (lhs))
1055 ao_ref_init (&r, lhs);
1056 if (refs_may_alias_p_1 (ref, &r, true))
1060 return call_may_clobber_ref_p_1 (stmt, ref);
1062 else if (is_gimple_assign (stmt))
1065 ao_ref_init (&r, gimple_assign_lhs (stmt));
1066 return refs_may_alias_p_1 (ref, &r, true);
1068 else if (gimple_code (stmt) == GIMPLE_ASM)
1075 stmt_may_clobber_ref_p (gimple stmt, tree ref)
1078 ao_ref_init (&r, ref);
1079 return stmt_may_clobber_ref_p_1 (stmt, &r);
1083 static tree get_continuation_for_phi (gimple, ao_ref *, bitmap *);
1085 /* Walk the virtual use-def chain of VUSE until hitting the virtual operand
1086 TARGET or a statement clobbering the memory reference REF in which
1087 case false is returned. The walk starts with VUSE, one argument of PHI. */
1090 maybe_skip_until (gimple phi, tree target, ao_ref *ref,
1091 tree vuse, bitmap *visited)
1094 *visited = BITMAP_ALLOC (NULL);
1096 bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
1098 /* Walk until we hit the target. */
1099 while (vuse != target)
1101 gimple def_stmt = SSA_NAME_DEF_STMT (vuse);
1102 /* Recurse for PHI nodes. */
1103 if (gimple_code (def_stmt) == GIMPLE_PHI)
1105 /* An already visited PHI node ends the walk successfully. */
1106 if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt))))
1108 vuse = get_continuation_for_phi (def_stmt, ref, visited);
1113 /* A clobbering statement or the end of the IL ends it failing. */
1114 else if (gimple_nop_p (def_stmt)
1115 || stmt_may_clobber_ref_p_1 (def_stmt, ref))
1117 vuse = gimple_vuse (def_stmt);
1122 /* Starting from a PHI node for the virtual operand of the memory reference
1123 REF find a continuation virtual operand that allows to continue walking
1124 statements dominating PHI skipping only statements that cannot possibly
1125 clobber REF. Returns NULL_TREE if no suitable virtual operand can
1129 get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited)
1131 unsigned nargs = gimple_phi_num_args (phi);
1133 /* Through a single-argument PHI we can simply look through. */
1135 return PHI_ARG_DEF (phi, 0);
1137 /* For two arguments try to skip non-aliasing code until we hit
1138 the phi argument definition that dominates the other one. */
1141 tree arg0 = PHI_ARG_DEF (phi, 0);
1142 tree arg1 = PHI_ARG_DEF (phi, 1);
1143 gimple def0 = SSA_NAME_DEF_STMT (arg0);
1144 gimple def1 = SSA_NAME_DEF_STMT (arg1);
1148 else if (gimple_nop_p (def0)
1149 || (!gimple_nop_p (def1)
1150 && dominated_by_p (CDI_DOMINATORS,
1151 gimple_bb (def1), gimple_bb (def0))))
1153 if (maybe_skip_until (phi, arg0, ref, arg1, visited))
1156 else if (gimple_nop_p (def1)
1157 || dominated_by_p (CDI_DOMINATORS,
1158 gimple_bb (def0), gimple_bb (def1)))
1160 if (maybe_skip_until (phi, arg1, ref, arg0, visited))
1168 /* Based on the memory reference REF and its virtual use VUSE call
1169 WALKER for each virtual use that is equivalent to VUSE, including VUSE
1170 itself. That is, for each virtual use for which its defining statement
1171 does not clobber REF.
1173 WALKER is called with REF, the current virtual use and DATA. If
1174 WALKER returns non-NULL the walk stops and its result is returned.
1175 At the end of a non-successful walk NULL is returned.
1177 TRANSLATE if non-NULL is called with a pointer to REF, the virtual
1178 use which definition is a statement that may clobber REF and DATA.
1179 If TRANSLATE returns (void *)-1 the walk stops and NULL is returned.
1180 If TRANSLATE returns non-NULL the walk stops and its result is returned.
1181 If TRANSLATE returns NULL the walk continues and TRANSLATE is supposed
1182 to adjust REF and *DATA to make that valid.
1184 TODO: Cache the vector of equivalent vuses per ref, vuse pair. */
1187 walk_non_aliased_vuses (ao_ref *ref, tree vuse,
1188 void *(*walker)(ao_ref *, tree, void *),
1189 void *(*translate)(ao_ref *, tree, void *), void *data)
1191 bitmap visited = NULL;
1194 timevar_push (TV_ALIAS_STMT_WALK);
1200 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1201 res = (*walker) (ref, vuse, data);
1205 def_stmt = SSA_NAME_DEF_STMT (vuse);
1206 if (gimple_nop_p (def_stmt))
1208 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1209 vuse = get_continuation_for_phi (def_stmt, ref, &visited);
1212 if (stmt_may_clobber_ref_p_1 (def_stmt, ref))
1216 res = (*translate) (ref, vuse, data);
1217 /* Failed lookup and translation. */
1218 if (res == (void *)-1)
1223 /* Lookup succeeded. */
1224 else if (res != NULL)
1226 /* Translation succeeded, continue walking. */
1228 vuse = gimple_vuse (def_stmt);
1234 BITMAP_FREE (visited);
1236 timevar_pop (TV_ALIAS_STMT_WALK);
1242 /* Based on the memory reference REF call WALKER for each vdef which
1243 defining statement may clobber REF, starting with VDEF. If REF
1244 is NULL_TREE, each defining statement is visited.
1246 WALKER is called with REF, the current vdef and DATA. If WALKER
1247 returns true the walk is stopped, otherwise it continues.
1249 At PHI nodes walk_aliased_vdefs forks into one walk for reach
1250 PHI argument (but only one walk continues on merge points), the
1251 return value is true if any of the walks was successful.
1253 The function returns the number of statements walked. */
1256 walk_aliased_vdefs_1 (tree ref, tree vdef,
1257 bool (*walker)(tree, tree, void *), void *data,
1258 bitmap *visited, unsigned int cnt)
1262 gimple def_stmt = SSA_NAME_DEF_STMT (vdef);
1265 && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef)))
1268 if (gimple_nop_p (def_stmt))
1270 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1274 *visited = BITMAP_ALLOC (NULL);
1275 for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
1276 cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i),
1277 walker, data, visited, 0);
1281 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1284 || stmt_may_clobber_ref_p (def_stmt, ref))
1285 && (*walker) (ref, vdef, data))
1288 vdef = gimple_vuse (def_stmt);
1294 walk_aliased_vdefs (tree ref, tree vdef,
1295 bool (*walker)(tree, tree, void *), void *data,
1298 bitmap local_visited = NULL;
1301 timevar_push (TV_ALIAS_STMT_WALK);
1303 ret = walk_aliased_vdefs_1 (ref, vdef, walker, data,
1304 visited ? visited : &local_visited, 0);
1306 BITMAP_FREE (local_visited);
1308 timevar_pop (TV_ALIAS_STMT_WALK);