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, "\n\nFlow-insensitive points-to information for %s\n\n", funcname);
335 for (i = 1; i < num_ssa_names; i++)
337 tree ptr = ssa_name (i);
338 struct ptr_info_def *pi;
341 || SSA_NAME_IN_FREE_LIST (ptr))
344 pi = SSA_NAME_PTR_INFO (ptr);
346 dump_points_to_info_for (file, ptr);
349 fprintf (file, "\n");
353 /* Dump alias information on stderr. */
356 debug_alias_info (void)
358 dump_alias_info (stderr);
362 /* Return the alias information associated with pointer T. It creates a
363 new instance if none existed. */
365 struct ptr_info_def *
366 get_ptr_info (tree t)
368 struct ptr_info_def *pi;
370 gcc_assert (POINTER_TYPE_P (TREE_TYPE (t)));
372 pi = SSA_NAME_PTR_INFO (t);
375 pi = GGC_CNEW (struct ptr_info_def);
376 pt_solution_reset (&pi->pt);
377 SSA_NAME_PTR_INFO (t) = pi;
383 /* Dump points-to information for SSA_NAME PTR into FILE. */
386 dump_points_to_info_for (FILE *file, tree ptr)
388 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
390 print_generic_expr (file, ptr, dump_flags);
395 fprintf (file, ", points-to anything");
398 fprintf (file, ", points-to non-local");
401 fprintf (file, ", points-to escaped");
404 fprintf (file, ", points-to NULL");
408 fprintf (file, ", points-to vars: ");
409 dump_decl_set (file, pi->pt.vars);
410 if (pi->pt.vars_contains_global)
411 fprintf (file, " (includes global vars)");
415 fprintf (file, "\n");
419 /* Dump points-to information for VAR into stderr. */
422 debug_points_to_info_for (tree var)
424 dump_points_to_info_for (stderr, var);
427 /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the
428 purpose of TBAA. Return 0 if they are distinct and -1 if we cannot
432 same_type_for_tbaa (tree type1, tree type2)
434 type1 = TYPE_MAIN_VARIANT (type1);
435 type2 = TYPE_MAIN_VARIANT (type2);
437 /* If we would have to do structural comparison bail out. */
438 if (TYPE_STRUCTURAL_EQUALITY_P (type1)
439 || TYPE_STRUCTURAL_EQUALITY_P (type2))
442 /* Compare the canonical types. */
443 if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
446 /* ??? Array types are not properly unified in all cases as we have
447 spurious changes in the index types for example. Removing this
448 causes all sorts of problems with the Fortran frontend. */
449 if (TREE_CODE (type1) == ARRAY_TYPE
450 && TREE_CODE (type2) == ARRAY_TYPE)
453 /* The types are known to be not equal. */
457 /* Determine if the two component references REF1 and REF2 which are
458 based on access types TYPE1 and TYPE2 and of which at least one is based
459 on an indirect reference may alias. */
462 nonaliasing_component_refs_p (tree ref1, tree type1,
463 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
464 tree ref2, tree type2,
465 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
467 /* If one reference is a component references through pointers try to find a
468 common base and apply offset based disambiguation. This handles
470 struct A { int i; int j; } *q;
471 struct B { struct A a; int k; } *p;
472 disambiguating q->i and p->a.j. */
476 /* Now search for the type1 in the access path of ref2. This
477 would be a common base for doing offset based disambiguation on. */
478 /* Skip the outermost ref - we would have caught that earlier. */
479 refp = &TREE_OPERAND (ref2, 0);
480 while (handled_component_p (*refp)
481 && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
482 refp = &TREE_OPERAND (*refp, 0);
483 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
484 /* If we couldn't compare types we have to bail out. */
487 else if (same_p == 1)
489 HOST_WIDE_INT offadj, sztmp, msztmp;
490 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
492 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
494 /* If we didn't find a common base, try the other way around. */
495 refp = &TREE_OPERAND (ref1, 0);
496 while (handled_component_p (*refp)
497 && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
498 refp = &TREE_OPERAND (*refp, 0);
499 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2);
500 /* If we couldn't compare types we have to bail out. */
503 else if (same_p == 1)
505 HOST_WIDE_INT offadj, sztmp, msztmp;
506 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
508 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
510 /* If we have two type access paths B1.path1 and B2.path2 they may
511 only alias if either B1 is in B2.path2 or B2 is in B1.path1. */
515 /* Return true if two memory references based on the variables BASE1
516 and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
517 [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. */
520 decl_refs_may_alias_p (tree base1,
521 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
523 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
525 gcc_assert (SSA_VAR_P (base1) && SSA_VAR_P (base2));
527 /* If both references are based on different variables, they cannot alias. */
528 if (!operand_equal_p (base1, base2, 0))
531 /* If both references are based on the same variable, they cannot alias if
532 the accesses do not overlap. */
533 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
536 /* Return true if an indirect reference based on *PTR1 constrained
537 to [OFFSET1, OFFSET1 + MAX_SIZE1[ may alias a variable based on BASE2
538 constrained to [OFFSET2, OFFSET2 + MAX_SIZE2[. *PTR1 and BASE2 have
539 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
540 in which case they are computed on-demand. REF1 and REF2
541 if non-NULL are the complete memory reference trees. */
544 indirect_ref_may_alias_decl_p (tree ref1, tree ptr1,
545 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
546 alias_set_type base1_alias_set,
547 tree ref2, tree base2,
548 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
549 alias_set_type base2_alias_set)
551 /* If only one reference is based on a variable, they cannot alias if
552 the pointer access is beyond the extent of the variable access.
553 (the pointer base cannot validly point to an offset less than zero
555 They also cannot alias if the pointer may not point to the decl. */
557 && !ranges_overlap_p (offset1, max_size1, 0, offset2 + max_size2))
559 if (!ptr_deref_may_alias_decl_p (ptr1, base2))
562 /* Disambiguations that rely on strict aliasing rules follow. */
563 if (!flag_strict_aliasing)
566 /* If the alias set for a pointer access is zero all bets are off. */
567 if (base1_alias_set == -1)
568 base1_alias_set = get_deref_alias_set (ptr1);
569 if (base1_alias_set == 0)
571 if (base2_alias_set == -1)
572 base2_alias_set = get_alias_set (base2);
574 /* If both references are through the same type, they do not alias
575 if the accesses do not overlap. This does extra disambiguation
576 for mixed/pointer accesses but requires strict aliasing. */
577 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
578 TREE_TYPE (base2)) == 1)
579 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
581 /* The only way to access a variable is through a pointer dereference
582 of the same alias set or a subset of it. */
583 if (base1_alias_set != base2_alias_set
584 && !alias_set_subset_of (base1_alias_set, base2_alias_set))
587 /* Do access-path based disambiguation. */
589 && handled_component_p (ref1)
590 && handled_component_p (ref2))
591 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
593 ref2, TREE_TYPE (base2),
599 /* Return true if two indirect references based on *PTR1
600 and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1[ and
601 [OFFSET2, OFFSET2 + MAX_SIZE2[ may alias. *PTR1 and *PTR2 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_refs_may_alias_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 ptr2,
611 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
612 alias_set_type base2_alias_set)
614 /* If both bases are based on pointers they cannot alias if they may not
615 point to the same memory object or if they point to the same object
616 and the accesses do not overlap. */
617 if (operand_equal_p (ptr1, ptr2, 0))
618 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
619 if (!ptr_derefs_may_alias_p (ptr1, ptr2))
622 /* Disambiguations that rely on strict aliasing rules follow. */
623 if (!flag_strict_aliasing)
626 /* If the alias set for a pointer access is zero all bets are off. */
627 if (base1_alias_set == -1)
628 base1_alias_set = get_deref_alias_set (ptr1);
629 if (base1_alias_set == 0)
631 if (base2_alias_set == -1)
632 base2_alias_set = get_deref_alias_set (ptr2);
633 if (base2_alias_set == 0)
636 /* If both references are through the same type, they do not alias
637 if the accesses do not overlap. This does extra disambiguation
638 for mixed/pointer accesses but requires strict aliasing. */
639 if (same_type_for_tbaa (TREE_TYPE (TREE_TYPE (ptr1)),
640 TREE_TYPE (TREE_TYPE (ptr2))) == 1)
641 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
643 /* Do type-based disambiguation. */
644 if (base1_alias_set != base2_alias_set
645 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
648 /* Do access-path based disambiguation. */
650 && handled_component_p (ref1)
651 && handled_component_p (ref2))
652 return nonaliasing_component_refs_p (ref1, TREE_TYPE (TREE_TYPE (ptr1)),
654 ref2, TREE_TYPE (TREE_TYPE (ptr2)),
660 /* Return true, if the two memory references REF1 and REF2 may alias. */
663 refs_may_alias_p_1 (tree ref1, tree ref2, bool tbaa_p)
666 HOST_WIDE_INT offset1 = 0, offset2 = 0;
667 HOST_WIDE_INT size1 = -1, size2 = -1;
668 HOST_WIDE_INT max_size1 = -1, max_size2 = -1;
669 bool var1_p, var2_p, ind1_p, ind2_p;
672 gcc_assert ((SSA_VAR_P (ref1)
673 || handled_component_p (ref1)
674 || INDIRECT_REF_P (ref1)
675 || TREE_CODE (ref1) == TARGET_MEM_REF)
677 || handled_component_p (ref2)
678 || INDIRECT_REF_P (ref2)
679 || TREE_CODE (ref2) == TARGET_MEM_REF));
681 /* Decompose the references into their base objects and the access. */
682 base1 = get_ref_base_and_extent (ref1, &offset1, &size1, &max_size1);
683 base2 = get_ref_base_and_extent (ref2, &offset2, &size2, &max_size2);
685 /* We can end up with registers or constants as bases for example from
686 *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59);
687 which is seen as a struct copy. */
688 if (TREE_CODE (base1) == SSA_NAME
689 || TREE_CODE (base2) == SSA_NAME
690 || is_gimple_min_invariant (base1)
691 || is_gimple_min_invariant (base2))
694 /* Defer to simple offset based disambiguation if we have
695 references based on two decls. Do this before defering to
696 TBAA to handle must-alias cases in conformance with the
697 GCC extension of allowing type-punning through unions. */
698 var1_p = SSA_VAR_P (base1);
699 var2_p = SSA_VAR_P (base2);
700 if (var1_p && var2_p)
701 return decl_refs_may_alias_p (base1, offset1, max_size1,
702 base2, offset2, max_size2);
704 /* First defer to TBAA if possible. */
706 && flag_strict_aliasing
707 && !alias_sets_conflict_p (get_alias_set (ref1), get_alias_set (ref2)))
710 /* If one reference is a TARGET_MEM_REF weird things are allowed. Still
711 TBAA disambiguation based on the access type is possible, so bail
712 out only after that check. */
713 if (TREE_CODE (ref1) == TARGET_MEM_REF
714 || TREE_CODE (ref2) == TARGET_MEM_REF)
717 /* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */
718 ind1_p = INDIRECT_REF_P (base1);
719 ind2_p = INDIRECT_REF_P (base2);
720 set = tbaa_p ? -1 : 0;
721 if (var1_p && ind2_p)
722 return indirect_ref_may_alias_decl_p (ref2, TREE_OPERAND (base2, 0),
723 offset2, max_size2, set,
725 offset1, max_size1, set);
726 else if (ind1_p && var2_p)
727 return indirect_ref_may_alias_decl_p (ref1, TREE_OPERAND (base1, 0),
728 offset1, max_size1, set,
730 offset2, max_size2, set);
731 else if (ind1_p && ind2_p)
732 return indirect_refs_may_alias_p (ref1, TREE_OPERAND (base1, 0),
733 offset1, max_size1, set,
734 ref2, TREE_OPERAND (base2, 0),
735 offset2, max_size2, set);
741 refs_may_alias_p (tree ref1, tree ref2)
743 bool res = refs_may_alias_p_1 (ref1, ref2, true);
745 ++alias_stats.refs_may_alias_p_may_alias;
747 ++alias_stats.refs_may_alias_p_no_alias;
751 /* Returns true if there is a anti-dependence for the STORE that
752 executes after the LOAD. */
755 refs_anti_dependent_p (tree load, tree store)
757 return refs_may_alias_p_1 (load, store, false);
760 /* Returns true if there is a output dependence for the stores
761 STORE1 and STORE2. */
764 refs_output_dependent_p (tree store1, tree store2)
766 return refs_may_alias_p_1 (store1, store2, false);
769 /* If the call CALL may use the memory reference REF return true,
770 otherwise return false. */
773 ref_maybe_used_by_call_p_1 (gimple call, tree ref)
777 int flags = gimple_call_flags (call);
779 /* Const functions without a static chain do not implicitly use memory. */
780 if (!gimple_call_chain (call)
781 && (flags & (ECF_CONST|ECF_NOVOPS)))
784 /* If the reference is not based on a decl give up.
785 ??? Handle indirect references by intersecting the call-used
786 solution with that of the pointer. */
787 base = get_base_address (ref);
792 /* If the reference is based on a decl that is not aliased the call
793 cannot possibly use it. */
795 && !may_be_aliased (base)
796 /* But local statics can be used through recursion. */
797 && !is_global_var (base))
800 /* Check if base is a global static variable that is not read
802 if (TREE_CODE (base) == VAR_DECL
803 && TREE_STATIC (base)
804 && !TREE_PUBLIC (base))
806 tree callee = gimple_call_fndecl (call);
809 if (callee != NULL_TREE
811 = ipa_reference_get_not_read_global (cgraph_node (callee)))
812 && bitmap_bit_p (not_read, DECL_UID (base)))
816 /* If the base variable is call-used or call-clobbered then
818 if (flags & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
820 if (is_call_used (base))
825 if (is_call_clobbered (base))
829 /* Inspect call arguments for passed-by-value aliases. */
831 for (i = 0; i < gimple_call_num_args (call); ++i)
833 tree op = gimple_call_arg (call, i);
835 if (TREE_CODE (op) == EXC_PTR_EXPR
836 || TREE_CODE (op) == FILTER_EXPR)
839 if (TREE_CODE (op) == WITH_SIZE_EXPR)
840 op = TREE_OPERAND (op, 0);
842 if (TREE_CODE (op) != SSA_NAME
843 && !is_gimple_min_invariant (op)
844 && refs_may_alias_p (op, ref))
852 ref_maybe_used_by_call_p (gimple call, tree ref)
854 bool res = ref_maybe_used_by_call_p_1 (call, ref);
856 ++alias_stats.ref_maybe_used_by_call_p_may_alias;
858 ++alias_stats.ref_maybe_used_by_call_p_no_alias;
863 /* If the statement STMT may use the memory reference REF return
864 true, otherwise return false. */
867 ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
869 if (is_gimple_assign (stmt))
873 /* All memory assign statements are single. */
874 if (!gimple_assign_single_p (stmt))
877 rhs = gimple_assign_rhs1 (stmt);
878 if (is_gimple_reg (rhs)
879 || is_gimple_min_invariant (rhs)
880 || gimple_assign_rhs_code (stmt) == CONSTRUCTOR)
883 return refs_may_alias_p (rhs, ref);
885 else if (is_gimple_call (stmt))
886 return ref_maybe_used_by_call_p (stmt, ref);
891 /* If the call in statement CALL may clobber the memory reference REF
892 return true, otherwise return false. */
895 call_may_clobber_ref_p_1 (gimple call, tree ref)
899 /* If the call is pure or const it cannot clobber anything. */
900 if (gimple_call_flags (call)
901 & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
904 base = get_base_address (ref);
908 if (TREE_CODE (base) == SSA_NAME
909 || CONSTANT_CLASS_P (base))
912 /* If the reference is based on a decl that is not aliased the call
913 cannot possibly clobber it. */
915 && !may_be_aliased (base)
916 /* But local non-readonly statics can be modified through recursion
917 or the call may implement a threading barrier which we must
919 && (TREE_READONLY (base)
920 || !is_global_var (base)))
923 /* Check if base is a global static variable that is not written
925 if (TREE_CODE (base) == VAR_DECL
926 && TREE_STATIC (base)
927 && !TREE_PUBLIC (base))
929 tree callee = gimple_call_fndecl (call);
932 if (callee != NULL_TREE
934 = ipa_reference_get_not_written_global (cgraph_node (callee)))
935 && bitmap_bit_p (not_written, DECL_UID (base)))
940 return is_call_clobbered (base);
946 call_may_clobber_ref_p (gimple call, tree ref)
948 bool res = call_may_clobber_ref_p_1 (call, ref);
950 ++alias_stats.call_may_clobber_ref_p_may_alias;
952 ++alias_stats.call_may_clobber_ref_p_no_alias;
957 /* If the statement STMT may clobber the memory reference REF return true,
958 otherwise return false. */
961 stmt_may_clobber_ref_p (gimple stmt, tree ref)
963 if (is_gimple_call (stmt))
965 tree lhs = gimple_call_lhs (stmt);
967 && !is_gimple_reg (lhs)
968 && refs_may_alias_p (ref, lhs))
971 return call_may_clobber_ref_p (stmt, ref);
973 else if (is_gimple_assign (stmt))
974 return refs_may_alias_p (ref, gimple_assign_lhs (stmt));
975 else if (gimple_code (stmt) == GIMPLE_ASM)
981 static tree get_continuation_for_phi (gimple, tree, bitmap *);
983 /* Walk the virtual use-def chain of VUSE until hitting the virtual operand
984 TARGET or a statement clobbering the memory reference REF in which
985 case false is returned. The walk starts with VUSE, one argument of PHI. */
988 maybe_skip_until (gimple phi, tree target, tree ref, tree vuse, bitmap *visited)
991 *visited = BITMAP_ALLOC (NULL);
993 bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
995 /* Walk until we hit the target. */
996 while (vuse != target)
998 gimple def_stmt = SSA_NAME_DEF_STMT (vuse);
999 /* Recurse for PHI nodes. */
1000 if (gimple_code (def_stmt) == GIMPLE_PHI)
1002 /* An already visited PHI node ends the walk successfully. */
1003 if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt))))
1005 vuse = get_continuation_for_phi (def_stmt, ref, visited);
1010 /* A clobbering statement or the end of the IL ends it failing. */
1011 else if (gimple_nop_p (def_stmt)
1012 || stmt_may_clobber_ref_p (def_stmt, ref))
1014 vuse = gimple_vuse (def_stmt);
1019 /* Starting from a PHI node for the virtual operand of the memory reference
1020 REF find a continuation virtual operand that allows to continue walking
1021 statements dominating PHI skipping only statements that cannot possibly
1022 clobber REF. Returns NULL_TREE if no suitable virtual operand can
1026 get_continuation_for_phi (gimple phi, tree ref, bitmap *visited)
1028 unsigned nargs = gimple_phi_num_args (phi);
1030 /* Through a single-argument PHI we can simply look through. */
1032 return PHI_ARG_DEF (phi, 0);
1034 /* For two arguments try to skip non-aliasing code until we hit
1035 the phi argument definition that dominates the other one. */
1038 tree arg0 = PHI_ARG_DEF (phi, 0);
1039 tree arg1 = PHI_ARG_DEF (phi, 1);
1040 gimple def0 = SSA_NAME_DEF_STMT (arg0);
1041 gimple def1 = SSA_NAME_DEF_STMT (arg1);
1045 else if (gimple_nop_p (def0)
1046 || (!gimple_nop_p (def1)
1047 && dominated_by_p (CDI_DOMINATORS,
1048 gimple_bb (def1), gimple_bb (def0))))
1050 if (maybe_skip_until (phi, arg0, ref, arg1, visited))
1053 else if (gimple_nop_p (def1)
1054 || dominated_by_p (CDI_DOMINATORS,
1055 gimple_bb (def0), gimple_bb (def1)))
1057 if (maybe_skip_until (phi, arg1, ref, arg0, visited))
1065 /* Based on the memory reference REF and its virtual use VUSE call
1066 WALKER for each virtual use that is equivalent to VUSE, including VUSE
1067 itself. That is, for each virtual use for which its defining statement
1068 does not clobber REF.
1070 WALKER is called with REF, the current virtual use and DATA. If
1071 WALKER returns non-NULL the walk stops and its result is returned.
1072 At the end of a non-successful walk NULL is returned.
1074 TODO: Cache the vector of equivalent vuses per ref, vuse pair. */
1077 walk_non_aliased_vuses (tree ref, tree vuse,
1078 void *(*walker)(tree, tree, void *), void *data)
1080 bitmap visited = NULL;
1083 timevar_push (TV_ALIAS_STMT_WALK);
1089 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1090 res = (*walker) (ref, vuse, data);
1094 def_stmt = SSA_NAME_DEF_STMT (vuse);
1095 if (gimple_nop_p (def_stmt))
1097 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1098 vuse = get_continuation_for_phi (def_stmt, ref, &visited);
1101 if (stmt_may_clobber_ref_p (def_stmt, ref))
1103 vuse = gimple_vuse (def_stmt);
1109 BITMAP_FREE (visited);
1111 timevar_pop (TV_ALIAS_STMT_WALK);
1117 /* Based on the memory reference REF call WALKER for each vdef which
1118 defining statement may clobber REF, starting with VDEF. If REF
1119 is NULL_TREE, each defining statement is visited.
1121 WALKER is called with REF, the current vdef and DATA. If WALKER
1122 returns true the walk is stopped, otherwise it continues.
1124 At PHI nodes walk_aliased_vdefs forks into one walk for reach
1125 PHI argument (but only one walk continues on merge points), the
1126 return value is true if any of the walks was successful.
1128 The function returns the number of statements walked. */
1131 walk_aliased_vdefs_1 (tree ref, tree vdef,
1132 bool (*walker)(tree, tree, void *), void *data,
1133 bitmap *visited, unsigned int cnt)
1137 gimple def_stmt = SSA_NAME_DEF_STMT (vdef);
1140 && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef)))
1143 if (gimple_nop_p (def_stmt))
1145 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1149 *visited = BITMAP_ALLOC (NULL);
1150 for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
1151 cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i),
1152 walker, data, visited, 0);
1156 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1159 || stmt_may_clobber_ref_p (def_stmt, ref))
1160 && (*walker) (ref, vdef, data))
1163 vdef = gimple_vuse (def_stmt);
1169 walk_aliased_vdefs (tree ref, tree vdef,
1170 bool (*walker)(tree, tree, void *), void *data,
1173 bitmap local_visited = NULL;
1176 timevar_push (TV_ALIAS_STMT_WALK);
1178 ret = walk_aliased_vdefs_1 (ref, vdef, walker, data,
1179 visited ? visited : &local_visited, 0);
1181 BITMAP_FREE (local_visited);
1183 timevar_pop (TV_ALIAS_STMT_WALK);