1 /* Alias analysis for trees.
2 Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
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 "basic-block.h"
32 #include "langhooks.h"
35 #include "tree-pretty-print.h"
36 #include "tree-dump.h"
38 #include "tree-flow.h"
39 #include "tree-inline.h"
40 #include "tree-pass.h"
46 #include "pointer-set.h"
47 #include "alloc-pool.h"
48 #include "tree-ssa-alias.h"
50 /* Broad overview of how alias analysis on gimple works:
52 Statements clobbering or using memory are linked through the
53 virtual operand factored use-def chain. The virtual operand
54 is unique per function, its symbol is accessible via gimple_vop (cfun).
55 Virtual operands are used for efficiently walking memory statements
56 in the gimple IL and are useful for things like value-numbering as
57 a generation count for memory references.
59 SSA_NAME pointers may have associated points-to information
60 accessible via the SSA_NAME_PTR_INFO macro. Flow-insensitive
61 points-to information is (re-)computed by the TODO_rebuild_alias
62 pass manager todo. Points-to information is also used for more
63 precise tracking of call-clobbered and call-used variables and
64 related disambiguations.
66 This file contains functions for disambiguating memory references,
67 the so called alias-oracle and tools for walking of the gimple IL.
69 The main alias-oracle entry-points are
71 bool stmt_may_clobber_ref_p (gimple, tree)
73 This function queries if a statement may invalidate (parts of)
74 the memory designated by the reference tree argument.
76 bool ref_maybe_used_by_stmt_p (gimple, tree)
78 This function queries if a statement may need (parts of) the
79 memory designated by the reference tree argument.
81 There are variants of these functions that only handle the call
82 part of a statement, call_may_clobber_ref_p and ref_maybe_used_by_call_p.
83 Note that these do not disambiguate against a possible call lhs.
85 bool refs_may_alias_p (tree, tree)
87 This function tries to disambiguate two reference trees.
89 bool ptr_deref_may_alias_global_p (tree)
91 This function queries if dereferencing a pointer variable may
94 More low-level disambiguators are available and documented in
95 this file. Low-level disambiguators dealing with points-to
96 information are in tree-ssa-structalias.c. */
99 /* Query statistics for the different low-level disambiguators.
100 A high-level query may trigger multiple of them. */
103 unsigned HOST_WIDE_INT refs_may_alias_p_may_alias;
104 unsigned HOST_WIDE_INT refs_may_alias_p_no_alias;
105 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_may_alias;
106 unsigned HOST_WIDE_INT ref_maybe_used_by_call_p_no_alias;
107 unsigned HOST_WIDE_INT call_may_clobber_ref_p_may_alias;
108 unsigned HOST_WIDE_INT call_may_clobber_ref_p_no_alias;
112 dump_alias_stats (FILE *s)
114 fprintf (s, "\nAlias oracle query stats:\n");
115 fprintf (s, " refs_may_alias_p: "
116 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
117 HOST_WIDE_INT_PRINT_DEC" queries\n",
118 alias_stats.refs_may_alias_p_no_alias,
119 alias_stats.refs_may_alias_p_no_alias
120 + alias_stats.refs_may_alias_p_may_alias);
121 fprintf (s, " ref_maybe_used_by_call_p: "
122 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
123 HOST_WIDE_INT_PRINT_DEC" queries\n",
124 alias_stats.ref_maybe_used_by_call_p_no_alias,
125 alias_stats.refs_may_alias_p_no_alias
126 + alias_stats.ref_maybe_used_by_call_p_may_alias);
127 fprintf (s, " call_may_clobber_ref_p: "
128 HOST_WIDE_INT_PRINT_DEC" disambiguations, "
129 HOST_WIDE_INT_PRINT_DEC" queries\n",
130 alias_stats.call_may_clobber_ref_p_no_alias,
131 alias_stats.call_may_clobber_ref_p_no_alias
132 + alias_stats.call_may_clobber_ref_p_may_alias);
136 /* Return true, if dereferencing PTR may alias with a global variable. */
139 ptr_deref_may_alias_global_p (tree ptr)
141 struct ptr_info_def *pi;
143 /* If we end up with a pointer constant here that may point
145 if (TREE_CODE (ptr) != SSA_NAME)
148 pi = SSA_NAME_PTR_INFO (ptr);
150 /* If we do not have points-to information for this variable,
155 /* ??? This does not use TBAA to prune globals ptr may not access. */
156 return pt_solution_includes_global (&pi->pt);
159 /* Return true if dereferencing PTR may alias DECL.
160 The caller is responsible for applying TBAA to see if PTR
161 may access DECL at all. */
164 ptr_deref_may_alias_decl_p (tree ptr, tree decl)
166 struct ptr_info_def *pi;
168 /* Conversions are irrelevant for points-to information and
169 data-dependence analysis can feed us those. */
172 /* Anything we do not explicilty handle aliases. */
173 if ((TREE_CODE (ptr) != SSA_NAME
174 && TREE_CODE (ptr) != ADDR_EXPR
175 && TREE_CODE (ptr) != POINTER_PLUS_EXPR)
176 || !POINTER_TYPE_P (TREE_TYPE (ptr))
177 || (TREE_CODE (decl) != VAR_DECL
178 && TREE_CODE (decl) != PARM_DECL
179 && TREE_CODE (decl) != RESULT_DECL))
182 /* Disregard pointer offsetting. */
183 if (TREE_CODE (ptr) == POINTER_PLUS_EXPR)
187 ptr = TREE_OPERAND (ptr, 0);
189 while (TREE_CODE (ptr) == POINTER_PLUS_EXPR);
190 return ptr_deref_may_alias_decl_p (ptr, decl);
193 /* ADDR_EXPR pointers either just offset another pointer or directly
194 specify the pointed-to set. */
195 if (TREE_CODE (ptr) == ADDR_EXPR)
197 tree base = get_base_address (TREE_OPERAND (ptr, 0));
199 && (TREE_CODE (base) == MEM_REF
200 || TREE_CODE (base) == TARGET_MEM_REF))
201 ptr = TREE_OPERAND (base, 0);
206 && CONSTANT_CLASS_P (base))
212 /* Non-aliased variables can not be pointed to. */
213 if (!may_be_aliased (decl))
216 /* If we do not have useful points-to information for this pointer
217 we cannot disambiguate anything else. */
218 pi = SSA_NAME_PTR_INFO (ptr);
222 /* If the decl can be used as a restrict tag and we have a restrict
223 pointer and that pointers points-to set doesn't contain this decl
224 then they can't alias. */
225 if (DECL_RESTRICTED_P (decl)
226 && pi->pt.vars_contains_restrict)
227 return bitmap_bit_p (pi->pt.vars, DECL_PT_UID (decl));
229 return pt_solution_includes (&pi->pt, decl);
232 /* Return true if dereferenced PTR1 and PTR2 may alias.
233 The caller is responsible for applying TBAA to see if accesses
234 through PTR1 and PTR2 may conflict at all. */
237 ptr_derefs_may_alias_p (tree ptr1, tree ptr2)
239 struct ptr_info_def *pi1, *pi2;
241 /* Conversions are irrelevant for points-to information and
242 data-dependence analysis can feed us those. */
246 /* Anything we do not explicilty handle aliases. */
247 if ((TREE_CODE (ptr1) != SSA_NAME
248 && TREE_CODE (ptr1) != ADDR_EXPR
249 && TREE_CODE (ptr1) != POINTER_PLUS_EXPR)
250 || (TREE_CODE (ptr2) != SSA_NAME
251 && TREE_CODE (ptr2) != ADDR_EXPR
252 && TREE_CODE (ptr2) != POINTER_PLUS_EXPR)
253 || !POINTER_TYPE_P (TREE_TYPE (ptr1))
254 || !POINTER_TYPE_P (TREE_TYPE (ptr2)))
257 /* Disregard pointer offsetting. */
258 if (TREE_CODE (ptr1) == POINTER_PLUS_EXPR)
262 ptr1 = TREE_OPERAND (ptr1, 0);
264 while (TREE_CODE (ptr1) == POINTER_PLUS_EXPR);
265 return ptr_derefs_may_alias_p (ptr1, ptr2);
267 if (TREE_CODE (ptr2) == POINTER_PLUS_EXPR)
271 ptr2 = TREE_OPERAND (ptr2, 0);
273 while (TREE_CODE (ptr2) == POINTER_PLUS_EXPR);
274 return ptr_derefs_may_alias_p (ptr1, ptr2);
277 /* ADDR_EXPR pointers either just offset another pointer or directly
278 specify the pointed-to set. */
279 if (TREE_CODE (ptr1) == ADDR_EXPR)
281 tree base = get_base_address (TREE_OPERAND (ptr1, 0));
283 && (TREE_CODE (base) == MEM_REF
284 || TREE_CODE (base) == TARGET_MEM_REF))
285 ptr1 = TREE_OPERAND (base, 0);
288 return ptr_deref_may_alias_decl_p (ptr2, base);
292 if (TREE_CODE (ptr2) == ADDR_EXPR)
294 tree base = get_base_address (TREE_OPERAND (ptr2, 0));
296 && (TREE_CODE (base) == MEM_REF
297 || TREE_CODE (base) == TARGET_MEM_REF))
298 ptr2 = TREE_OPERAND (base, 0);
301 return ptr_deref_may_alias_decl_p (ptr1, base);
306 /* We may end up with two empty points-to solutions for two same pointers.
307 In this case we still want to say both pointers alias, so shortcut
312 /* If we do not have useful points-to information for either pointer
313 we cannot disambiguate anything else. */
314 pi1 = SSA_NAME_PTR_INFO (ptr1);
315 pi2 = SSA_NAME_PTR_INFO (ptr2);
319 /* If both pointers are restrict-qualified try to disambiguate
320 with restrict information. */
321 if (!pt_solutions_same_restrict_base (&pi1->pt, &pi2->pt))
324 /* ??? This does not use TBAA to prune decls from the intersection
325 that not both pointers may access. */
326 return pt_solutions_intersect (&pi1->pt, &pi2->pt);
329 /* Return true if dereferencing PTR may alias *REF.
330 The caller is responsible for applying TBAA to see if PTR
331 may access *REF at all. */
334 ptr_deref_may_alias_ref_p_1 (tree ptr, ao_ref *ref)
336 tree base = ao_ref_base (ref);
338 if (TREE_CODE (base) == MEM_REF
339 || TREE_CODE (base) == TARGET_MEM_REF)
340 return ptr_derefs_may_alias_p (ptr, TREE_OPERAND (base, 0));
341 else if (DECL_P (base))
342 return ptr_deref_may_alias_decl_p (ptr, base);
348 /* Dump alias information on FILE. */
351 dump_alias_info (FILE *file)
355 = lang_hooks.decl_printable_name (current_function_decl, 2);
356 referenced_var_iterator rvi;
359 fprintf (file, "\n\nAlias information for %s\n\n", funcname);
361 fprintf (file, "Aliased symbols\n\n");
363 FOR_EACH_REFERENCED_VAR (cfun, var, rvi)
365 if (may_be_aliased (var))
366 dump_variable (file, var);
369 fprintf (file, "\nCall clobber information\n");
371 fprintf (file, "\nESCAPED");
372 dump_points_to_solution (file, &cfun->gimple_df->escaped);
374 fprintf (file, "\n\nFlow-insensitive points-to information\n\n");
376 for (i = 1; i < num_ssa_names; i++)
378 tree ptr = ssa_name (i);
379 struct ptr_info_def *pi;
382 || SSA_NAME_IN_FREE_LIST (ptr))
385 pi = SSA_NAME_PTR_INFO (ptr);
387 dump_points_to_info_for (file, ptr);
390 fprintf (file, "\n");
394 /* Dump alias information on stderr. */
397 debug_alias_info (void)
399 dump_alias_info (stderr);
403 /* Dump the points-to set *PT into FILE. */
406 dump_points_to_solution (FILE *file, struct pt_solution *pt)
409 fprintf (file, ", points-to anything");
412 fprintf (file, ", points-to non-local");
415 fprintf (file, ", points-to escaped");
418 fprintf (file, ", points-to unit escaped");
421 fprintf (file, ", points-to NULL");
425 fprintf (file, ", points-to vars: ");
426 dump_decl_set (file, pt->vars);
427 if (pt->vars_contains_global)
428 fprintf (file, " (includes global vars)");
429 if (pt->vars_contains_restrict)
430 fprintf (file, " (includes restrict tags)");
434 /* Dump points-to information for SSA_NAME PTR into FILE. */
437 dump_points_to_info_for (FILE *file, tree ptr)
439 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (ptr);
441 print_generic_expr (file, ptr, dump_flags);
444 dump_points_to_solution (file, &pi->pt);
446 fprintf (file, ", points-to anything");
448 fprintf (file, "\n");
452 /* Dump points-to information for VAR into stderr. */
455 debug_points_to_info_for (tree var)
457 dump_points_to_info_for (stderr, var);
461 /* Initializes the alias-oracle reference representation *R from REF. */
464 ao_ref_init (ao_ref *r, tree ref)
471 r->ref_alias_set = -1;
472 r->base_alias_set = -1;
475 /* Returns the base object of the memory reference *REF. */
478 ao_ref_base (ao_ref *ref)
482 ref->base = get_ref_base_and_extent (ref->ref, &ref->offset, &ref->size,
487 /* Returns the base object alias set of the memory reference *REF. */
489 static alias_set_type
490 ao_ref_base_alias_set (ao_ref *ref)
493 if (ref->base_alias_set != -1)
494 return ref->base_alias_set;
498 while (handled_component_p (base_ref))
499 base_ref = TREE_OPERAND (base_ref, 0);
500 ref->base_alias_set = get_alias_set (base_ref);
501 return ref->base_alias_set;
504 /* Returns the reference alias set of the memory reference *REF. */
507 ao_ref_alias_set (ao_ref *ref)
509 if (ref->ref_alias_set != -1)
510 return ref->ref_alias_set;
511 ref->ref_alias_set = get_alias_set (ref->ref);
512 return ref->ref_alias_set;
515 /* Init an alias-oracle reference representation from a gimple pointer
516 PTR and a gimple size SIZE in bytes. If SIZE is NULL_TREE the the
517 size is assumed to be unknown. The access is assumed to be only
518 to or after of the pointer target, not before it. */
521 ao_ref_init_from_ptr_and_size (ao_ref *ref, tree ptr, tree size)
523 HOST_WIDE_INT t1, t2;
524 ref->ref = NULL_TREE;
525 if (TREE_CODE (ptr) == ADDR_EXPR)
526 ref->base = get_ref_base_and_extent (TREE_OPERAND (ptr, 0),
527 &ref->offset, &t1, &t2);
530 ref->base = build2 (MEM_REF, char_type_node,
531 ptr, null_pointer_node);
535 && host_integerp (size, 0)
536 && TREE_INT_CST_LOW (size) * 8 / 8 == TREE_INT_CST_LOW (size))
537 ref->max_size = ref->size = TREE_INT_CST_LOW (size) * 8;
539 ref->max_size = ref->size = -1;
540 ref->ref_alias_set = 0;
541 ref->base_alias_set = 0;
544 /* Return 1 if TYPE1 and TYPE2 are to be considered equivalent for the
545 purpose of TBAA. Return 0 if they are distinct and -1 if we cannot
549 same_type_for_tbaa (tree type1, tree type2)
551 type1 = TYPE_MAIN_VARIANT (type1);
552 type2 = TYPE_MAIN_VARIANT (type2);
554 /* If we would have to do structural comparison bail out. */
555 if (TYPE_STRUCTURAL_EQUALITY_P (type1)
556 || TYPE_STRUCTURAL_EQUALITY_P (type2))
559 /* Compare the canonical types. */
560 if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2))
563 /* ??? Array types are not properly unified in all cases as we have
564 spurious changes in the index types for example. Removing this
565 causes all sorts of problems with the Fortran frontend. */
566 if (TREE_CODE (type1) == ARRAY_TYPE
567 && TREE_CODE (type2) == ARRAY_TYPE)
570 /* ??? In Ada, an lvalue of an unconstrained type can be used to access an
571 object of one of its constrained subtypes, e.g. when a function with an
572 unconstrained parameter passed by reference is called on an object and
573 inlined. But, even in the case of a fixed size, type and subtypes are
574 not equivalent enough as to share the same TYPE_CANONICAL, since this
575 would mean that conversions between them are useless, whereas they are
576 not (e.g. type and subtypes can have different modes). So, in the end,
577 they are only guaranteed to have the same alias set. */
578 if (get_alias_set (type1) == get_alias_set (type2))
581 /* The types are known to be not equal. */
585 /* Determine if the two component references REF1 and REF2 which are
586 based on access types TYPE1 and TYPE2 and of which at least one is based
587 on an indirect reference may alias. REF2 is the only one that can
588 be a decl in which case REF2_IS_DECL is true.
589 REF1_ALIAS_SET, BASE1_ALIAS_SET, REF2_ALIAS_SET and BASE2_ALIAS_SET
590 are the respective alias sets. */
593 aliasing_component_refs_p (tree ref1,
594 alias_set_type ref1_alias_set,
595 alias_set_type base1_alias_set,
596 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
598 alias_set_type ref2_alias_set,
599 alias_set_type base2_alias_set,
600 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
603 /* If one reference is a component references through pointers try to find a
604 common base and apply offset based disambiguation. This handles
606 struct A { int i; int j; } *q;
607 struct B { struct A a; int k; } *p;
608 disambiguating q->i and p->a.j. */
614 /* Choose bases and base types to search for. */
616 while (handled_component_p (base1))
617 base1 = TREE_OPERAND (base1, 0);
618 type1 = TREE_TYPE (base1);
620 while (handled_component_p (base2))
621 base2 = TREE_OPERAND (base2, 0);
622 type2 = TREE_TYPE (base2);
624 /* Now search for the type1 in the access path of ref2. This
625 would be a common base for doing offset based disambiguation on. */
627 while (handled_component_p (*refp)
628 && same_type_for_tbaa (TREE_TYPE (*refp), type1) == 0)
629 refp = &TREE_OPERAND (*refp, 0);
630 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type1);
631 /* If we couldn't compare types we have to bail out. */
634 else if (same_p == 1)
636 HOST_WIDE_INT offadj, sztmp, msztmp;
637 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
639 get_ref_base_and_extent (base1, &offadj, &sztmp, &msztmp);
641 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
643 /* If we didn't find a common base, try the other way around. */
645 while (handled_component_p (*refp)
646 && same_type_for_tbaa (TREE_TYPE (*refp), type2) == 0)
647 refp = &TREE_OPERAND (*refp, 0);
648 same_p = same_type_for_tbaa (TREE_TYPE (*refp), type2);
649 /* If we couldn't compare types we have to bail out. */
652 else if (same_p == 1)
654 HOST_WIDE_INT offadj, sztmp, msztmp;
655 get_ref_base_and_extent (*refp, &offadj, &sztmp, &msztmp);
657 get_ref_base_and_extent (base2, &offadj, &sztmp, &msztmp);
659 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
662 /* If we have two type access paths B1.path1 and B2.path2 they may
663 only alias if either B1 is in B2.path2 or B2 is in B1.path1.
664 But we can still have a path that goes B1.path1...B2.path2 with
665 a part that we do not see. So we can only disambiguate now
666 if there is no B2 in the tail of path1 and no B1 on the
668 if (base1_alias_set == ref2_alias_set
669 || alias_set_subset_of (base1_alias_set, ref2_alias_set))
671 /* If this is ptr vs. decl then we know there is no ptr ... decl path. */
673 return (base2_alias_set == ref1_alias_set
674 || alias_set_subset_of (base2_alias_set, ref1_alias_set));
678 /* Return true if two memory references based on the variables BASE1
679 and BASE2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1) and
680 [OFFSET2, OFFSET2 + MAX_SIZE2) may alias. */
683 decl_refs_may_alias_p (tree base1,
684 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
686 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2)
688 gcc_checking_assert (DECL_P (base1) && DECL_P (base2));
690 /* If both references are based on different variables, they cannot alias. */
694 /* If both references are based on the same variable, they cannot alias if
695 the accesses do not overlap. */
696 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
699 /* Return true if an indirect reference based on *PTR1 constrained
700 to [OFFSET1, OFFSET1 + MAX_SIZE1) may alias a variable based on BASE2
701 constrained to [OFFSET2, OFFSET2 + MAX_SIZE2). *PTR1 and BASE2 have
702 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
703 in which case they are computed on-demand. REF1 and REF2
704 if non-NULL are the complete memory reference trees. */
707 indirect_ref_may_alias_decl_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
708 HOST_WIDE_INT offset1,
709 HOST_WIDE_INT max_size1 ATTRIBUTE_UNUSED,
710 alias_set_type ref1_alias_set,
711 alias_set_type base1_alias_set,
712 tree ref2 ATTRIBUTE_UNUSED, tree base2,
713 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
714 alias_set_type ref2_alias_set,
715 alias_set_type base2_alias_set, bool tbaa_p)
718 tree ptrtype1, dbase2;
719 HOST_WIDE_INT offset1p = offset1, offset2p = offset2;
720 HOST_WIDE_INT doffset1, doffset2;
723 gcc_checking_assert ((TREE_CODE (base1) == MEM_REF
724 || TREE_CODE (base1) == TARGET_MEM_REF)
727 ptr1 = TREE_OPERAND (base1, 0);
729 /* The offset embedded in MEM_REFs can be negative. Bias them
730 so that the resulting offset adjustment is positive. */
731 moff = mem_ref_offset (base1);
732 moff = double_int_lshift (moff,
734 ? 3 : exact_log2 (BITS_PER_UNIT),
735 HOST_BITS_PER_DOUBLE_INT, true);
736 if (double_int_negative_p (moff))
737 offset2p += double_int_neg (moff).low;
739 offset1p += moff.low;
741 /* If only one reference is based on a variable, they cannot alias if
742 the pointer access is beyond the extent of the variable access.
743 (the pointer base cannot validly point to an offset less than zero
745 ??? IVOPTs creates bases that do not honor this restriction,
746 so do not apply this optimization for TARGET_MEM_REFs. */
747 if (TREE_CODE (base1) != TARGET_MEM_REF
748 && !ranges_overlap_p (MAX (0, offset1p), -1, offset2p, max_size2))
750 /* They also cannot alias if the pointer may not point to the decl. */
751 if (!ptr_deref_may_alias_decl_p (ptr1, base2))
754 /* Disambiguations that rely on strict aliasing rules follow. */
755 if (!flag_strict_aliasing || !tbaa_p)
758 ptrtype1 = TREE_TYPE (TREE_OPERAND (base1, 1));
760 /* If the alias set for a pointer access is zero all bets are off. */
761 if (base1_alias_set == -1)
762 base1_alias_set = get_deref_alias_set (ptrtype1);
763 if (base1_alias_set == 0)
765 if (base2_alias_set == -1)
766 base2_alias_set = get_alias_set (base2);
768 /* When we are trying to disambiguate an access with a pointer dereference
769 as base versus one with a decl as base we can use both the size
770 of the decl and its dynamic type for extra disambiguation.
771 ??? We do not know anything about the dynamic type of the decl
772 other than that its alias-set contains base2_alias_set as a subset
773 which does not help us here. */
774 /* As we know nothing useful about the dynamic type of the decl just
775 use the usual conflict check rather than a subset test.
776 ??? We could introduce -fvery-strict-aliasing when the language
777 does not allow decls to have a dynamic type that differs from their
778 static type. Then we can check
779 !alias_set_subset_of (base1_alias_set, base2_alias_set) instead. */
780 if (base1_alias_set != base2_alias_set
781 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
783 /* If the size of the access relevant for TBAA through the pointer
784 is bigger than the size of the decl we can't possibly access the
785 decl via that pointer. */
786 if (DECL_SIZE (base2) && COMPLETE_TYPE_P (TREE_TYPE (ptrtype1))
787 && TREE_CODE (DECL_SIZE (base2)) == INTEGER_CST
788 && TREE_CODE (TYPE_SIZE (TREE_TYPE (ptrtype1))) == INTEGER_CST
789 /* ??? This in turn may run afoul when a decl of type T which is
790 a member of union type U is accessed through a pointer to
791 type U and sizeof T is smaller than sizeof U. */
792 && TREE_CODE (TREE_TYPE (ptrtype1)) != UNION_TYPE
793 && TREE_CODE (TREE_TYPE (ptrtype1)) != QUAL_UNION_TYPE
794 && tree_int_cst_lt (DECL_SIZE (base2), TYPE_SIZE (TREE_TYPE (ptrtype1))))
800 /* If the decl is accessed via a MEM_REF, reconstruct the base
801 we can use for TBAA and an appropriately adjusted offset. */
803 while (handled_component_p (dbase2))
804 dbase2 = TREE_OPERAND (dbase2, 0);
807 if (TREE_CODE (dbase2) == MEM_REF
808 || TREE_CODE (dbase2) == TARGET_MEM_REF)
810 double_int moff = mem_ref_offset (dbase2);
811 moff = double_int_lshift (moff,
813 ? 3 : exact_log2 (BITS_PER_UNIT),
814 HOST_BITS_PER_DOUBLE_INT, true);
815 if (double_int_negative_p (moff))
816 doffset1 -= double_int_neg (moff).low;
818 doffset2 -= moff.low;
821 /* If either reference is view-converted, give up now. */
822 if (same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) != 1
823 || same_type_for_tbaa (TREE_TYPE (dbase2),
824 TREE_TYPE (reference_alias_ptr_type (dbase2))) != 1)
827 /* If both references are through the same type, they do not alias
828 if the accesses do not overlap. This does extra disambiguation
829 for mixed/pointer accesses but requires strict aliasing.
830 For MEM_REFs we require that the component-ref offset we computed
831 is relative to the start of the type which we ensure by
832 comparing rvalue and access type and disregarding the constant
834 if ((TREE_CODE (base1) != TARGET_MEM_REF
835 || (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
836 && same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (dbase2)) == 1)
837 return ranges_overlap_p (doffset1, max_size1, doffset2, max_size2);
839 /* Do access-path based disambiguation. */
841 && (handled_component_p (ref1) || handled_component_p (ref2)))
842 return aliasing_component_refs_p (ref1,
843 ref1_alias_set, base1_alias_set,
846 ref2_alias_set, base2_alias_set,
847 offset2, max_size2, true);
852 /* Return true if two indirect references based on *PTR1
853 and *PTR2 constrained to [OFFSET1, OFFSET1 + MAX_SIZE1) and
854 [OFFSET2, OFFSET2 + MAX_SIZE2) may alias. *PTR1 and *PTR2 have
855 the alias sets BASE1_ALIAS_SET and BASE2_ALIAS_SET which can be -1
856 in which case they are computed on-demand. REF1 and REF2
857 if non-NULL are the complete memory reference trees. */
860 indirect_refs_may_alias_p (tree ref1 ATTRIBUTE_UNUSED, tree base1,
861 HOST_WIDE_INT offset1, HOST_WIDE_INT max_size1,
862 alias_set_type ref1_alias_set,
863 alias_set_type base1_alias_set,
864 tree ref2 ATTRIBUTE_UNUSED, tree base2,
865 HOST_WIDE_INT offset2, HOST_WIDE_INT max_size2,
866 alias_set_type ref2_alias_set,
867 alias_set_type base2_alias_set, bool tbaa_p)
871 tree ptrtype1, ptrtype2;
873 gcc_checking_assert ((TREE_CODE (base1) == MEM_REF
874 || TREE_CODE (base1) == TARGET_MEM_REF)
875 && (TREE_CODE (base2) == MEM_REF
876 || TREE_CODE (base2) == TARGET_MEM_REF));
878 ptr1 = TREE_OPERAND (base1, 0);
879 ptr2 = TREE_OPERAND (base2, 0);
881 /* If both bases are based on pointers they cannot alias if they may not
882 point to the same memory object or if they point to the same object
883 and the accesses do not overlap. */
884 if ((!cfun || gimple_in_ssa_p (cfun))
885 && operand_equal_p (ptr1, ptr2, 0)
886 && (((TREE_CODE (base1) != TARGET_MEM_REF
887 || (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
888 && (TREE_CODE (base2) != TARGET_MEM_REF
889 || (!TMR_INDEX (base2) && !TMR_INDEX2 (base2))))
890 || (TREE_CODE (base1) == TARGET_MEM_REF
891 && TREE_CODE (base2) == TARGET_MEM_REF
892 && (TMR_STEP (base1) == TMR_STEP (base2)
893 || (TMR_STEP (base1) && TMR_STEP (base2)
894 && operand_equal_p (TMR_STEP (base1),
895 TMR_STEP (base2), 0)))
896 && (TMR_INDEX (base1) == TMR_INDEX (base2)
897 || (TMR_INDEX (base1) && TMR_INDEX (base2)
898 && operand_equal_p (TMR_INDEX (base1),
899 TMR_INDEX (base2), 0)))
900 && (TMR_INDEX2 (base1) == TMR_INDEX2 (base2)
901 || (TMR_INDEX2 (base1) && TMR_INDEX2 (base2)
902 && operand_equal_p (TMR_INDEX2 (base1),
903 TMR_INDEX2 (base2), 0))))))
906 /* The offset embedded in MEM_REFs can be negative. Bias them
907 so that the resulting offset adjustment is positive. */
908 moff = mem_ref_offset (base1);
909 moff = double_int_lshift (moff,
911 ? 3 : exact_log2 (BITS_PER_UNIT),
912 HOST_BITS_PER_DOUBLE_INT, true);
913 if (double_int_negative_p (moff))
914 offset2 += double_int_neg (moff).low;
917 moff = mem_ref_offset (base2);
918 moff = double_int_lshift (moff,
920 ? 3 : exact_log2 (BITS_PER_UNIT),
921 HOST_BITS_PER_DOUBLE_INT, true);
922 if (double_int_negative_p (moff))
923 offset1 += double_int_neg (moff).low;
926 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
928 if (!ptr_derefs_may_alias_p (ptr1, ptr2))
931 /* Disambiguations that rely on strict aliasing rules follow. */
932 if (!flag_strict_aliasing || !tbaa_p)
935 ptrtype1 = TREE_TYPE (TREE_OPERAND (base1, 1));
936 ptrtype2 = TREE_TYPE (TREE_OPERAND (base2, 1));
938 /* If the alias set for a pointer access is zero all bets are off. */
939 if (base1_alias_set == -1)
940 base1_alias_set = get_deref_alias_set (ptrtype1);
941 if (base1_alias_set == 0)
943 if (base2_alias_set == -1)
944 base2_alias_set = get_deref_alias_set (ptrtype2);
945 if (base2_alias_set == 0)
948 /* If both references are through the same type, they do not alias
949 if the accesses do not overlap. This does extra disambiguation
950 for mixed/pointer accesses but requires strict aliasing. */
951 if ((TREE_CODE (base1) != TARGET_MEM_REF
952 || (!TMR_INDEX (base1) && !TMR_INDEX2 (base1)))
953 && (TREE_CODE (base2) != TARGET_MEM_REF
954 || (!TMR_INDEX (base2) && !TMR_INDEX2 (base2)))
955 && same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) == 1
956 && same_type_for_tbaa (TREE_TYPE (base2), TREE_TYPE (ptrtype2)) == 1
957 && same_type_for_tbaa (TREE_TYPE (ptrtype1),
958 TREE_TYPE (ptrtype2)) == 1)
959 return ranges_overlap_p (offset1, max_size1, offset2, max_size2);
961 /* Do type-based disambiguation. */
962 if (base1_alias_set != base2_alias_set
963 && !alias_sets_conflict_p (base1_alias_set, base2_alias_set))
966 /* Do access-path based disambiguation. */
968 && (handled_component_p (ref1) || handled_component_p (ref2))
969 && same_type_for_tbaa (TREE_TYPE (base1), TREE_TYPE (ptrtype1)) == 1
970 && same_type_for_tbaa (TREE_TYPE (base2), TREE_TYPE (ptrtype2)) == 1)
971 return aliasing_component_refs_p (ref1,
972 ref1_alias_set, base1_alias_set,
975 ref2_alias_set, base2_alias_set,
976 offset2, max_size2, false);
981 /* Return true, if the two memory references REF1 and REF2 may alias. */
984 refs_may_alias_p_1 (ao_ref *ref1, ao_ref *ref2, bool tbaa_p)
987 HOST_WIDE_INT offset1 = 0, offset2 = 0;
988 HOST_WIDE_INT max_size1 = -1, max_size2 = -1;
989 bool var1_p, var2_p, ind1_p, ind2_p;
991 gcc_checking_assert ((!ref1->ref
992 || TREE_CODE (ref1->ref) == SSA_NAME
993 || DECL_P (ref1->ref)
994 || TREE_CODE (ref1->ref) == STRING_CST
995 || handled_component_p (ref1->ref)
996 || TREE_CODE (ref1->ref) == MEM_REF
997 || TREE_CODE (ref1->ref) == TARGET_MEM_REF)
999 || TREE_CODE (ref2->ref) == SSA_NAME
1000 || DECL_P (ref2->ref)
1001 || TREE_CODE (ref2->ref) == STRING_CST
1002 || handled_component_p (ref2->ref)
1003 || TREE_CODE (ref2->ref) == MEM_REF
1004 || TREE_CODE (ref2->ref) == TARGET_MEM_REF));
1006 /* Decompose the references into their base objects and the access. */
1007 base1 = ao_ref_base (ref1);
1008 offset1 = ref1->offset;
1009 max_size1 = ref1->max_size;
1010 base2 = ao_ref_base (ref2);
1011 offset2 = ref2->offset;
1012 max_size2 = ref2->max_size;
1014 /* We can end up with registers or constants as bases for example from
1015 *D.1663_44 = VIEW_CONVERT_EXPR<struct DB_LSN>(__tmp$B0F64_59);
1016 which is seen as a struct copy. */
1017 if (TREE_CODE (base1) == SSA_NAME
1018 || TREE_CODE (base1) == CONST_DECL
1019 || TREE_CODE (base1) == CONSTRUCTOR
1020 || TREE_CODE (base1) == ADDR_EXPR
1021 || CONSTANT_CLASS_P (base1)
1022 || TREE_CODE (base2) == SSA_NAME
1023 || TREE_CODE (base2) == CONST_DECL
1024 || TREE_CODE (base2) == CONSTRUCTOR
1025 || TREE_CODE (base2) == ADDR_EXPR
1026 || CONSTANT_CLASS_P (base2))
1029 /* We can end up refering to code via function and label decls.
1030 As we likely do not properly track code aliases conservatively
1032 if (TREE_CODE (base1) == FUNCTION_DECL
1033 || TREE_CODE (base1) == LABEL_DECL
1034 || TREE_CODE (base2) == FUNCTION_DECL
1035 || TREE_CODE (base2) == LABEL_DECL)
1038 /* Defer to simple offset based disambiguation if we have
1039 references based on two decls. Do this before defering to
1040 TBAA to handle must-alias cases in conformance with the
1041 GCC extension of allowing type-punning through unions. */
1042 var1_p = DECL_P (base1);
1043 var2_p = DECL_P (base2);
1044 if (var1_p && var2_p)
1045 return decl_refs_may_alias_p (base1, offset1, max_size1,
1046 base2, offset2, max_size2);
1048 ind1_p = (TREE_CODE (base1) == MEM_REF
1049 || TREE_CODE (base1) == TARGET_MEM_REF);
1050 ind2_p = (TREE_CODE (base2) == MEM_REF
1051 || TREE_CODE (base2) == TARGET_MEM_REF);
1053 /* Canonicalize the pointer-vs-decl case. */
1054 if (ind1_p && var2_p)
1059 tmp1 = offset1; offset1 = offset2; offset2 = tmp1;
1060 tmp1 = max_size1; max_size1 = max_size2; max_size2 = tmp1;
1061 tmp2 = base1; base1 = base2; base2 = tmp2;
1062 tmp3 = ref1; ref1 = ref2; ref2 = tmp3;
1069 /* First defer to TBAA if possible. */
1071 && flag_strict_aliasing
1072 && !alias_sets_conflict_p (ao_ref_alias_set (ref1),
1073 ao_ref_alias_set (ref2)))
1076 /* Dispatch to the pointer-vs-decl or pointer-vs-pointer disambiguators. */
1077 if (var1_p && ind2_p)
1078 return indirect_ref_may_alias_decl_p (ref2->ref, base2,
1080 ao_ref_alias_set (ref2), -1,
1083 ao_ref_alias_set (ref1),
1084 ao_ref_base_alias_set (ref1),
1086 else if (ind1_p && ind2_p)
1087 return indirect_refs_may_alias_p (ref1->ref, base1,
1089 ao_ref_alias_set (ref1), -1,
1092 ao_ref_alias_set (ref2), -1,
1095 /* We really do not want to end up here, but returning true is safe. */
1096 #ifdef ENABLE_CHECKING
1104 refs_may_alias_p (tree ref1, tree ref2)
1108 ao_ref_init (&r1, ref1);
1109 ao_ref_init (&r2, ref2);
1110 res = refs_may_alias_p_1 (&r1, &r2, true);
1112 ++alias_stats.refs_may_alias_p_may_alias;
1114 ++alias_stats.refs_may_alias_p_no_alias;
1118 /* Returns true if there is a anti-dependence for the STORE that
1119 executes after the LOAD. */
1122 refs_anti_dependent_p (tree load, tree store)
1125 ao_ref_init (&r1, load);
1126 ao_ref_init (&r2, store);
1127 return refs_may_alias_p_1 (&r1, &r2, false);
1130 /* Returns true if there is a output dependence for the stores
1131 STORE1 and STORE2. */
1134 refs_output_dependent_p (tree store1, tree store2)
1137 ao_ref_init (&r1, store1);
1138 ao_ref_init (&r2, store2);
1139 return refs_may_alias_p_1 (&r1, &r2, false);
1142 /* If the call CALL may use the memory reference REF return true,
1143 otherwise return false. */
1146 ref_maybe_used_by_call_p_1 (gimple call, ao_ref *ref)
1150 int flags = gimple_call_flags (call);
1152 /* Const functions without a static chain do not implicitly use memory. */
1153 if (!gimple_call_chain (call)
1154 && (flags & (ECF_CONST|ECF_NOVOPS)))
1157 base = ao_ref_base (ref);
1161 /* If the reference is based on a decl that is not aliased the call
1162 cannot possibly use it. */
1164 && !may_be_aliased (base)
1165 /* But local statics can be used through recursion. */
1166 && !is_global_var (base))
1169 callee = gimple_call_fndecl (call);
1171 /* Handle those builtin functions explicitly that do not act as
1172 escape points. See tree-ssa-structalias.c:find_func_aliases
1173 for the list of builtins we might need to handle here. */
1174 if (callee != NULL_TREE
1175 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
1176 switch (DECL_FUNCTION_CODE (callee))
1178 /* All the following functions read memory pointed to by
1179 their second argument. strcat/strncat additionally
1180 reads memory pointed to by the first argument. */
1181 case BUILT_IN_STRCAT:
1182 case BUILT_IN_STRNCAT:
1185 ao_ref_init_from_ptr_and_size (&dref,
1186 gimple_call_arg (call, 0),
1188 if (refs_may_alias_p_1 (&dref, ref, false))
1192 case BUILT_IN_STRCPY:
1193 case BUILT_IN_STRNCPY:
1194 case BUILT_IN_MEMCPY:
1195 case BUILT_IN_MEMMOVE:
1196 case BUILT_IN_MEMPCPY:
1197 case BUILT_IN_STPCPY:
1198 case BUILT_IN_STPNCPY:
1201 tree size = NULL_TREE;
1202 if (gimple_call_num_args (call) == 3)
1203 size = gimple_call_arg (call, 2);
1204 ao_ref_init_from_ptr_and_size (&dref,
1205 gimple_call_arg (call, 1),
1207 return refs_may_alias_p_1 (&dref, ref, false);
1209 case BUILT_IN_STRCAT_CHK:
1210 case BUILT_IN_STRNCAT_CHK:
1213 ao_ref_init_from_ptr_and_size (&dref,
1214 gimple_call_arg (call, 0),
1216 if (refs_may_alias_p_1 (&dref, ref, false))
1220 case BUILT_IN_STRCPY_CHK:
1221 case BUILT_IN_STRNCPY_CHK:
1222 case BUILT_IN_MEMCPY_CHK:
1223 case BUILT_IN_MEMMOVE_CHK:
1224 case BUILT_IN_MEMPCPY_CHK:
1225 case BUILT_IN_STPCPY_CHK:
1228 tree size = NULL_TREE;
1229 if (gimple_call_num_args (call) == 4)
1230 size = gimple_call_arg (call, 2);
1231 ao_ref_init_from_ptr_and_size (&dref,
1232 gimple_call_arg (call, 1),
1234 return refs_may_alias_p_1 (&dref, ref, false);
1236 case BUILT_IN_BCOPY:
1239 tree size = gimple_call_arg (call, 2);
1240 ao_ref_init_from_ptr_and_size (&dref,
1241 gimple_call_arg (call, 0),
1243 return refs_may_alias_p_1 (&dref, ref, false);
1245 /* These read memory pointed to by the first argument. */
1246 case BUILT_IN_STRDUP:
1247 case BUILT_IN_STRNDUP:
1250 tree size = NULL_TREE;
1251 if (gimple_call_num_args (call) == 2)
1252 size = gimple_call_arg (call, 1);
1253 ao_ref_init_from_ptr_and_size (&dref,
1254 gimple_call_arg (call, 0),
1256 return refs_may_alias_p_1 (&dref, ref, false);
1258 /* The following builtins do not read from memory. */
1260 case BUILT_IN_MALLOC:
1261 case BUILT_IN_CALLOC:
1262 case BUILT_IN_ALLOCA:
1263 case BUILT_IN_ALLOCA_WITH_ALIGN:
1264 case BUILT_IN_STACK_SAVE:
1265 case BUILT_IN_STACK_RESTORE:
1266 case BUILT_IN_MEMSET:
1267 case BUILT_IN_MEMSET_CHK:
1268 case BUILT_IN_FREXP:
1269 case BUILT_IN_FREXPF:
1270 case BUILT_IN_FREXPL:
1271 case BUILT_IN_GAMMA_R:
1272 case BUILT_IN_GAMMAF_R:
1273 case BUILT_IN_GAMMAL_R:
1274 case BUILT_IN_LGAMMA_R:
1275 case BUILT_IN_LGAMMAF_R:
1276 case BUILT_IN_LGAMMAL_R:
1278 case BUILT_IN_MODFF:
1279 case BUILT_IN_MODFL:
1280 case BUILT_IN_REMQUO:
1281 case BUILT_IN_REMQUOF:
1282 case BUILT_IN_REMQUOL:
1283 case BUILT_IN_SINCOS:
1284 case BUILT_IN_SINCOSF:
1285 case BUILT_IN_SINCOSL:
1286 case BUILT_IN_ASSUME_ALIGNED:
1287 case BUILT_IN_VA_END:
1289 /* __sync_* builtins and some OpenMP builtins act as threading
1291 #undef DEF_SYNC_BUILTIN
1292 #define DEF_SYNC_BUILTIN(ENUM, NAME, TYPE, ATTRS) case ENUM:
1293 #include "sync-builtins.def"
1294 #undef DEF_SYNC_BUILTIN
1295 case BUILT_IN_GOMP_ATOMIC_START:
1296 case BUILT_IN_GOMP_ATOMIC_END:
1297 case BUILT_IN_GOMP_BARRIER:
1298 case BUILT_IN_GOMP_TASKWAIT:
1299 case BUILT_IN_GOMP_CRITICAL_START:
1300 case BUILT_IN_GOMP_CRITICAL_END:
1301 case BUILT_IN_GOMP_CRITICAL_NAME_START:
1302 case BUILT_IN_GOMP_CRITICAL_NAME_END:
1303 case BUILT_IN_GOMP_LOOP_END:
1304 case BUILT_IN_GOMP_ORDERED_START:
1305 case BUILT_IN_GOMP_ORDERED_END:
1306 case BUILT_IN_GOMP_PARALLEL_END:
1307 case BUILT_IN_GOMP_SECTIONS_END:
1308 case BUILT_IN_GOMP_SINGLE_COPY_START:
1309 case BUILT_IN_GOMP_SINGLE_COPY_END:
1313 /* Fallthru to general call handling. */;
1316 /* Check if base is a global static variable that is not read
1318 if (callee != NULL_TREE
1319 && TREE_CODE (base) == VAR_DECL
1320 && TREE_STATIC (base))
1322 struct cgraph_node *node = cgraph_get_node (callee);
1325 /* FIXME: Callee can be an OMP builtin that does not have a call graph
1326 node yet. We should enforce that there are nodes for all decls in the
1327 IL and remove this check instead. */
1329 && (not_read = ipa_reference_get_not_read_global (node))
1330 && bitmap_bit_p (not_read, DECL_UID (base)))
1334 /* Check if the base variable is call-used. */
1337 if (pt_solution_includes (gimple_call_use_set (call), base))
1340 else if ((TREE_CODE (base) == MEM_REF
1341 || TREE_CODE (base) == TARGET_MEM_REF)
1342 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
1344 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0));
1348 if (pt_solutions_intersect (gimple_call_use_set (call), &pi->pt))
1354 /* Inspect call arguments for passed-by-value aliases. */
1356 for (i = 0; i < gimple_call_num_args (call); ++i)
1358 tree op = gimple_call_arg (call, i);
1359 int flags = gimple_call_arg_flags (call, i);
1361 if (flags & EAF_UNUSED)
1364 if (TREE_CODE (op) == WITH_SIZE_EXPR)
1365 op = TREE_OPERAND (op, 0);
1367 if (TREE_CODE (op) != SSA_NAME
1368 && !is_gimple_min_invariant (op))
1371 ao_ref_init (&r, op);
1372 if (refs_may_alias_p_1 (&r, ref, true))
1381 ref_maybe_used_by_call_p (gimple call, tree ref)
1385 ao_ref_init (&r, ref);
1386 res = ref_maybe_used_by_call_p_1 (call, &r);
1388 ++alias_stats.ref_maybe_used_by_call_p_may_alias;
1390 ++alias_stats.ref_maybe_used_by_call_p_no_alias;
1395 /* If the statement STMT may use the memory reference REF return
1396 true, otherwise return false. */
1399 ref_maybe_used_by_stmt_p (gimple stmt, tree ref)
1401 if (is_gimple_assign (stmt))
1405 /* All memory assign statements are single. */
1406 if (!gimple_assign_single_p (stmt))
1409 rhs = gimple_assign_rhs1 (stmt);
1410 if (is_gimple_reg (rhs)
1411 || is_gimple_min_invariant (rhs)
1412 || gimple_assign_rhs_code (stmt) == CONSTRUCTOR)
1415 return refs_may_alias_p (rhs, ref);
1417 else if (is_gimple_call (stmt))
1418 return ref_maybe_used_by_call_p (stmt, ref);
1419 else if (gimple_code (stmt) == GIMPLE_RETURN)
1421 tree retval = gimple_return_retval (stmt);
1424 && TREE_CODE (retval) != SSA_NAME
1425 && !is_gimple_min_invariant (retval)
1426 && refs_may_alias_p (retval, ref))
1428 /* If ref escapes the function then the return acts as a use. */
1429 base = get_base_address (ref);
1432 else if (DECL_P (base))
1433 return is_global_var (base);
1434 else if (TREE_CODE (base) == MEM_REF
1435 || TREE_CODE (base) == TARGET_MEM_REF)
1436 return ptr_deref_may_alias_global_p (TREE_OPERAND (base, 0));
1443 /* If the call in statement CALL may clobber the memory reference REF
1444 return true, otherwise return false. */
1447 call_may_clobber_ref_p_1 (gimple call, ao_ref *ref)
1452 /* If the call is pure or const it cannot clobber anything. */
1453 if (gimple_call_flags (call)
1454 & (ECF_PURE|ECF_CONST|ECF_LOOPING_CONST_OR_PURE|ECF_NOVOPS))
1457 base = ao_ref_base (ref);
1461 if (TREE_CODE (base) == SSA_NAME
1462 || CONSTANT_CLASS_P (base))
1465 /* If the reference is based on a decl that is not aliased the call
1466 cannot possibly clobber it. */
1468 && !may_be_aliased (base)
1469 /* But local non-readonly statics can be modified through recursion
1470 or the call may implement a threading barrier which we must
1471 treat as may-def. */
1472 && (TREE_READONLY (base)
1473 || !is_global_var (base)))
1476 callee = gimple_call_fndecl (call);
1478 /* Handle those builtin functions explicitly that do not act as
1479 escape points. See tree-ssa-structalias.c:find_func_aliases
1480 for the list of builtins we might need to handle here. */
1481 if (callee != NULL_TREE
1482 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
1483 switch (DECL_FUNCTION_CODE (callee))
1485 /* All the following functions clobber memory pointed to by
1486 their first argument. */
1487 case BUILT_IN_STRCPY:
1488 case BUILT_IN_STRNCPY:
1489 case BUILT_IN_MEMCPY:
1490 case BUILT_IN_MEMMOVE:
1491 case BUILT_IN_MEMPCPY:
1492 case BUILT_IN_STPCPY:
1493 case BUILT_IN_STPNCPY:
1494 case BUILT_IN_STRCAT:
1495 case BUILT_IN_STRNCAT:
1496 case BUILT_IN_MEMSET:
1499 tree size = NULL_TREE;
1500 /* Don't pass in size for strncat, as the maximum size
1501 is strlen (dest) + n + 1 instead of n, resp.
1502 n + 1 at dest + strlen (dest), but strlen (dest) isn't
1504 if (gimple_call_num_args (call) == 3
1505 && DECL_FUNCTION_CODE (callee) != BUILT_IN_STRNCAT)
1506 size = gimple_call_arg (call, 2);
1507 ao_ref_init_from_ptr_and_size (&dref,
1508 gimple_call_arg (call, 0),
1510 return refs_may_alias_p_1 (&dref, ref, false);
1512 case BUILT_IN_STRCPY_CHK:
1513 case BUILT_IN_STRNCPY_CHK:
1514 case BUILT_IN_MEMCPY_CHK:
1515 case BUILT_IN_MEMMOVE_CHK:
1516 case BUILT_IN_MEMPCPY_CHK:
1517 case BUILT_IN_STPCPY_CHK:
1518 case BUILT_IN_STRCAT_CHK:
1519 case BUILT_IN_STRNCAT_CHK:
1520 case BUILT_IN_MEMSET_CHK:
1523 tree size = NULL_TREE;
1524 /* Don't pass in size for __strncat_chk, as the maximum size
1525 is strlen (dest) + n + 1 instead of n, resp.
1526 n + 1 at dest + strlen (dest), but strlen (dest) isn't
1528 if (gimple_call_num_args (call) == 4
1529 && DECL_FUNCTION_CODE (callee) != BUILT_IN_STRNCAT_CHK)
1530 size = gimple_call_arg (call, 2);
1531 ao_ref_init_from_ptr_and_size (&dref,
1532 gimple_call_arg (call, 0),
1534 return refs_may_alias_p_1 (&dref, ref, false);
1536 case BUILT_IN_BCOPY:
1539 tree size = gimple_call_arg (call, 2);
1540 ao_ref_init_from_ptr_and_size (&dref,
1541 gimple_call_arg (call, 1),
1543 return refs_may_alias_p_1 (&dref, ref, false);
1545 /* Allocating memory does not have any side-effects apart from
1546 being the definition point for the pointer. */
1547 case BUILT_IN_MALLOC:
1548 case BUILT_IN_CALLOC:
1549 case BUILT_IN_STRDUP:
1550 case BUILT_IN_STRNDUP:
1551 /* Unix98 specifies that errno is set on allocation failure. */
1553 && targetm.ref_may_alias_errno (ref))
1556 case BUILT_IN_STACK_SAVE:
1557 case BUILT_IN_ALLOCA:
1558 case BUILT_IN_ALLOCA_WITH_ALIGN:
1559 case BUILT_IN_ASSUME_ALIGNED:
1561 /* Freeing memory kills the pointed-to memory. More importantly
1562 the call has to serve as a barrier for moving loads and stores
1565 case BUILT_IN_VA_END:
1567 tree ptr = gimple_call_arg (call, 0);
1568 return ptr_deref_may_alias_ref_p_1 (ptr, ref);
1570 case BUILT_IN_GAMMA_R:
1571 case BUILT_IN_GAMMAF_R:
1572 case BUILT_IN_GAMMAL_R:
1573 case BUILT_IN_LGAMMA_R:
1574 case BUILT_IN_LGAMMAF_R:
1575 case BUILT_IN_LGAMMAL_R:
1577 tree out = gimple_call_arg (call, 1);
1578 if (ptr_deref_may_alias_ref_p_1 (out, ref))
1580 if (flag_errno_math)
1584 case BUILT_IN_FREXP:
1585 case BUILT_IN_FREXPF:
1586 case BUILT_IN_FREXPL:
1588 case BUILT_IN_MODFF:
1589 case BUILT_IN_MODFL:
1591 tree out = gimple_call_arg (call, 1);
1592 return ptr_deref_may_alias_ref_p_1 (out, ref);
1594 case BUILT_IN_REMQUO:
1595 case BUILT_IN_REMQUOF:
1596 case BUILT_IN_REMQUOL:
1598 tree out = gimple_call_arg (call, 2);
1599 if (ptr_deref_may_alias_ref_p_1 (out, ref))
1601 if (flag_errno_math)
1605 case BUILT_IN_SINCOS:
1606 case BUILT_IN_SINCOSF:
1607 case BUILT_IN_SINCOSL:
1609 tree sin = gimple_call_arg (call, 1);
1610 tree cos = gimple_call_arg (call, 2);
1611 return (ptr_deref_may_alias_ref_p_1 (sin, ref)
1612 || ptr_deref_may_alias_ref_p_1 (cos, ref));
1614 /* __sync_* builtins and some OpenMP builtins act as threading
1616 #undef DEF_SYNC_BUILTIN
1617 #define DEF_SYNC_BUILTIN(ENUM, NAME, TYPE, ATTRS) case ENUM:
1618 #include "sync-builtins.def"
1619 #undef DEF_SYNC_BUILTIN
1620 case BUILT_IN_GOMP_ATOMIC_START:
1621 case BUILT_IN_GOMP_ATOMIC_END:
1622 case BUILT_IN_GOMP_BARRIER:
1623 case BUILT_IN_GOMP_TASKWAIT:
1624 case BUILT_IN_GOMP_CRITICAL_START:
1625 case BUILT_IN_GOMP_CRITICAL_END:
1626 case BUILT_IN_GOMP_CRITICAL_NAME_START:
1627 case BUILT_IN_GOMP_CRITICAL_NAME_END:
1628 case BUILT_IN_GOMP_LOOP_END:
1629 case BUILT_IN_GOMP_ORDERED_START:
1630 case BUILT_IN_GOMP_ORDERED_END:
1631 case BUILT_IN_GOMP_PARALLEL_END:
1632 case BUILT_IN_GOMP_SECTIONS_END:
1633 case BUILT_IN_GOMP_SINGLE_COPY_START:
1634 case BUILT_IN_GOMP_SINGLE_COPY_END:
1637 /* Fallthru to general call handling. */;
1640 /* Check if base is a global static variable that is not written
1642 if (callee != NULL_TREE
1643 && TREE_CODE (base) == VAR_DECL
1644 && TREE_STATIC (base))
1646 struct cgraph_node *node = cgraph_get_node (callee);
1650 && (not_written = ipa_reference_get_not_written_global (node))
1651 && bitmap_bit_p (not_written, DECL_UID (base)))
1655 /* Check if the base variable is call-clobbered. */
1657 return pt_solution_includes (gimple_call_clobber_set (call), base);
1658 else if ((TREE_CODE (base) == MEM_REF
1659 || TREE_CODE (base) == TARGET_MEM_REF)
1660 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME)
1662 struct ptr_info_def *pi = SSA_NAME_PTR_INFO (TREE_OPERAND (base, 0));
1666 return pt_solutions_intersect (gimple_call_clobber_set (call), &pi->pt);
1672 /* If the call in statement CALL may clobber the memory reference REF
1673 return true, otherwise return false. */
1676 call_may_clobber_ref_p (gimple call, tree ref)
1680 ao_ref_init (&r, ref);
1681 res = call_may_clobber_ref_p_1 (call, &r);
1683 ++alias_stats.call_may_clobber_ref_p_may_alias;
1685 ++alias_stats.call_may_clobber_ref_p_no_alias;
1690 /* If the statement STMT may clobber the memory reference REF return true,
1691 otherwise return false. */
1694 stmt_may_clobber_ref_p_1 (gimple stmt, ao_ref *ref)
1696 if (is_gimple_call (stmt))
1698 tree lhs = gimple_call_lhs (stmt);
1700 && TREE_CODE (lhs) != SSA_NAME)
1703 ao_ref_init (&r, lhs);
1704 if (refs_may_alias_p_1 (ref, &r, true))
1708 return call_may_clobber_ref_p_1 (stmt, ref);
1710 else if (gimple_assign_single_p (stmt))
1712 tree lhs = gimple_assign_lhs (stmt);
1713 if (TREE_CODE (lhs) != SSA_NAME)
1716 ao_ref_init (&r, lhs);
1717 return refs_may_alias_p_1 (ref, &r, true);
1720 else if (gimple_code (stmt) == GIMPLE_ASM)
1727 stmt_may_clobber_ref_p (gimple stmt, tree ref)
1730 ao_ref_init (&r, ref);
1731 return stmt_may_clobber_ref_p_1 (stmt, &r);
1734 /* If STMT kills the memory reference REF return true, otherwise
1738 stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
1740 /* For a must-alias check we need to be able to constrain
1741 the access properly. */
1743 if (ref->max_size == -1)
1746 if (gimple_has_lhs (stmt)
1747 && TREE_CODE (gimple_get_lhs (stmt)) != SSA_NAME
1748 /* The assignment is not necessarily carried out if it can throw
1749 and we can catch it in the current function where we could inspect
1751 ??? We only need to care about the RHS throwing. For aggregate
1752 assignments or similar calls and non-call exceptions the LHS
1753 might throw as well. */
1754 && !stmt_can_throw_internal (stmt))
1756 tree base, lhs = gimple_get_lhs (stmt);
1757 HOST_WIDE_INT size, offset, max_size;
1758 base = get_ref_base_and_extent (lhs, &offset, &size, &max_size);
1759 /* We can get MEM[symbol: sZ, index: D.8862_1] here,
1760 so base == ref->base does not always hold. */
1761 if (base == ref->base)
1763 /* For a must-alias check we need to be able to constrain
1764 the access properly. */
1765 if (size != -1 && size == max_size)
1767 if (offset <= ref->offset
1768 && offset + size >= ref->offset + ref->max_size)
1774 if (is_gimple_call (stmt))
1776 tree callee = gimple_call_fndecl (stmt);
1777 if (callee != NULL_TREE
1778 && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
1779 switch (DECL_FUNCTION_CODE (callee))
1781 case BUILT_IN_MEMCPY:
1782 case BUILT_IN_MEMPCPY:
1783 case BUILT_IN_MEMMOVE:
1784 case BUILT_IN_MEMSET:
1785 case BUILT_IN_MEMCPY_CHK:
1786 case BUILT_IN_MEMPCPY_CHK:
1787 case BUILT_IN_MEMMOVE_CHK:
1788 case BUILT_IN_MEMSET_CHK:
1790 tree dest = gimple_call_arg (stmt, 0);
1791 tree len = gimple_call_arg (stmt, 2);
1792 tree base = NULL_TREE;
1793 HOST_WIDE_INT offset = 0;
1794 if (!host_integerp (len, 0))
1796 if (TREE_CODE (dest) == ADDR_EXPR)
1797 base = get_addr_base_and_unit_offset (TREE_OPERAND (dest, 0),
1799 else if (TREE_CODE (dest) == SSA_NAME)
1802 && base == ao_ref_base (ref))
1804 HOST_WIDE_INT size = TREE_INT_CST_LOW (len);
1805 if (offset <= ref->offset / BITS_PER_UNIT
1807 >= ((ref->offset + ref->max_size + BITS_PER_UNIT - 1)
1814 case BUILT_IN_VA_END:
1816 tree ptr = gimple_call_arg (stmt, 0);
1817 if (TREE_CODE (ptr) == ADDR_EXPR)
1819 tree base = ao_ref_base (ref);
1820 if (TREE_OPERAND (ptr, 0) == base)
1833 stmt_kills_ref_p (gimple stmt, tree ref)
1836 ao_ref_init (&r, ref);
1837 return stmt_kills_ref_p_1 (stmt, &r);
1841 /* Walk the virtual use-def chain of VUSE until hitting the virtual operand
1842 TARGET or a statement clobbering the memory reference REF in which
1843 case false is returned. The walk starts with VUSE, one argument of PHI. */
1846 maybe_skip_until (gimple phi, tree target, ao_ref *ref,
1847 tree vuse, bitmap *visited)
1850 *visited = BITMAP_ALLOC (NULL);
1852 bitmap_set_bit (*visited, SSA_NAME_VERSION (PHI_RESULT (phi)));
1854 /* Walk until we hit the target. */
1855 while (vuse != target)
1857 gimple def_stmt = SSA_NAME_DEF_STMT (vuse);
1858 /* Recurse for PHI nodes. */
1859 if (gimple_code (def_stmt) == GIMPLE_PHI)
1861 /* An already visited PHI node ends the walk successfully. */
1862 if (bitmap_bit_p (*visited, SSA_NAME_VERSION (PHI_RESULT (def_stmt))))
1864 vuse = get_continuation_for_phi (def_stmt, ref, visited);
1869 /* A clobbering statement or the end of the IL ends it failing. */
1870 else if (gimple_nop_p (def_stmt)
1871 || stmt_may_clobber_ref_p_1 (def_stmt, ref))
1873 vuse = gimple_vuse (def_stmt);
1878 /* Starting from a PHI node for the virtual operand of the memory reference
1879 REF find a continuation virtual operand that allows to continue walking
1880 statements dominating PHI skipping only statements that cannot possibly
1881 clobber REF. Returns NULL_TREE if no suitable virtual operand can
1885 get_continuation_for_phi (gimple phi, ao_ref *ref, bitmap *visited)
1887 unsigned nargs = gimple_phi_num_args (phi);
1889 /* Through a single-argument PHI we can simply look through. */
1891 return PHI_ARG_DEF (phi, 0);
1893 /* For two arguments try to skip non-aliasing code until we hit
1894 the phi argument definition that dominates the other one. */
1897 tree arg0 = PHI_ARG_DEF (phi, 0);
1898 tree arg1 = PHI_ARG_DEF (phi, 1);
1899 gimple def0 = SSA_NAME_DEF_STMT (arg0);
1900 gimple def1 = SSA_NAME_DEF_STMT (arg1);
1905 else if (gimple_nop_p (def0)
1906 || (!gimple_nop_p (def1)
1907 && dominated_by_p (CDI_DOMINATORS,
1908 gimple_bb (def1), gimple_bb (def0))))
1910 if (maybe_skip_until (phi, arg0, ref, arg1, visited))
1913 else if (gimple_nop_p (def1)
1914 || dominated_by_p (CDI_DOMINATORS,
1915 gimple_bb (def0), gimple_bb (def1)))
1917 if (maybe_skip_until (phi, arg1, ref, arg0, visited))
1920 /* Special case of a diamond:
1922 goto (cond) ? L1 : L2
1923 L1: store1 = ... #MEM_2 = vuse(MEM_1)
1925 L2: store2 = ... #MEM_3 = vuse(MEM_1)
1926 L3: MEM_4 = PHI<MEM_2, MEM_3>
1927 We were called with the PHI at L3, MEM_2 and MEM_3 don't
1928 dominate each other, but still we can easily skip this PHI node
1929 if we recognize that the vuse MEM operand is the same for both,
1930 and that we can skip both statements (they don't clobber us).
1931 This is still linear. Don't use maybe_skip_until, that might
1932 potentially be slow. */
1933 else if ((common_vuse = gimple_vuse (def0))
1934 && common_vuse == gimple_vuse (def1))
1936 if (!stmt_may_clobber_ref_p_1 (def0, ref)
1937 && !stmt_may_clobber_ref_p_1 (def1, ref))
1945 /* Based on the memory reference REF and its virtual use VUSE call
1946 WALKER for each virtual use that is equivalent to VUSE, including VUSE
1947 itself. That is, for each virtual use for which its defining statement
1948 does not clobber REF.
1950 WALKER is called with REF, the current virtual use and DATA. If
1951 WALKER returns non-NULL the walk stops and its result is returned.
1952 At the end of a non-successful walk NULL is returned.
1954 TRANSLATE if non-NULL is called with a pointer to REF, the virtual
1955 use which definition is a statement that may clobber REF and DATA.
1956 If TRANSLATE returns (void *)-1 the walk stops and NULL is returned.
1957 If TRANSLATE returns non-NULL the walk stops and its result is returned.
1958 If TRANSLATE returns NULL the walk continues and TRANSLATE is supposed
1959 to adjust REF and *DATA to make that valid.
1961 TODO: Cache the vector of equivalent vuses per ref, vuse pair. */
1964 walk_non_aliased_vuses (ao_ref *ref, tree vuse,
1965 void *(*walker)(ao_ref *, tree, void *),
1966 void *(*translate)(ao_ref *, tree, void *), void *data)
1968 bitmap visited = NULL;
1971 timevar_push (TV_ALIAS_STMT_WALK);
1977 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
1978 res = (*walker) (ref, vuse, data);
1982 def_stmt = SSA_NAME_DEF_STMT (vuse);
1983 if (gimple_nop_p (def_stmt))
1985 else if (gimple_code (def_stmt) == GIMPLE_PHI)
1986 vuse = get_continuation_for_phi (def_stmt, ref, &visited);
1989 if (stmt_may_clobber_ref_p_1 (def_stmt, ref))
1993 res = (*translate) (ref, vuse, data);
1994 /* Failed lookup and translation. */
1995 if (res == (void *)-1)
2000 /* Lookup succeeded. */
2001 else if (res != NULL)
2003 /* Translation succeeded, continue walking. */
2005 vuse = gimple_vuse (def_stmt);
2011 BITMAP_FREE (visited);
2013 timevar_pop (TV_ALIAS_STMT_WALK);
2019 /* Based on the memory reference REF call WALKER for each vdef which
2020 defining statement may clobber REF, starting with VDEF. If REF
2021 is NULL_TREE, each defining statement is visited.
2023 WALKER is called with REF, the current vdef and DATA. If WALKER
2024 returns true the walk is stopped, otherwise it continues.
2026 At PHI nodes walk_aliased_vdefs forks into one walk for reach
2027 PHI argument (but only one walk continues on merge points), the
2028 return value is true if any of the walks was successful.
2030 The function returns the number of statements walked. */
2033 walk_aliased_vdefs_1 (ao_ref *ref, tree vdef,
2034 bool (*walker)(ao_ref *, tree, void *), void *data,
2035 bitmap *visited, unsigned int cnt)
2039 gimple def_stmt = SSA_NAME_DEF_STMT (vdef);
2042 && !bitmap_set_bit (*visited, SSA_NAME_VERSION (vdef)))
2045 if (gimple_nop_p (def_stmt))
2047 else if (gimple_code (def_stmt) == GIMPLE_PHI)
2051 *visited = BITMAP_ALLOC (NULL);
2052 for (i = 0; i < gimple_phi_num_args (def_stmt); ++i)
2053 cnt += walk_aliased_vdefs_1 (ref, gimple_phi_arg_def (def_stmt, i),
2054 walker, data, visited, 0);
2058 /* ??? Do we want to account this to TV_ALIAS_STMT_WALK? */
2061 || stmt_may_clobber_ref_p_1 (def_stmt, ref))
2062 && (*walker) (ref, vdef, data))
2065 vdef = gimple_vuse (def_stmt);
2071 walk_aliased_vdefs (ao_ref *ref, tree vdef,
2072 bool (*walker)(ao_ref *, tree, void *), void *data,
2075 bitmap local_visited = NULL;
2078 timevar_push (TV_ALIAS_STMT_WALK);
2080 ret = walk_aliased_vdefs_1 (ref, vdef, walker, data,
2081 visited ? visited : &local_visited, 0);
2083 BITMAP_FREE (local_visited);
2085 timevar_pop (TV_ALIAS_STMT_WALK);