1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
46 #include "tree-pass.h"
47 #include "ipa-type-escape.h"
50 /* The aliasing API provided here solves related but different problems:
52 Say there exists (in c)
66 Consider the four questions:
68 Can a store to x1 interfere with px2->y1?
69 Can a store to x1 interfere with px2->z2?
71 Can a store to x1 change the value pointed to by with py?
72 Can a store to x1 change the value pointed to by with pz?
74 The answer to these questions can be yes, yes, yes, and maybe.
76 The first two questions can be answered with a simple examination
77 of the type system. If structure X contains a field of type Y then
78 a store thru a pointer to an X can overwrite any field that is
79 contained (recursively) in an X (unless we know that px1 != px2).
81 The last two of the questions can be solved in the same way as the
82 first two questions but this is too conservative. The observation
83 is that in some cases analysis we can know if which (if any) fields
84 are addressed and if those addresses are used in bad ways. This
85 analysis may be language specific. In C, arbitrary operations may
86 be applied to pointers. However, there is some indication that
87 this may be too conservative for some C++ types.
89 The pass ipa-type-escape does this analysis for the types whose
90 instances do not escape across the compilation boundary.
92 Historically in GCC, these two problems were combined and a single
93 data structure was used to represent the solution to these
94 problems. We now have two similar but different data structures,
95 The data structure to solve the last two question is similar to the
96 first, but does not contain have the fields in it whose address are
97 never taken. For types that do escape the compilation unit, the
98 data structures will have identical information.
101 /* The alias sets assigned to MEMs assist the back-end in determining
102 which MEMs can alias which other MEMs. In general, two MEMs in
103 different alias sets cannot alias each other, with one important
104 exception. Consider something like:
106 struct S { int i; double d; };
108 a store to an `S' can alias something of either type `int' or type
109 `double'. (However, a store to an `int' cannot alias a `double'
110 and vice versa.) We indicate this via a tree structure that looks
118 (The arrows are directed and point downwards.)
119 In this situation we say the alias set for `struct S' is the
120 `superset' and that those for `int' and `double' are `subsets'.
122 To see whether two alias sets can point to the same memory, we must
123 see if either alias set is a subset of the other. We need not trace
124 past immediate descendants, however, since we propagate all
125 grandchildren up one level.
127 Alias set zero is implicitly a superset of all other alias sets.
128 However, this is no actual entry for alias set zero. It is an
129 error to attempt to explicitly construct a subset of zero. */
131 struct alias_set_entry GTY(())
133 /* The alias set number, as stored in MEM_ALIAS_SET. */
134 alias_set_type alias_set;
136 /* Nonzero if would have a child of zero: this effectively makes this
137 alias set the same as alias set zero. */
140 /* The children of the alias set. These are not just the immediate
141 children, but, in fact, all descendants. So, if we have:
143 struct T { struct S s; float f; }
145 continuing our example above, the children here will be all of
146 `int', `double', `float', and `struct S'. */
147 splay_tree GTY((param1_is (int), param2_is (int))) children;
149 typedef struct alias_set_entry *alias_set_entry;
151 static int rtx_equal_for_memref_p (const_rtx, const_rtx);
152 static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT);
153 static void record_set (rtx, const_rtx, void *);
154 static int base_alias_check (rtx, rtx, enum machine_mode,
156 static rtx find_base_value (rtx);
157 static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx);
158 static int insert_subset_children (splay_tree_node, void*);
159 static tree find_base_decl (tree);
160 static alias_set_entry get_alias_set_entry (alias_set_type);
161 static const_rtx fixed_scalar_and_varying_struct_p (const_rtx, const_rtx, rtx, rtx,
162 bool (*) (const_rtx, bool));
163 static int aliases_everything_p (const_rtx);
164 static bool nonoverlapping_component_refs_p (const_tree, const_tree);
165 static tree decl_for_component_ref (tree);
166 static rtx adjust_offset_for_component_ref (tree, rtx);
167 static int write_dependence_p (const_rtx, const_rtx, int);
169 static void memory_modified_1 (rtx, const_rtx, void *);
170 static void record_alias_subset (alias_set_type, alias_set_type);
172 /* Set up all info needed to perform alias analysis on memory references. */
174 /* Returns the size in bytes of the mode of X. */
175 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
177 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
178 different alias sets. We ignore alias sets in functions making use
179 of variable arguments because the va_arg macros on some systems are
181 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
182 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
184 /* Cap the number of passes we make over the insns propagating alias
185 information through set chains. 10 is a completely arbitrary choice. */
186 #define MAX_ALIAS_LOOP_PASSES 10
188 /* reg_base_value[N] gives an address to which register N is related.
189 If all sets after the first add or subtract to the current value
190 or otherwise modify it so it does not point to a different top level
191 object, reg_base_value[N] is equal to the address part of the source
194 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
195 expressions represent certain special values: function arguments and
196 the stack, frame, and argument pointers.
198 The contents of an ADDRESS is not normally used, the mode of the
199 ADDRESS determines whether the ADDRESS is a function argument or some
200 other special value. Pointer equality, not rtx_equal_p, determines whether
201 two ADDRESS expressions refer to the same base address.
203 The only use of the contents of an ADDRESS is for determining if the
204 current function performs nonlocal memory memory references for the
205 purposes of marking the function as a constant function. */
207 static GTY(()) VEC(rtx,gc) *reg_base_value;
208 static rtx *new_reg_base_value;
210 /* We preserve the copy of old array around to avoid amount of garbage
211 produced. About 8% of garbage produced were attributed to this
213 static GTY((deletable)) VEC(rtx,gc) *old_reg_base_value;
215 /* Static hunks of RTL used by the aliasing code; these are initialized
216 once per function to avoid unnecessary RTL allocations. */
217 static GTY (()) rtx static_reg_base_value[FIRST_PSEUDO_REGISTER];
219 #define REG_BASE_VALUE(X) \
220 (REGNO (X) < VEC_length (rtx, reg_base_value) \
221 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
223 /* Vector indexed by N giving the initial (unchanging) value known for
224 pseudo-register N. This array is initialized in init_alias_analysis,
225 and does not change until end_alias_analysis is called. */
226 static GTY((length("reg_known_value_size"))) rtx *reg_known_value;
228 /* Indicates number of valid entries in reg_known_value. */
229 static GTY(()) unsigned int reg_known_value_size;
231 /* Vector recording for each reg_known_value whether it is due to a
232 REG_EQUIV note. Future passes (viz., reload) may replace the
233 pseudo with the equivalent expression and so we account for the
234 dependences that would be introduced if that happens.
236 The REG_EQUIV notes created in assign_parms may mention the arg
237 pointer, and there are explicit insns in the RTL that modify the
238 arg pointer. Thus we must ensure that such insns don't get
239 scheduled across each other because that would invalidate the
240 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
241 wrong, but solving the problem in the scheduler will likely give
242 better code, so we do it here. */
243 static bool *reg_known_equiv_p;
245 /* True when scanning insns from the start of the rtl to the
246 NOTE_INSN_FUNCTION_BEG note. */
247 static bool copying_arguments;
249 DEF_VEC_P(alias_set_entry);
250 DEF_VEC_ALLOC_P(alias_set_entry,gc);
252 /* The splay-tree used to store the various alias set entries. */
253 static GTY (()) VEC(alias_set_entry,gc) *alias_sets;
255 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
256 such an entry, or NULL otherwise. */
258 static inline alias_set_entry
259 get_alias_set_entry (alias_set_type alias_set)
261 return VEC_index (alias_set_entry, alias_sets, alias_set);
264 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
265 the two MEMs cannot alias each other. */
268 mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2)
270 /* Perform a basic sanity check. Namely, that there are no alias sets
271 if we're not using strict aliasing. This helps to catch bugs
272 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
273 where a MEM is allocated in some way other than by the use of
274 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
275 use alias sets to indicate that spilled registers cannot alias each
276 other, we might need to remove this check. */
277 gcc_assert (flag_strict_aliasing
278 || (!MEM_ALIAS_SET (mem1) && !MEM_ALIAS_SET (mem2)));
280 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
283 /* Insert the NODE into the splay tree given by DATA. Used by
284 record_alias_subset via splay_tree_foreach. */
287 insert_subset_children (splay_tree_node node, void *data)
289 splay_tree_insert ((splay_tree) data, node->key, node->value);
294 /* Return true if the first alias set is a subset of the second. */
297 alias_set_subset_of (alias_set_type set1, alias_set_type set2)
301 /* Everything is a subset of the "aliases everything" set. */
305 /* Otherwise, check if set1 is a subset of set2. */
306 ase = get_alias_set_entry (set2);
308 && ((ase->has_zero_child && set1 == 0)
309 || splay_tree_lookup (ase->children,
310 (splay_tree_key) set1)))
315 /* Return 1 if the two specified alias sets may conflict. */
318 alias_sets_conflict_p (alias_set_type set1, alias_set_type set2)
323 if (alias_sets_must_conflict_p (set1, set2))
326 /* See if the first alias set is a subset of the second. */
327 ase = get_alias_set_entry (set1);
329 && (ase->has_zero_child
330 || splay_tree_lookup (ase->children,
331 (splay_tree_key) set2)))
334 /* Now do the same, but with the alias sets reversed. */
335 ase = get_alias_set_entry (set2);
337 && (ase->has_zero_child
338 || splay_tree_lookup (ase->children,
339 (splay_tree_key) set1)))
342 /* The two alias sets are distinct and neither one is the
343 child of the other. Therefore, they cannot conflict. */
348 walk_mems_2 (rtx *x, rtx mem)
352 if (alias_sets_conflict_p (MEM_ALIAS_SET(*x), MEM_ALIAS_SET(mem)))
361 walk_mems_1 (rtx *x, rtx *pat)
365 /* Visit all MEMs in *PAT and check indepedence. */
366 if (for_each_rtx (pat, (rtx_function) walk_mems_2, *x))
367 /* Indicate that dependence was determined and stop traversal. */
375 /* Return 1 if two specified instructions have mem expr with conflict alias sets*/
377 insn_alias_sets_conflict_p (rtx insn1, rtx insn2)
379 /* For each pair of MEMs in INSN1 and INSN2 check their independence. */
380 return for_each_rtx (&PATTERN (insn1), (rtx_function) walk_mems_1,
384 /* Return 1 if the two specified alias sets will always conflict. */
387 alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2)
389 if (set1 == 0 || set2 == 0 || set1 == set2)
395 /* Return 1 if any MEM object of type T1 will always conflict (using the
396 dependency routines in this file) with any MEM object of type T2.
397 This is used when allocating temporary storage. If T1 and/or T2 are
398 NULL_TREE, it means we know nothing about the storage. */
401 objects_must_conflict_p (tree t1, tree t2)
403 alias_set_type set1, set2;
405 /* If neither has a type specified, we don't know if they'll conflict
406 because we may be using them to store objects of various types, for
407 example the argument and local variables areas of inlined functions. */
408 if (t1 == 0 && t2 == 0)
411 /* If they are the same type, they must conflict. */
413 /* Likewise if both are volatile. */
414 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
417 set1 = t1 ? get_alias_set (t1) : 0;
418 set2 = t2 ? get_alias_set (t2) : 0;
420 /* We can't use alias_sets_conflict_p because we must make sure
421 that every subtype of t1 will conflict with every subtype of
422 t2 for which a pair of subobjects of these respective subtypes
423 overlaps on the stack. */
424 return alias_sets_must_conflict_p (set1, set2);
427 /* T is an expression with pointer type. Find the DECL on which this
428 expression is based. (For example, in `a[i]' this would be `a'.)
429 If there is no such DECL, or a unique decl cannot be determined,
430 NULL_TREE is returned. */
433 find_base_decl (tree t)
437 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
440 /* If this is a declaration, return it. If T is based on a restrict
441 qualified decl, return that decl. */
444 if (TREE_CODE (t) == VAR_DECL && DECL_BASED_ON_RESTRICT_P (t))
445 t = DECL_GET_RESTRICT_BASE (t);
449 /* Handle general expressions. It would be nice to deal with
450 COMPONENT_REFs here. If we could tell that `a' and `b' were the
451 same, then `a->f' and `b->f' are also the same. */
452 switch (TREE_CODE_CLASS (TREE_CODE (t)))
455 return find_base_decl (TREE_OPERAND (t, 0));
458 /* Return 0 if found in neither or both are the same. */
459 d0 = find_base_decl (TREE_OPERAND (t, 0));
460 d1 = find_base_decl (TREE_OPERAND (t, 1));
475 /* Return true if all nested component references handled by
476 get_inner_reference in T are such that we should use the alias set
477 provided by the object at the heart of T.
479 This is true for non-addressable components (which don't have their
480 own alias set), as well as components of objects in alias set zero.
481 This later point is a special case wherein we wish to override the
482 alias set used by the component, but we don't have per-FIELD_DECL
483 assignable alias sets. */
486 component_uses_parent_alias_set (const_tree t)
490 /* If we're at the end, it vacuously uses its own alias set. */
491 if (!handled_component_p (t))
494 switch (TREE_CODE (t))
497 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
502 case ARRAY_RANGE_REF:
503 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))))
512 /* Bitfields and casts are never addressable. */
516 t = TREE_OPERAND (t, 0);
517 if (get_alias_set (TREE_TYPE (t)) == 0)
522 /* Return the alias set for T, which may be either a type or an
523 expression. Call language-specific routine for help, if needed. */
526 get_alias_set (tree t)
530 /* If we're not doing any alias analysis, just assume everything
531 aliases everything else. Also return 0 if this or its type is
533 if (! flag_strict_aliasing || t == error_mark_node
535 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
538 /* We can be passed either an expression or a type. This and the
539 language-specific routine may make mutually-recursive calls to each other
540 to figure out what to do. At each juncture, we see if this is a tree
541 that the language may need to handle specially. First handle things that
547 /* Remove any nops, then give the language a chance to do
548 something with this tree before we look at it. */
550 set = lang_hooks.get_alias_set (t);
554 /* First see if the actual object referenced is an INDIRECT_REF from a
555 restrict-qualified pointer or a "void *". */
556 while (handled_component_p (inner))
558 inner = TREE_OPERAND (inner, 0);
562 /* Check for accesses through restrict-qualified pointers. */
563 if (INDIRECT_REF_P (inner))
567 if (TREE_CODE (TREE_OPERAND (inner, 0)) == SSA_NAME)
568 decl = SSA_NAME_VAR (TREE_OPERAND (inner, 0));
570 decl = find_base_decl (TREE_OPERAND (inner, 0));
572 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
574 /* If we haven't computed the actual alias set, do it now. */
575 if (DECL_POINTER_ALIAS_SET (decl) == -2)
577 tree pointed_to_type = TREE_TYPE (TREE_TYPE (decl));
579 /* No two restricted pointers can point at the same thing.
580 However, a restricted pointer can point at the same thing
581 as an unrestricted pointer, if that unrestricted pointer
582 is based on the restricted pointer. So, we make the
583 alias set for the restricted pointer a subset of the
584 alias set for the type pointed to by the type of the
586 alias_set_type pointed_to_alias_set
587 = get_alias_set (pointed_to_type);
589 if (pointed_to_alias_set == 0)
590 /* It's not legal to make a subset of alias set zero. */
591 DECL_POINTER_ALIAS_SET (decl) = 0;
592 else if (AGGREGATE_TYPE_P (pointed_to_type))
593 /* For an aggregate, we must treat the restricted
594 pointer the same as an ordinary pointer. If we
595 were to make the type pointed to by the
596 restricted pointer a subset of the pointed-to
597 type, then we would believe that other subsets
598 of the pointed-to type (such as fields of that
599 type) do not conflict with the type pointed to
600 by the restricted pointer. */
601 DECL_POINTER_ALIAS_SET (decl)
602 = pointed_to_alias_set;
605 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
606 record_alias_subset (pointed_to_alias_set,
607 DECL_POINTER_ALIAS_SET (decl));
611 /* We use the alias set indicated in the declaration. */
612 return DECL_POINTER_ALIAS_SET (decl);
615 /* If we have an INDIRECT_REF via a void pointer, we don't
616 know anything about what that might alias. Likewise if the
617 pointer is marked that way. */
618 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE
619 || (TYPE_REF_CAN_ALIAS_ALL
620 (TREE_TYPE (TREE_OPERAND (inner, 0)))))
624 /* Otherwise, pick up the outermost object that we could have a pointer
625 to, processing conversions as above. */
626 while (component_uses_parent_alias_set (t))
628 t = TREE_OPERAND (t, 0);
632 /* If we've already determined the alias set for a decl, just return
633 it. This is necessary for C++ anonymous unions, whose component
634 variables don't look like union members (boo!). */
635 if (TREE_CODE (t) == VAR_DECL
636 && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t)))
637 return MEM_ALIAS_SET (DECL_RTL (t));
639 /* Now all we care about is the type. */
643 /* Variant qualifiers don't affect the alias set, so get the main
644 variant. Always use the canonical type as well.
645 If this is a type with a known alias set, return it. */
646 t = TYPE_MAIN_VARIANT (t);
647 if (TYPE_CANONICAL (t))
648 t = TYPE_CANONICAL (t);
649 if (TYPE_ALIAS_SET_KNOWN_P (t))
650 return TYPE_ALIAS_SET (t);
652 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
653 if (!COMPLETE_TYPE_P (t))
655 /* For arrays with unknown size the conservative answer is the
656 alias set of the element type. */
657 if (TREE_CODE (t) == ARRAY_TYPE)
658 return get_alias_set (TREE_TYPE (t));
660 /* But return zero as a conservative answer for incomplete types. */
664 /* See if the language has special handling for this type. */
665 set = lang_hooks.get_alias_set (t);
669 /* There are no objects of FUNCTION_TYPE, so there's no point in
670 using up an alias set for them. (There are, of course, pointers
671 and references to functions, but that's different.) */
672 else if (TREE_CODE (t) == FUNCTION_TYPE
673 || TREE_CODE (t) == METHOD_TYPE)
676 /* Unless the language specifies otherwise, let vector types alias
677 their components. This avoids some nasty type punning issues in
678 normal usage. And indeed lets vectors be treated more like an
680 else if (TREE_CODE (t) == VECTOR_TYPE)
681 set = get_alias_set (TREE_TYPE (t));
683 /* Unless the language specifies otherwise, treat array types the
684 same as their components. This avoids the asymmetry we get
685 through recording the components. Consider accessing a
686 character(kind=1) through a reference to a character(kind=1)[1:1].
687 Or consider if we want to assign integer(kind=4)[0:D.1387] and
688 integer(kind=4)[4] the same alias set or not.
689 Just be pragmatic here and make sure the array and its element
690 type get the same alias set assigned. */
691 else if (TREE_CODE (t) == ARRAY_TYPE
692 && !TYPE_NONALIASED_COMPONENT (t))
693 set = get_alias_set (TREE_TYPE (t));
696 /* Otherwise make a new alias set for this type. */
697 set = new_alias_set ();
699 TYPE_ALIAS_SET (t) = set;
701 /* If this is an aggregate type, we must record any component aliasing
703 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
704 record_component_aliases (t);
709 /* Return a brand-new alias set. */
714 if (flag_strict_aliasing)
717 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
718 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
719 return VEC_length (alias_set_entry, alias_sets) - 1;
725 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
726 not everything that aliases SUPERSET also aliases SUBSET. For example,
727 in C, a store to an `int' can alias a load of a structure containing an
728 `int', and vice versa. But it can't alias a load of a 'double' member
729 of the same structure. Here, the structure would be the SUPERSET and
730 `int' the SUBSET. This relationship is also described in the comment at
731 the beginning of this file.
733 This function should be called only once per SUPERSET/SUBSET pair.
735 It is illegal for SUPERSET to be zero; everything is implicitly a
736 subset of alias set zero. */
739 record_alias_subset (alias_set_type superset, alias_set_type subset)
741 alias_set_entry superset_entry;
742 alias_set_entry subset_entry;
744 /* It is possible in complex type situations for both sets to be the same,
745 in which case we can ignore this operation. */
746 if (superset == subset)
749 gcc_assert (superset);
751 superset_entry = get_alias_set_entry (superset);
752 if (superset_entry == 0)
754 /* Create an entry for the SUPERSET, so that we have a place to
755 attach the SUBSET. */
756 superset_entry = GGC_NEW (struct alias_set_entry);
757 superset_entry->alias_set = superset;
758 superset_entry->children
759 = splay_tree_new_ggc (splay_tree_compare_ints);
760 superset_entry->has_zero_child = 0;
761 VEC_replace (alias_set_entry, alias_sets, superset, superset_entry);
765 superset_entry->has_zero_child = 1;
768 subset_entry = get_alias_set_entry (subset);
769 /* If there is an entry for the subset, enter all of its children
770 (if they are not already present) as children of the SUPERSET. */
773 if (subset_entry->has_zero_child)
774 superset_entry->has_zero_child = 1;
776 splay_tree_foreach (subset_entry->children, insert_subset_children,
777 superset_entry->children);
780 /* Enter the SUBSET itself as a child of the SUPERSET. */
781 splay_tree_insert (superset_entry->children,
782 (splay_tree_key) subset, 0);
786 /* Record that component types of TYPE, if any, are part of that type for
787 aliasing purposes. For record types, we only record component types
788 for fields that are not marked non-addressable. For array types, we
789 only record the component type if it is not marked non-aliased. */
792 record_component_aliases (tree type)
794 alias_set_type superset = get_alias_set (type);
800 switch (TREE_CODE (type))
804 case QUAL_UNION_TYPE:
805 /* Recursively record aliases for the base classes, if there are any. */
806 if (TYPE_BINFO (type))
809 tree binfo, base_binfo;
811 for (binfo = TYPE_BINFO (type), i = 0;
812 BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
813 record_alias_subset (superset,
814 get_alias_set (BINFO_TYPE (base_binfo)));
816 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
817 if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
818 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
822 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
825 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
833 /* Allocate an alias set for use in storing and reading from the varargs
836 static GTY(()) alias_set_type varargs_set = -1;
839 get_varargs_alias_set (void)
842 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
843 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
844 consistently use the varargs alias set for loads from the varargs
845 area. So don't use it anywhere. */
848 if (varargs_set == -1)
849 varargs_set = new_alias_set ();
855 /* Likewise, but used for the fixed portions of the frame, e.g., register
858 static GTY(()) alias_set_type frame_set = -1;
861 get_frame_alias_set (void)
864 frame_set = new_alias_set ();
869 /* Inside SRC, the source of a SET, find a base address. */
872 find_base_value (rtx src)
876 #if defined (FIND_BASE_TERM)
877 /* Try machine-dependent ways to find the base term. */
878 src = FIND_BASE_TERM (src);
881 switch (GET_CODE (src))
889 /* At the start of a function, argument registers have known base
890 values which may be lost later. Returning an ADDRESS
891 expression here allows optimization based on argument values
892 even when the argument registers are used for other purposes. */
893 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
894 return new_reg_base_value[regno];
896 /* If a pseudo has a known base value, return it. Do not do this
897 for non-fixed hard regs since it can result in a circular
898 dependency chain for registers which have values at function entry.
900 The test above is not sufficient because the scheduler may move
901 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
902 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
903 && regno < VEC_length (rtx, reg_base_value))
905 /* If we're inside init_alias_analysis, use new_reg_base_value
906 to reduce the number of relaxation iterations. */
907 if (new_reg_base_value && new_reg_base_value[regno]
908 && DF_REG_DEF_COUNT (regno) == 1)
909 return new_reg_base_value[regno];
911 if (VEC_index (rtx, reg_base_value, regno))
912 return VEC_index (rtx, reg_base_value, regno);
918 /* Check for an argument passed in memory. Only record in the
919 copying-arguments block; it is too hard to track changes
921 if (copying_arguments
922 && (XEXP (src, 0) == arg_pointer_rtx
923 || (GET_CODE (XEXP (src, 0)) == PLUS
924 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
925 return gen_rtx_ADDRESS (VOIDmode, src);
930 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
933 /* ... fall through ... */
938 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
940 /* If either operand is a REG that is a known pointer, then it
942 if (REG_P (src_0) && REG_POINTER (src_0))
943 return find_base_value (src_0);
944 if (REG_P (src_1) && REG_POINTER (src_1))
945 return find_base_value (src_1);
947 /* If either operand is a REG, then see if we already have
948 a known value for it. */
951 temp = find_base_value (src_0);
958 temp = find_base_value (src_1);
963 /* If either base is named object or a special address
964 (like an argument or stack reference), then use it for the
967 && (GET_CODE (src_0) == SYMBOL_REF
968 || GET_CODE (src_0) == LABEL_REF
969 || (GET_CODE (src_0) == ADDRESS
970 && GET_MODE (src_0) != VOIDmode)))
974 && (GET_CODE (src_1) == SYMBOL_REF
975 || GET_CODE (src_1) == LABEL_REF
976 || (GET_CODE (src_1) == ADDRESS
977 && GET_MODE (src_1) != VOIDmode)))
980 /* Guess which operand is the base address:
981 If either operand is a symbol, then it is the base. If
982 either operand is a CONST_INT, then the other is the base. */
983 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
984 return find_base_value (src_0);
985 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
986 return find_base_value (src_1);
992 /* The standard form is (lo_sum reg sym) so look only at the
994 return find_base_value (XEXP (src, 1));
997 /* If the second operand is constant set the base
998 address to the first operand. */
999 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
1000 return find_base_value (XEXP (src, 0));
1004 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
1014 return find_base_value (XEXP (src, 0));
1017 case SIGN_EXTEND: /* used for NT/Alpha pointers */
1019 rtx temp = find_base_value (XEXP (src, 0));
1021 if (temp != 0 && CONSTANT_P (temp))
1022 temp = convert_memory_address (Pmode, temp);
1034 /* Called from init_alias_analysis indirectly through note_stores. */
1036 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1037 register N has been set in this function. */
1038 static char *reg_seen;
1040 /* Addresses which are known not to alias anything else are identified
1041 by a unique integer. */
1042 static int unique_id;
1045 record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED)
1054 regno = REGNO (dest);
1056 gcc_assert (regno < VEC_length (rtx, reg_base_value));
1058 /* If this spans multiple hard registers, then we must indicate that every
1059 register has an unusable value. */
1060 if (regno < FIRST_PSEUDO_REGISTER)
1061 n = hard_regno_nregs[regno][GET_MODE (dest)];
1068 reg_seen[regno + n] = 1;
1069 new_reg_base_value[regno + n] = 0;
1076 /* A CLOBBER wipes out any old value but does not prevent a previously
1077 unset register from acquiring a base address (i.e. reg_seen is not
1079 if (GET_CODE (set) == CLOBBER)
1081 new_reg_base_value[regno] = 0;
1084 src = SET_SRC (set);
1088 if (reg_seen[regno])
1090 new_reg_base_value[regno] = 0;
1093 reg_seen[regno] = 1;
1094 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
1095 GEN_INT (unique_id++));
1099 /* If this is not the first set of REGNO, see whether the new value
1100 is related to the old one. There are two cases of interest:
1102 (1) The register might be assigned an entirely new value
1103 that has the same base term as the original set.
1105 (2) The set might be a simple self-modification that
1106 cannot change REGNO's base value.
1108 If neither case holds, reject the original base value as invalid.
1109 Note that the following situation is not detected:
1111 extern int x, y; int *p = &x; p += (&y-&x);
1113 ANSI C does not allow computing the difference of addresses
1114 of distinct top level objects. */
1115 if (new_reg_base_value[regno] != 0
1116 && find_base_value (src) != new_reg_base_value[regno])
1117 switch (GET_CODE (src))
1121 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1122 new_reg_base_value[regno] = 0;
1125 /* If the value we add in the PLUS is also a valid base value,
1126 this might be the actual base value, and the original value
1129 rtx other = NULL_RTX;
1131 if (XEXP (src, 0) == dest)
1132 other = XEXP (src, 1);
1133 else if (XEXP (src, 1) == dest)
1134 other = XEXP (src, 0);
1136 if (! other || find_base_value (other))
1137 new_reg_base_value[regno] = 0;
1141 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
1142 new_reg_base_value[regno] = 0;
1145 new_reg_base_value[regno] = 0;
1148 /* If this is the first set of a register, record the value. */
1149 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1150 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1151 new_reg_base_value[regno] = find_base_value (src);
1153 reg_seen[regno] = 1;
1156 /* If a value is known for REGNO, return it. */
1159 get_reg_known_value (unsigned int regno)
1161 if (regno >= FIRST_PSEUDO_REGISTER)
1163 regno -= FIRST_PSEUDO_REGISTER;
1164 if (regno < reg_known_value_size)
1165 return reg_known_value[regno];
1173 set_reg_known_value (unsigned int regno, rtx val)
1175 if (regno >= FIRST_PSEUDO_REGISTER)
1177 regno -= FIRST_PSEUDO_REGISTER;
1178 if (regno < reg_known_value_size)
1179 reg_known_value[regno] = val;
1183 /* Similarly for reg_known_equiv_p. */
1186 get_reg_known_equiv_p (unsigned int regno)
1188 if (regno >= FIRST_PSEUDO_REGISTER)
1190 regno -= FIRST_PSEUDO_REGISTER;
1191 if (regno < reg_known_value_size)
1192 return reg_known_equiv_p[regno];
1198 set_reg_known_equiv_p (unsigned int regno, bool val)
1200 if (regno >= FIRST_PSEUDO_REGISTER)
1202 regno -= FIRST_PSEUDO_REGISTER;
1203 if (regno < reg_known_value_size)
1204 reg_known_equiv_p[regno] = val;
1209 /* Returns a canonical version of X, from the point of view alias
1210 analysis. (For example, if X is a MEM whose address is a register,
1211 and the register has a known value (say a SYMBOL_REF), then a MEM
1212 whose address is the SYMBOL_REF is returned.) */
1217 /* Recursively look for equivalences. */
1218 if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER)
1220 rtx t = get_reg_known_value (REGNO (x));
1224 return canon_rtx (t);
1227 if (GET_CODE (x) == PLUS)
1229 rtx x0 = canon_rtx (XEXP (x, 0));
1230 rtx x1 = canon_rtx (XEXP (x, 1));
1232 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1234 if (GET_CODE (x0) == CONST_INT)
1235 return plus_constant (x1, INTVAL (x0));
1236 else if (GET_CODE (x1) == CONST_INT)
1237 return plus_constant (x0, INTVAL (x1));
1238 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1242 /* This gives us much better alias analysis when called from
1243 the loop optimizer. Note we want to leave the original
1244 MEM alone, but need to return the canonicalized MEM with
1245 all the flags with their original values. */
1247 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1252 /* Return 1 if X and Y are identical-looking rtx's.
1253 Expect that X and Y has been already canonicalized.
1255 We use the data in reg_known_value above to see if two registers with
1256 different numbers are, in fact, equivalent. */
1259 rtx_equal_for_memref_p (const_rtx x, const_rtx y)
1266 if (x == 0 && y == 0)
1268 if (x == 0 || y == 0)
1274 code = GET_CODE (x);
1275 /* Rtx's of different codes cannot be equal. */
1276 if (code != GET_CODE (y))
1279 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1280 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1282 if (GET_MODE (x) != GET_MODE (y))
1285 /* Some RTL can be compared without a recursive examination. */
1289 return REGNO (x) == REGNO (y);
1292 return XEXP (x, 0) == XEXP (y, 0);
1295 return XSTR (x, 0) == XSTR (y, 0);
1301 /* There's no need to compare the contents of CONST_DOUBLEs or
1302 CONST_INTs because pointer equality is a good enough
1303 comparison for these nodes. */
1310 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1312 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1313 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1314 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1315 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1316 /* For commutative operations, the RTX match if the operand match in any
1317 order. Also handle the simple binary and unary cases without a loop. */
1318 if (COMMUTATIVE_P (x))
1320 rtx xop0 = canon_rtx (XEXP (x, 0));
1321 rtx yop0 = canon_rtx (XEXP (y, 0));
1322 rtx yop1 = canon_rtx (XEXP (y, 1));
1324 return ((rtx_equal_for_memref_p (xop0, yop0)
1325 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1326 || (rtx_equal_for_memref_p (xop0, yop1)
1327 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1329 else if (NON_COMMUTATIVE_P (x))
1331 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1332 canon_rtx (XEXP (y, 0)))
1333 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1334 canon_rtx (XEXP (y, 1))));
1336 else if (UNARY_P (x))
1337 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1338 canon_rtx (XEXP (y, 0)));
1340 /* Compare the elements. If any pair of corresponding elements
1341 fail to match, return 0 for the whole things.
1343 Limit cases to types which actually appear in addresses. */
1345 fmt = GET_RTX_FORMAT (code);
1346 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1351 if (XINT (x, i) != XINT (y, i))
1356 /* Two vectors must have the same length. */
1357 if (XVECLEN (x, i) != XVECLEN (y, i))
1360 /* And the corresponding elements must match. */
1361 for (j = 0; j < XVECLEN (x, i); j++)
1362 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1363 canon_rtx (XVECEXP (y, i, j))) == 0)
1368 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1369 canon_rtx (XEXP (y, i))) == 0)
1373 /* This can happen for asm operands. */
1375 if (strcmp (XSTR (x, i), XSTR (y, i)))
1379 /* This can happen for an asm which clobbers memory. */
1383 /* It is believed that rtx's at this level will never
1384 contain anything but integers and other rtx's,
1385 except for within LABEL_REFs and SYMBOL_REFs. */
1394 find_base_term (rtx x)
1397 struct elt_loc_list *l;
1399 #if defined (FIND_BASE_TERM)
1400 /* Try machine-dependent ways to find the base term. */
1401 x = FIND_BASE_TERM (x);
1404 switch (GET_CODE (x))
1407 return REG_BASE_VALUE (x);
1410 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1420 return find_base_term (XEXP (x, 0));
1423 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1425 rtx temp = find_base_term (XEXP (x, 0));
1427 if (temp != 0 && CONSTANT_P (temp))
1428 temp = convert_memory_address (Pmode, temp);
1434 val = CSELIB_VAL_PTR (x);
1437 for (l = val->locs; l; l = l->next)
1438 if ((x = find_base_term (l->loc)) != 0)
1444 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1448 /* The standard form is (lo_sum reg sym) so look only at the
1450 return find_base_term (XEXP (x, 1));
1454 rtx tmp1 = XEXP (x, 0);
1455 rtx tmp2 = XEXP (x, 1);
1457 /* This is a little bit tricky since we have to determine which of
1458 the two operands represents the real base address. Otherwise this
1459 routine may return the index register instead of the base register.
1461 That may cause us to believe no aliasing was possible, when in
1462 fact aliasing is possible.
1464 We use a few simple tests to guess the base register. Additional
1465 tests can certainly be added. For example, if one of the operands
1466 is a shift or multiply, then it must be the index register and the
1467 other operand is the base register. */
1469 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1470 return find_base_term (tmp2);
1472 /* If either operand is known to be a pointer, then use it
1473 to determine the base term. */
1474 if (REG_P (tmp1) && REG_POINTER (tmp1))
1475 return find_base_term (tmp1);
1477 if (REG_P (tmp2) && REG_POINTER (tmp2))
1478 return find_base_term (tmp2);
1480 /* Neither operand was known to be a pointer. Go ahead and find the
1481 base term for both operands. */
1482 tmp1 = find_base_term (tmp1);
1483 tmp2 = find_base_term (tmp2);
1485 /* If either base term is named object or a special address
1486 (like an argument or stack reference), then use it for the
1489 && (GET_CODE (tmp1) == SYMBOL_REF
1490 || GET_CODE (tmp1) == LABEL_REF
1491 || (GET_CODE (tmp1) == ADDRESS
1492 && GET_MODE (tmp1) != VOIDmode)))
1496 && (GET_CODE (tmp2) == SYMBOL_REF
1497 || GET_CODE (tmp2) == LABEL_REF
1498 || (GET_CODE (tmp2) == ADDRESS
1499 && GET_MODE (tmp2) != VOIDmode)))
1502 /* We could not determine which of the two operands was the
1503 base register and which was the index. So we can determine
1504 nothing from the base alias check. */
1509 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1510 return find_base_term (XEXP (x, 0));
1522 /* Return 0 if the addresses X and Y are known to point to different
1523 objects, 1 if they might be pointers to the same object. */
1526 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1527 enum machine_mode y_mode)
1529 rtx x_base = find_base_term (x);
1530 rtx y_base = find_base_term (y);
1532 /* If the address itself has no known base see if a known equivalent
1533 value has one. If either address still has no known base, nothing
1534 is known about aliasing. */
1539 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1542 x_base = find_base_term (x_c);
1550 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1553 y_base = find_base_term (y_c);
1558 /* If the base addresses are equal nothing is known about aliasing. */
1559 if (rtx_equal_p (x_base, y_base))
1562 /* The base addresses are different expressions. If they are not accessed
1563 via AND, there is no conflict. We can bring knowledge of object
1564 alignment into play here. For example, on alpha, "char a, b;" can
1565 alias one another, though "char a; long b;" cannot. AND addesses may
1566 implicitly alias surrounding objects; i.e. unaligned access in DImode
1567 via AND address can alias all surrounding object types except those
1568 with aligment 8 or higher. */
1569 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1571 if (GET_CODE (x) == AND
1572 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1573 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1575 if (GET_CODE (y) == AND
1576 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1577 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1580 /* Differing symbols not accessed via AND never alias. */
1581 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1584 /* If one address is a stack reference there can be no alias:
1585 stack references using different base registers do not alias,
1586 a stack reference can not alias a parameter, and a stack reference
1587 can not alias a global. */
1588 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1589 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1592 if (! flag_argument_noalias)
1595 if (flag_argument_noalias > 1)
1598 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1599 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1602 /* Convert the address X into something we can use. This is done by returning
1603 it unchanged unless it is a value; in the latter case we call cselib to get
1604 a more useful rtx. */
1610 struct elt_loc_list *l;
1612 if (GET_CODE (x) != VALUE)
1614 v = CSELIB_VAL_PTR (x);
1617 for (l = v->locs; l; l = l->next)
1618 if (CONSTANT_P (l->loc))
1620 for (l = v->locs; l; l = l->next)
1621 if (!REG_P (l->loc) && !MEM_P (l->loc))
1624 return v->locs->loc;
1629 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1630 where SIZE is the size in bytes of the memory reference. If ADDR
1631 is not modified by the memory reference then ADDR is returned. */
1634 addr_side_effect_eval (rtx addr, int size, int n_refs)
1638 switch (GET_CODE (addr))
1641 offset = (n_refs + 1) * size;
1644 offset = -(n_refs + 1) * size;
1647 offset = n_refs * size;
1650 offset = -n_refs * size;
1658 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1661 addr = XEXP (addr, 0);
1662 addr = canon_rtx (addr);
1667 /* Return nonzero if X and Y (memory addresses) could reference the
1668 same location in memory. C is an offset accumulator. When
1669 C is nonzero, we are testing aliases between X and Y + C.
1670 XSIZE is the size in bytes of the X reference,
1671 similarly YSIZE is the size in bytes for Y.
1672 Expect that canon_rtx has been already called for X and Y.
1674 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1675 referenced (the reference was BLKmode), so make the most pessimistic
1678 If XSIZE or YSIZE is negative, we may access memory outside the object
1679 being referenced as a side effect. This can happen when using AND to
1680 align memory references, as is done on the Alpha.
1682 Nice to notice that varying addresses cannot conflict with fp if no
1683 local variables had their addresses taken, but that's too hard now. */
1686 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1688 if (GET_CODE (x) == VALUE)
1690 if (GET_CODE (y) == VALUE)
1692 if (GET_CODE (x) == HIGH)
1694 else if (GET_CODE (x) == LO_SUM)
1697 x = addr_side_effect_eval (x, xsize, 0);
1698 if (GET_CODE (y) == HIGH)
1700 else if (GET_CODE (y) == LO_SUM)
1703 y = addr_side_effect_eval (y, ysize, 0);
1705 if (rtx_equal_for_memref_p (x, y))
1707 if (xsize <= 0 || ysize <= 0)
1709 if (c >= 0 && xsize > c)
1711 if (c < 0 && ysize+c > 0)
1716 /* This code used to check for conflicts involving stack references and
1717 globals but the base address alias code now handles these cases. */
1719 if (GET_CODE (x) == PLUS)
1721 /* The fact that X is canonicalized means that this
1722 PLUS rtx is canonicalized. */
1723 rtx x0 = XEXP (x, 0);
1724 rtx x1 = XEXP (x, 1);
1726 if (GET_CODE (y) == PLUS)
1728 /* The fact that Y is canonicalized means that this
1729 PLUS rtx is canonicalized. */
1730 rtx y0 = XEXP (y, 0);
1731 rtx y1 = XEXP (y, 1);
1733 if (rtx_equal_for_memref_p (x1, y1))
1734 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1735 if (rtx_equal_for_memref_p (x0, y0))
1736 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1737 if (GET_CODE (x1) == CONST_INT)
1739 if (GET_CODE (y1) == CONST_INT)
1740 return memrefs_conflict_p (xsize, x0, ysize, y0,
1741 c - INTVAL (x1) + INTVAL (y1));
1743 return memrefs_conflict_p (xsize, x0, ysize, y,
1746 else if (GET_CODE (y1) == CONST_INT)
1747 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1751 else if (GET_CODE (x1) == CONST_INT)
1752 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1754 else if (GET_CODE (y) == PLUS)
1756 /* The fact that Y is canonicalized means that this
1757 PLUS rtx is canonicalized. */
1758 rtx y0 = XEXP (y, 0);
1759 rtx y1 = XEXP (y, 1);
1761 if (GET_CODE (y1) == CONST_INT)
1762 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1767 if (GET_CODE (x) == GET_CODE (y))
1768 switch (GET_CODE (x))
1772 /* Handle cases where we expect the second operands to be the
1773 same, and check only whether the first operand would conflict
1776 rtx x1 = canon_rtx (XEXP (x, 1));
1777 rtx y1 = canon_rtx (XEXP (y, 1));
1778 if (! rtx_equal_for_memref_p (x1, y1))
1780 x0 = canon_rtx (XEXP (x, 0));
1781 y0 = canon_rtx (XEXP (y, 0));
1782 if (rtx_equal_for_memref_p (x0, y0))
1783 return (xsize == 0 || ysize == 0
1784 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1786 /* Can't properly adjust our sizes. */
1787 if (GET_CODE (x1) != CONST_INT)
1789 xsize /= INTVAL (x1);
1790 ysize /= INTVAL (x1);
1792 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1799 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1800 as an access with indeterminate size. Assume that references
1801 besides AND are aligned, so if the size of the other reference is
1802 at least as large as the alignment, assume no other overlap. */
1803 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1805 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1807 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1809 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1811 /* ??? If we are indexing far enough into the array/structure, we
1812 may yet be able to determine that we can not overlap. But we
1813 also need to that we are far enough from the end not to overlap
1814 a following reference, so we do nothing with that for now. */
1815 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1817 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1822 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1824 c += (INTVAL (y) - INTVAL (x));
1825 return (xsize <= 0 || ysize <= 0
1826 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1829 if (GET_CODE (x) == CONST)
1831 if (GET_CODE (y) == CONST)
1832 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1833 ysize, canon_rtx (XEXP (y, 0)), c);
1835 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1838 if (GET_CODE (y) == CONST)
1839 return memrefs_conflict_p (xsize, x, ysize,
1840 canon_rtx (XEXP (y, 0)), c);
1843 return (xsize <= 0 || ysize <= 0
1844 || (rtx_equal_for_memref_p (x, y)
1845 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1852 /* Functions to compute memory dependencies.
1854 Since we process the insns in execution order, we can build tables
1855 to keep track of what registers are fixed (and not aliased), what registers
1856 are varying in known ways, and what registers are varying in unknown
1859 If both memory references are volatile, then there must always be a
1860 dependence between the two references, since their order can not be
1861 changed. A volatile and non-volatile reference can be interchanged
1864 A MEM_IN_STRUCT reference at a non-AND varying address can never
1865 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1866 also must allow AND addresses, because they may generate accesses
1867 outside the object being referenced. This is used to generate
1868 aligned addresses from unaligned addresses, for instance, the alpha
1869 storeqi_unaligned pattern. */
1871 /* Read dependence: X is read after read in MEM takes place. There can
1872 only be a dependence here if both reads are volatile. */
1875 read_dependence (const_rtx mem, const_rtx x)
1877 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1880 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1881 MEM2 is a reference to a structure at a varying address, or returns
1882 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1883 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1884 to decide whether or not an address may vary; it should return
1885 nonzero whenever variation is possible.
1886 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1889 fixed_scalar_and_varying_struct_p (const_rtx mem1, const_rtx mem2, rtx mem1_addr,
1891 bool (*varies_p) (const_rtx, bool))
1893 if (! flag_strict_aliasing)
1896 if (MEM_ALIAS_SET (mem2)
1897 && MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1898 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1899 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1903 if (MEM_ALIAS_SET (mem1)
1904 && MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1905 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1906 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1913 /* Returns nonzero if something about the mode or address format MEM1
1914 indicates that it might well alias *anything*. */
1917 aliases_everything_p (const_rtx mem)
1919 if (GET_CODE (XEXP (mem, 0)) == AND)
1920 /* If the address is an AND, it's very hard to know at what it is
1921 actually pointing. */
1927 /* Return true if we can determine that the fields referenced cannot
1928 overlap for any pair of objects. */
1931 nonoverlapping_component_refs_p (const_tree x, const_tree y)
1933 const_tree fieldx, fieldy, typex, typey, orig_y;
1937 /* The comparison has to be done at a common type, since we don't
1938 know how the inheritance hierarchy works. */
1942 fieldx = TREE_OPERAND (x, 1);
1943 typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx));
1948 fieldy = TREE_OPERAND (y, 1);
1949 typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy));
1954 y = TREE_OPERAND (y, 0);
1956 while (y && TREE_CODE (y) == COMPONENT_REF);
1958 x = TREE_OPERAND (x, 0);
1960 while (x && TREE_CODE (x) == COMPONENT_REF);
1961 /* Never found a common type. */
1965 /* If we're left with accessing different fields of a structure,
1967 if (TREE_CODE (typex) == RECORD_TYPE
1968 && fieldx != fieldy)
1971 /* The comparison on the current field failed. If we're accessing
1972 a very nested structure, look at the next outer level. */
1973 x = TREE_OPERAND (x, 0);
1974 y = TREE_OPERAND (y, 0);
1977 && TREE_CODE (x) == COMPONENT_REF
1978 && TREE_CODE (y) == COMPONENT_REF);
1983 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1986 decl_for_component_ref (tree x)
1990 x = TREE_OPERAND (x, 0);
1992 while (x && TREE_CODE (x) == COMPONENT_REF);
1994 return x && DECL_P (x) ? x : NULL_TREE;
1997 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1998 offset of the field reference. */
2001 adjust_offset_for_component_ref (tree x, rtx offset)
2003 HOST_WIDE_INT ioffset;
2008 ioffset = INTVAL (offset);
2011 tree offset = component_ref_field_offset (x);
2012 tree field = TREE_OPERAND (x, 1);
2014 if (! host_integerp (offset, 1))
2016 ioffset += (tree_low_cst (offset, 1)
2017 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
2020 x = TREE_OPERAND (x, 0);
2022 while (x && TREE_CODE (x) == COMPONENT_REF);
2024 return GEN_INT (ioffset);
2027 /* Return nonzero if we can determine the exprs corresponding to memrefs
2028 X and Y and they do not overlap. */
2031 nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
2033 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
2036 rtx moffsetx, moffsety;
2037 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
2039 /* Unless both have exprs, we can't tell anything. */
2040 if (exprx == 0 || expry == 0)
2043 /* If both are field references, we may be able to determine something. */
2044 if (TREE_CODE (exprx) == COMPONENT_REF
2045 && TREE_CODE (expry) == COMPONENT_REF
2046 && nonoverlapping_component_refs_p (exprx, expry))
2050 /* If the field reference test failed, look at the DECLs involved. */
2051 moffsetx = MEM_OFFSET (x);
2052 if (TREE_CODE (exprx) == COMPONENT_REF)
2054 if (TREE_CODE (expry) == VAR_DECL
2055 && POINTER_TYPE_P (TREE_TYPE (expry)))
2057 tree field = TREE_OPERAND (exprx, 1);
2058 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2059 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2064 tree t = decl_for_component_ref (exprx);
2067 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
2071 else if (INDIRECT_REF_P (exprx))
2073 exprx = TREE_OPERAND (exprx, 0);
2074 if (flag_argument_noalias < 2
2075 || TREE_CODE (exprx) != PARM_DECL)
2079 moffsety = MEM_OFFSET (y);
2080 if (TREE_CODE (expry) == COMPONENT_REF)
2082 if (TREE_CODE (exprx) == VAR_DECL
2083 && POINTER_TYPE_P (TREE_TYPE (exprx)))
2085 tree field = TREE_OPERAND (expry, 1);
2086 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2087 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2092 tree t = decl_for_component_ref (expry);
2095 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2099 else if (INDIRECT_REF_P (expry))
2101 expry = TREE_OPERAND (expry, 0);
2102 if (flag_argument_noalias < 2
2103 || TREE_CODE (expry) != PARM_DECL)
2107 if (! DECL_P (exprx) || ! DECL_P (expry))
2110 rtlx = DECL_RTL (exprx);
2111 rtly = DECL_RTL (expry);
2113 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2114 can't overlap unless they are the same because we never reuse that part
2115 of the stack frame used for locals for spilled pseudos. */
2116 if ((!MEM_P (rtlx) || !MEM_P (rtly))
2117 && ! rtx_equal_p (rtlx, rtly))
2120 /* Get the base and offsets of both decls. If either is a register, we
2121 know both are and are the same, so use that as the base. The only
2122 we can avoid overlap is if we can deduce that they are nonoverlapping
2123 pieces of that decl, which is very rare. */
2124 basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx;
2125 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2126 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2128 basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly;
2129 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2130 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2132 /* If the bases are different, we know they do not overlap if both
2133 are constants or if one is a constant and the other a pointer into the
2134 stack frame. Otherwise a different base means we can't tell if they
2136 if (! rtx_equal_p (basex, basey))
2137 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2138 || (CONSTANT_P (basex) && REG_P (basey)
2139 && REGNO_PTR_FRAME_P (REGNO (basey)))
2140 || (CONSTANT_P (basey) && REG_P (basex)
2141 && REGNO_PTR_FRAME_P (REGNO (basex))));
2143 sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2144 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2146 sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2147 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2150 /* If we have an offset for either memref, it can update the values computed
2153 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2155 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2157 /* If a memref has both a size and an offset, we can use the smaller size.
2158 We can't do this if the offset isn't known because we must view this
2159 memref as being anywhere inside the DECL's MEM. */
2160 if (MEM_SIZE (x) && moffsetx)
2161 sizex = INTVAL (MEM_SIZE (x));
2162 if (MEM_SIZE (y) && moffsety)
2163 sizey = INTVAL (MEM_SIZE (y));
2165 /* Put the values of the memref with the lower offset in X's values. */
2166 if (offsetx > offsety)
2168 tem = offsetx, offsetx = offsety, offsety = tem;
2169 tem = sizex, sizex = sizey, sizey = tem;
2172 /* If we don't know the size of the lower-offset value, we can't tell
2173 if they conflict. Otherwise, we do the test. */
2174 return sizex >= 0 && offsety >= offsetx + sizex;
2177 /* True dependence: X is read after store in MEM takes place. */
2180 true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x,
2181 bool (*varies) (const_rtx, bool))
2183 rtx x_addr, mem_addr;
2186 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2189 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2190 This is used in epilogue deallocation functions, and in cselib. */
2191 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2193 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2195 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2196 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2199 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2202 /* Read-only memory is by definition never modified, and therefore can't
2203 conflict with anything. We don't expect to find read-only set on MEM,
2204 but stupid user tricks can produce them, so don't die. */
2205 if (MEM_READONLY_P (x))
2208 if (nonoverlapping_memrefs_p (mem, x))
2211 if (mem_mode == VOIDmode)
2212 mem_mode = GET_MODE (mem);
2214 x_addr = get_addr (XEXP (x, 0));
2215 mem_addr = get_addr (XEXP (mem, 0));
2217 base = find_base_term (x_addr);
2218 if (base && (GET_CODE (base) == LABEL_REF
2219 || (GET_CODE (base) == SYMBOL_REF
2220 && CONSTANT_POOL_ADDRESS_P (base))))
2223 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2226 x_addr = canon_rtx (x_addr);
2227 mem_addr = canon_rtx (mem_addr);
2229 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2230 SIZE_FOR_MODE (x), x_addr, 0))
2233 if (aliases_everything_p (x))
2236 /* We cannot use aliases_everything_p to test MEM, since we must look
2237 at MEM_MODE, rather than GET_MODE (MEM). */
2238 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2241 /* In true_dependence we also allow BLKmode to alias anything. Why
2242 don't we do this in anti_dependence and output_dependence? */
2243 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2246 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2250 /* Canonical true dependence: X is read after store in MEM takes place.
2251 Variant of true_dependence which assumes MEM has already been
2252 canonicalized (hence we no longer do that here).
2253 The mem_addr argument has been added, since true_dependence computed
2254 this value prior to canonicalizing. */
2257 canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2258 const_rtx x, bool (*varies) (const_rtx, bool))
2262 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2265 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2266 This is used in epilogue deallocation functions. */
2267 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2269 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2271 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2272 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2275 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2278 /* Read-only memory is by definition never modified, and therefore can't
2279 conflict with anything. We don't expect to find read-only set on MEM,
2280 but stupid user tricks can produce them, so don't die. */
2281 if (MEM_READONLY_P (x))
2284 if (nonoverlapping_memrefs_p (x, mem))
2287 x_addr = get_addr (XEXP (x, 0));
2289 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2292 x_addr = canon_rtx (x_addr);
2293 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2294 SIZE_FOR_MODE (x), x_addr, 0))
2297 if (aliases_everything_p (x))
2300 /* We cannot use aliases_everything_p to test MEM, since we must look
2301 at MEM_MODE, rather than GET_MODE (MEM). */
2302 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2305 /* In true_dependence we also allow BLKmode to alias anything. Why
2306 don't we do this in anti_dependence and output_dependence? */
2307 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2310 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2314 /* Returns nonzero if a write to X might alias a previous read from
2315 (or, if WRITEP is nonzero, a write to) MEM. */
2318 write_dependence_p (const_rtx mem, const_rtx x, int writep)
2320 rtx x_addr, mem_addr;
2321 const_rtx fixed_scalar;
2324 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2327 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2328 This is used in epilogue deallocation functions. */
2329 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2331 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2333 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2334 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2337 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2340 /* A read from read-only memory can't conflict with read-write memory. */
2341 if (!writep && MEM_READONLY_P (mem))
2344 if (nonoverlapping_memrefs_p (x, mem))
2347 x_addr = get_addr (XEXP (x, 0));
2348 mem_addr = get_addr (XEXP (mem, 0));
2352 base = find_base_term (mem_addr);
2353 if (base && (GET_CODE (base) == LABEL_REF
2354 || (GET_CODE (base) == SYMBOL_REF
2355 && CONSTANT_POOL_ADDRESS_P (base))))
2359 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2363 x_addr = canon_rtx (x_addr);
2364 mem_addr = canon_rtx (mem_addr);
2366 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2367 SIZE_FOR_MODE (x), x_addr, 0))
2371 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2374 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2375 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2378 /* Anti dependence: X is written after read in MEM takes place. */
2381 anti_dependence (const_rtx mem, const_rtx x)
2383 return write_dependence_p (mem, x, /*writep=*/0);
2386 /* Output dependence: X is written after store in MEM takes place. */
2389 output_dependence (const_rtx mem, const_rtx x)
2391 return write_dependence_p (mem, x, /*writep=*/1);
2396 init_alias_target (void)
2400 memset (static_reg_base_value, 0, sizeof static_reg_base_value);
2402 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2403 /* Check whether this register can hold an incoming pointer
2404 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2405 numbers, so translate if necessary due to register windows. */
2406 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2407 && HARD_REGNO_MODE_OK (i, Pmode))
2408 static_reg_base_value[i]
2409 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2411 static_reg_base_value[STACK_POINTER_REGNUM]
2412 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2413 static_reg_base_value[ARG_POINTER_REGNUM]
2414 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2415 static_reg_base_value[FRAME_POINTER_REGNUM]
2416 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2417 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2418 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2419 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2423 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2424 to be memory reference. */
2425 static bool memory_modified;
2427 memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
2431 if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data))
2432 memory_modified = true;
2437 /* Return true when INSN possibly modify memory contents of MEM
2438 (i.e. address can be modified). */
2440 memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
2444 memory_modified = false;
2445 note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
2446 return memory_modified;
2449 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2453 init_alias_analysis (void)
2455 unsigned int maxreg = max_reg_num ();
2461 timevar_push (TV_ALIAS_ANALYSIS);
2463 reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER;
2464 reg_known_value = GGC_CNEWVEC (rtx, reg_known_value_size);
2465 reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size);
2467 /* If we have memory allocated from the previous run, use it. */
2468 if (old_reg_base_value)
2469 reg_base_value = old_reg_base_value;
2472 VEC_truncate (rtx, reg_base_value, 0);
2474 VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg);
2476 new_reg_base_value = XNEWVEC (rtx, maxreg);
2477 reg_seen = XNEWVEC (char, maxreg);
2479 /* The basic idea is that each pass through this loop will use the
2480 "constant" information from the previous pass to propagate alias
2481 information through another level of assignments.
2483 This could get expensive if the assignment chains are long. Maybe
2484 we should throttle the number of iterations, possibly based on
2485 the optimization level or flag_expensive_optimizations.
2487 We could propagate more information in the first pass by making use
2488 of DF_REG_DEF_COUNT to determine immediately that the alias information
2489 for a pseudo is "constant".
2491 A program with an uninitialized variable can cause an infinite loop
2492 here. Instead of doing a full dataflow analysis to detect such problems
2493 we just cap the number of iterations for the loop.
2495 The state of the arrays for the set chain in question does not matter
2496 since the program has undefined behavior. */
2501 /* Assume nothing will change this iteration of the loop. */
2504 /* We want to assign the same IDs each iteration of this loop, so
2505 start counting from zero each iteration of the loop. */
2508 /* We're at the start of the function each iteration through the
2509 loop, so we're copying arguments. */
2510 copying_arguments = true;
2512 /* Wipe the potential alias information clean for this pass. */
2513 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2515 /* Wipe the reg_seen array clean. */
2516 memset (reg_seen, 0, maxreg);
2518 /* Mark all hard registers which may contain an address.
2519 The stack, frame and argument pointers may contain an address.
2520 An argument register which can hold a Pmode value may contain
2521 an address even if it is not in BASE_REGS.
2523 The address expression is VOIDmode for an argument and
2524 Pmode for other registers. */
2526 memcpy (new_reg_base_value, static_reg_base_value,
2527 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2529 /* Walk the insns adding values to the new_reg_base_value array. */
2530 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2536 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2537 /* The prologue/epilogue insns are not threaded onto the
2538 insn chain until after reload has completed. Thus,
2539 there is no sense wasting time checking if INSN is in
2540 the prologue/epilogue until after reload has completed. */
2541 if (reload_completed
2542 && prologue_epilogue_contains (insn))
2546 /* If this insn has a noalias note, process it, Otherwise,
2547 scan for sets. A simple set will have no side effects
2548 which could change the base value of any other register. */
2550 if (GET_CODE (PATTERN (insn)) == SET
2551 && REG_NOTES (insn) != 0
2552 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2553 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2555 note_stores (PATTERN (insn), record_set, NULL);
2557 set = single_set (insn);
2560 && REG_P (SET_DEST (set))
2561 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2563 unsigned int regno = REGNO (SET_DEST (set));
2564 rtx src = SET_SRC (set);
2567 note = find_reg_equal_equiv_note (insn);
2568 if (note && REG_NOTE_KIND (note) == REG_EQUAL
2569 && DF_REG_DEF_COUNT (regno) != 1)
2572 if (note != NULL_RTX
2573 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2574 && ! rtx_varies_p (XEXP (note, 0), 1)
2575 && ! reg_overlap_mentioned_p (SET_DEST (set),
2578 set_reg_known_value (regno, XEXP (note, 0));
2579 set_reg_known_equiv_p (regno,
2580 REG_NOTE_KIND (note) == REG_EQUIV);
2582 else if (DF_REG_DEF_COUNT (regno) == 1
2583 && GET_CODE (src) == PLUS
2584 && REG_P (XEXP (src, 0))
2585 && (t = get_reg_known_value (REGNO (XEXP (src, 0))))
2586 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2588 t = plus_constant (t, INTVAL (XEXP (src, 1)));
2589 set_reg_known_value (regno, t);
2590 set_reg_known_equiv_p (regno, 0);
2592 else if (DF_REG_DEF_COUNT (regno) == 1
2593 && ! rtx_varies_p (src, 1))
2595 set_reg_known_value (regno, src);
2596 set_reg_known_equiv_p (regno, 0);
2600 else if (NOTE_P (insn)
2601 && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG)
2602 copying_arguments = false;
2605 /* Now propagate values from new_reg_base_value to reg_base_value. */
2606 gcc_assert (maxreg == (unsigned int) max_reg_num ());
2608 for (ui = 0; ui < maxreg; ui++)
2610 if (new_reg_base_value[ui]
2611 && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui)
2612 && ! rtx_equal_p (new_reg_base_value[ui],
2613 VEC_index (rtx, reg_base_value, ui)))
2615 VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]);
2620 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2622 /* Fill in the remaining entries. */
2623 for (i = 0; i < (int)reg_known_value_size; i++)
2624 if (reg_known_value[i] == 0)
2625 reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER];
2628 free (new_reg_base_value);
2629 new_reg_base_value = 0;
2632 timevar_pop (TV_ALIAS_ANALYSIS);
2636 end_alias_analysis (void)
2638 old_reg_base_value = reg_base_value;
2639 ggc_free (reg_known_value);
2640 reg_known_value = 0;
2641 reg_known_value_size = 0;
2642 free (reg_known_equiv_p);
2643 reg_known_equiv_p = 0;
2646 #include "gt-alias.h"