1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009 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 GTY(()) alias_set_entry {
132 /* The alias set number, as stored in MEM_ALIAS_SET. */
133 alias_set_type alias_set;
135 /* Nonzero if would have a child of zero: this effectively makes this
136 alias set the same as alias set zero. */
139 /* The children of the alias set. These are not just the immediate
140 children, but, in fact, all descendants. So, if we have:
142 struct T { struct S s; float f; }
144 continuing our example above, the children here will be all of
145 `int', `double', `float', and `struct S'. */
146 splay_tree GTY((param1_is (int), param2_is (int))) children;
148 typedef struct alias_set_entry *alias_set_entry;
150 static int rtx_equal_for_memref_p (const_rtx, const_rtx);
151 static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT);
152 static void record_set (rtx, const_rtx, void *);
153 static int base_alias_check (rtx, rtx, enum machine_mode,
155 static rtx find_base_value (rtx);
156 static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx);
157 static int insert_subset_children (splay_tree_node, void*);
158 static tree find_base_decl (tree);
159 static alias_set_entry get_alias_set_entry (alias_set_type);
160 static const_rtx fixed_scalar_and_varying_struct_p (const_rtx, const_rtx, rtx, rtx,
161 bool (*) (const_rtx, bool));
162 static int aliases_everything_p (const_rtx);
163 static bool nonoverlapping_component_refs_p (const_tree, const_tree);
164 static tree decl_for_component_ref (tree);
165 static rtx adjust_offset_for_component_ref (tree, rtx);
166 static int write_dependence_p (const_rtx, const_rtx, int);
168 static void memory_modified_1 (rtx, const_rtx, void *);
170 /* Set up all info needed to perform alias analysis on memory references. */
172 /* Returns the size in bytes of the mode of X. */
173 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
175 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
176 different alias sets. We ignore alias sets in functions making use
177 of variable arguments because the va_arg macros on some systems are
179 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
180 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
182 /* Cap the number of passes we make over the insns propagating alias
183 information through set chains. 10 is a completely arbitrary choice. */
184 #define MAX_ALIAS_LOOP_PASSES 10
186 /* reg_base_value[N] gives an address to which register N is related.
187 If all sets after the first add or subtract to the current value
188 or otherwise modify it so it does not point to a different top level
189 object, reg_base_value[N] is equal to the address part of the source
192 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
193 expressions represent certain special values: function arguments and
194 the stack, frame, and argument pointers.
196 The contents of an ADDRESS is not normally used, the mode of the
197 ADDRESS determines whether the ADDRESS is a function argument or some
198 other special value. Pointer equality, not rtx_equal_p, determines whether
199 two ADDRESS expressions refer to the same base address.
201 The only use of the contents of an ADDRESS is for determining if the
202 current function performs nonlocal memory memory references for the
203 purposes of marking the function as a constant function. */
205 static GTY(()) VEC(rtx,gc) *reg_base_value;
206 static rtx *new_reg_base_value;
208 /* We preserve the copy of old array around to avoid amount of garbage
209 produced. About 8% of garbage produced were attributed to this
211 static GTY((deletable)) VEC(rtx,gc) *old_reg_base_value;
213 /* Static hunks of RTL used by the aliasing code; these are initialized
214 once per function to avoid unnecessary RTL allocations. */
215 static GTY (()) rtx static_reg_base_value[FIRST_PSEUDO_REGISTER];
217 #define REG_BASE_VALUE(X) \
218 (REGNO (X) < VEC_length (rtx, reg_base_value) \
219 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
221 /* Vector indexed by N giving the initial (unchanging) value known for
222 pseudo-register N. This array is initialized in init_alias_analysis,
223 and does not change until end_alias_analysis is called. */
224 static GTY((length("reg_known_value_size"))) rtx *reg_known_value;
226 /* Indicates number of valid entries in reg_known_value. */
227 static GTY(()) unsigned int reg_known_value_size;
229 /* Vector recording for each reg_known_value whether it is due to a
230 REG_EQUIV note. Future passes (viz., reload) may replace the
231 pseudo with the equivalent expression and so we account for the
232 dependences that would be introduced if that happens.
234 The REG_EQUIV notes created in assign_parms may mention the arg
235 pointer, and there are explicit insns in the RTL that modify the
236 arg pointer. Thus we must ensure that such insns don't get
237 scheduled across each other because that would invalidate the
238 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
239 wrong, but solving the problem in the scheduler will likely give
240 better code, so we do it here. */
241 static bool *reg_known_equiv_p;
243 /* True when scanning insns from the start of the rtl to the
244 NOTE_INSN_FUNCTION_BEG note. */
245 static bool copying_arguments;
247 DEF_VEC_P(alias_set_entry);
248 DEF_VEC_ALLOC_P(alias_set_entry,gc);
250 /* The splay-tree used to store the various alias set entries. */
251 static GTY (()) VEC(alias_set_entry,gc) *alias_sets;
253 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
254 such an entry, or NULL otherwise. */
256 static inline alias_set_entry
257 get_alias_set_entry (alias_set_type alias_set)
259 return VEC_index (alias_set_entry, alias_sets, alias_set);
262 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
263 the two MEMs cannot alias each other. */
266 mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2)
268 /* Perform a basic sanity check. Namely, that there are no alias sets
269 if we're not using strict aliasing. This helps to catch bugs
270 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
271 where a MEM is allocated in some way other than by the use of
272 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
273 use alias sets to indicate that spilled registers cannot alias each
274 other, we might need to remove this check. */
275 gcc_assert (flag_strict_aliasing
276 || (!MEM_ALIAS_SET (mem1) && !MEM_ALIAS_SET (mem2)));
278 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
281 /* Insert the NODE into the splay tree given by DATA. Used by
282 record_alias_subset via splay_tree_foreach. */
285 insert_subset_children (splay_tree_node node, void *data)
287 splay_tree_insert ((splay_tree) data, node->key, node->value);
292 /* Return true if the first alias set is a subset of the second. */
295 alias_set_subset_of (alias_set_type set1, alias_set_type set2)
299 /* Everything is a subset of the "aliases everything" set. */
303 /* Otherwise, check if set1 is a subset of set2. */
304 ase = get_alias_set_entry (set2);
306 && ((ase->has_zero_child && set1 == 0)
307 || splay_tree_lookup (ase->children,
308 (splay_tree_key) set1)))
313 /* Return 1 if the two specified alias sets may conflict. */
316 alias_sets_conflict_p (alias_set_type set1, alias_set_type set2)
321 if (alias_sets_must_conflict_p (set1, set2))
324 /* See if the first alias set is a subset of the second. */
325 ase = get_alias_set_entry (set1);
327 && (ase->has_zero_child
328 || splay_tree_lookup (ase->children,
329 (splay_tree_key) set2)))
332 /* Now do the same, but with the alias sets reversed. */
333 ase = get_alias_set_entry (set2);
335 && (ase->has_zero_child
336 || splay_tree_lookup (ase->children,
337 (splay_tree_key) set1)))
340 /* The two alias sets are distinct and neither one is the
341 child of the other. Therefore, they cannot conflict. */
346 walk_mems_2 (rtx *x, rtx mem)
350 if (alias_sets_conflict_p (MEM_ALIAS_SET(*x), MEM_ALIAS_SET(mem)))
359 walk_mems_1 (rtx *x, rtx *pat)
363 /* Visit all MEMs in *PAT and check indepedence. */
364 if (for_each_rtx (pat, (rtx_function) walk_mems_2, *x))
365 /* Indicate that dependence was determined and stop traversal. */
373 /* Return 1 if two specified instructions have mem expr with conflict alias sets*/
375 insn_alias_sets_conflict_p (rtx insn1, rtx insn2)
377 /* For each pair of MEMs in INSN1 and INSN2 check their independence. */
378 return for_each_rtx (&PATTERN (insn1), (rtx_function) walk_mems_1,
382 /* Return 1 if the two specified alias sets will always conflict. */
385 alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2)
387 if (set1 == 0 || set2 == 0 || set1 == set2)
393 /* Return 1 if any MEM object of type T1 will always conflict (using the
394 dependency routines in this file) with any MEM object of type T2.
395 This is used when allocating temporary storage. If T1 and/or T2 are
396 NULL_TREE, it means we know nothing about the storage. */
399 objects_must_conflict_p (tree t1, tree t2)
401 alias_set_type set1, set2;
403 /* If neither has a type specified, we don't know if they'll conflict
404 because we may be using them to store objects of various types, for
405 example the argument and local variables areas of inlined functions. */
406 if (t1 == 0 && t2 == 0)
409 /* If they are the same type, they must conflict. */
411 /* Likewise if both are volatile. */
412 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
415 set1 = t1 ? get_alias_set (t1) : 0;
416 set2 = t2 ? get_alias_set (t2) : 0;
418 /* We can't use alias_sets_conflict_p because we must make sure
419 that every subtype of t1 will conflict with every subtype of
420 t2 for which a pair of subobjects of these respective subtypes
421 overlaps on the stack. */
422 return alias_sets_must_conflict_p (set1, set2);
425 /* T is an expression with pointer type. Find the DECL on which this
426 expression is based. (For example, in `a[i]' this would be `a'.)
427 If there is no such DECL, or a unique decl cannot be determined,
428 NULL_TREE is returned. */
431 find_base_decl (tree t)
435 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
438 /* If this is a declaration, return it. If T is based on a restrict
439 qualified decl, return that decl. */
442 if (TREE_CODE (t) == VAR_DECL && DECL_BASED_ON_RESTRICT_P (t))
443 t = DECL_GET_RESTRICT_BASE (t);
447 /* Handle general expressions. It would be nice to deal with
448 COMPONENT_REFs here. If we could tell that `a' and `b' were the
449 same, then `a->f' and `b->f' are also the same. */
450 switch (TREE_CODE_CLASS (TREE_CODE (t)))
453 return find_base_decl (TREE_OPERAND (t, 0));
456 /* Return 0 if found in neither or both are the same. */
457 d0 = find_base_decl (TREE_OPERAND (t, 0));
458 d1 = find_base_decl (TREE_OPERAND (t, 1));
473 /* Return true if all nested component references handled by
474 get_inner_reference in T are such that we should use the alias set
475 provided by the object at the heart of T.
477 This is true for non-addressable components (which don't have their
478 own alias set), as well as components of objects in alias set zero.
479 This later point is a special case wherein we wish to override the
480 alias set used by the component, but we don't have per-FIELD_DECL
481 assignable alias sets. */
484 component_uses_parent_alias_set (const_tree t)
488 /* If we're at the end, it vacuously uses its own alias set. */
489 if (!handled_component_p (t))
492 switch (TREE_CODE (t))
495 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
500 case ARRAY_RANGE_REF:
501 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))))
510 /* Bitfields and casts are never addressable. */
514 t = TREE_OPERAND (t, 0);
515 if (get_alias_set (TREE_TYPE (t)) == 0)
520 /* Return the alias set for the memory pointed to by T, which may be
521 either a type or an expression. Return -1 if there is nothing
522 special about dereferencing T. */
524 static alias_set_type
525 get_deref_alias_set_1 (tree t)
527 /* If we're not doing any alias analysis, just assume everything
528 aliases everything else. */
529 if (!flag_strict_aliasing)
534 tree decl = find_base_decl (t);
536 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
538 /* If we haven't computed the actual alias set, do it now. */
539 if (DECL_POINTER_ALIAS_SET (decl) == -2)
541 tree pointed_to_type = TREE_TYPE (TREE_TYPE (decl));
543 /* No two restricted pointers can point at the same thing.
544 However, a restricted pointer can point at the same thing
545 as an unrestricted pointer, if that unrestricted pointer
546 is based on the restricted pointer. So, we make the
547 alias set for the restricted pointer a subset of the
548 alias set for the type pointed to by the type of the
550 alias_set_type pointed_to_alias_set
551 = get_alias_set (pointed_to_type);
553 if (pointed_to_alias_set == 0)
554 /* It's not legal to make a subset of alias set zero. */
555 DECL_POINTER_ALIAS_SET (decl) = 0;
556 else if (AGGREGATE_TYPE_P (pointed_to_type))
557 /* For an aggregate, we must treat the restricted
558 pointer the same as an ordinary pointer. If we
559 were to make the type pointed to by the
560 restricted pointer a subset of the pointed-to
561 type, then we would believe that other subsets
562 of the pointed-to type (such as fields of that
563 type) do not conflict with the type pointed to
564 by the restricted pointer. */
565 DECL_POINTER_ALIAS_SET (decl)
566 = pointed_to_alias_set;
569 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
570 record_alias_subset (pointed_to_alias_set,
571 DECL_POINTER_ALIAS_SET (decl));
575 /* We use the alias set indicated in the declaration. */
576 return DECL_POINTER_ALIAS_SET (decl);
579 /* Now all we care about is the type. */
583 /* If we have an INDIRECT_REF via a void pointer, we don't
584 know anything about what that might alias. Likewise if the
585 pointer is marked that way. */
586 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE
587 || TYPE_REF_CAN_ALIAS_ALL (t))
593 /* Return the alias set for the memory pointed to by T, which may be
594 either a type or an expression. */
597 get_deref_alias_set (tree t)
599 alias_set_type set = get_deref_alias_set_1 (t);
601 /* Fall back to the alias-set of the pointed-to type. */
606 set = get_alias_set (TREE_TYPE (t));
612 /* Return the alias set for T, which may be either a type or an
613 expression. Call language-specific routine for help, if needed. */
616 get_alias_set (tree t)
620 /* If we're not doing any alias analysis, just assume everything
621 aliases everything else. Also return 0 if this or its type is
623 if (! flag_strict_aliasing || t == error_mark_node
625 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
628 /* We can be passed either an expression or a type. This and the
629 language-specific routine may make mutually-recursive calls to each other
630 to figure out what to do. At each juncture, we see if this is a tree
631 that the language may need to handle specially. First handle things that
637 /* Remove any nops, then give the language a chance to do
638 something with this tree before we look at it. */
640 set = lang_hooks.get_alias_set (t);
644 /* First see if the actual object referenced is an INDIRECT_REF from a
645 restrict-qualified pointer or a "void *". */
646 while (handled_component_p (inner))
648 inner = TREE_OPERAND (inner, 0);
652 if (INDIRECT_REF_P (inner))
654 set = get_deref_alias_set_1 (TREE_OPERAND (inner, 0));
659 /* Otherwise, pick up the outermost object that we could have a pointer
660 to, processing conversions as above. */
661 while (component_uses_parent_alias_set (t))
663 t = TREE_OPERAND (t, 0);
667 /* If we've already determined the alias set for a decl, just return
668 it. This is necessary for C++ anonymous unions, whose component
669 variables don't look like union members (boo!). */
670 if (TREE_CODE (t) == VAR_DECL
671 && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t)))
672 return MEM_ALIAS_SET (DECL_RTL (t));
674 /* Now all we care about is the type. */
678 /* Variant qualifiers don't affect the alias set, so get the main
679 variant. Always use the canonical type as well.
680 If this is a type with a known alias set, return it. */
681 t = TYPE_MAIN_VARIANT (t);
682 if (TYPE_CANONICAL (t))
683 t = TYPE_CANONICAL (t);
684 if (TYPE_ALIAS_SET_KNOWN_P (t))
685 return TYPE_ALIAS_SET (t);
687 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
688 if (!COMPLETE_TYPE_P (t))
690 /* For arrays with unknown size the conservative answer is the
691 alias set of the element type. */
692 if (TREE_CODE (t) == ARRAY_TYPE)
693 return get_alias_set (TREE_TYPE (t));
695 /* But return zero as a conservative answer for incomplete types. */
699 /* See if the language has special handling for this type. */
700 set = lang_hooks.get_alias_set (t);
704 /* There are no objects of FUNCTION_TYPE, so there's no point in
705 using up an alias set for them. (There are, of course, pointers
706 and references to functions, but that's different.) */
707 else if (TREE_CODE (t) == FUNCTION_TYPE
708 || TREE_CODE (t) == METHOD_TYPE)
711 /* Unless the language specifies otherwise, let vector types alias
712 their components. This avoids some nasty type punning issues in
713 normal usage. And indeed lets vectors be treated more like an
715 else if (TREE_CODE (t) == VECTOR_TYPE)
716 set = get_alias_set (TREE_TYPE (t));
718 /* Unless the language specifies otherwise, treat array types the
719 same as their components. This avoids the asymmetry we get
720 through recording the components. Consider accessing a
721 character(kind=1) through a reference to a character(kind=1)[1:1].
722 Or consider if we want to assign integer(kind=4)[0:D.1387] and
723 integer(kind=4)[4] the same alias set or not.
724 Just be pragmatic here and make sure the array and its element
725 type get the same alias set assigned. */
726 else if (TREE_CODE (t) == ARRAY_TYPE
727 && !TYPE_NONALIASED_COMPONENT (t))
728 set = get_alias_set (TREE_TYPE (t));
731 /* Otherwise make a new alias set for this type. */
732 set = new_alias_set ();
734 TYPE_ALIAS_SET (t) = set;
736 /* If this is an aggregate type, we must record any component aliasing
738 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
739 record_component_aliases (t);
744 /* Return a brand-new alias set. */
749 if (flag_strict_aliasing)
752 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
753 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
754 return VEC_length (alias_set_entry, alias_sets) - 1;
760 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
761 not everything that aliases SUPERSET also aliases SUBSET. For example,
762 in C, a store to an `int' can alias a load of a structure containing an
763 `int', and vice versa. But it can't alias a load of a 'double' member
764 of the same structure. Here, the structure would be the SUPERSET and
765 `int' the SUBSET. This relationship is also described in the comment at
766 the beginning of this file.
768 This function should be called only once per SUPERSET/SUBSET pair.
770 It is illegal for SUPERSET to be zero; everything is implicitly a
771 subset of alias set zero. */
774 record_alias_subset (alias_set_type superset, alias_set_type subset)
776 alias_set_entry superset_entry;
777 alias_set_entry subset_entry;
779 /* It is possible in complex type situations for both sets to be the same,
780 in which case we can ignore this operation. */
781 if (superset == subset)
784 gcc_assert (superset);
786 superset_entry = get_alias_set_entry (superset);
787 if (superset_entry == 0)
789 /* Create an entry for the SUPERSET, so that we have a place to
790 attach the SUBSET. */
791 superset_entry = GGC_NEW (struct alias_set_entry);
792 superset_entry->alias_set = superset;
793 superset_entry->children
794 = splay_tree_new_ggc (splay_tree_compare_ints);
795 superset_entry->has_zero_child = 0;
796 VEC_replace (alias_set_entry, alias_sets, superset, superset_entry);
800 superset_entry->has_zero_child = 1;
803 subset_entry = get_alias_set_entry (subset);
804 /* If there is an entry for the subset, enter all of its children
805 (if they are not already present) as children of the SUPERSET. */
808 if (subset_entry->has_zero_child)
809 superset_entry->has_zero_child = 1;
811 splay_tree_foreach (subset_entry->children, insert_subset_children,
812 superset_entry->children);
815 /* Enter the SUBSET itself as a child of the SUPERSET. */
816 splay_tree_insert (superset_entry->children,
817 (splay_tree_key) subset, 0);
821 /* Record that component types of TYPE, if any, are part of that type for
822 aliasing purposes. For record types, we only record component types
823 for fields that are not marked non-addressable. For array types, we
824 only record the component type if it is not marked non-aliased. */
827 record_component_aliases (tree type)
829 alias_set_type superset = get_alias_set (type);
835 switch (TREE_CODE (type))
839 case QUAL_UNION_TYPE:
840 /* Recursively record aliases for the base classes, if there are any. */
841 if (TYPE_BINFO (type))
844 tree binfo, base_binfo;
846 for (binfo = TYPE_BINFO (type), i = 0;
847 BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
848 record_alias_subset (superset,
849 get_alias_set (BINFO_TYPE (base_binfo)));
851 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
852 if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
853 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
857 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
860 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
868 /* Allocate an alias set for use in storing and reading from the varargs
871 static GTY(()) alias_set_type varargs_set = -1;
874 get_varargs_alias_set (void)
877 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
878 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
879 consistently use the varargs alias set for loads from the varargs
880 area. So don't use it anywhere. */
883 if (varargs_set == -1)
884 varargs_set = new_alias_set ();
890 /* Likewise, but used for the fixed portions of the frame, e.g., register
893 static GTY(()) alias_set_type frame_set = -1;
896 get_frame_alias_set (void)
899 frame_set = new_alias_set ();
904 /* Inside SRC, the source of a SET, find a base address. */
907 find_base_value (rtx src)
911 #if defined (FIND_BASE_TERM)
912 /* Try machine-dependent ways to find the base term. */
913 src = FIND_BASE_TERM (src);
916 switch (GET_CODE (src))
924 /* At the start of a function, argument registers have known base
925 values which may be lost later. Returning an ADDRESS
926 expression here allows optimization based on argument values
927 even when the argument registers are used for other purposes. */
928 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
929 return new_reg_base_value[regno];
931 /* If a pseudo has a known base value, return it. Do not do this
932 for non-fixed hard regs since it can result in a circular
933 dependency chain for registers which have values at function entry.
935 The test above is not sufficient because the scheduler may move
936 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
937 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
938 && regno < VEC_length (rtx, reg_base_value))
940 /* If we're inside init_alias_analysis, use new_reg_base_value
941 to reduce the number of relaxation iterations. */
942 if (new_reg_base_value && new_reg_base_value[regno]
943 && DF_REG_DEF_COUNT (regno) == 1)
944 return new_reg_base_value[regno];
946 if (VEC_index (rtx, reg_base_value, regno))
947 return VEC_index (rtx, reg_base_value, regno);
953 /* Check for an argument passed in memory. Only record in the
954 copying-arguments block; it is too hard to track changes
956 if (copying_arguments
957 && (XEXP (src, 0) == arg_pointer_rtx
958 || (GET_CODE (XEXP (src, 0)) == PLUS
959 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
960 return gen_rtx_ADDRESS (VOIDmode, src);
965 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
968 /* ... fall through ... */
973 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
975 /* If either operand is a REG that is a known pointer, then it
977 if (REG_P (src_0) && REG_POINTER (src_0))
978 return find_base_value (src_0);
979 if (REG_P (src_1) && REG_POINTER (src_1))
980 return find_base_value (src_1);
982 /* If either operand is a REG, then see if we already have
983 a known value for it. */
986 temp = find_base_value (src_0);
993 temp = find_base_value (src_1);
998 /* If either base is named object or a special address
999 (like an argument or stack reference), then use it for the
1002 && (GET_CODE (src_0) == SYMBOL_REF
1003 || GET_CODE (src_0) == LABEL_REF
1004 || (GET_CODE (src_0) == ADDRESS
1005 && GET_MODE (src_0) != VOIDmode)))
1009 && (GET_CODE (src_1) == SYMBOL_REF
1010 || GET_CODE (src_1) == LABEL_REF
1011 || (GET_CODE (src_1) == ADDRESS
1012 && GET_MODE (src_1) != VOIDmode)))
1015 /* Guess which operand is the base address:
1016 If either operand is a symbol, then it is the base. If
1017 either operand is a CONST_INT, then the other is the base. */
1018 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
1019 return find_base_value (src_0);
1020 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
1021 return find_base_value (src_1);
1027 /* The standard form is (lo_sum reg sym) so look only at the
1029 return find_base_value (XEXP (src, 1));
1032 /* If the second operand is constant set the base
1033 address to the first operand. */
1034 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
1035 return find_base_value (XEXP (src, 0));
1039 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
1049 return find_base_value (XEXP (src, 0));
1052 case SIGN_EXTEND: /* used for NT/Alpha pointers */
1054 rtx temp = find_base_value (XEXP (src, 0));
1056 if (temp != 0 && CONSTANT_P (temp))
1057 temp = convert_memory_address (Pmode, temp);
1069 /* Called from init_alias_analysis indirectly through note_stores. */
1071 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1072 register N has been set in this function. */
1073 static char *reg_seen;
1075 /* Addresses which are known not to alias anything else are identified
1076 by a unique integer. */
1077 static int unique_id;
1080 record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED)
1089 regno = REGNO (dest);
1091 gcc_assert (regno < VEC_length (rtx, reg_base_value));
1093 /* If this spans multiple hard registers, then we must indicate that every
1094 register has an unusable value. */
1095 if (regno < FIRST_PSEUDO_REGISTER)
1096 n = hard_regno_nregs[regno][GET_MODE (dest)];
1103 reg_seen[regno + n] = 1;
1104 new_reg_base_value[regno + n] = 0;
1111 /* A CLOBBER wipes out any old value but does not prevent a previously
1112 unset register from acquiring a base address (i.e. reg_seen is not
1114 if (GET_CODE (set) == CLOBBER)
1116 new_reg_base_value[regno] = 0;
1119 src = SET_SRC (set);
1123 if (reg_seen[regno])
1125 new_reg_base_value[regno] = 0;
1128 reg_seen[regno] = 1;
1129 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
1130 GEN_INT (unique_id++));
1134 /* If this is not the first set of REGNO, see whether the new value
1135 is related to the old one. There are two cases of interest:
1137 (1) The register might be assigned an entirely new value
1138 that has the same base term as the original set.
1140 (2) The set might be a simple self-modification that
1141 cannot change REGNO's base value.
1143 If neither case holds, reject the original base value as invalid.
1144 Note that the following situation is not detected:
1146 extern int x, y; int *p = &x; p += (&y-&x);
1148 ANSI C does not allow computing the difference of addresses
1149 of distinct top level objects. */
1150 if (new_reg_base_value[regno] != 0
1151 && find_base_value (src) != new_reg_base_value[regno])
1152 switch (GET_CODE (src))
1156 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1157 new_reg_base_value[regno] = 0;
1160 /* If the value we add in the PLUS is also a valid base value,
1161 this might be the actual base value, and the original value
1164 rtx other = NULL_RTX;
1166 if (XEXP (src, 0) == dest)
1167 other = XEXP (src, 1);
1168 else if (XEXP (src, 1) == dest)
1169 other = XEXP (src, 0);
1171 if (! other || find_base_value (other))
1172 new_reg_base_value[regno] = 0;
1176 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
1177 new_reg_base_value[regno] = 0;
1180 new_reg_base_value[regno] = 0;
1183 /* If this is the first set of a register, record the value. */
1184 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1185 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1186 new_reg_base_value[regno] = find_base_value (src);
1188 reg_seen[regno] = 1;
1191 /* If a value is known for REGNO, return it. */
1194 get_reg_known_value (unsigned int regno)
1196 if (regno >= FIRST_PSEUDO_REGISTER)
1198 regno -= FIRST_PSEUDO_REGISTER;
1199 if (regno < reg_known_value_size)
1200 return reg_known_value[regno];
1208 set_reg_known_value (unsigned int regno, rtx val)
1210 if (regno >= FIRST_PSEUDO_REGISTER)
1212 regno -= FIRST_PSEUDO_REGISTER;
1213 if (regno < reg_known_value_size)
1214 reg_known_value[regno] = val;
1218 /* Similarly for reg_known_equiv_p. */
1221 get_reg_known_equiv_p (unsigned int regno)
1223 if (regno >= FIRST_PSEUDO_REGISTER)
1225 regno -= FIRST_PSEUDO_REGISTER;
1226 if (regno < reg_known_value_size)
1227 return reg_known_equiv_p[regno];
1233 set_reg_known_equiv_p (unsigned int regno, bool val)
1235 if (regno >= FIRST_PSEUDO_REGISTER)
1237 regno -= FIRST_PSEUDO_REGISTER;
1238 if (regno < reg_known_value_size)
1239 reg_known_equiv_p[regno] = val;
1244 /* Returns a canonical version of X, from the point of view alias
1245 analysis. (For example, if X is a MEM whose address is a register,
1246 and the register has a known value (say a SYMBOL_REF), then a MEM
1247 whose address is the SYMBOL_REF is returned.) */
1252 /* Recursively look for equivalences. */
1253 if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER)
1255 rtx t = get_reg_known_value (REGNO (x));
1259 return canon_rtx (t);
1262 if (GET_CODE (x) == PLUS)
1264 rtx x0 = canon_rtx (XEXP (x, 0));
1265 rtx x1 = canon_rtx (XEXP (x, 1));
1267 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1269 if (GET_CODE (x0) == CONST_INT)
1270 return plus_constant (x1, INTVAL (x0));
1271 else if (GET_CODE (x1) == CONST_INT)
1272 return plus_constant (x0, INTVAL (x1));
1273 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1277 /* This gives us much better alias analysis when called from
1278 the loop optimizer. Note we want to leave the original
1279 MEM alone, but need to return the canonicalized MEM with
1280 all the flags with their original values. */
1282 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1287 /* Return 1 if X and Y are identical-looking rtx's.
1288 Expect that X and Y has been already canonicalized.
1290 We use the data in reg_known_value above to see if two registers with
1291 different numbers are, in fact, equivalent. */
1294 rtx_equal_for_memref_p (const_rtx x, const_rtx y)
1301 if (x == 0 && y == 0)
1303 if (x == 0 || y == 0)
1309 code = GET_CODE (x);
1310 /* Rtx's of different codes cannot be equal. */
1311 if (code != GET_CODE (y))
1314 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1315 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1317 if (GET_MODE (x) != GET_MODE (y))
1320 /* Some RTL can be compared without a recursive examination. */
1324 return REGNO (x) == REGNO (y);
1327 return XEXP (x, 0) == XEXP (y, 0);
1330 return XSTR (x, 0) == XSTR (y, 0);
1336 /* There's no need to compare the contents of CONST_DOUBLEs or
1337 CONST_INTs because pointer equality is a good enough
1338 comparison for these nodes. */
1345 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1347 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1348 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1349 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1350 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1351 /* For commutative operations, the RTX match if the operand match in any
1352 order. Also handle the simple binary and unary cases without a loop. */
1353 if (COMMUTATIVE_P (x))
1355 rtx xop0 = canon_rtx (XEXP (x, 0));
1356 rtx yop0 = canon_rtx (XEXP (y, 0));
1357 rtx yop1 = canon_rtx (XEXP (y, 1));
1359 return ((rtx_equal_for_memref_p (xop0, yop0)
1360 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1361 || (rtx_equal_for_memref_p (xop0, yop1)
1362 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1364 else if (NON_COMMUTATIVE_P (x))
1366 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1367 canon_rtx (XEXP (y, 0)))
1368 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1369 canon_rtx (XEXP (y, 1))));
1371 else if (UNARY_P (x))
1372 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1373 canon_rtx (XEXP (y, 0)));
1375 /* Compare the elements. If any pair of corresponding elements
1376 fail to match, return 0 for the whole things.
1378 Limit cases to types which actually appear in addresses. */
1380 fmt = GET_RTX_FORMAT (code);
1381 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1386 if (XINT (x, i) != XINT (y, i))
1391 /* Two vectors must have the same length. */
1392 if (XVECLEN (x, i) != XVECLEN (y, i))
1395 /* And the corresponding elements must match. */
1396 for (j = 0; j < XVECLEN (x, i); j++)
1397 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1398 canon_rtx (XVECEXP (y, i, j))) == 0)
1403 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1404 canon_rtx (XEXP (y, i))) == 0)
1408 /* This can happen for asm operands. */
1410 if (strcmp (XSTR (x, i), XSTR (y, i)))
1414 /* This can happen for an asm which clobbers memory. */
1418 /* It is believed that rtx's at this level will never
1419 contain anything but integers and other rtx's,
1420 except for within LABEL_REFs and SYMBOL_REFs. */
1429 find_base_term (rtx x)
1432 struct elt_loc_list *l;
1434 #if defined (FIND_BASE_TERM)
1435 /* Try machine-dependent ways to find the base term. */
1436 x = FIND_BASE_TERM (x);
1439 switch (GET_CODE (x))
1442 return REG_BASE_VALUE (x);
1445 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1455 return find_base_term (XEXP (x, 0));
1458 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1460 rtx temp = find_base_term (XEXP (x, 0));
1462 if (temp != 0 && CONSTANT_P (temp))
1463 temp = convert_memory_address (Pmode, temp);
1469 val = CSELIB_VAL_PTR (x);
1472 for (l = val->locs; l; l = l->next)
1473 if ((x = find_base_term (l->loc)) != 0)
1478 /* The standard form is (lo_sum reg sym) so look only at the
1480 return find_base_term (XEXP (x, 1));
1484 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1490 rtx tmp1 = XEXP (x, 0);
1491 rtx tmp2 = XEXP (x, 1);
1493 /* This is a little bit tricky since we have to determine which of
1494 the two operands represents the real base address. Otherwise this
1495 routine may return the index register instead of the base register.
1497 That may cause us to believe no aliasing was possible, when in
1498 fact aliasing is possible.
1500 We use a few simple tests to guess the base register. Additional
1501 tests can certainly be added. For example, if one of the operands
1502 is a shift or multiply, then it must be the index register and the
1503 other operand is the base register. */
1505 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1506 return find_base_term (tmp2);
1508 /* If either operand is known to be a pointer, then use it
1509 to determine the base term. */
1510 if (REG_P (tmp1) && REG_POINTER (tmp1))
1511 return find_base_term (tmp1);
1513 if (REG_P (tmp2) && REG_POINTER (tmp2))
1514 return find_base_term (tmp2);
1516 /* Neither operand was known to be a pointer. Go ahead and find the
1517 base term for both operands. */
1518 tmp1 = find_base_term (tmp1);
1519 tmp2 = find_base_term (tmp2);
1521 /* If either base term is named object or a special address
1522 (like an argument or stack reference), then use it for the
1525 && (GET_CODE (tmp1) == SYMBOL_REF
1526 || GET_CODE (tmp1) == LABEL_REF
1527 || (GET_CODE (tmp1) == ADDRESS
1528 && GET_MODE (tmp1) != VOIDmode)))
1532 && (GET_CODE (tmp2) == SYMBOL_REF
1533 || GET_CODE (tmp2) == LABEL_REF
1534 || (GET_CODE (tmp2) == ADDRESS
1535 && GET_MODE (tmp2) != VOIDmode)))
1538 /* We could not determine which of the two operands was the
1539 base register and which was the index. So we can determine
1540 nothing from the base alias check. */
1545 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1546 return find_base_term (XEXP (x, 0));
1558 /* Return 0 if the addresses X and Y are known to point to different
1559 objects, 1 if they might be pointers to the same object. */
1562 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1563 enum machine_mode y_mode)
1565 rtx x_base = find_base_term (x);
1566 rtx y_base = find_base_term (y);
1568 /* If the address itself has no known base see if a known equivalent
1569 value has one. If either address still has no known base, nothing
1570 is known about aliasing. */
1575 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1578 x_base = find_base_term (x_c);
1586 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1589 y_base = find_base_term (y_c);
1594 /* If the base addresses are equal nothing is known about aliasing. */
1595 if (rtx_equal_p (x_base, y_base))
1598 /* The base addresses are different expressions. If they are not accessed
1599 via AND, there is no conflict. We can bring knowledge of object
1600 alignment into play here. For example, on alpha, "char a, b;" can
1601 alias one another, though "char a; long b;" cannot. AND addesses may
1602 implicitly alias surrounding objects; i.e. unaligned access in DImode
1603 via AND address can alias all surrounding object types except those
1604 with aligment 8 or higher. */
1605 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1607 if (GET_CODE (x) == AND
1608 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1609 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1611 if (GET_CODE (y) == AND
1612 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1613 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1616 /* Differing symbols not accessed via AND never alias. */
1617 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1620 /* If one address is a stack reference there can be no alias:
1621 stack references using different base registers do not alias,
1622 a stack reference can not alias a parameter, and a stack reference
1623 can not alias a global. */
1624 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1625 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1628 if (! flag_argument_noalias)
1631 if (flag_argument_noalias > 1)
1634 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1635 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1638 /* Convert the address X into something we can use. This is done by returning
1639 it unchanged unless it is a value; in the latter case we call cselib to get
1640 a more useful rtx. */
1646 struct elt_loc_list *l;
1648 if (GET_CODE (x) != VALUE)
1650 v = CSELIB_VAL_PTR (x);
1653 for (l = v->locs; l; l = l->next)
1654 if (CONSTANT_P (l->loc))
1656 for (l = v->locs; l; l = l->next)
1657 if (!REG_P (l->loc) && !MEM_P (l->loc))
1660 return v->locs->loc;
1665 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1666 where SIZE is the size in bytes of the memory reference. If ADDR
1667 is not modified by the memory reference then ADDR is returned. */
1670 addr_side_effect_eval (rtx addr, int size, int n_refs)
1674 switch (GET_CODE (addr))
1677 offset = (n_refs + 1) * size;
1680 offset = -(n_refs + 1) * size;
1683 offset = n_refs * size;
1686 offset = -n_refs * size;
1694 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1697 addr = XEXP (addr, 0);
1698 addr = canon_rtx (addr);
1703 /* Return nonzero if X and Y (memory addresses) could reference the
1704 same location in memory. C is an offset accumulator. When
1705 C is nonzero, we are testing aliases between X and Y + C.
1706 XSIZE is the size in bytes of the X reference,
1707 similarly YSIZE is the size in bytes for Y.
1708 Expect that canon_rtx has been already called for X and Y.
1710 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1711 referenced (the reference was BLKmode), so make the most pessimistic
1714 If XSIZE or YSIZE is negative, we may access memory outside the object
1715 being referenced as a side effect. This can happen when using AND to
1716 align memory references, as is done on the Alpha.
1718 Nice to notice that varying addresses cannot conflict with fp if no
1719 local variables had their addresses taken, but that's too hard now. */
1722 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1724 if (GET_CODE (x) == VALUE)
1726 if (GET_CODE (y) == VALUE)
1728 if (GET_CODE (x) == HIGH)
1730 else if (GET_CODE (x) == LO_SUM)
1733 x = addr_side_effect_eval (x, xsize, 0);
1734 if (GET_CODE (y) == HIGH)
1736 else if (GET_CODE (y) == LO_SUM)
1739 y = addr_side_effect_eval (y, ysize, 0);
1741 if (rtx_equal_for_memref_p (x, y))
1743 if (xsize <= 0 || ysize <= 0)
1745 if (c >= 0 && xsize > c)
1747 if (c < 0 && ysize+c > 0)
1752 /* This code used to check for conflicts involving stack references and
1753 globals but the base address alias code now handles these cases. */
1755 if (GET_CODE (x) == PLUS)
1757 /* The fact that X is canonicalized means that this
1758 PLUS rtx is canonicalized. */
1759 rtx x0 = XEXP (x, 0);
1760 rtx x1 = XEXP (x, 1);
1762 if (GET_CODE (y) == PLUS)
1764 /* The fact that Y is canonicalized means that this
1765 PLUS rtx is canonicalized. */
1766 rtx y0 = XEXP (y, 0);
1767 rtx y1 = XEXP (y, 1);
1769 if (rtx_equal_for_memref_p (x1, y1))
1770 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1771 if (rtx_equal_for_memref_p (x0, y0))
1772 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1773 if (GET_CODE (x1) == CONST_INT)
1775 if (GET_CODE (y1) == CONST_INT)
1776 return memrefs_conflict_p (xsize, x0, ysize, y0,
1777 c - INTVAL (x1) + INTVAL (y1));
1779 return memrefs_conflict_p (xsize, x0, ysize, y,
1782 else if (GET_CODE (y1) == CONST_INT)
1783 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1787 else if (GET_CODE (x1) == CONST_INT)
1788 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1790 else if (GET_CODE (y) == PLUS)
1792 /* The fact that Y is canonicalized means that this
1793 PLUS rtx is canonicalized. */
1794 rtx y0 = XEXP (y, 0);
1795 rtx y1 = XEXP (y, 1);
1797 if (GET_CODE (y1) == CONST_INT)
1798 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1803 if (GET_CODE (x) == GET_CODE (y))
1804 switch (GET_CODE (x))
1808 /* Handle cases where we expect the second operands to be the
1809 same, and check only whether the first operand would conflict
1812 rtx x1 = canon_rtx (XEXP (x, 1));
1813 rtx y1 = canon_rtx (XEXP (y, 1));
1814 if (! rtx_equal_for_memref_p (x1, y1))
1816 x0 = canon_rtx (XEXP (x, 0));
1817 y0 = canon_rtx (XEXP (y, 0));
1818 if (rtx_equal_for_memref_p (x0, y0))
1819 return (xsize == 0 || ysize == 0
1820 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1822 /* Can't properly adjust our sizes. */
1823 if (GET_CODE (x1) != CONST_INT)
1825 xsize /= INTVAL (x1);
1826 ysize /= INTVAL (x1);
1828 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1835 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1836 as an access with indeterminate size. Assume that references
1837 besides AND are aligned, so if the size of the other reference is
1838 at least as large as the alignment, assume no other overlap. */
1839 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1841 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1843 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1845 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1847 /* ??? If we are indexing far enough into the array/structure, we
1848 may yet be able to determine that we can not overlap. But we
1849 also need to that we are far enough from the end not to overlap
1850 a following reference, so we do nothing with that for now. */
1851 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1853 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1858 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1860 c += (INTVAL (y) - INTVAL (x));
1861 return (xsize <= 0 || ysize <= 0
1862 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1865 if (GET_CODE (x) == CONST)
1867 if (GET_CODE (y) == CONST)
1868 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1869 ysize, canon_rtx (XEXP (y, 0)), c);
1871 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1874 if (GET_CODE (y) == CONST)
1875 return memrefs_conflict_p (xsize, x, ysize,
1876 canon_rtx (XEXP (y, 0)), c);
1879 return (xsize <= 0 || ysize <= 0
1880 || (rtx_equal_for_memref_p (x, y)
1881 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1888 /* Functions to compute memory dependencies.
1890 Since we process the insns in execution order, we can build tables
1891 to keep track of what registers are fixed (and not aliased), what registers
1892 are varying in known ways, and what registers are varying in unknown
1895 If both memory references are volatile, then there must always be a
1896 dependence between the two references, since their order can not be
1897 changed. A volatile and non-volatile reference can be interchanged
1900 A MEM_IN_STRUCT reference at a non-AND varying address can never
1901 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1902 also must allow AND addresses, because they may generate accesses
1903 outside the object being referenced. This is used to generate
1904 aligned addresses from unaligned addresses, for instance, the alpha
1905 storeqi_unaligned pattern. */
1907 /* Read dependence: X is read after read in MEM takes place. There can
1908 only be a dependence here if both reads are volatile. */
1911 read_dependence (const_rtx mem, const_rtx x)
1913 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1916 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1917 MEM2 is a reference to a structure at a varying address, or returns
1918 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1919 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1920 to decide whether or not an address may vary; it should return
1921 nonzero whenever variation is possible.
1922 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1925 fixed_scalar_and_varying_struct_p (const_rtx mem1, const_rtx mem2, rtx mem1_addr,
1927 bool (*varies_p) (const_rtx, bool))
1929 if (! flag_strict_aliasing)
1932 if (MEM_ALIAS_SET (mem2)
1933 && MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1934 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1935 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1939 if (MEM_ALIAS_SET (mem1)
1940 && MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1941 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1942 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1949 /* Returns nonzero if something about the mode or address format MEM1
1950 indicates that it might well alias *anything*. */
1953 aliases_everything_p (const_rtx mem)
1955 if (GET_CODE (XEXP (mem, 0)) == AND)
1956 /* If the address is an AND, it's very hard to know at what it is
1957 actually pointing. */
1963 /* Return true if we can determine that the fields referenced cannot
1964 overlap for any pair of objects. */
1967 nonoverlapping_component_refs_p (const_tree x, const_tree y)
1969 const_tree fieldx, fieldy, typex, typey, orig_y;
1973 /* The comparison has to be done at a common type, since we don't
1974 know how the inheritance hierarchy works. */
1978 fieldx = TREE_OPERAND (x, 1);
1979 typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx));
1984 fieldy = TREE_OPERAND (y, 1);
1985 typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy));
1990 y = TREE_OPERAND (y, 0);
1992 while (y && TREE_CODE (y) == COMPONENT_REF);
1994 x = TREE_OPERAND (x, 0);
1996 while (x && TREE_CODE (x) == COMPONENT_REF);
1997 /* Never found a common type. */
2001 /* If we're left with accessing different fields of a structure,
2003 if (TREE_CODE (typex) == RECORD_TYPE
2004 && fieldx != fieldy)
2007 /* The comparison on the current field failed. If we're accessing
2008 a very nested structure, look at the next outer level. */
2009 x = TREE_OPERAND (x, 0);
2010 y = TREE_OPERAND (y, 0);
2013 && TREE_CODE (x) == COMPONENT_REF
2014 && TREE_CODE (y) == COMPONENT_REF);
2019 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2022 decl_for_component_ref (tree x)
2026 x = TREE_OPERAND (x, 0);
2028 while (x && TREE_CODE (x) == COMPONENT_REF);
2030 return x && DECL_P (x) ? x : NULL_TREE;
2033 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
2034 offset of the field reference. */
2037 adjust_offset_for_component_ref (tree x, rtx offset)
2039 HOST_WIDE_INT ioffset;
2044 ioffset = INTVAL (offset);
2047 tree offset = component_ref_field_offset (x);
2048 tree field = TREE_OPERAND (x, 1);
2050 if (! host_integerp (offset, 1))
2052 ioffset += (tree_low_cst (offset, 1)
2053 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
2056 x = TREE_OPERAND (x, 0);
2058 while (x && TREE_CODE (x) == COMPONENT_REF);
2060 return GEN_INT (ioffset);
2063 /* Return nonzero if we can determine the exprs corresponding to memrefs
2064 X and Y and they do not overlap. */
2067 nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
2069 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
2072 rtx moffsetx, moffsety;
2073 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
2075 /* Unless both have exprs, we can't tell anything. */
2076 if (exprx == 0 || expry == 0)
2079 /* If both are field references, we may be able to determine something. */
2080 if (TREE_CODE (exprx) == COMPONENT_REF
2081 && TREE_CODE (expry) == COMPONENT_REF
2082 && nonoverlapping_component_refs_p (exprx, expry))
2086 /* If the field reference test failed, look at the DECLs involved. */
2087 moffsetx = MEM_OFFSET (x);
2088 if (TREE_CODE (exprx) == COMPONENT_REF)
2090 if (TREE_CODE (expry) == VAR_DECL
2091 && POINTER_TYPE_P (TREE_TYPE (expry)))
2093 tree field = TREE_OPERAND (exprx, 1);
2094 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2095 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2100 tree t = decl_for_component_ref (exprx);
2103 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
2107 else if (INDIRECT_REF_P (exprx))
2109 exprx = TREE_OPERAND (exprx, 0);
2110 if (flag_argument_noalias < 2
2111 || TREE_CODE (exprx) != PARM_DECL)
2115 moffsety = MEM_OFFSET (y);
2116 if (TREE_CODE (expry) == COMPONENT_REF)
2118 if (TREE_CODE (exprx) == VAR_DECL
2119 && POINTER_TYPE_P (TREE_TYPE (exprx)))
2121 tree field = TREE_OPERAND (expry, 1);
2122 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2123 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2128 tree t = decl_for_component_ref (expry);
2131 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2135 else if (INDIRECT_REF_P (expry))
2137 expry = TREE_OPERAND (expry, 0);
2138 if (flag_argument_noalias < 2
2139 || TREE_CODE (expry) != PARM_DECL)
2143 if (! DECL_P (exprx) || ! DECL_P (expry))
2146 rtlx = DECL_RTL (exprx);
2147 rtly = DECL_RTL (expry);
2149 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2150 can't overlap unless they are the same because we never reuse that part
2151 of the stack frame used for locals for spilled pseudos. */
2152 if ((!MEM_P (rtlx) || !MEM_P (rtly))
2153 && ! rtx_equal_p (rtlx, rtly))
2156 /* Get the base and offsets of both decls. If either is a register, we
2157 know both are and are the same, so use that as the base. The only
2158 we can avoid overlap is if we can deduce that they are nonoverlapping
2159 pieces of that decl, which is very rare. */
2160 basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx;
2161 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2162 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2164 basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly;
2165 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2166 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2168 /* If the bases are different, we know they do not overlap if both
2169 are constants or if one is a constant and the other a pointer into the
2170 stack frame. Otherwise a different base means we can't tell if they
2172 if (! rtx_equal_p (basex, basey))
2173 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2174 || (CONSTANT_P (basex) && REG_P (basey)
2175 && REGNO_PTR_FRAME_P (REGNO (basey)))
2176 || (CONSTANT_P (basey) && REG_P (basex)
2177 && REGNO_PTR_FRAME_P (REGNO (basex))));
2179 sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2180 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2182 sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2183 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2186 /* If we have an offset for either memref, it can update the values computed
2189 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2191 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2193 /* If a memref has both a size and an offset, we can use the smaller size.
2194 We can't do this if the offset isn't known because we must view this
2195 memref as being anywhere inside the DECL's MEM. */
2196 if (MEM_SIZE (x) && moffsetx)
2197 sizex = INTVAL (MEM_SIZE (x));
2198 if (MEM_SIZE (y) && moffsety)
2199 sizey = INTVAL (MEM_SIZE (y));
2201 /* Put the values of the memref with the lower offset in X's values. */
2202 if (offsetx > offsety)
2204 tem = offsetx, offsetx = offsety, offsety = tem;
2205 tem = sizex, sizex = sizey, sizey = tem;
2208 /* If we don't know the size of the lower-offset value, we can't tell
2209 if they conflict. Otherwise, we do the test. */
2210 return sizex >= 0 && offsety >= offsetx + sizex;
2213 /* True dependence: X is read after store in MEM takes place. */
2216 true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x,
2217 bool (*varies) (const_rtx, bool))
2219 rtx x_addr, mem_addr;
2222 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2225 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2226 This is used in epilogue deallocation functions, and in cselib. */
2227 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2229 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2231 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2232 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2235 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2238 /* Read-only memory is by definition never modified, and therefore can't
2239 conflict with anything. We don't expect to find read-only set on MEM,
2240 but stupid user tricks can produce them, so don't die. */
2241 if (MEM_READONLY_P (x))
2244 if (nonoverlapping_memrefs_p (mem, x))
2247 if (mem_mode == VOIDmode)
2248 mem_mode = GET_MODE (mem);
2250 x_addr = get_addr (XEXP (x, 0));
2251 mem_addr = get_addr (XEXP (mem, 0));
2253 base = find_base_term (x_addr);
2254 if (base && (GET_CODE (base) == LABEL_REF
2255 || (GET_CODE (base) == SYMBOL_REF
2256 && CONSTANT_POOL_ADDRESS_P (base))))
2259 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2262 x_addr = canon_rtx (x_addr);
2263 mem_addr = canon_rtx (mem_addr);
2265 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2266 SIZE_FOR_MODE (x), x_addr, 0))
2269 if (aliases_everything_p (x))
2272 /* We cannot use aliases_everything_p to test MEM, since we must look
2273 at MEM_MODE, rather than GET_MODE (MEM). */
2274 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2277 /* In true_dependence we also allow BLKmode to alias anything. Why
2278 don't we do this in anti_dependence and output_dependence? */
2279 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2282 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2286 /* Canonical true dependence: X is read after store in MEM takes place.
2287 Variant of true_dependence which assumes MEM has already been
2288 canonicalized (hence we no longer do that here).
2289 The mem_addr argument has been added, since true_dependence computed
2290 this value prior to canonicalizing. */
2293 canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2294 const_rtx x, bool (*varies) (const_rtx, bool))
2298 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2301 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2302 This is used in epilogue deallocation functions. */
2303 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2305 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2307 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2308 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2311 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2314 /* Read-only memory is by definition never modified, and therefore can't
2315 conflict with anything. We don't expect to find read-only set on MEM,
2316 but stupid user tricks can produce them, so don't die. */
2317 if (MEM_READONLY_P (x))
2320 if (nonoverlapping_memrefs_p (x, mem))
2323 x_addr = get_addr (XEXP (x, 0));
2325 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2328 x_addr = canon_rtx (x_addr);
2329 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2330 SIZE_FOR_MODE (x), x_addr, 0))
2333 if (aliases_everything_p (x))
2336 /* We cannot use aliases_everything_p to test MEM, since we must look
2337 at MEM_MODE, rather than GET_MODE (MEM). */
2338 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2341 /* In true_dependence we also allow BLKmode to alias anything. Why
2342 don't we do this in anti_dependence and output_dependence? */
2343 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2346 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2350 /* Returns nonzero if a write to X might alias a previous read from
2351 (or, if WRITEP is nonzero, a write to) MEM. */
2354 write_dependence_p (const_rtx mem, const_rtx x, int writep)
2356 rtx x_addr, mem_addr;
2357 const_rtx fixed_scalar;
2360 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2363 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2364 This is used in epilogue deallocation functions. */
2365 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2367 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2369 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2370 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2373 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2376 /* A read from read-only memory can't conflict with read-write memory. */
2377 if (!writep && MEM_READONLY_P (mem))
2380 if (nonoverlapping_memrefs_p (x, mem))
2383 x_addr = get_addr (XEXP (x, 0));
2384 mem_addr = get_addr (XEXP (mem, 0));
2388 base = find_base_term (mem_addr);
2389 if (base && (GET_CODE (base) == LABEL_REF
2390 || (GET_CODE (base) == SYMBOL_REF
2391 && CONSTANT_POOL_ADDRESS_P (base))))
2395 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2399 x_addr = canon_rtx (x_addr);
2400 mem_addr = canon_rtx (mem_addr);
2402 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2403 SIZE_FOR_MODE (x), x_addr, 0))
2407 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2410 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2411 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2414 /* Anti dependence: X is written after read in MEM takes place. */
2417 anti_dependence (const_rtx mem, const_rtx x)
2419 return write_dependence_p (mem, x, /*writep=*/0);
2422 /* Output dependence: X is written after store in MEM takes place. */
2425 output_dependence (const_rtx mem, const_rtx x)
2427 return write_dependence_p (mem, x, /*writep=*/1);
2432 init_alias_target (void)
2436 memset (static_reg_base_value, 0, sizeof static_reg_base_value);
2438 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2439 /* Check whether this register can hold an incoming pointer
2440 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2441 numbers, so translate if necessary due to register windows. */
2442 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2443 && HARD_REGNO_MODE_OK (i, Pmode))
2444 static_reg_base_value[i]
2445 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2447 static_reg_base_value[STACK_POINTER_REGNUM]
2448 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2449 static_reg_base_value[ARG_POINTER_REGNUM]
2450 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2451 static_reg_base_value[FRAME_POINTER_REGNUM]
2452 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2453 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2454 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2455 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2459 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2460 to be memory reference. */
2461 static bool memory_modified;
2463 memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
2467 if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data))
2468 memory_modified = true;
2473 /* Return true when INSN possibly modify memory contents of MEM
2474 (i.e. address can be modified). */
2476 memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
2480 memory_modified = false;
2481 note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
2482 return memory_modified;
2485 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2489 init_alias_analysis (void)
2491 unsigned int maxreg = max_reg_num ();
2497 timevar_push (TV_ALIAS_ANALYSIS);
2499 reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER;
2500 reg_known_value = GGC_CNEWVEC (rtx, reg_known_value_size);
2501 reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size);
2503 /* If we have memory allocated from the previous run, use it. */
2504 if (old_reg_base_value)
2505 reg_base_value = old_reg_base_value;
2508 VEC_truncate (rtx, reg_base_value, 0);
2510 VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg);
2512 new_reg_base_value = XNEWVEC (rtx, maxreg);
2513 reg_seen = XNEWVEC (char, maxreg);
2515 /* The basic idea is that each pass through this loop will use the
2516 "constant" information from the previous pass to propagate alias
2517 information through another level of assignments.
2519 This could get expensive if the assignment chains are long. Maybe
2520 we should throttle the number of iterations, possibly based on
2521 the optimization level or flag_expensive_optimizations.
2523 We could propagate more information in the first pass by making use
2524 of DF_REG_DEF_COUNT to determine immediately that the alias information
2525 for a pseudo is "constant".
2527 A program with an uninitialized variable can cause an infinite loop
2528 here. Instead of doing a full dataflow analysis to detect such problems
2529 we just cap the number of iterations for the loop.
2531 The state of the arrays for the set chain in question does not matter
2532 since the program has undefined behavior. */
2537 /* Assume nothing will change this iteration of the loop. */
2540 /* We want to assign the same IDs each iteration of this loop, so
2541 start counting from zero each iteration of the loop. */
2544 /* We're at the start of the function each iteration through the
2545 loop, so we're copying arguments. */
2546 copying_arguments = true;
2548 /* Wipe the potential alias information clean for this pass. */
2549 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2551 /* Wipe the reg_seen array clean. */
2552 memset (reg_seen, 0, maxreg);
2554 /* Mark all hard registers which may contain an address.
2555 The stack, frame and argument pointers may contain an address.
2556 An argument register which can hold a Pmode value may contain
2557 an address even if it is not in BASE_REGS.
2559 The address expression is VOIDmode for an argument and
2560 Pmode for other registers. */
2562 memcpy (new_reg_base_value, static_reg_base_value,
2563 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2565 /* Walk the insns adding values to the new_reg_base_value array. */
2566 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2572 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2573 /* The prologue/epilogue insns are not threaded onto the
2574 insn chain until after reload has completed. Thus,
2575 there is no sense wasting time checking if INSN is in
2576 the prologue/epilogue until after reload has completed. */
2577 if (reload_completed
2578 && prologue_epilogue_contains (insn))
2582 /* If this insn has a noalias note, process it, Otherwise,
2583 scan for sets. A simple set will have no side effects
2584 which could change the base value of any other register. */
2586 if (GET_CODE (PATTERN (insn)) == SET
2587 && REG_NOTES (insn) != 0
2588 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2589 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2591 note_stores (PATTERN (insn), record_set, NULL);
2593 set = single_set (insn);
2596 && REG_P (SET_DEST (set))
2597 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2599 unsigned int regno = REGNO (SET_DEST (set));
2600 rtx src = SET_SRC (set);
2603 note = find_reg_equal_equiv_note (insn);
2604 if (note && REG_NOTE_KIND (note) == REG_EQUAL
2605 && DF_REG_DEF_COUNT (regno) != 1)
2608 if (note != NULL_RTX
2609 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2610 && ! rtx_varies_p (XEXP (note, 0), 1)
2611 && ! reg_overlap_mentioned_p (SET_DEST (set),
2614 set_reg_known_value (regno, XEXP (note, 0));
2615 set_reg_known_equiv_p (regno,
2616 REG_NOTE_KIND (note) == REG_EQUIV);
2618 else if (DF_REG_DEF_COUNT (regno) == 1
2619 && GET_CODE (src) == PLUS
2620 && REG_P (XEXP (src, 0))
2621 && (t = get_reg_known_value (REGNO (XEXP (src, 0))))
2622 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2624 t = plus_constant (t, INTVAL (XEXP (src, 1)));
2625 set_reg_known_value (regno, t);
2626 set_reg_known_equiv_p (regno, 0);
2628 else if (DF_REG_DEF_COUNT (regno) == 1
2629 && ! rtx_varies_p (src, 1))
2631 set_reg_known_value (regno, src);
2632 set_reg_known_equiv_p (regno, 0);
2636 else if (NOTE_P (insn)
2637 && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG)
2638 copying_arguments = false;
2641 /* Now propagate values from new_reg_base_value to reg_base_value. */
2642 gcc_assert (maxreg == (unsigned int) max_reg_num ());
2644 for (ui = 0; ui < maxreg; ui++)
2646 if (new_reg_base_value[ui]
2647 && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui)
2648 && ! rtx_equal_p (new_reg_base_value[ui],
2649 VEC_index (rtx, reg_base_value, ui)))
2651 VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]);
2656 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2658 /* Fill in the remaining entries. */
2659 for (i = 0; i < (int)reg_known_value_size; i++)
2660 if (reg_known_value[i] == 0)
2661 reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER];
2664 free (new_reg_base_value);
2665 new_reg_base_value = 0;
2668 timevar_pop (TV_ALIAS_ANALYSIS);
2672 end_alias_analysis (void)
2674 old_reg_base_value = reg_base_value;
2675 ggc_free (reg_known_value);
2676 reg_known_value = 0;
2677 reg_known_value_size = 0;
2678 free (reg_known_equiv_p);
2679 reg_known_equiv_p = 0;
2682 #include "gt-alias.h"