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. */
347 /* Return 1 if the two specified alias sets will always conflict. */
350 alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2)
352 if (set1 == 0 || set2 == 0 || set1 == set2)
358 /* Return 1 if any MEM object of type T1 will always conflict (using the
359 dependency routines in this file) with any MEM object of type T2.
360 This is used when allocating temporary storage. If T1 and/or T2 are
361 NULL_TREE, it means we know nothing about the storage. */
364 objects_must_conflict_p (tree t1, tree t2)
366 alias_set_type set1, set2;
368 /* If neither has a type specified, we don't know if they'll conflict
369 because we may be using them to store objects of various types, for
370 example the argument and local variables areas of inlined functions. */
371 if (t1 == 0 && t2 == 0)
374 /* If they are the same type, they must conflict. */
376 /* Likewise if both are volatile. */
377 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
380 set1 = t1 ? get_alias_set (t1) : 0;
381 set2 = t2 ? get_alias_set (t2) : 0;
383 /* We can't use alias_sets_conflict_p because we must make sure
384 that every subtype of t1 will conflict with every subtype of
385 t2 for which a pair of subobjects of these respective subtypes
386 overlaps on the stack. */
387 return alias_sets_must_conflict_p (set1, set2);
390 /* T is an expression with pointer type. Find the DECL on which this
391 expression is based. (For example, in `a[i]' this would be `a'.)
392 If there is no such DECL, or a unique decl cannot be determined,
393 NULL_TREE is returned. */
396 find_base_decl (tree t)
400 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
403 /* If this is a declaration, return it. If T is based on a restrict
404 qualified decl, return that decl. */
407 if (TREE_CODE (t) == VAR_DECL && DECL_BASED_ON_RESTRICT_P (t))
408 t = DECL_GET_RESTRICT_BASE (t);
412 /* Handle general expressions. It would be nice to deal with
413 COMPONENT_REFs here. If we could tell that `a' and `b' were the
414 same, then `a->f' and `b->f' are also the same. */
415 switch (TREE_CODE_CLASS (TREE_CODE (t)))
418 return find_base_decl (TREE_OPERAND (t, 0));
421 /* Return 0 if found in neither or both are the same. */
422 d0 = find_base_decl (TREE_OPERAND (t, 0));
423 d1 = find_base_decl (TREE_OPERAND (t, 1));
438 /* Return true if all nested component references handled by
439 get_inner_reference in T are such that we should use the alias set
440 provided by the object at the heart of T.
442 This is true for non-addressable components (which don't have their
443 own alias set), as well as components of objects in alias set zero.
444 This later point is a special case wherein we wish to override the
445 alias set used by the component, but we don't have per-FIELD_DECL
446 assignable alias sets. */
449 component_uses_parent_alias_set (const_tree t)
453 /* If we're at the end, it vacuously uses its own alias set. */
454 if (!handled_component_p (t))
457 switch (TREE_CODE (t))
460 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
465 case ARRAY_RANGE_REF:
466 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))))
475 /* Bitfields and casts are never addressable. */
479 t = TREE_OPERAND (t, 0);
480 if (get_alias_set (TREE_TYPE (t)) == 0)
485 /* Return the alias set for T, which may be either a type or an
486 expression. Call language-specific routine for help, if needed. */
489 get_alias_set (tree t)
493 /* If we're not doing any alias analysis, just assume everything
494 aliases everything else. Also return 0 if this or its type is
496 if (! flag_strict_aliasing || t == error_mark_node
498 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
501 /* We can be passed either an expression or a type. This and the
502 language-specific routine may make mutually-recursive calls to each other
503 to figure out what to do. At each juncture, we see if this is a tree
504 that the language may need to handle specially. First handle things that
510 /* Remove any nops, then give the language a chance to do
511 something with this tree before we look at it. */
513 set = lang_hooks.get_alias_set (t);
517 /* First see if the actual object referenced is an INDIRECT_REF from a
518 restrict-qualified pointer or a "void *". */
519 while (handled_component_p (inner))
521 inner = TREE_OPERAND (inner, 0);
525 /* Check for accesses through restrict-qualified pointers. */
526 if (INDIRECT_REF_P (inner))
530 if (TREE_CODE (TREE_OPERAND (inner, 0)) == SSA_NAME)
531 decl = SSA_NAME_VAR (TREE_OPERAND (inner, 0));
533 decl = find_base_decl (TREE_OPERAND (inner, 0));
535 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
537 /* If we haven't computed the actual alias set, do it now. */
538 if (DECL_POINTER_ALIAS_SET (decl) == -2)
540 tree pointed_to_type = TREE_TYPE (TREE_TYPE (decl));
542 /* No two restricted pointers can point at the same thing.
543 However, a restricted pointer can point at the same thing
544 as an unrestricted pointer, if that unrestricted pointer
545 is based on the restricted pointer. So, we make the
546 alias set for the restricted pointer a subset of the
547 alias set for the type pointed to by the type of the
549 alias_set_type pointed_to_alias_set
550 = get_alias_set (pointed_to_type);
552 if (pointed_to_alias_set == 0)
553 /* It's not legal to make a subset of alias set zero. */
554 DECL_POINTER_ALIAS_SET (decl) = 0;
555 else if (AGGREGATE_TYPE_P (pointed_to_type))
556 /* For an aggregate, we must treat the restricted
557 pointer the same as an ordinary pointer. If we
558 were to make the type pointed to by the
559 restricted pointer a subset of the pointed-to
560 type, then we would believe that other subsets
561 of the pointed-to type (such as fields of that
562 type) do not conflict with the type pointed to
563 by the restricted pointer. */
564 DECL_POINTER_ALIAS_SET (decl)
565 = pointed_to_alias_set;
568 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
569 record_alias_subset (pointed_to_alias_set,
570 DECL_POINTER_ALIAS_SET (decl));
574 /* We use the alias set indicated in the declaration. */
575 return DECL_POINTER_ALIAS_SET (decl);
578 /* If we have an INDIRECT_REF via a void pointer, we don't
579 know anything about what that might alias. Likewise if the
580 pointer is marked that way. */
581 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE
582 || (TYPE_REF_CAN_ALIAS_ALL
583 (TREE_TYPE (TREE_OPERAND (inner, 0)))))
587 /* Otherwise, pick up the outermost object that we could have a pointer
588 to, processing conversions as above. */
589 while (component_uses_parent_alias_set (t))
591 t = TREE_OPERAND (t, 0);
595 /* If we've already determined the alias set for a decl, just return
596 it. This is necessary for C++ anonymous unions, whose component
597 variables don't look like union members (boo!). */
598 if (TREE_CODE (t) == VAR_DECL
599 && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t)))
600 return MEM_ALIAS_SET (DECL_RTL (t));
602 /* Now all we care about is the type. */
606 /* Variant qualifiers don't affect the alias set, so get the main
607 variant. Always use the canonical type as well.
608 If this is a type with a known alias set, return it. */
609 t = TYPE_MAIN_VARIANT (t);
610 if (TYPE_CANONICAL (t))
611 t = TYPE_CANONICAL (t);
612 if (TYPE_ALIAS_SET_KNOWN_P (t))
613 return TYPE_ALIAS_SET (t);
615 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
616 if (!COMPLETE_TYPE_P (t))
618 /* For arrays with unknown size the conservative answer is the
619 alias set of the element type. */
620 if (TREE_CODE (t) == ARRAY_TYPE)
621 return get_alias_set (TREE_TYPE (t));
623 /* But return zero as a conservative answer for incomplete types. */
627 /* See if the language has special handling for this type. */
628 set = lang_hooks.get_alias_set (t);
632 /* There are no objects of FUNCTION_TYPE, so there's no point in
633 using up an alias set for them. (There are, of course, pointers
634 and references to functions, but that's different.) */
635 else if (TREE_CODE (t) == FUNCTION_TYPE
636 || TREE_CODE (t) == METHOD_TYPE)
639 /* Unless the language specifies otherwise, let vector types alias
640 their components. This avoids some nasty type punning issues in
641 normal usage. And indeed lets vectors be treated more like an
643 else if (TREE_CODE (t) == VECTOR_TYPE)
644 set = get_alias_set (TREE_TYPE (t));
646 /* Unless the language specifies otherwise, treat array types the
647 same as their components. This avoids the asymmetry we get
648 through recording the components. Consider accessing a
649 character(kind=1) through a reference to a character(kind=1)[1:1].
650 Or consider if we want to assign integer(kind=4)[0:D.1387] and
651 integer(kind=4)[4] the same alias set or not.
652 Just be pragmatic here and make sure the array and its element
653 type get the same alias set assigned. */
654 else if (TREE_CODE (t) == ARRAY_TYPE
655 && !TYPE_NONALIASED_COMPONENT (t))
656 set = get_alias_set (TREE_TYPE (t));
659 /* Otherwise make a new alias set for this type. */
660 set = new_alias_set ();
662 TYPE_ALIAS_SET (t) = set;
664 /* If this is an aggregate type, we must record any component aliasing
666 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
667 record_component_aliases (t);
672 /* Return a brand-new alias set. */
677 if (flag_strict_aliasing)
680 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
681 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
682 return VEC_length (alias_set_entry, alias_sets) - 1;
688 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
689 not everything that aliases SUPERSET also aliases SUBSET. For example,
690 in C, a store to an `int' can alias a load of a structure containing an
691 `int', and vice versa. But it can't alias a load of a 'double' member
692 of the same structure. Here, the structure would be the SUPERSET and
693 `int' the SUBSET. This relationship is also described in the comment at
694 the beginning of this file.
696 This function should be called only once per SUPERSET/SUBSET pair.
698 It is illegal for SUPERSET to be zero; everything is implicitly a
699 subset of alias set zero. */
702 record_alias_subset (alias_set_type superset, alias_set_type subset)
704 alias_set_entry superset_entry;
705 alias_set_entry subset_entry;
707 /* It is possible in complex type situations for both sets to be the same,
708 in which case we can ignore this operation. */
709 if (superset == subset)
712 gcc_assert (superset);
714 superset_entry = get_alias_set_entry (superset);
715 if (superset_entry == 0)
717 /* Create an entry for the SUPERSET, so that we have a place to
718 attach the SUBSET. */
719 superset_entry = GGC_NEW (struct alias_set_entry);
720 superset_entry->alias_set = superset;
721 superset_entry->children
722 = splay_tree_new_ggc (splay_tree_compare_ints);
723 superset_entry->has_zero_child = 0;
724 VEC_replace (alias_set_entry, alias_sets, superset, superset_entry);
728 superset_entry->has_zero_child = 1;
731 subset_entry = get_alias_set_entry (subset);
732 /* If there is an entry for the subset, enter all of its children
733 (if they are not already present) as children of the SUPERSET. */
736 if (subset_entry->has_zero_child)
737 superset_entry->has_zero_child = 1;
739 splay_tree_foreach (subset_entry->children, insert_subset_children,
740 superset_entry->children);
743 /* Enter the SUBSET itself as a child of the SUPERSET. */
744 splay_tree_insert (superset_entry->children,
745 (splay_tree_key) subset, 0);
749 /* Record that component types of TYPE, if any, are part of that type for
750 aliasing purposes. For record types, we only record component types
751 for fields that are not marked non-addressable. For array types, we
752 only record the component type if it is not marked non-aliased. */
755 record_component_aliases (tree type)
757 alias_set_type superset = get_alias_set (type);
763 switch (TREE_CODE (type))
767 case QUAL_UNION_TYPE:
768 /* Recursively record aliases for the base classes, if there are any. */
769 if (TYPE_BINFO (type))
772 tree binfo, base_binfo;
774 for (binfo = TYPE_BINFO (type), i = 0;
775 BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
776 record_alias_subset (superset,
777 get_alias_set (BINFO_TYPE (base_binfo)));
779 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
780 if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
781 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
785 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
788 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
796 /* Allocate an alias set for use in storing and reading from the varargs
799 static GTY(()) alias_set_type varargs_set = -1;
802 get_varargs_alias_set (void)
805 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
806 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
807 consistently use the varargs alias set for loads from the varargs
808 area. So don't use it anywhere. */
811 if (varargs_set == -1)
812 varargs_set = new_alias_set ();
818 /* Likewise, but used for the fixed portions of the frame, e.g., register
821 static GTY(()) alias_set_type frame_set = -1;
824 get_frame_alias_set (void)
827 frame_set = new_alias_set ();
832 /* Inside SRC, the source of a SET, find a base address. */
835 find_base_value (rtx src)
839 #if defined (FIND_BASE_TERM)
840 /* Try machine-dependent ways to find the base term. */
841 src = FIND_BASE_TERM (src);
844 switch (GET_CODE (src))
852 /* At the start of a function, argument registers have known base
853 values which may be lost later. Returning an ADDRESS
854 expression here allows optimization based on argument values
855 even when the argument registers are used for other purposes. */
856 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
857 return new_reg_base_value[regno];
859 /* If a pseudo has a known base value, return it. Do not do this
860 for non-fixed hard regs since it can result in a circular
861 dependency chain for registers which have values at function entry.
863 The test above is not sufficient because the scheduler may move
864 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
865 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
866 && regno < VEC_length (rtx, reg_base_value))
868 /* If we're inside init_alias_analysis, use new_reg_base_value
869 to reduce the number of relaxation iterations. */
870 if (new_reg_base_value && new_reg_base_value[regno]
871 && DF_REG_DEF_COUNT (regno) == 1)
872 return new_reg_base_value[regno];
874 if (VEC_index (rtx, reg_base_value, regno))
875 return VEC_index (rtx, reg_base_value, regno);
881 /* Check for an argument passed in memory. Only record in the
882 copying-arguments block; it is too hard to track changes
884 if (copying_arguments
885 && (XEXP (src, 0) == arg_pointer_rtx
886 || (GET_CODE (XEXP (src, 0)) == PLUS
887 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
888 return gen_rtx_ADDRESS (VOIDmode, src);
893 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
896 /* ... fall through ... */
901 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
903 /* If either operand is a REG that is a known pointer, then it
905 if (REG_P (src_0) && REG_POINTER (src_0))
906 return find_base_value (src_0);
907 if (REG_P (src_1) && REG_POINTER (src_1))
908 return find_base_value (src_1);
910 /* If either operand is a REG, then see if we already have
911 a known value for it. */
914 temp = find_base_value (src_0);
921 temp = find_base_value (src_1);
926 /* If either base is named object or a special address
927 (like an argument or stack reference), then use it for the
930 && (GET_CODE (src_0) == SYMBOL_REF
931 || GET_CODE (src_0) == LABEL_REF
932 || (GET_CODE (src_0) == ADDRESS
933 && GET_MODE (src_0) != VOIDmode)))
937 && (GET_CODE (src_1) == SYMBOL_REF
938 || GET_CODE (src_1) == LABEL_REF
939 || (GET_CODE (src_1) == ADDRESS
940 && GET_MODE (src_1) != VOIDmode)))
943 /* Guess which operand is the base address:
944 If either operand is a symbol, then it is the base. If
945 either operand is a CONST_INT, then the other is the base. */
946 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
947 return find_base_value (src_0);
948 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
949 return find_base_value (src_1);
955 /* The standard form is (lo_sum reg sym) so look only at the
957 return find_base_value (XEXP (src, 1));
960 /* If the second operand is constant set the base
961 address to the first operand. */
962 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
963 return find_base_value (XEXP (src, 0));
967 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
977 return find_base_value (XEXP (src, 0));
980 case SIGN_EXTEND: /* used for NT/Alpha pointers */
982 rtx temp = find_base_value (XEXP (src, 0));
984 if (temp != 0 && CONSTANT_P (temp))
985 temp = convert_memory_address (Pmode, temp);
997 /* Called from init_alias_analysis indirectly through note_stores. */
999 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1000 register N has been set in this function. */
1001 static char *reg_seen;
1003 /* Addresses which are known not to alias anything else are identified
1004 by a unique integer. */
1005 static int unique_id;
1008 record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED)
1017 regno = REGNO (dest);
1019 gcc_assert (regno < VEC_length (rtx, reg_base_value));
1021 /* If this spans multiple hard registers, then we must indicate that every
1022 register has an unusable value. */
1023 if (regno < FIRST_PSEUDO_REGISTER)
1024 n = hard_regno_nregs[regno][GET_MODE (dest)];
1031 reg_seen[regno + n] = 1;
1032 new_reg_base_value[regno + n] = 0;
1039 /* A CLOBBER wipes out any old value but does not prevent a previously
1040 unset register from acquiring a base address (i.e. reg_seen is not
1042 if (GET_CODE (set) == CLOBBER)
1044 new_reg_base_value[regno] = 0;
1047 src = SET_SRC (set);
1051 if (reg_seen[regno])
1053 new_reg_base_value[regno] = 0;
1056 reg_seen[regno] = 1;
1057 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
1058 GEN_INT (unique_id++));
1062 /* If this is not the first set of REGNO, see whether the new value
1063 is related to the old one. There are two cases of interest:
1065 (1) The register might be assigned an entirely new value
1066 that has the same base term as the original set.
1068 (2) The set might be a simple self-modification that
1069 cannot change REGNO's base value.
1071 If neither case holds, reject the original base value as invalid.
1072 Note that the following situation is not detected:
1074 extern int x, y; int *p = &x; p += (&y-&x);
1076 ANSI C does not allow computing the difference of addresses
1077 of distinct top level objects. */
1078 if (new_reg_base_value[regno] != 0
1079 && find_base_value (src) != new_reg_base_value[regno])
1080 switch (GET_CODE (src))
1084 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1085 new_reg_base_value[regno] = 0;
1088 /* If the value we add in the PLUS is also a valid base value,
1089 this might be the actual base value, and the original value
1092 rtx other = NULL_RTX;
1094 if (XEXP (src, 0) == dest)
1095 other = XEXP (src, 1);
1096 else if (XEXP (src, 1) == dest)
1097 other = XEXP (src, 0);
1099 if (! other || find_base_value (other))
1100 new_reg_base_value[regno] = 0;
1104 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
1105 new_reg_base_value[regno] = 0;
1108 new_reg_base_value[regno] = 0;
1111 /* If this is the first set of a register, record the value. */
1112 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1113 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1114 new_reg_base_value[regno] = find_base_value (src);
1116 reg_seen[regno] = 1;
1119 /* If a value is known for REGNO, return it. */
1122 get_reg_known_value (unsigned int regno)
1124 if (regno >= FIRST_PSEUDO_REGISTER)
1126 regno -= FIRST_PSEUDO_REGISTER;
1127 if (regno < reg_known_value_size)
1128 return reg_known_value[regno];
1136 set_reg_known_value (unsigned int regno, rtx val)
1138 if (regno >= FIRST_PSEUDO_REGISTER)
1140 regno -= FIRST_PSEUDO_REGISTER;
1141 if (regno < reg_known_value_size)
1142 reg_known_value[regno] = val;
1146 /* Similarly for reg_known_equiv_p. */
1149 get_reg_known_equiv_p (unsigned int regno)
1151 if (regno >= FIRST_PSEUDO_REGISTER)
1153 regno -= FIRST_PSEUDO_REGISTER;
1154 if (regno < reg_known_value_size)
1155 return reg_known_equiv_p[regno];
1161 set_reg_known_equiv_p (unsigned int regno, bool val)
1163 if (regno >= FIRST_PSEUDO_REGISTER)
1165 regno -= FIRST_PSEUDO_REGISTER;
1166 if (regno < reg_known_value_size)
1167 reg_known_equiv_p[regno] = val;
1172 /* Returns a canonical version of X, from the point of view alias
1173 analysis. (For example, if X is a MEM whose address is a register,
1174 and the register has a known value (say a SYMBOL_REF), then a MEM
1175 whose address is the SYMBOL_REF is returned.) */
1180 /* Recursively look for equivalences. */
1181 if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER)
1183 rtx t = get_reg_known_value (REGNO (x));
1187 return canon_rtx (t);
1190 if (GET_CODE (x) == PLUS)
1192 rtx x0 = canon_rtx (XEXP (x, 0));
1193 rtx x1 = canon_rtx (XEXP (x, 1));
1195 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1197 if (GET_CODE (x0) == CONST_INT)
1198 return plus_constant (x1, INTVAL (x0));
1199 else if (GET_CODE (x1) == CONST_INT)
1200 return plus_constant (x0, INTVAL (x1));
1201 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1205 /* This gives us much better alias analysis when called from
1206 the loop optimizer. Note we want to leave the original
1207 MEM alone, but need to return the canonicalized MEM with
1208 all the flags with their original values. */
1210 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1215 /* Return 1 if X and Y are identical-looking rtx's.
1216 Expect that X and Y has been already canonicalized.
1218 We use the data in reg_known_value above to see if two registers with
1219 different numbers are, in fact, equivalent. */
1222 rtx_equal_for_memref_p (const_rtx x, const_rtx y)
1229 if (x == 0 && y == 0)
1231 if (x == 0 || y == 0)
1237 code = GET_CODE (x);
1238 /* Rtx's of different codes cannot be equal. */
1239 if (code != GET_CODE (y))
1242 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1243 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1245 if (GET_MODE (x) != GET_MODE (y))
1248 /* Some RTL can be compared without a recursive examination. */
1252 return REGNO (x) == REGNO (y);
1255 return XEXP (x, 0) == XEXP (y, 0);
1258 return XSTR (x, 0) == XSTR (y, 0);
1264 /* There's no need to compare the contents of CONST_DOUBLEs or
1265 CONST_INTs because pointer equality is a good enough
1266 comparison for these nodes. */
1273 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1275 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1276 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1277 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1278 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1279 /* For commutative operations, the RTX match if the operand match in any
1280 order. Also handle the simple binary and unary cases without a loop. */
1281 if (COMMUTATIVE_P (x))
1283 rtx xop0 = canon_rtx (XEXP (x, 0));
1284 rtx yop0 = canon_rtx (XEXP (y, 0));
1285 rtx yop1 = canon_rtx (XEXP (y, 1));
1287 return ((rtx_equal_for_memref_p (xop0, yop0)
1288 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1289 || (rtx_equal_for_memref_p (xop0, yop1)
1290 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1292 else if (NON_COMMUTATIVE_P (x))
1294 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1295 canon_rtx (XEXP (y, 0)))
1296 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1297 canon_rtx (XEXP (y, 1))));
1299 else if (UNARY_P (x))
1300 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1301 canon_rtx (XEXP (y, 0)));
1303 /* Compare the elements. If any pair of corresponding elements
1304 fail to match, return 0 for the whole things.
1306 Limit cases to types which actually appear in addresses. */
1308 fmt = GET_RTX_FORMAT (code);
1309 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1314 if (XINT (x, i) != XINT (y, i))
1319 /* Two vectors must have the same length. */
1320 if (XVECLEN (x, i) != XVECLEN (y, i))
1323 /* And the corresponding elements must match. */
1324 for (j = 0; j < XVECLEN (x, i); j++)
1325 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1326 canon_rtx (XVECEXP (y, i, j))) == 0)
1331 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1332 canon_rtx (XEXP (y, i))) == 0)
1336 /* This can happen for asm operands. */
1338 if (strcmp (XSTR (x, i), XSTR (y, i)))
1342 /* This can happen for an asm which clobbers memory. */
1346 /* It is believed that rtx's at this level will never
1347 contain anything but integers and other rtx's,
1348 except for within LABEL_REFs and SYMBOL_REFs. */
1357 find_base_term (rtx x)
1360 struct elt_loc_list *l;
1362 #if defined (FIND_BASE_TERM)
1363 /* Try machine-dependent ways to find the base term. */
1364 x = FIND_BASE_TERM (x);
1367 switch (GET_CODE (x))
1370 return REG_BASE_VALUE (x);
1373 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1383 return find_base_term (XEXP (x, 0));
1386 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1388 rtx temp = find_base_term (XEXP (x, 0));
1390 if (temp != 0 && CONSTANT_P (temp))
1391 temp = convert_memory_address (Pmode, temp);
1397 val = CSELIB_VAL_PTR (x);
1400 for (l = val->locs; l; l = l->next)
1401 if ((x = find_base_term (l->loc)) != 0)
1407 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1411 /* The standard form is (lo_sum reg sym) so look only at the
1413 return find_base_term (XEXP (x, 1));
1417 rtx tmp1 = XEXP (x, 0);
1418 rtx tmp2 = XEXP (x, 1);
1420 /* This is a little bit tricky since we have to determine which of
1421 the two operands represents the real base address. Otherwise this
1422 routine may return the index register instead of the base register.
1424 That may cause us to believe no aliasing was possible, when in
1425 fact aliasing is possible.
1427 We use a few simple tests to guess the base register. Additional
1428 tests can certainly be added. For example, if one of the operands
1429 is a shift or multiply, then it must be the index register and the
1430 other operand is the base register. */
1432 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1433 return find_base_term (tmp2);
1435 /* If either operand is known to be a pointer, then use it
1436 to determine the base term. */
1437 if (REG_P (tmp1) && REG_POINTER (tmp1))
1438 return find_base_term (tmp1);
1440 if (REG_P (tmp2) && REG_POINTER (tmp2))
1441 return find_base_term (tmp2);
1443 /* Neither operand was known to be a pointer. Go ahead and find the
1444 base term for both operands. */
1445 tmp1 = find_base_term (tmp1);
1446 tmp2 = find_base_term (tmp2);
1448 /* If either base term is named object or a special address
1449 (like an argument or stack reference), then use it for the
1452 && (GET_CODE (tmp1) == SYMBOL_REF
1453 || GET_CODE (tmp1) == LABEL_REF
1454 || (GET_CODE (tmp1) == ADDRESS
1455 && GET_MODE (tmp1) != VOIDmode)))
1459 && (GET_CODE (tmp2) == SYMBOL_REF
1460 || GET_CODE (tmp2) == LABEL_REF
1461 || (GET_CODE (tmp2) == ADDRESS
1462 && GET_MODE (tmp2) != VOIDmode)))
1465 /* We could not determine which of the two operands was the
1466 base register and which was the index. So we can determine
1467 nothing from the base alias check. */
1472 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1473 return find_base_term (XEXP (x, 0));
1485 /* Return 0 if the addresses X and Y are known to point to different
1486 objects, 1 if they might be pointers to the same object. */
1489 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1490 enum machine_mode y_mode)
1492 rtx x_base = find_base_term (x);
1493 rtx y_base = find_base_term (y);
1495 /* If the address itself has no known base see if a known equivalent
1496 value has one. If either address still has no known base, nothing
1497 is known about aliasing. */
1502 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1505 x_base = find_base_term (x_c);
1513 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1516 y_base = find_base_term (y_c);
1521 /* If the base addresses are equal nothing is known about aliasing. */
1522 if (rtx_equal_p (x_base, y_base))
1525 /* The base addresses of the read and write are different expressions.
1526 If they are both symbols and they are not accessed via AND, there is
1527 no conflict. We can bring knowledge of object alignment into play
1528 here. For example, on alpha, "char a, b;" can alias one another,
1529 though "char a; long b;" cannot. */
1530 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1532 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1534 if (GET_CODE (x) == AND
1535 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1536 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1538 if (GET_CODE (y) == AND
1539 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1540 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1542 /* Differing symbols never alias. */
1546 /* If one address is a stack reference there can be no alias:
1547 stack references using different base registers do not alias,
1548 a stack reference can not alias a parameter, and a stack reference
1549 can not alias a global. */
1550 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1551 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1554 if (! flag_argument_noalias)
1557 if (flag_argument_noalias > 1)
1560 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1561 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1564 /* Convert the address X into something we can use. This is done by returning
1565 it unchanged unless it is a value; in the latter case we call cselib to get
1566 a more useful rtx. */
1572 struct elt_loc_list *l;
1574 if (GET_CODE (x) != VALUE)
1576 v = CSELIB_VAL_PTR (x);
1579 for (l = v->locs; l; l = l->next)
1580 if (CONSTANT_P (l->loc))
1582 for (l = v->locs; l; l = l->next)
1583 if (!REG_P (l->loc) && !MEM_P (l->loc))
1586 return v->locs->loc;
1591 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1592 where SIZE is the size in bytes of the memory reference. If ADDR
1593 is not modified by the memory reference then ADDR is returned. */
1596 addr_side_effect_eval (rtx addr, int size, int n_refs)
1600 switch (GET_CODE (addr))
1603 offset = (n_refs + 1) * size;
1606 offset = -(n_refs + 1) * size;
1609 offset = n_refs * size;
1612 offset = -n_refs * size;
1620 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1623 addr = XEXP (addr, 0);
1624 addr = canon_rtx (addr);
1629 /* Return nonzero if X and Y (memory addresses) could reference the
1630 same location in memory. C is an offset accumulator. When
1631 C is nonzero, we are testing aliases between X and Y + C.
1632 XSIZE is the size in bytes of the X reference,
1633 similarly YSIZE is the size in bytes for Y.
1634 Expect that canon_rtx has been already called for X and Y.
1636 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1637 referenced (the reference was BLKmode), so make the most pessimistic
1640 If XSIZE or YSIZE is negative, we may access memory outside the object
1641 being referenced as a side effect. This can happen when using AND to
1642 align memory references, as is done on the Alpha.
1644 Nice to notice that varying addresses cannot conflict with fp if no
1645 local variables had their addresses taken, but that's too hard now. */
1648 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1650 if (GET_CODE (x) == VALUE)
1652 if (GET_CODE (y) == VALUE)
1654 if (GET_CODE (x) == HIGH)
1656 else if (GET_CODE (x) == LO_SUM)
1659 x = addr_side_effect_eval (x, xsize, 0);
1660 if (GET_CODE (y) == HIGH)
1662 else if (GET_CODE (y) == LO_SUM)
1665 y = addr_side_effect_eval (y, ysize, 0);
1667 if (rtx_equal_for_memref_p (x, y))
1669 if (xsize <= 0 || ysize <= 0)
1671 if (c >= 0 && xsize > c)
1673 if (c < 0 && ysize+c > 0)
1678 /* This code used to check for conflicts involving stack references and
1679 globals but the base address alias code now handles these cases. */
1681 if (GET_CODE (x) == PLUS)
1683 /* The fact that X is canonicalized means that this
1684 PLUS rtx is canonicalized. */
1685 rtx x0 = XEXP (x, 0);
1686 rtx x1 = XEXP (x, 1);
1688 if (GET_CODE (y) == PLUS)
1690 /* The fact that Y is canonicalized means that this
1691 PLUS rtx is canonicalized. */
1692 rtx y0 = XEXP (y, 0);
1693 rtx y1 = XEXP (y, 1);
1695 if (rtx_equal_for_memref_p (x1, y1))
1696 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1697 if (rtx_equal_for_memref_p (x0, y0))
1698 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1699 if (GET_CODE (x1) == CONST_INT)
1701 if (GET_CODE (y1) == CONST_INT)
1702 return memrefs_conflict_p (xsize, x0, ysize, y0,
1703 c - INTVAL (x1) + INTVAL (y1));
1705 return memrefs_conflict_p (xsize, x0, ysize, y,
1708 else if (GET_CODE (y1) == CONST_INT)
1709 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1713 else if (GET_CODE (x1) == CONST_INT)
1714 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1716 else if (GET_CODE (y) == PLUS)
1718 /* The fact that Y is canonicalized means that this
1719 PLUS rtx is canonicalized. */
1720 rtx y0 = XEXP (y, 0);
1721 rtx y1 = XEXP (y, 1);
1723 if (GET_CODE (y1) == CONST_INT)
1724 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1729 if (GET_CODE (x) == GET_CODE (y))
1730 switch (GET_CODE (x))
1734 /* Handle cases where we expect the second operands to be the
1735 same, and check only whether the first operand would conflict
1738 rtx x1 = canon_rtx (XEXP (x, 1));
1739 rtx y1 = canon_rtx (XEXP (y, 1));
1740 if (! rtx_equal_for_memref_p (x1, y1))
1742 x0 = canon_rtx (XEXP (x, 0));
1743 y0 = canon_rtx (XEXP (y, 0));
1744 if (rtx_equal_for_memref_p (x0, y0))
1745 return (xsize == 0 || ysize == 0
1746 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1748 /* Can't properly adjust our sizes. */
1749 if (GET_CODE (x1) != CONST_INT)
1751 xsize /= INTVAL (x1);
1752 ysize /= INTVAL (x1);
1754 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1761 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1762 as an access with indeterminate size. Assume that references
1763 besides AND are aligned, so if the size of the other reference is
1764 at least as large as the alignment, assume no other overlap. */
1765 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1767 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1769 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1771 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1773 /* ??? If we are indexing far enough into the array/structure, we
1774 may yet be able to determine that we can not overlap. But we
1775 also need to that we are far enough from the end not to overlap
1776 a following reference, so we do nothing with that for now. */
1777 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1779 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1784 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1786 c += (INTVAL (y) - INTVAL (x));
1787 return (xsize <= 0 || ysize <= 0
1788 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1791 if (GET_CODE (x) == CONST)
1793 if (GET_CODE (y) == CONST)
1794 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1795 ysize, canon_rtx (XEXP (y, 0)), c);
1797 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1800 if (GET_CODE (y) == CONST)
1801 return memrefs_conflict_p (xsize, x, ysize,
1802 canon_rtx (XEXP (y, 0)), c);
1805 return (xsize <= 0 || ysize <= 0
1806 || (rtx_equal_for_memref_p (x, y)
1807 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1814 /* Functions to compute memory dependencies.
1816 Since we process the insns in execution order, we can build tables
1817 to keep track of what registers are fixed (and not aliased), what registers
1818 are varying in known ways, and what registers are varying in unknown
1821 If both memory references are volatile, then there must always be a
1822 dependence between the two references, since their order can not be
1823 changed. A volatile and non-volatile reference can be interchanged
1826 A MEM_IN_STRUCT reference at a non-AND varying address can never
1827 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1828 also must allow AND addresses, because they may generate accesses
1829 outside the object being referenced. This is used to generate
1830 aligned addresses from unaligned addresses, for instance, the alpha
1831 storeqi_unaligned pattern. */
1833 /* Read dependence: X is read after read in MEM takes place. There can
1834 only be a dependence here if both reads are volatile. */
1837 read_dependence (const_rtx mem, const_rtx x)
1839 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1842 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1843 MEM2 is a reference to a structure at a varying address, or returns
1844 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1845 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1846 to decide whether or not an address may vary; it should return
1847 nonzero whenever variation is possible.
1848 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1851 fixed_scalar_and_varying_struct_p (const_rtx mem1, const_rtx mem2, rtx mem1_addr,
1853 bool (*varies_p) (const_rtx, bool))
1855 if (! flag_strict_aliasing)
1858 if (MEM_ALIAS_SET (mem2)
1859 && MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1860 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1861 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1865 if (MEM_ALIAS_SET (mem1)
1866 && MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1867 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1868 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1875 /* Returns nonzero if something about the mode or address format MEM1
1876 indicates that it might well alias *anything*. */
1879 aliases_everything_p (const_rtx mem)
1881 if (GET_CODE (XEXP (mem, 0)) == AND)
1882 /* If the address is an AND, it's very hard to know at what it is
1883 actually pointing. */
1889 /* Return true if we can determine that the fields referenced cannot
1890 overlap for any pair of objects. */
1893 nonoverlapping_component_refs_p (const_tree x, const_tree y)
1895 const_tree fieldx, fieldy, typex, typey, orig_y;
1899 /* The comparison has to be done at a common type, since we don't
1900 know how the inheritance hierarchy works. */
1904 fieldx = TREE_OPERAND (x, 1);
1905 typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx));
1910 fieldy = TREE_OPERAND (y, 1);
1911 typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy));
1916 y = TREE_OPERAND (y, 0);
1918 while (y && TREE_CODE (y) == COMPONENT_REF);
1920 x = TREE_OPERAND (x, 0);
1922 while (x && TREE_CODE (x) == COMPONENT_REF);
1923 /* Never found a common type. */
1927 /* If we're left with accessing different fields of a structure,
1929 if (TREE_CODE (typex) == RECORD_TYPE
1930 && fieldx != fieldy)
1933 /* The comparison on the current field failed. If we're accessing
1934 a very nested structure, look at the next outer level. */
1935 x = TREE_OPERAND (x, 0);
1936 y = TREE_OPERAND (y, 0);
1939 && TREE_CODE (x) == COMPONENT_REF
1940 && TREE_CODE (y) == COMPONENT_REF);
1945 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1948 decl_for_component_ref (tree x)
1952 x = TREE_OPERAND (x, 0);
1954 while (x && TREE_CODE (x) == COMPONENT_REF);
1956 return x && DECL_P (x) ? x : NULL_TREE;
1959 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1960 offset of the field reference. */
1963 adjust_offset_for_component_ref (tree x, rtx offset)
1965 HOST_WIDE_INT ioffset;
1970 ioffset = INTVAL (offset);
1973 tree offset = component_ref_field_offset (x);
1974 tree field = TREE_OPERAND (x, 1);
1976 if (! host_integerp (offset, 1))
1978 ioffset += (tree_low_cst (offset, 1)
1979 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1982 x = TREE_OPERAND (x, 0);
1984 while (x && TREE_CODE (x) == COMPONENT_REF);
1986 return GEN_INT (ioffset);
1989 /* Return nonzero if we can determine the exprs corresponding to memrefs
1990 X and Y and they do not overlap. */
1993 nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
1995 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1998 rtx moffsetx, moffsety;
1999 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
2001 /* Unless both have exprs, we can't tell anything. */
2002 if (exprx == 0 || expry == 0)
2005 /* If both are field references, we may be able to determine something. */
2006 if (TREE_CODE (exprx) == COMPONENT_REF
2007 && TREE_CODE (expry) == COMPONENT_REF
2008 && nonoverlapping_component_refs_p (exprx, expry))
2012 /* If the field reference test failed, look at the DECLs involved. */
2013 moffsetx = MEM_OFFSET (x);
2014 if (TREE_CODE (exprx) == COMPONENT_REF)
2016 if (TREE_CODE (expry) == VAR_DECL
2017 && POINTER_TYPE_P (TREE_TYPE (expry)))
2019 tree field = TREE_OPERAND (exprx, 1);
2020 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2021 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2026 tree t = decl_for_component_ref (exprx);
2029 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
2033 else if (INDIRECT_REF_P (exprx))
2035 exprx = TREE_OPERAND (exprx, 0);
2036 if (flag_argument_noalias < 2
2037 || TREE_CODE (exprx) != PARM_DECL)
2041 moffsety = MEM_OFFSET (y);
2042 if (TREE_CODE (expry) == COMPONENT_REF)
2044 if (TREE_CODE (exprx) == VAR_DECL
2045 && POINTER_TYPE_P (TREE_TYPE (exprx)))
2047 tree field = TREE_OPERAND (expry, 1);
2048 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2049 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2054 tree t = decl_for_component_ref (expry);
2057 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2061 else if (INDIRECT_REF_P (expry))
2063 expry = TREE_OPERAND (expry, 0);
2064 if (flag_argument_noalias < 2
2065 || TREE_CODE (expry) != PARM_DECL)
2069 if (! DECL_P (exprx) || ! DECL_P (expry))
2072 rtlx = DECL_RTL (exprx);
2073 rtly = DECL_RTL (expry);
2075 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2076 can't overlap unless they are the same because we never reuse that part
2077 of the stack frame used for locals for spilled pseudos. */
2078 if ((!MEM_P (rtlx) || !MEM_P (rtly))
2079 && ! rtx_equal_p (rtlx, rtly))
2082 /* Get the base and offsets of both decls. If either is a register, we
2083 know both are and are the same, so use that as the base. The only
2084 we can avoid overlap is if we can deduce that they are nonoverlapping
2085 pieces of that decl, which is very rare. */
2086 basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx;
2087 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2088 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2090 basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly;
2091 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2092 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2094 /* If the bases are different, we know they do not overlap if both
2095 are constants or if one is a constant and the other a pointer into the
2096 stack frame. Otherwise a different base means we can't tell if they
2098 if (! rtx_equal_p (basex, basey))
2099 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2100 || (CONSTANT_P (basex) && REG_P (basey)
2101 && REGNO_PTR_FRAME_P (REGNO (basey)))
2102 || (CONSTANT_P (basey) && REG_P (basex)
2103 && REGNO_PTR_FRAME_P (REGNO (basex))));
2105 sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2106 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2108 sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2109 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2112 /* If we have an offset for either memref, it can update the values computed
2115 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2117 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2119 /* If a memref has both a size and an offset, we can use the smaller size.
2120 We can't do this if the offset isn't known because we must view this
2121 memref as being anywhere inside the DECL's MEM. */
2122 if (MEM_SIZE (x) && moffsetx)
2123 sizex = INTVAL (MEM_SIZE (x));
2124 if (MEM_SIZE (y) && moffsety)
2125 sizey = INTVAL (MEM_SIZE (y));
2127 /* Put the values of the memref with the lower offset in X's values. */
2128 if (offsetx > offsety)
2130 tem = offsetx, offsetx = offsety, offsety = tem;
2131 tem = sizex, sizex = sizey, sizey = tem;
2134 /* If we don't know the size of the lower-offset value, we can't tell
2135 if they conflict. Otherwise, we do the test. */
2136 return sizex >= 0 && offsety >= offsetx + sizex;
2139 /* True dependence: X is read after store in MEM takes place. */
2142 true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x,
2143 bool (*varies) (const_rtx, bool))
2145 rtx x_addr, mem_addr;
2148 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2151 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2152 This is used in epilogue deallocation functions, and in cselib. */
2153 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2155 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2157 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2158 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2161 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2164 /* Read-only memory is by definition never modified, and therefore can't
2165 conflict with anything. We don't expect to find read-only set on MEM,
2166 but stupid user tricks can produce them, so don't die. */
2167 if (MEM_READONLY_P (x))
2170 if (nonoverlapping_memrefs_p (mem, x))
2173 if (mem_mode == VOIDmode)
2174 mem_mode = GET_MODE (mem);
2176 x_addr = get_addr (XEXP (x, 0));
2177 mem_addr = get_addr (XEXP (mem, 0));
2179 base = find_base_term (x_addr);
2180 if (base && (GET_CODE (base) == LABEL_REF
2181 || (GET_CODE (base) == SYMBOL_REF
2182 && CONSTANT_POOL_ADDRESS_P (base))))
2185 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2188 x_addr = canon_rtx (x_addr);
2189 mem_addr = canon_rtx (mem_addr);
2191 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2192 SIZE_FOR_MODE (x), x_addr, 0))
2195 if (aliases_everything_p (x))
2198 /* We cannot use aliases_everything_p to test MEM, since we must look
2199 at MEM_MODE, rather than GET_MODE (MEM). */
2200 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2203 /* In true_dependence we also allow BLKmode to alias anything. Why
2204 don't we do this in anti_dependence and output_dependence? */
2205 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2208 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2212 /* Canonical true dependence: X is read after store in MEM takes place.
2213 Variant of true_dependence which assumes MEM has already been
2214 canonicalized (hence we no longer do that here).
2215 The mem_addr argument has been added, since true_dependence computed
2216 this value prior to canonicalizing. */
2219 canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2220 const_rtx x, bool (*varies) (const_rtx, bool))
2224 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2227 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2228 This is used in epilogue deallocation functions. */
2229 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2231 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2233 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2234 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2237 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2240 /* Read-only memory is by definition never modified, and therefore can't
2241 conflict with anything. We don't expect to find read-only set on MEM,
2242 but stupid user tricks can produce them, so don't die. */
2243 if (MEM_READONLY_P (x))
2246 if (nonoverlapping_memrefs_p (x, mem))
2249 x_addr = get_addr (XEXP (x, 0));
2251 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2254 x_addr = canon_rtx (x_addr);
2255 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2256 SIZE_FOR_MODE (x), x_addr, 0))
2259 if (aliases_everything_p (x))
2262 /* We cannot use aliases_everything_p to test MEM, since we must look
2263 at MEM_MODE, rather than GET_MODE (MEM). */
2264 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2267 /* In true_dependence we also allow BLKmode to alias anything. Why
2268 don't we do this in anti_dependence and output_dependence? */
2269 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2272 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2276 /* Returns nonzero if a write to X might alias a previous read from
2277 (or, if WRITEP is nonzero, a write to) MEM. */
2280 write_dependence_p (const_rtx mem, const_rtx x, int writep)
2282 rtx x_addr, mem_addr;
2283 const_rtx fixed_scalar;
2286 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2289 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2290 This is used in epilogue deallocation functions. */
2291 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2293 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2295 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2296 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2299 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2302 /* A read from read-only memory can't conflict with read-write memory. */
2303 if (!writep && MEM_READONLY_P (mem))
2306 if (nonoverlapping_memrefs_p (x, mem))
2309 x_addr = get_addr (XEXP (x, 0));
2310 mem_addr = get_addr (XEXP (mem, 0));
2314 base = find_base_term (mem_addr);
2315 if (base && (GET_CODE (base) == LABEL_REF
2316 || (GET_CODE (base) == SYMBOL_REF
2317 && CONSTANT_POOL_ADDRESS_P (base))))
2321 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2325 x_addr = canon_rtx (x_addr);
2326 mem_addr = canon_rtx (mem_addr);
2328 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2329 SIZE_FOR_MODE (x), x_addr, 0))
2333 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2336 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2337 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2340 /* Anti dependence: X is written after read in MEM takes place. */
2343 anti_dependence (const_rtx mem, const_rtx x)
2345 return write_dependence_p (mem, x, /*writep=*/0);
2348 /* Output dependence: X is written after store in MEM takes place. */
2351 output_dependence (const_rtx mem, const_rtx x)
2353 return write_dependence_p (mem, x, /*writep=*/1);
2358 init_alias_target (void)
2362 memset (static_reg_base_value, 0, sizeof static_reg_base_value);
2364 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2365 /* Check whether this register can hold an incoming pointer
2366 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2367 numbers, so translate if necessary due to register windows. */
2368 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2369 && HARD_REGNO_MODE_OK (i, Pmode))
2370 static_reg_base_value[i]
2371 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2373 static_reg_base_value[STACK_POINTER_REGNUM]
2374 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2375 static_reg_base_value[ARG_POINTER_REGNUM]
2376 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2377 static_reg_base_value[FRAME_POINTER_REGNUM]
2378 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2379 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2380 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2381 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2385 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2386 to be memory reference. */
2387 static bool memory_modified;
2389 memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
2393 if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data))
2394 memory_modified = true;
2399 /* Return true when INSN possibly modify memory contents of MEM
2400 (i.e. address can be modified). */
2402 memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
2406 memory_modified = false;
2407 note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
2408 return memory_modified;
2411 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2415 init_alias_analysis (void)
2417 unsigned int maxreg = max_reg_num ();
2423 timevar_push (TV_ALIAS_ANALYSIS);
2425 reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER;
2426 reg_known_value = GGC_CNEWVEC (rtx, reg_known_value_size);
2427 reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size);
2429 /* If we have memory allocated from the previous run, use it. */
2430 if (old_reg_base_value)
2431 reg_base_value = old_reg_base_value;
2434 VEC_truncate (rtx, reg_base_value, 0);
2436 VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg);
2438 new_reg_base_value = XNEWVEC (rtx, maxreg);
2439 reg_seen = XNEWVEC (char, maxreg);
2441 /* The basic idea is that each pass through this loop will use the
2442 "constant" information from the previous pass to propagate alias
2443 information through another level of assignments.
2445 This could get expensive if the assignment chains are long. Maybe
2446 we should throttle the number of iterations, possibly based on
2447 the optimization level or flag_expensive_optimizations.
2449 We could propagate more information in the first pass by making use
2450 of DF_REG_DEF_COUNT to determine immediately that the alias information
2451 for a pseudo is "constant".
2453 A program with an uninitialized variable can cause an infinite loop
2454 here. Instead of doing a full dataflow analysis to detect such problems
2455 we just cap the number of iterations for the loop.
2457 The state of the arrays for the set chain in question does not matter
2458 since the program has undefined behavior. */
2463 /* Assume nothing will change this iteration of the loop. */
2466 /* We want to assign the same IDs each iteration of this loop, so
2467 start counting from zero each iteration of the loop. */
2470 /* We're at the start of the function each iteration through the
2471 loop, so we're copying arguments. */
2472 copying_arguments = true;
2474 /* Wipe the potential alias information clean for this pass. */
2475 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2477 /* Wipe the reg_seen array clean. */
2478 memset (reg_seen, 0, maxreg);
2480 /* Mark all hard registers which may contain an address.
2481 The stack, frame and argument pointers may contain an address.
2482 An argument register which can hold a Pmode value may contain
2483 an address even if it is not in BASE_REGS.
2485 The address expression is VOIDmode for an argument and
2486 Pmode for other registers. */
2488 memcpy (new_reg_base_value, static_reg_base_value,
2489 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2491 /* Walk the insns adding values to the new_reg_base_value array. */
2492 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2498 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2499 /* The prologue/epilogue insns are not threaded onto the
2500 insn chain until after reload has completed. Thus,
2501 there is no sense wasting time checking if INSN is in
2502 the prologue/epilogue until after reload has completed. */
2503 if (reload_completed
2504 && prologue_epilogue_contains (insn))
2508 /* If this insn has a noalias note, process it, Otherwise,
2509 scan for sets. A simple set will have no side effects
2510 which could change the base value of any other register. */
2512 if (GET_CODE (PATTERN (insn)) == SET
2513 && REG_NOTES (insn) != 0
2514 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2515 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2517 note_stores (PATTERN (insn), record_set, NULL);
2519 set = single_set (insn);
2522 && REG_P (SET_DEST (set))
2523 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2525 unsigned int regno = REGNO (SET_DEST (set));
2526 rtx src = SET_SRC (set);
2529 note = find_reg_equal_equiv_note (insn);
2530 if (note && REG_NOTE_KIND (note) == REG_EQUAL
2531 && DF_REG_DEF_COUNT (regno) != 1)
2534 if (note != NULL_RTX
2535 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2536 && ! rtx_varies_p (XEXP (note, 0), 1)
2537 && ! reg_overlap_mentioned_p (SET_DEST (set),
2540 set_reg_known_value (regno, XEXP (note, 0));
2541 set_reg_known_equiv_p (regno,
2542 REG_NOTE_KIND (note) == REG_EQUIV);
2544 else if (DF_REG_DEF_COUNT (regno) == 1
2545 && GET_CODE (src) == PLUS
2546 && REG_P (XEXP (src, 0))
2547 && (t = get_reg_known_value (REGNO (XEXP (src, 0))))
2548 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2550 t = plus_constant (t, INTVAL (XEXP (src, 1)));
2551 set_reg_known_value (regno, t);
2552 set_reg_known_equiv_p (regno, 0);
2554 else if (DF_REG_DEF_COUNT (regno) == 1
2555 && ! rtx_varies_p (src, 1))
2557 set_reg_known_value (regno, src);
2558 set_reg_known_equiv_p (regno, 0);
2562 else if (NOTE_P (insn)
2563 && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG)
2564 copying_arguments = false;
2567 /* Now propagate values from new_reg_base_value to reg_base_value. */
2568 gcc_assert (maxreg == (unsigned int) max_reg_num ());
2570 for (ui = 0; ui < maxreg; ui++)
2572 if (new_reg_base_value[ui]
2573 && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui)
2574 && ! rtx_equal_p (new_reg_base_value[ui],
2575 VEC_index (rtx, reg_base_value, ui)))
2577 VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]);
2582 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2584 /* Fill in the remaining entries. */
2585 for (i = 0; i < (int)reg_known_value_size; i++)
2586 if (reg_known_value[i] == 0)
2587 reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER];
2590 free (new_reg_base_value);
2591 new_reg_base_value = 0;
2594 timevar_pop (TV_ALIAS_ANALYSIS);
2598 end_alias_analysis (void)
2600 old_reg_base_value = reg_base_value;
2601 ggc_free (reg_known_value);
2602 reg_known_value = 0;
2603 reg_known_value_size = 0;
2604 free (reg_known_equiv_p);
2605 reg_known_equiv_p = 0;
2608 #include "gt-alias.h"