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. If this is a type with a known alias set, return it. */
608 t
= TYPE_MAIN_VARIANT (t
);
609 if (TYPE_ALIAS_SET_KNOWN_P (t
))
610 return TYPE_ALIAS_SET (t
);
612 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
613 if (!COMPLETE_TYPE_P (t
))
615 /* For arrays with unknown size the conservative answer is the
616 alias set of the element type. */
617 if (TREE_CODE (t
) == ARRAY_TYPE
)
618 return get_alias_set (TREE_TYPE (t
));
620 /* But return zero as a conservative answer for incomplete types. */
624 /* See if the language has special handling for this type. */
625 set
= lang_hooks
.get_alias_set (t
);
629 /* There are no objects of FUNCTION_TYPE, so there's no point in
630 using up an alias set for them. (There are, of course, pointers
631 and references to functions, but that's different.) */
632 else if (TREE_CODE (t
) == FUNCTION_TYPE
633 || TREE_CODE (t
) == METHOD_TYPE
)
636 /* Unless the language specifies otherwise, let vector types alias
637 their components. This avoids some nasty type punning issues in
638 normal usage. And indeed lets vectors be treated more like an
640 else if (TREE_CODE (t
) == VECTOR_TYPE
)
641 set
= get_alias_set (TREE_TYPE (t
));
644 /* Otherwise make a new alias set for this type. */
645 set
= new_alias_set ();
647 TYPE_ALIAS_SET (t
) = set
;
649 /* If this is an aggregate type, we must record any component aliasing
651 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
652 record_component_aliases (t
);
657 /* Return a brand-new alias set. */
662 if (flag_strict_aliasing
)
665 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
666 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
667 return VEC_length (alias_set_entry
, alias_sets
) - 1;
673 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
674 not everything that aliases SUPERSET also aliases SUBSET. For example,
675 in C, a store to an `int' can alias a load of a structure containing an
676 `int', and vice versa. But it can't alias a load of a 'double' member
677 of the same structure. Here, the structure would be the SUPERSET and
678 `int' the SUBSET. This relationship is also described in the comment at
679 the beginning of this file.
681 This function should be called only once per SUPERSET/SUBSET pair.
683 It is illegal for SUPERSET to be zero; everything is implicitly a
684 subset of alias set zero. */
687 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
689 alias_set_entry superset_entry
;
690 alias_set_entry subset_entry
;
692 /* It is possible in complex type situations for both sets to be the same,
693 in which case we can ignore this operation. */
694 if (superset
== subset
)
697 gcc_assert (superset
);
699 superset_entry
= get_alias_set_entry (superset
);
700 if (superset_entry
== 0)
702 /* Create an entry for the SUPERSET, so that we have a place to
703 attach the SUBSET. */
704 superset_entry
= ggc_alloc (sizeof (struct alias_set_entry
));
705 superset_entry
->alias_set
= superset
;
706 superset_entry
->children
707 = splay_tree_new_ggc (splay_tree_compare_ints
);
708 superset_entry
->has_zero_child
= 0;
709 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
713 superset_entry
->has_zero_child
= 1;
716 subset_entry
= get_alias_set_entry (subset
);
717 /* If there is an entry for the subset, enter all of its children
718 (if they are not already present) as children of the SUPERSET. */
721 if (subset_entry
->has_zero_child
)
722 superset_entry
->has_zero_child
= 1;
724 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
725 superset_entry
->children
);
728 /* Enter the SUBSET itself as a child of the SUPERSET. */
729 splay_tree_insert (superset_entry
->children
,
730 (splay_tree_key
) subset
, 0);
734 /* Record that component types of TYPE, if any, are part of that type for
735 aliasing purposes. For record types, we only record component types
736 for fields that are not marked non-addressable. For array types, we
737 only record the component type if it is not marked non-aliased. */
740 record_component_aliases (tree type
)
742 alias_set_type superset
= get_alias_set (type
);
748 switch (TREE_CODE (type
))
751 if (!TYPE_NONALIASED_COMPONENT (type
))
752 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
757 case QUAL_UNION_TYPE
:
758 /* Recursively record aliases for the base classes, if there are any. */
759 if (TYPE_BINFO (type
))
762 tree binfo
, base_binfo
;
764 for (binfo
= TYPE_BINFO (type
), i
= 0;
765 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
766 record_alias_subset (superset
,
767 get_alias_set (BINFO_TYPE (base_binfo
)));
769 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
770 if (TREE_CODE (field
) == FIELD_DECL
&& !DECL_NONADDRESSABLE_P (field
))
771 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
775 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
783 /* Allocate an alias set for use in storing and reading from the varargs
786 static GTY(()) alias_set_type varargs_set
= -1;
789 get_varargs_alias_set (void)
792 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
793 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
794 consistently use the varargs alias set for loads from the varargs
795 area. So don't use it anywhere. */
798 if (varargs_set
== -1)
799 varargs_set
= new_alias_set ();
805 /* Likewise, but used for the fixed portions of the frame, e.g., register
808 static GTY(()) alias_set_type frame_set
= -1;
811 get_frame_alias_set (void)
814 frame_set
= new_alias_set ();
819 /* Inside SRC, the source of a SET, find a base address. */
822 find_base_value (rtx src
)
826 switch (GET_CODE (src
))
834 /* At the start of a function, argument registers have known base
835 values which may be lost later. Returning an ADDRESS
836 expression here allows optimization based on argument values
837 even when the argument registers are used for other purposes. */
838 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
839 return new_reg_base_value
[regno
];
841 /* If a pseudo has a known base value, return it. Do not do this
842 for non-fixed hard regs since it can result in a circular
843 dependency chain for registers which have values at function entry.
845 The test above is not sufficient because the scheduler may move
846 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
847 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
848 && regno
< VEC_length (rtx
, reg_base_value
))
850 /* If we're inside init_alias_analysis, use new_reg_base_value
851 to reduce the number of relaxation iterations. */
852 if (new_reg_base_value
&& new_reg_base_value
[regno
]
853 && DF_REG_DEF_COUNT (regno
) == 1)
854 return new_reg_base_value
[regno
];
856 if (VEC_index (rtx
, reg_base_value
, regno
))
857 return VEC_index (rtx
, reg_base_value
, regno
);
863 /* Check for an argument passed in memory. Only record in the
864 copying-arguments block; it is too hard to track changes
866 if (copying_arguments
867 && (XEXP (src
, 0) == arg_pointer_rtx
868 || (GET_CODE (XEXP (src
, 0)) == PLUS
869 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
870 return gen_rtx_ADDRESS (VOIDmode
, src
);
875 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
878 /* ... fall through ... */
883 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
885 /* If either operand is a REG that is a known pointer, then it
887 if (REG_P (src_0
) && REG_POINTER (src_0
))
888 return find_base_value (src_0
);
889 if (REG_P (src_1
) && REG_POINTER (src_1
))
890 return find_base_value (src_1
);
892 /* If either operand is a REG, then see if we already have
893 a known value for it. */
896 temp
= find_base_value (src_0
);
903 temp
= find_base_value (src_1
);
908 /* If either base is named object or a special address
909 (like an argument or stack reference), then use it for the
912 && (GET_CODE (src_0
) == SYMBOL_REF
913 || GET_CODE (src_0
) == LABEL_REF
914 || (GET_CODE (src_0
) == ADDRESS
915 && GET_MODE (src_0
) != VOIDmode
)))
919 && (GET_CODE (src_1
) == SYMBOL_REF
920 || GET_CODE (src_1
) == LABEL_REF
921 || (GET_CODE (src_1
) == ADDRESS
922 && GET_MODE (src_1
) != VOIDmode
)))
925 /* Guess which operand is the base address:
926 If either operand is a symbol, then it is the base. If
927 either operand is a CONST_INT, then the other is the base. */
928 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
929 return find_base_value (src_0
);
930 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
931 return find_base_value (src_1
);
937 /* The standard form is (lo_sum reg sym) so look only at the
939 return find_base_value (XEXP (src
, 1));
942 /* If the second operand is constant set the base
943 address to the first operand. */
944 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
945 return find_base_value (XEXP (src
, 0));
949 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
959 return find_base_value (XEXP (src
, 0));
962 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
964 rtx temp
= find_base_value (XEXP (src
, 0));
966 if (temp
!= 0 && CONSTANT_P (temp
))
967 temp
= convert_memory_address (Pmode
, temp
);
979 /* Called from init_alias_analysis indirectly through note_stores. */
981 /* While scanning insns to find base values, reg_seen[N] is nonzero if
982 register N has been set in this function. */
983 static char *reg_seen
;
985 /* Addresses which are known not to alias anything else are identified
986 by a unique integer. */
987 static int unique_id
;
990 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
999 regno
= REGNO (dest
);
1001 gcc_assert (regno
< VEC_length (rtx
, reg_base_value
));
1003 /* If this spans multiple hard registers, then we must indicate that every
1004 register has an unusable value. */
1005 if (regno
< FIRST_PSEUDO_REGISTER
)
1006 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1013 reg_seen
[regno
+ n
] = 1;
1014 new_reg_base_value
[regno
+ n
] = 0;
1021 /* A CLOBBER wipes out any old value but does not prevent a previously
1022 unset register from acquiring a base address (i.e. reg_seen is not
1024 if (GET_CODE (set
) == CLOBBER
)
1026 new_reg_base_value
[regno
] = 0;
1029 src
= SET_SRC (set
);
1033 if (reg_seen
[regno
])
1035 new_reg_base_value
[regno
] = 0;
1038 reg_seen
[regno
] = 1;
1039 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
1040 GEN_INT (unique_id
++));
1044 /* If this is not the first set of REGNO, see whether the new value
1045 is related to the old one. There are two cases of interest:
1047 (1) The register might be assigned an entirely new value
1048 that has the same base term as the original set.
1050 (2) The set might be a simple self-modification that
1051 cannot change REGNO's base value.
1053 If neither case holds, reject the original base value as invalid.
1054 Note that the following situation is not detected:
1056 extern int x, y; int *p = &x; p += (&y-&x);
1058 ANSI C does not allow computing the difference of addresses
1059 of distinct top level objects. */
1060 if (new_reg_base_value
[regno
] != 0
1061 && find_base_value (src
) != new_reg_base_value
[regno
])
1062 switch (GET_CODE (src
))
1066 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1067 new_reg_base_value
[regno
] = 0;
1070 /* If the value we add in the PLUS is also a valid base value,
1071 this might be the actual base value, and the original value
1074 rtx other
= NULL_RTX
;
1076 if (XEXP (src
, 0) == dest
)
1077 other
= XEXP (src
, 1);
1078 else if (XEXP (src
, 1) == dest
)
1079 other
= XEXP (src
, 0);
1081 if (! other
|| find_base_value (other
))
1082 new_reg_base_value
[regno
] = 0;
1086 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
1087 new_reg_base_value
[regno
] = 0;
1090 new_reg_base_value
[regno
] = 0;
1093 /* If this is the first set of a register, record the value. */
1094 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1095 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1096 new_reg_base_value
[regno
] = find_base_value (src
);
1098 reg_seen
[regno
] = 1;
1101 /* If a value is known for REGNO, return it. */
1104 get_reg_known_value (unsigned int regno
)
1106 if (regno
>= FIRST_PSEUDO_REGISTER
)
1108 regno
-= FIRST_PSEUDO_REGISTER
;
1109 if (regno
< reg_known_value_size
)
1110 return reg_known_value
[regno
];
1118 set_reg_known_value (unsigned int regno
, rtx val
)
1120 if (regno
>= FIRST_PSEUDO_REGISTER
)
1122 regno
-= FIRST_PSEUDO_REGISTER
;
1123 if (regno
< reg_known_value_size
)
1124 reg_known_value
[regno
] = val
;
1128 /* Similarly for reg_known_equiv_p. */
1131 get_reg_known_equiv_p (unsigned int regno
)
1133 if (regno
>= FIRST_PSEUDO_REGISTER
)
1135 regno
-= FIRST_PSEUDO_REGISTER
;
1136 if (regno
< reg_known_value_size
)
1137 return reg_known_equiv_p
[regno
];
1143 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1145 if (regno
>= FIRST_PSEUDO_REGISTER
)
1147 regno
-= FIRST_PSEUDO_REGISTER
;
1148 if (regno
< reg_known_value_size
)
1149 reg_known_equiv_p
[regno
] = val
;
1154 /* Returns a canonical version of X, from the point of view alias
1155 analysis. (For example, if X is a MEM whose address is a register,
1156 and the register has a known value (say a SYMBOL_REF), then a MEM
1157 whose address is the SYMBOL_REF is returned.) */
1162 /* Recursively look for equivalences. */
1163 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1165 rtx t
= get_reg_known_value (REGNO (x
));
1169 return canon_rtx (t
);
1172 if (GET_CODE (x
) == PLUS
)
1174 rtx x0
= canon_rtx (XEXP (x
, 0));
1175 rtx x1
= canon_rtx (XEXP (x
, 1));
1177 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1179 if (GET_CODE (x0
) == CONST_INT
)
1180 return plus_constant (x1
, INTVAL (x0
));
1181 else if (GET_CODE (x1
) == CONST_INT
)
1182 return plus_constant (x0
, INTVAL (x1
));
1183 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1187 /* This gives us much better alias analysis when called from
1188 the loop optimizer. Note we want to leave the original
1189 MEM alone, but need to return the canonicalized MEM with
1190 all the flags with their original values. */
1192 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1197 /* Return 1 if X and Y are identical-looking rtx's.
1198 Expect that X and Y has been already canonicalized.
1200 We use the data in reg_known_value above to see if two registers with
1201 different numbers are, in fact, equivalent. */
1204 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1211 if (x
== 0 && y
== 0)
1213 if (x
== 0 || y
== 0)
1219 code
= GET_CODE (x
);
1220 /* Rtx's of different codes cannot be equal. */
1221 if (code
!= GET_CODE (y
))
1224 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1225 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1227 if (GET_MODE (x
) != GET_MODE (y
))
1230 /* Some RTL can be compared without a recursive examination. */
1234 return REGNO (x
) == REGNO (y
);
1237 return XEXP (x
, 0) == XEXP (y
, 0);
1240 return XSTR (x
, 0) == XSTR (y
, 0);
1246 /* There's no need to compare the contents of CONST_DOUBLEs or
1247 CONST_INTs because pointer equality is a good enough
1248 comparison for these nodes. */
1255 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1257 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1258 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1259 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1260 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1261 /* For commutative operations, the RTX match if the operand match in any
1262 order. Also handle the simple binary and unary cases without a loop. */
1263 if (COMMUTATIVE_P (x
))
1265 rtx xop0
= canon_rtx (XEXP (x
, 0));
1266 rtx yop0
= canon_rtx (XEXP (y
, 0));
1267 rtx yop1
= canon_rtx (XEXP (y
, 1));
1269 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1270 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1271 || (rtx_equal_for_memref_p (xop0
, yop1
)
1272 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1274 else if (NON_COMMUTATIVE_P (x
))
1276 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1277 canon_rtx (XEXP (y
, 0)))
1278 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1279 canon_rtx (XEXP (y
, 1))));
1281 else if (UNARY_P (x
))
1282 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1283 canon_rtx (XEXP (y
, 0)));
1285 /* Compare the elements. If any pair of corresponding elements
1286 fail to match, return 0 for the whole things.
1288 Limit cases to types which actually appear in addresses. */
1290 fmt
= GET_RTX_FORMAT (code
);
1291 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1296 if (XINT (x
, i
) != XINT (y
, i
))
1301 /* Two vectors must have the same length. */
1302 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1305 /* And the corresponding elements must match. */
1306 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1307 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1308 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1313 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1314 canon_rtx (XEXP (y
, i
))) == 0)
1318 /* This can happen for asm operands. */
1320 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1324 /* This can happen for an asm which clobbers memory. */
1328 /* It is believed that rtx's at this level will never
1329 contain anything but integers and other rtx's,
1330 except for within LABEL_REFs and SYMBOL_REFs. */
1339 find_base_term (rtx x
)
1342 struct elt_loc_list
*l
;
1344 #if defined (FIND_BASE_TERM)
1345 /* Try machine-dependent ways to find the base term. */
1346 x
= FIND_BASE_TERM (x
);
1349 switch (GET_CODE (x
))
1352 return REG_BASE_VALUE (x
);
1355 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1365 return find_base_term (XEXP (x
, 0));
1368 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1370 rtx temp
= find_base_term (XEXP (x
, 0));
1372 if (temp
!= 0 && CONSTANT_P (temp
))
1373 temp
= convert_memory_address (Pmode
, temp
);
1379 val
= CSELIB_VAL_PTR (x
);
1382 for (l
= val
->locs
; l
; l
= l
->next
)
1383 if ((x
= find_base_term (l
->loc
)) != 0)
1389 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1396 rtx tmp1
= XEXP (x
, 0);
1397 rtx tmp2
= XEXP (x
, 1);
1399 /* This is a little bit tricky since we have to determine which of
1400 the two operands represents the real base address. Otherwise this
1401 routine may return the index register instead of the base register.
1403 That may cause us to believe no aliasing was possible, when in
1404 fact aliasing is possible.
1406 We use a few simple tests to guess the base register. Additional
1407 tests can certainly be added. For example, if one of the operands
1408 is a shift or multiply, then it must be the index register and the
1409 other operand is the base register. */
1411 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1412 return find_base_term (tmp2
);
1414 /* If either operand is known to be a pointer, then use it
1415 to determine the base term. */
1416 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1417 return find_base_term (tmp1
);
1419 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1420 return find_base_term (tmp2
);
1422 /* Neither operand was known to be a pointer. Go ahead and find the
1423 base term for both operands. */
1424 tmp1
= find_base_term (tmp1
);
1425 tmp2
= find_base_term (tmp2
);
1427 /* If either base term is named object or a special address
1428 (like an argument or stack reference), then use it for the
1431 && (GET_CODE (tmp1
) == SYMBOL_REF
1432 || GET_CODE (tmp1
) == LABEL_REF
1433 || (GET_CODE (tmp1
) == ADDRESS
1434 && GET_MODE (tmp1
) != VOIDmode
)))
1438 && (GET_CODE (tmp2
) == SYMBOL_REF
1439 || GET_CODE (tmp2
) == LABEL_REF
1440 || (GET_CODE (tmp2
) == ADDRESS
1441 && GET_MODE (tmp2
) != VOIDmode
)))
1444 /* We could not determine which of the two operands was the
1445 base register and which was the index. So we can determine
1446 nothing from the base alias check. */
1451 if (GET_CODE (XEXP (x
, 1)) == CONST_INT
&& INTVAL (XEXP (x
, 1)) != 0)
1452 return find_base_term (XEXP (x
, 0));
1464 /* Return 0 if the addresses X and Y are known to point to different
1465 objects, 1 if they might be pointers to the same object. */
1468 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1469 enum machine_mode y_mode
)
1471 rtx x_base
= find_base_term (x
);
1472 rtx y_base
= find_base_term (y
);
1474 /* If the address itself has no known base see if a known equivalent
1475 value has one. If either address still has no known base, nothing
1476 is known about aliasing. */
1481 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1484 x_base
= find_base_term (x_c
);
1492 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1495 y_base
= find_base_term (y_c
);
1500 /* If the base addresses are equal nothing is known about aliasing. */
1501 if (rtx_equal_p (x_base
, y_base
))
1504 /* The base addresses of the read and write are different expressions.
1505 If they are both symbols and they are not accessed via AND, there is
1506 no conflict. We can bring knowledge of object alignment into play
1507 here. For example, on alpha, "char a, b;" can alias one another,
1508 though "char a; long b;" cannot. */
1509 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1511 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1513 if (GET_CODE (x
) == AND
1514 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1515 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1517 if (GET_CODE (y
) == AND
1518 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1519 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1521 /* Differing symbols never alias. */
1525 /* If one address is a stack reference there can be no alias:
1526 stack references using different base registers do not alias,
1527 a stack reference can not alias a parameter, and a stack reference
1528 can not alias a global. */
1529 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1530 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1533 if (! flag_argument_noalias
)
1536 if (flag_argument_noalias
> 1)
1539 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1540 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1543 /* Convert the address X into something we can use. This is done by returning
1544 it unchanged unless it is a value; in the latter case we call cselib to get
1545 a more useful rtx. */
1551 struct elt_loc_list
*l
;
1553 if (GET_CODE (x
) != VALUE
)
1555 v
= CSELIB_VAL_PTR (x
);
1558 for (l
= v
->locs
; l
; l
= l
->next
)
1559 if (CONSTANT_P (l
->loc
))
1561 for (l
= v
->locs
; l
; l
= l
->next
)
1562 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
))
1565 return v
->locs
->loc
;
1570 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1571 where SIZE is the size in bytes of the memory reference. If ADDR
1572 is not modified by the memory reference then ADDR is returned. */
1575 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1579 switch (GET_CODE (addr
))
1582 offset
= (n_refs
+ 1) * size
;
1585 offset
= -(n_refs
+ 1) * size
;
1588 offset
= n_refs
* size
;
1591 offset
= -n_refs
* size
;
1599 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1602 addr
= XEXP (addr
, 0);
1603 addr
= canon_rtx (addr
);
1608 /* Return nonzero if X and Y (memory addresses) could reference the
1609 same location in memory. C is an offset accumulator. When
1610 C is nonzero, we are testing aliases between X and Y + C.
1611 XSIZE is the size in bytes of the X reference,
1612 similarly YSIZE is the size in bytes for Y.
1613 Expect that canon_rtx has been already called for X and Y.
1615 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1616 referenced (the reference was BLKmode), so make the most pessimistic
1619 If XSIZE or YSIZE is negative, we may access memory outside the object
1620 being referenced as a side effect. This can happen when using AND to
1621 align memory references, as is done on the Alpha.
1623 Nice to notice that varying addresses cannot conflict with fp if no
1624 local variables had their addresses taken, but that's too hard now. */
1627 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1629 if (GET_CODE (x
) == VALUE
)
1631 if (GET_CODE (y
) == VALUE
)
1633 if (GET_CODE (x
) == HIGH
)
1635 else if (GET_CODE (x
) == LO_SUM
)
1638 x
= addr_side_effect_eval (x
, xsize
, 0);
1639 if (GET_CODE (y
) == HIGH
)
1641 else if (GET_CODE (y
) == LO_SUM
)
1644 y
= addr_side_effect_eval (y
, ysize
, 0);
1646 if (rtx_equal_for_memref_p (x
, y
))
1648 if (xsize
<= 0 || ysize
<= 0)
1650 if (c
>= 0 && xsize
> c
)
1652 if (c
< 0 && ysize
+c
> 0)
1657 /* This code used to check for conflicts involving stack references and
1658 globals but the base address alias code now handles these cases. */
1660 if (GET_CODE (x
) == PLUS
)
1662 /* The fact that X is canonicalized means that this
1663 PLUS rtx is canonicalized. */
1664 rtx x0
= XEXP (x
, 0);
1665 rtx x1
= XEXP (x
, 1);
1667 if (GET_CODE (y
) == PLUS
)
1669 /* The fact that Y is canonicalized means that this
1670 PLUS rtx is canonicalized. */
1671 rtx y0
= XEXP (y
, 0);
1672 rtx y1
= XEXP (y
, 1);
1674 if (rtx_equal_for_memref_p (x1
, y1
))
1675 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1676 if (rtx_equal_for_memref_p (x0
, y0
))
1677 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1678 if (GET_CODE (x1
) == CONST_INT
)
1680 if (GET_CODE (y1
) == CONST_INT
)
1681 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1682 c
- INTVAL (x1
) + INTVAL (y1
));
1684 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1687 else if (GET_CODE (y1
) == CONST_INT
)
1688 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1692 else if (GET_CODE (x1
) == CONST_INT
)
1693 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1695 else if (GET_CODE (y
) == PLUS
)
1697 /* The fact that Y is canonicalized means that this
1698 PLUS rtx is canonicalized. */
1699 rtx y0
= XEXP (y
, 0);
1700 rtx y1
= XEXP (y
, 1);
1702 if (GET_CODE (y1
) == CONST_INT
)
1703 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1708 if (GET_CODE (x
) == GET_CODE (y
))
1709 switch (GET_CODE (x
))
1713 /* Handle cases where we expect the second operands to be the
1714 same, and check only whether the first operand would conflict
1717 rtx x1
= canon_rtx (XEXP (x
, 1));
1718 rtx y1
= canon_rtx (XEXP (y
, 1));
1719 if (! rtx_equal_for_memref_p (x1
, y1
))
1721 x0
= canon_rtx (XEXP (x
, 0));
1722 y0
= canon_rtx (XEXP (y
, 0));
1723 if (rtx_equal_for_memref_p (x0
, y0
))
1724 return (xsize
== 0 || ysize
== 0
1725 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1727 /* Can't properly adjust our sizes. */
1728 if (GET_CODE (x1
) != CONST_INT
)
1730 xsize
/= INTVAL (x1
);
1731 ysize
/= INTVAL (x1
);
1733 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1740 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1741 as an access with indeterminate size. Assume that references
1742 besides AND are aligned, so if the size of the other reference is
1743 at least as large as the alignment, assume no other overlap. */
1744 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1746 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1748 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
1750 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1752 /* ??? If we are indexing far enough into the array/structure, we
1753 may yet be able to determine that we can not overlap. But we
1754 also need to that we are far enough from the end not to overlap
1755 a following reference, so we do nothing with that for now. */
1756 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1758 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
1763 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1765 c
+= (INTVAL (y
) - INTVAL (x
));
1766 return (xsize
<= 0 || ysize
<= 0
1767 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1770 if (GET_CODE (x
) == CONST
)
1772 if (GET_CODE (y
) == CONST
)
1773 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1774 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1776 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1779 if (GET_CODE (y
) == CONST
)
1780 return memrefs_conflict_p (xsize
, x
, ysize
,
1781 canon_rtx (XEXP (y
, 0)), c
);
1784 return (xsize
<= 0 || ysize
<= 0
1785 || (rtx_equal_for_memref_p (x
, y
)
1786 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1793 /* Functions to compute memory dependencies.
1795 Since we process the insns in execution order, we can build tables
1796 to keep track of what registers are fixed (and not aliased), what registers
1797 are varying in known ways, and what registers are varying in unknown
1800 If both memory references are volatile, then there must always be a
1801 dependence between the two references, since their order can not be
1802 changed. A volatile and non-volatile reference can be interchanged
1805 A MEM_IN_STRUCT reference at a non-AND varying address can never
1806 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1807 also must allow AND addresses, because they may generate accesses
1808 outside the object being referenced. This is used to generate
1809 aligned addresses from unaligned addresses, for instance, the alpha
1810 storeqi_unaligned pattern. */
1812 /* Read dependence: X is read after read in MEM takes place. There can
1813 only be a dependence here if both reads are volatile. */
1816 read_dependence (const_rtx mem
, const_rtx x
)
1818 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1821 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1822 MEM2 is a reference to a structure at a varying address, or returns
1823 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1824 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1825 to decide whether or not an address may vary; it should return
1826 nonzero whenever variation is possible.
1827 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1830 fixed_scalar_and_varying_struct_p (const_rtx mem1
, const_rtx mem2
, rtx mem1_addr
,
1832 bool (*varies_p
) (const_rtx
, bool))
1834 if (! flag_strict_aliasing
)
1837 if (MEM_ALIAS_SET (mem2
)
1838 && MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1839 && !varies_p (mem1_addr
, 1) && varies_p (mem2_addr
, 1))
1840 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1844 if (MEM_ALIAS_SET (mem1
)
1845 && MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1846 && varies_p (mem1_addr
, 1) && !varies_p (mem2_addr
, 1))
1847 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1854 /* Returns nonzero if something about the mode or address format MEM1
1855 indicates that it might well alias *anything*. */
1858 aliases_everything_p (const_rtx mem
)
1860 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1861 /* If the address is an AND, it's very hard to know at what it is
1862 actually pointing. */
1868 /* Return true if we can determine that the fields referenced cannot
1869 overlap for any pair of objects. */
1872 nonoverlapping_component_refs_p (const_tree x
, const_tree y
)
1874 const_tree fieldx
, fieldy
, typex
, typey
, orig_y
;
1878 /* The comparison has to be done at a common type, since we don't
1879 know how the inheritance hierarchy works. */
1883 fieldx
= TREE_OPERAND (x
, 1);
1884 typex
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx
));
1889 fieldy
= TREE_OPERAND (y
, 1);
1890 typey
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy
));
1895 y
= TREE_OPERAND (y
, 0);
1897 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
1899 x
= TREE_OPERAND (x
, 0);
1901 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1902 /* Never found a common type. */
1906 /* If we're left with accessing different fields of a structure,
1908 if (TREE_CODE (typex
) == RECORD_TYPE
1909 && fieldx
!= fieldy
)
1912 /* The comparison on the current field failed. If we're accessing
1913 a very nested structure, look at the next outer level. */
1914 x
= TREE_OPERAND (x
, 0);
1915 y
= TREE_OPERAND (y
, 0);
1918 && TREE_CODE (x
) == COMPONENT_REF
1919 && TREE_CODE (y
) == COMPONENT_REF
);
1924 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1927 decl_for_component_ref (tree x
)
1931 x
= TREE_OPERAND (x
, 0);
1933 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1935 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
1938 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1939 offset of the field reference. */
1942 adjust_offset_for_component_ref (tree x
, rtx offset
)
1944 HOST_WIDE_INT ioffset
;
1949 ioffset
= INTVAL (offset
);
1952 tree offset
= component_ref_field_offset (x
);
1953 tree field
= TREE_OPERAND (x
, 1);
1955 if (! host_integerp (offset
, 1))
1957 ioffset
+= (tree_low_cst (offset
, 1)
1958 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
1961 x
= TREE_OPERAND (x
, 0);
1963 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1965 return GEN_INT (ioffset
);
1968 /* Return nonzero if we can determine the exprs corresponding to memrefs
1969 X and Y and they do not overlap. */
1972 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
)
1974 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
1977 rtx moffsetx
, moffsety
;
1978 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
1980 /* Unless both have exprs, we can't tell anything. */
1981 if (exprx
== 0 || expry
== 0)
1984 /* If both are field references, we may be able to determine something. */
1985 if (TREE_CODE (exprx
) == COMPONENT_REF
1986 && TREE_CODE (expry
) == COMPONENT_REF
1987 && nonoverlapping_component_refs_p (exprx
, expry
))
1991 /* If the field reference test failed, look at the DECLs involved. */
1992 moffsetx
= MEM_OFFSET (x
);
1993 if (TREE_CODE (exprx
) == COMPONENT_REF
)
1995 if (TREE_CODE (expry
) == VAR_DECL
1996 && POINTER_TYPE_P (TREE_TYPE (expry
)))
1998 tree field
= TREE_OPERAND (exprx
, 1);
1999 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2000 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2005 tree t
= decl_for_component_ref (exprx
);
2008 moffsetx
= adjust_offset_for_component_ref (exprx
, moffsetx
);
2012 else if (INDIRECT_REF_P (exprx
))
2014 exprx
= TREE_OPERAND (exprx
, 0);
2015 if (flag_argument_noalias
< 2
2016 || TREE_CODE (exprx
) != PARM_DECL
)
2020 moffsety
= MEM_OFFSET (y
);
2021 if (TREE_CODE (expry
) == COMPONENT_REF
)
2023 if (TREE_CODE (exprx
) == VAR_DECL
2024 && POINTER_TYPE_P (TREE_TYPE (exprx
)))
2026 tree field
= TREE_OPERAND (expry
, 1);
2027 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2028 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2033 tree t
= decl_for_component_ref (expry
);
2036 moffsety
= adjust_offset_for_component_ref (expry
, moffsety
);
2040 else if (INDIRECT_REF_P (expry
))
2042 expry
= TREE_OPERAND (expry
, 0);
2043 if (flag_argument_noalias
< 2
2044 || TREE_CODE (expry
) != PARM_DECL
)
2048 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2051 rtlx
= DECL_RTL (exprx
);
2052 rtly
= DECL_RTL (expry
);
2054 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2055 can't overlap unless they are the same because we never reuse that part
2056 of the stack frame used for locals for spilled pseudos. */
2057 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2058 && ! rtx_equal_p (rtlx
, rtly
))
2061 /* Get the base and offsets of both decls. If either is a register, we
2062 know both are and are the same, so use that as the base. The only
2063 we can avoid overlap is if we can deduce that they are nonoverlapping
2064 pieces of that decl, which is very rare. */
2065 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2066 if (GET_CODE (basex
) == PLUS
&& GET_CODE (XEXP (basex
, 1)) == CONST_INT
)
2067 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2069 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2070 if (GET_CODE (basey
) == PLUS
&& GET_CODE (XEXP (basey
, 1)) == CONST_INT
)
2071 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2073 /* If the bases are different, we know they do not overlap if both
2074 are constants or if one is a constant and the other a pointer into the
2075 stack frame. Otherwise a different base means we can't tell if they
2077 if (! rtx_equal_p (basex
, basey
))
2078 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2079 || (CONSTANT_P (basex
) && REG_P (basey
)
2080 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2081 || (CONSTANT_P (basey
) && REG_P (basex
)
2082 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2084 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2085 : MEM_SIZE (rtlx
) ? INTVAL (MEM_SIZE (rtlx
))
2087 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2088 : MEM_SIZE (rtly
) ? INTVAL (MEM_SIZE (rtly
)) :
2091 /* If we have an offset for either memref, it can update the values computed
2094 offsetx
+= INTVAL (moffsetx
), sizex
-= INTVAL (moffsetx
);
2096 offsety
+= INTVAL (moffsety
), sizey
-= INTVAL (moffsety
);
2098 /* If a memref has both a size and an offset, we can use the smaller size.
2099 We can't do this if the offset isn't known because we must view this
2100 memref as being anywhere inside the DECL's MEM. */
2101 if (MEM_SIZE (x
) && moffsetx
)
2102 sizex
= INTVAL (MEM_SIZE (x
));
2103 if (MEM_SIZE (y
) && moffsety
)
2104 sizey
= INTVAL (MEM_SIZE (y
));
2106 /* Put the values of the memref with the lower offset in X's values. */
2107 if (offsetx
> offsety
)
2109 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2110 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2113 /* If we don't know the size of the lower-offset value, we can't tell
2114 if they conflict. Otherwise, we do the test. */
2115 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2118 /* True dependence: X is read after store in MEM takes place. */
2121 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
,
2122 bool (*varies
) (const_rtx
, bool))
2124 rtx x_addr
, mem_addr
;
2127 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2130 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2131 This is used in epilogue deallocation functions, and in cselib. */
2132 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2134 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2136 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2137 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2140 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2143 /* Read-only memory is by definition never modified, and therefore can't
2144 conflict with anything. We don't expect to find read-only set on MEM,
2145 but stupid user tricks can produce them, so don't die. */
2146 if (MEM_READONLY_P (x
))
2149 if (nonoverlapping_memrefs_p (mem
, x
))
2152 if (mem_mode
== VOIDmode
)
2153 mem_mode
= GET_MODE (mem
);
2155 x_addr
= get_addr (XEXP (x
, 0));
2156 mem_addr
= get_addr (XEXP (mem
, 0));
2158 base
= find_base_term (x_addr
);
2159 if (base
&& (GET_CODE (base
) == LABEL_REF
2160 || (GET_CODE (base
) == SYMBOL_REF
2161 && CONSTANT_POOL_ADDRESS_P (base
))))
2164 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2167 x_addr
= canon_rtx (x_addr
);
2168 mem_addr
= canon_rtx (mem_addr
);
2170 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2171 SIZE_FOR_MODE (x
), x_addr
, 0))
2174 if (aliases_everything_p (x
))
2177 /* We cannot use aliases_everything_p to test MEM, since we must look
2178 at MEM_MODE, rather than GET_MODE (MEM). */
2179 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2182 /* In true_dependence we also allow BLKmode to alias anything. Why
2183 don't we do this in anti_dependence and output_dependence? */
2184 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2187 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2191 /* Canonical true dependence: X is read after store in MEM takes place.
2192 Variant of true_dependence which assumes MEM has already been
2193 canonicalized (hence we no longer do that here).
2194 The mem_addr argument has been added, since true_dependence computed
2195 this value prior to canonicalizing. */
2198 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2199 const_rtx x
, bool (*varies
) (const_rtx
, bool))
2203 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2206 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2207 This is used in epilogue deallocation functions. */
2208 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2210 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2212 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2213 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2216 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2219 /* Read-only memory is by definition never modified, and therefore can't
2220 conflict with anything. We don't expect to find read-only set on MEM,
2221 but stupid user tricks can produce them, so don't die. */
2222 if (MEM_READONLY_P (x
))
2225 if (nonoverlapping_memrefs_p (x
, mem
))
2228 x_addr
= get_addr (XEXP (x
, 0));
2230 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2233 x_addr
= canon_rtx (x_addr
);
2234 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2235 SIZE_FOR_MODE (x
), x_addr
, 0))
2238 if (aliases_everything_p (x
))
2241 /* We cannot use aliases_everything_p to test MEM, since we must look
2242 at MEM_MODE, rather than GET_MODE (MEM). */
2243 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2246 /* In true_dependence we also allow BLKmode to alias anything. Why
2247 don't we do this in anti_dependence and output_dependence? */
2248 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2251 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2255 /* Returns nonzero if a write to X might alias a previous read from
2256 (or, if WRITEP is nonzero, a write to) MEM. */
2259 write_dependence_p (const_rtx mem
, const_rtx x
, int writep
)
2261 rtx x_addr
, mem_addr
;
2262 const_rtx fixed_scalar
;
2265 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2268 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2269 This is used in epilogue deallocation functions. */
2270 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2272 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2274 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2275 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2278 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2281 /* A read from read-only memory can't conflict with read-write memory. */
2282 if (!writep
&& MEM_READONLY_P (mem
))
2285 if (nonoverlapping_memrefs_p (x
, mem
))
2288 x_addr
= get_addr (XEXP (x
, 0));
2289 mem_addr
= get_addr (XEXP (mem
, 0));
2293 base
= find_base_term (mem_addr
);
2294 if (base
&& (GET_CODE (base
) == LABEL_REF
2295 || (GET_CODE (base
) == SYMBOL_REF
2296 && CONSTANT_POOL_ADDRESS_P (base
))))
2300 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2304 x_addr
= canon_rtx (x_addr
);
2305 mem_addr
= canon_rtx (mem_addr
);
2307 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2308 SIZE_FOR_MODE (x
), x_addr
, 0))
2312 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2315 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2316 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2319 /* Anti dependence: X is written after read in MEM takes place. */
2322 anti_dependence (const_rtx mem
, const_rtx x
)
2324 return write_dependence_p (mem
, x
, /*writep=*/0);
2327 /* Output dependence: X is written after store in MEM takes place. */
2330 output_dependence (const_rtx mem
, const_rtx x
)
2332 return write_dependence_p (mem
, x
, /*writep=*/1);
2337 init_alias_target (void)
2341 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2343 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2344 /* Check whether this register can hold an incoming pointer
2345 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2346 numbers, so translate if necessary due to register windows. */
2347 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2348 && HARD_REGNO_MODE_OK (i
, Pmode
))
2349 static_reg_base_value
[i
]
2350 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2352 static_reg_base_value
[STACK_POINTER_REGNUM
]
2353 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2354 static_reg_base_value
[ARG_POINTER_REGNUM
]
2355 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2356 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2357 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2358 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2359 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2360 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2364 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2365 to be memory reference. */
2366 static bool memory_modified
;
2368 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2372 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2373 memory_modified
= true;
2378 /* Return true when INSN possibly modify memory contents of MEM
2379 (i.e. address can be modified). */
2381 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2385 memory_modified
= false;
2386 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2387 return memory_modified
;
2390 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2394 init_alias_analysis (void)
2396 unsigned int maxreg
= max_reg_num ();
2402 timevar_push (TV_ALIAS_ANALYSIS
);
2404 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2405 reg_known_value
= ggc_calloc (reg_known_value_size
, sizeof (rtx
));
2406 reg_known_equiv_p
= xcalloc (reg_known_value_size
, sizeof (bool));
2408 /* If we have memory allocated from the previous run, use it. */
2409 if (old_reg_base_value
)
2410 reg_base_value
= old_reg_base_value
;
2413 VEC_truncate (rtx
, reg_base_value
, 0);
2415 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2417 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2418 reg_seen
= XNEWVEC (char, maxreg
);
2420 /* The basic idea is that each pass through this loop will use the
2421 "constant" information from the previous pass to propagate alias
2422 information through another level of assignments.
2424 This could get expensive if the assignment chains are long. Maybe
2425 we should throttle the number of iterations, possibly based on
2426 the optimization level or flag_expensive_optimizations.
2428 We could propagate more information in the first pass by making use
2429 of DF_REG_DEF_COUNT to determine immediately that the alias information
2430 for a pseudo is "constant".
2432 A program with an uninitialized variable can cause an infinite loop
2433 here. Instead of doing a full dataflow analysis to detect such problems
2434 we just cap the number of iterations for the loop.
2436 The state of the arrays for the set chain in question does not matter
2437 since the program has undefined behavior. */
2442 /* Assume nothing will change this iteration of the loop. */
2445 /* We want to assign the same IDs each iteration of this loop, so
2446 start counting from zero each iteration of the loop. */
2449 /* We're at the start of the function each iteration through the
2450 loop, so we're copying arguments. */
2451 copying_arguments
= true;
2453 /* Wipe the potential alias information clean for this pass. */
2454 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2456 /* Wipe the reg_seen array clean. */
2457 memset (reg_seen
, 0, maxreg
);
2459 /* Mark all hard registers which may contain an address.
2460 The stack, frame and argument pointers may contain an address.
2461 An argument register which can hold a Pmode value may contain
2462 an address even if it is not in BASE_REGS.
2464 The address expression is VOIDmode for an argument and
2465 Pmode for other registers. */
2467 memcpy (new_reg_base_value
, static_reg_base_value
,
2468 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2470 /* Walk the insns adding values to the new_reg_base_value array. */
2471 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2477 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2478 /* The prologue/epilogue insns are not threaded onto the
2479 insn chain until after reload has completed. Thus,
2480 there is no sense wasting time checking if INSN is in
2481 the prologue/epilogue until after reload has completed. */
2482 if (reload_completed
2483 && prologue_epilogue_contains (insn
))
2487 /* If this insn has a noalias note, process it, Otherwise,
2488 scan for sets. A simple set will have no side effects
2489 which could change the base value of any other register. */
2491 if (GET_CODE (PATTERN (insn
)) == SET
2492 && REG_NOTES (insn
) != 0
2493 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2494 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2496 note_stores (PATTERN (insn
), record_set
, NULL
);
2498 set
= single_set (insn
);
2501 && REG_P (SET_DEST (set
))
2502 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2504 unsigned int regno
= REGNO (SET_DEST (set
));
2505 rtx src
= SET_SRC (set
);
2508 note
= find_reg_equal_equiv_note (insn
);
2509 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2510 && DF_REG_DEF_COUNT (regno
) != 1)
2513 if (note
!= NULL_RTX
2514 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2515 && ! rtx_varies_p (XEXP (note
, 0), 1)
2516 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2519 set_reg_known_value (regno
, XEXP (note
, 0));
2520 set_reg_known_equiv_p (regno
,
2521 REG_NOTE_KIND (note
) == REG_EQUIV
);
2523 else if (DF_REG_DEF_COUNT (regno
) == 1
2524 && GET_CODE (src
) == PLUS
2525 && REG_P (XEXP (src
, 0))
2526 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2527 && GET_CODE (XEXP (src
, 1)) == CONST_INT
)
2529 t
= plus_constant (t
, INTVAL (XEXP (src
, 1)));
2530 set_reg_known_value (regno
, t
);
2531 set_reg_known_equiv_p (regno
, 0);
2533 else if (DF_REG_DEF_COUNT (regno
) == 1
2534 && ! rtx_varies_p (src
, 1))
2536 set_reg_known_value (regno
, src
);
2537 set_reg_known_equiv_p (regno
, 0);
2541 else if (NOTE_P (insn
)
2542 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2543 copying_arguments
= false;
2546 /* Now propagate values from new_reg_base_value to reg_base_value. */
2547 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2549 for (ui
= 0; ui
< maxreg
; ui
++)
2551 if (new_reg_base_value
[ui
]
2552 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2553 && ! rtx_equal_p (new_reg_base_value
[ui
],
2554 VEC_index (rtx
, reg_base_value
, ui
)))
2556 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2561 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2563 /* Fill in the remaining entries. */
2564 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2565 if (reg_known_value
[i
] == 0)
2566 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2569 free (new_reg_base_value
);
2570 new_reg_base_value
= 0;
2573 timevar_pop (TV_ALIAS_ANALYSIS
);
2577 end_alias_analysis (void)
2579 old_reg_base_value
= reg_base_value
;
2580 ggc_free (reg_known_value
);
2581 reg_known_value
= 0;
2582 reg_known_value_size
= 0;
2583 free (reg_known_equiv_p
);
2584 reg_known_equiv_p
= 0;
2587 #include "gt-alias.h"