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 HOST_WIDE_INT alias_set
;
136 /* The children of the alias set. These are not just the immediate
137 children, but, in fact, all descendants. So, if we have:
139 struct T { struct S s; float f; }
141 continuing our example above, the children here will be all of
142 `int', `double', `float', and `struct S'. */
143 splay_tree
GTY((param1_is (int), param2_is (int))) children
;
145 /* Nonzero if would have a child of zero: this effectively makes this
146 alias set the same as alias set zero. */
149 typedef struct alias_set_entry
*alias_set_entry
;
151 static int rtx_equal_for_memref_p (rtx
, 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 (HOST_WIDE_INT
);
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 nonoverlapping_memrefs_p (const_rtx
, const_rtx
);
168 static int write_dependence_p (const_rtx
, const_rtx
, int);
170 static void memory_modified_1 (rtx
, const_rtx
, void *);
171 static void record_alias_subset (HOST_WIDE_INT
, HOST_WIDE_INT
);
173 /* Set up all info needed to perform alias analysis on memory references. */
175 /* Returns the size in bytes of the mode of X. */
176 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
178 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
179 different alias sets. We ignore alias sets in functions making use
180 of variable arguments because the va_arg macros on some systems are
182 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
183 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
185 /* Cap the number of passes we make over the insns propagating alias
186 information through set chains. 10 is a completely arbitrary choice. */
187 #define MAX_ALIAS_LOOP_PASSES 10
189 /* reg_base_value[N] gives an address to which register N is related.
190 If all sets after the first add or subtract to the current value
191 or otherwise modify it so it does not point to a different top level
192 object, reg_base_value[N] is equal to the address part of the source
195 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
196 expressions represent certain special values: function arguments and
197 the stack, frame, and argument pointers.
199 The contents of an ADDRESS is not normally used, the mode of the
200 ADDRESS determines whether the ADDRESS is a function argument or some
201 other special value. Pointer equality, not rtx_equal_p, determines whether
202 two ADDRESS expressions refer to the same base address.
204 The only use of the contents of an ADDRESS is for determining if the
205 current function performs nonlocal memory memory references for the
206 purposes of marking the function as a constant function. */
208 static GTY(()) VEC(rtx
,gc
) *reg_base_value
;
209 static rtx
*new_reg_base_value
;
211 /* We preserve the copy of old array around to avoid amount of garbage
212 produced. About 8% of garbage produced were attributed to this
214 static GTY((deletable
)) VEC(rtx
,gc
) *old_reg_base_value
;
216 /* Static hunks of RTL used by the aliasing code; these are initialized
217 once per function to avoid unnecessary RTL allocations. */
218 static GTY (()) rtx static_reg_base_value
[FIRST_PSEUDO_REGISTER
];
220 #define REG_BASE_VALUE(X) \
221 (REGNO (X) < VEC_length (rtx, reg_base_value) \
222 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
224 /* Vector indexed by N giving the initial (unchanging) value known for
225 pseudo-register N. This array is initialized in init_alias_analysis,
226 and does not change until end_alias_analysis is called. */
227 static GTY((length("reg_known_value_size"))) rtx
*reg_known_value
;
229 /* Indicates number of valid entries in reg_known_value. */
230 static GTY(()) unsigned int reg_known_value_size
;
232 /* Vector recording for each reg_known_value whether it is due to a
233 REG_EQUIV note. Future passes (viz., reload) may replace the
234 pseudo with the equivalent expression and so we account for the
235 dependences that would be introduced if that happens.
237 The REG_EQUIV notes created in assign_parms may mention the arg
238 pointer, and there are explicit insns in the RTL that modify the
239 arg pointer. Thus we must ensure that such insns don't get
240 scheduled across each other because that would invalidate the
241 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
242 wrong, but solving the problem in the scheduler will likely give
243 better code, so we do it here. */
244 static bool *reg_known_equiv_p
;
246 /* True when scanning insns from the start of the rtl to the
247 NOTE_INSN_FUNCTION_BEG note. */
248 static bool copying_arguments
;
250 DEF_VEC_P(alias_set_entry
);
251 DEF_VEC_ALLOC_P(alias_set_entry
,gc
);
253 /* The splay-tree used to store the various alias set entries. */
254 static GTY (()) VEC(alias_set_entry
,gc
) *alias_sets
;
256 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
257 such an entry, or NULL otherwise. */
259 static inline alias_set_entry
260 get_alias_set_entry (HOST_WIDE_INT alias_set
)
262 return VEC_index (alias_set_entry
, alias_sets
, alias_set
);
265 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
266 the two MEMs cannot alias each other. */
269 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
271 /* Perform a basic sanity check. Namely, that there are no alias sets
272 if we're not using strict aliasing. This helps to catch bugs
273 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
274 where a MEM is allocated in some way other than by the use of
275 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
276 use alias sets to indicate that spilled registers cannot alias each
277 other, we might need to remove this check. */
278 gcc_assert (flag_strict_aliasing
279 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
281 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
284 /* Insert the NODE into the splay tree given by DATA. Used by
285 record_alias_subset via splay_tree_foreach. */
288 insert_subset_children (splay_tree_node node
, void *data
)
290 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
295 /* Return true if the first alias set is a subset of the second. */
298 alias_set_subset_of (HOST_WIDE_INT set1
, HOST_WIDE_INT set2
)
302 /* Everything is a subset of the "aliases everything" set. */
306 /* Otherwise, check if set1 is a subset of set2. */
307 ase
= get_alias_set_entry (set2
);
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 (HOST_WIDE_INT set1
, HOST_WIDE_INT 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 (HOST_WIDE_INT set1
, HOST_WIDE_INT 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 HOST_WIDE_INT 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 (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
))
528 tree decl
= find_base_decl (TREE_OPERAND (inner
, 0));
530 if (decl
&& DECL_POINTER_ALIAS_SET_KNOWN_P (decl
))
532 /* If we haven't computed the actual alias set, do it now. */
533 if (DECL_POINTER_ALIAS_SET (decl
) == -2)
535 tree pointed_to_type
= TREE_TYPE (TREE_TYPE (decl
));
537 /* No two restricted pointers can point at the same thing.
538 However, a restricted pointer can point at the same thing
539 as an unrestricted pointer, if that unrestricted pointer
540 is based on the restricted pointer. So, we make the
541 alias set for the restricted pointer a subset of the
542 alias set for the type pointed to by the type of the
544 HOST_WIDE_INT pointed_to_alias_set
545 = get_alias_set (pointed_to_type
);
547 if (pointed_to_alias_set
== 0)
548 /* It's not legal to make a subset of alias set zero. */
549 DECL_POINTER_ALIAS_SET (decl
) = 0;
550 else if (AGGREGATE_TYPE_P (pointed_to_type
))
551 /* For an aggregate, we must treat the restricted
552 pointer the same as an ordinary pointer. If we
553 were to make the type pointed to by the
554 restricted pointer a subset of the pointed-to
555 type, then we would believe that other subsets
556 of the pointed-to type (such as fields of that
557 type) do not conflict with the type pointed to
558 by the restricted pointer. */
559 DECL_POINTER_ALIAS_SET (decl
)
560 = pointed_to_alias_set
;
563 DECL_POINTER_ALIAS_SET (decl
) = new_alias_set ();
564 record_alias_subset (pointed_to_alias_set
,
565 DECL_POINTER_ALIAS_SET (decl
));
569 /* We use the alias set indicated in the declaration. */
570 return DECL_POINTER_ALIAS_SET (decl
);
573 /* If we have an INDIRECT_REF via a void pointer, we don't
574 know anything about what that might alias. Likewise if the
575 pointer is marked that way. */
576 else if (TREE_CODE (TREE_TYPE (inner
)) == VOID_TYPE
577 || (TYPE_REF_CAN_ALIAS_ALL
578 (TREE_TYPE (TREE_OPERAND (inner
, 0)))))
582 /* For non-addressable fields we return the alias set of the
583 outermost object that could have its address taken. If this
584 is an SFT use the precomputed value. */
585 if (TREE_CODE (t
) == STRUCT_FIELD_TAG
586 && SFT_NONADDRESSABLE_P (t
))
587 return SFT_ALIAS_SET (t
);
589 /* Otherwise, pick up the outermost object that we could have a pointer
590 to, processing conversions as above. */
591 while (component_uses_parent_alias_set (t
))
593 t
= TREE_OPERAND (t
, 0);
597 /* If we've already determined the alias set for a decl, just return
598 it. This is necessary for C++ anonymous unions, whose component
599 variables don't look like union members (boo!). */
600 if (TREE_CODE (t
) == VAR_DECL
601 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
602 return MEM_ALIAS_SET (DECL_RTL (t
));
604 /* Now all we care about is the type. */
608 /* Variant qualifiers don't affect the alias set, so get the main
609 variant. If this is a type with a known alias set, return it. */
610 t
= TYPE_MAIN_VARIANT (t
);
611 if (TYPE_ALIAS_SET_KNOWN_P (t
))
612 return TYPE_ALIAS_SET (t
);
614 /* See if the language has special handling for this type. */
615 set
= lang_hooks
.get_alias_set (t
);
619 /* There are no objects of FUNCTION_TYPE, so there's no point in
620 using up an alias set for them. (There are, of course, pointers
621 and references to functions, but that's different.) */
622 else if (TREE_CODE (t
) == FUNCTION_TYPE
623 || TREE_CODE (t
) == METHOD_TYPE
)
626 /* Unless the language specifies otherwise, let vector types alias
627 their components. This avoids some nasty type punning issues in
628 normal usage. And indeed lets vectors be treated more like an
630 else if (TREE_CODE (t
) == VECTOR_TYPE
)
631 set
= get_alias_set (TREE_TYPE (t
));
634 /* Otherwise make a new alias set for this type. */
635 set
= new_alias_set ();
637 TYPE_ALIAS_SET (t
) = set
;
639 /* If this is an aggregate type, we must record any component aliasing
641 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
642 record_component_aliases (t
);
647 /* Return a brand-new alias set. */
652 if (flag_strict_aliasing
)
655 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
656 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
657 return VEC_length (alias_set_entry
, alias_sets
) - 1;
663 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
664 not everything that aliases SUPERSET also aliases SUBSET. For example,
665 in C, a store to an `int' can alias a load of a structure containing an
666 `int', and vice versa. But it can't alias a load of a 'double' member
667 of the same structure. Here, the structure would be the SUPERSET and
668 `int' the SUBSET. This relationship is also described in the comment at
669 the beginning of this file.
671 This function should be called only once per SUPERSET/SUBSET pair.
673 It is illegal for SUPERSET to be zero; everything is implicitly a
674 subset of alias set zero. */
677 record_alias_subset (HOST_WIDE_INT superset
, HOST_WIDE_INT subset
)
679 alias_set_entry superset_entry
;
680 alias_set_entry subset_entry
;
682 /* It is possible in complex type situations for both sets to be the same,
683 in which case we can ignore this operation. */
684 if (superset
== subset
)
687 gcc_assert (superset
);
689 superset_entry
= get_alias_set_entry (superset
);
690 if (superset_entry
== 0)
692 /* Create an entry for the SUPERSET, so that we have a place to
693 attach the SUBSET. */
694 superset_entry
= ggc_alloc (sizeof (struct alias_set_entry
));
695 superset_entry
->alias_set
= superset
;
696 superset_entry
->children
697 = splay_tree_new_ggc (splay_tree_compare_ints
);
698 superset_entry
->has_zero_child
= 0;
699 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
703 superset_entry
->has_zero_child
= 1;
706 subset_entry
= get_alias_set_entry (subset
);
707 /* If there is an entry for the subset, enter all of its children
708 (if they are not already present) as children of the SUPERSET. */
711 if (subset_entry
->has_zero_child
)
712 superset_entry
->has_zero_child
= 1;
714 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
715 superset_entry
->children
);
718 /* Enter the SUBSET itself as a child of the SUPERSET. */
719 splay_tree_insert (superset_entry
->children
,
720 (splay_tree_key
) subset
, 0);
724 /* Record that component types of TYPE, if any, are part of that type for
725 aliasing purposes. For record types, we only record component types
726 for fields that are marked addressable. For array types, we always
727 record the component types, so the front end should not call this
728 function if the individual component aren't addressable. */
731 record_component_aliases (tree type
)
733 HOST_WIDE_INT superset
= get_alias_set (type
);
739 switch (TREE_CODE (type
))
742 if (! TYPE_NONALIASED_COMPONENT (type
))
743 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
748 case QUAL_UNION_TYPE
:
749 /* Recursively record aliases for the base classes, if there are any. */
750 if (TYPE_BINFO (type
))
753 tree binfo
, base_binfo
;
755 for (binfo
= TYPE_BINFO (type
), i
= 0;
756 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
757 record_alias_subset (superset
,
758 get_alias_set (BINFO_TYPE (base_binfo
)));
760 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
761 if (TREE_CODE (field
) == FIELD_DECL
&& ! DECL_NONADDRESSABLE_P (field
))
762 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
766 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
774 /* Allocate an alias set for use in storing and reading from the varargs
777 static GTY(()) HOST_WIDE_INT varargs_set
= -1;
780 get_varargs_alias_set (void)
783 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
784 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
785 consistently use the varargs alias set for loads from the varargs
786 area. So don't use it anywhere. */
789 if (varargs_set
== -1)
790 varargs_set
= new_alias_set ();
796 /* Likewise, but used for the fixed portions of the frame, e.g., register
799 static GTY(()) HOST_WIDE_INT frame_set
= -1;
802 get_frame_alias_set (void)
805 frame_set
= new_alias_set ();
810 /* Inside SRC, the source of a SET, find a base address. */
813 find_base_value (rtx src
)
817 switch (GET_CODE (src
))
825 /* At the start of a function, argument registers have known base
826 values which may be lost later. Returning an ADDRESS
827 expression here allows optimization based on argument values
828 even when the argument registers are used for other purposes. */
829 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
830 return new_reg_base_value
[regno
];
832 /* If a pseudo has a known base value, return it. Do not do this
833 for non-fixed hard regs since it can result in a circular
834 dependency chain for registers which have values at function entry.
836 The test above is not sufficient because the scheduler may move
837 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
838 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
839 && regno
< VEC_length (rtx
, reg_base_value
))
841 /* If we're inside init_alias_analysis, use new_reg_base_value
842 to reduce the number of relaxation iterations. */
843 if (new_reg_base_value
&& new_reg_base_value
[regno
]
844 && DF_REG_DEF_COUNT (regno
) == 1)
845 return new_reg_base_value
[regno
];
847 if (VEC_index (rtx
, reg_base_value
, regno
))
848 return VEC_index (rtx
, reg_base_value
, regno
);
854 /* Check for an argument passed in memory. Only record in the
855 copying-arguments block; it is too hard to track changes
857 if (copying_arguments
858 && (XEXP (src
, 0) == arg_pointer_rtx
859 || (GET_CODE (XEXP (src
, 0)) == PLUS
860 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
861 return gen_rtx_ADDRESS (VOIDmode
, src
);
866 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
869 /* ... fall through ... */
874 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
876 /* If either operand is a REG that is a known pointer, then it
878 if (REG_P (src_0
) && REG_POINTER (src_0
))
879 return find_base_value (src_0
);
880 if (REG_P (src_1
) && REG_POINTER (src_1
))
881 return find_base_value (src_1
);
883 /* If either operand is a REG, then see if we already have
884 a known value for it. */
887 temp
= find_base_value (src_0
);
894 temp
= find_base_value (src_1
);
899 /* If either base is named object or a special address
900 (like an argument or stack reference), then use it for the
903 && (GET_CODE (src_0
) == SYMBOL_REF
904 || GET_CODE (src_0
) == LABEL_REF
905 || (GET_CODE (src_0
) == ADDRESS
906 && GET_MODE (src_0
) != VOIDmode
)))
910 && (GET_CODE (src_1
) == SYMBOL_REF
911 || GET_CODE (src_1
) == LABEL_REF
912 || (GET_CODE (src_1
) == ADDRESS
913 && GET_MODE (src_1
) != VOIDmode
)))
916 /* Guess which operand is the base address:
917 If either operand is a symbol, then it is the base. If
918 either operand is a CONST_INT, then the other is the base. */
919 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
920 return find_base_value (src_0
);
921 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
922 return find_base_value (src_1
);
928 /* The standard form is (lo_sum reg sym) so look only at the
930 return find_base_value (XEXP (src
, 1));
933 /* If the second operand is constant set the base
934 address to the first operand. */
935 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
936 return find_base_value (XEXP (src
, 0));
940 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
950 return find_base_value (XEXP (src
, 0));
953 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
955 rtx temp
= find_base_value (XEXP (src
, 0));
957 if (temp
!= 0 && CONSTANT_P (temp
))
958 temp
= convert_memory_address (Pmode
, temp
);
970 /* Called from init_alias_analysis indirectly through note_stores. */
972 /* While scanning insns to find base values, reg_seen[N] is nonzero if
973 register N has been set in this function. */
974 static char *reg_seen
;
976 /* Addresses which are known not to alias anything else are identified
977 by a unique integer. */
978 static int unique_id
;
981 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
990 regno
= REGNO (dest
);
992 gcc_assert (regno
< VEC_length (rtx
, reg_base_value
));
994 /* If this spans multiple hard registers, then we must indicate that every
995 register has an unusable value. */
996 if (regno
< FIRST_PSEUDO_REGISTER
)
997 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1004 reg_seen
[regno
+ n
] = 1;
1005 new_reg_base_value
[regno
+ n
] = 0;
1012 /* A CLOBBER wipes out any old value but does not prevent a previously
1013 unset register from acquiring a base address (i.e. reg_seen is not
1015 if (GET_CODE (set
) == CLOBBER
)
1017 new_reg_base_value
[regno
] = 0;
1020 src
= SET_SRC (set
);
1024 if (reg_seen
[regno
])
1026 new_reg_base_value
[regno
] = 0;
1029 reg_seen
[regno
] = 1;
1030 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
1031 GEN_INT (unique_id
++));
1035 /* If this is not the first set of REGNO, see whether the new value
1036 is related to the old one. There are two cases of interest:
1038 (1) The register might be assigned an entirely new value
1039 that has the same base term as the original set.
1041 (2) The set might be a simple self-modification that
1042 cannot change REGNO's base value.
1044 If neither case holds, reject the original base value as invalid.
1045 Note that the following situation is not detected:
1047 extern int x, y; int *p = &x; p += (&y-&x);
1049 ANSI C does not allow computing the difference of addresses
1050 of distinct top level objects. */
1051 if (new_reg_base_value
[regno
] != 0
1052 && find_base_value (src
) != new_reg_base_value
[regno
])
1053 switch (GET_CODE (src
))
1057 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1058 new_reg_base_value
[regno
] = 0;
1061 /* If the value we add in the PLUS is also a valid base value,
1062 this might be the actual base value, and the original value
1065 rtx other
= NULL_RTX
;
1067 if (XEXP (src
, 0) == dest
)
1068 other
= XEXP (src
, 1);
1069 else if (XEXP (src
, 1) == dest
)
1070 other
= XEXP (src
, 0);
1072 if (! other
|| find_base_value (other
))
1073 new_reg_base_value
[regno
] = 0;
1077 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
1078 new_reg_base_value
[regno
] = 0;
1081 new_reg_base_value
[regno
] = 0;
1084 /* If this is the first set of a register, record the value. */
1085 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1086 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1087 new_reg_base_value
[regno
] = find_base_value (src
);
1089 reg_seen
[regno
] = 1;
1092 /* If a value is known for REGNO, return it. */
1095 get_reg_known_value (unsigned int regno
)
1097 if (regno
>= FIRST_PSEUDO_REGISTER
)
1099 regno
-= FIRST_PSEUDO_REGISTER
;
1100 if (regno
< reg_known_value_size
)
1101 return reg_known_value
[regno
];
1109 set_reg_known_value (unsigned int regno
, rtx val
)
1111 if (regno
>= FIRST_PSEUDO_REGISTER
)
1113 regno
-= FIRST_PSEUDO_REGISTER
;
1114 if (regno
< reg_known_value_size
)
1115 reg_known_value
[regno
] = val
;
1119 /* Similarly for reg_known_equiv_p. */
1122 get_reg_known_equiv_p (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_equiv_p
[regno
];
1134 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1136 if (regno
>= FIRST_PSEUDO_REGISTER
)
1138 regno
-= FIRST_PSEUDO_REGISTER
;
1139 if (regno
< reg_known_value_size
)
1140 reg_known_equiv_p
[regno
] = val
;
1145 /* Returns a canonical version of X, from the point of view alias
1146 analysis. (For example, if X is a MEM whose address is a register,
1147 and the register has a known value (say a SYMBOL_REF), then a MEM
1148 whose address is the SYMBOL_REF is returned.) */
1153 /* Recursively look for equivalences. */
1154 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1156 rtx t
= get_reg_known_value (REGNO (x
));
1160 return canon_rtx (t
);
1163 if (GET_CODE (x
) == PLUS
)
1165 rtx x0
= canon_rtx (XEXP (x
, 0));
1166 rtx x1
= canon_rtx (XEXP (x
, 1));
1168 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1170 if (GET_CODE (x0
) == CONST_INT
)
1171 return plus_constant (x1
, INTVAL (x0
));
1172 else if (GET_CODE (x1
) == CONST_INT
)
1173 return plus_constant (x0
, INTVAL (x1
));
1174 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1178 /* This gives us much better alias analysis when called from
1179 the loop optimizer. Note we want to leave the original
1180 MEM alone, but need to return the canonicalized MEM with
1181 all the flags with their original values. */
1183 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1188 /* Return 1 if X and Y are identical-looking rtx's.
1189 Expect that X and Y has been already canonicalized.
1191 We use the data in reg_known_value above to see if two registers with
1192 different numbers are, in fact, equivalent. */
1195 rtx_equal_for_memref_p (rtx x
, rtx y
)
1202 if (x
== 0 && y
== 0)
1204 if (x
== 0 || y
== 0)
1210 code
= GET_CODE (x
);
1211 /* Rtx's of different codes cannot be equal. */
1212 if (code
!= GET_CODE (y
))
1215 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1216 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1218 if (GET_MODE (x
) != GET_MODE (y
))
1221 /* Some RTL can be compared without a recursive examination. */
1225 return REGNO (x
) == REGNO (y
);
1228 return XEXP (x
, 0) == XEXP (y
, 0);
1231 return XSTR (x
, 0) == XSTR (y
, 0);
1236 /* There's no need to compare the contents of CONST_DOUBLEs or
1237 CONST_INTs because pointer equality is a good enough
1238 comparison for these nodes. */
1245 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1247 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1248 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1249 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1250 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1251 /* For commutative operations, the RTX match if the operand match in any
1252 order. Also handle the simple binary and unary cases without a loop. */
1253 if (COMMUTATIVE_P (x
))
1255 rtx xop0
= canon_rtx (XEXP (x
, 0));
1256 rtx yop0
= canon_rtx (XEXP (y
, 0));
1257 rtx yop1
= canon_rtx (XEXP (y
, 1));
1259 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1260 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1261 || (rtx_equal_for_memref_p (xop0
, yop1
)
1262 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1264 else if (NON_COMMUTATIVE_P (x
))
1266 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1267 canon_rtx (XEXP (y
, 0)))
1268 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1269 canon_rtx (XEXP (y
, 1))));
1271 else if (UNARY_P (x
))
1272 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1273 canon_rtx (XEXP (y
, 0)));
1275 /* Compare the elements. If any pair of corresponding elements
1276 fail to match, return 0 for the whole things.
1278 Limit cases to types which actually appear in addresses. */
1280 fmt
= GET_RTX_FORMAT (code
);
1281 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1286 if (XINT (x
, i
) != XINT (y
, i
))
1291 /* Two vectors must have the same length. */
1292 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1295 /* And the corresponding elements must match. */
1296 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1297 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1298 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1303 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1304 canon_rtx (XEXP (y
, i
))) == 0)
1308 /* This can happen for asm operands. */
1310 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1314 /* This can happen for an asm which clobbers memory. */
1318 /* It is believed that rtx's at this level will never
1319 contain anything but integers and other rtx's,
1320 except for within LABEL_REFs and SYMBOL_REFs. */
1329 find_base_term (rtx x
)
1332 struct elt_loc_list
*l
;
1334 #if defined (FIND_BASE_TERM)
1335 /* Try machine-dependent ways to find the base term. */
1336 x
= FIND_BASE_TERM (x
);
1339 switch (GET_CODE (x
))
1342 return REG_BASE_VALUE (x
);
1345 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1355 return find_base_term (XEXP (x
, 0));
1358 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1360 rtx temp
= find_base_term (XEXP (x
, 0));
1362 if (temp
!= 0 && CONSTANT_P (temp
))
1363 temp
= convert_memory_address (Pmode
, temp
);
1369 val
= CSELIB_VAL_PTR (x
);
1372 for (l
= val
->locs
; l
; l
= l
->next
)
1373 if ((x
= find_base_term (l
->loc
)) != 0)
1379 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1386 rtx tmp1
= XEXP (x
, 0);
1387 rtx tmp2
= XEXP (x
, 1);
1389 /* This is a little bit tricky since we have to determine which of
1390 the two operands represents the real base address. Otherwise this
1391 routine may return the index register instead of the base register.
1393 That may cause us to believe no aliasing was possible, when in
1394 fact aliasing is possible.
1396 We use a few simple tests to guess the base register. Additional
1397 tests can certainly be added. For example, if one of the operands
1398 is a shift or multiply, then it must be the index register and the
1399 other operand is the base register. */
1401 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1402 return find_base_term (tmp2
);
1404 /* If either operand is known to be a pointer, then use it
1405 to determine the base term. */
1406 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1407 return find_base_term (tmp1
);
1409 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1410 return find_base_term (tmp2
);
1412 /* Neither operand was known to be a pointer. Go ahead and find the
1413 base term for both operands. */
1414 tmp1
= find_base_term (tmp1
);
1415 tmp2
= find_base_term (tmp2
);
1417 /* If either base term is named object or a special address
1418 (like an argument or stack reference), then use it for the
1421 && (GET_CODE (tmp1
) == SYMBOL_REF
1422 || GET_CODE (tmp1
) == LABEL_REF
1423 || (GET_CODE (tmp1
) == ADDRESS
1424 && GET_MODE (tmp1
) != VOIDmode
)))
1428 && (GET_CODE (tmp2
) == SYMBOL_REF
1429 || GET_CODE (tmp2
) == LABEL_REF
1430 || (GET_CODE (tmp2
) == ADDRESS
1431 && GET_MODE (tmp2
) != VOIDmode
)))
1434 /* We could not determine which of the two operands was the
1435 base register and which was the index. So we can determine
1436 nothing from the base alias check. */
1441 if (GET_CODE (XEXP (x
, 1)) == CONST_INT
&& INTVAL (XEXP (x
, 1)) != 0)
1442 return find_base_term (XEXP (x
, 0));
1454 /* Return 0 if the addresses X and Y are known to point to different
1455 objects, 1 if they might be pointers to the same object. */
1458 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1459 enum machine_mode y_mode
)
1461 rtx x_base
= find_base_term (x
);
1462 rtx y_base
= find_base_term (y
);
1464 /* If the address itself has no known base see if a known equivalent
1465 value has one. If either address still has no known base, nothing
1466 is known about aliasing. */
1471 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1474 x_base
= find_base_term (x_c
);
1482 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1485 y_base
= find_base_term (y_c
);
1490 /* If the base addresses are equal nothing is known about aliasing. */
1491 if (rtx_equal_p (x_base
, y_base
))
1494 /* The base addresses of the read and write are different expressions.
1495 If they are both symbols and they are not accessed via AND, there is
1496 no conflict. We can bring knowledge of object alignment into play
1497 here. For example, on alpha, "char a, b;" can alias one another,
1498 though "char a; long b;" cannot. */
1499 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1501 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1503 if (GET_CODE (x
) == AND
1504 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1505 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1507 if (GET_CODE (y
) == AND
1508 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1509 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1511 /* Differing symbols never alias. */
1515 /* If one address is a stack reference there can be no alias:
1516 stack references using different base registers do not alias,
1517 a stack reference can not alias a parameter, and a stack reference
1518 can not alias a global. */
1519 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1520 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1523 if (! flag_argument_noalias
)
1526 if (flag_argument_noalias
> 1)
1529 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1530 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1533 /* Convert the address X into something we can use. This is done by returning
1534 it unchanged unless it is a value; in the latter case we call cselib to get
1535 a more useful rtx. */
1541 struct elt_loc_list
*l
;
1543 if (GET_CODE (x
) != VALUE
)
1545 v
= CSELIB_VAL_PTR (x
);
1548 for (l
= v
->locs
; l
; l
= l
->next
)
1549 if (CONSTANT_P (l
->loc
))
1551 for (l
= v
->locs
; l
; l
= l
->next
)
1552 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
))
1555 return v
->locs
->loc
;
1560 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1561 where SIZE is the size in bytes of the memory reference. If ADDR
1562 is not modified by the memory reference then ADDR is returned. */
1565 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1569 switch (GET_CODE (addr
))
1572 offset
= (n_refs
+ 1) * size
;
1575 offset
= -(n_refs
+ 1) * size
;
1578 offset
= n_refs
* size
;
1581 offset
= -n_refs
* size
;
1589 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1592 addr
= XEXP (addr
, 0);
1593 addr
= canon_rtx (addr
);
1598 /* Return nonzero if X and Y (memory addresses) could reference the
1599 same location in memory. C is an offset accumulator. When
1600 C is nonzero, we are testing aliases between X and Y + C.
1601 XSIZE is the size in bytes of the X reference,
1602 similarly YSIZE is the size in bytes for Y.
1603 Expect that canon_rtx has been already called for X and Y.
1605 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1606 referenced (the reference was BLKmode), so make the most pessimistic
1609 If XSIZE or YSIZE is negative, we may access memory outside the object
1610 being referenced as a side effect. This can happen when using AND to
1611 align memory references, as is done on the Alpha.
1613 Nice to notice that varying addresses cannot conflict with fp if no
1614 local variables had their addresses taken, but that's too hard now. */
1617 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1619 if (GET_CODE (x
) == VALUE
)
1621 if (GET_CODE (y
) == VALUE
)
1623 if (GET_CODE (x
) == HIGH
)
1625 else if (GET_CODE (x
) == LO_SUM
)
1628 x
= addr_side_effect_eval (x
, xsize
, 0);
1629 if (GET_CODE (y
) == HIGH
)
1631 else if (GET_CODE (y
) == LO_SUM
)
1634 y
= addr_side_effect_eval (y
, ysize
, 0);
1636 if (rtx_equal_for_memref_p (x
, y
))
1638 if (xsize
<= 0 || ysize
<= 0)
1640 if (c
>= 0 && xsize
> c
)
1642 if (c
< 0 && ysize
+c
> 0)
1647 /* This code used to check for conflicts involving stack references and
1648 globals but the base address alias code now handles these cases. */
1650 if (GET_CODE (x
) == PLUS
)
1652 /* The fact that X is canonicalized means that this
1653 PLUS rtx is canonicalized. */
1654 rtx x0
= XEXP (x
, 0);
1655 rtx x1
= XEXP (x
, 1);
1657 if (GET_CODE (y
) == PLUS
)
1659 /* The fact that Y is canonicalized means that this
1660 PLUS rtx is canonicalized. */
1661 rtx y0
= XEXP (y
, 0);
1662 rtx y1
= XEXP (y
, 1);
1664 if (rtx_equal_for_memref_p (x1
, y1
))
1665 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1666 if (rtx_equal_for_memref_p (x0
, y0
))
1667 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1668 if (GET_CODE (x1
) == CONST_INT
)
1670 if (GET_CODE (y1
) == CONST_INT
)
1671 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1672 c
- INTVAL (x1
) + INTVAL (y1
));
1674 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1677 else if (GET_CODE (y1
) == CONST_INT
)
1678 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1682 else if (GET_CODE (x1
) == CONST_INT
)
1683 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1685 else if (GET_CODE (y
) == PLUS
)
1687 /* The fact that Y is canonicalized means that this
1688 PLUS rtx is canonicalized. */
1689 rtx y0
= XEXP (y
, 0);
1690 rtx y1
= XEXP (y
, 1);
1692 if (GET_CODE (y1
) == CONST_INT
)
1693 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1698 if (GET_CODE (x
) == GET_CODE (y
))
1699 switch (GET_CODE (x
))
1703 /* Handle cases where we expect the second operands to be the
1704 same, and check only whether the first operand would conflict
1707 rtx x1
= canon_rtx (XEXP (x
, 1));
1708 rtx y1
= canon_rtx (XEXP (y
, 1));
1709 if (! rtx_equal_for_memref_p (x1
, y1
))
1711 x0
= canon_rtx (XEXP (x
, 0));
1712 y0
= canon_rtx (XEXP (y
, 0));
1713 if (rtx_equal_for_memref_p (x0
, y0
))
1714 return (xsize
== 0 || ysize
== 0
1715 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1717 /* Can't properly adjust our sizes. */
1718 if (GET_CODE (x1
) != CONST_INT
)
1720 xsize
/= INTVAL (x1
);
1721 ysize
/= INTVAL (x1
);
1723 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1730 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1731 as an access with indeterminate size. Assume that references
1732 besides AND are aligned, so if the size of the other reference is
1733 at least as large as the alignment, assume no other overlap. */
1734 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1736 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1738 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
1740 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1742 /* ??? If we are indexing far enough into the array/structure, we
1743 may yet be able to determine that we can not overlap. But we
1744 also need to that we are far enough from the end not to overlap
1745 a following reference, so we do nothing with that for now. */
1746 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1748 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
1753 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1755 c
+= (INTVAL (y
) - INTVAL (x
));
1756 return (xsize
<= 0 || ysize
<= 0
1757 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1760 if (GET_CODE (x
) == CONST
)
1762 if (GET_CODE (y
) == CONST
)
1763 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1764 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1766 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1769 if (GET_CODE (y
) == CONST
)
1770 return memrefs_conflict_p (xsize
, x
, ysize
,
1771 canon_rtx (XEXP (y
, 0)), c
);
1774 return (xsize
<= 0 || ysize
<= 0
1775 || (rtx_equal_for_memref_p (x
, y
)
1776 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1783 /* Functions to compute memory dependencies.
1785 Since we process the insns in execution order, we can build tables
1786 to keep track of what registers are fixed (and not aliased), what registers
1787 are varying in known ways, and what registers are varying in unknown
1790 If both memory references are volatile, then there must always be a
1791 dependence between the two references, since their order can not be
1792 changed. A volatile and non-volatile reference can be interchanged
1795 A MEM_IN_STRUCT reference at a non-AND varying address can never
1796 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1797 also must allow AND addresses, because they may generate accesses
1798 outside the object being referenced. This is used to generate
1799 aligned addresses from unaligned addresses, for instance, the alpha
1800 storeqi_unaligned pattern. */
1802 /* Read dependence: X is read after read in MEM takes place. There can
1803 only be a dependence here if both reads are volatile. */
1806 read_dependence (const_rtx mem
, const_rtx x
)
1808 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1811 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1812 MEM2 is a reference to a structure at a varying address, or returns
1813 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1814 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1815 to decide whether or not an address may vary; it should return
1816 nonzero whenever variation is possible.
1817 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1820 fixed_scalar_and_varying_struct_p (const_rtx mem1
, const_rtx mem2
, rtx mem1_addr
,
1822 bool (*varies_p
) (const_rtx
, bool))
1824 if (! flag_strict_aliasing
)
1827 if (MEM_ALIAS_SET (mem2
)
1828 && MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1829 && !varies_p (mem1_addr
, 1) && varies_p (mem2_addr
, 1))
1830 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1834 if (MEM_ALIAS_SET (mem1
)
1835 && MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1836 && varies_p (mem1_addr
, 1) && !varies_p (mem2_addr
, 1))
1837 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1844 /* Returns nonzero if something about the mode or address format MEM1
1845 indicates that it might well alias *anything*. */
1848 aliases_everything_p (const_rtx mem
)
1850 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1851 /* If the address is an AND, it's very hard to know at what it is
1852 actually pointing. */
1858 /* Return true if we can determine that the fields referenced cannot
1859 overlap for any pair of objects. */
1862 nonoverlapping_component_refs_p (const_tree x
, const_tree y
)
1864 const_tree fieldx
, fieldy
, typex
, typey
, orig_y
;
1868 /* The comparison has to be done at a common type, since we don't
1869 know how the inheritance hierarchy works. */
1873 fieldx
= TREE_OPERAND (x
, 1);
1874 typex
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx
));
1879 fieldy
= TREE_OPERAND (y
, 1);
1880 typey
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy
));
1885 y
= TREE_OPERAND (y
, 0);
1887 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
1889 x
= TREE_OPERAND (x
, 0);
1891 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1892 /* Never found a common type. */
1896 /* If we're left with accessing different fields of a structure,
1898 if (TREE_CODE (typex
) == RECORD_TYPE
1899 && fieldx
!= fieldy
)
1902 /* The comparison on the current field failed. If we're accessing
1903 a very nested structure, look at the next outer level. */
1904 x
= TREE_OPERAND (x
, 0);
1905 y
= TREE_OPERAND (y
, 0);
1908 && TREE_CODE (x
) == COMPONENT_REF
1909 && TREE_CODE (y
) == COMPONENT_REF
);
1914 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1917 decl_for_component_ref (tree x
)
1921 x
= TREE_OPERAND (x
, 0);
1923 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1925 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
1928 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1929 offset of the field reference. */
1932 adjust_offset_for_component_ref (tree x
, rtx offset
)
1934 HOST_WIDE_INT ioffset
;
1939 ioffset
= INTVAL (offset
);
1942 tree offset
= component_ref_field_offset (x
);
1943 tree field
= TREE_OPERAND (x
, 1);
1945 if (! host_integerp (offset
, 1))
1947 ioffset
+= (tree_low_cst (offset
, 1)
1948 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
1951 x
= TREE_OPERAND (x
, 0);
1953 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1955 return GEN_INT (ioffset
);
1958 /* Return nonzero if we can determine the exprs corresponding to memrefs
1959 X and Y and they do not overlap. */
1962 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
)
1964 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
1967 rtx moffsetx
, moffsety
;
1968 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
1970 /* Unless both have exprs, we can't tell anything. */
1971 if (exprx
== 0 || expry
== 0)
1974 /* If both are field references, we may be able to determine something. */
1975 if (TREE_CODE (exprx
) == COMPONENT_REF
1976 && TREE_CODE (expry
) == COMPONENT_REF
1977 && nonoverlapping_component_refs_p (exprx
, expry
))
1981 /* If the field reference test failed, look at the DECLs involved. */
1982 moffsetx
= MEM_OFFSET (x
);
1983 if (TREE_CODE (exprx
) == COMPONENT_REF
)
1985 if (TREE_CODE (expry
) == VAR_DECL
1986 && POINTER_TYPE_P (TREE_TYPE (expry
)))
1988 tree field
= TREE_OPERAND (exprx
, 1);
1989 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
1990 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
1995 tree t
= decl_for_component_ref (exprx
);
1998 moffsetx
= adjust_offset_for_component_ref (exprx
, moffsetx
);
2002 else if (INDIRECT_REF_P (exprx
))
2004 exprx
= TREE_OPERAND (exprx
, 0);
2005 if (flag_argument_noalias
< 2
2006 || TREE_CODE (exprx
) != PARM_DECL
)
2010 moffsety
= MEM_OFFSET (y
);
2011 if (TREE_CODE (expry
) == COMPONENT_REF
)
2013 if (TREE_CODE (exprx
) == VAR_DECL
2014 && POINTER_TYPE_P (TREE_TYPE (exprx
)))
2016 tree field
= TREE_OPERAND (expry
, 1);
2017 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2018 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2023 tree t
= decl_for_component_ref (expry
);
2026 moffsety
= adjust_offset_for_component_ref (expry
, moffsety
);
2030 else if (INDIRECT_REF_P (expry
))
2032 expry
= TREE_OPERAND (expry
, 0);
2033 if (flag_argument_noalias
< 2
2034 || TREE_CODE (expry
) != PARM_DECL
)
2038 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2041 rtlx
= DECL_RTL (exprx
);
2042 rtly
= DECL_RTL (expry
);
2044 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2045 can't overlap unless they are the same because we never reuse that part
2046 of the stack frame used for locals for spilled pseudos. */
2047 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2048 && ! rtx_equal_p (rtlx
, rtly
))
2051 /* Get the base and offsets of both decls. If either is a register, we
2052 know both are and are the same, so use that as the base. The only
2053 we can avoid overlap is if we can deduce that they are nonoverlapping
2054 pieces of that decl, which is very rare. */
2055 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2056 if (GET_CODE (basex
) == PLUS
&& GET_CODE (XEXP (basex
, 1)) == CONST_INT
)
2057 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2059 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2060 if (GET_CODE (basey
) == PLUS
&& GET_CODE (XEXP (basey
, 1)) == CONST_INT
)
2061 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2063 /* If the bases are different, we know they do not overlap if both
2064 are constants or if one is a constant and the other a pointer into the
2065 stack frame. Otherwise a different base means we can't tell if they
2067 if (! rtx_equal_p (basex
, basey
))
2068 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2069 || (CONSTANT_P (basex
) && REG_P (basey
)
2070 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2071 || (CONSTANT_P (basey
) && REG_P (basex
)
2072 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2074 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2075 : MEM_SIZE (rtlx
) ? INTVAL (MEM_SIZE (rtlx
))
2077 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2078 : MEM_SIZE (rtly
) ? INTVAL (MEM_SIZE (rtly
)) :
2081 /* If we have an offset for either memref, it can update the values computed
2084 offsetx
+= INTVAL (moffsetx
), sizex
-= INTVAL (moffsetx
);
2086 offsety
+= INTVAL (moffsety
), sizey
-= INTVAL (moffsety
);
2088 /* If a memref has both a size and an offset, we can use the smaller size.
2089 We can't do this if the offset isn't known because we must view this
2090 memref as being anywhere inside the DECL's MEM. */
2091 if (MEM_SIZE (x
) && moffsetx
)
2092 sizex
= INTVAL (MEM_SIZE (x
));
2093 if (MEM_SIZE (y
) && moffsety
)
2094 sizey
= INTVAL (MEM_SIZE (y
));
2096 /* Put the values of the memref with the lower offset in X's values. */
2097 if (offsetx
> offsety
)
2099 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2100 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2103 /* If we don't know the size of the lower-offset value, we can't tell
2104 if they conflict. Otherwise, we do the test. */
2105 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2108 /* True dependence: X is read after store in MEM takes place. */
2111 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
,
2112 bool (*varies
) (const_rtx
, bool))
2114 rtx x_addr
, mem_addr
;
2117 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2120 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2121 This is used in epilogue deallocation functions, and in cselib. */
2122 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2124 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2126 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2127 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2130 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2133 /* Read-only memory is by definition never modified, and therefore can't
2134 conflict with anything. We don't expect to find read-only set on MEM,
2135 but stupid user tricks can produce them, so don't die. */
2136 if (MEM_READONLY_P (x
))
2139 if (nonoverlapping_memrefs_p (mem
, x
))
2142 if (mem_mode
== VOIDmode
)
2143 mem_mode
= GET_MODE (mem
);
2145 x_addr
= get_addr (XEXP (x
, 0));
2146 mem_addr
= get_addr (XEXP (mem
, 0));
2148 base
= find_base_term (x_addr
);
2149 if (base
&& (GET_CODE (base
) == LABEL_REF
2150 || (GET_CODE (base
) == SYMBOL_REF
2151 && CONSTANT_POOL_ADDRESS_P (base
))))
2154 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2157 x_addr
= canon_rtx (x_addr
);
2158 mem_addr
= canon_rtx (mem_addr
);
2160 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2161 SIZE_FOR_MODE (x
), x_addr
, 0))
2164 if (aliases_everything_p (x
))
2167 /* We cannot use aliases_everything_p to test MEM, since we must look
2168 at MEM_MODE, rather than GET_MODE (MEM). */
2169 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2172 /* In true_dependence we also allow BLKmode to alias anything. Why
2173 don't we do this in anti_dependence and output_dependence? */
2174 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2177 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2181 /* Canonical true dependence: X is read after store in MEM takes place.
2182 Variant of true_dependence which assumes MEM has already been
2183 canonicalized (hence we no longer do that here).
2184 The mem_addr argument has been added, since true_dependence computed
2185 this value prior to canonicalizing. */
2188 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2189 const_rtx x
, bool (*varies
) (const_rtx
, bool))
2193 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2196 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2197 This is used in epilogue deallocation functions. */
2198 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2200 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2202 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2203 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2206 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2209 /* Read-only memory is by definition never modified, and therefore can't
2210 conflict with anything. We don't expect to find read-only set on MEM,
2211 but stupid user tricks can produce them, so don't die. */
2212 if (MEM_READONLY_P (x
))
2215 if (nonoverlapping_memrefs_p (x
, mem
))
2218 x_addr
= get_addr (XEXP (x
, 0));
2220 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2223 x_addr
= canon_rtx (x_addr
);
2224 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2225 SIZE_FOR_MODE (x
), x_addr
, 0))
2228 if (aliases_everything_p (x
))
2231 /* We cannot use aliases_everything_p to test MEM, since we must look
2232 at MEM_MODE, rather than GET_MODE (MEM). */
2233 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2236 /* In true_dependence we also allow BLKmode to alias anything. Why
2237 don't we do this in anti_dependence and output_dependence? */
2238 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2241 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2245 /* Returns nonzero if a write to X might alias a previous read from
2246 (or, if WRITEP is nonzero, a write to) MEM. */
2249 write_dependence_p (const_rtx mem
, const_rtx x
, int writep
)
2251 rtx x_addr
, mem_addr
;
2252 const_rtx fixed_scalar
;
2255 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2258 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2259 This is used in epilogue deallocation functions. */
2260 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2262 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2264 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2265 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2268 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2271 /* A read from read-only memory can't conflict with read-write memory. */
2272 if (!writep
&& MEM_READONLY_P (mem
))
2275 if (nonoverlapping_memrefs_p (x
, mem
))
2278 x_addr
= get_addr (XEXP (x
, 0));
2279 mem_addr
= get_addr (XEXP (mem
, 0));
2283 base
= find_base_term (mem_addr
);
2284 if (base
&& (GET_CODE (base
) == LABEL_REF
2285 || (GET_CODE (base
) == SYMBOL_REF
2286 && CONSTANT_POOL_ADDRESS_P (base
))))
2290 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2294 x_addr
= canon_rtx (x_addr
);
2295 mem_addr
= canon_rtx (mem_addr
);
2297 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2298 SIZE_FOR_MODE (x
), x_addr
, 0))
2302 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2305 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2306 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2309 /* Anti dependence: X is written after read in MEM takes place. */
2312 anti_dependence (const_rtx mem
, const_rtx x
)
2314 return write_dependence_p (mem
, x
, /*writep=*/0);
2317 /* Output dependence: X is written after store in MEM takes place. */
2320 output_dependence (const_rtx mem
, const_rtx x
)
2322 return write_dependence_p (mem
, x
, /*writep=*/1);
2327 init_alias_once (void)
2331 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2332 /* Check whether this register can hold an incoming pointer
2333 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2334 numbers, so translate if necessary due to register windows. */
2335 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2336 && HARD_REGNO_MODE_OK (i
, Pmode
))
2337 static_reg_base_value
[i
]
2338 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2340 static_reg_base_value
[STACK_POINTER_REGNUM
]
2341 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2342 static_reg_base_value
[ARG_POINTER_REGNUM
]
2343 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2344 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2345 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2346 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2347 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2348 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2352 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2353 to be memory reference. */
2354 static bool memory_modified
;
2356 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2360 if (anti_dependence (x
, (rtx
)data
) || output_dependence (x
, (rtx
)data
))
2361 memory_modified
= true;
2366 /* Return true when INSN possibly modify memory contents of MEM
2367 (i.e. address can be modified). */
2369 memory_modified_in_insn_p (rtx mem
, rtx insn
)
2373 memory_modified
= false;
2374 note_stores (PATTERN (insn
), memory_modified_1
, mem
);
2375 return memory_modified
;
2378 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2382 init_alias_analysis (void)
2384 unsigned int maxreg
= max_reg_num ();
2390 timevar_push (TV_ALIAS_ANALYSIS
);
2392 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2393 reg_known_value
= ggc_calloc (reg_known_value_size
, sizeof (rtx
));
2394 reg_known_equiv_p
= xcalloc (reg_known_value_size
, sizeof (bool));
2396 /* If we have memory allocated from the previous run, use it. */
2397 if (old_reg_base_value
)
2398 reg_base_value
= old_reg_base_value
;
2401 VEC_truncate (rtx
, reg_base_value
, 0);
2403 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2405 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2406 reg_seen
= XNEWVEC (char, maxreg
);
2408 /* The basic idea is that each pass through this loop will use the
2409 "constant" information from the previous pass to propagate alias
2410 information through another level of assignments.
2412 This could get expensive if the assignment chains are long. Maybe
2413 we should throttle the number of iterations, possibly based on
2414 the optimization level or flag_expensive_optimizations.
2416 We could propagate more information in the first pass by making use
2417 of DF_REG_DEF_COUNT to determine immediately that the alias information
2418 for a pseudo is "constant".
2420 A program with an uninitialized variable can cause an infinite loop
2421 here. Instead of doing a full dataflow analysis to detect such problems
2422 we just cap the number of iterations for the loop.
2424 The state of the arrays for the set chain in question does not matter
2425 since the program has undefined behavior. */
2430 /* Assume nothing will change this iteration of the loop. */
2433 /* We want to assign the same IDs each iteration of this loop, so
2434 start counting from zero each iteration of the loop. */
2437 /* We're at the start of the function each iteration through the
2438 loop, so we're copying arguments. */
2439 copying_arguments
= true;
2441 /* Wipe the potential alias information clean for this pass. */
2442 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2444 /* Wipe the reg_seen array clean. */
2445 memset (reg_seen
, 0, maxreg
);
2447 /* Mark all hard registers which may contain an address.
2448 The stack, frame and argument pointers may contain an address.
2449 An argument register which can hold a Pmode value may contain
2450 an address even if it is not in BASE_REGS.
2452 The address expression is VOIDmode for an argument and
2453 Pmode for other registers. */
2455 memcpy (new_reg_base_value
, static_reg_base_value
,
2456 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2458 /* Walk the insns adding values to the new_reg_base_value array. */
2459 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2465 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2466 /* The prologue/epilogue insns are not threaded onto the
2467 insn chain until after reload has completed. Thus,
2468 there is no sense wasting time checking if INSN is in
2469 the prologue/epilogue until after reload has completed. */
2470 if (reload_completed
2471 && prologue_epilogue_contains (insn
))
2475 /* If this insn has a noalias note, process it, Otherwise,
2476 scan for sets. A simple set will have no side effects
2477 which could change the base value of any other register. */
2479 if (GET_CODE (PATTERN (insn
)) == SET
2480 && REG_NOTES (insn
) != 0
2481 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2482 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2484 note_stores (PATTERN (insn
), record_set
, NULL
);
2486 set
= single_set (insn
);
2489 && REG_P (SET_DEST (set
))
2490 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2492 unsigned int regno
= REGNO (SET_DEST (set
));
2493 rtx src
= SET_SRC (set
);
2496 note
= find_reg_equal_equiv_note (insn
);
2497 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2498 && DF_REG_DEF_COUNT (regno
) != 1)
2501 if (note
!= NULL_RTX
2502 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2503 && ! rtx_varies_p (XEXP (note
, 0), 1)
2504 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2507 set_reg_known_value (regno
, XEXP (note
, 0));
2508 set_reg_known_equiv_p (regno
,
2509 REG_NOTE_KIND (note
) == REG_EQUIV
);
2511 else if (DF_REG_DEF_COUNT (regno
) == 1
2512 && GET_CODE (src
) == PLUS
2513 && REG_P (XEXP (src
, 0))
2514 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2515 && GET_CODE (XEXP (src
, 1)) == CONST_INT
)
2517 t
= plus_constant (t
, INTVAL (XEXP (src
, 1)));
2518 set_reg_known_value (regno
, t
);
2519 set_reg_known_equiv_p (regno
, 0);
2521 else if (DF_REG_DEF_COUNT (regno
) == 1
2522 && ! rtx_varies_p (src
, 1))
2524 set_reg_known_value (regno
, src
);
2525 set_reg_known_equiv_p (regno
, 0);
2529 else if (NOTE_P (insn
)
2530 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2531 copying_arguments
= false;
2534 /* Now propagate values from new_reg_base_value to reg_base_value. */
2535 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2537 for (ui
= 0; ui
< maxreg
; ui
++)
2539 if (new_reg_base_value
[ui
]
2540 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2541 && ! rtx_equal_p (new_reg_base_value
[ui
],
2542 VEC_index (rtx
, reg_base_value
, ui
)))
2544 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2549 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2551 /* Fill in the remaining entries. */
2552 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2553 if (reg_known_value
[i
] == 0)
2554 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2557 free (new_reg_base_value
);
2558 new_reg_base_value
= 0;
2561 timevar_pop (TV_ALIAS_ANALYSIS
);
2565 end_alias_analysis (void)
2567 old_reg_base_value
= reg_base_value
;
2568 ggc_free (reg_known_value
);
2569 reg_known_value
= 0;
2570 reg_known_value_size
= 0;
2571 free (reg_known_equiv_p
);
2572 reg_known_equiv_p
= 0;
2575 #include "gt-alias.h"