1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
46 #include "tree-pass.h"
47 #include "ipa-type-escape.h"
50 /* The aliasing API provided here solves related but different problems:
52 Say there exists (in c)
66 Consider the four questions:
68 Can a store to x1 interfere with px2->y1?
69 Can a store to x1 interfere with px2->z2?
71 Can a store to x1 change the value pointed to by with py?
72 Can a store to x1 change the value pointed to by with pz?
74 The answer to these questions can be yes, yes, yes, and maybe.
76 The first two questions can be answered with a simple examination
77 of the type system. If structure X contains a field of type Y then
78 a store thru a pointer to an X can overwrite any field that is
79 contained (recursively) in an X (unless we know that px1 != px2).
81 The last two of the questions can be solved in the same way as the
82 first two questions but this is too conservative. The observation
83 is that in some cases analysis we can know if which (if any) fields
84 are addressed and if those addresses are used in bad ways. This
85 analysis may be language specific. In C, arbitrary operations may
86 be applied to pointers. However, there is some indication that
87 this may be too conservative for some C++ types.
89 The pass ipa-type-escape does this analysis for the types whose
90 instances do not escape across the compilation boundary.
92 Historically in GCC, these two problems were combined and a single
93 data structure was used to represent the solution to these
94 problems. We now have two similar but different data structures,
95 The data structure to solve the last two question is similar to the
96 first, but does not contain have the fields in it whose address are
97 never taken. For types that do escape the compilation unit, the
98 data structures will have identical information.
101 /* The alias sets assigned to MEMs assist the back-end in determining
102 which MEMs can alias which other MEMs. In general, two MEMs in
103 different alias sets cannot alias each other, with one important
104 exception. Consider something like:
106 struct S { int i; double d; };
108 a store to an `S' can alias something of either type `int' or type
109 `double'. (However, a store to an `int' cannot alias a `double'
110 and vice versa.) We indicate this via a tree structure that looks
118 (The arrows are directed and point downwards.)
119 In this situation we say the alias set for `struct S' is the
120 `superset' and that those for `int' and `double' are `subsets'.
122 To see whether two alias sets can point to the same memory, we must
123 see if either alias set is a subset of the other. We need not trace
124 past immediate descendants, however, since we propagate all
125 grandchildren up one level.
127 Alias set zero is implicitly a superset of all other alias sets.
128 However, this is no actual entry for alias set zero. It is an
129 error to attempt to explicitly construct a subset of zero. */
131 struct GTY(()) alias_set_entry_d
{
132 /* The alias set number, as stored in MEM_ALIAS_SET. */
133 alias_set_type alias_set
;
135 /* Nonzero if would have a child of zero: this effectively makes this
136 alias set the same as alias set zero. */
139 /* The children of the alias set. These are not just the immediate
140 children, but, in fact, all descendants. So, if we have:
142 struct T { struct S s; float f; }
144 continuing our example above, the children here will be all of
145 `int', `double', `float', and `struct S'. */
146 splay_tree
GTY((param1_is (int), param2_is (int))) children
;
148 typedef struct alias_set_entry_d
*alias_set_entry
;
150 static int rtx_equal_for_memref_p (const_rtx
, const_rtx
);
151 static int memrefs_conflict_p (int, rtx
, int, rtx
, HOST_WIDE_INT
);
152 static void record_set (rtx
, const_rtx
, void *);
153 static int base_alias_check (rtx
, rtx
, enum machine_mode
,
155 static rtx
find_base_value (rtx
);
156 static int mems_in_disjoint_alias_sets_p (const_rtx
, const_rtx
);
157 static int insert_subset_children (splay_tree_node
, void*);
158 static alias_set_entry
get_alias_set_entry (alias_set_type
);
159 static const_rtx
fixed_scalar_and_varying_struct_p (const_rtx
, const_rtx
, rtx
, rtx
,
160 bool (*) (const_rtx
, bool));
161 static int aliases_everything_p (const_rtx
);
162 static bool nonoverlapping_component_refs_p (const_tree
, const_tree
);
163 static tree
decl_for_component_ref (tree
);
164 static rtx
adjust_offset_for_component_ref (tree
, rtx
);
165 static int write_dependence_p (const_rtx
, const_rtx
, int);
167 static void memory_modified_1 (rtx
, const_rtx
, void *);
169 /* Set up all info needed to perform alias analysis on memory references. */
171 /* Returns the size in bytes of the mode of X. */
172 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
174 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
175 different alias sets. We ignore alias sets in functions making use
176 of variable arguments because the va_arg macros on some systems are
178 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
179 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
181 /* Cap the number of passes we make over the insns propagating alias
182 information through set chains. 10 is a completely arbitrary choice. */
183 #define MAX_ALIAS_LOOP_PASSES 10
185 /* reg_base_value[N] gives an address to which register N is related.
186 If all sets after the first add or subtract to the current value
187 or otherwise modify it so it does not point to a different top level
188 object, reg_base_value[N] is equal to the address part of the source
191 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
192 expressions represent certain special values: function arguments and
193 the stack, frame, and argument pointers.
195 The contents of an ADDRESS is not normally used, the mode of the
196 ADDRESS determines whether the ADDRESS is a function argument or some
197 other special value. Pointer equality, not rtx_equal_p, determines whether
198 two ADDRESS expressions refer to the same base address.
200 The only use of the contents of an ADDRESS is for determining if the
201 current function performs nonlocal memory memory references for the
202 purposes of marking the function as a constant function. */
204 static GTY(()) VEC(rtx
,gc
) *reg_base_value
;
205 static rtx
*new_reg_base_value
;
207 /* We preserve the copy of old array around to avoid amount of garbage
208 produced. About 8% of garbage produced were attributed to this
210 static GTY((deletable
)) VEC(rtx
,gc
) *old_reg_base_value
;
212 /* Static hunks of RTL used by the aliasing code; these are initialized
213 once per function to avoid unnecessary RTL allocations. */
214 static GTY (()) rtx static_reg_base_value
[FIRST_PSEUDO_REGISTER
];
216 #define REG_BASE_VALUE(X) \
217 (REGNO (X) < VEC_length (rtx, reg_base_value) \
218 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
220 /* Vector indexed by N giving the initial (unchanging) value known for
221 pseudo-register N. This array is initialized in init_alias_analysis,
222 and does not change until end_alias_analysis is called. */
223 static GTY((length("reg_known_value_size"))) rtx
*reg_known_value
;
225 /* Indicates number of valid entries in reg_known_value. */
226 static GTY(()) unsigned int reg_known_value_size
;
228 /* Vector recording for each reg_known_value whether it is due to a
229 REG_EQUIV note. Future passes (viz., reload) may replace the
230 pseudo with the equivalent expression and so we account for the
231 dependences that would be introduced if that happens.
233 The REG_EQUIV notes created in assign_parms may mention the arg
234 pointer, and there are explicit insns in the RTL that modify the
235 arg pointer. Thus we must ensure that such insns don't get
236 scheduled across each other because that would invalidate the
237 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
238 wrong, but solving the problem in the scheduler will likely give
239 better code, so we do it here. */
240 static bool *reg_known_equiv_p
;
242 /* True when scanning insns from the start of the rtl to the
243 NOTE_INSN_FUNCTION_BEG note. */
244 static bool copying_arguments
;
246 DEF_VEC_P(alias_set_entry
);
247 DEF_VEC_ALLOC_P(alias_set_entry
,gc
);
249 /* The splay-tree used to store the various alias set entries. */
250 static GTY (()) VEC(alias_set_entry
,gc
) *alias_sets
;
252 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
253 such an entry, or NULL otherwise. */
255 static inline alias_set_entry
256 get_alias_set_entry (alias_set_type alias_set
)
258 return VEC_index (alias_set_entry
, alias_sets
, alias_set
);
261 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
262 the two MEMs cannot alias each other. */
265 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
267 /* Perform a basic sanity check. Namely, that there are no alias sets
268 if we're not using strict aliasing. This helps to catch bugs
269 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
270 where a MEM is allocated in some way other than by the use of
271 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
272 use alias sets to indicate that spilled registers cannot alias each
273 other, we might need to remove this check. */
274 gcc_assert (flag_strict_aliasing
275 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
277 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
280 /* Insert the NODE into the splay tree given by DATA. Used by
281 record_alias_subset via splay_tree_foreach. */
284 insert_subset_children (splay_tree_node node
, void *data
)
286 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
291 /* Return true if the first alias set is a subset of the second. */
294 alias_set_subset_of (alias_set_type set1
, alias_set_type set2
)
298 /* Everything is a subset of the "aliases everything" set. */
302 /* Otherwise, check if set1 is a subset of set2. */
303 ase
= get_alias_set_entry (set2
);
305 && ((ase
->has_zero_child
&& set1
== 0)
306 || splay_tree_lookup (ase
->children
,
307 (splay_tree_key
) set1
)))
312 /* Return 1 if the two specified alias sets may conflict. */
315 alias_sets_conflict_p (alias_set_type set1
, alias_set_type set2
)
320 if (alias_sets_must_conflict_p (set1
, set2
))
323 /* See if the first alias set is a subset of the second. */
324 ase
= get_alias_set_entry (set1
);
326 && (ase
->has_zero_child
327 || splay_tree_lookup (ase
->children
,
328 (splay_tree_key
) set2
)))
331 /* Now do the same, but with the alias sets reversed. */
332 ase
= get_alias_set_entry (set2
);
334 && (ase
->has_zero_child
335 || splay_tree_lookup (ase
->children
,
336 (splay_tree_key
) set1
)))
339 /* The two alias sets are distinct and neither one is the
340 child of the other. Therefore, they cannot conflict. */
345 walk_mems_2 (rtx
*x
, rtx mem
)
349 if (alias_sets_conflict_p (MEM_ALIAS_SET(*x
), MEM_ALIAS_SET(mem
)))
358 walk_mems_1 (rtx
*x
, rtx
*pat
)
362 /* Visit all MEMs in *PAT and check indepedence. */
363 if (for_each_rtx (pat
, (rtx_function
) walk_mems_2
, *x
))
364 /* Indicate that dependence was determined and stop traversal. */
372 /* Return 1 if two specified instructions have mem expr with conflict alias sets*/
374 insn_alias_sets_conflict_p (rtx insn1
, rtx insn2
)
376 /* For each pair of MEMs in INSN1 and INSN2 check their independence. */
377 return for_each_rtx (&PATTERN (insn1
), (rtx_function
) walk_mems_1
,
381 /* Return 1 if the two specified alias sets will always conflict. */
384 alias_sets_must_conflict_p (alias_set_type set1
, alias_set_type set2
)
386 if (set1
== 0 || set2
== 0 || set1
== set2
)
392 /* Return 1 if any MEM object of type T1 will always conflict (using the
393 dependency routines in this file) with any MEM object of type T2.
394 This is used when allocating temporary storage. If T1 and/or T2 are
395 NULL_TREE, it means we know nothing about the storage. */
398 objects_must_conflict_p (tree t1
, tree t2
)
400 alias_set_type set1
, set2
;
402 /* If neither has a type specified, we don't know if they'll conflict
403 because we may be using them to store objects of various types, for
404 example the argument and local variables areas of inlined functions. */
405 if (t1
== 0 && t2
== 0)
408 /* If they are the same type, they must conflict. */
410 /* Likewise if both are volatile. */
411 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
414 set1
= t1
? get_alias_set (t1
) : 0;
415 set2
= t2
? get_alias_set (t2
) : 0;
417 /* We can't use alias_sets_conflict_p because we must make sure
418 that every subtype of t1 will conflict with every subtype of
419 t2 for which a pair of subobjects of these respective subtypes
420 overlaps on the stack. */
421 return alias_sets_must_conflict_p (set1
, set2
);
424 /* Return true if all nested component references handled by
425 get_inner_reference in T are such that we should use the alias set
426 provided by the object at the heart of T.
428 This is true for non-addressable components (which don't have their
429 own alias set), as well as components of objects in alias set zero.
430 This later point is a special case wherein we wish to override the
431 alias set used by the component, but we don't have per-FIELD_DECL
432 assignable alias sets. */
435 component_uses_parent_alias_set (const_tree t
)
439 /* If we're at the end, it vacuously uses its own alias set. */
440 if (!handled_component_p (t
))
443 switch (TREE_CODE (t
))
446 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1)))
451 case ARRAY_RANGE_REF
:
452 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0))))
461 /* Bitfields and casts are never addressable. */
465 t
= TREE_OPERAND (t
, 0);
466 if (get_alias_set (TREE_TYPE (t
)) == 0)
471 /* Return the alias set for the memory pointed to by T, which may be
472 either a type or an expression. Return -1 if there is nothing
473 special about dereferencing T. */
475 static alias_set_type
476 get_deref_alias_set_1 (tree t
)
478 /* If we're not doing any alias analysis, just assume everything
479 aliases everything else. */
480 if (!flag_strict_aliasing
)
483 /* All we care about is the type. */
487 /* If we have an INDIRECT_REF via a void pointer, we don't
488 know anything about what that might alias. Likewise if the
489 pointer is marked that way. */
490 if (TREE_CODE (TREE_TYPE (t
)) == VOID_TYPE
491 || TYPE_REF_CAN_ALIAS_ALL (t
))
497 /* Return the alias set for the memory pointed to by T, which may be
498 either a type or an expression. */
501 get_deref_alias_set (tree t
)
503 alias_set_type set
= get_deref_alias_set_1 (t
);
505 /* Fall back to the alias-set of the pointed-to type. */
510 set
= get_alias_set (TREE_TYPE (t
));
516 /* Return the alias set for T, which may be either a type or an
517 expression. Call language-specific routine for help, if needed. */
520 get_alias_set (tree t
)
524 /* If we're not doing any alias analysis, just assume everything
525 aliases everything else. Also return 0 if this or its type is
527 if (! flag_strict_aliasing
|| t
== error_mark_node
529 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
532 /* We can be passed either an expression or a type. This and the
533 language-specific routine may make mutually-recursive calls to each other
534 to figure out what to do. At each juncture, we see if this is a tree
535 that the language may need to handle specially. First handle things that
541 /* Remove any nops, then give the language a chance to do
542 something with this tree before we look at it. */
544 set
= lang_hooks
.get_alias_set (t
);
548 /* First see if the actual object referenced is an INDIRECT_REF from a
549 restrict-qualified pointer or a "void *". */
550 while (handled_component_p (inner
))
552 inner
= TREE_OPERAND (inner
, 0);
556 if (INDIRECT_REF_P (inner
))
558 set
= get_deref_alias_set_1 (TREE_OPERAND (inner
, 0));
563 /* Otherwise, pick up the outermost object that we could have a pointer
564 to, processing conversions as above. */
565 while (component_uses_parent_alias_set (t
))
567 t
= TREE_OPERAND (t
, 0);
571 /* If we've already determined the alias set for a decl, just return
572 it. This is necessary for C++ anonymous unions, whose component
573 variables don't look like union members (boo!). */
574 if (TREE_CODE (t
) == VAR_DECL
575 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
576 return MEM_ALIAS_SET (DECL_RTL (t
));
578 /* Now all we care about is the type. */
582 /* Variant qualifiers don't affect the alias set, so get the main
583 variant. Always use the canonical type as well.
584 If this is a type with a known alias set, return it. */
585 t
= TYPE_MAIN_VARIANT (t
);
586 if (TYPE_CANONICAL (t
))
587 t
= TYPE_CANONICAL (t
);
588 if (TYPE_ALIAS_SET_KNOWN_P (t
))
589 return TYPE_ALIAS_SET (t
);
591 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
592 if (!COMPLETE_TYPE_P (t
))
594 /* For arrays with unknown size the conservative answer is the
595 alias set of the element type. */
596 if (TREE_CODE (t
) == ARRAY_TYPE
)
597 return get_alias_set (TREE_TYPE (t
));
599 /* But return zero as a conservative answer for incomplete types. */
603 /* See if the language has special handling for this type. */
604 set
= lang_hooks
.get_alias_set (t
);
608 /* There are no objects of FUNCTION_TYPE, so there's no point in
609 using up an alias set for them. (There are, of course, pointers
610 and references to functions, but that's different.) */
611 else if (TREE_CODE (t
) == FUNCTION_TYPE
612 || TREE_CODE (t
) == METHOD_TYPE
)
615 /* Unless the language specifies otherwise, let vector types alias
616 their components. This avoids some nasty type punning issues in
617 normal usage. And indeed lets vectors be treated more like an
619 else if (TREE_CODE (t
) == VECTOR_TYPE
)
620 set
= get_alias_set (TREE_TYPE (t
));
622 /* Unless the language specifies otherwise, treat array types the
623 same as their components. This avoids the asymmetry we get
624 through recording the components. Consider accessing a
625 character(kind=1) through a reference to a character(kind=1)[1:1].
626 Or consider if we want to assign integer(kind=4)[0:D.1387] and
627 integer(kind=4)[4] the same alias set or not.
628 Just be pragmatic here and make sure the array and its element
629 type get the same alias set assigned. */
630 else if (TREE_CODE (t
) == ARRAY_TYPE
631 && !TYPE_NONALIASED_COMPONENT (t
))
632 set
= get_alias_set (TREE_TYPE (t
));
635 /* Otherwise make a new alias set for this type. */
636 set
= new_alias_set ();
638 TYPE_ALIAS_SET (t
) = set
;
640 /* If this is an aggregate type, we must record any component aliasing
642 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
643 record_component_aliases (t
);
648 /* Return a brand-new alias set. */
653 if (flag_strict_aliasing
)
656 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
657 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
658 return VEC_length (alias_set_entry
, alias_sets
) - 1;
664 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
665 not everything that aliases SUPERSET also aliases SUBSET. For example,
666 in C, a store to an `int' can alias a load of a structure containing an
667 `int', and vice versa. But it can't alias a load of a 'double' member
668 of the same structure. Here, the structure would be the SUPERSET and
669 `int' the SUBSET. This relationship is also described in the comment at
670 the beginning of this file.
672 This function should be called only once per SUPERSET/SUBSET pair.
674 It is illegal for SUPERSET to be zero; everything is implicitly a
675 subset of alias set zero. */
678 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
680 alias_set_entry superset_entry
;
681 alias_set_entry subset_entry
;
683 /* It is possible in complex type situations for both sets to be the same,
684 in which case we can ignore this operation. */
685 if (superset
== subset
)
688 gcc_assert (superset
);
690 superset_entry
= get_alias_set_entry (superset
);
691 if (superset_entry
== 0)
693 /* Create an entry for the SUPERSET, so that we have a place to
694 attach the SUBSET. */
695 superset_entry
= GGC_NEW (struct alias_set_entry_d
);
696 superset_entry
->alias_set
= superset
;
697 superset_entry
->children
698 = splay_tree_new_ggc (splay_tree_compare_ints
);
699 superset_entry
->has_zero_child
= 0;
700 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
704 superset_entry
->has_zero_child
= 1;
707 subset_entry
= get_alias_set_entry (subset
);
708 /* If there is an entry for the subset, enter all of its children
709 (if they are not already present) as children of the SUPERSET. */
712 if (subset_entry
->has_zero_child
)
713 superset_entry
->has_zero_child
= 1;
715 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
716 superset_entry
->children
);
719 /* Enter the SUBSET itself as a child of the SUPERSET. */
720 splay_tree_insert (superset_entry
->children
,
721 (splay_tree_key
) subset
, 0);
725 /* Record that component types of TYPE, if any, are part of that type for
726 aliasing purposes. For record types, we only record component types
727 for fields that are not marked non-addressable. For array types, we
728 only record the component type if it is not marked non-aliased. */
731 record_component_aliases (tree type
)
733 alias_set_type superset
= get_alias_set (type
);
739 switch (TREE_CODE (type
))
743 case QUAL_UNION_TYPE
:
744 /* Recursively record aliases for the base classes, if there are any. */
745 if (TYPE_BINFO (type
))
748 tree binfo
, base_binfo
;
750 for (binfo
= TYPE_BINFO (type
), i
= 0;
751 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
752 record_alias_subset (superset
,
753 get_alias_set (BINFO_TYPE (base_binfo
)));
755 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
756 if (TREE_CODE (field
) == FIELD_DECL
&& !DECL_NONADDRESSABLE_P (field
))
757 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
761 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
764 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
772 /* Allocate an alias set for use in storing and reading from the varargs
775 static GTY(()) alias_set_type varargs_set
= -1;
778 get_varargs_alias_set (void)
781 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
782 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
783 consistently use the varargs alias set for loads from the varargs
784 area. So don't use it anywhere. */
787 if (varargs_set
== -1)
788 varargs_set
= new_alias_set ();
794 /* Likewise, but used for the fixed portions of the frame, e.g., register
797 static GTY(()) alias_set_type frame_set
= -1;
800 get_frame_alias_set (void)
803 frame_set
= new_alias_set ();
808 /* Inside SRC, the source of a SET, find a base address. */
811 find_base_value (rtx src
)
815 #if defined (FIND_BASE_TERM)
816 /* Try machine-dependent ways to find the base term. */
817 src
= FIND_BASE_TERM (src
);
820 switch (GET_CODE (src
))
828 /* At the start of a function, argument registers have known base
829 values which may be lost later. Returning an ADDRESS
830 expression here allows optimization based on argument values
831 even when the argument registers are used for other purposes. */
832 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
833 return new_reg_base_value
[regno
];
835 /* If a pseudo has a known base value, return it. Do not do this
836 for non-fixed hard regs since it can result in a circular
837 dependency chain for registers which have values at function entry.
839 The test above is not sufficient because the scheduler may move
840 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
841 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
842 && regno
< VEC_length (rtx
, reg_base_value
))
844 /* If we're inside init_alias_analysis, use new_reg_base_value
845 to reduce the number of relaxation iterations. */
846 if (new_reg_base_value
&& new_reg_base_value
[regno
]
847 && DF_REG_DEF_COUNT (regno
) == 1)
848 return new_reg_base_value
[regno
];
850 if (VEC_index (rtx
, reg_base_value
, regno
))
851 return VEC_index (rtx
, reg_base_value
, regno
);
857 /* Check for an argument passed in memory. Only record in the
858 copying-arguments block; it is too hard to track changes
860 if (copying_arguments
861 && (XEXP (src
, 0) == arg_pointer_rtx
862 || (GET_CODE (XEXP (src
, 0)) == PLUS
863 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
864 return gen_rtx_ADDRESS (VOIDmode
, src
);
869 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
872 /* ... fall through ... */
877 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
879 /* If either operand is a REG that is a known pointer, then it
881 if (REG_P (src_0
) && REG_POINTER (src_0
))
882 return find_base_value (src_0
);
883 if (REG_P (src_1
) && REG_POINTER (src_1
))
884 return find_base_value (src_1
);
886 /* If either operand is a REG, then see if we already have
887 a known value for it. */
890 temp
= find_base_value (src_0
);
897 temp
= find_base_value (src_1
);
902 /* If either base is named object or a special address
903 (like an argument or stack reference), then use it for the
906 && (GET_CODE (src_0
) == SYMBOL_REF
907 || GET_CODE (src_0
) == LABEL_REF
908 || (GET_CODE (src_0
) == ADDRESS
909 && GET_MODE (src_0
) != VOIDmode
)))
913 && (GET_CODE (src_1
) == SYMBOL_REF
914 || GET_CODE (src_1
) == LABEL_REF
915 || (GET_CODE (src_1
) == ADDRESS
916 && GET_MODE (src_1
) != VOIDmode
)))
919 /* Guess which operand is the base address:
920 If either operand is a symbol, then it is the base. If
921 either operand is a CONST_INT, then the other is the base. */
922 if (CONST_INT_P (src_1
) || CONSTANT_P (src_0
))
923 return find_base_value (src_0
);
924 else if (CONST_INT_P (src_0
) || CONSTANT_P (src_1
))
925 return find_base_value (src_1
);
931 /* The standard form is (lo_sum reg sym) so look only at the
933 return find_base_value (XEXP (src
, 1));
936 /* If the second operand is constant set the base
937 address to the first operand. */
938 if (CONST_INT_P (XEXP (src
, 1)) && INTVAL (XEXP (src
, 1)) != 0)
939 return find_base_value (XEXP (src
, 0));
943 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
953 return find_base_value (XEXP (src
, 0));
956 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
958 rtx temp
= find_base_value (XEXP (src
, 0));
960 if (temp
!= 0 && CONSTANT_P (temp
))
961 temp
= convert_memory_address (Pmode
, temp
);
973 /* Called from init_alias_analysis indirectly through note_stores. */
975 /* While scanning insns to find base values, reg_seen[N] is nonzero if
976 register N has been set in this function. */
977 static char *reg_seen
;
979 /* Addresses which are known not to alias anything else are identified
980 by a unique integer. */
981 static int unique_id
;
984 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
993 regno
= REGNO (dest
);
995 gcc_assert (regno
< VEC_length (rtx
, reg_base_value
));
997 /* If this spans multiple hard registers, then we must indicate that every
998 register has an unusable value. */
999 if (regno
< FIRST_PSEUDO_REGISTER
)
1000 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1007 reg_seen
[regno
+ n
] = 1;
1008 new_reg_base_value
[regno
+ n
] = 0;
1015 /* A CLOBBER wipes out any old value but does not prevent a previously
1016 unset register from acquiring a base address (i.e. reg_seen is not
1018 if (GET_CODE (set
) == CLOBBER
)
1020 new_reg_base_value
[regno
] = 0;
1023 src
= SET_SRC (set
);
1027 if (reg_seen
[regno
])
1029 new_reg_base_value
[regno
] = 0;
1032 reg_seen
[regno
] = 1;
1033 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
1034 GEN_INT (unique_id
++));
1038 /* If this is not the first set of REGNO, see whether the new value
1039 is related to the old one. There are two cases of interest:
1041 (1) The register might be assigned an entirely new value
1042 that has the same base term as the original set.
1044 (2) The set might be a simple self-modification that
1045 cannot change REGNO's base value.
1047 If neither case holds, reject the original base value as invalid.
1048 Note that the following situation is not detected:
1050 extern int x, y; int *p = &x; p += (&y-&x);
1052 ANSI C does not allow computing the difference of addresses
1053 of distinct top level objects. */
1054 if (new_reg_base_value
[regno
] != 0
1055 && find_base_value (src
) != new_reg_base_value
[regno
])
1056 switch (GET_CODE (src
))
1060 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1061 new_reg_base_value
[regno
] = 0;
1064 /* If the value we add in the PLUS is also a valid base value,
1065 this might be the actual base value, and the original value
1068 rtx other
= NULL_RTX
;
1070 if (XEXP (src
, 0) == dest
)
1071 other
= XEXP (src
, 1);
1072 else if (XEXP (src
, 1) == dest
)
1073 other
= XEXP (src
, 0);
1075 if (! other
|| find_base_value (other
))
1076 new_reg_base_value
[regno
] = 0;
1080 if (XEXP (src
, 0) != dest
|| !CONST_INT_P (XEXP (src
, 1)))
1081 new_reg_base_value
[regno
] = 0;
1084 new_reg_base_value
[regno
] = 0;
1087 /* If this is the first set of a register, record the value. */
1088 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1089 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1090 new_reg_base_value
[regno
] = find_base_value (src
);
1092 reg_seen
[regno
] = 1;
1095 /* If a value is known for REGNO, return it. */
1098 get_reg_known_value (unsigned int regno
)
1100 if (regno
>= FIRST_PSEUDO_REGISTER
)
1102 regno
-= FIRST_PSEUDO_REGISTER
;
1103 if (regno
< reg_known_value_size
)
1104 return reg_known_value
[regno
];
1112 set_reg_known_value (unsigned int regno
, rtx val
)
1114 if (regno
>= FIRST_PSEUDO_REGISTER
)
1116 regno
-= FIRST_PSEUDO_REGISTER
;
1117 if (regno
< reg_known_value_size
)
1118 reg_known_value
[regno
] = val
;
1122 /* Similarly for reg_known_equiv_p. */
1125 get_reg_known_equiv_p (unsigned int regno
)
1127 if (regno
>= FIRST_PSEUDO_REGISTER
)
1129 regno
-= FIRST_PSEUDO_REGISTER
;
1130 if (regno
< reg_known_value_size
)
1131 return reg_known_equiv_p
[regno
];
1137 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1139 if (regno
>= FIRST_PSEUDO_REGISTER
)
1141 regno
-= FIRST_PSEUDO_REGISTER
;
1142 if (regno
< reg_known_value_size
)
1143 reg_known_equiv_p
[regno
] = val
;
1148 /* Returns a canonical version of X, from the point of view alias
1149 analysis. (For example, if X is a MEM whose address is a register,
1150 and the register has a known value (say a SYMBOL_REF), then a MEM
1151 whose address is the SYMBOL_REF is returned.) */
1156 /* Recursively look for equivalences. */
1157 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1159 rtx t
= get_reg_known_value (REGNO (x
));
1163 return canon_rtx (t
);
1166 if (GET_CODE (x
) == PLUS
)
1168 rtx x0
= canon_rtx (XEXP (x
, 0));
1169 rtx x1
= canon_rtx (XEXP (x
, 1));
1171 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1173 if (CONST_INT_P (x0
))
1174 return plus_constant (x1
, INTVAL (x0
));
1175 else if (CONST_INT_P (x1
))
1176 return plus_constant (x0
, INTVAL (x1
));
1177 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1181 /* This gives us much better alias analysis when called from
1182 the loop optimizer. Note we want to leave the original
1183 MEM alone, but need to return the canonicalized MEM with
1184 all the flags with their original values. */
1186 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1191 /* Return 1 if X and Y are identical-looking rtx's.
1192 Expect that X and Y has been already canonicalized.
1194 We use the data in reg_known_value above to see if two registers with
1195 different numbers are, in fact, equivalent. */
1198 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1205 if (x
== 0 && y
== 0)
1207 if (x
== 0 || y
== 0)
1213 code
= GET_CODE (x
);
1214 /* Rtx's of different codes cannot be equal. */
1215 if (code
!= GET_CODE (y
))
1218 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1219 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1221 if (GET_MODE (x
) != GET_MODE (y
))
1224 /* Some RTL can be compared without a recursive examination. */
1228 return REGNO (x
) == REGNO (y
);
1231 return XEXP (x
, 0) == XEXP (y
, 0);
1234 return XSTR (x
, 0) == XSTR (y
, 0);
1240 /* There's no need to compare the contents of CONST_DOUBLEs or
1241 CONST_INTs because pointer equality is a good enough
1242 comparison for these nodes. */
1249 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1251 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1252 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1253 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1254 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1255 /* For commutative operations, the RTX match if the operand match in any
1256 order. Also handle the simple binary and unary cases without a loop. */
1257 if (COMMUTATIVE_P (x
))
1259 rtx xop0
= canon_rtx (XEXP (x
, 0));
1260 rtx yop0
= canon_rtx (XEXP (y
, 0));
1261 rtx yop1
= canon_rtx (XEXP (y
, 1));
1263 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1264 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1265 || (rtx_equal_for_memref_p (xop0
, yop1
)
1266 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1268 else if (NON_COMMUTATIVE_P (x
))
1270 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1271 canon_rtx (XEXP (y
, 0)))
1272 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1273 canon_rtx (XEXP (y
, 1))));
1275 else if (UNARY_P (x
))
1276 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1277 canon_rtx (XEXP (y
, 0)));
1279 /* Compare the elements. If any pair of corresponding elements
1280 fail to match, return 0 for the whole things.
1282 Limit cases to types which actually appear in addresses. */
1284 fmt
= GET_RTX_FORMAT (code
);
1285 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1290 if (XINT (x
, i
) != XINT (y
, i
))
1295 /* Two vectors must have the same length. */
1296 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1299 /* And the corresponding elements must match. */
1300 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1301 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1302 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1307 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1308 canon_rtx (XEXP (y
, i
))) == 0)
1312 /* This can happen for asm operands. */
1314 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1318 /* This can happen for an asm which clobbers memory. */
1322 /* It is believed that rtx's at this level will never
1323 contain anything but integers and other rtx's,
1324 except for within LABEL_REFs and SYMBOL_REFs. */
1333 find_base_term (rtx x
)
1336 struct elt_loc_list
*l
;
1338 #if defined (FIND_BASE_TERM)
1339 /* Try machine-dependent ways to find the base term. */
1340 x
= FIND_BASE_TERM (x
);
1343 switch (GET_CODE (x
))
1346 return REG_BASE_VALUE (x
);
1349 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1359 return find_base_term (XEXP (x
, 0));
1362 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1364 rtx temp
= find_base_term (XEXP (x
, 0));
1366 if (temp
!= 0 && CONSTANT_P (temp
))
1367 temp
= convert_memory_address (Pmode
, temp
);
1373 val
= CSELIB_VAL_PTR (x
);
1376 for (l
= val
->locs
; l
; l
= l
->next
)
1377 if ((x
= find_base_term (l
->loc
)) != 0)
1382 /* The standard form is (lo_sum reg sym) so look only at the
1384 return find_base_term (XEXP (x
, 1));
1388 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1394 rtx tmp1
= XEXP (x
, 0);
1395 rtx tmp2
= XEXP (x
, 1);
1397 /* This is a little bit tricky since we have to determine which of
1398 the two operands represents the real base address. Otherwise this
1399 routine may return the index register instead of the base register.
1401 That may cause us to believe no aliasing was possible, when in
1402 fact aliasing is possible.
1404 We use a few simple tests to guess the base register. Additional
1405 tests can certainly be added. For example, if one of the operands
1406 is a shift or multiply, then it must be the index register and the
1407 other operand is the base register. */
1409 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1410 return find_base_term (tmp2
);
1412 /* If either operand is known to be a pointer, then use it
1413 to determine the base term. */
1414 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1416 rtx base
= find_base_term (tmp1
);
1421 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1423 rtx base
= find_base_term (tmp2
);
1428 /* Neither operand was known to be a pointer. Go ahead and find the
1429 base term for both operands. */
1430 tmp1
= find_base_term (tmp1
);
1431 tmp2
= find_base_term (tmp2
);
1433 /* If either base term is named object or a special address
1434 (like an argument or stack reference), then use it for the
1437 && (GET_CODE (tmp1
) == SYMBOL_REF
1438 || GET_CODE (tmp1
) == LABEL_REF
1439 || (GET_CODE (tmp1
) == ADDRESS
1440 && GET_MODE (tmp1
) != VOIDmode
)))
1444 && (GET_CODE (tmp2
) == SYMBOL_REF
1445 || GET_CODE (tmp2
) == LABEL_REF
1446 || (GET_CODE (tmp2
) == ADDRESS
1447 && GET_MODE (tmp2
) != VOIDmode
)))
1450 /* We could not determine which of the two operands was the
1451 base register and which was the index. So we can determine
1452 nothing from the base alias check. */
1457 if (CONST_INT_P (XEXP (x
, 1)) && INTVAL (XEXP (x
, 1)) != 0)
1458 return find_base_term (XEXP (x
, 0));
1470 /* Return 0 if the addresses X and Y are known to point to different
1471 objects, 1 if they might be pointers to the same object. */
1474 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1475 enum machine_mode y_mode
)
1477 rtx x_base
= find_base_term (x
);
1478 rtx y_base
= find_base_term (y
);
1480 /* If the address itself has no known base see if a known equivalent
1481 value has one. If either address still has no known base, nothing
1482 is known about aliasing. */
1487 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1490 x_base
= find_base_term (x_c
);
1498 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1501 y_base
= find_base_term (y_c
);
1506 /* If the base addresses are equal nothing is known about aliasing. */
1507 if (rtx_equal_p (x_base
, y_base
))
1510 /* The base addresses are different expressions. If they are not accessed
1511 via AND, there is no conflict. We can bring knowledge of object
1512 alignment into play here. For example, on alpha, "char a, b;" can
1513 alias one another, though "char a; long b;" cannot. AND addesses may
1514 implicitly alias surrounding objects; i.e. unaligned access in DImode
1515 via AND address can alias all surrounding object types except those
1516 with aligment 8 or higher. */
1517 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1519 if (GET_CODE (x
) == AND
1520 && (!CONST_INT_P (XEXP (x
, 1))
1521 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1523 if (GET_CODE (y
) == AND
1524 && (!CONST_INT_P (XEXP (y
, 1))
1525 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1528 /* Differing symbols not accessed via AND never alias. */
1529 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1532 /* If one address is a stack reference there can be no alias:
1533 stack references using different base registers do not alias,
1534 a stack reference can not alias a parameter, and a stack reference
1535 can not alias a global. */
1536 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1537 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1540 if (! flag_argument_noalias
)
1543 if (flag_argument_noalias
> 1)
1546 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1547 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1550 /* Convert the address X into something we can use. This is done by returning
1551 it unchanged unless it is a value; in the latter case we call cselib to get
1552 a more useful rtx. */
1558 struct elt_loc_list
*l
;
1560 if (GET_CODE (x
) != VALUE
)
1562 v
= CSELIB_VAL_PTR (x
);
1565 for (l
= v
->locs
; l
; l
= l
->next
)
1566 if (CONSTANT_P (l
->loc
))
1568 for (l
= v
->locs
; l
; l
= l
->next
)
1569 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
))
1572 return v
->locs
->loc
;
1577 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1578 where SIZE is the size in bytes of the memory reference. If ADDR
1579 is not modified by the memory reference then ADDR is returned. */
1582 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1586 switch (GET_CODE (addr
))
1589 offset
= (n_refs
+ 1) * size
;
1592 offset
= -(n_refs
+ 1) * size
;
1595 offset
= n_refs
* size
;
1598 offset
= -n_refs
* size
;
1606 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1609 addr
= XEXP (addr
, 0);
1610 addr
= canon_rtx (addr
);
1615 /* Return nonzero if X and Y (memory addresses) could reference the
1616 same location in memory. C is an offset accumulator. When
1617 C is nonzero, we are testing aliases between X and Y + C.
1618 XSIZE is the size in bytes of the X reference,
1619 similarly YSIZE is the size in bytes for Y.
1620 Expect that canon_rtx has been already called for X and Y.
1622 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1623 referenced (the reference was BLKmode), so make the most pessimistic
1626 If XSIZE or YSIZE is negative, we may access memory outside the object
1627 being referenced as a side effect. This can happen when using AND to
1628 align memory references, as is done on the Alpha.
1630 Nice to notice that varying addresses cannot conflict with fp if no
1631 local variables had their addresses taken, but that's too hard now. */
1634 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1636 if (GET_CODE (x
) == VALUE
)
1638 if (GET_CODE (y
) == VALUE
)
1640 if (GET_CODE (x
) == HIGH
)
1642 else if (GET_CODE (x
) == LO_SUM
)
1645 x
= addr_side_effect_eval (x
, xsize
, 0);
1646 if (GET_CODE (y
) == HIGH
)
1648 else if (GET_CODE (y
) == LO_SUM
)
1651 y
= addr_side_effect_eval (y
, ysize
, 0);
1653 if (rtx_equal_for_memref_p (x
, y
))
1655 if (xsize
<= 0 || ysize
<= 0)
1657 if (c
>= 0 && xsize
> c
)
1659 if (c
< 0 && ysize
+c
> 0)
1664 /* This code used to check for conflicts involving stack references and
1665 globals but the base address alias code now handles these cases. */
1667 if (GET_CODE (x
) == PLUS
)
1669 /* The fact that X is canonicalized means that this
1670 PLUS rtx is canonicalized. */
1671 rtx x0
= XEXP (x
, 0);
1672 rtx x1
= XEXP (x
, 1);
1674 if (GET_CODE (y
) == PLUS
)
1676 /* The fact that Y is canonicalized means that this
1677 PLUS rtx is canonicalized. */
1678 rtx y0
= XEXP (y
, 0);
1679 rtx y1
= XEXP (y
, 1);
1681 if (rtx_equal_for_memref_p (x1
, y1
))
1682 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1683 if (rtx_equal_for_memref_p (x0
, y0
))
1684 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1685 if (CONST_INT_P (x1
))
1687 if (CONST_INT_P (y1
))
1688 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1689 c
- INTVAL (x1
) + INTVAL (y1
));
1691 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1694 else if (CONST_INT_P (y1
))
1695 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1699 else if (CONST_INT_P (x1
))
1700 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1702 else if (GET_CODE (y
) == PLUS
)
1704 /* The fact that Y is canonicalized means that this
1705 PLUS rtx is canonicalized. */
1706 rtx y0
= XEXP (y
, 0);
1707 rtx y1
= XEXP (y
, 1);
1709 if (CONST_INT_P (y1
))
1710 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1715 if (GET_CODE (x
) == GET_CODE (y
))
1716 switch (GET_CODE (x
))
1720 /* Handle cases where we expect the second operands to be the
1721 same, and check only whether the first operand would conflict
1724 rtx x1
= canon_rtx (XEXP (x
, 1));
1725 rtx y1
= canon_rtx (XEXP (y
, 1));
1726 if (! rtx_equal_for_memref_p (x1
, y1
))
1728 x0
= canon_rtx (XEXP (x
, 0));
1729 y0
= canon_rtx (XEXP (y
, 0));
1730 if (rtx_equal_for_memref_p (x0
, y0
))
1731 return (xsize
== 0 || ysize
== 0
1732 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1734 /* Can't properly adjust our sizes. */
1735 if (!CONST_INT_P (x1
))
1737 xsize
/= INTVAL (x1
);
1738 ysize
/= INTVAL (x1
);
1740 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1747 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1748 as an access with indeterminate size. Assume that references
1749 besides AND are aligned, so if the size of the other reference is
1750 at least as large as the alignment, assume no other overlap. */
1751 if (GET_CODE (x
) == AND
&& CONST_INT_P (XEXP (x
, 1)))
1753 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1755 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
1757 if (GET_CODE (y
) == AND
&& CONST_INT_P (XEXP (y
, 1)))
1759 /* ??? If we are indexing far enough into the array/structure, we
1760 may yet be able to determine that we can not overlap. But we
1761 also need to that we are far enough from the end not to overlap
1762 a following reference, so we do nothing with that for now. */
1763 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1765 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
1770 if (CONST_INT_P (x
) && CONST_INT_P (y
))
1772 c
+= (INTVAL (y
) - INTVAL (x
));
1773 return (xsize
<= 0 || ysize
<= 0
1774 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1777 if (GET_CODE (x
) == CONST
)
1779 if (GET_CODE (y
) == CONST
)
1780 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1781 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1783 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1786 if (GET_CODE (y
) == CONST
)
1787 return memrefs_conflict_p (xsize
, x
, ysize
,
1788 canon_rtx (XEXP (y
, 0)), c
);
1791 return (xsize
<= 0 || ysize
<= 0
1792 || (rtx_equal_for_memref_p (x
, y
)
1793 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1800 /* Functions to compute memory dependencies.
1802 Since we process the insns in execution order, we can build tables
1803 to keep track of what registers are fixed (and not aliased), what registers
1804 are varying in known ways, and what registers are varying in unknown
1807 If both memory references are volatile, then there must always be a
1808 dependence between the two references, since their order can not be
1809 changed. A volatile and non-volatile reference can be interchanged
1812 A MEM_IN_STRUCT reference at a non-AND varying address can never
1813 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1814 also must allow AND addresses, because they may generate accesses
1815 outside the object being referenced. This is used to generate
1816 aligned addresses from unaligned addresses, for instance, the alpha
1817 storeqi_unaligned pattern. */
1819 /* Read dependence: X is read after read in MEM takes place. There can
1820 only be a dependence here if both reads are volatile. */
1823 read_dependence (const_rtx mem
, const_rtx x
)
1825 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1828 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1829 MEM2 is a reference to a structure at a varying address, or returns
1830 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1831 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1832 to decide whether or not an address may vary; it should return
1833 nonzero whenever variation is possible.
1834 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1837 fixed_scalar_and_varying_struct_p (const_rtx mem1
, const_rtx mem2
, rtx mem1_addr
,
1839 bool (*varies_p
) (const_rtx
, bool))
1841 if (! flag_strict_aliasing
)
1844 if (MEM_ALIAS_SET (mem2
)
1845 && MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1846 && !varies_p (mem1_addr
, 1) && varies_p (mem2_addr
, 1))
1847 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1851 if (MEM_ALIAS_SET (mem1
)
1852 && MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1853 && varies_p (mem1_addr
, 1) && !varies_p (mem2_addr
, 1))
1854 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1861 /* Returns nonzero if something about the mode or address format MEM1
1862 indicates that it might well alias *anything*. */
1865 aliases_everything_p (const_rtx mem
)
1867 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1868 /* If the address is an AND, it's very hard to know at what it is
1869 actually pointing. */
1875 /* Return true if we can determine that the fields referenced cannot
1876 overlap for any pair of objects. */
1879 nonoverlapping_component_refs_p (const_tree x
, const_tree y
)
1881 const_tree fieldx
, fieldy
, typex
, typey
, orig_y
;
1885 /* The comparison has to be done at a common type, since we don't
1886 know how the inheritance hierarchy works. */
1890 fieldx
= TREE_OPERAND (x
, 1);
1891 typex
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx
));
1896 fieldy
= TREE_OPERAND (y
, 1);
1897 typey
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy
));
1902 y
= TREE_OPERAND (y
, 0);
1904 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
1906 x
= TREE_OPERAND (x
, 0);
1908 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1909 /* Never found a common type. */
1913 /* If we're left with accessing different fields of a structure,
1915 if (TREE_CODE (typex
) == RECORD_TYPE
1916 && fieldx
!= fieldy
)
1919 /* The comparison on the current field failed. If we're accessing
1920 a very nested structure, look at the next outer level. */
1921 x
= TREE_OPERAND (x
, 0);
1922 y
= TREE_OPERAND (y
, 0);
1925 && TREE_CODE (x
) == COMPONENT_REF
1926 && TREE_CODE (y
) == COMPONENT_REF
);
1931 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1934 decl_for_component_ref (tree x
)
1938 x
= TREE_OPERAND (x
, 0);
1940 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1942 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
1945 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1946 offset of the field reference. */
1949 adjust_offset_for_component_ref (tree x
, rtx offset
)
1951 HOST_WIDE_INT ioffset
;
1956 ioffset
= INTVAL (offset
);
1959 tree offset
= component_ref_field_offset (x
);
1960 tree field
= TREE_OPERAND (x
, 1);
1962 if (! host_integerp (offset
, 1))
1964 ioffset
+= (tree_low_cst (offset
, 1)
1965 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
1968 x
= TREE_OPERAND (x
, 0);
1970 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1972 return GEN_INT (ioffset
);
1975 /* Return nonzero if we can determine the exprs corresponding to memrefs
1976 X and Y and they do not overlap. */
1979 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
)
1981 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
1984 rtx moffsetx
, moffsety
;
1985 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
1987 /* Unless both have exprs, we can't tell anything. */
1988 if (exprx
== 0 || expry
== 0)
1991 /* If both are field references, we may be able to determine something. */
1992 if (TREE_CODE (exprx
) == COMPONENT_REF
1993 && TREE_CODE (expry
) == COMPONENT_REF
1994 && nonoverlapping_component_refs_p (exprx
, expry
))
1998 /* If the field reference test failed, look at the DECLs involved. */
1999 moffsetx
= MEM_OFFSET (x
);
2000 if (TREE_CODE (exprx
) == COMPONENT_REF
)
2002 if (TREE_CODE (expry
) == VAR_DECL
2003 && POINTER_TYPE_P (TREE_TYPE (expry
)))
2005 tree field
= TREE_OPERAND (exprx
, 1);
2006 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2007 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2012 tree t
= decl_for_component_ref (exprx
);
2015 moffsetx
= adjust_offset_for_component_ref (exprx
, moffsetx
);
2019 else if (INDIRECT_REF_P (exprx
))
2021 exprx
= TREE_OPERAND (exprx
, 0);
2022 if (flag_argument_noalias
< 2
2023 || TREE_CODE (exprx
) != PARM_DECL
)
2027 moffsety
= MEM_OFFSET (y
);
2028 if (TREE_CODE (expry
) == COMPONENT_REF
)
2030 if (TREE_CODE (exprx
) == VAR_DECL
2031 && POINTER_TYPE_P (TREE_TYPE (exprx
)))
2033 tree field
= TREE_OPERAND (expry
, 1);
2034 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2035 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2040 tree t
= decl_for_component_ref (expry
);
2043 moffsety
= adjust_offset_for_component_ref (expry
, moffsety
);
2047 else if (INDIRECT_REF_P (expry
))
2049 expry
= TREE_OPERAND (expry
, 0);
2050 if (flag_argument_noalias
< 2
2051 || TREE_CODE (expry
) != PARM_DECL
)
2055 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2058 rtlx
= DECL_RTL (exprx
);
2059 rtly
= DECL_RTL (expry
);
2061 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2062 can't overlap unless they are the same because we never reuse that part
2063 of the stack frame used for locals for spilled pseudos. */
2064 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2065 && ! rtx_equal_p (rtlx
, rtly
))
2068 /* Get the base and offsets of both decls. If either is a register, we
2069 know both are and are the same, so use that as the base. The only
2070 we can avoid overlap is if we can deduce that they are nonoverlapping
2071 pieces of that decl, which is very rare. */
2072 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2073 if (GET_CODE (basex
) == PLUS
&& CONST_INT_P (XEXP (basex
, 1)))
2074 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2076 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2077 if (GET_CODE (basey
) == PLUS
&& CONST_INT_P (XEXP (basey
, 1)))
2078 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2080 /* If the bases are different, we know they do not overlap if both
2081 are constants or if one is a constant and the other a pointer into the
2082 stack frame. Otherwise a different base means we can't tell if they
2084 if (! rtx_equal_p (basex
, basey
))
2085 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2086 || (CONSTANT_P (basex
) && REG_P (basey
)
2087 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2088 || (CONSTANT_P (basey
) && REG_P (basex
)
2089 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2091 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2092 : MEM_SIZE (rtlx
) ? INTVAL (MEM_SIZE (rtlx
))
2094 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2095 : MEM_SIZE (rtly
) ? INTVAL (MEM_SIZE (rtly
)) :
2098 /* If we have an offset for either memref, it can update the values computed
2101 offsetx
+= INTVAL (moffsetx
), sizex
-= INTVAL (moffsetx
);
2103 offsety
+= INTVAL (moffsety
), sizey
-= INTVAL (moffsety
);
2105 /* If a memref has both a size and an offset, we can use the smaller size.
2106 We can't do this if the offset isn't known because we must view this
2107 memref as being anywhere inside the DECL's MEM. */
2108 if (MEM_SIZE (x
) && moffsetx
)
2109 sizex
= INTVAL (MEM_SIZE (x
));
2110 if (MEM_SIZE (y
) && moffsety
)
2111 sizey
= INTVAL (MEM_SIZE (y
));
2113 /* Put the values of the memref with the lower offset in X's values. */
2114 if (offsetx
> offsety
)
2116 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2117 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2120 /* If we don't know the size of the lower-offset value, we can't tell
2121 if they conflict. Otherwise, we do the test. */
2122 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2125 /* True dependence: X is read after store in MEM takes place. */
2128 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
,
2129 bool (*varies
) (const_rtx
, bool))
2131 rtx x_addr
, mem_addr
;
2134 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2137 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2138 This is used in epilogue deallocation functions, and in cselib. */
2139 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2141 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2143 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2144 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2147 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2150 /* Read-only memory is by definition never modified, and therefore can't
2151 conflict with anything. We don't expect to find read-only set on MEM,
2152 but stupid user tricks can produce them, so don't die. */
2153 if (MEM_READONLY_P (x
))
2156 if (nonoverlapping_memrefs_p (mem
, x
))
2159 if (mem_mode
== VOIDmode
)
2160 mem_mode
= GET_MODE (mem
);
2162 x_addr
= get_addr (XEXP (x
, 0));
2163 mem_addr
= get_addr (XEXP (mem
, 0));
2165 base
= find_base_term (x_addr
);
2166 if (base
&& (GET_CODE (base
) == LABEL_REF
2167 || (GET_CODE (base
) == SYMBOL_REF
2168 && CONSTANT_POOL_ADDRESS_P (base
))))
2171 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2174 x_addr
= canon_rtx (x_addr
);
2175 mem_addr
= canon_rtx (mem_addr
);
2177 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2178 SIZE_FOR_MODE (x
), x_addr
, 0))
2181 if (aliases_everything_p (x
))
2184 /* We cannot use aliases_everything_p to test MEM, since we must look
2185 at MEM_MODE, rather than GET_MODE (MEM). */
2186 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2189 /* In true_dependence we also allow BLKmode to alias anything. Why
2190 don't we do this in anti_dependence and output_dependence? */
2191 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2194 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2198 /* Canonical true dependence: X is read after store in MEM takes place.
2199 Variant of true_dependence which assumes MEM has already been
2200 canonicalized (hence we no longer do that here).
2201 The mem_addr argument has been added, since true_dependence computed
2202 this value prior to canonicalizing.
2203 If x_addr is non-NULL, it is used in preference of XEXP (x, 0). */
2206 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2207 const_rtx x
, rtx x_addr
, bool (*varies
) (const_rtx
, bool))
2209 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2212 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2213 This is used in epilogue deallocation functions. */
2214 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2216 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2218 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2219 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2222 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2225 /* Read-only memory is by definition never modified, and therefore can't
2226 conflict with anything. We don't expect to find read-only set on MEM,
2227 but stupid user tricks can produce them, so don't die. */
2228 if (MEM_READONLY_P (x
))
2231 if (nonoverlapping_memrefs_p (x
, mem
))
2235 x_addr
= get_addr (XEXP (x
, 0));
2237 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2240 x_addr
= canon_rtx (x_addr
);
2241 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2242 SIZE_FOR_MODE (x
), x_addr
, 0))
2245 if (aliases_everything_p (x
))
2248 /* We cannot use aliases_everything_p to test MEM, since we must look
2249 at MEM_MODE, rather than GET_MODE (MEM). */
2250 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2253 /* In true_dependence we also allow BLKmode to alias anything. Why
2254 don't we do this in anti_dependence and output_dependence? */
2255 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2258 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2262 /* Returns nonzero if a write to X might alias a previous read from
2263 (or, if WRITEP is nonzero, a write to) MEM. */
2266 write_dependence_p (const_rtx mem
, const_rtx x
, int writep
)
2268 rtx x_addr
, mem_addr
;
2269 const_rtx fixed_scalar
;
2272 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2275 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2276 This is used in epilogue deallocation functions. */
2277 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2279 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2281 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2282 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2285 /* A read from read-only memory can't conflict with read-write memory. */
2286 if (!writep
&& MEM_READONLY_P (mem
))
2289 if (nonoverlapping_memrefs_p (x
, mem
))
2292 x_addr
= get_addr (XEXP (x
, 0));
2293 mem_addr
= get_addr (XEXP (mem
, 0));
2297 base
= find_base_term (mem_addr
);
2298 if (base
&& (GET_CODE (base
) == LABEL_REF
2299 || (GET_CODE (base
) == SYMBOL_REF
2300 && CONSTANT_POOL_ADDRESS_P (base
))))
2304 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2308 x_addr
= canon_rtx (x_addr
);
2309 mem_addr
= canon_rtx (mem_addr
);
2311 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2312 SIZE_FOR_MODE (x
), x_addr
, 0))
2316 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2319 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2320 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2323 /* Anti dependence: X is written after read in MEM takes place. */
2326 anti_dependence (const_rtx mem
, const_rtx x
)
2328 return write_dependence_p (mem
, x
, /*writep=*/0);
2331 /* Output dependence: X is written after store in MEM takes place. */
2334 output_dependence (const_rtx mem
, const_rtx x
)
2336 return write_dependence_p (mem
, x
, /*writep=*/1);
2341 init_alias_target (void)
2345 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2347 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2348 /* Check whether this register can hold an incoming pointer
2349 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2350 numbers, so translate if necessary due to register windows. */
2351 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2352 && HARD_REGNO_MODE_OK (i
, Pmode
))
2353 static_reg_base_value
[i
]
2354 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2356 static_reg_base_value
[STACK_POINTER_REGNUM
]
2357 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2358 static_reg_base_value
[ARG_POINTER_REGNUM
]
2359 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2360 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2361 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2362 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2363 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2364 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2368 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2369 to be memory reference. */
2370 static bool memory_modified
;
2372 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2376 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2377 memory_modified
= true;
2382 /* Return true when INSN possibly modify memory contents of MEM
2383 (i.e. address can be modified). */
2385 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2389 memory_modified
= false;
2390 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2391 return memory_modified
;
2394 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2398 init_alias_analysis (void)
2400 unsigned int maxreg
= max_reg_num ();
2406 timevar_push (TV_ALIAS_ANALYSIS
);
2408 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2409 reg_known_value
= GGC_CNEWVEC (rtx
, reg_known_value_size
);
2410 reg_known_equiv_p
= XCNEWVEC (bool, reg_known_value_size
);
2412 /* If we have memory allocated from the previous run, use it. */
2413 if (old_reg_base_value
)
2414 reg_base_value
= old_reg_base_value
;
2417 VEC_truncate (rtx
, reg_base_value
, 0);
2419 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2421 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2422 reg_seen
= XNEWVEC (char, maxreg
);
2424 /* The basic idea is that each pass through this loop will use the
2425 "constant" information from the previous pass to propagate alias
2426 information through another level of assignments.
2428 This could get expensive if the assignment chains are long. Maybe
2429 we should throttle the number of iterations, possibly based on
2430 the optimization level or flag_expensive_optimizations.
2432 We could propagate more information in the first pass by making use
2433 of DF_REG_DEF_COUNT to determine immediately that the alias information
2434 for a pseudo is "constant".
2436 A program with an uninitialized variable can cause an infinite loop
2437 here. Instead of doing a full dataflow analysis to detect such problems
2438 we just cap the number of iterations for the loop.
2440 The state of the arrays for the set chain in question does not matter
2441 since the program has undefined behavior. */
2446 /* Assume nothing will change this iteration of the loop. */
2449 /* We want to assign the same IDs each iteration of this loop, so
2450 start counting from zero each iteration of the loop. */
2453 /* We're at the start of the function each iteration through the
2454 loop, so we're copying arguments. */
2455 copying_arguments
= true;
2457 /* Wipe the potential alias information clean for this pass. */
2458 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2460 /* Wipe the reg_seen array clean. */
2461 memset (reg_seen
, 0, maxreg
);
2463 /* Mark all hard registers which may contain an address.
2464 The stack, frame and argument pointers may contain an address.
2465 An argument register which can hold a Pmode value may contain
2466 an address even if it is not in BASE_REGS.
2468 The address expression is VOIDmode for an argument and
2469 Pmode for other registers. */
2471 memcpy (new_reg_base_value
, static_reg_base_value
,
2472 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2474 /* Walk the insns adding values to the new_reg_base_value array. */
2475 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2481 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2482 /* The prologue/epilogue insns are not threaded onto the
2483 insn chain until after reload has completed. Thus,
2484 there is no sense wasting time checking if INSN is in
2485 the prologue/epilogue until after reload has completed. */
2486 if (reload_completed
2487 && prologue_epilogue_contains (insn
))
2491 /* If this insn has a noalias note, process it, Otherwise,
2492 scan for sets. A simple set will have no side effects
2493 which could change the base value of any other register. */
2495 if (GET_CODE (PATTERN (insn
)) == SET
2496 && REG_NOTES (insn
) != 0
2497 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2498 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2500 note_stores (PATTERN (insn
), record_set
, NULL
);
2502 set
= single_set (insn
);
2505 && REG_P (SET_DEST (set
))
2506 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2508 unsigned int regno
= REGNO (SET_DEST (set
));
2509 rtx src
= SET_SRC (set
);
2512 note
= find_reg_equal_equiv_note (insn
);
2513 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2514 && DF_REG_DEF_COUNT (regno
) != 1)
2517 if (note
!= NULL_RTX
2518 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2519 && ! rtx_varies_p (XEXP (note
, 0), 1)
2520 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2523 set_reg_known_value (regno
, XEXP (note
, 0));
2524 set_reg_known_equiv_p (regno
,
2525 REG_NOTE_KIND (note
) == REG_EQUIV
);
2527 else if (DF_REG_DEF_COUNT (regno
) == 1
2528 && GET_CODE (src
) == PLUS
2529 && REG_P (XEXP (src
, 0))
2530 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2531 && CONST_INT_P (XEXP (src
, 1)))
2533 t
= plus_constant (t
, INTVAL (XEXP (src
, 1)));
2534 set_reg_known_value (regno
, t
);
2535 set_reg_known_equiv_p (regno
, 0);
2537 else if (DF_REG_DEF_COUNT (regno
) == 1
2538 && ! rtx_varies_p (src
, 1))
2540 set_reg_known_value (regno
, src
);
2541 set_reg_known_equiv_p (regno
, 0);
2545 else if (NOTE_P (insn
)
2546 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2547 copying_arguments
= false;
2550 /* Now propagate values from new_reg_base_value to reg_base_value. */
2551 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2553 for (ui
= 0; ui
< maxreg
; ui
++)
2555 if (new_reg_base_value
[ui
]
2556 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2557 && ! rtx_equal_p (new_reg_base_value
[ui
],
2558 VEC_index (rtx
, reg_base_value
, ui
)))
2560 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2565 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2567 /* Fill in the remaining entries. */
2568 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2569 if (reg_known_value
[i
] == 0)
2570 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2573 free (new_reg_base_value
);
2574 new_reg_base_value
= 0;
2577 timevar_pop (TV_ALIAS_ANALYSIS
);
2581 end_alias_analysis (void)
2583 old_reg_base_value
= reg_base_value
;
2584 ggc_free (reg_known_value
);
2585 reg_known_value
= 0;
2586 reg_known_value_size
= 0;
2587 free (reg_known_equiv_p
);
2588 reg_known_equiv_p
= 0;
2591 #include "gt-alias.h"