1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
46 #include "tree-pass.h"
47 #include "ipa-type-escape.h"
50 /* The aliasing API provided here solves related but different problems:
52 Say there exists (in c)
66 Consider the four questions:
68 Can a store to x1 interfere with px2->y1?
69 Can a store to x1 interfere with px2->z2?
71 Can a store to x1 change the value pointed to by with py?
72 Can a store to x1 change the value pointed to by with pz?
74 The answer to these questions can be yes, yes, yes, and maybe.
76 The first two questions can be answered with a simple examination
77 of the type system. If structure X contains a field of type Y then
78 a store thru a pointer to an X can overwrite any field that is
79 contained (recursively) in an X (unless we know that px1 != px2).
81 The last two of the questions can be solved in the same way as the
82 first two questions but this is too conservative. The observation
83 is that in some cases analysis we can know if which (if any) fields
84 are addressed and if those addresses are used in bad ways. This
85 analysis may be language specific. In C, arbitrary operations may
86 be applied to pointers. However, there is some indication that
87 this may be too conservative for some C++ types.
89 The pass ipa-type-escape does this analysis for the types whose
90 instances do not escape across the compilation boundary.
92 Historically in GCC, these two problems were combined and a single
93 data structure was used to represent the solution to these
94 problems. We now have two similar but different data structures,
95 The data structure to solve the last two question is similar to the
96 first, but does not contain have the fields in it whose address are
97 never taken. For types that do escape the compilation unit, the
98 data structures will have identical information.
101 /* The alias sets assigned to MEMs assist the back-end in determining
102 which MEMs can alias which other MEMs. In general, two MEMs in
103 different alias sets cannot alias each other, with one important
104 exception. Consider something like:
106 struct S { int i; double d; };
108 a store to an `S' can alias something of either type `int' or type
109 `double'. (However, a store to an `int' cannot alias a `double'
110 and vice versa.) We indicate this via a tree structure that looks
118 (The arrows are directed and point downwards.)
119 In this situation we say the alias set for `struct S' is the
120 `superset' and that those for `int' and `double' are `subsets'.
122 To see whether two alias sets can point to the same memory, we must
123 see if either alias set is a subset of the other. We need not trace
124 past immediate descendants, however, since we propagate all
125 grandchildren up one level.
127 Alias set zero is implicitly a superset of all other alias sets.
128 However, this is no actual entry for alias set zero. It is an
129 error to attempt to explicitly construct a subset of zero. */
131 struct GTY(()) alias_set_entry
{
132 /* The alias set number, as stored in MEM_ALIAS_SET. */
133 alias_set_type alias_set
;
135 /* Nonzero if would have a child of zero: this effectively makes this
136 alias set the same as alias set zero. */
139 /* The children of the alias set. These are not just the immediate
140 children, but, in fact, all descendants. So, if we have:
142 struct T { struct S s; float f; }
144 continuing our example above, the children here will be all of
145 `int', `double', `float', and `struct S'. */
146 splay_tree
GTY((param1_is (int), param2_is (int))) children
;
148 typedef struct alias_set_entry
*alias_set_entry
;
150 static int rtx_equal_for_memref_p (const_rtx
, const_rtx
);
151 static int memrefs_conflict_p (int, rtx
, int, rtx
, HOST_WIDE_INT
);
152 static void record_set (rtx
, const_rtx
, void *);
153 static int base_alias_check (rtx
, rtx
, enum machine_mode
,
155 static rtx
find_base_value (rtx
);
156 static int mems_in_disjoint_alias_sets_p (const_rtx
, const_rtx
);
157 static int insert_subset_children (splay_tree_node
, void*);
158 static tree
find_base_decl (tree
);
159 static alias_set_entry
get_alias_set_entry (alias_set_type
);
160 static const_rtx
fixed_scalar_and_varying_struct_p (const_rtx
, const_rtx
, rtx
, rtx
,
161 bool (*) (const_rtx
, bool));
162 static int aliases_everything_p (const_rtx
);
163 static bool nonoverlapping_component_refs_p (const_tree
, const_tree
);
164 static tree
decl_for_component_ref (tree
);
165 static rtx
adjust_offset_for_component_ref (tree
, rtx
);
166 static int write_dependence_p (const_rtx
, const_rtx
, int);
168 static void memory_modified_1 (rtx
, const_rtx
, void *);
170 /* Set up all info needed to perform alias analysis on memory references. */
172 /* Returns the size in bytes of the mode of X. */
173 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
175 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
176 different alias sets. We ignore alias sets in functions making use
177 of variable arguments because the va_arg macros on some systems are
179 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
180 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
182 /* Cap the number of passes we make over the insns propagating alias
183 information through set chains. 10 is a completely arbitrary choice. */
184 #define MAX_ALIAS_LOOP_PASSES 10
186 /* reg_base_value[N] gives an address to which register N is related.
187 If all sets after the first add or subtract to the current value
188 or otherwise modify it so it does not point to a different top level
189 object, reg_base_value[N] is equal to the address part of the source
192 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
193 expressions represent certain special values: function arguments and
194 the stack, frame, and argument pointers.
196 The contents of an ADDRESS is not normally used, the mode of the
197 ADDRESS determines whether the ADDRESS is a function argument or some
198 other special value. Pointer equality, not rtx_equal_p, determines whether
199 two ADDRESS expressions refer to the same base address.
201 The only use of the contents of an ADDRESS is for determining if the
202 current function performs nonlocal memory memory references for the
203 purposes of marking the function as a constant function. */
205 static GTY(()) VEC(rtx
,gc
) *reg_base_value
;
206 static rtx
*new_reg_base_value
;
208 /* We preserve the copy of old array around to avoid amount of garbage
209 produced. About 8% of garbage produced were attributed to this
211 static GTY((deletable
)) VEC(rtx
,gc
) *old_reg_base_value
;
213 /* Static hunks of RTL used by the aliasing code; these are initialized
214 once per function to avoid unnecessary RTL allocations. */
215 static GTY (()) rtx static_reg_base_value
[FIRST_PSEUDO_REGISTER
];
217 #define REG_BASE_VALUE(X) \
218 (REGNO (X) < VEC_length (rtx, reg_base_value) \
219 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
221 /* Vector indexed by N giving the initial (unchanging) value known for
222 pseudo-register N. This array is initialized in init_alias_analysis,
223 and does not change until end_alias_analysis is called. */
224 static GTY((length("reg_known_value_size"))) rtx
*reg_known_value
;
226 /* Indicates number of valid entries in reg_known_value. */
227 static GTY(()) unsigned int reg_known_value_size
;
229 /* Vector recording for each reg_known_value whether it is due to a
230 REG_EQUIV note. Future passes (viz., reload) may replace the
231 pseudo with the equivalent expression and so we account for the
232 dependences that would be introduced if that happens.
234 The REG_EQUIV notes created in assign_parms may mention the arg
235 pointer, and there are explicit insns in the RTL that modify the
236 arg pointer. Thus we must ensure that such insns don't get
237 scheduled across each other because that would invalidate the
238 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
239 wrong, but solving the problem in the scheduler will likely give
240 better code, so we do it here. */
241 static bool *reg_known_equiv_p
;
243 /* True when scanning insns from the start of the rtl to the
244 NOTE_INSN_FUNCTION_BEG note. */
245 static bool copying_arguments
;
247 DEF_VEC_P(alias_set_entry
);
248 DEF_VEC_ALLOC_P(alias_set_entry
,gc
);
250 /* The splay-tree used to store the various alias set entries. */
251 static GTY (()) VEC(alias_set_entry
,gc
) *alias_sets
;
253 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
254 such an entry, or NULL otherwise. */
256 static inline alias_set_entry
257 get_alias_set_entry (alias_set_type alias_set
)
259 return VEC_index (alias_set_entry
, alias_sets
, alias_set
);
262 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
263 the two MEMs cannot alias each other. */
266 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
268 /* Perform a basic sanity check. Namely, that there are no alias sets
269 if we're not using strict aliasing. This helps to catch bugs
270 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
271 where a MEM is allocated in some way other than by the use of
272 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
273 use alias sets to indicate that spilled registers cannot alias each
274 other, we might need to remove this check. */
275 gcc_assert (flag_strict_aliasing
276 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
278 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
281 /* Insert the NODE into the splay tree given by DATA. Used by
282 record_alias_subset via splay_tree_foreach. */
285 insert_subset_children (splay_tree_node node
, void *data
)
287 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
292 /* Return true if the first alias set is a subset of the second. */
295 alias_set_subset_of (alias_set_type set1
, alias_set_type set2
)
299 /* Everything is a subset of the "aliases everything" set. */
303 /* Otherwise, check if set1 is a subset of set2. */
304 ase
= get_alias_set_entry (set2
);
306 && ((ase
->has_zero_child
&& set1
== 0)
307 || splay_tree_lookup (ase
->children
,
308 (splay_tree_key
) set1
)))
313 /* Return 1 if the two specified alias sets may conflict. */
316 alias_sets_conflict_p (alias_set_type set1
, alias_set_type set2
)
321 if (alias_sets_must_conflict_p (set1
, set2
))
324 /* See if the first alias set is a subset of the second. */
325 ase
= get_alias_set_entry (set1
);
327 && (ase
->has_zero_child
328 || splay_tree_lookup (ase
->children
,
329 (splay_tree_key
) set2
)))
332 /* Now do the same, but with the alias sets reversed. */
333 ase
= get_alias_set_entry (set2
);
335 && (ase
->has_zero_child
336 || splay_tree_lookup (ase
->children
,
337 (splay_tree_key
) set1
)))
340 /* The two alias sets are distinct and neither one is the
341 child of the other. Therefore, they cannot conflict. */
346 walk_mems_2 (rtx
*x
, rtx mem
)
350 if (alias_sets_conflict_p (MEM_ALIAS_SET(*x
), MEM_ALIAS_SET(mem
)))
359 walk_mems_1 (rtx
*x
, rtx
*pat
)
363 /* Visit all MEMs in *PAT and check indepedence. */
364 if (for_each_rtx (pat
, (rtx_function
) walk_mems_2
, *x
))
365 /* Indicate that dependence was determined and stop traversal. */
373 /* Return 1 if two specified instructions have mem expr with conflict alias sets*/
375 insn_alias_sets_conflict_p (rtx insn1
, rtx insn2
)
377 /* For each pair of MEMs in INSN1 and INSN2 check their independence. */
378 return for_each_rtx (&PATTERN (insn1
), (rtx_function
) walk_mems_1
,
382 /* Return 1 if the two specified alias sets will always conflict. */
385 alias_sets_must_conflict_p (alias_set_type set1
, alias_set_type set2
)
387 if (set1
== 0 || set2
== 0 || set1
== set2
)
393 /* Return 1 if any MEM object of type T1 will always conflict (using the
394 dependency routines in this file) with any MEM object of type T2.
395 This is used when allocating temporary storage. If T1 and/or T2 are
396 NULL_TREE, it means we know nothing about the storage. */
399 objects_must_conflict_p (tree t1
, tree t2
)
401 alias_set_type set1
, set2
;
403 /* If neither has a type specified, we don't know if they'll conflict
404 because we may be using them to store objects of various types, for
405 example the argument and local variables areas of inlined functions. */
406 if (t1
== 0 && t2
== 0)
409 /* If they are the same type, they must conflict. */
411 /* Likewise if both are volatile. */
412 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
415 set1
= t1
? get_alias_set (t1
) : 0;
416 set2
= t2
? get_alias_set (t2
) : 0;
418 /* We can't use alias_sets_conflict_p because we must make sure
419 that every subtype of t1 will conflict with every subtype of
420 t2 for which a pair of subobjects of these respective subtypes
421 overlaps on the stack. */
422 return alias_sets_must_conflict_p (set1
, set2
);
425 /* T is an expression with pointer type. Find the DECL on which this
426 expression is based. (For example, in `a[i]' this would be `a'.)
427 If there is no such DECL, or a unique decl cannot be determined,
428 NULL_TREE is returned. */
431 find_base_decl (tree t
)
435 if (t
== 0 || t
== error_mark_node
|| ! POINTER_TYPE_P (TREE_TYPE (t
)))
438 if (TREE_CODE (t
) == SSA_NAME
)
439 t
= SSA_NAME_VAR (t
);
441 /* If this is a declaration, return it. If T is based on a restrict
442 qualified decl, return that decl. */
445 if (TREE_CODE (t
) == VAR_DECL
&& DECL_BASED_ON_RESTRICT_P (t
))
446 t
= DECL_GET_RESTRICT_BASE (t
);
450 /* Handle general expressions. It would be nice to deal with
451 COMPONENT_REFs here. If we could tell that `a' and `b' were the
452 same, then `a->f' and `b->f' are also the same. */
453 switch (TREE_CODE_CLASS (TREE_CODE (t
)))
456 return find_base_decl (TREE_OPERAND (t
, 0));
459 /* Return 0 if found in neither or both are the same. */
460 d0
= find_base_decl (TREE_OPERAND (t
, 0));
461 d1
= find_base_decl (TREE_OPERAND (t
, 1));
476 /* Return true if all nested component references handled by
477 get_inner_reference in T are such that we should use the alias set
478 provided by the object at the heart of T.
480 This is true for non-addressable components (which don't have their
481 own alias set), as well as components of objects in alias set zero.
482 This later point is a special case wherein we wish to override the
483 alias set used by the component, but we don't have per-FIELD_DECL
484 assignable alias sets. */
487 component_uses_parent_alias_set (const_tree t
)
491 /* If we're at the end, it vacuously uses its own alias set. */
492 if (!handled_component_p (t
))
495 switch (TREE_CODE (t
))
498 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1)))
503 case ARRAY_RANGE_REF
:
504 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0))))
513 /* Bitfields and casts are never addressable. */
517 t
= TREE_OPERAND (t
, 0);
518 if (get_alias_set (TREE_TYPE (t
)) == 0)
523 /* Return the alias set for the memory pointed to by T, which may be
524 either a type or an expression. Return -1 if there is nothing
525 special about dereferencing T. */
527 static alias_set_type
528 get_deref_alias_set_1 (tree t
)
530 /* If we're not doing any alias analysis, just assume everything
531 aliases everything else. */
532 if (!flag_strict_aliasing
)
537 tree decl
= find_base_decl (t
);
539 if (decl
&& DECL_POINTER_ALIAS_SET_KNOWN_P (decl
))
541 /* If we haven't computed the actual alias set, do it now. */
542 if (DECL_POINTER_ALIAS_SET (decl
) == -2)
544 tree pointed_to_type
= TREE_TYPE (TREE_TYPE (decl
));
546 /* No two restricted pointers can point at the same thing.
547 However, a restricted pointer can point at the same thing
548 as an unrestricted pointer, if that unrestricted pointer
549 is based on the restricted pointer. So, we make the
550 alias set for the restricted pointer a subset of the
551 alias set for the type pointed to by the type of the
553 alias_set_type pointed_to_alias_set
554 = get_alias_set (pointed_to_type
);
556 if (pointed_to_alias_set
== 0)
557 /* It's not legal to make a subset of alias set zero. */
558 DECL_POINTER_ALIAS_SET (decl
) = 0;
559 else if (AGGREGATE_TYPE_P (pointed_to_type
))
560 /* For an aggregate, we must treat the restricted
561 pointer the same as an ordinary pointer. If we
562 were to make the type pointed to by the
563 restricted pointer a subset of the pointed-to
564 type, then we would believe that other subsets
565 of the pointed-to type (such as fields of that
566 type) do not conflict with the type pointed to
567 by the restricted pointer. */
568 DECL_POINTER_ALIAS_SET (decl
)
569 = pointed_to_alias_set
;
572 DECL_POINTER_ALIAS_SET (decl
) = new_alias_set ();
573 record_alias_subset (pointed_to_alias_set
,
574 DECL_POINTER_ALIAS_SET (decl
));
578 /* We use the alias set indicated in the declaration. */
579 return DECL_POINTER_ALIAS_SET (decl
);
582 /* Now all we care about is the type. */
586 /* If we have an INDIRECT_REF via a void pointer, we don't
587 know anything about what that might alias. Likewise if the
588 pointer is marked that way. */
589 if (TREE_CODE (TREE_TYPE (t
)) == VOID_TYPE
590 || TYPE_REF_CAN_ALIAS_ALL (t
))
596 /* Return the alias set for the memory pointed to by T, which may be
597 either a type or an expression. */
600 get_deref_alias_set (tree t
)
602 alias_set_type set
= get_deref_alias_set_1 (t
);
604 /* Fall back to the alias-set of the pointed-to type. */
609 set
= get_alias_set (TREE_TYPE (t
));
615 /* Return the alias set for T, which may be either a type or an
616 expression. Call language-specific routine for help, if needed. */
619 get_alias_set (tree t
)
623 /* If we're not doing any alias analysis, just assume everything
624 aliases everything else. Also return 0 if this or its type is
626 if (! flag_strict_aliasing
|| t
== error_mark_node
628 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
631 /* We can be passed either an expression or a type. This and the
632 language-specific routine may make mutually-recursive calls to each other
633 to figure out what to do. At each juncture, we see if this is a tree
634 that the language may need to handle specially. First handle things that
640 /* Remove any nops, then give the language a chance to do
641 something with this tree before we look at it. */
643 set
= lang_hooks
.get_alias_set (t
);
647 /* First see if the actual object referenced is an INDIRECT_REF from a
648 restrict-qualified pointer or a "void *". */
649 while (handled_component_p (inner
))
651 inner
= TREE_OPERAND (inner
, 0);
655 if (INDIRECT_REF_P (inner
))
657 set
= get_deref_alias_set_1 (TREE_OPERAND (inner
, 0));
662 /* Otherwise, pick up the outermost object that we could have a pointer
663 to, processing conversions as above. */
664 while (component_uses_parent_alias_set (t
))
666 t
= TREE_OPERAND (t
, 0);
670 /* If we've already determined the alias set for a decl, just return
671 it. This is necessary for C++ anonymous unions, whose component
672 variables don't look like union members (boo!). */
673 if (TREE_CODE (t
) == VAR_DECL
674 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
675 return MEM_ALIAS_SET (DECL_RTL (t
));
677 /* Now all we care about is the type. */
681 /* Variant qualifiers don't affect the alias set, so get the main
682 variant. Always use the canonical type as well.
683 If this is a type with a known alias set, return it. */
684 t
= TYPE_MAIN_VARIANT (t
);
685 if (TYPE_CANONICAL (t
))
686 t
= TYPE_CANONICAL (t
);
687 if (TYPE_ALIAS_SET_KNOWN_P (t
))
688 return TYPE_ALIAS_SET (t
);
690 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
691 if (!COMPLETE_TYPE_P (t
))
693 /* For arrays with unknown size the conservative answer is the
694 alias set of the element type. */
695 if (TREE_CODE (t
) == ARRAY_TYPE
)
696 return get_alias_set (TREE_TYPE (t
));
698 /* But return zero as a conservative answer for incomplete types. */
702 /* See if the language has special handling for this type. */
703 set
= lang_hooks
.get_alias_set (t
);
707 /* There are no objects of FUNCTION_TYPE, so there's no point in
708 using up an alias set for them. (There are, of course, pointers
709 and references to functions, but that's different.) */
710 else if (TREE_CODE (t
) == FUNCTION_TYPE
711 || TREE_CODE (t
) == METHOD_TYPE
)
714 /* Unless the language specifies otherwise, let vector types alias
715 their components. This avoids some nasty type punning issues in
716 normal usage. And indeed lets vectors be treated more like an
718 else if (TREE_CODE (t
) == VECTOR_TYPE
)
719 set
= get_alias_set (TREE_TYPE (t
));
721 /* Unless the language specifies otherwise, treat array types the
722 same as their components. This avoids the asymmetry we get
723 through recording the components. Consider accessing a
724 character(kind=1) through a reference to a character(kind=1)[1:1].
725 Or consider if we want to assign integer(kind=4)[0:D.1387] and
726 integer(kind=4)[4] the same alias set or not.
727 Just be pragmatic here and make sure the array and its element
728 type get the same alias set assigned. */
729 else if (TREE_CODE (t
) == ARRAY_TYPE
730 && !TYPE_NONALIASED_COMPONENT (t
))
731 set
= get_alias_set (TREE_TYPE (t
));
734 /* Otherwise make a new alias set for this type. */
735 set
= new_alias_set ();
737 TYPE_ALIAS_SET (t
) = set
;
739 /* If this is an aggregate type, we must record any component aliasing
741 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
742 record_component_aliases (t
);
747 /* Return a brand-new alias set. */
752 if (flag_strict_aliasing
)
755 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
756 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
757 return VEC_length (alias_set_entry
, alias_sets
) - 1;
763 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
764 not everything that aliases SUPERSET also aliases SUBSET. For example,
765 in C, a store to an `int' can alias a load of a structure containing an
766 `int', and vice versa. But it can't alias a load of a 'double' member
767 of the same structure. Here, the structure would be the SUPERSET and
768 `int' the SUBSET. This relationship is also described in the comment at
769 the beginning of this file.
771 This function should be called only once per SUPERSET/SUBSET pair.
773 It is illegal for SUPERSET to be zero; everything is implicitly a
774 subset of alias set zero. */
777 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
779 alias_set_entry superset_entry
;
780 alias_set_entry subset_entry
;
782 /* It is possible in complex type situations for both sets to be the same,
783 in which case we can ignore this operation. */
784 if (superset
== subset
)
787 gcc_assert (superset
);
789 superset_entry
= get_alias_set_entry (superset
);
790 if (superset_entry
== 0)
792 /* Create an entry for the SUPERSET, so that we have a place to
793 attach the SUBSET. */
794 superset_entry
= GGC_NEW (struct alias_set_entry
);
795 superset_entry
->alias_set
= superset
;
796 superset_entry
->children
797 = splay_tree_new_ggc (splay_tree_compare_ints
);
798 superset_entry
->has_zero_child
= 0;
799 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
803 superset_entry
->has_zero_child
= 1;
806 subset_entry
= get_alias_set_entry (subset
);
807 /* If there is an entry for the subset, enter all of its children
808 (if they are not already present) as children of the SUPERSET. */
811 if (subset_entry
->has_zero_child
)
812 superset_entry
->has_zero_child
= 1;
814 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
815 superset_entry
->children
);
818 /* Enter the SUBSET itself as a child of the SUPERSET. */
819 splay_tree_insert (superset_entry
->children
,
820 (splay_tree_key
) subset
, 0);
824 /* Record that component types of TYPE, if any, are part of that type for
825 aliasing purposes. For record types, we only record component types
826 for fields that are not marked non-addressable. For array types, we
827 only record the component type if it is not marked non-aliased. */
830 record_component_aliases (tree type
)
832 alias_set_type superset
= get_alias_set (type
);
838 switch (TREE_CODE (type
))
842 case QUAL_UNION_TYPE
:
843 /* Recursively record aliases for the base classes, if there are any. */
844 if (TYPE_BINFO (type
))
847 tree binfo
, base_binfo
;
849 for (binfo
= TYPE_BINFO (type
), i
= 0;
850 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
851 record_alias_subset (superset
,
852 get_alias_set (BINFO_TYPE (base_binfo
)));
854 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
855 if (TREE_CODE (field
) == FIELD_DECL
&& !DECL_NONADDRESSABLE_P (field
))
856 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
860 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
863 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
871 /* Allocate an alias set for use in storing and reading from the varargs
874 static GTY(()) alias_set_type varargs_set
= -1;
877 get_varargs_alias_set (void)
880 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
881 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
882 consistently use the varargs alias set for loads from the varargs
883 area. So don't use it anywhere. */
886 if (varargs_set
== -1)
887 varargs_set
= new_alias_set ();
893 /* Likewise, but used for the fixed portions of the frame, e.g., register
896 static GTY(()) alias_set_type frame_set
= -1;
899 get_frame_alias_set (void)
902 frame_set
= new_alias_set ();
907 /* Inside SRC, the source of a SET, find a base address. */
910 find_base_value (rtx src
)
914 #if defined (FIND_BASE_TERM)
915 /* Try machine-dependent ways to find the base term. */
916 src
= FIND_BASE_TERM (src
);
919 switch (GET_CODE (src
))
927 /* At the start of a function, argument registers have known base
928 values which may be lost later. Returning an ADDRESS
929 expression here allows optimization based on argument values
930 even when the argument registers are used for other purposes. */
931 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
932 return new_reg_base_value
[regno
];
934 /* If a pseudo has a known base value, return it. Do not do this
935 for non-fixed hard regs since it can result in a circular
936 dependency chain for registers which have values at function entry.
938 The test above is not sufficient because the scheduler may move
939 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
940 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
941 && regno
< VEC_length (rtx
, reg_base_value
))
943 /* If we're inside init_alias_analysis, use new_reg_base_value
944 to reduce the number of relaxation iterations. */
945 if (new_reg_base_value
&& new_reg_base_value
[regno
]
946 && DF_REG_DEF_COUNT (regno
) == 1)
947 return new_reg_base_value
[regno
];
949 if (VEC_index (rtx
, reg_base_value
, regno
))
950 return VEC_index (rtx
, reg_base_value
, regno
);
956 /* Check for an argument passed in memory. Only record in the
957 copying-arguments block; it is too hard to track changes
959 if (copying_arguments
960 && (XEXP (src
, 0) == arg_pointer_rtx
961 || (GET_CODE (XEXP (src
, 0)) == PLUS
962 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
963 return gen_rtx_ADDRESS (VOIDmode
, src
);
968 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
971 /* ... fall through ... */
976 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
978 /* If either operand is a REG that is a known pointer, then it
980 if (REG_P (src_0
) && REG_POINTER (src_0
))
981 return find_base_value (src_0
);
982 if (REG_P (src_1
) && REG_POINTER (src_1
))
983 return find_base_value (src_1
);
985 /* If either operand is a REG, then see if we already have
986 a known value for it. */
989 temp
= find_base_value (src_0
);
996 temp
= find_base_value (src_1
);
1001 /* If either base is named object or a special address
1002 (like an argument or stack reference), then use it for the
1005 && (GET_CODE (src_0
) == SYMBOL_REF
1006 || GET_CODE (src_0
) == LABEL_REF
1007 || (GET_CODE (src_0
) == ADDRESS
1008 && GET_MODE (src_0
) != VOIDmode
)))
1012 && (GET_CODE (src_1
) == SYMBOL_REF
1013 || GET_CODE (src_1
) == LABEL_REF
1014 || (GET_CODE (src_1
) == ADDRESS
1015 && GET_MODE (src_1
) != VOIDmode
)))
1018 /* Guess which operand is the base address:
1019 If either operand is a symbol, then it is the base. If
1020 either operand is a CONST_INT, then the other is the base. */
1021 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
1022 return find_base_value (src_0
);
1023 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
1024 return find_base_value (src_1
);
1030 /* The standard form is (lo_sum reg sym) so look only at the
1032 return find_base_value (XEXP (src
, 1));
1035 /* If the second operand is constant set the base
1036 address to the first operand. */
1037 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
1038 return find_base_value (XEXP (src
, 0));
1042 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
1052 return find_base_value (XEXP (src
, 0));
1055 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
1057 rtx temp
= find_base_value (XEXP (src
, 0));
1059 if (temp
!= 0 && CONSTANT_P (temp
))
1060 temp
= convert_memory_address (Pmode
, temp
);
1072 /* Called from init_alias_analysis indirectly through note_stores. */
1074 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1075 register N has been set in this function. */
1076 static char *reg_seen
;
1078 /* Addresses which are known not to alias anything else are identified
1079 by a unique integer. */
1080 static int unique_id
;
1083 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
1092 regno
= REGNO (dest
);
1094 gcc_assert (regno
< VEC_length (rtx
, reg_base_value
));
1096 /* If this spans multiple hard registers, then we must indicate that every
1097 register has an unusable value. */
1098 if (regno
< FIRST_PSEUDO_REGISTER
)
1099 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1106 reg_seen
[regno
+ n
] = 1;
1107 new_reg_base_value
[regno
+ n
] = 0;
1114 /* A CLOBBER wipes out any old value but does not prevent a previously
1115 unset register from acquiring a base address (i.e. reg_seen is not
1117 if (GET_CODE (set
) == CLOBBER
)
1119 new_reg_base_value
[regno
] = 0;
1122 src
= SET_SRC (set
);
1126 if (reg_seen
[regno
])
1128 new_reg_base_value
[regno
] = 0;
1131 reg_seen
[regno
] = 1;
1132 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
1133 GEN_INT (unique_id
++));
1137 /* If this is not the first set of REGNO, see whether the new value
1138 is related to the old one. There are two cases of interest:
1140 (1) The register might be assigned an entirely new value
1141 that has the same base term as the original set.
1143 (2) The set might be a simple self-modification that
1144 cannot change REGNO's base value.
1146 If neither case holds, reject the original base value as invalid.
1147 Note that the following situation is not detected:
1149 extern int x, y; int *p = &x; p += (&y-&x);
1151 ANSI C does not allow computing the difference of addresses
1152 of distinct top level objects. */
1153 if (new_reg_base_value
[regno
] != 0
1154 && find_base_value (src
) != new_reg_base_value
[regno
])
1155 switch (GET_CODE (src
))
1159 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1160 new_reg_base_value
[regno
] = 0;
1163 /* If the value we add in the PLUS is also a valid base value,
1164 this might be the actual base value, and the original value
1167 rtx other
= NULL_RTX
;
1169 if (XEXP (src
, 0) == dest
)
1170 other
= XEXP (src
, 1);
1171 else if (XEXP (src
, 1) == dest
)
1172 other
= XEXP (src
, 0);
1174 if (! other
|| find_base_value (other
))
1175 new_reg_base_value
[regno
] = 0;
1179 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
1180 new_reg_base_value
[regno
] = 0;
1183 new_reg_base_value
[regno
] = 0;
1186 /* If this is the first set of a register, record the value. */
1187 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1188 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1189 new_reg_base_value
[regno
] = find_base_value (src
);
1191 reg_seen
[regno
] = 1;
1194 /* If a value is known for REGNO, return it. */
1197 get_reg_known_value (unsigned int regno
)
1199 if (regno
>= FIRST_PSEUDO_REGISTER
)
1201 regno
-= FIRST_PSEUDO_REGISTER
;
1202 if (regno
< reg_known_value_size
)
1203 return reg_known_value
[regno
];
1211 set_reg_known_value (unsigned int regno
, rtx val
)
1213 if (regno
>= FIRST_PSEUDO_REGISTER
)
1215 regno
-= FIRST_PSEUDO_REGISTER
;
1216 if (regno
< reg_known_value_size
)
1217 reg_known_value
[regno
] = val
;
1221 /* Similarly for reg_known_equiv_p. */
1224 get_reg_known_equiv_p (unsigned int regno
)
1226 if (regno
>= FIRST_PSEUDO_REGISTER
)
1228 regno
-= FIRST_PSEUDO_REGISTER
;
1229 if (regno
< reg_known_value_size
)
1230 return reg_known_equiv_p
[regno
];
1236 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1238 if (regno
>= FIRST_PSEUDO_REGISTER
)
1240 regno
-= FIRST_PSEUDO_REGISTER
;
1241 if (regno
< reg_known_value_size
)
1242 reg_known_equiv_p
[regno
] = val
;
1247 /* Returns a canonical version of X, from the point of view alias
1248 analysis. (For example, if X is a MEM whose address is a register,
1249 and the register has a known value (say a SYMBOL_REF), then a MEM
1250 whose address is the SYMBOL_REF is returned.) */
1255 /* Recursively look for equivalences. */
1256 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1258 rtx t
= get_reg_known_value (REGNO (x
));
1262 return canon_rtx (t
);
1265 if (GET_CODE (x
) == PLUS
)
1267 rtx x0
= canon_rtx (XEXP (x
, 0));
1268 rtx x1
= canon_rtx (XEXP (x
, 1));
1270 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1272 if (GET_CODE (x0
) == CONST_INT
)
1273 return plus_constant (x1
, INTVAL (x0
));
1274 else if (GET_CODE (x1
) == CONST_INT
)
1275 return plus_constant (x0
, INTVAL (x1
));
1276 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1280 /* This gives us much better alias analysis when called from
1281 the loop optimizer. Note we want to leave the original
1282 MEM alone, but need to return the canonicalized MEM with
1283 all the flags with their original values. */
1285 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1290 /* Return 1 if X and Y are identical-looking rtx's.
1291 Expect that X and Y has been already canonicalized.
1293 We use the data in reg_known_value above to see if two registers with
1294 different numbers are, in fact, equivalent. */
1297 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1304 if (x
== 0 && y
== 0)
1306 if (x
== 0 || y
== 0)
1312 code
= GET_CODE (x
);
1313 /* Rtx's of different codes cannot be equal. */
1314 if (code
!= GET_CODE (y
))
1317 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1318 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1320 if (GET_MODE (x
) != GET_MODE (y
))
1323 /* Some RTL can be compared without a recursive examination. */
1327 return REGNO (x
) == REGNO (y
);
1330 return XEXP (x
, 0) == XEXP (y
, 0);
1333 return XSTR (x
, 0) == XSTR (y
, 0);
1339 /* There's no need to compare the contents of CONST_DOUBLEs or
1340 CONST_INTs because pointer equality is a good enough
1341 comparison for these nodes. */
1348 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1350 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1351 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1352 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1353 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1354 /* For commutative operations, the RTX match if the operand match in any
1355 order. Also handle the simple binary and unary cases without a loop. */
1356 if (COMMUTATIVE_P (x
))
1358 rtx xop0
= canon_rtx (XEXP (x
, 0));
1359 rtx yop0
= canon_rtx (XEXP (y
, 0));
1360 rtx yop1
= canon_rtx (XEXP (y
, 1));
1362 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1363 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1364 || (rtx_equal_for_memref_p (xop0
, yop1
)
1365 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1367 else if (NON_COMMUTATIVE_P (x
))
1369 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1370 canon_rtx (XEXP (y
, 0)))
1371 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1372 canon_rtx (XEXP (y
, 1))));
1374 else if (UNARY_P (x
))
1375 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1376 canon_rtx (XEXP (y
, 0)));
1378 /* Compare the elements. If any pair of corresponding elements
1379 fail to match, return 0 for the whole things.
1381 Limit cases to types which actually appear in addresses. */
1383 fmt
= GET_RTX_FORMAT (code
);
1384 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1389 if (XINT (x
, i
) != XINT (y
, i
))
1394 /* Two vectors must have the same length. */
1395 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1398 /* And the corresponding elements must match. */
1399 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1400 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1401 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1406 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1407 canon_rtx (XEXP (y
, i
))) == 0)
1411 /* This can happen for asm operands. */
1413 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1417 /* This can happen for an asm which clobbers memory. */
1421 /* It is believed that rtx's at this level will never
1422 contain anything but integers and other rtx's,
1423 except for within LABEL_REFs and SYMBOL_REFs. */
1432 find_base_term (rtx x
)
1435 struct elt_loc_list
*l
;
1437 #if defined (FIND_BASE_TERM)
1438 /* Try machine-dependent ways to find the base term. */
1439 x
= FIND_BASE_TERM (x
);
1442 switch (GET_CODE (x
))
1445 return REG_BASE_VALUE (x
);
1448 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1458 return find_base_term (XEXP (x
, 0));
1461 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1463 rtx temp
= find_base_term (XEXP (x
, 0));
1465 if (temp
!= 0 && CONSTANT_P (temp
))
1466 temp
= convert_memory_address (Pmode
, temp
);
1472 val
= CSELIB_VAL_PTR (x
);
1475 for (l
= val
->locs
; l
; l
= l
->next
)
1476 if ((x
= find_base_term (l
->loc
)) != 0)
1481 /* The standard form is (lo_sum reg sym) so look only at the
1483 return find_base_term (XEXP (x
, 1));
1487 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1493 rtx tmp1
= XEXP (x
, 0);
1494 rtx tmp2
= XEXP (x
, 1);
1496 /* This is a little bit tricky since we have to determine which of
1497 the two operands represents the real base address. Otherwise this
1498 routine may return the index register instead of the base register.
1500 That may cause us to believe no aliasing was possible, when in
1501 fact aliasing is possible.
1503 We use a few simple tests to guess the base register. Additional
1504 tests can certainly be added. For example, if one of the operands
1505 is a shift or multiply, then it must be the index register and the
1506 other operand is the base register. */
1508 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1509 return find_base_term (tmp2
);
1511 /* If either operand is known to be a pointer, then use it
1512 to determine the base term. */
1513 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1514 return find_base_term (tmp1
);
1516 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1517 return find_base_term (tmp2
);
1519 /* Neither operand was known to be a pointer. Go ahead and find the
1520 base term for both operands. */
1521 tmp1
= find_base_term (tmp1
);
1522 tmp2
= find_base_term (tmp2
);
1524 /* If either base term is named object or a special address
1525 (like an argument or stack reference), then use it for the
1528 && (GET_CODE (tmp1
) == SYMBOL_REF
1529 || GET_CODE (tmp1
) == LABEL_REF
1530 || (GET_CODE (tmp1
) == ADDRESS
1531 && GET_MODE (tmp1
) != VOIDmode
)))
1535 && (GET_CODE (tmp2
) == SYMBOL_REF
1536 || GET_CODE (tmp2
) == LABEL_REF
1537 || (GET_CODE (tmp2
) == ADDRESS
1538 && GET_MODE (tmp2
) != VOIDmode
)))
1541 /* We could not determine which of the two operands was the
1542 base register and which was the index. So we can determine
1543 nothing from the base alias check. */
1548 if (GET_CODE (XEXP (x
, 1)) == CONST_INT
&& INTVAL (XEXP (x
, 1)) != 0)
1549 return find_base_term (XEXP (x
, 0));
1561 /* Return 0 if the addresses X and Y are known to point to different
1562 objects, 1 if they might be pointers to the same object. */
1565 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1566 enum machine_mode y_mode
)
1568 rtx x_base
= find_base_term (x
);
1569 rtx y_base
= find_base_term (y
);
1571 /* If the address itself has no known base see if a known equivalent
1572 value has one. If either address still has no known base, nothing
1573 is known about aliasing. */
1578 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1581 x_base
= find_base_term (x_c
);
1589 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1592 y_base
= find_base_term (y_c
);
1597 /* If the base addresses are equal nothing is known about aliasing. */
1598 if (rtx_equal_p (x_base
, y_base
))
1601 /* The base addresses are different expressions. If they are not accessed
1602 via AND, there is no conflict. We can bring knowledge of object
1603 alignment into play here. For example, on alpha, "char a, b;" can
1604 alias one another, though "char a; long b;" cannot. AND addesses may
1605 implicitly alias surrounding objects; i.e. unaligned access in DImode
1606 via AND address can alias all surrounding object types except those
1607 with aligment 8 or higher. */
1608 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1610 if (GET_CODE (x
) == AND
1611 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1612 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1614 if (GET_CODE (y
) == AND
1615 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1616 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1619 /* Differing symbols not accessed via AND never alias. */
1620 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1623 /* If one address is a stack reference there can be no alias:
1624 stack references using different base registers do not alias,
1625 a stack reference can not alias a parameter, and a stack reference
1626 can not alias a global. */
1627 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1628 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1631 if (! flag_argument_noalias
)
1634 if (flag_argument_noalias
> 1)
1637 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1638 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1641 /* Convert the address X into something we can use. This is done by returning
1642 it unchanged unless it is a value; in the latter case we call cselib to get
1643 a more useful rtx. */
1649 struct elt_loc_list
*l
;
1651 if (GET_CODE (x
) != VALUE
)
1653 v
= CSELIB_VAL_PTR (x
);
1656 for (l
= v
->locs
; l
; l
= l
->next
)
1657 if (CONSTANT_P (l
->loc
))
1659 for (l
= v
->locs
; l
; l
= l
->next
)
1660 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
))
1663 return v
->locs
->loc
;
1668 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1669 where SIZE is the size in bytes of the memory reference. If ADDR
1670 is not modified by the memory reference then ADDR is returned. */
1673 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1677 switch (GET_CODE (addr
))
1680 offset
= (n_refs
+ 1) * size
;
1683 offset
= -(n_refs
+ 1) * size
;
1686 offset
= n_refs
* size
;
1689 offset
= -n_refs
* size
;
1697 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1700 addr
= XEXP (addr
, 0);
1701 addr
= canon_rtx (addr
);
1706 /* Return nonzero if X and Y (memory addresses) could reference the
1707 same location in memory. C is an offset accumulator. When
1708 C is nonzero, we are testing aliases between X and Y + C.
1709 XSIZE is the size in bytes of the X reference,
1710 similarly YSIZE is the size in bytes for Y.
1711 Expect that canon_rtx has been already called for X and Y.
1713 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1714 referenced (the reference was BLKmode), so make the most pessimistic
1717 If XSIZE or YSIZE is negative, we may access memory outside the object
1718 being referenced as a side effect. This can happen when using AND to
1719 align memory references, as is done on the Alpha.
1721 Nice to notice that varying addresses cannot conflict with fp if no
1722 local variables had their addresses taken, but that's too hard now. */
1725 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1727 if (GET_CODE (x
) == VALUE
)
1729 if (GET_CODE (y
) == VALUE
)
1731 if (GET_CODE (x
) == HIGH
)
1733 else if (GET_CODE (x
) == LO_SUM
)
1736 x
= addr_side_effect_eval (x
, xsize
, 0);
1737 if (GET_CODE (y
) == HIGH
)
1739 else if (GET_CODE (y
) == LO_SUM
)
1742 y
= addr_side_effect_eval (y
, ysize
, 0);
1744 if (rtx_equal_for_memref_p (x
, y
))
1746 if (xsize
<= 0 || ysize
<= 0)
1748 if (c
>= 0 && xsize
> c
)
1750 if (c
< 0 && ysize
+c
> 0)
1755 /* This code used to check for conflicts involving stack references and
1756 globals but the base address alias code now handles these cases. */
1758 if (GET_CODE (x
) == PLUS
)
1760 /* The fact that X is canonicalized means that this
1761 PLUS rtx is canonicalized. */
1762 rtx x0
= XEXP (x
, 0);
1763 rtx x1
= XEXP (x
, 1);
1765 if (GET_CODE (y
) == PLUS
)
1767 /* The fact that Y is canonicalized means that this
1768 PLUS rtx is canonicalized. */
1769 rtx y0
= XEXP (y
, 0);
1770 rtx y1
= XEXP (y
, 1);
1772 if (rtx_equal_for_memref_p (x1
, y1
))
1773 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1774 if (rtx_equal_for_memref_p (x0
, y0
))
1775 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1776 if (GET_CODE (x1
) == CONST_INT
)
1778 if (GET_CODE (y1
) == CONST_INT
)
1779 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1780 c
- INTVAL (x1
) + INTVAL (y1
));
1782 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1785 else if (GET_CODE (y1
) == CONST_INT
)
1786 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1790 else if (GET_CODE (x1
) == CONST_INT
)
1791 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1793 else if (GET_CODE (y
) == PLUS
)
1795 /* The fact that Y is canonicalized means that this
1796 PLUS rtx is canonicalized. */
1797 rtx y0
= XEXP (y
, 0);
1798 rtx y1
= XEXP (y
, 1);
1800 if (GET_CODE (y1
) == CONST_INT
)
1801 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1806 if (GET_CODE (x
) == GET_CODE (y
))
1807 switch (GET_CODE (x
))
1811 /* Handle cases where we expect the second operands to be the
1812 same, and check only whether the first operand would conflict
1815 rtx x1
= canon_rtx (XEXP (x
, 1));
1816 rtx y1
= canon_rtx (XEXP (y
, 1));
1817 if (! rtx_equal_for_memref_p (x1
, y1
))
1819 x0
= canon_rtx (XEXP (x
, 0));
1820 y0
= canon_rtx (XEXP (y
, 0));
1821 if (rtx_equal_for_memref_p (x0
, y0
))
1822 return (xsize
== 0 || ysize
== 0
1823 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1825 /* Can't properly adjust our sizes. */
1826 if (GET_CODE (x1
) != CONST_INT
)
1828 xsize
/= INTVAL (x1
);
1829 ysize
/= INTVAL (x1
);
1831 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1838 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1839 as an access with indeterminate size. Assume that references
1840 besides AND are aligned, so if the size of the other reference is
1841 at least as large as the alignment, assume no other overlap. */
1842 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1844 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1846 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
1848 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1850 /* ??? If we are indexing far enough into the array/structure, we
1851 may yet be able to determine that we can not overlap. But we
1852 also need to that we are far enough from the end not to overlap
1853 a following reference, so we do nothing with that for now. */
1854 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1856 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
1861 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1863 c
+= (INTVAL (y
) - INTVAL (x
));
1864 return (xsize
<= 0 || ysize
<= 0
1865 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1868 if (GET_CODE (x
) == CONST
)
1870 if (GET_CODE (y
) == CONST
)
1871 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1872 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1874 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1877 if (GET_CODE (y
) == CONST
)
1878 return memrefs_conflict_p (xsize
, x
, ysize
,
1879 canon_rtx (XEXP (y
, 0)), c
);
1882 return (xsize
<= 0 || ysize
<= 0
1883 || (rtx_equal_for_memref_p (x
, y
)
1884 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1891 /* Functions to compute memory dependencies.
1893 Since we process the insns in execution order, we can build tables
1894 to keep track of what registers are fixed (and not aliased), what registers
1895 are varying in known ways, and what registers are varying in unknown
1898 If both memory references are volatile, then there must always be a
1899 dependence between the two references, since their order can not be
1900 changed. A volatile and non-volatile reference can be interchanged
1903 A MEM_IN_STRUCT reference at a non-AND varying address can never
1904 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1905 also must allow AND addresses, because they may generate accesses
1906 outside the object being referenced. This is used to generate
1907 aligned addresses from unaligned addresses, for instance, the alpha
1908 storeqi_unaligned pattern. */
1910 /* Read dependence: X is read after read in MEM takes place. There can
1911 only be a dependence here if both reads are volatile. */
1914 read_dependence (const_rtx mem
, const_rtx x
)
1916 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1919 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1920 MEM2 is a reference to a structure at a varying address, or returns
1921 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1922 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1923 to decide whether or not an address may vary; it should return
1924 nonzero whenever variation is possible.
1925 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1928 fixed_scalar_and_varying_struct_p (const_rtx mem1
, const_rtx mem2
, rtx mem1_addr
,
1930 bool (*varies_p
) (const_rtx
, bool))
1932 if (! flag_strict_aliasing
)
1935 if (MEM_ALIAS_SET (mem2
)
1936 && MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1937 && !varies_p (mem1_addr
, 1) && varies_p (mem2_addr
, 1))
1938 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1942 if (MEM_ALIAS_SET (mem1
)
1943 && MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1944 && varies_p (mem1_addr
, 1) && !varies_p (mem2_addr
, 1))
1945 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1952 /* Returns nonzero if something about the mode or address format MEM1
1953 indicates that it might well alias *anything*. */
1956 aliases_everything_p (const_rtx mem
)
1958 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1959 /* If the address is an AND, it's very hard to know at what it is
1960 actually pointing. */
1966 /* Return true if we can determine that the fields referenced cannot
1967 overlap for any pair of objects. */
1970 nonoverlapping_component_refs_p (const_tree x
, const_tree y
)
1972 const_tree fieldx
, fieldy
, typex
, typey
, orig_y
;
1976 /* The comparison has to be done at a common type, since we don't
1977 know how the inheritance hierarchy works. */
1981 fieldx
= TREE_OPERAND (x
, 1);
1982 typex
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx
));
1987 fieldy
= TREE_OPERAND (y
, 1);
1988 typey
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy
));
1993 y
= TREE_OPERAND (y
, 0);
1995 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
1997 x
= TREE_OPERAND (x
, 0);
1999 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2000 /* Never found a common type. */
2004 /* If we're left with accessing different fields of a structure,
2006 if (TREE_CODE (typex
) == RECORD_TYPE
2007 && fieldx
!= fieldy
)
2010 /* The comparison on the current field failed. If we're accessing
2011 a very nested structure, look at the next outer level. */
2012 x
= TREE_OPERAND (x
, 0);
2013 y
= TREE_OPERAND (y
, 0);
2016 && TREE_CODE (x
) == COMPONENT_REF
2017 && TREE_CODE (y
) == COMPONENT_REF
);
2022 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2025 decl_for_component_ref (tree x
)
2029 x
= TREE_OPERAND (x
, 0);
2031 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2033 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
2036 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
2037 offset of the field reference. */
2040 adjust_offset_for_component_ref (tree x
, rtx offset
)
2042 HOST_WIDE_INT ioffset
;
2047 ioffset
= INTVAL (offset
);
2050 tree offset
= component_ref_field_offset (x
);
2051 tree field
= TREE_OPERAND (x
, 1);
2053 if (! host_integerp (offset
, 1))
2055 ioffset
+= (tree_low_cst (offset
, 1)
2056 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
2059 x
= TREE_OPERAND (x
, 0);
2061 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2063 return GEN_INT (ioffset
);
2066 /* Return nonzero if we can determine the exprs corresponding to memrefs
2067 X and Y and they do not overlap. */
2070 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
)
2072 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
2075 rtx moffsetx
, moffsety
;
2076 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
2078 /* Unless both have exprs, we can't tell anything. */
2079 if (exprx
== 0 || expry
== 0)
2082 /* If both are field references, we may be able to determine something. */
2083 if (TREE_CODE (exprx
) == COMPONENT_REF
2084 && TREE_CODE (expry
) == COMPONENT_REF
2085 && nonoverlapping_component_refs_p (exprx
, expry
))
2089 /* If the field reference test failed, look at the DECLs involved. */
2090 moffsetx
= MEM_OFFSET (x
);
2091 if (TREE_CODE (exprx
) == COMPONENT_REF
)
2093 if (TREE_CODE (expry
) == VAR_DECL
2094 && POINTER_TYPE_P (TREE_TYPE (expry
)))
2096 tree field
= TREE_OPERAND (exprx
, 1);
2097 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2098 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2103 tree t
= decl_for_component_ref (exprx
);
2106 moffsetx
= adjust_offset_for_component_ref (exprx
, moffsetx
);
2110 else if (INDIRECT_REF_P (exprx
))
2112 exprx
= TREE_OPERAND (exprx
, 0);
2113 if (flag_argument_noalias
< 2
2114 || TREE_CODE (exprx
) != PARM_DECL
)
2118 moffsety
= MEM_OFFSET (y
);
2119 if (TREE_CODE (expry
) == COMPONENT_REF
)
2121 if (TREE_CODE (exprx
) == VAR_DECL
2122 && POINTER_TYPE_P (TREE_TYPE (exprx
)))
2124 tree field
= TREE_OPERAND (expry
, 1);
2125 tree fieldcontext
= DECL_FIELD_CONTEXT (field
);
2126 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext
,
2131 tree t
= decl_for_component_ref (expry
);
2134 moffsety
= adjust_offset_for_component_ref (expry
, moffsety
);
2138 else if (INDIRECT_REF_P (expry
))
2140 expry
= TREE_OPERAND (expry
, 0);
2141 if (flag_argument_noalias
< 2
2142 || TREE_CODE (expry
) != PARM_DECL
)
2146 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2149 rtlx
= DECL_RTL (exprx
);
2150 rtly
= DECL_RTL (expry
);
2152 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2153 can't overlap unless they are the same because we never reuse that part
2154 of the stack frame used for locals for spilled pseudos. */
2155 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2156 && ! rtx_equal_p (rtlx
, rtly
))
2159 /* Get the base and offsets of both decls. If either is a register, we
2160 know both are and are the same, so use that as the base. The only
2161 we can avoid overlap is if we can deduce that they are nonoverlapping
2162 pieces of that decl, which is very rare. */
2163 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2164 if (GET_CODE (basex
) == PLUS
&& GET_CODE (XEXP (basex
, 1)) == CONST_INT
)
2165 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2167 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2168 if (GET_CODE (basey
) == PLUS
&& GET_CODE (XEXP (basey
, 1)) == CONST_INT
)
2169 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2171 /* If the bases are different, we know they do not overlap if both
2172 are constants or if one is a constant and the other a pointer into the
2173 stack frame. Otherwise a different base means we can't tell if they
2175 if (! rtx_equal_p (basex
, basey
))
2176 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2177 || (CONSTANT_P (basex
) && REG_P (basey
)
2178 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2179 || (CONSTANT_P (basey
) && REG_P (basex
)
2180 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2182 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2183 : MEM_SIZE (rtlx
) ? INTVAL (MEM_SIZE (rtlx
))
2185 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2186 : MEM_SIZE (rtly
) ? INTVAL (MEM_SIZE (rtly
)) :
2189 /* If we have an offset for either memref, it can update the values computed
2192 offsetx
+= INTVAL (moffsetx
), sizex
-= INTVAL (moffsetx
);
2194 offsety
+= INTVAL (moffsety
), sizey
-= INTVAL (moffsety
);
2196 /* If a memref has both a size and an offset, we can use the smaller size.
2197 We can't do this if the offset isn't known because we must view this
2198 memref as being anywhere inside the DECL's MEM. */
2199 if (MEM_SIZE (x
) && moffsetx
)
2200 sizex
= INTVAL (MEM_SIZE (x
));
2201 if (MEM_SIZE (y
) && moffsety
)
2202 sizey
= INTVAL (MEM_SIZE (y
));
2204 /* Put the values of the memref with the lower offset in X's values. */
2205 if (offsetx
> offsety
)
2207 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2208 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2211 /* If we don't know the size of the lower-offset value, we can't tell
2212 if they conflict. Otherwise, we do the test. */
2213 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2216 /* True dependence: X is read after store in MEM takes place. */
2219 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
,
2220 bool (*varies
) (const_rtx
, bool))
2222 rtx x_addr
, mem_addr
;
2225 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2228 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2229 This is used in epilogue deallocation functions, and in cselib. */
2230 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2232 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2234 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2235 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2238 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2241 /* Read-only memory is by definition never modified, and therefore can't
2242 conflict with anything. We don't expect to find read-only set on MEM,
2243 but stupid user tricks can produce them, so don't die. */
2244 if (MEM_READONLY_P (x
))
2247 if (nonoverlapping_memrefs_p (mem
, x
))
2250 if (mem_mode
== VOIDmode
)
2251 mem_mode
= GET_MODE (mem
);
2253 x_addr
= get_addr (XEXP (x
, 0));
2254 mem_addr
= get_addr (XEXP (mem
, 0));
2256 base
= find_base_term (x_addr
);
2257 if (base
&& (GET_CODE (base
) == LABEL_REF
2258 || (GET_CODE (base
) == SYMBOL_REF
2259 && CONSTANT_POOL_ADDRESS_P (base
))))
2262 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2265 x_addr
= canon_rtx (x_addr
);
2266 mem_addr
= canon_rtx (mem_addr
);
2268 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2269 SIZE_FOR_MODE (x
), x_addr
, 0))
2272 if (aliases_everything_p (x
))
2275 /* We cannot use aliases_everything_p to test MEM, since we must look
2276 at MEM_MODE, rather than GET_MODE (MEM). */
2277 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2280 /* In true_dependence we also allow BLKmode to alias anything. Why
2281 don't we do this in anti_dependence and output_dependence? */
2282 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2285 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2289 /* Canonical true dependence: X is read after store in MEM takes place.
2290 Variant of true_dependence which assumes MEM has already been
2291 canonicalized (hence we no longer do that here).
2292 The mem_addr argument has been added, since true_dependence computed
2293 this value prior to canonicalizing.
2294 If x_addr is non-NULL, it is used in preference of XEXP (x, 0). */
2297 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2298 const_rtx x
, rtx x_addr
, bool (*varies
) (const_rtx
, bool))
2300 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2303 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2304 This is used in epilogue deallocation functions. */
2305 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2307 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2309 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2310 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2313 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2316 /* Read-only memory is by definition never modified, and therefore can't
2317 conflict with anything. We don't expect to find read-only set on MEM,
2318 but stupid user tricks can produce them, so don't die. */
2319 if (MEM_READONLY_P (x
))
2322 if (nonoverlapping_memrefs_p (x
, mem
))
2326 x_addr
= get_addr (XEXP (x
, 0));
2328 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2331 x_addr
= canon_rtx (x_addr
);
2332 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2333 SIZE_FOR_MODE (x
), x_addr
, 0))
2336 if (aliases_everything_p (x
))
2339 /* We cannot use aliases_everything_p to test MEM, since we must look
2340 at MEM_MODE, rather than GET_MODE (MEM). */
2341 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2344 /* In true_dependence we also allow BLKmode to alias anything. Why
2345 don't we do this in anti_dependence and output_dependence? */
2346 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2349 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2353 /* Returns nonzero if a write to X might alias a previous read from
2354 (or, if WRITEP is nonzero, a write to) MEM. */
2357 write_dependence_p (const_rtx mem
, const_rtx x
, int writep
)
2359 rtx x_addr
, mem_addr
;
2360 const_rtx fixed_scalar
;
2363 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2366 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2367 This is used in epilogue deallocation functions. */
2368 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2370 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2372 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2373 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2376 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2379 /* A read from read-only memory can't conflict with read-write memory. */
2380 if (!writep
&& MEM_READONLY_P (mem
))
2383 if (nonoverlapping_memrefs_p (x
, mem
))
2386 x_addr
= get_addr (XEXP (x
, 0));
2387 mem_addr
= get_addr (XEXP (mem
, 0));
2391 base
= find_base_term (mem_addr
);
2392 if (base
&& (GET_CODE (base
) == LABEL_REF
2393 || (GET_CODE (base
) == SYMBOL_REF
2394 && CONSTANT_POOL_ADDRESS_P (base
))))
2398 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2402 x_addr
= canon_rtx (x_addr
);
2403 mem_addr
= canon_rtx (mem_addr
);
2405 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2406 SIZE_FOR_MODE (x
), x_addr
, 0))
2410 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2413 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2414 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2417 /* Anti dependence: X is written after read in MEM takes place. */
2420 anti_dependence (const_rtx mem
, const_rtx x
)
2422 return write_dependence_p (mem
, x
, /*writep=*/0);
2425 /* Output dependence: X is written after store in MEM takes place. */
2428 output_dependence (const_rtx mem
, const_rtx x
)
2430 return write_dependence_p (mem
, x
, /*writep=*/1);
2435 init_alias_target (void)
2439 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2441 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2442 /* Check whether this register can hold an incoming pointer
2443 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2444 numbers, so translate if necessary due to register windows. */
2445 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2446 && HARD_REGNO_MODE_OK (i
, Pmode
))
2447 static_reg_base_value
[i
]
2448 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2450 static_reg_base_value
[STACK_POINTER_REGNUM
]
2451 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2452 static_reg_base_value
[ARG_POINTER_REGNUM
]
2453 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2454 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2455 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2456 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2457 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2458 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2462 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2463 to be memory reference. */
2464 static bool memory_modified
;
2466 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2470 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2471 memory_modified
= true;
2476 /* Return true when INSN possibly modify memory contents of MEM
2477 (i.e. address can be modified). */
2479 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2483 memory_modified
= false;
2484 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2485 return memory_modified
;
2488 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2492 init_alias_analysis (void)
2494 unsigned int maxreg
= max_reg_num ();
2500 timevar_push (TV_ALIAS_ANALYSIS
);
2502 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2503 reg_known_value
= GGC_CNEWVEC (rtx
, reg_known_value_size
);
2504 reg_known_equiv_p
= XCNEWVEC (bool, reg_known_value_size
);
2506 /* If we have memory allocated from the previous run, use it. */
2507 if (old_reg_base_value
)
2508 reg_base_value
= old_reg_base_value
;
2511 VEC_truncate (rtx
, reg_base_value
, 0);
2513 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2515 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2516 reg_seen
= XNEWVEC (char, maxreg
);
2518 /* The basic idea is that each pass through this loop will use the
2519 "constant" information from the previous pass to propagate alias
2520 information through another level of assignments.
2522 This could get expensive if the assignment chains are long. Maybe
2523 we should throttle the number of iterations, possibly based on
2524 the optimization level or flag_expensive_optimizations.
2526 We could propagate more information in the first pass by making use
2527 of DF_REG_DEF_COUNT to determine immediately that the alias information
2528 for a pseudo is "constant".
2530 A program with an uninitialized variable can cause an infinite loop
2531 here. Instead of doing a full dataflow analysis to detect such problems
2532 we just cap the number of iterations for the loop.
2534 The state of the arrays for the set chain in question does not matter
2535 since the program has undefined behavior. */
2540 /* Assume nothing will change this iteration of the loop. */
2543 /* We want to assign the same IDs each iteration of this loop, so
2544 start counting from zero each iteration of the loop. */
2547 /* We're at the start of the function each iteration through the
2548 loop, so we're copying arguments. */
2549 copying_arguments
= true;
2551 /* Wipe the potential alias information clean for this pass. */
2552 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2554 /* Wipe the reg_seen array clean. */
2555 memset (reg_seen
, 0, maxreg
);
2557 /* Mark all hard registers which may contain an address.
2558 The stack, frame and argument pointers may contain an address.
2559 An argument register which can hold a Pmode value may contain
2560 an address even if it is not in BASE_REGS.
2562 The address expression is VOIDmode for an argument and
2563 Pmode for other registers. */
2565 memcpy (new_reg_base_value
, static_reg_base_value
,
2566 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2568 /* Walk the insns adding values to the new_reg_base_value array. */
2569 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2575 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2576 /* The prologue/epilogue insns are not threaded onto the
2577 insn chain until after reload has completed. Thus,
2578 there is no sense wasting time checking if INSN is in
2579 the prologue/epilogue until after reload has completed. */
2580 if (reload_completed
2581 && prologue_epilogue_contains (insn
))
2585 /* If this insn has a noalias note, process it, Otherwise,
2586 scan for sets. A simple set will have no side effects
2587 which could change the base value of any other register. */
2589 if (GET_CODE (PATTERN (insn
)) == SET
2590 && REG_NOTES (insn
) != 0
2591 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2592 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2594 note_stores (PATTERN (insn
), record_set
, NULL
);
2596 set
= single_set (insn
);
2599 && REG_P (SET_DEST (set
))
2600 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2602 unsigned int regno
= REGNO (SET_DEST (set
));
2603 rtx src
= SET_SRC (set
);
2606 note
= find_reg_equal_equiv_note (insn
);
2607 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2608 && DF_REG_DEF_COUNT (regno
) != 1)
2611 if (note
!= NULL_RTX
2612 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2613 && ! rtx_varies_p (XEXP (note
, 0), 1)
2614 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2617 set_reg_known_value (regno
, XEXP (note
, 0));
2618 set_reg_known_equiv_p (regno
,
2619 REG_NOTE_KIND (note
) == REG_EQUIV
);
2621 else if (DF_REG_DEF_COUNT (regno
) == 1
2622 && GET_CODE (src
) == PLUS
2623 && REG_P (XEXP (src
, 0))
2624 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2625 && GET_CODE (XEXP (src
, 1)) == CONST_INT
)
2627 t
= plus_constant (t
, INTVAL (XEXP (src
, 1)));
2628 set_reg_known_value (regno
, t
);
2629 set_reg_known_equiv_p (regno
, 0);
2631 else if (DF_REG_DEF_COUNT (regno
) == 1
2632 && ! rtx_varies_p (src
, 1))
2634 set_reg_known_value (regno
, src
);
2635 set_reg_known_equiv_p (regno
, 0);
2639 else if (NOTE_P (insn
)
2640 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2641 copying_arguments
= false;
2644 /* Now propagate values from new_reg_base_value to reg_base_value. */
2645 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2647 for (ui
= 0; ui
< maxreg
; ui
++)
2649 if (new_reg_base_value
[ui
]
2650 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2651 && ! rtx_equal_p (new_reg_base_value
[ui
],
2652 VEC_index (rtx
, reg_base_value
, ui
)))
2654 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2659 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2661 /* Fill in the remaining entries. */
2662 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2663 if (reg_known_value
[i
] == 0)
2664 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2667 free (new_reg_base_value
);
2668 new_reg_base_value
= 0;
2671 timevar_pop (TV_ALIAS_ANALYSIS
);
2675 end_alias_analysis (void)
2677 old_reg_base_value
= reg_base_value
;
2678 ggc_free (reg_known_value
);
2679 reg_known_value
= 0;
2680 reg_known_value_size
= 0;
2681 free (reg_known_equiv_p
);
2682 reg_known_equiv_p
= 0;
2685 #include "gt-alias.h"