1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
46 #include "tree-pass.h"
47 #include "ipa-type-escape.h"
50 /* The aliasing API provided here solves related but different problems:
52 Say there exists (in c)
66 Consider the four questions:
68 Can a store to x1 interfere with px2->y1?
69 Can a store to x1 interfere with px2->z2?
71 Can a store to x1 change the value pointed to by with py?
72 Can a store to x1 change the value pointed to by with pz?
74 The answer to these questions can be yes, yes, yes, and maybe.
76 The first two questions can be answered with a simple examination
77 of the type system. If structure X contains a field of type Y then
78 a store thru a pointer to an X can overwrite any field that is
79 contained (recursively) in an X (unless we know that px1 != px2).
81 The last two of the questions can be solved in the same way as the
82 first two questions but this is too conservative. The observation
83 is that in some cases analysis we can know if which (if any) fields
84 are addressed and if those addresses are used in bad ways. This
85 analysis may be language specific. In C, arbitrary operations may
86 be applied to pointers. However, there is some indication that
87 this may be too conservative for some C++ types.
89 The pass ipa-type-escape does this analysis for the types whose
90 instances do not escape across the compilation boundary.
92 Historically in GCC, these two problems were combined and a single
93 data structure was used to represent the solution to these
94 problems. We now have two similar but different data structures,
95 The data structure to solve the last two question is similar to the
96 first, but does not contain have the fields in it whose address are
97 never taken. For types that do escape the compilation unit, the
98 data structures will have identical information.
101 /* The alias sets assigned to MEMs assist the back-end in determining
102 which MEMs can alias which other MEMs. In general, two MEMs in
103 different alias sets cannot alias each other, with one important
104 exception. Consider something like:
106 struct S { int i; double d; };
108 a store to an `S' can alias something of either type `int' or type
109 `double'. (However, a store to an `int' cannot alias a `double'
110 and vice versa.) We indicate this via a tree structure that looks
118 (The arrows are directed and point downwards.)
119 In this situation we say the alias set for `struct S' is the
120 `superset' and that those for `int' and `double' are `subsets'.
122 To see whether two alias sets can point to the same memory, we must
123 see if either alias set is a subset of the other. We need not trace
124 past immediate descendants, however, since we propagate all
125 grandchildren up one level.
127 Alias set zero is implicitly a superset of all other alias sets.
128 However, this is no actual entry for alias set zero. It is an
129 error to attempt to explicitly construct a subset of zero. */
131 struct alias_set_entry
GTY(())
133 /* The alias set number, as stored in MEM_ALIAS_SET. */
134 alias_set_type alias_set
;
136 /* Nonzero if would have a child of zero: this effectively makes this
137 alias set the same as alias set zero. */
140 /* The children of the alias set. These are not just the immediate
141 children, but, in fact, all descendants. So, if we have:
143 struct T { struct S s; float f; }
145 continuing our example above, the children here will be all of
146 `int', `double', `float', and `struct S'. */
147 splay_tree
GTY((param1_is (int), param2_is (int))) children
;
149 typedef struct alias_set_entry
*alias_set_entry
;
151 static int rtx_equal_for_memref_p (const_rtx
, const_rtx
);
152 static int memrefs_conflict_p (int, rtx
, int, rtx
, HOST_WIDE_INT
);
153 static void record_set (rtx
, const_rtx
, void *);
154 static int base_alias_check (rtx
, rtx
, enum machine_mode
,
156 static rtx
find_base_value (rtx
);
157 static int mems_in_disjoint_alias_sets_p (const_rtx
, const_rtx
);
158 static int insert_subset_children (splay_tree_node
, void*);
159 static tree
find_base_decl (tree
);
160 static alias_set_entry
get_alias_set_entry (alias_set_type
);
161 static const_rtx
fixed_scalar_and_varying_struct_p (const_rtx
, const_rtx
, rtx
, rtx
,
162 bool (*) (const_rtx
, bool));
163 static int aliases_everything_p (const_rtx
);
164 static bool nonoverlapping_component_refs_p (const_tree
, const_tree
);
165 static tree
decl_for_component_ref (tree
);
166 static rtx
adjust_offset_for_component_ref (tree
, rtx
);
167 static int write_dependence_p (const_rtx
, const_rtx
, int);
169 static void memory_modified_1 (rtx
, const_rtx
, void *);
170 static void record_alias_subset (alias_set_type
, alias_set_type
);
172 /* Set up all info needed to perform alias analysis on memory references. */
174 /* Returns the size in bytes of the mode of X. */
175 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
177 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
178 different alias sets. We ignore alias sets in functions making use
179 of variable arguments because the va_arg macros on some systems are
181 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
182 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
184 /* Cap the number of passes we make over the insns propagating alias
185 information through set chains. 10 is a completely arbitrary choice. */
186 #define MAX_ALIAS_LOOP_PASSES 10
188 /* reg_base_value[N] gives an address to which register N is related.
189 If all sets after the first add or subtract to the current value
190 or otherwise modify it so it does not point to a different top level
191 object, reg_base_value[N] is equal to the address part of the source
194 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
195 expressions represent certain special values: function arguments and
196 the stack, frame, and argument pointers.
198 The contents of an ADDRESS is not normally used, the mode of the
199 ADDRESS determines whether the ADDRESS is a function argument or some
200 other special value. Pointer equality, not rtx_equal_p, determines whether
201 two ADDRESS expressions refer to the same base address.
203 The only use of the contents of an ADDRESS is for determining if the
204 current function performs nonlocal memory memory references for the
205 purposes of marking the function as a constant function. */
207 static GTY(()) VEC(rtx
,gc
) *reg_base_value
;
208 static rtx
*new_reg_base_value
;
210 /* We preserve the copy of old array around to avoid amount of garbage
211 produced. About 8% of garbage produced were attributed to this
213 static GTY((deletable
)) VEC(rtx
,gc
) *old_reg_base_value
;
215 /* Static hunks of RTL used by the aliasing code; these are initialized
216 once per function to avoid unnecessary RTL allocations. */
217 static GTY (()) rtx static_reg_base_value
[FIRST_PSEUDO_REGISTER
];
219 #define REG_BASE_VALUE(X) \
220 (REGNO (X) < VEC_length (rtx, reg_base_value) \
221 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
223 /* Vector indexed by N giving the initial (unchanging) value known for
224 pseudo-register N. This array is initialized in init_alias_analysis,
225 and does not change until end_alias_analysis is called. */
226 static GTY((length("reg_known_value_size"))) rtx
*reg_known_value
;
228 /* Indicates number of valid entries in reg_known_value. */
229 static GTY(()) unsigned int reg_known_value_size
;
231 /* Vector recording for each reg_known_value whether it is due to a
232 REG_EQUIV note. Future passes (viz., reload) may replace the
233 pseudo with the equivalent expression and so we account for the
234 dependences that would be introduced if that happens.
236 The REG_EQUIV notes created in assign_parms may mention the arg
237 pointer, and there are explicit insns in the RTL that modify the
238 arg pointer. Thus we must ensure that such insns don't get
239 scheduled across each other because that would invalidate the
240 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
241 wrong, but solving the problem in the scheduler will likely give
242 better code, so we do it here. */
243 static bool *reg_known_equiv_p
;
245 /* True when scanning insns from the start of the rtl to the
246 NOTE_INSN_FUNCTION_BEG note. */
247 static bool copying_arguments
;
249 DEF_VEC_P(alias_set_entry
);
250 DEF_VEC_ALLOC_P(alias_set_entry
,gc
);
252 /* The splay-tree used to store the various alias set entries. */
253 static GTY (()) VEC(alias_set_entry
,gc
) *alias_sets
;
255 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
256 such an entry, or NULL otherwise. */
258 static inline alias_set_entry
259 get_alias_set_entry (alias_set_type alias_set
)
261 return VEC_index (alias_set_entry
, alias_sets
, alias_set
);
264 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
265 the two MEMs cannot alias each other. */
268 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
270 /* Perform a basic sanity check. Namely, that there are no alias sets
271 if we're not using strict aliasing. This helps to catch bugs
272 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
273 where a MEM is allocated in some way other than by the use of
274 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
275 use alias sets to indicate that spilled registers cannot alias each
276 other, we might need to remove this check. */
277 gcc_assert (flag_strict_aliasing
278 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
280 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
283 /* Insert the NODE into the splay tree given by DATA. Used by
284 record_alias_subset via splay_tree_foreach. */
287 insert_subset_children (splay_tree_node node
, void *data
)
289 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
294 /* Return true if the first alias set is a subset of the second. */
297 alias_set_subset_of (alias_set_type set1
, alias_set_type set2
)
301 /* Everything is a subset of the "aliases everything" set. */
305 /* Otherwise, check if set1 is a subset of set2. */
306 ase
= get_alias_set_entry (set2
);
308 && (splay_tree_lookup (ase
->children
,
309 (splay_tree_key
) set1
)))
314 /* Return 1 if the two specified alias sets may conflict. */
317 alias_sets_conflict_p (alias_set_type set1
, alias_set_type set2
)
322 if (alias_sets_must_conflict_p (set1
, set2
))
325 /* See if the first alias set is a subset of the second. */
326 ase
= get_alias_set_entry (set1
);
328 && (ase
->has_zero_child
329 || splay_tree_lookup (ase
->children
,
330 (splay_tree_key
) set2
)))
333 /* Now do the same, but with the alias sets reversed. */
334 ase
= get_alias_set_entry (set2
);
336 && (ase
->has_zero_child
337 || splay_tree_lookup (ase
->children
,
338 (splay_tree_key
) set1
)))
341 /* The two alias sets are distinct and neither one is the
342 child of the other. Therefore, they cannot conflict. */
346 /* Return 1 if the two specified alias sets will always conflict. */
349 alias_sets_must_conflict_p (alias_set_type set1
, alias_set_type set2
)
351 if (set1
== 0 || set2
== 0 || set1
== set2
)
357 /* Return 1 if any MEM object of type T1 will always conflict (using the
358 dependency routines in this file) with any MEM object of type T2.
359 This is used when allocating temporary storage. If T1 and/or T2 are
360 NULL_TREE, it means we know nothing about the storage. */
363 objects_must_conflict_p (tree t1
, tree t2
)
365 alias_set_type set1
, set2
;
367 /* If neither has a type specified, we don't know if they'll conflict
368 because we may be using them to store objects of various types, for
369 example the argument and local variables areas of inlined functions. */
370 if (t1
== 0 && t2
== 0)
373 /* If they are the same type, they must conflict. */
375 /* Likewise if both are volatile. */
376 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
379 set1
= t1
? get_alias_set (t1
) : 0;
380 set2
= t2
? get_alias_set (t2
) : 0;
382 /* We can't use alias_sets_conflict_p because we must make sure
383 that every subtype of t1 will conflict with every subtype of
384 t2 for which a pair of subobjects of these respective subtypes
385 overlaps on the stack. */
386 return alias_sets_must_conflict_p (set1
, set2
);
389 /* T is an expression with pointer type. Find the DECL on which this
390 expression is based. (For example, in `a[i]' this would be `a'.)
391 If there is no such DECL, or a unique decl cannot be determined,
392 NULL_TREE is returned. */
395 find_base_decl (tree t
)
399 if (t
== 0 || t
== error_mark_node
|| ! POINTER_TYPE_P (TREE_TYPE (t
)))
402 /* If this is a declaration, return it. If T is based on a restrict
403 qualified decl, return that decl. */
406 if (TREE_CODE (t
) == VAR_DECL
&& DECL_BASED_ON_RESTRICT_P (t
))
407 t
= DECL_GET_RESTRICT_BASE (t
);
411 /* Handle general expressions. It would be nice to deal with
412 COMPONENT_REFs here. If we could tell that `a' and `b' were the
413 same, then `a->f' and `b->f' are also the same. */
414 switch (TREE_CODE_CLASS (TREE_CODE (t
)))
417 return find_base_decl (TREE_OPERAND (t
, 0));
420 /* Return 0 if found in neither or both are the same. */
421 d0
= find_base_decl (TREE_OPERAND (t
, 0));
422 d1
= find_base_decl (TREE_OPERAND (t
, 1));
437 /* Return true if all nested component references handled by
438 get_inner_reference in T are such that we should use the alias set
439 provided by the object at the heart of T.
441 This is true for non-addressable components (which don't have their
442 own alias set), as well as components of objects in alias set zero.
443 This later point is a special case wherein we wish to override the
444 alias set used by the component, but we don't have per-FIELD_DECL
445 assignable alias sets. */
448 component_uses_parent_alias_set (const_tree t
)
452 /* If we're at the end, it vacuously uses its own alias set. */
453 if (!handled_component_p (t
))
456 switch (TREE_CODE (t
))
459 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1)))
464 case ARRAY_RANGE_REF
:
465 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0))))
474 /* Bitfields and casts are never addressable. */
478 t
= TREE_OPERAND (t
, 0);
479 if (get_alias_set (TREE_TYPE (t
)) == 0)
484 /* Return the alias set for T, which may be either a type or an
485 expression. Call language-specific routine for help, if needed. */
488 get_alias_set (tree t
)
492 /* If we're not doing any alias analysis, just assume everything
493 aliases everything else. Also return 0 if this or its type is
495 if (! flag_strict_aliasing
|| t
== error_mark_node
497 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
500 /* We can be passed either an expression or a type. This and the
501 language-specific routine may make mutually-recursive calls to each other
502 to figure out what to do. At each juncture, we see if this is a tree
503 that the language may need to handle specially. First handle things that
509 /* Remove any nops, then give the language a chance to do
510 something with this tree before we look at it. */
512 set
= lang_hooks
.get_alias_set (t
);
516 /* First see if the actual object referenced is an INDIRECT_REF from a
517 restrict-qualified pointer or a "void *". */
518 while (handled_component_p (inner
))
520 inner
= TREE_OPERAND (inner
, 0);
524 /* Check for accesses through restrict-qualified pointers. */
525 if (INDIRECT_REF_P (inner
))
529 if (TREE_CODE (TREE_OPERAND (inner
, 0)) == SSA_NAME
)
530 decl
= SSA_NAME_VAR (TREE_OPERAND (inner
, 0));
532 decl
= find_base_decl (TREE_OPERAND (inner
, 0));
534 if (decl
&& DECL_POINTER_ALIAS_SET_KNOWN_P (decl
))
536 /* If we haven't computed the actual alias set, do it now. */
537 if (DECL_POINTER_ALIAS_SET (decl
) == -2)
539 tree pointed_to_type
= TREE_TYPE (TREE_TYPE (decl
));
541 /* No two restricted pointers can point at the same thing.
542 However, a restricted pointer can point at the same thing
543 as an unrestricted pointer, if that unrestricted pointer
544 is based on the restricted pointer. So, we make the
545 alias set for the restricted pointer a subset of the
546 alias set for the type pointed to by the type of the
548 alias_set_type pointed_to_alias_set
549 = get_alias_set (pointed_to_type
);
551 if (pointed_to_alias_set
== 0)
552 /* It's not legal to make a subset of alias set zero. */
553 DECL_POINTER_ALIAS_SET (decl
) = 0;
554 else if (AGGREGATE_TYPE_P (pointed_to_type
))
555 /* For an aggregate, we must treat the restricted
556 pointer the same as an ordinary pointer. If we
557 were to make the type pointed to by the
558 restricted pointer a subset of the pointed-to
559 type, then we would believe that other subsets
560 of the pointed-to type (such as fields of that
561 type) do not conflict with the type pointed to
562 by the restricted pointer. */
563 DECL_POINTER_ALIAS_SET (decl
)
564 = pointed_to_alias_set
;
567 DECL_POINTER_ALIAS_SET (decl
) = new_alias_set ();
568 record_alias_subset (pointed_to_alias_set
,
569 DECL_POINTER_ALIAS_SET (decl
));
573 /* We use the alias set indicated in the declaration. */
574 return DECL_POINTER_ALIAS_SET (decl
);
577 /* If we have an INDIRECT_REF via a void pointer, we don't
578 know anything about what that might alias. Likewise if the
579 pointer is marked that way. */
580 else if (TREE_CODE (TREE_TYPE (inner
)) == VOID_TYPE
581 || (TYPE_REF_CAN_ALIAS_ALL
582 (TREE_TYPE (TREE_OPERAND (inner
, 0)))))
586 /* For non-addressable fields we return the alias set of the
587 outermost object that could have its address taken. If this
588 is an SFT use the precomputed value. */
589 if (TREE_CODE (t
) == STRUCT_FIELD_TAG
590 && SFT_NONADDRESSABLE_P (t
))
591 return SFT_ALIAS_SET (t
);
593 /* Otherwise, pick up the outermost object that we could have a pointer
594 to, processing conversions as above. */
595 while (component_uses_parent_alias_set (t
))
597 t
= TREE_OPERAND (t
, 0);
601 /* If we've already determined the alias set for a decl, just return
602 it. This is necessary for C++ anonymous unions, whose component
603 variables don't look like union members (boo!). */
604 if (TREE_CODE (t
) == VAR_DECL
605 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
606 return MEM_ALIAS_SET (DECL_RTL (t
));
608 /* Now all we care about is the type. */
612 /* Variant qualifiers don't affect the alias set, so get the main
613 variant. If this is a type with a known alias set, return it. */
614 t
= TYPE_MAIN_VARIANT (t
);
615 if (TYPE_ALIAS_SET_KNOWN_P (t
))
616 return TYPE_ALIAS_SET (t
);
618 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
619 if (!COMPLETE_TYPE_P (t
))
621 /* For arrays with unknown size the conservative answer is the
622 alias set of the element type. */
623 if (TREE_CODE (t
) == ARRAY_TYPE
)
624 return get_alias_set (TREE_TYPE (t
));
626 /* But return zero as a conservative answer for incomplete types. */
630 /* See if the language has special handling for this type. */
631 set
= lang_hooks
.get_alias_set (t
);
635 /* There are no objects of FUNCTION_TYPE, so there's no point in
636 using up an alias set for them. (There are, of course, pointers
637 and references to functions, but that's different.) */
638 else if (TREE_CODE (t
) == FUNCTION_TYPE
639 || TREE_CODE (t
) == METHOD_TYPE
)
642 /* Unless the language specifies otherwise, let vector types alias
643 their components. This avoids some nasty type punning issues in
644 normal usage. And indeed lets vectors be treated more like an
646 else if (TREE_CODE (t
) == VECTOR_TYPE
)
647 set
= get_alias_set (TREE_TYPE (t
));
650 /* Otherwise make a new alias set for this type. */
651 set
= new_alias_set ();
653 TYPE_ALIAS_SET (t
) = set
;
655 /* If this is an aggregate type, we must record any component aliasing
657 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
658 record_component_aliases (t
);
663 /* Return a brand-new alias set. */
668 if (flag_strict_aliasing
)
671 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
672 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
673 return VEC_length (alias_set_entry
, alias_sets
) - 1;
679 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
680 not everything that aliases SUPERSET also aliases SUBSET. For example,
681 in C, a store to an `int' can alias a load of a structure containing an
682 `int', and vice versa. But it can't alias a load of a 'double' member
683 of the same structure. Here, the structure would be the SUPERSET and
684 `int' the SUBSET. This relationship is also described in the comment at
685 the beginning of this file.
687 This function should be called only once per SUPERSET/SUBSET pair.
689 It is illegal for SUPERSET to be zero; everything is implicitly a
690 subset of alias set zero. */
693 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
695 alias_set_entry superset_entry
;
696 alias_set_entry subset_entry
;
698 /* It is possible in complex type situations for both sets to be the same,
699 in which case we can ignore this operation. */
700 if (superset
== subset
)
703 gcc_assert (superset
);
705 superset_entry
= get_alias_set_entry (superset
);
706 if (superset_entry
== 0)
708 /* Create an entry for the SUPERSET, so that we have a place to
709 attach the SUBSET. */
710 superset_entry
= ggc_alloc (sizeof (struct alias_set_entry
));
711 superset_entry
->alias_set
= superset
;
712 superset_entry
->children
713 = splay_tree_new_ggc (splay_tree_compare_ints
);
714 superset_entry
->has_zero_child
= 0;
715 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
719 superset_entry
->has_zero_child
= 1;
722 subset_entry
= get_alias_set_entry (subset
);
723 /* If there is an entry for the subset, enter all of its children
724 (if they are not already present) as children of the SUPERSET. */
727 if (subset_entry
->has_zero_child
)
728 superset_entry
->has_zero_child
= 1;
730 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
731 superset_entry
->children
);
734 /* Enter the SUBSET itself as a child of the SUPERSET. */
735 splay_tree_insert (superset_entry
->children
,
736 (splay_tree_key
) subset
, 0);
740 /* Record that component types of TYPE, if any, are part of that type for
741 aliasing purposes. For record types, we only record component types
742 for fields that are marked addressable. For array types, we always
743 record the component types, so the front end should not call this
744 function if the individual component aren't addressable. */
747 record_component_aliases (tree type
)
749 alias_set_type superset
= get_alias_set (type
);
755 switch (TREE_CODE (type
))
758 if (! TYPE_NONALIASED_COMPONENT (type
))
759 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
764 case QUAL_UNION_TYPE
:
765 /* Recursively record aliases for the base classes, if there are any. */
766 if (TYPE_BINFO (type
))
769 tree binfo
, base_binfo
;
771 for (binfo
= TYPE_BINFO (type
), i
= 0;
772 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
773 record_alias_subset (superset
,
774 get_alias_set (BINFO_TYPE (base_binfo
)));
776 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
777 if (TREE_CODE (field
) == FIELD_DECL
&& ! DECL_NONADDRESSABLE_P (field
))
778 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
782 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
790 /* Allocate an alias set for use in storing and reading from the varargs
793 static GTY(()) alias_set_type varargs_set
= -1;
796 get_varargs_alias_set (void)
799 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
800 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
801 consistently use the varargs alias set for loads from the varargs
802 area. So don't use it anywhere. */
805 if (varargs_set
== -1)
806 varargs_set
= new_alias_set ();
812 /* Likewise, but used for the fixed portions of the frame, e.g., register
815 static GTY(()) alias_set_type frame_set
= -1;
818 get_frame_alias_set (void)
821 frame_set
= new_alias_set ();
826 /* Inside SRC, the source of a SET, find a base address. */
829 find_base_value (rtx src
)
833 switch (GET_CODE (src
))
841 /* At the start of a function, argument registers have known base
842 values which may be lost later. Returning an ADDRESS
843 expression here allows optimization based on argument values
844 even when the argument registers are used for other purposes. */
845 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
846 return new_reg_base_value
[regno
];
848 /* If a pseudo has a known base value, return it. Do not do this
849 for non-fixed hard regs since it can result in a circular
850 dependency chain for registers which have values at function entry.
852 The test above is not sufficient because the scheduler may move
853 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
854 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
855 && regno
< VEC_length (rtx
, reg_base_value
))
857 /* If we're inside init_alias_analysis, use new_reg_base_value
858 to reduce the number of relaxation iterations. */
859 if (new_reg_base_value
&& new_reg_base_value
[regno
]
860 && DF_REG_DEF_COUNT (regno
) == 1)
861 return new_reg_base_value
[regno
];
863 if (VEC_index (rtx
, reg_base_value
, regno
))
864 return VEC_index (rtx
, reg_base_value
, regno
);
870 /* Check for an argument passed in memory. Only record in the
871 copying-arguments block; it is too hard to track changes
873 if (copying_arguments
874 && (XEXP (src
, 0) == arg_pointer_rtx
875 || (GET_CODE (XEXP (src
, 0)) == PLUS
876 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
877 return gen_rtx_ADDRESS (VOIDmode
, src
);
882 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
885 /* ... fall through ... */
890 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
892 /* If either operand is a REG that is a known pointer, then it
894 if (REG_P (src_0
) && REG_POINTER (src_0
))
895 return find_base_value (src_0
);
896 if (REG_P (src_1
) && REG_POINTER (src_1
))
897 return find_base_value (src_1
);
899 /* If either operand is a REG, then see if we already have
900 a known value for it. */
903 temp
= find_base_value (src_0
);
910 temp
= find_base_value (src_1
);
915 /* If either base is named object or a special address
916 (like an argument or stack reference), then use it for the
919 && (GET_CODE (src_0
) == SYMBOL_REF
920 || GET_CODE (src_0
) == LABEL_REF
921 || (GET_CODE (src_0
) == ADDRESS
922 && GET_MODE (src_0
) != VOIDmode
)))
926 && (GET_CODE (src_1
) == SYMBOL_REF
927 || GET_CODE (src_1
) == LABEL_REF
928 || (GET_CODE (src_1
) == ADDRESS
929 && GET_MODE (src_1
) != VOIDmode
)))
932 /* Guess which operand is the base address:
933 If either operand is a symbol, then it is the base. If
934 either operand is a CONST_INT, then the other is the base. */
935 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
936 return find_base_value (src_0
);
937 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
938 return find_base_value (src_1
);
944 /* The standard form is (lo_sum reg sym) so look only at the
946 return find_base_value (XEXP (src
, 1));
949 /* If the second operand is constant set the base
950 address to the first operand. */
951 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
952 return find_base_value (XEXP (src
, 0));
956 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
966 return find_base_value (XEXP (src
, 0));
969 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
971 rtx temp
= find_base_value (XEXP (src
, 0));
973 if (temp
!= 0 && CONSTANT_P (temp
))
974 temp
= convert_memory_address (Pmode
, temp
);
986 /* Called from init_alias_analysis indirectly through note_stores. */
988 /* While scanning insns to find base values, reg_seen[N] is nonzero if
989 register N has been set in this function. */
990 static char *reg_seen
;
992 /* Addresses which are known not to alias anything else are identified
993 by a unique integer. */
994 static int unique_id
;
997 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
1006 regno
= REGNO (dest
);
1008 gcc_assert (regno
< VEC_length (rtx
, reg_base_value
));
1010 /* If this spans multiple hard registers, then we must indicate that every
1011 register has an unusable value. */
1012 if (regno
< FIRST_PSEUDO_REGISTER
)
1013 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1020 reg_seen
[regno
+ n
] = 1;
1021 new_reg_base_value
[regno
+ n
] = 0;
1028 /* A CLOBBER wipes out any old value but does not prevent a previously
1029 unset register from acquiring a base address (i.e. reg_seen is not
1031 if (GET_CODE (set
) == CLOBBER
)
1033 new_reg_base_value
[regno
] = 0;
1036 src
= SET_SRC (set
);
1040 if (reg_seen
[regno
])
1042 new_reg_base_value
[regno
] = 0;
1045 reg_seen
[regno
] = 1;
1046 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
1047 GEN_INT (unique_id
++));
1051 /* If this is not the first set of REGNO, see whether the new value
1052 is related to the old one. There are two cases of interest:
1054 (1) The register might be assigned an entirely new value
1055 that has the same base term as the original set.
1057 (2) The set might be a simple self-modification that
1058 cannot change REGNO's base value.
1060 If neither case holds, reject the original base value as invalid.
1061 Note that the following situation is not detected:
1063 extern int x, y; int *p = &x; p += (&y-&x);
1065 ANSI C does not allow computing the difference of addresses
1066 of distinct top level objects. */
1067 if (new_reg_base_value
[regno
] != 0
1068 && find_base_value (src
) != new_reg_base_value
[regno
])
1069 switch (GET_CODE (src
))
1073 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1074 new_reg_base_value
[regno
] = 0;
1077 /* If the value we add in the PLUS is also a valid base value,
1078 this might be the actual base value, and the original value
1081 rtx other
= NULL_RTX
;
1083 if (XEXP (src
, 0) == dest
)
1084 other
= XEXP (src
, 1);
1085 else if (XEXP (src
, 1) == dest
)
1086 other
= XEXP (src
, 0);
1088 if (! other
|| find_base_value (other
))
1089 new_reg_base_value
[regno
] = 0;
1093 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
1094 new_reg_base_value
[regno
] = 0;
1097 new_reg_base_value
[regno
] = 0;
1100 /* If this is the first set of a register, record the value. */
1101 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1102 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1103 new_reg_base_value
[regno
] = find_base_value (src
);
1105 reg_seen
[regno
] = 1;
1108 /* If a value is known for REGNO, return it. */
1111 get_reg_known_value (unsigned int regno
)
1113 if (regno
>= FIRST_PSEUDO_REGISTER
)
1115 regno
-= FIRST_PSEUDO_REGISTER
;
1116 if (regno
< reg_known_value_size
)
1117 return reg_known_value
[regno
];
1125 set_reg_known_value (unsigned int regno
, rtx val
)
1127 if (regno
>= FIRST_PSEUDO_REGISTER
)
1129 regno
-= FIRST_PSEUDO_REGISTER
;
1130 if (regno
< reg_known_value_size
)
1131 reg_known_value
[regno
] = val
;
1135 /* Similarly for reg_known_equiv_p. */
1138 get_reg_known_equiv_p (unsigned int regno
)
1140 if (regno
>= FIRST_PSEUDO_REGISTER
)
1142 regno
-= FIRST_PSEUDO_REGISTER
;
1143 if (regno
< reg_known_value_size
)
1144 return reg_known_equiv_p
[regno
];
1150 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1152 if (regno
>= FIRST_PSEUDO_REGISTER
)
1154 regno
-= FIRST_PSEUDO_REGISTER
;
1155 if (regno
< reg_known_value_size
)
1156 reg_known_equiv_p
[regno
] = val
;
1161 /* Returns a canonical version of X, from the point of view alias
1162 analysis. (For example, if X is a MEM whose address is a register,
1163 and the register has a known value (say a SYMBOL_REF), then a MEM
1164 whose address is the SYMBOL_REF is returned.) */
1169 /* Recursively look for equivalences. */
1170 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1172 rtx t
= get_reg_known_value (REGNO (x
));
1176 return canon_rtx (t
);
1179 if (GET_CODE (x
) == PLUS
)
1181 rtx x0
= canon_rtx (XEXP (x
, 0));
1182 rtx x1
= canon_rtx (XEXP (x
, 1));
1184 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1186 if (GET_CODE (x0
) == CONST_INT
)
1187 return plus_constant (x1
, INTVAL (x0
));
1188 else if (GET_CODE (x1
) == CONST_INT
)
1189 return plus_constant (x0
, INTVAL (x1
));
1190 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1194 /* This gives us much better alias analysis when called from
1195 the loop optimizer. Note we want to leave the original
1196 MEM alone, but need to return the canonicalized MEM with
1197 all the flags with their original values. */
1199 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1204 /* Return 1 if X and Y are identical-looking rtx's.
1205 Expect that X and Y has been already canonicalized.
1207 We use the data in reg_known_value above to see if two registers with
1208 different numbers are, in fact, equivalent. */
1211 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1218 if (x
== 0 && y
== 0)
1220 if (x
== 0 || y
== 0)
1226 code
= GET_CODE (x
);
1227 /* Rtx's of different codes cannot be equal. */
1228 if (code
!= GET_CODE (y
))
1231 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1232 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1234 if (GET_MODE (x
) != GET_MODE (y
))
1237 /* Some RTL can be compared without a recursive examination. */
1241 return REGNO (x
) == REGNO (y
);
1244 return XEXP (x
, 0) == XEXP (y
, 0);
1247 return XSTR (x
, 0) == XSTR (y
, 0);
1253 /* There's no need to compare the contents of CONST_DOUBLEs or
1254 CONST_INTs because pointer equality is a good enough
1255 comparison for these nodes. */
1262 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1264 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1265 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1266 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1267 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1268 /* For commutative operations, the RTX match if the operand match in any
1269 order. Also handle the simple binary and unary cases without a loop. */
1270 if (COMMUTATIVE_P (x
))
1272 rtx xop0
= canon_rtx (XEXP (x
, 0));
1273 rtx yop0
= canon_rtx (XEXP (y
, 0));
1274 rtx yop1
= canon_rtx (XEXP (y
, 1));
1276 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1277 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1278 || (rtx_equal_for_memref_p (xop0
, yop1
)
1279 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1281 else if (NON_COMMUTATIVE_P (x
))
1283 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1284 canon_rtx (XEXP (y
, 0)))
1285 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1286 canon_rtx (XEXP (y
, 1))));
1288 else if (UNARY_P (x
))
1289 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1290 canon_rtx (XEXP (y
, 0)));
1292 /* Compare the elements. If any pair of corresponding elements
1293 fail to match, return 0 for the whole things.
1295 Limit cases to types which actually appear in addresses. */
1297 fmt
= GET_RTX_FORMAT (code
);
1298 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1303 if (XINT (x
, i
) != XINT (y
, i
))
1308 /* Two vectors must have the same length. */
1309 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1312 /* And the corresponding elements must match. */
1313 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1314 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1315 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1320 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1321 canon_rtx (XEXP (y
, i
))) == 0)
1325 /* This can happen for asm operands. */
1327 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1331 /* This can happen for an asm which clobbers memory. */
1335 /* It is believed that rtx's at this level will never
1336 contain anything but integers and other rtx's,
1337 except for within LABEL_REFs and SYMBOL_REFs. */
1346 find_base_term (rtx x
)
1349 struct elt_loc_list
*l
;
1351 #if defined (FIND_BASE_TERM)
1352 /* Try machine-dependent ways to find the base term. */
1353 x
= FIND_BASE_TERM (x
);
1356 switch (GET_CODE (x
))
1359 return REG_BASE_VALUE (x
);
1362 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1372 return find_base_term (XEXP (x
, 0));
1375 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1377 rtx temp
= find_base_term (XEXP (x
, 0));
1379 if (temp
!= 0 && CONSTANT_P (temp
))
1380 temp
= convert_memory_address (Pmode
, temp
);
1386 val
= CSELIB_VAL_PTR (x
);
1389 for (l
= val
->locs
; l
; l
= l
->next
)
1390 if ((x
= find_base_term (l
->loc
)) != 0)
1396 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1403 rtx tmp1
= XEXP (x
, 0);
1404 rtx tmp2
= XEXP (x
, 1);
1406 /* This is a little bit tricky since we have to determine which of
1407 the two operands represents the real base address. Otherwise this
1408 routine may return the index register instead of the base register.
1410 That may cause us to believe no aliasing was possible, when in
1411 fact aliasing is possible.
1413 We use a few simple tests to guess the base register. Additional
1414 tests can certainly be added. For example, if one of the operands
1415 is a shift or multiply, then it must be the index register and the
1416 other operand is the base register. */
1418 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1419 return find_base_term (tmp2
);
1421 /* If either operand is known to be a pointer, then use it
1422 to determine the base term. */
1423 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1424 return find_base_term (tmp1
);
1426 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1427 return find_base_term (tmp2
);
1429 /* Neither operand was known to be a pointer. Go ahead and find the
1430 base term for both operands. */
1431 tmp1
= find_base_term (tmp1
);
1432 tmp2
= find_base_term (tmp2
);
1434 /* If either base term is named object or a special address
1435 (like an argument or stack reference), then use it for the
1438 && (GET_CODE (tmp1
) == SYMBOL_REF
1439 || GET_CODE (tmp1
) == LABEL_REF
1440 || (GET_CODE (tmp1
) == ADDRESS
1441 && GET_MODE (tmp1
) != VOIDmode
)))
1445 && (GET_CODE (tmp2
) == SYMBOL_REF
1446 || GET_CODE (tmp2
) == LABEL_REF
1447 || (GET_CODE (tmp2
) == ADDRESS
1448 && GET_MODE (tmp2
) != VOIDmode
)))
1451 /* We could not determine which of the two operands was the
1452 base register and which was the index. So we can determine
1453 nothing from the base alias check. */
1458 if (GET_CODE (XEXP (x
, 1)) == CONST_INT
&& INTVAL (XEXP (x
, 1)) != 0)
1459 return find_base_term (XEXP (x
, 0));
1471 /* Return 0 if the addresses X and Y are known to point to different
1472 objects, 1 if they might be pointers to the same object. */
1475 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1476 enum machine_mode y_mode
)
1478 rtx x_base
= find_base_term (x
);
1479 rtx y_base
= find_base_term (y
);
1481 /* If the address itself has no known base see if a known equivalent
1482 value has one. If either address still has no known base, nothing
1483 is known about aliasing. */
1488 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1491 x_base
= find_base_term (x_c
);
1499 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1502 y_base
= find_base_term (y_c
);
1507 /* If the base addresses are equal nothing is known about aliasing. */
1508 if (rtx_equal_p (x_base
, y_base
))
1511 /* The base addresses of the read and write are different expressions.
1512 If they are both symbols and they are not accessed via AND, there is
1513 no conflict. We can bring knowledge of object alignment into play
1514 here. For example, on alpha, "char a, b;" can alias one another,
1515 though "char a; long b;" cannot. */
1516 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1518 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1520 if (GET_CODE (x
) == AND
1521 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1522 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1524 if (GET_CODE (y
) == AND
1525 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1526 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1528 /* Differing symbols never alias. */
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 (GET_CODE (x1
) == CONST_INT
)
1687 if (GET_CODE (y1
) == CONST_INT
)
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 (GET_CODE (y1
) == CONST_INT
)
1695 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1699 else if (GET_CODE (x1
) == CONST_INT
)
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 (GET_CODE (y1
) == CONST_INT
)
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 (GET_CODE (x1
) != CONST_INT
)
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
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
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
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
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 (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
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
&& GET_CODE (XEXP (basex
, 1)) == CONST_INT
)
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
&& GET_CODE (XEXP (basey
, 1)) == CONST_INT
)
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. */
2205 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2206 const_rtx x
, bool (*varies
) (const_rtx
, bool))
2210 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2213 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2214 This is used in epilogue deallocation functions. */
2215 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2217 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2219 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2220 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2223 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2226 /* Read-only memory is by definition never modified, and therefore can't
2227 conflict with anything. We don't expect to find read-only set on MEM,
2228 but stupid user tricks can produce them, so don't die. */
2229 if (MEM_READONLY_P (x
))
2232 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 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2288 /* A read from read-only memory can't conflict with read-write memory. */
2289 if (!writep
&& MEM_READONLY_P (mem
))
2292 if (nonoverlapping_memrefs_p (x
, mem
))
2295 x_addr
= get_addr (XEXP (x
, 0));
2296 mem_addr
= get_addr (XEXP (mem
, 0));
2300 base
= find_base_term (mem_addr
);
2301 if (base
&& (GET_CODE (base
) == LABEL_REF
2302 || (GET_CODE (base
) == SYMBOL_REF
2303 && CONSTANT_POOL_ADDRESS_P (base
))))
2307 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2311 x_addr
= canon_rtx (x_addr
);
2312 mem_addr
= canon_rtx (mem_addr
);
2314 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2315 SIZE_FOR_MODE (x
), x_addr
, 0))
2319 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2322 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2323 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2326 /* Anti dependence: X is written after read in MEM takes place. */
2329 anti_dependence (const_rtx mem
, const_rtx x
)
2331 return write_dependence_p (mem
, x
, /*writep=*/0);
2334 /* Output dependence: X is written after store in MEM takes place. */
2337 output_dependence (const_rtx mem
, const_rtx x
)
2339 return write_dependence_p (mem
, x
, /*writep=*/1);
2344 init_alias_target (void)
2348 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2350 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2351 /* Check whether this register can hold an incoming pointer
2352 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2353 numbers, so translate if necessary due to register windows. */
2354 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2355 && HARD_REGNO_MODE_OK (i
, Pmode
))
2356 static_reg_base_value
[i
]
2357 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2359 static_reg_base_value
[STACK_POINTER_REGNUM
]
2360 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2361 static_reg_base_value
[ARG_POINTER_REGNUM
]
2362 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2363 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2364 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2365 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2366 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2367 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2371 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2372 to be memory reference. */
2373 static bool memory_modified
;
2375 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2379 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2380 memory_modified
= true;
2385 /* Return true when INSN possibly modify memory contents of MEM
2386 (i.e. address can be modified). */
2388 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2392 memory_modified
= false;
2393 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2394 return memory_modified
;
2397 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2401 init_alias_analysis (void)
2403 unsigned int maxreg
= max_reg_num ();
2409 timevar_push (TV_ALIAS_ANALYSIS
);
2411 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2412 reg_known_value
= ggc_calloc (reg_known_value_size
, sizeof (rtx
));
2413 reg_known_equiv_p
= xcalloc (reg_known_value_size
, sizeof (bool));
2415 /* If we have memory allocated from the previous run, use it. */
2416 if (old_reg_base_value
)
2417 reg_base_value
= old_reg_base_value
;
2420 VEC_truncate (rtx
, reg_base_value
, 0);
2422 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2424 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2425 reg_seen
= XNEWVEC (char, maxreg
);
2427 /* The basic idea is that each pass through this loop will use the
2428 "constant" information from the previous pass to propagate alias
2429 information through another level of assignments.
2431 This could get expensive if the assignment chains are long. Maybe
2432 we should throttle the number of iterations, possibly based on
2433 the optimization level or flag_expensive_optimizations.
2435 We could propagate more information in the first pass by making use
2436 of DF_REG_DEF_COUNT to determine immediately that the alias information
2437 for a pseudo is "constant".
2439 A program with an uninitialized variable can cause an infinite loop
2440 here. Instead of doing a full dataflow analysis to detect such problems
2441 we just cap the number of iterations for the loop.
2443 The state of the arrays for the set chain in question does not matter
2444 since the program has undefined behavior. */
2449 /* Assume nothing will change this iteration of the loop. */
2452 /* We want to assign the same IDs each iteration of this loop, so
2453 start counting from zero each iteration of the loop. */
2456 /* We're at the start of the function each iteration through the
2457 loop, so we're copying arguments. */
2458 copying_arguments
= true;
2460 /* Wipe the potential alias information clean for this pass. */
2461 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2463 /* Wipe the reg_seen array clean. */
2464 memset (reg_seen
, 0, maxreg
);
2466 /* Mark all hard registers which may contain an address.
2467 The stack, frame and argument pointers may contain an address.
2468 An argument register which can hold a Pmode value may contain
2469 an address even if it is not in BASE_REGS.
2471 The address expression is VOIDmode for an argument and
2472 Pmode for other registers. */
2474 memcpy (new_reg_base_value
, static_reg_base_value
,
2475 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2477 /* Walk the insns adding values to the new_reg_base_value array. */
2478 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2484 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2485 /* The prologue/epilogue insns are not threaded onto the
2486 insn chain until after reload has completed. Thus,
2487 there is no sense wasting time checking if INSN is in
2488 the prologue/epilogue until after reload has completed. */
2489 if (reload_completed
2490 && prologue_epilogue_contains (insn
))
2494 /* If this insn has a noalias note, process it, Otherwise,
2495 scan for sets. A simple set will have no side effects
2496 which could change the base value of any other register. */
2498 if (GET_CODE (PATTERN (insn
)) == SET
2499 && REG_NOTES (insn
) != 0
2500 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2501 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2503 note_stores (PATTERN (insn
), record_set
, NULL
);
2505 set
= single_set (insn
);
2508 && REG_P (SET_DEST (set
))
2509 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2511 unsigned int regno
= REGNO (SET_DEST (set
));
2512 rtx src
= SET_SRC (set
);
2515 note
= find_reg_equal_equiv_note (insn
);
2516 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2517 && DF_REG_DEF_COUNT (regno
) != 1)
2520 if (note
!= NULL_RTX
2521 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2522 && ! rtx_varies_p (XEXP (note
, 0), 1)
2523 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2526 set_reg_known_value (regno
, XEXP (note
, 0));
2527 set_reg_known_equiv_p (regno
,
2528 REG_NOTE_KIND (note
) == REG_EQUIV
);
2530 else if (DF_REG_DEF_COUNT (regno
) == 1
2531 && GET_CODE (src
) == PLUS
2532 && REG_P (XEXP (src
, 0))
2533 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2534 && GET_CODE (XEXP (src
, 1)) == CONST_INT
)
2536 t
= plus_constant (t
, INTVAL (XEXP (src
, 1)));
2537 set_reg_known_value (regno
, t
);
2538 set_reg_known_equiv_p (regno
, 0);
2540 else if (DF_REG_DEF_COUNT (regno
) == 1
2541 && ! rtx_varies_p (src
, 1))
2543 set_reg_known_value (regno
, src
);
2544 set_reg_known_equiv_p (regno
, 0);
2548 else if (NOTE_P (insn
)
2549 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2550 copying_arguments
= false;
2553 /* Now propagate values from new_reg_base_value to reg_base_value. */
2554 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2556 for (ui
= 0; ui
< maxreg
; ui
++)
2558 if (new_reg_base_value
[ui
]
2559 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2560 && ! rtx_equal_p (new_reg_base_value
[ui
],
2561 VEC_index (rtx
, reg_base_value
, ui
)))
2563 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2568 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2570 /* Fill in the remaining entries. */
2571 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2572 if (reg_known_value
[i
] == 0)
2573 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2576 free (new_reg_base_value
);
2577 new_reg_base_value
= 0;
2580 timevar_pop (TV_ALIAS_ANALYSIS
);
2584 end_alias_analysis (void)
2586 old_reg_base_value
= reg_base_value
;
2587 ggc_free (reg_known_value
);
2588 reg_known_value
= 0;
2589 reg_known_value_size
= 0;
2590 free (reg_known_equiv_p
);
2591 reg_known_equiv_p
= 0;
2594 #include "gt-alias.h"