1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009, 2010, 2011, 2012 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"
37 #include "diagnostic-core.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
45 #include "tree-pass.h"
47 #include "tree-ssa-alias.h"
48 #include "pointer-set.h"
49 #include "tree-flow.h"
51 /* The aliasing API provided here solves related but different problems:
53 Say there exists (in c)
67 Consider the four questions:
69 Can a store to x1 interfere with px2->y1?
70 Can a store to x1 interfere with px2->z2?
72 Can a store to x1 change the value pointed to by with py?
73 Can a store to x1 change the value pointed to by with pz?
75 The answer to these questions can be yes, yes, yes, and maybe.
77 The first two questions can be answered with a simple examination
78 of the type system. If structure X contains a field of type Y then
79 a store thru a pointer to an X can overwrite any field that is
80 contained (recursively) in an X (unless we know that px1 != px2).
82 The last two of the questions can be solved in the same way as the
83 first two questions but this is too conservative. The observation
84 is that in some cases analysis we can know if which (if any) fields
85 are addressed and if those addresses are used in bad ways. This
86 analysis may be language specific. In C, arbitrary operations may
87 be applied to pointers. However, there is some indication that
88 this may be too conservative for some C++ types.
90 The pass ipa-type-escape does this analysis for the types whose
91 instances do not escape across the compilation boundary.
93 Historically in GCC, these two problems were combined and a single
94 data structure was used to represent the solution to these
95 problems. We now have two similar but different data structures,
96 The data structure to solve the last two question is similar to the
97 first, but does not contain have the fields in it whose address are
98 never taken. For types that do escape the compilation unit, the
99 data structures will have identical information.
102 /* The alias sets assigned to MEMs assist the back-end in determining
103 which MEMs can alias which other MEMs. In general, two MEMs in
104 different alias sets cannot alias each other, with one important
105 exception. Consider something like:
107 struct S { int i; double d; };
109 a store to an `S' can alias something of either type `int' or type
110 `double'. (However, a store to an `int' cannot alias a `double'
111 and vice versa.) We indicate this via a tree structure that looks
119 (The arrows are directed and point downwards.)
120 In this situation we say the alias set for `struct S' is the
121 `superset' and that those for `int' and `double' are `subsets'.
123 To see whether two alias sets can point to the same memory, we must
124 see if either alias set is a subset of the other. We need not trace
125 past immediate descendants, however, since we propagate all
126 grandchildren up one level.
128 Alias set zero is implicitly a superset of all other alias sets.
129 However, this is no actual entry for alias set zero. It is an
130 error to attempt to explicitly construct a subset of zero. */
132 struct GTY(()) alias_set_entry_d
{
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_d
*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 alias_set_entry
get_alias_set_entry (alias_set_type
);
160 static int aliases_everything_p (const_rtx
);
161 static bool nonoverlapping_component_refs_p (const_tree
, const_tree
);
162 static tree
decl_for_component_ref (tree
);
163 static int write_dependence_p (const_rtx
, const_rtx
, int);
165 static void memory_modified_1 (rtx
, const_rtx
, void *);
167 /* Set up all info needed to perform alias analysis on memory references. */
169 /* Returns the size in bytes of the mode of X. */
170 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
172 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
173 different alias sets. We ignore alias sets in functions making use
174 of variable arguments because the va_arg macros on some systems are
176 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
177 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
179 /* Cap the number of passes we make over the insns propagating alias
180 information through set chains. 10 is a completely arbitrary choice. */
181 #define MAX_ALIAS_LOOP_PASSES 10
183 /* reg_base_value[N] gives an address to which register N is related.
184 If all sets after the first add or subtract to the current value
185 or otherwise modify it so it does not point to a different top level
186 object, reg_base_value[N] is equal to the address part of the source
189 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
190 expressions represent three types of base:
192 1. incoming arguments. There is just one ADDRESS to represent all
193 arguments, since we do not know at this level whether accesses
194 based on different arguments can alias. The ADDRESS has id 0.
196 2. stack_pointer_rtx, frame_pointer_rtx, hard_frame_pointer_rtx
197 (if distinct from frame_pointer_rtx) and arg_pointer_rtx.
198 Each of these rtxes has a separate ADDRESS associated with it,
199 each with a negative id.
201 GCC is (and is required to be) precise in which register it
202 chooses to access a particular region of stack. We can therefore
203 assume that accesses based on one of these rtxes do not alias
204 accesses based on another of these rtxes.
206 3. bases that are derived from malloc()ed memory (REG_NOALIAS).
207 Each such piece of memory has a separate ADDRESS associated
208 with it, each with an id greater than 0.
210 Accesses based on one ADDRESS do not alias accesses based on other
211 ADDRESSes. Accesses based on ADDRESSes in groups (2) and (3) do not
212 alias globals either; the ADDRESSes have Pmode to indicate this.
213 The ADDRESS in group (1) _may_ alias globals; it has VOIDmode to
216 static GTY(()) VEC(rtx
,gc
) *reg_base_value
;
217 static rtx
*new_reg_base_value
;
219 /* The single VOIDmode ADDRESS that represents all argument bases.
221 static GTY(()) rtx arg_base_value
;
223 /* Used to allocate unique ids to each REG_NOALIAS ADDRESS. */
224 static int unique_id
;
226 /* We preserve the copy of old array around to avoid amount of garbage
227 produced. About 8% of garbage produced were attributed to this
229 static GTY((deletable
)) VEC(rtx
,gc
) *old_reg_base_value
;
231 /* Values of XINT (address, 0) of Pmode ADDRESS rtxes for special
233 #define UNIQUE_BASE_VALUE_SP -1
234 #define UNIQUE_BASE_VALUE_ARGP -2
235 #define UNIQUE_BASE_VALUE_FP -3
236 #define UNIQUE_BASE_VALUE_HFP -4
238 #define static_reg_base_value \
239 (this_target_rtl->x_static_reg_base_value)
241 #define REG_BASE_VALUE(X) \
242 (REGNO (X) < VEC_length (rtx, reg_base_value) \
243 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
245 /* Vector indexed by N giving the initial (unchanging) value known for
246 pseudo-register N. This array is initialized in init_alias_analysis,
247 and does not change until end_alias_analysis is called. */
248 static GTY((length("reg_known_value_size"))) rtx
*reg_known_value
;
250 /* Indicates number of valid entries in reg_known_value. */
251 static GTY(()) unsigned int reg_known_value_size
;
253 /* Vector recording for each reg_known_value whether it is due to a
254 REG_EQUIV note. Future passes (viz., reload) may replace the
255 pseudo with the equivalent expression and so we account for the
256 dependences that would be introduced if that happens.
258 The REG_EQUIV notes created in assign_parms may mention the arg
259 pointer, and there are explicit insns in the RTL that modify the
260 arg pointer. Thus we must ensure that such insns don't get
261 scheduled across each other because that would invalidate the
262 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
263 wrong, but solving the problem in the scheduler will likely give
264 better code, so we do it here. */
265 static bool *reg_known_equiv_p
;
267 /* True when scanning insns from the start of the rtl to the
268 NOTE_INSN_FUNCTION_BEG note. */
269 static bool copying_arguments
;
271 DEF_VEC_P(alias_set_entry
);
272 DEF_VEC_ALLOC_P(alias_set_entry
,gc
);
274 /* The splay-tree used to store the various alias set entries. */
275 static GTY (()) VEC(alias_set_entry
,gc
) *alias_sets
;
277 /* Build a decomposed reference object for querying the alias-oracle
278 from the MEM rtx and store it in *REF.
279 Returns false if MEM is not suitable for the alias-oracle. */
282 ao_ref_from_mem (ao_ref
*ref
, const_rtx mem
)
284 tree expr
= MEM_EXPR (mem
);
290 ao_ref_init (ref
, expr
);
292 /* Get the base of the reference and see if we have to reject or
294 base
= ao_ref_base (ref
);
295 if (base
== NULL_TREE
)
298 /* The tree oracle doesn't like to have these. */
299 if (TREE_CODE (base
) == FUNCTION_DECL
300 || TREE_CODE (base
) == LABEL_DECL
)
303 /* If this is a pointer dereference of a non-SSA_NAME punt.
304 ??? We could replace it with a pointer to anything. */
305 if ((INDIRECT_REF_P (base
)
306 || TREE_CODE (base
) == MEM_REF
)
307 && TREE_CODE (TREE_OPERAND (base
, 0)) != SSA_NAME
)
309 if (TREE_CODE (base
) == TARGET_MEM_REF
311 && TREE_CODE (TMR_BASE (base
)) != SSA_NAME
)
314 /* If this is a reference based on a partitioned decl replace the
315 base with an INDIRECT_REF of the pointer representative we
316 created during stack slot partitioning. */
317 if (TREE_CODE (base
) == VAR_DECL
318 && ! TREE_STATIC (base
)
319 && cfun
->gimple_df
->decls_to_pointers
!= NULL
)
322 namep
= pointer_map_contains (cfun
->gimple_df
->decls_to_pointers
, base
);
324 ref
->base
= build_simple_mem_ref (*(tree
*)namep
);
326 else if (TREE_CODE (base
) == TARGET_MEM_REF
327 && TREE_CODE (TMR_BASE (base
)) == ADDR_EXPR
328 && TREE_CODE (TREE_OPERAND (TMR_BASE (base
), 0)) == VAR_DECL
329 && ! TREE_STATIC (TREE_OPERAND (TMR_BASE (base
), 0))
330 && cfun
->gimple_df
->decls_to_pointers
!= NULL
)
333 namep
= pointer_map_contains (cfun
->gimple_df
->decls_to_pointers
,
334 TREE_OPERAND (TMR_BASE (base
), 0));
336 ref
->base
= build_simple_mem_ref (*(tree
*)namep
);
339 ref
->ref_alias_set
= MEM_ALIAS_SET (mem
);
341 /* If MEM_OFFSET or MEM_SIZE are unknown we have to punt.
342 Keep points-to related information though. */
343 if (!MEM_OFFSET_KNOWN_P (mem
)
344 || !MEM_SIZE_KNOWN_P (mem
))
346 ref
->ref
= NULL_TREE
;
353 /* If the base decl is a parameter we can have negative MEM_OFFSET in
354 case of promoted subregs on bigendian targets. Trust the MEM_EXPR
356 if (MEM_OFFSET (mem
) < 0
357 && (MEM_SIZE (mem
) + MEM_OFFSET (mem
)) * BITS_PER_UNIT
== ref
->size
)
360 ref
->offset
+= MEM_OFFSET (mem
) * BITS_PER_UNIT
;
361 ref
->size
= MEM_SIZE (mem
) * BITS_PER_UNIT
;
363 /* The MEM may extend into adjacent fields, so adjust max_size if
365 if (ref
->max_size
!= -1
366 && ref
->size
> ref
->max_size
)
367 ref
->max_size
= ref
->size
;
369 /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of
370 the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */
371 if (MEM_EXPR (mem
) != get_spill_slot_decl (false)
373 || (DECL_P (ref
->base
)
374 && (!host_integerp (DECL_SIZE (ref
->base
), 1)
375 || (TREE_INT_CST_LOW (DECL_SIZE ((ref
->base
)))
376 < (unsigned HOST_WIDE_INT
)(ref
->offset
+ ref
->size
))))))
382 /* Query the alias-oracle on whether the two memory rtx X and MEM may
383 alias. If TBAA_P is set also apply TBAA. Returns true if the
384 two rtxen may alias, false otherwise. */
387 rtx_refs_may_alias_p (const_rtx x
, const_rtx mem
, bool tbaa_p
)
391 if (!ao_ref_from_mem (&ref1
, x
)
392 || !ao_ref_from_mem (&ref2
, mem
))
395 return refs_may_alias_p_1 (&ref1
, &ref2
,
397 && MEM_ALIAS_SET (x
) != 0
398 && MEM_ALIAS_SET (mem
) != 0);
401 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
402 such an entry, or NULL otherwise. */
404 static inline alias_set_entry
405 get_alias_set_entry (alias_set_type alias_set
)
407 return VEC_index (alias_set_entry
, alias_sets
, alias_set
);
410 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
411 the two MEMs cannot alias each other. */
414 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
416 /* Perform a basic sanity check. Namely, that there are no alias sets
417 if we're not using strict aliasing. This helps to catch bugs
418 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
419 where a MEM is allocated in some way other than by the use of
420 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
421 use alias sets to indicate that spilled registers cannot alias each
422 other, we might need to remove this check. */
423 gcc_assert (flag_strict_aliasing
424 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
426 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
429 /* Insert the NODE into the splay tree given by DATA. Used by
430 record_alias_subset via splay_tree_foreach. */
433 insert_subset_children (splay_tree_node node
, void *data
)
435 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
440 /* Return true if the first alias set is a subset of the second. */
443 alias_set_subset_of (alias_set_type set1
, alias_set_type set2
)
447 /* Everything is a subset of the "aliases everything" set. */
451 /* Otherwise, check if set1 is a subset of set2. */
452 ase
= get_alias_set_entry (set2
);
454 && (ase
->has_zero_child
455 || splay_tree_lookup (ase
->children
,
456 (splay_tree_key
) set1
)))
461 /* Return 1 if the two specified alias sets may conflict. */
464 alias_sets_conflict_p (alias_set_type set1
, alias_set_type set2
)
469 if (alias_sets_must_conflict_p (set1
, set2
))
472 /* See if the first alias set is a subset of the second. */
473 ase
= get_alias_set_entry (set1
);
475 && (ase
->has_zero_child
476 || splay_tree_lookup (ase
->children
,
477 (splay_tree_key
) set2
)))
480 /* Now do the same, but with the alias sets reversed. */
481 ase
= get_alias_set_entry (set2
);
483 && (ase
->has_zero_child
484 || splay_tree_lookup (ase
->children
,
485 (splay_tree_key
) set1
)))
488 /* The two alias sets are distinct and neither one is the
489 child of the other. Therefore, they cannot conflict. */
493 /* Return 1 if the two specified alias sets will always conflict. */
496 alias_sets_must_conflict_p (alias_set_type set1
, alias_set_type set2
)
498 if (set1
== 0 || set2
== 0 || set1
== set2
)
504 /* Return 1 if any MEM object of type T1 will always conflict (using the
505 dependency routines in this file) with any MEM object of type T2.
506 This is used when allocating temporary storage. If T1 and/or T2 are
507 NULL_TREE, it means we know nothing about the storage. */
510 objects_must_conflict_p (tree t1
, tree t2
)
512 alias_set_type set1
, set2
;
514 /* If neither has a type specified, we don't know if they'll conflict
515 because we may be using them to store objects of various types, for
516 example the argument and local variables areas of inlined functions. */
517 if (t1
== 0 && t2
== 0)
520 /* If they are the same type, they must conflict. */
522 /* Likewise if both are volatile. */
523 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
526 set1
= t1
? get_alias_set (t1
) : 0;
527 set2
= t2
? get_alias_set (t2
) : 0;
529 /* We can't use alias_sets_conflict_p because we must make sure
530 that every subtype of t1 will conflict with every subtype of
531 t2 for which a pair of subobjects of these respective subtypes
532 overlaps on the stack. */
533 return alias_sets_must_conflict_p (set1
, set2
);
536 /* Return true if all nested component references handled by
537 get_inner_reference in T are such that we should use the alias set
538 provided by the object at the heart of T.
540 This is true for non-addressable components (which don't have their
541 own alias set), as well as components of objects in alias set zero.
542 This later point is a special case wherein we wish to override the
543 alias set used by the component, but we don't have per-FIELD_DECL
544 assignable alias sets. */
547 component_uses_parent_alias_set (const_tree t
)
551 /* If we're at the end, it vacuously uses its own alias set. */
552 if (!handled_component_p (t
))
555 switch (TREE_CODE (t
))
558 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1)))
563 case ARRAY_RANGE_REF
:
564 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0))))
573 /* Bitfields and casts are never addressable. */
577 t
= TREE_OPERAND (t
, 0);
578 if (get_alias_set (TREE_TYPE (t
)) == 0)
583 /* Return the alias set for the memory pointed to by T, which may be
584 either a type or an expression. Return -1 if there is nothing
585 special about dereferencing T. */
587 static alias_set_type
588 get_deref_alias_set_1 (tree t
)
590 /* If we're not doing any alias analysis, just assume everything
591 aliases everything else. */
592 if (!flag_strict_aliasing
)
595 /* All we care about is the type. */
599 /* If we have an INDIRECT_REF via a void pointer, we don't
600 know anything about what that might alias. Likewise if the
601 pointer is marked that way. */
602 if (TREE_CODE (TREE_TYPE (t
)) == VOID_TYPE
603 || TYPE_REF_CAN_ALIAS_ALL (t
))
609 /* Return the alias set for the memory pointed to by T, which may be
610 either a type or an expression. */
613 get_deref_alias_set (tree t
)
615 alias_set_type set
= get_deref_alias_set_1 (t
);
617 /* Fall back to the alias-set of the pointed-to type. */
622 set
= get_alias_set (TREE_TYPE (t
));
628 /* Return the alias set for T, which may be either a type or an
629 expression. Call language-specific routine for help, if needed. */
632 get_alias_set (tree t
)
636 /* If we're not doing any alias analysis, just assume everything
637 aliases everything else. Also return 0 if this or its type is
639 if (! flag_strict_aliasing
|| t
== error_mark_node
641 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
644 /* We can be passed either an expression or a type. This and the
645 language-specific routine may make mutually-recursive calls to each other
646 to figure out what to do. At each juncture, we see if this is a tree
647 that the language may need to handle specially. First handle things that
653 /* Give the language a chance to do something with this tree
654 before we look at it. */
656 set
= lang_hooks
.get_alias_set (t
);
660 /* Get the base object of the reference. */
662 while (handled_component_p (inner
))
664 /* If there is a VIEW_CONVERT_EXPR in the chain we cannot use
665 the type of any component references that wrap it to
666 determine the alias-set. */
667 if (TREE_CODE (inner
) == VIEW_CONVERT_EXPR
)
668 t
= TREE_OPERAND (inner
, 0);
669 inner
= TREE_OPERAND (inner
, 0);
672 /* Handle pointer dereferences here, they can override the
674 if (INDIRECT_REF_P (inner
))
676 set
= get_deref_alias_set_1 (TREE_OPERAND (inner
, 0));
680 else if (TREE_CODE (inner
) == TARGET_MEM_REF
)
681 return get_deref_alias_set (TMR_OFFSET (inner
));
682 else if (TREE_CODE (inner
) == MEM_REF
)
684 set
= get_deref_alias_set_1 (TREE_OPERAND (inner
, 1));
689 /* If the innermost reference is a MEM_REF that has a
690 conversion embedded treat it like a VIEW_CONVERT_EXPR above,
691 using the memory access type for determining the alias-set. */
692 if (TREE_CODE (inner
) == MEM_REF
693 && TYPE_MAIN_VARIANT (TREE_TYPE (inner
))
695 (TREE_TYPE (TREE_TYPE (TREE_OPERAND (inner
, 1)))))
696 return get_deref_alias_set (TREE_OPERAND (inner
, 1));
698 /* Otherwise, pick up the outermost object that we could have a pointer
699 to, processing conversions as above. */
700 while (component_uses_parent_alias_set (t
))
702 t
= TREE_OPERAND (t
, 0);
706 /* If we've already determined the alias set for a decl, just return
707 it. This is necessary for C++ anonymous unions, whose component
708 variables don't look like union members (boo!). */
709 if (TREE_CODE (t
) == VAR_DECL
710 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
711 return MEM_ALIAS_SET (DECL_RTL (t
));
713 /* Now all we care about is the type. */
717 /* Variant qualifiers don't affect the alias set, so get the main
719 t
= TYPE_MAIN_VARIANT (t
);
721 /* Always use the canonical type as well. If this is a type that
722 requires structural comparisons to identify compatible types
723 use alias set zero. */
724 if (TYPE_STRUCTURAL_EQUALITY_P (t
))
726 /* Allow the language to specify another alias set for this
728 set
= lang_hooks
.get_alias_set (t
);
734 t
= TYPE_CANONICAL (t
);
736 /* The canonical type should not require structural equality checks. */
737 gcc_checking_assert (!TYPE_STRUCTURAL_EQUALITY_P (t
));
739 /* If this is a type with a known alias set, return it. */
740 if (TYPE_ALIAS_SET_KNOWN_P (t
))
741 return TYPE_ALIAS_SET (t
);
743 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
744 if (!COMPLETE_TYPE_P (t
))
746 /* For arrays with unknown size the conservative answer is the
747 alias set of the element type. */
748 if (TREE_CODE (t
) == ARRAY_TYPE
)
749 return get_alias_set (TREE_TYPE (t
));
751 /* But return zero as a conservative answer for incomplete types. */
755 /* See if the language has special handling for this type. */
756 set
= lang_hooks
.get_alias_set (t
);
760 /* There are no objects of FUNCTION_TYPE, so there's no point in
761 using up an alias set for them. (There are, of course, pointers
762 and references to functions, but that's different.) */
763 else if (TREE_CODE (t
) == FUNCTION_TYPE
|| TREE_CODE (t
) == METHOD_TYPE
)
766 /* Unless the language specifies otherwise, let vector types alias
767 their components. This avoids some nasty type punning issues in
768 normal usage. And indeed lets vectors be treated more like an
770 else if (TREE_CODE (t
) == VECTOR_TYPE
)
771 set
= get_alias_set (TREE_TYPE (t
));
773 /* Unless the language specifies otherwise, treat array types the
774 same as their components. This avoids the asymmetry we get
775 through recording the components. Consider accessing a
776 character(kind=1) through a reference to a character(kind=1)[1:1].
777 Or consider if we want to assign integer(kind=4)[0:D.1387] and
778 integer(kind=4)[4] the same alias set or not.
779 Just be pragmatic here and make sure the array and its element
780 type get the same alias set assigned. */
781 else if (TREE_CODE (t
) == ARRAY_TYPE
&& !TYPE_NONALIASED_COMPONENT (t
))
782 set
= get_alias_set (TREE_TYPE (t
));
784 /* From the former common C and C++ langhook implementation:
786 Unfortunately, there is no canonical form of a pointer type.
787 In particular, if we have `typedef int I', then `int *', and
788 `I *' are different types. So, we have to pick a canonical
789 representative. We do this below.
791 Technically, this approach is actually more conservative that
792 it needs to be. In particular, `const int *' and `int *'
793 should be in different alias sets, according to the C and C++
794 standard, since their types are not the same, and so,
795 technically, an `int **' and `const int **' cannot point at
798 But, the standard is wrong. In particular, this code is
803 const int* const* cipp = ipp;
804 And, it doesn't make sense for that to be legal unless you
805 can dereference IPP and CIPP. So, we ignore cv-qualifiers on
806 the pointed-to types. This issue has been reported to the
809 In addition to the above canonicalization issue, with LTO
810 we should also canonicalize `T (*)[]' to `T *' avoiding
811 alias issues with pointer-to element types and pointer-to
814 Likewise we need to deal with the situation of incomplete
815 pointed-to types and make `*(struct X **)&a' and
816 `*(struct X {} **)&a' alias. Otherwise we will have to
817 guarantee that all pointer-to incomplete type variants
818 will be replaced by pointer-to complete type variants if
821 With LTO the convenient situation of using `void *' to
822 access and store any pointer type will also become
823 more apparent (and `void *' is just another pointer-to
824 incomplete type). Assigning alias-set zero to `void *'
825 and all pointer-to incomplete types is a not appealing
826 solution. Assigning an effective alias-set zero only
827 affecting pointers might be - by recording proper subset
828 relationships of all pointer alias-sets.
830 Pointer-to function types are another grey area which
831 needs caution. Globbing them all into one alias-set
832 or the above effective zero set would work.
834 For now just assign the same alias-set to all pointers.
835 That's simple and avoids all the above problems. */
836 else if (POINTER_TYPE_P (t
)
837 && t
!= ptr_type_node
)
838 set
= get_alias_set (ptr_type_node
);
840 /* Otherwise make a new alias set for this type. */
843 /* Each canonical type gets its own alias set, so canonical types
844 shouldn't form a tree. It doesn't really matter for types
845 we handle specially above, so only check it where it possibly
846 would result in a bogus alias set. */
847 gcc_checking_assert (TYPE_CANONICAL (t
) == t
);
849 set
= new_alias_set ();
852 TYPE_ALIAS_SET (t
) = set
;
854 /* If this is an aggregate type or a complex type, we must record any
855 component aliasing information. */
856 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
857 record_component_aliases (t
);
862 /* Return a brand-new alias set. */
867 if (flag_strict_aliasing
)
870 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
871 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
872 return VEC_length (alias_set_entry
, alias_sets
) - 1;
878 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
879 not everything that aliases SUPERSET also aliases SUBSET. For example,
880 in C, a store to an `int' can alias a load of a structure containing an
881 `int', and vice versa. But it can't alias a load of a 'double' member
882 of the same structure. Here, the structure would be the SUPERSET and
883 `int' the SUBSET. This relationship is also described in the comment at
884 the beginning of this file.
886 This function should be called only once per SUPERSET/SUBSET pair.
888 It is illegal for SUPERSET to be zero; everything is implicitly a
889 subset of alias set zero. */
892 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
894 alias_set_entry superset_entry
;
895 alias_set_entry subset_entry
;
897 /* It is possible in complex type situations for both sets to be the same,
898 in which case we can ignore this operation. */
899 if (superset
== subset
)
902 gcc_assert (superset
);
904 superset_entry
= get_alias_set_entry (superset
);
905 if (superset_entry
== 0)
907 /* Create an entry for the SUPERSET, so that we have a place to
908 attach the SUBSET. */
909 superset_entry
= ggc_alloc_cleared_alias_set_entry_d ();
910 superset_entry
->alias_set
= superset
;
911 superset_entry
->children
912 = splay_tree_new_ggc (splay_tree_compare_ints
,
913 ggc_alloc_splay_tree_scalar_scalar_splay_tree_s
,
914 ggc_alloc_splay_tree_scalar_scalar_splay_tree_node_s
);
915 superset_entry
->has_zero_child
= 0;
916 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
920 superset_entry
->has_zero_child
= 1;
923 subset_entry
= get_alias_set_entry (subset
);
924 /* If there is an entry for the subset, enter all of its children
925 (if they are not already present) as children of the SUPERSET. */
928 if (subset_entry
->has_zero_child
)
929 superset_entry
->has_zero_child
= 1;
931 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
932 superset_entry
->children
);
935 /* Enter the SUBSET itself as a child of the SUPERSET. */
936 splay_tree_insert (superset_entry
->children
,
937 (splay_tree_key
) subset
, 0);
941 /* Record that component types of TYPE, if any, are part of that type for
942 aliasing purposes. For record types, we only record component types
943 for fields that are not marked non-addressable. For array types, we
944 only record the component type if it is not marked non-aliased. */
947 record_component_aliases (tree type
)
949 alias_set_type superset
= get_alias_set (type
);
955 switch (TREE_CODE (type
))
959 case QUAL_UNION_TYPE
:
960 /* Recursively record aliases for the base classes, if there are any. */
961 if (TYPE_BINFO (type
))
964 tree binfo
, base_binfo
;
966 for (binfo
= TYPE_BINFO (type
), i
= 0;
967 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
968 record_alias_subset (superset
,
969 get_alias_set (BINFO_TYPE (base_binfo
)));
971 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= DECL_CHAIN (field
))
972 if (TREE_CODE (field
) == FIELD_DECL
&& !DECL_NONADDRESSABLE_P (field
))
973 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
977 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
980 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
988 /* Allocate an alias set for use in storing and reading from the varargs
991 static GTY(()) alias_set_type varargs_set
= -1;
994 get_varargs_alias_set (void)
997 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
998 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
999 consistently use the varargs alias set for loads from the varargs
1000 area. So don't use it anywhere. */
1003 if (varargs_set
== -1)
1004 varargs_set
= new_alias_set ();
1010 /* Likewise, but used for the fixed portions of the frame, e.g., register
1013 static GTY(()) alias_set_type frame_set
= -1;
1016 get_frame_alias_set (void)
1018 if (frame_set
== -1)
1019 frame_set
= new_alias_set ();
1024 /* Create a new, unique base with id ID. */
1027 unique_base_value (HOST_WIDE_INT id
)
1029 return gen_rtx_ADDRESS (Pmode
, id
);
1032 /* Return true if accesses based on any other base value cannot alias
1033 those based on X. */
1036 unique_base_value_p (rtx x
)
1038 return GET_CODE (x
) == ADDRESS
&& GET_MODE (x
) == Pmode
;
1041 /* Return true if X is known to be a base value. */
1044 known_base_value_p (rtx x
)
1046 switch (GET_CODE (x
))
1053 /* Arguments may or may not be bases; we don't know for sure. */
1054 return GET_MODE (x
) != VOIDmode
;
1061 /* Inside SRC, the source of a SET, find a base address. */
1064 find_base_value (rtx src
)
1068 #if defined (FIND_BASE_TERM)
1069 /* Try machine-dependent ways to find the base term. */
1070 src
= FIND_BASE_TERM (src
);
1073 switch (GET_CODE (src
))
1080 regno
= REGNO (src
);
1081 /* At the start of a function, argument registers have known base
1082 values which may be lost later. Returning an ADDRESS
1083 expression here allows optimization based on argument values
1084 even when the argument registers are used for other purposes. */
1085 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
1086 return new_reg_base_value
[regno
];
1088 /* If a pseudo has a known base value, return it. Do not do this
1089 for non-fixed hard regs since it can result in a circular
1090 dependency chain for registers which have values at function entry.
1092 The test above is not sufficient because the scheduler may move
1093 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
1094 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
1095 && regno
< VEC_length (rtx
, reg_base_value
))
1097 /* If we're inside init_alias_analysis, use new_reg_base_value
1098 to reduce the number of relaxation iterations. */
1099 if (new_reg_base_value
&& new_reg_base_value
[regno
]
1100 && DF_REG_DEF_COUNT (regno
) == 1)
1101 return new_reg_base_value
[regno
];
1103 if (VEC_index (rtx
, reg_base_value
, regno
))
1104 return VEC_index (rtx
, reg_base_value
, regno
);
1110 /* Check for an argument passed in memory. Only record in the
1111 copying-arguments block; it is too hard to track changes
1113 if (copying_arguments
1114 && (XEXP (src
, 0) == arg_pointer_rtx
1115 || (GET_CODE (XEXP (src
, 0)) == PLUS
1116 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
1117 return arg_base_value
;
1121 src
= XEXP (src
, 0);
1122 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
1125 /* ... fall through ... */
1130 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
1132 /* If either operand is a REG that is a known pointer, then it
1134 if (REG_P (src_0
) && REG_POINTER (src_0
))
1135 return find_base_value (src_0
);
1136 if (REG_P (src_1
) && REG_POINTER (src_1
))
1137 return find_base_value (src_1
);
1139 /* If either operand is a REG, then see if we already have
1140 a known value for it. */
1143 temp
= find_base_value (src_0
);
1150 temp
= find_base_value (src_1
);
1155 /* If either base is named object or a special address
1156 (like an argument or stack reference), then use it for the
1158 if (src_0
!= 0 && known_base_value_p (src_0
))
1161 if (src_1
!= 0 && known_base_value_p (src_1
))
1164 /* Guess which operand is the base address:
1165 If either operand is a symbol, then it is the base. If
1166 either operand is a CONST_INT, then the other is the base. */
1167 if (CONST_INT_P (src_1
) || CONSTANT_P (src_0
))
1168 return find_base_value (src_0
);
1169 else if (CONST_INT_P (src_0
) || CONSTANT_P (src_1
))
1170 return find_base_value (src_1
);
1176 /* The standard form is (lo_sum reg sym) so look only at the
1178 return find_base_value (XEXP (src
, 1));
1181 /* If the second operand is constant set the base
1182 address to the first operand. */
1183 if (CONST_INT_P (XEXP (src
, 1)) && INTVAL (XEXP (src
, 1)) != 0)
1184 return find_base_value (XEXP (src
, 0));
1188 /* As we do not know which address space the pointer is referring to, we can
1189 handle this only if the target does not support different pointer or
1190 address modes depending on the address space. */
1191 if (!target_default_pointer_address_modes_p ())
1193 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
1203 return find_base_value (XEXP (src
, 0));
1206 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
1207 /* As we do not know which address space the pointer is referring to, we can
1208 handle this only if the target does not support different pointer or
1209 address modes depending on the address space. */
1210 if (!target_default_pointer_address_modes_p ())
1214 rtx temp
= find_base_value (XEXP (src
, 0));
1216 if (temp
!= 0 && CONSTANT_P (temp
))
1217 temp
= convert_memory_address (Pmode
, temp
);
1229 /* Called from init_alias_analysis indirectly through note_stores,
1230 or directly if DEST is a register with a REG_NOALIAS note attached.
1231 SET is null in the latter case. */
1233 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1234 register N has been set in this function. */
1235 static char *reg_seen
;
1238 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
1247 regno
= REGNO (dest
);
1249 gcc_checking_assert (regno
< VEC_length (rtx
, reg_base_value
));
1251 /* If this spans multiple hard registers, then we must indicate that every
1252 register has an unusable value. */
1253 if (regno
< FIRST_PSEUDO_REGISTER
)
1254 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1261 reg_seen
[regno
+ n
] = 1;
1262 new_reg_base_value
[regno
+ n
] = 0;
1269 /* A CLOBBER wipes out any old value but does not prevent a previously
1270 unset register from acquiring a base address (i.e. reg_seen is not
1272 if (GET_CODE (set
) == CLOBBER
)
1274 new_reg_base_value
[regno
] = 0;
1277 src
= SET_SRC (set
);
1281 /* There's a REG_NOALIAS note against DEST. */
1282 if (reg_seen
[regno
])
1284 new_reg_base_value
[regno
] = 0;
1287 reg_seen
[regno
] = 1;
1288 new_reg_base_value
[regno
] = unique_base_value (unique_id
++);
1292 /* If this is not the first set of REGNO, see whether the new value
1293 is related to the old one. There are two cases of interest:
1295 (1) The register might be assigned an entirely new value
1296 that has the same base term as the original set.
1298 (2) The set might be a simple self-modification that
1299 cannot change REGNO's base value.
1301 If neither case holds, reject the original base value as invalid.
1302 Note that the following situation is not detected:
1304 extern int x, y; int *p = &x; p += (&y-&x);
1306 ANSI C does not allow computing the difference of addresses
1307 of distinct top level objects. */
1308 if (new_reg_base_value
[regno
] != 0
1309 && find_base_value (src
) != new_reg_base_value
[regno
])
1310 switch (GET_CODE (src
))
1314 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1315 new_reg_base_value
[regno
] = 0;
1318 /* If the value we add in the PLUS is also a valid base value,
1319 this might be the actual base value, and the original value
1322 rtx other
= NULL_RTX
;
1324 if (XEXP (src
, 0) == dest
)
1325 other
= XEXP (src
, 1);
1326 else if (XEXP (src
, 1) == dest
)
1327 other
= XEXP (src
, 0);
1329 if (! other
|| find_base_value (other
))
1330 new_reg_base_value
[regno
] = 0;
1334 if (XEXP (src
, 0) != dest
|| !CONST_INT_P (XEXP (src
, 1)))
1335 new_reg_base_value
[regno
] = 0;
1338 new_reg_base_value
[regno
] = 0;
1341 /* If this is the first set of a register, record the value. */
1342 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1343 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1344 new_reg_base_value
[regno
] = find_base_value (src
);
1346 reg_seen
[regno
] = 1;
1349 /* Return REG_BASE_VALUE for REGNO. Selective scheduler uses this to avoid
1350 using hard registers with non-null REG_BASE_VALUE for renaming. */
1352 get_reg_base_value (unsigned int regno
)
1354 return VEC_index (rtx
, reg_base_value
, regno
);
1357 /* If a value is known for REGNO, return it. */
1360 get_reg_known_value (unsigned int regno
)
1362 if (regno
>= FIRST_PSEUDO_REGISTER
)
1364 regno
-= FIRST_PSEUDO_REGISTER
;
1365 if (regno
< reg_known_value_size
)
1366 return reg_known_value
[regno
];
1374 set_reg_known_value (unsigned int regno
, rtx val
)
1376 if (regno
>= FIRST_PSEUDO_REGISTER
)
1378 regno
-= FIRST_PSEUDO_REGISTER
;
1379 if (regno
< reg_known_value_size
)
1380 reg_known_value
[regno
] = val
;
1384 /* Similarly for reg_known_equiv_p. */
1387 get_reg_known_equiv_p (unsigned int regno
)
1389 if (regno
>= FIRST_PSEUDO_REGISTER
)
1391 regno
-= FIRST_PSEUDO_REGISTER
;
1392 if (regno
< reg_known_value_size
)
1393 return reg_known_equiv_p
[regno
];
1399 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1401 if (regno
>= FIRST_PSEUDO_REGISTER
)
1403 regno
-= FIRST_PSEUDO_REGISTER
;
1404 if (regno
< reg_known_value_size
)
1405 reg_known_equiv_p
[regno
] = val
;
1410 /* Returns a canonical version of X, from the point of view alias
1411 analysis. (For example, if X is a MEM whose address is a register,
1412 and the register has a known value (say a SYMBOL_REF), then a MEM
1413 whose address is the SYMBOL_REF is returned.) */
1418 /* Recursively look for equivalences. */
1419 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1421 rtx t
= get_reg_known_value (REGNO (x
));
1425 return canon_rtx (t
);
1428 if (GET_CODE (x
) == PLUS
)
1430 rtx x0
= canon_rtx (XEXP (x
, 0));
1431 rtx x1
= canon_rtx (XEXP (x
, 1));
1433 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1435 if (CONST_INT_P (x0
))
1436 return plus_constant (GET_MODE (x
), x1
, INTVAL (x0
));
1437 else if (CONST_INT_P (x1
))
1438 return plus_constant (GET_MODE (x
), x0
, INTVAL (x1
));
1439 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1443 /* This gives us much better alias analysis when called from
1444 the loop optimizer. Note we want to leave the original
1445 MEM alone, but need to return the canonicalized MEM with
1446 all the flags with their original values. */
1448 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1453 /* Return 1 if X and Y are identical-looking rtx's.
1454 Expect that X and Y has been already canonicalized.
1456 We use the data in reg_known_value above to see if two registers with
1457 different numbers are, in fact, equivalent. */
1460 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1467 if (x
== 0 && y
== 0)
1469 if (x
== 0 || y
== 0)
1475 code
= GET_CODE (x
);
1476 /* Rtx's of different codes cannot be equal. */
1477 if (code
!= GET_CODE (y
))
1480 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1481 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1483 if (GET_MODE (x
) != GET_MODE (y
))
1486 /* Some RTL can be compared without a recursive examination. */
1490 return REGNO (x
) == REGNO (y
);
1493 return XEXP (x
, 0) == XEXP (y
, 0);
1496 return XSTR (x
, 0) == XSTR (y
, 0);
1502 /* There's no need to compare the contents of CONST_DOUBLEs or
1503 CONST_INTs because pointer equality is a good enough
1504 comparison for these nodes. */
1511 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1513 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1514 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1515 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1516 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1517 /* For commutative operations, the RTX match if the operand match in any
1518 order. Also handle the simple binary and unary cases without a loop. */
1519 if (COMMUTATIVE_P (x
))
1521 rtx xop0
= canon_rtx (XEXP (x
, 0));
1522 rtx yop0
= canon_rtx (XEXP (y
, 0));
1523 rtx yop1
= canon_rtx (XEXP (y
, 1));
1525 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1526 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1527 || (rtx_equal_for_memref_p (xop0
, yop1
)
1528 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1530 else if (NON_COMMUTATIVE_P (x
))
1532 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1533 canon_rtx (XEXP (y
, 0)))
1534 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1535 canon_rtx (XEXP (y
, 1))));
1537 else if (UNARY_P (x
))
1538 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1539 canon_rtx (XEXP (y
, 0)));
1541 /* Compare the elements. If any pair of corresponding elements
1542 fail to match, return 0 for the whole things.
1544 Limit cases to types which actually appear in addresses. */
1546 fmt
= GET_RTX_FORMAT (code
);
1547 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1552 if (XINT (x
, i
) != XINT (y
, i
))
1557 /* Two vectors must have the same length. */
1558 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1561 /* And the corresponding elements must match. */
1562 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1563 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1564 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1569 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1570 canon_rtx (XEXP (y
, i
))) == 0)
1574 /* This can happen for asm operands. */
1576 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1580 /* This can happen for an asm which clobbers memory. */
1584 /* It is believed that rtx's at this level will never
1585 contain anything but integers and other rtx's,
1586 except for within LABEL_REFs and SYMBOL_REFs. */
1595 find_base_term (rtx x
)
1598 struct elt_loc_list
*l
, *f
;
1601 #if defined (FIND_BASE_TERM)
1602 /* Try machine-dependent ways to find the base term. */
1603 x
= FIND_BASE_TERM (x
);
1606 switch (GET_CODE (x
))
1609 return REG_BASE_VALUE (x
);
1612 /* As we do not know which address space the pointer is referring to, we can
1613 handle this only if the target does not support different pointer or
1614 address modes depending on the address space. */
1615 if (!target_default_pointer_address_modes_p ())
1617 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1627 return find_base_term (XEXP (x
, 0));
1630 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1631 /* As we do not know which address space the pointer is referring to, we can
1632 handle this only if the target does not support different pointer or
1633 address modes depending on the address space. */
1634 if (!target_default_pointer_address_modes_p ())
1638 rtx temp
= find_base_term (XEXP (x
, 0));
1640 if (temp
!= 0 && CONSTANT_P (temp
))
1641 temp
= convert_memory_address (Pmode
, temp
);
1647 val
= CSELIB_VAL_PTR (x
);
1654 /* Temporarily reset val->locs to avoid infinite recursion. */
1657 for (l
= f
; l
; l
= l
->next
)
1658 if (GET_CODE (l
->loc
) == VALUE
1659 && CSELIB_VAL_PTR (l
->loc
)->locs
1660 && !CSELIB_VAL_PTR (l
->loc
)->locs
->next
1661 && CSELIB_VAL_PTR (l
->loc
)->locs
->loc
== x
)
1663 else if ((ret
= find_base_term (l
->loc
)) != 0)
1670 /* The standard form is (lo_sum reg sym) so look only at the
1672 return find_base_term (XEXP (x
, 1));
1676 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1682 rtx tmp1
= XEXP (x
, 0);
1683 rtx tmp2
= XEXP (x
, 1);
1685 /* This is a little bit tricky since we have to determine which of
1686 the two operands represents the real base address. Otherwise this
1687 routine may return the index register instead of the base register.
1689 That may cause us to believe no aliasing was possible, when in
1690 fact aliasing is possible.
1692 We use a few simple tests to guess the base register. Additional
1693 tests can certainly be added. For example, if one of the operands
1694 is a shift or multiply, then it must be the index register and the
1695 other operand is the base register. */
1697 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1698 return find_base_term (tmp2
);
1700 /* If either operand is known to be a pointer, then use it
1701 to determine the base term. */
1702 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1704 rtx base
= find_base_term (tmp1
);
1709 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1711 rtx base
= find_base_term (tmp2
);
1716 /* Neither operand was known to be a pointer. Go ahead and find the
1717 base term for both operands. */
1718 tmp1
= find_base_term (tmp1
);
1719 tmp2
= find_base_term (tmp2
);
1721 /* If either base term is named object or a special address
1722 (like an argument or stack reference), then use it for the
1724 if (tmp1
!= 0 && known_base_value_p (tmp1
))
1727 if (tmp2
!= 0 && known_base_value_p (tmp2
))
1730 /* We could not determine which of the two operands was the
1731 base register and which was the index. So we can determine
1732 nothing from the base alias check. */
1737 if (CONST_INT_P (XEXP (x
, 1)) && INTVAL (XEXP (x
, 1)) != 0)
1738 return find_base_term (XEXP (x
, 0));
1750 /* Return true if accesses to address X may alias accesses based
1751 on the stack pointer. */
1754 may_be_sp_based_p (rtx x
)
1756 rtx base
= find_base_term (x
);
1757 return !base
|| base
== static_reg_base_value
[STACK_POINTER_REGNUM
];
1760 /* Return 0 if the addresses X and Y are known to point to different
1761 objects, 1 if they might be pointers to the same object. */
1764 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1765 enum machine_mode y_mode
)
1767 rtx x_base
= find_base_term (x
);
1768 rtx y_base
= find_base_term (y
);
1770 /* If the address itself has no known base see if a known equivalent
1771 value has one. If either address still has no known base, nothing
1772 is known about aliasing. */
1777 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1780 x_base
= find_base_term (x_c
);
1788 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1791 y_base
= find_base_term (y_c
);
1796 /* If the base addresses are equal nothing is known about aliasing. */
1797 if (rtx_equal_p (x_base
, y_base
))
1800 /* The base addresses are different expressions. If they are not accessed
1801 via AND, there is no conflict. We can bring knowledge of object
1802 alignment into play here. For example, on alpha, "char a, b;" can
1803 alias one another, though "char a; long b;" cannot. AND addesses may
1804 implicitly alias surrounding objects; i.e. unaligned access in DImode
1805 via AND address can alias all surrounding object types except those
1806 with aligment 8 or higher. */
1807 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1809 if (GET_CODE (x
) == AND
1810 && (!CONST_INT_P (XEXP (x
, 1))
1811 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1813 if (GET_CODE (y
) == AND
1814 && (!CONST_INT_P (XEXP (y
, 1))
1815 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1818 /* Differing symbols not accessed via AND never alias. */
1819 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1822 if (unique_base_value_p (x_base
) || unique_base_value_p (y_base
))
1828 /* Callback for for_each_rtx, that returns 1 upon encountering a VALUE
1829 whose UID is greater than the int uid that D points to. */
1832 refs_newer_value_cb (rtx
*x
, void *d
)
1834 if (GET_CODE (*x
) == VALUE
&& CSELIB_VAL_PTR (*x
)->uid
> *(int *)d
)
1840 /* Return TRUE if EXPR refers to a VALUE whose uid is greater than
1844 refs_newer_value_p (rtx expr
, rtx v
)
1846 int minuid
= CSELIB_VAL_PTR (v
)->uid
;
1848 return for_each_rtx (&expr
, refs_newer_value_cb
, &minuid
);
1851 /* Convert the address X into something we can use. This is done by returning
1852 it unchanged unless it is a value; in the latter case we call cselib to get
1853 a more useful rtx. */
1859 struct elt_loc_list
*l
;
1861 if (GET_CODE (x
) != VALUE
)
1863 v
= CSELIB_VAL_PTR (x
);
1866 bool have_equivs
= cselib_have_permanent_equivalences ();
1868 v
= canonical_cselib_val (v
);
1869 for (l
= v
->locs
; l
; l
= l
->next
)
1870 if (CONSTANT_P (l
->loc
))
1872 for (l
= v
->locs
; l
; l
= l
->next
)
1873 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
)
1874 /* Avoid infinite recursion when potentially dealing with
1875 var-tracking artificial equivalences, by skipping the
1876 equivalences themselves, and not choosing expressions
1877 that refer to newer VALUEs. */
1879 || (GET_CODE (l
->loc
) != VALUE
1880 && !refs_newer_value_p (l
->loc
, x
))))
1884 for (l
= v
->locs
; l
; l
= l
->next
)
1886 || (GET_CODE (l
->loc
) != VALUE
1887 && !refs_newer_value_p (l
->loc
, x
)))
1889 /* Return the canonical value. */
1893 return v
->locs
->loc
;
1898 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1899 where SIZE is the size in bytes of the memory reference. If ADDR
1900 is not modified by the memory reference then ADDR is returned. */
1903 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1907 switch (GET_CODE (addr
))
1910 offset
= (n_refs
+ 1) * size
;
1913 offset
= -(n_refs
+ 1) * size
;
1916 offset
= n_refs
* size
;
1919 offset
= -n_refs
* size
;
1927 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1930 addr
= XEXP (addr
, 0);
1931 addr
= canon_rtx (addr
);
1936 /* Return one if X and Y (memory addresses) reference the
1937 same location in memory or if the references overlap.
1938 Return zero if they do not overlap, else return
1939 minus one in which case they still might reference the same location.
1941 C is an offset accumulator. When
1942 C is nonzero, we are testing aliases between X and Y + C.
1943 XSIZE is the size in bytes of the X reference,
1944 similarly YSIZE is the size in bytes for Y.
1945 Expect that canon_rtx has been already called for X and Y.
1947 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1948 referenced (the reference was BLKmode), so make the most pessimistic
1951 If XSIZE or YSIZE is negative, we may access memory outside the object
1952 being referenced as a side effect. This can happen when using AND to
1953 align memory references, as is done on the Alpha.
1955 Nice to notice that varying addresses cannot conflict with fp if no
1956 local variables had their addresses taken, but that's too hard now.
1958 ??? Contrary to the tree alias oracle this does not return
1959 one for X + non-constant and Y + non-constant when X and Y are equal.
1960 If that is fixed the TBAA hack for union type-punning can be removed. */
1963 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1965 if (GET_CODE (x
) == VALUE
)
1969 struct elt_loc_list
*l
= NULL
;
1970 if (CSELIB_VAL_PTR (x
))
1971 for (l
= canonical_cselib_val (CSELIB_VAL_PTR (x
))->locs
;
1973 if (REG_P (l
->loc
) && rtx_equal_for_memref_p (l
->loc
, y
))
1980 /* Don't call get_addr if y is the same VALUE. */
1984 if (GET_CODE (y
) == VALUE
)
1988 struct elt_loc_list
*l
= NULL
;
1989 if (CSELIB_VAL_PTR (y
))
1990 for (l
= canonical_cselib_val (CSELIB_VAL_PTR (y
))->locs
;
1992 if (REG_P (l
->loc
) && rtx_equal_for_memref_p (l
->loc
, x
))
1999 /* Don't call get_addr if x is the same VALUE. */
2003 if (GET_CODE (x
) == HIGH
)
2005 else if (GET_CODE (x
) == LO_SUM
)
2008 x
= addr_side_effect_eval (x
, xsize
, 0);
2009 if (GET_CODE (y
) == HIGH
)
2011 else if (GET_CODE (y
) == LO_SUM
)
2014 y
= addr_side_effect_eval (y
, ysize
, 0);
2016 if (rtx_equal_for_memref_p (x
, y
))
2018 if (xsize
<= 0 || ysize
<= 0)
2020 if (c
>= 0 && xsize
> c
)
2022 if (c
< 0 && ysize
+c
> 0)
2027 /* This code used to check for conflicts involving stack references and
2028 globals but the base address alias code now handles these cases. */
2030 if (GET_CODE (x
) == PLUS
)
2032 /* The fact that X is canonicalized means that this
2033 PLUS rtx is canonicalized. */
2034 rtx x0
= XEXP (x
, 0);
2035 rtx x1
= XEXP (x
, 1);
2037 if (GET_CODE (y
) == PLUS
)
2039 /* The fact that Y is canonicalized means that this
2040 PLUS rtx is canonicalized. */
2041 rtx y0
= XEXP (y
, 0);
2042 rtx y1
= XEXP (y
, 1);
2044 if (rtx_equal_for_memref_p (x1
, y1
))
2045 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
2046 if (rtx_equal_for_memref_p (x0
, y0
))
2047 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
2048 if (CONST_INT_P (x1
))
2050 if (CONST_INT_P (y1
))
2051 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
2052 c
- INTVAL (x1
) + INTVAL (y1
));
2054 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
2057 else if (CONST_INT_P (y1
))
2058 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
2062 else if (CONST_INT_P (x1
))
2063 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
2065 else if (GET_CODE (y
) == PLUS
)
2067 /* The fact that Y is canonicalized means that this
2068 PLUS rtx is canonicalized. */
2069 rtx y0
= XEXP (y
, 0);
2070 rtx y1
= XEXP (y
, 1);
2072 if (CONST_INT_P (y1
))
2073 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
2078 if (GET_CODE (x
) == GET_CODE (y
))
2079 switch (GET_CODE (x
))
2083 /* Handle cases where we expect the second operands to be the
2084 same, and check only whether the first operand would conflict
2087 rtx x1
= canon_rtx (XEXP (x
, 1));
2088 rtx y1
= canon_rtx (XEXP (y
, 1));
2089 if (! rtx_equal_for_memref_p (x1
, y1
))
2091 x0
= canon_rtx (XEXP (x
, 0));
2092 y0
= canon_rtx (XEXP (y
, 0));
2093 if (rtx_equal_for_memref_p (x0
, y0
))
2094 return (xsize
== 0 || ysize
== 0
2095 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
2097 /* Can't properly adjust our sizes. */
2098 if (!CONST_INT_P (x1
))
2100 xsize
/= INTVAL (x1
);
2101 ysize
/= INTVAL (x1
);
2103 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
2110 /* Treat an access through an AND (e.g. a subword access on an Alpha)
2111 as an access with indeterminate size. Assume that references
2112 besides AND are aligned, so if the size of the other reference is
2113 at least as large as the alignment, assume no other overlap. */
2114 if (GET_CODE (x
) == AND
&& CONST_INT_P (XEXP (x
, 1)))
2116 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
2118 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
2120 if (GET_CODE (y
) == AND
&& CONST_INT_P (XEXP (y
, 1)))
2122 /* ??? If we are indexing far enough into the array/structure, we
2123 may yet be able to determine that we can not overlap. But we
2124 also need to that we are far enough from the end not to overlap
2125 a following reference, so we do nothing with that for now. */
2126 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
2128 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
2133 if (CONST_INT_P (x
) && CONST_INT_P (y
))
2135 c
+= (INTVAL (y
) - INTVAL (x
));
2136 return (xsize
<= 0 || ysize
<= 0
2137 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
2140 if (GET_CODE (x
) == CONST
)
2142 if (GET_CODE (y
) == CONST
)
2143 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2144 ysize
, canon_rtx (XEXP (y
, 0)), c
);
2146 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2149 if (GET_CODE (y
) == CONST
)
2150 return memrefs_conflict_p (xsize
, x
, ysize
,
2151 canon_rtx (XEXP (y
, 0)), c
);
2154 return (xsize
<= 0 || ysize
<= 0
2155 || (rtx_equal_for_memref_p (x
, y
)
2156 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
2164 /* Functions to compute memory dependencies.
2166 Since we process the insns in execution order, we can build tables
2167 to keep track of what registers are fixed (and not aliased), what registers
2168 are varying in known ways, and what registers are varying in unknown
2171 If both memory references are volatile, then there must always be a
2172 dependence between the two references, since their order can not be
2173 changed. A volatile and non-volatile reference can be interchanged
2176 We also must allow AND addresses, because they may generate accesses
2177 outside the object being referenced. This is used to generate aligned
2178 addresses from unaligned addresses, for instance, the alpha
2179 storeqi_unaligned pattern. */
2181 /* Read dependence: X is read after read in MEM takes place. There can
2182 only be a dependence here if both reads are volatile. */
2185 read_dependence (const_rtx mem
, const_rtx x
)
2187 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
2190 /* Returns nonzero if something about the mode or address format MEM1
2191 indicates that it might well alias *anything*. */
2194 aliases_everything_p (const_rtx mem
)
2196 if (GET_CODE (XEXP (mem
, 0)) == AND
)
2197 /* If the address is an AND, it's very hard to know at what it is
2198 actually pointing. */
2204 /* Return true if we can determine that the fields referenced cannot
2205 overlap for any pair of objects. */
2208 nonoverlapping_component_refs_p (const_tree x
, const_tree y
)
2210 const_tree fieldx
, fieldy
, typex
, typey
, orig_y
;
2212 if (!flag_strict_aliasing
)
2217 /* The comparison has to be done at a common type, since we don't
2218 know how the inheritance hierarchy works. */
2222 fieldx
= TREE_OPERAND (x
, 1);
2223 typex
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx
));
2228 fieldy
= TREE_OPERAND (y
, 1);
2229 typey
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy
));
2234 y
= TREE_OPERAND (y
, 0);
2236 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
2238 x
= TREE_OPERAND (x
, 0);
2240 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2241 /* Never found a common type. */
2245 /* If we're left with accessing different fields of a structure,
2247 if (TREE_CODE (typex
) == RECORD_TYPE
2248 && fieldx
!= fieldy
)
2251 /* The comparison on the current field failed. If we're accessing
2252 a very nested structure, look at the next outer level. */
2253 x
= TREE_OPERAND (x
, 0);
2254 y
= TREE_OPERAND (y
, 0);
2257 && TREE_CODE (x
) == COMPONENT_REF
2258 && TREE_CODE (y
) == COMPONENT_REF
);
2263 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2266 decl_for_component_ref (tree x
)
2270 x
= TREE_OPERAND (x
, 0);
2272 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2274 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
2277 /* Walk up the COMPONENT_REF list in X and adjust *OFFSET to compensate
2278 for the offset of the field reference. *KNOWN_P says whether the
2282 adjust_offset_for_component_ref (tree x
, bool *known_p
,
2283 HOST_WIDE_INT
*offset
)
2289 tree xoffset
= component_ref_field_offset (x
);
2290 tree field
= TREE_OPERAND (x
, 1);
2292 if (! host_integerp (xoffset
, 1))
2297 *offset
+= (tree_low_cst (xoffset
, 1)
2298 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
2301 x
= TREE_OPERAND (x
, 0);
2303 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2306 /* Return nonzero if we can determine the exprs corresponding to memrefs
2307 X and Y and they do not overlap.
2308 If LOOP_VARIANT is set, skip offset-based disambiguation */
2311 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
, bool loop_invariant
)
2313 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
2316 bool moffsetx_known_p
, moffsety_known_p
;
2317 HOST_WIDE_INT moffsetx
= 0, moffsety
= 0;
2318 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
2320 /* Unless both have exprs, we can't tell anything. */
2321 if (exprx
== 0 || expry
== 0)
2324 /* For spill-slot accesses make sure we have valid offsets. */
2325 if ((exprx
== get_spill_slot_decl (false)
2326 && ! MEM_OFFSET_KNOWN_P (x
))
2327 || (expry
== get_spill_slot_decl (false)
2328 && ! MEM_OFFSET_KNOWN_P (y
)))
2331 /* If both are field references, we may be able to determine something. */
2332 if (TREE_CODE (exprx
) == COMPONENT_REF
2333 && TREE_CODE (expry
) == COMPONENT_REF
2334 && nonoverlapping_component_refs_p (exprx
, expry
))
2338 /* If the field reference test failed, look at the DECLs involved. */
2339 moffsetx_known_p
= MEM_OFFSET_KNOWN_P (x
);
2340 if (moffsetx_known_p
)
2341 moffsetx
= MEM_OFFSET (x
);
2342 if (TREE_CODE (exprx
) == COMPONENT_REF
)
2344 tree t
= decl_for_component_ref (exprx
);
2347 adjust_offset_for_component_ref (exprx
, &moffsetx_known_p
, &moffsetx
);
2351 moffsety_known_p
= MEM_OFFSET_KNOWN_P (y
);
2352 if (moffsety_known_p
)
2353 moffsety
= MEM_OFFSET (y
);
2354 if (TREE_CODE (expry
) == COMPONENT_REF
)
2356 tree t
= decl_for_component_ref (expry
);
2359 adjust_offset_for_component_ref (expry
, &moffsety_known_p
, &moffsety
);
2363 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2366 /* With invalid code we can end up storing into the constant pool.
2367 Bail out to avoid ICEing when creating RTL for this.
2368 See gfortran.dg/lto/20091028-2_0.f90. */
2369 if (TREE_CODE (exprx
) == CONST_DECL
2370 || TREE_CODE (expry
) == CONST_DECL
)
2373 rtlx
= DECL_RTL (exprx
);
2374 rtly
= DECL_RTL (expry
);
2376 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2377 can't overlap unless they are the same because we never reuse that part
2378 of the stack frame used for locals for spilled pseudos. */
2379 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2380 && ! rtx_equal_p (rtlx
, rtly
))
2383 /* If we have MEMs referring to different address spaces (which can
2384 potentially overlap), we cannot easily tell from the addresses
2385 whether the references overlap. */
2386 if (MEM_P (rtlx
) && MEM_P (rtly
)
2387 && MEM_ADDR_SPACE (rtlx
) != MEM_ADDR_SPACE (rtly
))
2390 /* Get the base and offsets of both decls. If either is a register, we
2391 know both are and are the same, so use that as the base. The only
2392 we can avoid overlap is if we can deduce that they are nonoverlapping
2393 pieces of that decl, which is very rare. */
2394 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2395 if (GET_CODE (basex
) == PLUS
&& CONST_INT_P (XEXP (basex
, 1)))
2396 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2398 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2399 if (GET_CODE (basey
) == PLUS
&& CONST_INT_P (XEXP (basey
, 1)))
2400 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2402 /* If the bases are different, we know they do not overlap if both
2403 are constants or if one is a constant and the other a pointer into the
2404 stack frame. Otherwise a different base means we can't tell if they
2406 if (! rtx_equal_p (basex
, basey
))
2407 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2408 || (CONSTANT_P (basex
) && REG_P (basey
)
2409 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2410 || (CONSTANT_P (basey
) && REG_P (basex
)
2411 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2413 /* Offset based disambiguation not appropriate for loop invariant */
2417 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2418 : MEM_SIZE_KNOWN_P (rtlx
) ? MEM_SIZE (rtlx
)
2420 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2421 : MEM_SIZE_KNOWN_P (rtly
) ? MEM_SIZE (rtly
)
2424 /* If we have an offset for either memref, it can update the values computed
2426 if (moffsetx_known_p
)
2427 offsetx
+= moffsetx
, sizex
-= moffsetx
;
2428 if (moffsety_known_p
)
2429 offsety
+= moffsety
, sizey
-= moffsety
;
2431 /* If a memref has both a size and an offset, we can use the smaller size.
2432 We can't do this if the offset isn't known because we must view this
2433 memref as being anywhere inside the DECL's MEM. */
2434 if (MEM_SIZE_KNOWN_P (x
) && moffsetx_known_p
)
2435 sizex
= MEM_SIZE (x
);
2436 if (MEM_SIZE_KNOWN_P (y
) && moffsety_known_p
)
2437 sizey
= MEM_SIZE (y
);
2439 /* Put the values of the memref with the lower offset in X's values. */
2440 if (offsetx
> offsety
)
2442 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2443 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2446 /* If we don't know the size of the lower-offset value, we can't tell
2447 if they conflict. Otherwise, we do the test. */
2448 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2451 /* Helper for true_dependence and canon_true_dependence.
2452 Checks for true dependence: X is read after store in MEM takes place.
2454 If MEM_CANONICALIZED is FALSE, then X_ADDR and MEM_ADDR should be
2455 NULL_RTX, and the canonical addresses of MEM and X are both computed
2456 here. If MEM_CANONICALIZED, then MEM must be already canonicalized.
2458 If X_ADDR is non-NULL, it is used in preference of XEXP (x, 0).
2460 Returns 1 if there is a true dependence, 0 otherwise. */
2463 true_dependence_1 (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2464 const_rtx x
, rtx x_addr
, bool mem_canonicalized
)
2469 gcc_checking_assert (mem_canonicalized
? (mem_addr
!= NULL_RTX
)
2470 : (mem_addr
== NULL_RTX
&& x_addr
== NULL_RTX
));
2472 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2475 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2476 This is used in epilogue deallocation functions, and in cselib. */
2477 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2479 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2481 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2482 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2485 /* Read-only memory is by definition never modified, and therefore can't
2486 conflict with anything. We don't expect to find read-only set on MEM,
2487 but stupid user tricks can produce them, so don't die. */
2488 if (MEM_READONLY_P (x
))
2491 /* If we have MEMs referring to different address spaces (which can
2492 potentially overlap), we cannot easily tell from the addresses
2493 whether the references overlap. */
2494 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2499 mem_addr
= XEXP (mem
, 0);
2500 if (mem_mode
== VOIDmode
)
2501 mem_mode
= GET_MODE (mem
);
2506 x_addr
= XEXP (x
, 0);
2507 if (!((GET_CODE (x_addr
) == VALUE
2508 && GET_CODE (mem_addr
) != VALUE
2509 && reg_mentioned_p (x_addr
, mem_addr
))
2510 || (GET_CODE (x_addr
) != VALUE
2511 && GET_CODE (mem_addr
) == VALUE
2512 && reg_mentioned_p (mem_addr
, x_addr
))))
2514 x_addr
= get_addr (x_addr
);
2515 if (! mem_canonicalized
)
2516 mem_addr
= get_addr (mem_addr
);
2520 base
= find_base_term (x_addr
);
2521 if (base
&& (GET_CODE (base
) == LABEL_REF
2522 || (GET_CODE (base
) == SYMBOL_REF
2523 && CONSTANT_POOL_ADDRESS_P (base
))))
2526 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2529 x_addr
= canon_rtx (x_addr
);
2530 if (!mem_canonicalized
)
2531 mem_addr
= canon_rtx (mem_addr
);
2533 if ((ret
= memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2534 SIZE_FOR_MODE (x
), x_addr
, 0)) != -1)
2537 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2540 if (nonoverlapping_memrefs_p (mem
, x
, false))
2543 if (aliases_everything_p (x
))
2546 /* We cannot use aliases_everything_p to test MEM, since we must look
2547 at MEM_ADDR, rather than XEXP (mem, 0). */
2548 if (GET_CODE (mem_addr
) == AND
)
2551 /* ??? In true_dependence we also allow BLKmode to alias anything. Why
2552 don't we do this in anti_dependence and output_dependence? */
2553 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2556 return rtx_refs_may_alias_p (x
, mem
, true);
2559 /* True dependence: X is read after store in MEM takes place. */
2562 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
)
2564 return true_dependence_1 (mem
, mem_mode
, NULL_RTX
,
2565 x
, NULL_RTX
, /*mem_canonicalized=*/false);
2568 /* Canonical true dependence: X is read after store in MEM takes place.
2569 Variant of true_dependence which assumes MEM has already been
2570 canonicalized (hence we no longer do that here).
2571 The mem_addr argument has been added, since true_dependence_1 computed
2572 this value prior to canonicalizing. */
2575 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2576 const_rtx x
, rtx x_addr
)
2578 return true_dependence_1 (mem
, mem_mode
, mem_addr
,
2579 x
, x_addr
, /*mem_canonicalized=*/true);
2582 /* Returns nonzero if a write to X might alias a previous read from
2583 (or, if WRITEP is nonzero, a write to) MEM. */
2586 write_dependence_p (const_rtx mem
, const_rtx x
, int writep
)
2588 rtx x_addr
, mem_addr
;
2592 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2595 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2596 This is used in epilogue deallocation functions. */
2597 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2599 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2601 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2602 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2605 /* A read from read-only memory can't conflict with read-write memory. */
2606 if (!writep
&& MEM_READONLY_P (mem
))
2609 /* If we have MEMs referring to different address spaces (which can
2610 potentially overlap), we cannot easily tell from the addresses
2611 whether the references overlap. */
2612 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2615 x_addr
= XEXP (x
, 0);
2616 mem_addr
= XEXP (mem
, 0);
2617 if (!((GET_CODE (x_addr
) == VALUE
2618 && GET_CODE (mem_addr
) != VALUE
2619 && reg_mentioned_p (x_addr
, mem_addr
))
2620 || (GET_CODE (x_addr
) != VALUE
2621 && GET_CODE (mem_addr
) == VALUE
2622 && reg_mentioned_p (mem_addr
, x_addr
))))
2624 x_addr
= get_addr (x_addr
);
2625 mem_addr
= get_addr (mem_addr
);
2630 base
= find_base_term (mem_addr
);
2631 if (base
&& (GET_CODE (base
) == LABEL_REF
2632 || (GET_CODE (base
) == SYMBOL_REF
2633 && CONSTANT_POOL_ADDRESS_P (base
))))
2637 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2641 x_addr
= canon_rtx (x_addr
);
2642 mem_addr
= canon_rtx (mem_addr
);
2644 if ((ret
= memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2645 SIZE_FOR_MODE (x
), x_addr
, 0)) != -1)
2648 if (nonoverlapping_memrefs_p (x
, mem
, false))
2651 return rtx_refs_may_alias_p (x
, mem
, false);
2654 /* Anti dependence: X is written after read in MEM takes place. */
2657 anti_dependence (const_rtx mem
, const_rtx x
)
2659 return write_dependence_p (mem
, x
, /*writep=*/0);
2662 /* Output dependence: X is written after store in MEM takes place. */
2665 output_dependence (const_rtx mem
, const_rtx x
)
2667 return write_dependence_p (mem
, x
, /*writep=*/1);
2672 /* Check whether X may be aliased with MEM. Don't do offset-based
2673 memory disambiguation & TBAA. */
2675 may_alias_p (const_rtx mem
, const_rtx x
)
2677 rtx x_addr
, mem_addr
;
2679 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2682 /* ??? In true_dependence we also allow BLKmode to alias anything. */
2683 if (GET_MODE (mem
) == BLKmode
|| GET_MODE (x
) == BLKmode
)
2686 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2687 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2690 /* Read-only memory is by definition never modified, and therefore can't
2691 conflict with anything. We don't expect to find read-only set on MEM,
2692 but stupid user tricks can produce them, so don't die. */
2693 if (MEM_READONLY_P (x
))
2696 /* If we have MEMs referring to different address spaces (which can
2697 potentially overlap), we cannot easily tell from the addresses
2698 whether the references overlap. */
2699 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2702 x_addr
= XEXP (x
, 0);
2703 mem_addr
= XEXP (mem
, 0);
2704 if (!((GET_CODE (x_addr
) == VALUE
2705 && GET_CODE (mem_addr
) != VALUE
2706 && reg_mentioned_p (x_addr
, mem_addr
))
2707 || (GET_CODE (x_addr
) != VALUE
2708 && GET_CODE (mem_addr
) == VALUE
2709 && reg_mentioned_p (mem_addr
, x_addr
))))
2711 x_addr
= get_addr (x_addr
);
2712 mem_addr
= get_addr (mem_addr
);
2715 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), GET_MODE (mem_addr
)))
2718 x_addr
= canon_rtx (x_addr
);
2719 mem_addr
= canon_rtx (mem_addr
);
2721 if (nonoverlapping_memrefs_p (mem
, x
, true))
2724 if (aliases_everything_p (x
))
2727 /* We cannot use aliases_everything_p to test MEM, since we must look
2728 at MEM_ADDR, rather than XEXP (mem, 0). */
2729 if (GET_CODE (mem_addr
) == AND
)
2732 /* TBAA not valid for loop_invarint */
2733 return rtx_refs_may_alias_p (x
, mem
, false);
2737 init_alias_target (void)
2741 if (!arg_base_value
)
2742 arg_base_value
= gen_rtx_ADDRESS (VOIDmode
, 0);
2744 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2746 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2747 /* Check whether this register can hold an incoming pointer
2748 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2749 numbers, so translate if necessary due to register windows. */
2750 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2751 && HARD_REGNO_MODE_OK (i
, Pmode
))
2752 static_reg_base_value
[i
] = arg_base_value
;
2754 static_reg_base_value
[STACK_POINTER_REGNUM
]
2755 = unique_base_value (UNIQUE_BASE_VALUE_SP
);
2756 static_reg_base_value
[ARG_POINTER_REGNUM
]
2757 = unique_base_value (UNIQUE_BASE_VALUE_ARGP
);
2758 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2759 = unique_base_value (UNIQUE_BASE_VALUE_FP
);
2760 #if !HARD_FRAME_POINTER_IS_FRAME_POINTER
2761 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2762 = unique_base_value (UNIQUE_BASE_VALUE_HFP
);
2766 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2767 to be memory reference. */
2768 static bool memory_modified
;
2770 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2774 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2775 memory_modified
= true;
2780 /* Return true when INSN possibly modify memory contents of MEM
2781 (i.e. address can be modified). */
2783 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2787 memory_modified
= false;
2788 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2789 return memory_modified
;
2792 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2796 init_alias_analysis (void)
2798 unsigned int maxreg
= max_reg_num ();
2804 timevar_push (TV_ALIAS_ANALYSIS
);
2806 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2807 reg_known_value
= ggc_alloc_cleared_vec_rtx (reg_known_value_size
);
2808 reg_known_equiv_p
= XCNEWVEC (bool, reg_known_value_size
);
2810 /* If we have memory allocated from the previous run, use it. */
2811 if (old_reg_base_value
)
2812 reg_base_value
= old_reg_base_value
;
2815 VEC_truncate (rtx
, reg_base_value
, 0);
2817 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2819 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2820 reg_seen
= XNEWVEC (char, maxreg
);
2822 /* The basic idea is that each pass through this loop will use the
2823 "constant" information from the previous pass to propagate alias
2824 information through another level of assignments.
2826 This could get expensive if the assignment chains are long. Maybe
2827 we should throttle the number of iterations, possibly based on
2828 the optimization level or flag_expensive_optimizations.
2830 We could propagate more information in the first pass by making use
2831 of DF_REG_DEF_COUNT to determine immediately that the alias information
2832 for a pseudo is "constant".
2834 A program with an uninitialized variable can cause an infinite loop
2835 here. Instead of doing a full dataflow analysis to detect such problems
2836 we just cap the number of iterations for the loop.
2838 The state of the arrays for the set chain in question does not matter
2839 since the program has undefined behavior. */
2844 /* Assume nothing will change this iteration of the loop. */
2847 /* We want to assign the same IDs each iteration of this loop, so
2848 start counting from one each iteration of the loop. */
2851 /* We're at the start of the function each iteration through the
2852 loop, so we're copying arguments. */
2853 copying_arguments
= true;
2855 /* Wipe the potential alias information clean for this pass. */
2856 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2858 /* Wipe the reg_seen array clean. */
2859 memset (reg_seen
, 0, maxreg
);
2861 /* Mark all hard registers which may contain an address.
2862 The stack, frame and argument pointers may contain an address.
2863 An argument register which can hold a Pmode value may contain
2864 an address even if it is not in BASE_REGS.
2866 The address expression is VOIDmode for an argument and
2867 Pmode for other registers. */
2869 memcpy (new_reg_base_value
, static_reg_base_value
,
2870 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2872 /* Walk the insns adding values to the new_reg_base_value array. */
2873 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2879 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2880 /* The prologue/epilogue insns are not threaded onto the
2881 insn chain until after reload has completed. Thus,
2882 there is no sense wasting time checking if INSN is in
2883 the prologue/epilogue until after reload has completed. */
2884 if (reload_completed
2885 && prologue_epilogue_contains (insn
))
2889 /* If this insn has a noalias note, process it, Otherwise,
2890 scan for sets. A simple set will have no side effects
2891 which could change the base value of any other register. */
2893 if (GET_CODE (PATTERN (insn
)) == SET
2894 && REG_NOTES (insn
) != 0
2895 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2896 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2898 note_stores (PATTERN (insn
), record_set
, NULL
);
2900 set
= single_set (insn
);
2903 && REG_P (SET_DEST (set
))
2904 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2906 unsigned int regno
= REGNO (SET_DEST (set
));
2907 rtx src
= SET_SRC (set
);
2910 note
= find_reg_equal_equiv_note (insn
);
2911 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2912 && DF_REG_DEF_COUNT (regno
) != 1)
2915 if (note
!= NULL_RTX
2916 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2917 && ! rtx_varies_p (XEXP (note
, 0), 1)
2918 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2921 set_reg_known_value (regno
, XEXP (note
, 0));
2922 set_reg_known_equiv_p (regno
,
2923 REG_NOTE_KIND (note
) == REG_EQUIV
);
2925 else if (DF_REG_DEF_COUNT (regno
) == 1
2926 && GET_CODE (src
) == PLUS
2927 && REG_P (XEXP (src
, 0))
2928 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2929 && CONST_INT_P (XEXP (src
, 1)))
2931 t
= plus_constant (GET_MODE (src
), t
,
2932 INTVAL (XEXP (src
, 1)));
2933 set_reg_known_value (regno
, t
);
2934 set_reg_known_equiv_p (regno
, 0);
2936 else if (DF_REG_DEF_COUNT (regno
) == 1
2937 && ! rtx_varies_p (src
, 1))
2939 set_reg_known_value (regno
, src
);
2940 set_reg_known_equiv_p (regno
, 0);
2944 else if (NOTE_P (insn
)
2945 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2946 copying_arguments
= false;
2949 /* Now propagate values from new_reg_base_value to reg_base_value. */
2950 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2952 for (ui
= 0; ui
< maxreg
; ui
++)
2954 if (new_reg_base_value
[ui
]
2955 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2956 && ! rtx_equal_p (new_reg_base_value
[ui
],
2957 VEC_index (rtx
, reg_base_value
, ui
)))
2959 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2964 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2966 /* Fill in the remaining entries. */
2967 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2968 if (reg_known_value
[i
] == 0)
2969 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2972 free (new_reg_base_value
);
2973 new_reg_base_value
= 0;
2976 timevar_pop (TV_ALIAS_ANALYSIS
);
2979 /* Equate REG_BASE_VALUE (reg1) to REG_BASE_VALUE (reg2).
2980 Special API for var-tracking pass purposes. */
2983 vt_equate_reg_base_value (const_rtx reg1
, const_rtx reg2
)
2985 VEC_replace (rtx
, reg_base_value
, REGNO (reg1
), REG_BASE_VALUE (reg2
));
2989 end_alias_analysis (void)
2991 old_reg_base_value
= reg_base_value
;
2992 ggc_free (reg_known_value
);
2993 reg_known_value
= 0;
2994 reg_known_value_size
= 0;
2995 free (reg_known_equiv_p
);
2996 reg_known_equiv_p
= 0;
2999 #include "gt-alias.h"