1 /* Alias analysis for GNU C
2 Copyright (C) 1997-2014 Free Software Foundation, Inc.
3 Contributed by John Carr (jfc@mit.edu).
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 3, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
34 #include "hard-reg-set.h"
36 #include "diagnostic-core.h"
38 #include "splay-tree.h"
39 #include "langhooks.h"
44 #include "tree-ssa-alias.h"
45 #include "internal-fn.h"
46 #include "gimple-expr.h"
49 #include "gimple-ssa.h"
52 /* The aliasing API provided here solves related but different problems:
54 Say there exists (in c)
68 Consider the four questions:
70 Can a store to x1 interfere with px2->y1?
71 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 through 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 questions can be solved in the same way as the first
83 two questions but this is too conservative. The observation is
84 that in some cases we can know which (if any) fields are addressed
85 and if those addresses are used in bad ways. This analysis may be
86 language specific. In C, arbitrary operations may be applied to
87 pointers. However, there is some indication that this may be too
88 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 that 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 questions is similar to
97 the first, but does not contain the fields whose address are never
98 taken. For types that do escape the compilation unit, the data
99 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
, 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 tree
decl_for_component_ref (tree
);
161 static int write_dependence_p (const_rtx
,
162 const_rtx
, enum machine_mode
, rtx
,
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 /* Cap the number of passes we make over the insns propagating alias
173 information through set chains.
174 ??? 10 is a completely arbitrary choice. This should be based on the
175 maximum loop depth in the CFG, but we do not have this information
176 available (even if current_loops _is_ available). */
177 #define MAX_ALIAS_LOOP_PASSES 10
179 /* reg_base_value[N] gives an address to which register N is related.
180 If all sets after the first add or subtract to the current value
181 or otherwise modify it so it does not point to a different top level
182 object, reg_base_value[N] is equal to the address part of the source
185 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
186 expressions represent three types of base:
188 1. incoming arguments. There is just one ADDRESS to represent all
189 arguments, since we do not know at this level whether accesses
190 based on different arguments can alias. The ADDRESS has id 0.
192 2. stack_pointer_rtx, frame_pointer_rtx, hard_frame_pointer_rtx
193 (if distinct from frame_pointer_rtx) and arg_pointer_rtx.
194 Each of these rtxes has a separate ADDRESS associated with it,
195 each with a negative id.
197 GCC is (and is required to be) precise in which register it
198 chooses to access a particular region of stack. We can therefore
199 assume that accesses based on one of these rtxes do not alias
200 accesses based on another of these rtxes.
202 3. bases that are derived from malloc()ed memory (REG_NOALIAS).
203 Each such piece of memory has a separate ADDRESS associated
204 with it, each with an id greater than 0.
206 Accesses based on one ADDRESS do not alias accesses based on other
207 ADDRESSes. Accesses based on ADDRESSes in groups (2) and (3) do not
208 alias globals either; the ADDRESSes have Pmode to indicate this.
209 The ADDRESS in group (1) _may_ alias globals; it has VOIDmode to
212 static GTY(()) vec
<rtx
, va_gc
> *reg_base_value
;
213 static rtx
*new_reg_base_value
;
215 /* The single VOIDmode ADDRESS that represents all argument bases.
217 static GTY(()) rtx arg_base_value
;
219 /* Used to allocate unique ids to each REG_NOALIAS ADDRESS. */
220 static int unique_id
;
222 /* We preserve the copy of old array around to avoid amount of garbage
223 produced. About 8% of garbage produced were attributed to this
225 static GTY((deletable
)) vec
<rtx
, va_gc
> *old_reg_base_value
;
227 /* Values of XINT (address, 0) of Pmode ADDRESS rtxes for special
229 #define UNIQUE_BASE_VALUE_SP -1
230 #define UNIQUE_BASE_VALUE_ARGP -2
231 #define UNIQUE_BASE_VALUE_FP -3
232 #define UNIQUE_BASE_VALUE_HFP -4
234 #define static_reg_base_value \
235 (this_target_rtl->x_static_reg_base_value)
237 #define REG_BASE_VALUE(X) \
238 (REGNO (X) < vec_safe_length (reg_base_value) \
239 ? (*reg_base_value)[REGNO (X)] : 0)
241 /* Vector indexed by N giving the initial (unchanging) value known for
242 pseudo-register N. This vector is initialized in init_alias_analysis,
243 and does not change until end_alias_analysis is called. */
244 static GTY(()) vec
<rtx
, va_gc
> *reg_known_value
;
246 /* Vector recording for each reg_known_value whether it is due to a
247 REG_EQUIV note. Future passes (viz., reload) may replace the
248 pseudo with the equivalent expression and so we account for the
249 dependences that would be introduced if that happens.
251 The REG_EQUIV notes created in assign_parms may mention the arg
252 pointer, and there are explicit insns in the RTL that modify the
253 arg pointer. Thus we must ensure that such insns don't get
254 scheduled across each other because that would invalidate the
255 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
256 wrong, but solving the problem in the scheduler will likely give
257 better code, so we do it here. */
258 static sbitmap reg_known_equiv_p
;
260 /* True when scanning insns from the start of the rtl to the
261 NOTE_INSN_FUNCTION_BEG note. */
262 static bool copying_arguments
;
265 /* The splay-tree used to store the various alias set entries. */
266 static GTY (()) vec
<alias_set_entry
, va_gc
> *alias_sets
;
268 /* Build a decomposed reference object for querying the alias-oracle
269 from the MEM rtx and store it in *REF.
270 Returns false if MEM is not suitable for the alias-oracle. */
273 ao_ref_from_mem (ao_ref
*ref
, const_rtx mem
)
275 tree expr
= MEM_EXPR (mem
);
281 ao_ref_init (ref
, expr
);
283 /* Get the base of the reference and see if we have to reject or
285 base
= ao_ref_base (ref
);
286 if (base
== NULL_TREE
)
289 /* The tree oracle doesn't like bases that are neither decls
290 nor indirect references of SSA names. */
292 || (TREE_CODE (base
) == MEM_REF
293 && TREE_CODE (TREE_OPERAND (base
, 0)) == SSA_NAME
)
294 || (TREE_CODE (base
) == TARGET_MEM_REF
295 && TREE_CODE (TMR_BASE (base
)) == SSA_NAME
)))
298 /* If this is a reference based on a partitioned decl replace the
299 base with a MEM_REF of the pointer representative we
300 created during stack slot partitioning. */
301 if (TREE_CODE (base
) == VAR_DECL
302 && ! is_global_var (base
)
303 && cfun
->gimple_df
->decls_to_pointers
!= NULL
)
305 tree
*namep
= cfun
->gimple_df
->decls_to_pointers
->get (base
);
307 ref
->base
= build_simple_mem_ref (*namep
);
310 ref
->ref_alias_set
= MEM_ALIAS_SET (mem
);
312 /* If MEM_OFFSET or MEM_SIZE are unknown what we got from MEM_EXPR
313 is conservative, so trust it. */
314 if (!MEM_OFFSET_KNOWN_P (mem
)
315 || !MEM_SIZE_KNOWN_P (mem
))
318 /* If the base decl is a parameter we can have negative MEM_OFFSET in
319 case of promoted subregs on bigendian targets. Trust the MEM_EXPR
321 if (MEM_OFFSET (mem
) < 0
322 && (MEM_SIZE (mem
) + MEM_OFFSET (mem
)) * BITS_PER_UNIT
== ref
->size
)
325 /* Otherwise continue and refine size and offset we got from analyzing
326 MEM_EXPR by using MEM_SIZE and MEM_OFFSET. */
328 ref
->offset
+= MEM_OFFSET (mem
) * BITS_PER_UNIT
;
329 ref
->size
= MEM_SIZE (mem
) * BITS_PER_UNIT
;
331 /* The MEM may extend into adjacent fields, so adjust max_size if
333 if (ref
->max_size
!= -1
334 && ref
->size
> ref
->max_size
)
335 ref
->max_size
= ref
->size
;
337 /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of
338 the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */
339 if (MEM_EXPR (mem
) != get_spill_slot_decl (false)
341 || (DECL_P (ref
->base
)
342 && (DECL_SIZE (ref
->base
) == NULL_TREE
343 || TREE_CODE (DECL_SIZE (ref
->base
)) != INTEGER_CST
344 || wi::ltu_p (wi::to_offset (DECL_SIZE (ref
->base
)),
345 ref
->offset
+ ref
->size
)))))
351 /* Query the alias-oracle on whether the two memory rtx X and MEM may
352 alias. If TBAA_P is set also apply TBAA. Returns true if the
353 two rtxen may alias, false otherwise. */
356 rtx_refs_may_alias_p (const_rtx x
, const_rtx mem
, bool tbaa_p
)
360 if (!ao_ref_from_mem (&ref1
, x
)
361 || !ao_ref_from_mem (&ref2
, mem
))
364 return refs_may_alias_p_1 (&ref1
, &ref2
,
366 && MEM_ALIAS_SET (x
) != 0
367 && MEM_ALIAS_SET (mem
) != 0);
370 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
371 such an entry, or NULL otherwise. */
373 static inline alias_set_entry
374 get_alias_set_entry (alias_set_type alias_set
)
376 return (*alias_sets
)[alias_set
];
379 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
380 the two MEMs cannot alias each other. */
383 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
385 /* Perform a basic sanity check. Namely, that there are no alias sets
386 if we're not using strict aliasing. This helps to catch bugs
387 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
388 where a MEM is allocated in some way other than by the use of
389 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
390 use alias sets to indicate that spilled registers cannot alias each
391 other, we might need to remove this check. */
392 gcc_assert (flag_strict_aliasing
393 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
395 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
398 /* Insert the NODE into the splay tree given by DATA. Used by
399 record_alias_subset via splay_tree_foreach. */
402 insert_subset_children (splay_tree_node node
, void *data
)
404 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
409 /* Return true if the first alias set is a subset of the second. */
412 alias_set_subset_of (alias_set_type set1
, alias_set_type set2
)
416 /* Everything is a subset of the "aliases everything" set. */
420 /* Otherwise, check if set1 is a subset of set2. */
421 ase
= get_alias_set_entry (set2
);
423 && (ase
->has_zero_child
424 || splay_tree_lookup (ase
->children
,
425 (splay_tree_key
) set1
)))
430 /* Return 1 if the two specified alias sets may conflict. */
433 alias_sets_conflict_p (alias_set_type set1
, alias_set_type set2
)
438 if (alias_sets_must_conflict_p (set1
, set2
))
441 /* See if the first alias set is a subset of the second. */
442 ase
= get_alias_set_entry (set1
);
444 && (ase
->has_zero_child
445 || splay_tree_lookup (ase
->children
,
446 (splay_tree_key
) set2
)))
449 /* Now do the same, but with the alias sets reversed. */
450 ase
= get_alias_set_entry (set2
);
452 && (ase
->has_zero_child
453 || splay_tree_lookup (ase
->children
,
454 (splay_tree_key
) set1
)))
457 /* The two alias sets are distinct and neither one is the
458 child of the other. Therefore, they cannot conflict. */
462 /* Return 1 if the two specified alias sets will always conflict. */
465 alias_sets_must_conflict_p (alias_set_type set1
, alias_set_type set2
)
467 if (set1
== 0 || set2
== 0 || set1
== set2
)
473 /* Return 1 if any MEM object of type T1 will always conflict (using the
474 dependency routines in this file) with any MEM object of type T2.
475 This is used when allocating temporary storage. If T1 and/or T2 are
476 NULL_TREE, it means we know nothing about the storage. */
479 objects_must_conflict_p (tree t1
, tree t2
)
481 alias_set_type set1
, set2
;
483 /* If neither has a type specified, we don't know if they'll conflict
484 because we may be using them to store objects of various types, for
485 example the argument and local variables areas of inlined functions. */
486 if (t1
== 0 && t2
== 0)
489 /* If they are the same type, they must conflict. */
491 /* Likewise if both are volatile. */
492 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
495 set1
= t1
? get_alias_set (t1
) : 0;
496 set2
= t2
? get_alias_set (t2
) : 0;
498 /* We can't use alias_sets_conflict_p because we must make sure
499 that every subtype of t1 will conflict with every subtype of
500 t2 for which a pair of subobjects of these respective subtypes
501 overlaps on the stack. */
502 return alias_sets_must_conflict_p (set1
, set2
);
505 /* Return the outermost parent of component present in the chain of
506 component references handled by get_inner_reference in T with the
508 - the component is non-addressable, or
509 - the parent has alias set zero,
510 or NULL_TREE if no such parent exists. In the former cases, the alias
511 set of this parent is the alias set that must be used for T itself. */
514 component_uses_parent_alias_set_from (const_tree t
)
516 const_tree found
= NULL_TREE
;
518 while (handled_component_p (t
))
520 switch (TREE_CODE (t
))
523 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1)))
528 case ARRAY_RANGE_REF
:
529 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0))))
538 case VIEW_CONVERT_EXPR
:
539 /* Bitfields and casts are never addressable. */
547 if (get_alias_set (TREE_TYPE (TREE_OPERAND (t
, 0))) == 0)
550 t
= TREE_OPERAND (t
, 0);
554 return TREE_OPERAND (found
, 0);
560 /* Return whether the pointer-type T effective for aliasing may
561 access everything and thus the reference has to be assigned
565 ref_all_alias_ptr_type_p (const_tree t
)
567 return (TREE_CODE (TREE_TYPE (t
)) == VOID_TYPE
568 || TYPE_REF_CAN_ALIAS_ALL (t
));
571 /* Return the alias set for the memory pointed to by T, which may be
572 either a type or an expression. Return -1 if there is nothing
573 special about dereferencing T. */
575 static alias_set_type
576 get_deref_alias_set_1 (tree t
)
578 /* All we care about is the type. */
582 /* If we have an INDIRECT_REF via a void pointer, we don't
583 know anything about what that might alias. Likewise if the
584 pointer is marked that way. */
585 if (ref_all_alias_ptr_type_p (t
))
591 /* Return the alias set for the memory pointed to by T, which may be
592 either a type or an expression. */
595 get_deref_alias_set (tree t
)
597 /* If we're not doing any alias analysis, just assume everything
598 aliases everything else. */
599 if (!flag_strict_aliasing
)
602 alias_set_type set
= get_deref_alias_set_1 (t
);
604 /* Fall back to the alias-set of the pointed-to type. */
609 set
= get_alias_set (TREE_TYPE (t
));
615 /* Return the pointer-type relevant for TBAA purposes from the
616 memory reference tree *T or NULL_TREE in which case *T is
617 adjusted to point to the outermost component reference that
618 can be used for assigning an alias set. */
621 reference_alias_ptr_type_1 (tree
*t
)
625 /* Get the base object of the reference. */
627 while (handled_component_p (inner
))
629 /* If there is a VIEW_CONVERT_EXPR in the chain we cannot use
630 the type of any component references that wrap it to
631 determine the alias-set. */
632 if (TREE_CODE (inner
) == VIEW_CONVERT_EXPR
)
633 *t
= TREE_OPERAND (inner
, 0);
634 inner
= TREE_OPERAND (inner
, 0);
637 /* Handle pointer dereferences here, they can override the
639 if (INDIRECT_REF_P (inner
)
640 && ref_all_alias_ptr_type_p (TREE_TYPE (TREE_OPERAND (inner
, 0))))
641 return TREE_TYPE (TREE_OPERAND (inner
, 0));
642 else if (TREE_CODE (inner
) == TARGET_MEM_REF
)
643 return TREE_TYPE (TMR_OFFSET (inner
));
644 else if (TREE_CODE (inner
) == MEM_REF
645 && ref_all_alias_ptr_type_p (TREE_TYPE (TREE_OPERAND (inner
, 1))))
646 return TREE_TYPE (TREE_OPERAND (inner
, 1));
648 /* If the innermost reference is a MEM_REF that has a
649 conversion embedded treat it like a VIEW_CONVERT_EXPR above,
650 using the memory access type for determining the alias-set. */
651 if (TREE_CODE (inner
) == MEM_REF
652 && (TYPE_MAIN_VARIANT (TREE_TYPE (inner
))
654 (TREE_TYPE (TREE_TYPE (TREE_OPERAND (inner
, 1))))))
655 return TREE_TYPE (TREE_OPERAND (inner
, 1));
657 /* Otherwise, pick up the outermost object that we could have
659 tree tem
= component_uses_parent_alias_set_from (*t
);
666 /* Return the pointer-type relevant for TBAA purposes from the
667 gimple memory reference tree T. This is the type to be used for
668 the offset operand of MEM_REF or TARGET_MEM_REF replacements of T
669 and guarantees that get_alias_set will return the same alias
670 set for T and the replacement. */
673 reference_alias_ptr_type (tree t
)
675 tree ptype
= reference_alias_ptr_type_1 (&t
);
676 /* If there is a given pointer type for aliasing purposes, return it. */
677 if (ptype
!= NULL_TREE
)
680 /* Otherwise build one from the outermost component reference we
682 if (TREE_CODE (t
) == MEM_REF
683 || TREE_CODE (t
) == TARGET_MEM_REF
)
684 return TREE_TYPE (TREE_OPERAND (t
, 1));
686 return build_pointer_type (TYPE_MAIN_VARIANT (TREE_TYPE (t
)));
689 /* Return whether the pointer-types T1 and T2 used to determine
690 two alias sets of two references will yield the same answer
691 from get_deref_alias_set. */
694 alias_ptr_types_compatible_p (tree t1
, tree t2
)
696 if (TYPE_MAIN_VARIANT (t1
) == TYPE_MAIN_VARIANT (t2
))
699 if (ref_all_alias_ptr_type_p (t1
)
700 || ref_all_alias_ptr_type_p (t2
))
703 return (TYPE_MAIN_VARIANT (TREE_TYPE (t1
))
704 == TYPE_MAIN_VARIANT (TREE_TYPE (t2
)));
707 /* Return the alias set for T, which may be either a type or an
708 expression. Call language-specific routine for help, if needed. */
711 get_alias_set (tree t
)
715 /* If we're not doing any alias analysis, just assume everything
716 aliases everything else. Also return 0 if this or its type is
718 if (! flag_strict_aliasing
|| t
== error_mark_node
720 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
723 /* We can be passed either an expression or a type. This and the
724 language-specific routine may make mutually-recursive calls to each other
725 to figure out what to do. At each juncture, we see if this is a tree
726 that the language may need to handle specially. First handle things that
730 /* Give the language a chance to do something with this tree
731 before we look at it. */
733 set
= lang_hooks
.get_alias_set (t
);
737 /* Get the alias pointer-type to use or the outermost object
738 that we could have a pointer to. */
739 tree ptype
= reference_alias_ptr_type_1 (&t
);
741 return get_deref_alias_set (ptype
);
743 /* If we've already determined the alias set for a decl, just return
744 it. This is necessary for C++ anonymous unions, whose component
745 variables don't look like union members (boo!). */
746 if (TREE_CODE (t
) == VAR_DECL
747 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
748 return MEM_ALIAS_SET (DECL_RTL (t
));
750 /* Now all we care about is the type. */
754 /* Variant qualifiers don't affect the alias set, so get the main
756 t
= TYPE_MAIN_VARIANT (t
);
758 /* Always use the canonical type as well. If this is a type that
759 requires structural comparisons to identify compatible types
760 use alias set zero. */
761 if (TYPE_STRUCTURAL_EQUALITY_P (t
))
763 /* Allow the language to specify another alias set for this
765 set
= lang_hooks
.get_alias_set (t
);
771 t
= TYPE_CANONICAL (t
);
773 /* The canonical type should not require structural equality checks. */
774 gcc_checking_assert (!TYPE_STRUCTURAL_EQUALITY_P (t
));
776 /* If this is a type with a known alias set, return it. */
777 if (TYPE_ALIAS_SET_KNOWN_P (t
))
778 return TYPE_ALIAS_SET (t
);
780 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
781 if (!COMPLETE_TYPE_P (t
))
783 /* For arrays with unknown size the conservative answer is the
784 alias set of the element type. */
785 if (TREE_CODE (t
) == ARRAY_TYPE
)
786 return get_alias_set (TREE_TYPE (t
));
788 /* But return zero as a conservative answer for incomplete types. */
792 /* See if the language has special handling for this type. */
793 set
= lang_hooks
.get_alias_set (t
);
797 /* There are no objects of FUNCTION_TYPE, so there's no point in
798 using up an alias set for them. (There are, of course, pointers
799 and references to functions, but that's different.) */
800 else if (TREE_CODE (t
) == FUNCTION_TYPE
|| TREE_CODE (t
) == METHOD_TYPE
)
803 /* Unless the language specifies otherwise, let vector types alias
804 their components. This avoids some nasty type punning issues in
805 normal usage. And indeed lets vectors be treated more like an
807 else if (TREE_CODE (t
) == VECTOR_TYPE
)
808 set
= get_alias_set (TREE_TYPE (t
));
810 /* Unless the language specifies otherwise, treat array types the
811 same as their components. This avoids the asymmetry we get
812 through recording the components. Consider accessing a
813 character(kind=1) through a reference to a character(kind=1)[1:1].
814 Or consider if we want to assign integer(kind=4)[0:D.1387] and
815 integer(kind=4)[4] the same alias set or not.
816 Just be pragmatic here and make sure the array and its element
817 type get the same alias set assigned. */
818 else if (TREE_CODE (t
) == ARRAY_TYPE
&& !TYPE_NONALIASED_COMPONENT (t
))
819 set
= get_alias_set (TREE_TYPE (t
));
821 /* From the former common C and C++ langhook implementation:
823 Unfortunately, there is no canonical form of a pointer type.
824 In particular, if we have `typedef int I', then `int *', and
825 `I *' are different types. So, we have to pick a canonical
826 representative. We do this below.
828 Technically, this approach is actually more conservative that
829 it needs to be. In particular, `const int *' and `int *'
830 should be in different alias sets, according to the C and C++
831 standard, since their types are not the same, and so,
832 technically, an `int **' and `const int **' cannot point at
835 But, the standard is wrong. In particular, this code is
840 const int* const* cipp = ipp;
841 And, it doesn't make sense for that to be legal unless you
842 can dereference IPP and CIPP. So, we ignore cv-qualifiers on
843 the pointed-to types. This issue has been reported to the
846 In addition to the above canonicalization issue, with LTO
847 we should also canonicalize `T (*)[]' to `T *' avoiding
848 alias issues with pointer-to element types and pointer-to
851 Likewise we need to deal with the situation of incomplete
852 pointed-to types and make `*(struct X **)&a' and
853 `*(struct X {} **)&a' alias. Otherwise we will have to
854 guarantee that all pointer-to incomplete type variants
855 will be replaced by pointer-to complete type variants if
858 With LTO the convenient situation of using `void *' to
859 access and store any pointer type will also become
860 more apparent (and `void *' is just another pointer-to
861 incomplete type). Assigning alias-set zero to `void *'
862 and all pointer-to incomplete types is a not appealing
863 solution. Assigning an effective alias-set zero only
864 affecting pointers might be - by recording proper subset
865 relationships of all pointer alias-sets.
867 Pointer-to function types are another grey area which
868 needs caution. Globbing them all into one alias-set
869 or the above effective zero set would work.
871 For now just assign the same alias-set to all pointers.
872 That's simple and avoids all the above problems. */
873 else if (POINTER_TYPE_P (t
)
874 && t
!= ptr_type_node
)
875 set
= get_alias_set (ptr_type_node
);
877 /* Otherwise make a new alias set for this type. */
880 /* Each canonical type gets its own alias set, so canonical types
881 shouldn't form a tree. It doesn't really matter for types
882 we handle specially above, so only check it where it possibly
883 would result in a bogus alias set. */
884 gcc_checking_assert (TYPE_CANONICAL (t
) == t
);
886 set
= new_alias_set ();
889 TYPE_ALIAS_SET (t
) = set
;
891 /* If this is an aggregate type or a complex type, we must record any
892 component aliasing information. */
893 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
894 record_component_aliases (t
);
899 /* Return a brand-new alias set. */
904 if (flag_strict_aliasing
)
907 vec_safe_push (alias_sets
, (alias_set_entry
) 0);
908 vec_safe_push (alias_sets
, (alias_set_entry
) 0);
909 return alias_sets
->length () - 1;
915 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
916 not everything that aliases SUPERSET also aliases SUBSET. For example,
917 in C, a store to an `int' can alias a load of a structure containing an
918 `int', and vice versa. But it can't alias a load of a 'double' member
919 of the same structure. Here, the structure would be the SUPERSET and
920 `int' the SUBSET. This relationship is also described in the comment at
921 the beginning of this file.
923 This function should be called only once per SUPERSET/SUBSET pair.
925 It is illegal for SUPERSET to be zero; everything is implicitly a
926 subset of alias set zero. */
929 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
931 alias_set_entry superset_entry
;
932 alias_set_entry subset_entry
;
934 /* It is possible in complex type situations for both sets to be the same,
935 in which case we can ignore this operation. */
936 if (superset
== subset
)
939 gcc_assert (superset
);
941 superset_entry
= get_alias_set_entry (superset
);
942 if (superset_entry
== 0)
944 /* Create an entry for the SUPERSET, so that we have a place to
945 attach the SUBSET. */
946 superset_entry
= ggc_cleared_alloc
<alias_set_entry_d
> ();
947 superset_entry
->alias_set
= superset
;
948 superset_entry
->children
949 = splay_tree_new_ggc (splay_tree_compare_ints
,
950 ggc_alloc_splay_tree_scalar_scalar_splay_tree_s
,
951 ggc_alloc_splay_tree_scalar_scalar_splay_tree_node_s
);
952 superset_entry
->has_zero_child
= 0;
953 (*alias_sets
)[superset
] = superset_entry
;
957 superset_entry
->has_zero_child
= 1;
960 subset_entry
= get_alias_set_entry (subset
);
961 /* If there is an entry for the subset, enter all of its children
962 (if they are not already present) as children of the SUPERSET. */
965 if (subset_entry
->has_zero_child
)
966 superset_entry
->has_zero_child
= 1;
968 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
969 superset_entry
->children
);
972 /* Enter the SUBSET itself as a child of the SUPERSET. */
973 splay_tree_insert (superset_entry
->children
,
974 (splay_tree_key
) subset
, 0);
978 /* Record that component types of TYPE, if any, are part of that type for
979 aliasing purposes. For record types, we only record component types
980 for fields that are not marked non-addressable. For array types, we
981 only record the component type if it is not marked non-aliased. */
984 record_component_aliases (tree type
)
986 alias_set_type superset
= get_alias_set (type
);
992 switch (TREE_CODE (type
))
996 case QUAL_UNION_TYPE
:
997 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= DECL_CHAIN (field
))
998 if (TREE_CODE (field
) == FIELD_DECL
&& !DECL_NONADDRESSABLE_P (field
))
999 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
1003 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
1006 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
1014 /* Allocate an alias set for use in storing and reading from the varargs
1017 static GTY(()) alias_set_type varargs_set
= -1;
1020 get_varargs_alias_set (void)
1023 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
1024 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
1025 consistently use the varargs alias set for loads from the varargs
1026 area. So don't use it anywhere. */
1029 if (varargs_set
== -1)
1030 varargs_set
= new_alias_set ();
1036 /* Likewise, but used for the fixed portions of the frame, e.g., register
1039 static GTY(()) alias_set_type frame_set
= -1;
1042 get_frame_alias_set (void)
1044 if (frame_set
== -1)
1045 frame_set
= new_alias_set ();
1050 /* Create a new, unique base with id ID. */
1053 unique_base_value (HOST_WIDE_INT id
)
1055 return gen_rtx_ADDRESS (Pmode
, id
);
1058 /* Return true if accesses based on any other base value cannot alias
1059 those based on X. */
1062 unique_base_value_p (rtx x
)
1064 return GET_CODE (x
) == ADDRESS
&& GET_MODE (x
) == Pmode
;
1067 /* Return true if X is known to be a base value. */
1070 known_base_value_p (rtx x
)
1072 switch (GET_CODE (x
))
1079 /* Arguments may or may not be bases; we don't know for sure. */
1080 return GET_MODE (x
) != VOIDmode
;
1087 /* Inside SRC, the source of a SET, find a base address. */
1090 find_base_value (rtx src
)
1094 #if defined (FIND_BASE_TERM)
1095 /* Try machine-dependent ways to find the base term. */
1096 src
= FIND_BASE_TERM (src
);
1099 switch (GET_CODE (src
))
1106 regno
= REGNO (src
);
1107 /* At the start of a function, argument registers have known base
1108 values which may be lost later. Returning an ADDRESS
1109 expression here allows optimization based on argument values
1110 even when the argument registers are used for other purposes. */
1111 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
1112 return new_reg_base_value
[regno
];
1114 /* If a pseudo has a known base value, return it. Do not do this
1115 for non-fixed hard regs since it can result in a circular
1116 dependency chain for registers which have values at function entry.
1118 The test above is not sufficient because the scheduler may move
1119 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
1120 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
1121 && regno
< vec_safe_length (reg_base_value
))
1123 /* If we're inside init_alias_analysis, use new_reg_base_value
1124 to reduce the number of relaxation iterations. */
1125 if (new_reg_base_value
&& new_reg_base_value
[regno
]
1126 && DF_REG_DEF_COUNT (regno
) == 1)
1127 return new_reg_base_value
[regno
];
1129 if ((*reg_base_value
)[regno
])
1130 return (*reg_base_value
)[regno
];
1136 /* Check for an argument passed in memory. Only record in the
1137 copying-arguments block; it is too hard to track changes
1139 if (copying_arguments
1140 && (XEXP (src
, 0) == arg_pointer_rtx
1141 || (GET_CODE (XEXP (src
, 0)) == PLUS
1142 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
1143 return arg_base_value
;
1147 src
= XEXP (src
, 0);
1148 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
1151 /* ... fall through ... */
1156 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
1158 /* If either operand is a REG that is a known pointer, then it
1160 if (REG_P (src_0
) && REG_POINTER (src_0
))
1161 return find_base_value (src_0
);
1162 if (REG_P (src_1
) && REG_POINTER (src_1
))
1163 return find_base_value (src_1
);
1165 /* If either operand is a REG, then see if we already have
1166 a known value for it. */
1169 temp
= find_base_value (src_0
);
1176 temp
= find_base_value (src_1
);
1181 /* If either base is named object or a special address
1182 (like an argument or stack reference), then use it for the
1184 if (src_0
!= 0 && known_base_value_p (src_0
))
1187 if (src_1
!= 0 && known_base_value_p (src_1
))
1190 /* Guess which operand is the base address:
1191 If either operand is a symbol, then it is the base. If
1192 either operand is a CONST_INT, then the other is the base. */
1193 if (CONST_INT_P (src_1
) || CONSTANT_P (src_0
))
1194 return find_base_value (src_0
);
1195 else if (CONST_INT_P (src_0
) || CONSTANT_P (src_1
))
1196 return find_base_value (src_1
);
1202 /* The standard form is (lo_sum reg sym) so look only at the
1204 return find_base_value (XEXP (src
, 1));
1207 /* If the second operand is constant set the base
1208 address to the first operand. */
1209 if (CONST_INT_P (XEXP (src
, 1)) && INTVAL (XEXP (src
, 1)) != 0)
1210 return find_base_value (XEXP (src
, 0));
1214 /* As we do not know which address space the pointer is referring to, we can
1215 handle this only if the target does not support different pointer or
1216 address modes depending on the address space. */
1217 if (!target_default_pointer_address_modes_p ())
1219 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
1229 return find_base_value (XEXP (src
, 0));
1232 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
1233 /* As we do not know which address space the pointer is referring to, we can
1234 handle this only if the target does not support different pointer or
1235 address modes depending on the address space. */
1236 if (!target_default_pointer_address_modes_p ())
1240 rtx temp
= find_base_value (XEXP (src
, 0));
1242 if (temp
!= 0 && CONSTANT_P (temp
))
1243 temp
= convert_memory_address (Pmode
, temp
);
1255 /* Called from init_alias_analysis indirectly through note_stores,
1256 or directly if DEST is a register with a REG_NOALIAS note attached.
1257 SET is null in the latter case. */
1259 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1260 register N has been set in this function. */
1261 static sbitmap reg_seen
;
1264 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
1273 regno
= REGNO (dest
);
1275 gcc_checking_assert (regno
< reg_base_value
->length ());
1277 /* If this spans multiple hard registers, then we must indicate that every
1278 register has an unusable value. */
1279 if (regno
< FIRST_PSEUDO_REGISTER
)
1280 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1287 bitmap_set_bit (reg_seen
, regno
+ n
);
1288 new_reg_base_value
[regno
+ n
] = 0;
1295 /* A CLOBBER wipes out any old value but does not prevent a previously
1296 unset register from acquiring a base address (i.e. reg_seen is not
1298 if (GET_CODE (set
) == CLOBBER
)
1300 new_reg_base_value
[regno
] = 0;
1303 src
= SET_SRC (set
);
1307 /* There's a REG_NOALIAS note against DEST. */
1308 if (bitmap_bit_p (reg_seen
, regno
))
1310 new_reg_base_value
[regno
] = 0;
1313 bitmap_set_bit (reg_seen
, regno
);
1314 new_reg_base_value
[regno
] = unique_base_value (unique_id
++);
1318 /* If this is not the first set of REGNO, see whether the new value
1319 is related to the old one. There are two cases of interest:
1321 (1) The register might be assigned an entirely new value
1322 that has the same base term as the original set.
1324 (2) The set might be a simple self-modification that
1325 cannot change REGNO's base value.
1327 If neither case holds, reject the original base value as invalid.
1328 Note that the following situation is not detected:
1330 extern int x, y; int *p = &x; p += (&y-&x);
1332 ANSI C does not allow computing the difference of addresses
1333 of distinct top level objects. */
1334 if (new_reg_base_value
[regno
] != 0
1335 && find_base_value (src
) != new_reg_base_value
[regno
])
1336 switch (GET_CODE (src
))
1340 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1341 new_reg_base_value
[regno
] = 0;
1344 /* If the value we add in the PLUS is also a valid base value,
1345 this might be the actual base value, and the original value
1348 rtx other
= NULL_RTX
;
1350 if (XEXP (src
, 0) == dest
)
1351 other
= XEXP (src
, 1);
1352 else if (XEXP (src
, 1) == dest
)
1353 other
= XEXP (src
, 0);
1355 if (! other
|| find_base_value (other
))
1356 new_reg_base_value
[regno
] = 0;
1360 if (XEXP (src
, 0) != dest
|| !CONST_INT_P (XEXP (src
, 1)))
1361 new_reg_base_value
[regno
] = 0;
1364 new_reg_base_value
[regno
] = 0;
1367 /* If this is the first set of a register, record the value. */
1368 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1369 && ! bitmap_bit_p (reg_seen
, regno
) && new_reg_base_value
[regno
] == 0)
1370 new_reg_base_value
[regno
] = find_base_value (src
);
1372 bitmap_set_bit (reg_seen
, regno
);
1375 /* Return REG_BASE_VALUE for REGNO. Selective scheduler uses this to avoid
1376 using hard registers with non-null REG_BASE_VALUE for renaming. */
1378 get_reg_base_value (unsigned int regno
)
1380 return (*reg_base_value
)[regno
];
1383 /* If a value is known for REGNO, return it. */
1386 get_reg_known_value (unsigned int regno
)
1388 if (regno
>= FIRST_PSEUDO_REGISTER
)
1390 regno
-= FIRST_PSEUDO_REGISTER
;
1391 if (regno
< vec_safe_length (reg_known_value
))
1392 return (*reg_known_value
)[regno
];
1400 set_reg_known_value (unsigned int regno
, rtx val
)
1402 if (regno
>= FIRST_PSEUDO_REGISTER
)
1404 regno
-= FIRST_PSEUDO_REGISTER
;
1405 if (regno
< vec_safe_length (reg_known_value
))
1406 (*reg_known_value
)[regno
] = val
;
1410 /* Similarly for reg_known_equiv_p. */
1413 get_reg_known_equiv_p (unsigned int regno
)
1415 if (regno
>= FIRST_PSEUDO_REGISTER
)
1417 regno
-= FIRST_PSEUDO_REGISTER
;
1418 if (regno
< vec_safe_length (reg_known_value
))
1419 return bitmap_bit_p (reg_known_equiv_p
, regno
);
1425 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1427 if (regno
>= FIRST_PSEUDO_REGISTER
)
1429 regno
-= FIRST_PSEUDO_REGISTER
;
1430 if (regno
< vec_safe_length (reg_known_value
))
1433 bitmap_set_bit (reg_known_equiv_p
, regno
);
1435 bitmap_clear_bit (reg_known_equiv_p
, regno
);
1441 /* Returns a canonical version of X, from the point of view alias
1442 analysis. (For example, if X is a MEM whose address is a register,
1443 and the register has a known value (say a SYMBOL_REF), then a MEM
1444 whose address is the SYMBOL_REF is returned.) */
1449 /* Recursively look for equivalences. */
1450 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1452 rtx t
= get_reg_known_value (REGNO (x
));
1456 return canon_rtx (t
);
1459 if (GET_CODE (x
) == PLUS
)
1461 rtx x0
= canon_rtx (XEXP (x
, 0));
1462 rtx x1
= canon_rtx (XEXP (x
, 1));
1464 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1466 if (CONST_INT_P (x0
))
1467 return plus_constant (GET_MODE (x
), x1
, INTVAL (x0
));
1468 else if (CONST_INT_P (x1
))
1469 return plus_constant (GET_MODE (x
), x0
, INTVAL (x1
));
1470 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1474 /* This gives us much better alias analysis when called from
1475 the loop optimizer. Note we want to leave the original
1476 MEM alone, but need to return the canonicalized MEM with
1477 all the flags with their original values. */
1479 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1484 /* Return 1 if X and Y are identical-looking rtx's.
1485 Expect that X and Y has been already canonicalized.
1487 We use the data in reg_known_value above to see if two registers with
1488 different numbers are, in fact, equivalent. */
1491 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1498 if (x
== 0 && y
== 0)
1500 if (x
== 0 || y
== 0)
1506 code
= GET_CODE (x
);
1507 /* Rtx's of different codes cannot be equal. */
1508 if (code
!= GET_CODE (y
))
1511 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1512 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1514 if (GET_MODE (x
) != GET_MODE (y
))
1517 /* Some RTL can be compared without a recursive examination. */
1521 return REGNO (x
) == REGNO (y
);
1524 return LABEL_REF_LABEL (x
) == LABEL_REF_LABEL (y
);
1527 return XSTR (x
, 0) == XSTR (y
, 0);
1530 /* This is magic, don't go through canonicalization et al. */
1531 return rtx_equal_p (ENTRY_VALUE_EXP (x
), ENTRY_VALUE_EXP (y
));
1535 /* Pointer equality guarantees equality for these nodes. */
1542 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1544 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1545 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1546 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1547 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1548 /* For commutative operations, the RTX match if the operand match in any
1549 order. Also handle the simple binary and unary cases without a loop. */
1550 if (COMMUTATIVE_P (x
))
1552 rtx xop0
= canon_rtx (XEXP (x
, 0));
1553 rtx yop0
= canon_rtx (XEXP (y
, 0));
1554 rtx yop1
= canon_rtx (XEXP (y
, 1));
1556 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1557 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1558 || (rtx_equal_for_memref_p (xop0
, yop1
)
1559 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1561 else if (NON_COMMUTATIVE_P (x
))
1563 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1564 canon_rtx (XEXP (y
, 0)))
1565 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1566 canon_rtx (XEXP (y
, 1))));
1568 else if (UNARY_P (x
))
1569 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1570 canon_rtx (XEXP (y
, 0)));
1572 /* Compare the elements. If any pair of corresponding elements
1573 fail to match, return 0 for the whole things.
1575 Limit cases to types which actually appear in addresses. */
1577 fmt
= GET_RTX_FORMAT (code
);
1578 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1583 if (XINT (x
, i
) != XINT (y
, i
))
1588 /* Two vectors must have the same length. */
1589 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1592 /* And the corresponding elements must match. */
1593 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1594 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1595 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1600 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1601 canon_rtx (XEXP (y
, i
))) == 0)
1605 /* This can happen for asm operands. */
1607 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1611 /* This can happen for an asm which clobbers memory. */
1615 /* It is believed that rtx's at this level will never
1616 contain anything but integers and other rtx's,
1617 except for within LABEL_REFs and SYMBOL_REFs. */
1626 find_base_term (rtx x
)
1629 struct elt_loc_list
*l
, *f
;
1632 #if defined (FIND_BASE_TERM)
1633 /* Try machine-dependent ways to find the base term. */
1634 x
= FIND_BASE_TERM (x
);
1637 switch (GET_CODE (x
))
1640 return REG_BASE_VALUE (x
);
1643 /* As we do not know which address space the pointer is referring to, we can
1644 handle this only if the target does not support different pointer or
1645 address modes depending on the address space. */
1646 if (!target_default_pointer_address_modes_p ())
1648 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1658 return find_base_term (XEXP (x
, 0));
1661 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1662 /* As we do not know which address space the pointer is referring to, we can
1663 handle this only if the target does not support different pointer or
1664 address modes depending on the address space. */
1665 if (!target_default_pointer_address_modes_p ())
1669 rtx temp
= find_base_term (XEXP (x
, 0));
1671 if (temp
!= 0 && CONSTANT_P (temp
))
1672 temp
= convert_memory_address (Pmode
, temp
);
1678 val
= CSELIB_VAL_PTR (x
);
1684 if (cselib_sp_based_value_p (val
))
1685 return static_reg_base_value
[STACK_POINTER_REGNUM
];
1688 /* Temporarily reset val->locs to avoid infinite recursion. */
1691 for (l
= f
; l
; l
= l
->next
)
1692 if (GET_CODE (l
->loc
) == VALUE
1693 && CSELIB_VAL_PTR (l
->loc
)->locs
1694 && !CSELIB_VAL_PTR (l
->loc
)->locs
->next
1695 && CSELIB_VAL_PTR (l
->loc
)->locs
->loc
== x
)
1697 else if ((ret
= find_base_term (l
->loc
)) != 0)
1704 /* The standard form is (lo_sum reg sym) so look only at the
1706 return find_base_term (XEXP (x
, 1));
1710 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1716 rtx tmp1
= XEXP (x
, 0);
1717 rtx tmp2
= XEXP (x
, 1);
1719 /* This is a little bit tricky since we have to determine which of
1720 the two operands represents the real base address. Otherwise this
1721 routine may return the index register instead of the base register.
1723 That may cause us to believe no aliasing was possible, when in
1724 fact aliasing is possible.
1726 We use a few simple tests to guess the base register. Additional
1727 tests can certainly be added. For example, if one of the operands
1728 is a shift or multiply, then it must be the index register and the
1729 other operand is the base register. */
1731 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1732 return find_base_term (tmp2
);
1734 /* If either operand is known to be a pointer, then prefer it
1735 to determine the base term. */
1736 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1738 else if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1745 /* Go ahead and find the base term for both operands. If either base
1746 term is from a pointer or is a named object or a special address
1747 (like an argument or stack reference), then use it for the
1749 rtx base
= find_base_term (tmp1
);
1750 if (base
!= NULL_RTX
1751 && ((REG_P (tmp1
) && REG_POINTER (tmp1
))
1752 || known_base_value_p (base
)))
1754 base
= find_base_term (tmp2
);
1755 if (base
!= NULL_RTX
1756 && ((REG_P (tmp2
) && REG_POINTER (tmp2
))
1757 || known_base_value_p (base
)))
1760 /* We could not determine which of the two operands was the
1761 base register and which was the index. So we can determine
1762 nothing from the base alias check. */
1767 if (CONST_INT_P (XEXP (x
, 1)) && INTVAL (XEXP (x
, 1)) != 0)
1768 return find_base_term (XEXP (x
, 0));
1780 /* Return true if accesses to address X may alias accesses based
1781 on the stack pointer. */
1784 may_be_sp_based_p (rtx x
)
1786 rtx base
= find_base_term (x
);
1787 return !base
|| base
== static_reg_base_value
[STACK_POINTER_REGNUM
];
1790 /* Return 0 if the addresses X and Y are known to point to different
1791 objects, 1 if they might be pointers to the same object. */
1794 base_alias_check (rtx x
, rtx x_base
, rtx y
, rtx y_base
,
1795 enum machine_mode x_mode
, enum machine_mode y_mode
)
1797 /* If the address itself has no known base see if a known equivalent
1798 value has one. If either address still has no known base, nothing
1799 is known about aliasing. */
1804 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1807 x_base
= find_base_term (x_c
);
1815 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1818 y_base
= find_base_term (y_c
);
1823 /* If the base addresses are equal nothing is known about aliasing. */
1824 if (rtx_equal_p (x_base
, y_base
))
1827 /* The base addresses are different expressions. If they are not accessed
1828 via AND, there is no conflict. We can bring knowledge of object
1829 alignment into play here. For example, on alpha, "char a, b;" can
1830 alias one another, though "char a; long b;" cannot. AND addesses may
1831 implicitly alias surrounding objects; i.e. unaligned access in DImode
1832 via AND address can alias all surrounding object types except those
1833 with aligment 8 or higher. */
1834 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1836 if (GET_CODE (x
) == AND
1837 && (!CONST_INT_P (XEXP (x
, 1))
1838 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1840 if (GET_CODE (y
) == AND
1841 && (!CONST_INT_P (XEXP (y
, 1))
1842 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1845 /* Differing symbols not accessed via AND never alias. */
1846 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1849 if (unique_base_value_p (x_base
) || unique_base_value_p (y_base
))
1855 /* Return TRUE if EXPR refers to a VALUE whose uid is greater than
1859 refs_newer_value_p (const_rtx expr
, rtx v
)
1861 int minuid
= CSELIB_VAL_PTR (v
)->uid
;
1862 subrtx_iterator::array_type array
;
1863 FOR_EACH_SUBRTX (iter
, array
, expr
, NONCONST
)
1864 if (GET_CODE (*iter
) == VALUE
&& CSELIB_VAL_PTR (*iter
)->uid
> minuid
)
1869 /* Convert the address X into something we can use. This is done by returning
1870 it unchanged unless it is a value; in the latter case we call cselib to get
1871 a more useful rtx. */
1877 struct elt_loc_list
*l
;
1879 if (GET_CODE (x
) != VALUE
)
1881 v
= CSELIB_VAL_PTR (x
);
1884 bool have_equivs
= cselib_have_permanent_equivalences ();
1886 v
= canonical_cselib_val (v
);
1887 for (l
= v
->locs
; l
; l
= l
->next
)
1888 if (CONSTANT_P (l
->loc
))
1890 for (l
= v
->locs
; l
; l
= l
->next
)
1891 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
)
1892 /* Avoid infinite recursion when potentially dealing with
1893 var-tracking artificial equivalences, by skipping the
1894 equivalences themselves, and not choosing expressions
1895 that refer to newer VALUEs. */
1897 || (GET_CODE (l
->loc
) != VALUE
1898 && !refs_newer_value_p (l
->loc
, x
))))
1902 for (l
= v
->locs
; l
; l
= l
->next
)
1904 || (GET_CODE (l
->loc
) != VALUE
1905 && !refs_newer_value_p (l
->loc
, x
)))
1907 /* Return the canonical value. */
1911 return v
->locs
->loc
;
1916 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1917 where SIZE is the size in bytes of the memory reference. If ADDR
1918 is not modified by the memory reference then ADDR is returned. */
1921 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1925 switch (GET_CODE (addr
))
1928 offset
= (n_refs
+ 1) * size
;
1931 offset
= -(n_refs
+ 1) * size
;
1934 offset
= n_refs
* size
;
1937 offset
= -n_refs
* size
;
1945 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1946 gen_int_mode (offset
, GET_MODE (addr
)));
1948 addr
= XEXP (addr
, 0);
1949 addr
= canon_rtx (addr
);
1954 /* Return TRUE if an object X sized at XSIZE bytes and another object
1955 Y sized at YSIZE bytes, starting C bytes after X, may overlap. If
1956 any of the sizes is zero, assume an overlap, otherwise use the
1957 absolute value of the sizes as the actual sizes. */
1960 offset_overlap_p (HOST_WIDE_INT c
, int xsize
, int ysize
)
1962 return (xsize
== 0 || ysize
== 0
1965 : (abs (ysize
) > -c
)));
1968 /* Return one if X and Y (memory addresses) reference the
1969 same location in memory or if the references overlap.
1970 Return zero if they do not overlap, else return
1971 minus one in which case they still might reference the same location.
1973 C is an offset accumulator. When
1974 C is nonzero, we are testing aliases between X and Y + C.
1975 XSIZE is the size in bytes of the X reference,
1976 similarly YSIZE is the size in bytes for Y.
1977 Expect that canon_rtx has been already called for X and Y.
1979 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1980 referenced (the reference was BLKmode), so make the most pessimistic
1983 If XSIZE or YSIZE is negative, we may access memory outside the object
1984 being referenced as a side effect. This can happen when using AND to
1985 align memory references, as is done on the Alpha.
1987 Nice to notice that varying addresses cannot conflict with fp if no
1988 local variables had their addresses taken, but that's too hard now.
1990 ??? Contrary to the tree alias oracle this does not return
1991 one for X + non-constant and Y + non-constant when X and Y are equal.
1992 If that is fixed the TBAA hack for union type-punning can be removed. */
1995 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1997 if (GET_CODE (x
) == VALUE
)
2001 struct elt_loc_list
*l
= NULL
;
2002 if (CSELIB_VAL_PTR (x
))
2003 for (l
= canonical_cselib_val (CSELIB_VAL_PTR (x
))->locs
;
2005 if (REG_P (l
->loc
) && rtx_equal_for_memref_p (l
->loc
, y
))
2012 /* Don't call get_addr if y is the same VALUE. */
2016 if (GET_CODE (y
) == VALUE
)
2020 struct elt_loc_list
*l
= NULL
;
2021 if (CSELIB_VAL_PTR (y
))
2022 for (l
= canonical_cselib_val (CSELIB_VAL_PTR (y
))->locs
;
2024 if (REG_P (l
->loc
) && rtx_equal_for_memref_p (l
->loc
, x
))
2031 /* Don't call get_addr if x is the same VALUE. */
2035 if (GET_CODE (x
) == HIGH
)
2037 else if (GET_CODE (x
) == LO_SUM
)
2040 x
= addr_side_effect_eval (x
, abs (xsize
), 0);
2041 if (GET_CODE (y
) == HIGH
)
2043 else if (GET_CODE (y
) == LO_SUM
)
2046 y
= addr_side_effect_eval (y
, abs (ysize
), 0);
2048 if (rtx_equal_for_memref_p (x
, y
))
2050 return offset_overlap_p (c
, xsize
, ysize
);
2053 /* This code used to check for conflicts involving stack references and
2054 globals but the base address alias code now handles these cases. */
2056 if (GET_CODE (x
) == PLUS
)
2058 /* The fact that X is canonicalized means that this
2059 PLUS rtx is canonicalized. */
2060 rtx x0
= XEXP (x
, 0);
2061 rtx x1
= XEXP (x
, 1);
2063 if (GET_CODE (y
) == PLUS
)
2065 /* The fact that Y is canonicalized means that this
2066 PLUS rtx is canonicalized. */
2067 rtx y0
= XEXP (y
, 0);
2068 rtx y1
= XEXP (y
, 1);
2070 if (rtx_equal_for_memref_p (x1
, y1
))
2071 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
2072 if (rtx_equal_for_memref_p (x0
, y0
))
2073 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
2074 if (CONST_INT_P (x1
))
2076 if (CONST_INT_P (y1
))
2077 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
2078 c
- INTVAL (x1
) + INTVAL (y1
));
2080 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
2083 else if (CONST_INT_P (y1
))
2084 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
2088 else if (CONST_INT_P (x1
))
2089 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
2091 else if (GET_CODE (y
) == PLUS
)
2093 /* The fact that Y is canonicalized means that this
2094 PLUS rtx is canonicalized. */
2095 rtx y0
= XEXP (y
, 0);
2096 rtx y1
= XEXP (y
, 1);
2098 if (CONST_INT_P (y1
))
2099 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
2104 if (GET_CODE (x
) == GET_CODE (y
))
2105 switch (GET_CODE (x
))
2109 /* Handle cases where we expect the second operands to be the
2110 same, and check only whether the first operand would conflict
2113 rtx x1
= canon_rtx (XEXP (x
, 1));
2114 rtx y1
= canon_rtx (XEXP (y
, 1));
2115 if (! rtx_equal_for_memref_p (x1
, y1
))
2117 x0
= canon_rtx (XEXP (x
, 0));
2118 y0
= canon_rtx (XEXP (y
, 0));
2119 if (rtx_equal_for_memref_p (x0
, y0
))
2120 return offset_overlap_p (c
, xsize
, ysize
);
2122 /* Can't properly adjust our sizes. */
2123 if (!CONST_INT_P (x1
))
2125 xsize
/= INTVAL (x1
);
2126 ysize
/= INTVAL (x1
);
2128 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
2135 /* Deal with alignment ANDs by adjusting offset and size so as to
2136 cover the maximum range, without taking any previously known
2137 alignment into account. Make a size negative after such an
2138 adjustments, so that, if we end up with e.g. two SYMBOL_REFs, we
2139 assume a potential overlap, because they may end up in contiguous
2140 memory locations and the stricter-alignment access may span over
2142 if (GET_CODE (x
) == AND
&& CONST_INT_P (XEXP (x
, 1)))
2144 HOST_WIDE_INT sc
= INTVAL (XEXP (x
, 1));
2145 unsigned HOST_WIDE_INT uc
= sc
;
2146 if (sc
< 0 && -uc
== (uc
& -uc
))
2153 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2157 if (GET_CODE (y
) == AND
&& CONST_INT_P (XEXP (y
, 1)))
2159 HOST_WIDE_INT sc
= INTVAL (XEXP (y
, 1));
2160 unsigned HOST_WIDE_INT uc
= sc
;
2161 if (sc
< 0 && -uc
== (uc
& -uc
))
2168 return memrefs_conflict_p (xsize
, x
,
2169 ysize
, canon_rtx (XEXP (y
, 0)), c
);
2175 if (CONST_INT_P (x
) && CONST_INT_P (y
))
2177 c
+= (INTVAL (y
) - INTVAL (x
));
2178 return offset_overlap_p (c
, xsize
, ysize
);
2181 if (GET_CODE (x
) == CONST
)
2183 if (GET_CODE (y
) == CONST
)
2184 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2185 ysize
, canon_rtx (XEXP (y
, 0)), c
);
2187 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2190 if (GET_CODE (y
) == CONST
)
2191 return memrefs_conflict_p (xsize
, x
, ysize
,
2192 canon_rtx (XEXP (y
, 0)), c
);
2194 /* Assume a potential overlap for symbolic addresses that went
2195 through alignment adjustments (i.e., that have negative
2196 sizes), because we can't know how far they are from each
2199 return (xsize
< 0 || ysize
< 0 || offset_overlap_p (c
, xsize
, ysize
));
2207 /* Functions to compute memory dependencies.
2209 Since we process the insns in execution order, we can build tables
2210 to keep track of what registers are fixed (and not aliased), what registers
2211 are varying in known ways, and what registers are varying in unknown
2214 If both memory references are volatile, then there must always be a
2215 dependence between the two references, since their order can not be
2216 changed. A volatile and non-volatile reference can be interchanged
2219 We also must allow AND addresses, because they may generate accesses
2220 outside the object being referenced. This is used to generate aligned
2221 addresses from unaligned addresses, for instance, the alpha
2222 storeqi_unaligned pattern. */
2224 /* Read dependence: X is read after read in MEM takes place. There can
2225 only be a dependence here if both reads are volatile, or if either is
2226 an explicit barrier. */
2229 read_dependence (const_rtx mem
, const_rtx x
)
2231 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2233 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2234 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2239 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2242 decl_for_component_ref (tree x
)
2246 x
= TREE_OPERAND (x
, 0);
2248 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2250 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
2253 /* Walk up the COMPONENT_REF list in X and adjust *OFFSET to compensate
2254 for the offset of the field reference. *KNOWN_P says whether the
2258 adjust_offset_for_component_ref (tree x
, bool *known_p
,
2259 HOST_WIDE_INT
*offset
)
2265 tree xoffset
= component_ref_field_offset (x
);
2266 tree field
= TREE_OPERAND (x
, 1);
2267 if (TREE_CODE (xoffset
) != INTEGER_CST
)
2274 = (wi::to_offset (xoffset
)
2275 + wi::lrshift (wi::to_offset (DECL_FIELD_BIT_OFFSET (field
)),
2276 LOG2_BITS_PER_UNIT
));
2277 if (!wi::fits_uhwi_p (woffset
))
2282 *offset
+= woffset
.to_uhwi ();
2284 x
= TREE_OPERAND (x
, 0);
2286 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2289 /* Return nonzero if we can determine the exprs corresponding to memrefs
2290 X and Y and they do not overlap.
2291 If LOOP_VARIANT is set, skip offset-based disambiguation */
2294 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
, bool loop_invariant
)
2296 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
2299 bool moffsetx_known_p
, moffsety_known_p
;
2300 HOST_WIDE_INT moffsetx
= 0, moffsety
= 0;
2301 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
2303 /* Unless both have exprs, we can't tell anything. */
2304 if (exprx
== 0 || expry
== 0)
2307 /* For spill-slot accesses make sure we have valid offsets. */
2308 if ((exprx
== get_spill_slot_decl (false)
2309 && ! MEM_OFFSET_KNOWN_P (x
))
2310 || (expry
== get_spill_slot_decl (false)
2311 && ! MEM_OFFSET_KNOWN_P (y
)))
2314 /* If the field reference test failed, look at the DECLs involved. */
2315 moffsetx_known_p
= MEM_OFFSET_KNOWN_P (x
);
2316 if (moffsetx_known_p
)
2317 moffsetx
= MEM_OFFSET (x
);
2318 if (TREE_CODE (exprx
) == COMPONENT_REF
)
2320 tree t
= decl_for_component_ref (exprx
);
2323 adjust_offset_for_component_ref (exprx
, &moffsetx_known_p
, &moffsetx
);
2327 moffsety_known_p
= MEM_OFFSET_KNOWN_P (y
);
2328 if (moffsety_known_p
)
2329 moffsety
= MEM_OFFSET (y
);
2330 if (TREE_CODE (expry
) == COMPONENT_REF
)
2332 tree t
= decl_for_component_ref (expry
);
2335 adjust_offset_for_component_ref (expry
, &moffsety_known_p
, &moffsety
);
2339 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2342 /* With invalid code we can end up storing into the constant pool.
2343 Bail out to avoid ICEing when creating RTL for this.
2344 See gfortran.dg/lto/20091028-2_0.f90. */
2345 if (TREE_CODE (exprx
) == CONST_DECL
2346 || TREE_CODE (expry
) == CONST_DECL
)
2349 rtlx
= DECL_RTL (exprx
);
2350 rtly
= DECL_RTL (expry
);
2352 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2353 can't overlap unless they are the same because we never reuse that part
2354 of the stack frame used for locals for spilled pseudos. */
2355 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2356 && ! rtx_equal_p (rtlx
, rtly
))
2359 /* If we have MEMs referring to different address spaces (which can
2360 potentially overlap), we cannot easily tell from the addresses
2361 whether the references overlap. */
2362 if (MEM_P (rtlx
) && MEM_P (rtly
)
2363 && MEM_ADDR_SPACE (rtlx
) != MEM_ADDR_SPACE (rtly
))
2366 /* Get the base and offsets of both decls. If either is a register, we
2367 know both are and are the same, so use that as the base. The only
2368 we can avoid overlap is if we can deduce that they are nonoverlapping
2369 pieces of that decl, which is very rare. */
2370 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2371 if (GET_CODE (basex
) == PLUS
&& CONST_INT_P (XEXP (basex
, 1)))
2372 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2374 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2375 if (GET_CODE (basey
) == PLUS
&& CONST_INT_P (XEXP (basey
, 1)))
2376 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2378 /* If the bases are different, we know they do not overlap if both
2379 are constants or if one is a constant and the other a pointer into the
2380 stack frame. Otherwise a different base means we can't tell if they
2382 if (! rtx_equal_p (basex
, basey
))
2383 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2384 || (CONSTANT_P (basex
) && REG_P (basey
)
2385 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2386 || (CONSTANT_P (basey
) && REG_P (basex
)
2387 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2389 /* Offset based disambiguation not appropriate for loop invariant */
2393 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2394 : MEM_SIZE_KNOWN_P (rtlx
) ? MEM_SIZE (rtlx
)
2396 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2397 : MEM_SIZE_KNOWN_P (rtly
) ? MEM_SIZE (rtly
)
2400 /* If we have an offset for either memref, it can update the values computed
2402 if (moffsetx_known_p
)
2403 offsetx
+= moffsetx
, sizex
-= moffsetx
;
2404 if (moffsety_known_p
)
2405 offsety
+= moffsety
, sizey
-= moffsety
;
2407 /* If a memref has both a size and an offset, we can use the smaller size.
2408 We can't do this if the offset isn't known because we must view this
2409 memref as being anywhere inside the DECL's MEM. */
2410 if (MEM_SIZE_KNOWN_P (x
) && moffsetx_known_p
)
2411 sizex
= MEM_SIZE (x
);
2412 if (MEM_SIZE_KNOWN_P (y
) && moffsety_known_p
)
2413 sizey
= MEM_SIZE (y
);
2415 /* Put the values of the memref with the lower offset in X's values. */
2416 if (offsetx
> offsety
)
2418 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2419 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2422 /* If we don't know the size of the lower-offset value, we can't tell
2423 if they conflict. Otherwise, we do the test. */
2424 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2427 /* Helper for true_dependence and canon_true_dependence.
2428 Checks for true dependence: X is read after store in MEM takes place.
2430 If MEM_CANONICALIZED is FALSE, then X_ADDR and MEM_ADDR should be
2431 NULL_RTX, and the canonical addresses of MEM and X are both computed
2432 here. If MEM_CANONICALIZED, then MEM must be already canonicalized.
2434 If X_ADDR is non-NULL, it is used in preference of XEXP (x, 0).
2436 Returns 1 if there is a true dependence, 0 otherwise. */
2439 true_dependence_1 (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2440 const_rtx x
, rtx x_addr
, bool mem_canonicalized
)
2446 gcc_checking_assert (mem_canonicalized
? (mem_addr
!= NULL_RTX
)
2447 : (mem_addr
== NULL_RTX
&& x_addr
== NULL_RTX
));
2449 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2452 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2453 This is used in epilogue deallocation functions, and in cselib. */
2454 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2456 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2458 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2459 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2463 x_addr
= XEXP (x
, 0);
2464 x_addr
= get_addr (x_addr
);
2468 mem_addr
= XEXP (mem
, 0);
2469 if (mem_mode
== VOIDmode
)
2470 mem_mode
= GET_MODE (mem
);
2472 true_mem_addr
= get_addr (mem_addr
);
2474 /* Read-only memory is by definition never modified, and therefore can't
2475 conflict with anything. However, don't assume anything when AND
2476 addresses are involved and leave to the code below to determine
2477 dependence. We don't expect to find read-only set on MEM, but
2478 stupid user tricks can produce them, so don't die. */
2479 if (MEM_READONLY_P (x
)
2480 && GET_CODE (x_addr
) != AND
2481 && GET_CODE (true_mem_addr
) != AND
)
2484 /* If we have MEMs referring to different address spaces (which can
2485 potentially overlap), we cannot easily tell from the addresses
2486 whether the references overlap. */
2487 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2490 base
= find_base_term (x_addr
);
2491 if (base
&& (GET_CODE (base
) == LABEL_REF
2492 || (GET_CODE (base
) == SYMBOL_REF
2493 && CONSTANT_POOL_ADDRESS_P (base
))))
2496 rtx mem_base
= find_base_term (true_mem_addr
);
2497 if (! base_alias_check (x_addr
, base
, true_mem_addr
, mem_base
,
2498 GET_MODE (x
), mem_mode
))
2501 x_addr
= canon_rtx (x_addr
);
2502 if (!mem_canonicalized
)
2503 mem_addr
= canon_rtx (true_mem_addr
);
2505 if ((ret
= memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2506 SIZE_FOR_MODE (x
), x_addr
, 0)) != -1)
2509 if (mems_in_disjoint_alias_sets_p (x
, mem
))
2512 if (nonoverlapping_memrefs_p (mem
, x
, false))
2515 return rtx_refs_may_alias_p (x
, mem
, true);
2518 /* True dependence: X is read after store in MEM takes place. */
2521 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
)
2523 return true_dependence_1 (mem
, mem_mode
, NULL_RTX
,
2524 x
, NULL_RTX
, /*mem_canonicalized=*/false);
2527 /* Canonical true dependence: X is read after store in MEM takes place.
2528 Variant of true_dependence which assumes MEM has already been
2529 canonicalized (hence we no longer do that here).
2530 The mem_addr argument has been added, since true_dependence_1 computed
2531 this value prior to canonicalizing. */
2534 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2535 const_rtx x
, rtx x_addr
)
2537 return true_dependence_1 (mem
, mem_mode
, mem_addr
,
2538 x
, x_addr
, /*mem_canonicalized=*/true);
2541 /* Returns nonzero if a write to X might alias a previous read from
2542 (or, if WRITEP is true, a write to) MEM.
2543 If X_CANONCALIZED is true, then X_ADDR is the canonicalized address of X,
2544 and X_MODE the mode for that access.
2545 If MEM_CANONICALIZED is true, MEM is canonicalized. */
2548 write_dependence_p (const_rtx mem
,
2549 const_rtx x
, enum machine_mode x_mode
, rtx x_addr
,
2550 bool mem_canonicalized
, bool x_canonicalized
, bool writep
)
2553 rtx true_mem_addr
, true_x_addr
;
2557 gcc_checking_assert (x_canonicalized
2558 ? (x_addr
!= NULL_RTX
&& x_mode
!= VOIDmode
)
2559 : (x_addr
== NULL_RTX
&& x_mode
== VOIDmode
));
2561 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2564 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2565 This is used in epilogue deallocation functions. */
2566 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2568 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2570 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2571 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2575 x_addr
= XEXP (x
, 0);
2576 true_x_addr
= get_addr (x_addr
);
2578 mem_addr
= XEXP (mem
, 0);
2579 true_mem_addr
= get_addr (mem_addr
);
2581 /* A read from read-only memory can't conflict with read-write memory.
2582 Don't assume anything when AND addresses are involved and leave to
2583 the code below to determine dependence. */
2585 && MEM_READONLY_P (mem
)
2586 && GET_CODE (true_x_addr
) != AND
2587 && GET_CODE (true_mem_addr
) != AND
)
2590 /* If we have MEMs referring to different address spaces (which can
2591 potentially overlap), we cannot easily tell from the addresses
2592 whether the references overlap. */
2593 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2596 base
= find_base_term (true_mem_addr
);
2599 && (GET_CODE (base
) == LABEL_REF
2600 || (GET_CODE (base
) == SYMBOL_REF
2601 && CONSTANT_POOL_ADDRESS_P (base
))))
2604 rtx x_base
= find_base_term (true_x_addr
);
2605 if (! base_alias_check (true_x_addr
, x_base
, true_mem_addr
, base
,
2606 GET_MODE (x
), GET_MODE (mem
)))
2609 if (!x_canonicalized
)
2611 x_addr
= canon_rtx (true_x_addr
);
2612 x_mode
= GET_MODE (x
);
2614 if (!mem_canonicalized
)
2615 mem_addr
= canon_rtx (true_mem_addr
);
2617 if ((ret
= memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2618 GET_MODE_SIZE (x_mode
), x_addr
, 0)) != -1)
2621 if (nonoverlapping_memrefs_p (x
, mem
, false))
2624 return rtx_refs_may_alias_p (x
, mem
, false);
2627 /* Anti dependence: X is written after read in MEM takes place. */
2630 anti_dependence (const_rtx mem
, const_rtx x
)
2632 return write_dependence_p (mem
, x
, VOIDmode
, NULL_RTX
,
2633 /*mem_canonicalized=*/false,
2634 /*x_canonicalized*/false, /*writep=*/false);
2637 /* Likewise, but we already have a canonicalized MEM, and X_ADDR for X.
2638 Also, consider X in X_MODE (which might be from an enclosing
2639 STRICT_LOW_PART / ZERO_EXTRACT).
2640 If MEM_CANONICALIZED is true, MEM is canonicalized. */
2643 canon_anti_dependence (const_rtx mem
, bool mem_canonicalized
,
2644 const_rtx x
, enum machine_mode x_mode
, rtx x_addr
)
2646 return write_dependence_p (mem
, x
, x_mode
, x_addr
,
2647 mem_canonicalized
, /*x_canonicalized=*/true,
2651 /* Output dependence: X is written after store in MEM takes place. */
2654 output_dependence (const_rtx mem
, const_rtx x
)
2656 return write_dependence_p (mem
, x
, VOIDmode
, NULL_RTX
,
2657 /*mem_canonicalized=*/false,
2658 /*x_canonicalized*/false, /*writep=*/true);
2663 /* Check whether X may be aliased with MEM. Don't do offset-based
2664 memory disambiguation & TBAA. */
2666 may_alias_p (const_rtx mem
, const_rtx x
)
2668 rtx x_addr
, mem_addr
;
2670 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2673 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2674 This is used in epilogue deallocation functions. */
2675 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2677 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2679 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2680 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2683 x_addr
= XEXP (x
, 0);
2684 x_addr
= get_addr (x_addr
);
2686 mem_addr
= XEXP (mem
, 0);
2687 mem_addr
= get_addr (mem_addr
);
2689 /* Read-only memory is by definition never modified, and therefore can't
2690 conflict with anything. However, don't assume anything when AND
2691 addresses are involved and leave to the code below to determine
2692 dependence. We don't expect to find read-only set on MEM, but
2693 stupid user tricks can produce them, so don't die. */
2694 if (MEM_READONLY_P (x
)
2695 && GET_CODE (x_addr
) != AND
2696 && GET_CODE (mem_addr
) != AND
)
2699 /* If we have MEMs referring to different address spaces (which can
2700 potentially overlap), we cannot easily tell from the addresses
2701 whether the references overlap. */
2702 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2705 rtx x_base
= find_base_term (x_addr
);
2706 rtx mem_base
= find_base_term (mem_addr
);
2707 if (! base_alias_check (x_addr
, x_base
, mem_addr
, mem_base
,
2708 GET_MODE (x
), GET_MODE (mem_addr
)))
2711 if (nonoverlapping_memrefs_p (mem
, x
, true))
2714 /* TBAA not valid for loop_invarint */
2715 return rtx_refs_may_alias_p (x
, mem
, false);
2719 init_alias_target (void)
2723 if (!arg_base_value
)
2724 arg_base_value
= gen_rtx_ADDRESS (VOIDmode
, 0);
2726 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2728 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2729 /* Check whether this register can hold an incoming pointer
2730 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2731 numbers, so translate if necessary due to register windows. */
2732 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2733 && HARD_REGNO_MODE_OK (i
, Pmode
))
2734 static_reg_base_value
[i
] = arg_base_value
;
2736 static_reg_base_value
[STACK_POINTER_REGNUM
]
2737 = unique_base_value (UNIQUE_BASE_VALUE_SP
);
2738 static_reg_base_value
[ARG_POINTER_REGNUM
]
2739 = unique_base_value (UNIQUE_BASE_VALUE_ARGP
);
2740 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2741 = unique_base_value (UNIQUE_BASE_VALUE_FP
);
2742 #if !HARD_FRAME_POINTER_IS_FRAME_POINTER
2743 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2744 = unique_base_value (UNIQUE_BASE_VALUE_HFP
);
2748 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2749 to be memory reference. */
2750 static bool memory_modified
;
2752 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2756 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2757 memory_modified
= true;
2762 /* Return true when INSN possibly modify memory contents of MEM
2763 (i.e. address can be modified). */
2765 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2769 memory_modified
= false;
2770 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2771 return memory_modified
;
2774 /* Return TRUE if the destination of a set is rtx identical to
2777 set_dest_equal_p (const_rtx set
, const_rtx item
)
2779 rtx dest
= SET_DEST (set
);
2780 return rtx_equal_p (dest
, item
);
2783 /* Like memory_modified_in_insn_p, but return TRUE if INSN will
2784 *DEFINITELY* modify the memory contents of MEM. */
2786 memory_must_be_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2790 insn
= PATTERN (insn
);
2791 if (GET_CODE (insn
) == SET
)
2792 return set_dest_equal_p (insn
, mem
);
2793 else if (GET_CODE (insn
) == PARALLEL
)
2796 for (i
= 0; i
< XVECLEN (insn
, 0); i
++)
2798 rtx sub
= XVECEXP (insn
, 0, i
);
2799 if (GET_CODE (sub
) == SET
2800 && set_dest_equal_p (sub
, mem
))
2807 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2811 init_alias_analysis (void)
2813 unsigned int maxreg
= max_reg_num ();
2822 timevar_push (TV_ALIAS_ANALYSIS
);
2824 vec_safe_grow_cleared (reg_known_value
, maxreg
- FIRST_PSEUDO_REGISTER
);
2825 reg_known_equiv_p
= sbitmap_alloc (maxreg
- FIRST_PSEUDO_REGISTER
);
2826 bitmap_clear (reg_known_equiv_p
);
2828 /* If we have memory allocated from the previous run, use it. */
2829 if (old_reg_base_value
)
2830 reg_base_value
= old_reg_base_value
;
2833 reg_base_value
->truncate (0);
2835 vec_safe_grow_cleared (reg_base_value
, maxreg
);
2837 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2838 reg_seen
= sbitmap_alloc (maxreg
);
2840 /* The basic idea is that each pass through this loop will use the
2841 "constant" information from the previous pass to propagate alias
2842 information through another level of assignments.
2844 The propagation is done on the CFG in reverse post-order, to propagate
2845 things forward as far as possible in each iteration.
2847 This could get expensive if the assignment chains are long. Maybe
2848 we should throttle the number of iterations, possibly based on
2849 the optimization level or flag_expensive_optimizations.
2851 We could propagate more information in the first pass by making use
2852 of DF_REG_DEF_COUNT to determine immediately that the alias information
2853 for a pseudo is "constant".
2855 A program with an uninitialized variable can cause an infinite loop
2856 here. Instead of doing a full dataflow analysis to detect such problems
2857 we just cap the number of iterations for the loop.
2859 The state of the arrays for the set chain in question does not matter
2860 since the program has undefined behavior. */
2862 rpo
= XNEWVEC (int, n_basic_blocks_for_fn (cfun
));
2863 rpo_cnt
= pre_and_rev_post_order_compute (NULL
, rpo
, false);
2868 /* Assume nothing will change this iteration of the loop. */
2871 /* We want to assign the same IDs each iteration of this loop, so
2872 start counting from one each iteration of the loop. */
2875 /* We're at the start of the function each iteration through the
2876 loop, so we're copying arguments. */
2877 copying_arguments
= true;
2879 /* Wipe the potential alias information clean for this pass. */
2880 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2882 /* Wipe the reg_seen array clean. */
2883 bitmap_clear (reg_seen
);
2885 /* Initialize the alias information for this pass. */
2886 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2887 if (static_reg_base_value
[i
])
2889 new_reg_base_value
[i
] = static_reg_base_value
[i
];
2890 bitmap_set_bit (reg_seen
, i
);
2893 /* Walk the insns adding values to the new_reg_base_value array. */
2894 for (i
= 0; i
< rpo_cnt
; i
++)
2896 basic_block bb
= BASIC_BLOCK_FOR_FN (cfun
, rpo
[i
]);
2897 FOR_BB_INSNS (bb
, insn
)
2899 if (NONDEBUG_INSN_P (insn
))
2903 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2904 /* The prologue/epilogue insns are not threaded onto the
2905 insn chain until after reload has completed. Thus,
2906 there is no sense wasting time checking if INSN is in
2907 the prologue/epilogue until after reload has completed. */
2908 if (reload_completed
2909 && prologue_epilogue_contains (insn
))
2913 /* If this insn has a noalias note, process it, Otherwise,
2914 scan for sets. A simple set will have no side effects
2915 which could change the base value of any other register. */
2917 if (GET_CODE (PATTERN (insn
)) == SET
2918 && REG_NOTES (insn
) != 0
2919 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2920 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2922 note_stores (PATTERN (insn
), record_set
, NULL
);
2924 set
= single_set (insn
);
2927 && REG_P (SET_DEST (set
))
2928 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2930 unsigned int regno
= REGNO (SET_DEST (set
));
2931 rtx src
= SET_SRC (set
);
2934 note
= find_reg_equal_equiv_note (insn
);
2935 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2936 && DF_REG_DEF_COUNT (regno
) != 1)
2939 if (note
!= NULL_RTX
2940 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2941 && ! rtx_varies_p (XEXP (note
, 0), 1)
2942 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2945 set_reg_known_value (regno
, XEXP (note
, 0));
2946 set_reg_known_equiv_p (regno
,
2947 REG_NOTE_KIND (note
) == REG_EQUIV
);
2949 else if (DF_REG_DEF_COUNT (regno
) == 1
2950 && GET_CODE (src
) == PLUS
2951 && REG_P (XEXP (src
, 0))
2952 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2953 && CONST_INT_P (XEXP (src
, 1)))
2955 t
= plus_constant (GET_MODE (src
), t
,
2956 INTVAL (XEXP (src
, 1)));
2957 set_reg_known_value (regno
, t
);
2958 set_reg_known_equiv_p (regno
, false);
2960 else if (DF_REG_DEF_COUNT (regno
) == 1
2961 && ! rtx_varies_p (src
, 1))
2963 set_reg_known_value (regno
, src
);
2964 set_reg_known_equiv_p (regno
, false);
2968 else if (NOTE_P (insn
)
2969 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2970 copying_arguments
= false;
2974 /* Now propagate values from new_reg_base_value to reg_base_value. */
2975 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2977 for (ui
= 0; ui
< maxreg
; ui
++)
2979 if (new_reg_base_value
[ui
]
2980 && new_reg_base_value
[ui
] != (*reg_base_value
)[ui
]
2981 && ! rtx_equal_p (new_reg_base_value
[ui
], (*reg_base_value
)[ui
]))
2983 (*reg_base_value
)[ui
] = new_reg_base_value
[ui
];
2988 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2991 /* Fill in the remaining entries. */
2992 FOR_EACH_VEC_ELT (*reg_known_value
, i
, val
)
2994 int regno
= i
+ FIRST_PSEUDO_REGISTER
;
2996 set_reg_known_value (regno
, regno_reg_rtx
[regno
]);
3000 free (new_reg_base_value
);
3001 new_reg_base_value
= 0;
3002 sbitmap_free (reg_seen
);
3004 timevar_pop (TV_ALIAS_ANALYSIS
);
3007 /* Equate REG_BASE_VALUE (reg1) to REG_BASE_VALUE (reg2).
3008 Special API for var-tracking pass purposes. */
3011 vt_equate_reg_base_value (const_rtx reg1
, const_rtx reg2
)
3013 (*reg_base_value
)[REGNO (reg1
)] = REG_BASE_VALUE (reg2
);
3017 end_alias_analysis (void)
3019 old_reg_base_value
= reg_base_value
;
3020 vec_free (reg_known_value
);
3021 sbitmap_free (reg_known_equiv_p
);
3024 #include "gt-alias.h"