1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
46 #include "tree-pass.h"
47 #include "ipa-type-escape.h"
49 #include "tree-ssa-alias.h"
50 #include "pointer-set.h"
51 #include "tree-flow.h"
53 /* The aliasing API provided here solves related but different problems:
55 Say there exists (in c)
69 Consider the four questions:
71 Can a store to x1 interfere with px2->y1?
72 Can a store to x1 interfere with px2->z2?
74 Can a store to x1 change the value pointed to by with py?
75 Can a store to x1 change the value pointed to by with pz?
77 The answer to these questions can be yes, yes, yes, and maybe.
79 The first two questions can be answered with a simple examination
80 of the type system. If structure X contains a field of type Y then
81 a store thru a pointer to an X can overwrite any field that is
82 contained (recursively) in an X (unless we know that px1 != px2).
84 The last two of the questions can be solved in the same way as the
85 first two questions but this is too conservative. The observation
86 is that in some cases analysis we can know if which (if any) fields
87 are addressed and if those addresses are used in bad ways. This
88 analysis may be language specific. In C, arbitrary operations may
89 be applied to pointers. However, there is some indication that
90 this may be too conservative for some C++ types.
92 The pass ipa-type-escape does this analysis for the types whose
93 instances do not escape across the compilation boundary.
95 Historically in GCC, these two problems were combined and a single
96 data structure was used to represent the solution to these
97 problems. We now have two similar but different data structures,
98 The data structure to solve the last two question is similar to the
99 first, but does not contain have the fields in it whose address are
100 never taken. For types that do escape the compilation unit, the
101 data structures will have identical information.
104 /* The alias sets assigned to MEMs assist the back-end in determining
105 which MEMs can alias which other MEMs. In general, two MEMs in
106 different alias sets cannot alias each other, with one important
107 exception. Consider something like:
109 struct S { int i; double d; };
111 a store to an `S' can alias something of either type `int' or type
112 `double'. (However, a store to an `int' cannot alias a `double'
113 and vice versa.) We indicate this via a tree structure that looks
121 (The arrows are directed and point downwards.)
122 In this situation we say the alias set for `struct S' is the
123 `superset' and that those for `int' and `double' are `subsets'.
125 To see whether two alias sets can point to the same memory, we must
126 see if either alias set is a subset of the other. We need not trace
127 past immediate descendants, however, since we propagate all
128 grandchildren up one level.
130 Alias set zero is implicitly a superset of all other alias sets.
131 However, this is no actual entry for alias set zero. It is an
132 error to attempt to explicitly construct a subset of zero. */
134 struct GTY(()) alias_set_entry_d {
135 /* The alias set number, as stored in MEM_ALIAS_SET. */
136 alias_set_type alias_set;
138 /* Nonzero if would have a child of zero: this effectively makes this
139 alias set the same as alias set zero. */
142 /* The children of the alias set. These are not just the immediate
143 children, but, in fact, all descendants. So, if we have:
145 struct T { struct S s; float f; }
147 continuing our example above, the children here will be all of
148 `int', `double', `float', and `struct S'. */
149 splay_tree GTY((param1_is (int), param2_is (int))) children;
151 typedef struct alias_set_entry_d *alias_set_entry;
153 static int rtx_equal_for_memref_p (const_rtx, const_rtx);
154 static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT);
155 static void record_set (rtx, const_rtx, void *);
156 static int base_alias_check (rtx, rtx, enum machine_mode,
158 static rtx find_base_value (rtx);
159 static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx);
160 static int insert_subset_children (splay_tree_node, void*);
161 static alias_set_entry get_alias_set_entry (alias_set_type);
162 static const_rtx fixed_scalar_and_varying_struct_p (const_rtx, const_rtx, rtx, rtx,
163 bool (*) (const_rtx, bool));
164 static int aliases_everything_p (const_rtx);
165 static bool nonoverlapping_component_refs_p (const_tree, const_tree);
166 static tree decl_for_component_ref (tree);
167 static rtx adjust_offset_for_component_ref (tree, rtx);
168 static int write_dependence_p (const_rtx, const_rtx, int);
170 static void memory_modified_1 (rtx, const_rtx, void *);
172 /* Set up all info needed to perform alias analysis on memory references. */
174 /* Returns the size in bytes of the mode of X. */
175 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
177 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
178 different alias sets. We ignore alias sets in functions making use
179 of variable arguments because the va_arg macros on some systems are
181 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
182 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
184 /* Cap the number of passes we make over the insns propagating alias
185 information through set chains. 10 is a completely arbitrary choice. */
186 #define MAX_ALIAS_LOOP_PASSES 10
188 /* reg_base_value[N] gives an address to which register N is related.
189 If all sets after the first add or subtract to the current value
190 or otherwise modify it so it does not point to a different top level
191 object, reg_base_value[N] is equal to the address part of the source
194 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
195 expressions represent certain special values: function arguments and
196 the stack, frame, and argument pointers.
198 The contents of an ADDRESS is not normally used, the mode of the
199 ADDRESS determines whether the ADDRESS is a function argument or some
200 other special value. Pointer equality, not rtx_equal_p, determines whether
201 two ADDRESS expressions refer to the same base address.
203 The only use of the contents of an ADDRESS is for determining if the
204 current function performs nonlocal memory memory references for the
205 purposes of marking the function as a constant function. */
207 static GTY(()) VEC(rtx,gc) *reg_base_value;
208 static rtx *new_reg_base_value;
210 /* We preserve the copy of old array around to avoid amount of garbage
211 produced. About 8% of garbage produced were attributed to this
213 static GTY((deletable)) VEC(rtx,gc) *old_reg_base_value;
215 /* Static hunks of RTL used by the aliasing code; these are initialized
216 once per function to avoid unnecessary RTL allocations. */
217 static GTY (()) rtx static_reg_base_value[FIRST_PSEUDO_REGISTER];
219 #define REG_BASE_VALUE(X) \
220 (REGNO (X) < VEC_length (rtx, reg_base_value) \
221 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
223 /* Vector indexed by N giving the initial (unchanging) value known for
224 pseudo-register N. This array is initialized in init_alias_analysis,
225 and does not change until end_alias_analysis is called. */
226 static GTY((length("reg_known_value_size"))) rtx *reg_known_value;
228 /* Indicates number of valid entries in reg_known_value. */
229 static GTY(()) unsigned int reg_known_value_size;
231 /* Vector recording for each reg_known_value whether it is due to a
232 REG_EQUIV note. Future passes (viz., reload) may replace the
233 pseudo with the equivalent expression and so we account for the
234 dependences that would be introduced if that happens.
236 The REG_EQUIV notes created in assign_parms may mention the arg
237 pointer, and there are explicit insns in the RTL that modify the
238 arg pointer. Thus we must ensure that such insns don't get
239 scheduled across each other because that would invalidate the
240 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
241 wrong, but solving the problem in the scheduler will likely give
242 better code, so we do it here. */
243 static bool *reg_known_equiv_p;
245 /* True when scanning insns from the start of the rtl to the
246 NOTE_INSN_FUNCTION_BEG note. */
247 static bool copying_arguments;
249 DEF_VEC_P(alias_set_entry);
250 DEF_VEC_ALLOC_P(alias_set_entry,gc);
252 /* The splay-tree used to store the various alias set entries. */
253 static GTY (()) VEC(alias_set_entry,gc) *alias_sets;
255 /* Build a decomposed reference object for querying the alias-oracle
256 from the MEM rtx and store it in *REF.
257 Returns false if MEM is not suitable for the alias-oracle. */
260 ao_ref_from_mem (ao_ref *ref, const_rtx mem)
262 tree expr = MEM_EXPR (mem);
268 /* If MEM_OFFSET or MEM_SIZE are NULL punt. */
269 if (!MEM_OFFSET (mem)
273 ao_ref_init (ref, expr);
275 /* Get the base of the reference and see if we have to reject or
277 base = ao_ref_base (ref);
278 if (base == NULL_TREE)
281 /* If this is a pointer dereference of a non-SSA_NAME punt.
282 ??? We could replace it with a pointer to anything. */
283 if (INDIRECT_REF_P (base)
284 && TREE_CODE (TREE_OPERAND (base, 0)) != SSA_NAME)
287 /* The tree oracle doesn't like to have these. */
288 if (TREE_CODE (base) == FUNCTION_DECL
289 || TREE_CODE (base) == LABEL_DECL)
292 /* If this is a reference based on a partitioned decl replace the
293 base with an INDIRECT_REF of the pointer representative we
294 created during stack slot partitioning. */
295 if (TREE_CODE (base) == VAR_DECL
296 && ! TREE_STATIC (base)
297 && cfun->gimple_df->decls_to_pointers != NULL)
300 namep = pointer_map_contains (cfun->gimple_df->decls_to_pointers, base);
303 ref->base_alias_set = get_alias_set (base);
304 ref->base = build1 (INDIRECT_REF, TREE_TYPE (base), *(tree *)namep);
308 ref->ref_alias_set = MEM_ALIAS_SET (mem);
310 /* If the base decl is a parameter we can have negative MEM_OFFSET in
311 case of promoted subregs on bigendian targets. Trust the MEM_EXPR
313 if (INTVAL (MEM_OFFSET (mem)) < 0
314 && ((INTVAL (MEM_SIZE (mem)) + INTVAL (MEM_OFFSET (mem)))
315 * BITS_PER_UNIT) == ref->size)
318 ref->offset += INTVAL (MEM_OFFSET (mem)) * BITS_PER_UNIT;
319 ref->size = INTVAL (MEM_SIZE (mem)) * BITS_PER_UNIT;
321 /* The MEM may extend into adjacent fields, so adjust max_size if
323 if (ref->max_size != -1
324 && ref->size > ref->max_size)
325 ref->max_size = ref->size;
327 /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of
328 the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */
329 if (MEM_EXPR (mem) != get_spill_slot_decl (false)
331 || (DECL_P (ref->base)
332 && (!host_integerp (DECL_SIZE (ref->base), 1)
333 || (TREE_INT_CST_LOW (DECL_SIZE ((ref->base)))
334 < (unsigned HOST_WIDE_INT)(ref->offset + ref->size))))))
340 /* Query the alias-oracle on whether the two memory rtx X and MEM may
341 alias. If TBAA_P is set also apply TBAA. Returns true if the
342 two rtxen may alias, false otherwise. */
345 rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p)
349 if (!ao_ref_from_mem (&ref1, x)
350 || !ao_ref_from_mem (&ref2, mem))
353 return refs_may_alias_p_1 (&ref1, &ref2, tbaa_p);
356 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
357 such an entry, or NULL otherwise. */
359 static inline alias_set_entry
360 get_alias_set_entry (alias_set_type alias_set)
362 return VEC_index (alias_set_entry, alias_sets, alias_set);
365 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
366 the two MEMs cannot alias each other. */
369 mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2)
371 /* Perform a basic sanity check. Namely, that there are no alias sets
372 if we're not using strict aliasing. This helps to catch bugs
373 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
374 where a MEM is allocated in some way other than by the use of
375 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
376 use alias sets to indicate that spilled registers cannot alias each
377 other, we might need to remove this check. */
378 gcc_assert (flag_strict_aliasing
379 || (!MEM_ALIAS_SET (mem1) && !MEM_ALIAS_SET (mem2)));
381 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
384 /* Insert the NODE into the splay tree given by DATA. Used by
385 record_alias_subset via splay_tree_foreach. */
388 insert_subset_children (splay_tree_node node, void *data)
390 splay_tree_insert ((splay_tree) data, node->key, node->value);
395 /* Return true if the first alias set is a subset of the second. */
398 alias_set_subset_of (alias_set_type set1, alias_set_type set2)
402 /* Everything is a subset of the "aliases everything" set. */
406 /* Otherwise, check if set1 is a subset of set2. */
407 ase = get_alias_set_entry (set2);
409 && ((ase->has_zero_child && set1 == 0)
410 || splay_tree_lookup (ase->children,
411 (splay_tree_key) set1)))
416 /* Return 1 if the two specified alias sets may conflict. */
419 alias_sets_conflict_p (alias_set_type set1, alias_set_type set2)
424 if (alias_sets_must_conflict_p (set1, set2))
427 /* See if the first alias set is a subset of the second. */
428 ase = get_alias_set_entry (set1);
430 && (ase->has_zero_child
431 || splay_tree_lookup (ase->children,
432 (splay_tree_key) set2)))
435 /* Now do the same, but with the alias sets reversed. */
436 ase = get_alias_set_entry (set2);
438 && (ase->has_zero_child
439 || splay_tree_lookup (ase->children,
440 (splay_tree_key) set1)))
443 /* The two alias sets are distinct and neither one is the
444 child of the other. Therefore, they cannot conflict. */
449 walk_mems_2 (rtx *x, rtx mem)
453 if (alias_sets_conflict_p (MEM_ALIAS_SET(*x), MEM_ALIAS_SET(mem)))
462 walk_mems_1 (rtx *x, rtx *pat)
466 /* Visit all MEMs in *PAT and check indepedence. */
467 if (for_each_rtx (pat, (rtx_function) walk_mems_2, *x))
468 /* Indicate that dependence was determined and stop traversal. */
476 /* Return 1 if two specified instructions have mem expr with conflict alias sets*/
478 insn_alias_sets_conflict_p (rtx insn1, rtx insn2)
480 /* For each pair of MEMs in INSN1 and INSN2 check their independence. */
481 return for_each_rtx (&PATTERN (insn1), (rtx_function) walk_mems_1,
485 /* Return 1 if the two specified alias sets will always conflict. */
488 alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2)
490 if (set1 == 0 || set2 == 0 || set1 == set2)
496 /* Return 1 if any MEM object of type T1 will always conflict (using the
497 dependency routines in this file) with any MEM object of type T2.
498 This is used when allocating temporary storage. If T1 and/or T2 are
499 NULL_TREE, it means we know nothing about the storage. */
502 objects_must_conflict_p (tree t1, tree t2)
504 alias_set_type set1, set2;
506 /* If neither has a type specified, we don't know if they'll conflict
507 because we may be using them to store objects of various types, for
508 example the argument and local variables areas of inlined functions. */
509 if (t1 == 0 && t2 == 0)
512 /* If they are the same type, they must conflict. */
514 /* Likewise if both are volatile. */
515 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
518 set1 = t1 ? get_alias_set (t1) : 0;
519 set2 = t2 ? get_alias_set (t2) : 0;
521 /* We can't use alias_sets_conflict_p because we must make sure
522 that every subtype of t1 will conflict with every subtype of
523 t2 for which a pair of subobjects of these respective subtypes
524 overlaps on the stack. */
525 return alias_sets_must_conflict_p (set1, set2);
528 /* Return true if all nested component references handled by
529 get_inner_reference in T are such that we should use the alias set
530 provided by the object at the heart of T.
532 This is true for non-addressable components (which don't have their
533 own alias set), as well as components of objects in alias set zero.
534 This later point is a special case wherein we wish to override the
535 alias set used by the component, but we don't have per-FIELD_DECL
536 assignable alias sets. */
539 component_uses_parent_alias_set (const_tree t)
543 /* If we're at the end, it vacuously uses its own alias set. */
544 if (!handled_component_p (t))
547 switch (TREE_CODE (t))
550 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
555 case ARRAY_RANGE_REF:
556 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))))
565 /* Bitfields and casts are never addressable. */
569 t = TREE_OPERAND (t, 0);
570 if (get_alias_set (TREE_TYPE (t)) == 0)
575 /* Return the alias set for the memory pointed to by T, which may be
576 either a type or an expression. Return -1 if there is nothing
577 special about dereferencing T. */
579 static alias_set_type
580 get_deref_alias_set_1 (tree t)
582 /* If we're not doing any alias analysis, just assume everything
583 aliases everything else. */
584 if (!flag_strict_aliasing)
587 /* All we care about is the type. */
591 /* If we have an INDIRECT_REF via a void pointer, we don't
592 know anything about what that might alias. Likewise if the
593 pointer is marked that way. */
594 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE
595 || TYPE_REF_CAN_ALIAS_ALL (t))
601 /* Return the alias set for the memory pointed to by T, which may be
602 either a type or an expression. */
605 get_deref_alias_set (tree t)
607 alias_set_type set = get_deref_alias_set_1 (t);
609 /* Fall back to the alias-set of the pointed-to type. */
614 set = get_alias_set (TREE_TYPE (t));
620 /* Return the alias set for T, which may be either a type or an
621 expression. Call language-specific routine for help, if needed. */
624 get_alias_set (tree t)
628 /* If we're not doing any alias analysis, just assume everything
629 aliases everything else. Also return 0 if this or its type is
631 if (! flag_strict_aliasing || t == error_mark_node
633 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
636 /* We can be passed either an expression or a type. This and the
637 language-specific routine may make mutually-recursive calls to each other
638 to figure out what to do. At each juncture, we see if this is a tree
639 that the language may need to handle specially. First handle things that
645 /* Remove any nops, then give the language a chance to do
646 something with this tree before we look at it. */
648 set = lang_hooks.get_alias_set (t);
652 /* First see if the actual object referenced is an INDIRECT_REF from a
653 restrict-qualified pointer or a "void *". */
654 while (handled_component_p (inner))
656 inner = TREE_OPERAND (inner, 0);
660 if (INDIRECT_REF_P (inner))
662 set = get_deref_alias_set_1 (TREE_OPERAND (inner, 0));
667 /* Otherwise, pick up the outermost object that we could have a pointer
668 to, processing conversions as above. */
669 while (component_uses_parent_alias_set (t))
671 t = TREE_OPERAND (t, 0);
675 /* If we've already determined the alias set for a decl, just return
676 it. This is necessary for C++ anonymous unions, whose component
677 variables don't look like union members (boo!). */
678 if (TREE_CODE (t) == VAR_DECL
679 && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t)))
680 return MEM_ALIAS_SET (DECL_RTL (t));
682 /* Now all we care about is the type. */
686 /* Variant qualifiers don't affect the alias set, so get the main
688 t = TYPE_MAIN_VARIANT (t);
690 /* Always use the canonical type as well. If this is a type that
691 requires structural comparisons to identify compatible types
692 use alias set zero. */
693 if (TYPE_STRUCTURAL_EQUALITY_P (t))
695 /* Allow the language to specify another alias set for this
697 set = lang_hooks.get_alias_set (t);
702 t = TYPE_CANONICAL (t);
703 /* Canonical types shouldn't form a tree nor should the canonical
704 type require structural equality checks. */
705 gcc_assert (!TYPE_STRUCTURAL_EQUALITY_P (t) && TYPE_CANONICAL (t) == t);
707 /* If this is a type with a known alias set, return it. */
708 if (TYPE_ALIAS_SET_KNOWN_P (t))
709 return TYPE_ALIAS_SET (t);
711 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
712 if (!COMPLETE_TYPE_P (t))
714 /* For arrays with unknown size the conservative answer is the
715 alias set of the element type. */
716 if (TREE_CODE (t) == ARRAY_TYPE)
717 return get_alias_set (TREE_TYPE (t));
719 /* But return zero as a conservative answer for incomplete types. */
723 /* See if the language has special handling for this type. */
724 set = lang_hooks.get_alias_set (t);
728 /* There are no objects of FUNCTION_TYPE, so there's no point in
729 using up an alias set for them. (There are, of course, pointers
730 and references to functions, but that's different.) */
731 else if (TREE_CODE (t) == FUNCTION_TYPE
732 || TREE_CODE (t) == METHOD_TYPE)
735 /* Unless the language specifies otherwise, let vector types alias
736 their components. This avoids some nasty type punning issues in
737 normal usage. And indeed lets vectors be treated more like an
739 else if (TREE_CODE (t) == VECTOR_TYPE)
740 set = get_alias_set (TREE_TYPE (t));
742 /* Unless the language specifies otherwise, treat array types the
743 same as their components. This avoids the asymmetry we get
744 through recording the components. Consider accessing a
745 character(kind=1) through a reference to a character(kind=1)[1:1].
746 Or consider if we want to assign integer(kind=4)[0:D.1387] and
747 integer(kind=4)[4] the same alias set or not.
748 Just be pragmatic here and make sure the array and its element
749 type get the same alias set assigned. */
750 else if (TREE_CODE (t) == ARRAY_TYPE
751 && !TYPE_NONALIASED_COMPONENT (t))
752 set = get_alias_set (TREE_TYPE (t));
755 /* Otherwise make a new alias set for this type. */
756 set = new_alias_set ();
758 TYPE_ALIAS_SET (t) = set;
760 /* If this is an aggregate type, we must record any component aliasing
762 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
763 record_component_aliases (t);
768 /* Return a brand-new alias set. */
773 if (flag_strict_aliasing)
776 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
777 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
778 return VEC_length (alias_set_entry, alias_sets) - 1;
784 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
785 not everything that aliases SUPERSET also aliases SUBSET. For example,
786 in C, a store to an `int' can alias a load of a structure containing an
787 `int', and vice versa. But it can't alias a load of a 'double' member
788 of the same structure. Here, the structure would be the SUPERSET and
789 `int' the SUBSET. This relationship is also described in the comment at
790 the beginning of this file.
792 This function should be called only once per SUPERSET/SUBSET pair.
794 It is illegal for SUPERSET to be zero; everything is implicitly a
795 subset of alias set zero. */
798 record_alias_subset (alias_set_type superset, alias_set_type subset)
800 alias_set_entry superset_entry;
801 alias_set_entry subset_entry;
803 /* It is possible in complex type situations for both sets to be the same,
804 in which case we can ignore this operation. */
805 if (superset == subset)
808 gcc_assert (superset);
810 superset_entry = get_alias_set_entry (superset);
811 if (superset_entry == 0)
813 /* Create an entry for the SUPERSET, so that we have a place to
814 attach the SUBSET. */
815 superset_entry = GGC_NEW (struct alias_set_entry_d);
816 superset_entry->alias_set = superset;
817 superset_entry->children
818 = splay_tree_new_ggc (splay_tree_compare_ints);
819 superset_entry->has_zero_child = 0;
820 VEC_replace (alias_set_entry, alias_sets, superset, superset_entry);
824 superset_entry->has_zero_child = 1;
827 subset_entry = get_alias_set_entry (subset);
828 /* If there is an entry for the subset, enter all of its children
829 (if they are not already present) as children of the SUPERSET. */
832 if (subset_entry->has_zero_child)
833 superset_entry->has_zero_child = 1;
835 splay_tree_foreach (subset_entry->children, insert_subset_children,
836 superset_entry->children);
839 /* Enter the SUBSET itself as a child of the SUPERSET. */
840 splay_tree_insert (superset_entry->children,
841 (splay_tree_key) subset, 0);
845 /* Record that component types of TYPE, if any, are part of that type for
846 aliasing purposes. For record types, we only record component types
847 for fields that are not marked non-addressable. For array types, we
848 only record the component type if it is not marked non-aliased. */
851 record_component_aliases (tree type)
853 alias_set_type superset = get_alias_set (type);
859 switch (TREE_CODE (type))
863 case QUAL_UNION_TYPE:
864 /* Recursively record aliases for the base classes, if there are any. */
865 if (TYPE_BINFO (type))
868 tree binfo, base_binfo;
870 for (binfo = TYPE_BINFO (type), i = 0;
871 BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
872 record_alias_subset (superset,
873 get_alias_set (BINFO_TYPE (base_binfo)));
875 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
876 if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
877 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
881 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
884 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
892 /* Allocate an alias set for use in storing and reading from the varargs
895 static GTY(()) alias_set_type varargs_set = -1;
898 get_varargs_alias_set (void)
901 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
902 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
903 consistently use the varargs alias set for loads from the varargs
904 area. So don't use it anywhere. */
907 if (varargs_set == -1)
908 varargs_set = new_alias_set ();
914 /* Likewise, but used for the fixed portions of the frame, e.g., register
917 static GTY(()) alias_set_type frame_set = -1;
920 get_frame_alias_set (void)
923 frame_set = new_alias_set ();
928 /* Inside SRC, the source of a SET, find a base address. */
931 find_base_value (rtx src)
935 #if defined (FIND_BASE_TERM)
936 /* Try machine-dependent ways to find the base term. */
937 src = FIND_BASE_TERM (src);
940 switch (GET_CODE (src))
948 /* At the start of a function, argument registers have known base
949 values which may be lost later. Returning an ADDRESS
950 expression here allows optimization based on argument values
951 even when the argument registers are used for other purposes. */
952 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
953 return new_reg_base_value[regno];
955 /* If a pseudo has a known base value, return it. Do not do this
956 for non-fixed hard regs since it can result in a circular
957 dependency chain for registers which have values at function entry.
959 The test above is not sufficient because the scheduler may move
960 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
961 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
962 && regno < VEC_length (rtx, reg_base_value))
964 /* If we're inside init_alias_analysis, use new_reg_base_value
965 to reduce the number of relaxation iterations. */
966 if (new_reg_base_value && new_reg_base_value[regno]
967 && DF_REG_DEF_COUNT (regno) == 1)
968 return new_reg_base_value[regno];
970 if (VEC_index (rtx, reg_base_value, regno))
971 return VEC_index (rtx, reg_base_value, regno);
977 /* Check for an argument passed in memory. Only record in the
978 copying-arguments block; it is too hard to track changes
980 if (copying_arguments
981 && (XEXP (src, 0) == arg_pointer_rtx
982 || (GET_CODE (XEXP (src, 0)) == PLUS
983 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
984 return gen_rtx_ADDRESS (VOIDmode, src);
989 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
992 /* ... fall through ... */
997 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
999 /* If either operand is a REG that is a known pointer, then it
1001 if (REG_P (src_0) && REG_POINTER (src_0))
1002 return find_base_value (src_0);
1003 if (REG_P (src_1) && REG_POINTER (src_1))
1004 return find_base_value (src_1);
1006 /* If either operand is a REG, then see if we already have
1007 a known value for it. */
1010 temp = find_base_value (src_0);
1017 temp = find_base_value (src_1);
1022 /* If either base is named object or a special address
1023 (like an argument or stack reference), then use it for the
1026 && (GET_CODE (src_0) == SYMBOL_REF
1027 || GET_CODE (src_0) == LABEL_REF
1028 || (GET_CODE (src_0) == ADDRESS
1029 && GET_MODE (src_0) != VOIDmode)))
1033 && (GET_CODE (src_1) == SYMBOL_REF
1034 || GET_CODE (src_1) == LABEL_REF
1035 || (GET_CODE (src_1) == ADDRESS
1036 && GET_MODE (src_1) != VOIDmode)))
1039 /* Guess which operand is the base address:
1040 If either operand is a symbol, then it is the base. If
1041 either operand is a CONST_INT, then the other is the base. */
1042 if (CONST_INT_P (src_1) || CONSTANT_P (src_0))
1043 return find_base_value (src_0);
1044 else if (CONST_INT_P (src_0) || CONSTANT_P (src_1))
1045 return find_base_value (src_1);
1051 /* The standard form is (lo_sum reg sym) so look only at the
1053 return find_base_value (XEXP (src, 1));
1056 /* If the second operand is constant set the base
1057 address to the first operand. */
1058 if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0)
1059 return find_base_value (XEXP (src, 0));
1063 /* As we do not know which address space the pointer is refering to, we can
1064 handle this only if the target does not support different pointer or
1065 address modes depending on the address space. */
1066 if (!target_default_pointer_address_modes_p ())
1068 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
1078 return find_base_value (XEXP (src, 0));
1081 case SIGN_EXTEND: /* used for NT/Alpha pointers */
1082 /* As we do not know which address space the pointer is refering to, we can
1083 handle this only if the target does not support different pointer or
1084 address modes depending on the address space. */
1085 if (!target_default_pointer_address_modes_p ())
1089 rtx temp = find_base_value (XEXP (src, 0));
1091 if (temp != 0 && CONSTANT_P (temp))
1092 temp = convert_memory_address (Pmode, temp);
1104 /* Called from init_alias_analysis indirectly through note_stores. */
1106 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1107 register N has been set in this function. */
1108 static char *reg_seen;
1110 /* Addresses which are known not to alias anything else are identified
1111 by a unique integer. */
1112 static int unique_id;
1115 record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED)
1124 regno = REGNO (dest);
1126 gcc_assert (regno < VEC_length (rtx, reg_base_value));
1128 /* If this spans multiple hard registers, then we must indicate that every
1129 register has an unusable value. */
1130 if (regno < FIRST_PSEUDO_REGISTER)
1131 n = hard_regno_nregs[regno][GET_MODE (dest)];
1138 reg_seen[regno + n] = 1;
1139 new_reg_base_value[regno + n] = 0;
1146 /* A CLOBBER wipes out any old value but does not prevent a previously
1147 unset register from acquiring a base address (i.e. reg_seen is not
1149 if (GET_CODE (set) == CLOBBER)
1151 new_reg_base_value[regno] = 0;
1154 src = SET_SRC (set);
1158 if (reg_seen[regno])
1160 new_reg_base_value[regno] = 0;
1163 reg_seen[regno] = 1;
1164 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
1165 GEN_INT (unique_id++));
1169 /* If this is not the first set of REGNO, see whether the new value
1170 is related to the old one. There are two cases of interest:
1172 (1) The register might be assigned an entirely new value
1173 that has the same base term as the original set.
1175 (2) The set might be a simple self-modification that
1176 cannot change REGNO's base value.
1178 If neither case holds, reject the original base value as invalid.
1179 Note that the following situation is not detected:
1181 extern int x, y; int *p = &x; p += (&y-&x);
1183 ANSI C does not allow computing the difference of addresses
1184 of distinct top level objects. */
1185 if (new_reg_base_value[regno] != 0
1186 && find_base_value (src) != new_reg_base_value[regno])
1187 switch (GET_CODE (src))
1191 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1192 new_reg_base_value[regno] = 0;
1195 /* If the value we add in the PLUS is also a valid base value,
1196 this might be the actual base value, and the original value
1199 rtx other = NULL_RTX;
1201 if (XEXP (src, 0) == dest)
1202 other = XEXP (src, 1);
1203 else if (XEXP (src, 1) == dest)
1204 other = XEXP (src, 0);
1206 if (! other || find_base_value (other))
1207 new_reg_base_value[regno] = 0;
1211 if (XEXP (src, 0) != dest || !CONST_INT_P (XEXP (src, 1)))
1212 new_reg_base_value[regno] = 0;
1215 new_reg_base_value[regno] = 0;
1218 /* If this is the first set of a register, record the value. */
1219 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1220 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1221 new_reg_base_value[regno] = find_base_value (src);
1223 reg_seen[regno] = 1;
1226 /* If a value is known for REGNO, return it. */
1229 get_reg_known_value (unsigned int regno)
1231 if (regno >= FIRST_PSEUDO_REGISTER)
1233 regno -= FIRST_PSEUDO_REGISTER;
1234 if (regno < reg_known_value_size)
1235 return reg_known_value[regno];
1243 set_reg_known_value (unsigned int regno, rtx val)
1245 if (regno >= FIRST_PSEUDO_REGISTER)
1247 regno -= FIRST_PSEUDO_REGISTER;
1248 if (regno < reg_known_value_size)
1249 reg_known_value[regno] = val;
1253 /* Similarly for reg_known_equiv_p. */
1256 get_reg_known_equiv_p (unsigned int regno)
1258 if (regno >= FIRST_PSEUDO_REGISTER)
1260 regno -= FIRST_PSEUDO_REGISTER;
1261 if (regno < reg_known_value_size)
1262 return reg_known_equiv_p[regno];
1268 set_reg_known_equiv_p (unsigned int regno, bool val)
1270 if (regno >= FIRST_PSEUDO_REGISTER)
1272 regno -= FIRST_PSEUDO_REGISTER;
1273 if (regno < reg_known_value_size)
1274 reg_known_equiv_p[regno] = val;
1279 /* Returns a canonical version of X, from the point of view alias
1280 analysis. (For example, if X is a MEM whose address is a register,
1281 and the register has a known value (say a SYMBOL_REF), then a MEM
1282 whose address is the SYMBOL_REF is returned.) */
1287 /* Recursively look for equivalences. */
1288 if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER)
1290 rtx t = get_reg_known_value (REGNO (x));
1294 return canon_rtx (t);
1297 if (GET_CODE (x) == PLUS)
1299 rtx x0 = canon_rtx (XEXP (x, 0));
1300 rtx x1 = canon_rtx (XEXP (x, 1));
1302 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1304 if (CONST_INT_P (x0))
1305 return plus_constant (x1, INTVAL (x0));
1306 else if (CONST_INT_P (x1))
1307 return plus_constant (x0, INTVAL (x1));
1308 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1312 /* This gives us much better alias analysis when called from
1313 the loop optimizer. Note we want to leave the original
1314 MEM alone, but need to return the canonicalized MEM with
1315 all the flags with their original values. */
1317 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1322 /* Return 1 if X and Y are identical-looking rtx's.
1323 Expect that X and Y has been already canonicalized.
1325 We use the data in reg_known_value above to see if two registers with
1326 different numbers are, in fact, equivalent. */
1329 rtx_equal_for_memref_p (const_rtx x, const_rtx y)
1336 if (x == 0 && y == 0)
1338 if (x == 0 || y == 0)
1344 code = GET_CODE (x);
1345 /* Rtx's of different codes cannot be equal. */
1346 if (code != GET_CODE (y))
1349 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1350 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1352 if (GET_MODE (x) != GET_MODE (y))
1355 /* Some RTL can be compared without a recursive examination. */
1359 return REGNO (x) == REGNO (y);
1362 return XEXP (x, 0) == XEXP (y, 0);
1365 return XSTR (x, 0) == XSTR (y, 0);
1371 /* There's no need to compare the contents of CONST_DOUBLEs or
1372 CONST_INTs because pointer equality is a good enough
1373 comparison for these nodes. */
1380 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1382 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1383 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1384 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1385 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1386 /* For commutative operations, the RTX match if the operand match in any
1387 order. Also handle the simple binary and unary cases without a loop. */
1388 if (COMMUTATIVE_P (x))
1390 rtx xop0 = canon_rtx (XEXP (x, 0));
1391 rtx yop0 = canon_rtx (XEXP (y, 0));
1392 rtx yop1 = canon_rtx (XEXP (y, 1));
1394 return ((rtx_equal_for_memref_p (xop0, yop0)
1395 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1396 || (rtx_equal_for_memref_p (xop0, yop1)
1397 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1399 else if (NON_COMMUTATIVE_P (x))
1401 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1402 canon_rtx (XEXP (y, 0)))
1403 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1404 canon_rtx (XEXP (y, 1))));
1406 else if (UNARY_P (x))
1407 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1408 canon_rtx (XEXP (y, 0)));
1410 /* Compare the elements. If any pair of corresponding elements
1411 fail to match, return 0 for the whole things.
1413 Limit cases to types which actually appear in addresses. */
1415 fmt = GET_RTX_FORMAT (code);
1416 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1421 if (XINT (x, i) != XINT (y, i))
1426 /* Two vectors must have the same length. */
1427 if (XVECLEN (x, i) != XVECLEN (y, i))
1430 /* And the corresponding elements must match. */
1431 for (j = 0; j < XVECLEN (x, i); j++)
1432 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1433 canon_rtx (XVECEXP (y, i, j))) == 0)
1438 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1439 canon_rtx (XEXP (y, i))) == 0)
1443 /* This can happen for asm operands. */
1445 if (strcmp (XSTR (x, i), XSTR (y, i)))
1449 /* This can happen for an asm which clobbers memory. */
1453 /* It is believed that rtx's at this level will never
1454 contain anything but integers and other rtx's,
1455 except for within LABEL_REFs and SYMBOL_REFs. */
1464 find_base_term (rtx x)
1467 struct elt_loc_list *l;
1469 #if defined (FIND_BASE_TERM)
1470 /* Try machine-dependent ways to find the base term. */
1471 x = FIND_BASE_TERM (x);
1474 switch (GET_CODE (x))
1477 return REG_BASE_VALUE (x);
1480 /* As we do not know which address space the pointer is refering to, we can
1481 handle this only if the target does not support different pointer or
1482 address modes depending on the address space. */
1483 if (!target_default_pointer_address_modes_p ())
1485 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1495 return find_base_term (XEXP (x, 0));
1498 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1499 /* As we do not know which address space the pointer is refering to, we can
1500 handle this only if the target does not support different pointer or
1501 address modes depending on the address space. */
1502 if (!target_default_pointer_address_modes_p ())
1506 rtx temp = find_base_term (XEXP (x, 0));
1508 if (temp != 0 && CONSTANT_P (temp))
1509 temp = convert_memory_address (Pmode, temp);
1515 val = CSELIB_VAL_PTR (x);
1518 for (l = val->locs; l; l = l->next)
1519 if ((x = find_base_term (l->loc)) != 0)
1524 /* The standard form is (lo_sum reg sym) so look only at the
1526 return find_base_term (XEXP (x, 1));
1530 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1536 rtx tmp1 = XEXP (x, 0);
1537 rtx tmp2 = XEXP (x, 1);
1539 /* This is a little bit tricky since we have to determine which of
1540 the two operands represents the real base address. Otherwise this
1541 routine may return the index register instead of the base register.
1543 That may cause us to believe no aliasing was possible, when in
1544 fact aliasing is possible.
1546 We use a few simple tests to guess the base register. Additional
1547 tests can certainly be added. For example, if one of the operands
1548 is a shift or multiply, then it must be the index register and the
1549 other operand is the base register. */
1551 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1552 return find_base_term (tmp2);
1554 /* If either operand is known to be a pointer, then use it
1555 to determine the base term. */
1556 if (REG_P (tmp1) && REG_POINTER (tmp1))
1558 rtx base = find_base_term (tmp1);
1563 if (REG_P (tmp2) && REG_POINTER (tmp2))
1565 rtx base = find_base_term (tmp2);
1570 /* Neither operand was known to be a pointer. Go ahead and find the
1571 base term for both operands. */
1572 tmp1 = find_base_term (tmp1);
1573 tmp2 = find_base_term (tmp2);
1575 /* If either base term is named object or a special address
1576 (like an argument or stack reference), then use it for the
1579 && (GET_CODE (tmp1) == SYMBOL_REF
1580 || GET_CODE (tmp1) == LABEL_REF
1581 || (GET_CODE (tmp1) == ADDRESS
1582 && GET_MODE (tmp1) != VOIDmode)))
1586 && (GET_CODE (tmp2) == SYMBOL_REF
1587 || GET_CODE (tmp2) == LABEL_REF
1588 || (GET_CODE (tmp2) == ADDRESS
1589 && GET_MODE (tmp2) != VOIDmode)))
1592 /* We could not determine which of the two operands was the
1593 base register and which was the index. So we can determine
1594 nothing from the base alias check. */
1599 if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0)
1600 return find_base_term (XEXP (x, 0));
1612 /* Return 0 if the addresses X and Y are known to point to different
1613 objects, 1 if they might be pointers to the same object. */
1616 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1617 enum machine_mode y_mode)
1619 rtx x_base = find_base_term (x);
1620 rtx y_base = find_base_term (y);
1622 /* If the address itself has no known base see if a known equivalent
1623 value has one. If either address still has no known base, nothing
1624 is known about aliasing. */
1629 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1632 x_base = find_base_term (x_c);
1640 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1643 y_base = find_base_term (y_c);
1648 /* If the base addresses are equal nothing is known about aliasing. */
1649 if (rtx_equal_p (x_base, y_base))
1652 /* The base addresses are different expressions. If they are not accessed
1653 via AND, there is no conflict. We can bring knowledge of object
1654 alignment into play here. For example, on alpha, "char a, b;" can
1655 alias one another, though "char a; long b;" cannot. AND addesses may
1656 implicitly alias surrounding objects; i.e. unaligned access in DImode
1657 via AND address can alias all surrounding object types except those
1658 with aligment 8 or higher. */
1659 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1661 if (GET_CODE (x) == AND
1662 && (!CONST_INT_P (XEXP (x, 1))
1663 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1665 if (GET_CODE (y) == AND
1666 && (!CONST_INT_P (XEXP (y, 1))
1667 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1670 /* Differing symbols not accessed via AND never alias. */
1671 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1674 /* If one address is a stack reference there can be no alias:
1675 stack references using different base registers do not alias,
1676 a stack reference can not alias a parameter, and a stack reference
1677 can not alias a global. */
1678 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1679 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1682 if (! flag_argument_noalias)
1685 if (flag_argument_noalias > 1)
1688 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1689 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1692 /* Convert the address X into something we can use. This is done by returning
1693 it unchanged unless it is a value; in the latter case we call cselib to get
1694 a more useful rtx. */
1700 struct elt_loc_list *l;
1702 if (GET_CODE (x) != VALUE)
1704 v = CSELIB_VAL_PTR (x);
1707 for (l = v->locs; l; l = l->next)
1708 if (CONSTANT_P (l->loc))
1710 for (l = v->locs; l; l = l->next)
1711 if (!REG_P (l->loc) && !MEM_P (l->loc))
1714 return v->locs->loc;
1719 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1720 where SIZE is the size in bytes of the memory reference. If ADDR
1721 is not modified by the memory reference then ADDR is returned. */
1724 addr_side_effect_eval (rtx addr, int size, int n_refs)
1728 switch (GET_CODE (addr))
1731 offset = (n_refs + 1) * size;
1734 offset = -(n_refs + 1) * size;
1737 offset = n_refs * size;
1740 offset = -n_refs * size;
1748 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1751 addr = XEXP (addr, 0);
1752 addr = canon_rtx (addr);
1757 /* Return nonzero if X and Y (memory addresses) could reference the
1758 same location in memory. C is an offset accumulator. When
1759 C is nonzero, we are testing aliases between X and Y + C.
1760 XSIZE is the size in bytes of the X reference,
1761 similarly YSIZE is the size in bytes for Y.
1762 Expect that canon_rtx has been already called for X and Y.
1764 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1765 referenced (the reference was BLKmode), so make the most pessimistic
1768 If XSIZE or YSIZE is negative, we may access memory outside the object
1769 being referenced as a side effect. This can happen when using AND to
1770 align memory references, as is done on the Alpha.
1772 Nice to notice that varying addresses cannot conflict with fp if no
1773 local variables had their addresses taken, but that's too hard now. */
1776 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1778 if (GET_CODE (x) == VALUE)
1780 if (GET_CODE (y) == VALUE)
1782 if (GET_CODE (x) == HIGH)
1784 else if (GET_CODE (x) == LO_SUM)
1787 x = addr_side_effect_eval (x, xsize, 0);
1788 if (GET_CODE (y) == HIGH)
1790 else if (GET_CODE (y) == LO_SUM)
1793 y = addr_side_effect_eval (y, ysize, 0);
1795 if (rtx_equal_for_memref_p (x, y))
1797 if (xsize <= 0 || ysize <= 0)
1799 if (c >= 0 && xsize > c)
1801 if (c < 0 && ysize+c > 0)
1806 /* This code used to check for conflicts involving stack references and
1807 globals but the base address alias code now handles these cases. */
1809 if (GET_CODE (x) == PLUS)
1811 /* The fact that X is canonicalized means that this
1812 PLUS rtx is canonicalized. */
1813 rtx x0 = XEXP (x, 0);
1814 rtx x1 = XEXP (x, 1);
1816 if (GET_CODE (y) == PLUS)
1818 /* The fact that Y is canonicalized means that this
1819 PLUS rtx is canonicalized. */
1820 rtx y0 = XEXP (y, 0);
1821 rtx y1 = XEXP (y, 1);
1823 if (rtx_equal_for_memref_p (x1, y1))
1824 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1825 if (rtx_equal_for_memref_p (x0, y0))
1826 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1827 if (CONST_INT_P (x1))
1829 if (CONST_INT_P (y1))
1830 return memrefs_conflict_p (xsize, x0, ysize, y0,
1831 c - INTVAL (x1) + INTVAL (y1));
1833 return memrefs_conflict_p (xsize, x0, ysize, y,
1836 else if (CONST_INT_P (y1))
1837 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1841 else if (CONST_INT_P (x1))
1842 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1844 else if (GET_CODE (y) == PLUS)
1846 /* The fact that Y is canonicalized means that this
1847 PLUS rtx is canonicalized. */
1848 rtx y0 = XEXP (y, 0);
1849 rtx y1 = XEXP (y, 1);
1851 if (CONST_INT_P (y1))
1852 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1857 if (GET_CODE (x) == GET_CODE (y))
1858 switch (GET_CODE (x))
1862 /* Handle cases where we expect the second operands to be the
1863 same, and check only whether the first operand would conflict
1866 rtx x1 = canon_rtx (XEXP (x, 1));
1867 rtx y1 = canon_rtx (XEXP (y, 1));
1868 if (! rtx_equal_for_memref_p (x1, y1))
1870 x0 = canon_rtx (XEXP (x, 0));
1871 y0 = canon_rtx (XEXP (y, 0));
1872 if (rtx_equal_for_memref_p (x0, y0))
1873 return (xsize == 0 || ysize == 0
1874 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1876 /* Can't properly adjust our sizes. */
1877 if (!CONST_INT_P (x1))
1879 xsize /= INTVAL (x1);
1880 ysize /= INTVAL (x1);
1882 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1889 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1890 as an access with indeterminate size. Assume that references
1891 besides AND are aligned, so if the size of the other reference is
1892 at least as large as the alignment, assume no other overlap. */
1893 if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1)))
1895 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1897 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1899 if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1)))
1901 /* ??? If we are indexing far enough into the array/structure, we
1902 may yet be able to determine that we can not overlap. But we
1903 also need to that we are far enough from the end not to overlap
1904 a following reference, so we do nothing with that for now. */
1905 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1907 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1912 if (CONST_INT_P (x) && CONST_INT_P (y))
1914 c += (INTVAL (y) - INTVAL (x));
1915 return (xsize <= 0 || ysize <= 0
1916 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1919 if (GET_CODE (x) == CONST)
1921 if (GET_CODE (y) == CONST)
1922 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1923 ysize, canon_rtx (XEXP (y, 0)), c);
1925 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1928 if (GET_CODE (y) == CONST)
1929 return memrefs_conflict_p (xsize, x, ysize,
1930 canon_rtx (XEXP (y, 0)), c);
1933 return (xsize <= 0 || ysize <= 0
1934 || (rtx_equal_for_memref_p (x, y)
1935 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1942 /* Functions to compute memory dependencies.
1944 Since we process the insns in execution order, we can build tables
1945 to keep track of what registers are fixed (and not aliased), what registers
1946 are varying in known ways, and what registers are varying in unknown
1949 If both memory references are volatile, then there must always be a
1950 dependence between the two references, since their order can not be
1951 changed. A volatile and non-volatile reference can be interchanged
1954 A MEM_IN_STRUCT reference at a non-AND varying address can never
1955 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1956 also must allow AND addresses, because they may generate accesses
1957 outside the object being referenced. This is used to generate
1958 aligned addresses from unaligned addresses, for instance, the alpha
1959 storeqi_unaligned pattern. */
1961 /* Read dependence: X is read after read in MEM takes place. There can
1962 only be a dependence here if both reads are volatile. */
1965 read_dependence (const_rtx mem, const_rtx x)
1967 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1970 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1971 MEM2 is a reference to a structure at a varying address, or returns
1972 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1973 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1974 to decide whether or not an address may vary; it should return
1975 nonzero whenever variation is possible.
1976 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1979 fixed_scalar_and_varying_struct_p (const_rtx mem1, const_rtx mem2, rtx mem1_addr,
1981 bool (*varies_p) (const_rtx, bool))
1983 if (! flag_strict_aliasing)
1986 if (MEM_ALIAS_SET (mem2)
1987 && MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1988 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1989 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1993 if (MEM_ALIAS_SET (mem1)
1994 && MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1995 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1996 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
2003 /* Returns nonzero if something about the mode or address format MEM1
2004 indicates that it might well alias *anything*. */
2007 aliases_everything_p (const_rtx mem)
2009 if (GET_CODE (XEXP (mem, 0)) == AND)
2010 /* If the address is an AND, it's very hard to know at what it is
2011 actually pointing. */
2017 /* Return true if we can determine that the fields referenced cannot
2018 overlap for any pair of objects. */
2021 nonoverlapping_component_refs_p (const_tree x, const_tree y)
2023 const_tree fieldx, fieldy, typex, typey, orig_y;
2025 if (!flag_strict_aliasing)
2030 /* The comparison has to be done at a common type, since we don't
2031 know how the inheritance hierarchy works. */
2035 fieldx = TREE_OPERAND (x, 1);
2036 typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx));
2041 fieldy = TREE_OPERAND (y, 1);
2042 typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy));
2047 y = TREE_OPERAND (y, 0);
2049 while (y && TREE_CODE (y) == COMPONENT_REF);
2051 x = TREE_OPERAND (x, 0);
2053 while (x && TREE_CODE (x) == COMPONENT_REF);
2054 /* Never found a common type. */
2058 /* If we're left with accessing different fields of a structure,
2060 if (TREE_CODE (typex) == RECORD_TYPE
2061 && fieldx != fieldy)
2064 /* The comparison on the current field failed. If we're accessing
2065 a very nested structure, look at the next outer level. */
2066 x = TREE_OPERAND (x, 0);
2067 y = TREE_OPERAND (y, 0);
2070 && TREE_CODE (x) == COMPONENT_REF
2071 && TREE_CODE (y) == COMPONENT_REF);
2076 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2079 decl_for_component_ref (tree x)
2083 x = TREE_OPERAND (x, 0);
2085 while (x && TREE_CODE (x) == COMPONENT_REF);
2087 return x && DECL_P (x) ? x : NULL_TREE;
2090 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
2091 offset of the field reference. */
2094 adjust_offset_for_component_ref (tree x, rtx offset)
2096 HOST_WIDE_INT ioffset;
2101 ioffset = INTVAL (offset);
2104 tree offset = component_ref_field_offset (x);
2105 tree field = TREE_OPERAND (x, 1);
2107 if (! host_integerp (offset, 1))
2109 ioffset += (tree_low_cst (offset, 1)
2110 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
2113 x = TREE_OPERAND (x, 0);
2115 while (x && TREE_CODE (x) == COMPONENT_REF);
2117 return GEN_INT (ioffset);
2120 /* Return nonzero if we can determine the exprs corresponding to memrefs
2121 X and Y and they do not overlap. */
2124 nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
2126 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
2129 rtx moffsetx, moffsety;
2130 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
2132 /* Unless both have exprs, we can't tell anything. */
2133 if (exprx == 0 || expry == 0)
2136 /* If both are field references, we may be able to determine something. */
2137 if (TREE_CODE (exprx) == COMPONENT_REF
2138 && TREE_CODE (expry) == COMPONENT_REF
2139 && nonoverlapping_component_refs_p (exprx, expry))
2143 /* If the field reference test failed, look at the DECLs involved. */
2144 moffsetx = MEM_OFFSET (x);
2145 if (TREE_CODE (exprx) == COMPONENT_REF)
2147 if (TREE_CODE (expry) == VAR_DECL
2148 && POINTER_TYPE_P (TREE_TYPE (expry)))
2150 tree field = TREE_OPERAND (exprx, 1);
2151 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2152 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2157 tree t = decl_for_component_ref (exprx);
2160 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
2164 else if (INDIRECT_REF_P (exprx))
2166 exprx = TREE_OPERAND (exprx, 0);
2167 if (flag_argument_noalias < 2
2168 || TREE_CODE (exprx) != PARM_DECL)
2172 moffsety = MEM_OFFSET (y);
2173 if (TREE_CODE (expry) == COMPONENT_REF)
2175 if (TREE_CODE (exprx) == VAR_DECL
2176 && POINTER_TYPE_P (TREE_TYPE (exprx)))
2178 tree field = TREE_OPERAND (expry, 1);
2179 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2180 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2185 tree t = decl_for_component_ref (expry);
2188 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2192 else if (INDIRECT_REF_P (expry))
2194 expry = TREE_OPERAND (expry, 0);
2195 if (flag_argument_noalias < 2
2196 || TREE_CODE (expry) != PARM_DECL)
2200 if (! DECL_P (exprx) || ! DECL_P (expry))
2203 rtlx = DECL_RTL (exprx);
2204 rtly = DECL_RTL (expry);
2206 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2207 can't overlap unless they are the same because we never reuse that part
2208 of the stack frame used for locals for spilled pseudos. */
2209 if ((!MEM_P (rtlx) || !MEM_P (rtly))
2210 && ! rtx_equal_p (rtlx, rtly))
2213 /* If we have MEMs refering to different address spaces (which can
2214 potentially overlap), we cannot easily tell from the addresses
2215 whether the references overlap. */
2216 if (MEM_P (rtlx) && MEM_P (rtly)
2217 && MEM_ADDR_SPACE (rtlx) != MEM_ADDR_SPACE (rtly))
2220 /* Get the base and offsets of both decls. If either is a register, we
2221 know both are and are the same, so use that as the base. The only
2222 we can avoid overlap is if we can deduce that they are nonoverlapping
2223 pieces of that decl, which is very rare. */
2224 basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx;
2225 if (GET_CODE (basex) == PLUS && CONST_INT_P (XEXP (basex, 1)))
2226 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2228 basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly;
2229 if (GET_CODE (basey) == PLUS && CONST_INT_P (XEXP (basey, 1)))
2230 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2232 /* If the bases are different, we know they do not overlap if both
2233 are constants or if one is a constant and the other a pointer into the
2234 stack frame. Otherwise a different base means we can't tell if they
2236 if (! rtx_equal_p (basex, basey))
2237 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2238 || (CONSTANT_P (basex) && REG_P (basey)
2239 && REGNO_PTR_FRAME_P (REGNO (basey)))
2240 || (CONSTANT_P (basey) && REG_P (basex)
2241 && REGNO_PTR_FRAME_P (REGNO (basex))));
2243 sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2244 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2246 sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2247 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2250 /* If we have an offset for either memref, it can update the values computed
2253 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2255 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2257 /* If a memref has both a size and an offset, we can use the smaller size.
2258 We can't do this if the offset isn't known because we must view this
2259 memref as being anywhere inside the DECL's MEM. */
2260 if (MEM_SIZE (x) && moffsetx)
2261 sizex = INTVAL (MEM_SIZE (x));
2262 if (MEM_SIZE (y) && moffsety)
2263 sizey = INTVAL (MEM_SIZE (y));
2265 /* Put the values of the memref with the lower offset in X's values. */
2266 if (offsetx > offsety)
2268 tem = offsetx, offsetx = offsety, offsety = tem;
2269 tem = sizex, sizex = sizey, sizey = tem;
2272 /* If we don't know the size of the lower-offset value, we can't tell
2273 if they conflict. Otherwise, we do the test. */
2274 return sizex >= 0 && offsety >= offsetx + sizex;
2277 /* True dependence: X is read after store in MEM takes place. */
2280 true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x,
2281 bool (*varies) (const_rtx, bool))
2283 rtx x_addr, mem_addr;
2286 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2289 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2290 This is used in epilogue deallocation functions, and in cselib. */
2291 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2293 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2295 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2296 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2299 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2302 /* Read-only memory is by definition never modified, and therefore can't
2303 conflict with anything. We don't expect to find read-only set on MEM,
2304 but stupid user tricks can produce them, so don't die. */
2305 if (MEM_READONLY_P (x))
2308 if (nonoverlapping_memrefs_p (mem, x))
2311 /* If we have MEMs refering to different address spaces (which can
2312 potentially overlap), we cannot easily tell from the addresses
2313 whether the references overlap. */
2314 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
2317 if (mem_mode == VOIDmode)
2318 mem_mode = GET_MODE (mem);
2320 x_addr = get_addr (XEXP (x, 0));
2321 mem_addr = get_addr (XEXP (mem, 0));
2323 base = find_base_term (x_addr);
2324 if (base && (GET_CODE (base) == LABEL_REF
2325 || (GET_CODE (base) == SYMBOL_REF
2326 && CONSTANT_POOL_ADDRESS_P (base))))
2329 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2332 x_addr = canon_rtx (x_addr);
2333 mem_addr = canon_rtx (mem_addr);
2335 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2336 SIZE_FOR_MODE (x), x_addr, 0))
2339 if (aliases_everything_p (x))
2342 /* We cannot use aliases_everything_p to test MEM, since we must look
2343 at MEM_MODE, rather than GET_MODE (MEM). */
2344 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2347 /* In true_dependence we also allow BLKmode to alias anything. Why
2348 don't we do this in anti_dependence and output_dependence? */
2349 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2352 if (fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, varies))
2355 return rtx_refs_may_alias_p (x, mem, true);
2358 /* Canonical true dependence: X is read after store in MEM takes place.
2359 Variant of true_dependence which assumes MEM has already been
2360 canonicalized (hence we no longer do that here).
2361 The mem_addr argument has been added, since true_dependence computed
2362 this value prior to canonicalizing.
2363 If x_addr is non-NULL, it is used in preference of XEXP (x, 0). */
2366 canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2367 const_rtx x, rtx x_addr, bool (*varies) (const_rtx, bool))
2369 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2372 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2373 This is used in epilogue deallocation functions. */
2374 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2376 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2378 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2379 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2382 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2385 /* Read-only memory is by definition never modified, and therefore can't
2386 conflict with anything. We don't expect to find read-only set on MEM,
2387 but stupid user tricks can produce them, so don't die. */
2388 if (MEM_READONLY_P (x))
2391 if (nonoverlapping_memrefs_p (x, mem))
2394 /* If we have MEMs refering to different address spaces (which can
2395 potentially overlap), we cannot easily tell from the addresses
2396 whether the references overlap. */
2397 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
2401 x_addr = get_addr (XEXP (x, 0));
2403 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2406 x_addr = canon_rtx (x_addr);
2407 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2408 SIZE_FOR_MODE (x), x_addr, 0))
2411 if (aliases_everything_p (x))
2414 /* We cannot use aliases_everything_p to test MEM, since we must look
2415 at MEM_MODE, rather than GET_MODE (MEM). */
2416 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2419 /* In true_dependence we also allow BLKmode to alias anything. Why
2420 don't we do this in anti_dependence and output_dependence? */
2421 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2424 if (fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, varies))
2427 return rtx_refs_may_alias_p (x, mem, true);
2430 /* Returns nonzero if a write to X might alias a previous read from
2431 (or, if WRITEP is nonzero, a write to) MEM. */
2434 write_dependence_p (const_rtx mem, const_rtx x, int writep)
2436 rtx x_addr, mem_addr;
2437 const_rtx fixed_scalar;
2440 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2443 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2444 This is used in epilogue deallocation functions. */
2445 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2447 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2449 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2450 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2453 /* A read from read-only memory can't conflict with read-write memory. */
2454 if (!writep && MEM_READONLY_P (mem))
2457 if (nonoverlapping_memrefs_p (x, mem))
2460 /* If we have MEMs refering to different address spaces (which can
2461 potentially overlap), we cannot easily tell from the addresses
2462 whether the references overlap. */
2463 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
2466 x_addr = get_addr (XEXP (x, 0));
2467 mem_addr = get_addr (XEXP (mem, 0));
2471 base = find_base_term (mem_addr);
2472 if (base && (GET_CODE (base) == LABEL_REF
2473 || (GET_CODE (base) == SYMBOL_REF
2474 && CONSTANT_POOL_ADDRESS_P (base))))
2478 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2482 x_addr = canon_rtx (x_addr);
2483 mem_addr = canon_rtx (mem_addr);
2485 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2486 SIZE_FOR_MODE (x), x_addr, 0))
2490 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2493 if ((fixed_scalar == mem && !aliases_everything_p (x))
2494 || (fixed_scalar == x && !aliases_everything_p (mem)))
2497 return rtx_refs_may_alias_p (x, mem, false);
2500 /* Anti dependence: X is written after read in MEM takes place. */
2503 anti_dependence (const_rtx mem, const_rtx x)
2505 return write_dependence_p (mem, x, /*writep=*/0);
2508 /* Output dependence: X is written after store in MEM takes place. */
2511 output_dependence (const_rtx mem, const_rtx x)
2513 return write_dependence_p (mem, x, /*writep=*/1);
2518 init_alias_target (void)
2522 memset (static_reg_base_value, 0, sizeof static_reg_base_value);
2524 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2525 /* Check whether this register can hold an incoming pointer
2526 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2527 numbers, so translate if necessary due to register windows. */
2528 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2529 && HARD_REGNO_MODE_OK (i, Pmode))
2530 static_reg_base_value[i]
2531 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2533 static_reg_base_value[STACK_POINTER_REGNUM]
2534 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2535 static_reg_base_value[ARG_POINTER_REGNUM]
2536 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2537 static_reg_base_value[FRAME_POINTER_REGNUM]
2538 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2539 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2540 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2541 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2545 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2546 to be memory reference. */
2547 static bool memory_modified;
2549 memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
2553 if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data))
2554 memory_modified = true;
2559 /* Return true when INSN possibly modify memory contents of MEM
2560 (i.e. address can be modified). */
2562 memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
2566 memory_modified = false;
2567 note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
2568 return memory_modified;
2571 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2575 init_alias_analysis (void)
2577 unsigned int maxreg = max_reg_num ();
2583 timevar_push (TV_ALIAS_ANALYSIS);
2585 reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER;
2586 reg_known_value = GGC_CNEWVEC (rtx, reg_known_value_size);
2587 reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size);
2589 /* If we have memory allocated from the previous run, use it. */
2590 if (old_reg_base_value)
2591 reg_base_value = old_reg_base_value;
2594 VEC_truncate (rtx, reg_base_value, 0);
2596 VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg);
2598 new_reg_base_value = XNEWVEC (rtx, maxreg);
2599 reg_seen = XNEWVEC (char, maxreg);
2601 /* The basic idea is that each pass through this loop will use the
2602 "constant" information from the previous pass to propagate alias
2603 information through another level of assignments.
2605 This could get expensive if the assignment chains are long. Maybe
2606 we should throttle the number of iterations, possibly based on
2607 the optimization level or flag_expensive_optimizations.
2609 We could propagate more information in the first pass by making use
2610 of DF_REG_DEF_COUNT to determine immediately that the alias information
2611 for a pseudo is "constant".
2613 A program with an uninitialized variable can cause an infinite loop
2614 here. Instead of doing a full dataflow analysis to detect such problems
2615 we just cap the number of iterations for the loop.
2617 The state of the arrays for the set chain in question does not matter
2618 since the program has undefined behavior. */
2623 /* Assume nothing will change this iteration of the loop. */
2626 /* We want to assign the same IDs each iteration of this loop, so
2627 start counting from zero each iteration of the loop. */
2630 /* We're at the start of the function each iteration through the
2631 loop, so we're copying arguments. */
2632 copying_arguments = true;
2634 /* Wipe the potential alias information clean for this pass. */
2635 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2637 /* Wipe the reg_seen array clean. */
2638 memset (reg_seen, 0, maxreg);
2640 /* Mark all hard registers which may contain an address.
2641 The stack, frame and argument pointers may contain an address.
2642 An argument register which can hold a Pmode value may contain
2643 an address even if it is not in BASE_REGS.
2645 The address expression is VOIDmode for an argument and
2646 Pmode for other registers. */
2648 memcpy (new_reg_base_value, static_reg_base_value,
2649 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2651 /* Walk the insns adding values to the new_reg_base_value array. */
2652 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2658 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2659 /* The prologue/epilogue insns are not threaded onto the
2660 insn chain until after reload has completed. Thus,
2661 there is no sense wasting time checking if INSN is in
2662 the prologue/epilogue until after reload has completed. */
2663 if (reload_completed
2664 && prologue_epilogue_contains (insn))
2668 /* If this insn has a noalias note, process it, Otherwise,
2669 scan for sets. A simple set will have no side effects
2670 which could change the base value of any other register. */
2672 if (GET_CODE (PATTERN (insn)) == SET
2673 && REG_NOTES (insn) != 0
2674 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2675 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2677 note_stores (PATTERN (insn), record_set, NULL);
2679 set = single_set (insn);
2682 && REG_P (SET_DEST (set))
2683 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2685 unsigned int regno = REGNO (SET_DEST (set));
2686 rtx src = SET_SRC (set);
2689 note = find_reg_equal_equiv_note (insn);
2690 if (note && REG_NOTE_KIND (note) == REG_EQUAL
2691 && DF_REG_DEF_COUNT (regno) != 1)
2694 if (note != NULL_RTX
2695 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2696 && ! rtx_varies_p (XEXP (note, 0), 1)
2697 && ! reg_overlap_mentioned_p (SET_DEST (set),
2700 set_reg_known_value (regno, XEXP (note, 0));
2701 set_reg_known_equiv_p (regno,
2702 REG_NOTE_KIND (note) == REG_EQUIV);
2704 else if (DF_REG_DEF_COUNT (regno) == 1
2705 && GET_CODE (src) == PLUS
2706 && REG_P (XEXP (src, 0))
2707 && (t = get_reg_known_value (REGNO (XEXP (src, 0))))
2708 && CONST_INT_P (XEXP (src, 1)))
2710 t = plus_constant (t, INTVAL (XEXP (src, 1)));
2711 set_reg_known_value (regno, t);
2712 set_reg_known_equiv_p (regno, 0);
2714 else if (DF_REG_DEF_COUNT (regno) == 1
2715 && ! rtx_varies_p (src, 1))
2717 set_reg_known_value (regno, src);
2718 set_reg_known_equiv_p (regno, 0);
2722 else if (NOTE_P (insn)
2723 && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG)
2724 copying_arguments = false;
2727 /* Now propagate values from new_reg_base_value to reg_base_value. */
2728 gcc_assert (maxreg == (unsigned int) max_reg_num ());
2730 for (ui = 0; ui < maxreg; ui++)
2732 if (new_reg_base_value[ui]
2733 && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui)
2734 && ! rtx_equal_p (new_reg_base_value[ui],
2735 VEC_index (rtx, reg_base_value, ui)))
2737 VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]);
2742 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2744 /* Fill in the remaining entries. */
2745 for (i = 0; i < (int)reg_known_value_size; i++)
2746 if (reg_known_value[i] == 0)
2747 reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER];
2750 free (new_reg_base_value);
2751 new_reg_base_value = 0;
2754 timevar_pop (TV_ALIAS_ANALYSIS);
2758 end_alias_analysis (void)
2760 old_reg_base_value = reg_base_value;
2761 ggc_free (reg_known_value);
2762 reg_known_value = 0;
2763 reg_known_value_size = 0;
2764 free (reg_known_equiv_p);
2765 reg_known_equiv_p = 0;
2768 #include "gt-alias.h"