1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009, 2010 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 ao_ref_init (ref, expr);
270 /* Get the base of the reference and see if we have to reject or
272 base = ao_ref_base (ref);
273 if (base == NULL_TREE)
276 /* The tree oracle doesn't like to have these. */
277 if (TREE_CODE (base) == FUNCTION_DECL
278 || TREE_CODE (base) == LABEL_DECL)
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 /* If this is a reference based on a partitioned decl replace the
288 base with an INDIRECT_REF of the pointer representative we
289 created during stack slot partitioning. */
290 if (TREE_CODE (base) == VAR_DECL
291 && ! TREE_STATIC (base)
292 && cfun->gimple_df->decls_to_pointers != NULL)
295 namep = pointer_map_contains (cfun->gimple_df->decls_to_pointers, base);
298 ref->base_alias_set = get_alias_set (base);
299 ref->base = build1 (INDIRECT_REF, TREE_TYPE (base), *(tree *)namep);
303 ref->ref_alias_set = MEM_ALIAS_SET (mem);
305 /* If MEM_OFFSET or MEM_SIZE are NULL we have to punt.
306 Keep points-to related information though. */
307 if (!MEM_OFFSET (mem)
310 ref->ref = NULL_TREE;
317 /* If the base decl is a parameter we can have negative MEM_OFFSET in
318 case of promoted subregs on bigendian targets. Trust the MEM_EXPR
320 if (INTVAL (MEM_OFFSET (mem)) < 0
321 && ((INTVAL (MEM_SIZE (mem)) + INTVAL (MEM_OFFSET (mem)))
322 * BITS_PER_UNIT) == ref->size)
325 ref->offset += INTVAL (MEM_OFFSET (mem)) * BITS_PER_UNIT;
326 ref->size = INTVAL (MEM_SIZE (mem)) * BITS_PER_UNIT;
328 /* The MEM may extend into adjacent fields, so adjust max_size if
330 if (ref->max_size != -1
331 && ref->size > ref->max_size)
332 ref->max_size = ref->size;
334 /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of
335 the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */
336 if (MEM_EXPR (mem) != get_spill_slot_decl (false)
338 || (DECL_P (ref->base)
339 && (!host_integerp (DECL_SIZE (ref->base), 1)
340 || (TREE_INT_CST_LOW (DECL_SIZE ((ref->base)))
341 < (unsigned HOST_WIDE_INT)(ref->offset + ref->size))))))
347 /* Query the alias-oracle on whether the two memory rtx X and MEM may
348 alias. If TBAA_P is set also apply TBAA. Returns true if the
349 two rtxen may alias, false otherwise. */
352 rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p)
356 if (!ao_ref_from_mem (&ref1, x)
357 || !ao_ref_from_mem (&ref2, mem))
360 return refs_may_alias_p_1 (&ref1, &ref2, tbaa_p);
363 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
364 such an entry, or NULL otherwise. */
366 static inline alias_set_entry
367 get_alias_set_entry (alias_set_type alias_set)
369 return VEC_index (alias_set_entry, alias_sets, alias_set);
372 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
373 the two MEMs cannot alias each other. */
376 mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2)
378 /* Perform a basic sanity check. Namely, that there are no alias sets
379 if we're not using strict aliasing. This helps to catch bugs
380 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
381 where a MEM is allocated in some way other than by the use of
382 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
383 use alias sets to indicate that spilled registers cannot alias each
384 other, we might need to remove this check. */
385 gcc_assert (flag_strict_aliasing
386 || (!MEM_ALIAS_SET (mem1) && !MEM_ALIAS_SET (mem2)));
388 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
391 /* Insert the NODE into the splay tree given by DATA. Used by
392 record_alias_subset via splay_tree_foreach. */
395 insert_subset_children (splay_tree_node node, void *data)
397 splay_tree_insert ((splay_tree) data, node->key, node->value);
402 /* Return true if the first alias set is a subset of the second. */
405 alias_set_subset_of (alias_set_type set1, alias_set_type set2)
409 /* Everything is a subset of the "aliases everything" set. */
413 /* Otherwise, check if set1 is a subset of set2. */
414 ase = get_alias_set_entry (set2);
416 && ((ase->has_zero_child && set1 == 0)
417 || splay_tree_lookup (ase->children,
418 (splay_tree_key) set1)))
423 /* Return 1 if the two specified alias sets may conflict. */
426 alias_sets_conflict_p (alias_set_type set1, alias_set_type set2)
431 if (alias_sets_must_conflict_p (set1, set2))
434 /* See if the first alias set is a subset of the second. */
435 ase = get_alias_set_entry (set1);
437 && (ase->has_zero_child
438 || splay_tree_lookup (ase->children,
439 (splay_tree_key) set2)))
442 /* Now do the same, but with the alias sets reversed. */
443 ase = get_alias_set_entry (set2);
445 && (ase->has_zero_child
446 || splay_tree_lookup (ase->children,
447 (splay_tree_key) set1)))
450 /* The two alias sets are distinct and neither one is the
451 child of the other. Therefore, they cannot conflict. */
456 walk_mems_2 (rtx *x, rtx mem)
460 if (alias_sets_conflict_p (MEM_ALIAS_SET(*x), MEM_ALIAS_SET(mem)))
469 walk_mems_1 (rtx *x, rtx *pat)
473 /* Visit all MEMs in *PAT and check indepedence. */
474 if (for_each_rtx (pat, (rtx_function) walk_mems_2, *x))
475 /* Indicate that dependence was determined and stop traversal. */
483 /* Return 1 if two specified instructions have mem expr with conflict alias sets*/
485 insn_alias_sets_conflict_p (rtx insn1, rtx insn2)
487 /* For each pair of MEMs in INSN1 and INSN2 check their independence. */
488 return for_each_rtx (&PATTERN (insn1), (rtx_function) walk_mems_1,
492 /* Return 1 if the two specified alias sets will always conflict. */
495 alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2)
497 if (set1 == 0 || set2 == 0 || set1 == set2)
503 /* Return 1 if any MEM object of type T1 will always conflict (using the
504 dependency routines in this file) with any MEM object of type T2.
505 This is used when allocating temporary storage. If T1 and/or T2 are
506 NULL_TREE, it means we know nothing about the storage. */
509 objects_must_conflict_p (tree t1, tree t2)
511 alias_set_type set1, set2;
513 /* If neither has a type specified, we don't know if they'll conflict
514 because we may be using them to store objects of various types, for
515 example the argument and local variables areas of inlined functions. */
516 if (t1 == 0 && t2 == 0)
519 /* If they are the same type, they must conflict. */
521 /* Likewise if both are volatile. */
522 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
525 set1 = t1 ? get_alias_set (t1) : 0;
526 set2 = t2 ? get_alias_set (t2) : 0;
528 /* We can't use alias_sets_conflict_p because we must make sure
529 that every subtype of t1 will conflict with every subtype of
530 t2 for which a pair of subobjects of these respective subtypes
531 overlaps on the stack. */
532 return alias_sets_must_conflict_p (set1, set2);
535 /* Return true if all nested component references handled by
536 get_inner_reference in T are such that we should use the alias set
537 provided by the object at the heart of T.
539 This is true for non-addressable components (which don't have their
540 own alias set), as well as components of objects in alias set zero.
541 This later point is a special case wherein we wish to override the
542 alias set used by the component, but we don't have per-FIELD_DECL
543 assignable alias sets. */
546 component_uses_parent_alias_set (const_tree t)
550 /* If we're at the end, it vacuously uses its own alias set. */
551 if (!handled_component_p (t))
554 switch (TREE_CODE (t))
557 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
562 case ARRAY_RANGE_REF:
563 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))))
572 /* Bitfields and casts are never addressable. */
576 t = TREE_OPERAND (t, 0);
577 if (get_alias_set (TREE_TYPE (t)) == 0)
582 /* Return the alias set for the memory pointed to by T, which may be
583 either a type or an expression. Return -1 if there is nothing
584 special about dereferencing T. */
586 static alias_set_type
587 get_deref_alias_set_1 (tree t)
589 /* If we're not doing any alias analysis, just assume everything
590 aliases everything else. */
591 if (!flag_strict_aliasing)
594 /* All we care about is the type. */
598 /* If we have an INDIRECT_REF via a void pointer, we don't
599 know anything about what that might alias. Likewise if the
600 pointer is marked that way. */
601 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE
602 || TYPE_REF_CAN_ALIAS_ALL (t))
608 /* Return the alias set for the memory pointed to by T, which may be
609 either a type or an expression. */
612 get_deref_alias_set (tree t)
614 alias_set_type set = get_deref_alias_set_1 (t);
616 /* Fall back to the alias-set of the pointed-to type. */
621 set = get_alias_set (TREE_TYPE (t));
627 /* Return the alias set for T, which may be either a type or an
628 expression. Call language-specific routine for help, if needed. */
631 get_alias_set (tree t)
635 /* If we're not doing any alias analysis, just assume everything
636 aliases everything else. Also return 0 if this or its type is
638 if (! flag_strict_aliasing || t == error_mark_node
640 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
643 /* We can be passed either an expression or a type. This and the
644 language-specific routine may make mutually-recursive calls to each other
645 to figure out what to do. At each juncture, we see if this is a tree
646 that the language may need to handle specially. First handle things that
652 /* Remove any nops, then give the language a chance to do
653 something with this tree before we look at it. */
655 set = lang_hooks.get_alias_set (t);
659 /* Retrieve the original memory reference if needed. */
660 if (TREE_CODE (t) == TARGET_MEM_REF)
661 t = TMR_ORIGINAL (t);
663 /* First see if the actual object referenced is an INDIRECT_REF from a
664 restrict-qualified pointer or a "void *". */
666 while (handled_component_p (inner))
668 inner = TREE_OPERAND (inner, 0);
672 if (INDIRECT_REF_P (inner))
674 set = get_deref_alias_set_1 (TREE_OPERAND (inner, 0));
679 /* Otherwise, pick up the outermost object that we could have a pointer
680 to, processing conversions as above. */
681 while (component_uses_parent_alias_set (t))
683 t = TREE_OPERAND (t, 0);
687 /* If we've already determined the alias set for a decl, just return
688 it. This is necessary for C++ anonymous unions, whose component
689 variables don't look like union members (boo!). */
690 if (TREE_CODE (t) == VAR_DECL
691 && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t)))
692 return MEM_ALIAS_SET (DECL_RTL (t));
694 /* Now all we care about is the type. */
698 /* Variant qualifiers don't affect the alias set, so get the main
700 t = TYPE_MAIN_VARIANT (t);
702 /* Always use the canonical type as well. If this is a type that
703 requires structural comparisons to identify compatible types
704 use alias set zero. */
705 if (TYPE_STRUCTURAL_EQUALITY_P (t))
707 /* Allow the language to specify another alias set for this
709 set = lang_hooks.get_alias_set (t);
714 t = TYPE_CANONICAL (t);
715 /* Canonical types shouldn't form a tree nor should the canonical
716 type require structural equality checks. */
717 gcc_assert (!TYPE_STRUCTURAL_EQUALITY_P (t) && TYPE_CANONICAL (t) == t);
719 /* If this is a type with a known alias set, return it. */
720 if (TYPE_ALIAS_SET_KNOWN_P (t))
721 return TYPE_ALIAS_SET (t);
723 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
724 if (!COMPLETE_TYPE_P (t))
726 /* For arrays with unknown size the conservative answer is the
727 alias set of the element type. */
728 if (TREE_CODE (t) == ARRAY_TYPE)
729 return get_alias_set (TREE_TYPE (t));
731 /* But return zero as a conservative answer for incomplete types. */
735 /* See if the language has special handling for this type. */
736 set = lang_hooks.get_alias_set (t);
740 /* There are no objects of FUNCTION_TYPE, so there's no point in
741 using up an alias set for them. (There are, of course, pointers
742 and references to functions, but that's different.) */
743 else if (TREE_CODE (t) == FUNCTION_TYPE
744 || TREE_CODE (t) == METHOD_TYPE)
747 /* Unless the language specifies otherwise, let vector types alias
748 their components. This avoids some nasty type punning issues in
749 normal usage. And indeed lets vectors be treated more like an
751 else if (TREE_CODE (t) == VECTOR_TYPE)
752 set = get_alias_set (TREE_TYPE (t));
754 /* Unless the language specifies otherwise, treat array types the
755 same as their components. This avoids the asymmetry we get
756 through recording the components. Consider accessing a
757 character(kind=1) through a reference to a character(kind=1)[1:1].
758 Or consider if we want to assign integer(kind=4)[0:D.1387] and
759 integer(kind=4)[4] the same alias set or not.
760 Just be pragmatic here and make sure the array and its element
761 type get the same alias set assigned. */
762 else if (TREE_CODE (t) == ARRAY_TYPE
763 && !TYPE_NONALIASED_COMPONENT (t))
764 set = get_alias_set (TREE_TYPE (t));
767 /* Otherwise make a new alias set for this type. */
768 set = new_alias_set ();
770 TYPE_ALIAS_SET (t) = set;
772 /* If this is an aggregate type, we must record any component aliasing
774 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
775 record_component_aliases (t);
780 /* Return a brand-new alias set. */
785 if (flag_strict_aliasing)
788 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
789 VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
790 return VEC_length (alias_set_entry, alias_sets) - 1;
796 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
797 not everything that aliases SUPERSET also aliases SUBSET. For example,
798 in C, a store to an `int' can alias a load of a structure containing an
799 `int', and vice versa. But it can't alias a load of a 'double' member
800 of the same structure. Here, the structure would be the SUPERSET and
801 `int' the SUBSET. This relationship is also described in the comment at
802 the beginning of this file.
804 This function should be called only once per SUPERSET/SUBSET pair.
806 It is illegal for SUPERSET to be zero; everything is implicitly a
807 subset of alias set zero. */
810 record_alias_subset (alias_set_type superset, alias_set_type subset)
812 alias_set_entry superset_entry;
813 alias_set_entry subset_entry;
815 /* It is possible in complex type situations for both sets to be the same,
816 in which case we can ignore this operation. */
817 if (superset == subset)
820 gcc_assert (superset);
822 superset_entry = get_alias_set_entry (superset);
823 if (superset_entry == 0)
825 /* Create an entry for the SUPERSET, so that we have a place to
826 attach the SUBSET. */
827 superset_entry = GGC_NEW (struct alias_set_entry_d);
828 superset_entry->alias_set = superset;
829 superset_entry->children
830 = splay_tree_new_ggc (splay_tree_compare_ints);
831 superset_entry->has_zero_child = 0;
832 VEC_replace (alias_set_entry, alias_sets, superset, superset_entry);
836 superset_entry->has_zero_child = 1;
839 subset_entry = get_alias_set_entry (subset);
840 /* If there is an entry for the subset, enter all of its children
841 (if they are not already present) as children of the SUPERSET. */
844 if (subset_entry->has_zero_child)
845 superset_entry->has_zero_child = 1;
847 splay_tree_foreach (subset_entry->children, insert_subset_children,
848 superset_entry->children);
851 /* Enter the SUBSET itself as a child of the SUPERSET. */
852 splay_tree_insert (superset_entry->children,
853 (splay_tree_key) subset, 0);
857 /* Record that component types of TYPE, if any, are part of that type for
858 aliasing purposes. For record types, we only record component types
859 for fields that are not marked non-addressable. For array types, we
860 only record the component type if it is not marked non-aliased. */
863 record_component_aliases (tree type)
865 alias_set_type superset = get_alias_set (type);
871 switch (TREE_CODE (type))
875 case QUAL_UNION_TYPE:
876 /* Recursively record aliases for the base classes, if there are any. */
877 if (TYPE_BINFO (type))
880 tree binfo, base_binfo;
882 for (binfo = TYPE_BINFO (type), i = 0;
883 BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
884 record_alias_subset (superset,
885 get_alias_set (BINFO_TYPE (base_binfo)));
887 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
888 if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
889 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
893 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
896 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
904 /* Allocate an alias set for use in storing and reading from the varargs
907 static GTY(()) alias_set_type varargs_set = -1;
910 get_varargs_alias_set (void)
913 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
914 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
915 consistently use the varargs alias set for loads from the varargs
916 area. So don't use it anywhere. */
919 if (varargs_set == -1)
920 varargs_set = new_alias_set ();
926 /* Likewise, but used for the fixed portions of the frame, e.g., register
929 static GTY(()) alias_set_type frame_set = -1;
932 get_frame_alias_set (void)
935 frame_set = new_alias_set ();
940 /* Inside SRC, the source of a SET, find a base address. */
943 find_base_value (rtx src)
947 #if defined (FIND_BASE_TERM)
948 /* Try machine-dependent ways to find the base term. */
949 src = FIND_BASE_TERM (src);
952 switch (GET_CODE (src))
960 /* At the start of a function, argument registers have known base
961 values which may be lost later. Returning an ADDRESS
962 expression here allows optimization based on argument values
963 even when the argument registers are used for other purposes. */
964 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
965 return new_reg_base_value[regno];
967 /* If a pseudo has a known base value, return it. Do not do this
968 for non-fixed hard regs since it can result in a circular
969 dependency chain for registers which have values at function entry.
971 The test above is not sufficient because the scheduler may move
972 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
973 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
974 && regno < VEC_length (rtx, reg_base_value))
976 /* If we're inside init_alias_analysis, use new_reg_base_value
977 to reduce the number of relaxation iterations. */
978 if (new_reg_base_value && new_reg_base_value[regno]
979 && DF_REG_DEF_COUNT (regno) == 1)
980 return new_reg_base_value[regno];
982 if (VEC_index (rtx, reg_base_value, regno))
983 return VEC_index (rtx, reg_base_value, regno);
989 /* Check for an argument passed in memory. Only record in the
990 copying-arguments block; it is too hard to track changes
992 if (copying_arguments
993 && (XEXP (src, 0) == arg_pointer_rtx
994 || (GET_CODE (XEXP (src, 0)) == PLUS
995 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
996 return gen_rtx_ADDRESS (VOIDmode, src);
1000 src = XEXP (src, 0);
1001 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
1004 /* ... fall through ... */
1009 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
1011 /* If either operand is a REG that is a known pointer, then it
1013 if (REG_P (src_0) && REG_POINTER (src_0))
1014 return find_base_value (src_0);
1015 if (REG_P (src_1) && REG_POINTER (src_1))
1016 return find_base_value (src_1);
1018 /* If either operand is a REG, then see if we already have
1019 a known value for it. */
1022 temp = find_base_value (src_0);
1029 temp = find_base_value (src_1);
1034 /* If either base is named object or a special address
1035 (like an argument or stack reference), then use it for the
1038 && (GET_CODE (src_0) == SYMBOL_REF
1039 || GET_CODE (src_0) == LABEL_REF
1040 || (GET_CODE (src_0) == ADDRESS
1041 && GET_MODE (src_0) != VOIDmode)))
1045 && (GET_CODE (src_1) == SYMBOL_REF
1046 || GET_CODE (src_1) == LABEL_REF
1047 || (GET_CODE (src_1) == ADDRESS
1048 && GET_MODE (src_1) != VOIDmode)))
1051 /* Guess which operand is the base address:
1052 If either operand is a symbol, then it is the base. If
1053 either operand is a CONST_INT, then the other is the base. */
1054 if (CONST_INT_P (src_1) || CONSTANT_P (src_0))
1055 return find_base_value (src_0);
1056 else if (CONST_INT_P (src_0) || CONSTANT_P (src_1))
1057 return find_base_value (src_1);
1063 /* The standard form is (lo_sum reg sym) so look only at the
1065 return find_base_value (XEXP (src, 1));
1068 /* If the second operand is constant set the base
1069 address to the first operand. */
1070 if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0)
1071 return find_base_value (XEXP (src, 0));
1075 /* As we do not know which address space the pointer is refering to, we can
1076 handle this only if the target does not support different pointer or
1077 address modes depending on the address space. */
1078 if (!target_default_pointer_address_modes_p ())
1080 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
1090 return find_base_value (XEXP (src, 0));
1093 case SIGN_EXTEND: /* used for NT/Alpha pointers */
1094 /* As we do not know which address space the pointer is refering to, we can
1095 handle this only if the target does not support different pointer or
1096 address modes depending on the address space. */
1097 if (!target_default_pointer_address_modes_p ())
1101 rtx temp = find_base_value (XEXP (src, 0));
1103 if (temp != 0 && CONSTANT_P (temp))
1104 temp = convert_memory_address (Pmode, temp);
1116 /* Called from init_alias_analysis indirectly through note_stores. */
1118 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1119 register N has been set in this function. */
1120 static char *reg_seen;
1122 /* Addresses which are known not to alias anything else are identified
1123 by a unique integer. */
1124 static int unique_id;
1127 record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED)
1136 regno = REGNO (dest);
1138 gcc_assert (regno < VEC_length (rtx, reg_base_value));
1140 /* If this spans multiple hard registers, then we must indicate that every
1141 register has an unusable value. */
1142 if (regno < FIRST_PSEUDO_REGISTER)
1143 n = hard_regno_nregs[regno][GET_MODE (dest)];
1150 reg_seen[regno + n] = 1;
1151 new_reg_base_value[regno + n] = 0;
1158 /* A CLOBBER wipes out any old value but does not prevent a previously
1159 unset register from acquiring a base address (i.e. reg_seen is not
1161 if (GET_CODE (set) == CLOBBER)
1163 new_reg_base_value[regno] = 0;
1166 src = SET_SRC (set);
1170 if (reg_seen[regno])
1172 new_reg_base_value[regno] = 0;
1175 reg_seen[regno] = 1;
1176 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
1177 GEN_INT (unique_id++));
1181 /* If this is not the first set of REGNO, see whether the new value
1182 is related to the old one. There are two cases of interest:
1184 (1) The register might be assigned an entirely new value
1185 that has the same base term as the original set.
1187 (2) The set might be a simple self-modification that
1188 cannot change REGNO's base value.
1190 If neither case holds, reject the original base value as invalid.
1191 Note that the following situation is not detected:
1193 extern int x, y; int *p = &x; p += (&y-&x);
1195 ANSI C does not allow computing the difference of addresses
1196 of distinct top level objects. */
1197 if (new_reg_base_value[regno] != 0
1198 && find_base_value (src) != new_reg_base_value[regno])
1199 switch (GET_CODE (src))
1203 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1204 new_reg_base_value[regno] = 0;
1207 /* If the value we add in the PLUS is also a valid base value,
1208 this might be the actual base value, and the original value
1211 rtx other = NULL_RTX;
1213 if (XEXP (src, 0) == dest)
1214 other = XEXP (src, 1);
1215 else if (XEXP (src, 1) == dest)
1216 other = XEXP (src, 0);
1218 if (! other || find_base_value (other))
1219 new_reg_base_value[regno] = 0;
1223 if (XEXP (src, 0) != dest || !CONST_INT_P (XEXP (src, 1)))
1224 new_reg_base_value[regno] = 0;
1227 new_reg_base_value[regno] = 0;
1230 /* If this is the first set of a register, record the value. */
1231 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1232 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1233 new_reg_base_value[regno] = find_base_value (src);
1235 reg_seen[regno] = 1;
1238 /* If a value is known for REGNO, return it. */
1241 get_reg_known_value (unsigned int regno)
1243 if (regno >= FIRST_PSEUDO_REGISTER)
1245 regno -= FIRST_PSEUDO_REGISTER;
1246 if (regno < reg_known_value_size)
1247 return reg_known_value[regno];
1255 set_reg_known_value (unsigned int regno, rtx val)
1257 if (regno >= FIRST_PSEUDO_REGISTER)
1259 regno -= FIRST_PSEUDO_REGISTER;
1260 if (regno < reg_known_value_size)
1261 reg_known_value[regno] = val;
1265 /* Similarly for reg_known_equiv_p. */
1268 get_reg_known_equiv_p (unsigned int regno)
1270 if (regno >= FIRST_PSEUDO_REGISTER)
1272 regno -= FIRST_PSEUDO_REGISTER;
1273 if (regno < reg_known_value_size)
1274 return reg_known_equiv_p[regno];
1280 set_reg_known_equiv_p (unsigned int regno, bool val)
1282 if (regno >= FIRST_PSEUDO_REGISTER)
1284 regno -= FIRST_PSEUDO_REGISTER;
1285 if (regno < reg_known_value_size)
1286 reg_known_equiv_p[regno] = val;
1291 /* Returns a canonical version of X, from the point of view alias
1292 analysis. (For example, if X is a MEM whose address is a register,
1293 and the register has a known value (say a SYMBOL_REF), then a MEM
1294 whose address is the SYMBOL_REF is returned.) */
1299 /* Recursively look for equivalences. */
1300 if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER)
1302 rtx t = get_reg_known_value (REGNO (x));
1306 return canon_rtx (t);
1309 if (GET_CODE (x) == PLUS)
1311 rtx x0 = canon_rtx (XEXP (x, 0));
1312 rtx x1 = canon_rtx (XEXP (x, 1));
1314 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1316 if (CONST_INT_P (x0))
1317 return plus_constant (x1, INTVAL (x0));
1318 else if (CONST_INT_P (x1))
1319 return plus_constant (x0, INTVAL (x1));
1320 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1324 /* This gives us much better alias analysis when called from
1325 the loop optimizer. Note we want to leave the original
1326 MEM alone, but need to return the canonicalized MEM with
1327 all the flags with their original values. */
1329 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1334 /* Return 1 if X and Y are identical-looking rtx's.
1335 Expect that X and Y has been already canonicalized.
1337 We use the data in reg_known_value above to see if two registers with
1338 different numbers are, in fact, equivalent. */
1341 rtx_equal_for_memref_p (const_rtx x, const_rtx y)
1348 if (x == 0 && y == 0)
1350 if (x == 0 || y == 0)
1356 code = GET_CODE (x);
1357 /* Rtx's of different codes cannot be equal. */
1358 if (code != GET_CODE (y))
1361 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1362 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1364 if (GET_MODE (x) != GET_MODE (y))
1367 /* Some RTL can be compared without a recursive examination. */
1371 return REGNO (x) == REGNO (y);
1374 return XEXP (x, 0) == XEXP (y, 0);
1377 return XSTR (x, 0) == XSTR (y, 0);
1383 /* There's no need to compare the contents of CONST_DOUBLEs or
1384 CONST_INTs because pointer equality is a good enough
1385 comparison for these nodes. */
1392 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1394 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1395 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1396 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1397 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1398 /* For commutative operations, the RTX match if the operand match in any
1399 order. Also handle the simple binary and unary cases without a loop. */
1400 if (COMMUTATIVE_P (x))
1402 rtx xop0 = canon_rtx (XEXP (x, 0));
1403 rtx yop0 = canon_rtx (XEXP (y, 0));
1404 rtx yop1 = canon_rtx (XEXP (y, 1));
1406 return ((rtx_equal_for_memref_p (xop0, yop0)
1407 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1408 || (rtx_equal_for_memref_p (xop0, yop1)
1409 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1411 else if (NON_COMMUTATIVE_P (x))
1413 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1414 canon_rtx (XEXP (y, 0)))
1415 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1416 canon_rtx (XEXP (y, 1))));
1418 else if (UNARY_P (x))
1419 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1420 canon_rtx (XEXP (y, 0)));
1422 /* Compare the elements. If any pair of corresponding elements
1423 fail to match, return 0 for the whole things.
1425 Limit cases to types which actually appear in addresses. */
1427 fmt = GET_RTX_FORMAT (code);
1428 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1433 if (XINT (x, i) != XINT (y, i))
1438 /* Two vectors must have the same length. */
1439 if (XVECLEN (x, i) != XVECLEN (y, i))
1442 /* And the corresponding elements must match. */
1443 for (j = 0; j < XVECLEN (x, i); j++)
1444 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1445 canon_rtx (XVECEXP (y, i, j))) == 0)
1450 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1451 canon_rtx (XEXP (y, i))) == 0)
1455 /* This can happen for asm operands. */
1457 if (strcmp (XSTR (x, i), XSTR (y, i)))
1461 /* This can happen for an asm which clobbers memory. */
1465 /* It is believed that rtx's at this level will never
1466 contain anything but integers and other rtx's,
1467 except for within LABEL_REFs and SYMBOL_REFs. */
1476 find_base_term (rtx x)
1479 struct elt_loc_list *l;
1481 #if defined (FIND_BASE_TERM)
1482 /* Try machine-dependent ways to find the base term. */
1483 x = FIND_BASE_TERM (x);
1486 switch (GET_CODE (x))
1489 return REG_BASE_VALUE (x);
1492 /* As we do not know which address space the pointer is refering to, we can
1493 handle this only if the target does not support different pointer or
1494 address modes depending on the address space. */
1495 if (!target_default_pointer_address_modes_p ())
1497 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1507 return find_base_term (XEXP (x, 0));
1510 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1511 /* As we do not know which address space the pointer is refering to, we can
1512 handle this only if the target does not support different pointer or
1513 address modes depending on the address space. */
1514 if (!target_default_pointer_address_modes_p ())
1518 rtx temp = find_base_term (XEXP (x, 0));
1520 if (temp != 0 && CONSTANT_P (temp))
1521 temp = convert_memory_address (Pmode, temp);
1527 val = CSELIB_VAL_PTR (x);
1530 for (l = val->locs; l; l = l->next)
1531 if ((x = find_base_term (l->loc)) != 0)
1536 /* The standard form is (lo_sum reg sym) so look only at the
1538 return find_base_term (XEXP (x, 1));
1542 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1548 rtx tmp1 = XEXP (x, 0);
1549 rtx tmp2 = XEXP (x, 1);
1551 /* This is a little bit tricky since we have to determine which of
1552 the two operands represents the real base address. Otherwise this
1553 routine may return the index register instead of the base register.
1555 That may cause us to believe no aliasing was possible, when in
1556 fact aliasing is possible.
1558 We use a few simple tests to guess the base register. Additional
1559 tests can certainly be added. For example, if one of the operands
1560 is a shift or multiply, then it must be the index register and the
1561 other operand is the base register. */
1563 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1564 return find_base_term (tmp2);
1566 /* If either operand is known to be a pointer, then use it
1567 to determine the base term. */
1568 if (REG_P (tmp1) && REG_POINTER (tmp1))
1570 rtx base = find_base_term (tmp1);
1575 if (REG_P (tmp2) && REG_POINTER (tmp2))
1577 rtx base = find_base_term (tmp2);
1582 /* Neither operand was known to be a pointer. Go ahead and find the
1583 base term for both operands. */
1584 tmp1 = find_base_term (tmp1);
1585 tmp2 = find_base_term (tmp2);
1587 /* If either base term is named object or a special address
1588 (like an argument or stack reference), then use it for the
1591 && (GET_CODE (tmp1) == SYMBOL_REF
1592 || GET_CODE (tmp1) == LABEL_REF
1593 || (GET_CODE (tmp1) == ADDRESS
1594 && GET_MODE (tmp1) != VOIDmode)))
1598 && (GET_CODE (tmp2) == SYMBOL_REF
1599 || GET_CODE (tmp2) == LABEL_REF
1600 || (GET_CODE (tmp2) == ADDRESS
1601 && GET_MODE (tmp2) != VOIDmode)))
1604 /* We could not determine which of the two operands was the
1605 base register and which was the index. So we can determine
1606 nothing from the base alias check. */
1611 if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0)
1612 return find_base_term (XEXP (x, 0));
1624 /* Return 0 if the addresses X and Y are known to point to different
1625 objects, 1 if they might be pointers to the same object. */
1628 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1629 enum machine_mode y_mode)
1631 rtx x_base = find_base_term (x);
1632 rtx y_base = find_base_term (y);
1634 /* If the address itself has no known base see if a known equivalent
1635 value has one. If either address still has no known base, nothing
1636 is known about aliasing. */
1641 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1644 x_base = find_base_term (x_c);
1652 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1655 y_base = find_base_term (y_c);
1660 /* If the base addresses are equal nothing is known about aliasing. */
1661 if (rtx_equal_p (x_base, y_base))
1664 /* The base addresses are different expressions. If they are not accessed
1665 via AND, there is no conflict. We can bring knowledge of object
1666 alignment into play here. For example, on alpha, "char a, b;" can
1667 alias one another, though "char a; long b;" cannot. AND addesses may
1668 implicitly alias surrounding objects; i.e. unaligned access in DImode
1669 via AND address can alias all surrounding object types except those
1670 with aligment 8 or higher. */
1671 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1673 if (GET_CODE (x) == AND
1674 && (!CONST_INT_P (XEXP (x, 1))
1675 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1677 if (GET_CODE (y) == AND
1678 && (!CONST_INT_P (XEXP (y, 1))
1679 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1682 /* Differing symbols not accessed via AND never alias. */
1683 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1686 /* If one address is a stack reference there can be no alias:
1687 stack references using different base registers do not alias,
1688 a stack reference can not alias a parameter, and a stack reference
1689 can not alias a global. */
1690 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1691 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1697 /* Convert the address X into something we can use. This is done by returning
1698 it unchanged unless it is a value; in the latter case we call cselib to get
1699 a more useful rtx. */
1705 struct elt_loc_list *l;
1707 if (GET_CODE (x) != VALUE)
1709 v = CSELIB_VAL_PTR (x);
1712 for (l = v->locs; l; l = l->next)
1713 if (CONSTANT_P (l->loc))
1715 for (l = v->locs; l; l = l->next)
1716 if (!REG_P (l->loc) && !MEM_P (l->loc))
1719 return v->locs->loc;
1724 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1725 where SIZE is the size in bytes of the memory reference. If ADDR
1726 is not modified by the memory reference then ADDR is returned. */
1729 addr_side_effect_eval (rtx addr, int size, int n_refs)
1733 switch (GET_CODE (addr))
1736 offset = (n_refs + 1) * size;
1739 offset = -(n_refs + 1) * size;
1742 offset = n_refs * size;
1745 offset = -n_refs * size;
1753 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1756 addr = XEXP (addr, 0);
1757 addr = canon_rtx (addr);
1762 /* Return one if X and Y (memory addresses) reference the
1763 same location in memory or if the references overlap.
1764 Return zero if they do not overlap, else return
1765 minus one in which case they still might reference the same location.
1767 C is an offset accumulator. When
1768 C is nonzero, we are testing aliases between X and Y + C.
1769 XSIZE is the size in bytes of the X reference,
1770 similarly YSIZE is the size in bytes for Y.
1771 Expect that canon_rtx has been already called for X and Y.
1773 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1774 referenced (the reference was BLKmode), so make the most pessimistic
1777 If XSIZE or YSIZE is negative, we may access memory outside the object
1778 being referenced as a side effect. This can happen when using AND to
1779 align memory references, as is done on the Alpha.
1781 Nice to notice that varying addresses cannot conflict with fp if no
1782 local variables had their addresses taken, but that's too hard now.
1784 ??? Contrary to the tree alias oracle this does not return
1785 one for X + non-constant and Y + non-constant when X and Y are equal.
1786 If that is fixed the TBAA hack for union type-punning can be removed. */
1789 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1791 if (GET_CODE (x) == VALUE)
1793 if (GET_CODE (y) == VALUE)
1795 if (GET_CODE (x) == HIGH)
1797 else if (GET_CODE (x) == LO_SUM)
1800 x = addr_side_effect_eval (x, xsize, 0);
1801 if (GET_CODE (y) == HIGH)
1803 else if (GET_CODE (y) == LO_SUM)
1806 y = addr_side_effect_eval (y, ysize, 0);
1808 if (rtx_equal_for_memref_p (x, y))
1810 if (xsize <= 0 || ysize <= 0)
1812 if (c >= 0 && xsize > c)
1814 if (c < 0 && ysize+c > 0)
1819 /* This code used to check for conflicts involving stack references and
1820 globals but the base address alias code now handles these cases. */
1822 if (GET_CODE (x) == PLUS)
1824 /* The fact that X is canonicalized means that this
1825 PLUS rtx is canonicalized. */
1826 rtx x0 = XEXP (x, 0);
1827 rtx x1 = XEXP (x, 1);
1829 if (GET_CODE (y) == PLUS)
1831 /* The fact that Y is canonicalized means that this
1832 PLUS rtx is canonicalized. */
1833 rtx y0 = XEXP (y, 0);
1834 rtx y1 = XEXP (y, 1);
1836 if (rtx_equal_for_memref_p (x1, y1))
1837 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1838 if (rtx_equal_for_memref_p (x0, y0))
1839 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1840 if (CONST_INT_P (x1))
1842 if (CONST_INT_P (y1))
1843 return memrefs_conflict_p (xsize, x0, ysize, y0,
1844 c - INTVAL (x1) + INTVAL (y1));
1846 return memrefs_conflict_p (xsize, x0, ysize, y,
1849 else if (CONST_INT_P (y1))
1850 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1854 else if (CONST_INT_P (x1))
1855 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1857 else if (GET_CODE (y) == PLUS)
1859 /* The fact that Y is canonicalized means that this
1860 PLUS rtx is canonicalized. */
1861 rtx y0 = XEXP (y, 0);
1862 rtx y1 = XEXP (y, 1);
1864 if (CONST_INT_P (y1))
1865 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1870 if (GET_CODE (x) == GET_CODE (y))
1871 switch (GET_CODE (x))
1875 /* Handle cases where we expect the second operands to be the
1876 same, and check only whether the first operand would conflict
1879 rtx x1 = canon_rtx (XEXP (x, 1));
1880 rtx y1 = canon_rtx (XEXP (y, 1));
1881 if (! rtx_equal_for_memref_p (x1, y1))
1883 x0 = canon_rtx (XEXP (x, 0));
1884 y0 = canon_rtx (XEXP (y, 0));
1885 if (rtx_equal_for_memref_p (x0, y0))
1886 return (xsize == 0 || ysize == 0
1887 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1889 /* Can't properly adjust our sizes. */
1890 if (!CONST_INT_P (x1))
1892 xsize /= INTVAL (x1);
1893 ysize /= INTVAL (x1);
1895 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1902 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1903 as an access with indeterminate size. Assume that references
1904 besides AND are aligned, so if the size of the other reference is
1905 at least as large as the alignment, assume no other overlap. */
1906 if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1)))
1908 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1910 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1912 if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1)))
1914 /* ??? If we are indexing far enough into the array/structure, we
1915 may yet be able to determine that we can not overlap. But we
1916 also need to that we are far enough from the end not to overlap
1917 a following reference, so we do nothing with that for now. */
1918 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1920 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1925 if (CONST_INT_P (x) && CONST_INT_P (y))
1927 c += (INTVAL (y) - INTVAL (x));
1928 return (xsize <= 0 || ysize <= 0
1929 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1932 if (GET_CODE (x) == CONST)
1934 if (GET_CODE (y) == CONST)
1935 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1936 ysize, canon_rtx (XEXP (y, 0)), c);
1938 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1941 if (GET_CODE (y) == CONST)
1942 return memrefs_conflict_p (xsize, x, ysize,
1943 canon_rtx (XEXP (y, 0)), c);
1946 return (xsize <= 0 || ysize <= 0
1947 || (rtx_equal_for_memref_p (x, y)
1948 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1956 /* Functions to compute memory dependencies.
1958 Since we process the insns in execution order, we can build tables
1959 to keep track of what registers are fixed (and not aliased), what registers
1960 are varying in known ways, and what registers are varying in unknown
1963 If both memory references are volatile, then there must always be a
1964 dependence between the two references, since their order can not be
1965 changed. A volatile and non-volatile reference can be interchanged
1968 A MEM_IN_STRUCT reference at a non-AND varying address can never
1969 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1970 also must allow AND addresses, because they may generate accesses
1971 outside the object being referenced. This is used to generate
1972 aligned addresses from unaligned addresses, for instance, the alpha
1973 storeqi_unaligned pattern. */
1975 /* Read dependence: X is read after read in MEM takes place. There can
1976 only be a dependence here if both reads are volatile. */
1979 read_dependence (const_rtx mem, const_rtx x)
1981 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1984 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1985 MEM2 is a reference to a structure at a varying address, or returns
1986 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1987 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1988 to decide whether or not an address may vary; it should return
1989 nonzero whenever variation is possible.
1990 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1993 fixed_scalar_and_varying_struct_p (const_rtx mem1, const_rtx mem2, rtx mem1_addr,
1995 bool (*varies_p) (const_rtx, bool))
1997 if (! flag_strict_aliasing)
2000 if (MEM_ALIAS_SET (mem2)
2001 && MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
2002 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
2003 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
2007 if (MEM_ALIAS_SET (mem1)
2008 && MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
2009 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
2010 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
2017 /* Returns nonzero if something about the mode or address format MEM1
2018 indicates that it might well alias *anything*. */
2021 aliases_everything_p (const_rtx mem)
2023 if (GET_CODE (XEXP (mem, 0)) == AND)
2024 /* If the address is an AND, it's very hard to know at what it is
2025 actually pointing. */
2031 /* Return true if we can determine that the fields referenced cannot
2032 overlap for any pair of objects. */
2035 nonoverlapping_component_refs_p (const_tree x, const_tree y)
2037 const_tree fieldx, fieldy, typex, typey, orig_y;
2039 if (!flag_strict_aliasing)
2044 /* The comparison has to be done at a common type, since we don't
2045 know how the inheritance hierarchy works. */
2049 fieldx = TREE_OPERAND (x, 1);
2050 typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx));
2055 fieldy = TREE_OPERAND (y, 1);
2056 typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy));
2061 y = TREE_OPERAND (y, 0);
2063 while (y && TREE_CODE (y) == COMPONENT_REF);
2065 x = TREE_OPERAND (x, 0);
2067 while (x && TREE_CODE (x) == COMPONENT_REF);
2068 /* Never found a common type. */
2072 /* If we're left with accessing different fields of a structure,
2074 if (TREE_CODE (typex) == RECORD_TYPE
2075 && fieldx != fieldy)
2078 /* The comparison on the current field failed. If we're accessing
2079 a very nested structure, look at the next outer level. */
2080 x = TREE_OPERAND (x, 0);
2081 y = TREE_OPERAND (y, 0);
2084 && TREE_CODE (x) == COMPONENT_REF
2085 && TREE_CODE (y) == COMPONENT_REF);
2090 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2093 decl_for_component_ref (tree x)
2097 x = TREE_OPERAND (x, 0);
2099 while (x && TREE_CODE (x) == COMPONENT_REF);
2101 return x && DECL_P (x) ? x : NULL_TREE;
2104 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
2105 offset of the field reference. */
2108 adjust_offset_for_component_ref (tree x, rtx offset)
2110 HOST_WIDE_INT ioffset;
2115 ioffset = INTVAL (offset);
2118 tree offset = component_ref_field_offset (x);
2119 tree field = TREE_OPERAND (x, 1);
2121 if (! host_integerp (offset, 1))
2123 ioffset += (tree_low_cst (offset, 1)
2124 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
2127 x = TREE_OPERAND (x, 0);
2129 while (x && TREE_CODE (x) == COMPONENT_REF);
2131 return GEN_INT (ioffset);
2134 /* Return nonzero if we can determine the exprs corresponding to memrefs
2135 X and Y and they do not overlap. */
2138 nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
2140 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
2143 rtx moffsetx, moffsety;
2144 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
2146 /* Unless both have exprs, we can't tell anything. */
2147 if (exprx == 0 || expry == 0)
2150 /* For spill-slot accesses make sure we have valid offsets. */
2151 if ((exprx == get_spill_slot_decl (false)
2152 && ! MEM_OFFSET (x))
2153 || (expry == get_spill_slot_decl (false)
2154 && ! MEM_OFFSET (y)))
2157 /* If both are field references, we may be able to determine something. */
2158 if (TREE_CODE (exprx) == COMPONENT_REF
2159 && TREE_CODE (expry) == COMPONENT_REF
2160 && nonoverlapping_component_refs_p (exprx, expry))
2164 /* If the field reference test failed, look at the DECLs involved. */
2165 moffsetx = MEM_OFFSET (x);
2166 if (TREE_CODE (exprx) == COMPONENT_REF)
2168 if (TREE_CODE (expry) == VAR_DECL
2169 && POINTER_TYPE_P (TREE_TYPE (expry)))
2171 tree field = TREE_OPERAND (exprx, 1);
2172 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2173 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2178 tree t = decl_for_component_ref (exprx);
2181 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
2186 moffsety = MEM_OFFSET (y);
2187 if (TREE_CODE (expry) == COMPONENT_REF)
2189 if (TREE_CODE (exprx) == VAR_DECL
2190 && POINTER_TYPE_P (TREE_TYPE (exprx)))
2192 tree field = TREE_OPERAND (expry, 1);
2193 tree fieldcontext = DECL_FIELD_CONTEXT (field);
2194 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
2199 tree t = decl_for_component_ref (expry);
2202 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2207 if (! DECL_P (exprx) || ! DECL_P (expry))
2210 /* With invalid code we can end up storing into the constant pool.
2211 Bail out to avoid ICEing when creating RTL for this.
2212 See gfortran.dg/lto/20091028-2_0.f90. */
2213 if (TREE_CODE (exprx) == CONST_DECL
2214 || TREE_CODE (expry) == CONST_DECL)
2217 rtlx = DECL_RTL (exprx);
2218 rtly = DECL_RTL (expry);
2220 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2221 can't overlap unless they are the same because we never reuse that part
2222 of the stack frame used for locals for spilled pseudos. */
2223 if ((!MEM_P (rtlx) || !MEM_P (rtly))
2224 && ! rtx_equal_p (rtlx, rtly))
2227 /* If we have MEMs refering to different address spaces (which can
2228 potentially overlap), we cannot easily tell from the addresses
2229 whether the references overlap. */
2230 if (MEM_P (rtlx) && MEM_P (rtly)
2231 && MEM_ADDR_SPACE (rtlx) != MEM_ADDR_SPACE (rtly))
2234 /* Get the base and offsets of both decls. If either is a register, we
2235 know both are and are the same, so use that as the base. The only
2236 we can avoid overlap is if we can deduce that they are nonoverlapping
2237 pieces of that decl, which is very rare. */
2238 basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx;
2239 if (GET_CODE (basex) == PLUS && CONST_INT_P (XEXP (basex, 1)))
2240 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2242 basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly;
2243 if (GET_CODE (basey) == PLUS && CONST_INT_P (XEXP (basey, 1)))
2244 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2246 /* If the bases are different, we know they do not overlap if both
2247 are constants or if one is a constant and the other a pointer into the
2248 stack frame. Otherwise a different base means we can't tell if they
2250 if (! rtx_equal_p (basex, basey))
2251 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2252 || (CONSTANT_P (basex) && REG_P (basey)
2253 && REGNO_PTR_FRAME_P (REGNO (basey)))
2254 || (CONSTANT_P (basey) && REG_P (basex)
2255 && REGNO_PTR_FRAME_P (REGNO (basex))));
2257 sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2258 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2260 sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2261 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2264 /* If we have an offset for either memref, it can update the values computed
2267 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2269 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2271 /* If a memref has both a size and an offset, we can use the smaller size.
2272 We can't do this if the offset isn't known because we must view this
2273 memref as being anywhere inside the DECL's MEM. */
2274 if (MEM_SIZE (x) && moffsetx)
2275 sizex = INTVAL (MEM_SIZE (x));
2276 if (MEM_SIZE (y) && moffsety)
2277 sizey = INTVAL (MEM_SIZE (y));
2279 /* Put the values of the memref with the lower offset in X's values. */
2280 if (offsetx > offsety)
2282 tem = offsetx, offsetx = offsety, offsety = tem;
2283 tem = sizex, sizex = sizey, sizey = tem;
2286 /* If we don't know the size of the lower-offset value, we can't tell
2287 if they conflict. Otherwise, we do the test. */
2288 return sizex >= 0 && offsety >= offsetx + sizex;
2291 /* True dependence: X is read after store in MEM takes place. */
2294 true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x,
2295 bool (*varies) (const_rtx, bool))
2297 rtx x_addr, mem_addr;
2301 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2304 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2305 This is used in epilogue deallocation functions, and in cselib. */
2306 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2308 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2310 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2311 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2314 /* Read-only memory is by definition never modified, and therefore can't
2315 conflict with anything. We don't expect to find read-only set on MEM,
2316 but stupid user tricks can produce them, so don't die. */
2317 if (MEM_READONLY_P (x))
2320 /* If we have MEMs refering to different address spaces (which can
2321 potentially overlap), we cannot easily tell from the addresses
2322 whether the references overlap. */
2323 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
2326 if (mem_mode == VOIDmode)
2327 mem_mode = GET_MODE (mem);
2329 x_addr = get_addr (XEXP (x, 0));
2330 mem_addr = get_addr (XEXP (mem, 0));
2332 base = find_base_term (x_addr);
2333 if (base && (GET_CODE (base) == LABEL_REF
2334 || (GET_CODE (base) == SYMBOL_REF
2335 && CONSTANT_POOL_ADDRESS_P (base))))
2338 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2341 x_addr = canon_rtx (x_addr);
2342 mem_addr = canon_rtx (mem_addr);
2344 if ((ret = memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2345 SIZE_FOR_MODE (x), x_addr, 0)) != -1)
2348 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2351 if (nonoverlapping_memrefs_p (mem, x))
2354 if (aliases_everything_p (x))
2357 /* We cannot use aliases_everything_p to test MEM, since we must look
2358 at MEM_MODE, rather than GET_MODE (MEM). */
2359 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2362 /* In true_dependence we also allow BLKmode to alias anything. Why
2363 don't we do this in anti_dependence and output_dependence? */
2364 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2367 if (fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, varies))
2370 return rtx_refs_may_alias_p (x, mem, true);
2373 /* Canonical true dependence: X is read after store in MEM takes place.
2374 Variant of true_dependence which assumes MEM has already been
2375 canonicalized (hence we no longer do that here).
2376 The mem_addr argument has been added, since true_dependence computed
2377 this value prior to canonicalizing.
2378 If x_addr is non-NULL, it is used in preference of XEXP (x, 0). */
2381 canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2382 const_rtx x, rtx x_addr, bool (*varies) (const_rtx, bool))
2386 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2389 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2390 This is used in epilogue deallocation functions. */
2391 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2393 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2395 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2396 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2399 /* Read-only memory is by definition never modified, and therefore can't
2400 conflict with anything. We don't expect to find read-only set on MEM,
2401 but stupid user tricks can produce them, so don't die. */
2402 if (MEM_READONLY_P (x))
2405 /* If we have MEMs refering to different address spaces (which can
2406 potentially overlap), we cannot easily tell from the addresses
2407 whether the references overlap. */
2408 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
2412 x_addr = get_addr (XEXP (x, 0));
2414 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2417 x_addr = canon_rtx (x_addr);
2418 if ((ret = memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2419 SIZE_FOR_MODE (x), x_addr, 0)) != -1)
2422 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2425 if (nonoverlapping_memrefs_p (x, mem))
2428 if (aliases_everything_p (x))
2431 /* We cannot use aliases_everything_p to test MEM, since we must look
2432 at MEM_MODE, rather than GET_MODE (MEM). */
2433 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2436 /* In true_dependence we also allow BLKmode to alias anything. Why
2437 don't we do this in anti_dependence and output_dependence? */
2438 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2441 if (fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, varies))
2444 return rtx_refs_may_alias_p (x, mem, true);
2447 /* Returns nonzero if a write to X might alias a previous read from
2448 (or, if WRITEP is nonzero, a write to) MEM. */
2451 write_dependence_p (const_rtx mem, const_rtx x, int writep)
2453 rtx x_addr, mem_addr;
2454 const_rtx fixed_scalar;
2458 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2461 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2462 This is used in epilogue deallocation functions. */
2463 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2465 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2467 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
2468 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
2471 /* A read from read-only memory can't conflict with read-write memory. */
2472 if (!writep && MEM_READONLY_P (mem))
2475 /* If we have MEMs refering to different address spaces (which can
2476 potentially overlap), we cannot easily tell from the addresses
2477 whether the references overlap. */
2478 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
2481 x_addr = get_addr (XEXP (x, 0));
2482 mem_addr = get_addr (XEXP (mem, 0));
2486 base = find_base_term (mem_addr);
2487 if (base && (GET_CODE (base) == LABEL_REF
2488 || (GET_CODE (base) == SYMBOL_REF
2489 && CONSTANT_POOL_ADDRESS_P (base))))
2493 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2497 x_addr = canon_rtx (x_addr);
2498 mem_addr = canon_rtx (mem_addr);
2500 if ((ret = memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2501 SIZE_FOR_MODE (x), x_addr, 0)) != -1)
2504 if (nonoverlapping_memrefs_p (x, mem))
2508 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2511 if ((fixed_scalar == mem && !aliases_everything_p (x))
2512 || (fixed_scalar == x && !aliases_everything_p (mem)))
2515 return rtx_refs_may_alias_p (x, mem, false);
2518 /* Anti dependence: X is written after read in MEM takes place. */
2521 anti_dependence (const_rtx mem, const_rtx x)
2523 return write_dependence_p (mem, x, /*writep=*/0);
2526 /* Output dependence: X is written after store in MEM takes place. */
2529 output_dependence (const_rtx mem, const_rtx x)
2531 return write_dependence_p (mem, x, /*writep=*/1);
2536 init_alias_target (void)
2540 memset (static_reg_base_value, 0, sizeof static_reg_base_value);
2542 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2543 /* Check whether this register can hold an incoming pointer
2544 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2545 numbers, so translate if necessary due to register windows. */
2546 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2547 && HARD_REGNO_MODE_OK (i, Pmode))
2548 static_reg_base_value[i]
2549 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2551 static_reg_base_value[STACK_POINTER_REGNUM]
2552 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2553 static_reg_base_value[ARG_POINTER_REGNUM]
2554 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2555 static_reg_base_value[FRAME_POINTER_REGNUM]
2556 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2557 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2558 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2559 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2563 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2564 to be memory reference. */
2565 static bool memory_modified;
2567 memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
2571 if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data))
2572 memory_modified = true;
2577 /* Return true when INSN possibly modify memory contents of MEM
2578 (i.e. address can be modified). */
2580 memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
2584 memory_modified = false;
2585 note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
2586 return memory_modified;
2589 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2593 init_alias_analysis (void)
2595 unsigned int maxreg = max_reg_num ();
2601 timevar_push (TV_ALIAS_ANALYSIS);
2603 reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER;
2604 reg_known_value = GGC_CNEWVEC (rtx, reg_known_value_size);
2605 reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size);
2607 /* If we have memory allocated from the previous run, use it. */
2608 if (old_reg_base_value)
2609 reg_base_value = old_reg_base_value;
2612 VEC_truncate (rtx, reg_base_value, 0);
2614 VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg);
2616 new_reg_base_value = XNEWVEC (rtx, maxreg);
2617 reg_seen = XNEWVEC (char, maxreg);
2619 /* The basic idea is that each pass through this loop will use the
2620 "constant" information from the previous pass to propagate alias
2621 information through another level of assignments.
2623 This could get expensive if the assignment chains are long. Maybe
2624 we should throttle the number of iterations, possibly based on
2625 the optimization level or flag_expensive_optimizations.
2627 We could propagate more information in the first pass by making use
2628 of DF_REG_DEF_COUNT to determine immediately that the alias information
2629 for a pseudo is "constant".
2631 A program with an uninitialized variable can cause an infinite loop
2632 here. Instead of doing a full dataflow analysis to detect such problems
2633 we just cap the number of iterations for the loop.
2635 The state of the arrays for the set chain in question does not matter
2636 since the program has undefined behavior. */
2641 /* Assume nothing will change this iteration of the loop. */
2644 /* We want to assign the same IDs each iteration of this loop, so
2645 start counting from zero each iteration of the loop. */
2648 /* We're at the start of the function each iteration through the
2649 loop, so we're copying arguments. */
2650 copying_arguments = true;
2652 /* Wipe the potential alias information clean for this pass. */
2653 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2655 /* Wipe the reg_seen array clean. */
2656 memset (reg_seen, 0, maxreg);
2658 /* Mark all hard registers which may contain an address.
2659 The stack, frame and argument pointers may contain an address.
2660 An argument register which can hold a Pmode value may contain
2661 an address even if it is not in BASE_REGS.
2663 The address expression is VOIDmode for an argument and
2664 Pmode for other registers. */
2666 memcpy (new_reg_base_value, static_reg_base_value,
2667 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2669 /* Walk the insns adding values to the new_reg_base_value array. */
2670 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2676 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2677 /* The prologue/epilogue insns are not threaded onto the
2678 insn chain until after reload has completed. Thus,
2679 there is no sense wasting time checking if INSN is in
2680 the prologue/epilogue until after reload has completed. */
2681 if (reload_completed
2682 && prologue_epilogue_contains (insn))
2686 /* If this insn has a noalias note, process it, Otherwise,
2687 scan for sets. A simple set will have no side effects
2688 which could change the base value of any other register. */
2690 if (GET_CODE (PATTERN (insn)) == SET
2691 && REG_NOTES (insn) != 0
2692 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2693 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2695 note_stores (PATTERN (insn), record_set, NULL);
2697 set = single_set (insn);
2700 && REG_P (SET_DEST (set))
2701 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2703 unsigned int regno = REGNO (SET_DEST (set));
2704 rtx src = SET_SRC (set);
2707 note = find_reg_equal_equiv_note (insn);
2708 if (note && REG_NOTE_KIND (note) == REG_EQUAL
2709 && DF_REG_DEF_COUNT (regno) != 1)
2712 if (note != NULL_RTX
2713 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2714 && ! rtx_varies_p (XEXP (note, 0), 1)
2715 && ! reg_overlap_mentioned_p (SET_DEST (set),
2718 set_reg_known_value (regno, XEXP (note, 0));
2719 set_reg_known_equiv_p (regno,
2720 REG_NOTE_KIND (note) == REG_EQUIV);
2722 else if (DF_REG_DEF_COUNT (regno) == 1
2723 && GET_CODE (src) == PLUS
2724 && REG_P (XEXP (src, 0))
2725 && (t = get_reg_known_value (REGNO (XEXP (src, 0))))
2726 && CONST_INT_P (XEXP (src, 1)))
2728 t = plus_constant (t, INTVAL (XEXP (src, 1)));
2729 set_reg_known_value (regno, t);
2730 set_reg_known_equiv_p (regno, 0);
2732 else if (DF_REG_DEF_COUNT (regno) == 1
2733 && ! rtx_varies_p (src, 1))
2735 set_reg_known_value (regno, src);
2736 set_reg_known_equiv_p (regno, 0);
2740 else if (NOTE_P (insn)
2741 && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG)
2742 copying_arguments = false;
2745 /* Now propagate values from new_reg_base_value to reg_base_value. */
2746 gcc_assert (maxreg == (unsigned int) max_reg_num ());
2748 for (ui = 0; ui < maxreg; ui++)
2750 if (new_reg_base_value[ui]
2751 && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui)
2752 && ! rtx_equal_p (new_reg_base_value[ui],
2753 VEC_index (rtx, reg_base_value, ui)))
2755 VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]);
2760 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2762 /* Fill in the remaining entries. */
2763 for (i = 0; i < (int)reg_known_value_size; i++)
2764 if (reg_known_value[i] == 0)
2765 reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER];
2768 free (new_reg_base_value);
2769 new_reg_base_value = 0;
2772 timevar_pop (TV_ALIAS_ANALYSIS);
2776 end_alias_analysis (void)
2778 old_reg_base_value = reg_base_value;
2779 ggc_free (reg_known_value);
2780 reg_known_value = 0;
2781 reg_known_value_size = 0;
2782 free (reg_known_equiv_p);
2783 reg_known_equiv_p = 0;
2786 #include "gt-alias.h"