1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004
3 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 2, 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 COPYING. If not, write to the Free
20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
25 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
47 /* The alias sets assigned to MEMs assist the back-end in determining
48 which MEMs can alias which other MEMs. In general, two MEMs in
49 different alias sets cannot alias each other, with one important
50 exception. Consider something like:
52 struct S { int i; double d; };
54 a store to an `S' can alias something of either type `int' or type
55 `double'. (However, a store to an `int' cannot alias a `double'
56 and vice versa.) We indicate this via a tree structure that looks
64 (The arrows are directed and point downwards.)
65 In this situation we say the alias set for `struct S' is the
66 `superset' and that those for `int' and `double' are `subsets'.
68 To see whether two alias sets can point to the same memory, we must
69 see if either alias set is a subset of the other. We need not trace
70 past immediate descendants, however, since we propagate all
71 grandchildren up one level.
73 Alias set zero is implicitly a superset of all other alias sets.
74 However, this is no actual entry for alias set zero. It is an
75 error to attempt to explicitly construct a subset of zero. */
77 struct alias_set_entry GTY(())
79 /* The alias set number, as stored in MEM_ALIAS_SET. */
80 HOST_WIDE_INT alias_set;
82 /* The children of the alias set. These are not just the immediate
83 children, but, in fact, all descendants. So, if we have:
85 struct T { struct S s; float f; }
87 continuing our example above, the children here will be all of
88 `int', `double', `float', and `struct S'. */
89 splay_tree GTY((param1_is (int), param2_is (int))) children;
91 /* Nonzero if would have a child of zero: this effectively makes this
92 alias set the same as alias set zero. */
95 typedef struct alias_set_entry *alias_set_entry;
97 static int rtx_equal_for_memref_p (rtx, rtx);
98 static rtx find_symbolic_term (rtx);
99 static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT);
100 static void record_set (rtx, rtx, void *);
101 static int base_alias_check (rtx, rtx, enum machine_mode,
103 static rtx find_base_value (rtx);
104 static int mems_in_disjoint_alias_sets_p (rtx, rtx);
105 static int insert_subset_children (splay_tree_node, void*);
106 static tree find_base_decl (tree);
107 static alias_set_entry get_alias_set_entry (HOST_WIDE_INT);
108 static rtx fixed_scalar_and_varying_struct_p (rtx, rtx, rtx, rtx,
110 static int aliases_everything_p (rtx);
111 static bool nonoverlapping_component_refs_p (tree, tree);
112 static tree decl_for_component_ref (tree);
113 static rtx adjust_offset_for_component_ref (tree, rtx);
114 static int nonoverlapping_memrefs_p (rtx, rtx);
115 static int write_dependence_p (rtx, rtx, int, int);
117 static int nonlocal_mentioned_p_1 (rtx *, void *);
118 static int nonlocal_mentioned_p (rtx);
119 static int nonlocal_referenced_p_1 (rtx *, void *);
120 static int nonlocal_referenced_p (rtx);
121 static int nonlocal_set_p_1 (rtx *, void *);
122 static int nonlocal_set_p (rtx);
123 static void memory_modified_1 (rtx, rtx, void *);
125 /* Set up all info needed to perform alias analysis on memory references. */
127 /* Returns the size in bytes of the mode of X. */
128 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
130 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
131 different alias sets. We ignore alias sets in functions making use
132 of variable arguments because the va_arg macros on some systems are
134 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
135 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
137 /* Cap the number of passes we make over the insns propagating alias
138 information through set chains. 10 is a completely arbitrary choice. */
139 #define MAX_ALIAS_LOOP_PASSES 10
141 /* reg_base_value[N] gives an address to which register N is related.
142 If all sets after the first add or subtract to the current value
143 or otherwise modify it so it does not point to a different top level
144 object, reg_base_value[N] is equal to the address part of the source
147 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
148 expressions represent certain special values: function arguments and
149 the stack, frame, and argument pointers.
151 The contents of an ADDRESS is not normally used, the mode of the
152 ADDRESS determines whether the ADDRESS is a function argument or some
153 other special value. Pointer equality, not rtx_equal_p, determines whether
154 two ADDRESS expressions refer to the same base address.
156 The only use of the contents of an ADDRESS is for determining if the
157 current function performs nonlocal memory memory references for the
158 purposes of marking the function as a constant function. */
160 static GTY(()) varray_type reg_base_value;
161 static rtx *new_reg_base_value;
163 /* We preserve the copy of old array around to avoid amount of garbage
164 produced. About 8% of garbage produced were attributed to this
166 static GTY((deletable (""))) varray_type old_reg_base_value;
168 /* Static hunks of RTL used by the aliasing code; these are initialized
169 once per function to avoid unnecessary RTL allocations. */
170 static GTY (()) rtx static_reg_base_value[FIRST_PSEUDO_REGISTER];
172 #define REG_BASE_VALUE(X) \
173 (reg_base_value && REGNO (X) < VARRAY_SIZE (reg_base_value) \
174 ? VARRAY_RTX (reg_base_value, REGNO (X)) : 0)
176 /* Vector of known invariant relationships between registers. Set in
177 loop unrolling. Indexed by register number, if nonzero the value
178 is an expression describing this register in terms of another.
180 The length of this array is REG_BASE_VALUE_SIZE.
182 Because this array contains only pseudo registers it has no effect
184 static rtx *alias_invariant;
185 unsigned int alias_invariant_size;
187 /* Vector indexed by N giving the initial (unchanging) value known for
188 pseudo-register N. This array is initialized in
189 init_alias_analysis, and does not change until end_alias_analysis
191 rtx *reg_known_value;
193 /* Indicates number of valid entries in reg_known_value. */
194 static unsigned int reg_known_value_size;
196 /* Vector recording for each reg_known_value whether it is due to a
197 REG_EQUIV note. Future passes (viz., reload) may replace the
198 pseudo with the equivalent expression and so we account for the
199 dependences that would be introduced if that happens.
201 The REG_EQUIV notes created in assign_parms may mention the arg
202 pointer, and there are explicit insns in the RTL that modify the
203 arg pointer. Thus we must ensure that such insns don't get
204 scheduled across each other because that would invalidate the
205 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
206 wrong, but solving the problem in the scheduler will likely give
207 better code, so we do it here. */
208 char *reg_known_equiv_p;
210 /* True when scanning insns from the start of the rtl to the
211 NOTE_INSN_FUNCTION_BEG note. */
212 static bool copying_arguments;
214 /* The splay-tree used to store the various alias set entries. */
215 static GTY ((param_is (struct alias_set_entry))) varray_type alias_sets;
217 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
218 such an entry, or NULL otherwise. */
220 static inline alias_set_entry
221 get_alias_set_entry (HOST_WIDE_INT alias_set)
223 return (alias_set_entry)VARRAY_GENERIC_PTR (alias_sets, alias_set);
226 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
227 the two MEMs cannot alias each other. */
230 mems_in_disjoint_alias_sets_p (rtx mem1, rtx mem2)
232 #ifdef ENABLE_CHECKING
233 /* Perform a basic sanity check. Namely, that there are no alias sets
234 if we're not using strict aliasing. This helps to catch bugs
235 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
236 where a MEM is allocated in some way other than by the use of
237 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
238 use alias sets to indicate that spilled registers cannot alias each
239 other, we might need to remove this check. */
240 if (! flag_strict_aliasing
241 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
245 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
248 /* Insert the NODE into the splay tree given by DATA. Used by
249 record_alias_subset via splay_tree_foreach. */
252 insert_subset_children (splay_tree_node node, void *data)
254 splay_tree_insert ((splay_tree) data, node->key, node->value);
259 /* Return 1 if the two specified alias sets may conflict. */
262 alias_sets_conflict_p (HOST_WIDE_INT set1, HOST_WIDE_INT set2)
266 /* If have no alias set information for one of the operands, we have
267 to assume it can alias anything. */
268 if (set1 == 0 || set2 == 0
269 /* If the two alias sets are the same, they may alias. */
273 /* See if the first alias set is a subset of the second. */
274 ase = get_alias_set_entry (set1);
276 && (ase->has_zero_child
277 || splay_tree_lookup (ase->children,
278 (splay_tree_key) set2)))
281 /* Now do the same, but with the alias sets reversed. */
282 ase = get_alias_set_entry (set2);
284 && (ase->has_zero_child
285 || splay_tree_lookup (ase->children,
286 (splay_tree_key) set1)))
289 /* The two alias sets are distinct and neither one is the
290 child of the other. Therefore, they cannot alias. */
294 /* Return 1 if the two specified alias sets might conflict, or if any subtype
295 of these alias sets might conflict. */
298 alias_sets_might_conflict_p (HOST_WIDE_INT set1, HOST_WIDE_INT set2)
300 if (set1 == 0 || set2 == 0 || set1 == set2)
307 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
308 has any readonly fields. If any of the fields have types that
309 contain readonly fields, return true as well. */
312 readonly_fields_p (tree type)
316 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
317 && TREE_CODE (type) != QUAL_UNION_TYPE)
320 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
321 if (TREE_CODE (field) == FIELD_DECL
322 && (TREE_READONLY (field)
323 || readonly_fields_p (TREE_TYPE (field))))
329 /* Return 1 if any MEM object of type T1 will always conflict (using the
330 dependency routines in this file) with any MEM object of type T2.
331 This is used when allocating temporary storage. If T1 and/or T2 are
332 NULL_TREE, it means we know nothing about the storage. */
335 objects_must_conflict_p (tree t1, tree t2)
337 HOST_WIDE_INT set1, set2;
339 /* If neither has a type specified, we don't know if they'll conflict
340 because we may be using them to store objects of various types, for
341 example the argument and local variables areas of inlined functions. */
342 if (t1 == 0 && t2 == 0)
345 /* If one or the other has readonly fields or is readonly,
346 then they may not conflict. */
347 if ((t1 != 0 && readonly_fields_p (t1))
348 || (t2 != 0 && readonly_fields_p (t2))
349 || (t1 != 0 && lang_hooks.honor_readonly && TYPE_READONLY (t1))
350 || (t2 != 0 && lang_hooks.honor_readonly && TYPE_READONLY (t2)))
353 /* If they are the same type, they must conflict. */
355 /* Likewise if both are volatile. */
356 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
359 set1 = t1 ? get_alias_set (t1) : 0;
360 set2 = t2 ? get_alias_set (t2) : 0;
362 /* Otherwise they conflict if they have no alias set or the same. We
363 can't simply use alias_sets_conflict_p here, because we must make
364 sure that every subtype of t1 will conflict with every subtype of
365 t2 for which a pair of subobjects of these respective subtypes
366 overlaps on the stack. */
367 return set1 == 0 || set2 == 0 || set1 == set2;
370 /* T is an expression with pointer type. Find the DECL on which this
371 expression is based. (For example, in `a[i]' this would be `a'.)
372 If there is no such DECL, or a unique decl cannot be determined,
373 NULL_TREE is returned. */
376 find_base_decl (tree t)
380 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
383 /* If this is a declaration, return it. */
384 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
387 /* Handle general expressions. It would be nice to deal with
388 COMPONENT_REFs here. If we could tell that `a' and `b' were the
389 same, then `a->f' and `b->f' are also the same. */
390 switch (TREE_CODE_CLASS (TREE_CODE (t)))
393 return find_base_decl (TREE_OPERAND (t, 0));
396 /* Return 0 if found in neither or both are the same. */
397 d0 = find_base_decl (TREE_OPERAND (t, 0));
398 d1 = find_base_decl (TREE_OPERAND (t, 1));
409 d0 = find_base_decl (TREE_OPERAND (t, 0));
410 d1 = find_base_decl (TREE_OPERAND (t, 1));
411 d2 = find_base_decl (TREE_OPERAND (t, 2));
413 /* Set any nonzero values from the last, then from the first. */
414 if (d1 == 0) d1 = d2;
415 if (d0 == 0) d0 = d1;
416 if (d1 == 0) d1 = d0;
417 if (d2 == 0) d2 = d1;
419 /* At this point all are nonzero or all are zero. If all three are the
420 same, return it. Otherwise, return zero. */
421 return (d0 == d1 && d1 == d2) ? d0 : 0;
428 /* Return 1 if all the nested component references handled by
429 get_inner_reference in T are such that we can address the object in T. */
432 can_address_p (tree t)
434 /* If we're at the end, it is vacuously addressable. */
435 if (! handled_component_p (t))
438 /* Bitfields are never addressable. */
439 else if (TREE_CODE (t) == BIT_FIELD_REF)
442 /* Fields are addressable unless they are marked as nonaddressable or
443 the containing type has alias set 0. */
444 else if (TREE_CODE (t) == COMPONENT_REF
445 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
446 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
447 && can_address_p (TREE_OPERAND (t, 0)))
450 /* Likewise for arrays. */
451 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
452 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
453 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
454 && can_address_p (TREE_OPERAND (t, 0)))
460 /* Return the alias set for T, which may be either a type or an
461 expression. Call language-specific routine for help, if needed. */
464 get_alias_set (tree t)
468 /* If we're not doing any alias analysis, just assume everything
469 aliases everything else. Also return 0 if this or its type is
471 if (! flag_strict_aliasing || t == error_mark_node
473 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
476 /* We can be passed either an expression or a type. This and the
477 language-specific routine may make mutually-recursive calls to each other
478 to figure out what to do. At each juncture, we see if this is a tree
479 that the language may need to handle specially. First handle things that
484 tree placeholder_ptr = 0;
486 /* Remove any nops, then give the language a chance to do
487 something with this tree before we look at it. */
489 set = lang_hooks.get_alias_set (t);
493 /* First see if the actual object referenced is an INDIRECT_REF from a
494 restrict-qualified pointer or a "void *". Replace
495 PLACEHOLDER_EXPRs. */
496 while (TREE_CODE (inner) == PLACEHOLDER_EXPR
497 || handled_component_p (inner))
499 if (TREE_CODE (inner) == PLACEHOLDER_EXPR)
500 inner = find_placeholder (inner, &placeholder_ptr);
502 inner = TREE_OPERAND (inner, 0);
507 /* Check for accesses through restrict-qualified pointers. */
508 if (TREE_CODE (inner) == INDIRECT_REF)
510 tree decl = find_base_decl (TREE_OPERAND (inner, 0));
512 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
514 /* If we haven't computed the actual alias set, do it now. */
515 if (DECL_POINTER_ALIAS_SET (decl) == -2)
517 /* No two restricted pointers can point at the same thing.
518 However, a restricted pointer can point at the same thing
519 as an unrestricted pointer, if that unrestricted pointer
520 is based on the restricted pointer. So, we make the
521 alias set for the restricted pointer a subset of the
522 alias set for the type pointed to by the type of the
524 HOST_WIDE_INT pointed_to_alias_set
525 = get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
527 if (pointed_to_alias_set == 0)
528 /* It's not legal to make a subset of alias set zero. */
529 DECL_POINTER_ALIAS_SET (decl) = 0;
532 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
533 record_alias_subset (pointed_to_alias_set,
534 DECL_POINTER_ALIAS_SET (decl));
538 /* We use the alias set indicated in the declaration. */
539 return DECL_POINTER_ALIAS_SET (decl);
542 /* If we have an INDIRECT_REF via a void pointer, we don't
543 know anything about what that might alias. */
544 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE)
548 /* Otherwise, pick up the outermost object that we could have a pointer
549 to, processing conversion and PLACEHOLDER_EXPR as above. */
551 while (TREE_CODE (t) == PLACEHOLDER_EXPR
552 || (handled_component_p (t) && ! can_address_p (t)))
554 if (TREE_CODE (t) == PLACEHOLDER_EXPR)
555 t = find_placeholder (t, &placeholder_ptr);
557 t = TREE_OPERAND (t, 0);
562 /* If we've already determined the alias set for a decl, just return
563 it. This is necessary for C++ anonymous unions, whose component
564 variables don't look like union members (boo!). */
565 if (TREE_CODE (t) == VAR_DECL
566 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
567 return MEM_ALIAS_SET (DECL_RTL (t));
569 /* Now all we care about is the type. */
573 /* Variant qualifiers don't affect the alias set, so get the main
574 variant. If this is a type with a known alias set, return it. */
575 t = TYPE_MAIN_VARIANT (t);
576 if (TYPE_ALIAS_SET_KNOWN_P (t))
577 return TYPE_ALIAS_SET (t);
579 /* See if the language has special handling for this type. */
580 set = lang_hooks.get_alias_set (t);
584 /* There are no objects of FUNCTION_TYPE, so there's no point in
585 using up an alias set for them. (There are, of course, pointers
586 and references to functions, but that's different.) */
587 else if (TREE_CODE (t) == FUNCTION_TYPE)
590 /* Unless the language specifies otherwise, let vector types alias
591 their components. This avoids some nasty type punning issues in
592 normal usage. And indeed lets vectors be treated more like an
594 else if (TREE_CODE (t) == VECTOR_TYPE)
595 set = get_alias_set (TREE_TYPE (t));
598 /* Otherwise make a new alias set for this type. */
599 set = new_alias_set ();
601 TYPE_ALIAS_SET (t) = set;
603 /* If this is an aggregate type, we must record any component aliasing
605 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
606 record_component_aliases (t);
611 /* Return a brand-new alias set. */
613 static GTY(()) HOST_WIDE_INT last_alias_set;
618 if (flag_strict_aliasing)
621 VARRAY_GENERIC_PTR_INIT (alias_sets, 10, "alias sets");
623 VARRAY_GROW (alias_sets, last_alias_set + 2);
624 return ++last_alias_set;
630 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
631 not everything that aliases SUPERSET also aliases SUBSET. For example,
632 in C, a store to an `int' can alias a load of a structure containing an
633 `int', and vice versa. But it can't alias a load of a 'double' member
634 of the same structure. Here, the structure would be the SUPERSET and
635 `int' the SUBSET. This relationship is also described in the comment at
636 the beginning of this file.
638 This function should be called only once per SUPERSET/SUBSET pair.
640 It is illegal for SUPERSET to be zero; everything is implicitly a
641 subset of alias set zero. */
644 record_alias_subset (HOST_WIDE_INT superset, HOST_WIDE_INT subset)
646 alias_set_entry superset_entry;
647 alias_set_entry subset_entry;
649 /* It is possible in complex type situations for both sets to be the same,
650 in which case we can ignore this operation. */
651 if (superset == subset)
657 superset_entry = get_alias_set_entry (superset);
658 if (superset_entry == 0)
660 /* Create an entry for the SUPERSET, so that we have a place to
661 attach the SUBSET. */
662 superset_entry = ggc_alloc (sizeof (struct alias_set_entry));
663 superset_entry->alias_set = superset;
664 superset_entry->children
665 = splay_tree_new_ggc (splay_tree_compare_ints);
666 superset_entry->has_zero_child = 0;
667 VARRAY_GENERIC_PTR (alias_sets, superset) = superset_entry;
671 superset_entry->has_zero_child = 1;
674 subset_entry = get_alias_set_entry (subset);
675 /* If there is an entry for the subset, enter all of its children
676 (if they are not already present) as children of the SUPERSET. */
679 if (subset_entry->has_zero_child)
680 superset_entry->has_zero_child = 1;
682 splay_tree_foreach (subset_entry->children, insert_subset_children,
683 superset_entry->children);
686 /* Enter the SUBSET itself as a child of the SUPERSET. */
687 splay_tree_insert (superset_entry->children,
688 (splay_tree_key) subset, 0);
692 /* Record that component types of TYPE, if any, are part of that type for
693 aliasing purposes. For record types, we only record component types
694 for fields that are marked addressable. For array types, we always
695 record the component types, so the front end should not call this
696 function if the individual component aren't addressable. */
699 record_component_aliases (tree type)
701 HOST_WIDE_INT superset = get_alias_set (type);
707 switch (TREE_CODE (type))
710 if (! TYPE_NONALIASED_COMPONENT (type))
711 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
716 case QUAL_UNION_TYPE:
717 /* Recursively record aliases for the base classes, if there are any. */
718 if (TYPE_BINFO (type) != NULL && TYPE_BINFO_BASETYPES (type) != NULL)
721 for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type)); i++)
723 tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), i);
724 record_alias_subset (superset,
725 get_alias_set (BINFO_TYPE (binfo)));
728 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
729 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
730 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
734 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
742 /* Allocate an alias set for use in storing and reading from the varargs
745 static GTY(()) HOST_WIDE_INT varargs_set = -1;
748 get_varargs_alias_set (void)
750 if (varargs_set == -1)
751 varargs_set = new_alias_set ();
756 /* Likewise, but used for the fixed portions of the frame, e.g., register
759 static GTY(()) HOST_WIDE_INT frame_set = -1;
762 get_frame_alias_set (void)
765 frame_set = new_alias_set ();
770 /* Inside SRC, the source of a SET, find a base address. */
773 find_base_value (rtx src)
777 switch (GET_CODE (src))
785 /* At the start of a function, argument registers have known base
786 values which may be lost later. Returning an ADDRESS
787 expression here allows optimization based on argument values
788 even when the argument registers are used for other purposes. */
789 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
790 return new_reg_base_value[regno];
792 /* If a pseudo has a known base value, return it. Do not do this
793 for non-fixed hard regs since it can result in a circular
794 dependency chain for registers which have values at function entry.
796 The test above is not sufficient because the scheduler may move
797 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
798 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
799 && regno < VARRAY_SIZE (reg_base_value))
801 /* If we're inside init_alias_analysis, use new_reg_base_value
802 to reduce the number of relaxation iterations. */
803 if (new_reg_base_value && new_reg_base_value[regno]
804 && REG_N_SETS (regno) == 1)
805 return new_reg_base_value[regno];
807 if (VARRAY_RTX (reg_base_value, regno))
808 return VARRAY_RTX (reg_base_value, regno);
814 /* Check for an argument passed in memory. Only record in the
815 copying-arguments block; it is too hard to track changes
817 if (copying_arguments
818 && (XEXP (src, 0) == arg_pointer_rtx
819 || (GET_CODE (XEXP (src, 0)) == PLUS
820 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
821 return gen_rtx_ADDRESS (VOIDmode, src);
826 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
829 /* ... fall through ... */
834 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
836 /* If either operand is a REG that is a known pointer, then it
838 if (REG_P (src_0) && REG_POINTER (src_0))
839 return find_base_value (src_0);
840 if (REG_P (src_1) && REG_POINTER (src_1))
841 return find_base_value (src_1);
843 /* If either operand is a REG, then see if we already have
844 a known value for it. */
847 temp = find_base_value (src_0);
854 temp = find_base_value (src_1);
859 /* If either base is named object or a special address
860 (like an argument or stack reference), then use it for the
863 && (GET_CODE (src_0) == SYMBOL_REF
864 || GET_CODE (src_0) == LABEL_REF
865 || (GET_CODE (src_0) == ADDRESS
866 && GET_MODE (src_0) != VOIDmode)))
870 && (GET_CODE (src_1) == SYMBOL_REF
871 || GET_CODE (src_1) == LABEL_REF
872 || (GET_CODE (src_1) == ADDRESS
873 && GET_MODE (src_1) != VOIDmode)))
876 /* Guess which operand is the base address:
877 If either operand is a symbol, then it is the base. If
878 either operand is a CONST_INT, then the other is the base. */
879 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
880 return find_base_value (src_0);
881 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
882 return find_base_value (src_1);
888 /* The standard form is (lo_sum reg sym) so look only at the
890 return find_base_value (XEXP (src, 1));
893 /* If the second operand is constant set the base
894 address to the first operand. */
895 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
896 return find_base_value (XEXP (src, 0));
900 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
910 return find_base_value (XEXP (src, 0));
913 case SIGN_EXTEND: /* used for NT/Alpha pointers */
915 rtx temp = find_base_value (XEXP (src, 0));
917 if (temp != 0 && CONSTANT_P (temp))
918 temp = convert_memory_address (Pmode, temp);
930 /* Called from init_alias_analysis indirectly through note_stores. */
932 /* While scanning insns to find base values, reg_seen[N] is nonzero if
933 register N has been set in this function. */
934 static char *reg_seen;
936 /* Addresses which are known not to alias anything else are identified
937 by a unique integer. */
938 static int unique_id;
941 record_set (rtx dest, rtx set, void *data ATTRIBUTE_UNUSED)
947 if (GET_CODE (dest) != REG)
950 regno = REGNO (dest);
952 if (regno >= VARRAY_SIZE (reg_base_value))
955 /* If this spans multiple hard registers, then we must indicate that every
956 register has an unusable value. */
957 if (regno < FIRST_PSEUDO_REGISTER)
958 n = hard_regno_nregs[regno][GET_MODE (dest)];
965 reg_seen[regno + n] = 1;
966 new_reg_base_value[regno + n] = 0;
973 /* A CLOBBER wipes out any old value but does not prevent a previously
974 unset register from acquiring a base address (i.e. reg_seen is not
976 if (GET_CODE (set) == CLOBBER)
978 new_reg_base_value[regno] = 0;
987 new_reg_base_value[regno] = 0;
991 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
992 GEN_INT (unique_id++));
996 /* This is not the first set. If the new value is not related to the
997 old value, forget the base value. Note that the following code is
999 extern int x, y; int *p = &x; p += (&y-&x);
1000 ANSI C does not allow computing the difference of addresses
1001 of distinct top level objects. */
1002 if (new_reg_base_value[regno])
1003 switch (GET_CODE (src))
1007 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1008 new_reg_base_value[regno] = 0;
1011 /* If the value we add in the PLUS is also a valid base value,
1012 this might be the actual base value, and the original value
1015 rtx other = NULL_RTX;
1017 if (XEXP (src, 0) == dest)
1018 other = XEXP (src, 1);
1019 else if (XEXP (src, 1) == dest)
1020 other = XEXP (src, 0);
1022 if (! other || find_base_value (other))
1023 new_reg_base_value[regno] = 0;
1027 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
1028 new_reg_base_value[regno] = 0;
1031 new_reg_base_value[regno] = 0;
1034 /* If this is the first set of a register, record the value. */
1035 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1036 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1037 new_reg_base_value[regno] = find_base_value (src);
1039 reg_seen[regno] = 1;
1042 /* Called from loop optimization when a new pseudo-register is
1043 created. It indicates that REGNO is being set to VAL. f INVARIANT
1044 is true then this value also describes an invariant relationship
1045 which can be used to deduce that two registers with unknown values
1049 record_base_value (unsigned int regno, rtx val, int invariant)
1051 if (invariant && alias_invariant && regno < alias_invariant_size)
1052 alias_invariant[regno] = val;
1054 if (regno >= VARRAY_SIZE (reg_base_value))
1055 VARRAY_GROW (reg_base_value, max_reg_num ());
1057 if (GET_CODE (val) == REG)
1059 VARRAY_RTX (reg_base_value, regno)
1060 = REG_BASE_VALUE (val);
1063 VARRAY_RTX (reg_base_value, regno)
1064 = find_base_value (val);
1067 /* Clear alias info for a register. This is used if an RTL transformation
1068 changes the value of a register. This is used in flow by AUTO_INC_DEC
1069 optimizations. We don't need to clear reg_base_value, since flow only
1070 changes the offset. */
1073 clear_reg_alias_info (rtx reg)
1075 unsigned int regno = REGNO (reg);
1077 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1078 reg_known_value[regno] = reg;
1081 /* Returns a canonical version of X, from the point of view alias
1082 analysis. (For example, if X is a MEM whose address is a register,
1083 and the register has a known value (say a SYMBOL_REF), then a MEM
1084 whose address is the SYMBOL_REF is returned.) */
1089 /* Recursively look for equivalences. */
1090 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1091 && REGNO (x) < reg_known_value_size)
1092 return reg_known_value[REGNO (x)] == x
1093 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1094 else if (GET_CODE (x) == PLUS)
1096 rtx x0 = canon_rtx (XEXP (x, 0));
1097 rtx x1 = canon_rtx (XEXP (x, 1));
1099 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1101 if (GET_CODE (x0) == CONST_INT)
1102 return plus_constant (x1, INTVAL (x0));
1103 else if (GET_CODE (x1) == CONST_INT)
1104 return plus_constant (x0, INTVAL (x1));
1105 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1109 /* This gives us much better alias analysis when called from
1110 the loop optimizer. Note we want to leave the original
1111 MEM alone, but need to return the canonicalized MEM with
1112 all the flags with their original values. */
1113 else if (GET_CODE (x) == MEM)
1114 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1119 /* Return 1 if X and Y are identical-looking rtx's.
1120 Expect that X and Y has been already canonicalized.
1122 We use the data in reg_known_value above to see if two registers with
1123 different numbers are, in fact, equivalent. */
1126 rtx_equal_for_memref_p (rtx x, rtx y)
1133 if (x == 0 && y == 0)
1135 if (x == 0 || y == 0)
1141 code = GET_CODE (x);
1142 /* Rtx's of different codes cannot be equal. */
1143 if (code != GET_CODE (y))
1146 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1147 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1149 if (GET_MODE (x) != GET_MODE (y))
1152 /* Some RTL can be compared without a recursive examination. */
1156 return REGNO (x) == REGNO (y);
1159 return XEXP (x, 0) == XEXP (y, 0);
1162 return XSTR (x, 0) == XSTR (y, 0);
1167 /* There's no need to compare the contents of CONST_DOUBLEs or
1168 CONST_INTs because pointer equality is a good enough
1169 comparison for these nodes. */
1173 return (XINT (x, 1) == XINT (y, 1)
1174 && rtx_equal_for_memref_p (XEXP (x, 0),
1181 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1183 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1184 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1185 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1186 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1187 /* For commutative operations, the RTX match if the operand match in any
1188 order. Also handle the simple binary and unary cases without a loop. */
1189 if (COMMUTATIVE_P (x))
1191 rtx xop0 = canon_rtx (XEXP (x, 0));
1192 rtx yop0 = canon_rtx (XEXP (y, 0));
1193 rtx yop1 = canon_rtx (XEXP (y, 1));
1195 return ((rtx_equal_for_memref_p (xop0, yop0)
1196 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1197 || (rtx_equal_for_memref_p (xop0, yop1)
1198 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1200 else if (NON_COMMUTATIVE_P (x))
1202 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1203 canon_rtx (XEXP (y, 0)))
1204 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1205 canon_rtx (XEXP (y, 1))));
1207 else if (UNARY_P (x))
1208 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1209 canon_rtx (XEXP (y, 0)));
1211 /* Compare the elements. If any pair of corresponding elements
1212 fail to match, return 0 for the whole things.
1214 Limit cases to types which actually appear in addresses. */
1216 fmt = GET_RTX_FORMAT (code);
1217 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1222 if (XINT (x, i) != XINT (y, i))
1227 /* Two vectors must have the same length. */
1228 if (XVECLEN (x, i) != XVECLEN (y, i))
1231 /* And the corresponding elements must match. */
1232 for (j = 0; j < XVECLEN (x, i); j++)
1233 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1234 canon_rtx (XVECEXP (y, i, j))) == 0)
1239 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1240 canon_rtx (XEXP (y, i))) == 0)
1244 /* This can happen for asm operands. */
1246 if (strcmp (XSTR (x, i), XSTR (y, i)))
1250 /* This can happen for an asm which clobbers memory. */
1254 /* It is believed that rtx's at this level will never
1255 contain anything but integers and other rtx's,
1256 except for within LABEL_REFs and SYMBOL_REFs. */
1264 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1265 X and return it, or return 0 if none found. */
1268 find_symbolic_term (rtx x)
1274 code = GET_CODE (x);
1275 if (code == SYMBOL_REF || code == LABEL_REF)
1280 fmt = GET_RTX_FORMAT (code);
1281 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1287 t = find_symbolic_term (XEXP (x, i));
1291 else if (fmt[i] == 'E')
1298 find_base_term (rtx x)
1301 struct elt_loc_list *l;
1303 #if defined (FIND_BASE_TERM)
1304 /* Try machine-dependent ways to find the base term. */
1305 x = FIND_BASE_TERM (x);
1308 switch (GET_CODE (x))
1311 return REG_BASE_VALUE (x);
1314 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1324 return find_base_term (XEXP (x, 0));
1327 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1329 rtx temp = find_base_term (XEXP (x, 0));
1331 if (temp != 0 && CONSTANT_P (temp))
1332 temp = convert_memory_address (Pmode, temp);
1338 val = CSELIB_VAL_PTR (x);
1341 for (l = val->locs; l; l = l->next)
1342 if ((x = find_base_term (l->loc)) != 0)
1348 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1355 rtx tmp1 = XEXP (x, 0);
1356 rtx tmp2 = XEXP (x, 1);
1358 /* This is a little bit tricky since we have to determine which of
1359 the two operands represents the real base address. Otherwise this
1360 routine may return the index register instead of the base register.
1362 That may cause us to believe no aliasing was possible, when in
1363 fact aliasing is possible.
1365 We use a few simple tests to guess the base register. Additional
1366 tests can certainly be added. For example, if one of the operands
1367 is a shift or multiply, then it must be the index register and the
1368 other operand is the base register. */
1370 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1371 return find_base_term (tmp2);
1373 /* If either operand is known to be a pointer, then use it
1374 to determine the base term. */
1375 if (REG_P (tmp1) && REG_POINTER (tmp1))
1376 return find_base_term (tmp1);
1378 if (REG_P (tmp2) && REG_POINTER (tmp2))
1379 return find_base_term (tmp2);
1381 /* Neither operand was known to be a pointer. Go ahead and find the
1382 base term for both operands. */
1383 tmp1 = find_base_term (tmp1);
1384 tmp2 = find_base_term (tmp2);
1386 /* If either base term is named object or a special address
1387 (like an argument or stack reference), then use it for the
1390 && (GET_CODE (tmp1) == SYMBOL_REF
1391 || GET_CODE (tmp1) == LABEL_REF
1392 || (GET_CODE (tmp1) == ADDRESS
1393 && GET_MODE (tmp1) != VOIDmode)))
1397 && (GET_CODE (tmp2) == SYMBOL_REF
1398 || GET_CODE (tmp2) == LABEL_REF
1399 || (GET_CODE (tmp2) == ADDRESS
1400 && GET_MODE (tmp2) != VOIDmode)))
1403 /* We could not determine which of the two operands was the
1404 base register and which was the index. So we can determine
1405 nothing from the base alias check. */
1410 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1411 return find_base_term (XEXP (x, 0));
1419 return REG_BASE_VALUE (frame_pointer_rtx);
1426 /* Return 0 if the addresses X and Y are known to point to different
1427 objects, 1 if they might be pointers to the same object. */
1430 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1431 enum machine_mode y_mode)
1433 rtx x_base = find_base_term (x);
1434 rtx y_base = find_base_term (y);
1436 /* If the address itself has no known base see if a known equivalent
1437 value has one. If either address still has no known base, nothing
1438 is known about aliasing. */
1443 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1446 x_base = find_base_term (x_c);
1454 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1457 y_base = find_base_term (y_c);
1462 /* If the base addresses are equal nothing is known about aliasing. */
1463 if (rtx_equal_p (x_base, y_base))
1466 /* The base addresses of the read and write are different expressions.
1467 If they are both symbols and they are not accessed via AND, there is
1468 no conflict. We can bring knowledge of object alignment into play
1469 here. For example, on alpha, "char a, b;" can alias one another,
1470 though "char a; long b;" cannot. */
1471 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1473 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1475 if (GET_CODE (x) == AND
1476 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1477 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1479 if (GET_CODE (y) == AND
1480 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1481 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1483 /* Differing symbols never alias. */
1487 /* If one address is a stack reference there can be no alias:
1488 stack references using different base registers do not alias,
1489 a stack reference can not alias a parameter, and a stack reference
1490 can not alias a global. */
1491 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1492 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1495 if (! flag_argument_noalias)
1498 if (flag_argument_noalias > 1)
1501 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1502 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1505 /* Convert the address X into something we can use. This is done by returning
1506 it unchanged unless it is a value; in the latter case we call cselib to get
1507 a more useful rtx. */
1513 struct elt_loc_list *l;
1515 if (GET_CODE (x) != VALUE)
1517 v = CSELIB_VAL_PTR (x);
1520 for (l = v->locs; l; l = l->next)
1521 if (CONSTANT_P (l->loc))
1523 for (l = v->locs; l; l = l->next)
1524 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1527 return v->locs->loc;
1532 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1533 where SIZE is the size in bytes of the memory reference. If ADDR
1534 is not modified by the memory reference then ADDR is returned. */
1537 addr_side_effect_eval (rtx addr, int size, int n_refs)
1541 switch (GET_CODE (addr))
1544 offset = (n_refs + 1) * size;
1547 offset = -(n_refs + 1) * size;
1550 offset = n_refs * size;
1553 offset = -n_refs * size;
1561 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1564 addr = XEXP (addr, 0);
1565 addr = canon_rtx (addr);
1570 /* Return nonzero if X and Y (memory addresses) could reference the
1571 same location in memory. C is an offset accumulator. When
1572 C is nonzero, we are testing aliases between X and Y + C.
1573 XSIZE is the size in bytes of the X reference,
1574 similarly YSIZE is the size in bytes for Y.
1575 Expect that canon_rtx has been already called for X and Y.
1577 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1578 referenced (the reference was BLKmode), so make the most pessimistic
1581 If XSIZE or YSIZE is negative, we may access memory outside the object
1582 being referenced as a side effect. This can happen when using AND to
1583 align memory references, as is done on the Alpha.
1585 Nice to notice that varying addresses cannot conflict with fp if no
1586 local variables had their addresses taken, but that's too hard now. */
1589 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1591 if (GET_CODE (x) == VALUE)
1593 if (GET_CODE (y) == VALUE)
1595 if (GET_CODE (x) == HIGH)
1597 else if (GET_CODE (x) == LO_SUM)
1600 x = addr_side_effect_eval (x, xsize, 0);
1601 if (GET_CODE (y) == HIGH)
1603 else if (GET_CODE (y) == LO_SUM)
1606 y = addr_side_effect_eval (y, ysize, 0);
1608 if (rtx_equal_for_memref_p (x, y))
1610 if (xsize <= 0 || ysize <= 0)
1612 if (c >= 0 && xsize > c)
1614 if (c < 0 && ysize+c > 0)
1619 /* This code used to check for conflicts involving stack references and
1620 globals but the base address alias code now handles these cases. */
1622 if (GET_CODE (x) == PLUS)
1624 /* The fact that X is canonicalized means that this
1625 PLUS rtx is canonicalized. */
1626 rtx x0 = XEXP (x, 0);
1627 rtx x1 = XEXP (x, 1);
1629 if (GET_CODE (y) == PLUS)
1631 /* The fact that Y is canonicalized means that this
1632 PLUS rtx is canonicalized. */
1633 rtx y0 = XEXP (y, 0);
1634 rtx y1 = XEXP (y, 1);
1636 if (rtx_equal_for_memref_p (x1, y1))
1637 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1638 if (rtx_equal_for_memref_p (x0, y0))
1639 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1640 if (GET_CODE (x1) == CONST_INT)
1642 if (GET_CODE (y1) == CONST_INT)
1643 return memrefs_conflict_p (xsize, x0, ysize, y0,
1644 c - INTVAL (x1) + INTVAL (y1));
1646 return memrefs_conflict_p (xsize, x0, ysize, y,
1649 else if (GET_CODE (y1) == CONST_INT)
1650 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1654 else if (GET_CODE (x1) == CONST_INT)
1655 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1657 else if (GET_CODE (y) == PLUS)
1659 /* The fact that Y is canonicalized means that this
1660 PLUS rtx is canonicalized. */
1661 rtx y0 = XEXP (y, 0);
1662 rtx y1 = XEXP (y, 1);
1664 if (GET_CODE (y1) == CONST_INT)
1665 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1670 if (GET_CODE (x) == GET_CODE (y))
1671 switch (GET_CODE (x))
1675 /* Handle cases where we expect the second operands to be the
1676 same, and check only whether the first operand would conflict
1679 rtx x1 = canon_rtx (XEXP (x, 1));
1680 rtx y1 = canon_rtx (XEXP (y, 1));
1681 if (! rtx_equal_for_memref_p (x1, y1))
1683 x0 = canon_rtx (XEXP (x, 0));
1684 y0 = canon_rtx (XEXP (y, 0));
1685 if (rtx_equal_for_memref_p (x0, y0))
1686 return (xsize == 0 || ysize == 0
1687 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1689 /* Can't properly adjust our sizes. */
1690 if (GET_CODE (x1) != CONST_INT)
1692 xsize /= INTVAL (x1);
1693 ysize /= INTVAL (x1);
1695 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1699 /* Are these registers known not to be equal? */
1700 if (alias_invariant)
1702 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1703 rtx i_x, i_y; /* invariant relationships of X and Y */
1705 i_x = r_x >= alias_invariant_size ? 0 : alias_invariant[r_x];
1706 i_y = r_y >= alias_invariant_size ? 0 : alias_invariant[r_y];
1708 if (i_x == 0 && i_y == 0)
1711 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1712 ysize, i_y ? i_y : y, c))
1721 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1722 as an access with indeterminate size. Assume that references
1723 besides AND are aligned, so if the size of the other reference is
1724 at least as large as the alignment, assume no other overlap. */
1725 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1727 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1729 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1731 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1733 /* ??? If we are indexing far enough into the array/structure, we
1734 may yet be able to determine that we can not overlap. But we
1735 also need to that we are far enough from the end not to overlap
1736 a following reference, so we do nothing with that for now. */
1737 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1739 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1742 if (GET_CODE (x) == ADDRESSOF)
1744 if (y == frame_pointer_rtx
1745 || GET_CODE (y) == ADDRESSOF)
1746 return xsize <= 0 || ysize <= 0;
1748 if (GET_CODE (y) == ADDRESSOF)
1750 if (x == frame_pointer_rtx)
1751 return xsize <= 0 || ysize <= 0;
1756 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1758 c += (INTVAL (y) - INTVAL (x));
1759 return (xsize <= 0 || ysize <= 0
1760 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1763 if (GET_CODE (x) == CONST)
1765 if (GET_CODE (y) == CONST)
1766 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1767 ysize, canon_rtx (XEXP (y, 0)), c);
1769 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1772 if (GET_CODE (y) == CONST)
1773 return memrefs_conflict_p (xsize, x, ysize,
1774 canon_rtx (XEXP (y, 0)), c);
1777 return (xsize <= 0 || ysize <= 0
1778 || (rtx_equal_for_memref_p (x, y)
1779 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1786 /* Functions to compute memory dependencies.
1788 Since we process the insns in execution order, we can build tables
1789 to keep track of what registers are fixed (and not aliased), what registers
1790 are varying in known ways, and what registers are varying in unknown
1793 If both memory references are volatile, then there must always be a
1794 dependence between the two references, since their order can not be
1795 changed. A volatile and non-volatile reference can be interchanged
1798 A MEM_IN_STRUCT reference at a non-AND varying address can never
1799 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1800 also must allow AND addresses, because they may generate accesses
1801 outside the object being referenced. This is used to generate
1802 aligned addresses from unaligned addresses, for instance, the alpha
1803 storeqi_unaligned pattern. */
1805 /* Read dependence: X is read after read in MEM takes place. There can
1806 only be a dependence here if both reads are volatile. */
1809 read_dependence (rtx mem, rtx x)
1811 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1814 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1815 MEM2 is a reference to a structure at a varying address, or returns
1816 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1817 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1818 to decide whether or not an address may vary; it should return
1819 nonzero whenever variation is possible.
1820 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1823 fixed_scalar_and_varying_struct_p (rtx mem1, rtx mem2, rtx mem1_addr,
1825 int (*varies_p) (rtx, int))
1827 if (! flag_strict_aliasing)
1830 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1831 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1832 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1836 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1837 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1838 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1845 /* Returns nonzero if something about the mode or address format MEM1
1846 indicates that it might well alias *anything*. */
1849 aliases_everything_p (rtx mem)
1851 if (GET_CODE (XEXP (mem, 0)) == AND)
1852 /* If the address is an AND, its very hard to know at what it is
1853 actually pointing. */
1859 /* Return true if we can determine that the fields referenced cannot
1860 overlap for any pair of objects. */
1863 nonoverlapping_component_refs_p (tree x, tree y)
1865 tree fieldx, fieldy, typex, typey, orig_y;
1869 /* The comparison has to be done at a common type, since we don't
1870 know how the inheritance hierarchy works. */
1874 fieldx = TREE_OPERAND (x, 1);
1875 typex = DECL_FIELD_CONTEXT (fieldx);
1880 fieldy = TREE_OPERAND (y, 1);
1881 typey = DECL_FIELD_CONTEXT (fieldy);
1886 y = TREE_OPERAND (y, 0);
1888 while (y && TREE_CODE (y) == COMPONENT_REF);
1890 x = TREE_OPERAND (x, 0);
1892 while (x && TREE_CODE (x) == COMPONENT_REF);
1894 /* Never found a common type. */
1898 /* If we're left with accessing different fields of a structure,
1900 if (TREE_CODE (typex) == RECORD_TYPE
1901 && fieldx != fieldy)
1904 /* The comparison on the current field failed. If we're accessing
1905 a very nested structure, look at the next outer level. */
1906 x = TREE_OPERAND (x, 0);
1907 y = TREE_OPERAND (y, 0);
1910 && TREE_CODE (x) == COMPONENT_REF
1911 && TREE_CODE (y) == COMPONENT_REF);
1916 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1919 decl_for_component_ref (tree x)
1923 x = TREE_OPERAND (x, 0);
1925 while (x && TREE_CODE (x) == COMPONENT_REF);
1927 return x && DECL_P (x) ? x : NULL_TREE;
1930 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1931 offset of the field reference. */
1934 adjust_offset_for_component_ref (tree x, rtx offset)
1936 HOST_WIDE_INT ioffset;
1941 ioffset = INTVAL (offset);
1944 tree field = TREE_OPERAND (x, 1);
1946 if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
1948 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
1949 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1952 x = TREE_OPERAND (x, 0);
1954 while (x && TREE_CODE (x) == COMPONENT_REF);
1956 return GEN_INT (ioffset);
1959 /* Return nonzero if we can determine the exprs corresponding to memrefs
1960 X and Y and they do not overlap. */
1963 nonoverlapping_memrefs_p (rtx x, rtx y)
1965 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1968 rtx moffsetx, moffsety;
1969 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1971 /* Unless both have exprs, we can't tell anything. */
1972 if (exprx == 0 || expry == 0)
1975 /* If both are field references, we may be able to determine something. */
1976 if (TREE_CODE (exprx) == COMPONENT_REF
1977 && TREE_CODE (expry) == COMPONENT_REF
1978 && nonoverlapping_component_refs_p (exprx, expry))
1981 /* If the field reference test failed, look at the DECLs involved. */
1982 moffsetx = MEM_OFFSET (x);
1983 if (TREE_CODE (exprx) == COMPONENT_REF)
1985 tree t = decl_for_component_ref (exprx);
1988 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
1991 else if (TREE_CODE (exprx) == INDIRECT_REF)
1993 exprx = TREE_OPERAND (exprx, 0);
1994 if (flag_argument_noalias < 2
1995 || TREE_CODE (exprx) != PARM_DECL)
1999 moffsety = MEM_OFFSET (y);
2000 if (TREE_CODE (expry) == COMPONENT_REF)
2002 tree t = decl_for_component_ref (expry);
2005 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2008 else if (TREE_CODE (expry) == INDIRECT_REF)
2010 expry = TREE_OPERAND (expry, 0);
2011 if (flag_argument_noalias < 2
2012 || TREE_CODE (expry) != PARM_DECL)
2016 if (! DECL_P (exprx) || ! DECL_P (expry))
2019 rtlx = DECL_RTL (exprx);
2020 rtly = DECL_RTL (expry);
2022 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2023 can't overlap unless they are the same because we never reuse that part
2024 of the stack frame used for locals for spilled pseudos. */
2025 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
2026 && ! rtx_equal_p (rtlx, rtly))
2029 /* Get the base and offsets of both decls. If either is a register, we
2030 know both are and are the same, so use that as the base. The only
2031 we can avoid overlap is if we can deduce that they are nonoverlapping
2032 pieces of that decl, which is very rare. */
2033 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
2034 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2035 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2037 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
2038 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2039 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2041 /* If the bases are different, we know they do not overlap if both
2042 are constants or if one is a constant and the other a pointer into the
2043 stack frame. Otherwise a different base means we can't tell if they
2045 if (! rtx_equal_p (basex, basey))
2046 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2047 || (CONSTANT_P (basex) && REG_P (basey)
2048 && REGNO_PTR_FRAME_P (REGNO (basey)))
2049 || (CONSTANT_P (basey) && REG_P (basex)
2050 && REGNO_PTR_FRAME_P (REGNO (basex))));
2052 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2053 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2055 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2056 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2059 /* If we have an offset for either memref, it can update the values computed
2062 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2064 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2066 /* If a memref has both a size and an offset, we can use the smaller size.
2067 We can't do this if the offset isn't known because we must view this
2068 memref as being anywhere inside the DECL's MEM. */
2069 if (MEM_SIZE (x) && moffsetx)
2070 sizex = INTVAL (MEM_SIZE (x));
2071 if (MEM_SIZE (y) && moffsety)
2072 sizey = INTVAL (MEM_SIZE (y));
2074 /* Put the values of the memref with the lower offset in X's values. */
2075 if (offsetx > offsety)
2077 tem = offsetx, offsetx = offsety, offsety = tem;
2078 tem = sizex, sizex = sizey, sizey = tem;
2081 /* If we don't know the size of the lower-offset value, we can't tell
2082 if they conflict. Otherwise, we do the test. */
2083 return sizex >= 0 && offsety >= offsetx + sizex;
2086 /* True dependence: X is read after store in MEM takes place. */
2089 true_dependence (rtx mem, enum machine_mode mem_mode, rtx x,
2090 int (*varies) (rtx, int))
2092 rtx x_addr, mem_addr;
2095 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2098 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2099 This is used in epilogue deallocation functions. */
2100 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2102 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2105 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2108 /* Unchanging memory can't conflict with non-unchanging memory.
2109 A non-unchanging read can conflict with a non-unchanging write.
2110 An unchanging read can conflict with an unchanging write since
2111 there may be a single store to this address to initialize it.
2112 Note that an unchanging store can conflict with a non-unchanging read
2113 since we have to make conservative assumptions when we have a
2114 record with readonly fields and we are copying the whole thing.
2115 Just fall through to the code below to resolve potential conflicts.
2116 This won't handle all cases optimally, but the possible performance
2117 loss should be negligible. */
2118 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2121 if (nonoverlapping_memrefs_p (mem, x))
2124 if (mem_mode == VOIDmode)
2125 mem_mode = GET_MODE (mem);
2127 x_addr = get_addr (XEXP (x, 0));
2128 mem_addr = get_addr (XEXP (mem, 0));
2130 base = find_base_term (x_addr);
2131 if (base && (GET_CODE (base) == LABEL_REF
2132 || (GET_CODE (base) == SYMBOL_REF
2133 && CONSTANT_POOL_ADDRESS_P (base))))
2136 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2139 x_addr = canon_rtx (x_addr);
2140 mem_addr = canon_rtx (mem_addr);
2142 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2143 SIZE_FOR_MODE (x), x_addr, 0))
2146 if (aliases_everything_p (x))
2149 /* We cannot use aliases_everything_p to test MEM, since we must look
2150 at MEM_MODE, rather than GET_MODE (MEM). */
2151 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2154 /* In true_dependence we also allow BLKmode to alias anything. Why
2155 don't we do this in anti_dependence and output_dependence? */
2156 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2159 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2163 /* Canonical true dependence: X is read after store in MEM takes place.
2164 Variant of true_dependence which assumes MEM has already been
2165 canonicalized (hence we no longer do that here).
2166 The mem_addr argument has been added, since true_dependence computed
2167 this value prior to canonicalizing. */
2170 canon_true_dependence (rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2171 rtx x, int (*varies) (rtx, int))
2175 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2178 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2179 This is used in epilogue deallocation functions. */
2180 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2182 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2185 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2188 /* If X is an unchanging read, then it can't possibly conflict with any
2189 non-unchanging store. It may conflict with an unchanging write though,
2190 because there may be a single store to this address to initialize it.
2191 Just fall through to the code below to resolve the case where we have
2192 both an unchanging read and an unchanging write. This won't handle all
2193 cases optimally, but the possible performance loss should be
2195 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2198 if (nonoverlapping_memrefs_p (x, mem))
2201 x_addr = get_addr (XEXP (x, 0));
2203 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2206 x_addr = canon_rtx (x_addr);
2207 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2208 SIZE_FOR_MODE (x), x_addr, 0))
2211 if (aliases_everything_p (x))
2214 /* We cannot use aliases_everything_p to test MEM, since we must look
2215 at MEM_MODE, rather than GET_MODE (MEM). */
2216 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2219 /* In true_dependence we also allow BLKmode to alias anything. Why
2220 don't we do this in anti_dependence and output_dependence? */
2221 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2224 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2228 /* Returns nonzero if a write to X might alias a previous read from
2229 (or, if WRITEP is nonzero, a write to) MEM. If CONSTP is nonzero,
2230 honor the RTX_UNCHANGING_P flags on X and MEM. */
2233 write_dependence_p (rtx mem, rtx x, int writep, int constp)
2235 rtx x_addr, mem_addr;
2239 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2242 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2243 This is used in epilogue deallocation functions. */
2244 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2246 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2249 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2254 /* Unchanging memory can't conflict with non-unchanging memory. */
2255 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
2258 /* If MEM is an unchanging read, then it can't possibly conflict with
2259 the store to X, because there is at most one store to MEM, and it
2260 must have occurred somewhere before MEM. */
2261 if (! writep && RTX_UNCHANGING_P (mem))
2265 if (nonoverlapping_memrefs_p (x, mem))
2268 x_addr = get_addr (XEXP (x, 0));
2269 mem_addr = get_addr (XEXP (mem, 0));
2273 base = find_base_term (mem_addr);
2274 if (base && (GET_CODE (base) == LABEL_REF
2275 || (GET_CODE (base) == SYMBOL_REF
2276 && CONSTANT_POOL_ADDRESS_P (base))))
2280 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2284 x_addr = canon_rtx (x_addr);
2285 mem_addr = canon_rtx (mem_addr);
2287 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2288 SIZE_FOR_MODE (x), x_addr, 0))
2292 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2295 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2296 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2299 /* Anti dependence: X is written after read in MEM takes place. */
2302 anti_dependence (rtx mem, rtx x)
2304 return write_dependence_p (mem, x, /*writep=*/0, /*constp*/1);
2307 /* Output dependence: X is written after store in MEM takes place. */
2310 output_dependence (rtx mem, rtx x)
2312 return write_dependence_p (mem, x, /*writep=*/1, /*constp*/1);
2315 /* Unchanging anti dependence: Like anti_dependence but ignores
2316 the UNCHANGING_RTX_P property on const variable references. */
2319 unchanging_anti_dependence (rtx mem, rtx x)
2321 return write_dependence_p (mem, x, /*writep=*/0, /*constp*/0);
2324 /* A subroutine of nonlocal_mentioned_p, returns 1 if *LOC mentions
2325 something which is not local to the function and is not constant. */
2328 nonlocal_mentioned_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2337 switch (GET_CODE (x))
2340 if (GET_CODE (SUBREG_REG (x)) == REG)
2342 /* Global registers are not local. */
2343 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2344 && global_regs[subreg_regno (x)])
2352 /* Global registers are not local. */
2353 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2368 /* Constants in the function's constants pool are constant. */
2369 if (CONSTANT_POOL_ADDRESS_P (x))
2374 /* Non-constant calls and recursion are not local. */
2378 /* Be overly conservative and consider any volatile memory
2379 reference as not local. */
2380 if (MEM_VOLATILE_P (x))
2382 base = find_base_term (XEXP (x, 0));
2385 /* A Pmode ADDRESS could be a reference via the structure value
2386 address or static chain. Such memory references are nonlocal.
2388 Thus, we have to examine the contents of the ADDRESS to find
2389 out if this is a local reference or not. */
2390 if (GET_CODE (base) == ADDRESS
2391 && GET_MODE (base) == Pmode
2392 && (XEXP (base, 0) == stack_pointer_rtx
2393 || XEXP (base, 0) == arg_pointer_rtx
2394 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2395 || XEXP (base, 0) == hard_frame_pointer_rtx
2397 || XEXP (base, 0) == frame_pointer_rtx))
2399 /* Constants in the function's constant pool are constant. */
2400 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2405 case UNSPEC_VOLATILE:
2410 if (MEM_VOLATILE_P (x))
2422 /* Returns nonzero if X might mention something which is not
2423 local to the function and is not constant. */
2426 nonlocal_mentioned_p (rtx x)
2430 if (GET_CODE (x) == CALL_INSN)
2432 if (! CONST_OR_PURE_CALL_P (x))
2434 x = CALL_INSN_FUNCTION_USAGE (x);
2442 return for_each_rtx (&x, nonlocal_mentioned_p_1, NULL);
2445 /* A subroutine of nonlocal_referenced_p, returns 1 if *LOC references
2446 something which is not local to the function and is not constant. */
2449 nonlocal_referenced_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2456 switch (GET_CODE (x))
2462 return nonlocal_mentioned_p (x);
2465 /* Non-constant calls and recursion are not local. */
2469 if (nonlocal_mentioned_p (SET_SRC (x)))
2472 if (GET_CODE (SET_DEST (x)) == MEM)
2473 return nonlocal_mentioned_p (XEXP (SET_DEST (x), 0));
2475 /* If the destination is anything other than a CC0, PC,
2476 MEM, REG, or a SUBREG of a REG that occupies all of
2477 the REG, then X references nonlocal memory if it is
2478 mentioned in the destination. */
2479 if (GET_CODE (SET_DEST (x)) != CC0
2480 && GET_CODE (SET_DEST (x)) != PC
2481 && GET_CODE (SET_DEST (x)) != REG
2482 && ! (GET_CODE (SET_DEST (x)) == SUBREG
2483 && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
2484 && (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (x))))
2485 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
2486 == ((GET_MODE_SIZE (GET_MODE (SET_DEST (x)))
2487 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD))))
2488 return nonlocal_mentioned_p (SET_DEST (x));
2492 if (GET_CODE (XEXP (x, 0)) == MEM)
2493 return nonlocal_mentioned_p (XEXP (XEXP (x, 0), 0));
2497 return nonlocal_mentioned_p (XEXP (x, 0));
2500 case UNSPEC_VOLATILE:
2504 if (MEM_VOLATILE_P (x))
2516 /* Returns nonzero if X might reference something which is not
2517 local to the function and is not constant. */
2520 nonlocal_referenced_p (rtx x)
2524 if (GET_CODE (x) == CALL_INSN)
2526 if (! CONST_OR_PURE_CALL_P (x))
2528 x = CALL_INSN_FUNCTION_USAGE (x);
2536 return for_each_rtx (&x, nonlocal_referenced_p_1, NULL);
2539 /* A subroutine of nonlocal_set_p, returns 1 if *LOC sets
2540 something which is not local to the function and is not constant. */
2543 nonlocal_set_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2550 switch (GET_CODE (x))
2553 /* Non-constant calls and recursion are not local. */
2562 return nonlocal_mentioned_p (XEXP (x, 0));
2565 if (nonlocal_mentioned_p (SET_DEST (x)))
2567 return nonlocal_set_p (SET_SRC (x));
2570 return nonlocal_mentioned_p (XEXP (x, 0));
2576 case UNSPEC_VOLATILE:
2580 if (MEM_VOLATILE_P (x))
2592 /* Returns nonzero if X might set something which is not
2593 local to the function and is not constant. */
2596 nonlocal_set_p (rtx x)
2600 if (GET_CODE (x) == CALL_INSN)
2602 if (! CONST_OR_PURE_CALL_P (x))
2604 x = CALL_INSN_FUNCTION_USAGE (x);
2612 return for_each_rtx (&x, nonlocal_set_p_1, NULL);
2615 /* Mark the function if it is pure or constant. */
2618 mark_constant_function (void)
2621 int nonlocal_memory_referenced;
2623 if (TREE_READONLY (current_function_decl)
2624 || DECL_IS_PURE (current_function_decl)
2625 || TREE_THIS_VOLATILE (current_function_decl)
2626 || current_function_has_nonlocal_goto
2627 || !(*targetm.binds_local_p) (current_function_decl))
2630 /* A loop might not return which counts as a side effect. */
2631 if (mark_dfs_back_edges ())
2634 nonlocal_memory_referenced = 0;
2636 init_alias_analysis ();
2638 /* Determine if this is a constant or pure function. */
2640 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2642 if (! INSN_P (insn))
2645 if (nonlocal_set_p (insn) || global_reg_mentioned_p (insn)
2646 || volatile_refs_p (PATTERN (insn)))
2649 if (! nonlocal_memory_referenced)
2650 nonlocal_memory_referenced = nonlocal_referenced_p (insn);
2653 end_alias_analysis ();
2655 /* Mark the function. */
2659 else if (nonlocal_memory_referenced)
2661 cgraph_rtl_info (current_function_decl)->pure_function = 1;
2662 DECL_IS_PURE (current_function_decl) = 1;
2666 cgraph_rtl_info (current_function_decl)->const_function = 1;
2667 TREE_READONLY (current_function_decl) = 1;
2673 init_alias_once (void)
2677 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2678 /* Check whether this register can hold an incoming pointer
2679 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2680 numbers, so translate if necessary due to register windows. */
2681 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2682 && HARD_REGNO_MODE_OK (i, Pmode))
2683 static_reg_base_value[i]
2684 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2686 static_reg_base_value[STACK_POINTER_REGNUM]
2687 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2688 static_reg_base_value[ARG_POINTER_REGNUM]
2689 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2690 static_reg_base_value[FRAME_POINTER_REGNUM]
2691 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2692 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2693 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2694 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2698 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2699 to be memory reference. */
2700 static bool memory_modified;
2702 memory_modified_1 (rtx x, rtx pat ATTRIBUTE_UNUSED, void *data)
2704 if (GET_CODE (x) == MEM)
2706 if (anti_dependence (x, (rtx)data) || output_dependence (x, (rtx)data))
2707 memory_modified = true;
2712 /* Return true when INSN possibly modify memory contents of MEM
2713 (ie address can be modified). */
2715 memory_modified_in_insn_p (rtx mem, rtx insn)
2719 memory_modified = false;
2720 note_stores (PATTERN (insn), memory_modified_1, mem);
2721 return memory_modified;
2724 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2728 init_alias_analysis (void)
2730 unsigned int maxreg = max_reg_num ();
2736 timevar_push (TV_ALIAS_ANALYSIS);
2738 reg_known_value_size = maxreg;
2741 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2742 - FIRST_PSEUDO_REGISTER;
2744 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2745 - FIRST_PSEUDO_REGISTER;
2747 /* Overallocate reg_base_value to allow some growth during loop
2748 optimization. Loop unrolling can create a large number of
2750 if (old_reg_base_value)
2752 reg_base_value = old_reg_base_value;
2753 /* If varray gets large zeroing cost may get important. */
2754 if (VARRAY_SIZE (reg_base_value) > 256
2755 && VARRAY_SIZE (reg_base_value) > 4 * maxreg)
2756 VARRAY_GROW (reg_base_value, maxreg);
2757 VARRAY_CLEAR (reg_base_value);
2758 if (VARRAY_SIZE (reg_base_value) < maxreg)
2759 VARRAY_GROW (reg_base_value, maxreg);
2763 VARRAY_RTX_INIT (reg_base_value, maxreg, "reg_base_value");
2766 new_reg_base_value = xmalloc (maxreg * sizeof (rtx));
2767 reg_seen = xmalloc (maxreg);
2768 if (! reload_completed && flag_old_unroll_loops)
2770 /* ??? Why are we realloc'ing if we're just going to zero it? */
2771 alias_invariant = xrealloc (alias_invariant,
2772 maxreg * sizeof (rtx));
2773 memset (alias_invariant, 0, maxreg * sizeof (rtx));
2774 alias_invariant_size = maxreg;
2777 /* The basic idea is that each pass through this loop will use the
2778 "constant" information from the previous pass to propagate alias
2779 information through another level of assignments.
2781 This could get expensive if the assignment chains are long. Maybe
2782 we should throttle the number of iterations, possibly based on
2783 the optimization level or flag_expensive_optimizations.
2785 We could propagate more information in the first pass by making use
2786 of REG_N_SETS to determine immediately that the alias information
2787 for a pseudo is "constant".
2789 A program with an uninitialized variable can cause an infinite loop
2790 here. Instead of doing a full dataflow analysis to detect such problems
2791 we just cap the number of iterations for the loop.
2793 The state of the arrays for the set chain in question does not matter
2794 since the program has undefined behavior. */
2799 /* Assume nothing will change this iteration of the loop. */
2802 /* We want to assign the same IDs each iteration of this loop, so
2803 start counting from zero each iteration of the loop. */
2806 /* We're at the start of the function each iteration through the
2807 loop, so we're copying arguments. */
2808 copying_arguments = true;
2810 /* Wipe the potential alias information clean for this pass. */
2811 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2813 /* Wipe the reg_seen array clean. */
2814 memset (reg_seen, 0, maxreg);
2816 /* Mark all hard registers which may contain an address.
2817 The stack, frame and argument pointers may contain an address.
2818 An argument register which can hold a Pmode value may contain
2819 an address even if it is not in BASE_REGS.
2821 The address expression is VOIDmode for an argument and
2822 Pmode for other registers. */
2824 memcpy (new_reg_base_value, static_reg_base_value,
2825 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2827 /* Walk the insns adding values to the new_reg_base_value array. */
2828 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2834 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2835 /* The prologue/epilogue insns are not threaded onto the
2836 insn chain until after reload has completed. Thus,
2837 there is no sense wasting time checking if INSN is in
2838 the prologue/epilogue until after reload has completed. */
2839 if (reload_completed
2840 && prologue_epilogue_contains (insn))
2844 /* If this insn has a noalias note, process it, Otherwise,
2845 scan for sets. A simple set will have no side effects
2846 which could change the base value of any other register. */
2848 if (GET_CODE (PATTERN (insn)) == SET
2849 && REG_NOTES (insn) != 0
2850 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2851 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2853 note_stores (PATTERN (insn), record_set, NULL);
2855 set = single_set (insn);
2858 && GET_CODE (SET_DEST (set)) == REG
2859 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2861 unsigned int regno = REGNO (SET_DEST (set));
2862 rtx src = SET_SRC (set);
2864 if (REG_NOTES (insn) != 0
2865 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2866 && REG_N_SETS (regno) == 1)
2867 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2868 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2869 && ! rtx_varies_p (XEXP (note, 0), 1)
2870 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2872 reg_known_value[regno] = XEXP (note, 0);
2873 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2875 else if (REG_N_SETS (regno) == 1
2876 && GET_CODE (src) == PLUS
2877 && GET_CODE (XEXP (src, 0)) == REG
2878 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2879 && (reg_known_value[REGNO (XEXP (src, 0))])
2880 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2882 rtx op0 = XEXP (src, 0);
2883 op0 = reg_known_value[REGNO (op0)];
2884 reg_known_value[regno]
2885 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2886 reg_known_equiv_p[regno] = 0;
2888 else if (REG_N_SETS (regno) == 1
2889 && ! rtx_varies_p (src, 1))
2891 reg_known_value[regno] = src;
2892 reg_known_equiv_p[regno] = 0;
2896 else if (GET_CODE (insn) == NOTE
2897 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2898 copying_arguments = false;
2901 /* Now propagate values from new_reg_base_value to reg_base_value. */
2902 if (maxreg != (unsigned int) max_reg_num())
2904 for (ui = 0; ui < maxreg; ui++)
2906 if (new_reg_base_value[ui]
2907 && new_reg_base_value[ui] != VARRAY_RTX (reg_base_value, ui)
2908 && ! rtx_equal_p (new_reg_base_value[ui],
2909 VARRAY_RTX (reg_base_value, ui)))
2911 VARRAY_RTX (reg_base_value, ui) = new_reg_base_value[ui];
2916 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2918 /* Fill in the remaining entries. */
2919 for (i = FIRST_PSEUDO_REGISTER; i < (int)maxreg; i++)
2920 if (reg_known_value[i] == 0)
2921 reg_known_value[i] = regno_reg_rtx[i];
2923 /* Simplify the reg_base_value array so that no register refers to
2924 another register, except to special registers indirectly through
2925 ADDRESS expressions.
2927 In theory this loop can take as long as O(registers^2), but unless
2928 there are very long dependency chains it will run in close to linear
2931 This loop may not be needed any longer now that the main loop does
2932 a better job at propagating alias information. */
2938 for (ui = 0; ui < maxreg; ui++)
2940 rtx base = VARRAY_RTX (reg_base_value, ui);
2941 if (base && GET_CODE (base) == REG)
2943 unsigned int base_regno = REGNO (base);
2944 if (base_regno == ui) /* register set from itself */
2945 VARRAY_RTX (reg_base_value, ui) = 0;
2947 VARRAY_RTX (reg_base_value, ui)
2948 = VARRAY_RTX (reg_base_value, base_regno);
2953 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2956 free (new_reg_base_value);
2957 new_reg_base_value = 0;
2960 timevar_pop (TV_ALIAS_ANALYSIS);
2964 end_alias_analysis (void)
2966 old_reg_base_value = reg_base_value;
2967 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2968 reg_known_value = 0;
2969 reg_known_value_size = 0;
2970 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2971 reg_known_equiv_p = 0;
2972 if (alias_invariant)
2974 free (alias_invariant);
2975 alias_invariant = 0;
2976 alias_invariant_size = 0;
2980 #include "gt-alias.h"