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 TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
295 has any readonly fields. If any of the fields have types that
296 contain readonly fields, return true as well. */
299 readonly_fields_p (tree type)
303 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
304 && TREE_CODE (type) != QUAL_UNION_TYPE)
307 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
308 if (TREE_CODE (field) == FIELD_DECL
309 && (TREE_READONLY (field)
310 || readonly_fields_p (TREE_TYPE (field))))
316 /* Return 1 if any MEM object of type T1 will always conflict (using the
317 dependency routines in this file) with any MEM object of type T2.
318 This is used when allocating temporary storage. If T1 and/or T2 are
319 NULL_TREE, it means we know nothing about the storage. */
322 objects_must_conflict_p (tree t1, tree t2)
324 HOST_WIDE_INT set1, set2;
326 /* If neither has a type specified, we don't know if they'll conflict
327 because we may be using them to store objects of various types, for
328 example the argument and local variables areas of inlined functions. */
329 if (t1 == 0 && t2 == 0)
332 /* If one or the other has readonly fields or is readonly,
333 then they may not conflict. */
334 if ((t1 != 0 && readonly_fields_p (t1))
335 || (t2 != 0 && readonly_fields_p (t2))
336 || (t1 != 0 && lang_hooks.honor_readonly && TYPE_READONLY (t1))
337 || (t2 != 0 && lang_hooks.honor_readonly && TYPE_READONLY (t2)))
340 /* If they are the same type, they must conflict. */
342 /* Likewise if both are volatile. */
343 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
346 set1 = t1 ? get_alias_set (t1) : 0;
347 set2 = t2 ? get_alias_set (t2) : 0;
349 /* Otherwise they conflict if they have no alias set or the same. We
350 can't simply use alias_sets_conflict_p here, because we must make
351 sure that every subtype of t1 will conflict with every subtype of
352 t2 for which a pair of subobjects of these respective subtypes
353 overlaps on the stack. */
354 return set1 == 0 || set2 == 0 || set1 == set2;
357 /* T is an expression with pointer type. Find the DECL on which this
358 expression is based. (For example, in `a[i]' this would be `a'.)
359 If there is no such DECL, or a unique decl cannot be determined,
360 NULL_TREE is returned. */
363 find_base_decl (tree t)
367 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
370 /* If this is a declaration, return it. */
371 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
374 /* Handle general expressions. It would be nice to deal with
375 COMPONENT_REFs here. If we could tell that `a' and `b' were the
376 same, then `a->f' and `b->f' are also the same. */
377 switch (TREE_CODE_CLASS (TREE_CODE (t)))
380 return find_base_decl (TREE_OPERAND (t, 0));
383 /* Return 0 if found in neither or both are the same. */
384 d0 = find_base_decl (TREE_OPERAND (t, 0));
385 d1 = find_base_decl (TREE_OPERAND (t, 1));
396 d0 = find_base_decl (TREE_OPERAND (t, 0));
397 d1 = find_base_decl (TREE_OPERAND (t, 1));
398 d2 = find_base_decl (TREE_OPERAND (t, 2));
400 /* Set any nonzero values from the last, then from the first. */
401 if (d1 == 0) d1 = d2;
402 if (d0 == 0) d0 = d1;
403 if (d1 == 0) d1 = d0;
404 if (d2 == 0) d2 = d1;
406 /* At this point all are nonzero or all are zero. If all three are the
407 same, return it. Otherwise, return zero. */
408 return (d0 == d1 && d1 == d2) ? d0 : 0;
415 /* Return 1 if all the nested component references handled by
416 get_inner_reference in T are such that we can address the object in T. */
419 can_address_p (tree t)
421 /* If we're at the end, it is vacuously addressable. */
422 if (! handled_component_p (t))
425 /* Bitfields are never addressable. */
426 else if (TREE_CODE (t) == BIT_FIELD_REF)
429 /* Fields are addressable unless they are marked as nonaddressable or
430 the containing type has alias set 0. */
431 else if (TREE_CODE (t) == COMPONENT_REF
432 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
433 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
434 && can_address_p (TREE_OPERAND (t, 0)))
437 /* Likewise for arrays. */
438 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
439 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
440 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
441 && can_address_p (TREE_OPERAND (t, 0)))
447 /* Return the alias set for T, which may be either a type or an
448 expression. Call language-specific routine for help, if needed. */
451 get_alias_set (tree t)
455 /* If we're not doing any alias analysis, just assume everything
456 aliases everything else. Also return 0 if this or its type is
458 if (! flag_strict_aliasing || t == error_mark_node
460 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
463 /* We can be passed either an expression or a type. This and the
464 language-specific routine may make mutually-recursive calls to each other
465 to figure out what to do. At each juncture, we see if this is a tree
466 that the language may need to handle specially. First handle things that
471 tree placeholder_ptr = 0;
473 /* Remove any nops, then give the language a chance to do
474 something with this tree before we look at it. */
476 set = (*lang_hooks.get_alias_set) (t);
480 /* First see if the actual object referenced is an INDIRECT_REF from a
481 restrict-qualified pointer or a "void *". Replace
482 PLACEHOLDER_EXPRs. */
483 while (TREE_CODE (inner) == PLACEHOLDER_EXPR
484 || handled_component_p (inner))
486 if (TREE_CODE (inner) == PLACEHOLDER_EXPR)
487 inner = find_placeholder (inner, &placeholder_ptr);
489 inner = TREE_OPERAND (inner, 0);
494 /* Check for accesses through restrict-qualified pointers. */
495 if (TREE_CODE (inner) == INDIRECT_REF)
497 tree decl = find_base_decl (TREE_OPERAND (inner, 0));
499 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
501 /* If we haven't computed the actual alias set, do it now. */
502 if (DECL_POINTER_ALIAS_SET (decl) == -2)
504 /* No two restricted pointers can point at the same thing.
505 However, a restricted pointer can point at the same thing
506 as an unrestricted pointer, if that unrestricted pointer
507 is based on the restricted pointer. So, we make the
508 alias set for the restricted pointer a subset of the
509 alias set for the type pointed to by the type of the
511 HOST_WIDE_INT pointed_to_alias_set
512 = get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
514 if (pointed_to_alias_set == 0)
515 /* It's not legal to make a subset of alias set zero. */
516 DECL_POINTER_ALIAS_SET (decl) = 0;
519 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
520 record_alias_subset (pointed_to_alias_set,
521 DECL_POINTER_ALIAS_SET (decl));
525 /* We use the alias set indicated in the declaration. */
526 return DECL_POINTER_ALIAS_SET (decl);
529 /* If we have an INDIRECT_REF via a void pointer, we don't
530 know anything about what that might alias. */
531 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE)
535 /* Otherwise, pick up the outermost object that we could have a pointer
536 to, processing conversion and PLACEHOLDER_EXPR as above. */
538 while (TREE_CODE (t) == PLACEHOLDER_EXPR
539 || (handled_component_p (t) && ! can_address_p (t)))
541 if (TREE_CODE (t) == PLACEHOLDER_EXPR)
542 t = find_placeholder (t, &placeholder_ptr);
544 t = TREE_OPERAND (t, 0);
549 /* If we've already determined the alias set for a decl, just return
550 it. This is necessary for C++ anonymous unions, whose component
551 variables don't look like union members (boo!). */
552 if (TREE_CODE (t) == VAR_DECL
553 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
554 return MEM_ALIAS_SET (DECL_RTL (t));
556 /* Now all we care about is the type. */
560 /* Variant qualifiers don't affect the alias set, so get the main
561 variant. If this is a type with a known alias set, return it. */
562 t = TYPE_MAIN_VARIANT (t);
563 if (TYPE_ALIAS_SET_KNOWN_P (t))
564 return TYPE_ALIAS_SET (t);
566 /* See if the language has special handling for this type. */
567 set = (*lang_hooks.get_alias_set) (t);
571 /* There are no objects of FUNCTION_TYPE, so there's no point in
572 using up an alias set for them. (There are, of course, pointers
573 and references to functions, but that's different.) */
574 else if (TREE_CODE (t) == FUNCTION_TYPE)
577 /* Unless the language specifies otherwise, let vector types alias
578 their components. This avoids some nasty type punning issues in
579 normal usage. And indeed lets vectors be treated more like an
581 else if (TREE_CODE (t) == VECTOR_TYPE)
582 set = get_alias_set (TREE_TYPE (t));
585 /* Otherwise make a new alias set for this type. */
586 set = new_alias_set ();
588 TYPE_ALIAS_SET (t) = set;
590 /* If this is an aggregate type, we must record any component aliasing
592 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
593 record_component_aliases (t);
598 /* Return a brand-new alias set. */
600 static GTY(()) HOST_WIDE_INT last_alias_set;
605 if (flag_strict_aliasing)
608 VARRAY_GENERIC_PTR_INIT (alias_sets, 10, "alias sets");
610 VARRAY_GROW (alias_sets, last_alias_set + 2);
611 return ++last_alias_set;
617 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
618 not everything that aliases SUPERSET also aliases SUBSET. For example,
619 in C, a store to an `int' can alias a load of a structure containing an
620 `int', and vice versa. But it can't alias a load of a 'double' member
621 of the same structure. Here, the structure would be the SUPERSET and
622 `int' the SUBSET. This relationship is also described in the comment at
623 the beginning of this file.
625 This function should be called only once per SUPERSET/SUBSET pair.
627 It is illegal for SUPERSET to be zero; everything is implicitly a
628 subset of alias set zero. */
631 record_alias_subset (HOST_WIDE_INT superset, HOST_WIDE_INT subset)
633 alias_set_entry superset_entry;
634 alias_set_entry subset_entry;
636 /* It is possible in complex type situations for both sets to be the same,
637 in which case we can ignore this operation. */
638 if (superset == subset)
644 superset_entry = get_alias_set_entry (superset);
645 if (superset_entry == 0)
647 /* Create an entry for the SUPERSET, so that we have a place to
648 attach the SUBSET. */
649 superset_entry = ggc_alloc (sizeof (struct alias_set_entry));
650 superset_entry->alias_set = superset;
651 superset_entry->children
652 = splay_tree_new_ggc (splay_tree_compare_ints);
653 superset_entry->has_zero_child = 0;
654 VARRAY_GENERIC_PTR (alias_sets, superset) = superset_entry;
658 superset_entry->has_zero_child = 1;
661 subset_entry = get_alias_set_entry (subset);
662 /* If there is an entry for the subset, enter all of its children
663 (if they are not already present) as children of the SUPERSET. */
666 if (subset_entry->has_zero_child)
667 superset_entry->has_zero_child = 1;
669 splay_tree_foreach (subset_entry->children, insert_subset_children,
670 superset_entry->children);
673 /* Enter the SUBSET itself as a child of the SUPERSET. */
674 splay_tree_insert (superset_entry->children,
675 (splay_tree_key) subset, 0);
679 /* Record that component types of TYPE, if any, are part of that type for
680 aliasing purposes. For record types, we only record component types
681 for fields that are marked addressable. For array types, we always
682 record the component types, so the front end should not call this
683 function if the individual component aren't addressable. */
686 record_component_aliases (tree type)
688 HOST_WIDE_INT superset = get_alias_set (type);
694 switch (TREE_CODE (type))
697 if (! TYPE_NONALIASED_COMPONENT (type))
698 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
703 case QUAL_UNION_TYPE:
704 /* Recursively record aliases for the base classes, if there are any. */
705 if (TYPE_BINFO (type) != NULL && TYPE_BINFO_BASETYPES (type) != NULL)
708 for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type)); i++)
710 tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), i);
711 record_alias_subset (superset,
712 get_alias_set (BINFO_TYPE (binfo)));
715 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
716 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
717 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
721 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
729 /* Allocate an alias set for use in storing and reading from the varargs
732 static GTY(()) HOST_WIDE_INT varargs_set = -1;
735 get_varargs_alias_set (void)
737 if (varargs_set == -1)
738 varargs_set = new_alias_set ();
743 /* Likewise, but used for the fixed portions of the frame, e.g., register
746 static GTY(()) HOST_WIDE_INT frame_set = -1;
749 get_frame_alias_set (void)
752 frame_set = new_alias_set ();
757 /* Inside SRC, the source of a SET, find a base address. */
760 find_base_value (rtx src)
764 switch (GET_CODE (src))
772 /* At the start of a function, argument registers have known base
773 values which may be lost later. Returning an ADDRESS
774 expression here allows optimization based on argument values
775 even when the argument registers are used for other purposes. */
776 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
777 return new_reg_base_value[regno];
779 /* If a pseudo has a known base value, return it. Do not do this
780 for non-fixed hard regs since it can result in a circular
781 dependency chain for registers which have values at function entry.
783 The test above is not sufficient because the scheduler may move
784 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
785 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
786 && regno < VARRAY_SIZE (reg_base_value))
788 /* If we're inside init_alias_analysis, use new_reg_base_value
789 to reduce the number of relaxation iterations. */
790 if (new_reg_base_value && new_reg_base_value[regno]
791 && REG_N_SETS (regno) == 1)
792 return new_reg_base_value[regno];
794 if (VARRAY_RTX (reg_base_value, regno))
795 return VARRAY_RTX (reg_base_value, regno);
801 /* Check for an argument passed in memory. Only record in the
802 copying-arguments block; it is too hard to track changes
804 if (copying_arguments
805 && (XEXP (src, 0) == arg_pointer_rtx
806 || (GET_CODE (XEXP (src, 0)) == PLUS
807 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
808 return gen_rtx_ADDRESS (VOIDmode, src);
813 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
816 /* ... fall through ... */
821 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
823 /* If either operand is a REG that is a known pointer, then it
825 if (REG_P (src_0) && REG_POINTER (src_0))
826 return find_base_value (src_0);
827 if (REG_P (src_1) && REG_POINTER (src_1))
828 return find_base_value (src_1);
830 /* If either operand is a REG, then see if we already have
831 a known value for it. */
834 temp = find_base_value (src_0);
841 temp = find_base_value (src_1);
846 /* If either base is named object or a special address
847 (like an argument or stack reference), then use it for the
850 && (GET_CODE (src_0) == SYMBOL_REF
851 || GET_CODE (src_0) == LABEL_REF
852 || (GET_CODE (src_0) == ADDRESS
853 && GET_MODE (src_0) != VOIDmode)))
857 && (GET_CODE (src_1) == SYMBOL_REF
858 || GET_CODE (src_1) == LABEL_REF
859 || (GET_CODE (src_1) == ADDRESS
860 && GET_MODE (src_1) != VOIDmode)))
863 /* Guess which operand is the base address:
864 If either operand is a symbol, then it is the base. If
865 either operand is a CONST_INT, then the other is the base. */
866 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
867 return find_base_value (src_0);
868 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
869 return find_base_value (src_1);
875 /* The standard form is (lo_sum reg sym) so look only at the
877 return find_base_value (XEXP (src, 1));
880 /* If the second operand is constant set the base
881 address to the first operand. */
882 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
883 return find_base_value (XEXP (src, 0));
887 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
897 return find_base_value (XEXP (src, 0));
900 case SIGN_EXTEND: /* used for NT/Alpha pointers */
902 rtx temp = find_base_value (XEXP (src, 0));
904 if (temp != 0 && CONSTANT_P (temp))
905 temp = convert_memory_address (Pmode, temp);
917 /* Called from init_alias_analysis indirectly through note_stores. */
919 /* While scanning insns to find base values, reg_seen[N] is nonzero if
920 register N has been set in this function. */
921 static char *reg_seen;
923 /* Addresses which are known not to alias anything else are identified
924 by a unique integer. */
925 static int unique_id;
928 record_set (rtx dest, rtx set, void *data ATTRIBUTE_UNUSED)
934 if (GET_CODE (dest) != REG)
937 regno = REGNO (dest);
939 if (regno >= VARRAY_SIZE (reg_base_value))
942 /* If this spans multiple hard registers, then we must indicate that every
943 register has an unusable value. */
944 if (regno < FIRST_PSEUDO_REGISTER)
945 n = hard_regno_nregs[regno][GET_MODE (dest)];
952 reg_seen[regno + n] = 1;
953 new_reg_base_value[regno + n] = 0;
960 /* A CLOBBER wipes out any old value but does not prevent a previously
961 unset register from acquiring a base address (i.e. reg_seen is not
963 if (GET_CODE (set) == CLOBBER)
965 new_reg_base_value[regno] = 0;
974 new_reg_base_value[regno] = 0;
978 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
979 GEN_INT (unique_id++));
983 /* This is not the first set. If the new value is not related to the
984 old value, forget the base value. Note that the following code is
986 extern int x, y; int *p = &x; p += (&y-&x);
987 ANSI C does not allow computing the difference of addresses
988 of distinct top level objects. */
989 if (new_reg_base_value[regno])
990 switch (GET_CODE (src))
994 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
995 new_reg_base_value[regno] = 0;
998 /* If the value we add in the PLUS is also a valid base value,
999 this might be the actual base value, and the original value
1002 rtx other = NULL_RTX;
1004 if (XEXP (src, 0) == dest)
1005 other = XEXP (src, 1);
1006 else if (XEXP (src, 1) == dest)
1007 other = XEXP (src, 0);
1009 if (! other || find_base_value (other))
1010 new_reg_base_value[regno] = 0;
1014 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
1015 new_reg_base_value[regno] = 0;
1018 new_reg_base_value[regno] = 0;
1021 /* If this is the first set of a register, record the value. */
1022 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1023 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1024 new_reg_base_value[regno] = find_base_value (src);
1026 reg_seen[regno] = 1;
1029 /* Called from loop optimization when a new pseudo-register is
1030 created. It indicates that REGNO is being set to VAL. f INVARIANT
1031 is true then this value also describes an invariant relationship
1032 which can be used to deduce that two registers with unknown values
1036 record_base_value (unsigned int regno, rtx val, int invariant)
1038 if (invariant && alias_invariant && regno < alias_invariant_size)
1039 alias_invariant[regno] = val;
1041 if (regno >= VARRAY_SIZE (reg_base_value))
1042 VARRAY_GROW (reg_base_value, max_reg_num ());
1044 if (GET_CODE (val) == REG)
1046 VARRAY_RTX (reg_base_value, regno)
1047 = REG_BASE_VALUE (val);
1050 VARRAY_RTX (reg_base_value, regno)
1051 = find_base_value (val);
1054 /* Clear alias info for a register. This is used if an RTL transformation
1055 changes the value of a register. This is used in flow by AUTO_INC_DEC
1056 optimizations. We don't need to clear reg_base_value, since flow only
1057 changes the offset. */
1060 clear_reg_alias_info (rtx reg)
1062 unsigned int regno = REGNO (reg);
1064 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1065 reg_known_value[regno] = reg;
1068 /* Returns a canonical version of X, from the point of view alias
1069 analysis. (For example, if X is a MEM whose address is a register,
1070 and the register has a known value (say a SYMBOL_REF), then a MEM
1071 whose address is the SYMBOL_REF is returned.) */
1076 /* Recursively look for equivalences. */
1077 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1078 && REGNO (x) < reg_known_value_size)
1079 return reg_known_value[REGNO (x)] == x
1080 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1081 else if (GET_CODE (x) == PLUS)
1083 rtx x0 = canon_rtx (XEXP (x, 0));
1084 rtx x1 = canon_rtx (XEXP (x, 1));
1086 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1088 if (GET_CODE (x0) == CONST_INT)
1089 return plus_constant (x1, INTVAL (x0));
1090 else if (GET_CODE (x1) == CONST_INT)
1091 return plus_constant (x0, INTVAL (x1));
1092 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1096 /* This gives us much better alias analysis when called from
1097 the loop optimizer. Note we want to leave the original
1098 MEM alone, but need to return the canonicalized MEM with
1099 all the flags with their original values. */
1100 else if (GET_CODE (x) == MEM)
1101 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1106 /* Return 1 if X and Y are identical-looking rtx's.
1107 Expect that X and Y has been already canonicalized.
1109 We use the data in reg_known_value above to see if two registers with
1110 different numbers are, in fact, equivalent. */
1113 rtx_equal_for_memref_p (rtx x, rtx y)
1120 if (x == 0 && y == 0)
1122 if (x == 0 || y == 0)
1128 code = GET_CODE (x);
1129 /* Rtx's of different codes cannot be equal. */
1130 if (code != GET_CODE (y))
1133 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1134 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1136 if (GET_MODE (x) != GET_MODE (y))
1139 /* Some RTL can be compared without a recursive examination. */
1143 return REGNO (x) == REGNO (y);
1146 return XEXP (x, 0) == XEXP (y, 0);
1149 return XSTR (x, 0) == XSTR (y, 0);
1154 /* There's no need to compare the contents of CONST_DOUBLEs or
1155 CONST_INTs because pointer equality is a good enough
1156 comparison for these nodes. */
1160 return (XINT (x, 1) == XINT (y, 1)
1161 && rtx_equal_for_memref_p (XEXP (x, 0),
1168 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1170 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1171 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1172 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1173 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1174 /* For commutative operations, the RTX match if the operand match in any
1175 order. Also handle the simple binary and unary cases without a loop. */
1176 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1178 rtx xop0 = canon_rtx (XEXP (x, 0));
1179 rtx yop0 = canon_rtx (XEXP (y, 0));
1180 rtx yop1 = canon_rtx (XEXP (y, 1));
1182 return ((rtx_equal_for_memref_p (xop0, yop0)
1183 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1184 || (rtx_equal_for_memref_p (xop0, yop1)
1185 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1187 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1189 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1190 canon_rtx (XEXP (y, 0)))
1191 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1192 canon_rtx (XEXP (y, 1))));
1194 else if (GET_RTX_CLASS (code) == '1')
1195 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1196 canon_rtx (XEXP (y, 0)));
1198 /* Compare the elements. If any pair of corresponding elements
1199 fail to match, return 0 for the whole things.
1201 Limit cases to types which actually appear in addresses. */
1203 fmt = GET_RTX_FORMAT (code);
1204 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1209 if (XINT (x, i) != XINT (y, i))
1214 /* Two vectors must have the same length. */
1215 if (XVECLEN (x, i) != XVECLEN (y, i))
1218 /* And the corresponding elements must match. */
1219 for (j = 0; j < XVECLEN (x, i); j++)
1220 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1221 canon_rtx (XVECEXP (y, i, j))) == 0)
1226 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1227 canon_rtx (XEXP (y, i))) == 0)
1231 /* This can happen for asm operands. */
1233 if (strcmp (XSTR (x, i), XSTR (y, i)))
1237 /* This can happen for an asm which clobbers memory. */
1241 /* It is believed that rtx's at this level will never
1242 contain anything but integers and other rtx's,
1243 except for within LABEL_REFs and SYMBOL_REFs. */
1251 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1252 X and return it, or return 0 if none found. */
1255 find_symbolic_term (rtx x)
1261 code = GET_CODE (x);
1262 if (code == SYMBOL_REF || code == LABEL_REF)
1264 if (GET_RTX_CLASS (code) == 'o')
1267 fmt = GET_RTX_FORMAT (code);
1268 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1274 t = find_symbolic_term (XEXP (x, i));
1278 else if (fmt[i] == 'E')
1285 find_base_term (rtx x)
1288 struct elt_loc_list *l;
1290 #if defined (FIND_BASE_TERM)
1291 /* Try machine-dependent ways to find the base term. */
1292 x = FIND_BASE_TERM (x);
1295 switch (GET_CODE (x))
1298 return REG_BASE_VALUE (x);
1301 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1311 return find_base_term (XEXP (x, 0));
1314 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1316 rtx temp = find_base_term (XEXP (x, 0));
1318 if (temp != 0 && CONSTANT_P (temp))
1319 temp = convert_memory_address (Pmode, temp);
1325 val = CSELIB_VAL_PTR (x);
1328 for (l = val->locs; l; l = l->next)
1329 if ((x = find_base_term (l->loc)) != 0)
1335 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1342 rtx tmp1 = XEXP (x, 0);
1343 rtx tmp2 = XEXP (x, 1);
1345 /* This is a little bit tricky since we have to determine which of
1346 the two operands represents the real base address. Otherwise this
1347 routine may return the index register instead of the base register.
1349 That may cause us to believe no aliasing was possible, when in
1350 fact aliasing is possible.
1352 We use a few simple tests to guess the base register. Additional
1353 tests can certainly be added. For example, if one of the operands
1354 is a shift or multiply, then it must be the index register and the
1355 other operand is the base register. */
1357 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1358 return find_base_term (tmp2);
1360 /* If either operand is known to be a pointer, then use it
1361 to determine the base term. */
1362 if (REG_P (tmp1) && REG_POINTER (tmp1))
1363 return find_base_term (tmp1);
1365 if (REG_P (tmp2) && REG_POINTER (tmp2))
1366 return find_base_term (tmp2);
1368 /* Neither operand was known to be a pointer. Go ahead and find the
1369 base term for both operands. */
1370 tmp1 = find_base_term (tmp1);
1371 tmp2 = find_base_term (tmp2);
1373 /* If either base term is named object or a special address
1374 (like an argument or stack reference), then use it for the
1377 && (GET_CODE (tmp1) == SYMBOL_REF
1378 || GET_CODE (tmp1) == LABEL_REF
1379 || (GET_CODE (tmp1) == ADDRESS
1380 && GET_MODE (tmp1) != VOIDmode)))
1384 && (GET_CODE (tmp2) == SYMBOL_REF
1385 || GET_CODE (tmp2) == LABEL_REF
1386 || (GET_CODE (tmp2) == ADDRESS
1387 && GET_MODE (tmp2) != VOIDmode)))
1390 /* We could not determine which of the two operands was the
1391 base register and which was the index. So we can determine
1392 nothing from the base alias check. */
1397 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1398 return find_base_term (XEXP (x, 0));
1406 return REG_BASE_VALUE (frame_pointer_rtx);
1413 /* Return 0 if the addresses X and Y are known to point to different
1414 objects, 1 if they might be pointers to the same object. */
1417 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1418 enum machine_mode y_mode)
1420 rtx x_base = find_base_term (x);
1421 rtx y_base = find_base_term (y);
1423 /* If the address itself has no known base see if a known equivalent
1424 value has one. If either address still has no known base, nothing
1425 is known about aliasing. */
1430 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1433 x_base = find_base_term (x_c);
1441 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1444 y_base = find_base_term (y_c);
1449 /* If the base addresses are equal nothing is known about aliasing. */
1450 if (rtx_equal_p (x_base, y_base))
1453 /* The base addresses of the read and write are different expressions.
1454 If they are both symbols and they are not accessed via AND, there is
1455 no conflict. We can bring knowledge of object alignment into play
1456 here. For example, on alpha, "char a, b;" can alias one another,
1457 though "char a; long b;" cannot. */
1458 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1460 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1462 if (GET_CODE (x) == AND
1463 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1464 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1466 if (GET_CODE (y) == AND
1467 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1468 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1470 /* Differing symbols never alias. */
1474 /* If one address is a stack reference there can be no alias:
1475 stack references using different base registers do not alias,
1476 a stack reference can not alias a parameter, and a stack reference
1477 can not alias a global. */
1478 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1479 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1482 if (! flag_argument_noalias)
1485 if (flag_argument_noalias > 1)
1488 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1489 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1492 /* Convert the address X into something we can use. This is done by returning
1493 it unchanged unless it is a value; in the latter case we call cselib to get
1494 a more useful rtx. */
1500 struct elt_loc_list *l;
1502 if (GET_CODE (x) != VALUE)
1504 v = CSELIB_VAL_PTR (x);
1507 for (l = v->locs; l; l = l->next)
1508 if (CONSTANT_P (l->loc))
1510 for (l = v->locs; l; l = l->next)
1511 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1514 return v->locs->loc;
1519 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1520 where SIZE is the size in bytes of the memory reference. If ADDR
1521 is not modified by the memory reference then ADDR is returned. */
1524 addr_side_effect_eval (rtx addr, int size, int n_refs)
1528 switch (GET_CODE (addr))
1531 offset = (n_refs + 1) * size;
1534 offset = -(n_refs + 1) * size;
1537 offset = n_refs * size;
1540 offset = -n_refs * size;
1548 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1551 addr = XEXP (addr, 0);
1552 addr = canon_rtx (addr);
1557 /* Return nonzero if X and Y (memory addresses) could reference the
1558 same location in memory. C is an offset accumulator. When
1559 C is nonzero, we are testing aliases between X and Y + C.
1560 XSIZE is the size in bytes of the X reference,
1561 similarly YSIZE is the size in bytes for Y.
1562 Expect that canon_rtx has been already called for X and Y.
1564 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1565 referenced (the reference was BLKmode), so make the most pessimistic
1568 If XSIZE or YSIZE is negative, we may access memory outside the object
1569 being referenced as a side effect. This can happen when using AND to
1570 align memory references, as is done on the Alpha.
1572 Nice to notice that varying addresses cannot conflict with fp if no
1573 local variables had their addresses taken, but that's too hard now. */
1576 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1578 if (GET_CODE (x) == VALUE)
1580 if (GET_CODE (y) == VALUE)
1582 if (GET_CODE (x) == HIGH)
1584 else if (GET_CODE (x) == LO_SUM)
1587 x = addr_side_effect_eval (x, xsize, 0);
1588 if (GET_CODE (y) == HIGH)
1590 else if (GET_CODE (y) == LO_SUM)
1593 y = addr_side_effect_eval (y, ysize, 0);
1595 if (rtx_equal_for_memref_p (x, y))
1597 if (xsize <= 0 || ysize <= 0)
1599 if (c >= 0 && xsize > c)
1601 if (c < 0 && ysize+c > 0)
1606 /* This code used to check for conflicts involving stack references and
1607 globals but the base address alias code now handles these cases. */
1609 if (GET_CODE (x) == PLUS)
1611 /* The fact that X is canonicalized means that this
1612 PLUS rtx is canonicalized. */
1613 rtx x0 = XEXP (x, 0);
1614 rtx x1 = XEXP (x, 1);
1616 if (GET_CODE (y) == PLUS)
1618 /* The fact that Y is canonicalized means that this
1619 PLUS rtx is canonicalized. */
1620 rtx y0 = XEXP (y, 0);
1621 rtx y1 = XEXP (y, 1);
1623 if (rtx_equal_for_memref_p (x1, y1))
1624 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1625 if (rtx_equal_for_memref_p (x0, y0))
1626 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1627 if (GET_CODE (x1) == CONST_INT)
1629 if (GET_CODE (y1) == CONST_INT)
1630 return memrefs_conflict_p (xsize, x0, ysize, y0,
1631 c - INTVAL (x1) + INTVAL (y1));
1633 return memrefs_conflict_p (xsize, x0, ysize, y,
1636 else if (GET_CODE (y1) == CONST_INT)
1637 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1641 else if (GET_CODE (x1) == CONST_INT)
1642 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1644 else if (GET_CODE (y) == PLUS)
1646 /* The fact that Y is canonicalized means that this
1647 PLUS rtx is canonicalized. */
1648 rtx y0 = XEXP (y, 0);
1649 rtx y1 = XEXP (y, 1);
1651 if (GET_CODE (y1) == CONST_INT)
1652 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1657 if (GET_CODE (x) == GET_CODE (y))
1658 switch (GET_CODE (x))
1662 /* Handle cases where we expect the second operands to be the
1663 same, and check only whether the first operand would conflict
1666 rtx x1 = canon_rtx (XEXP (x, 1));
1667 rtx y1 = canon_rtx (XEXP (y, 1));
1668 if (! rtx_equal_for_memref_p (x1, y1))
1670 x0 = canon_rtx (XEXP (x, 0));
1671 y0 = canon_rtx (XEXP (y, 0));
1672 if (rtx_equal_for_memref_p (x0, y0))
1673 return (xsize == 0 || ysize == 0
1674 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1676 /* Can't properly adjust our sizes. */
1677 if (GET_CODE (x1) != CONST_INT)
1679 xsize /= INTVAL (x1);
1680 ysize /= INTVAL (x1);
1682 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1686 /* Are these registers known not to be equal? */
1687 if (alias_invariant)
1689 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1690 rtx i_x, i_y; /* invariant relationships of X and Y */
1692 i_x = r_x >= alias_invariant_size ? 0 : alias_invariant[r_x];
1693 i_y = r_y >= alias_invariant_size ? 0 : alias_invariant[r_y];
1695 if (i_x == 0 && i_y == 0)
1698 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1699 ysize, i_y ? i_y : y, c))
1708 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1709 as an access with indeterminate size. Assume that references
1710 besides AND are aligned, so if the size of the other reference is
1711 at least as large as the alignment, assume no other overlap. */
1712 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1714 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1716 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1718 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1720 /* ??? If we are indexing far enough into the array/structure, we
1721 may yet be able to determine that we can not overlap. But we
1722 also need to that we are far enough from the end not to overlap
1723 a following reference, so we do nothing with that for now. */
1724 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1726 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1729 if (GET_CODE (x) == ADDRESSOF)
1731 if (y == frame_pointer_rtx
1732 || GET_CODE (y) == ADDRESSOF)
1733 return xsize <= 0 || ysize <= 0;
1735 if (GET_CODE (y) == ADDRESSOF)
1737 if (x == frame_pointer_rtx)
1738 return xsize <= 0 || ysize <= 0;
1743 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1745 c += (INTVAL (y) - INTVAL (x));
1746 return (xsize <= 0 || ysize <= 0
1747 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1750 if (GET_CODE (x) == CONST)
1752 if (GET_CODE (y) == CONST)
1753 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1754 ysize, canon_rtx (XEXP (y, 0)), c);
1756 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1759 if (GET_CODE (y) == CONST)
1760 return memrefs_conflict_p (xsize, x, ysize,
1761 canon_rtx (XEXP (y, 0)), c);
1764 return (xsize <= 0 || ysize <= 0
1765 || (rtx_equal_for_memref_p (x, y)
1766 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1773 /* Functions to compute memory dependencies.
1775 Since we process the insns in execution order, we can build tables
1776 to keep track of what registers are fixed (and not aliased), what registers
1777 are varying in known ways, and what registers are varying in unknown
1780 If both memory references are volatile, then there must always be a
1781 dependence between the two references, since their order can not be
1782 changed. A volatile and non-volatile reference can be interchanged
1785 A MEM_IN_STRUCT reference at a non-AND varying address can never
1786 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1787 also must allow AND addresses, because they may generate accesses
1788 outside the object being referenced. This is used to generate
1789 aligned addresses from unaligned addresses, for instance, the alpha
1790 storeqi_unaligned pattern. */
1792 /* Read dependence: X is read after read in MEM takes place. There can
1793 only be a dependence here if both reads are volatile. */
1796 read_dependence (rtx mem, rtx x)
1798 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1801 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1802 MEM2 is a reference to a structure at a varying address, or returns
1803 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1804 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1805 to decide whether or not an address may vary; it should return
1806 nonzero whenever variation is possible.
1807 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1810 fixed_scalar_and_varying_struct_p (rtx mem1, rtx mem2, rtx mem1_addr,
1812 int (*varies_p) (rtx, int))
1814 if (! flag_strict_aliasing)
1817 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1818 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1819 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1823 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1824 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1825 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1832 /* Returns nonzero if something about the mode or address format MEM1
1833 indicates that it might well alias *anything*. */
1836 aliases_everything_p (rtx mem)
1838 if (GET_CODE (XEXP (mem, 0)) == AND)
1839 /* If the address is an AND, its very hard to know at what it is
1840 actually pointing. */
1846 /* Return true if we can determine that the fields referenced cannot
1847 overlap for any pair of objects. */
1850 nonoverlapping_component_refs_p (tree x, tree y)
1852 tree fieldx, fieldy, typex, typey, orig_y;
1856 /* The comparison has to be done at a common type, since we don't
1857 know how the inheritance hierarchy works. */
1861 fieldx = TREE_OPERAND (x, 1);
1862 typex = DECL_FIELD_CONTEXT (fieldx);
1867 fieldy = TREE_OPERAND (y, 1);
1868 typey = DECL_FIELD_CONTEXT (fieldy);
1873 y = TREE_OPERAND (y, 0);
1875 while (y && TREE_CODE (y) == COMPONENT_REF);
1877 x = TREE_OPERAND (x, 0);
1879 while (x && TREE_CODE (x) == COMPONENT_REF);
1881 /* Never found a common type. */
1885 /* If we're left with accessing different fields of a structure,
1887 if (TREE_CODE (typex) == RECORD_TYPE
1888 && fieldx != fieldy)
1891 /* The comparison on the current field failed. If we're accessing
1892 a very nested structure, look at the next outer level. */
1893 x = TREE_OPERAND (x, 0);
1894 y = TREE_OPERAND (y, 0);
1897 && TREE_CODE (x) == COMPONENT_REF
1898 && TREE_CODE (y) == COMPONENT_REF);
1903 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1906 decl_for_component_ref (tree x)
1910 x = TREE_OPERAND (x, 0);
1912 while (x && TREE_CODE (x) == COMPONENT_REF);
1914 return x && DECL_P (x) ? x : NULL_TREE;
1917 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1918 offset of the field reference. */
1921 adjust_offset_for_component_ref (tree x, rtx offset)
1923 HOST_WIDE_INT ioffset;
1928 ioffset = INTVAL (offset);
1931 tree field = TREE_OPERAND (x, 1);
1933 if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
1935 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
1936 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1939 x = TREE_OPERAND (x, 0);
1941 while (x && TREE_CODE (x) == COMPONENT_REF);
1943 return GEN_INT (ioffset);
1946 /* Return nonzero if we can determine the exprs corresponding to memrefs
1947 X and Y and they do not overlap. */
1950 nonoverlapping_memrefs_p (rtx x, rtx y)
1952 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1955 rtx moffsetx, moffsety;
1956 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1958 /* Unless both have exprs, we can't tell anything. */
1959 if (exprx == 0 || expry == 0)
1962 /* If both are field references, we may be able to determine something. */
1963 if (TREE_CODE (exprx) == COMPONENT_REF
1964 && TREE_CODE (expry) == COMPONENT_REF
1965 && nonoverlapping_component_refs_p (exprx, expry))
1968 /* If the field reference test failed, look at the DECLs involved. */
1969 moffsetx = MEM_OFFSET (x);
1970 if (TREE_CODE (exprx) == COMPONENT_REF)
1972 tree t = decl_for_component_ref (exprx);
1975 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
1978 else if (TREE_CODE (exprx) == INDIRECT_REF)
1980 exprx = TREE_OPERAND (exprx, 0);
1981 if (flag_argument_noalias < 2
1982 || TREE_CODE (exprx) != PARM_DECL)
1986 moffsety = MEM_OFFSET (y);
1987 if (TREE_CODE (expry) == COMPONENT_REF)
1989 tree t = decl_for_component_ref (expry);
1992 moffsety = adjust_offset_for_component_ref (expry, moffsety);
1995 else if (TREE_CODE (expry) == INDIRECT_REF)
1997 expry = TREE_OPERAND (expry, 0);
1998 if (flag_argument_noalias < 2
1999 || TREE_CODE (expry) != PARM_DECL)
2003 if (! DECL_P (exprx) || ! DECL_P (expry))
2006 rtlx = DECL_RTL (exprx);
2007 rtly = DECL_RTL (expry);
2009 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2010 can't overlap unless they are the same because we never reuse that part
2011 of the stack frame used for locals for spilled pseudos. */
2012 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
2013 && ! rtx_equal_p (rtlx, rtly))
2016 /* Get the base and offsets of both decls. If either is a register, we
2017 know both are and are the same, so use that as the base. The only
2018 we can avoid overlap is if we can deduce that they are nonoverlapping
2019 pieces of that decl, which is very rare. */
2020 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
2021 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2022 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2024 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
2025 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2026 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2028 /* If the bases are different, we know they do not overlap if both
2029 are constants or if one is a constant and the other a pointer into the
2030 stack frame. Otherwise a different base means we can't tell if they
2032 if (! rtx_equal_p (basex, basey))
2033 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2034 || (CONSTANT_P (basex) && REG_P (basey)
2035 && REGNO_PTR_FRAME_P (REGNO (basey)))
2036 || (CONSTANT_P (basey) && REG_P (basex)
2037 && REGNO_PTR_FRAME_P (REGNO (basex))));
2039 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2040 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2042 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2043 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2046 /* If we have an offset for either memref, it can update the values computed
2049 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2051 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2053 /* If a memref has both a size and an offset, we can use the smaller size.
2054 We can't do this if the offset isn't known because we must view this
2055 memref as being anywhere inside the DECL's MEM. */
2056 if (MEM_SIZE (x) && moffsetx)
2057 sizex = INTVAL (MEM_SIZE (x));
2058 if (MEM_SIZE (y) && moffsety)
2059 sizey = INTVAL (MEM_SIZE (y));
2061 /* Put the values of the memref with the lower offset in X's values. */
2062 if (offsetx > offsety)
2064 tem = offsetx, offsetx = offsety, offsety = tem;
2065 tem = sizex, sizex = sizey, sizey = tem;
2068 /* If we don't know the size of the lower-offset value, we can't tell
2069 if they conflict. Otherwise, we do the test. */
2070 return sizex >= 0 && offsety >= offsetx + sizex;
2073 /* True dependence: X is read after store in MEM takes place. */
2076 true_dependence (rtx mem, enum machine_mode mem_mode, rtx x,
2077 int (*varies) (rtx, int))
2079 rtx x_addr, mem_addr;
2082 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2085 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2086 This is used in epilogue deallocation functions. */
2087 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2089 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2092 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2095 /* Unchanging memory can't conflict with non-unchanging memory.
2096 A non-unchanging read can conflict with a non-unchanging write.
2097 An unchanging read can conflict with an unchanging write since
2098 there may be a single store to this address to initialize it.
2099 Note that an unchanging store can conflict with a non-unchanging read
2100 since we have to make conservative assumptions when we have a
2101 record with readonly fields and we are copying the whole thing.
2102 Just fall through to the code below to resolve potential conflicts.
2103 This won't handle all cases optimally, but the possible performance
2104 loss should be negligible. */
2105 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2108 if (nonoverlapping_memrefs_p (mem, x))
2111 if (mem_mode == VOIDmode)
2112 mem_mode = GET_MODE (mem);
2114 x_addr = get_addr (XEXP (x, 0));
2115 mem_addr = get_addr (XEXP (mem, 0));
2117 base = find_base_term (x_addr);
2118 if (base && (GET_CODE (base) == LABEL_REF
2119 || (GET_CODE (base) == SYMBOL_REF
2120 && CONSTANT_POOL_ADDRESS_P (base))))
2123 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2126 x_addr = canon_rtx (x_addr);
2127 mem_addr = canon_rtx (mem_addr);
2129 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2130 SIZE_FOR_MODE (x), x_addr, 0))
2133 if (aliases_everything_p (x))
2136 /* We cannot use aliases_everything_p to test MEM, since we must look
2137 at MEM_MODE, rather than GET_MODE (MEM). */
2138 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2141 /* In true_dependence we also allow BLKmode to alias anything. Why
2142 don't we do this in anti_dependence and output_dependence? */
2143 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2146 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2150 /* Canonical true dependence: X is read after store in MEM takes place.
2151 Variant of true_dependence which assumes MEM has already been
2152 canonicalized (hence we no longer do that here).
2153 The mem_addr argument has been added, since true_dependence computed
2154 this value prior to canonicalizing. */
2157 canon_true_dependence (rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2158 rtx x, int (*varies) (rtx, int))
2162 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2165 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2166 This is used in epilogue deallocation functions. */
2167 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2169 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2172 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2175 /* If X is an unchanging read, then it can't possibly conflict with any
2176 non-unchanging store. It may conflict with an unchanging write though,
2177 because there may be a single store to this address to initialize it.
2178 Just fall through to the code below to resolve the case where we have
2179 both an unchanging read and an unchanging write. This won't handle all
2180 cases optimally, but the possible performance loss should be
2182 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2185 if (nonoverlapping_memrefs_p (x, mem))
2188 x_addr = get_addr (XEXP (x, 0));
2190 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2193 x_addr = canon_rtx (x_addr);
2194 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2195 SIZE_FOR_MODE (x), x_addr, 0))
2198 if (aliases_everything_p (x))
2201 /* We cannot use aliases_everything_p to test MEM, since we must look
2202 at MEM_MODE, rather than GET_MODE (MEM). */
2203 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2206 /* In true_dependence we also allow BLKmode to alias anything. Why
2207 don't we do this in anti_dependence and output_dependence? */
2208 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2211 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2215 /* Returns nonzero if a write to X might alias a previous read from
2216 (or, if WRITEP is nonzero, a write to) MEM. If CONSTP is nonzero,
2217 honor the RTX_UNCHANGING_P flags on X and MEM. */
2220 write_dependence_p (rtx mem, rtx x, int writep, int constp)
2222 rtx x_addr, mem_addr;
2226 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2229 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2230 This is used in epilogue deallocation functions. */
2231 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2233 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2236 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2241 /* Unchanging memory can't conflict with non-unchanging memory. */
2242 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
2245 /* If MEM is an unchanging read, then it can't possibly conflict with
2246 the store to X, because there is at most one store to MEM, and it
2247 must have occurred somewhere before MEM. */
2248 if (! writep && RTX_UNCHANGING_P (mem))
2252 if (nonoverlapping_memrefs_p (x, mem))
2255 x_addr = get_addr (XEXP (x, 0));
2256 mem_addr = get_addr (XEXP (mem, 0));
2260 base = find_base_term (mem_addr);
2261 if (base && (GET_CODE (base) == LABEL_REF
2262 || (GET_CODE (base) == SYMBOL_REF
2263 && CONSTANT_POOL_ADDRESS_P (base))))
2267 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2271 x_addr = canon_rtx (x_addr);
2272 mem_addr = canon_rtx (mem_addr);
2274 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2275 SIZE_FOR_MODE (x), x_addr, 0))
2279 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2282 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2283 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2286 /* Anti dependence: X is written after read in MEM takes place. */
2289 anti_dependence (rtx mem, rtx x)
2291 return write_dependence_p (mem, x, /*writep=*/0, /*constp*/1);
2294 /* Output dependence: X is written after store in MEM takes place. */
2297 output_dependence (rtx mem, rtx x)
2299 return write_dependence_p (mem, x, /*writep=*/1, /*constp*/1);
2302 /* Unchanging anti dependence: Like anti_dependence but ignores
2303 the UNCHANGING_RTX_P property on const variable references. */
2306 unchanging_anti_dependence (rtx mem, rtx x)
2308 return write_dependence_p (mem, x, /*writep=*/0, /*constp*/0);
2311 /* A subroutine of nonlocal_mentioned_p, returns 1 if *LOC mentions
2312 something which is not local to the function and is not constant. */
2315 nonlocal_mentioned_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2324 switch (GET_CODE (x))
2327 if (GET_CODE (SUBREG_REG (x)) == REG)
2329 /* Global registers are not local. */
2330 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2331 && global_regs[subreg_regno (x)])
2339 /* Global registers are not local. */
2340 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2355 /* Constants in the function's constants pool are constant. */
2356 if (CONSTANT_POOL_ADDRESS_P (x))
2361 /* Non-constant calls and recursion are not local. */
2365 /* Be overly conservative and consider any volatile memory
2366 reference as not local. */
2367 if (MEM_VOLATILE_P (x))
2369 base = find_base_term (XEXP (x, 0));
2372 /* A Pmode ADDRESS could be a reference via the structure value
2373 address or static chain. Such memory references are nonlocal.
2375 Thus, we have to examine the contents of the ADDRESS to find
2376 out if this is a local reference or not. */
2377 if (GET_CODE (base) == ADDRESS
2378 && GET_MODE (base) == Pmode
2379 && (XEXP (base, 0) == stack_pointer_rtx
2380 || XEXP (base, 0) == arg_pointer_rtx
2381 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2382 || XEXP (base, 0) == hard_frame_pointer_rtx
2384 || XEXP (base, 0) == frame_pointer_rtx))
2386 /* Constants in the function's constant pool are constant. */
2387 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2392 case UNSPEC_VOLATILE:
2397 if (MEM_VOLATILE_P (x))
2409 /* Returns nonzero if X might mention something which is not
2410 local to the function and is not constant. */
2413 nonlocal_mentioned_p (rtx x)
2417 if (GET_CODE (x) == CALL_INSN)
2419 if (! CONST_OR_PURE_CALL_P (x))
2421 x = CALL_INSN_FUNCTION_USAGE (x);
2429 return for_each_rtx (&x, nonlocal_mentioned_p_1, NULL);
2432 /* A subroutine of nonlocal_referenced_p, returns 1 if *LOC references
2433 something which is not local to the function and is not constant. */
2436 nonlocal_referenced_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2443 switch (GET_CODE (x))
2449 return nonlocal_mentioned_p (x);
2452 /* Non-constant calls and recursion are not local. */
2456 if (nonlocal_mentioned_p (SET_SRC (x)))
2459 if (GET_CODE (SET_DEST (x)) == MEM)
2460 return nonlocal_mentioned_p (XEXP (SET_DEST (x), 0));
2462 /* If the destination is anything other than a CC0, PC,
2463 MEM, REG, or a SUBREG of a REG that occupies all of
2464 the REG, then X references nonlocal memory if it is
2465 mentioned in the destination. */
2466 if (GET_CODE (SET_DEST (x)) != CC0
2467 && GET_CODE (SET_DEST (x)) != PC
2468 && GET_CODE (SET_DEST (x)) != REG
2469 && ! (GET_CODE (SET_DEST (x)) == SUBREG
2470 && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
2471 && (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (x))))
2472 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
2473 == ((GET_MODE_SIZE (GET_MODE (SET_DEST (x)))
2474 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD))))
2475 return nonlocal_mentioned_p (SET_DEST (x));
2479 if (GET_CODE (XEXP (x, 0)) == MEM)
2480 return nonlocal_mentioned_p (XEXP (XEXP (x, 0), 0));
2484 return nonlocal_mentioned_p (XEXP (x, 0));
2487 case UNSPEC_VOLATILE:
2491 if (MEM_VOLATILE_P (x))
2503 /* Returns nonzero if X might reference something which is not
2504 local to the function and is not constant. */
2507 nonlocal_referenced_p (rtx x)
2511 if (GET_CODE (x) == CALL_INSN)
2513 if (! CONST_OR_PURE_CALL_P (x))
2515 x = CALL_INSN_FUNCTION_USAGE (x);
2523 return for_each_rtx (&x, nonlocal_referenced_p_1, NULL);
2526 /* A subroutine of nonlocal_set_p, returns 1 if *LOC sets
2527 something which is not local to the function and is not constant. */
2530 nonlocal_set_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2537 switch (GET_CODE (x))
2540 /* Non-constant calls and recursion are not local. */
2549 return nonlocal_mentioned_p (XEXP (x, 0));
2552 if (nonlocal_mentioned_p (SET_DEST (x)))
2554 return nonlocal_set_p (SET_SRC (x));
2557 return nonlocal_mentioned_p (XEXP (x, 0));
2563 case UNSPEC_VOLATILE:
2567 if (MEM_VOLATILE_P (x))
2579 /* Returns nonzero if X might set something which is not
2580 local to the function and is not constant. */
2583 nonlocal_set_p (rtx x)
2587 if (GET_CODE (x) == CALL_INSN)
2589 if (! CONST_OR_PURE_CALL_P (x))
2591 x = CALL_INSN_FUNCTION_USAGE (x);
2599 return for_each_rtx (&x, nonlocal_set_p_1, NULL);
2602 /* Mark the function if it is pure or constant. */
2605 mark_constant_function (void)
2608 int nonlocal_memory_referenced;
2610 if (TREE_READONLY (current_function_decl)
2611 || DECL_IS_PURE (current_function_decl)
2612 || TREE_THIS_VOLATILE (current_function_decl)
2613 || current_function_has_nonlocal_goto
2614 || !(*targetm.binds_local_p) (current_function_decl))
2617 /* A loop might not return which counts as a side effect. */
2618 if (mark_dfs_back_edges ())
2621 nonlocal_memory_referenced = 0;
2623 init_alias_analysis ();
2625 /* Determine if this is a constant or pure function. */
2627 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2629 if (! INSN_P (insn))
2632 if (nonlocal_set_p (insn) || global_reg_mentioned_p (insn)
2633 || volatile_refs_p (PATTERN (insn)))
2636 if (! nonlocal_memory_referenced)
2637 nonlocal_memory_referenced = nonlocal_referenced_p (insn);
2640 end_alias_analysis ();
2642 /* Mark the function. */
2646 else if (nonlocal_memory_referenced)
2648 cgraph_rtl_info (current_function_decl)->pure_function = 1;
2649 DECL_IS_PURE (current_function_decl) = 1;
2653 cgraph_rtl_info (current_function_decl)->const_function = 1;
2654 TREE_READONLY (current_function_decl) = 1;
2660 init_alias_once (void)
2664 #ifndef OUTGOING_REGNO
2665 #define OUTGOING_REGNO(N) N
2667 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2668 /* Check whether this register can hold an incoming pointer
2669 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2670 numbers, so translate if necessary due to register windows. */
2671 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2672 && HARD_REGNO_MODE_OK (i, Pmode))
2673 static_reg_base_value[i]
2674 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2676 static_reg_base_value[STACK_POINTER_REGNUM]
2677 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2678 static_reg_base_value[ARG_POINTER_REGNUM]
2679 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2680 static_reg_base_value[FRAME_POINTER_REGNUM]
2681 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2682 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2683 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2684 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2688 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2689 to be memory reference. */
2690 static bool memory_modified;
2692 memory_modified_1 (rtx x, rtx pat ATTRIBUTE_UNUSED, void *data)
2694 if (GET_CODE (x) == MEM)
2696 if (anti_dependence (x, (rtx)data) || output_dependence (x, (rtx)data))
2697 memory_modified = true;
2702 /* Return true when INSN possibly modify memory contents of MEM
2703 (ie address can be modified). */
2705 memory_modified_in_insn_p (rtx mem, rtx insn)
2709 memory_modified = false;
2710 note_stores (PATTERN (insn), memory_modified_1, mem);
2711 return memory_modified;
2714 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2718 init_alias_analysis (void)
2720 unsigned int maxreg = max_reg_num ();
2726 timevar_push (TV_ALIAS_ANALYSIS);
2728 reg_known_value_size = maxreg;
2731 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2732 - FIRST_PSEUDO_REGISTER;
2734 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2735 - FIRST_PSEUDO_REGISTER;
2737 /* Overallocate reg_base_value to allow some growth during loop
2738 optimization. Loop unrolling can create a large number of
2740 if (old_reg_base_value)
2742 reg_base_value = old_reg_base_value;
2743 /* If varray gets large zeroing cost may get important. */
2744 if (VARRAY_SIZE (reg_base_value) > 256
2745 && VARRAY_SIZE (reg_base_value) > 4 * maxreg)
2746 VARRAY_GROW (reg_base_value, maxreg);
2747 VARRAY_CLEAR (reg_base_value);
2748 if (VARRAY_SIZE (reg_base_value) < maxreg)
2749 VARRAY_GROW (reg_base_value, maxreg);
2753 VARRAY_RTX_INIT (reg_base_value, maxreg, "reg_base_value");
2756 new_reg_base_value = xmalloc (maxreg * sizeof (rtx));
2757 reg_seen = xmalloc (maxreg);
2758 if (! reload_completed && flag_old_unroll_loops)
2760 /* ??? Why are we realloc'ing if we're just going to zero it? */
2761 alias_invariant = xrealloc (alias_invariant,
2762 maxreg * sizeof (rtx));
2763 memset (alias_invariant, 0, maxreg * sizeof (rtx));
2764 alias_invariant_size = maxreg;
2767 /* The basic idea is that each pass through this loop will use the
2768 "constant" information from the previous pass to propagate alias
2769 information through another level of assignments.
2771 This could get expensive if the assignment chains are long. Maybe
2772 we should throttle the number of iterations, possibly based on
2773 the optimization level or flag_expensive_optimizations.
2775 We could propagate more information in the first pass by making use
2776 of REG_N_SETS to determine immediately that the alias information
2777 for a pseudo is "constant".
2779 A program with an uninitialized variable can cause an infinite loop
2780 here. Instead of doing a full dataflow analysis to detect such problems
2781 we just cap the number of iterations for the loop.
2783 The state of the arrays for the set chain in question does not matter
2784 since the program has undefined behavior. */
2789 /* Assume nothing will change this iteration of the loop. */
2792 /* We want to assign the same IDs each iteration of this loop, so
2793 start counting from zero each iteration of the loop. */
2796 /* We're at the start of the function each iteration through the
2797 loop, so we're copying arguments. */
2798 copying_arguments = true;
2800 /* Wipe the potential alias information clean for this pass. */
2801 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2803 /* Wipe the reg_seen array clean. */
2804 memset (reg_seen, 0, maxreg);
2806 /* Mark all hard registers which may contain an address.
2807 The stack, frame and argument pointers may contain an address.
2808 An argument register which can hold a Pmode value may contain
2809 an address even if it is not in BASE_REGS.
2811 The address expression is VOIDmode for an argument and
2812 Pmode for other registers. */
2814 memcpy (new_reg_base_value, static_reg_base_value,
2815 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2817 /* Walk the insns adding values to the new_reg_base_value array. */
2818 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2824 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2825 /* The prologue/epilogue insns are not threaded onto the
2826 insn chain until after reload has completed. Thus,
2827 there is no sense wasting time checking if INSN is in
2828 the prologue/epilogue until after reload has completed. */
2829 if (reload_completed
2830 && prologue_epilogue_contains (insn))
2834 /* If this insn has a noalias note, process it, Otherwise,
2835 scan for sets. A simple set will have no side effects
2836 which could change the base value of any other register. */
2838 if (GET_CODE (PATTERN (insn)) == SET
2839 && REG_NOTES (insn) != 0
2840 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2841 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2843 note_stores (PATTERN (insn), record_set, NULL);
2845 set = single_set (insn);
2848 && GET_CODE (SET_DEST (set)) == REG
2849 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2851 unsigned int regno = REGNO (SET_DEST (set));
2852 rtx src = SET_SRC (set);
2854 if (REG_NOTES (insn) != 0
2855 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2856 && REG_N_SETS (regno) == 1)
2857 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2858 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2859 && ! rtx_varies_p (XEXP (note, 0), 1)
2860 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2862 reg_known_value[regno] = XEXP (note, 0);
2863 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2865 else if (REG_N_SETS (regno) == 1
2866 && GET_CODE (src) == PLUS
2867 && GET_CODE (XEXP (src, 0)) == REG
2868 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2869 && (reg_known_value[REGNO (XEXP (src, 0))])
2870 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2872 rtx op0 = XEXP (src, 0);
2873 op0 = reg_known_value[REGNO (op0)];
2874 reg_known_value[regno]
2875 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2876 reg_known_equiv_p[regno] = 0;
2878 else if (REG_N_SETS (regno) == 1
2879 && ! rtx_varies_p (src, 1))
2881 reg_known_value[regno] = src;
2882 reg_known_equiv_p[regno] = 0;
2886 else if (GET_CODE (insn) == NOTE
2887 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2888 copying_arguments = false;
2891 /* Now propagate values from new_reg_base_value to reg_base_value. */
2892 if (maxreg != (unsigned int) max_reg_num())
2894 for (ui = 0; ui < maxreg; ui++)
2896 if (new_reg_base_value[ui]
2897 && new_reg_base_value[ui] != VARRAY_RTX (reg_base_value, ui)
2898 && ! rtx_equal_p (new_reg_base_value[ui],
2899 VARRAY_RTX (reg_base_value, ui)))
2901 VARRAY_RTX (reg_base_value, ui) = new_reg_base_value[ui];
2906 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2908 /* Fill in the remaining entries. */
2909 for (i = FIRST_PSEUDO_REGISTER; i < (int)maxreg; i++)
2910 if (reg_known_value[i] == 0)
2911 reg_known_value[i] = regno_reg_rtx[i];
2913 /* Simplify the reg_base_value array so that no register refers to
2914 another register, except to special registers indirectly through
2915 ADDRESS expressions.
2917 In theory this loop can take as long as O(registers^2), but unless
2918 there are very long dependency chains it will run in close to linear
2921 This loop may not be needed any longer now that the main loop does
2922 a better job at propagating alias information. */
2928 for (ui = 0; ui < maxreg; ui++)
2930 rtx base = VARRAY_RTX (reg_base_value, ui);
2931 if (base && GET_CODE (base) == REG)
2933 unsigned int base_regno = REGNO (base);
2934 if (base_regno == ui) /* register set from itself */
2935 VARRAY_RTX (reg_base_value, ui) = 0;
2937 VARRAY_RTX (reg_base_value, ui)
2938 = VARRAY_RTX (reg_base_value, base_regno);
2943 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2946 free (new_reg_base_value);
2947 new_reg_base_value = 0;
2950 timevar_pop (TV_ALIAS_ANALYSIS);
2954 end_alias_analysis (void)
2956 old_reg_base_value = reg_base_value;
2957 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2958 reg_known_value = 0;
2959 reg_known_value_size = 0;
2960 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2961 reg_known_equiv_p = 0;
2962 if (alias_invariant)
2964 free (alias_invariant);
2965 alias_invariant = 0;
2966 alias_invariant_size = 0;
2970 #include "gt-alias.h"