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
485 /* Remove any nops, then give the language a chance to do
486 something with this tree before we look at it. */
488 set = lang_hooks.get_alias_set (t);
492 /* First see if the actual object referenced is an INDIRECT_REF from a
493 restrict-qualified pointer or a "void *". */
494 while (handled_component_p (inner))
496 inner = TREE_OPERAND (inner, 0);
500 /* Check for accesses through restrict-qualified pointers. */
501 if (TREE_CODE (inner) == INDIRECT_REF)
503 tree decl = find_base_decl (TREE_OPERAND (inner, 0));
505 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
507 /* If we haven't computed the actual alias set, do it now. */
508 if (DECL_POINTER_ALIAS_SET (decl) == -2)
510 /* No two restricted pointers can point at the same thing.
511 However, a restricted pointer can point at the same thing
512 as an unrestricted pointer, if that unrestricted pointer
513 is based on the restricted pointer. So, we make the
514 alias set for the restricted pointer a subset of the
515 alias set for the type pointed to by the type of the
517 HOST_WIDE_INT pointed_to_alias_set
518 = get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
520 if (pointed_to_alias_set == 0)
521 /* It's not legal to make a subset of alias set zero. */
522 DECL_POINTER_ALIAS_SET (decl) = 0;
525 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
526 record_alias_subset (pointed_to_alias_set,
527 DECL_POINTER_ALIAS_SET (decl));
531 /* We use the alias set indicated in the declaration. */
532 return DECL_POINTER_ALIAS_SET (decl);
535 /* If we have an INDIRECT_REF via a void pointer, we don't
536 know anything about what that might alias. Likewise if the
537 pointer is marked that way. */
538 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE
539 || (TYPE_REF_CAN_ALIAS_ALL
540 (TREE_TYPE (TREE_OPERAND (inner, 0)))))
544 /* Otherwise, pick up the outermost object that we could have a pointer
545 to, processing conversions as above. */
546 while (handled_component_p (t) && ! can_address_p (t))
548 t = TREE_OPERAND (t, 0);
552 /* If we've already determined the alias set for a decl, just return
553 it. This is necessary for C++ anonymous unions, whose component
554 variables don't look like union members (boo!). */
555 if (TREE_CODE (t) == VAR_DECL
556 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
557 return MEM_ALIAS_SET (DECL_RTL (t));
559 /* Now all we care about is the type. */
563 /* Variant qualifiers don't affect the alias set, so get the main
564 variant. If this is a type with a known alias set, return it. */
565 t = TYPE_MAIN_VARIANT (t);
566 if (TYPE_ALIAS_SET_KNOWN_P (t))
567 return TYPE_ALIAS_SET (t);
569 /* See if the language has special handling for this type. */
570 set = lang_hooks.get_alias_set (t);
574 /* There are no objects of FUNCTION_TYPE, so there's no point in
575 using up an alias set for them. (There are, of course, pointers
576 and references to functions, but that's different.) */
577 else if (TREE_CODE (t) == FUNCTION_TYPE)
580 /* Unless the language specifies otherwise, let vector types alias
581 their components. This avoids some nasty type punning issues in
582 normal usage. And indeed lets vectors be treated more like an
584 else if (TREE_CODE (t) == VECTOR_TYPE)
585 set = get_alias_set (TREE_TYPE (t));
588 /* Otherwise make a new alias set for this type. */
589 set = new_alias_set ();
591 TYPE_ALIAS_SET (t) = set;
593 /* If this is an aggregate type, we must record any component aliasing
595 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
596 record_component_aliases (t);
601 /* Return a brand-new alias set. */
603 static GTY(()) HOST_WIDE_INT last_alias_set;
608 if (flag_strict_aliasing)
611 VARRAY_GENERIC_PTR_INIT (alias_sets, 10, "alias sets");
613 VARRAY_GROW (alias_sets, last_alias_set + 2);
614 return ++last_alias_set;
620 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
621 not everything that aliases SUPERSET also aliases SUBSET. For example,
622 in C, a store to an `int' can alias a load of a structure containing an
623 `int', and vice versa. But it can't alias a load of a 'double' member
624 of the same structure. Here, the structure would be the SUPERSET and
625 `int' the SUBSET. This relationship is also described in the comment at
626 the beginning of this file.
628 This function should be called only once per SUPERSET/SUBSET pair.
630 It is illegal for SUPERSET to be zero; everything is implicitly a
631 subset of alias set zero. */
634 record_alias_subset (HOST_WIDE_INT superset, HOST_WIDE_INT subset)
636 alias_set_entry superset_entry;
637 alias_set_entry subset_entry;
639 /* It is possible in complex type situations for both sets to be the same,
640 in which case we can ignore this operation. */
641 if (superset == subset)
647 superset_entry = get_alias_set_entry (superset);
648 if (superset_entry == 0)
650 /* Create an entry for the SUPERSET, so that we have a place to
651 attach the SUBSET. */
652 superset_entry = ggc_alloc (sizeof (struct alias_set_entry));
653 superset_entry->alias_set = superset;
654 superset_entry->children
655 = splay_tree_new_ggc (splay_tree_compare_ints);
656 superset_entry->has_zero_child = 0;
657 VARRAY_GENERIC_PTR (alias_sets, superset) = superset_entry;
661 superset_entry->has_zero_child = 1;
664 subset_entry = get_alias_set_entry (subset);
665 /* If there is an entry for the subset, enter all of its children
666 (if they are not already present) as children of the SUPERSET. */
669 if (subset_entry->has_zero_child)
670 superset_entry->has_zero_child = 1;
672 splay_tree_foreach (subset_entry->children, insert_subset_children,
673 superset_entry->children);
676 /* Enter the SUBSET itself as a child of the SUPERSET. */
677 splay_tree_insert (superset_entry->children,
678 (splay_tree_key) subset, 0);
682 /* Record that component types of TYPE, if any, are part of that type for
683 aliasing purposes. For record types, we only record component types
684 for fields that are marked addressable. For array types, we always
685 record the component types, so the front end should not call this
686 function if the individual component aren't addressable. */
689 record_component_aliases (tree type)
691 HOST_WIDE_INT superset = get_alias_set (type);
697 switch (TREE_CODE (type))
700 if (! TYPE_NONALIASED_COMPONENT (type))
701 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
706 case QUAL_UNION_TYPE:
707 /* Recursively record aliases for the base classes, if there are any. */
708 if (TYPE_BINFO (type) != NULL && TYPE_BINFO_BASETYPES (type) != NULL)
711 for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type)); i++)
713 tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), i);
714 record_alias_subset (superset,
715 get_alias_set (BINFO_TYPE (binfo)));
718 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
719 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
720 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
724 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
732 /* Allocate an alias set for use in storing and reading from the varargs
735 static GTY(()) HOST_WIDE_INT varargs_set = -1;
738 get_varargs_alias_set (void)
740 if (varargs_set == -1)
741 varargs_set = new_alias_set ();
746 /* Likewise, but used for the fixed portions of the frame, e.g., register
749 static GTY(()) HOST_WIDE_INT frame_set = -1;
752 get_frame_alias_set (void)
755 frame_set = new_alias_set ();
760 /* Inside SRC, the source of a SET, find a base address. */
763 find_base_value (rtx src)
767 switch (GET_CODE (src))
775 /* At the start of a function, argument registers have known base
776 values which may be lost later. Returning an ADDRESS
777 expression here allows optimization based on argument values
778 even when the argument registers are used for other purposes. */
779 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
780 return new_reg_base_value[regno];
782 /* If a pseudo has a known base value, return it. Do not do this
783 for non-fixed hard regs since it can result in a circular
784 dependency chain for registers which have values at function entry.
786 The test above is not sufficient because the scheduler may move
787 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
788 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
789 && regno < VARRAY_SIZE (reg_base_value))
791 /* If we're inside init_alias_analysis, use new_reg_base_value
792 to reduce the number of relaxation iterations. */
793 if (new_reg_base_value && new_reg_base_value[regno]
794 && REG_N_SETS (regno) == 1)
795 return new_reg_base_value[regno];
797 if (VARRAY_RTX (reg_base_value, regno))
798 return VARRAY_RTX (reg_base_value, regno);
804 /* Check for an argument passed in memory. Only record in the
805 copying-arguments block; it is too hard to track changes
807 if (copying_arguments
808 && (XEXP (src, 0) == arg_pointer_rtx
809 || (GET_CODE (XEXP (src, 0)) == PLUS
810 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
811 return gen_rtx_ADDRESS (VOIDmode, src);
816 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
819 /* ... fall through ... */
824 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
826 /* If either operand is a REG that is a known pointer, then it
828 if (REG_P (src_0) && REG_POINTER (src_0))
829 return find_base_value (src_0);
830 if (REG_P (src_1) && REG_POINTER (src_1))
831 return find_base_value (src_1);
833 /* If either operand is a REG, then see if we already have
834 a known value for it. */
837 temp = find_base_value (src_0);
844 temp = find_base_value (src_1);
849 /* If either base is named object or a special address
850 (like an argument or stack reference), then use it for the
853 && (GET_CODE (src_0) == SYMBOL_REF
854 || GET_CODE (src_0) == LABEL_REF
855 || (GET_CODE (src_0) == ADDRESS
856 && GET_MODE (src_0) != VOIDmode)))
860 && (GET_CODE (src_1) == SYMBOL_REF
861 || GET_CODE (src_1) == LABEL_REF
862 || (GET_CODE (src_1) == ADDRESS
863 && GET_MODE (src_1) != VOIDmode)))
866 /* Guess which operand is the base address:
867 If either operand is a symbol, then it is the base. If
868 either operand is a CONST_INT, then the other is the base. */
869 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
870 return find_base_value (src_0);
871 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
872 return find_base_value (src_1);
878 /* The standard form is (lo_sum reg sym) so look only at the
880 return find_base_value (XEXP (src, 1));
883 /* If the second operand is constant set the base
884 address to the first operand. */
885 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
886 return find_base_value (XEXP (src, 0));
890 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
900 return find_base_value (XEXP (src, 0));
903 case SIGN_EXTEND: /* used for NT/Alpha pointers */
905 rtx temp = find_base_value (XEXP (src, 0));
907 if (temp != 0 && CONSTANT_P (temp))
908 temp = convert_memory_address (Pmode, temp);
920 /* Called from init_alias_analysis indirectly through note_stores. */
922 /* While scanning insns to find base values, reg_seen[N] is nonzero if
923 register N has been set in this function. */
924 static char *reg_seen;
926 /* Addresses which are known not to alias anything else are identified
927 by a unique integer. */
928 static int unique_id;
931 record_set (rtx dest, rtx set, void *data ATTRIBUTE_UNUSED)
937 if (GET_CODE (dest) != REG)
940 regno = REGNO (dest);
942 if (regno >= VARRAY_SIZE (reg_base_value))
945 /* If this spans multiple hard registers, then we must indicate that every
946 register has an unusable value. */
947 if (regno < FIRST_PSEUDO_REGISTER)
948 n = hard_regno_nregs[regno][GET_MODE (dest)];
955 reg_seen[regno + n] = 1;
956 new_reg_base_value[regno + n] = 0;
963 /* A CLOBBER wipes out any old value but does not prevent a previously
964 unset register from acquiring a base address (i.e. reg_seen is not
966 if (GET_CODE (set) == CLOBBER)
968 new_reg_base_value[regno] = 0;
977 new_reg_base_value[regno] = 0;
981 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
982 GEN_INT (unique_id++));
986 /* If this is not the first set of REGNO, see whether the new value
987 is related to the old one. There are two cases of interest:
989 (1) The register might be assigned an entirely new value
990 that has the same base term as the original set.
992 (2) The set might be a simple self-modification that
993 cannot change REGNO's base value.
995 If neither case holds, reject the original base value as invalid.
996 Note that the following situation is not detected:
998 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] != 0
1003 && find_base_value (src) != new_reg_base_value[regno])
1004 switch (GET_CODE (src))
1008 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
1009 new_reg_base_value[regno] = 0;
1012 /* If the value we add in the PLUS is also a valid base value,
1013 this might be the actual base value, and the original value
1016 rtx other = NULL_RTX;
1018 if (XEXP (src, 0) == dest)
1019 other = XEXP (src, 1);
1020 else if (XEXP (src, 1) == dest)
1021 other = XEXP (src, 0);
1023 if (! other || find_base_value (other))
1024 new_reg_base_value[regno] = 0;
1028 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
1029 new_reg_base_value[regno] = 0;
1032 new_reg_base_value[regno] = 0;
1035 /* If this is the first set of a register, record the value. */
1036 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1037 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1038 new_reg_base_value[regno] = find_base_value (src);
1040 reg_seen[regno] = 1;
1043 /* Called from loop optimization when a new pseudo-register is
1044 created. It indicates that REGNO is being set to VAL. f INVARIANT
1045 is true then this value also describes an invariant relationship
1046 which can be used to deduce that two registers with unknown values
1050 record_base_value (unsigned int regno, rtx val, int invariant)
1052 if (invariant && alias_invariant && regno < alias_invariant_size)
1053 alias_invariant[regno] = val;
1055 if (regno >= VARRAY_SIZE (reg_base_value))
1056 VARRAY_GROW (reg_base_value, max_reg_num ());
1058 if (GET_CODE (val) == REG)
1060 VARRAY_RTX (reg_base_value, regno)
1061 = REG_BASE_VALUE (val);
1064 VARRAY_RTX (reg_base_value, regno)
1065 = find_base_value (val);
1068 /* Clear alias info for a register. This is used if an RTL transformation
1069 changes the value of a register. This is used in flow by AUTO_INC_DEC
1070 optimizations. We don't need to clear reg_base_value, since flow only
1071 changes the offset. */
1074 clear_reg_alias_info (rtx reg)
1076 unsigned int regno = REGNO (reg);
1078 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1079 reg_known_value[regno] = reg;
1082 /* Returns a canonical version of X, from the point of view alias
1083 analysis. (For example, if X is a MEM whose address is a register,
1084 and the register has a known value (say a SYMBOL_REF), then a MEM
1085 whose address is the SYMBOL_REF is returned.) */
1090 /* Recursively look for equivalences. */
1091 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1092 && REGNO (x) < reg_known_value_size)
1093 return reg_known_value[REGNO (x)] == x
1094 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1095 else if (GET_CODE (x) == PLUS)
1097 rtx x0 = canon_rtx (XEXP (x, 0));
1098 rtx x1 = canon_rtx (XEXP (x, 1));
1100 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1102 if (GET_CODE (x0) == CONST_INT)
1103 return plus_constant (x1, INTVAL (x0));
1104 else if (GET_CODE (x1) == CONST_INT)
1105 return plus_constant (x0, INTVAL (x1));
1106 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1110 /* This gives us much better alias analysis when called from
1111 the loop optimizer. Note we want to leave the original
1112 MEM alone, but need to return the canonicalized MEM with
1113 all the flags with their original values. */
1114 else if (GET_CODE (x) == MEM)
1115 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1120 /* Return 1 if X and Y are identical-looking rtx's.
1121 Expect that X and Y has been already canonicalized.
1123 We use the data in reg_known_value above to see if two registers with
1124 different numbers are, in fact, equivalent. */
1127 rtx_equal_for_memref_p (rtx x, rtx y)
1134 if (x == 0 && y == 0)
1136 if (x == 0 || y == 0)
1142 code = GET_CODE (x);
1143 /* Rtx's of different codes cannot be equal. */
1144 if (code != GET_CODE (y))
1147 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1148 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1150 if (GET_MODE (x) != GET_MODE (y))
1153 /* Some RTL can be compared without a recursive examination. */
1157 return REGNO (x) == REGNO (y);
1160 return XEXP (x, 0) == XEXP (y, 0);
1163 return XSTR (x, 0) == XSTR (y, 0);
1168 /* There's no need to compare the contents of CONST_DOUBLEs or
1169 CONST_INTs because pointer equality is a good enough
1170 comparison for these nodes. */
1174 return (XINT (x, 1) == XINT (y, 1)
1175 && rtx_equal_for_memref_p (XEXP (x, 0),
1182 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1184 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1185 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1186 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1187 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1188 /* For commutative operations, the RTX match if the operand match in any
1189 order. Also handle the simple binary and unary cases without a loop. */
1190 if (COMMUTATIVE_P (x))
1192 rtx xop0 = canon_rtx (XEXP (x, 0));
1193 rtx yop0 = canon_rtx (XEXP (y, 0));
1194 rtx yop1 = canon_rtx (XEXP (y, 1));
1196 return ((rtx_equal_for_memref_p (xop0, yop0)
1197 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
1198 || (rtx_equal_for_memref_p (xop0, yop1)
1199 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
1201 else if (NON_COMMUTATIVE_P (x))
1203 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1204 canon_rtx (XEXP (y, 0)))
1205 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
1206 canon_rtx (XEXP (y, 1))));
1208 else if (UNARY_P (x))
1209 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
1210 canon_rtx (XEXP (y, 0)));
1212 /* Compare the elements. If any pair of corresponding elements
1213 fail to match, return 0 for the whole things.
1215 Limit cases to types which actually appear in addresses. */
1217 fmt = GET_RTX_FORMAT (code);
1218 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1223 if (XINT (x, i) != XINT (y, i))
1228 /* Two vectors must have the same length. */
1229 if (XVECLEN (x, i) != XVECLEN (y, i))
1232 /* And the corresponding elements must match. */
1233 for (j = 0; j < XVECLEN (x, i); j++)
1234 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
1235 canon_rtx (XVECEXP (y, i, j))) == 0)
1240 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
1241 canon_rtx (XEXP (y, i))) == 0)
1245 /* This can happen for asm operands. */
1247 if (strcmp (XSTR (x, i), XSTR (y, i)))
1251 /* This can happen for an asm which clobbers memory. */
1255 /* It is believed that rtx's at this level will never
1256 contain anything but integers and other rtx's,
1257 except for within LABEL_REFs and SYMBOL_REFs. */
1265 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1266 X and return it, or return 0 if none found. */
1269 find_symbolic_term (rtx x)
1275 code = GET_CODE (x);
1276 if (code == SYMBOL_REF || code == LABEL_REF)
1281 fmt = GET_RTX_FORMAT (code);
1282 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1288 t = find_symbolic_term (XEXP (x, i));
1292 else if (fmt[i] == 'E')
1299 find_base_term (rtx x)
1302 struct elt_loc_list *l;
1304 #if defined (FIND_BASE_TERM)
1305 /* Try machine-dependent ways to find the base term. */
1306 x = FIND_BASE_TERM (x);
1309 switch (GET_CODE (x))
1312 return REG_BASE_VALUE (x);
1315 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1325 return find_base_term (XEXP (x, 0));
1328 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1330 rtx temp = find_base_term (XEXP (x, 0));
1332 if (temp != 0 && CONSTANT_P (temp))
1333 temp = convert_memory_address (Pmode, temp);
1339 val = CSELIB_VAL_PTR (x);
1342 for (l = val->locs; l; l = l->next)
1343 if ((x = find_base_term (l->loc)) != 0)
1349 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1356 rtx tmp1 = XEXP (x, 0);
1357 rtx tmp2 = XEXP (x, 1);
1359 /* This is a little bit tricky since we have to determine which of
1360 the two operands represents the real base address. Otherwise this
1361 routine may return the index register instead of the base register.
1363 That may cause us to believe no aliasing was possible, when in
1364 fact aliasing is possible.
1366 We use a few simple tests to guess the base register. Additional
1367 tests can certainly be added. For example, if one of the operands
1368 is a shift or multiply, then it must be the index register and the
1369 other operand is the base register. */
1371 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1372 return find_base_term (tmp2);
1374 /* If either operand is known to be a pointer, then use it
1375 to determine the base term. */
1376 if (REG_P (tmp1) && REG_POINTER (tmp1))
1377 return find_base_term (tmp1);
1379 if (REG_P (tmp2) && REG_POINTER (tmp2))
1380 return find_base_term (tmp2);
1382 /* Neither operand was known to be a pointer. Go ahead and find the
1383 base term for both operands. */
1384 tmp1 = find_base_term (tmp1);
1385 tmp2 = find_base_term (tmp2);
1387 /* If either base term is named object or a special address
1388 (like an argument or stack reference), then use it for the
1391 && (GET_CODE (tmp1) == SYMBOL_REF
1392 || GET_CODE (tmp1) == LABEL_REF
1393 || (GET_CODE (tmp1) == ADDRESS
1394 && GET_MODE (tmp1) != VOIDmode)))
1398 && (GET_CODE (tmp2) == SYMBOL_REF
1399 || GET_CODE (tmp2) == LABEL_REF
1400 || (GET_CODE (tmp2) == ADDRESS
1401 && GET_MODE (tmp2) != VOIDmode)))
1404 /* We could not determine which of the two operands was the
1405 base register and which was the index. So we can determine
1406 nothing from the base alias check. */
1411 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1412 return find_base_term (XEXP (x, 0));
1420 return REG_BASE_VALUE (frame_pointer_rtx);
1427 /* Return 0 if the addresses X and Y are known to point to different
1428 objects, 1 if they might be pointers to the same object. */
1431 base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
1432 enum machine_mode y_mode)
1434 rtx x_base = find_base_term (x);
1435 rtx y_base = find_base_term (y);
1437 /* If the address itself has no known base see if a known equivalent
1438 value has one. If either address still has no known base, nothing
1439 is known about aliasing. */
1444 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1447 x_base = find_base_term (x_c);
1455 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1458 y_base = find_base_term (y_c);
1463 /* If the base addresses are equal nothing is known about aliasing. */
1464 if (rtx_equal_p (x_base, y_base))
1467 /* The base addresses of the read and write are different expressions.
1468 If they are both symbols and they are not accessed via AND, there is
1469 no conflict. We can bring knowledge of object alignment into play
1470 here. For example, on alpha, "char a, b;" can alias one another,
1471 though "char a; long b;" cannot. */
1472 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1474 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1476 if (GET_CODE (x) == AND
1477 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1478 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1480 if (GET_CODE (y) == AND
1481 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1482 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1484 /* Differing symbols never alias. */
1488 /* If one address is a stack reference there can be no alias:
1489 stack references using different base registers do not alias,
1490 a stack reference can not alias a parameter, and a stack reference
1491 can not alias a global. */
1492 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1493 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1496 if (! flag_argument_noalias)
1499 if (flag_argument_noalias > 1)
1502 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1503 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1506 /* Convert the address X into something we can use. This is done by returning
1507 it unchanged unless it is a value; in the latter case we call cselib to get
1508 a more useful rtx. */
1514 struct elt_loc_list *l;
1516 if (GET_CODE (x) != VALUE)
1518 v = CSELIB_VAL_PTR (x);
1521 for (l = v->locs; l; l = l->next)
1522 if (CONSTANT_P (l->loc))
1524 for (l = v->locs; l; l = l->next)
1525 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1528 return v->locs->loc;
1533 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1534 where SIZE is the size in bytes of the memory reference. If ADDR
1535 is not modified by the memory reference then ADDR is returned. */
1538 addr_side_effect_eval (rtx addr, int size, int n_refs)
1542 switch (GET_CODE (addr))
1545 offset = (n_refs + 1) * size;
1548 offset = -(n_refs + 1) * size;
1551 offset = n_refs * size;
1554 offset = -n_refs * size;
1562 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
1565 addr = XEXP (addr, 0);
1566 addr = canon_rtx (addr);
1571 /* Return nonzero if X and Y (memory addresses) could reference the
1572 same location in memory. C is an offset accumulator. When
1573 C is nonzero, we are testing aliases between X and Y + C.
1574 XSIZE is the size in bytes of the X reference,
1575 similarly YSIZE is the size in bytes for Y.
1576 Expect that canon_rtx has been already called for X and Y.
1578 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1579 referenced (the reference was BLKmode), so make the most pessimistic
1582 If XSIZE or YSIZE is negative, we may access memory outside the object
1583 being referenced as a side effect. This can happen when using AND to
1584 align memory references, as is done on the Alpha.
1586 Nice to notice that varying addresses cannot conflict with fp if no
1587 local variables had their addresses taken, but that's too hard now. */
1590 memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
1592 if (GET_CODE (x) == VALUE)
1594 if (GET_CODE (y) == VALUE)
1596 if (GET_CODE (x) == HIGH)
1598 else if (GET_CODE (x) == LO_SUM)
1601 x = addr_side_effect_eval (x, xsize, 0);
1602 if (GET_CODE (y) == HIGH)
1604 else if (GET_CODE (y) == LO_SUM)
1607 y = addr_side_effect_eval (y, ysize, 0);
1609 if (rtx_equal_for_memref_p (x, y))
1611 if (xsize <= 0 || ysize <= 0)
1613 if (c >= 0 && xsize > c)
1615 if (c < 0 && ysize+c > 0)
1620 /* This code used to check for conflicts involving stack references and
1621 globals but the base address alias code now handles these cases. */
1623 if (GET_CODE (x) == PLUS)
1625 /* The fact that X is canonicalized means that this
1626 PLUS rtx is canonicalized. */
1627 rtx x0 = XEXP (x, 0);
1628 rtx x1 = XEXP (x, 1);
1630 if (GET_CODE (y) == PLUS)
1632 /* The fact that Y is canonicalized means that this
1633 PLUS rtx is canonicalized. */
1634 rtx y0 = XEXP (y, 0);
1635 rtx y1 = XEXP (y, 1);
1637 if (rtx_equal_for_memref_p (x1, y1))
1638 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1639 if (rtx_equal_for_memref_p (x0, y0))
1640 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1641 if (GET_CODE (x1) == CONST_INT)
1643 if (GET_CODE (y1) == CONST_INT)
1644 return memrefs_conflict_p (xsize, x0, ysize, y0,
1645 c - INTVAL (x1) + INTVAL (y1));
1647 return memrefs_conflict_p (xsize, x0, ysize, y,
1650 else if (GET_CODE (y1) == CONST_INT)
1651 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1655 else if (GET_CODE (x1) == CONST_INT)
1656 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1658 else if (GET_CODE (y) == PLUS)
1660 /* The fact that Y is canonicalized means that this
1661 PLUS rtx is canonicalized. */
1662 rtx y0 = XEXP (y, 0);
1663 rtx y1 = XEXP (y, 1);
1665 if (GET_CODE (y1) == CONST_INT)
1666 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1671 if (GET_CODE (x) == GET_CODE (y))
1672 switch (GET_CODE (x))
1676 /* Handle cases where we expect the second operands to be the
1677 same, and check only whether the first operand would conflict
1680 rtx x1 = canon_rtx (XEXP (x, 1));
1681 rtx y1 = canon_rtx (XEXP (y, 1));
1682 if (! rtx_equal_for_memref_p (x1, y1))
1684 x0 = canon_rtx (XEXP (x, 0));
1685 y0 = canon_rtx (XEXP (y, 0));
1686 if (rtx_equal_for_memref_p (x0, y0))
1687 return (xsize == 0 || ysize == 0
1688 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1690 /* Can't properly adjust our sizes. */
1691 if (GET_CODE (x1) != CONST_INT)
1693 xsize /= INTVAL (x1);
1694 ysize /= INTVAL (x1);
1696 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1700 /* Are these registers known not to be equal? */
1701 if (alias_invariant)
1703 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1704 rtx i_x, i_y; /* invariant relationships of X and Y */
1706 i_x = r_x >= alias_invariant_size ? 0 : alias_invariant[r_x];
1707 i_y = r_y >= alias_invariant_size ? 0 : alias_invariant[r_y];
1709 if (i_x == 0 && i_y == 0)
1712 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1713 ysize, i_y ? i_y : y, c))
1722 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1723 as an access with indeterminate size. Assume that references
1724 besides AND are aligned, so if the size of the other reference is
1725 at least as large as the alignment, assume no other overlap. */
1726 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1728 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1730 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
1732 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1734 /* ??? If we are indexing far enough into the array/structure, we
1735 may yet be able to determine that we can not overlap. But we
1736 also need to that we are far enough from the end not to overlap
1737 a following reference, so we do nothing with that for now. */
1738 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1740 return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
1743 if (GET_CODE (x) == ADDRESSOF)
1745 if (y == frame_pointer_rtx
1746 || GET_CODE (y) == ADDRESSOF)
1747 return xsize <= 0 || ysize <= 0;
1749 if (GET_CODE (y) == ADDRESSOF)
1751 if (x == frame_pointer_rtx)
1752 return xsize <= 0 || ysize <= 0;
1757 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1759 c += (INTVAL (y) - INTVAL (x));
1760 return (xsize <= 0 || ysize <= 0
1761 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1764 if (GET_CODE (x) == CONST)
1766 if (GET_CODE (y) == CONST)
1767 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1768 ysize, canon_rtx (XEXP (y, 0)), c);
1770 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1773 if (GET_CODE (y) == CONST)
1774 return memrefs_conflict_p (xsize, x, ysize,
1775 canon_rtx (XEXP (y, 0)), c);
1778 return (xsize <= 0 || ysize <= 0
1779 || (rtx_equal_for_memref_p (x, y)
1780 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1787 /* Functions to compute memory dependencies.
1789 Since we process the insns in execution order, we can build tables
1790 to keep track of what registers are fixed (and not aliased), what registers
1791 are varying in known ways, and what registers are varying in unknown
1794 If both memory references are volatile, then there must always be a
1795 dependence between the two references, since their order can not be
1796 changed. A volatile and non-volatile reference can be interchanged
1799 A MEM_IN_STRUCT reference at a non-AND varying address can never
1800 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1801 also must allow AND addresses, because they may generate accesses
1802 outside the object being referenced. This is used to generate
1803 aligned addresses from unaligned addresses, for instance, the alpha
1804 storeqi_unaligned pattern. */
1806 /* Read dependence: X is read after read in MEM takes place. There can
1807 only be a dependence here if both reads are volatile. */
1810 read_dependence (rtx mem, rtx x)
1812 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1815 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1816 MEM2 is a reference to a structure at a varying address, or returns
1817 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1818 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1819 to decide whether or not an address may vary; it should return
1820 nonzero whenever variation is possible.
1821 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1824 fixed_scalar_and_varying_struct_p (rtx mem1, rtx mem2, rtx mem1_addr,
1826 int (*varies_p) (rtx, int))
1828 if (! flag_strict_aliasing)
1831 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1832 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1833 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1837 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1838 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1839 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1846 /* Returns nonzero if something about the mode or address format MEM1
1847 indicates that it might well alias *anything*. */
1850 aliases_everything_p (rtx mem)
1852 if (GET_CODE (XEXP (mem, 0)) == AND)
1853 /* If the address is an AND, its very hard to know at what it is
1854 actually pointing. */
1860 /* Return true if we can determine that the fields referenced cannot
1861 overlap for any pair of objects. */
1864 nonoverlapping_component_refs_p (tree x, tree y)
1866 tree fieldx, fieldy, typex, typey, orig_y;
1870 /* The comparison has to be done at a common type, since we don't
1871 know how the inheritance hierarchy works. */
1875 fieldx = TREE_OPERAND (x, 1);
1876 typex = DECL_FIELD_CONTEXT (fieldx);
1881 fieldy = TREE_OPERAND (y, 1);
1882 typey = DECL_FIELD_CONTEXT (fieldy);
1887 y = TREE_OPERAND (y, 0);
1889 while (y && TREE_CODE (y) == COMPONENT_REF);
1891 x = TREE_OPERAND (x, 0);
1893 while (x && TREE_CODE (x) == COMPONENT_REF);
1895 /* Never found a common type. */
1899 /* If we're left with accessing different fields of a structure,
1901 if (TREE_CODE (typex) == RECORD_TYPE
1902 && fieldx != fieldy)
1905 /* The comparison on the current field failed. If we're accessing
1906 a very nested structure, look at the next outer level. */
1907 x = TREE_OPERAND (x, 0);
1908 y = TREE_OPERAND (y, 0);
1911 && TREE_CODE (x) == COMPONENT_REF
1912 && TREE_CODE (y) == COMPONENT_REF);
1917 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1920 decl_for_component_ref (tree x)
1924 x = TREE_OPERAND (x, 0);
1926 while (x && TREE_CODE (x) == COMPONENT_REF);
1928 return x && DECL_P (x) ? x : NULL_TREE;
1931 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1932 offset of the field reference. */
1935 adjust_offset_for_component_ref (tree x, rtx offset)
1937 HOST_WIDE_INT ioffset;
1942 ioffset = INTVAL (offset);
1945 tree field = TREE_OPERAND (x, 1);
1947 if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
1949 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
1950 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1953 x = TREE_OPERAND (x, 0);
1955 while (x && TREE_CODE (x) == COMPONENT_REF);
1957 return GEN_INT (ioffset);
1960 /* Return nonzero if we can determine the exprs corresponding to memrefs
1961 X and Y and they do not overlap. */
1964 nonoverlapping_memrefs_p (rtx x, rtx y)
1966 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1969 rtx moffsetx, moffsety;
1970 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1972 /* Unless both have exprs, we can't tell anything. */
1973 if (exprx == 0 || expry == 0)
1976 /* If both are field references, we may be able to determine something. */
1977 if (TREE_CODE (exprx) == COMPONENT_REF
1978 && TREE_CODE (expry) == COMPONENT_REF
1979 && nonoverlapping_component_refs_p (exprx, expry))
1982 /* If the field reference test failed, look at the DECLs involved. */
1983 moffsetx = MEM_OFFSET (x);
1984 if (TREE_CODE (exprx) == COMPONENT_REF)
1986 tree t = decl_for_component_ref (exprx);
1989 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
1992 else if (TREE_CODE (exprx) == INDIRECT_REF)
1994 exprx = TREE_OPERAND (exprx, 0);
1995 if (flag_argument_noalias < 2
1996 || TREE_CODE (exprx) != PARM_DECL)
2000 moffsety = MEM_OFFSET (y);
2001 if (TREE_CODE (expry) == COMPONENT_REF)
2003 tree t = decl_for_component_ref (expry);
2006 moffsety = adjust_offset_for_component_ref (expry, moffsety);
2009 else if (TREE_CODE (expry) == INDIRECT_REF)
2011 expry = TREE_OPERAND (expry, 0);
2012 if (flag_argument_noalias < 2
2013 || TREE_CODE (expry) != PARM_DECL)
2017 if (! DECL_P (exprx) || ! DECL_P (expry))
2020 rtlx = DECL_RTL (exprx);
2021 rtly = DECL_RTL (expry);
2023 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2024 can't overlap unless they are the same because we never reuse that part
2025 of the stack frame used for locals for spilled pseudos. */
2026 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
2027 && ! rtx_equal_p (rtlx, rtly))
2030 /* Get the base and offsets of both decls. If either is a register, we
2031 know both are and are the same, so use that as the base. The only
2032 we can avoid overlap is if we can deduce that they are nonoverlapping
2033 pieces of that decl, which is very rare. */
2034 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
2035 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2036 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2038 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
2039 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2040 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2042 /* If the bases are different, we know they do not overlap if both
2043 are constants or if one is a constant and the other a pointer into the
2044 stack frame. Otherwise a different base means we can't tell if they
2046 if (! rtx_equal_p (basex, basey))
2047 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2048 || (CONSTANT_P (basex) && REG_P (basey)
2049 && REGNO_PTR_FRAME_P (REGNO (basey)))
2050 || (CONSTANT_P (basey) && REG_P (basex)
2051 && REGNO_PTR_FRAME_P (REGNO (basex))));
2053 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2054 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2056 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2057 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2060 /* If we have an offset for either memref, it can update the values computed
2063 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2065 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2067 /* If a memref has both a size and an offset, we can use the smaller size.
2068 We can't do this if the offset isn't known because we must view this
2069 memref as being anywhere inside the DECL's MEM. */
2070 if (MEM_SIZE (x) && moffsetx)
2071 sizex = INTVAL (MEM_SIZE (x));
2072 if (MEM_SIZE (y) && moffsety)
2073 sizey = INTVAL (MEM_SIZE (y));
2075 /* Put the values of the memref with the lower offset in X's values. */
2076 if (offsetx > offsety)
2078 tem = offsetx, offsetx = offsety, offsety = tem;
2079 tem = sizex, sizex = sizey, sizey = tem;
2082 /* If we don't know the size of the lower-offset value, we can't tell
2083 if they conflict. Otherwise, we do the test. */
2084 return sizex >= 0 && offsety >= offsetx + sizex;
2087 /* True dependence: X is read after store in MEM takes place. */
2090 true_dependence (rtx mem, enum machine_mode mem_mode, rtx x,
2091 int (*varies) (rtx, int))
2093 rtx x_addr, mem_addr;
2096 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2099 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2100 This is used in epilogue deallocation functions. */
2101 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2103 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2106 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2109 /* Unchanging memory can't conflict with non-unchanging memory.
2110 A non-unchanging read can conflict with a non-unchanging write.
2111 An unchanging read can conflict with an unchanging write since
2112 there may be a single store to this address to initialize it.
2113 Note that an unchanging store can conflict with a non-unchanging read
2114 since we have to make conservative assumptions when we have a
2115 record with readonly fields and we are copying the whole thing.
2116 Just fall through to the code below to resolve potential conflicts.
2117 This won't handle all cases optimally, but the possible performance
2118 loss should be negligible. */
2119 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2122 if (nonoverlapping_memrefs_p (mem, x))
2125 if (mem_mode == VOIDmode)
2126 mem_mode = GET_MODE (mem);
2128 x_addr = get_addr (XEXP (x, 0));
2129 mem_addr = get_addr (XEXP (mem, 0));
2131 base = find_base_term (x_addr);
2132 if (base && (GET_CODE (base) == LABEL_REF
2133 || (GET_CODE (base) == SYMBOL_REF
2134 && CONSTANT_POOL_ADDRESS_P (base))))
2137 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2140 x_addr = canon_rtx (x_addr);
2141 mem_addr = canon_rtx (mem_addr);
2143 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2144 SIZE_FOR_MODE (x), x_addr, 0))
2147 if (aliases_everything_p (x))
2150 /* We cannot use aliases_everything_p to test MEM, since we must look
2151 at MEM_MODE, rather than GET_MODE (MEM). */
2152 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2155 /* In true_dependence we also allow BLKmode to alias anything. Why
2156 don't we do this in anti_dependence and output_dependence? */
2157 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2160 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2164 /* Canonical true dependence: X is read after store in MEM takes place.
2165 Variant of true_dependence which assumes MEM has already been
2166 canonicalized (hence we no longer do that here).
2167 The mem_addr argument has been added, since true_dependence computed
2168 this value prior to canonicalizing. */
2171 canon_true_dependence (rtx mem, enum machine_mode mem_mode, rtx mem_addr,
2172 rtx x, int (*varies) (rtx, int))
2176 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2179 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2180 This is used in epilogue deallocation functions. */
2181 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2183 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2186 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2189 /* If X is an unchanging read, then it can't possibly conflict with any
2190 non-unchanging store. It may conflict with an unchanging write though,
2191 because there may be a single store to this address to initialize it.
2192 Just fall through to the code below to resolve the case where we have
2193 both an unchanging read and an unchanging write. This won't handle all
2194 cases optimally, but the possible performance loss should be
2196 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2199 if (nonoverlapping_memrefs_p (x, mem))
2202 x_addr = get_addr (XEXP (x, 0));
2204 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2207 x_addr = canon_rtx (x_addr);
2208 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2209 SIZE_FOR_MODE (x), x_addr, 0))
2212 if (aliases_everything_p (x))
2215 /* We cannot use aliases_everything_p to test MEM, since we must look
2216 at MEM_MODE, rather than GET_MODE (MEM). */
2217 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2220 /* In true_dependence we also allow BLKmode to alias anything. Why
2221 don't we do this in anti_dependence and output_dependence? */
2222 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2225 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2229 /* Returns nonzero if a write to X might alias a previous read from
2230 (or, if WRITEP is nonzero, a write to) MEM. If CONSTP is nonzero,
2231 honor the RTX_UNCHANGING_P flags on X and MEM. */
2234 write_dependence_p (rtx mem, rtx x, int writep, int constp)
2236 rtx x_addr, mem_addr;
2240 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2243 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2244 This is used in epilogue deallocation functions. */
2245 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2247 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2250 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2255 /* Unchanging memory can't conflict with non-unchanging memory. */
2256 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
2259 /* If MEM is an unchanging read, then it can't possibly conflict with
2260 the store to X, because there is at most one store to MEM, and it
2261 must have occurred somewhere before MEM. */
2262 if (! writep && RTX_UNCHANGING_P (mem))
2266 if (nonoverlapping_memrefs_p (x, mem))
2269 x_addr = get_addr (XEXP (x, 0));
2270 mem_addr = get_addr (XEXP (mem, 0));
2274 base = find_base_term (mem_addr);
2275 if (base && (GET_CODE (base) == LABEL_REF
2276 || (GET_CODE (base) == SYMBOL_REF
2277 && CONSTANT_POOL_ADDRESS_P (base))))
2281 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2285 x_addr = canon_rtx (x_addr);
2286 mem_addr = canon_rtx (mem_addr);
2288 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2289 SIZE_FOR_MODE (x), x_addr, 0))
2293 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2296 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2297 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2300 /* Anti dependence: X is written after read in MEM takes place. */
2303 anti_dependence (rtx mem, rtx x)
2305 return write_dependence_p (mem, x, /*writep=*/0, /*constp*/1);
2308 /* Output dependence: X is written after store in MEM takes place. */
2311 output_dependence (rtx mem, rtx x)
2313 return write_dependence_p (mem, x, /*writep=*/1, /*constp*/1);
2316 /* Unchanging anti dependence: Like anti_dependence but ignores
2317 the UNCHANGING_RTX_P property on const variable references. */
2320 unchanging_anti_dependence (rtx mem, rtx x)
2322 return write_dependence_p (mem, x, /*writep=*/0, /*constp*/0);
2325 /* A subroutine of nonlocal_mentioned_p, returns 1 if *LOC mentions
2326 something which is not local to the function and is not constant. */
2329 nonlocal_mentioned_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2338 switch (GET_CODE (x))
2341 if (GET_CODE (SUBREG_REG (x)) == REG)
2343 /* Global registers are not local. */
2344 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2345 && global_regs[subreg_regno (x)])
2353 /* Global registers are not local. */
2354 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2369 /* Constants in the function's constants pool are constant. */
2370 if (CONSTANT_POOL_ADDRESS_P (x))
2375 /* Non-constant calls and recursion are not local. */
2379 /* Be overly conservative and consider any volatile memory
2380 reference as not local. */
2381 if (MEM_VOLATILE_P (x))
2383 base = find_base_term (XEXP (x, 0));
2386 /* A Pmode ADDRESS could be a reference via the structure value
2387 address or static chain. Such memory references are nonlocal.
2389 Thus, we have to examine the contents of the ADDRESS to find
2390 out if this is a local reference or not. */
2391 if (GET_CODE (base) == ADDRESS
2392 && GET_MODE (base) == Pmode
2393 && (XEXP (base, 0) == stack_pointer_rtx
2394 || XEXP (base, 0) == arg_pointer_rtx
2395 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2396 || XEXP (base, 0) == hard_frame_pointer_rtx
2398 || XEXP (base, 0) == frame_pointer_rtx))
2400 /* Constants in the function's constant pool are constant. */
2401 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2406 case UNSPEC_VOLATILE:
2411 if (MEM_VOLATILE_P (x))
2423 /* Returns nonzero if X might mention something which is not
2424 local to the function and is not constant. */
2427 nonlocal_mentioned_p (rtx x)
2431 if (GET_CODE (x) == CALL_INSN)
2433 if (! CONST_OR_PURE_CALL_P (x))
2435 x = CALL_INSN_FUNCTION_USAGE (x);
2443 return for_each_rtx (&x, nonlocal_mentioned_p_1, NULL);
2446 /* A subroutine of nonlocal_referenced_p, returns 1 if *LOC references
2447 something which is not local to the function and is not constant. */
2450 nonlocal_referenced_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2457 switch (GET_CODE (x))
2463 return nonlocal_mentioned_p (x);
2466 /* Non-constant calls and recursion are not local. */
2470 if (nonlocal_mentioned_p (SET_SRC (x)))
2473 if (GET_CODE (SET_DEST (x)) == MEM)
2474 return nonlocal_mentioned_p (XEXP (SET_DEST (x), 0));
2476 /* If the destination is anything other than a CC0, PC,
2477 MEM, REG, or a SUBREG of a REG that occupies all of
2478 the REG, then X references nonlocal memory if it is
2479 mentioned in the destination. */
2480 if (GET_CODE (SET_DEST (x)) != CC0
2481 && GET_CODE (SET_DEST (x)) != PC
2482 && GET_CODE (SET_DEST (x)) != REG
2483 && ! (GET_CODE (SET_DEST (x)) == SUBREG
2484 && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
2485 && (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (x))))
2486 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
2487 == ((GET_MODE_SIZE (GET_MODE (SET_DEST (x)))
2488 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD))))
2489 return nonlocal_mentioned_p (SET_DEST (x));
2493 if (GET_CODE (XEXP (x, 0)) == MEM)
2494 return nonlocal_mentioned_p (XEXP (XEXP (x, 0), 0));
2498 return nonlocal_mentioned_p (XEXP (x, 0));
2501 case UNSPEC_VOLATILE:
2505 if (MEM_VOLATILE_P (x))
2517 /* Returns nonzero if X might reference something which is not
2518 local to the function and is not constant. */
2521 nonlocal_referenced_p (rtx x)
2525 if (GET_CODE (x) == CALL_INSN)
2527 if (! CONST_OR_PURE_CALL_P (x))
2529 x = CALL_INSN_FUNCTION_USAGE (x);
2537 return for_each_rtx (&x, nonlocal_referenced_p_1, NULL);
2540 /* A subroutine of nonlocal_set_p, returns 1 if *LOC sets
2541 something which is not local to the function and is not constant. */
2544 nonlocal_set_p_1 (rtx *loc, void *data ATTRIBUTE_UNUSED)
2551 switch (GET_CODE (x))
2554 /* Non-constant calls and recursion are not local. */
2563 return nonlocal_mentioned_p (XEXP (x, 0));
2566 if (nonlocal_mentioned_p (SET_DEST (x)))
2568 return nonlocal_set_p (SET_SRC (x));
2571 return nonlocal_mentioned_p (XEXP (x, 0));
2577 case UNSPEC_VOLATILE:
2581 if (MEM_VOLATILE_P (x))
2593 /* Returns nonzero if X might set something which is not
2594 local to the function and is not constant. */
2597 nonlocal_set_p (rtx x)
2601 if (GET_CODE (x) == CALL_INSN)
2603 if (! CONST_OR_PURE_CALL_P (x))
2605 x = CALL_INSN_FUNCTION_USAGE (x);
2613 return for_each_rtx (&x, nonlocal_set_p_1, NULL);
2616 /* Mark the function if it is pure or constant. */
2619 mark_constant_function (void)
2622 int nonlocal_memory_referenced;
2624 if (TREE_READONLY (current_function_decl)
2625 || DECL_IS_PURE (current_function_decl)
2626 || TREE_THIS_VOLATILE (current_function_decl)
2627 || current_function_has_nonlocal_goto
2628 || !targetm.binds_local_p (current_function_decl))
2631 /* A loop might not return which counts as a side effect. */
2632 if (mark_dfs_back_edges ())
2635 nonlocal_memory_referenced = 0;
2637 init_alias_analysis ();
2639 /* Determine if this is a constant or pure function. */
2641 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2643 if (! INSN_P (insn))
2646 if (nonlocal_set_p (insn) || global_reg_mentioned_p (insn)
2647 || volatile_refs_p (PATTERN (insn)))
2650 if (! nonlocal_memory_referenced)
2651 nonlocal_memory_referenced = nonlocal_referenced_p (insn);
2654 end_alias_analysis ();
2656 /* Mark the function. */
2660 else if (nonlocal_memory_referenced)
2662 cgraph_rtl_info (current_function_decl)->pure_function = 1;
2663 DECL_IS_PURE (current_function_decl) = 1;
2667 cgraph_rtl_info (current_function_decl)->const_function = 1;
2668 TREE_READONLY (current_function_decl) = 1;
2674 init_alias_once (void)
2678 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2679 /* Check whether this register can hold an incoming pointer
2680 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2681 numbers, so translate if necessary due to register windows. */
2682 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2683 && HARD_REGNO_MODE_OK (i, Pmode))
2684 static_reg_base_value[i]
2685 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2687 static_reg_base_value[STACK_POINTER_REGNUM]
2688 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2689 static_reg_base_value[ARG_POINTER_REGNUM]
2690 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2691 static_reg_base_value[FRAME_POINTER_REGNUM]
2692 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2693 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2694 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2695 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2699 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2700 to be memory reference. */
2701 static bool memory_modified;
2703 memory_modified_1 (rtx x, rtx pat ATTRIBUTE_UNUSED, void *data)
2705 if (GET_CODE (x) == MEM)
2707 if (anti_dependence (x, (rtx)data) || output_dependence (x, (rtx)data))
2708 memory_modified = true;
2713 /* Return true when INSN possibly modify memory contents of MEM
2714 (ie address can be modified). */
2716 memory_modified_in_insn_p (rtx mem, rtx insn)
2720 memory_modified = false;
2721 note_stores (PATTERN (insn), memory_modified_1, mem);
2722 return memory_modified;
2725 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2729 init_alias_analysis (void)
2731 unsigned int maxreg = max_reg_num ();
2737 timevar_push (TV_ALIAS_ANALYSIS);
2739 reg_known_value_size = maxreg;
2742 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2743 - FIRST_PSEUDO_REGISTER;
2745 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2746 - FIRST_PSEUDO_REGISTER;
2748 /* Overallocate reg_base_value to allow some growth during loop
2749 optimization. Loop unrolling can create a large number of
2751 if (old_reg_base_value)
2753 reg_base_value = old_reg_base_value;
2754 /* If varray gets large zeroing cost may get important. */
2755 if (VARRAY_SIZE (reg_base_value) > 256
2756 && VARRAY_SIZE (reg_base_value) > 4 * maxreg)
2757 VARRAY_GROW (reg_base_value, maxreg);
2758 VARRAY_CLEAR (reg_base_value);
2759 if (VARRAY_SIZE (reg_base_value) < maxreg)
2760 VARRAY_GROW (reg_base_value, maxreg);
2764 VARRAY_RTX_INIT (reg_base_value, maxreg, "reg_base_value");
2767 new_reg_base_value = xmalloc (maxreg * sizeof (rtx));
2768 reg_seen = xmalloc (maxreg);
2769 if (! reload_completed && flag_old_unroll_loops)
2771 /* ??? Why are we realloc'ing if we're just going to zero it? */
2772 alias_invariant = xrealloc (alias_invariant,
2773 maxreg * sizeof (rtx));
2774 memset (alias_invariant, 0, maxreg * sizeof (rtx));
2775 alias_invariant_size = maxreg;
2778 /* The basic idea is that each pass through this loop will use the
2779 "constant" information from the previous pass to propagate alias
2780 information through another level of assignments.
2782 This could get expensive if the assignment chains are long. Maybe
2783 we should throttle the number of iterations, possibly based on
2784 the optimization level or flag_expensive_optimizations.
2786 We could propagate more information in the first pass by making use
2787 of REG_N_SETS to determine immediately that the alias information
2788 for a pseudo is "constant".
2790 A program with an uninitialized variable can cause an infinite loop
2791 here. Instead of doing a full dataflow analysis to detect such problems
2792 we just cap the number of iterations for the loop.
2794 The state of the arrays for the set chain in question does not matter
2795 since the program has undefined behavior. */
2800 /* Assume nothing will change this iteration of the loop. */
2803 /* We want to assign the same IDs each iteration of this loop, so
2804 start counting from zero each iteration of the loop. */
2807 /* We're at the start of the function each iteration through the
2808 loop, so we're copying arguments. */
2809 copying_arguments = true;
2811 /* Wipe the potential alias information clean for this pass. */
2812 memset (new_reg_base_value, 0, maxreg * sizeof (rtx));
2814 /* Wipe the reg_seen array clean. */
2815 memset (reg_seen, 0, maxreg);
2817 /* Mark all hard registers which may contain an address.
2818 The stack, frame and argument pointers may contain an address.
2819 An argument register which can hold a Pmode value may contain
2820 an address even if it is not in BASE_REGS.
2822 The address expression is VOIDmode for an argument and
2823 Pmode for other registers. */
2825 memcpy (new_reg_base_value, static_reg_base_value,
2826 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2828 /* Walk the insns adding values to the new_reg_base_value array. */
2829 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2835 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2836 /* The prologue/epilogue insns are not threaded onto the
2837 insn chain until after reload has completed. Thus,
2838 there is no sense wasting time checking if INSN is in
2839 the prologue/epilogue until after reload has completed. */
2840 if (reload_completed
2841 && prologue_epilogue_contains (insn))
2845 /* If this insn has a noalias note, process it, Otherwise,
2846 scan for sets. A simple set will have no side effects
2847 which could change the base value of any other register. */
2849 if (GET_CODE (PATTERN (insn)) == SET
2850 && REG_NOTES (insn) != 0
2851 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2852 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2854 note_stores (PATTERN (insn), record_set, NULL);
2856 set = single_set (insn);
2859 && GET_CODE (SET_DEST (set)) == REG
2860 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2862 unsigned int regno = REGNO (SET_DEST (set));
2863 rtx src = SET_SRC (set);
2865 if (REG_NOTES (insn) != 0
2866 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2867 && REG_N_SETS (regno) == 1)
2868 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2869 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2870 && ! rtx_varies_p (XEXP (note, 0), 1)
2871 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2873 reg_known_value[regno] = XEXP (note, 0);
2874 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2876 else if (REG_N_SETS (regno) == 1
2877 && GET_CODE (src) == PLUS
2878 && GET_CODE (XEXP (src, 0)) == REG
2879 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2880 && (reg_known_value[REGNO (XEXP (src, 0))])
2881 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2883 rtx op0 = XEXP (src, 0);
2884 op0 = reg_known_value[REGNO (op0)];
2885 reg_known_value[regno]
2886 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2887 reg_known_equiv_p[regno] = 0;
2889 else if (REG_N_SETS (regno) == 1
2890 && ! rtx_varies_p (src, 1))
2892 reg_known_value[regno] = src;
2893 reg_known_equiv_p[regno] = 0;
2897 else if (GET_CODE (insn) == NOTE
2898 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2899 copying_arguments = false;
2902 /* Now propagate values from new_reg_base_value to reg_base_value. */
2903 if (maxreg != (unsigned int) max_reg_num())
2905 for (ui = 0; ui < maxreg; ui++)
2907 if (new_reg_base_value[ui]
2908 && new_reg_base_value[ui] != VARRAY_RTX (reg_base_value, ui)
2909 && ! rtx_equal_p (new_reg_base_value[ui],
2910 VARRAY_RTX (reg_base_value, ui)))
2912 VARRAY_RTX (reg_base_value, ui) = new_reg_base_value[ui];
2917 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2919 /* Fill in the remaining entries. */
2920 for (i = FIRST_PSEUDO_REGISTER; i < (int)maxreg; i++)
2921 if (reg_known_value[i] == 0)
2922 reg_known_value[i] = regno_reg_rtx[i];
2924 /* Simplify the reg_base_value array so that no register refers to
2925 another register, except to special registers indirectly through
2926 ADDRESS expressions.
2928 In theory this loop can take as long as O(registers^2), but unless
2929 there are very long dependency chains it will run in close to linear
2932 This loop may not be needed any longer now that the main loop does
2933 a better job at propagating alias information. */
2939 for (ui = 0; ui < maxreg; ui++)
2941 rtx base = VARRAY_RTX (reg_base_value, ui);
2942 if (base && GET_CODE (base) == REG)
2944 unsigned int base_regno = REGNO (base);
2945 if (base_regno == ui) /* register set from itself */
2946 VARRAY_RTX (reg_base_value, ui) = 0;
2948 VARRAY_RTX (reg_base_value, ui)
2949 = VARRAY_RTX (reg_base_value, base_regno);
2954 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2957 free (new_reg_base_value);
2958 new_reg_base_value = 0;
2961 timevar_pop (TV_ALIAS_ANALYSIS);
2965 end_alias_analysis (void)
2967 old_reg_base_value = reg_base_value;
2968 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2969 reg_known_value = 0;
2970 reg_known_value_size = 0;
2971 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2972 reg_known_equiv_p = 0;
2973 if (alias_invariant)
2975 free (alias_invariant);
2976 alias_invariant = 0;
2977 alias_invariant_size = 0;
2981 #include "gt-alias.h"