1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
3 Contributed by John Carr (jfc@mit.edu).
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
30 #include "hard-reg-set.h"
31 #include "basic-block.h"
36 #include "splay-tree.h"
38 #include "langhooks.h"
41 /* The alias sets assigned to MEMs assist the back-end in determining
42 which MEMs can alias which other MEMs. In general, two MEMs in
43 different alias sets cannot alias each other, with one important
44 exception. Consider something like:
46 struct S {int i; double d; };
48 a store to an `S' can alias something of either type `int' or type
49 `double'. (However, a store to an `int' cannot alias a `double'
50 and vice versa.) We indicate this via a tree structure that looks
58 (The arrows are directed and point downwards.)
59 In this situation we say the alias set for `struct S' is the
60 `superset' and that those for `int' and `double' are `subsets'.
62 To see whether two alias sets can point to the same memory, we must
63 see if either alias set is a subset of the other. We need not trace
64 past immediate descendents, however, since we propagate all
65 grandchildren up one level.
67 Alias set zero is implicitly a superset of all other alias sets.
68 However, this is no actual entry for alias set zero. It is an
69 error to attempt to explicitly construct a subset of zero. */
71 typedef struct alias_set_entry
73 /* The alias set number, as stored in MEM_ALIAS_SET. */
74 HOST_WIDE_INT alias_set;
76 /* The children of the alias set. These are not just the immediate
77 children, but, in fact, all descendents. So, if we have:
79 struct T { struct S s; float f; }
81 continuing our example above, the children here will be all of
82 `int', `double', `float', and `struct S'. */
85 /* Nonzero if would have a child of zero: this effectively makes this
86 alias set the same as alias set zero. */
90 static int rtx_equal_for_memref_p PARAMS ((rtx, rtx));
91 static rtx find_symbolic_term PARAMS ((rtx));
92 rtx get_addr PARAMS ((rtx));
93 static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx,
95 static void record_set PARAMS ((rtx, rtx, void *));
96 static rtx find_base_term PARAMS ((rtx));
97 static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode,
99 static rtx find_base_value PARAMS ((rtx));
100 static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx));
101 static int insert_subset_children PARAMS ((splay_tree_node, void*));
102 static tree find_base_decl PARAMS ((tree));
103 static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT));
104 static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx,
105 int (*) (rtx, int)));
106 static int aliases_everything_p PARAMS ((rtx));
107 static bool nonoverlapping_component_refs_p PARAMS ((tree, tree));
108 static tree decl_for_component_ref PARAMS ((tree));
109 static rtx adjust_offset_for_component_ref PARAMS ((tree, rtx));
110 static int nonoverlapping_memrefs_p PARAMS ((rtx, rtx));
111 static int write_dependence_p PARAMS ((rtx, rtx, int));
113 static int nonlocal_mentioned_p_1 PARAMS ((rtx *, void *));
114 static int nonlocal_mentioned_p PARAMS ((rtx));
115 static int nonlocal_referenced_p_1 PARAMS ((rtx *, void *));
116 static int nonlocal_referenced_p PARAMS ((rtx));
117 static int nonlocal_set_p_1 PARAMS ((rtx *, void *));
118 static int nonlocal_set_p PARAMS ((rtx));
120 /* Set up all info needed to perform alias analysis on memory references. */
122 /* Returns the size in bytes of the mode of X. */
123 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
125 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
126 different alias sets. We ignore alias sets in functions making use
127 of variable arguments because the va_arg macros on some systems are
129 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
130 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
132 /* Cap the number of passes we make over the insns propagating alias
133 information through set chains. 10 is a completely arbitrary choice. */
134 #define MAX_ALIAS_LOOP_PASSES 10
136 /* reg_base_value[N] gives an address to which register N is related.
137 If all sets after the first add or subtract to the current value
138 or otherwise modify it so it does not point to a different top level
139 object, reg_base_value[N] is equal to the address part of the source
142 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
143 expressions represent certain special values: function arguments and
144 the stack, frame, and argument pointers.
146 The contents of an ADDRESS is not normally used, the mode of the
147 ADDRESS determines whether the ADDRESS is a function argument or some
148 other special value. Pointer equality, not rtx_equal_p, determines whether
149 two ADDRESS expressions refer to the same base address.
151 The only use of the contents of an ADDRESS is for determining if the
152 current function performs nonlocal memory memory references for the
153 purposes of marking the function as a constant function. */
155 static GTY((length ("reg_base_value_size"))) rtx *reg_base_value;
156 static rtx *new_reg_base_value;
157 static unsigned int reg_base_value_size; /* size of reg_base_value array */
159 /* Static hunks of RTL used by the aliasing code; these are initialized
160 once per function to avoid unnecessary RTL allocations. */
161 static GTY (()) rtx static_reg_base_value[FIRST_PSEUDO_REGISTER];
163 #define REG_BASE_VALUE(X) \
164 (REGNO (X) < reg_base_value_size \
165 ? reg_base_value[REGNO (X)] : 0)
167 /* Vector of known invariant relationships between registers. Set in
168 loop unrolling. Indexed by register number, if nonzero the value
169 is an expression describing this register in terms of another.
171 The length of this array is REG_BASE_VALUE_SIZE.
173 Because this array contains only pseudo registers it has no effect
175 static rtx *alias_invariant;
177 /* Vector indexed by N giving the initial (unchanging) value known for
178 pseudo-register N. This array is initialized in
179 init_alias_analysis, and does not change until end_alias_analysis
181 rtx *reg_known_value;
183 /* Indicates number of valid entries in reg_known_value. */
184 static unsigned int reg_known_value_size;
186 /* Vector recording for each reg_known_value whether it is due to a
187 REG_EQUIV note. Future passes (viz., reload) may replace the
188 pseudo with the equivalent expression and so we account for the
189 dependences that would be introduced if that happens.
191 The REG_EQUIV notes created in assign_parms may mention the arg
192 pointer, and there are explicit insns in the RTL that modify the
193 arg pointer. Thus we must ensure that such insns don't get
194 scheduled across each other because that would invalidate the
195 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
196 wrong, but solving the problem in the scheduler will likely give
197 better code, so we do it here. */
198 char *reg_known_equiv_p;
200 /* True when scanning insns from the start of the rtl to the
201 NOTE_INSN_FUNCTION_BEG note. */
202 static bool copying_arguments;
204 /* The splay-tree used to store the various alias set entries. */
205 static splay_tree alias_sets;
207 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
208 such an entry, or NULL otherwise. */
210 static alias_set_entry
211 get_alias_set_entry (alias_set)
212 HOST_WIDE_INT alias_set;
215 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
217 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
220 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
221 the two MEMs cannot alias each other. */
224 mems_in_disjoint_alias_sets_p (mem1, mem2)
228 #ifdef ENABLE_CHECKING
229 /* Perform a basic sanity check. Namely, that there are no alias sets
230 if we're not using strict aliasing. This helps to catch bugs
231 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
232 where a MEM is allocated in some way other than by the use of
233 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
234 use alias sets to indicate that spilled registers cannot alias each
235 other, we might need to remove this check. */
236 if (! flag_strict_aliasing
237 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
241 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
244 /* Insert the NODE into the splay tree given by DATA. Used by
245 record_alias_subset via splay_tree_foreach. */
248 insert_subset_children (node, data)
249 splay_tree_node node;
252 splay_tree_insert ((splay_tree) data, node->key, node->value);
257 /* Return 1 if the two specified alias sets may conflict. */
260 alias_sets_conflict_p (set1, set2)
261 HOST_WIDE_INT set1, set2;
265 /* If have no alias set information for one of the operands, we have
266 to assume it can alias anything. */
267 if (set1 == 0 || set2 == 0
268 /* If the two alias sets are the same, they may alias. */
272 /* See if the first alias set is a subset of the second. */
273 ase = get_alias_set_entry (set1);
275 && (ase->has_zero_child
276 || splay_tree_lookup (ase->children,
277 (splay_tree_key) set2)))
280 /* Now do the same, but with the alias sets reversed. */
281 ase = get_alias_set_entry (set2);
283 && (ase->has_zero_child
284 || splay_tree_lookup (ase->children,
285 (splay_tree_key) set1)))
288 /* The two alias sets are distinct and neither one is the
289 child of the other. Therefore, they cannot alias. */
293 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
294 has any readonly fields. If any of the fields have types that
295 contain readonly fields, return true as well. */
298 readonly_fields_p (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 (t1, t2)
325 /* If neither has a type specified, we don't know if they'll conflict
326 because we may be using them to store objects of various types, for
327 example the argument and local variables areas of inlined functions. */
328 if (t1 == 0 && t2 == 0)
331 /* If one or the other has readonly fields or is readonly,
332 then they may not conflict. */
333 if ((t1 != 0 && readonly_fields_p (t1))
334 || (t2 != 0 && readonly_fields_p (t2))
335 || (t1 != 0 && lang_hooks.honor_readonly && TYPE_READONLY (t1))
336 || (t2 != 0 && lang_hooks.honor_readonly && TYPE_READONLY (t2)))
339 /* If they are the same type, they must conflict. */
341 /* Likewise if both are volatile. */
342 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
345 /* If one is aggregate and the other is scalar then they may not
347 if ((t1 != 0 && AGGREGATE_TYPE_P (t1))
348 != (t2 != 0 && AGGREGATE_TYPE_P (t2)))
351 /* Otherwise they conflict only if the alias sets conflict. */
352 return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0,
353 t2 ? get_alias_set (t2) : 0);
356 /* T is an expression with pointer type. Find the DECL on which this
357 expression is based. (For example, in `a[i]' this would be `a'.)
358 If there is no such DECL, or a unique decl cannot be determined,
359 NULL_TREE is returned. */
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. */
422 /* If we're at the end, it is vacuously addressable. */
423 if (! handled_component_p (t))
426 /* Bitfields are never addressable. */
427 else if (TREE_CODE (t) == BIT_FIELD_REF)
430 /* Fields are addressable unless they are marked as nonaddressable or
431 the containing type has alias set 0. */
432 else if (TREE_CODE (t) == COMPONENT_REF
433 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
434 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
435 && can_address_p (TREE_OPERAND (t, 0)))
438 /* Likewise for arrays. */
439 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
440 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
441 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
442 && can_address_p (TREE_OPERAND (t, 0)))
448 /* Return the alias set for T, which may be either a type or an
449 expression. Call language-specific routine for help, if needed. */
457 /* If we're not doing any alias analysis, just assume everything
458 aliases everything else. Also return 0 if this or its type is
460 if (! flag_strict_aliasing || t == error_mark_node
462 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
465 /* We can be passed either an expression or a type. This and the
466 language-specific routine may make mutually-recursive calls to each other
467 to figure out what to do. At each juncture, we see if this is a tree
468 that the language may need to handle specially. First handle things that
473 tree placeholder_ptr = 0;
475 /* Remove any nops, then give the language a chance to do
476 something with this tree before we look at it. */
478 set = (*lang_hooks.get_alias_set) (t);
482 /* First see if the actual object referenced is an INDIRECT_REF from a
483 restrict-qualified pointer or a "void *". Replace
484 PLACEHOLDER_EXPRs. */
485 while (TREE_CODE (inner) == PLACEHOLDER_EXPR
486 || handled_component_p (inner))
488 if (TREE_CODE (inner) == PLACEHOLDER_EXPR)
489 inner = find_placeholder (inner, &placeholder_ptr);
491 inner = TREE_OPERAND (inner, 0);
496 /* Check for accesses through restrict-qualified pointers. */
497 if (TREE_CODE (inner) == INDIRECT_REF)
499 tree decl = find_base_decl (TREE_OPERAND (inner, 0));
501 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
503 /* If we haven't computed the actual alias set, do it now. */
504 if (DECL_POINTER_ALIAS_SET (decl) == -2)
506 /* No two restricted pointers can point at the same thing.
507 However, a restricted pointer can point at the same thing
508 as an unrestricted pointer, if that unrestricted pointer
509 is based on the restricted pointer. So, we make the
510 alias set for the restricted pointer a subset of the
511 alias set for the type pointed to by the type of the
513 HOST_WIDE_INT pointed_to_alias_set
514 = get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
516 if (pointed_to_alias_set == 0)
517 /* It's not legal to make a subset of alias set zero. */
521 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
522 record_alias_subset (pointed_to_alias_set,
523 DECL_POINTER_ALIAS_SET (decl));
527 /* We use the alias set indicated in the declaration. */
528 return DECL_POINTER_ALIAS_SET (decl);
531 /* If we have an INDIRECT_REF via a void pointer, we don't
532 know anything about what that might alias. */
533 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE)
537 /* Otherwise, pick up the outermost object that we could have a pointer
538 to, processing conversion and PLACEHOLDER_EXPR as above. */
540 while (TREE_CODE (t) == PLACEHOLDER_EXPR
541 || (handled_component_p (t) && ! can_address_p (t)))
543 if (TREE_CODE (t) == PLACEHOLDER_EXPR)
544 t = find_placeholder (t, &placeholder_ptr);
546 t = TREE_OPERAND (t, 0);
551 /* If we've already determined the alias set for a decl, just return
552 it. This is necessary for C++ anonymous unions, whose component
553 variables don't look like union members (boo!). */
554 if (TREE_CODE (t) == VAR_DECL
555 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
556 return MEM_ALIAS_SET (DECL_RTL (t));
558 /* Now all we care about is the type. */
562 /* Variant qualifiers don't affect the alias set, so get the main
563 variant. If this is a type with a known alias set, return it. */
564 t = TYPE_MAIN_VARIANT (t);
565 if (TYPE_ALIAS_SET_KNOWN_P (t))
566 return TYPE_ALIAS_SET (t);
568 /* See if the language has special handling for this type. */
569 set = (*lang_hooks.get_alias_set) (t);
573 /* There are no objects of FUNCTION_TYPE, so there's no point in
574 using up an alias set for them. (There are, of course, pointers
575 and references to functions, but that's different.) */
576 else if (TREE_CODE (t) == FUNCTION_TYPE)
579 /* Unless the language specifies otherwise, let vector types alias
580 their components. This avoids some nasty type punning issues in
581 normal usage. And indeed lets vectors be treated more like an
583 else if (TREE_CODE (t) == VECTOR_TYPE)
584 set = get_alias_set (TREE_TYPE (t));
587 /* Otherwise make a new alias set for this type. */
588 set = new_alias_set ();
590 TYPE_ALIAS_SET (t) = set;
592 /* If this is an aggregate type, we must record any component aliasing
594 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
595 record_component_aliases (t);
600 /* Return a brand-new alias set. */
605 static HOST_WIDE_INT last_alias_set;
607 if (flag_strict_aliasing)
608 return ++last_alias_set;
613 /* Indicate that things in SUBSET can alias things in SUPERSET, but
614 not vice versa. For example, in C, a store to an `int' can alias a
615 structure containing an `int', but not vice versa. Here, the
616 structure would be the SUPERSET and `int' the SUBSET. This
617 function should be called only once per SUPERSET/SUBSET pair.
619 It is illegal for SUPERSET to be zero; everything is implicitly a
620 subset of alias set zero. */
623 record_alias_subset (superset, subset)
624 HOST_WIDE_INT superset;
625 HOST_WIDE_INT subset;
627 alias_set_entry superset_entry;
628 alias_set_entry subset_entry;
630 /* It is possible in complex type situations for both sets to be the same,
631 in which case we can ignore this operation. */
632 if (superset == subset)
638 superset_entry = get_alias_set_entry (superset);
639 if (superset_entry == 0)
641 /* Create an entry for the SUPERSET, so that we have a place to
642 attach the SUBSET. */
644 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
645 superset_entry->alias_set = superset;
646 superset_entry->children
647 = splay_tree_new (splay_tree_compare_ints, 0, 0);
648 superset_entry->has_zero_child = 0;
649 splay_tree_insert (alias_sets, (splay_tree_key) superset,
650 (splay_tree_value) superset_entry);
654 superset_entry->has_zero_child = 1;
657 subset_entry = get_alias_set_entry (subset);
658 /* If there is an entry for the subset, enter all of its children
659 (if they are not already present) as children of the SUPERSET. */
662 if (subset_entry->has_zero_child)
663 superset_entry->has_zero_child = 1;
665 splay_tree_foreach (subset_entry->children, insert_subset_children,
666 superset_entry->children);
669 /* Enter the SUBSET itself as a child of the SUPERSET. */
670 splay_tree_insert (superset_entry->children,
671 (splay_tree_key) subset, 0);
675 /* Record that component types of TYPE, if any, are part of that type for
676 aliasing purposes. For record types, we only record component types
677 for fields that are marked addressable. For array types, we always
678 record the component types, so the front end should not call this
679 function if the individual component aren't addressable. */
682 record_component_aliases (type)
685 HOST_WIDE_INT superset = get_alias_set (type);
691 switch (TREE_CODE (type))
694 if (! TYPE_NONALIASED_COMPONENT (type))
695 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
700 case QUAL_UNION_TYPE:
701 /* Recursively record aliases for the base classes, if there are any */
702 if (TYPE_BINFO (type) != NULL && TYPE_BINFO_BASETYPES (type) != NULL)
705 for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type)); i++)
707 tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), i);
708 record_alias_subset (superset,
709 get_alias_set (BINFO_TYPE (binfo)));
712 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
713 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
714 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
718 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
726 /* Allocate an alias set for use in storing and reading from the varargs
730 get_varargs_alias_set ()
732 static HOST_WIDE_INT set = -1;
735 set = new_alias_set ();
740 /* Likewise, but used for the fixed portions of the frame, e.g., register
744 get_frame_alias_set ()
746 static HOST_WIDE_INT set = -1;
749 set = new_alias_set ();
754 /* Inside SRC, the source of a SET, find a base address. */
757 find_base_value (src)
762 switch (GET_CODE (src))
770 /* At the start of a function, argument registers have known base
771 values which may be lost later. Returning an ADDRESS
772 expression here allows optimization based on argument values
773 even when the argument registers are used for other purposes. */
774 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
775 return new_reg_base_value[regno];
777 /* If a pseudo has a known base value, return it. Do not do this
778 for non-fixed hard regs since it can result in a circular
779 dependency chain for registers which have values at function entry.
781 The test above is not sufficient because the scheduler may move
782 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
783 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
784 && regno < reg_base_value_size)
786 /* If we're inside init_alias_analysis, use new_reg_base_value
787 to reduce the number of relaxation iterations. */
788 if (new_reg_base_value && new_reg_base_value[regno])
789 return new_reg_base_value[regno];
791 if (reg_base_value[regno])
792 return reg_base_value[regno];
798 /* Check for an argument passed in memory. Only record in the
799 copying-arguments block; it is too hard to track changes
801 if (copying_arguments
802 && (XEXP (src, 0) == arg_pointer_rtx
803 || (GET_CODE (XEXP (src, 0)) == PLUS
804 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
805 return gen_rtx_ADDRESS (VOIDmode, src);
810 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
813 /* ... fall through ... */
818 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
820 /* If either operand is a REG that is a known pointer, then it
822 if (REG_P (src_0) && REG_POINTER (src_0))
823 return find_base_value (src_0);
824 if (REG_P (src_1) && REG_POINTER (src_1))
825 return find_base_value (src_1);
827 /* If either operand is a REG, then see if we already have
828 a known value for it. */
831 temp = find_base_value (src_0);
838 temp = find_base_value (src_1);
843 /* If either base is named object or a special address
844 (like an argument or stack reference), then use it for the
847 && (GET_CODE (src_0) == SYMBOL_REF
848 || GET_CODE (src_0) == LABEL_REF
849 || (GET_CODE (src_0) == ADDRESS
850 && GET_MODE (src_0) != VOIDmode)))
854 && (GET_CODE (src_1) == SYMBOL_REF
855 || GET_CODE (src_1) == LABEL_REF
856 || (GET_CODE (src_1) == ADDRESS
857 && GET_MODE (src_1) != VOIDmode)))
860 /* Guess which operand is the base address:
861 If either operand is a symbol, then it is the base. If
862 either operand is a CONST_INT, then the other is the base. */
863 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
864 return find_base_value (src_0);
865 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
866 return find_base_value (src_1);
872 /* The standard form is (lo_sum reg sym) so look only at the
874 return find_base_value (XEXP (src, 1));
877 /* If the second operand is constant set the base
878 address to the first operand. */
879 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
880 return find_base_value (XEXP (src, 0));
884 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
894 return find_base_value (XEXP (src, 0));
897 case SIGN_EXTEND: /* used for NT/Alpha pointers */
899 rtx temp = find_base_value (XEXP (src, 0));
901 #ifdef POINTERS_EXTEND_UNSIGNED
902 if (temp != 0 && CONSTANT_P (temp) && GET_MODE (temp) != Pmode)
903 temp = convert_memory_address (Pmode, temp);
916 /* Called from init_alias_analysis indirectly through note_stores. */
918 /* While scanning insns to find base values, reg_seen[N] is nonzero if
919 register N has been set in this function. */
920 static char *reg_seen;
922 /* Addresses which are known not to alias anything else are identified
923 by a unique integer. */
924 static int unique_id;
927 record_set (dest, set, data)
929 void *data ATTRIBUTE_UNUSED;
934 if (GET_CODE (dest) != REG)
937 regno = REGNO (dest);
939 if (regno >= reg_base_value_size)
944 /* A CLOBBER wipes out any old value but does not prevent a previously
945 unset register from acquiring a base address (i.e. reg_seen is not
947 if (GET_CODE (set) == CLOBBER)
949 new_reg_base_value[regno] = 0;
958 new_reg_base_value[regno] = 0;
962 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
963 GEN_INT (unique_id++));
967 /* This is not the first set. If the new value is not related to the
968 old value, forget the base value. Note that the following code is
970 extern int x, y; int *p = &x; p += (&y-&x);
971 ANSI C does not allow computing the difference of addresses
972 of distinct top level objects. */
973 if (new_reg_base_value[regno])
974 switch (GET_CODE (src))
978 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
979 new_reg_base_value[regno] = 0;
982 /* If the value we add in the PLUS is also a valid base value,
983 this might be the actual base value, and the original value
986 rtx other = NULL_RTX;
988 if (XEXP (src, 0) == dest)
989 other = XEXP (src, 1);
990 else if (XEXP (src, 1) == dest)
991 other = XEXP (src, 0);
993 if (! other || find_base_value (other))
994 new_reg_base_value[regno] = 0;
998 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
999 new_reg_base_value[regno] = 0;
1002 new_reg_base_value[regno] = 0;
1005 /* If this is the first set of a register, record the value. */
1006 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
1007 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
1008 new_reg_base_value[regno] = find_base_value (src);
1010 reg_seen[regno] = 1;
1013 /* Called from loop optimization when a new pseudo-register is
1014 created. It indicates that REGNO is being set to VAL. f INVARIANT
1015 is true then this value also describes an invariant relationship
1016 which can be used to deduce that two registers with unknown values
1020 record_base_value (regno, val, invariant)
1025 if (regno >= reg_base_value_size)
1028 if (invariant && alias_invariant)
1029 alias_invariant[regno] = val;
1031 if (GET_CODE (val) == REG)
1033 if (REGNO (val) < reg_base_value_size)
1034 reg_base_value[regno] = reg_base_value[REGNO (val)];
1039 reg_base_value[regno] = find_base_value (val);
1042 /* Clear alias info for a register. This is used if an RTL transformation
1043 changes the value of a register. This is used in flow by AUTO_INC_DEC
1044 optimizations. We don't need to clear reg_base_value, since flow only
1045 changes the offset. */
1048 clear_reg_alias_info (reg)
1051 unsigned int regno = REGNO (reg);
1053 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1054 reg_known_value[regno] = reg;
1057 /* Returns a canonical version of X, from the point of view alias
1058 analysis. (For example, if X is a MEM whose address is a register,
1059 and the register has a known value (say a SYMBOL_REF), then a MEM
1060 whose address is the SYMBOL_REF is returned.) */
1066 /* Recursively look for equivalences. */
1067 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1068 && REGNO (x) < reg_known_value_size)
1069 return reg_known_value[REGNO (x)] == x
1070 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1071 else if (GET_CODE (x) == PLUS)
1073 rtx x0 = canon_rtx (XEXP (x, 0));
1074 rtx x1 = canon_rtx (XEXP (x, 1));
1076 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1078 if (GET_CODE (x0) == CONST_INT)
1079 return plus_constant (x1, INTVAL (x0));
1080 else if (GET_CODE (x1) == CONST_INT)
1081 return plus_constant (x0, INTVAL (x1));
1082 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1086 /* This gives us much better alias analysis when called from
1087 the loop optimizer. Note we want to leave the original
1088 MEM alone, but need to return the canonicalized MEM with
1089 all the flags with their original values. */
1090 else if (GET_CODE (x) == MEM)
1091 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1096 /* Return 1 if X and Y are identical-looking rtx's.
1098 We use the data in reg_known_value above to see if two registers with
1099 different numbers are, in fact, equivalent. */
1102 rtx_equal_for_memref_p (x, y)
1110 if (x == 0 && y == 0)
1112 if (x == 0 || y == 0)
1121 code = GET_CODE (x);
1122 /* Rtx's of different codes cannot be equal. */
1123 if (code != GET_CODE (y))
1126 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1127 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1129 if (GET_MODE (x) != GET_MODE (y))
1132 /* Some RTL can be compared without a recursive examination. */
1136 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1139 return REGNO (x) == REGNO (y);
1142 return XEXP (x, 0) == XEXP (y, 0);
1145 return XSTR (x, 0) == XSTR (y, 0);
1149 /* There's no need to compare the contents of CONST_DOUBLEs or
1150 CONST_INTs because pointer equality is a good enough
1151 comparison for these nodes. */
1155 return (XINT (x, 1) == XINT (y, 1)
1156 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1162 /* For commutative operations, the RTX match if the operand match in any
1163 order. Also handle the simple binary and unary cases without a loop. */
1164 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1165 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1166 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1167 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1168 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1169 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
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 else if (GET_RTX_CLASS (code) == '1')
1173 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1175 /* Compare the elements. If any pair of corresponding elements
1176 fail to match, return 0 for the whole things.
1178 Limit cases to types which actually appear in addresses. */
1180 fmt = GET_RTX_FORMAT (code);
1181 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1186 if (XINT (x, i) != XINT (y, i))
1191 /* Two vectors must have the same length. */
1192 if (XVECLEN (x, i) != XVECLEN (y, i))
1195 /* And the corresponding elements must match. */
1196 for (j = 0; j < XVECLEN (x, i); j++)
1197 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1198 XVECEXP (y, i, j)) == 0)
1203 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1207 /* This can happen for asm operands. */
1209 if (strcmp (XSTR (x, i), XSTR (y, i)))
1213 /* This can happen for an asm which clobbers memory. */
1217 /* It is believed that rtx's at this level will never
1218 contain anything but integers and other rtx's,
1219 except for within LABEL_REFs and SYMBOL_REFs. */
1227 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1228 X and return it, or return 0 if none found. */
1231 find_symbolic_term (x)
1238 code = GET_CODE (x);
1239 if (code == SYMBOL_REF || code == LABEL_REF)
1241 if (GET_RTX_CLASS (code) == 'o')
1244 fmt = GET_RTX_FORMAT (code);
1245 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1251 t = find_symbolic_term (XEXP (x, i));
1255 else if (fmt[i] == 'E')
1266 struct elt_loc_list *l;
1268 #if defined (FIND_BASE_TERM)
1269 /* Try machine-dependent ways to find the base term. */
1270 x = FIND_BASE_TERM (x);
1273 switch (GET_CODE (x))
1276 return REG_BASE_VALUE (x);
1279 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1289 return find_base_term (XEXP (x, 0));
1292 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1294 rtx temp = find_base_term (XEXP (x, 0));
1296 #ifdef POINTERS_EXTEND_UNSIGNED
1297 if (temp != 0 && CONSTANT_P (temp) && GET_MODE (temp) != Pmode)
1298 temp = convert_memory_address (Pmode, temp);
1305 val = CSELIB_VAL_PTR (x);
1306 for (l = val->locs; l; l = l->next)
1307 if ((x = find_base_term (l->loc)) != 0)
1313 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1320 rtx tmp1 = XEXP (x, 0);
1321 rtx tmp2 = XEXP (x, 1);
1323 /* This is a little bit tricky since we have to determine which of
1324 the two operands represents the real base address. Otherwise this
1325 routine may return the index register instead of the base register.
1327 That may cause us to believe no aliasing was possible, when in
1328 fact aliasing is possible.
1330 We use a few simple tests to guess the base register. Additional
1331 tests can certainly be added. For example, if one of the operands
1332 is a shift or multiply, then it must be the index register and the
1333 other operand is the base register. */
1335 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1336 return find_base_term (tmp2);
1338 /* If either operand is known to be a pointer, then use it
1339 to determine the base term. */
1340 if (REG_P (tmp1) && REG_POINTER (tmp1))
1341 return find_base_term (tmp1);
1343 if (REG_P (tmp2) && REG_POINTER (tmp2))
1344 return find_base_term (tmp2);
1346 /* Neither operand was known to be a pointer. Go ahead and find the
1347 base term for both operands. */
1348 tmp1 = find_base_term (tmp1);
1349 tmp2 = find_base_term (tmp2);
1351 /* If either base term is named object or a special address
1352 (like an argument or stack reference), then use it for the
1355 && (GET_CODE (tmp1) == SYMBOL_REF
1356 || GET_CODE (tmp1) == LABEL_REF
1357 || (GET_CODE (tmp1) == ADDRESS
1358 && GET_MODE (tmp1) != VOIDmode)))
1362 && (GET_CODE (tmp2) == SYMBOL_REF
1363 || GET_CODE (tmp2) == LABEL_REF
1364 || (GET_CODE (tmp2) == ADDRESS
1365 && GET_MODE (tmp2) != VOIDmode)))
1368 /* We could not determine which of the two operands was the
1369 base register and which was the index. So we can determine
1370 nothing from the base alias check. */
1375 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1376 return find_base_term (XEXP (x, 0));
1384 return REG_BASE_VALUE (frame_pointer_rtx);
1391 /* Return 0 if the addresses X and Y are known to point to different
1392 objects, 1 if they might be pointers to the same object. */
1395 base_alias_check (x, y, x_mode, y_mode)
1397 enum machine_mode x_mode, y_mode;
1399 rtx x_base = find_base_term (x);
1400 rtx y_base = find_base_term (y);
1402 /* If the address itself has no known base see if a known equivalent
1403 value has one. If either address still has no known base, nothing
1404 is known about aliasing. */
1409 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1412 x_base = find_base_term (x_c);
1420 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1423 y_base = find_base_term (y_c);
1428 /* If the base addresses are equal nothing is known about aliasing. */
1429 if (rtx_equal_p (x_base, y_base))
1432 /* The base addresses of the read and write are different expressions.
1433 If they are both symbols and they are not accessed via AND, there is
1434 no conflict. We can bring knowledge of object alignment into play
1435 here. For example, on alpha, "char a, b;" can alias one another,
1436 though "char a; long b;" cannot. */
1437 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1439 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1441 if (GET_CODE (x) == AND
1442 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1443 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1445 if (GET_CODE (y) == AND
1446 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1447 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1449 /* Differing symbols never alias. */
1453 /* If one address is a stack reference there can be no alias:
1454 stack references using different base registers do not alias,
1455 a stack reference can not alias a parameter, and a stack reference
1456 can not alias a global. */
1457 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1458 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1461 if (! flag_argument_noalias)
1464 if (flag_argument_noalias > 1)
1467 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1468 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1471 /* Convert the address X into something we can use. This is done by returning
1472 it unchanged unless it is a value; in the latter case we call cselib to get
1473 a more useful rtx. */
1480 struct elt_loc_list *l;
1482 if (GET_CODE (x) != VALUE)
1484 v = CSELIB_VAL_PTR (x);
1485 for (l = v->locs; l; l = l->next)
1486 if (CONSTANT_P (l->loc))
1488 for (l = v->locs; l; l = l->next)
1489 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1492 return v->locs->loc;
1496 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1497 where SIZE is the size in bytes of the memory reference. If ADDR
1498 is not modified by the memory reference then ADDR is returned. */
1501 addr_side_effect_eval (addr, size, n_refs)
1508 switch (GET_CODE (addr))
1511 offset = (n_refs + 1) * size;
1514 offset = -(n_refs + 1) * size;
1517 offset = n_refs * size;
1520 offset = -n_refs * size;
1528 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1530 addr = XEXP (addr, 0);
1535 /* Return nonzero if X and Y (memory addresses) could reference the
1536 same location in memory. C is an offset accumulator. When
1537 C is nonzero, we are testing aliases between X and Y + C.
1538 XSIZE is the size in bytes of the X reference,
1539 similarly YSIZE is the size in bytes for Y.
1541 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1542 referenced (the reference was BLKmode), so make the most pessimistic
1545 If XSIZE or YSIZE is negative, we may access memory outside the object
1546 being referenced as a side effect. This can happen when using AND to
1547 align memory references, as is done on the Alpha.
1549 Nice to notice that varying addresses cannot conflict with fp if no
1550 local variables had their addresses taken, but that's too hard now. */
1553 memrefs_conflict_p (xsize, x, ysize, y, c)
1558 if (GET_CODE (x) == VALUE)
1560 if (GET_CODE (y) == VALUE)
1562 if (GET_CODE (x) == HIGH)
1564 else if (GET_CODE (x) == LO_SUM)
1567 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1568 if (GET_CODE (y) == HIGH)
1570 else if (GET_CODE (y) == LO_SUM)
1573 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1575 if (rtx_equal_for_memref_p (x, y))
1577 if (xsize <= 0 || ysize <= 0)
1579 if (c >= 0 && xsize > c)
1581 if (c < 0 && ysize+c > 0)
1586 /* This code used to check for conflicts involving stack references and
1587 globals but the base address alias code now handles these cases. */
1589 if (GET_CODE (x) == PLUS)
1591 /* The fact that X is canonicalized means that this
1592 PLUS rtx is canonicalized. */
1593 rtx x0 = XEXP (x, 0);
1594 rtx x1 = XEXP (x, 1);
1596 if (GET_CODE (y) == PLUS)
1598 /* The fact that Y is canonicalized means that this
1599 PLUS rtx is canonicalized. */
1600 rtx y0 = XEXP (y, 0);
1601 rtx y1 = XEXP (y, 1);
1603 if (rtx_equal_for_memref_p (x1, y1))
1604 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1605 if (rtx_equal_for_memref_p (x0, y0))
1606 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1607 if (GET_CODE (x1) == CONST_INT)
1609 if (GET_CODE (y1) == CONST_INT)
1610 return memrefs_conflict_p (xsize, x0, ysize, y0,
1611 c - INTVAL (x1) + INTVAL (y1));
1613 return memrefs_conflict_p (xsize, x0, ysize, y,
1616 else if (GET_CODE (y1) == CONST_INT)
1617 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1621 else if (GET_CODE (x1) == CONST_INT)
1622 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1624 else if (GET_CODE (y) == PLUS)
1626 /* The fact that Y is canonicalized means that this
1627 PLUS rtx is canonicalized. */
1628 rtx y0 = XEXP (y, 0);
1629 rtx y1 = XEXP (y, 1);
1631 if (GET_CODE (y1) == CONST_INT)
1632 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1637 if (GET_CODE (x) == GET_CODE (y))
1638 switch (GET_CODE (x))
1642 /* Handle cases where we expect the second operands to be the
1643 same, and check only whether the first operand would conflict
1646 rtx x1 = canon_rtx (XEXP (x, 1));
1647 rtx y1 = canon_rtx (XEXP (y, 1));
1648 if (! rtx_equal_for_memref_p (x1, y1))
1650 x0 = canon_rtx (XEXP (x, 0));
1651 y0 = canon_rtx (XEXP (y, 0));
1652 if (rtx_equal_for_memref_p (x0, y0))
1653 return (xsize == 0 || ysize == 0
1654 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1656 /* Can't properly adjust our sizes. */
1657 if (GET_CODE (x1) != CONST_INT)
1659 xsize /= INTVAL (x1);
1660 ysize /= INTVAL (x1);
1662 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1666 /* Are these registers known not to be equal? */
1667 if (alias_invariant)
1669 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1670 rtx i_x, i_y; /* invariant relationships of X and Y */
1672 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1673 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1675 if (i_x == 0 && i_y == 0)
1678 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1679 ysize, i_y ? i_y : y, c))
1688 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1689 as an access with indeterminate size. Assume that references
1690 besides AND are aligned, so if the size of the other reference is
1691 at least as large as the alignment, assume no other overlap. */
1692 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1694 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1696 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1698 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1700 /* ??? If we are indexing far enough into the array/structure, we
1701 may yet be able to determine that we can not overlap. But we
1702 also need to that we are far enough from the end not to overlap
1703 a following reference, so we do nothing with that for now. */
1704 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1706 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1709 if (GET_CODE (x) == ADDRESSOF)
1711 if (y == frame_pointer_rtx
1712 || GET_CODE (y) == ADDRESSOF)
1713 return xsize <= 0 || ysize <= 0;
1715 if (GET_CODE (y) == ADDRESSOF)
1717 if (x == frame_pointer_rtx)
1718 return xsize <= 0 || ysize <= 0;
1723 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1725 c += (INTVAL (y) - INTVAL (x));
1726 return (xsize <= 0 || ysize <= 0
1727 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1730 if (GET_CODE (x) == CONST)
1732 if (GET_CODE (y) == CONST)
1733 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1734 ysize, canon_rtx (XEXP (y, 0)), c);
1736 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1739 if (GET_CODE (y) == CONST)
1740 return memrefs_conflict_p (xsize, x, ysize,
1741 canon_rtx (XEXP (y, 0)), c);
1744 return (xsize <= 0 || ysize <= 0
1745 || (rtx_equal_for_memref_p (x, y)
1746 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1753 /* Functions to compute memory dependencies.
1755 Since we process the insns in execution order, we can build tables
1756 to keep track of what registers are fixed (and not aliased), what registers
1757 are varying in known ways, and what registers are varying in unknown
1760 If both memory references are volatile, then there must always be a
1761 dependence between the two references, since their order can not be
1762 changed. A volatile and non-volatile reference can be interchanged
1765 A MEM_IN_STRUCT reference at a non-AND varying address can never
1766 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1767 also must allow AND addresses, because they may generate accesses
1768 outside the object being referenced. This is used to generate
1769 aligned addresses from unaligned addresses, for instance, the alpha
1770 storeqi_unaligned pattern. */
1772 /* Read dependence: X is read after read in MEM takes place. There can
1773 only be a dependence here if both reads are volatile. */
1776 read_dependence (mem, x)
1780 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1783 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1784 MEM2 is a reference to a structure at a varying address, or returns
1785 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1786 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1787 to decide whether or not an address may vary; it should return
1788 nonzero whenever variation is possible.
1789 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1792 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1794 rtx mem1_addr, mem2_addr;
1795 int (*varies_p) PARAMS ((rtx, int));
1797 if (! flag_strict_aliasing)
1800 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1801 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1802 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1806 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1807 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1808 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1815 /* Returns nonzero if something about the mode or address format MEM1
1816 indicates that it might well alias *anything*. */
1819 aliases_everything_p (mem)
1822 if (GET_CODE (XEXP (mem, 0)) == AND)
1823 /* If the address is an AND, its very hard to know at what it is
1824 actually pointing. */
1830 /* Return true if we can determine that the fields referenced cannot
1831 overlap for any pair of objects. */
1834 nonoverlapping_component_refs_p (x, y)
1837 tree fieldx, fieldy, typex, typey, orig_y;
1841 /* The comparison has to be done at a common type, since we don't
1842 know how the inheritance hierarchy works. */
1846 fieldx = TREE_OPERAND (x, 1);
1847 typex = DECL_FIELD_CONTEXT (fieldx);
1852 fieldy = TREE_OPERAND (y, 1);
1853 typey = DECL_FIELD_CONTEXT (fieldy);
1858 y = TREE_OPERAND (y, 0);
1860 while (y && TREE_CODE (y) == COMPONENT_REF);
1862 x = TREE_OPERAND (x, 0);
1864 while (x && TREE_CODE (x) == COMPONENT_REF);
1866 /* Never found a common type. */
1870 /* If we're left with accessing different fields of a structure,
1872 if (TREE_CODE (typex) == RECORD_TYPE
1873 && fieldx != fieldy)
1876 /* The comparison on the current field failed. If we're accessing
1877 a very nested structure, look at the next outer level. */
1878 x = TREE_OPERAND (x, 0);
1879 y = TREE_OPERAND (y, 0);
1882 && TREE_CODE (x) == COMPONENT_REF
1883 && TREE_CODE (y) == COMPONENT_REF);
1888 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1891 decl_for_component_ref (x)
1896 x = TREE_OPERAND (x, 0);
1898 while (x && TREE_CODE (x) == COMPONENT_REF);
1900 return x && DECL_P (x) ? x : NULL_TREE;
1903 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1904 offset of the field reference. */
1907 adjust_offset_for_component_ref (x, offset)
1911 HOST_WIDE_INT ioffset;
1916 ioffset = INTVAL (offset);
1919 tree field = TREE_OPERAND (x, 1);
1921 if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
1923 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
1924 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1927 x = TREE_OPERAND (x, 0);
1929 while (x && TREE_CODE (x) == COMPONENT_REF);
1931 return GEN_INT (ioffset);
1934 /* Return nonzero if we can deterimine the exprs corresponding to memrefs
1935 X and Y and they do not overlap. */
1938 nonoverlapping_memrefs_p (x, y)
1941 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1944 rtx moffsetx, moffsety;
1945 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1947 /* Unless both have exprs, we can't tell anything. */
1948 if (exprx == 0 || expry == 0)
1951 /* If both are field references, we may be able to determine something. */
1952 if (TREE_CODE (exprx) == COMPONENT_REF
1953 && TREE_CODE (expry) == COMPONENT_REF
1954 && nonoverlapping_component_refs_p (exprx, expry))
1957 /* If the field reference test failed, look at the DECLs involved. */
1958 moffsetx = MEM_OFFSET (x);
1959 if (TREE_CODE (exprx) == COMPONENT_REF)
1961 tree t = decl_for_component_ref (exprx);
1964 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
1967 else if (TREE_CODE (exprx) == INDIRECT_REF)
1969 exprx = TREE_OPERAND (exprx, 0);
1970 if (flag_argument_noalias < 2
1971 || TREE_CODE (exprx) != PARM_DECL)
1975 moffsety = MEM_OFFSET (y);
1976 if (TREE_CODE (expry) == COMPONENT_REF)
1978 tree t = decl_for_component_ref (expry);
1981 moffsety = adjust_offset_for_component_ref (expry, moffsety);
1984 else if (TREE_CODE (expry) == INDIRECT_REF)
1986 expry = TREE_OPERAND (expry, 0);
1987 if (flag_argument_noalias < 2
1988 || TREE_CODE (expry) != PARM_DECL)
1992 if (! DECL_P (exprx) || ! DECL_P (expry))
1995 rtlx = DECL_RTL (exprx);
1996 rtly = DECL_RTL (expry);
1998 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
1999 can't overlap unless they are the same because we never reuse that part
2000 of the stack frame used for locals for spilled pseudos. */
2001 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
2002 && ! rtx_equal_p (rtlx, rtly))
2005 /* Get the base and offsets of both decls. If either is a register, we
2006 know both are and are the same, so use that as the base. The only
2007 we can avoid overlap is if we can deduce that they are nonoverlapping
2008 pieces of that decl, which is very rare. */
2009 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
2010 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
2011 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
2013 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
2014 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
2015 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
2017 /* If the bases are different, we know they do not overlap if both
2018 are constants or if one is a constant and the other a pointer into the
2019 stack frame. Otherwise a different base means we can't tell if they
2021 if (! rtx_equal_p (basex, basey))
2022 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
2023 || (CONSTANT_P (basex) && REG_P (basey)
2024 && REGNO_PTR_FRAME_P (REGNO (basey)))
2025 || (CONSTANT_P (basey) && REG_P (basex)
2026 && REGNO_PTR_FRAME_P (REGNO (basex))));
2028 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
2029 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
2031 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
2032 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
2035 /* If we have an offset for either memref, it can update the values computed
2038 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
2040 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2042 /* If a memref has both a size and an offset, we can use the smaller size.
2043 We can't do this if the offset isn't known because we must view this
2044 memref as being anywhere inside the DECL's MEM. */
2045 if (MEM_SIZE (x) && moffsetx)
2046 sizex = INTVAL (MEM_SIZE (x));
2047 if (MEM_SIZE (y) && moffsety)
2048 sizey = INTVAL (MEM_SIZE (y));
2050 /* Put the values of the memref with the lower offset in X's values. */
2051 if (offsetx > offsety)
2053 tem = offsetx, offsetx = offsety, offsety = tem;
2054 tem = sizex, sizex = sizey, sizey = tem;
2057 /* If we don't know the size of the lower-offset value, we can't tell
2058 if they conflict. Otherwise, we do the test. */
2059 return sizex >= 0 && offsety >= offsetx + sizex;
2062 /* True dependence: X is read after store in MEM takes place. */
2065 true_dependence (mem, mem_mode, x, varies)
2067 enum machine_mode mem_mode;
2069 int (*varies) PARAMS ((rtx, int));
2071 rtx x_addr, mem_addr;
2074 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2077 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2078 This is used in epilogue deallocation functions. */
2079 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2081 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2084 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2087 /* Unchanging memory can't conflict with non-unchanging memory.
2088 A non-unchanging read can conflict with a non-unchanging write.
2089 An unchanging read can conflict with an unchanging write since
2090 there may be a single store to this address to initialize it.
2091 Note that an unchanging store can conflict with a non-unchanging read
2092 since we have to make conservative assumptions when we have a
2093 record with readonly fields and we are copying the whole thing.
2094 Just fall through to the code below to resolve potential conflicts.
2095 This won't handle all cases optimally, but the possible performance
2096 loss should be negligible. */
2097 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2100 if (nonoverlapping_memrefs_p (mem, x))
2103 if (mem_mode == VOIDmode)
2104 mem_mode = GET_MODE (mem);
2106 x_addr = get_addr (XEXP (x, 0));
2107 mem_addr = get_addr (XEXP (mem, 0));
2109 base = find_base_term (x_addr);
2110 if (base && (GET_CODE (base) == LABEL_REF
2111 || (GET_CODE (base) == SYMBOL_REF
2112 && CONSTANT_POOL_ADDRESS_P (base))))
2115 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2118 x_addr = canon_rtx (x_addr);
2119 mem_addr = canon_rtx (mem_addr);
2121 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2122 SIZE_FOR_MODE (x), x_addr, 0))
2125 if (aliases_everything_p (x))
2128 /* We cannot use aliases_everything_p to test MEM, since we must look
2129 at MEM_MODE, rather than GET_MODE (MEM). */
2130 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2133 /* In true_dependence we also allow BLKmode to alias anything. Why
2134 don't we do this in anti_dependence and output_dependence? */
2135 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2138 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2142 /* Canonical true dependence: X is read after store in MEM takes place.
2143 Variant of true_dependence which assumes MEM has already been
2144 canonicalized (hence we no longer do that here).
2145 The mem_addr argument has been added, since true_dependence computed
2146 this value prior to canonicalizing. */
2149 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
2150 rtx mem, mem_addr, x;
2151 enum machine_mode mem_mode;
2152 int (*varies) PARAMS ((rtx, int));
2156 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2159 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2160 This is used in epilogue deallocation functions. */
2161 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2163 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2166 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2169 /* If X is an unchanging read, then it can't possibly conflict with any
2170 non-unchanging store. It may conflict with an unchanging write though,
2171 because there may be a single store to this address to initialize it.
2172 Just fall through to the code below to resolve the case where we have
2173 both an unchanging read and an unchanging write. This won't handle all
2174 cases optimally, but the possible performance loss should be
2176 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2179 if (nonoverlapping_memrefs_p (x, mem))
2182 x_addr = get_addr (XEXP (x, 0));
2184 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2187 x_addr = canon_rtx (x_addr);
2188 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2189 SIZE_FOR_MODE (x), x_addr, 0))
2192 if (aliases_everything_p (x))
2195 /* We cannot use aliases_everything_p to test MEM, since we must look
2196 at MEM_MODE, rather than GET_MODE (MEM). */
2197 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2200 /* In true_dependence we also allow BLKmode to alias anything. Why
2201 don't we do this in anti_dependence and output_dependence? */
2202 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2205 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2209 /* Returns nonzero if a write to X might alias a previous read from
2210 (or, if WRITEP is nonzero, a write to) MEM. */
2213 write_dependence_p (mem, x, writep)
2218 rtx x_addr, mem_addr;
2222 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2225 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2226 This is used in epilogue deallocation functions. */
2227 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
2229 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
2232 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2235 /* Unchanging memory can't conflict with non-unchanging memory. */
2236 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
2239 /* If MEM is an unchanging read, then it can't possibly conflict with
2240 the store to X, because there is at most one store to MEM, and it must
2241 have occurred somewhere before MEM. */
2242 if (! writep && RTX_UNCHANGING_P (mem))
2245 if (nonoverlapping_memrefs_p (x, mem))
2248 x_addr = get_addr (XEXP (x, 0));
2249 mem_addr = get_addr (XEXP (mem, 0));
2253 base = find_base_term (mem_addr);
2254 if (base && (GET_CODE (base) == LABEL_REF
2255 || (GET_CODE (base) == SYMBOL_REF
2256 && CONSTANT_POOL_ADDRESS_P (base))))
2260 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2264 x_addr = canon_rtx (x_addr);
2265 mem_addr = canon_rtx (mem_addr);
2267 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2268 SIZE_FOR_MODE (x), x_addr, 0))
2272 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2275 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2276 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2279 /* Anti dependence: X is written after read in MEM takes place. */
2282 anti_dependence (mem, x)
2286 return write_dependence_p (mem, x, /*writep=*/0);
2289 /* Output dependence: X is written after store in MEM takes place. */
2292 output_dependence (mem, x)
2296 return write_dependence_p (mem, x, /*writep=*/1);
2299 /* A subroutine of nonlocal_mentioned_p, returns 1 if *LOC mentions
2300 something which is not local to the function and is not constant. */
2303 nonlocal_mentioned_p_1 (loc, data)
2305 void *data ATTRIBUTE_UNUSED;
2314 switch (GET_CODE (x))
2317 if (GET_CODE (SUBREG_REG (x)) == REG)
2319 /* Global registers are not local. */
2320 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2321 && global_regs[subreg_regno (x)])
2329 /* Global registers are not local. */
2330 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2345 /* Constants in the function's constants pool are constant. */
2346 if (CONSTANT_POOL_ADDRESS_P (x))
2351 /* Non-constant calls and recursion are not local. */
2355 /* Be overly conservative and consider any volatile memory
2356 reference as not local. */
2357 if (MEM_VOLATILE_P (x))
2359 base = find_base_term (XEXP (x, 0));
2362 /* A Pmode ADDRESS could be a reference via the structure value
2363 address or static chain. Such memory references are nonlocal.
2365 Thus, we have to examine the contents of the ADDRESS to find
2366 out if this is a local reference or not. */
2367 if (GET_CODE (base) == ADDRESS
2368 && GET_MODE (base) == Pmode
2369 && (XEXP (base, 0) == stack_pointer_rtx
2370 || XEXP (base, 0) == arg_pointer_rtx
2371 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2372 || XEXP (base, 0) == hard_frame_pointer_rtx
2374 || XEXP (base, 0) == frame_pointer_rtx))
2376 /* Constants in the function's constant pool are constant. */
2377 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2382 case UNSPEC_VOLATILE:
2387 if (MEM_VOLATILE_P (x))
2399 /* Returns nonzero if X might mention something which is not
2400 local to the function and is not constant. */
2403 nonlocal_mentioned_p (x)
2409 if (GET_CODE (x) == CALL_INSN)
2411 if (! CONST_OR_PURE_CALL_P (x))
2413 x = CALL_INSN_FUNCTION_USAGE (x);
2421 return for_each_rtx (&x, nonlocal_mentioned_p_1, NULL);
2424 /* A subroutine of nonlocal_referenced_p, returns 1 if *LOC references
2425 something which is not local to the function and is not constant. */
2428 nonlocal_referenced_p_1 (loc, data)
2430 void *data ATTRIBUTE_UNUSED;
2437 switch (GET_CODE (x))
2443 return nonlocal_mentioned_p (x);
2446 /* Non-constant calls and recursion are not local. */
2450 if (nonlocal_mentioned_p (SET_SRC (x)))
2453 if (GET_CODE (SET_DEST (x)) == MEM)
2454 return nonlocal_mentioned_p (XEXP (SET_DEST (x), 0));
2456 /* If the destination is anything other than a CC0, PC,
2457 MEM, REG, or a SUBREG of a REG that occupies all of
2458 the REG, then X references nonlocal memory if it is
2459 mentioned in the destination. */
2460 if (GET_CODE (SET_DEST (x)) != CC0
2461 && GET_CODE (SET_DEST (x)) != PC
2462 && GET_CODE (SET_DEST (x)) != REG
2463 && ! (GET_CODE (SET_DEST (x)) == SUBREG
2464 && GET_CODE (SUBREG_REG (SET_DEST (x))) == REG
2465 && (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (x))))
2466 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD)
2467 == ((GET_MODE_SIZE (GET_MODE (SET_DEST (x)))
2468 + (UNITS_PER_WORD - 1)) / UNITS_PER_WORD))))
2469 return nonlocal_mentioned_p (SET_DEST (x));
2473 if (GET_CODE (XEXP (x, 0)) == MEM)
2474 return nonlocal_mentioned_p (XEXP (XEXP (x, 0), 0));
2478 return nonlocal_mentioned_p (XEXP (x, 0));
2481 case UNSPEC_VOLATILE:
2485 if (MEM_VOLATILE_P (x))
2497 /* Returns nonzero if X might reference something which is not
2498 local to the function and is not constant. */
2501 nonlocal_referenced_p (x)
2507 if (GET_CODE (x) == CALL_INSN)
2509 if (! CONST_OR_PURE_CALL_P (x))
2511 x = CALL_INSN_FUNCTION_USAGE (x);
2519 return for_each_rtx (&x, nonlocal_referenced_p_1, NULL);
2522 /* A subroutine of nonlocal_set_p, returns 1 if *LOC sets
2523 something which is not local to the function and is not constant. */
2526 nonlocal_set_p_1 (loc, data)
2528 void *data ATTRIBUTE_UNUSED;
2535 switch (GET_CODE (x))
2538 /* Non-constant calls and recursion are not local. */
2547 return nonlocal_mentioned_p (XEXP (x, 0));
2550 if (nonlocal_mentioned_p (SET_DEST (x)))
2552 return nonlocal_set_p (SET_SRC (x));
2555 return nonlocal_mentioned_p (XEXP (x, 0));
2561 case UNSPEC_VOLATILE:
2565 if (MEM_VOLATILE_P (x))
2577 /* Returns nonzero if X might set something which is not
2578 local to the function and is not constant. */
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 constant. */
2605 mark_constant_function ()
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 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode
2614 || current_function_has_nonlocal_goto
2615 || !(*targetm.binds_local_p) (current_function_decl))
2618 /* A loop might not return which counts as a side effect. */
2619 if (mark_dfs_back_edges ())
2622 nonlocal_memory_referenced = 0;
2624 init_alias_analysis ();
2626 /* Determine if this is a constant or pure function. */
2628 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2630 if (! INSN_P (insn))
2633 if (nonlocal_set_p (insn) || global_reg_mentioned_p (insn)
2634 || volatile_refs_p (PATTERN (insn)))
2637 if (! nonlocal_memory_referenced)
2638 nonlocal_memory_referenced = nonlocal_referenced_p (insn);
2641 end_alias_analysis ();
2643 /* Mark the function. */
2647 else if (nonlocal_memory_referenced)
2648 DECL_IS_PURE (current_function_decl) = 1;
2650 TREE_READONLY (current_function_decl) = 1;
2659 #ifndef OUTGOING_REGNO
2660 #define OUTGOING_REGNO(N) N
2662 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2663 /* Check whether this register can hold an incoming pointer
2664 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2665 numbers, so translate if necessary due to register windows. */
2666 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2667 && HARD_REGNO_MODE_OK (i, Pmode))
2668 static_reg_base_value[i]
2669 = gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));
2671 static_reg_base_value[STACK_POINTER_REGNUM]
2672 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2673 static_reg_base_value[ARG_POINTER_REGNUM]
2674 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2675 static_reg_base_value[FRAME_POINTER_REGNUM]
2676 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2677 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2678 static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2679 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2682 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2685 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2689 init_alias_analysis ()
2691 int maxreg = max_reg_num ();
2697 reg_known_value_size = maxreg;
2700 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2701 - FIRST_PSEUDO_REGISTER;
2703 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2704 - FIRST_PSEUDO_REGISTER;
2706 /* Overallocate reg_base_value to allow some growth during loop
2707 optimization. Loop unrolling can create a large number of
2709 reg_base_value_size = maxreg * 2;
2710 reg_base_value = (rtx *) ggc_alloc_cleared (reg_base_value_size
2713 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2714 reg_seen = (char *) xmalloc (reg_base_value_size);
2715 if (! reload_completed && flag_unroll_loops)
2717 /* ??? Why are we realloc'ing if we're just going to zero it? */
2718 alias_invariant = (rtx *)xrealloc (alias_invariant,
2719 reg_base_value_size * sizeof (rtx));
2720 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2723 /* The basic idea is that each pass through this loop will use the
2724 "constant" information from the previous pass to propagate alias
2725 information through another level of assignments.
2727 This could get expensive if the assignment chains are long. Maybe
2728 we should throttle the number of iterations, possibly based on
2729 the optimization level or flag_expensive_optimizations.
2731 We could propagate more information in the first pass by making use
2732 of REG_N_SETS to determine immediately that the alias information
2733 for a pseudo is "constant".
2735 A program with an uninitialized variable can cause an infinite loop
2736 here. Instead of doing a full dataflow analysis to detect such problems
2737 we just cap the number of iterations for the loop.
2739 The state of the arrays for the set chain in question does not matter
2740 since the program has undefined behavior. */
2745 /* Assume nothing will change this iteration of the loop. */
2748 /* We want to assign the same IDs each iteration of this loop, so
2749 start counting from zero each iteration of the loop. */
2752 /* We're at the start of the function each iteration through the
2753 loop, so we're copying arguments. */
2754 copying_arguments = true;
2756 /* Wipe the potential alias information clean for this pass. */
2757 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2759 /* Wipe the reg_seen array clean. */
2760 memset ((char *) reg_seen, 0, reg_base_value_size);
2762 /* Mark all hard registers which may contain an address.
2763 The stack, frame and argument pointers may contain an address.
2764 An argument register which can hold a Pmode value may contain
2765 an address even if it is not in BASE_REGS.
2767 The address expression is VOIDmode for an argument and
2768 Pmode for other registers. */
2770 memcpy (new_reg_base_value, static_reg_base_value,
2771 FIRST_PSEUDO_REGISTER * sizeof (rtx));
2773 /* Walk the insns adding values to the new_reg_base_value array. */
2774 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2780 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2781 /* The prologue/epilogue insns are not threaded onto the
2782 insn chain until after reload has completed. Thus,
2783 there is no sense wasting time checking if INSN is in
2784 the prologue/epilogue until after reload has completed. */
2785 if (reload_completed
2786 && prologue_epilogue_contains (insn))
2790 /* If this insn has a noalias note, process it, Otherwise,
2791 scan for sets. A simple set will have no side effects
2792 which could change the base value of any other register. */
2794 if (GET_CODE (PATTERN (insn)) == SET
2795 && REG_NOTES (insn) != 0
2796 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2797 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2799 note_stores (PATTERN (insn), record_set, NULL);
2801 set = single_set (insn);
2804 && GET_CODE (SET_DEST (set)) == REG
2805 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2807 unsigned int regno = REGNO (SET_DEST (set));
2808 rtx src = SET_SRC (set);
2810 if (REG_NOTES (insn) != 0
2811 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2812 && REG_N_SETS (regno) == 1)
2813 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2814 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2815 && ! rtx_varies_p (XEXP (note, 0), 1)
2816 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2818 reg_known_value[regno] = XEXP (note, 0);
2819 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2821 else if (REG_N_SETS (regno) == 1
2822 && GET_CODE (src) == PLUS
2823 && GET_CODE (XEXP (src, 0)) == REG
2824 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2825 && (reg_known_value[REGNO (XEXP (src, 0))])
2826 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2828 rtx op0 = XEXP (src, 0);
2829 op0 = reg_known_value[REGNO (op0)];
2830 reg_known_value[regno]
2831 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2832 reg_known_equiv_p[regno] = 0;
2834 else if (REG_N_SETS (regno) == 1
2835 && ! rtx_varies_p (src, 1))
2837 reg_known_value[regno] = src;
2838 reg_known_equiv_p[regno] = 0;
2842 else if (GET_CODE (insn) == NOTE
2843 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2844 copying_arguments = false;
2847 /* Now propagate values from new_reg_base_value to reg_base_value. */
2848 for (ui = 0; ui < reg_base_value_size; ui++)
2850 if (new_reg_base_value[ui]
2851 && new_reg_base_value[ui] != reg_base_value[ui]
2852 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2854 reg_base_value[ui] = new_reg_base_value[ui];
2859 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2861 /* Fill in the remaining entries. */
2862 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2863 if (reg_known_value[i] == 0)
2864 reg_known_value[i] = regno_reg_rtx[i];
2866 /* Simplify the reg_base_value array so that no register refers to
2867 another register, except to special registers indirectly through
2868 ADDRESS expressions.
2870 In theory this loop can take as long as O(registers^2), but unless
2871 there are very long dependency chains it will run in close to linear
2874 This loop may not be needed any longer now that the main loop does
2875 a better job at propagating alias information. */
2881 for (ui = 0; ui < reg_base_value_size; ui++)
2883 rtx base = reg_base_value[ui];
2884 if (base && GET_CODE (base) == REG)
2886 unsigned int base_regno = REGNO (base);
2887 if (base_regno == ui) /* register set from itself */
2888 reg_base_value[ui] = 0;
2890 reg_base_value[ui] = reg_base_value[base_regno];
2895 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2898 free (new_reg_base_value);
2899 new_reg_base_value = 0;
2905 end_alias_analysis ()
2907 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2908 reg_known_value = 0;
2909 reg_known_value_size = 0;
2910 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2911 reg_known_equiv_p = 0;
2913 reg_base_value_size = 0;
2914 if (alias_invariant)
2916 free (alias_invariant);
2917 alias_invariant = 0;
2921 #include "gt-alias.h"