1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001 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"
40 /* The alias sets assigned to MEMs assist the back-end in determining
41 which MEMs can alias which other MEMs. In general, two MEMs in
42 different alias sets cannot alias each other, with one important
43 exception. Consider something like:
45 struct S {int i; double d; };
47 a store to an `S' can alias something of either type `int' or type
48 `double'. (However, a store to an `int' cannot alias a `double'
49 and vice versa.) We indicate this via a tree structure that looks
57 (The arrows are directed and point downwards.)
58 In this situation we say the alias set for `struct S' is the
59 `superset' and that those for `int' and `double' are `subsets'.
61 To see whether two alias sets can point to the same memory, we must
62 see if either alias set is a subset of the other. We need not trace
63 past immediate descendents, however, since we propagate all
64 grandchildren up one level.
66 Alias set zero is implicitly a superset of all other alias sets.
67 However, this is no actual entry for alias set zero. It is an
68 error to attempt to explicitly construct a subset of zero. */
70 typedef struct alias_set_entry
72 /* The alias set number, as stored in MEM_ALIAS_SET. */
73 HOST_WIDE_INT alias_set;
75 /* The children of the alias set. These are not just the immediate
76 children, but, in fact, all descendents. So, if we have:
78 struct T { struct S s; float f; }
80 continuing our example above, the children here will be all of
81 `int', `double', `float', and `struct S'. */
84 /* Nonzero if would have a child of zero: this effectively makes this
85 alias set the same as alias set zero. */
89 static int rtx_equal_for_memref_p PARAMS ((rtx, rtx));
90 static rtx find_symbolic_term PARAMS ((rtx));
91 rtx get_addr PARAMS ((rtx));
92 static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx,
94 static void record_set PARAMS ((rtx, rtx, void *));
95 static rtx find_base_term PARAMS ((rtx));
96 static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode,
98 static rtx find_base_value PARAMS ((rtx));
99 static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx));
100 static int insert_subset_children PARAMS ((splay_tree_node, void*));
101 static tree find_base_decl PARAMS ((tree));
102 static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT));
103 static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx,
104 int (*) (rtx, int)));
105 static int aliases_everything_p PARAMS ((rtx));
106 static bool nonoverlapping_component_refs_p PARAMS ((tree, tree));
107 static tree decl_for_component_ref PARAMS ((tree));
108 static rtx adjust_offset_for_component_ref PARAMS ((tree, rtx));
109 static int nonoverlapping_memrefs_p PARAMS ((rtx, rtx));
110 static int write_dependence_p PARAMS ((rtx, rtx, int));
111 static int nonlocal_mentioned_p PARAMS ((rtx));
113 /* Set up all info needed to perform alias analysis on memory references. */
115 /* Returns the size in bytes of the mode of X. */
116 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
118 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
119 different alias sets. We ignore alias sets in functions making use
120 of variable arguments because the va_arg macros on some systems are
122 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
123 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
125 /* Cap the number of passes we make over the insns propagating alias
126 information through set chains. 10 is a completely arbitrary choice. */
127 #define MAX_ALIAS_LOOP_PASSES 10
129 /* reg_base_value[N] gives an address to which register N is related.
130 If all sets after the first add or subtract to the current value
131 or otherwise modify it so it does not point to a different top level
132 object, reg_base_value[N] is equal to the address part of the source
135 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
136 expressions represent certain special values: function arguments and
137 the stack, frame, and argument pointers.
139 The contents of an ADDRESS is not normally used, the mode of the
140 ADDRESS determines whether the ADDRESS is a function argument or some
141 other special value. Pointer equality, not rtx_equal_p, determines whether
142 two ADDRESS expressions refer to the same base address.
144 The only use of the contents of an ADDRESS is for determining if the
145 current function performs nonlocal memory memory references for the
146 purposes of marking the function as a constant function. */
148 static rtx *reg_base_value;
149 static rtx *new_reg_base_value;
150 static unsigned int reg_base_value_size; /* size of reg_base_value array */
152 #define REG_BASE_VALUE(X) \
153 (REGNO (X) < reg_base_value_size \
154 ? reg_base_value[REGNO (X)] : 0)
156 /* Vector of known invariant relationships between registers. Set in
157 loop unrolling. Indexed by register number, if nonzero the value
158 is an expression describing this register in terms of another.
160 The length of this array is REG_BASE_VALUE_SIZE.
162 Because this array contains only pseudo registers it has no effect
164 static rtx *alias_invariant;
166 /* Vector indexed by N giving the initial (unchanging) value known for
167 pseudo-register N. This array is initialized in
168 init_alias_analysis, and does not change until end_alias_analysis
170 rtx *reg_known_value;
172 /* Indicates number of valid entries in reg_known_value. */
173 static unsigned int reg_known_value_size;
175 /* Vector recording for each reg_known_value whether it is due to a
176 REG_EQUIV note. Future passes (viz., reload) may replace the
177 pseudo with the equivalent expression and so we account for the
178 dependences that would be introduced if that happens.
180 The REG_EQUIV notes created in assign_parms may mention the arg
181 pointer, and there are explicit insns in the RTL that modify the
182 arg pointer. Thus we must ensure that such insns don't get
183 scheduled across each other because that would invalidate the
184 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
185 wrong, but solving the problem in the scheduler will likely give
186 better code, so we do it here. */
187 char *reg_known_equiv_p;
189 /* True when scanning insns from the start of the rtl to the
190 NOTE_INSN_FUNCTION_BEG note. */
191 static int copying_arguments;
193 /* The splay-tree used to store the various alias set entries. */
194 static splay_tree alias_sets;
196 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
197 such an entry, or NULL otherwise. */
199 static alias_set_entry
200 get_alias_set_entry (alias_set)
201 HOST_WIDE_INT alias_set;
204 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
206 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
209 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
210 the two MEMs cannot alias each other. */
213 mems_in_disjoint_alias_sets_p (mem1, mem2)
217 #ifdef ENABLE_CHECKING
218 /* Perform a basic sanity check. Namely, that there are no alias sets
219 if we're not using strict aliasing. This helps to catch bugs
220 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
221 where a MEM is allocated in some way other than by the use of
222 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
223 use alias sets to indicate that spilled registers cannot alias each
224 other, we might need to remove this check. */
225 if (! flag_strict_aliasing
226 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
230 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
233 /* Insert the NODE into the splay tree given by DATA. Used by
234 record_alias_subset via splay_tree_foreach. */
237 insert_subset_children (node, data)
238 splay_tree_node node;
241 splay_tree_insert ((splay_tree) data, node->key, node->value);
246 /* Return 1 if the two specified alias sets may conflict. */
249 alias_sets_conflict_p (set1, set2)
250 HOST_WIDE_INT set1, set2;
254 /* If have no alias set information for one of the operands, we have
255 to assume it can alias anything. */
256 if (set1 == 0 || set2 == 0
257 /* If the two alias sets are the same, they may alias. */
261 /* See if the first alias set is a subset of the second. */
262 ase = get_alias_set_entry (set1);
264 && (ase->has_zero_child
265 || splay_tree_lookup (ase->children,
266 (splay_tree_key) set2)))
269 /* Now do the same, but with the alias sets reversed. */
270 ase = get_alias_set_entry (set2);
272 && (ase->has_zero_child
273 || splay_tree_lookup (ase->children,
274 (splay_tree_key) set1)))
277 /* The two alias sets are distinct and neither one is the
278 child of the other. Therefore, they cannot alias. */
282 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
283 has any readonly fields. If any of the fields have types that
284 contain readonly fields, return true as well. */
287 readonly_fields_p (type)
292 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
293 && TREE_CODE (type) != QUAL_UNION_TYPE)
296 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
297 if (TREE_CODE (field) == FIELD_DECL
298 && (TREE_READONLY (field)
299 || readonly_fields_p (TREE_TYPE (field))))
305 /* Return 1 if any MEM object of type T1 will always conflict (using the
306 dependency routines in this file) with any MEM object of type T2.
307 This is used when allocating temporary storage. If T1 and/or T2 are
308 NULL_TREE, it means we know nothing about the storage. */
311 objects_must_conflict_p (t1, t2)
314 /* If neither has a type specified, we don't know if they'll conflict
315 because we may be using them to store objects of various types, for
316 example the argument and local variables areas of inlined functions. */
317 if (t1 == 0 && t2 == 0)
320 /* If one or the other has readonly fields or is readonly,
321 then they may not conflict. */
322 if ((t1 != 0 && readonly_fields_p (t1))
323 || (t2 != 0 && readonly_fields_p (t2))
324 || (t1 != 0 && TYPE_READONLY (t1))
325 || (t2 != 0 && TYPE_READONLY (t2)))
328 /* If they are the same type, they must conflict. */
330 /* Likewise if both are volatile. */
331 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
334 /* If one is aggregate and the other is scalar then they may not
336 if ((t1 != 0 && AGGREGATE_TYPE_P (t1))
337 != (t2 != 0 && AGGREGATE_TYPE_P (t2)))
340 /* Otherwise they conflict only if the alias sets conflict. */
341 return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0,
342 t2 ? get_alias_set (t2) : 0);
345 /* T is an expression with pointer type. Find the DECL on which this
346 expression is based. (For example, in `a[i]' this would be `a'.)
347 If there is no such DECL, or a unique decl cannot be determined,
348 NULL_TREE is returned. */
356 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
359 /* If this is a declaration, return it. */
360 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
363 /* Handle general expressions. It would be nice to deal with
364 COMPONENT_REFs here. If we could tell that `a' and `b' were the
365 same, then `a->f' and `b->f' are also the same. */
366 switch (TREE_CODE_CLASS (TREE_CODE (t)))
369 return find_base_decl (TREE_OPERAND (t, 0));
372 /* Return 0 if found in neither or both are the same. */
373 d0 = find_base_decl (TREE_OPERAND (t, 0));
374 d1 = find_base_decl (TREE_OPERAND (t, 1));
385 d0 = find_base_decl (TREE_OPERAND (t, 0));
386 d1 = find_base_decl (TREE_OPERAND (t, 1));
387 d2 = find_base_decl (TREE_OPERAND (t, 2));
389 /* Set any nonzero values from the last, then from the first. */
390 if (d1 == 0) d1 = d2;
391 if (d0 == 0) d0 = d1;
392 if (d1 == 0) d1 = d0;
393 if (d2 == 0) d2 = d1;
395 /* At this point all are nonzero or all are zero. If all three are the
396 same, return it. Otherwise, return zero. */
397 return (d0 == d1 && d1 == d2) ? d0 : 0;
404 /* Return 1 if all the nested component references handled by
405 get_inner_reference in T are such that we can address the object in T. */
411 /* If we're at the end, it is vacuously addressable. */
412 if (! handled_component_p (t))
415 /* Bitfields are never addressable. */
416 else if (TREE_CODE (t) == BIT_FIELD_REF)
419 /* Fields are addressable unless they are marked as nonaddressable or
420 the containing type has alias set 0. */
421 else if (TREE_CODE (t) == COMPONENT_REF
422 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
423 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
424 && can_address_p (TREE_OPERAND (t, 0)))
427 /* Likewise for arrays. */
428 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
429 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
430 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
431 && can_address_p (TREE_OPERAND (t, 0)))
437 /* Return the alias set for T, which may be either a type or an
438 expression. Call language-specific routine for help, if needed. */
446 /* If we're not doing any alias analysis, just assume everything
447 aliases everything else. Also return 0 if this or its type is
449 if (! flag_strict_aliasing || t == error_mark_node
451 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
454 /* We can be passed either an expression or a type. This and the
455 language-specific routine may make mutually-recursive calls to each other
456 to figure out what to do. At each juncture, we see if this is a tree
457 that the language may need to handle specially. First handle things that
462 tree placeholder_ptr = 0;
464 /* Remove any nops, then give the language a chance to do
465 something with this tree before we look at it. */
467 set = (*lang_hooks.get_alias_set) (t);
471 /* First see if the actual object referenced is an INDIRECT_REF from a
472 restrict-qualified pointer or a "void *". Replace
473 PLACEHOLDER_EXPRs. */
474 while (TREE_CODE (inner) == PLACEHOLDER_EXPR
475 || handled_component_p (inner))
477 if (TREE_CODE (inner) == PLACEHOLDER_EXPR)
478 inner = find_placeholder (inner, &placeholder_ptr);
480 inner = TREE_OPERAND (inner, 0);
485 /* Check for accesses through restrict-qualified pointers. */
486 if (TREE_CODE (inner) == INDIRECT_REF)
488 tree decl = find_base_decl (TREE_OPERAND (inner, 0));
490 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
492 /* If we haven't computed the actual alias set, do it now. */
493 if (DECL_POINTER_ALIAS_SET (decl) == -2)
495 /* No two restricted pointers can point at the same thing.
496 However, a restricted pointer can point at the same thing
497 as an unrestricted pointer, if that unrestricted pointer
498 is based on the restricted pointer. So, we make the
499 alias set for the restricted pointer a subset of the
500 alias set for the type pointed to by the type of the
502 HOST_WIDE_INT pointed_to_alias_set
503 = get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
505 if (pointed_to_alias_set == 0)
506 /* It's not legal to make a subset of alias set zero. */
510 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
511 record_alias_subset (pointed_to_alias_set,
512 DECL_POINTER_ALIAS_SET (decl));
516 /* We use the alias set indicated in the declaration. */
517 return DECL_POINTER_ALIAS_SET (decl);
520 /* If we have an INDIRECT_REF via a void pointer, we don't
521 know anything about what that might alias. */
522 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE)
526 /* Otherwise, pick up the outermost object that we could have a pointer
527 to, processing conversion and PLACEHOLDER_EXPR as above. */
529 while (TREE_CODE (t) == PLACEHOLDER_EXPR
530 || (handled_component_p (t) && ! can_address_p (t)))
532 if (TREE_CODE (t) == PLACEHOLDER_EXPR)
533 t = find_placeholder (t, &placeholder_ptr);
535 t = TREE_OPERAND (t, 0);
540 /* If we've already determined the alias set for a decl, just return
541 it. This is necessary for C++ anonymous unions, whose component
542 variables don't look like union members (boo!). */
543 if (TREE_CODE (t) == VAR_DECL
544 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
545 return MEM_ALIAS_SET (DECL_RTL (t));
547 /* Now all we care about is the type. */
551 /* Variant qualifiers don't affect the alias set, so get the main
552 variant. If this is a type with a known alias set, return it. */
553 t = TYPE_MAIN_VARIANT (t);
554 if (TYPE_ALIAS_SET_KNOWN_P (t))
555 return TYPE_ALIAS_SET (t);
557 /* See if the language has special handling for this type. */
558 set = (*lang_hooks.get_alias_set) (t);
562 /* There are no objects of FUNCTION_TYPE, so there's no point in
563 using up an alias set for them. (There are, of course, pointers
564 and references to functions, but that's different.) */
565 else if (TREE_CODE (t) == FUNCTION_TYPE)
568 /* Otherwise make a new alias set for this type. */
569 set = new_alias_set ();
571 TYPE_ALIAS_SET (t) = set;
573 /* If this is an aggregate type, we must record any component aliasing
575 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
576 record_component_aliases (t);
581 /* Return a brand-new alias set. */
586 static HOST_WIDE_INT last_alias_set;
588 if (flag_strict_aliasing)
589 return ++last_alias_set;
594 /* Indicate that things in SUBSET can alias things in SUPERSET, but
595 not vice versa. For example, in C, a store to an `int' can alias a
596 structure containing an `int', but not vice versa. Here, the
597 structure would be the SUPERSET and `int' the SUBSET. This
598 function should be called only once per SUPERSET/SUBSET pair.
600 It is illegal for SUPERSET to be zero; everything is implicitly a
601 subset of alias set zero. */
604 record_alias_subset (superset, subset)
605 HOST_WIDE_INT superset;
606 HOST_WIDE_INT subset;
608 alias_set_entry superset_entry;
609 alias_set_entry subset_entry;
611 /* It is possible in complex type situations for both sets to be the same,
612 in which case we can ignore this operation. */
613 if (superset == subset)
619 superset_entry = get_alias_set_entry (superset);
620 if (superset_entry == 0)
622 /* Create an entry for the SUPERSET, so that we have a place to
623 attach the SUBSET. */
625 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
626 superset_entry->alias_set = superset;
627 superset_entry->children
628 = splay_tree_new (splay_tree_compare_ints, 0, 0);
629 superset_entry->has_zero_child = 0;
630 splay_tree_insert (alias_sets, (splay_tree_key) superset,
631 (splay_tree_value) superset_entry);
635 superset_entry->has_zero_child = 1;
638 subset_entry = get_alias_set_entry (subset);
639 /* If there is an entry for the subset, enter all of its children
640 (if they are not already present) as children of the SUPERSET. */
643 if (subset_entry->has_zero_child)
644 superset_entry->has_zero_child = 1;
646 splay_tree_foreach (subset_entry->children, insert_subset_children,
647 superset_entry->children);
650 /* Enter the SUBSET itself as a child of the SUPERSET. */
651 splay_tree_insert (superset_entry->children,
652 (splay_tree_key) subset, 0);
656 /* Record that component types of TYPE, if any, are part of that type for
657 aliasing purposes. For record types, we only record component types
658 for fields that are marked addressable. For array types, we always
659 record the component types, so the front end should not call this
660 function if the individual component aren't addressable. */
663 record_component_aliases (type)
666 HOST_WIDE_INT superset = get_alias_set (type);
672 switch (TREE_CODE (type))
675 if (! TYPE_NONALIASED_COMPONENT (type))
676 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
681 case QUAL_UNION_TYPE:
682 /* Recursively record aliases for the base classes, if there are any */
683 if (TYPE_BINFO (type) != NULL && TYPE_BINFO_BASETYPES (type) != NULL)
686 for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type)); i++)
688 tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), i);
689 record_alias_subset (superset,
690 get_alias_set (BINFO_TYPE (binfo)));
693 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
694 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
695 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
699 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
707 /* Allocate an alias set for use in storing and reading from the varargs
711 get_varargs_alias_set ()
713 static HOST_WIDE_INT set = -1;
716 set = new_alias_set ();
721 /* Likewise, but used for the fixed portions of the frame, e.g., register
725 get_frame_alias_set ()
727 static HOST_WIDE_INT set = -1;
730 set = new_alias_set ();
735 /* Inside SRC, the source of a SET, find a base address. */
738 find_base_value (src)
743 switch (GET_CODE (src))
751 /* At the start of a function, argument registers have known base
752 values which may be lost later. Returning an ADDRESS
753 expression here allows optimization based on argument values
754 even when the argument registers are used for other purposes. */
755 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
756 return new_reg_base_value[regno];
758 /* If a pseudo has a known base value, return it. Do not do this
759 for non-fixed hard regs since it can result in a circular
760 dependency chain for registers which have values at function entry.
762 The test above is not sufficient because the scheduler may move
763 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
764 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
765 && regno < reg_base_value_size
766 && reg_base_value[regno])
767 return reg_base_value[regno];
772 /* Check for an argument passed in memory. Only record in the
773 copying-arguments block; it is too hard to track changes
775 if (copying_arguments
776 && (XEXP (src, 0) == arg_pointer_rtx
777 || (GET_CODE (XEXP (src, 0)) == PLUS
778 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
779 return gen_rtx_ADDRESS (VOIDmode, src);
784 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
787 /* ... fall through ... */
792 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
794 /* If either operand is a REG that is a known pointer, then it
796 if (REG_P (src_0) && REG_POINTER (src_0))
797 return find_base_value (src_0);
798 if (REG_P (src_1) && REG_POINTER (src_1))
799 return find_base_value (src_1);
801 /* If either operand is a REG, then see if we already have
802 a known value for it. */
805 temp = find_base_value (src_0);
812 temp = find_base_value (src_1);
817 /* If either base is named object or a special address
818 (like an argument or stack reference), then use it for the
821 && (GET_CODE (src_0) == SYMBOL_REF
822 || GET_CODE (src_0) == LABEL_REF
823 || (GET_CODE (src_0) == ADDRESS
824 && GET_MODE (src_0) != VOIDmode)))
828 && (GET_CODE (src_1) == SYMBOL_REF
829 || GET_CODE (src_1) == LABEL_REF
830 || (GET_CODE (src_1) == ADDRESS
831 && GET_MODE (src_1) != VOIDmode)))
834 /* Guess which operand is the base address:
835 If either operand is a symbol, then it is the base. If
836 either operand is a CONST_INT, then the other is the base. */
837 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
838 return find_base_value (src_0);
839 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
840 return find_base_value (src_1);
846 /* The standard form is (lo_sum reg sym) so look only at the
848 return find_base_value (XEXP (src, 1));
851 /* If the second operand is constant set the base
852 address to the first operand. */
853 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
854 return find_base_value (XEXP (src, 0));
858 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
868 return find_base_value (XEXP (src, 0));
871 case SIGN_EXTEND: /* used for NT/Alpha pointers */
873 rtx temp = find_base_value (XEXP (src, 0));
875 #ifdef POINTERS_EXTEND_UNSIGNED
876 if (temp != 0 && CONSTANT_P (temp) && GET_MODE (temp) != Pmode)
877 temp = convert_memory_address (Pmode, temp);
890 /* Called from init_alias_analysis indirectly through note_stores. */
892 /* While scanning insns to find base values, reg_seen[N] is nonzero if
893 register N has been set in this function. */
894 static char *reg_seen;
896 /* Addresses which are known not to alias anything else are identified
897 by a unique integer. */
898 static int unique_id;
901 record_set (dest, set, data)
903 void *data ATTRIBUTE_UNUSED;
908 if (GET_CODE (dest) != REG)
911 regno = REGNO (dest);
913 if (regno >= reg_base_value_size)
918 /* A CLOBBER wipes out any old value but does not prevent a previously
919 unset register from acquiring a base address (i.e. reg_seen is not
921 if (GET_CODE (set) == CLOBBER)
923 new_reg_base_value[regno] = 0;
932 new_reg_base_value[regno] = 0;
936 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
937 GEN_INT (unique_id++));
941 /* This is not the first set. If the new value is not related to the
942 old value, forget the base value. Note that the following code is
944 extern int x, y; int *p = &x; p += (&y-&x);
945 ANSI C does not allow computing the difference of addresses
946 of distinct top level objects. */
947 if (new_reg_base_value[regno])
948 switch (GET_CODE (src))
952 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
953 new_reg_base_value[regno] = 0;
956 /* If the value we add in the PLUS is also a valid base value,
957 this might be the actual base value, and the original value
960 rtx other = NULL_RTX;
962 if (XEXP (src, 0) == dest)
963 other = XEXP (src, 1);
964 else if (XEXP (src, 1) == dest)
965 other = XEXP (src, 0);
967 if (! other || find_base_value (other))
968 new_reg_base_value[regno] = 0;
972 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
973 new_reg_base_value[regno] = 0;
976 new_reg_base_value[regno] = 0;
979 /* If this is the first set of a register, record the value. */
980 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
981 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
982 new_reg_base_value[regno] = find_base_value (src);
987 /* Called from loop optimization when a new pseudo-register is
988 created. It indicates that REGNO is being set to VAL. f INVARIANT
989 is true then this value also describes an invariant relationship
990 which can be used to deduce that two registers with unknown values
994 record_base_value (regno, val, invariant)
999 if (regno >= reg_base_value_size)
1002 if (invariant && alias_invariant)
1003 alias_invariant[regno] = val;
1005 if (GET_CODE (val) == REG)
1007 if (REGNO (val) < reg_base_value_size)
1008 reg_base_value[regno] = reg_base_value[REGNO (val)];
1013 reg_base_value[regno] = find_base_value (val);
1016 /* Clear alias info for a register. This is used if an RTL transformation
1017 changes the value of a register. This is used in flow by AUTO_INC_DEC
1018 optimizations. We don't need to clear reg_base_value, since flow only
1019 changes the offset. */
1022 clear_reg_alias_info (reg)
1025 unsigned int regno = REGNO (reg);
1027 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1028 reg_known_value[regno] = reg;
1031 /* Returns a canonical version of X, from the point of view alias
1032 analysis. (For example, if X is a MEM whose address is a register,
1033 and the register has a known value (say a SYMBOL_REF), then a MEM
1034 whose address is the SYMBOL_REF is returned.) */
1040 /* Recursively look for equivalences. */
1041 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1042 && REGNO (x) < reg_known_value_size)
1043 return reg_known_value[REGNO (x)] == x
1044 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1045 else if (GET_CODE (x) == PLUS)
1047 rtx x0 = canon_rtx (XEXP (x, 0));
1048 rtx x1 = canon_rtx (XEXP (x, 1));
1050 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1052 if (GET_CODE (x0) == CONST_INT)
1053 return plus_constant (x1, INTVAL (x0));
1054 else if (GET_CODE (x1) == CONST_INT)
1055 return plus_constant (x0, INTVAL (x1));
1056 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1060 /* This gives us much better alias analysis when called from
1061 the loop optimizer. Note we want to leave the original
1062 MEM alone, but need to return the canonicalized MEM with
1063 all the flags with their original values. */
1064 else if (GET_CODE (x) == MEM)
1065 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1070 /* Return 1 if X and Y are identical-looking rtx's.
1072 We use the data in reg_known_value above to see if two registers with
1073 different numbers are, in fact, equivalent. */
1076 rtx_equal_for_memref_p (x, y)
1084 if (x == 0 && y == 0)
1086 if (x == 0 || y == 0)
1095 code = GET_CODE (x);
1096 /* Rtx's of different codes cannot be equal. */
1097 if (code != GET_CODE (y))
1100 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1101 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1103 if (GET_MODE (x) != GET_MODE (y))
1106 /* Some RTL can be compared without a recursive examination. */
1110 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1113 return REGNO (x) == REGNO (y);
1116 return XEXP (x, 0) == XEXP (y, 0);
1119 return XSTR (x, 0) == XSTR (y, 0);
1123 /* There's no need to compare the contents of CONST_DOUBLEs or
1124 CONST_INTs because pointer equality is a good enough
1125 comparison for these nodes. */
1129 return (XINT (x, 1) == XINT (y, 1)
1130 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1136 /* For commutative operations, the RTX match if the operand match in any
1137 order. Also handle the simple binary and unary cases without a loop. */
1138 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1139 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1140 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1141 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1142 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1143 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1144 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1145 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1146 else if (GET_RTX_CLASS (code) == '1')
1147 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1149 /* Compare the elements. If any pair of corresponding elements
1150 fail to match, return 0 for the whole things.
1152 Limit cases to types which actually appear in addresses. */
1154 fmt = GET_RTX_FORMAT (code);
1155 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1160 if (XINT (x, i) != XINT (y, i))
1165 /* Two vectors must have the same length. */
1166 if (XVECLEN (x, i) != XVECLEN (y, i))
1169 /* And the corresponding elements must match. */
1170 for (j = 0; j < XVECLEN (x, i); j++)
1171 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1172 XVECEXP (y, i, j)) == 0)
1177 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1181 /* This can happen for asm operands. */
1183 if (strcmp (XSTR (x, i), XSTR (y, i)))
1187 /* This can happen for an asm which clobbers memory. */
1191 /* It is believed that rtx's at this level will never
1192 contain anything but integers and other rtx's,
1193 except for within LABEL_REFs and SYMBOL_REFs. */
1201 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1202 X and return it, or return 0 if none found. */
1205 find_symbolic_term (x)
1212 code = GET_CODE (x);
1213 if (code == SYMBOL_REF || code == LABEL_REF)
1215 if (GET_RTX_CLASS (code) == 'o')
1218 fmt = GET_RTX_FORMAT (code);
1219 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1225 t = find_symbolic_term (XEXP (x, i));
1229 else if (fmt[i] == 'E')
1240 struct elt_loc_list *l;
1242 #if defined (FIND_BASE_TERM)
1243 /* Try machine-dependent ways to find the base term. */
1244 x = FIND_BASE_TERM (x);
1247 switch (GET_CODE (x))
1250 return REG_BASE_VALUE (x);
1253 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1263 return find_base_term (XEXP (x, 0));
1266 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1268 rtx temp = find_base_term (XEXP (x, 0));
1270 #ifdef POINTERS_EXTEND_UNSIGNED
1271 if (temp != 0 && CONSTANT_P (temp) && GET_MODE (temp) != Pmode)
1272 temp = convert_memory_address (Pmode, temp);
1279 val = CSELIB_VAL_PTR (x);
1280 for (l = val->locs; l; l = l->next)
1281 if ((x = find_base_term (l->loc)) != 0)
1287 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1294 rtx tmp1 = XEXP (x, 0);
1295 rtx tmp2 = XEXP (x, 1);
1297 /* This is a little bit tricky since we have to determine which of
1298 the two operands represents the real base address. Otherwise this
1299 routine may return the index register instead of the base register.
1301 That may cause us to believe no aliasing was possible, when in
1302 fact aliasing is possible.
1304 We use a few simple tests to guess the base register. Additional
1305 tests can certainly be added. For example, if one of the operands
1306 is a shift or multiply, then it must be the index register and the
1307 other operand is the base register. */
1309 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1310 return find_base_term (tmp2);
1312 /* If either operand is known to be a pointer, then use it
1313 to determine the base term. */
1314 if (REG_P (tmp1) && REG_POINTER (tmp1))
1315 return find_base_term (tmp1);
1317 if (REG_P (tmp2) && REG_POINTER (tmp2))
1318 return find_base_term (tmp2);
1320 /* Neither operand was known to be a pointer. Go ahead and find the
1321 base term for both operands. */
1322 tmp1 = find_base_term (tmp1);
1323 tmp2 = find_base_term (tmp2);
1325 /* If either base term is named object or a special address
1326 (like an argument or stack reference), then use it for the
1329 && (GET_CODE (tmp1) == SYMBOL_REF
1330 || GET_CODE (tmp1) == LABEL_REF
1331 || (GET_CODE (tmp1) == ADDRESS
1332 && GET_MODE (tmp1) != VOIDmode)))
1336 && (GET_CODE (tmp2) == SYMBOL_REF
1337 || GET_CODE (tmp2) == LABEL_REF
1338 || (GET_CODE (tmp2) == ADDRESS
1339 && GET_MODE (tmp2) != VOIDmode)))
1342 /* We could not determine which of the two operands was the
1343 base register and which was the index. So we can determine
1344 nothing from the base alias check. */
1349 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1350 return find_base_term (XEXP (x, 0));
1358 return REG_BASE_VALUE (frame_pointer_rtx);
1365 /* Return 0 if the addresses X and Y are known to point to different
1366 objects, 1 if they might be pointers to the same object. */
1369 base_alias_check (x, y, x_mode, y_mode)
1371 enum machine_mode x_mode, y_mode;
1373 rtx x_base = find_base_term (x);
1374 rtx y_base = find_base_term (y);
1376 /* If the address itself has no known base see if a known equivalent
1377 value has one. If either address still has no known base, nothing
1378 is known about aliasing. */
1383 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1386 x_base = find_base_term (x_c);
1394 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1397 y_base = find_base_term (y_c);
1402 /* If the base addresses are equal nothing is known about aliasing. */
1403 if (rtx_equal_p (x_base, y_base))
1406 /* The base addresses of the read and write are different expressions.
1407 If they are both symbols and they are not accessed via AND, there is
1408 no conflict. We can bring knowledge of object alignment into play
1409 here. For example, on alpha, "char a, b;" can alias one another,
1410 though "char a; long b;" cannot. */
1411 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1413 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1415 if (GET_CODE (x) == AND
1416 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1417 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1419 if (GET_CODE (y) == AND
1420 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1421 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1423 /* Differing symbols never alias. */
1427 /* If one address is a stack reference there can be no alias:
1428 stack references using different base registers do not alias,
1429 a stack reference can not alias a parameter, and a stack reference
1430 can not alias a global. */
1431 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1432 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1435 if (! flag_argument_noalias)
1438 if (flag_argument_noalias > 1)
1441 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1442 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1445 /* Convert the address X into something we can use. This is done by returning
1446 it unchanged unless it is a value; in the latter case we call cselib to get
1447 a more useful rtx. */
1454 struct elt_loc_list *l;
1456 if (GET_CODE (x) != VALUE)
1458 v = CSELIB_VAL_PTR (x);
1459 for (l = v->locs; l; l = l->next)
1460 if (CONSTANT_P (l->loc))
1462 for (l = v->locs; l; l = l->next)
1463 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1466 return v->locs->loc;
1470 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1471 where SIZE is the size in bytes of the memory reference. If ADDR
1472 is not modified by the memory reference then ADDR is returned. */
1475 addr_side_effect_eval (addr, size, n_refs)
1482 switch (GET_CODE (addr))
1485 offset = (n_refs + 1) * size;
1488 offset = -(n_refs + 1) * size;
1491 offset = n_refs * size;
1494 offset = -n_refs * size;
1502 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1504 addr = XEXP (addr, 0);
1509 /* Return nonzero if X and Y (memory addresses) could reference the
1510 same location in memory. C is an offset accumulator. When
1511 C is nonzero, we are testing aliases between X and Y + C.
1512 XSIZE is the size in bytes of the X reference,
1513 similarly YSIZE is the size in bytes for Y.
1515 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1516 referenced (the reference was BLKmode), so make the most pessimistic
1519 If XSIZE or YSIZE is negative, we may access memory outside the object
1520 being referenced as a side effect. This can happen when using AND to
1521 align memory references, as is done on the Alpha.
1523 Nice to notice that varying addresses cannot conflict with fp if no
1524 local variables had their addresses taken, but that's too hard now. */
1527 memrefs_conflict_p (xsize, x, ysize, y, c)
1532 if (GET_CODE (x) == VALUE)
1534 if (GET_CODE (y) == VALUE)
1536 if (GET_CODE (x) == HIGH)
1538 else if (GET_CODE (x) == LO_SUM)
1541 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1542 if (GET_CODE (y) == HIGH)
1544 else if (GET_CODE (y) == LO_SUM)
1547 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1549 if (rtx_equal_for_memref_p (x, y))
1551 if (xsize <= 0 || ysize <= 0)
1553 if (c >= 0 && xsize > c)
1555 if (c < 0 && ysize+c > 0)
1560 /* This code used to check for conflicts involving stack references and
1561 globals but the base address alias code now handles these cases. */
1563 if (GET_CODE (x) == PLUS)
1565 /* The fact that X is canonicalized means that this
1566 PLUS rtx is canonicalized. */
1567 rtx x0 = XEXP (x, 0);
1568 rtx x1 = XEXP (x, 1);
1570 if (GET_CODE (y) == PLUS)
1572 /* The fact that Y is canonicalized means that this
1573 PLUS rtx is canonicalized. */
1574 rtx y0 = XEXP (y, 0);
1575 rtx y1 = XEXP (y, 1);
1577 if (rtx_equal_for_memref_p (x1, y1))
1578 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1579 if (rtx_equal_for_memref_p (x0, y0))
1580 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1581 if (GET_CODE (x1) == CONST_INT)
1583 if (GET_CODE (y1) == CONST_INT)
1584 return memrefs_conflict_p (xsize, x0, ysize, y0,
1585 c - INTVAL (x1) + INTVAL (y1));
1587 return memrefs_conflict_p (xsize, x0, ysize, y,
1590 else if (GET_CODE (y1) == CONST_INT)
1591 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1595 else if (GET_CODE (x1) == CONST_INT)
1596 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1598 else if (GET_CODE (y) == PLUS)
1600 /* The fact that Y is canonicalized means that this
1601 PLUS rtx is canonicalized. */
1602 rtx y0 = XEXP (y, 0);
1603 rtx y1 = XEXP (y, 1);
1605 if (GET_CODE (y1) == CONST_INT)
1606 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1611 if (GET_CODE (x) == GET_CODE (y))
1612 switch (GET_CODE (x))
1616 /* Handle cases where we expect the second operands to be the
1617 same, and check only whether the first operand would conflict
1620 rtx x1 = canon_rtx (XEXP (x, 1));
1621 rtx y1 = canon_rtx (XEXP (y, 1));
1622 if (! rtx_equal_for_memref_p (x1, y1))
1624 x0 = canon_rtx (XEXP (x, 0));
1625 y0 = canon_rtx (XEXP (y, 0));
1626 if (rtx_equal_for_memref_p (x0, y0))
1627 return (xsize == 0 || ysize == 0
1628 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1630 /* Can't properly adjust our sizes. */
1631 if (GET_CODE (x1) != CONST_INT)
1633 xsize /= INTVAL (x1);
1634 ysize /= INTVAL (x1);
1636 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1640 /* Are these registers known not to be equal? */
1641 if (alias_invariant)
1643 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1644 rtx i_x, i_y; /* invariant relationships of X and Y */
1646 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1647 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1649 if (i_x == 0 && i_y == 0)
1652 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1653 ysize, i_y ? i_y : y, c))
1662 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1663 as an access with indeterminate size. Assume that references
1664 besides AND are aligned, so if the size of the other reference is
1665 at least as large as the alignment, assume no other overlap. */
1666 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1668 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1670 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1672 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1674 /* ??? If we are indexing far enough into the array/structure, we
1675 may yet be able to determine that we can not overlap. But we
1676 also need to that we are far enough from the end not to overlap
1677 a following reference, so we do nothing with that for now. */
1678 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1680 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1683 if (GET_CODE (x) == ADDRESSOF)
1685 if (y == frame_pointer_rtx
1686 || GET_CODE (y) == ADDRESSOF)
1687 return xsize <= 0 || ysize <= 0;
1689 if (GET_CODE (y) == ADDRESSOF)
1691 if (x == frame_pointer_rtx)
1692 return xsize <= 0 || ysize <= 0;
1697 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1699 c += (INTVAL (y) - INTVAL (x));
1700 return (xsize <= 0 || ysize <= 0
1701 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1704 if (GET_CODE (x) == CONST)
1706 if (GET_CODE (y) == CONST)
1707 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1708 ysize, canon_rtx (XEXP (y, 0)), c);
1710 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1713 if (GET_CODE (y) == CONST)
1714 return memrefs_conflict_p (xsize, x, ysize,
1715 canon_rtx (XEXP (y, 0)), c);
1718 return (xsize <= 0 || ysize <= 0
1719 || (rtx_equal_for_memref_p (x, y)
1720 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1727 /* Functions to compute memory dependencies.
1729 Since we process the insns in execution order, we can build tables
1730 to keep track of what registers are fixed (and not aliased), what registers
1731 are varying in known ways, and what registers are varying in unknown
1734 If both memory references are volatile, then there must always be a
1735 dependence between the two references, since their order can not be
1736 changed. A volatile and non-volatile reference can be interchanged
1739 A MEM_IN_STRUCT reference at a non-AND varying address can never
1740 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1741 also must allow AND addresses, because they may generate accesses
1742 outside the object being referenced. This is used to generate
1743 aligned addresses from unaligned addresses, for instance, the alpha
1744 storeqi_unaligned pattern. */
1746 /* Read dependence: X is read after read in MEM takes place. There can
1747 only be a dependence here if both reads are volatile. */
1750 read_dependence (mem, x)
1754 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1757 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1758 MEM2 is a reference to a structure at a varying address, or returns
1759 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1760 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1761 to decide whether or not an address may vary; it should return
1762 nonzero whenever variation is possible.
1763 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1766 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1768 rtx mem1_addr, mem2_addr;
1769 int (*varies_p) PARAMS ((rtx, int));
1771 if (! flag_strict_aliasing)
1774 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1775 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1776 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1780 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1781 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1782 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1789 /* Returns nonzero if something about the mode or address format MEM1
1790 indicates that it might well alias *anything*. */
1793 aliases_everything_p (mem)
1796 if (GET_CODE (XEXP (mem, 0)) == AND)
1797 /* If the address is an AND, its very hard to know at what it is
1798 actually pointing. */
1804 /* Return true if we can determine that the fields referenced cannot
1805 overlap for any pair of objects. */
1808 nonoverlapping_component_refs_p (x, y)
1811 tree fieldx, fieldy, typex, typey, orig_y;
1815 /* The comparison has to be done at a common type, since we don't
1816 know how the inheritance hierarchy works. */
1820 fieldx = TREE_OPERAND (x, 1);
1821 typex = DECL_FIELD_CONTEXT (fieldx);
1826 fieldy = TREE_OPERAND (y, 1);
1827 typey = DECL_FIELD_CONTEXT (fieldy);
1832 y = TREE_OPERAND (y, 0);
1834 while (y && TREE_CODE (y) == COMPONENT_REF);
1836 x = TREE_OPERAND (x, 0);
1838 while (x && TREE_CODE (x) == COMPONENT_REF);
1840 /* Never found a common type. */
1844 /* If we're left with accessing different fields of a structure,
1846 if (TREE_CODE (typex) == RECORD_TYPE
1847 && fieldx != fieldy)
1850 /* The comparison on the current field failed. If we're accessing
1851 a very nested structure, look at the next outer level. */
1852 x = TREE_OPERAND (x, 0);
1853 y = TREE_OPERAND (y, 0);
1856 && TREE_CODE (x) == COMPONENT_REF
1857 && TREE_CODE (y) == COMPONENT_REF);
1862 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1865 decl_for_component_ref (x)
1870 x = TREE_OPERAND (x, 0);
1872 while (x && TREE_CODE (x) == COMPONENT_REF);
1874 return x && DECL_P (x) ? x : NULL_TREE;
1877 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1878 offset of the field reference. */
1881 adjust_offset_for_component_ref (x, offset)
1885 HOST_WIDE_INT ioffset;
1890 ioffset = INTVAL (offset);
1893 tree field = TREE_OPERAND (x, 1);
1895 if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
1897 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
1898 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1901 x = TREE_OPERAND (x, 0);
1903 while (x && TREE_CODE (x) == COMPONENT_REF);
1905 return GEN_INT (ioffset);
1908 /* Return nonzero if we can deterimine the exprs corresponding to memrefs
1909 X and Y and they do not overlap. */
1912 nonoverlapping_memrefs_p (x, y)
1915 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1918 rtx moffsetx, moffsety;
1919 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1921 /* Unless both have exprs, we can't tell anything. */
1922 if (exprx == 0 || expry == 0)
1925 /* If both are field references, we may be able to determine something. */
1926 if (TREE_CODE (exprx) == COMPONENT_REF
1927 && TREE_CODE (expry) == COMPONENT_REF
1928 && nonoverlapping_component_refs_p (exprx, expry))
1931 /* If the field reference test failed, look at the DECLs involved. */
1932 moffsetx = MEM_OFFSET (x);
1933 if (TREE_CODE (exprx) == COMPONENT_REF)
1935 tree t = decl_for_component_ref (exprx);
1938 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
1941 moffsety = MEM_OFFSET (y);
1942 if (TREE_CODE (expry) == COMPONENT_REF)
1944 tree t = decl_for_component_ref (expry);
1947 moffsety = adjust_offset_for_component_ref (expry, moffsety);
1951 if (! DECL_P (exprx) || ! DECL_P (expry))
1954 rtlx = DECL_RTL (exprx);
1955 rtly = DECL_RTL (expry);
1957 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
1958 can't overlap unless they are the same because we never reuse that part
1959 of the stack frame used for locals for spilled pseudos. */
1960 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
1961 && ! rtx_equal_p (rtlx, rtly))
1964 /* Get the base and offsets of both decls. If either is a register, we
1965 know both are and are the same, so use that as the base. The only
1966 we can avoid overlap is if we can deduce that they are nonoverlapping
1967 pieces of that decl, which is very rare. */
1968 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
1969 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
1970 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
1972 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
1973 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
1974 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
1976 /* If the bases are different, we know they do not overlap if both
1977 are constants or if one is a constant and the other a pointer into the
1978 stack frame. Otherwise a different base means we can't tell if they
1980 if (! rtx_equal_p (basex, basey))
1981 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
1982 || (CONSTANT_P (basex) && REG_P (basey)
1983 && REGNO_PTR_FRAME_P (REGNO (basey)))
1984 || (CONSTANT_P (basey) && REG_P (basex)
1985 && REGNO_PTR_FRAME_P (REGNO (basex))));
1987 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
1988 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
1990 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
1991 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
1994 /* If we have an offset for either memref, it can update the values computed
1997 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
1999 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
2001 /* If a memref has both a size and an offset, we can use the smaller size.
2002 We can't do this if the offset isn't known because we must view this
2003 memref as being anywhere inside the DECL's MEM. */
2004 if (MEM_SIZE (x) && moffsetx)
2005 sizex = INTVAL (MEM_SIZE (x));
2006 if (MEM_SIZE (y) && moffsety)
2007 sizey = INTVAL (MEM_SIZE (y));
2009 /* Put the values of the memref with the lower offset in X's values. */
2010 if (offsetx > offsety)
2012 tem = offsetx, offsetx = offsety, offsety = tem;
2013 tem = sizex, sizex = sizey, sizey = tem;
2016 /* If we don't know the size of the lower-offset value, we can't tell
2017 if they conflict. Otherwise, we do the test. */
2018 return sizex >= 0 && offsety > offsetx + sizex;
2021 /* True dependence: X is read after store in MEM takes place. */
2024 true_dependence (mem, mem_mode, x, varies)
2026 enum machine_mode mem_mode;
2028 int (*varies) PARAMS ((rtx, int));
2030 rtx x_addr, mem_addr;
2033 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2036 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2039 /* Unchanging memory can't conflict with non-unchanging memory.
2040 A non-unchanging read can conflict with a non-unchanging write.
2041 An unchanging read can conflict with an unchanging write since
2042 there may be a single store to this address to initialize it.
2043 Note that an unchanging store can conflict with a non-unchanging read
2044 since we have to make conservative assumptions when we have a
2045 record with readonly fields and we are copying the whole thing.
2046 Just fall through to the code below to resolve potential conflicts.
2047 This won't handle all cases optimally, but the possible performance
2048 loss should be negligible. */
2049 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2052 if (nonoverlapping_memrefs_p (mem, x))
2055 if (mem_mode == VOIDmode)
2056 mem_mode = GET_MODE (mem);
2058 x_addr = get_addr (XEXP (x, 0));
2059 mem_addr = get_addr (XEXP (mem, 0));
2061 base = find_base_term (x_addr);
2062 if (base && (GET_CODE (base) == LABEL_REF
2063 || (GET_CODE (base) == SYMBOL_REF
2064 && CONSTANT_POOL_ADDRESS_P (base))))
2067 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2070 x_addr = canon_rtx (x_addr);
2071 mem_addr = canon_rtx (mem_addr);
2073 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2074 SIZE_FOR_MODE (x), x_addr, 0))
2077 if (aliases_everything_p (x))
2080 /* We cannot use aliases_everything_p to test MEM, since we must look
2081 at MEM_MODE, rather than GET_MODE (MEM). */
2082 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2085 /* In true_dependence we also allow BLKmode to alias anything. Why
2086 don't we do this in anti_dependence and output_dependence? */
2087 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2090 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2094 /* Canonical true dependence: X is read after store in MEM takes place.
2095 Variant of true_dependence which assumes MEM has already been
2096 canonicalized (hence we no longer do that here).
2097 The mem_addr argument has been added, since true_dependence computed
2098 this value prior to canonicalizing. */
2101 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
2102 rtx mem, mem_addr, x;
2103 enum machine_mode mem_mode;
2104 int (*varies) PARAMS ((rtx, int));
2108 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2111 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2114 /* If X is an unchanging read, then it can't possibly conflict with any
2115 non-unchanging store. It may conflict with an unchanging write though,
2116 because there may be a single store to this address to initialize it.
2117 Just fall through to the code below to resolve the case where we have
2118 both an unchanging read and an unchanging write. This won't handle all
2119 cases optimally, but the possible performance loss should be
2121 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2124 if (nonoverlapping_memrefs_p (x, mem))
2127 x_addr = get_addr (XEXP (x, 0));
2129 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2132 x_addr = canon_rtx (x_addr);
2133 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2134 SIZE_FOR_MODE (x), x_addr, 0))
2137 if (aliases_everything_p (x))
2140 /* We cannot use aliases_everything_p to test MEM, since we must look
2141 at MEM_MODE, rather than GET_MODE (MEM). */
2142 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2145 /* In true_dependence we also allow BLKmode to alias anything. Why
2146 don't we do this in anti_dependence and output_dependence? */
2147 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2150 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2154 /* Returns non-zero if a write to X might alias a previous read from
2155 (or, if WRITEP is non-zero, a write to) MEM. */
2158 write_dependence_p (mem, x, writep)
2163 rtx x_addr, mem_addr;
2167 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2170 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2173 /* Unchanging memory can't conflict with non-unchanging memory. */
2174 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
2177 /* If MEM is an unchanging read, then it can't possibly conflict with
2178 the store to X, because there is at most one store to MEM, and it must
2179 have occurred somewhere before MEM. */
2180 if (! writep && RTX_UNCHANGING_P (mem))
2183 if (nonoverlapping_memrefs_p (x, mem))
2186 x_addr = get_addr (XEXP (x, 0));
2187 mem_addr = get_addr (XEXP (mem, 0));
2191 base = find_base_term (mem_addr);
2192 if (base && (GET_CODE (base) == LABEL_REF
2193 || (GET_CODE (base) == SYMBOL_REF
2194 && CONSTANT_POOL_ADDRESS_P (base))))
2198 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2202 x_addr = canon_rtx (x_addr);
2203 mem_addr = canon_rtx (mem_addr);
2205 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2206 SIZE_FOR_MODE (x), x_addr, 0))
2210 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2213 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2214 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2217 /* Anti dependence: X is written after read in MEM takes place. */
2220 anti_dependence (mem, x)
2224 return write_dependence_p (mem, x, /*writep=*/0);
2227 /* Output dependence: X is written after store in MEM takes place. */
2230 output_dependence (mem, x)
2234 return write_dependence_p (mem, x, /*writep=*/1);
2237 /* Returns non-zero if X mentions something which is not
2238 local to the function and is not constant. */
2241 nonlocal_mentioned_p (x)
2248 code = GET_CODE (x);
2250 if (GET_RTX_CLASS (code) == 'i')
2252 /* Constant functions can be constant if they don't use
2253 scratch memory used to mark function w/o side effects. */
2254 if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x))
2256 x = CALL_INSN_FUNCTION_USAGE (x);
2262 code = GET_CODE (x);
2268 if (GET_CODE (SUBREG_REG (x)) == REG)
2270 /* Global registers are not local. */
2271 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2272 && global_regs[subreg_regno (x)])
2280 /* Global registers are not local. */
2281 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2296 /* Constants in the function's constants pool are constant. */
2297 if (CONSTANT_POOL_ADDRESS_P (x))
2302 /* Non-constant calls and recursion are not local. */
2306 /* Be overly conservative and consider any volatile memory
2307 reference as not local. */
2308 if (MEM_VOLATILE_P (x))
2310 base = find_base_term (XEXP (x, 0));
2313 /* A Pmode ADDRESS could be a reference via the structure value
2314 address or static chain. Such memory references are nonlocal.
2316 Thus, we have to examine the contents of the ADDRESS to find
2317 out if this is a local reference or not. */
2318 if (GET_CODE (base) == ADDRESS
2319 && GET_MODE (base) == Pmode
2320 && (XEXP (base, 0) == stack_pointer_rtx
2321 || XEXP (base, 0) == arg_pointer_rtx
2322 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2323 || XEXP (base, 0) == hard_frame_pointer_rtx
2325 || XEXP (base, 0) == frame_pointer_rtx))
2327 /* Constants in the function's constant pool are constant. */
2328 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2333 case UNSPEC_VOLATILE:
2338 if (MEM_VOLATILE_P (x))
2347 /* Recursively scan the operands of this expression. */
2350 const char *fmt = GET_RTX_FORMAT (code);
2353 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2355 if (fmt[i] == 'e' && XEXP (x, i))
2357 if (nonlocal_mentioned_p (XEXP (x, i)))
2360 else if (fmt[i] == 'E')
2363 for (j = 0; j < XVECLEN (x, i); j++)
2364 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2373 /* Mark the function if it is constant. */
2376 mark_constant_function ()
2379 int nonlocal_mentioned;
2381 if (TREE_PUBLIC (current_function_decl)
2382 || TREE_READONLY (current_function_decl)
2383 || DECL_IS_PURE (current_function_decl)
2384 || TREE_THIS_VOLATILE (current_function_decl)
2385 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2388 /* A loop might not return which counts as a side effect. */
2389 if (mark_dfs_back_edges ())
2392 nonlocal_mentioned = 0;
2394 init_alias_analysis ();
2396 /* Determine if this is a constant function. */
2398 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2399 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2401 nonlocal_mentioned = 1;
2405 end_alias_analysis ();
2407 /* Mark the function. */
2409 if (! nonlocal_mentioned)
2410 TREE_READONLY (current_function_decl) = 1;
2414 static HARD_REG_SET argument_registers;
2421 #ifndef OUTGOING_REGNO
2422 #define OUTGOING_REGNO(N) N
2424 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2425 /* Check whether this register can hold an incoming pointer
2426 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2427 numbers, so translate if necessary due to register windows. */
2428 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2429 && HARD_REGNO_MODE_OK (i, Pmode))
2430 SET_HARD_REG_BIT (argument_registers, i);
2432 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2435 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2439 init_alias_analysis ()
2441 int maxreg = max_reg_num ();
2447 reg_known_value_size = maxreg;
2450 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2451 - FIRST_PSEUDO_REGISTER;
2453 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2454 - FIRST_PSEUDO_REGISTER;
2456 /* Overallocate reg_base_value to allow some growth during loop
2457 optimization. Loop unrolling can create a large number of
2459 reg_base_value_size = maxreg * 2;
2460 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2461 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2463 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2464 reg_seen = (char *) xmalloc (reg_base_value_size);
2465 if (! reload_completed && flag_unroll_loops)
2467 /* ??? Why are we realloc'ing if we're just going to zero it? */
2468 alias_invariant = (rtx *)xrealloc (alias_invariant,
2469 reg_base_value_size * sizeof (rtx));
2470 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2473 /* The basic idea is that each pass through this loop will use the
2474 "constant" information from the previous pass to propagate alias
2475 information through another level of assignments.
2477 This could get expensive if the assignment chains are long. Maybe
2478 we should throttle the number of iterations, possibly based on
2479 the optimization level or flag_expensive_optimizations.
2481 We could propagate more information in the first pass by making use
2482 of REG_N_SETS to determine immediately that the alias information
2483 for a pseudo is "constant".
2485 A program with an uninitialized variable can cause an infinite loop
2486 here. Instead of doing a full dataflow analysis to detect such problems
2487 we just cap the number of iterations for the loop.
2489 The state of the arrays for the set chain in question does not matter
2490 since the program has undefined behavior. */
2495 /* Assume nothing will change this iteration of the loop. */
2498 /* We want to assign the same IDs each iteration of this loop, so
2499 start counting from zero each iteration of the loop. */
2502 /* We're at the start of the function each iteration through the
2503 loop, so we're copying arguments. */
2504 copying_arguments = 1;
2506 /* Wipe the potential alias information clean for this pass. */
2507 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2509 /* Wipe the reg_seen array clean. */
2510 memset ((char *) reg_seen, 0, reg_base_value_size);
2512 /* Mark all hard registers which may contain an address.
2513 The stack, frame and argument pointers may contain an address.
2514 An argument register which can hold a Pmode value may contain
2515 an address even if it is not in BASE_REGS.
2517 The address expression is VOIDmode for an argument and
2518 Pmode for other registers. */
2520 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2521 if (TEST_HARD_REG_BIT (argument_registers, i))
2522 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2523 gen_rtx_REG (Pmode, i));
2525 new_reg_base_value[STACK_POINTER_REGNUM]
2526 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2527 new_reg_base_value[ARG_POINTER_REGNUM]
2528 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2529 new_reg_base_value[FRAME_POINTER_REGNUM]
2530 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2531 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2532 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2533 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2536 /* Walk the insns adding values to the new_reg_base_value array. */
2537 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2543 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2544 /* The prologue/epilogue insns are not threaded onto the
2545 insn chain until after reload has completed. Thus,
2546 there is no sense wasting time checking if INSN is in
2547 the prologue/epilogue until after reload has completed. */
2548 if (reload_completed
2549 && prologue_epilogue_contains (insn))
2553 /* If this insn has a noalias note, process it, Otherwise,
2554 scan for sets. A simple set will have no side effects
2555 which could change the base value of any other register. */
2557 if (GET_CODE (PATTERN (insn)) == SET
2558 && REG_NOTES (insn) != 0
2559 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2560 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2562 note_stores (PATTERN (insn), record_set, NULL);
2564 set = single_set (insn);
2567 && GET_CODE (SET_DEST (set)) == REG
2568 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2570 unsigned int regno = REGNO (SET_DEST (set));
2571 rtx src = SET_SRC (set);
2573 if (REG_NOTES (insn) != 0
2574 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2575 && REG_N_SETS (regno) == 1)
2576 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2577 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2578 && ! rtx_varies_p (XEXP (note, 0), 1)
2579 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2581 reg_known_value[regno] = XEXP (note, 0);
2582 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2584 else if (REG_N_SETS (regno) == 1
2585 && GET_CODE (src) == PLUS
2586 && GET_CODE (XEXP (src, 0)) == REG
2587 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2588 && (reg_known_value[REGNO (XEXP (src, 0))])
2589 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2591 rtx op0 = XEXP (src, 0);
2592 op0 = reg_known_value[REGNO (op0)];
2593 reg_known_value[regno]
2594 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2595 reg_known_equiv_p[regno] = 0;
2597 else if (REG_N_SETS (regno) == 1
2598 && ! rtx_varies_p (src, 1))
2600 reg_known_value[regno] = src;
2601 reg_known_equiv_p[regno] = 0;
2605 else if (GET_CODE (insn) == NOTE
2606 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2607 copying_arguments = 0;
2610 /* Now propagate values from new_reg_base_value to reg_base_value. */
2611 for (ui = 0; ui < reg_base_value_size; ui++)
2613 if (new_reg_base_value[ui]
2614 && new_reg_base_value[ui] != reg_base_value[ui]
2615 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2617 reg_base_value[ui] = new_reg_base_value[ui];
2622 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2624 /* Fill in the remaining entries. */
2625 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2626 if (reg_known_value[i] == 0)
2627 reg_known_value[i] = regno_reg_rtx[i];
2629 /* Simplify the reg_base_value array so that no register refers to
2630 another register, except to special registers indirectly through
2631 ADDRESS expressions.
2633 In theory this loop can take as long as O(registers^2), but unless
2634 there are very long dependency chains it will run in close to linear
2637 This loop may not be needed any longer now that the main loop does
2638 a better job at propagating alias information. */
2644 for (ui = 0; ui < reg_base_value_size; ui++)
2646 rtx base = reg_base_value[ui];
2647 if (base && GET_CODE (base) == REG)
2649 unsigned int base_regno = REGNO (base);
2650 if (base_regno == ui) /* register set from itself */
2651 reg_base_value[ui] = 0;
2653 reg_base_value[ui] = reg_base_value[base_regno];
2658 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2661 free (new_reg_base_value);
2662 new_reg_base_value = 0;
2668 end_alias_analysis ()
2670 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2671 reg_known_value = 0;
2672 reg_known_value_size = 0;
2673 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2674 reg_known_equiv_p = 0;
2677 ggc_del_root (reg_base_value);
2678 free (reg_base_value);
2681 reg_base_value_size = 0;
2682 if (alias_invariant)
2684 free (alias_invariant);
2685 alias_invariant = 0;