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 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
683 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
684 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
688 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
696 /* Allocate an alias set for use in storing and reading from the varargs
700 get_varargs_alias_set ()
702 static HOST_WIDE_INT set = -1;
705 set = new_alias_set ();
710 /* Likewise, but used for the fixed portions of the frame, e.g., register
714 get_frame_alias_set ()
716 static HOST_WIDE_INT set = -1;
719 set = new_alias_set ();
724 /* Inside SRC, the source of a SET, find a base address. */
727 find_base_value (src)
731 switch (GET_CODE (src))
739 /* At the start of a function, argument registers have known base
740 values which may be lost later. Returning an ADDRESS
741 expression here allows optimization based on argument values
742 even when the argument registers are used for other purposes. */
743 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
744 return new_reg_base_value[regno];
746 /* If a pseudo has a known base value, return it. Do not do this
747 for hard regs since it can result in a circular dependency
748 chain for registers which have values at function entry.
750 The test above is not sufficient because the scheduler may move
751 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
752 if (regno >= FIRST_PSEUDO_REGISTER
753 && regno < reg_base_value_size
754 && reg_base_value[regno])
755 return reg_base_value[regno];
760 /* Check for an argument passed in memory. Only record in the
761 copying-arguments block; it is too hard to track changes
763 if (copying_arguments
764 && (XEXP (src, 0) == arg_pointer_rtx
765 || (GET_CODE (XEXP (src, 0)) == PLUS
766 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
767 return gen_rtx_ADDRESS (VOIDmode, src);
772 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
775 /* ... fall through ... */
780 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
782 /* If either operand is a REG that is a known pointer, then it
784 if (REG_P (src_0) && REG_POINTER (src_0))
785 return find_base_value (src_0);
786 if (REG_P (src_1) && REG_POINTER (src_1))
787 return find_base_value (src_1);
789 /* If either operand is a REG, then see if we already have
790 a known value for it. */
793 temp = find_base_value (src_0);
800 temp = find_base_value (src_1);
805 /* If either base is named object or a special address
806 (like an argument or stack reference), then use it for the
809 && (GET_CODE (src_0) == SYMBOL_REF
810 || GET_CODE (src_0) == LABEL_REF
811 || (GET_CODE (src_0) == ADDRESS
812 && GET_MODE (src_0) != VOIDmode)))
816 && (GET_CODE (src_1) == SYMBOL_REF
817 || GET_CODE (src_1) == LABEL_REF
818 || (GET_CODE (src_1) == ADDRESS
819 && GET_MODE (src_1) != VOIDmode)))
822 /* Guess which operand is the base address:
823 If either operand is a symbol, then it is the base. If
824 either operand is a CONST_INT, then the other is the base. */
825 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
826 return find_base_value (src_0);
827 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
828 return find_base_value (src_1);
834 /* The standard form is (lo_sum reg sym) so look only at the
836 return find_base_value (XEXP (src, 1));
839 /* If the second operand is constant set the base
840 address to the first operand. */
841 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
842 return find_base_value (XEXP (src, 0));
846 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
850 case SIGN_EXTEND: /* used for NT/Alpha pointers */
858 return find_base_value (XEXP (src, 0));
867 /* Called from init_alias_analysis indirectly through note_stores. */
869 /* While scanning insns to find base values, reg_seen[N] is nonzero if
870 register N has been set in this function. */
871 static char *reg_seen;
873 /* Addresses which are known not to alias anything else are identified
874 by a unique integer. */
875 static int unique_id;
878 record_set (dest, set, data)
880 void *data ATTRIBUTE_UNUSED;
885 if (GET_CODE (dest) != REG)
888 regno = REGNO (dest);
890 if (regno >= reg_base_value_size)
895 /* A CLOBBER wipes out any old value but does not prevent a previously
896 unset register from acquiring a base address (i.e. reg_seen is not
898 if (GET_CODE (set) == CLOBBER)
900 new_reg_base_value[regno] = 0;
909 new_reg_base_value[regno] = 0;
913 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
914 GEN_INT (unique_id++));
918 /* This is not the first set. If the new value is not related to the
919 old value, forget the base value. Note that the following code is
921 extern int x, y; int *p = &x; p += (&y-&x);
922 ANSI C does not allow computing the difference of addresses
923 of distinct top level objects. */
924 if (new_reg_base_value[regno])
925 switch (GET_CODE (src))
929 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
930 new_reg_base_value[regno] = 0;
933 /* If the value we add in the PLUS is also a valid base value,
934 this might be the actual base value, and the original value
937 rtx other = NULL_RTX;
939 if (XEXP (src, 0) == dest)
940 other = XEXP (src, 1);
941 else if (XEXP (src, 1) == dest)
942 other = XEXP (src, 0);
944 if (! other || find_base_value (other))
945 new_reg_base_value[regno] = 0;
949 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
950 new_reg_base_value[regno] = 0;
953 new_reg_base_value[regno] = 0;
956 /* If this is the first set of a register, record the value. */
957 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
958 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
959 new_reg_base_value[regno] = find_base_value (src);
964 /* Called from loop optimization when a new pseudo-register is
965 created. It indicates that REGNO is being set to VAL. f INVARIANT
966 is true then this value also describes an invariant relationship
967 which can be used to deduce that two registers with unknown values
971 record_base_value (regno, val, invariant)
976 if (regno >= reg_base_value_size)
979 if (invariant && alias_invariant)
980 alias_invariant[regno] = val;
982 if (GET_CODE (val) == REG)
984 if (REGNO (val) < reg_base_value_size)
985 reg_base_value[regno] = reg_base_value[REGNO (val)];
990 reg_base_value[regno] = find_base_value (val);
993 /* Clear alias info for a register. This is used if an RTL transformation
994 changes the value of a register. This is used in flow by AUTO_INC_DEC
995 optimizations. We don't need to clear reg_base_value, since flow only
996 changes the offset. */
999 clear_reg_alias_info (reg)
1002 unsigned int regno = REGNO (reg);
1004 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1005 reg_known_value[regno] = reg;
1008 /* Returns a canonical version of X, from the point of view alias
1009 analysis. (For example, if X is a MEM whose address is a register,
1010 and the register has a known value (say a SYMBOL_REF), then a MEM
1011 whose address is the SYMBOL_REF is returned.) */
1017 /* Recursively look for equivalences. */
1018 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1019 && REGNO (x) < reg_known_value_size)
1020 return reg_known_value[REGNO (x)] == x
1021 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1022 else if (GET_CODE (x) == PLUS)
1024 rtx x0 = canon_rtx (XEXP (x, 0));
1025 rtx x1 = canon_rtx (XEXP (x, 1));
1027 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1029 if (GET_CODE (x0) == CONST_INT)
1030 return plus_constant (x1, INTVAL (x0));
1031 else if (GET_CODE (x1) == CONST_INT)
1032 return plus_constant (x0, INTVAL (x1));
1033 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1037 /* This gives us much better alias analysis when called from
1038 the loop optimizer. Note we want to leave the original
1039 MEM alone, but need to return the canonicalized MEM with
1040 all the flags with their original values. */
1041 else if (GET_CODE (x) == MEM)
1042 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1047 /* Return 1 if X and Y are identical-looking rtx's.
1049 We use the data in reg_known_value above to see if two registers with
1050 different numbers are, in fact, equivalent. */
1053 rtx_equal_for_memref_p (x, y)
1061 if (x == 0 && y == 0)
1063 if (x == 0 || y == 0)
1072 code = GET_CODE (x);
1073 /* Rtx's of different codes cannot be equal. */
1074 if (code != GET_CODE (y))
1077 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1078 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1080 if (GET_MODE (x) != GET_MODE (y))
1083 /* Some RTL can be compared without a recursive examination. */
1087 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1090 return REGNO (x) == REGNO (y);
1093 return XEXP (x, 0) == XEXP (y, 0);
1096 return XSTR (x, 0) == XSTR (y, 0);
1100 /* There's no need to compare the contents of CONST_DOUBLEs or
1101 CONST_INTs because pointer equality is a good enough
1102 comparison for these nodes. */
1106 return (XINT (x, 1) == XINT (y, 1)
1107 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1113 /* For commutative operations, the RTX match if the operand match in any
1114 order. Also handle the simple binary and unary cases without a loop. */
1115 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1116 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1117 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1118 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1119 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1120 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1121 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1122 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1123 else if (GET_RTX_CLASS (code) == '1')
1124 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1126 /* Compare the elements. If any pair of corresponding elements
1127 fail to match, return 0 for the whole things.
1129 Limit cases to types which actually appear in addresses. */
1131 fmt = GET_RTX_FORMAT (code);
1132 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1137 if (XINT (x, i) != XINT (y, i))
1142 /* Two vectors must have the same length. */
1143 if (XVECLEN (x, i) != XVECLEN (y, i))
1146 /* And the corresponding elements must match. */
1147 for (j = 0; j < XVECLEN (x, i); j++)
1148 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1149 XVECEXP (y, i, j)) == 0)
1154 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1158 /* This can happen for asm operands. */
1160 if (strcmp (XSTR (x, i), XSTR (y, i)))
1164 /* This can happen for an asm which clobbers memory. */
1168 /* It is believed that rtx's at this level will never
1169 contain anything but integers and other rtx's,
1170 except for within LABEL_REFs and SYMBOL_REFs. */
1178 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1179 X and return it, or return 0 if none found. */
1182 find_symbolic_term (x)
1189 code = GET_CODE (x);
1190 if (code == SYMBOL_REF || code == LABEL_REF)
1192 if (GET_RTX_CLASS (code) == 'o')
1195 fmt = GET_RTX_FORMAT (code);
1196 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1202 t = find_symbolic_term (XEXP (x, i));
1206 else if (fmt[i] == 'E')
1217 struct elt_loc_list *l;
1219 #if defined (FIND_BASE_TERM)
1220 /* Try machine-dependent ways to find the base term. */
1221 x = FIND_BASE_TERM (x);
1224 switch (GET_CODE (x))
1227 return REG_BASE_VALUE (x);
1230 if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
1234 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1242 return find_base_term (XEXP (x, 0));
1245 val = CSELIB_VAL_PTR (x);
1246 for (l = val->locs; l; l = l->next)
1247 if ((x = find_base_term (l->loc)) != 0)
1253 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1260 rtx tmp1 = XEXP (x, 0);
1261 rtx tmp2 = XEXP (x, 1);
1263 /* This is a little bit tricky since we have to determine which of
1264 the two operands represents the real base address. Otherwise this
1265 routine may return the index register instead of the base register.
1267 That may cause us to believe no aliasing was possible, when in
1268 fact aliasing is possible.
1270 We use a few simple tests to guess the base register. Additional
1271 tests can certainly be added. For example, if one of the operands
1272 is a shift or multiply, then it must be the index register and the
1273 other operand is the base register. */
1275 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1276 return find_base_term (tmp2);
1278 /* If either operand is known to be a pointer, then use it
1279 to determine the base term. */
1280 if (REG_P (tmp1) && REG_POINTER (tmp1))
1281 return find_base_term (tmp1);
1283 if (REG_P (tmp2) && REG_POINTER (tmp2))
1284 return find_base_term (tmp2);
1286 /* Neither operand was known to be a pointer. Go ahead and find the
1287 base term for both operands. */
1288 tmp1 = find_base_term (tmp1);
1289 tmp2 = find_base_term (tmp2);
1291 /* If either base term is named object or a special address
1292 (like an argument or stack reference), then use it for the
1295 && (GET_CODE (tmp1) == SYMBOL_REF
1296 || GET_CODE (tmp1) == LABEL_REF
1297 || (GET_CODE (tmp1) == ADDRESS
1298 && GET_MODE (tmp1) != VOIDmode)))
1302 && (GET_CODE (tmp2) == SYMBOL_REF
1303 || GET_CODE (tmp2) == LABEL_REF
1304 || (GET_CODE (tmp2) == ADDRESS
1305 && GET_MODE (tmp2) != VOIDmode)))
1308 /* We could not determine which of the two operands was the
1309 base register and which was the index. So we can determine
1310 nothing from the base alias check. */
1315 if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
1316 return find_base_term (XEXP (x, 0));
1324 return REG_BASE_VALUE (frame_pointer_rtx);
1331 /* Return 0 if the addresses X and Y are known to point to different
1332 objects, 1 if they might be pointers to the same object. */
1335 base_alias_check (x, y, x_mode, y_mode)
1337 enum machine_mode x_mode, y_mode;
1339 rtx x_base = find_base_term (x);
1340 rtx y_base = find_base_term (y);
1342 /* If the address itself has no known base see if a known equivalent
1343 value has one. If either address still has no known base, nothing
1344 is known about aliasing. */
1349 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1352 x_base = find_base_term (x_c);
1360 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1363 y_base = find_base_term (y_c);
1368 /* If the base addresses are equal nothing is known about aliasing. */
1369 if (rtx_equal_p (x_base, y_base))
1372 /* The base addresses of the read and write are different expressions.
1373 If they are both symbols and they are not accessed via AND, there is
1374 no conflict. We can bring knowledge of object alignment into play
1375 here. For example, on alpha, "char a, b;" can alias one another,
1376 though "char a; long b;" cannot. */
1377 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1379 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1381 if (GET_CODE (x) == AND
1382 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1383 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1385 if (GET_CODE (y) == AND
1386 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1387 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1389 /* Differing symbols never alias. */
1393 /* If one address is a stack reference there can be no alias:
1394 stack references using different base registers do not alias,
1395 a stack reference can not alias a parameter, and a stack reference
1396 can not alias a global. */
1397 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1398 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1401 if (! flag_argument_noalias)
1404 if (flag_argument_noalias > 1)
1407 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1408 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1411 /* Convert the address X into something we can use. This is done by returning
1412 it unchanged unless it is a value; in the latter case we call cselib to get
1413 a more useful rtx. */
1420 struct elt_loc_list *l;
1422 if (GET_CODE (x) != VALUE)
1424 v = CSELIB_VAL_PTR (x);
1425 for (l = v->locs; l; l = l->next)
1426 if (CONSTANT_P (l->loc))
1428 for (l = v->locs; l; l = l->next)
1429 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1432 return v->locs->loc;
1436 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1437 where SIZE is the size in bytes of the memory reference. If ADDR
1438 is not modified by the memory reference then ADDR is returned. */
1441 addr_side_effect_eval (addr, size, n_refs)
1448 switch (GET_CODE (addr))
1451 offset = (n_refs + 1) * size;
1454 offset = -(n_refs + 1) * size;
1457 offset = n_refs * size;
1460 offset = -n_refs * size;
1468 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1470 addr = XEXP (addr, 0);
1475 /* Return nonzero if X and Y (memory addresses) could reference the
1476 same location in memory. C is an offset accumulator. When
1477 C is nonzero, we are testing aliases between X and Y + C.
1478 XSIZE is the size in bytes of the X reference,
1479 similarly YSIZE is the size in bytes for Y.
1481 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1482 referenced (the reference was BLKmode), so make the most pessimistic
1485 If XSIZE or YSIZE is negative, we may access memory outside the object
1486 being referenced as a side effect. This can happen when using AND to
1487 align memory references, as is done on the Alpha.
1489 Nice to notice that varying addresses cannot conflict with fp if no
1490 local variables had their addresses taken, but that's too hard now. */
1493 memrefs_conflict_p (xsize, x, ysize, y, c)
1498 if (GET_CODE (x) == VALUE)
1500 if (GET_CODE (y) == VALUE)
1502 if (GET_CODE (x) == HIGH)
1504 else if (GET_CODE (x) == LO_SUM)
1507 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1508 if (GET_CODE (y) == HIGH)
1510 else if (GET_CODE (y) == LO_SUM)
1513 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1515 if (rtx_equal_for_memref_p (x, y))
1517 if (xsize <= 0 || ysize <= 0)
1519 if (c >= 0 && xsize > c)
1521 if (c < 0 && ysize+c > 0)
1526 /* This code used to check for conflicts involving stack references and
1527 globals but the base address alias code now handles these cases. */
1529 if (GET_CODE (x) == PLUS)
1531 /* The fact that X is canonicalized means that this
1532 PLUS rtx is canonicalized. */
1533 rtx x0 = XEXP (x, 0);
1534 rtx x1 = XEXP (x, 1);
1536 if (GET_CODE (y) == PLUS)
1538 /* The fact that Y is canonicalized means that this
1539 PLUS rtx is canonicalized. */
1540 rtx y0 = XEXP (y, 0);
1541 rtx y1 = XEXP (y, 1);
1543 if (rtx_equal_for_memref_p (x1, y1))
1544 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1545 if (rtx_equal_for_memref_p (x0, y0))
1546 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1547 if (GET_CODE (x1) == CONST_INT)
1549 if (GET_CODE (y1) == CONST_INT)
1550 return memrefs_conflict_p (xsize, x0, ysize, y0,
1551 c - INTVAL (x1) + INTVAL (y1));
1553 return memrefs_conflict_p (xsize, x0, ysize, y,
1556 else if (GET_CODE (y1) == CONST_INT)
1557 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1561 else if (GET_CODE (x1) == CONST_INT)
1562 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1564 else if (GET_CODE (y) == PLUS)
1566 /* The fact that Y is canonicalized means that this
1567 PLUS rtx is canonicalized. */
1568 rtx y0 = XEXP (y, 0);
1569 rtx y1 = XEXP (y, 1);
1571 if (GET_CODE (y1) == CONST_INT)
1572 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1577 if (GET_CODE (x) == GET_CODE (y))
1578 switch (GET_CODE (x))
1582 /* Handle cases where we expect the second operands to be the
1583 same, and check only whether the first operand would conflict
1586 rtx x1 = canon_rtx (XEXP (x, 1));
1587 rtx y1 = canon_rtx (XEXP (y, 1));
1588 if (! rtx_equal_for_memref_p (x1, y1))
1590 x0 = canon_rtx (XEXP (x, 0));
1591 y0 = canon_rtx (XEXP (y, 0));
1592 if (rtx_equal_for_memref_p (x0, y0))
1593 return (xsize == 0 || ysize == 0
1594 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1596 /* Can't properly adjust our sizes. */
1597 if (GET_CODE (x1) != CONST_INT)
1599 xsize /= INTVAL (x1);
1600 ysize /= INTVAL (x1);
1602 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1606 /* Are these registers known not to be equal? */
1607 if (alias_invariant)
1609 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1610 rtx i_x, i_y; /* invariant relationships of X and Y */
1612 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1613 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1615 if (i_x == 0 && i_y == 0)
1618 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1619 ysize, i_y ? i_y : y, c))
1628 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1629 as an access with indeterminate size. Assume that references
1630 besides AND are aligned, so if the size of the other reference is
1631 at least as large as the alignment, assume no other overlap. */
1632 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1634 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1636 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1638 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1640 /* ??? If we are indexing far enough into the array/structure, we
1641 may yet be able to determine that we can not overlap. But we
1642 also need to that we are far enough from the end not to overlap
1643 a following reference, so we do nothing with that for now. */
1644 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1646 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1649 if (GET_CODE (x) == ADDRESSOF)
1651 if (y == frame_pointer_rtx
1652 || GET_CODE (y) == ADDRESSOF)
1653 return xsize <= 0 || ysize <= 0;
1655 if (GET_CODE (y) == ADDRESSOF)
1657 if (x == frame_pointer_rtx)
1658 return xsize <= 0 || ysize <= 0;
1663 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1665 c += (INTVAL (y) - INTVAL (x));
1666 return (xsize <= 0 || ysize <= 0
1667 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1670 if (GET_CODE (x) == CONST)
1672 if (GET_CODE (y) == CONST)
1673 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1674 ysize, canon_rtx (XEXP (y, 0)), c);
1676 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1679 if (GET_CODE (y) == CONST)
1680 return memrefs_conflict_p (xsize, x, ysize,
1681 canon_rtx (XEXP (y, 0)), c);
1684 return (xsize <= 0 || ysize <= 0
1685 || (rtx_equal_for_memref_p (x, y)
1686 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1693 /* Functions to compute memory dependencies.
1695 Since we process the insns in execution order, we can build tables
1696 to keep track of what registers are fixed (and not aliased), what registers
1697 are varying in known ways, and what registers are varying in unknown
1700 If both memory references are volatile, then there must always be a
1701 dependence between the two references, since their order can not be
1702 changed. A volatile and non-volatile reference can be interchanged
1705 A MEM_IN_STRUCT reference at a non-AND varying address can never
1706 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1707 also must allow AND addresses, because they may generate accesses
1708 outside the object being referenced. This is used to generate
1709 aligned addresses from unaligned addresses, for instance, the alpha
1710 storeqi_unaligned pattern. */
1712 /* Read dependence: X is read after read in MEM takes place. There can
1713 only be a dependence here if both reads are volatile. */
1716 read_dependence (mem, x)
1720 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1723 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1724 MEM2 is a reference to a structure at a varying address, or returns
1725 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1726 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1727 to decide whether or not an address may vary; it should return
1728 nonzero whenever variation is possible.
1729 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1732 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1734 rtx mem1_addr, mem2_addr;
1735 int (*varies_p) PARAMS ((rtx, int));
1737 if (! flag_strict_aliasing)
1740 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1741 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1742 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1746 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1747 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1748 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1755 /* Returns nonzero if something about the mode or address format MEM1
1756 indicates that it might well alias *anything*. */
1759 aliases_everything_p (mem)
1762 if (GET_CODE (XEXP (mem, 0)) == AND)
1763 /* If the address is an AND, its very hard to know at what it is
1764 actually pointing. */
1770 /* Return true if we can determine that the fields referenced cannot
1771 overlap for any pair of objects. */
1774 nonoverlapping_component_refs_p (x, y)
1777 tree fieldx, fieldy, typex, typey, orig_y;
1781 /* The comparison has to be done at a common type, since we don't
1782 know how the inheritance hierarchy works. */
1786 fieldx = TREE_OPERAND (x, 1);
1787 typex = DECL_FIELD_CONTEXT (fieldx);
1792 fieldy = TREE_OPERAND (y, 1);
1793 typey = DECL_FIELD_CONTEXT (fieldy);
1798 y = TREE_OPERAND (y, 0);
1800 while (y && TREE_CODE (y) == COMPONENT_REF);
1802 x = TREE_OPERAND (x, 0);
1804 while (x && TREE_CODE (x) == COMPONENT_REF);
1806 /* Never found a common type. */
1810 /* If we're left with accessing different fields of a structure,
1812 if (TREE_CODE (typex) == RECORD_TYPE
1813 && fieldx != fieldy)
1816 /* The comparison on the current field failed. If we're accessing
1817 a very nested structure, look at the next outer level. */
1818 x = TREE_OPERAND (x, 0);
1819 y = TREE_OPERAND (y, 0);
1822 && TREE_CODE (x) == COMPONENT_REF
1823 && TREE_CODE (y) == COMPONENT_REF);
1828 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1831 decl_for_component_ref (x)
1836 x = TREE_OPERAND (x, 0);
1838 while (x && TREE_CODE (x) == COMPONENT_REF);
1840 return x && DECL_P (x) ? x : NULL_TREE;
1843 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1844 offset of the field reference. */
1847 adjust_offset_for_component_ref (x, offset)
1851 HOST_WIDE_INT ioffset;
1856 ioffset = INTVAL (offset);
1859 tree field = TREE_OPERAND (x, 1);
1861 if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
1863 ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
1864 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
1867 x = TREE_OPERAND (x, 0);
1869 while (x && TREE_CODE (x) == COMPONENT_REF);
1871 return GEN_INT (ioffset);
1874 /* Return nonzero if we can deterimine the exprs corresponding to memrefs
1875 X and Y and they do not overlap. */
1878 nonoverlapping_memrefs_p (x, y)
1881 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
1884 rtx moffsetx, moffsety;
1885 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1887 /* Unless both have exprs, we can't tell anything. */
1888 if (exprx == 0 || expry == 0)
1891 /* If both are field references, we may be able to determine something. */
1892 if (TREE_CODE (exprx) == COMPONENT_REF
1893 && TREE_CODE (expry) == COMPONENT_REF
1894 && nonoverlapping_component_refs_p (exprx, expry))
1897 /* If the field reference test failed, look at the DECLs involved. */
1898 moffsetx = MEM_OFFSET (x);
1899 if (TREE_CODE (exprx) == COMPONENT_REF)
1901 tree t = decl_for_component_ref (exprx);
1904 moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
1907 moffsety = MEM_OFFSET (y);
1908 if (TREE_CODE (expry) == COMPONENT_REF)
1910 tree t = decl_for_component_ref (expry);
1913 moffsety = adjust_offset_for_component_ref (expry, moffsety);
1917 if (! DECL_P (exprx) || ! DECL_P (expry))
1920 rtlx = DECL_RTL (exprx);
1921 rtly = DECL_RTL (expry);
1923 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
1924 can't overlap unless they are the same because we never reuse that part
1925 of the stack frame used for locals for spilled pseudos. */
1926 if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
1927 && ! rtx_equal_p (rtlx, rtly))
1930 /* Get the base and offsets of both decls. If either is a register, we
1931 know both are and are the same, so use that as the base. The only
1932 we can avoid overlap is if we can deduce that they are nonoverlapping
1933 pieces of that decl, which is very rare. */
1934 basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
1935 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
1936 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
1938 basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
1939 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
1940 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
1942 /* If the bases are different, we know they do not overlap if both
1943 are constants or if one is a constant and the other a pointer into the
1944 stack frame. Otherwise a different base means we can't tell if they
1946 if (! rtx_equal_p (basex, basey))
1947 return ((CONSTANT_P (basex) && CONSTANT_P (basey))
1948 || (CONSTANT_P (basex) && REG_P (basey)
1949 && REGNO_PTR_FRAME_P (REGNO (basey)))
1950 || (CONSTANT_P (basey) && REG_P (basex)
1951 && REGNO_PTR_FRAME_P (REGNO (basex))));
1953 sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
1954 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
1956 sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
1957 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
1960 /* If we have an offset for either memref, it can update the values computed
1963 offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
1965 offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
1967 /* If a memref has both a size and an offset, we can use the smaller size.
1968 We can't do this if the offset isn't known because we must view this
1969 memref as being anywhere inside the DECL's MEM. */
1970 if (MEM_SIZE (x) && moffsetx)
1971 sizex = INTVAL (MEM_SIZE (x));
1972 if (MEM_SIZE (y) && moffsety)
1973 sizey = INTVAL (MEM_SIZE (y));
1975 /* Put the values of the memref with the lower offset in X's values. */
1976 if (offsetx > offsety)
1978 tem = offsetx, offsetx = offsety, offsety = tem;
1979 tem = sizex, sizex = sizey, sizey = tem;
1982 /* If we don't know the size of the lower-offset value, we can't tell
1983 if they conflict. Otherwise, we do the test. */
1984 return sizex >= 0 && offsety > offsetx + sizex;
1987 /* True dependence: X is read after store in MEM takes place. */
1990 true_dependence (mem, mem_mode, x, varies)
1992 enum machine_mode mem_mode;
1994 int (*varies) PARAMS ((rtx, int));
1996 rtx x_addr, mem_addr;
1999 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2002 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2005 /* Unchanging memory can't conflict with non-unchanging memory.
2006 A non-unchanging read can conflict with a non-unchanging write.
2007 An unchanging read can conflict with an unchanging write since
2008 there may be a single store to this address to initialize it.
2009 Note that an unchanging store can conflict with a non-unchanging read
2010 since we have to make conservative assumptions when we have a
2011 record with readonly fields and we are copying the whole thing.
2012 Just fall through to the code below to resolve potential conflicts.
2013 This won't handle all cases optimally, but the possible performance
2014 loss should be negligible. */
2015 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2018 if (nonoverlapping_memrefs_p (mem, x))
2021 if (mem_mode == VOIDmode)
2022 mem_mode = GET_MODE (mem);
2024 x_addr = get_addr (XEXP (x, 0));
2025 mem_addr = get_addr (XEXP (mem, 0));
2027 base = find_base_term (x_addr);
2028 if (base && (GET_CODE (base) == LABEL_REF
2029 || (GET_CODE (base) == SYMBOL_REF
2030 && CONSTANT_POOL_ADDRESS_P (base))))
2033 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2036 x_addr = canon_rtx (x_addr);
2037 mem_addr = canon_rtx (mem_addr);
2039 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2040 SIZE_FOR_MODE (x), x_addr, 0))
2043 if (aliases_everything_p (x))
2046 /* We cannot use aliases_everything_p to test MEM, since we must look
2047 at MEM_MODE, rather than GET_MODE (MEM). */
2048 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2051 /* In true_dependence we also allow BLKmode to alias anything. Why
2052 don't we do this in anti_dependence and output_dependence? */
2053 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2056 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2060 /* Canonical true dependence: X is read after store in MEM takes place.
2061 Variant of true_dependence which assumes MEM has already been
2062 canonicalized (hence we no longer do that here).
2063 The mem_addr argument has been added, since true_dependence computed
2064 this value prior to canonicalizing. */
2067 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
2068 rtx mem, mem_addr, x;
2069 enum machine_mode mem_mode;
2070 int (*varies) PARAMS ((rtx, int));
2074 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2077 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2080 /* If X is an unchanging read, then it can't possibly conflict with any
2081 non-unchanging store. It may conflict with an unchanging write though,
2082 because there may be a single store to this address to initialize it.
2083 Just fall through to the code below to resolve the case where we have
2084 both an unchanging read and an unchanging write. This won't handle all
2085 cases optimally, but the possible performance loss should be
2087 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
2090 if (nonoverlapping_memrefs_p (x, mem))
2093 x_addr = get_addr (XEXP (x, 0));
2095 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
2098 x_addr = canon_rtx (x_addr);
2099 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
2100 SIZE_FOR_MODE (x), x_addr, 0))
2103 if (aliases_everything_p (x))
2106 /* We cannot use aliases_everything_p to test MEM, since we must look
2107 at MEM_MODE, rather than GET_MODE (MEM). */
2108 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
2111 /* In true_dependence we also allow BLKmode to alias anything. Why
2112 don't we do this in anti_dependence and output_dependence? */
2113 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
2116 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2120 /* Returns non-zero if a write to X might alias a previous read from
2121 (or, if WRITEP is non-zero, a write to) MEM. */
2124 write_dependence_p (mem, x, writep)
2129 rtx x_addr, mem_addr;
2133 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
2136 if (DIFFERENT_ALIAS_SETS_P (x, mem))
2139 /* Unchanging memory can't conflict with non-unchanging memory. */
2140 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
2143 /* If MEM is an unchanging read, then it can't possibly conflict with
2144 the store to X, because there is at most one store to MEM, and it must
2145 have occurred somewhere before MEM. */
2146 if (! writep && RTX_UNCHANGING_P (mem))
2149 if (nonoverlapping_memrefs_p (x, mem))
2152 x_addr = get_addr (XEXP (x, 0));
2153 mem_addr = get_addr (XEXP (mem, 0));
2157 base = find_base_term (mem_addr);
2158 if (base && (GET_CODE (base) == LABEL_REF
2159 || (GET_CODE (base) == SYMBOL_REF
2160 && CONSTANT_POOL_ADDRESS_P (base))))
2164 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2168 x_addr = canon_rtx (x_addr);
2169 mem_addr = canon_rtx (mem_addr);
2171 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2172 SIZE_FOR_MODE (x), x_addr, 0))
2176 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2179 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2180 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2183 /* Anti dependence: X is written after read in MEM takes place. */
2186 anti_dependence (mem, x)
2190 return write_dependence_p (mem, x, /*writep=*/0);
2193 /* Output dependence: X is written after store in MEM takes place. */
2196 output_dependence (mem, x)
2200 return write_dependence_p (mem, x, /*writep=*/1);
2203 /* Returns non-zero if X mentions something which is not
2204 local to the function and is not constant. */
2207 nonlocal_mentioned_p (x)
2214 code = GET_CODE (x);
2216 if (GET_RTX_CLASS (code) == 'i')
2218 /* Constant functions can be constant if they don't use
2219 scratch memory used to mark function w/o side effects. */
2220 if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x))
2222 x = CALL_INSN_FUNCTION_USAGE (x);
2228 code = GET_CODE (x);
2234 if (GET_CODE (SUBREG_REG (x)) == REG)
2236 /* Global registers are not local. */
2237 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2238 && global_regs[subreg_regno (x)])
2246 /* Global registers are not local. */
2247 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2261 /* Constants in the function's constants pool are constant. */
2262 if (CONSTANT_POOL_ADDRESS_P (x))
2267 /* Non-constant calls and recursion are not local. */
2271 /* Be overly conservative and consider any volatile memory
2272 reference as not local. */
2273 if (MEM_VOLATILE_P (x))
2275 base = find_base_term (XEXP (x, 0));
2278 /* A Pmode ADDRESS could be a reference via the structure value
2279 address or static chain. Such memory references are nonlocal.
2281 Thus, we have to examine the contents of the ADDRESS to find
2282 out if this is a local reference or not. */
2283 if (GET_CODE (base) == ADDRESS
2284 && GET_MODE (base) == Pmode
2285 && (XEXP (base, 0) == stack_pointer_rtx
2286 || XEXP (base, 0) == arg_pointer_rtx
2287 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2288 || XEXP (base, 0) == hard_frame_pointer_rtx
2290 || XEXP (base, 0) == frame_pointer_rtx))
2292 /* Constants in the function's constant pool are constant. */
2293 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2298 case UNSPEC_VOLATILE:
2303 if (MEM_VOLATILE_P (x))
2312 /* Recursively scan the operands of this expression. */
2315 const char *fmt = GET_RTX_FORMAT (code);
2318 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2320 if (fmt[i] == 'e' && XEXP (x, i))
2322 if (nonlocal_mentioned_p (XEXP (x, i)))
2325 else if (fmt[i] == 'E')
2328 for (j = 0; j < XVECLEN (x, i); j++)
2329 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2338 /* Mark the function if it is constant. */
2341 mark_constant_function ()
2344 int nonlocal_mentioned;
2346 if (TREE_PUBLIC (current_function_decl)
2347 || TREE_READONLY (current_function_decl)
2348 || DECL_IS_PURE (current_function_decl)
2349 || TREE_THIS_VOLATILE (current_function_decl)
2350 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2353 /* A loop might not return which counts as a side effect. */
2354 if (mark_dfs_back_edges ())
2357 nonlocal_mentioned = 0;
2359 init_alias_analysis ();
2361 /* Determine if this is a constant function. */
2363 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2364 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2366 nonlocal_mentioned = 1;
2370 end_alias_analysis ();
2372 /* Mark the function. */
2374 if (! nonlocal_mentioned)
2375 TREE_READONLY (current_function_decl) = 1;
2379 static HARD_REG_SET argument_registers;
2386 #ifndef OUTGOING_REGNO
2387 #define OUTGOING_REGNO(N) N
2389 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2390 /* Check whether this register can hold an incoming pointer
2391 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2392 numbers, so translate if necessary due to register windows. */
2393 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2394 && HARD_REGNO_MODE_OK (i, Pmode))
2395 SET_HARD_REG_BIT (argument_registers, i);
2397 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2400 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2404 init_alias_analysis ()
2406 int maxreg = max_reg_num ();
2412 reg_known_value_size = maxreg;
2415 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2416 - FIRST_PSEUDO_REGISTER;
2418 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2419 - FIRST_PSEUDO_REGISTER;
2421 /* Overallocate reg_base_value to allow some growth during loop
2422 optimization. Loop unrolling can create a large number of
2424 reg_base_value_size = maxreg * 2;
2425 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2426 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2428 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2429 reg_seen = (char *) xmalloc (reg_base_value_size);
2430 if (! reload_completed && flag_unroll_loops)
2432 /* ??? Why are we realloc'ing if we're just going to zero it? */
2433 alias_invariant = (rtx *)xrealloc (alias_invariant,
2434 reg_base_value_size * sizeof (rtx));
2435 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2438 /* The basic idea is that each pass through this loop will use the
2439 "constant" information from the previous pass to propagate alias
2440 information through another level of assignments.
2442 This could get expensive if the assignment chains are long. Maybe
2443 we should throttle the number of iterations, possibly based on
2444 the optimization level or flag_expensive_optimizations.
2446 We could propagate more information in the first pass by making use
2447 of REG_N_SETS to determine immediately that the alias information
2448 for a pseudo is "constant".
2450 A program with an uninitialized variable can cause an infinite loop
2451 here. Instead of doing a full dataflow analysis to detect such problems
2452 we just cap the number of iterations for the loop.
2454 The state of the arrays for the set chain in question does not matter
2455 since the program has undefined behavior. */
2460 /* Assume nothing will change this iteration of the loop. */
2463 /* We want to assign the same IDs each iteration of this loop, so
2464 start counting from zero each iteration of the loop. */
2467 /* We're at the start of the function each iteration through the
2468 loop, so we're copying arguments. */
2469 copying_arguments = 1;
2471 /* Wipe the potential alias information clean for this pass. */
2472 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2474 /* Wipe the reg_seen array clean. */
2475 memset ((char *) reg_seen, 0, reg_base_value_size);
2477 /* Mark all hard registers which may contain an address.
2478 The stack, frame and argument pointers may contain an address.
2479 An argument register which can hold a Pmode value may contain
2480 an address even if it is not in BASE_REGS.
2482 The address expression is VOIDmode for an argument and
2483 Pmode for other registers. */
2485 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2486 if (TEST_HARD_REG_BIT (argument_registers, i))
2487 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2488 gen_rtx_REG (Pmode, i));
2490 new_reg_base_value[STACK_POINTER_REGNUM]
2491 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2492 new_reg_base_value[ARG_POINTER_REGNUM]
2493 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2494 new_reg_base_value[FRAME_POINTER_REGNUM]
2495 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2496 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2497 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2498 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2501 /* Walk the insns adding values to the new_reg_base_value array. */
2502 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2508 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2509 /* The prologue/epilogue insns are not threaded onto the
2510 insn chain until after reload has completed. Thus,
2511 there is no sense wasting time checking if INSN is in
2512 the prologue/epilogue until after reload has completed. */
2513 if (reload_completed
2514 && prologue_epilogue_contains (insn))
2518 /* If this insn has a noalias note, process it, Otherwise,
2519 scan for sets. A simple set will have no side effects
2520 which could change the base value of any other register. */
2522 if (GET_CODE (PATTERN (insn)) == SET
2523 && REG_NOTES (insn) != 0
2524 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2525 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2527 note_stores (PATTERN (insn), record_set, NULL);
2529 set = single_set (insn);
2532 && GET_CODE (SET_DEST (set)) == REG
2533 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2535 unsigned int regno = REGNO (SET_DEST (set));
2536 rtx src = SET_SRC (set);
2538 if (REG_NOTES (insn) != 0
2539 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2540 && REG_N_SETS (regno) == 1)
2541 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2542 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2543 && ! rtx_varies_p (XEXP (note, 0), 1)
2544 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2546 reg_known_value[regno] = XEXP (note, 0);
2547 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2549 else if (REG_N_SETS (regno) == 1
2550 && GET_CODE (src) == PLUS
2551 && GET_CODE (XEXP (src, 0)) == REG
2552 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2553 && (reg_known_value[REGNO (XEXP (src, 0))])
2554 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2556 rtx op0 = XEXP (src, 0);
2557 op0 = reg_known_value[REGNO (op0)];
2558 reg_known_value[regno]
2559 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2560 reg_known_equiv_p[regno] = 0;
2562 else if (REG_N_SETS (regno) == 1
2563 && ! rtx_varies_p (src, 1))
2565 reg_known_value[regno] = src;
2566 reg_known_equiv_p[regno] = 0;
2570 else if (GET_CODE (insn) == NOTE
2571 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2572 copying_arguments = 0;
2575 /* Now propagate values from new_reg_base_value to reg_base_value. */
2576 for (ui = 0; ui < reg_base_value_size; ui++)
2578 if (new_reg_base_value[ui]
2579 && new_reg_base_value[ui] != reg_base_value[ui]
2580 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2582 reg_base_value[ui] = new_reg_base_value[ui];
2587 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2589 /* Fill in the remaining entries. */
2590 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2591 if (reg_known_value[i] == 0)
2592 reg_known_value[i] = regno_reg_rtx[i];
2594 /* Simplify the reg_base_value array so that no register refers to
2595 another register, except to special registers indirectly through
2596 ADDRESS expressions.
2598 In theory this loop can take as long as O(registers^2), but unless
2599 there are very long dependency chains it will run in close to linear
2602 This loop may not be needed any longer now that the main loop does
2603 a better job at propagating alias information. */
2609 for (ui = 0; ui < reg_base_value_size; ui++)
2611 rtx base = reg_base_value[ui];
2612 if (base && GET_CODE (base) == REG)
2614 unsigned int base_regno = REGNO (base);
2615 if (base_regno == ui) /* register set from itself */
2616 reg_base_value[ui] = 0;
2618 reg_base_value[ui] = reg_base_value[base_regno];
2623 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2626 free (new_reg_base_value);
2627 new_reg_base_value = 0;
2633 end_alias_analysis ()
2635 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2636 reg_known_value = 0;
2637 reg_known_value_size = 0;
2638 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2639 reg_known_equiv_p = 0;
2642 ggc_del_root (reg_base_value);
2643 free (reg_base_value);
2646 reg_base_value_size = 0;
2647 if (alias_invariant)
2649 free (alias_invariant);
2650 alias_invariant = 0;