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 int handled_component_p PARAMS ((tree));
99 static rtx find_base_value PARAMS ((rtx));
100 static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx));
101 static int insert_subset_children PARAMS ((splay_tree_node, void*));
102 static tree find_base_decl PARAMS ((tree));
103 static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT));
104 static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx,
105 int (*) (rtx, int)));
106 static int aliases_everything_p PARAMS ((rtx));
107 static int nonoverlapping_memrefs_p PARAMS ((rtx, rtx));
108 static int write_dependence_p PARAMS ((rtx, rtx, int));
109 static int nonlocal_mentioned_p PARAMS ((rtx));
111 /* Set up all info needed to perform alias analysis on memory references. */
113 /* Returns the size in bytes of the mode of X. */
114 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
116 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
117 different alias sets. We ignore alias sets in functions making use
118 of variable arguments because the va_arg macros on some systems are
120 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
121 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
123 /* Cap the number of passes we make over the insns propagating alias
124 information through set chains. 10 is a completely arbitrary choice. */
125 #define MAX_ALIAS_LOOP_PASSES 10
127 /* reg_base_value[N] gives an address to which register N is related.
128 If all sets after the first add or subtract to the current value
129 or otherwise modify it so it does not point to a different top level
130 object, reg_base_value[N] is equal to the address part of the source
133 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
134 expressions represent certain special values: function arguments and
135 the stack, frame, and argument pointers.
137 The contents of an ADDRESS is not normally used, the mode of the
138 ADDRESS determines whether the ADDRESS is a function argument or some
139 other special value. Pointer equality, not rtx_equal_p, determines whether
140 two ADDRESS expressions refer to the same base address.
142 The only use of the contents of an ADDRESS is for determining if the
143 current function performs nonlocal memory memory references for the
144 purposes of marking the function as a constant function. */
146 static rtx *reg_base_value;
147 static rtx *new_reg_base_value;
148 static unsigned int reg_base_value_size; /* size of reg_base_value array */
150 #define REG_BASE_VALUE(X) \
151 (REGNO (X) < reg_base_value_size \
152 ? reg_base_value[REGNO (X)] : 0)
154 /* Vector of known invariant relationships between registers. Set in
155 loop unrolling. Indexed by register number, if nonzero the value
156 is an expression describing this register in terms of another.
158 The length of this array is REG_BASE_VALUE_SIZE.
160 Because this array contains only pseudo registers it has no effect
162 static rtx *alias_invariant;
164 /* Vector indexed by N giving the initial (unchanging) value known for
165 pseudo-register N. This array is initialized in
166 init_alias_analysis, and does not change until end_alias_analysis
168 rtx *reg_known_value;
170 /* Indicates number of valid entries in reg_known_value. */
171 static unsigned int reg_known_value_size;
173 /* Vector recording for each reg_known_value whether it is due to a
174 REG_EQUIV note. Future passes (viz., reload) may replace the
175 pseudo with the equivalent expression and so we account for the
176 dependences that would be introduced if that happens.
178 The REG_EQUIV notes created in assign_parms may mention the arg
179 pointer, and there are explicit insns in the RTL that modify the
180 arg pointer. Thus we must ensure that such insns don't get
181 scheduled across each other because that would invalidate the
182 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
183 wrong, but solving the problem in the scheduler will likely give
184 better code, so we do it here. */
185 char *reg_known_equiv_p;
187 /* True when scanning insns from the start of the rtl to the
188 NOTE_INSN_FUNCTION_BEG note. */
189 static int copying_arguments;
191 /* The splay-tree used to store the various alias set entries. */
192 static splay_tree alias_sets;
194 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
195 such an entry, or NULL otherwise. */
197 static alias_set_entry
198 get_alias_set_entry (alias_set)
199 HOST_WIDE_INT alias_set;
202 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
204 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
207 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
208 the two MEMs cannot alias each other. */
211 mems_in_disjoint_alias_sets_p (mem1, mem2)
215 #ifdef ENABLE_CHECKING
216 /* Perform a basic sanity check. Namely, that there are no alias sets
217 if we're not using strict aliasing. This helps to catch bugs
218 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
219 where a MEM is allocated in some way other than by the use of
220 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
221 use alias sets to indicate that spilled registers cannot alias each
222 other, we might need to remove this check. */
223 if (! flag_strict_aliasing
224 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
228 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
231 /* Insert the NODE into the splay tree given by DATA. Used by
232 record_alias_subset via splay_tree_foreach. */
235 insert_subset_children (node, data)
236 splay_tree_node node;
239 splay_tree_insert ((splay_tree) data, node->key, node->value);
244 /* Return 1 if the two specified alias sets may conflict. */
247 alias_sets_conflict_p (set1, set2)
248 HOST_WIDE_INT set1, set2;
252 /* If have no alias set information for one of the operands, we have
253 to assume it can alias anything. */
254 if (set1 == 0 || set2 == 0
255 /* If the two alias sets are the same, they may alias. */
259 /* See if the first alias set is a subset of the second. */
260 ase = get_alias_set_entry (set1);
262 && (ase->has_zero_child
263 || splay_tree_lookup (ase->children,
264 (splay_tree_key) set2)))
267 /* Now do the same, but with the alias sets reversed. */
268 ase = get_alias_set_entry (set2);
270 && (ase->has_zero_child
271 || splay_tree_lookup (ase->children,
272 (splay_tree_key) set1)))
275 /* The two alias sets are distinct and neither one is the
276 child of the other. Therefore, they cannot alias. */
280 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
281 has any readonly fields. If any of the fields have types that
282 contain readonly fields, return true as well. */
285 readonly_fields_p (type)
290 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
291 && TREE_CODE (type) != QUAL_UNION_TYPE)
294 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
295 if (TREE_CODE (field) == FIELD_DECL
296 && (TREE_READONLY (field)
297 || readonly_fields_p (TREE_TYPE (field))))
303 /* Return 1 if any MEM object of type T1 will always conflict (using the
304 dependency routines in this file) with any MEM object of type T2.
305 This is used when allocating temporary storage. If T1 and/or T2 are
306 NULL_TREE, it means we know nothing about the storage. */
309 objects_must_conflict_p (t1, t2)
312 /* If neither has a type specified, we don't know if they'll conflict
313 because we may be using them to store objects of various types, for
314 example the argument and local variables areas of inlined functions. */
315 if (t1 == 0 && t2 == 0)
318 /* If one or the other has readonly fields or is readonly,
319 then they may not conflict. */
320 if ((t1 != 0 && readonly_fields_p (t1))
321 || (t2 != 0 && readonly_fields_p (t2))
322 || (t1 != 0 && TYPE_READONLY (t1))
323 || (t2 != 0 && TYPE_READONLY (t2)))
326 /* If they are the same type, they must conflict. */
328 /* Likewise if both are volatile. */
329 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
332 /* If one is aggregate and the other is scalar then they may not
334 if ((t1 != 0 && AGGREGATE_TYPE_P (t1))
335 != (t2 != 0 && AGGREGATE_TYPE_P (t2)))
338 /* Otherwise they conflict only if the alias sets conflict. */
339 return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0,
340 t2 ? get_alias_set (t2) : 0);
343 /* T is an expression with pointer type. Find the DECL on which this
344 expression is based. (For example, in `a[i]' this would be `a'.)
345 If there is no such DECL, or a unique decl cannot be determined,
346 NULL_TREE is returned. */
354 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
357 /* If this is a declaration, return it. */
358 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
361 /* Handle general expressions. It would be nice to deal with
362 COMPONENT_REFs here. If we could tell that `a' and `b' were the
363 same, then `a->f' and `b->f' are also the same. */
364 switch (TREE_CODE_CLASS (TREE_CODE (t)))
367 return find_base_decl (TREE_OPERAND (t, 0));
370 /* Return 0 if found in neither or both are the same. */
371 d0 = find_base_decl (TREE_OPERAND (t, 0));
372 d1 = find_base_decl (TREE_OPERAND (t, 1));
383 d0 = find_base_decl (TREE_OPERAND (t, 0));
384 d1 = find_base_decl (TREE_OPERAND (t, 1));
385 d2 = find_base_decl (TREE_OPERAND (t, 2));
387 /* Set any nonzero values from the last, then from the first. */
388 if (d1 == 0) d1 = d2;
389 if (d0 == 0) d0 = d1;
390 if (d1 == 0) d1 = d0;
391 if (d2 == 0) d2 = d1;
393 /* At this point all are nonzero or all are zero. If all three are the
394 same, return it. Otherwise, return zero. */
395 return (d0 == d1 && d1 == d2) ? d0 : 0;
402 /* Return 1 if T is an expression that get_inner_reference handles. */
405 handled_component_p (t)
408 switch (TREE_CODE (t))
413 case ARRAY_RANGE_REF:
414 case NON_LVALUE_EXPR:
419 return (TYPE_MODE (TREE_TYPE (t))
420 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))));
427 /* Return 1 if all the nested component references handled by
428 get_inner_reference in T are such that we can address the object in T. */
434 /* If we're at the end, it is vacuously addressable. */
435 if (! handled_component_p (t))
438 /* Bitfields are never addressable. */
439 else if (TREE_CODE (t) == BIT_FIELD_REF)
442 /* Fields are addressable unless they are marked as nonaddressable or
443 the containing type has alias set 0. */
444 else if (TREE_CODE (t) == COMPONENT_REF
445 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
446 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
447 && can_address_p (TREE_OPERAND (t, 0)))
450 /* Likewise for arrays. */
451 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
452 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
453 && get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
454 && can_address_p (TREE_OPERAND (t, 0)))
460 /* Return the alias set for T, which may be either a type or an
461 expression. Call language-specific routine for help, if needed. */
469 /* If we're not doing any alias analysis, just assume everything
470 aliases everything else. Also return 0 if this or its type is
472 if (! flag_strict_aliasing || t == error_mark_node
474 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
477 /* We can be passed either an expression or a type. This and the
478 language-specific routine may make mutually-recursive calls to each other
479 to figure out what to do. At each juncture, we see if this is a tree
480 that the language may need to handle specially. First handle things that
485 tree placeholder_ptr = 0;
487 /* Remove any nops, then give the language a chance to do
488 something with this tree before we look at it. */
490 set = (*lang_hooks.get_alias_set) (t);
494 /* First see if the actual object referenced is an INDIRECT_REF from a
495 restrict-qualified pointer or a "void *". Replace
496 PLACEHOLDER_EXPRs. */
497 while (TREE_CODE (inner) == PLACEHOLDER_EXPR
498 || handled_component_p (inner))
500 if (TREE_CODE (inner) == PLACEHOLDER_EXPR)
501 inner = find_placeholder (inner, &placeholder_ptr);
503 inner = TREE_OPERAND (inner, 0);
508 /* Check for accesses through restrict-qualified pointers. */
509 if (TREE_CODE (inner) == INDIRECT_REF)
511 tree decl = find_base_decl (TREE_OPERAND (inner, 0));
513 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
515 /* If we haven't computed the actual alias set, do it now. */
516 if (DECL_POINTER_ALIAS_SET (decl) == -2)
518 /* No two restricted pointers can point at the same thing.
519 However, a restricted pointer can point at the same thing
520 as an unrestricted pointer, if that unrestricted pointer
521 is based on the restricted pointer. So, we make the
522 alias set for the restricted pointer a subset of the
523 alias set for the type pointed to by the type of the
525 HOST_WIDE_INT pointed_to_alias_set
526 = get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
528 if (pointed_to_alias_set == 0)
529 /* It's not legal to make a subset of alias set zero. */
533 DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
534 record_alias_subset (pointed_to_alias_set,
535 DECL_POINTER_ALIAS_SET (decl));
539 /* We use the alias set indicated in the declaration. */
540 return DECL_POINTER_ALIAS_SET (decl);
543 /* If we have an INDIRECT_REF via a void pointer, we don't
544 know anything about what that might alias. */
545 else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE)
549 /* Otherwise, pick up the outermost object that we could have a pointer
550 to, processing conversion and PLACEHOLDER_EXPR as above. */
552 while (TREE_CODE (t) == PLACEHOLDER_EXPR
553 || (handled_component_p (t) && ! can_address_p (t)))
555 if (TREE_CODE (t) == PLACEHOLDER_EXPR)
556 t = find_placeholder (t, &placeholder_ptr);
558 t = TREE_OPERAND (t, 0);
563 /* If we've already determined the alias set for a decl, just return
564 it. This is necessary for C++ anonymous unions, whose component
565 variables don't look like union members (boo!). */
566 if (TREE_CODE (t) == VAR_DECL
567 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
568 return MEM_ALIAS_SET (DECL_RTL (t));
570 /* Now all we care about is the type. */
574 /* Variant qualifiers don't affect the alias set, so get the main
575 variant. If this is a type with a known alias set, return it. */
576 t = TYPE_MAIN_VARIANT (t);
577 if (TYPE_ALIAS_SET_KNOWN_P (t))
578 return TYPE_ALIAS_SET (t);
580 /* See if the language has special handling for this type. */
581 set = (*lang_hooks.get_alias_set) (t);
585 /* There are no objects of FUNCTION_TYPE, so there's no point in
586 using up an alias set for them. (There are, of course, pointers
587 and references to functions, but that's different.) */
588 else if (TREE_CODE (t) == FUNCTION_TYPE)
591 /* Otherwise make a new alias set for this type. */
592 set = new_alias_set ();
594 TYPE_ALIAS_SET (t) = set;
596 /* If this is an aggregate type, we must record any component aliasing
598 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
599 record_component_aliases (t);
604 /* Return a brand-new alias set. */
609 static HOST_WIDE_INT last_alias_set;
611 if (flag_strict_aliasing)
612 return ++last_alias_set;
617 /* Indicate that things in SUBSET can alias things in SUPERSET, but
618 not vice versa. For example, in C, a store to an `int' can alias a
619 structure containing an `int', but not vice versa. Here, the
620 structure would be the SUPERSET and `int' the SUBSET. This
621 function should be called only once per SUPERSET/SUBSET pair.
623 It is illegal for SUPERSET to be zero; everything is implicitly a
624 subset of alias set zero. */
627 record_alias_subset (superset, subset)
628 HOST_WIDE_INT superset;
629 HOST_WIDE_INT subset;
631 alias_set_entry superset_entry;
632 alias_set_entry subset_entry;
634 /* It is possible in complex type situations for both sets to be the same,
635 in which case we can ignore this operation. */
636 if (superset == subset)
642 superset_entry = get_alias_set_entry (superset);
643 if (superset_entry == 0)
645 /* Create an entry for the SUPERSET, so that we have a place to
646 attach the SUBSET. */
648 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
649 superset_entry->alias_set = superset;
650 superset_entry->children
651 = splay_tree_new (splay_tree_compare_ints, 0, 0);
652 superset_entry->has_zero_child = 0;
653 splay_tree_insert (alias_sets, (splay_tree_key) superset,
654 (splay_tree_value) superset_entry);
658 superset_entry->has_zero_child = 1;
661 subset_entry = get_alias_set_entry (subset);
662 /* If there is an entry for the subset, enter all of its children
663 (if they are not already present) as children of the SUPERSET. */
666 if (subset_entry->has_zero_child)
667 superset_entry->has_zero_child = 1;
669 splay_tree_foreach (subset_entry->children, insert_subset_children,
670 superset_entry->children);
673 /* Enter the SUBSET itself as a child of the SUPERSET. */
674 splay_tree_insert (superset_entry->children,
675 (splay_tree_key) subset, 0);
679 /* Record that component types of TYPE, if any, are part of that type for
680 aliasing purposes. For record types, we only record component types
681 for fields that are marked addressable. For array types, we always
682 record the component types, so the front end should not call this
683 function if the individual component aren't addressable. */
686 record_component_aliases (type)
689 HOST_WIDE_INT superset = get_alias_set (type);
695 switch (TREE_CODE (type))
698 if (! TYPE_NONALIASED_COMPONENT (type))
699 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
704 case QUAL_UNION_TYPE:
705 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
706 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
707 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
711 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
719 /* Allocate an alias set for use in storing and reading from the varargs
723 get_varargs_alias_set ()
725 static HOST_WIDE_INT set = -1;
728 set = new_alias_set ();
733 /* Likewise, but used for the fixed portions of the frame, e.g., register
737 get_frame_alias_set ()
739 static HOST_WIDE_INT set = -1;
742 set = new_alias_set ();
747 /* Inside SRC, the source of a SET, find a base address. */
750 find_base_value (src)
754 switch (GET_CODE (src))
762 /* At the start of a function, argument registers have known base
763 values which may be lost later. Returning an ADDRESS
764 expression here allows optimization based on argument values
765 even when the argument registers are used for other purposes. */
766 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
767 return new_reg_base_value[regno];
769 /* If a pseudo has a known base value, return it. Do not do this
770 for hard regs since it can result in a circular dependency
771 chain for registers which have values at function entry.
773 The test above is not sufficient because the scheduler may move
774 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
775 if (regno >= FIRST_PSEUDO_REGISTER
776 && regno < reg_base_value_size
777 && reg_base_value[regno])
778 return reg_base_value[regno];
783 /* Check for an argument passed in memory. Only record in the
784 copying-arguments block; it is too hard to track changes
786 if (copying_arguments
787 && (XEXP (src, 0) == arg_pointer_rtx
788 || (GET_CODE (XEXP (src, 0)) == PLUS
789 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
790 return gen_rtx_ADDRESS (VOIDmode, src);
795 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
798 /* ... fall through ... */
803 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
805 /* If either operand is a REG, then see if we already have
806 a known value for it. */
807 if (GET_CODE (src_0) == REG)
809 temp = find_base_value (src_0);
814 if (GET_CODE (src_1) == REG)
816 temp = find_base_value (src_1);
821 /* Guess which operand is the base address:
822 If either operand is a symbol, then it is the base. If
823 either operand is a CONST_INT, then the other is the base. */
824 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
825 return find_base_value (src_0);
826 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
827 return find_base_value (src_1);
829 /* This might not be necessary anymore:
830 If either operand is a REG that is a known pointer, then it
832 else if (GET_CODE (src_0) == REG && REG_POINTER (src_0))
833 return find_base_value (src_0);
834 else if (GET_CODE (src_1) == REG && REG_POINTER (src_1))
835 return find_base_value (src_1);
841 /* The standard form is (lo_sum reg sym) so look only at the
843 return find_base_value (XEXP (src, 1));
846 /* If the second operand is constant set the base
847 address to the first operand. */
848 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
849 return find_base_value (XEXP (src, 0));
853 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
857 case SIGN_EXTEND: /* used for NT/Alpha pointers */
859 return find_base_value (XEXP (src, 0));
868 /* Called from init_alias_analysis indirectly through note_stores. */
870 /* While scanning insns to find base values, reg_seen[N] is nonzero if
871 register N has been set in this function. */
872 static char *reg_seen;
874 /* Addresses which are known not to alias anything else are identified
875 by a unique integer. */
876 static int unique_id;
879 record_set (dest, set, data)
881 void *data ATTRIBUTE_UNUSED;
886 if (GET_CODE (dest) != REG)
889 regno = REGNO (dest);
891 if (regno >= reg_base_value_size)
896 /* A CLOBBER wipes out any old value but does not prevent a previously
897 unset register from acquiring a base address (i.e. reg_seen is not
899 if (GET_CODE (set) == CLOBBER)
901 new_reg_base_value[regno] = 0;
910 new_reg_base_value[regno] = 0;
914 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
915 GEN_INT (unique_id++));
919 /* This is not the first set. If the new value is not related to the
920 old value, forget the base value. Note that the following code is
922 extern int x, y; int *p = &x; p += (&y-&x);
923 ANSI C does not allow computing the difference of addresses
924 of distinct top level objects. */
925 if (new_reg_base_value[regno])
926 switch (GET_CODE (src))
930 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
931 new_reg_base_value[regno] = 0;
934 /* If the value we add in the PLUS is also a valid base value,
935 this might be the actual base value, and the original value
938 rtx other = NULL_RTX;
940 if (XEXP (src, 0) == dest)
941 other = XEXP (src, 1);
942 else if (XEXP (src, 1) == dest)
943 other = XEXP (src, 0);
945 if (! other || find_base_value (other))
946 new_reg_base_value[regno] = 0;
950 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
951 new_reg_base_value[regno] = 0;
954 new_reg_base_value[regno] = 0;
957 /* If this is the first set of a register, record the value. */
958 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
959 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
960 new_reg_base_value[regno] = find_base_value (src);
965 /* Called from loop optimization when a new pseudo-register is
966 created. It indicates that REGNO is being set to VAL. f INVARIANT
967 is true then this value also describes an invariant relationship
968 which can be used to deduce that two registers with unknown values
972 record_base_value (regno, val, invariant)
977 if (regno >= reg_base_value_size)
980 if (invariant && alias_invariant)
981 alias_invariant[regno] = val;
983 if (GET_CODE (val) == REG)
985 if (REGNO (val) < reg_base_value_size)
986 reg_base_value[regno] = reg_base_value[REGNO (val)];
991 reg_base_value[regno] = find_base_value (val);
994 /* Clear alias info for a register. This is used if an RTL transformation
995 changes the value of a register. This is used in flow by AUTO_INC_DEC
996 optimizations. We don't need to clear reg_base_value, since flow only
997 changes the offset. */
1000 clear_reg_alias_info (reg)
1003 unsigned int regno = REGNO (reg);
1005 if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
1006 reg_known_value[regno] = reg;
1009 /* Returns a canonical version of X, from the point of view alias
1010 analysis. (For example, if X is a MEM whose address is a register,
1011 and the register has a known value (say a SYMBOL_REF), then a MEM
1012 whose address is the SYMBOL_REF is returned.) */
1018 /* Recursively look for equivalences. */
1019 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
1020 && REGNO (x) < reg_known_value_size)
1021 return reg_known_value[REGNO (x)] == x
1022 ? x : canon_rtx (reg_known_value[REGNO (x)]);
1023 else if (GET_CODE (x) == PLUS)
1025 rtx x0 = canon_rtx (XEXP (x, 0));
1026 rtx x1 = canon_rtx (XEXP (x, 1));
1028 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
1030 if (GET_CODE (x0) == CONST_INT)
1031 return plus_constant (x1, INTVAL (x0));
1032 else if (GET_CODE (x1) == CONST_INT)
1033 return plus_constant (x0, INTVAL (x1));
1034 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1038 /* This gives us much better alias analysis when called from
1039 the loop optimizer. Note we want to leave the original
1040 MEM alone, but need to return the canonicalized MEM with
1041 all the flags with their original values. */
1042 else if (GET_CODE (x) == MEM)
1043 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1048 /* Return 1 if X and Y are identical-looking rtx's.
1050 We use the data in reg_known_value above to see if two registers with
1051 different numbers are, in fact, equivalent. */
1054 rtx_equal_for_memref_p (x, y)
1062 if (x == 0 && y == 0)
1064 if (x == 0 || y == 0)
1073 code = GET_CODE (x);
1074 /* Rtx's of different codes cannot be equal. */
1075 if (code != GET_CODE (y))
1078 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1079 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1081 if (GET_MODE (x) != GET_MODE (y))
1084 /* Some RTL can be compared without a recursive examination. */
1088 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1091 return REGNO (x) == REGNO (y);
1094 return XEXP (x, 0) == XEXP (y, 0);
1097 return XSTR (x, 0) == XSTR (y, 0);
1101 /* There's no need to compare the contents of CONST_DOUBLEs or
1102 CONST_INTs because pointer equality is a good enough
1103 comparison for these nodes. */
1107 return (XINT (x, 1) == XINT (y, 1)
1108 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1114 /* For commutative operations, the RTX match if the operand match in any
1115 order. Also handle the simple binary and unary cases without a loop. */
1116 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1117 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1118 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1119 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1120 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1121 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1122 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1123 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1124 else if (GET_RTX_CLASS (code) == '1')
1125 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1127 /* Compare the elements. If any pair of corresponding elements
1128 fail to match, return 0 for the whole things.
1130 Limit cases to types which actually appear in addresses. */
1132 fmt = GET_RTX_FORMAT (code);
1133 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1138 if (XINT (x, i) != XINT (y, i))
1143 /* Two vectors must have the same length. */
1144 if (XVECLEN (x, i) != XVECLEN (y, i))
1147 /* And the corresponding elements must match. */
1148 for (j = 0; j < XVECLEN (x, i); j++)
1149 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1150 XVECEXP (y, i, j)) == 0)
1155 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1159 /* This can happen for asm operands. */
1161 if (strcmp (XSTR (x, i), XSTR (y, i)))
1165 /* This can happen for an asm which clobbers memory. */
1169 /* It is believed that rtx's at this level will never
1170 contain anything but integers and other rtx's,
1171 except for within LABEL_REFs and SYMBOL_REFs. */
1179 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1180 X and return it, or return 0 if none found. */
1183 find_symbolic_term (x)
1190 code = GET_CODE (x);
1191 if (code == SYMBOL_REF || code == LABEL_REF)
1193 if (GET_RTX_CLASS (code) == 'o')
1196 fmt = GET_RTX_FORMAT (code);
1197 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1203 t = find_symbolic_term (XEXP (x, i));
1207 else if (fmt[i] == 'E')
1218 struct elt_loc_list *l;
1220 #if defined (FIND_BASE_TERM)
1221 /* Try machine-dependent ways to find the base term. */
1222 x = FIND_BASE_TERM (x);
1225 switch (GET_CODE (x))
1228 return REG_BASE_VALUE (x);
1231 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1237 return find_base_term (XEXP (x, 0));
1240 val = CSELIB_VAL_PTR (x);
1241 for (l = val->locs; l; l = l->next)
1242 if ((x = find_base_term (l->loc)) != 0)
1248 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1255 rtx tmp1 = XEXP (x, 0);
1256 rtx tmp2 = XEXP (x, 1);
1258 /* This is a little bit tricky since we have to determine which of
1259 the two operands represents the real base address. Otherwise this
1260 routine may return the index register instead of the base register.
1262 That may cause us to believe no aliasing was possible, when in
1263 fact aliasing is possible.
1265 We use a few simple tests to guess the base register. Additional
1266 tests can certainly be added. For example, if one of the operands
1267 is a shift or multiply, then it must be the index register and the
1268 other operand is the base register. */
1270 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1271 return find_base_term (tmp2);
1273 /* If either operand is known to be a pointer, then use it
1274 to determine the base term. */
1275 if (REG_P (tmp1) && REG_POINTER (tmp1))
1276 return find_base_term (tmp1);
1278 if (REG_P (tmp2) && REG_POINTER (tmp2))
1279 return find_base_term (tmp2);
1281 /* Neither operand was known to be a pointer. Go ahead and find the
1282 base term for both operands. */
1283 tmp1 = find_base_term (tmp1);
1284 tmp2 = find_base_term (tmp2);
1286 /* If either base term is named object or a special address
1287 (like an argument or stack reference), then use it for the
1290 && (GET_CODE (tmp1) == SYMBOL_REF
1291 || GET_CODE (tmp1) == LABEL_REF
1292 || (GET_CODE (tmp1) == ADDRESS
1293 && GET_MODE (tmp1) != VOIDmode)))
1297 && (GET_CODE (tmp2) == SYMBOL_REF
1298 || GET_CODE (tmp2) == LABEL_REF
1299 || (GET_CODE (tmp2) == ADDRESS
1300 && GET_MODE (tmp2) != VOIDmode)))
1303 /* We could not determine which of the two operands was the
1304 base register and which was the index. So we can determine
1305 nothing from the base alias check. */
1310 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1311 return REG_BASE_VALUE (XEXP (x, 0));
1319 return REG_BASE_VALUE (frame_pointer_rtx);
1326 /* Return 0 if the addresses X and Y are known to point to different
1327 objects, 1 if they might be pointers to the same object. */
1330 base_alias_check (x, y, x_mode, y_mode)
1332 enum machine_mode x_mode, y_mode;
1334 rtx x_base = find_base_term (x);
1335 rtx y_base = find_base_term (y);
1337 /* If the address itself has no known base see if a known equivalent
1338 value has one. If either address still has no known base, nothing
1339 is known about aliasing. */
1344 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1347 x_base = find_base_term (x_c);
1355 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1358 y_base = find_base_term (y_c);
1363 /* If the base addresses are equal nothing is known about aliasing. */
1364 if (rtx_equal_p (x_base, y_base))
1367 /* The base addresses of the read and write are different expressions.
1368 If they are both symbols and they are not accessed via AND, there is
1369 no conflict. We can bring knowledge of object alignment into play
1370 here. For example, on alpha, "char a, b;" can alias one another,
1371 though "char a; long b;" cannot. */
1372 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1374 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1376 if (GET_CODE (x) == AND
1377 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1378 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1380 if (GET_CODE (y) == AND
1381 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1382 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1384 /* Differing symbols never alias. */
1388 /* If one address is a stack reference there can be no alias:
1389 stack references using different base registers do not alias,
1390 a stack reference can not alias a parameter, and a stack reference
1391 can not alias a global. */
1392 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1393 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1396 if (! flag_argument_noalias)
1399 if (flag_argument_noalias > 1)
1402 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1403 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1406 /* Convert the address X into something we can use. This is done by returning
1407 it unchanged unless it is a value; in the latter case we call cselib to get
1408 a more useful rtx. */
1415 struct elt_loc_list *l;
1417 if (GET_CODE (x) != VALUE)
1419 v = CSELIB_VAL_PTR (x);
1420 for (l = v->locs; l; l = l->next)
1421 if (CONSTANT_P (l->loc))
1423 for (l = v->locs; l; l = l->next)
1424 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1427 return v->locs->loc;
1431 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1432 where SIZE is the size in bytes of the memory reference. If ADDR
1433 is not modified by the memory reference then ADDR is returned. */
1436 addr_side_effect_eval (addr, size, n_refs)
1443 switch (GET_CODE (addr))
1446 offset = (n_refs + 1) * size;
1449 offset = -(n_refs + 1) * size;
1452 offset = n_refs * size;
1455 offset = -n_refs * size;
1463 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1465 addr = XEXP (addr, 0);
1470 /* Return nonzero if X and Y (memory addresses) could reference the
1471 same location in memory. C is an offset accumulator. When
1472 C is nonzero, we are testing aliases between X and Y + C.
1473 XSIZE is the size in bytes of the X reference,
1474 similarly YSIZE is the size in bytes for Y.
1476 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1477 referenced (the reference was BLKmode), so make the most pessimistic
1480 If XSIZE or YSIZE is negative, we may access memory outside the object
1481 being referenced as a side effect. This can happen when using AND to
1482 align memory references, as is done on the Alpha.
1484 Nice to notice that varying addresses cannot conflict with fp if no
1485 local variables had their addresses taken, but that's too hard now. */
1488 memrefs_conflict_p (xsize, x, ysize, y, c)
1493 if (GET_CODE (x) == VALUE)
1495 if (GET_CODE (y) == VALUE)
1497 if (GET_CODE (x) == HIGH)
1499 else if (GET_CODE (x) == LO_SUM)
1502 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1503 if (GET_CODE (y) == HIGH)
1505 else if (GET_CODE (y) == LO_SUM)
1508 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1510 if (rtx_equal_for_memref_p (x, y))
1512 if (xsize <= 0 || ysize <= 0)
1514 if (c >= 0 && xsize > c)
1516 if (c < 0 && ysize+c > 0)
1521 /* This code used to check for conflicts involving stack references and
1522 globals but the base address alias code now handles these cases. */
1524 if (GET_CODE (x) == PLUS)
1526 /* The fact that X is canonicalized means that this
1527 PLUS rtx is canonicalized. */
1528 rtx x0 = XEXP (x, 0);
1529 rtx x1 = XEXP (x, 1);
1531 if (GET_CODE (y) == PLUS)
1533 /* The fact that Y is canonicalized means that this
1534 PLUS rtx is canonicalized. */
1535 rtx y0 = XEXP (y, 0);
1536 rtx y1 = XEXP (y, 1);
1538 if (rtx_equal_for_memref_p (x1, y1))
1539 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1540 if (rtx_equal_for_memref_p (x0, y0))
1541 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1542 if (GET_CODE (x1) == CONST_INT)
1544 if (GET_CODE (y1) == CONST_INT)
1545 return memrefs_conflict_p (xsize, x0, ysize, y0,
1546 c - INTVAL (x1) + INTVAL (y1));
1548 return memrefs_conflict_p (xsize, x0, ysize, y,
1551 else if (GET_CODE (y1) == CONST_INT)
1552 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1556 else if (GET_CODE (x1) == CONST_INT)
1557 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1559 else if (GET_CODE (y) == PLUS)
1561 /* The fact that Y is canonicalized means that this
1562 PLUS rtx is canonicalized. */
1563 rtx y0 = XEXP (y, 0);
1564 rtx y1 = XEXP (y, 1);
1566 if (GET_CODE (y1) == CONST_INT)
1567 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1572 if (GET_CODE (x) == GET_CODE (y))
1573 switch (GET_CODE (x))
1577 /* Handle cases where we expect the second operands to be the
1578 same, and check only whether the first operand would conflict
1581 rtx x1 = canon_rtx (XEXP (x, 1));
1582 rtx y1 = canon_rtx (XEXP (y, 1));
1583 if (! rtx_equal_for_memref_p (x1, y1))
1585 x0 = canon_rtx (XEXP (x, 0));
1586 y0 = canon_rtx (XEXP (y, 0));
1587 if (rtx_equal_for_memref_p (x0, y0))
1588 return (xsize == 0 || ysize == 0
1589 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1591 /* Can't properly adjust our sizes. */
1592 if (GET_CODE (x1) != CONST_INT)
1594 xsize /= INTVAL (x1);
1595 ysize /= INTVAL (x1);
1597 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1601 /* Are these registers known not to be equal? */
1602 if (alias_invariant)
1604 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1605 rtx i_x, i_y; /* invariant relationships of X and Y */
1607 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1608 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1610 if (i_x == 0 && i_y == 0)
1613 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1614 ysize, i_y ? i_y : y, c))
1623 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1624 as an access with indeterminate size. Assume that references
1625 besides AND are aligned, so if the size of the other reference is
1626 at least as large as the alignment, assume no other overlap. */
1627 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1629 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1631 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1633 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1635 /* ??? If we are indexing far enough into the array/structure, we
1636 may yet be able to determine that we can not overlap. But we
1637 also need to that we are far enough from the end not to overlap
1638 a following reference, so we do nothing with that for now. */
1639 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1641 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1644 if (GET_CODE (x) == ADDRESSOF)
1646 if (y == frame_pointer_rtx
1647 || GET_CODE (y) == ADDRESSOF)
1648 return xsize <= 0 || ysize <= 0;
1650 if (GET_CODE (y) == ADDRESSOF)
1652 if (x == frame_pointer_rtx)
1653 return xsize <= 0 || ysize <= 0;
1658 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1660 c += (INTVAL (y) - INTVAL (x));
1661 return (xsize <= 0 || ysize <= 0
1662 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1665 if (GET_CODE (x) == CONST)
1667 if (GET_CODE (y) == CONST)
1668 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1669 ysize, canon_rtx (XEXP (y, 0)), c);
1671 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1674 if (GET_CODE (y) == CONST)
1675 return memrefs_conflict_p (xsize, x, ysize,
1676 canon_rtx (XEXP (y, 0)), c);
1679 return (xsize <= 0 || ysize <= 0
1680 || (rtx_equal_for_memref_p (x, y)
1681 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1688 /* Functions to compute memory dependencies.
1690 Since we process the insns in execution order, we can build tables
1691 to keep track of what registers are fixed (and not aliased), what registers
1692 are varying in known ways, and what registers are varying in unknown
1695 If both memory references are volatile, then there must always be a
1696 dependence between the two references, since their order can not be
1697 changed. A volatile and non-volatile reference can be interchanged
1700 A MEM_IN_STRUCT reference at a non-AND varying address can never
1701 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1702 also must allow AND addresses, because they may generate accesses
1703 outside the object being referenced. This is used to generate
1704 aligned addresses from unaligned addresses, for instance, the alpha
1705 storeqi_unaligned pattern. */
1707 /* Read dependence: X is read after read in MEM takes place. There can
1708 only be a dependence here if both reads are volatile. */
1711 read_dependence (mem, x)
1715 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1718 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1719 MEM2 is a reference to a structure at a varying address, or returns
1720 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1721 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1722 to decide whether or not an address may vary; it should return
1723 nonzero whenever variation is possible.
1724 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1727 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1729 rtx mem1_addr, mem2_addr;
1730 int (*varies_p) PARAMS ((rtx, int));
1732 if (! flag_strict_aliasing)
1735 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1736 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1737 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1741 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1742 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1743 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1750 /* Returns nonzero if something about the mode or address format MEM1
1751 indicates that it might well alias *anything*. */
1754 aliases_everything_p (mem)
1757 if (GET_CODE (XEXP (mem, 0)) == AND)
1758 /* If the address is an AND, its very hard to know at what it is
1759 actually pointing. */
1765 /* Return nonzero if we can deterimine the decls corresponding to memrefs
1766 X and Y and they do not overlap. */
1769 nonoverlapping_memrefs_p (x, y)
1774 HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
1776 /* Unless both have decls, we can't tell anything. */
1777 if (MEM_DECL (x) == 0 || MEM_DECL (y) == 0)
1780 rtlx = DECL_RTL (MEM_DECL (x));
1781 rtly = DECL_RTL (MEM_DECL (y));
1783 /* If either RTL is a REG, they can't overlap unless they are the same
1784 because we never reuse that part of the stack frame used for locals for
1786 if ((REG_P (rtlx) || REG_P (rtly)) && ! rtx_equal_p (rtlx, rtly))
1789 /* Get the base and offsets of both decls. If either is a register, we
1790 know both are and are the same, so use that as the base. The only
1791 we can avoid overlap is if we can deduce that they are nonoverlapping
1792 pieces of that decl, which is very rare. */
1793 basex = REG_P (rtlx) ? rtlx : XEXP (rtlx, 0);
1794 if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
1795 offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
1797 basey = REG_P (rtly) ? rtly : XEXP (rtly, 0);
1798 if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
1799 offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
1801 /* If the bases are both constant and they are different, we know these
1802 do not overlap. If they are both registers, we can only deduce
1803 something if they are the same register. */
1804 if (CONSTANT_P (basex) && CONSTANT_P (basey) && ! rtx_equal_p (basex, basey))
1806 else if (! rtx_equal_p (basex, basey))
1809 sizex = (REG_P (rtlx) ? GET_MODE_SIZE (GET_MODE (rtlx))
1810 : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
1812 sizey = (REG_P (rtly) ? GET_MODE_SIZE (GET_MODE (rtly))
1813 : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
1816 /* If we have an offset or size for either memref, it can update the values
1819 offsetx += INTVAL (MEM_OFFSET (x));
1821 offsety += INTVAL (MEM_OFFSET (y));
1824 sizex = INTVAL (MEM_SIZE (x));
1826 sizey = INTVAL (MEM_SIZE (y));
1828 /* Put the values of the memref with the lower offset in X's values. */
1829 if (offsetx > offsety)
1831 tem = offsetx, offsetx = offsety, offsety = tem;
1832 tem = sizex, sizex = sizey, sizey = tem;
1835 /* If we don't know the size of the lower-offset value, we can't tell
1836 if they conflict. Otherwise, we do the test. */
1837 return sizex >= 0 && offsety > offsetx + sizex;
1840 /* True dependence: X is read after store in MEM takes place. */
1843 true_dependence (mem, mem_mode, x, varies)
1845 enum machine_mode mem_mode;
1847 int (*varies) PARAMS ((rtx, int));
1849 rtx x_addr, mem_addr;
1852 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1855 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1858 /* Unchanging memory can't conflict with non-unchanging memory.
1859 A non-unchanging read can conflict with a non-unchanging write.
1860 An unchanging read can conflict with an unchanging write since
1861 there may be a single store to this address to initialize it.
1862 Note that an unchanging store can conflict with a non-unchanging read
1863 since we have to make conservative assumptions when we have a
1864 record with readonly fields and we are copying the whole thing.
1865 Just fall through to the code below to resolve potential conflicts.
1866 This won't handle all cases optimally, but the possible performance
1867 loss should be negligible. */
1868 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1871 if (nonoverlapping_memrefs_p (mem, x))
1874 if (mem_mode == VOIDmode)
1875 mem_mode = GET_MODE (mem);
1877 x_addr = get_addr (XEXP (x, 0));
1878 mem_addr = get_addr (XEXP (mem, 0));
1880 base = find_base_term (x_addr);
1881 if (base && (GET_CODE (base) == LABEL_REF
1882 || (GET_CODE (base) == SYMBOL_REF
1883 && CONSTANT_POOL_ADDRESS_P (base))))
1886 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1889 x_addr = canon_rtx (x_addr);
1890 mem_addr = canon_rtx (mem_addr);
1892 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1893 SIZE_FOR_MODE (x), x_addr, 0))
1896 if (aliases_everything_p (x))
1899 /* We cannot use aliases_everything_p to test MEM, since we must look
1900 at MEM_MODE, rather than GET_MODE (MEM). */
1901 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1904 /* In true_dependence we also allow BLKmode to alias anything. Why
1905 don't we do this in anti_dependence and output_dependence? */
1906 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1909 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1913 /* Canonical true dependence: X is read after store in MEM takes place.
1914 Variant of true_dependence which assumes MEM has already been
1915 canonicalized (hence we no longer do that here).
1916 The mem_addr argument has been added, since true_dependence computed
1917 this value prior to canonicalizing. */
1920 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
1921 rtx mem, mem_addr, x;
1922 enum machine_mode mem_mode;
1923 int (*varies) PARAMS ((rtx, int));
1927 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1930 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1933 /* If X is an unchanging read, then it can't possibly conflict with any
1934 non-unchanging store. It may conflict with an unchanging write though,
1935 because there may be a single store to this address to initialize it.
1936 Just fall through to the code below to resolve the case where we have
1937 both an unchanging read and an unchanging write. This won't handle all
1938 cases optimally, but the possible performance loss should be
1940 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1943 if (nonoverlapping_memrefs_p (x, mem))
1946 x_addr = get_addr (XEXP (x, 0));
1948 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1951 x_addr = canon_rtx (x_addr);
1952 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1953 SIZE_FOR_MODE (x), x_addr, 0))
1956 if (aliases_everything_p (x))
1959 /* We cannot use aliases_everything_p to test MEM, since we must look
1960 at MEM_MODE, rather than GET_MODE (MEM). */
1961 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1964 /* In true_dependence we also allow BLKmode to alias anything. Why
1965 don't we do this in anti_dependence and output_dependence? */
1966 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1969 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1973 /* Returns non-zero if a write to X might alias a previous read from
1974 (or, if WRITEP is non-zero, a write to) MEM. */
1977 write_dependence_p (mem, x, writep)
1982 rtx x_addr, mem_addr;
1986 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1989 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1992 /* Unchanging memory can't conflict with non-unchanging memory. */
1993 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1996 /* If MEM is an unchanging read, then it can't possibly conflict with
1997 the store to X, because there is at most one store to MEM, and it must
1998 have occurred somewhere before MEM. */
1999 if (! writep && RTX_UNCHANGING_P (mem))
2002 if (nonoverlapping_memrefs_p (x, mem))
2005 x_addr = get_addr (XEXP (x, 0));
2006 mem_addr = get_addr (XEXP (mem, 0));
2010 base = find_base_term (mem_addr);
2011 if (base && (GET_CODE (base) == LABEL_REF
2012 || (GET_CODE (base) == SYMBOL_REF
2013 && CONSTANT_POOL_ADDRESS_P (base))))
2017 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
2021 x_addr = canon_rtx (x_addr);
2022 mem_addr = canon_rtx (mem_addr);
2024 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
2025 SIZE_FOR_MODE (x), x_addr, 0))
2029 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
2032 return (!(fixed_scalar == mem && !aliases_everything_p (x))
2033 && !(fixed_scalar == x && !aliases_everything_p (mem)));
2036 /* Anti dependence: X is written after read in MEM takes place. */
2039 anti_dependence (mem, x)
2043 return write_dependence_p (mem, x, /*writep=*/0);
2046 /* Output dependence: X is written after store in MEM takes place. */
2049 output_dependence (mem, x)
2053 return write_dependence_p (mem, x, /*writep=*/1);
2056 /* Returns non-zero if X mentions something which is not
2057 local to the function and is not constant. */
2060 nonlocal_mentioned_p (x)
2067 code = GET_CODE (x);
2069 if (GET_RTX_CLASS (code) == 'i')
2071 /* Constant functions can be constant if they don't use
2072 scratch memory used to mark function w/o side effects. */
2073 if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x))
2075 x = CALL_INSN_FUNCTION_USAGE (x);
2081 code = GET_CODE (x);
2087 if (GET_CODE (SUBREG_REG (x)) == REG)
2089 /* Global registers are not local. */
2090 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
2091 && global_regs[subreg_regno (x)])
2099 /* Global registers are not local. */
2100 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
2114 /* Constants in the function's constants pool are constant. */
2115 if (CONSTANT_POOL_ADDRESS_P (x))
2120 /* Non-constant calls and recursion are not local. */
2124 /* Be overly conservative and consider any volatile memory
2125 reference as not local. */
2126 if (MEM_VOLATILE_P (x))
2128 base = find_base_term (XEXP (x, 0));
2131 /* A Pmode ADDRESS could be a reference via the structure value
2132 address or static chain. Such memory references are nonlocal.
2134 Thus, we have to examine the contents of the ADDRESS to find
2135 out if this is a local reference or not. */
2136 if (GET_CODE (base) == ADDRESS
2137 && GET_MODE (base) == Pmode
2138 && (XEXP (base, 0) == stack_pointer_rtx
2139 || XEXP (base, 0) == arg_pointer_rtx
2140 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2141 || XEXP (base, 0) == hard_frame_pointer_rtx
2143 || XEXP (base, 0) == frame_pointer_rtx))
2145 /* Constants in the function's constant pool are constant. */
2146 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2151 case UNSPEC_VOLATILE:
2156 if (MEM_VOLATILE_P (x))
2165 /* Recursively scan the operands of this expression. */
2168 const char *fmt = GET_RTX_FORMAT (code);
2171 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2173 if (fmt[i] == 'e' && XEXP (x, i))
2175 if (nonlocal_mentioned_p (XEXP (x, i)))
2178 else if (fmt[i] == 'E')
2181 for (j = 0; j < XVECLEN (x, i); j++)
2182 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2191 /* Mark the function if it is constant. */
2194 mark_constant_function ()
2197 int nonlocal_mentioned;
2199 if (TREE_PUBLIC (current_function_decl)
2200 || TREE_READONLY (current_function_decl)
2201 || DECL_IS_PURE (current_function_decl)
2202 || TREE_THIS_VOLATILE (current_function_decl)
2203 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2206 /* A loop might not return which counts as a side effect. */
2207 if (mark_dfs_back_edges ())
2210 nonlocal_mentioned = 0;
2212 init_alias_analysis ();
2214 /* Determine if this is a constant function. */
2216 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2217 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2219 nonlocal_mentioned = 1;
2223 end_alias_analysis ();
2225 /* Mark the function. */
2227 if (! nonlocal_mentioned)
2228 TREE_READONLY (current_function_decl) = 1;
2232 static HARD_REG_SET argument_registers;
2239 #ifndef OUTGOING_REGNO
2240 #define OUTGOING_REGNO(N) N
2242 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2243 /* Check whether this register can hold an incoming pointer
2244 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2245 numbers, so translate if necessary due to register windows. */
2246 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2247 && HARD_REGNO_MODE_OK (i, Pmode))
2248 SET_HARD_REG_BIT (argument_registers, i);
2250 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2253 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2257 init_alias_analysis ()
2259 int maxreg = max_reg_num ();
2265 reg_known_value_size = maxreg;
2268 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2269 - FIRST_PSEUDO_REGISTER;
2271 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2272 - FIRST_PSEUDO_REGISTER;
2274 /* Overallocate reg_base_value to allow some growth during loop
2275 optimization. Loop unrolling can create a large number of
2277 reg_base_value_size = maxreg * 2;
2278 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2279 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2281 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2282 reg_seen = (char *) xmalloc (reg_base_value_size);
2283 if (! reload_completed && flag_unroll_loops)
2285 /* ??? Why are we realloc'ing if we're just going to zero it? */
2286 alias_invariant = (rtx *)xrealloc (alias_invariant,
2287 reg_base_value_size * sizeof (rtx));
2288 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2291 /* The basic idea is that each pass through this loop will use the
2292 "constant" information from the previous pass to propagate alias
2293 information through another level of assignments.
2295 This could get expensive if the assignment chains are long. Maybe
2296 we should throttle the number of iterations, possibly based on
2297 the optimization level or flag_expensive_optimizations.
2299 We could propagate more information in the first pass by making use
2300 of REG_N_SETS to determine immediately that the alias information
2301 for a pseudo is "constant".
2303 A program with an uninitialized variable can cause an infinite loop
2304 here. Instead of doing a full dataflow analysis to detect such problems
2305 we just cap the number of iterations for the loop.
2307 The state of the arrays for the set chain in question does not matter
2308 since the program has undefined behavior. */
2313 /* Assume nothing will change this iteration of the loop. */
2316 /* We want to assign the same IDs each iteration of this loop, so
2317 start counting from zero each iteration of the loop. */
2320 /* We're at the start of the function each iteration through the
2321 loop, so we're copying arguments. */
2322 copying_arguments = 1;
2324 /* Wipe the potential alias information clean for this pass. */
2325 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2327 /* Wipe the reg_seen array clean. */
2328 memset ((char *) reg_seen, 0, reg_base_value_size);
2330 /* Mark all hard registers which may contain an address.
2331 The stack, frame and argument pointers may contain an address.
2332 An argument register which can hold a Pmode value may contain
2333 an address even if it is not in BASE_REGS.
2335 The address expression is VOIDmode for an argument and
2336 Pmode for other registers. */
2338 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2339 if (TEST_HARD_REG_BIT (argument_registers, i))
2340 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2341 gen_rtx_REG (Pmode, i));
2343 new_reg_base_value[STACK_POINTER_REGNUM]
2344 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2345 new_reg_base_value[ARG_POINTER_REGNUM]
2346 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2347 new_reg_base_value[FRAME_POINTER_REGNUM]
2348 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2349 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2350 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2351 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2354 /* Walk the insns adding values to the new_reg_base_value array. */
2355 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2361 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2362 /* The prologue/epilogue insns are not threaded onto the
2363 insn chain until after reload has completed. Thus,
2364 there is no sense wasting time checking if INSN is in
2365 the prologue/epilogue until after reload has completed. */
2366 if (reload_completed
2367 && prologue_epilogue_contains (insn))
2371 /* If this insn has a noalias note, process it, Otherwise,
2372 scan for sets. A simple set will have no side effects
2373 which could change the base value of any other register. */
2375 if (GET_CODE (PATTERN (insn)) == SET
2376 && REG_NOTES (insn) != 0
2377 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2378 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2380 note_stores (PATTERN (insn), record_set, NULL);
2382 set = single_set (insn);
2385 && GET_CODE (SET_DEST (set)) == REG
2386 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2388 unsigned int regno = REGNO (SET_DEST (set));
2389 rtx src = SET_SRC (set);
2391 if (REG_NOTES (insn) != 0
2392 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2393 && REG_N_SETS (regno) == 1)
2394 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2395 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2396 && ! rtx_varies_p (XEXP (note, 0), 1)
2397 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2399 reg_known_value[regno] = XEXP (note, 0);
2400 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2402 else if (REG_N_SETS (regno) == 1
2403 && GET_CODE (src) == PLUS
2404 && GET_CODE (XEXP (src, 0)) == REG
2405 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2406 && (reg_known_value[REGNO (XEXP (src, 0))])
2407 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2409 rtx op0 = XEXP (src, 0);
2410 op0 = reg_known_value[REGNO (op0)];
2411 reg_known_value[regno]
2412 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2413 reg_known_equiv_p[regno] = 0;
2415 else if (REG_N_SETS (regno) == 1
2416 && ! rtx_varies_p (src, 1))
2418 reg_known_value[regno] = src;
2419 reg_known_equiv_p[regno] = 0;
2423 else if (GET_CODE (insn) == NOTE
2424 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2425 copying_arguments = 0;
2428 /* Now propagate values from new_reg_base_value to reg_base_value. */
2429 for (ui = 0; ui < reg_base_value_size; ui++)
2431 if (new_reg_base_value[ui]
2432 && new_reg_base_value[ui] != reg_base_value[ui]
2433 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2435 reg_base_value[ui] = new_reg_base_value[ui];
2440 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2442 /* Fill in the remaining entries. */
2443 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2444 if (reg_known_value[i] == 0)
2445 reg_known_value[i] = regno_reg_rtx[i];
2447 /* Simplify the reg_base_value array so that no register refers to
2448 another register, except to special registers indirectly through
2449 ADDRESS expressions.
2451 In theory this loop can take as long as O(registers^2), but unless
2452 there are very long dependency chains it will run in close to linear
2455 This loop may not be needed any longer now that the main loop does
2456 a better job at propagating alias information. */
2462 for (ui = 0; ui < reg_base_value_size; ui++)
2464 rtx base = reg_base_value[ui];
2465 if (base && GET_CODE (base) == REG)
2467 unsigned int base_regno = REGNO (base);
2468 if (base_regno == ui) /* register set from itself */
2469 reg_base_value[ui] = 0;
2471 reg_base_value[ui] = reg_base_value[base_regno];
2476 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2479 free (new_reg_base_value);
2480 new_reg_base_value = 0;
2486 end_alias_analysis ()
2488 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2489 reg_known_value = 0;
2490 reg_known_value_size = 0;
2491 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2492 reg_known_equiv_p = 0;
2495 ggc_del_root (reg_base_value);
2496 free (reg_base_value);
2499 reg_base_value_size = 0;
2500 if (alias_invariant)
2502 free (alias_invariant);
2503 alias_invariant = 0;