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 GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
30 #include "hard-reg-set.h"
31 #include "basic-block.h"
36 #include "splay-tree.h"
39 /* The alias sets assigned to MEMs assist the back-end in determining
40 which MEMs can alias which other MEMs. In general, two MEMs in
41 different alias sets cannot alias each other, with one important
42 exception. Consider something like:
44 struct S {int i; double d; };
46 a store to an `S' can alias something of either type `int' or type
47 `double'. (However, a store to an `int' cannot alias a `double'
48 and vice versa.) We indicate this via a tree structure that looks
56 (The arrows are directed and point downwards.)
57 In this situation we say the alias set for `struct S' is the
58 `superset' and that those for `int' and `double' are `subsets'.
60 To see whether two alias sets can point to the same memory, we must
61 see if either alias set is a subset of the other. We need not trace
62 past immediate decendents, however, since we propagate all
63 grandchildren up one level.
65 Alias set zero is implicitly a superset of all other alias sets.
66 However, this is no actual entry for alias set zero. It is an
67 error to attempt to explicitly construct a subset of zero. */
69 typedef struct alias_set_entry
71 /* The alias set number, as stored in MEM_ALIAS_SET. */
72 HOST_WIDE_INT alias_set;
74 /* The children of the alias set. These are not just the immediate
75 children, but, in fact, all decendents. So, if we have:
77 struct T { struct S s; float f; }
79 continuing our example above, the children here will be all of
80 `int', `double', `float', and `struct S'. */
83 /* Nonzero if would have a child of zero: this effectively makes this
84 alias set the same as alias set zero. */
88 static int rtx_equal_for_memref_p PARAMS ((rtx, rtx));
89 static rtx find_symbolic_term PARAMS ((rtx));
90 rtx get_addr PARAMS ((rtx));
91 static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx,
93 static void record_set PARAMS ((rtx, rtx, void *));
94 static rtx find_base_term PARAMS ((rtx));
95 static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode,
97 static int handled_component_p PARAMS ((tree));
98 static int can_address_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 write_dependence_p PARAMS ((rtx, rtx, int));
108 static int nonlocal_mentioned_p PARAMS ((rtx));
110 static int loop_p PARAMS ((void));
112 /* Set up all info needed to perform alias analysis on memory references. */
114 /* Returns the size in bytes of the mode of X. */
115 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
117 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
118 different alias sets. We ignore alias sets in functions making use
119 of variable arguments because the va_arg macros on some systems are
121 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
122 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
124 /* Cap the number of passes we make over the insns propagating alias
125 information through set chains. 10 is a completely arbitrary choice. */
126 #define MAX_ALIAS_LOOP_PASSES 10
128 /* reg_base_value[N] gives an address to which register N is related.
129 If all sets after the first add or subtract to the current value
130 or otherwise modify it so it does not point to a different top level
131 object, reg_base_value[N] is equal to the address part of the source
134 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
135 expressions represent certain special values: function arguments and
136 the stack, frame, and argument pointers.
138 The contents of an ADDRESS is not normally used, the mode of the
139 ADDRESS determines whether the ADDRESS is a function argument or some
140 other special value. Pointer equality, not rtx_equal_p, determines whether
141 two ADDRESS expressions refer to the same base address.
143 The only use of the contents of an ADDRESS is for determining if the
144 current function performs nonlocal memory memory references for the
145 purposes of marking the function as a constant function. */
147 static rtx *reg_base_value;
148 static rtx *new_reg_base_value;
149 static unsigned int reg_base_value_size; /* size of reg_base_value array */
151 #define REG_BASE_VALUE(X) \
152 (REGNO (X) < reg_base_value_size \
153 ? reg_base_value[REGNO (X)] : 0)
155 /* Vector of known invariant relationships between registers. Set in
156 loop unrolling. Indexed by register number, if nonzero the value
157 is an expression describing this register in terms of another.
159 The length of this array is REG_BASE_VALUE_SIZE.
161 Because this array contains only pseudo registers it has no effect
163 static rtx *alias_invariant;
165 /* Vector indexed by N giving the initial (unchanging) value known for
166 pseudo-register N. This array is initialized in
167 init_alias_analysis, and does not change until end_alias_analysis
169 rtx *reg_known_value;
171 /* Indicates number of valid entries in reg_known_value. */
172 static unsigned int reg_known_value_size;
174 /* Vector recording for each reg_known_value whether it is due to a
175 REG_EQUIV note. Future passes (viz., reload) may replace the
176 pseudo with the equivalent expression and so we account for the
177 dependences that would be introduced if that happens.
179 The REG_EQUIV notes created in assign_parms may mention the arg
180 pointer, and there are explicit insns in the RTL that modify the
181 arg pointer. Thus we must ensure that such insns don't get
182 scheduled across each other because that would invalidate the
183 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
184 wrong, but solving the problem in the scheduler will likely give
185 better code, so we do it here. */
186 char *reg_known_equiv_p;
188 /* True when scanning insns from the start of the rtl to the
189 NOTE_INSN_FUNCTION_BEG note. */
190 static int copying_arguments;
192 /* The splay-tree used to store the various alias set entries. */
193 static splay_tree alias_sets;
195 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
196 such an entry, or NULL otherwise. */
198 static alias_set_entry
199 get_alias_set_entry (alias_set)
200 HOST_WIDE_INT alias_set;
203 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
205 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
208 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
209 the two MEMs cannot alias each other. */
212 mems_in_disjoint_alias_sets_p (mem1, mem2)
216 #ifdef ENABLE_CHECKING
217 /* Perform a basic sanity check. Namely, that there are no alias sets
218 if we're not using strict aliasing. This helps to catch bugs
219 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
220 where a MEM is allocated in some way other than by the use of
221 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
222 use alias sets to indicate that spilled registers cannot alias each
223 other, we might need to remove this check. */
224 if (! flag_strict_aliasing
225 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
229 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
232 /* Insert the NODE into the splay tree given by DATA. Used by
233 record_alias_subset via splay_tree_foreach. */
236 insert_subset_children (node, data)
237 splay_tree_node node;
240 splay_tree_insert ((splay_tree) data, node->key, node->value);
245 /* Return 1 if the two specified alias sets may conflict. */
248 alias_sets_conflict_p (set1, set2)
249 HOST_WIDE_INT set1, set2;
253 /* If have no alias set information for one of the operands, we have
254 to assume it can alias anything. */
255 if (set1 == 0 || set2 == 0
256 /* If the two alias sets are the same, they may alias. */
260 /* See if the first alias set is a subset of the second. */
261 ase = get_alias_set_entry (set1);
263 && (ase->has_zero_child
264 || splay_tree_lookup (ase->children,
265 (splay_tree_key) set2)))
268 /* Now do the same, but with the alias sets reversed. */
269 ase = get_alias_set_entry (set2);
271 && (ase->has_zero_child
272 || splay_tree_lookup (ase->children,
273 (splay_tree_key) set1)))
276 /* The two alias sets are distinct and neither one is the
277 child of the other. Therefore, they cannot alias. */
281 /* Set the alias set of MEM to SET. */
284 set_mem_alias_set (mem, set)
288 /* We would like to do this test but can't yet since when converting a
289 REG to a MEM, the alias set field is undefined. */
291 /* If the new and old alias sets don't conflict, something is wrong. */
292 if (!alias_sets_conflict_p (set, MEM_ALIAS_SET (mem)))
296 MEM_ALIAS_SET (mem) = set;
299 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
300 has any readonly fields. If any of the fields have types that
301 contain readonly fields, return true as well. */
304 readonly_fields_p (type)
309 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
310 && TREE_CODE (type) != QUAL_UNION_TYPE)
313 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
314 if (TREE_CODE (field) == FIELD_DECL
315 && (TREE_READONLY (field)
316 || readonly_fields_p (TREE_TYPE (field))))
322 /* Return 1 if any MEM object of type T1 will always conflict (using the
323 dependency routines in this file) with any MEM object of type T2.
324 This is used when allocating temporary storage. If T1 and/or T2 are
325 NULL_TREE, it means we know nothing about the storage. */
328 objects_must_conflict_p (t1, t2)
331 /* If neither has a type specified, we don't know if they'll conflict
332 because we may be using them to store objects of various types, for
333 example the argument and local variables areas of inlined functions. */
334 if (t1 == 0 && t2 == 0)
337 /* If one or the other has readonly fields or is readonly,
338 then they may not conflict. */
339 if ((t1 != 0 && readonly_fields_p (t1))
340 || (t2 != 0 && readonly_fields_p (t2))
341 || (t1 != 0 && TYPE_READONLY (t1))
342 || (t2 != 0 && TYPE_READONLY (t2)))
345 /* If they are the same type, they must conflict. */
347 /* Likewise if both are volatile. */
348 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
351 /* If one is aggregate and the other is scalar then they may not
353 if ((t1 != 0 && AGGREGATE_TYPE_P (t1))
354 != (t2 != 0 && AGGREGATE_TYPE_P (t2)))
357 /* Otherwise they conflict only if the alias sets conflict. */
358 return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0,
359 t2 ? get_alias_set (t2) : 0);
362 /* T is an expression with pointer type. Find the DECL on which this
363 expression is based. (For example, in `a[i]' this would be `a'.)
364 If there is no such DECL, or a unique decl cannot be determined,
365 NULL_TREE is retured. */
373 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
376 /* If this is a declaration, return it. */
377 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
380 /* Handle general expressions. It would be nice to deal with
381 COMPONENT_REFs here. If we could tell that `a' and `b' were the
382 same, then `a->f' and `b->f' are also the same. */
383 switch (TREE_CODE_CLASS (TREE_CODE (t)))
386 return find_base_decl (TREE_OPERAND (t, 0));
389 /* Return 0 if found in neither or both are the same. */
390 d0 = find_base_decl (TREE_OPERAND (t, 0));
391 d1 = find_base_decl (TREE_OPERAND (t, 1));
402 d0 = find_base_decl (TREE_OPERAND (t, 0));
403 d1 = find_base_decl (TREE_OPERAND (t, 1));
404 d0 = find_base_decl (TREE_OPERAND (t, 0));
405 d2 = find_base_decl (TREE_OPERAND (t, 2));
407 /* Set any nonzero values from the last, then from the first. */
408 if (d1 == 0) d1 = d2;
409 if (d0 == 0) d0 = d1;
410 if (d1 == 0) d1 = d0;
411 if (d2 == 0) d2 = d1;
413 /* At this point all are nonzero or all are zero. If all three are the
414 same, return it. Otherwise, return zero. */
415 return (d0 == d1 && d1 == d2) ? d0 : 0;
422 /* Return 1 if T is an expression that get_inner_reference handles. */
425 handled_component_p (t)
428 switch (TREE_CODE (t))
433 case ARRAY_RANGE_REF:
434 case NON_LVALUE_EXPR:
439 return (TYPE_MODE (TREE_TYPE (t))
440 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))));
447 /* Return 1 if all the nested component references handled by
448 get_inner_reference in T are such that we can address the object in T. */
454 /* If we're at the end, it is vacuously addressable. */
455 if (! handled_component_p (t))
458 /* Bitfields are never addressable. */
459 else if (TREE_CODE (t) == BIT_FIELD_REF)
462 else if (TREE_CODE (t) == COMPONENT_REF
463 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
464 && can_address_p (TREE_OPERAND (t, 0)))
467 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
468 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
469 && can_address_p (TREE_OPERAND (t, 0)))
475 /* Return the alias set for T, which may be either a type or an
476 expression. Call language-specific routine for help, if needed. */
485 /* If we're not doing any alias analysis, just assume everything
486 aliases everything else. Also return 0 if this or its type is
488 if (! flag_strict_aliasing || t == error_mark_node
490 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
493 /* We can be passed either an expression or a type. This and the
494 language-specific routine may make mutually-recursive calls to
495 each other to figure out what to do. At each juncture, we see if
496 this is a tree that the language may need to handle specially.
497 First handle things that aren't types and start by removing nops
498 since we care only about the actual object. */
501 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
502 || TREE_CODE (t) == NON_LVALUE_EXPR)
503 t = TREE_OPERAND (t, 0);
505 /* Now give the language a chance to do something but record what we
506 gave it this time. */
508 if ((set = lang_get_alias_set (t)) != -1)
511 /* Now loop the same way as get_inner_reference and get the alias
512 set to use. Pick up the outermost object that we could have
514 while (handled_component_p (t) && ! can_address_p (t))
515 t = TREE_OPERAND (t, 0);
517 if (TREE_CODE (t) == INDIRECT_REF)
519 /* Check for accesses through restrict-qualified pointers. */
520 tree decl = find_base_decl (TREE_OPERAND (t, 0));
522 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
523 /* We use the alias set indicated in the declaration. */
524 return DECL_POINTER_ALIAS_SET (decl);
526 /* If we have an INDIRECT_REF via a void pointer, we don't
527 know anything about what that might alias. */
528 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
532 /* Give the language another chance to do something special. */
534 && (set = lang_get_alias_set (t)) != -1)
537 /* Now all we care about is the type. */
541 /* Variant qualifiers don't affect the alias set, so get the main
542 variant. If this is a type with a known alias set, return it. */
543 t = TYPE_MAIN_VARIANT (t);
544 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
545 return TYPE_ALIAS_SET (t);
547 /* See if the language has special handling for this type. */
548 if ((set = lang_get_alias_set (t)) != -1)
550 /* If the alias set is now known, we are done. */
551 if (TYPE_ALIAS_SET_KNOWN_P (t))
552 return TYPE_ALIAS_SET (t);
555 /* There are no objects of FUNCTION_TYPE, so there's no point in
556 using up an alias set for them. (There are, of course, pointers
557 and references to functions, but that's different.) */
558 else if (TREE_CODE (t) == FUNCTION_TYPE)
561 /* Otherwise make a new alias set for this type. */
562 set = new_alias_set ();
564 TYPE_ALIAS_SET (t) = set;
566 /* If this is an aggregate type, we must record any component aliasing
568 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
569 record_component_aliases (t);
574 /* Return a brand-new alias set. */
579 static HOST_WIDE_INT last_alias_set;
581 if (flag_strict_aliasing)
582 return ++last_alias_set;
587 /* Indicate that things in SUBSET can alias things in SUPERSET, but
588 not vice versa. For example, in C, a store to an `int' can alias a
589 structure containing an `int', but not vice versa. Here, the
590 structure would be the SUPERSET and `int' the SUBSET. This
591 function should be called only once per SUPERSET/SUBSET pair.
593 It is illegal for SUPERSET to be zero; everything is implicitly a
594 subset of alias set zero. */
597 record_alias_subset (superset, subset)
598 HOST_WIDE_INT superset;
599 HOST_WIDE_INT subset;
601 alias_set_entry superset_entry;
602 alias_set_entry subset_entry;
607 superset_entry = get_alias_set_entry (superset);
608 if (superset_entry == 0)
610 /* Create an entry for the SUPERSET, so that we have a place to
611 attach the SUBSET. */
613 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
614 superset_entry->alias_set = superset;
615 superset_entry->children
616 = splay_tree_new (splay_tree_compare_ints, 0, 0);
617 superset_entry->has_zero_child = 0;
618 splay_tree_insert (alias_sets, (splay_tree_key) superset,
619 (splay_tree_value) superset_entry);
623 superset_entry->has_zero_child = 1;
626 subset_entry = get_alias_set_entry (subset);
627 /* If there is an entry for the subset, enter all of its children
628 (if they are not already present) as children of the SUPERSET. */
631 if (subset_entry->has_zero_child)
632 superset_entry->has_zero_child = 1;
634 splay_tree_foreach (subset_entry->children, insert_subset_children,
635 superset_entry->children);
638 /* Enter the SUBSET itself as a child of the SUPERSET. */
639 splay_tree_insert (superset_entry->children,
640 (splay_tree_key) subset, 0);
644 /* Record that component types of TYPE, if any, are part of that type for
645 aliasing purposes. For record types, we only record component types
646 for fields that are marked addressable. For array types, we always
647 record the component types, so the front end should not call this
648 function if the individual component aren't addressable. */
651 record_component_aliases (type)
654 HOST_WIDE_INT superset = get_alias_set (type);
660 switch (TREE_CODE (type))
663 if (! TYPE_NONALIASED_COMPONENT (type))
664 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
669 case QUAL_UNION_TYPE:
670 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
671 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
672 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
676 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
684 /* Allocate an alias set for use in storing and reading from the varargs
688 get_varargs_alias_set ()
690 static HOST_WIDE_INT set = -1;
693 set = new_alias_set ();
698 /* Likewise, but used for the fixed portions of the frame, e.g., register
702 get_frame_alias_set ()
704 static HOST_WIDE_INT set = -1;
707 set = new_alias_set ();
712 /* Inside SRC, the source of a SET, find a base address. */
715 find_base_value (src)
719 switch (GET_CODE (src))
727 /* At the start of a function, argument registers have known base
728 values which may be lost later. Returning an ADDRESS
729 expression here allows optimization based on argument values
730 even when the argument registers are used for other purposes. */
731 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
732 return new_reg_base_value[regno];
734 /* If a pseudo has a known base value, return it. Do not do this
735 for hard regs since it can result in a circular dependency
736 chain for registers which have values at function entry.
738 The test above is not sufficient because the scheduler may move
739 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
740 if (regno >= FIRST_PSEUDO_REGISTER
741 && regno < reg_base_value_size
742 && reg_base_value[regno])
743 return reg_base_value[regno];
748 /* Check for an argument passed in memory. Only record in the
749 copying-arguments block; it is too hard to track changes
751 if (copying_arguments
752 && (XEXP (src, 0) == arg_pointer_rtx
753 || (GET_CODE (XEXP (src, 0)) == PLUS
754 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
755 return gen_rtx_ADDRESS (VOIDmode, src);
760 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
763 /* ... fall through ... */
768 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
770 /* If either operand is a REG, then see if we already have
771 a known value for it. */
772 if (GET_CODE (src_0) == REG)
774 temp = find_base_value (src_0);
779 if (GET_CODE (src_1) == REG)
781 temp = find_base_value (src_1);
786 /* Guess which operand is the base address:
787 If either operand is a symbol, then it is the base. If
788 either operand is a CONST_INT, then the other is the base. */
789 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
790 return find_base_value (src_0);
791 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
792 return find_base_value (src_1);
794 /* This might not be necessary anymore:
795 If either operand is a REG that is a known pointer, then it
797 else if (GET_CODE (src_0) == REG && REG_POINTER (src_0))
798 return find_base_value (src_0);
799 else if (GET_CODE (src_1) == REG && REG_POINTER (src_1))
800 return find_base_value (src_1);
806 /* The standard form is (lo_sum reg sym) so look only at the
808 return find_base_value (XEXP (src, 1));
811 /* If the second operand is constant set the base
812 address to the first operand. */
813 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
814 return find_base_value (XEXP (src, 0));
818 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
822 case SIGN_EXTEND: /* used for NT/Alpha pointers */
824 return find_base_value (XEXP (src, 0));
833 /* Called from init_alias_analysis indirectly through note_stores. */
835 /* While scanning insns to find base values, reg_seen[N] is nonzero if
836 register N has been set in this function. */
837 static char *reg_seen;
839 /* Addresses which are known not to alias anything else are identified
840 by a unique integer. */
841 static int unique_id;
844 record_set (dest, set, data)
846 void *data ATTRIBUTE_UNUSED;
848 register unsigned regno;
851 if (GET_CODE (dest) != REG)
854 regno = REGNO (dest);
856 if (regno >= reg_base_value_size)
861 /* A CLOBBER wipes out any old value but does not prevent a previously
862 unset register from acquiring a base address (i.e. reg_seen is not
864 if (GET_CODE (set) == CLOBBER)
866 new_reg_base_value[regno] = 0;
875 new_reg_base_value[regno] = 0;
879 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
880 GEN_INT (unique_id++));
884 /* This is not the first set. If the new value is not related to the
885 old value, forget the base value. Note that the following code is
887 extern int x, y; int *p = &x; p += (&y-&x);
888 ANSI C does not allow computing the difference of addresses
889 of distinct top level objects. */
890 if (new_reg_base_value[regno])
891 switch (GET_CODE (src))
895 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
896 new_reg_base_value[regno] = 0;
899 /* If the value we add in the PLUS is also a valid base value,
900 this might be the actual base value, and the original value
903 rtx other = NULL_RTX;
905 if (XEXP (src, 0) == dest)
906 other = XEXP (src, 1);
907 else if (XEXP (src, 1) == dest)
908 other = XEXP (src, 0);
910 if (! other || find_base_value (other))
911 new_reg_base_value[regno] = 0;
915 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
916 new_reg_base_value[regno] = 0;
919 new_reg_base_value[regno] = 0;
922 /* If this is the first set of a register, record the value. */
923 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
924 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
925 new_reg_base_value[regno] = find_base_value (src);
930 /* Called from loop optimization when a new pseudo-register is
931 created. It indicates that REGNO is being set to VAL. f INVARIANT
932 is true then this value also describes an invariant relationship
933 which can be used to deduce that two registers with unknown values
937 record_base_value (regno, val, invariant)
942 if (regno >= reg_base_value_size)
945 if (invariant && alias_invariant)
946 alias_invariant[regno] = val;
948 if (GET_CODE (val) == REG)
950 if (REGNO (val) < reg_base_value_size)
951 reg_base_value[regno] = reg_base_value[REGNO (val)];
956 reg_base_value[regno] = find_base_value (val);
959 /* Returns a canonical version of X, from the point of view alias
960 analysis. (For example, if X is a MEM whose address is a register,
961 and the register has a known value (say a SYMBOL_REF), then a MEM
962 whose address is the SYMBOL_REF is returned.) */
968 /* Recursively look for equivalences. */
969 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
970 && REGNO (x) < reg_known_value_size)
971 return reg_known_value[REGNO (x)] == x
972 ? x : canon_rtx (reg_known_value[REGNO (x)]);
973 else if (GET_CODE (x) == PLUS)
975 rtx x0 = canon_rtx (XEXP (x, 0));
976 rtx x1 = canon_rtx (XEXP (x, 1));
978 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
980 if (GET_CODE (x0) == CONST_INT)
981 return plus_constant (x1, INTVAL (x0));
982 else if (GET_CODE (x1) == CONST_INT)
983 return plus_constant (x0, INTVAL (x1));
984 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
988 /* This gives us much better alias analysis when called from
989 the loop optimizer. Note we want to leave the original
990 MEM alone, but need to return the canonicalized MEM with
991 all the flags with their original values. */
992 else if (GET_CODE (x) == MEM)
993 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
998 /* Return 1 if X and Y are identical-looking rtx's.
1000 We use the data in reg_known_value above to see if two registers with
1001 different numbers are, in fact, equivalent. */
1004 rtx_equal_for_memref_p (x, y)
1009 register enum rtx_code code;
1010 register const char *fmt;
1012 if (x == 0 && y == 0)
1014 if (x == 0 || y == 0)
1023 code = GET_CODE (x);
1024 /* Rtx's of different codes cannot be equal. */
1025 if (code != GET_CODE (y))
1028 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1029 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1031 if (GET_MODE (x) != GET_MODE (y))
1034 /* Some RTL can be compared without a recursive examination. */
1038 return REGNO (x) == REGNO (y);
1041 return XEXP (x, 0) == XEXP (y, 0);
1044 return XSTR (x, 0) == XSTR (y, 0);
1048 /* There's no need to compare the contents of CONST_DOUBLEs or
1049 CONST_INTs because pointer equality is a good enough
1050 comparison for these nodes. */
1054 return (XINT (x, 1) == XINT (y, 1)
1055 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1061 /* For commutative operations, the RTX match if the operand match in any
1062 order. Also handle the simple binary and unary cases without a loop. */
1063 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1064 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1065 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1066 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1067 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1068 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1069 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1070 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1071 else if (GET_RTX_CLASS (code) == '1')
1072 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1074 /* Compare the elements. If any pair of corresponding elements
1075 fail to match, return 0 for the whole things.
1077 Limit cases to types which actually appear in addresses. */
1079 fmt = GET_RTX_FORMAT (code);
1080 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1085 if (XINT (x, i) != XINT (y, i))
1090 /* Two vectors must have the same length. */
1091 if (XVECLEN (x, i) != XVECLEN (y, i))
1094 /* And the corresponding elements must match. */
1095 for (j = 0; j < XVECLEN (x, i); j++)
1096 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1097 XVECEXP (y, i, j)) == 0)
1102 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1106 /* This can happen for asm operands. */
1108 if (strcmp (XSTR (x, i), XSTR (y, i)))
1112 /* This can happen for an asm which clobbers memory. */
1116 /* It is believed that rtx's at this level will never
1117 contain anything but integers and other rtx's,
1118 except for within LABEL_REFs and SYMBOL_REFs. */
1126 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1127 X and return it, or return 0 if none found. */
1130 find_symbolic_term (x)
1134 register enum rtx_code code;
1135 register const char *fmt;
1137 code = GET_CODE (x);
1138 if (code == SYMBOL_REF || code == LABEL_REF)
1140 if (GET_RTX_CLASS (code) == 'o')
1143 fmt = GET_RTX_FORMAT (code);
1144 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1150 t = find_symbolic_term (XEXP (x, i));
1154 else if (fmt[i] == 'E')
1165 struct elt_loc_list *l;
1167 #if defined (FIND_BASE_TERM)
1168 /* Try machine-dependent ways to find the base term. */
1169 x = FIND_BASE_TERM (x);
1172 switch (GET_CODE (x))
1175 return REG_BASE_VALUE (x);
1178 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1184 return find_base_term (XEXP (x, 0));
1187 val = CSELIB_VAL_PTR (x);
1188 for (l = val->locs; l; l = l->next)
1189 if ((x = find_base_term (l->loc)) != 0)
1195 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1202 rtx tmp1 = XEXP (x, 0);
1203 rtx tmp2 = XEXP (x, 1);
1205 /* This is a litle bit tricky since we have to determine which of
1206 the two operands represents the real base address. Otherwise this
1207 routine may return the index register instead of the base register.
1209 That may cause us to believe no aliasing was possible, when in
1210 fact aliasing is possible.
1212 We use a few simple tests to guess the base register. Additional
1213 tests can certainly be added. For example, if one of the operands
1214 is a shift or multiply, then it must be the index register and the
1215 other operand is the base register. */
1217 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1218 return find_base_term (tmp2);
1220 /* If either operand is known to be a pointer, then use it
1221 to determine the base term. */
1222 if (REG_P (tmp1) && REG_POINTER (tmp1))
1223 return find_base_term (tmp1);
1225 if (REG_P (tmp2) && REG_POINTER (tmp2))
1226 return find_base_term (tmp2);
1228 /* Neither operand was known to be a pointer. Go ahead and find the
1229 base term for both operands. */
1230 tmp1 = find_base_term (tmp1);
1231 tmp2 = find_base_term (tmp2);
1233 /* If either base term is named object or a special address
1234 (like an argument or stack reference), then use it for the
1237 && (GET_CODE (tmp1) == SYMBOL_REF
1238 || GET_CODE (tmp1) == LABEL_REF
1239 || (GET_CODE (tmp1) == ADDRESS
1240 && GET_MODE (tmp1) != VOIDmode)))
1244 && (GET_CODE (tmp2) == SYMBOL_REF
1245 || GET_CODE (tmp2) == LABEL_REF
1246 || (GET_CODE (tmp2) == ADDRESS
1247 && GET_MODE (tmp2) != VOIDmode)))
1250 /* We could not determine which of the two operands was the
1251 base register and which was the index. So we can determine
1252 nothing from the base alias check. */
1257 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1258 return REG_BASE_VALUE (XEXP (x, 0));
1266 return REG_BASE_VALUE (frame_pointer_rtx);
1273 /* Return 0 if the addresses X and Y are known to point to different
1274 objects, 1 if they might be pointers to the same object. */
1277 base_alias_check (x, y, x_mode, y_mode)
1279 enum machine_mode x_mode, y_mode;
1281 rtx x_base = find_base_term (x);
1282 rtx y_base = find_base_term (y);
1284 /* If the address itself has no known base see if a known equivalent
1285 value has one. If either address still has no known base, nothing
1286 is known about aliasing. */
1291 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1294 x_base = find_base_term (x_c);
1302 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1305 y_base = find_base_term (y_c);
1310 /* If the base addresses are equal nothing is known about aliasing. */
1311 if (rtx_equal_p (x_base, y_base))
1314 /* The base addresses of the read and write are different expressions.
1315 If they are both symbols and they are not accessed via AND, there is
1316 no conflict. We can bring knowledge of object alignment into play
1317 here. For example, on alpha, "char a, b;" can alias one another,
1318 though "char a; long b;" cannot. */
1319 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1321 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1323 if (GET_CODE (x) == AND
1324 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1325 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1327 if (GET_CODE (y) == AND
1328 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1329 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1331 /* Differing symbols never alias. */
1335 /* If one address is a stack reference there can be no alias:
1336 stack references using different base registers do not alias,
1337 a stack reference can not alias a parameter, and a stack reference
1338 can not alias a global. */
1339 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1340 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1343 if (! flag_argument_noalias)
1346 if (flag_argument_noalias > 1)
1349 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1350 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1353 /* Convert the address X into something we can use. This is done by returning
1354 it unchanged unless it is a value; in the latter case we call cselib to get
1355 a more useful rtx. */
1362 struct elt_loc_list *l;
1364 if (GET_CODE (x) != VALUE)
1366 v = CSELIB_VAL_PTR (x);
1367 for (l = v->locs; l; l = l->next)
1368 if (CONSTANT_P (l->loc))
1370 for (l = v->locs; l; l = l->next)
1371 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1374 return v->locs->loc;
1378 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1379 where SIZE is the size in bytes of the memory reference. If ADDR
1380 is not modified by the memory reference then ADDR is returned. */
1383 addr_side_effect_eval (addr, size, n_refs)
1390 switch (GET_CODE (addr))
1393 offset = (n_refs + 1) * size;
1396 offset = -(n_refs + 1) * size;
1399 offset = n_refs * size;
1402 offset = -n_refs * size;
1410 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1412 addr = XEXP (addr, 0);
1417 /* Return nonzero if X and Y (memory addresses) could reference the
1418 same location in memory. C is an offset accumulator. When
1419 C is nonzero, we are testing aliases between X and Y + C.
1420 XSIZE is the size in bytes of the X reference,
1421 similarly YSIZE is the size in bytes for Y.
1423 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1424 referenced (the reference was BLKmode), so make the most pessimistic
1427 If XSIZE or YSIZE is negative, we may access memory outside the object
1428 being referenced as a side effect. This can happen when using AND to
1429 align memory references, as is done on the Alpha.
1431 Nice to notice that varying addresses cannot conflict with fp if no
1432 local variables had their addresses taken, but that's too hard now. */
1435 memrefs_conflict_p (xsize, x, ysize, y, c)
1440 if (GET_CODE (x) == VALUE)
1442 if (GET_CODE (y) == VALUE)
1444 if (GET_CODE (x) == HIGH)
1446 else if (GET_CODE (x) == LO_SUM)
1449 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1450 if (GET_CODE (y) == HIGH)
1452 else if (GET_CODE (y) == LO_SUM)
1455 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1457 if (rtx_equal_for_memref_p (x, y))
1459 if (xsize <= 0 || ysize <= 0)
1461 if (c >= 0 && xsize > c)
1463 if (c < 0 && ysize+c > 0)
1468 /* This code used to check for conflicts involving stack references and
1469 globals but the base address alias code now handles these cases. */
1471 if (GET_CODE (x) == PLUS)
1473 /* The fact that X is canonicalized means that this
1474 PLUS rtx is canonicalized. */
1475 rtx x0 = XEXP (x, 0);
1476 rtx x1 = XEXP (x, 1);
1478 if (GET_CODE (y) == PLUS)
1480 /* The fact that Y is canonicalized means that this
1481 PLUS rtx is canonicalized. */
1482 rtx y0 = XEXP (y, 0);
1483 rtx y1 = XEXP (y, 1);
1485 if (rtx_equal_for_memref_p (x1, y1))
1486 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1487 if (rtx_equal_for_memref_p (x0, y0))
1488 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1489 if (GET_CODE (x1) == CONST_INT)
1491 if (GET_CODE (y1) == CONST_INT)
1492 return memrefs_conflict_p (xsize, x0, ysize, y0,
1493 c - INTVAL (x1) + INTVAL (y1));
1495 return memrefs_conflict_p (xsize, x0, ysize, y,
1498 else if (GET_CODE (y1) == CONST_INT)
1499 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1503 else if (GET_CODE (x1) == CONST_INT)
1504 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1506 else if (GET_CODE (y) == PLUS)
1508 /* The fact that Y is canonicalized means that this
1509 PLUS rtx is canonicalized. */
1510 rtx y0 = XEXP (y, 0);
1511 rtx y1 = XEXP (y, 1);
1513 if (GET_CODE (y1) == CONST_INT)
1514 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1519 if (GET_CODE (x) == GET_CODE (y))
1520 switch (GET_CODE (x))
1524 /* Handle cases where we expect the second operands to be the
1525 same, and check only whether the first operand would conflict
1528 rtx x1 = canon_rtx (XEXP (x, 1));
1529 rtx y1 = canon_rtx (XEXP (y, 1));
1530 if (! rtx_equal_for_memref_p (x1, y1))
1532 x0 = canon_rtx (XEXP (x, 0));
1533 y0 = canon_rtx (XEXP (y, 0));
1534 if (rtx_equal_for_memref_p (x0, y0))
1535 return (xsize == 0 || ysize == 0
1536 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1538 /* Can't properly adjust our sizes. */
1539 if (GET_CODE (x1) != CONST_INT)
1541 xsize /= INTVAL (x1);
1542 ysize /= INTVAL (x1);
1544 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1548 /* Are these registers known not to be equal? */
1549 if (alias_invariant)
1551 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1552 rtx i_x, i_y; /* invariant relationships of X and Y */
1554 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1555 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1557 if (i_x == 0 && i_y == 0)
1560 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1561 ysize, i_y ? i_y : y, c))
1570 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1571 as an access with indeterminate size. Assume that references
1572 besides AND are aligned, so if the size of the other reference is
1573 at least as large as the alignment, assume no other overlap. */
1574 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1576 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1578 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1580 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1582 /* ??? If we are indexing far enough into the array/structure, we
1583 may yet be able to determine that we can not overlap. But we
1584 also need to that we are far enough from the end not to overlap
1585 a following reference, so we do nothing with that for now. */
1586 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1588 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1591 if (GET_CODE (x) == ADDRESSOF)
1593 if (y == frame_pointer_rtx
1594 || GET_CODE (y) == ADDRESSOF)
1595 return xsize <= 0 || ysize <= 0;
1597 if (GET_CODE (y) == ADDRESSOF)
1599 if (x == frame_pointer_rtx)
1600 return xsize <= 0 || ysize <= 0;
1605 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1607 c += (INTVAL (y) - INTVAL (x));
1608 return (xsize <= 0 || ysize <= 0
1609 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1612 if (GET_CODE (x) == CONST)
1614 if (GET_CODE (y) == CONST)
1615 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1616 ysize, canon_rtx (XEXP (y, 0)), c);
1618 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1621 if (GET_CODE (y) == CONST)
1622 return memrefs_conflict_p (xsize, x, ysize,
1623 canon_rtx (XEXP (y, 0)), c);
1626 return (xsize <= 0 || ysize <= 0
1627 || (rtx_equal_for_memref_p (x, y)
1628 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1635 /* Functions to compute memory dependencies.
1637 Since we process the insns in execution order, we can build tables
1638 to keep track of what registers are fixed (and not aliased), what registers
1639 are varying in known ways, and what registers are varying in unknown
1642 If both memory references are volatile, then there must always be a
1643 dependence between the two references, since their order can not be
1644 changed. A volatile and non-volatile reference can be interchanged
1647 A MEM_IN_STRUCT reference at a non-AND varying address can never
1648 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1649 also must allow AND addresses, because they may generate accesses
1650 outside the object being referenced. This is used to generate
1651 aligned addresses from unaligned addresses, for instance, the alpha
1652 storeqi_unaligned pattern. */
1654 /* Read dependence: X is read after read in MEM takes place. There can
1655 only be a dependence here if both reads are volatile. */
1658 read_dependence (mem, x)
1662 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1665 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1666 MEM2 is a reference to a structure at a varying address, or returns
1667 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1668 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1669 to decide whether or not an address may vary; it should return
1670 nonzero whenever variation is possible.
1671 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1674 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1676 rtx mem1_addr, mem2_addr;
1677 int (*varies_p) PARAMS ((rtx, int));
1679 if (! flag_strict_aliasing)
1682 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1683 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1684 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1688 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1689 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1690 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1697 /* Returns nonzero if something about the mode or address format MEM1
1698 indicates that it might well alias *anything*. */
1701 aliases_everything_p (mem)
1704 if (GET_CODE (XEXP (mem, 0)) == AND)
1705 /* If the address is an AND, its very hard to know at what it is
1706 actually pointing. */
1712 /* True dependence: X is read after store in MEM takes place. */
1715 true_dependence (mem, mem_mode, x, varies)
1717 enum machine_mode mem_mode;
1719 int (*varies) PARAMS ((rtx, int));
1721 register rtx x_addr, mem_addr;
1724 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1727 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1730 /* Unchanging memory can't conflict with non-unchanging memory.
1731 A non-unchanging read can conflict with a non-unchanging write.
1732 An unchanging read can conflict with an unchanging write since
1733 there may be a single store to this address to initialize it.
1734 Note that an unchanging store can conflict with a non-unchanging read
1735 since we have to make conservative assumptions when we have a
1736 record with readonly fields and we are copying the whole thing.
1737 Just fall through to the code below to resolve potential conflicts.
1738 This won't handle all cases optimally, but the possible performance
1739 loss should be negligible. */
1740 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1743 if (mem_mode == VOIDmode)
1744 mem_mode = GET_MODE (mem);
1746 x_addr = get_addr (XEXP (x, 0));
1747 mem_addr = get_addr (XEXP (mem, 0));
1749 base = find_base_term (x_addr);
1750 if (base && (GET_CODE (base) == LABEL_REF
1751 || (GET_CODE (base) == SYMBOL_REF
1752 && CONSTANT_POOL_ADDRESS_P (base))))
1755 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1758 x_addr = canon_rtx (x_addr);
1759 mem_addr = canon_rtx (mem_addr);
1761 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1762 SIZE_FOR_MODE (x), x_addr, 0))
1765 if (aliases_everything_p (x))
1768 /* We cannot use aliases_everyting_p to test MEM, since we must look
1769 at MEM_MODE, rather than GET_MODE (MEM). */
1770 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1773 /* In true_dependence we also allow BLKmode to alias anything. Why
1774 don't we do this in anti_dependence and output_dependence? */
1775 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1778 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1782 /* Canonical true dependence: X is read after store in MEM takes place.
1783 Variant of true_dependece which assumes MEM has already been
1784 canonicalized (hence we no longer do that here).
1785 The mem_addr argument has been added, since true_dependence computed
1786 this value prior to canonicalizing. */
1789 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
1790 rtx mem, mem_addr, x;
1791 enum machine_mode mem_mode;
1792 int (*varies) PARAMS ((rtx, int));
1794 register rtx x_addr;
1796 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1799 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1802 /* If X is an unchanging read, then it can't possibly conflict with any
1803 non-unchanging store. It may conflict with an unchanging write though,
1804 because there may be a single store to this address to initialize it.
1805 Just fall through to the code below to resolve the case where we have
1806 both an unchanging read and an unchanging write. This won't handle all
1807 cases optimally, but the possible performance loss should be
1809 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1812 x_addr = get_addr (XEXP (x, 0));
1814 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1817 x_addr = canon_rtx (x_addr);
1818 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1819 SIZE_FOR_MODE (x), x_addr, 0))
1822 if (aliases_everything_p (x))
1825 /* We cannot use aliases_everyting_p to test MEM, since we must look
1826 at MEM_MODE, rather than GET_MODE (MEM). */
1827 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1830 /* In true_dependence we also allow BLKmode to alias anything. Why
1831 don't we do this in anti_dependence and output_dependence? */
1832 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1835 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1839 /* Returns non-zero if a write to X might alias a previous read from
1840 (or, if WRITEP is non-zero, a write to) MEM. */
1843 write_dependence_p (mem, x, writep)
1848 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 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1862 /* If MEM is an unchanging read, then it can't possibly conflict with
1863 the store to X, because there is at most one store to MEM, and it must
1864 have occurred somewhere before MEM. */
1865 if (! writep && RTX_UNCHANGING_P (mem))
1868 x_addr = get_addr (XEXP (x, 0));
1869 mem_addr = get_addr (XEXP (mem, 0));
1873 base = find_base_term (mem_addr);
1874 if (base && (GET_CODE (base) == LABEL_REF
1875 || (GET_CODE (base) == SYMBOL_REF
1876 && CONSTANT_POOL_ADDRESS_P (base))))
1880 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1884 x_addr = canon_rtx (x_addr);
1885 mem_addr = canon_rtx (mem_addr);
1887 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1888 SIZE_FOR_MODE (x), x_addr, 0))
1892 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1895 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1896 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1899 /* Anti dependence: X is written after read in MEM takes place. */
1902 anti_dependence (mem, x)
1906 return write_dependence_p (mem, x, /*writep=*/0);
1909 /* Output dependence: X is written after store in MEM takes place. */
1912 output_dependence (mem, x)
1916 return write_dependence_p (mem, x, /*writep=*/1);
1919 /* Returns non-zero if X mentions something which is not
1920 local to the function and is not constant. */
1923 nonlocal_mentioned_p (x)
1927 register RTX_CODE code;
1930 code = GET_CODE (x);
1932 if (GET_RTX_CLASS (code) == 'i')
1934 /* Constant functions can be constant if they don't use
1935 scratch memory used to mark function w/o side effects. */
1936 if (code == CALL_INSN && CONST_CALL_P (x))
1938 x = CALL_INSN_FUNCTION_USAGE (x);
1944 code = GET_CODE (x);
1950 if (GET_CODE (SUBREG_REG (x)) == REG)
1952 /* Global registers are not local. */
1953 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1954 && global_regs[subreg_regno (x)])
1962 /* Global registers are not local. */
1963 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1977 /* Constants in the function's constants pool are constant. */
1978 if (CONSTANT_POOL_ADDRESS_P (x))
1983 /* Non-constant calls and recursion are not local. */
1987 /* Be overly conservative and consider any volatile memory
1988 reference as not local. */
1989 if (MEM_VOLATILE_P (x))
1991 base = find_base_term (XEXP (x, 0));
1994 /* A Pmode ADDRESS could be a reference via the structure value
1995 address or static chain. Such memory references are nonlocal.
1997 Thus, we have to examine the contents of the ADDRESS to find
1998 out if this is a local reference or not. */
1999 if (GET_CODE (base) == ADDRESS
2000 && GET_MODE (base) == Pmode
2001 && (XEXP (base, 0) == stack_pointer_rtx
2002 || XEXP (base, 0) == arg_pointer_rtx
2003 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2004 || XEXP (base, 0) == hard_frame_pointer_rtx
2006 || XEXP (base, 0) == frame_pointer_rtx))
2008 /* Constants in the function's constant pool are constant. */
2009 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2014 case UNSPEC_VOLATILE:
2019 if (MEM_VOLATILE_P (x))
2028 /* Recursively scan the operands of this expression. */
2031 register const char *fmt = GET_RTX_FORMAT (code);
2034 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2036 if (fmt[i] == 'e' && XEXP (x, i))
2038 if (nonlocal_mentioned_p (XEXP (x, i)))
2041 else if (fmt[i] == 'E')
2044 for (j = 0; j < XVECLEN (x, i); j++)
2045 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2054 /* Return non-zero if a loop (natural or otherwise) is present.
2055 Inspired by Depth_First_Search_PP described in:
2057 Advanced Compiler Design and Implementation
2059 Morgan Kaufmann, 1997
2061 and heavily borrowed from flow_depth_first_order_compute. */
2074 /* Allocate the preorder and postorder number arrays. */
2075 pre = (int *) xcalloc (n_basic_blocks, sizeof (int));
2076 post = (int *) xcalloc (n_basic_blocks, sizeof (int));
2078 /* Allocate stack for back-tracking up CFG. */
2079 stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
2082 /* Allocate bitmap to track nodes that have been visited. */
2083 visited = sbitmap_alloc (n_basic_blocks);
2085 /* None of the nodes in the CFG have been visited yet. */
2086 sbitmap_zero (visited);
2088 /* Push the first edge on to the stack. */
2089 stack[sp++] = ENTRY_BLOCK_PTR->succ;
2097 /* Look at the edge on the top of the stack. */
2102 /* Check if the edge destination has been visited yet. */
2103 if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
2105 /* Mark that we have visited the destination. */
2106 SET_BIT (visited, dest->index);
2108 pre[dest->index] = prenum++;
2112 /* Since the DEST node has been visited for the first
2113 time, check its successors. */
2114 stack[sp++] = dest->succ;
2117 post[dest->index] = postnum++;
2121 if (dest != EXIT_BLOCK_PTR && src != ENTRY_BLOCK_PTR
2122 && pre[src->index] >= pre[dest->index]
2123 && post[dest->index] == 0)
2126 if (! e->succ_next && src != ENTRY_BLOCK_PTR)
2127 post[src->index] = postnum++;
2130 stack[sp - 1] = e->succ_next;
2139 sbitmap_free (visited);
2144 /* Mark the function if it is constant. */
2147 mark_constant_function ()
2150 int nonlocal_mentioned;
2152 if (TREE_PUBLIC (current_function_decl)
2153 || TREE_READONLY (current_function_decl)
2154 || DECL_IS_PURE (current_function_decl)
2155 || TREE_THIS_VOLATILE (current_function_decl)
2156 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2159 /* A loop might not return which counts as a side effect. */
2163 nonlocal_mentioned = 0;
2165 init_alias_analysis ();
2167 /* Determine if this is a constant function. */
2169 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2170 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2172 nonlocal_mentioned = 1;
2176 end_alias_analysis ();
2178 /* Mark the function. */
2180 if (! nonlocal_mentioned)
2181 TREE_READONLY (current_function_decl) = 1;
2185 static HARD_REG_SET argument_registers;
2192 #ifndef OUTGOING_REGNO
2193 #define OUTGOING_REGNO(N) N
2195 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2196 /* Check whether this register can hold an incoming pointer
2197 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2198 numbers, so translate if necessary due to register windows. */
2199 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2200 && HARD_REGNO_MODE_OK (i, Pmode))
2201 SET_HARD_REG_BIT (argument_registers, i);
2203 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2206 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2210 init_alias_analysis ()
2212 int maxreg = max_reg_num ();
2215 register unsigned int ui;
2218 reg_known_value_size = maxreg;
2221 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2222 - FIRST_PSEUDO_REGISTER;
2224 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2225 - FIRST_PSEUDO_REGISTER;
2227 /* Overallocate reg_base_value to allow some growth during loop
2228 optimization. Loop unrolling can create a large number of
2230 reg_base_value_size = maxreg * 2;
2231 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2232 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2234 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2235 reg_seen = (char *) xmalloc (reg_base_value_size);
2236 if (! reload_completed && flag_unroll_loops)
2238 /* ??? Why are we realloc'ing if we're just going to zero it? */
2239 alias_invariant = (rtx *)xrealloc (alias_invariant,
2240 reg_base_value_size * sizeof (rtx));
2241 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2244 /* The basic idea is that each pass through this loop will use the
2245 "constant" information from the previous pass to propagate alias
2246 information through another level of assignments.
2248 This could get expensive if the assignment chains are long. Maybe
2249 we should throttle the number of iterations, possibly based on
2250 the optimization level or flag_expensive_optimizations.
2252 We could propagate more information in the first pass by making use
2253 of REG_N_SETS to determine immediately that the alias information
2254 for a pseudo is "constant".
2256 A program with an uninitialized variable can cause an infinite loop
2257 here. Instead of doing a full dataflow analysis to detect such problems
2258 we just cap the number of iterations for the loop.
2260 The state of the arrays for the set chain in question does not matter
2261 since the program has undefined behavior. */
2266 /* Assume nothing will change this iteration of the loop. */
2269 /* We want to assign the same IDs each iteration of this loop, so
2270 start counting from zero each iteration of the loop. */
2273 /* We're at the start of the funtion each iteration through the
2274 loop, so we're copying arguments. */
2275 copying_arguments = 1;
2277 /* Wipe the potential alias information clean for this pass. */
2278 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2280 /* Wipe the reg_seen array clean. */
2281 memset ((char *) reg_seen, 0, reg_base_value_size);
2283 /* Mark all hard registers which may contain an address.
2284 The stack, frame and argument pointers may contain an address.
2285 An argument register which can hold a Pmode value may contain
2286 an address even if it is not in BASE_REGS.
2288 The address expression is VOIDmode for an argument and
2289 Pmode for other registers. */
2291 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2292 if (TEST_HARD_REG_BIT (argument_registers, i))
2293 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2294 gen_rtx_REG (Pmode, i));
2296 new_reg_base_value[STACK_POINTER_REGNUM]
2297 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2298 new_reg_base_value[ARG_POINTER_REGNUM]
2299 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2300 new_reg_base_value[FRAME_POINTER_REGNUM]
2301 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2302 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2303 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2304 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2307 /* Walk the insns adding values to the new_reg_base_value array. */
2308 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2314 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2315 /* The prologue/epilouge insns are not threaded onto the
2316 insn chain until after reload has completed. Thus,
2317 there is no sense wasting time checking if INSN is in
2318 the prologue/epilogue until after reload has completed. */
2319 if (reload_completed
2320 && prologue_epilogue_contains (insn))
2324 /* If this insn has a noalias note, process it, Otherwise,
2325 scan for sets. A simple set will have no side effects
2326 which could change the base value of any other register. */
2328 if (GET_CODE (PATTERN (insn)) == SET
2329 && REG_NOTES (insn) != 0
2330 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2331 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2333 note_stores (PATTERN (insn), record_set, NULL);
2335 set = single_set (insn);
2338 && GET_CODE (SET_DEST (set)) == REG
2339 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2341 unsigned int regno = REGNO (SET_DEST (set));
2342 rtx src = SET_SRC (set);
2344 if (REG_NOTES (insn) != 0
2345 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2346 && REG_N_SETS (regno) == 1)
2347 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2348 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2349 && ! rtx_varies_p (XEXP (note, 0), 1)
2350 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2352 reg_known_value[regno] = XEXP (note, 0);
2353 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2355 else if (REG_N_SETS (regno) == 1
2356 && GET_CODE (src) == PLUS
2357 && GET_CODE (XEXP (src, 0)) == REG
2358 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2359 && (reg_known_value[REGNO (XEXP (src, 0))])
2360 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2362 rtx op0 = XEXP (src, 0);
2363 op0 = reg_known_value[REGNO (op0)];
2364 reg_known_value[regno]
2365 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2366 reg_known_equiv_p[regno] = 0;
2368 else if (REG_N_SETS (regno) == 1
2369 && ! rtx_varies_p (src, 1))
2371 reg_known_value[regno] = src;
2372 reg_known_equiv_p[regno] = 0;
2376 else if (GET_CODE (insn) == NOTE
2377 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2378 copying_arguments = 0;
2381 /* Now propagate values from new_reg_base_value to reg_base_value. */
2382 for (ui = 0; ui < reg_base_value_size; ui++)
2384 if (new_reg_base_value[ui]
2385 && new_reg_base_value[ui] != reg_base_value[ui]
2386 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2388 reg_base_value[ui] = new_reg_base_value[ui];
2393 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2395 /* Fill in the remaining entries. */
2396 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2397 if (reg_known_value[i] == 0)
2398 reg_known_value[i] = regno_reg_rtx[i];
2400 /* Simplify the reg_base_value array so that no register refers to
2401 another register, except to special registers indirectly through
2402 ADDRESS expressions.
2404 In theory this loop can take as long as O(registers^2), but unless
2405 there are very long dependency chains it will run in close to linear
2408 This loop may not be needed any longer now that the main loop does
2409 a better job at propagating alias information. */
2415 for (ui = 0; ui < reg_base_value_size; ui++)
2417 rtx base = reg_base_value[ui];
2418 if (base && GET_CODE (base) == REG)
2420 unsigned int base_regno = REGNO (base);
2421 if (base_regno == ui) /* register set from itself */
2422 reg_base_value[ui] = 0;
2424 reg_base_value[ui] = reg_base_value[base_regno];
2429 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2432 free (new_reg_base_value);
2433 new_reg_base_value = 0;
2439 end_alias_analysis ()
2441 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2442 reg_known_value = 0;
2443 reg_known_value_size = 0;
2444 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2445 reg_known_equiv_p = 0;
2448 ggc_del_root (reg_base_value);
2449 free (reg_base_value);
2452 reg_base_value_size = 0;
2453 if (alias_invariant)
2455 free (alias_invariant);
2456 alias_invariant = 0;