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 an asm which clobbers memory. */
1110 /* It is believed that rtx's at this level will never
1111 contain anything but integers and other rtx's,
1112 except for within LABEL_REFs and SYMBOL_REFs. */
1120 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1121 X and return it, or return 0 if none found. */
1124 find_symbolic_term (x)
1128 register enum rtx_code code;
1129 register const char *fmt;
1131 code = GET_CODE (x);
1132 if (code == SYMBOL_REF || code == LABEL_REF)
1134 if (GET_RTX_CLASS (code) == 'o')
1137 fmt = GET_RTX_FORMAT (code);
1138 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1144 t = find_symbolic_term (XEXP (x, i));
1148 else if (fmt[i] == 'E')
1159 struct elt_loc_list *l;
1161 #if defined (FIND_BASE_TERM)
1162 /* Try machine-dependent ways to find the base term. */
1163 x = FIND_BASE_TERM (x);
1166 switch (GET_CODE (x))
1169 return REG_BASE_VALUE (x);
1172 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1178 return find_base_term (XEXP (x, 0));
1181 val = CSELIB_VAL_PTR (x);
1182 for (l = val->locs; l; l = l->next)
1183 if ((x = find_base_term (l->loc)) != 0)
1189 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1196 rtx tmp1 = XEXP (x, 0);
1197 rtx tmp2 = XEXP (x, 1);
1199 /* This is a litle bit tricky since we have to determine which of
1200 the two operands represents the real base address. Otherwise this
1201 routine may return the index register instead of the base register.
1203 That may cause us to believe no aliasing was possible, when in
1204 fact aliasing is possible.
1206 We use a few simple tests to guess the base register. Additional
1207 tests can certainly be added. For example, if one of the operands
1208 is a shift or multiply, then it must be the index register and the
1209 other operand is the base register. */
1211 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1212 return find_base_term (tmp2);
1214 /* If either operand is known to be a pointer, then use it
1215 to determine the base term. */
1216 if (REG_P (tmp1) && REG_POINTER (tmp1))
1217 return find_base_term (tmp1);
1219 if (REG_P (tmp2) && REG_POINTER (tmp2))
1220 return find_base_term (tmp2);
1222 /* Neither operand was known to be a pointer. Go ahead and find the
1223 base term for both operands. */
1224 tmp1 = find_base_term (tmp1);
1225 tmp2 = find_base_term (tmp2);
1227 /* If either base term is named object or a special address
1228 (like an argument or stack reference), then use it for the
1231 && (GET_CODE (tmp1) == SYMBOL_REF
1232 || GET_CODE (tmp1) == LABEL_REF
1233 || (GET_CODE (tmp1) == ADDRESS
1234 && GET_MODE (tmp1) != VOIDmode)))
1238 && (GET_CODE (tmp2) == SYMBOL_REF
1239 || GET_CODE (tmp2) == LABEL_REF
1240 || (GET_CODE (tmp2) == ADDRESS
1241 && GET_MODE (tmp2) != VOIDmode)))
1244 /* We could not determine which of the two operands was the
1245 base register and which was the index. So we can determine
1246 nothing from the base alias check. */
1251 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1252 return REG_BASE_VALUE (XEXP (x, 0));
1260 return REG_BASE_VALUE (frame_pointer_rtx);
1267 /* Return 0 if the addresses X and Y are known to point to different
1268 objects, 1 if they might be pointers to the same object. */
1271 base_alias_check (x, y, x_mode, y_mode)
1273 enum machine_mode x_mode, y_mode;
1275 rtx x_base = find_base_term (x);
1276 rtx y_base = find_base_term (y);
1278 /* If the address itself has no known base see if a known equivalent
1279 value has one. If either address still has no known base, nothing
1280 is known about aliasing. */
1285 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1288 x_base = find_base_term (x_c);
1296 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1299 y_base = find_base_term (y_c);
1304 /* If the base addresses are equal nothing is known about aliasing. */
1305 if (rtx_equal_p (x_base, y_base))
1308 /* The base addresses of the read and write are different expressions.
1309 If they are both symbols and they are not accessed via AND, there is
1310 no conflict. We can bring knowledge of object alignment into play
1311 here. For example, on alpha, "char a, b;" can alias one another,
1312 though "char a; long b;" cannot. */
1313 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1315 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1317 if (GET_CODE (x) == AND
1318 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1319 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1321 if (GET_CODE (y) == AND
1322 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1323 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1325 /* Differing symbols never alias. */
1329 /* If one address is a stack reference there can be no alias:
1330 stack references using different base registers do not alias,
1331 a stack reference can not alias a parameter, and a stack reference
1332 can not alias a global. */
1333 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1334 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1337 if (! flag_argument_noalias)
1340 if (flag_argument_noalias > 1)
1343 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1344 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1347 /* Convert the address X into something we can use. This is done by returning
1348 it unchanged unless it is a value; in the latter case we call cselib to get
1349 a more useful rtx. */
1356 struct elt_loc_list *l;
1358 if (GET_CODE (x) != VALUE)
1360 v = CSELIB_VAL_PTR (x);
1361 for (l = v->locs; l; l = l->next)
1362 if (CONSTANT_P (l->loc))
1364 for (l = v->locs; l; l = l->next)
1365 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1368 return v->locs->loc;
1372 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1373 where SIZE is the size in bytes of the memory reference. If ADDR
1374 is not modified by the memory reference then ADDR is returned. */
1377 addr_side_effect_eval (addr, size, n_refs)
1384 switch (GET_CODE (addr))
1387 offset = (n_refs + 1) * size;
1390 offset = -(n_refs + 1) * size;
1393 offset = n_refs * size;
1396 offset = -n_refs * size;
1404 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1406 addr = XEXP (addr, 0);
1411 /* Return nonzero if X and Y (memory addresses) could reference the
1412 same location in memory. C is an offset accumulator. When
1413 C is nonzero, we are testing aliases between X and Y + C.
1414 XSIZE is the size in bytes of the X reference,
1415 similarly YSIZE is the size in bytes for Y.
1417 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1418 referenced (the reference was BLKmode), so make the most pessimistic
1421 If XSIZE or YSIZE is negative, we may access memory outside the object
1422 being referenced as a side effect. This can happen when using AND to
1423 align memory references, as is done on the Alpha.
1425 Nice to notice that varying addresses cannot conflict with fp if no
1426 local variables had their addresses taken, but that's too hard now. */
1429 memrefs_conflict_p (xsize, x, ysize, y, c)
1434 if (GET_CODE (x) == VALUE)
1436 if (GET_CODE (y) == VALUE)
1438 if (GET_CODE (x) == HIGH)
1440 else if (GET_CODE (x) == LO_SUM)
1443 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1444 if (GET_CODE (y) == HIGH)
1446 else if (GET_CODE (y) == LO_SUM)
1449 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1451 if (rtx_equal_for_memref_p (x, y))
1453 if (xsize <= 0 || ysize <= 0)
1455 if (c >= 0 && xsize > c)
1457 if (c < 0 && ysize+c > 0)
1462 /* This code used to check for conflicts involving stack references and
1463 globals but the base address alias code now handles these cases. */
1465 if (GET_CODE (x) == PLUS)
1467 /* The fact that X is canonicalized means that this
1468 PLUS rtx is canonicalized. */
1469 rtx x0 = XEXP (x, 0);
1470 rtx x1 = XEXP (x, 1);
1472 if (GET_CODE (y) == PLUS)
1474 /* The fact that Y is canonicalized means that this
1475 PLUS rtx is canonicalized. */
1476 rtx y0 = XEXP (y, 0);
1477 rtx y1 = XEXP (y, 1);
1479 if (rtx_equal_for_memref_p (x1, y1))
1480 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1481 if (rtx_equal_for_memref_p (x0, y0))
1482 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1483 if (GET_CODE (x1) == CONST_INT)
1485 if (GET_CODE (y1) == CONST_INT)
1486 return memrefs_conflict_p (xsize, x0, ysize, y0,
1487 c - INTVAL (x1) + INTVAL (y1));
1489 return memrefs_conflict_p (xsize, x0, ysize, y,
1492 else if (GET_CODE (y1) == CONST_INT)
1493 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1497 else if (GET_CODE (x1) == CONST_INT)
1498 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1500 else if (GET_CODE (y) == PLUS)
1502 /* The fact that Y is canonicalized means that this
1503 PLUS rtx is canonicalized. */
1504 rtx y0 = XEXP (y, 0);
1505 rtx y1 = XEXP (y, 1);
1507 if (GET_CODE (y1) == CONST_INT)
1508 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1513 if (GET_CODE (x) == GET_CODE (y))
1514 switch (GET_CODE (x))
1518 /* Handle cases where we expect the second operands to be the
1519 same, and check only whether the first operand would conflict
1522 rtx x1 = canon_rtx (XEXP (x, 1));
1523 rtx y1 = canon_rtx (XEXP (y, 1));
1524 if (! rtx_equal_for_memref_p (x1, y1))
1526 x0 = canon_rtx (XEXP (x, 0));
1527 y0 = canon_rtx (XEXP (y, 0));
1528 if (rtx_equal_for_memref_p (x0, y0))
1529 return (xsize == 0 || ysize == 0
1530 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1532 /* Can't properly adjust our sizes. */
1533 if (GET_CODE (x1) != CONST_INT)
1535 xsize /= INTVAL (x1);
1536 ysize /= INTVAL (x1);
1538 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1542 /* Are these registers known not to be equal? */
1543 if (alias_invariant)
1545 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1546 rtx i_x, i_y; /* invariant relationships of X and Y */
1548 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1549 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1551 if (i_x == 0 && i_y == 0)
1554 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1555 ysize, i_y ? i_y : y, c))
1564 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1565 as an access with indeterminate size. Assume that references
1566 besides AND are aligned, so if the size of the other reference is
1567 at least as large as the alignment, assume no other overlap. */
1568 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1570 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1572 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1574 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1576 /* ??? If we are indexing far enough into the array/structure, we
1577 may yet be able to determine that we can not overlap. But we
1578 also need to that we are far enough from the end not to overlap
1579 a following reference, so we do nothing with that for now. */
1580 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1582 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1585 if (GET_CODE (x) == ADDRESSOF)
1587 if (y == frame_pointer_rtx
1588 || GET_CODE (y) == ADDRESSOF)
1589 return xsize <= 0 || ysize <= 0;
1591 if (GET_CODE (y) == ADDRESSOF)
1593 if (x == frame_pointer_rtx)
1594 return xsize <= 0 || ysize <= 0;
1599 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1601 c += (INTVAL (y) - INTVAL (x));
1602 return (xsize <= 0 || ysize <= 0
1603 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1606 if (GET_CODE (x) == CONST)
1608 if (GET_CODE (y) == CONST)
1609 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1610 ysize, canon_rtx (XEXP (y, 0)), c);
1612 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1615 if (GET_CODE (y) == CONST)
1616 return memrefs_conflict_p (xsize, x, ysize,
1617 canon_rtx (XEXP (y, 0)), c);
1620 return (xsize <= 0 || ysize <= 0
1621 || (rtx_equal_for_memref_p (x, y)
1622 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1629 /* Functions to compute memory dependencies.
1631 Since we process the insns in execution order, we can build tables
1632 to keep track of what registers are fixed (and not aliased), what registers
1633 are varying in known ways, and what registers are varying in unknown
1636 If both memory references are volatile, then there must always be a
1637 dependence between the two references, since their order can not be
1638 changed. A volatile and non-volatile reference can be interchanged
1641 A MEM_IN_STRUCT reference at a non-AND varying address can never
1642 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1643 also must allow AND addresses, because they may generate accesses
1644 outside the object being referenced. This is used to generate
1645 aligned addresses from unaligned addresses, for instance, the alpha
1646 storeqi_unaligned pattern. */
1648 /* Read dependence: X is read after read in MEM takes place. There can
1649 only be a dependence here if both reads are volatile. */
1652 read_dependence (mem, x)
1656 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1659 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1660 MEM2 is a reference to a structure at a varying address, or returns
1661 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1662 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1663 to decide whether or not an address may vary; it should return
1664 nonzero whenever variation is possible.
1665 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1668 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1670 rtx mem1_addr, mem2_addr;
1671 int (*varies_p) PARAMS ((rtx, int));
1673 if (! flag_strict_aliasing)
1676 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1677 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1678 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1682 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1683 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1684 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1691 /* Returns nonzero if something about the mode or address format MEM1
1692 indicates that it might well alias *anything*. */
1695 aliases_everything_p (mem)
1698 if (GET_CODE (XEXP (mem, 0)) == AND)
1699 /* If the address is an AND, its very hard to know at what it is
1700 actually pointing. */
1706 /* True dependence: X is read after store in MEM takes place. */
1709 true_dependence (mem, mem_mode, x, varies)
1711 enum machine_mode mem_mode;
1713 int (*varies) PARAMS ((rtx, int));
1715 register rtx x_addr, mem_addr;
1718 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1721 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1724 /* Unchanging memory can't conflict with non-unchanging memory.
1725 A non-unchanging read can conflict with a non-unchanging write.
1726 An unchanging read can conflict with an unchanging write since
1727 there may be a single store to this address to initialize it.
1728 Note that an unchanging store can conflict with a non-unchanging read
1729 since we have to make conservative assumptions when we have a
1730 record with readonly fields and we are copying the whole thing.
1731 Just fall through to the code below to resolve potential conflicts.
1732 This won't handle all cases optimally, but the possible performance
1733 loss should be negligible. */
1734 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1737 if (mem_mode == VOIDmode)
1738 mem_mode = GET_MODE (mem);
1740 x_addr = get_addr (XEXP (x, 0));
1741 mem_addr = get_addr (XEXP (mem, 0));
1743 base = find_base_term (x_addr);
1744 if (base && (GET_CODE (base) == LABEL_REF
1745 || (GET_CODE (base) == SYMBOL_REF
1746 && CONSTANT_POOL_ADDRESS_P (base))))
1749 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1752 x_addr = canon_rtx (x_addr);
1753 mem_addr = canon_rtx (mem_addr);
1755 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1756 SIZE_FOR_MODE (x), x_addr, 0))
1759 if (aliases_everything_p (x))
1762 /* We cannot use aliases_everyting_p to test MEM, since we must look
1763 at MEM_MODE, rather than GET_MODE (MEM). */
1764 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1767 /* In true_dependence we also allow BLKmode to alias anything. Why
1768 don't we do this in anti_dependence and output_dependence? */
1769 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1772 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1776 /* Canonical true dependence: X is read after store in MEM takes place.
1777 Variant of true_dependece which assumes MEM has already been
1778 canonicalized (hence we no longer do that here).
1779 The mem_addr argument has been added, since true_dependence computed
1780 this value prior to canonicalizing. */
1783 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
1784 rtx mem, mem_addr, x;
1785 enum machine_mode mem_mode;
1786 int (*varies) PARAMS ((rtx, int));
1788 register rtx x_addr;
1790 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1793 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1796 /* If X is an unchanging read, then it can't possibly conflict with any
1797 non-unchanging store. It may conflict with an unchanging write though,
1798 because there may be a single store to this address to initialize it.
1799 Just fall through to the code below to resolve the case where we have
1800 both an unchanging read and an unchanging write. This won't handle all
1801 cases optimally, but the possible performance loss should be
1803 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1806 x_addr = get_addr (XEXP (x, 0));
1808 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1811 x_addr = canon_rtx (x_addr);
1812 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1813 SIZE_FOR_MODE (x), x_addr, 0))
1816 if (aliases_everything_p (x))
1819 /* We cannot use aliases_everyting_p to test MEM, since we must look
1820 at MEM_MODE, rather than GET_MODE (MEM). */
1821 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1824 /* In true_dependence we also allow BLKmode to alias anything. Why
1825 don't we do this in anti_dependence and output_dependence? */
1826 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1829 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1833 /* Returns non-zero if a write to X might alias a previous read from
1834 (or, if WRITEP is non-zero, a write to) MEM. */
1837 write_dependence_p (mem, x, writep)
1842 rtx x_addr, mem_addr;
1846 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1849 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1852 /* Unchanging memory can't conflict with non-unchanging memory. */
1853 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1856 /* If MEM is an unchanging read, then it can't possibly conflict with
1857 the store to X, because there is at most one store to MEM, and it must
1858 have occurred somewhere before MEM. */
1859 if (! writep && RTX_UNCHANGING_P (mem))
1862 x_addr = get_addr (XEXP (x, 0));
1863 mem_addr = get_addr (XEXP (mem, 0));
1867 base = find_base_term (mem_addr);
1868 if (base && (GET_CODE (base) == LABEL_REF
1869 || (GET_CODE (base) == SYMBOL_REF
1870 && CONSTANT_POOL_ADDRESS_P (base))))
1874 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1878 x_addr = canon_rtx (x_addr);
1879 mem_addr = canon_rtx (mem_addr);
1881 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1882 SIZE_FOR_MODE (x), x_addr, 0))
1886 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1889 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1890 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1893 /* Anti dependence: X is written after read in MEM takes place. */
1896 anti_dependence (mem, x)
1900 return write_dependence_p (mem, x, /*writep=*/0);
1903 /* Output dependence: X is written after store in MEM takes place. */
1906 output_dependence (mem, x)
1910 return write_dependence_p (mem, x, /*writep=*/1);
1913 /* Returns non-zero if X mentions something which is not
1914 local to the function and is not constant. */
1917 nonlocal_mentioned_p (x)
1921 register RTX_CODE code;
1924 code = GET_CODE (x);
1926 if (GET_RTX_CLASS (code) == 'i')
1928 /* Constant functions can be constant if they don't use
1929 scratch memory used to mark function w/o side effects. */
1930 if (code == CALL_INSN && CONST_CALL_P (x))
1932 x = CALL_INSN_FUNCTION_USAGE (x);
1938 code = GET_CODE (x);
1944 if (GET_CODE (SUBREG_REG (x)) == REG)
1946 /* Global registers are not local. */
1947 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1948 && global_regs[subreg_regno (x)])
1956 /* Global registers are not local. */
1957 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1971 /* Constants in the function's constants pool are constant. */
1972 if (CONSTANT_POOL_ADDRESS_P (x))
1977 /* Non-constant calls and recursion are not local. */
1981 /* Be overly conservative and consider any volatile memory
1982 reference as not local. */
1983 if (MEM_VOLATILE_P (x))
1985 base = find_base_term (XEXP (x, 0));
1988 /* A Pmode ADDRESS could be a reference via the structure value
1989 address or static chain. Such memory references are nonlocal.
1991 Thus, we have to examine the contents of the ADDRESS to find
1992 out if this is a local reference or not. */
1993 if (GET_CODE (base) == ADDRESS
1994 && GET_MODE (base) == Pmode
1995 && (XEXP (base, 0) == stack_pointer_rtx
1996 || XEXP (base, 0) == arg_pointer_rtx
1997 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1998 || XEXP (base, 0) == hard_frame_pointer_rtx
2000 || XEXP (base, 0) == frame_pointer_rtx))
2002 /* Constants in the function's constant pool are constant. */
2003 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2008 case UNSPEC_VOLATILE:
2013 if (MEM_VOLATILE_P (x))
2022 /* Recursively scan the operands of this expression. */
2025 register const char *fmt = GET_RTX_FORMAT (code);
2028 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2030 if (fmt[i] == 'e' && XEXP (x, i))
2032 if (nonlocal_mentioned_p (XEXP (x, i)))
2035 else if (fmt[i] == 'E')
2038 for (j = 0; j < XVECLEN (x, i); j++)
2039 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2048 /* Return non-zero if a loop (natural or otherwise) is present.
2049 Inspired by Depth_First_Search_PP described in:
2051 Advanced Compiler Design and Implementation
2053 Morgan Kaufmann, 1997
2055 and heavily borrowed from flow_depth_first_order_compute. */
2068 /* Allocate the preorder and postorder number arrays. */
2069 pre = (int *) xcalloc (n_basic_blocks, sizeof (int));
2070 post = (int *) xcalloc (n_basic_blocks, sizeof (int));
2072 /* Allocate stack for back-tracking up CFG. */
2073 stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
2076 /* Allocate bitmap to track nodes that have been visited. */
2077 visited = sbitmap_alloc (n_basic_blocks);
2079 /* None of the nodes in the CFG have been visited yet. */
2080 sbitmap_zero (visited);
2082 /* Push the first edge on to the stack. */
2083 stack[sp++] = ENTRY_BLOCK_PTR->succ;
2091 /* Look at the edge on the top of the stack. */
2096 /* Check if the edge destination has been visited yet. */
2097 if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
2099 /* Mark that we have visited the destination. */
2100 SET_BIT (visited, dest->index);
2102 pre[dest->index] = prenum++;
2106 /* Since the DEST node has been visited for the first
2107 time, check its successors. */
2108 stack[sp++] = dest->succ;
2111 post[dest->index] = postnum++;
2115 if (dest != EXIT_BLOCK_PTR
2116 && pre[src->index] >= pre[dest->index]
2117 && post[dest->index] == 0)
2120 if (! e->succ_next && src != ENTRY_BLOCK_PTR)
2121 post[src->index] = postnum++;
2124 stack[sp - 1] = e->succ_next;
2133 sbitmap_free (visited);
2138 /* Mark the function if it is constant. */
2141 mark_constant_function ()
2144 int nonlocal_mentioned;
2146 if (TREE_PUBLIC (current_function_decl)
2147 || TREE_READONLY (current_function_decl)
2148 || DECL_IS_PURE (current_function_decl)
2149 || TREE_THIS_VOLATILE (current_function_decl)
2150 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2153 /* A loop might not return which counts as a side effect. */
2157 nonlocal_mentioned = 0;
2159 init_alias_analysis ();
2161 /* Determine if this is a constant function. */
2163 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2164 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2166 nonlocal_mentioned = 1;
2170 end_alias_analysis ();
2172 /* Mark the function. */
2174 if (! nonlocal_mentioned)
2175 TREE_READONLY (current_function_decl) = 1;
2179 static HARD_REG_SET argument_registers;
2186 #ifndef OUTGOING_REGNO
2187 #define OUTGOING_REGNO(N) N
2189 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2190 /* Check whether this register can hold an incoming pointer
2191 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2192 numbers, so translate if necessary due to register windows. */
2193 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2194 && HARD_REGNO_MODE_OK (i, Pmode))
2195 SET_HARD_REG_BIT (argument_registers, i);
2197 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2200 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2204 init_alias_analysis ()
2206 int maxreg = max_reg_num ();
2209 register unsigned int ui;
2212 reg_known_value_size = maxreg;
2215 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2216 - FIRST_PSEUDO_REGISTER;
2218 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2219 - FIRST_PSEUDO_REGISTER;
2221 /* Overallocate reg_base_value to allow some growth during loop
2222 optimization. Loop unrolling can create a large number of
2224 reg_base_value_size = maxreg * 2;
2225 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2226 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2228 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2229 reg_seen = (char *) xmalloc (reg_base_value_size);
2230 if (! reload_completed && flag_unroll_loops)
2232 /* ??? Why are we realloc'ing if we're just going to zero it? */
2233 alias_invariant = (rtx *)xrealloc (alias_invariant,
2234 reg_base_value_size * sizeof (rtx));
2235 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2238 /* The basic idea is that each pass through this loop will use the
2239 "constant" information from the previous pass to propagate alias
2240 information through another level of assignments.
2242 This could get expensive if the assignment chains are long. Maybe
2243 we should throttle the number of iterations, possibly based on
2244 the optimization level or flag_expensive_optimizations.
2246 We could propagate more information in the first pass by making use
2247 of REG_N_SETS to determine immediately that the alias information
2248 for a pseudo is "constant".
2250 A program with an uninitialized variable can cause an infinite loop
2251 here. Instead of doing a full dataflow analysis to detect such problems
2252 we just cap the number of iterations for the loop.
2254 The state of the arrays for the set chain in question does not matter
2255 since the program has undefined behavior. */
2260 /* Assume nothing will change this iteration of the loop. */
2263 /* We want to assign the same IDs each iteration of this loop, so
2264 start counting from zero each iteration of the loop. */
2267 /* We're at the start of the funtion each iteration through the
2268 loop, so we're copying arguments. */
2269 copying_arguments = 1;
2271 /* Wipe the potential alias information clean for this pass. */
2272 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2274 /* Wipe the reg_seen array clean. */
2275 memset ((char *) reg_seen, 0, reg_base_value_size);
2277 /* Mark all hard registers which may contain an address.
2278 The stack, frame and argument pointers may contain an address.
2279 An argument register which can hold a Pmode value may contain
2280 an address even if it is not in BASE_REGS.
2282 The address expression is VOIDmode for an argument and
2283 Pmode for other registers. */
2285 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2286 if (TEST_HARD_REG_BIT (argument_registers, i))
2287 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2288 gen_rtx_REG (Pmode, i));
2290 new_reg_base_value[STACK_POINTER_REGNUM]
2291 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2292 new_reg_base_value[ARG_POINTER_REGNUM]
2293 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2294 new_reg_base_value[FRAME_POINTER_REGNUM]
2295 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2296 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2297 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2298 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2301 /* Walk the insns adding values to the new_reg_base_value array. */
2302 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2308 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2309 /* The prologue/epilouge insns are not threaded onto the
2310 insn chain until after reload has completed. Thus,
2311 there is no sense wasting time checking if INSN is in
2312 the prologue/epilogue until after reload has completed. */
2313 if (reload_completed
2314 && prologue_epilogue_contains (insn))
2318 /* If this insn has a noalias note, process it, Otherwise,
2319 scan for sets. A simple set will have no side effects
2320 which could change the base value of any other register. */
2322 if (GET_CODE (PATTERN (insn)) == SET
2323 && REG_NOTES (insn) != 0
2324 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2325 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2327 note_stores (PATTERN (insn), record_set, NULL);
2329 set = single_set (insn);
2332 && GET_CODE (SET_DEST (set)) == REG
2333 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2335 unsigned int regno = REGNO (SET_DEST (set));
2336 rtx src = SET_SRC (set);
2338 if (REG_NOTES (insn) != 0
2339 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2340 && REG_N_SETS (regno) == 1)
2341 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2342 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2343 && ! rtx_varies_p (XEXP (note, 0), 1)
2344 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2346 reg_known_value[regno] = XEXP (note, 0);
2347 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2349 else if (REG_N_SETS (regno) == 1
2350 && GET_CODE (src) == PLUS
2351 && GET_CODE (XEXP (src, 0)) == REG
2352 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2353 && (reg_known_value[REGNO (XEXP (src, 0))])
2354 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2356 rtx op0 = XEXP (src, 0);
2357 op0 = reg_known_value[REGNO (op0)];
2358 reg_known_value[regno]
2359 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2360 reg_known_equiv_p[regno] = 0;
2362 else if (REG_N_SETS (regno) == 1
2363 && ! rtx_varies_p (src, 1))
2365 reg_known_value[regno] = src;
2366 reg_known_equiv_p[regno] = 0;
2370 else if (GET_CODE (insn) == NOTE
2371 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2372 copying_arguments = 0;
2375 /* Now propagate values from new_reg_base_value to reg_base_value. */
2376 for (ui = 0; ui < reg_base_value_size; ui++)
2378 if (new_reg_base_value[ui]
2379 && new_reg_base_value[ui] != reg_base_value[ui]
2380 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2382 reg_base_value[ui] = new_reg_base_value[ui];
2387 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2389 /* Fill in the remaining entries. */
2390 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2391 if (reg_known_value[i] == 0)
2392 reg_known_value[i] = regno_reg_rtx[i];
2394 /* Simplify the reg_base_value array so that no register refers to
2395 another register, except to special registers indirectly through
2396 ADDRESS expressions.
2398 In theory this loop can take as long as O(registers^2), but unless
2399 there are very long dependency chains it will run in close to linear
2402 This loop may not be needed any longer now that the main loop does
2403 a better job at propagating alias information. */
2409 for (ui = 0; ui < reg_base_value_size; ui++)
2411 rtx base = reg_base_value[ui];
2412 if (base && GET_CODE (base) == REG)
2414 unsigned int base_regno = REGNO (base);
2415 if (base_regno == ui) /* register set from itself */
2416 reg_base_value[ui] = 0;
2418 reg_base_value[ui] = reg_base_value[base_regno];
2423 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2426 free (new_reg_base_value);
2427 new_reg_base_value = 0;
2433 end_alias_analysis ()
2435 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2436 reg_known_value = 0;
2437 reg_known_value_size = 0;
2438 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2439 reg_known_equiv_p = 0;
2442 ggc_del_root (reg_base_value);
2443 free (reg_base_value);
2446 reg_base_value_size = 0;
2447 if (alias_invariant)
2449 free (alias_invariant);
2450 alias_invariant = 0;