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 /* Set up all info needed to perform alias analysis on memory references. */
112 /* Returns the size in bytes of the mode of X. */
113 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
115 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
116 different alias sets. We ignore alias sets in functions making use
117 of variable arguments because the va_arg macros on some systems are
119 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
120 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
122 /* Cap the number of passes we make over the insns propagating alias
123 information through set chains. 10 is a completely arbitrary choice. */
124 #define MAX_ALIAS_LOOP_PASSES 10
126 /* reg_base_value[N] gives an address to which register N is related.
127 If all sets after the first add or subtract to the current value
128 or otherwise modify it so it does not point to a different top level
129 object, reg_base_value[N] is equal to the address part of the source
132 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
133 expressions represent certain special values: function arguments and
134 the stack, frame, and argument pointers.
136 The contents of an ADDRESS is not normally used, the mode of the
137 ADDRESS determines whether the ADDRESS is a function argument or some
138 other special value. Pointer equality, not rtx_equal_p, determines whether
139 two ADDRESS expressions refer to the same base address.
141 The only use of the contents of an ADDRESS is for determining if the
142 current function performs nonlocal memory memory references for the
143 purposes of marking the function as a constant function. */
145 static rtx *reg_base_value;
146 static rtx *new_reg_base_value;
147 static unsigned int reg_base_value_size; /* size of reg_base_value array */
149 #define REG_BASE_VALUE(X) \
150 (REGNO (X) < reg_base_value_size \
151 ? reg_base_value[REGNO (X)] : 0)
153 /* Vector of known invariant relationships between registers. Set in
154 loop unrolling. Indexed by register number, if nonzero the value
155 is an expression describing this register in terms of another.
157 The length of this array is REG_BASE_VALUE_SIZE.
159 Because this array contains only pseudo registers it has no effect
161 static rtx *alias_invariant;
163 /* Vector indexed by N giving the initial (unchanging) value known for
164 pseudo-register N. This array is initialized in
165 init_alias_analysis, and does not change until end_alias_analysis
167 rtx *reg_known_value;
169 /* Indicates number of valid entries in reg_known_value. */
170 static unsigned int reg_known_value_size;
172 /* Vector recording for each reg_known_value whether it is due to a
173 REG_EQUIV note. Future passes (viz., reload) may replace the
174 pseudo with the equivalent expression and so we account for the
175 dependences that would be introduced if that happens.
177 The REG_EQUIV notes created in assign_parms may mention the arg
178 pointer, and there are explicit insns in the RTL that modify the
179 arg pointer. Thus we must ensure that such insns don't get
180 scheduled across each other because that would invalidate the
181 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
182 wrong, but solving the problem in the scheduler will likely give
183 better code, so we do it here. */
184 char *reg_known_equiv_p;
186 /* True when scanning insns from the start of the rtl to the
187 NOTE_INSN_FUNCTION_BEG note. */
188 static int copying_arguments;
190 /* The splay-tree used to store the various alias set entries. */
191 static splay_tree alias_sets;
193 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
194 such an entry, or NULL otherwise. */
196 static alias_set_entry
197 get_alias_set_entry (alias_set)
198 HOST_WIDE_INT alias_set;
201 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
203 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
206 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
207 the two MEMs cannot alias each other. */
210 mems_in_disjoint_alias_sets_p (mem1, mem2)
214 #ifdef ENABLE_CHECKING
215 /* Perform a basic sanity check. Namely, that there are no alias sets
216 if we're not using strict aliasing. This helps to catch bugs
217 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
218 where a MEM is allocated in some way other than by the use of
219 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
220 use alias sets to indicate that spilled registers cannot alias each
221 other, we might need to remove this check. */
222 if (! flag_strict_aliasing
223 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
227 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
230 /* Insert the NODE into the splay tree given by DATA. Used by
231 record_alias_subset via splay_tree_foreach. */
234 insert_subset_children (node, data)
235 splay_tree_node node;
238 splay_tree_insert ((splay_tree) data, node->key, node->value);
243 /* Return 1 if the two specified alias sets may conflict. */
246 alias_sets_conflict_p (set1, set2)
247 HOST_WIDE_INT set1, set2;
251 /* If have no alias set information for one of the operands, we have
252 to assume it can alias anything. */
253 if (set1 == 0 || set2 == 0
254 /* If the two alias sets are the same, they may alias. */
258 /* See if the first alias set is a subset of the second. */
259 ase = get_alias_set_entry (set1);
261 && (ase->has_zero_child
262 || splay_tree_lookup (ase->children,
263 (splay_tree_key) set2)))
266 /* Now do the same, but with the alias sets reversed. */
267 ase = get_alias_set_entry (set2);
269 && (ase->has_zero_child
270 || splay_tree_lookup (ase->children,
271 (splay_tree_key) set1)))
274 /* The two alias sets are distinct and neither one is the
275 child of the other. Therefore, they cannot alias. */
279 /* Set the alias set of MEM to SET. */
282 set_mem_alias_set (mem, set)
286 /* We would like to do this test but can't yet since when converting a
287 REG to a MEM, the alias set field is undefined. */
289 /* If the new and old alias sets don't conflict, something is wrong. */
290 if (!alias_sets_conflict_p (set, MEM_ALIAS_SET (mem)))
294 MEM_ALIAS_SET (mem) = set;
297 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
298 has any readonly fields. If any of the fields have types that
299 contain readonly fields, return true as well. */
302 readonly_fields_p (type)
307 if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
308 && TREE_CODE (type) != QUAL_UNION_TYPE)
311 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
312 if (TREE_CODE (field) == FIELD_DECL
313 && (TREE_READONLY (field)
314 || readonly_fields_p (TREE_TYPE (field))))
320 /* Return 1 if any MEM object of type T1 will always conflict (using the
321 dependency routines in this file) with any MEM object of type T2.
322 This is used when allocating temporary storage. If T1 and/or T2 are
323 NULL_TREE, it means we know nothing about the storage. */
326 objects_must_conflict_p (t1, t2)
329 /* If neither has a type specified, we don't know if they'll conflict
330 because we may be using them to store objects of various types, for
331 example the argument and local variables areas of inlined functions. */
332 if (t1 == 0 && t2 == 0)
335 /* If one or the other has readonly fields or is readonly,
336 then they may not conflict. */
337 if ((t1 != 0 && readonly_fields_p (t1))
338 || (t2 != 0 && readonly_fields_p (t2))
339 || (t1 != 0 && TYPE_READONLY (t1))
340 || (t2 != 0 && TYPE_READONLY (t2)))
343 /* If they are the same type, they must conflict. */
345 /* Likewise if both are volatile. */
346 || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
349 /* If one is aggregate and the other is scalar then they may not
351 if ((t1 != 0 && AGGREGATE_TYPE_P (t1))
352 != (t2 != 0 && AGGREGATE_TYPE_P (t2)))
355 /* Otherwise they conflict only if the alias sets conflict. */
356 return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0,
357 t2 ? get_alias_set (t2) : 0);
360 /* T is an expression with pointer type. Find the DECL on which this
361 expression is based. (For example, in `a[i]' this would be `a'.)
362 If there is no such DECL, or a unique decl cannot be determined,
363 NULL_TREE is retured. */
371 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
374 /* If this is a declaration, return it. */
375 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
378 /* Handle general expressions. It would be nice to deal with
379 COMPONENT_REFs here. If we could tell that `a' and `b' were the
380 same, then `a->f' and `b->f' are also the same. */
381 switch (TREE_CODE_CLASS (TREE_CODE (t)))
384 return find_base_decl (TREE_OPERAND (t, 0));
387 /* Return 0 if found in neither or both are the same. */
388 d0 = find_base_decl (TREE_OPERAND (t, 0));
389 d1 = find_base_decl (TREE_OPERAND (t, 1));
400 d0 = find_base_decl (TREE_OPERAND (t, 0));
401 d1 = find_base_decl (TREE_OPERAND (t, 1));
402 d0 = find_base_decl (TREE_OPERAND (t, 0));
403 d2 = find_base_decl (TREE_OPERAND (t, 2));
405 /* Set any nonzero values from the last, then from the first. */
406 if (d1 == 0) d1 = d2;
407 if (d0 == 0) d0 = d1;
408 if (d1 == 0) d1 = d0;
409 if (d2 == 0) d2 = d1;
411 /* At this point all are nonzero or all are zero. If all three are the
412 same, return it. Otherwise, return zero. */
413 return (d0 == d1 && d1 == d2) ? d0 : 0;
420 /* Return 1 if T is an expression that get_inner_reference handles. */
423 handled_component_p (t)
426 switch (TREE_CODE (t))
431 case ARRAY_RANGE_REF:
432 case NON_LVALUE_EXPR:
437 return (TYPE_MODE (TREE_TYPE (t))
438 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))));
445 /* Return 1 if all the nested component references handled by
446 get_inner_reference in T are such that we can address the object in T. */
452 /* If we're at the end, it is vacuously addressable. */
453 if (! handled_component_p (t))
456 /* Bitfields are never addressable. */
457 else if (TREE_CODE (t) == BIT_FIELD_REF)
460 else if (TREE_CODE (t) == COMPONENT_REF
461 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
462 && can_address_p (TREE_OPERAND (t, 0)))
465 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
466 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
467 && can_address_p (TREE_OPERAND (t, 0)))
473 /* Return the alias set for T, which may be either a type or an
474 expression. Call language-specific routine for help, if needed. */
483 /* If we're not doing any alias analysis, just assume everything
484 aliases everything else. Also return 0 if this or its type is
486 if (! flag_strict_aliasing || t == error_mark_node
488 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
491 /* We can be passed either an expression or a type. This and the
492 language-specific routine may make mutually-recursive calls to
493 each other to figure out what to do. At each juncture, we see if
494 this is a tree that the language may need to handle specially.
495 First handle things that aren't types and start by removing nops
496 since we care only about the actual object. */
499 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
500 || TREE_CODE (t) == NON_LVALUE_EXPR)
501 t = TREE_OPERAND (t, 0);
503 /* Now give the language a chance to do something but record what we
504 gave it this time. */
506 if ((set = lang_get_alias_set (t)) != -1)
509 /* Now loop the same way as get_inner_reference and get the alias
510 set to use. Pick up the outermost object that we could have
512 while (handled_component_p (t) && ! can_address_p (t))
513 t = TREE_OPERAND (t, 0);
515 if (TREE_CODE (t) == INDIRECT_REF)
517 /* Check for accesses through restrict-qualified pointers. */
518 tree decl = find_base_decl (TREE_OPERAND (t, 0));
520 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
521 /* We use the alias set indicated in the declaration. */
522 return DECL_POINTER_ALIAS_SET (decl);
524 /* If we have an INDIRECT_REF via a void pointer, we don't
525 know anything about what that might alias. */
526 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
530 /* If we've already determined the alias set for this decl, just
531 return it. This is necessary for C++ anonymous unions, whose
532 component variables don't look like union members (boo!). */
533 if (TREE_CODE (t) == VAR_DECL
534 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
535 return MEM_ALIAS_SET (DECL_RTL (t));
537 /* Give the language another chance to do something special. */
539 && (set = lang_get_alias_set (t)) != -1)
542 /* Now all we care about is the type. */
546 /* Variant qualifiers don't affect the alias set, so get the main
547 variant. If this is a type with a known alias set, return it. */
548 t = TYPE_MAIN_VARIANT (t);
549 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
550 return TYPE_ALIAS_SET (t);
552 /* See if the language has special handling for this type. */
553 if ((set = lang_get_alias_set (t)) != -1)
555 /* If the alias set is now known, we are done. */
556 if (TYPE_ALIAS_SET_KNOWN_P (t))
557 return TYPE_ALIAS_SET (t);
560 /* There are no objects of FUNCTION_TYPE, so there's no point in
561 using up an alias set for them. (There are, of course, pointers
562 and references to functions, but that's different.) */
563 else if (TREE_CODE (t) == FUNCTION_TYPE)
566 /* Otherwise make a new alias set for this type. */
567 set = new_alias_set ();
569 TYPE_ALIAS_SET (t) = set;
571 /* If this is an aggregate type, we must record any component aliasing
573 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
574 record_component_aliases (t);
579 /* Return a brand-new alias set. */
584 static HOST_WIDE_INT last_alias_set;
586 if (flag_strict_aliasing)
587 return ++last_alias_set;
592 /* Indicate that things in SUBSET can alias things in SUPERSET, but
593 not vice versa. For example, in C, a store to an `int' can alias a
594 structure containing an `int', but not vice versa. Here, the
595 structure would be the SUPERSET and `int' the SUBSET. This
596 function should be called only once per SUPERSET/SUBSET pair.
598 It is illegal for SUPERSET to be zero; everything is implicitly a
599 subset of alias set zero. */
602 record_alias_subset (superset, subset)
603 HOST_WIDE_INT superset;
604 HOST_WIDE_INT subset;
606 alias_set_entry superset_entry;
607 alias_set_entry subset_entry;
612 superset_entry = get_alias_set_entry (superset);
613 if (superset_entry == 0)
615 /* Create an entry for the SUPERSET, so that we have a place to
616 attach the SUBSET. */
618 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
619 superset_entry->alias_set = superset;
620 superset_entry->children
621 = splay_tree_new (splay_tree_compare_ints, 0, 0);
622 superset_entry->has_zero_child = 0;
623 splay_tree_insert (alias_sets, (splay_tree_key) superset,
624 (splay_tree_value) superset_entry);
628 superset_entry->has_zero_child = 1;
631 subset_entry = get_alias_set_entry (subset);
632 /* If there is an entry for the subset, enter all of its children
633 (if they are not already present) as children of the SUPERSET. */
636 if (subset_entry->has_zero_child)
637 superset_entry->has_zero_child = 1;
639 splay_tree_foreach (subset_entry->children, insert_subset_children,
640 superset_entry->children);
643 /* Enter the SUBSET itself as a child of the SUPERSET. */
644 splay_tree_insert (superset_entry->children,
645 (splay_tree_key) subset, 0);
649 /* Record that component types of TYPE, if any, are part of that type for
650 aliasing purposes. For record types, we only record component types
651 for fields that are marked addressable. For array types, we always
652 record the component types, so the front end should not call this
653 function if the individual component aren't addressable. */
656 record_component_aliases (type)
659 HOST_WIDE_INT superset = get_alias_set (type);
665 switch (TREE_CODE (type))
668 if (! TYPE_NONALIASED_COMPONENT (type))
669 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
674 case QUAL_UNION_TYPE:
675 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
676 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
677 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
681 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
689 /* Allocate an alias set for use in storing and reading from the varargs
693 get_varargs_alias_set ()
695 static HOST_WIDE_INT set = -1;
698 set = new_alias_set ();
703 /* Likewise, but used for the fixed portions of the frame, e.g., register
707 get_frame_alias_set ()
709 static HOST_WIDE_INT set = -1;
712 set = new_alias_set ();
717 /* Inside SRC, the source of a SET, find a base address. */
720 find_base_value (src)
724 switch (GET_CODE (src))
732 /* At the start of a function, argument registers have known base
733 values which may be lost later. Returning an ADDRESS
734 expression here allows optimization based on argument values
735 even when the argument registers are used for other purposes. */
736 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
737 return new_reg_base_value[regno];
739 /* If a pseudo has a known base value, return it. Do not do this
740 for hard regs since it can result in a circular dependency
741 chain for registers which have values at function entry.
743 The test above is not sufficient because the scheduler may move
744 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
745 if (regno >= FIRST_PSEUDO_REGISTER
746 && regno < reg_base_value_size
747 && reg_base_value[regno])
748 return reg_base_value[regno];
753 /* Check for an argument passed in memory. Only record in the
754 copying-arguments block; it is too hard to track changes
756 if (copying_arguments
757 && (XEXP (src, 0) == arg_pointer_rtx
758 || (GET_CODE (XEXP (src, 0)) == PLUS
759 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
760 return gen_rtx_ADDRESS (VOIDmode, src);
765 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
768 /* ... fall through ... */
773 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
775 /* If either operand is a REG, then see if we already have
776 a known value for it. */
777 if (GET_CODE (src_0) == REG)
779 temp = find_base_value (src_0);
784 if (GET_CODE (src_1) == REG)
786 temp = find_base_value (src_1);
791 /* Guess which operand is the base address:
792 If either operand is a symbol, then it is the base. If
793 either operand is a CONST_INT, then the other is the base. */
794 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
795 return find_base_value (src_0);
796 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
797 return find_base_value (src_1);
799 /* This might not be necessary anymore:
800 If either operand is a REG that is a known pointer, then it
802 else if (GET_CODE (src_0) == REG && REG_POINTER (src_0))
803 return find_base_value (src_0);
804 else if (GET_CODE (src_1) == REG && REG_POINTER (src_1))
805 return find_base_value (src_1);
811 /* The standard form is (lo_sum reg sym) so look only at the
813 return find_base_value (XEXP (src, 1));
816 /* If the second operand is constant set the base
817 address to the first operand. */
818 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
819 return find_base_value (XEXP (src, 0));
823 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
827 case SIGN_EXTEND: /* used for NT/Alpha pointers */
829 return find_base_value (XEXP (src, 0));
838 /* Called from init_alias_analysis indirectly through note_stores. */
840 /* While scanning insns to find base values, reg_seen[N] is nonzero if
841 register N has been set in this function. */
842 static char *reg_seen;
844 /* Addresses which are known not to alias anything else are identified
845 by a unique integer. */
846 static int unique_id;
849 record_set (dest, set, data)
851 void *data ATTRIBUTE_UNUSED;
853 register unsigned regno;
856 if (GET_CODE (dest) != REG)
859 regno = REGNO (dest);
861 if (regno >= reg_base_value_size)
866 /* A CLOBBER wipes out any old value but does not prevent a previously
867 unset register from acquiring a base address (i.e. reg_seen is not
869 if (GET_CODE (set) == CLOBBER)
871 new_reg_base_value[regno] = 0;
880 new_reg_base_value[regno] = 0;
884 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
885 GEN_INT (unique_id++));
889 /* This is not the first set. If the new value is not related to the
890 old value, forget the base value. Note that the following code is
892 extern int x, y; int *p = &x; p += (&y-&x);
893 ANSI C does not allow computing the difference of addresses
894 of distinct top level objects. */
895 if (new_reg_base_value[regno])
896 switch (GET_CODE (src))
900 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
901 new_reg_base_value[regno] = 0;
904 /* If the value we add in the PLUS is also a valid base value,
905 this might be the actual base value, and the original value
908 rtx other = NULL_RTX;
910 if (XEXP (src, 0) == dest)
911 other = XEXP (src, 1);
912 else if (XEXP (src, 1) == dest)
913 other = XEXP (src, 0);
915 if (! other || find_base_value (other))
916 new_reg_base_value[regno] = 0;
920 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
921 new_reg_base_value[regno] = 0;
924 new_reg_base_value[regno] = 0;
927 /* If this is the first set of a register, record the value. */
928 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
929 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
930 new_reg_base_value[regno] = find_base_value (src);
935 /* Called from loop optimization when a new pseudo-register is
936 created. It indicates that REGNO is being set to VAL. f INVARIANT
937 is true then this value also describes an invariant relationship
938 which can be used to deduce that two registers with unknown values
942 record_base_value (regno, val, invariant)
947 if (regno >= reg_base_value_size)
950 if (invariant && alias_invariant)
951 alias_invariant[regno] = val;
953 if (GET_CODE (val) == REG)
955 if (REGNO (val) < reg_base_value_size)
956 reg_base_value[regno] = reg_base_value[REGNO (val)];
961 reg_base_value[regno] = find_base_value (val);
964 /* Returns a canonical version of X, from the point of view alias
965 analysis. (For example, if X is a MEM whose address is a register,
966 and the register has a known value (say a SYMBOL_REF), then a MEM
967 whose address is the SYMBOL_REF is returned.) */
973 /* Recursively look for equivalences. */
974 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
975 && REGNO (x) < reg_known_value_size)
976 return reg_known_value[REGNO (x)] == x
977 ? x : canon_rtx (reg_known_value[REGNO (x)]);
978 else if (GET_CODE (x) == PLUS)
980 rtx x0 = canon_rtx (XEXP (x, 0));
981 rtx x1 = canon_rtx (XEXP (x, 1));
983 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
985 if (GET_CODE (x0) == CONST_INT)
986 return plus_constant (x1, INTVAL (x0));
987 else if (GET_CODE (x1) == CONST_INT)
988 return plus_constant (x0, INTVAL (x1));
989 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
993 /* This gives us much better alias analysis when called from
994 the loop optimizer. Note we want to leave the original
995 MEM alone, but need to return the canonicalized MEM with
996 all the flags with their original values. */
997 else if (GET_CODE (x) == MEM)
998 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1003 /* Return 1 if X and Y are identical-looking rtx's.
1005 We use the data in reg_known_value above to see if two registers with
1006 different numbers are, in fact, equivalent. */
1009 rtx_equal_for_memref_p (x, y)
1014 register enum rtx_code code;
1015 register const char *fmt;
1017 if (x == 0 && y == 0)
1019 if (x == 0 || y == 0)
1028 code = GET_CODE (x);
1029 /* Rtx's of different codes cannot be equal. */
1030 if (code != GET_CODE (y))
1033 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1034 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1036 if (GET_MODE (x) != GET_MODE (y))
1039 /* Some RTL can be compared without a recursive examination. */
1043 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1046 return REGNO (x) == REGNO (y);
1049 return XEXP (x, 0) == XEXP (y, 0);
1052 return XSTR (x, 0) == XSTR (y, 0);
1056 /* There's no need to compare the contents of CONST_DOUBLEs or
1057 CONST_INTs because pointer equality is a good enough
1058 comparison for these nodes. */
1062 return (XINT (x, 1) == XINT (y, 1)
1063 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1069 /* For commutative operations, the RTX match if the operand match in any
1070 order. Also handle the simple binary and unary cases without a loop. */
1071 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1072 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1073 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1074 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1075 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1076 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1077 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1078 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1079 else if (GET_RTX_CLASS (code) == '1')
1080 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1082 /* Compare the elements. If any pair of corresponding elements
1083 fail to match, return 0 for the whole things.
1085 Limit cases to types which actually appear in addresses. */
1087 fmt = GET_RTX_FORMAT (code);
1088 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1093 if (XINT (x, i) != XINT (y, i))
1098 /* Two vectors must have the same length. */
1099 if (XVECLEN (x, i) != XVECLEN (y, i))
1102 /* And the corresponding elements must match. */
1103 for (j = 0; j < XVECLEN (x, i); j++)
1104 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1105 XVECEXP (y, i, j)) == 0)
1110 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1114 /* This can happen for asm operands. */
1116 if (strcmp (XSTR (x, i), XSTR (y, i)))
1120 /* This can happen for an asm which clobbers memory. */
1124 /* It is believed that rtx's at this level will never
1125 contain anything but integers and other rtx's,
1126 except for within LABEL_REFs and SYMBOL_REFs. */
1134 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1135 X and return it, or return 0 if none found. */
1138 find_symbolic_term (x)
1142 register enum rtx_code code;
1143 register const char *fmt;
1145 code = GET_CODE (x);
1146 if (code == SYMBOL_REF || code == LABEL_REF)
1148 if (GET_RTX_CLASS (code) == 'o')
1151 fmt = GET_RTX_FORMAT (code);
1152 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1158 t = find_symbolic_term (XEXP (x, i));
1162 else if (fmt[i] == 'E')
1173 struct elt_loc_list *l;
1175 #if defined (FIND_BASE_TERM)
1176 /* Try machine-dependent ways to find the base term. */
1177 x = FIND_BASE_TERM (x);
1180 switch (GET_CODE (x))
1183 return REG_BASE_VALUE (x);
1186 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1192 return find_base_term (XEXP (x, 0));
1195 val = CSELIB_VAL_PTR (x);
1196 for (l = val->locs; l; l = l->next)
1197 if ((x = find_base_term (l->loc)) != 0)
1203 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1210 rtx tmp1 = XEXP (x, 0);
1211 rtx tmp2 = XEXP (x, 1);
1213 /* This is a litle bit tricky since we have to determine which of
1214 the two operands represents the real base address. Otherwise this
1215 routine may return the index register instead of the base register.
1217 That may cause us to believe no aliasing was possible, when in
1218 fact aliasing is possible.
1220 We use a few simple tests to guess the base register. Additional
1221 tests can certainly be added. For example, if one of the operands
1222 is a shift or multiply, then it must be the index register and the
1223 other operand is the base register. */
1225 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1226 return find_base_term (tmp2);
1228 /* If either operand is known to be a pointer, then use it
1229 to determine the base term. */
1230 if (REG_P (tmp1) && REG_POINTER (tmp1))
1231 return find_base_term (tmp1);
1233 if (REG_P (tmp2) && REG_POINTER (tmp2))
1234 return find_base_term (tmp2);
1236 /* Neither operand was known to be a pointer. Go ahead and find the
1237 base term for both operands. */
1238 tmp1 = find_base_term (tmp1);
1239 tmp2 = find_base_term (tmp2);
1241 /* If either base term is named object or a special address
1242 (like an argument or stack reference), then use it for the
1245 && (GET_CODE (tmp1) == SYMBOL_REF
1246 || GET_CODE (tmp1) == LABEL_REF
1247 || (GET_CODE (tmp1) == ADDRESS
1248 && GET_MODE (tmp1) != VOIDmode)))
1252 && (GET_CODE (tmp2) == SYMBOL_REF
1253 || GET_CODE (tmp2) == LABEL_REF
1254 || (GET_CODE (tmp2) == ADDRESS
1255 && GET_MODE (tmp2) != VOIDmode)))
1258 /* We could not determine which of the two operands was the
1259 base register and which was the index. So we can determine
1260 nothing from the base alias check. */
1265 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1266 return REG_BASE_VALUE (XEXP (x, 0));
1274 return REG_BASE_VALUE (frame_pointer_rtx);
1281 /* Return 0 if the addresses X and Y are known to point to different
1282 objects, 1 if they might be pointers to the same object. */
1285 base_alias_check (x, y, x_mode, y_mode)
1287 enum machine_mode x_mode, y_mode;
1289 rtx x_base = find_base_term (x);
1290 rtx y_base = find_base_term (y);
1292 /* If the address itself has no known base see if a known equivalent
1293 value has one. If either address still has no known base, nothing
1294 is known about aliasing. */
1299 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1302 x_base = find_base_term (x_c);
1310 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1313 y_base = find_base_term (y_c);
1318 /* If the base addresses are equal nothing is known about aliasing. */
1319 if (rtx_equal_p (x_base, y_base))
1322 /* The base addresses of the read and write are different expressions.
1323 If they are both symbols and they are not accessed via AND, there is
1324 no conflict. We can bring knowledge of object alignment into play
1325 here. For example, on alpha, "char a, b;" can alias one another,
1326 though "char a; long b;" cannot. */
1327 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1329 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1331 if (GET_CODE (x) == AND
1332 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1333 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1335 if (GET_CODE (y) == AND
1336 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1337 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1339 /* Differing symbols never alias. */
1343 /* If one address is a stack reference there can be no alias:
1344 stack references using different base registers do not alias,
1345 a stack reference can not alias a parameter, and a stack reference
1346 can not alias a global. */
1347 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1348 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1351 if (! flag_argument_noalias)
1354 if (flag_argument_noalias > 1)
1357 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1358 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1361 /* Convert the address X into something we can use. This is done by returning
1362 it unchanged unless it is a value; in the latter case we call cselib to get
1363 a more useful rtx. */
1370 struct elt_loc_list *l;
1372 if (GET_CODE (x) != VALUE)
1374 v = CSELIB_VAL_PTR (x);
1375 for (l = v->locs; l; l = l->next)
1376 if (CONSTANT_P (l->loc))
1378 for (l = v->locs; l; l = l->next)
1379 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1382 return v->locs->loc;
1386 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1387 where SIZE is the size in bytes of the memory reference. If ADDR
1388 is not modified by the memory reference then ADDR is returned. */
1391 addr_side_effect_eval (addr, size, n_refs)
1398 switch (GET_CODE (addr))
1401 offset = (n_refs + 1) * size;
1404 offset = -(n_refs + 1) * size;
1407 offset = n_refs * size;
1410 offset = -n_refs * size;
1418 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1420 addr = XEXP (addr, 0);
1425 /* Return nonzero if X and Y (memory addresses) could reference the
1426 same location in memory. C is an offset accumulator. When
1427 C is nonzero, we are testing aliases between X and Y + C.
1428 XSIZE is the size in bytes of the X reference,
1429 similarly YSIZE is the size in bytes for Y.
1431 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1432 referenced (the reference was BLKmode), so make the most pessimistic
1435 If XSIZE or YSIZE is negative, we may access memory outside the object
1436 being referenced as a side effect. This can happen when using AND to
1437 align memory references, as is done on the Alpha.
1439 Nice to notice that varying addresses cannot conflict with fp if no
1440 local variables had their addresses taken, but that's too hard now. */
1443 memrefs_conflict_p (xsize, x, ysize, y, c)
1448 if (GET_CODE (x) == VALUE)
1450 if (GET_CODE (y) == VALUE)
1452 if (GET_CODE (x) == HIGH)
1454 else if (GET_CODE (x) == LO_SUM)
1457 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1458 if (GET_CODE (y) == HIGH)
1460 else if (GET_CODE (y) == LO_SUM)
1463 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1465 if (rtx_equal_for_memref_p (x, y))
1467 if (xsize <= 0 || ysize <= 0)
1469 if (c >= 0 && xsize > c)
1471 if (c < 0 && ysize+c > 0)
1476 /* This code used to check for conflicts involving stack references and
1477 globals but the base address alias code now handles these cases. */
1479 if (GET_CODE (x) == PLUS)
1481 /* The fact that X is canonicalized means that this
1482 PLUS rtx is canonicalized. */
1483 rtx x0 = XEXP (x, 0);
1484 rtx x1 = XEXP (x, 1);
1486 if (GET_CODE (y) == PLUS)
1488 /* The fact that Y is canonicalized means that this
1489 PLUS rtx is canonicalized. */
1490 rtx y0 = XEXP (y, 0);
1491 rtx y1 = XEXP (y, 1);
1493 if (rtx_equal_for_memref_p (x1, y1))
1494 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1495 if (rtx_equal_for_memref_p (x0, y0))
1496 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1497 if (GET_CODE (x1) == CONST_INT)
1499 if (GET_CODE (y1) == CONST_INT)
1500 return memrefs_conflict_p (xsize, x0, ysize, y0,
1501 c - INTVAL (x1) + INTVAL (y1));
1503 return memrefs_conflict_p (xsize, x0, ysize, y,
1506 else if (GET_CODE (y1) == CONST_INT)
1507 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1511 else if (GET_CODE (x1) == CONST_INT)
1512 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1514 else if (GET_CODE (y) == PLUS)
1516 /* The fact that Y is canonicalized means that this
1517 PLUS rtx is canonicalized. */
1518 rtx y0 = XEXP (y, 0);
1519 rtx y1 = XEXP (y, 1);
1521 if (GET_CODE (y1) == CONST_INT)
1522 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1527 if (GET_CODE (x) == GET_CODE (y))
1528 switch (GET_CODE (x))
1532 /* Handle cases where we expect the second operands to be the
1533 same, and check only whether the first operand would conflict
1536 rtx x1 = canon_rtx (XEXP (x, 1));
1537 rtx y1 = canon_rtx (XEXP (y, 1));
1538 if (! rtx_equal_for_memref_p (x1, y1))
1540 x0 = canon_rtx (XEXP (x, 0));
1541 y0 = canon_rtx (XEXP (y, 0));
1542 if (rtx_equal_for_memref_p (x0, y0))
1543 return (xsize == 0 || ysize == 0
1544 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1546 /* Can't properly adjust our sizes. */
1547 if (GET_CODE (x1) != CONST_INT)
1549 xsize /= INTVAL (x1);
1550 ysize /= INTVAL (x1);
1552 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1556 /* Are these registers known not to be equal? */
1557 if (alias_invariant)
1559 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1560 rtx i_x, i_y; /* invariant relationships of X and Y */
1562 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1563 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1565 if (i_x == 0 && i_y == 0)
1568 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1569 ysize, i_y ? i_y : y, c))
1578 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1579 as an access with indeterminate size. Assume that references
1580 besides AND are aligned, so if the size of the other reference is
1581 at least as large as the alignment, assume no other overlap. */
1582 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1584 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1586 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1588 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1590 /* ??? If we are indexing far enough into the array/structure, we
1591 may yet be able to determine that we can not overlap. But we
1592 also need to that we are far enough from the end not to overlap
1593 a following reference, so we do nothing with that for now. */
1594 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1596 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1599 if (GET_CODE (x) == ADDRESSOF)
1601 if (y == frame_pointer_rtx
1602 || GET_CODE (y) == ADDRESSOF)
1603 return xsize <= 0 || ysize <= 0;
1605 if (GET_CODE (y) == ADDRESSOF)
1607 if (x == frame_pointer_rtx)
1608 return xsize <= 0 || ysize <= 0;
1613 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1615 c += (INTVAL (y) - INTVAL (x));
1616 return (xsize <= 0 || ysize <= 0
1617 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1620 if (GET_CODE (x) == CONST)
1622 if (GET_CODE (y) == CONST)
1623 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1624 ysize, canon_rtx (XEXP (y, 0)), c);
1626 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1629 if (GET_CODE (y) == CONST)
1630 return memrefs_conflict_p (xsize, x, ysize,
1631 canon_rtx (XEXP (y, 0)), c);
1634 return (xsize <= 0 || ysize <= 0
1635 || (rtx_equal_for_memref_p (x, y)
1636 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1643 /* Functions to compute memory dependencies.
1645 Since we process the insns in execution order, we can build tables
1646 to keep track of what registers are fixed (and not aliased), what registers
1647 are varying in known ways, and what registers are varying in unknown
1650 If both memory references are volatile, then there must always be a
1651 dependence between the two references, since their order can not be
1652 changed. A volatile and non-volatile reference can be interchanged
1655 A MEM_IN_STRUCT reference at a non-AND varying address can never
1656 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1657 also must allow AND addresses, because they may generate accesses
1658 outside the object being referenced. This is used to generate
1659 aligned addresses from unaligned addresses, for instance, the alpha
1660 storeqi_unaligned pattern. */
1662 /* Read dependence: X is read after read in MEM takes place. There can
1663 only be a dependence here if both reads are volatile. */
1666 read_dependence (mem, x)
1670 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1673 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1674 MEM2 is a reference to a structure at a varying address, or returns
1675 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1676 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1677 to decide whether or not an address may vary; it should return
1678 nonzero whenever variation is possible.
1679 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1682 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1684 rtx mem1_addr, mem2_addr;
1685 int (*varies_p) PARAMS ((rtx, int));
1687 if (! flag_strict_aliasing)
1690 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1691 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1692 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1696 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1697 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1698 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1705 /* Returns nonzero if something about the mode or address format MEM1
1706 indicates that it might well alias *anything*. */
1709 aliases_everything_p (mem)
1712 if (GET_CODE (XEXP (mem, 0)) == AND)
1713 /* If the address is an AND, its very hard to know at what it is
1714 actually pointing. */
1720 /* True dependence: X is read after store in MEM takes place. */
1723 true_dependence (mem, mem_mode, x, varies)
1725 enum machine_mode mem_mode;
1727 int (*varies) PARAMS ((rtx, int));
1729 register rtx x_addr, mem_addr;
1732 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1735 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1738 /* Unchanging memory can't conflict with non-unchanging memory.
1739 A non-unchanging read can conflict with a non-unchanging write.
1740 An unchanging read can conflict with an unchanging write since
1741 there may be a single store to this address to initialize it.
1742 Note that an unchanging store can conflict with a non-unchanging read
1743 since we have to make conservative assumptions when we have a
1744 record with readonly fields and we are copying the whole thing.
1745 Just fall through to the code below to resolve potential conflicts.
1746 This won't handle all cases optimally, but the possible performance
1747 loss should be negligible. */
1748 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1751 if (mem_mode == VOIDmode)
1752 mem_mode = GET_MODE (mem);
1754 x_addr = get_addr (XEXP (x, 0));
1755 mem_addr = get_addr (XEXP (mem, 0));
1757 base = find_base_term (x_addr);
1758 if (base && (GET_CODE (base) == LABEL_REF
1759 || (GET_CODE (base) == SYMBOL_REF
1760 && CONSTANT_POOL_ADDRESS_P (base))))
1763 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1766 x_addr = canon_rtx (x_addr);
1767 mem_addr = canon_rtx (mem_addr);
1769 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1770 SIZE_FOR_MODE (x), x_addr, 0))
1773 if (aliases_everything_p (x))
1776 /* We cannot use aliases_everyting_p to test MEM, since we must look
1777 at MEM_MODE, rather than GET_MODE (MEM). */
1778 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1781 /* In true_dependence we also allow BLKmode to alias anything. Why
1782 don't we do this in anti_dependence and output_dependence? */
1783 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1786 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1790 /* Canonical true dependence: X is read after store in MEM takes place.
1791 Variant of true_dependece which assumes MEM has already been
1792 canonicalized (hence we no longer do that here).
1793 The mem_addr argument has been added, since true_dependence computed
1794 this value prior to canonicalizing. */
1797 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
1798 rtx mem, mem_addr, x;
1799 enum machine_mode mem_mode;
1800 int (*varies) PARAMS ((rtx, int));
1802 register rtx x_addr;
1804 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1807 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1810 /* If X is an unchanging read, then it can't possibly conflict with any
1811 non-unchanging store. It may conflict with an unchanging write though,
1812 because there may be a single store to this address to initialize it.
1813 Just fall through to the code below to resolve the case where we have
1814 both an unchanging read and an unchanging write. This won't handle all
1815 cases optimally, but the possible performance loss should be
1817 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1820 x_addr = get_addr (XEXP (x, 0));
1822 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1825 x_addr = canon_rtx (x_addr);
1826 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1827 SIZE_FOR_MODE (x), x_addr, 0))
1830 if (aliases_everything_p (x))
1833 /* We cannot use aliases_everyting_p to test MEM, since we must look
1834 at MEM_MODE, rather than GET_MODE (MEM). */
1835 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1838 /* In true_dependence we also allow BLKmode to alias anything. Why
1839 don't we do this in anti_dependence and output_dependence? */
1840 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1843 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1847 /* Returns non-zero if a write to X might alias a previous read from
1848 (or, if WRITEP is non-zero, a write to) MEM. */
1851 write_dependence_p (mem, x, writep)
1856 rtx x_addr, mem_addr;
1860 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1863 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1866 /* Unchanging memory can't conflict with non-unchanging memory. */
1867 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1870 /* If MEM is an unchanging read, then it can't possibly conflict with
1871 the store to X, because there is at most one store to MEM, and it must
1872 have occurred somewhere before MEM. */
1873 if (! writep && RTX_UNCHANGING_P (mem))
1876 x_addr = get_addr (XEXP (x, 0));
1877 mem_addr = get_addr (XEXP (mem, 0));
1881 base = find_base_term (mem_addr);
1882 if (base && (GET_CODE (base) == LABEL_REF
1883 || (GET_CODE (base) == SYMBOL_REF
1884 && CONSTANT_POOL_ADDRESS_P (base))))
1888 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1892 x_addr = canon_rtx (x_addr);
1893 mem_addr = canon_rtx (mem_addr);
1895 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1896 SIZE_FOR_MODE (x), x_addr, 0))
1900 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1903 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1904 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1907 /* Anti dependence: X is written after read in MEM takes place. */
1910 anti_dependence (mem, x)
1914 return write_dependence_p (mem, x, /*writep=*/0);
1917 /* Output dependence: X is written after store in MEM takes place. */
1920 output_dependence (mem, x)
1924 return write_dependence_p (mem, x, /*writep=*/1);
1927 /* Returns non-zero if X mentions something which is not
1928 local to the function and is not constant. */
1931 nonlocal_mentioned_p (x)
1935 register RTX_CODE code;
1938 code = GET_CODE (x);
1940 if (GET_RTX_CLASS (code) == 'i')
1942 /* Constant functions can be constant if they don't use
1943 scratch memory used to mark function w/o side effects. */
1944 if (code == CALL_INSN && CONST_CALL_P (x))
1946 x = CALL_INSN_FUNCTION_USAGE (x);
1952 code = GET_CODE (x);
1958 if (GET_CODE (SUBREG_REG (x)) == REG)
1960 /* Global registers are not local. */
1961 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1962 && global_regs[subreg_regno (x)])
1970 /* Global registers are not local. */
1971 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1985 /* Constants in the function's constants pool are constant. */
1986 if (CONSTANT_POOL_ADDRESS_P (x))
1991 /* Non-constant calls and recursion are not local. */
1995 /* Be overly conservative and consider any volatile memory
1996 reference as not local. */
1997 if (MEM_VOLATILE_P (x))
1999 base = find_base_term (XEXP (x, 0));
2002 /* A Pmode ADDRESS could be a reference via the structure value
2003 address or static chain. Such memory references are nonlocal.
2005 Thus, we have to examine the contents of the ADDRESS to find
2006 out if this is a local reference or not. */
2007 if (GET_CODE (base) == ADDRESS
2008 && GET_MODE (base) == Pmode
2009 && (XEXP (base, 0) == stack_pointer_rtx
2010 || XEXP (base, 0) == arg_pointer_rtx
2011 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2012 || XEXP (base, 0) == hard_frame_pointer_rtx
2014 || XEXP (base, 0) == frame_pointer_rtx))
2016 /* Constants in the function's constant pool are constant. */
2017 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2022 case UNSPEC_VOLATILE:
2027 if (MEM_VOLATILE_P (x))
2036 /* Recursively scan the operands of this expression. */
2039 register const char *fmt = GET_RTX_FORMAT (code);
2042 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2044 if (fmt[i] == 'e' && XEXP (x, i))
2046 if (nonlocal_mentioned_p (XEXP (x, i)))
2049 else if (fmt[i] == 'E')
2052 for (j = 0; j < XVECLEN (x, i); j++)
2053 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2062 /* Mark the function if it is constant. */
2065 mark_constant_function ()
2068 int nonlocal_mentioned;
2070 if (TREE_PUBLIC (current_function_decl)
2071 || TREE_READONLY (current_function_decl)
2072 || DECL_IS_PURE (current_function_decl)
2073 || TREE_THIS_VOLATILE (current_function_decl)
2074 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2077 /* A loop might not return which counts as a side effect. */
2078 if (mark_dfs_back_edges ())
2081 nonlocal_mentioned = 0;
2083 init_alias_analysis ();
2085 /* Determine if this is a constant function. */
2087 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2088 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2090 nonlocal_mentioned = 1;
2094 end_alias_analysis ();
2096 /* Mark the function. */
2098 if (! nonlocal_mentioned)
2099 TREE_READONLY (current_function_decl) = 1;
2103 static HARD_REG_SET argument_registers;
2110 #ifndef OUTGOING_REGNO
2111 #define OUTGOING_REGNO(N) N
2113 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2114 /* Check whether this register can hold an incoming pointer
2115 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2116 numbers, so translate if necessary due to register windows. */
2117 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2118 && HARD_REGNO_MODE_OK (i, Pmode))
2119 SET_HARD_REG_BIT (argument_registers, i);
2121 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2124 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2128 init_alias_analysis ()
2130 int maxreg = max_reg_num ();
2133 register unsigned int ui;
2136 reg_known_value_size = maxreg;
2139 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2140 - FIRST_PSEUDO_REGISTER;
2142 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2143 - FIRST_PSEUDO_REGISTER;
2145 /* Overallocate reg_base_value to allow some growth during loop
2146 optimization. Loop unrolling can create a large number of
2148 reg_base_value_size = maxreg * 2;
2149 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2150 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2152 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2153 reg_seen = (char *) xmalloc (reg_base_value_size);
2154 if (! reload_completed && flag_unroll_loops)
2156 /* ??? Why are we realloc'ing if we're just going to zero it? */
2157 alias_invariant = (rtx *)xrealloc (alias_invariant,
2158 reg_base_value_size * sizeof (rtx));
2159 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2162 /* The basic idea is that each pass through this loop will use the
2163 "constant" information from the previous pass to propagate alias
2164 information through another level of assignments.
2166 This could get expensive if the assignment chains are long. Maybe
2167 we should throttle the number of iterations, possibly based on
2168 the optimization level or flag_expensive_optimizations.
2170 We could propagate more information in the first pass by making use
2171 of REG_N_SETS to determine immediately that the alias information
2172 for a pseudo is "constant".
2174 A program with an uninitialized variable can cause an infinite loop
2175 here. Instead of doing a full dataflow analysis to detect such problems
2176 we just cap the number of iterations for the loop.
2178 The state of the arrays for the set chain in question does not matter
2179 since the program has undefined behavior. */
2184 /* Assume nothing will change this iteration of the loop. */
2187 /* We want to assign the same IDs each iteration of this loop, so
2188 start counting from zero each iteration of the loop. */
2191 /* We're at the start of the funtion each iteration through the
2192 loop, so we're copying arguments. */
2193 copying_arguments = 1;
2195 /* Wipe the potential alias information clean for this pass. */
2196 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2198 /* Wipe the reg_seen array clean. */
2199 memset ((char *) reg_seen, 0, reg_base_value_size);
2201 /* Mark all hard registers which may contain an address.
2202 The stack, frame and argument pointers may contain an address.
2203 An argument register which can hold a Pmode value may contain
2204 an address even if it is not in BASE_REGS.
2206 The address expression is VOIDmode for an argument and
2207 Pmode for other registers. */
2209 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2210 if (TEST_HARD_REG_BIT (argument_registers, i))
2211 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2212 gen_rtx_REG (Pmode, i));
2214 new_reg_base_value[STACK_POINTER_REGNUM]
2215 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2216 new_reg_base_value[ARG_POINTER_REGNUM]
2217 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2218 new_reg_base_value[FRAME_POINTER_REGNUM]
2219 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2220 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2221 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2222 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2225 /* Walk the insns adding values to the new_reg_base_value array. */
2226 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2232 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2233 /* The prologue/epilouge insns are not threaded onto the
2234 insn chain until after reload has completed. Thus,
2235 there is no sense wasting time checking if INSN is in
2236 the prologue/epilogue until after reload has completed. */
2237 if (reload_completed
2238 && prologue_epilogue_contains (insn))
2242 /* If this insn has a noalias note, process it, Otherwise,
2243 scan for sets. A simple set will have no side effects
2244 which could change the base value of any other register. */
2246 if (GET_CODE (PATTERN (insn)) == SET
2247 && REG_NOTES (insn) != 0
2248 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2249 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2251 note_stores (PATTERN (insn), record_set, NULL);
2253 set = single_set (insn);
2256 && GET_CODE (SET_DEST (set)) == REG
2257 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2259 unsigned int regno = REGNO (SET_DEST (set));
2260 rtx src = SET_SRC (set);
2262 if (REG_NOTES (insn) != 0
2263 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2264 && REG_N_SETS (regno) == 1)
2265 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2266 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2267 && ! rtx_varies_p (XEXP (note, 0), 1)
2268 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2270 reg_known_value[regno] = XEXP (note, 0);
2271 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2273 else if (REG_N_SETS (regno) == 1
2274 && GET_CODE (src) == PLUS
2275 && GET_CODE (XEXP (src, 0)) == REG
2276 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2277 && (reg_known_value[REGNO (XEXP (src, 0))])
2278 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2280 rtx op0 = XEXP (src, 0);
2281 op0 = reg_known_value[REGNO (op0)];
2282 reg_known_value[regno]
2283 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2284 reg_known_equiv_p[regno] = 0;
2286 else if (REG_N_SETS (regno) == 1
2287 && ! rtx_varies_p (src, 1))
2289 reg_known_value[regno] = src;
2290 reg_known_equiv_p[regno] = 0;
2294 else if (GET_CODE (insn) == NOTE
2295 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2296 copying_arguments = 0;
2299 /* Now propagate values from new_reg_base_value to reg_base_value. */
2300 for (ui = 0; ui < reg_base_value_size; ui++)
2302 if (new_reg_base_value[ui]
2303 && new_reg_base_value[ui] != reg_base_value[ui]
2304 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2306 reg_base_value[ui] = new_reg_base_value[ui];
2311 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2313 /* Fill in the remaining entries. */
2314 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2315 if (reg_known_value[i] == 0)
2316 reg_known_value[i] = regno_reg_rtx[i];
2318 /* Simplify the reg_base_value array so that no register refers to
2319 another register, except to special registers indirectly through
2320 ADDRESS expressions.
2322 In theory this loop can take as long as O(registers^2), but unless
2323 there are very long dependency chains it will run in close to linear
2326 This loop may not be needed any longer now that the main loop does
2327 a better job at propagating alias information. */
2333 for (ui = 0; ui < reg_base_value_size; ui++)
2335 rtx base = reg_base_value[ui];
2336 if (base && GET_CODE (base) == REG)
2338 unsigned int base_regno = REGNO (base);
2339 if (base_regno == ui) /* register set from itself */
2340 reg_base_value[ui] = 0;
2342 reg_base_value[ui] = reg_base_value[base_regno];
2347 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2350 free (new_reg_base_value);
2351 new_reg_base_value = 0;
2357 end_alias_analysis ()
2359 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2360 reg_known_value = 0;
2361 reg_known_value_size = 0;
2362 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2363 reg_known_equiv_p = 0;
2366 ggc_del_root (reg_base_value);
2367 free (reg_base_value);
2370 reg_base_value_size = 0;
2371 if (alias_invariant)
2373 free (alias_invariant);
2374 alias_invariant = 0;