1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
3 Contributed by John Carr (jfc@mit.edu).
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
30 #include "hard-reg-set.h"
31 #include "basic-block.h"
36 #include "splay-tree.h"
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 d2 = find_base_decl (TREE_OPERAND (t, 2));
404 /* Set any nonzero values from the last, then from the first. */
405 if (d1 == 0) d1 = d2;
406 if (d0 == 0) d0 = d1;
407 if (d1 == 0) d1 = d0;
408 if (d2 == 0) d2 = d1;
410 /* At this point all are nonzero or all are zero. If all three are the
411 same, return it. Otherwise, return zero. */
412 return (d0 == d1 && d1 == d2) ? d0 : 0;
419 /* Return 1 if T is an expression that get_inner_reference handles. */
422 handled_component_p (t)
425 switch (TREE_CODE (t))
430 case ARRAY_RANGE_REF:
431 case NON_LVALUE_EXPR:
436 return (TYPE_MODE (TREE_TYPE (t))
437 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))));
444 /* Return 1 if all the nested component references handled by
445 get_inner_reference in T are such that we can address the object in T. */
451 /* If we're at the end, it is vacuously addressable. */
452 if (! handled_component_p (t))
455 /* Bitfields are never addressable. */
456 else if (TREE_CODE (t) == BIT_FIELD_REF)
459 else if (TREE_CODE (t) == COMPONENT_REF
460 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
461 && can_address_p (TREE_OPERAND (t, 0)))
464 else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
465 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
466 && can_address_p (TREE_OPERAND (t, 0)))
472 /* Return the alias set for T, which may be either a type or an
473 expression. Call language-specific routine for help, if needed. */
482 /* If we're not doing any alias analysis, just assume everything
483 aliases everything else. Also return 0 if this or its type is
485 if (! flag_strict_aliasing || t == error_mark_node
487 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
490 /* We can be passed either an expression or a type. This and the
491 language-specific routine may make mutually-recursive calls to
492 each other to figure out what to do. At each juncture, we see if
493 this is a tree that the language may need to handle specially.
494 First handle things that aren't types and start by removing nops
495 since we care only about the actual object. */
498 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
499 || TREE_CODE (t) == NON_LVALUE_EXPR)
500 t = TREE_OPERAND (t, 0);
502 /* Now give the language a chance to do something but record what we
503 gave it this time. */
505 if ((set = lang_get_alias_set (t)) != -1)
508 /* Now loop the same way as get_inner_reference and get the alias
509 set to use. Pick up the outermost object that we could have
511 while (handled_component_p (t) && ! can_address_p (t))
512 t = TREE_OPERAND (t, 0);
514 if (TREE_CODE (t) == INDIRECT_REF)
516 /* Check for accesses through restrict-qualified pointers. */
517 tree decl = find_base_decl (TREE_OPERAND (t, 0));
519 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
520 /* We use the alias set indicated in the declaration. */
521 return DECL_POINTER_ALIAS_SET (decl);
523 /* If we have an INDIRECT_REF via a void pointer, we don't
524 know anything about what that might alias. */
525 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
529 /* If we've already determined the alias set for this decl, just
530 return it. This is necessary for C++ anonymous unions, whose
531 component variables don't look like union members (boo!). */
532 if (TREE_CODE (t) == VAR_DECL
533 && DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
534 return MEM_ALIAS_SET (DECL_RTL (t));
536 /* Give the language another chance to do something special. */
538 && (set = lang_get_alias_set (t)) != -1)
541 /* Now all we care about is the type. */
545 /* Variant qualifiers don't affect the alias set, so get the main
546 variant. If this is a type with a known alias set, return it. */
547 t = TYPE_MAIN_VARIANT (t);
548 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
549 return TYPE_ALIAS_SET (t);
551 /* See if the language has special handling for this type. */
552 if ((set = lang_get_alias_set (t)) != -1)
554 /* If the alias set is now known, we are done. */
555 if (TYPE_ALIAS_SET_KNOWN_P (t))
556 return TYPE_ALIAS_SET (t);
559 /* There are no objects of FUNCTION_TYPE, so there's no point in
560 using up an alias set for them. (There are, of course, pointers
561 and references to functions, but that's different.) */
562 else if (TREE_CODE (t) == FUNCTION_TYPE)
565 /* Otherwise make a new alias set for this type. */
566 set = new_alias_set ();
568 TYPE_ALIAS_SET (t) = set;
570 /* If this is an aggregate type, we must record any component aliasing
572 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
573 record_component_aliases (t);
578 /* Return a brand-new alias set. */
583 static HOST_WIDE_INT last_alias_set;
585 if (flag_strict_aliasing)
586 return ++last_alias_set;
591 /* Indicate that things in SUBSET can alias things in SUPERSET, but
592 not vice versa. For example, in C, a store to an `int' can alias a
593 structure containing an `int', but not vice versa. Here, the
594 structure would be the SUPERSET and `int' the SUBSET. This
595 function should be called only once per SUPERSET/SUBSET pair.
597 It is illegal for SUPERSET to be zero; everything is implicitly a
598 subset of alias set zero. */
601 record_alias_subset (superset, subset)
602 HOST_WIDE_INT superset;
603 HOST_WIDE_INT subset;
605 alias_set_entry superset_entry;
606 alias_set_entry subset_entry;
611 superset_entry = get_alias_set_entry (superset);
612 if (superset_entry == 0)
614 /* Create an entry for the SUPERSET, so that we have a place to
615 attach the SUBSET. */
617 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
618 superset_entry->alias_set = superset;
619 superset_entry->children
620 = splay_tree_new (splay_tree_compare_ints, 0, 0);
621 superset_entry->has_zero_child = 0;
622 splay_tree_insert (alias_sets, (splay_tree_key) superset,
623 (splay_tree_value) superset_entry);
627 superset_entry->has_zero_child = 1;
630 subset_entry = get_alias_set_entry (subset);
631 /* If there is an entry for the subset, enter all of its children
632 (if they are not already present) as children of the SUPERSET. */
635 if (subset_entry->has_zero_child)
636 superset_entry->has_zero_child = 1;
638 splay_tree_foreach (subset_entry->children, insert_subset_children,
639 superset_entry->children);
642 /* Enter the SUBSET itself as a child of the SUPERSET. */
643 splay_tree_insert (superset_entry->children,
644 (splay_tree_key) subset, 0);
648 /* Record that component types of TYPE, if any, are part of that type for
649 aliasing purposes. For record types, we only record component types
650 for fields that are marked addressable. For array types, we always
651 record the component types, so the front end should not call this
652 function if the individual component aren't addressable. */
655 record_component_aliases (type)
658 HOST_WIDE_INT superset = get_alias_set (type);
664 switch (TREE_CODE (type))
667 if (! TYPE_NONALIASED_COMPONENT (type))
668 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
673 case QUAL_UNION_TYPE:
674 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
675 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
676 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
680 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
688 /* Allocate an alias set for use in storing and reading from the varargs
692 get_varargs_alias_set ()
694 static HOST_WIDE_INT set = -1;
697 set = new_alias_set ();
702 /* Likewise, but used for the fixed portions of the frame, e.g., register
706 get_frame_alias_set ()
708 static HOST_WIDE_INT set = -1;
711 set = new_alias_set ();
716 /* Inside SRC, the source of a SET, find a base address. */
719 find_base_value (src)
723 switch (GET_CODE (src))
731 /* At the start of a function, argument registers have known base
732 values which may be lost later. Returning an ADDRESS
733 expression here allows optimization based on argument values
734 even when the argument registers are used for other purposes. */
735 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
736 return new_reg_base_value[regno];
738 /* If a pseudo has a known base value, return it. Do not do this
739 for hard regs since it can result in a circular dependency
740 chain for registers which have values at function entry.
742 The test above is not sufficient because the scheduler may move
743 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
744 if (regno >= FIRST_PSEUDO_REGISTER
745 && regno < reg_base_value_size
746 && reg_base_value[regno])
747 return reg_base_value[regno];
752 /* Check for an argument passed in memory. Only record in the
753 copying-arguments block; it is too hard to track changes
755 if (copying_arguments
756 && (XEXP (src, 0) == arg_pointer_rtx
757 || (GET_CODE (XEXP (src, 0)) == PLUS
758 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
759 return gen_rtx_ADDRESS (VOIDmode, src);
764 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
767 /* ... fall through ... */
772 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
774 /* If either operand is a REG, then see if we already have
775 a known value for it. */
776 if (GET_CODE (src_0) == REG)
778 temp = find_base_value (src_0);
783 if (GET_CODE (src_1) == REG)
785 temp = find_base_value (src_1);
790 /* Guess which operand is the base address:
791 If either operand is a symbol, then it is the base. If
792 either operand is a CONST_INT, then the other is the base. */
793 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
794 return find_base_value (src_0);
795 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
796 return find_base_value (src_1);
798 /* This might not be necessary anymore:
799 If either operand is a REG that is a known pointer, then it
801 else if (GET_CODE (src_0) == REG && REG_POINTER (src_0))
802 return find_base_value (src_0);
803 else if (GET_CODE (src_1) == REG && REG_POINTER (src_1))
804 return find_base_value (src_1);
810 /* The standard form is (lo_sum reg sym) so look only at the
812 return find_base_value (XEXP (src, 1));
815 /* If the second operand is constant set the base
816 address to the first operand. */
817 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
818 return find_base_value (XEXP (src, 0));
822 if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
826 case SIGN_EXTEND: /* used for NT/Alpha pointers */
828 return find_base_value (XEXP (src, 0));
837 /* Called from init_alias_analysis indirectly through note_stores. */
839 /* While scanning insns to find base values, reg_seen[N] is nonzero if
840 register N has been set in this function. */
841 static char *reg_seen;
843 /* Addresses which are known not to alias anything else are identified
844 by a unique integer. */
845 static int unique_id;
848 record_set (dest, set, data)
850 void *data ATTRIBUTE_UNUSED;
852 register unsigned regno;
855 if (GET_CODE (dest) != REG)
858 regno = REGNO (dest);
860 if (regno >= reg_base_value_size)
865 /* A CLOBBER wipes out any old value but does not prevent a previously
866 unset register from acquiring a base address (i.e. reg_seen is not
868 if (GET_CODE (set) == CLOBBER)
870 new_reg_base_value[regno] = 0;
879 new_reg_base_value[regno] = 0;
883 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
884 GEN_INT (unique_id++));
888 /* This is not the first set. If the new value is not related to the
889 old value, forget the base value. Note that the following code is
891 extern int x, y; int *p = &x; p += (&y-&x);
892 ANSI C does not allow computing the difference of addresses
893 of distinct top level objects. */
894 if (new_reg_base_value[regno])
895 switch (GET_CODE (src))
899 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
900 new_reg_base_value[regno] = 0;
903 /* If the value we add in the PLUS is also a valid base value,
904 this might be the actual base value, and the original value
907 rtx other = NULL_RTX;
909 if (XEXP (src, 0) == dest)
910 other = XEXP (src, 1);
911 else if (XEXP (src, 1) == dest)
912 other = XEXP (src, 0);
914 if (! other || find_base_value (other))
915 new_reg_base_value[regno] = 0;
919 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
920 new_reg_base_value[regno] = 0;
923 new_reg_base_value[regno] = 0;
926 /* If this is the first set of a register, record the value. */
927 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
928 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
929 new_reg_base_value[regno] = find_base_value (src);
934 /* Called from loop optimization when a new pseudo-register is
935 created. It indicates that REGNO is being set to VAL. f INVARIANT
936 is true then this value also describes an invariant relationship
937 which can be used to deduce that two registers with unknown values
941 record_base_value (regno, val, invariant)
946 if (regno >= reg_base_value_size)
949 if (invariant && alias_invariant)
950 alias_invariant[regno] = val;
952 if (GET_CODE (val) == REG)
954 if (REGNO (val) < reg_base_value_size)
955 reg_base_value[regno] = reg_base_value[REGNO (val)];
960 reg_base_value[regno] = find_base_value (val);
963 /* Clear alias info for a register. This is used if an RTL transformation
964 changes the value of a register. This is used in flow by AUTO_INC_DEC
965 optimizations. We don't need to clear reg_base_value, since flow only
966 changes the offset. */
969 clear_reg_alias_info (rtx reg)
971 int regno = REGNO (reg);
973 if (regno < reg_known_value_size)
974 reg_known_value[regno] = reg;
977 /* Returns a canonical version of X, from the point of view alias
978 analysis. (For example, if X is a MEM whose address is a register,
979 and the register has a known value (say a SYMBOL_REF), then a MEM
980 whose address is the SYMBOL_REF is returned.) */
986 /* Recursively look for equivalences. */
987 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
988 && REGNO (x) < reg_known_value_size)
989 return reg_known_value[REGNO (x)] == x
990 ? x : canon_rtx (reg_known_value[REGNO (x)]);
991 else if (GET_CODE (x) == PLUS)
993 rtx x0 = canon_rtx (XEXP (x, 0));
994 rtx x1 = canon_rtx (XEXP (x, 1));
996 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
998 if (GET_CODE (x0) == CONST_INT)
999 return plus_constant (x1, INTVAL (x0));
1000 else if (GET_CODE (x1) == CONST_INT)
1001 return plus_constant (x0, INTVAL (x1));
1002 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1006 /* This gives us much better alias analysis when called from
1007 the loop optimizer. Note we want to leave the original
1008 MEM alone, but need to return the canonicalized MEM with
1009 all the flags with their original values. */
1010 else if (GET_CODE (x) == MEM)
1011 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1016 /* Return 1 if X and Y are identical-looking rtx's.
1018 We use the data in reg_known_value above to see if two registers with
1019 different numbers are, in fact, equivalent. */
1022 rtx_equal_for_memref_p (x, y)
1027 register enum rtx_code code;
1028 register const char *fmt;
1030 if (x == 0 && y == 0)
1032 if (x == 0 || y == 0)
1041 code = GET_CODE (x);
1042 /* Rtx's of different codes cannot be equal. */
1043 if (code != GET_CODE (y))
1046 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1047 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1049 if (GET_MODE (x) != GET_MODE (y))
1052 /* Some RTL can be compared without a recursive examination. */
1056 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1059 return REGNO (x) == REGNO (y);
1062 return XEXP (x, 0) == XEXP (y, 0);
1065 return XSTR (x, 0) == XSTR (y, 0);
1069 /* There's no need to compare the contents of CONST_DOUBLEs or
1070 CONST_INTs because pointer equality is a good enough
1071 comparison for these nodes. */
1075 return (XINT (x, 1) == XINT (y, 1)
1076 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1082 /* For commutative operations, the RTX match if the operand match in any
1083 order. Also handle the simple binary and unary cases without a loop. */
1084 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1085 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1086 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1087 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1088 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1089 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1090 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1091 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1092 else if (GET_RTX_CLASS (code) == '1')
1093 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1095 /* Compare the elements. If any pair of corresponding elements
1096 fail to match, return 0 for the whole things.
1098 Limit cases to types which actually appear in addresses. */
1100 fmt = GET_RTX_FORMAT (code);
1101 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1106 if (XINT (x, i) != XINT (y, i))
1111 /* Two vectors must have the same length. */
1112 if (XVECLEN (x, i) != XVECLEN (y, i))
1115 /* And the corresponding elements must match. */
1116 for (j = 0; j < XVECLEN (x, i); j++)
1117 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1118 XVECEXP (y, i, j)) == 0)
1123 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1127 /* This can happen for asm operands. */
1129 if (strcmp (XSTR (x, i), XSTR (y, i)))
1133 /* This can happen for an asm which clobbers memory. */
1137 /* It is believed that rtx's at this level will never
1138 contain anything but integers and other rtx's,
1139 except for within LABEL_REFs and SYMBOL_REFs. */
1147 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1148 X and return it, or return 0 if none found. */
1151 find_symbolic_term (x)
1155 register enum rtx_code code;
1156 register const char *fmt;
1158 code = GET_CODE (x);
1159 if (code == SYMBOL_REF || code == LABEL_REF)
1161 if (GET_RTX_CLASS (code) == 'o')
1164 fmt = GET_RTX_FORMAT (code);
1165 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1171 t = find_symbolic_term (XEXP (x, i));
1175 else if (fmt[i] == 'E')
1186 struct elt_loc_list *l;
1188 #if defined (FIND_BASE_TERM)
1189 /* Try machine-dependent ways to find the base term. */
1190 x = FIND_BASE_TERM (x);
1193 switch (GET_CODE (x))
1196 return REG_BASE_VALUE (x);
1199 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1205 return find_base_term (XEXP (x, 0));
1208 val = CSELIB_VAL_PTR (x);
1209 for (l = val->locs; l; l = l->next)
1210 if ((x = find_base_term (l->loc)) != 0)
1216 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1223 rtx tmp1 = XEXP (x, 0);
1224 rtx tmp2 = XEXP (x, 1);
1226 /* This is a litle bit tricky since we have to determine which of
1227 the two operands represents the real base address. Otherwise this
1228 routine may return the index register instead of the base register.
1230 That may cause us to believe no aliasing was possible, when in
1231 fact aliasing is possible.
1233 We use a few simple tests to guess the base register. Additional
1234 tests can certainly be added. For example, if one of the operands
1235 is a shift or multiply, then it must be the index register and the
1236 other operand is the base register. */
1238 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1239 return find_base_term (tmp2);
1241 /* If either operand is known to be a pointer, then use it
1242 to determine the base term. */
1243 if (REG_P (tmp1) && REG_POINTER (tmp1))
1244 return find_base_term (tmp1);
1246 if (REG_P (tmp2) && REG_POINTER (tmp2))
1247 return find_base_term (tmp2);
1249 /* Neither operand was known to be a pointer. Go ahead and find the
1250 base term for both operands. */
1251 tmp1 = find_base_term (tmp1);
1252 tmp2 = find_base_term (tmp2);
1254 /* If either base term is named object or a special address
1255 (like an argument or stack reference), then use it for the
1258 && (GET_CODE (tmp1) == SYMBOL_REF
1259 || GET_CODE (tmp1) == LABEL_REF
1260 || (GET_CODE (tmp1) == ADDRESS
1261 && GET_MODE (tmp1) != VOIDmode)))
1265 && (GET_CODE (tmp2) == SYMBOL_REF
1266 || GET_CODE (tmp2) == LABEL_REF
1267 || (GET_CODE (tmp2) == ADDRESS
1268 && GET_MODE (tmp2) != VOIDmode)))
1271 /* We could not determine which of the two operands was the
1272 base register and which was the index. So we can determine
1273 nothing from the base alias check. */
1278 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1279 return REG_BASE_VALUE (XEXP (x, 0));
1287 return REG_BASE_VALUE (frame_pointer_rtx);
1294 /* Return 0 if the addresses X and Y are known to point to different
1295 objects, 1 if they might be pointers to the same object. */
1298 base_alias_check (x, y, x_mode, y_mode)
1300 enum machine_mode x_mode, y_mode;
1302 rtx x_base = find_base_term (x);
1303 rtx y_base = find_base_term (y);
1305 /* If the address itself has no known base see if a known equivalent
1306 value has one. If either address still has no known base, nothing
1307 is known about aliasing. */
1312 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1315 x_base = find_base_term (x_c);
1323 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1326 y_base = find_base_term (y_c);
1331 /* If the base addresses are equal nothing is known about aliasing. */
1332 if (rtx_equal_p (x_base, y_base))
1335 /* The base addresses of the read and write are different expressions.
1336 If they are both symbols and they are not accessed via AND, there is
1337 no conflict. We can bring knowledge of object alignment into play
1338 here. For example, on alpha, "char a, b;" can alias one another,
1339 though "char a; long b;" cannot. */
1340 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1342 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1344 if (GET_CODE (x) == AND
1345 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1346 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1348 if (GET_CODE (y) == AND
1349 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1350 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1352 /* Differing symbols never alias. */
1356 /* If one address is a stack reference there can be no alias:
1357 stack references using different base registers do not alias,
1358 a stack reference can not alias a parameter, and a stack reference
1359 can not alias a global. */
1360 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1361 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1364 if (! flag_argument_noalias)
1367 if (flag_argument_noalias > 1)
1370 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1371 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1374 /* Convert the address X into something we can use. This is done by returning
1375 it unchanged unless it is a value; in the latter case we call cselib to get
1376 a more useful rtx. */
1383 struct elt_loc_list *l;
1385 if (GET_CODE (x) != VALUE)
1387 v = CSELIB_VAL_PTR (x);
1388 for (l = v->locs; l; l = l->next)
1389 if (CONSTANT_P (l->loc))
1391 for (l = v->locs; l; l = l->next)
1392 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1395 return v->locs->loc;
1399 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1400 where SIZE is the size in bytes of the memory reference. If ADDR
1401 is not modified by the memory reference then ADDR is returned. */
1404 addr_side_effect_eval (addr, size, n_refs)
1411 switch (GET_CODE (addr))
1414 offset = (n_refs + 1) * size;
1417 offset = -(n_refs + 1) * size;
1420 offset = n_refs * size;
1423 offset = -n_refs * size;
1431 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1433 addr = XEXP (addr, 0);
1438 /* Return nonzero if X and Y (memory addresses) could reference the
1439 same location in memory. C is an offset accumulator. When
1440 C is nonzero, we are testing aliases between X and Y + C.
1441 XSIZE is the size in bytes of the X reference,
1442 similarly YSIZE is the size in bytes for Y.
1444 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1445 referenced (the reference was BLKmode), so make the most pessimistic
1448 If XSIZE or YSIZE is negative, we may access memory outside the object
1449 being referenced as a side effect. This can happen when using AND to
1450 align memory references, as is done on the Alpha.
1452 Nice to notice that varying addresses cannot conflict with fp if no
1453 local variables had their addresses taken, but that's too hard now. */
1456 memrefs_conflict_p (xsize, x, ysize, y, c)
1461 if (GET_CODE (x) == VALUE)
1463 if (GET_CODE (y) == VALUE)
1465 if (GET_CODE (x) == HIGH)
1467 else if (GET_CODE (x) == LO_SUM)
1470 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1471 if (GET_CODE (y) == HIGH)
1473 else if (GET_CODE (y) == LO_SUM)
1476 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1478 if (rtx_equal_for_memref_p (x, y))
1480 if (xsize <= 0 || ysize <= 0)
1482 if (c >= 0 && xsize > c)
1484 if (c < 0 && ysize+c > 0)
1489 /* This code used to check for conflicts involving stack references and
1490 globals but the base address alias code now handles these cases. */
1492 if (GET_CODE (x) == PLUS)
1494 /* The fact that X is canonicalized means that this
1495 PLUS rtx is canonicalized. */
1496 rtx x0 = XEXP (x, 0);
1497 rtx x1 = XEXP (x, 1);
1499 if (GET_CODE (y) == PLUS)
1501 /* The fact that Y is canonicalized means that this
1502 PLUS rtx is canonicalized. */
1503 rtx y0 = XEXP (y, 0);
1504 rtx y1 = XEXP (y, 1);
1506 if (rtx_equal_for_memref_p (x1, y1))
1507 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1508 if (rtx_equal_for_memref_p (x0, y0))
1509 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1510 if (GET_CODE (x1) == CONST_INT)
1512 if (GET_CODE (y1) == CONST_INT)
1513 return memrefs_conflict_p (xsize, x0, ysize, y0,
1514 c - INTVAL (x1) + INTVAL (y1));
1516 return memrefs_conflict_p (xsize, x0, ysize, y,
1519 else if (GET_CODE (y1) == CONST_INT)
1520 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1524 else if (GET_CODE (x1) == CONST_INT)
1525 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1527 else if (GET_CODE (y) == PLUS)
1529 /* The fact that Y is canonicalized means that this
1530 PLUS rtx is canonicalized. */
1531 rtx y0 = XEXP (y, 0);
1532 rtx y1 = XEXP (y, 1);
1534 if (GET_CODE (y1) == CONST_INT)
1535 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1540 if (GET_CODE (x) == GET_CODE (y))
1541 switch (GET_CODE (x))
1545 /* Handle cases where we expect the second operands to be the
1546 same, and check only whether the first operand would conflict
1549 rtx x1 = canon_rtx (XEXP (x, 1));
1550 rtx y1 = canon_rtx (XEXP (y, 1));
1551 if (! rtx_equal_for_memref_p (x1, y1))
1553 x0 = canon_rtx (XEXP (x, 0));
1554 y0 = canon_rtx (XEXP (y, 0));
1555 if (rtx_equal_for_memref_p (x0, y0))
1556 return (xsize == 0 || ysize == 0
1557 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1559 /* Can't properly adjust our sizes. */
1560 if (GET_CODE (x1) != CONST_INT)
1562 xsize /= INTVAL (x1);
1563 ysize /= INTVAL (x1);
1565 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1569 /* Are these registers known not to be equal? */
1570 if (alias_invariant)
1572 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1573 rtx i_x, i_y; /* invariant relationships of X and Y */
1575 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1576 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1578 if (i_x == 0 && i_y == 0)
1581 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1582 ysize, i_y ? i_y : y, c))
1591 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1592 as an access with indeterminate size. Assume that references
1593 besides AND are aligned, so if the size of the other reference is
1594 at least as large as the alignment, assume no other overlap. */
1595 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1597 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1599 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1601 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1603 /* ??? If we are indexing far enough into the array/structure, we
1604 may yet be able to determine that we can not overlap. But we
1605 also need to that we are far enough from the end not to overlap
1606 a following reference, so we do nothing with that for now. */
1607 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1609 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1612 if (GET_CODE (x) == ADDRESSOF)
1614 if (y == frame_pointer_rtx
1615 || GET_CODE (y) == ADDRESSOF)
1616 return xsize <= 0 || ysize <= 0;
1618 if (GET_CODE (y) == ADDRESSOF)
1620 if (x == frame_pointer_rtx)
1621 return xsize <= 0 || ysize <= 0;
1626 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1628 c += (INTVAL (y) - INTVAL (x));
1629 return (xsize <= 0 || ysize <= 0
1630 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1633 if (GET_CODE (x) == CONST)
1635 if (GET_CODE (y) == CONST)
1636 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1637 ysize, canon_rtx (XEXP (y, 0)), c);
1639 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1642 if (GET_CODE (y) == CONST)
1643 return memrefs_conflict_p (xsize, x, ysize,
1644 canon_rtx (XEXP (y, 0)), c);
1647 return (xsize <= 0 || ysize <= 0
1648 || (rtx_equal_for_memref_p (x, y)
1649 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1656 /* Functions to compute memory dependencies.
1658 Since we process the insns in execution order, we can build tables
1659 to keep track of what registers are fixed (and not aliased), what registers
1660 are varying in known ways, and what registers are varying in unknown
1663 If both memory references are volatile, then there must always be a
1664 dependence between the two references, since their order can not be
1665 changed. A volatile and non-volatile reference can be interchanged
1668 A MEM_IN_STRUCT reference at a non-AND varying address can never
1669 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1670 also must allow AND addresses, because they may generate accesses
1671 outside the object being referenced. This is used to generate
1672 aligned addresses from unaligned addresses, for instance, the alpha
1673 storeqi_unaligned pattern. */
1675 /* Read dependence: X is read after read in MEM takes place. There can
1676 only be a dependence here if both reads are volatile. */
1679 read_dependence (mem, x)
1683 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1686 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1687 MEM2 is a reference to a structure at a varying address, or returns
1688 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1689 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1690 to decide whether or not an address may vary; it should return
1691 nonzero whenever variation is possible.
1692 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1695 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1697 rtx mem1_addr, mem2_addr;
1698 int (*varies_p) PARAMS ((rtx, int));
1700 if (! flag_strict_aliasing)
1703 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1704 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1705 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1709 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1710 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1711 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1718 /* Returns nonzero if something about the mode or address format MEM1
1719 indicates that it might well alias *anything*. */
1722 aliases_everything_p (mem)
1725 if (GET_CODE (XEXP (mem, 0)) == AND)
1726 /* If the address is an AND, its very hard to know at what it is
1727 actually pointing. */
1733 /* True dependence: X is read after store in MEM takes place. */
1736 true_dependence (mem, mem_mode, x, varies)
1738 enum machine_mode mem_mode;
1740 int (*varies) PARAMS ((rtx, int));
1742 register rtx x_addr, mem_addr;
1745 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1748 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1751 /* Unchanging memory can't conflict with non-unchanging memory.
1752 A non-unchanging read can conflict with a non-unchanging write.
1753 An unchanging read can conflict with an unchanging write since
1754 there may be a single store to this address to initialize it.
1755 Note that an unchanging store can conflict with a non-unchanging read
1756 since we have to make conservative assumptions when we have a
1757 record with readonly fields and we are copying the whole thing.
1758 Just fall through to the code below to resolve potential conflicts.
1759 This won't handle all cases optimally, but the possible performance
1760 loss should be negligible. */
1761 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1764 if (mem_mode == VOIDmode)
1765 mem_mode = GET_MODE (mem);
1767 x_addr = get_addr (XEXP (x, 0));
1768 mem_addr = get_addr (XEXP (mem, 0));
1770 base = find_base_term (x_addr);
1771 if (base && (GET_CODE (base) == LABEL_REF
1772 || (GET_CODE (base) == SYMBOL_REF
1773 && CONSTANT_POOL_ADDRESS_P (base))))
1776 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1779 x_addr = canon_rtx (x_addr);
1780 mem_addr = canon_rtx (mem_addr);
1782 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1783 SIZE_FOR_MODE (x), x_addr, 0))
1786 if (aliases_everything_p (x))
1789 /* We cannot use aliases_everyting_p to test MEM, since we must look
1790 at MEM_MODE, rather than GET_MODE (MEM). */
1791 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1794 /* In true_dependence we also allow BLKmode to alias anything. Why
1795 don't we do this in anti_dependence and output_dependence? */
1796 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1799 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1803 /* Canonical true dependence: X is read after store in MEM takes place.
1804 Variant of true_dependece which assumes MEM has already been
1805 canonicalized (hence we no longer do that here).
1806 The mem_addr argument has been added, since true_dependence computed
1807 this value prior to canonicalizing. */
1810 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
1811 rtx mem, mem_addr, x;
1812 enum machine_mode mem_mode;
1813 int (*varies) PARAMS ((rtx, int));
1815 register rtx x_addr;
1817 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1820 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1823 /* If X is an unchanging read, then it can't possibly conflict with any
1824 non-unchanging store. It may conflict with an unchanging write though,
1825 because there may be a single store to this address to initialize it.
1826 Just fall through to the code below to resolve the case where we have
1827 both an unchanging read and an unchanging write. This won't handle all
1828 cases optimally, but the possible performance loss should be
1830 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1833 x_addr = get_addr (XEXP (x, 0));
1835 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1838 x_addr = canon_rtx (x_addr);
1839 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1840 SIZE_FOR_MODE (x), x_addr, 0))
1843 if (aliases_everything_p (x))
1846 /* We cannot use aliases_everyting_p to test MEM, since we must look
1847 at MEM_MODE, rather than GET_MODE (MEM). */
1848 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1851 /* In true_dependence we also allow BLKmode to alias anything. Why
1852 don't we do this in anti_dependence and output_dependence? */
1853 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1856 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1860 /* Returns non-zero if a write to X might alias a previous read from
1861 (or, if WRITEP is non-zero, a write to) MEM. */
1864 write_dependence_p (mem, x, writep)
1869 rtx x_addr, mem_addr;
1873 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1876 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1879 /* Unchanging memory can't conflict with non-unchanging memory. */
1880 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1883 /* If MEM is an unchanging read, then it can't possibly conflict with
1884 the store to X, because there is at most one store to MEM, and it must
1885 have occurred somewhere before MEM. */
1886 if (! writep && RTX_UNCHANGING_P (mem))
1889 x_addr = get_addr (XEXP (x, 0));
1890 mem_addr = get_addr (XEXP (mem, 0));
1894 base = find_base_term (mem_addr);
1895 if (base && (GET_CODE (base) == LABEL_REF
1896 || (GET_CODE (base) == SYMBOL_REF
1897 && CONSTANT_POOL_ADDRESS_P (base))))
1901 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1905 x_addr = canon_rtx (x_addr);
1906 mem_addr = canon_rtx (mem_addr);
1908 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1909 SIZE_FOR_MODE (x), x_addr, 0))
1913 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1916 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1917 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1920 /* Anti dependence: X is written after read in MEM takes place. */
1923 anti_dependence (mem, x)
1927 return write_dependence_p (mem, x, /*writep=*/0);
1930 /* Output dependence: X is written after store in MEM takes place. */
1933 output_dependence (mem, x)
1937 return write_dependence_p (mem, x, /*writep=*/1);
1940 /* Returns non-zero if X mentions something which is not
1941 local to the function and is not constant. */
1944 nonlocal_mentioned_p (x)
1948 register RTX_CODE code;
1951 code = GET_CODE (x);
1953 if (GET_RTX_CLASS (code) == 'i')
1955 /* Constant functions can be constant if they don't use
1956 scratch memory used to mark function w/o side effects. */
1957 if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x))
1959 x = CALL_INSN_FUNCTION_USAGE (x);
1965 code = GET_CODE (x);
1971 if (GET_CODE (SUBREG_REG (x)) == REG)
1973 /* Global registers are not local. */
1974 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1975 && global_regs[subreg_regno (x)])
1983 /* Global registers are not local. */
1984 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1998 /* Constants in the function's constants pool are constant. */
1999 if (CONSTANT_POOL_ADDRESS_P (x))
2004 /* Non-constant calls and recursion are not local. */
2008 /* Be overly conservative and consider any volatile memory
2009 reference as not local. */
2010 if (MEM_VOLATILE_P (x))
2012 base = find_base_term (XEXP (x, 0));
2015 /* A Pmode ADDRESS could be a reference via the structure value
2016 address or static chain. Such memory references are nonlocal.
2018 Thus, we have to examine the contents of the ADDRESS to find
2019 out if this is a local reference or not. */
2020 if (GET_CODE (base) == ADDRESS
2021 && GET_MODE (base) == Pmode
2022 && (XEXP (base, 0) == stack_pointer_rtx
2023 || XEXP (base, 0) == arg_pointer_rtx
2024 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2025 || XEXP (base, 0) == hard_frame_pointer_rtx
2027 || XEXP (base, 0) == frame_pointer_rtx))
2029 /* Constants in the function's constant pool are constant. */
2030 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2035 case UNSPEC_VOLATILE:
2040 if (MEM_VOLATILE_P (x))
2049 /* Recursively scan the operands of this expression. */
2052 register const char *fmt = GET_RTX_FORMAT (code);
2055 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2057 if (fmt[i] == 'e' && XEXP (x, i))
2059 if (nonlocal_mentioned_p (XEXP (x, i)))
2062 else if (fmt[i] == 'E')
2065 for (j = 0; j < XVECLEN (x, i); j++)
2066 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2075 /* Mark the function if it is constant. */
2078 mark_constant_function ()
2081 int nonlocal_mentioned;
2083 if (TREE_PUBLIC (current_function_decl)
2084 || TREE_READONLY (current_function_decl)
2085 || DECL_IS_PURE (current_function_decl)
2086 || TREE_THIS_VOLATILE (current_function_decl)
2087 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2090 /* A loop might not return which counts as a side effect. */
2091 if (mark_dfs_back_edges ())
2094 nonlocal_mentioned = 0;
2096 init_alias_analysis ();
2098 /* Determine if this is a constant function. */
2100 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2101 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2103 nonlocal_mentioned = 1;
2107 end_alias_analysis ();
2109 /* Mark the function. */
2111 if (! nonlocal_mentioned)
2112 TREE_READONLY (current_function_decl) = 1;
2116 static HARD_REG_SET argument_registers;
2123 #ifndef OUTGOING_REGNO
2124 #define OUTGOING_REGNO(N) N
2126 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2127 /* Check whether this register can hold an incoming pointer
2128 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2129 numbers, so translate if necessary due to register windows. */
2130 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2131 && HARD_REGNO_MODE_OK (i, Pmode))
2132 SET_HARD_REG_BIT (argument_registers, i);
2134 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2137 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2141 init_alias_analysis ()
2143 int maxreg = max_reg_num ();
2146 register unsigned int ui;
2149 reg_known_value_size = maxreg;
2152 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2153 - FIRST_PSEUDO_REGISTER;
2155 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2156 - FIRST_PSEUDO_REGISTER;
2158 /* Overallocate reg_base_value to allow some growth during loop
2159 optimization. Loop unrolling can create a large number of
2161 reg_base_value_size = maxreg * 2;
2162 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2163 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2165 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2166 reg_seen = (char *) xmalloc (reg_base_value_size);
2167 if (! reload_completed && flag_unroll_loops)
2169 /* ??? Why are we realloc'ing if we're just going to zero it? */
2170 alias_invariant = (rtx *)xrealloc (alias_invariant,
2171 reg_base_value_size * sizeof (rtx));
2172 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2175 /* The basic idea is that each pass through this loop will use the
2176 "constant" information from the previous pass to propagate alias
2177 information through another level of assignments.
2179 This could get expensive if the assignment chains are long. Maybe
2180 we should throttle the number of iterations, possibly based on
2181 the optimization level or flag_expensive_optimizations.
2183 We could propagate more information in the first pass by making use
2184 of REG_N_SETS to determine immediately that the alias information
2185 for a pseudo is "constant".
2187 A program with an uninitialized variable can cause an infinite loop
2188 here. Instead of doing a full dataflow analysis to detect such problems
2189 we just cap the number of iterations for the loop.
2191 The state of the arrays for the set chain in question does not matter
2192 since the program has undefined behavior. */
2197 /* Assume nothing will change this iteration of the loop. */
2200 /* We want to assign the same IDs each iteration of this loop, so
2201 start counting from zero each iteration of the loop. */
2204 /* We're at the start of the funtion each iteration through the
2205 loop, so we're copying arguments. */
2206 copying_arguments = 1;
2208 /* Wipe the potential alias information clean for this pass. */
2209 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2211 /* Wipe the reg_seen array clean. */
2212 memset ((char *) reg_seen, 0, reg_base_value_size);
2214 /* Mark all hard registers which may contain an address.
2215 The stack, frame and argument pointers may contain an address.
2216 An argument register which can hold a Pmode value may contain
2217 an address even if it is not in BASE_REGS.
2219 The address expression is VOIDmode for an argument and
2220 Pmode for other registers. */
2222 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2223 if (TEST_HARD_REG_BIT (argument_registers, i))
2224 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2225 gen_rtx_REG (Pmode, i));
2227 new_reg_base_value[STACK_POINTER_REGNUM]
2228 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2229 new_reg_base_value[ARG_POINTER_REGNUM]
2230 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2231 new_reg_base_value[FRAME_POINTER_REGNUM]
2232 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2233 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2234 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2235 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2238 /* Walk the insns adding values to the new_reg_base_value array. */
2239 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2245 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2246 /* The prologue/epilouge insns are not threaded onto the
2247 insn chain until after reload has completed. Thus,
2248 there is no sense wasting time checking if INSN is in
2249 the prologue/epilogue until after reload has completed. */
2250 if (reload_completed
2251 && prologue_epilogue_contains (insn))
2255 /* If this insn has a noalias note, process it, Otherwise,
2256 scan for sets. A simple set will have no side effects
2257 which could change the base value of any other register. */
2259 if (GET_CODE (PATTERN (insn)) == SET
2260 && REG_NOTES (insn) != 0
2261 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2262 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2264 note_stores (PATTERN (insn), record_set, NULL);
2266 set = single_set (insn);
2269 && GET_CODE (SET_DEST (set)) == REG
2270 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2272 unsigned int regno = REGNO (SET_DEST (set));
2273 rtx src = SET_SRC (set);
2275 if (REG_NOTES (insn) != 0
2276 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2277 && REG_N_SETS (regno) == 1)
2278 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2279 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2280 && ! rtx_varies_p (XEXP (note, 0), 1)
2281 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2283 reg_known_value[regno] = XEXP (note, 0);
2284 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2286 else if (REG_N_SETS (regno) == 1
2287 && GET_CODE (src) == PLUS
2288 && GET_CODE (XEXP (src, 0)) == REG
2289 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2290 && (reg_known_value[REGNO (XEXP (src, 0))])
2291 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2293 rtx op0 = XEXP (src, 0);
2294 op0 = reg_known_value[REGNO (op0)];
2295 reg_known_value[regno]
2296 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2297 reg_known_equiv_p[regno] = 0;
2299 else if (REG_N_SETS (regno) == 1
2300 && ! rtx_varies_p (src, 1))
2302 reg_known_value[regno] = src;
2303 reg_known_equiv_p[regno] = 0;
2307 else if (GET_CODE (insn) == NOTE
2308 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2309 copying_arguments = 0;
2312 /* Now propagate values from new_reg_base_value to reg_base_value. */
2313 for (ui = 0; ui < reg_base_value_size; ui++)
2315 if (new_reg_base_value[ui]
2316 && new_reg_base_value[ui] != reg_base_value[ui]
2317 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2319 reg_base_value[ui] = new_reg_base_value[ui];
2324 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2326 /* Fill in the remaining entries. */
2327 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2328 if (reg_known_value[i] == 0)
2329 reg_known_value[i] = regno_reg_rtx[i];
2331 /* Simplify the reg_base_value array so that no register refers to
2332 another register, except to special registers indirectly through
2333 ADDRESS expressions.
2335 In theory this loop can take as long as O(registers^2), but unless
2336 there are very long dependency chains it will run in close to linear
2339 This loop may not be needed any longer now that the main loop does
2340 a better job at propagating alias information. */
2346 for (ui = 0; ui < reg_base_value_size; ui++)
2348 rtx base = reg_base_value[ui];
2349 if (base && GET_CODE (base) == REG)
2351 unsigned int base_regno = REGNO (base);
2352 if (base_regno == ui) /* register set from itself */
2353 reg_base_value[ui] = 0;
2355 reg_base_value[ui] = reg_base_value[base_regno];
2360 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2363 free (new_reg_base_value);
2364 new_reg_base_value = 0;
2370 end_alias_analysis ()
2372 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2373 reg_known_value = 0;
2374 reg_known_value_size = 0;
2375 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2376 reg_known_equiv_p = 0;
2379 ggc_del_root (reg_base_value);
2380 free (reg_base_value);
2383 reg_base_value_size = 0;
2384 if (alias_invariant)
2386 free (alias_invariant);
2387 alias_invariant = 0;