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 (reg)
972 if (REGNO (reg) < reg_known_value_size)
973 reg_known_value[REGNO (reg)] = reg;
976 /* Returns a canonical version of X, from the point of view alias
977 analysis. (For example, if X is a MEM whose address is a register,
978 and the register has a known value (say a SYMBOL_REF), then a MEM
979 whose address is the SYMBOL_REF is returned.) */
985 /* Recursively look for equivalences. */
986 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
987 && REGNO (x) < reg_known_value_size)
988 return reg_known_value[REGNO (x)] == x
989 ? x : canon_rtx (reg_known_value[REGNO (x)]);
990 else if (GET_CODE (x) == PLUS)
992 rtx x0 = canon_rtx (XEXP (x, 0));
993 rtx x1 = canon_rtx (XEXP (x, 1));
995 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
997 if (GET_CODE (x0) == CONST_INT)
998 return plus_constant (x1, INTVAL (x0));
999 else if (GET_CODE (x1) == CONST_INT)
1000 return plus_constant (x0, INTVAL (x1));
1001 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
1005 /* This gives us much better alias analysis when called from
1006 the loop optimizer. Note we want to leave the original
1007 MEM alone, but need to return the canonicalized MEM with
1008 all the flags with their original values. */
1009 else if (GET_CODE (x) == MEM)
1010 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
1015 /* Return 1 if X and Y are identical-looking rtx's.
1017 We use the data in reg_known_value above to see if two registers with
1018 different numbers are, in fact, equivalent. */
1021 rtx_equal_for_memref_p (x, y)
1026 register enum rtx_code code;
1027 register const char *fmt;
1029 if (x == 0 && y == 0)
1031 if (x == 0 || y == 0)
1040 code = GET_CODE (x);
1041 /* Rtx's of different codes cannot be equal. */
1042 if (code != GET_CODE (y))
1045 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1046 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1048 if (GET_MODE (x) != GET_MODE (y))
1051 /* Some RTL can be compared without a recursive examination. */
1055 return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
1058 return REGNO (x) == REGNO (y);
1061 return XEXP (x, 0) == XEXP (y, 0);
1064 return XSTR (x, 0) == XSTR (y, 0);
1068 /* There's no need to compare the contents of CONST_DOUBLEs or
1069 CONST_INTs because pointer equality is a good enough
1070 comparison for these nodes. */
1074 return (XINT (x, 1) == XINT (y, 1)
1075 && rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
1081 /* For commutative operations, the RTX match if the operand match in any
1082 order. Also handle the simple binary and unary cases without a loop. */
1083 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
1084 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1085 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
1086 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
1087 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
1088 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
1089 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
1090 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
1091 else if (GET_RTX_CLASS (code) == '1')
1092 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
1094 /* Compare the elements. If any pair of corresponding elements
1095 fail to match, return 0 for the whole things.
1097 Limit cases to types which actually appear in addresses. */
1099 fmt = GET_RTX_FORMAT (code);
1100 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1105 if (XINT (x, i) != XINT (y, i))
1110 /* Two vectors must have the same length. */
1111 if (XVECLEN (x, i) != XVECLEN (y, i))
1114 /* And the corresponding elements must match. */
1115 for (j = 0; j < XVECLEN (x, i); j++)
1116 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
1117 XVECEXP (y, i, j)) == 0)
1122 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
1126 /* This can happen for asm operands. */
1128 if (strcmp (XSTR (x, i), XSTR (y, i)))
1132 /* This can happen for an asm which clobbers memory. */
1136 /* It is believed that rtx's at this level will never
1137 contain anything but integers and other rtx's,
1138 except for within LABEL_REFs and SYMBOL_REFs. */
1146 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1147 X and return it, or return 0 if none found. */
1150 find_symbolic_term (x)
1154 register enum rtx_code code;
1155 register const char *fmt;
1157 code = GET_CODE (x);
1158 if (code == SYMBOL_REF || code == LABEL_REF)
1160 if (GET_RTX_CLASS (code) == 'o')
1163 fmt = GET_RTX_FORMAT (code);
1164 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1170 t = find_symbolic_term (XEXP (x, i));
1174 else if (fmt[i] == 'E')
1185 struct elt_loc_list *l;
1187 #if defined (FIND_BASE_TERM)
1188 /* Try machine-dependent ways to find the base term. */
1189 x = FIND_BASE_TERM (x);
1192 switch (GET_CODE (x))
1195 return REG_BASE_VALUE (x);
1198 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1204 return find_base_term (XEXP (x, 0));
1207 val = CSELIB_VAL_PTR (x);
1208 for (l = val->locs; l; l = l->next)
1209 if ((x = find_base_term (l->loc)) != 0)
1215 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1222 rtx tmp1 = XEXP (x, 0);
1223 rtx tmp2 = XEXP (x, 1);
1225 /* This is a litle bit tricky since we have to determine which of
1226 the two operands represents the real base address. Otherwise this
1227 routine may return the index register instead of the base register.
1229 That may cause us to believe no aliasing was possible, when in
1230 fact aliasing is possible.
1232 We use a few simple tests to guess the base register. Additional
1233 tests can certainly be added. For example, if one of the operands
1234 is a shift or multiply, then it must be the index register and the
1235 other operand is the base register. */
1237 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1238 return find_base_term (tmp2);
1240 /* If either operand is known to be a pointer, then use it
1241 to determine the base term. */
1242 if (REG_P (tmp1) && REG_POINTER (tmp1))
1243 return find_base_term (tmp1);
1245 if (REG_P (tmp2) && REG_POINTER (tmp2))
1246 return find_base_term (tmp2);
1248 /* Neither operand was known to be a pointer. Go ahead and find the
1249 base term for both operands. */
1250 tmp1 = find_base_term (tmp1);
1251 tmp2 = find_base_term (tmp2);
1253 /* If either base term is named object or a special address
1254 (like an argument or stack reference), then use it for the
1257 && (GET_CODE (tmp1) == SYMBOL_REF
1258 || GET_CODE (tmp1) == LABEL_REF
1259 || (GET_CODE (tmp1) == ADDRESS
1260 && GET_MODE (tmp1) != VOIDmode)))
1264 && (GET_CODE (tmp2) == SYMBOL_REF
1265 || GET_CODE (tmp2) == LABEL_REF
1266 || (GET_CODE (tmp2) == ADDRESS
1267 && GET_MODE (tmp2) != VOIDmode)))
1270 /* We could not determine which of the two operands was the
1271 base register and which was the index. So we can determine
1272 nothing from the base alias check. */
1277 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1278 return REG_BASE_VALUE (XEXP (x, 0));
1286 return REG_BASE_VALUE (frame_pointer_rtx);
1293 /* Return 0 if the addresses X and Y are known to point to different
1294 objects, 1 if they might be pointers to the same object. */
1297 base_alias_check (x, y, x_mode, y_mode)
1299 enum machine_mode x_mode, y_mode;
1301 rtx x_base = find_base_term (x);
1302 rtx y_base = find_base_term (y);
1304 /* If the address itself has no known base see if a known equivalent
1305 value has one. If either address still has no known base, nothing
1306 is known about aliasing. */
1311 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1314 x_base = find_base_term (x_c);
1322 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1325 y_base = find_base_term (y_c);
1330 /* If the base addresses are equal nothing is known about aliasing. */
1331 if (rtx_equal_p (x_base, y_base))
1334 /* The base addresses of the read and write are different expressions.
1335 If they are both symbols and they are not accessed via AND, there is
1336 no conflict. We can bring knowledge of object alignment into play
1337 here. For example, on alpha, "char a, b;" can alias one another,
1338 though "char a; long b;" cannot. */
1339 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1341 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1343 if (GET_CODE (x) == AND
1344 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1345 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1347 if (GET_CODE (y) == AND
1348 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1349 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1351 /* Differing symbols never alias. */
1355 /* If one address is a stack reference there can be no alias:
1356 stack references using different base registers do not alias,
1357 a stack reference can not alias a parameter, and a stack reference
1358 can not alias a global. */
1359 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1360 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1363 if (! flag_argument_noalias)
1366 if (flag_argument_noalias > 1)
1369 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1370 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1373 /* Convert the address X into something we can use. This is done by returning
1374 it unchanged unless it is a value; in the latter case we call cselib to get
1375 a more useful rtx. */
1382 struct elt_loc_list *l;
1384 if (GET_CODE (x) != VALUE)
1386 v = CSELIB_VAL_PTR (x);
1387 for (l = v->locs; l; l = l->next)
1388 if (CONSTANT_P (l->loc))
1390 for (l = v->locs; l; l = l->next)
1391 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1394 return v->locs->loc;
1398 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1399 where SIZE is the size in bytes of the memory reference. If ADDR
1400 is not modified by the memory reference then ADDR is returned. */
1403 addr_side_effect_eval (addr, size, n_refs)
1410 switch (GET_CODE (addr))
1413 offset = (n_refs + 1) * size;
1416 offset = -(n_refs + 1) * size;
1419 offset = n_refs * size;
1422 offset = -n_refs * size;
1430 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1432 addr = XEXP (addr, 0);
1437 /* Return nonzero if X and Y (memory addresses) could reference the
1438 same location in memory. C is an offset accumulator. When
1439 C is nonzero, we are testing aliases between X and Y + C.
1440 XSIZE is the size in bytes of the X reference,
1441 similarly YSIZE is the size in bytes for Y.
1443 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1444 referenced (the reference was BLKmode), so make the most pessimistic
1447 If XSIZE or YSIZE is negative, we may access memory outside the object
1448 being referenced as a side effect. This can happen when using AND to
1449 align memory references, as is done on the Alpha.
1451 Nice to notice that varying addresses cannot conflict with fp if no
1452 local variables had their addresses taken, but that's too hard now. */
1455 memrefs_conflict_p (xsize, x, ysize, y, c)
1460 if (GET_CODE (x) == VALUE)
1462 if (GET_CODE (y) == VALUE)
1464 if (GET_CODE (x) == HIGH)
1466 else if (GET_CODE (x) == LO_SUM)
1469 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1470 if (GET_CODE (y) == HIGH)
1472 else if (GET_CODE (y) == LO_SUM)
1475 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1477 if (rtx_equal_for_memref_p (x, y))
1479 if (xsize <= 0 || ysize <= 0)
1481 if (c >= 0 && xsize > c)
1483 if (c < 0 && ysize+c > 0)
1488 /* This code used to check for conflicts involving stack references and
1489 globals but the base address alias code now handles these cases. */
1491 if (GET_CODE (x) == PLUS)
1493 /* The fact that X is canonicalized means that this
1494 PLUS rtx is canonicalized. */
1495 rtx x0 = XEXP (x, 0);
1496 rtx x1 = XEXP (x, 1);
1498 if (GET_CODE (y) == PLUS)
1500 /* The fact that Y is canonicalized means that this
1501 PLUS rtx is canonicalized. */
1502 rtx y0 = XEXP (y, 0);
1503 rtx y1 = XEXP (y, 1);
1505 if (rtx_equal_for_memref_p (x1, y1))
1506 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1507 if (rtx_equal_for_memref_p (x0, y0))
1508 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1509 if (GET_CODE (x1) == CONST_INT)
1511 if (GET_CODE (y1) == CONST_INT)
1512 return memrefs_conflict_p (xsize, x0, ysize, y0,
1513 c - INTVAL (x1) + INTVAL (y1));
1515 return memrefs_conflict_p (xsize, x0, ysize, y,
1518 else if (GET_CODE (y1) == CONST_INT)
1519 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1523 else if (GET_CODE (x1) == CONST_INT)
1524 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1526 else if (GET_CODE (y) == PLUS)
1528 /* The fact that Y is canonicalized means that this
1529 PLUS rtx is canonicalized. */
1530 rtx y0 = XEXP (y, 0);
1531 rtx y1 = XEXP (y, 1);
1533 if (GET_CODE (y1) == CONST_INT)
1534 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1539 if (GET_CODE (x) == GET_CODE (y))
1540 switch (GET_CODE (x))
1544 /* Handle cases where we expect the second operands to be the
1545 same, and check only whether the first operand would conflict
1548 rtx x1 = canon_rtx (XEXP (x, 1));
1549 rtx y1 = canon_rtx (XEXP (y, 1));
1550 if (! rtx_equal_for_memref_p (x1, y1))
1552 x0 = canon_rtx (XEXP (x, 0));
1553 y0 = canon_rtx (XEXP (y, 0));
1554 if (rtx_equal_for_memref_p (x0, y0))
1555 return (xsize == 0 || ysize == 0
1556 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1558 /* Can't properly adjust our sizes. */
1559 if (GET_CODE (x1) != CONST_INT)
1561 xsize /= INTVAL (x1);
1562 ysize /= INTVAL (x1);
1564 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1568 /* Are these registers known not to be equal? */
1569 if (alias_invariant)
1571 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1572 rtx i_x, i_y; /* invariant relationships of X and Y */
1574 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1575 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1577 if (i_x == 0 && i_y == 0)
1580 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1581 ysize, i_y ? i_y : y, c))
1590 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1591 as an access with indeterminate size. Assume that references
1592 besides AND are aligned, so if the size of the other reference is
1593 at least as large as the alignment, assume no other overlap. */
1594 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1596 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1598 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1600 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1602 /* ??? If we are indexing far enough into the array/structure, we
1603 may yet be able to determine that we can not overlap. But we
1604 also need to that we are far enough from the end not to overlap
1605 a following reference, so we do nothing with that for now. */
1606 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1608 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1611 if (GET_CODE (x) == ADDRESSOF)
1613 if (y == frame_pointer_rtx
1614 || GET_CODE (y) == ADDRESSOF)
1615 return xsize <= 0 || ysize <= 0;
1617 if (GET_CODE (y) == ADDRESSOF)
1619 if (x == frame_pointer_rtx)
1620 return xsize <= 0 || ysize <= 0;
1625 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1627 c += (INTVAL (y) - INTVAL (x));
1628 return (xsize <= 0 || ysize <= 0
1629 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1632 if (GET_CODE (x) == CONST)
1634 if (GET_CODE (y) == CONST)
1635 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1636 ysize, canon_rtx (XEXP (y, 0)), c);
1638 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1641 if (GET_CODE (y) == CONST)
1642 return memrefs_conflict_p (xsize, x, ysize,
1643 canon_rtx (XEXP (y, 0)), c);
1646 return (xsize <= 0 || ysize <= 0
1647 || (rtx_equal_for_memref_p (x, y)
1648 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1655 /* Functions to compute memory dependencies.
1657 Since we process the insns in execution order, we can build tables
1658 to keep track of what registers are fixed (and not aliased), what registers
1659 are varying in known ways, and what registers are varying in unknown
1662 If both memory references are volatile, then there must always be a
1663 dependence between the two references, since their order can not be
1664 changed. A volatile and non-volatile reference can be interchanged
1667 A MEM_IN_STRUCT reference at a non-AND varying address can never
1668 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1669 also must allow AND addresses, because they may generate accesses
1670 outside the object being referenced. This is used to generate
1671 aligned addresses from unaligned addresses, for instance, the alpha
1672 storeqi_unaligned pattern. */
1674 /* Read dependence: X is read after read in MEM takes place. There can
1675 only be a dependence here if both reads are volatile. */
1678 read_dependence (mem, x)
1682 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1685 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1686 MEM2 is a reference to a structure at a varying address, or returns
1687 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1688 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1689 to decide whether or not an address may vary; it should return
1690 nonzero whenever variation is possible.
1691 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1694 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1696 rtx mem1_addr, mem2_addr;
1697 int (*varies_p) PARAMS ((rtx, int));
1699 if (! flag_strict_aliasing)
1702 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1703 && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
1704 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1708 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1709 && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
1710 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1717 /* Returns nonzero if something about the mode or address format MEM1
1718 indicates that it might well alias *anything*. */
1721 aliases_everything_p (mem)
1724 if (GET_CODE (XEXP (mem, 0)) == AND)
1725 /* If the address is an AND, its very hard to know at what it is
1726 actually pointing. */
1732 /* True dependence: X is read after store in MEM takes place. */
1735 true_dependence (mem, mem_mode, x, varies)
1737 enum machine_mode mem_mode;
1739 int (*varies) PARAMS ((rtx, int));
1741 register rtx x_addr, mem_addr;
1744 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1747 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1750 /* Unchanging memory can't conflict with non-unchanging memory.
1751 A non-unchanging read can conflict with a non-unchanging write.
1752 An unchanging read can conflict with an unchanging write since
1753 there may be a single store to this address to initialize it.
1754 Note that an unchanging store can conflict with a non-unchanging read
1755 since we have to make conservative assumptions when we have a
1756 record with readonly fields and we are copying the whole thing.
1757 Just fall through to the code below to resolve potential conflicts.
1758 This won't handle all cases optimally, but the possible performance
1759 loss should be negligible. */
1760 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1763 if (mem_mode == VOIDmode)
1764 mem_mode = GET_MODE (mem);
1766 x_addr = get_addr (XEXP (x, 0));
1767 mem_addr = get_addr (XEXP (mem, 0));
1769 base = find_base_term (x_addr);
1770 if (base && (GET_CODE (base) == LABEL_REF
1771 || (GET_CODE (base) == SYMBOL_REF
1772 && CONSTANT_POOL_ADDRESS_P (base))))
1775 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1778 x_addr = canon_rtx (x_addr);
1779 mem_addr = canon_rtx (mem_addr);
1781 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1782 SIZE_FOR_MODE (x), x_addr, 0))
1785 if (aliases_everything_p (x))
1788 /* We cannot use aliases_everyting_p to test MEM, since we must look
1789 at MEM_MODE, rather than GET_MODE (MEM). */
1790 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1793 /* In true_dependence we also allow BLKmode to alias anything. Why
1794 don't we do this in anti_dependence and output_dependence? */
1795 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1798 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1802 /* Canonical true dependence: X is read after store in MEM takes place.
1803 Variant of true_dependece which assumes MEM has already been
1804 canonicalized (hence we no longer do that here).
1805 The mem_addr argument has been added, since true_dependence computed
1806 this value prior to canonicalizing. */
1809 canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
1810 rtx mem, mem_addr, x;
1811 enum machine_mode mem_mode;
1812 int (*varies) PARAMS ((rtx, int));
1814 register rtx x_addr;
1816 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1819 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1822 /* If X is an unchanging read, then it can't possibly conflict with any
1823 non-unchanging store. It may conflict with an unchanging write though,
1824 because there may be a single store to this address to initialize it.
1825 Just fall through to the code below to resolve the case where we have
1826 both an unchanging read and an unchanging write. This won't handle all
1827 cases optimally, but the possible performance loss should be
1829 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1832 x_addr = get_addr (XEXP (x, 0));
1834 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1837 x_addr = canon_rtx (x_addr);
1838 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1839 SIZE_FOR_MODE (x), x_addr, 0))
1842 if (aliases_everything_p (x))
1845 /* We cannot use aliases_everyting_p to test MEM, since we must look
1846 at MEM_MODE, rather than GET_MODE (MEM). */
1847 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1850 /* In true_dependence we also allow BLKmode to alias anything. Why
1851 don't we do this in anti_dependence and output_dependence? */
1852 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1855 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1859 /* Returns non-zero if a write to X might alias a previous read from
1860 (or, if WRITEP is non-zero, a write to) MEM. */
1863 write_dependence_p (mem, x, writep)
1868 rtx x_addr, mem_addr;
1872 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1875 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1878 /* Unchanging memory can't conflict with non-unchanging memory. */
1879 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1882 /* If MEM is an unchanging read, then it can't possibly conflict with
1883 the store to X, because there is at most one store to MEM, and it must
1884 have occurred somewhere before MEM. */
1885 if (! writep && RTX_UNCHANGING_P (mem))
1888 x_addr = get_addr (XEXP (x, 0));
1889 mem_addr = get_addr (XEXP (mem, 0));
1893 base = find_base_term (mem_addr);
1894 if (base && (GET_CODE (base) == LABEL_REF
1895 || (GET_CODE (base) == SYMBOL_REF
1896 && CONSTANT_POOL_ADDRESS_P (base))))
1900 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1904 x_addr = canon_rtx (x_addr);
1905 mem_addr = canon_rtx (mem_addr);
1907 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1908 SIZE_FOR_MODE (x), x_addr, 0))
1912 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1915 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1916 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1919 /* Anti dependence: X is written after read in MEM takes place. */
1922 anti_dependence (mem, x)
1926 return write_dependence_p (mem, x, /*writep=*/0);
1929 /* Output dependence: X is written after store in MEM takes place. */
1932 output_dependence (mem, x)
1936 return write_dependence_p (mem, x, /*writep=*/1);
1939 /* Returns non-zero if X mentions something which is not
1940 local to the function and is not constant. */
1943 nonlocal_mentioned_p (x)
1947 register RTX_CODE code;
1950 code = GET_CODE (x);
1952 if (GET_RTX_CLASS (code) == 'i')
1954 /* Constant functions can be constant if they don't use
1955 scratch memory used to mark function w/o side effects. */
1956 if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x))
1958 x = CALL_INSN_FUNCTION_USAGE (x);
1964 code = GET_CODE (x);
1970 if (GET_CODE (SUBREG_REG (x)) == REG)
1972 /* Global registers are not local. */
1973 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1974 && global_regs[subreg_regno (x)])
1982 /* Global registers are not local. */
1983 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1997 /* Constants in the function's constants pool are constant. */
1998 if (CONSTANT_POOL_ADDRESS_P (x))
2003 /* Non-constant calls and recursion are not local. */
2007 /* Be overly conservative and consider any volatile memory
2008 reference as not local. */
2009 if (MEM_VOLATILE_P (x))
2011 base = find_base_term (XEXP (x, 0));
2014 /* A Pmode ADDRESS could be a reference via the structure value
2015 address or static chain. Such memory references are nonlocal.
2017 Thus, we have to examine the contents of the ADDRESS to find
2018 out if this is a local reference or not. */
2019 if (GET_CODE (base) == ADDRESS
2020 && GET_MODE (base) == Pmode
2021 && (XEXP (base, 0) == stack_pointer_rtx
2022 || XEXP (base, 0) == arg_pointer_rtx
2023 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2024 || XEXP (base, 0) == hard_frame_pointer_rtx
2026 || XEXP (base, 0) == frame_pointer_rtx))
2028 /* Constants in the function's constant pool are constant. */
2029 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
2034 case UNSPEC_VOLATILE:
2039 if (MEM_VOLATILE_P (x))
2048 /* Recursively scan the operands of this expression. */
2051 register const char *fmt = GET_RTX_FORMAT (code);
2054 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
2056 if (fmt[i] == 'e' && XEXP (x, i))
2058 if (nonlocal_mentioned_p (XEXP (x, i)))
2061 else if (fmt[i] == 'E')
2064 for (j = 0; j < XVECLEN (x, i); j++)
2065 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
2074 /* Mark the function if it is constant. */
2077 mark_constant_function ()
2080 int nonlocal_mentioned;
2082 if (TREE_PUBLIC (current_function_decl)
2083 || TREE_READONLY (current_function_decl)
2084 || DECL_IS_PURE (current_function_decl)
2085 || TREE_THIS_VOLATILE (current_function_decl)
2086 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
2089 /* A loop might not return which counts as a side effect. */
2090 if (mark_dfs_back_edges ())
2093 nonlocal_mentioned = 0;
2095 init_alias_analysis ();
2097 /* Determine if this is a constant function. */
2099 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2100 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
2102 nonlocal_mentioned = 1;
2106 end_alias_analysis ();
2108 /* Mark the function. */
2110 if (! nonlocal_mentioned)
2111 TREE_READONLY (current_function_decl) = 1;
2115 static HARD_REG_SET argument_registers;
2122 #ifndef OUTGOING_REGNO
2123 #define OUTGOING_REGNO(N) N
2125 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2126 /* Check whether this register can hold an incoming pointer
2127 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2128 numbers, so translate if necessary due to register windows. */
2129 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2130 && HARD_REGNO_MODE_OK (i, Pmode))
2131 SET_HARD_REG_BIT (argument_registers, i);
2133 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2136 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2140 init_alias_analysis ()
2142 int maxreg = max_reg_num ();
2145 register unsigned int ui;
2148 reg_known_value_size = maxreg;
2151 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2152 - FIRST_PSEUDO_REGISTER;
2154 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2155 - FIRST_PSEUDO_REGISTER;
2157 /* Overallocate reg_base_value to allow some growth during loop
2158 optimization. Loop unrolling can create a large number of
2160 reg_base_value_size = maxreg * 2;
2161 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2162 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2164 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2165 reg_seen = (char *) xmalloc (reg_base_value_size);
2166 if (! reload_completed && flag_unroll_loops)
2168 /* ??? Why are we realloc'ing if we're just going to zero it? */
2169 alias_invariant = (rtx *)xrealloc (alias_invariant,
2170 reg_base_value_size * sizeof (rtx));
2171 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2174 /* The basic idea is that each pass through this loop will use the
2175 "constant" information from the previous pass to propagate alias
2176 information through another level of assignments.
2178 This could get expensive if the assignment chains are long. Maybe
2179 we should throttle the number of iterations, possibly based on
2180 the optimization level or flag_expensive_optimizations.
2182 We could propagate more information in the first pass by making use
2183 of REG_N_SETS to determine immediately that the alias information
2184 for a pseudo is "constant".
2186 A program with an uninitialized variable can cause an infinite loop
2187 here. Instead of doing a full dataflow analysis to detect such problems
2188 we just cap the number of iterations for the loop.
2190 The state of the arrays for the set chain in question does not matter
2191 since the program has undefined behavior. */
2196 /* Assume nothing will change this iteration of the loop. */
2199 /* We want to assign the same IDs each iteration of this loop, so
2200 start counting from zero each iteration of the loop. */
2203 /* We're at the start of the funtion each iteration through the
2204 loop, so we're copying arguments. */
2205 copying_arguments = 1;
2207 /* Wipe the potential alias information clean for this pass. */
2208 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2210 /* Wipe the reg_seen array clean. */
2211 memset ((char *) reg_seen, 0, reg_base_value_size);
2213 /* Mark all hard registers which may contain an address.
2214 The stack, frame and argument pointers may contain an address.
2215 An argument register which can hold a Pmode value may contain
2216 an address even if it is not in BASE_REGS.
2218 The address expression is VOIDmode for an argument and
2219 Pmode for other registers. */
2221 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2222 if (TEST_HARD_REG_BIT (argument_registers, i))
2223 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2224 gen_rtx_REG (Pmode, i));
2226 new_reg_base_value[STACK_POINTER_REGNUM]
2227 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2228 new_reg_base_value[ARG_POINTER_REGNUM]
2229 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2230 new_reg_base_value[FRAME_POINTER_REGNUM]
2231 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2232 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2233 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2234 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2237 /* Walk the insns adding values to the new_reg_base_value array. */
2238 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2244 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2245 /* The prologue/epilouge insns are not threaded onto the
2246 insn chain until after reload has completed. Thus,
2247 there is no sense wasting time checking if INSN is in
2248 the prologue/epilogue until after reload has completed. */
2249 if (reload_completed
2250 && prologue_epilogue_contains (insn))
2254 /* If this insn has a noalias note, process it, Otherwise,
2255 scan for sets. A simple set will have no side effects
2256 which could change the base value of any other register. */
2258 if (GET_CODE (PATTERN (insn)) == SET
2259 && REG_NOTES (insn) != 0
2260 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2261 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2263 note_stores (PATTERN (insn), record_set, NULL);
2265 set = single_set (insn);
2268 && GET_CODE (SET_DEST (set)) == REG
2269 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
2271 unsigned int regno = REGNO (SET_DEST (set));
2272 rtx src = SET_SRC (set);
2274 if (REG_NOTES (insn) != 0
2275 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2276 && REG_N_SETS (regno) == 1)
2277 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2278 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2279 && ! rtx_varies_p (XEXP (note, 0), 1)
2280 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2282 reg_known_value[regno] = XEXP (note, 0);
2283 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2285 else if (REG_N_SETS (regno) == 1
2286 && GET_CODE (src) == PLUS
2287 && GET_CODE (XEXP (src, 0)) == REG
2288 && REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
2289 && (reg_known_value[REGNO (XEXP (src, 0))])
2290 && GET_CODE (XEXP (src, 1)) == CONST_INT)
2292 rtx op0 = XEXP (src, 0);
2293 op0 = reg_known_value[REGNO (op0)];
2294 reg_known_value[regno]
2295 = plus_constant (op0, INTVAL (XEXP (src, 1)));
2296 reg_known_equiv_p[regno] = 0;
2298 else if (REG_N_SETS (regno) == 1
2299 && ! rtx_varies_p (src, 1))
2301 reg_known_value[regno] = src;
2302 reg_known_equiv_p[regno] = 0;
2306 else if (GET_CODE (insn) == NOTE
2307 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2308 copying_arguments = 0;
2311 /* Now propagate values from new_reg_base_value to reg_base_value. */
2312 for (ui = 0; ui < reg_base_value_size; ui++)
2314 if (new_reg_base_value[ui]
2315 && new_reg_base_value[ui] != reg_base_value[ui]
2316 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2318 reg_base_value[ui] = new_reg_base_value[ui];
2323 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2325 /* Fill in the remaining entries. */
2326 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2327 if (reg_known_value[i] == 0)
2328 reg_known_value[i] = regno_reg_rtx[i];
2330 /* Simplify the reg_base_value array so that no register refers to
2331 another register, except to special registers indirectly through
2332 ADDRESS expressions.
2334 In theory this loop can take as long as O(registers^2), but unless
2335 there are very long dependency chains it will run in close to linear
2338 This loop may not be needed any longer now that the main loop does
2339 a better job at propagating alias information. */
2345 for (ui = 0; ui < reg_base_value_size; ui++)
2347 rtx base = reg_base_value[ui];
2348 if (base && GET_CODE (base) == REG)
2350 unsigned int base_regno = REGNO (base);
2351 if (base_regno == ui) /* register set from itself */
2352 reg_base_value[ui] = 0;
2354 reg_base_value[ui] = reg_base_value[base_regno];
2359 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2362 free (new_reg_base_value);
2363 new_reg_base_value = 0;
2369 end_alias_analysis ()
2371 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2372 reg_known_value = 0;
2373 reg_known_value_size = 0;
2374 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2375 reg_known_equiv_p = 0;
2378 ggc_del_root (reg_base_value);
2379 free (reg_base_value);
2382 reg_base_value_size = 0;
2383 if (alias_invariant)
2385 free (alias_invariant);
2386 alias_invariant = 0;