1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003
3 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 2, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to the Free
20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
25 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
46 /* The alias sets assigned to MEMs assist the back-end in determining
47 which MEMs can alias which other MEMs. In general, two MEMs in
48 different alias sets cannot alias each other, with one important
49 exception. Consider something like:
51 struct S {int i; double d; };
53 a store to an `S' can alias something of either type `int' or type
54 `double'. (However, a store to an `int' cannot alias a `double'
55 and vice versa.) We indicate this via a tree structure that looks
63 (The arrows are directed and point downwards.)
64 In this situation we say the alias set for `struct S' is the
65 `superset' and that those for `int' and `double' are `subsets'.
67 To see whether two alias sets can point to the same memory, we must
68 see if either alias set is a subset of the other. We need not trace
69 past immediate descendants, however, since we propagate all
70 grandchildren up one level.
72 Alias set zero is implicitly a superset of all other alias sets.
73 However, this is no actual entry for alias set zero. It is an
74 error to attempt to explicitly construct a subset of zero. */
76 typedef struct alias_set_entry
78 /* The alias set number, as stored in MEM_ALIAS_SET. */
79 HOST_WIDE_INT alias_set
;
81 /* The children of the alias set. These are not just the immediate
82 children, but, in fact, all descendants. So, if we have:
84 struct T { struct S s; float f; }
86 continuing our example above, the children here will be all of
87 `int', `double', `float', and `struct S'. */
90 /* Nonzero if would have a child of zero: this effectively makes this
91 alias set the same as alias set zero. */
95 static int rtx_equal_for_memref_p
PARAMS ((rtx
, rtx
));
96 static rtx find_symbolic_term
PARAMS ((rtx
));
97 rtx get_addr
PARAMS ((rtx
));
98 static int memrefs_conflict_p
PARAMS ((int, rtx
, int, rtx
,
100 static void record_set
PARAMS ((rtx
, rtx
, void *));
101 static int base_alias_check
PARAMS ((rtx
, rtx
, enum machine_mode
,
103 static rtx find_base_value
PARAMS ((rtx
));
104 static int mems_in_disjoint_alias_sets_p
PARAMS ((rtx
, rtx
));
105 static int insert_subset_children
PARAMS ((splay_tree_node
, void*));
106 static tree find_base_decl
PARAMS ((tree
));
107 static alias_set_entry get_alias_set_entry
PARAMS ((HOST_WIDE_INT
));
108 static rtx fixed_scalar_and_varying_struct_p
PARAMS ((rtx
, rtx
, rtx
, rtx
,
109 int (*) (rtx
, int)));
110 static int aliases_everything_p
PARAMS ((rtx
));
111 static bool nonoverlapping_component_refs_p
PARAMS ((tree
, tree
));
112 static tree decl_for_component_ref
PARAMS ((tree
));
113 static rtx adjust_offset_for_component_ref
PARAMS ((tree
, rtx
));
114 static int nonoverlapping_memrefs_p
PARAMS ((rtx
, rtx
));
115 static int write_dependence_p
PARAMS ((rtx
, rtx
, int));
117 static int nonlocal_mentioned_p_1
PARAMS ((rtx
*, void *));
118 static int nonlocal_mentioned_p
PARAMS ((rtx
));
119 static int nonlocal_referenced_p_1
PARAMS ((rtx
*, void *));
120 static int nonlocal_referenced_p
PARAMS ((rtx
));
121 static int nonlocal_set_p_1
PARAMS ((rtx
*, void *));
122 static int nonlocal_set_p
PARAMS ((rtx
));
123 static void memory_modified_1
PARAMS ((rtx
, rtx
, void *));
125 /* Set up all info needed to perform alias analysis on memory references. */
127 /* Returns the size in bytes of the mode of X. */
128 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
130 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
131 different alias sets. We ignore alias sets in functions making use
132 of variable arguments because the va_arg macros on some systems are
134 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
135 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
137 /* Cap the number of passes we make over the insns propagating alias
138 information through set chains. 10 is a completely arbitrary choice. */
139 #define MAX_ALIAS_LOOP_PASSES 10
141 /* reg_base_value[N] gives an address to which register N is related.
142 If all sets after the first add or subtract to the current value
143 or otherwise modify it so it does not point to a different top level
144 object, reg_base_value[N] is equal to the address part of the source
147 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
148 expressions represent certain special values: function arguments and
149 the stack, frame, and argument pointers.
151 The contents of an ADDRESS is not normally used, the mode of the
152 ADDRESS determines whether the ADDRESS is a function argument or some
153 other special value. Pointer equality, not rtx_equal_p, determines whether
154 two ADDRESS expressions refer to the same base address.
156 The only use of the contents of an ADDRESS is for determining if the
157 current function performs nonlocal memory memory references for the
158 purposes of marking the function as a constant function. */
160 static GTY((length ("reg_base_value_size"))) rtx
*reg_base_value
;
161 static rtx
*new_reg_base_value
;
162 static unsigned int reg_base_value_size
; /* size of reg_base_value array */
164 /* Static hunks of RTL used by the aliasing code; these are initialized
165 once per function to avoid unnecessary RTL allocations. */
166 static GTY (()) rtx static_reg_base_value
[FIRST_PSEUDO_REGISTER
];
168 #define REG_BASE_VALUE(X) \
169 (REGNO (X) < reg_base_value_size \
170 ? reg_base_value[REGNO (X)] : 0)
172 /* Vector of known invariant relationships between registers. Set in
173 loop unrolling. Indexed by register number, if nonzero the value
174 is an expression describing this register in terms of another.
176 The length of this array is REG_BASE_VALUE_SIZE.
178 Because this array contains only pseudo registers it has no effect
180 static rtx
*alias_invariant
;
182 /* Vector indexed by N giving the initial (unchanging) value known for
183 pseudo-register N. This array is initialized in
184 init_alias_analysis, and does not change until end_alias_analysis
186 rtx
*reg_known_value
;
188 /* Indicates number of valid entries in reg_known_value. */
189 static unsigned int reg_known_value_size
;
191 /* Vector recording for each reg_known_value whether it is due to a
192 REG_EQUIV note. Future passes (viz., reload) may replace the
193 pseudo with the equivalent expression and so we account for the
194 dependences that would be introduced if that happens.
196 The REG_EQUIV notes created in assign_parms may mention the arg
197 pointer, and there are explicit insns in the RTL that modify the
198 arg pointer. Thus we must ensure that such insns don't get
199 scheduled across each other because that would invalidate the
200 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
201 wrong, but solving the problem in the scheduler will likely give
202 better code, so we do it here. */
203 char *reg_known_equiv_p
;
205 /* True when scanning insns from the start of the rtl to the
206 NOTE_INSN_FUNCTION_BEG note. */
207 static bool copying_arguments
;
209 /* The splay-tree used to store the various alias set entries. */
210 static splay_tree alias_sets
;
212 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
213 such an entry, or NULL otherwise. */
215 static alias_set_entry
216 get_alias_set_entry (alias_set
)
217 HOST_WIDE_INT alias_set
;
220 = splay_tree_lookup (alias_sets
, (splay_tree_key
) alias_set
);
222 return sn
!= 0 ? ((alias_set_entry
) sn
->value
) : 0;
225 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
226 the two MEMs cannot alias each other. */
229 mems_in_disjoint_alias_sets_p (mem1
, mem2
)
233 #ifdef ENABLE_CHECKING
234 /* Perform a basic sanity check. Namely, that there are no alias sets
235 if we're not using strict aliasing. This helps to catch bugs
236 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
237 where a MEM is allocated in some way other than by the use of
238 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
239 use alias sets to indicate that spilled registers cannot alias each
240 other, we might need to remove this check. */
241 if (! flag_strict_aliasing
242 && (MEM_ALIAS_SET (mem1
) != 0 || MEM_ALIAS_SET (mem2
) != 0))
246 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
249 /* Insert the NODE into the splay tree given by DATA. Used by
250 record_alias_subset via splay_tree_foreach. */
253 insert_subset_children (node
, data
)
254 splay_tree_node node
;
257 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
262 /* Return 1 if the two specified alias sets may conflict. */
265 alias_sets_conflict_p (set1
, set2
)
266 HOST_WIDE_INT set1
, set2
;
270 /* If have no alias set information for one of the operands, we have
271 to assume it can alias anything. */
272 if (set1
== 0 || set2
== 0
273 /* If the two alias sets are the same, they may alias. */
277 /* See if the first alias set is a subset of the second. */
278 ase
= get_alias_set_entry (set1
);
280 && (ase
->has_zero_child
281 || splay_tree_lookup (ase
->children
,
282 (splay_tree_key
) set2
)))
285 /* Now do the same, but with the alias sets reversed. */
286 ase
= get_alias_set_entry (set2
);
288 && (ase
->has_zero_child
289 || splay_tree_lookup (ase
->children
,
290 (splay_tree_key
) set1
)))
293 /* The two alias sets are distinct and neither one is the
294 child of the other. Therefore, they cannot alias. */
298 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
299 has any readonly fields. If any of the fields have types that
300 contain readonly fields, return true as well. */
303 readonly_fields_p (type
)
308 if (TREE_CODE (type
) != RECORD_TYPE
&& TREE_CODE (type
) != UNION_TYPE
309 && TREE_CODE (type
) != QUAL_UNION_TYPE
)
312 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
313 if (TREE_CODE (field
) == FIELD_DECL
314 && (TREE_READONLY (field
)
315 || readonly_fields_p (TREE_TYPE (field
))))
321 /* Return 1 if any MEM object of type T1 will always conflict (using the
322 dependency routines in this file) with any MEM object of type T2.
323 This is used when allocating temporary storage. If T1 and/or T2 are
324 NULL_TREE, it means we know nothing about the storage. */
327 objects_must_conflict_p (t1
, t2
)
330 /* If neither has a type specified, we don't know if they'll conflict
331 because we may be using them to store objects of various types, for
332 example the argument and local variables areas of inlined functions. */
333 if (t1
== 0 && t2
== 0)
336 /* If one or the other has readonly fields or is readonly,
337 then they may not conflict. */
338 if ((t1
!= 0 && readonly_fields_p (t1
))
339 || (t2
!= 0 && readonly_fields_p (t2
))
340 || (t1
!= 0 && lang_hooks
.honor_readonly
&& TYPE_READONLY (t1
))
341 || (t2
!= 0 && lang_hooks
.honor_readonly
&& TYPE_READONLY (t2
)))
344 /* If they are the same type, they must conflict. */
346 /* Likewise if both are volatile. */
347 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
350 /* If one is aggregate and the other is scalar then they may not
352 if ((t1
!= 0 && AGGREGATE_TYPE_P (t1
))
353 != (t2
!= 0 && AGGREGATE_TYPE_P (t2
)))
356 /* Otherwise they conflict only if the alias sets conflict. */
357 return alias_sets_conflict_p (t1
? get_alias_set (t1
) : 0,
358 t2
? get_alias_set (t2
) : 0);
361 /* T is an expression with pointer type. Find the DECL on which this
362 expression is based. (For example, in `a[i]' this would be `a'.)
363 If there is no such DECL, or a unique decl cannot be determined,
364 NULL_TREE is returned. */
372 if (t
== 0 || t
== error_mark_node
|| ! POINTER_TYPE_P (TREE_TYPE (t
)))
375 /* If this is a declaration, return it. */
376 if (TREE_CODE_CLASS (TREE_CODE (t
)) == 'd')
379 /* Handle general expressions. It would be nice to deal with
380 COMPONENT_REFs here. If we could tell that `a' and `b' were the
381 same, then `a->f' and `b->f' are also the same. */
382 switch (TREE_CODE_CLASS (TREE_CODE (t
)))
385 return find_base_decl (TREE_OPERAND (t
, 0));
388 /* Return 0 if found in neither or both are the same. */
389 d0
= find_base_decl (TREE_OPERAND (t
, 0));
390 d1
= find_base_decl (TREE_OPERAND (t
, 1));
401 d0
= find_base_decl (TREE_OPERAND (t
, 0));
402 d1
= find_base_decl (TREE_OPERAND (t
, 1));
403 d2
= find_base_decl (TREE_OPERAND (t
, 2));
405 /* Set any nonzero values from the last, then from the first. */
406 if (d1
== 0) d1
= d2
;
407 if (d0
== 0) d0
= d1
;
408 if (d1
== 0) d1
= d0
;
409 if (d2
== 0) d2
= d1
;
411 /* At this point all are nonzero or all are zero. If all three are the
412 same, return it. Otherwise, return zero. */
413 return (d0
== d1
&& d1
== d2
) ? d0
: 0;
420 /* Return 1 if all the nested component references handled by
421 get_inner_reference in T are such that we can address the object in T. */
427 /* If we're at the end, it is vacuously addressable. */
428 if (! handled_component_p (t
))
431 /* Bitfields are never addressable. */
432 else if (TREE_CODE (t
) == BIT_FIELD_REF
)
435 /* Fields are addressable unless they are marked as nonaddressable or
436 the containing type has alias set 0. */
437 else if (TREE_CODE (t
) == COMPONENT_REF
438 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1))
439 && get_alias_set (TREE_TYPE (TREE_OPERAND (t
, 0))) != 0
440 && can_address_p (TREE_OPERAND (t
, 0)))
443 /* Likewise for arrays. */
444 else if ((TREE_CODE (t
) == ARRAY_REF
|| TREE_CODE (t
) == ARRAY_RANGE_REF
)
445 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0)))
446 && get_alias_set (TREE_TYPE (TREE_OPERAND (t
, 0))) != 0
447 && can_address_p (TREE_OPERAND (t
, 0)))
453 /* Return the alias set for T, which may be either a type or an
454 expression. Call language-specific routine for help, if needed. */
462 /* If we're not doing any alias analysis, just assume everything
463 aliases everything else. Also return 0 if this or its type is
465 if (! flag_strict_aliasing
|| t
== error_mark_node
467 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
470 /* We can be passed either an expression or a type. This and the
471 language-specific routine may make mutually-recursive calls to each other
472 to figure out what to do. At each juncture, we see if this is a tree
473 that the language may need to handle specially. First handle things that
478 tree placeholder_ptr
= 0;
480 /* Remove any nops, then give the language a chance to do
481 something with this tree before we look at it. */
483 set
= (*lang_hooks
.get_alias_set
) (t
);
487 /* First see if the actual object referenced is an INDIRECT_REF from a
488 restrict-qualified pointer or a "void *". Replace
489 PLACEHOLDER_EXPRs. */
490 while (TREE_CODE (inner
) == PLACEHOLDER_EXPR
491 || handled_component_p (inner
))
493 if (TREE_CODE (inner
) == PLACEHOLDER_EXPR
)
494 inner
= find_placeholder (inner
, &placeholder_ptr
);
496 inner
= TREE_OPERAND (inner
, 0);
501 /* Check for accesses through restrict-qualified pointers. */
502 if (TREE_CODE (inner
) == INDIRECT_REF
)
504 tree decl
= find_base_decl (TREE_OPERAND (inner
, 0));
506 if (decl
&& DECL_POINTER_ALIAS_SET_KNOWN_P (decl
))
508 /* If we haven't computed the actual alias set, do it now. */
509 if (DECL_POINTER_ALIAS_SET (decl
) == -2)
511 /* No two restricted pointers can point at the same thing.
512 However, a restricted pointer can point at the same thing
513 as an unrestricted pointer, if that unrestricted pointer
514 is based on the restricted pointer. So, we make the
515 alias set for the restricted pointer a subset of the
516 alias set for the type pointed to by the type of the
518 HOST_WIDE_INT pointed_to_alias_set
519 = get_alias_set (TREE_TYPE (TREE_TYPE (decl
)));
521 if (pointed_to_alias_set
== 0)
522 /* It's not legal to make a subset of alias set zero. */
526 DECL_POINTER_ALIAS_SET (decl
) = new_alias_set ();
527 record_alias_subset (pointed_to_alias_set
,
528 DECL_POINTER_ALIAS_SET (decl
));
532 /* We use the alias set indicated in the declaration. */
533 return DECL_POINTER_ALIAS_SET (decl
);
536 /* If we have an INDIRECT_REF via a void pointer, we don't
537 know anything about what that might alias. */
538 else if (TREE_CODE (TREE_TYPE (inner
)) == VOID_TYPE
)
542 /* Otherwise, pick up the outermost object that we could have a pointer
543 to, processing conversion and PLACEHOLDER_EXPR as above. */
545 while (TREE_CODE (t
) == PLACEHOLDER_EXPR
546 || (handled_component_p (t
) && ! can_address_p (t
)))
548 if (TREE_CODE (t
) == PLACEHOLDER_EXPR
)
549 t
= find_placeholder (t
, &placeholder_ptr
);
551 t
= TREE_OPERAND (t
, 0);
556 /* If we've already determined the alias set for a decl, just return
557 it. This is necessary for C++ anonymous unions, whose component
558 variables don't look like union members (boo!). */
559 if (TREE_CODE (t
) == VAR_DECL
560 && DECL_RTL_SET_P (t
) && GET_CODE (DECL_RTL (t
)) == MEM
)
561 return MEM_ALIAS_SET (DECL_RTL (t
));
563 /* Now all we care about is the type. */
567 /* Variant qualifiers don't affect the alias set, so get the main
568 variant. If this is a type with a known alias set, return it. */
569 t
= TYPE_MAIN_VARIANT (t
);
570 if (TYPE_ALIAS_SET_KNOWN_P (t
))
571 return TYPE_ALIAS_SET (t
);
573 /* See if the language has special handling for this type. */
574 set
= (*lang_hooks
.get_alias_set
) (t
);
578 /* There are no objects of FUNCTION_TYPE, so there's no point in
579 using up an alias set for them. (There are, of course, pointers
580 and references to functions, but that's different.) */
581 else if (TREE_CODE (t
) == FUNCTION_TYPE
)
584 /* Unless the language specifies otherwise, let vector types alias
585 their components. This avoids some nasty type punning issues in
586 normal usage. And indeed lets vectors be treated more like an
588 else if (TREE_CODE (t
) == VECTOR_TYPE
)
589 set
= get_alias_set (TREE_TYPE (t
));
592 /* Otherwise make a new alias set for this type. */
593 set
= new_alias_set ();
595 TYPE_ALIAS_SET (t
) = set
;
597 /* If this is an aggregate type, we must record any component aliasing
599 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
600 record_component_aliases (t
);
605 /* Return a brand-new alias set. */
610 static HOST_WIDE_INT last_alias_set
;
612 if (flag_strict_aliasing
)
613 return ++last_alias_set
;
618 /* Indicate that things in SUBSET can alias things in SUPERSET, but
619 not vice versa. For example, in C, a store to an `int' can alias a
620 structure containing an `int', but not vice versa. Here, the
621 structure would be the SUPERSET and `int' the SUBSET. This
622 function should be called only once per SUPERSET/SUBSET pair.
624 It is illegal for SUPERSET to be zero; everything is implicitly a
625 subset of alias set zero. */
628 record_alias_subset (superset
, subset
)
629 HOST_WIDE_INT superset
;
630 HOST_WIDE_INT subset
;
632 alias_set_entry superset_entry
;
633 alias_set_entry subset_entry
;
635 /* It is possible in complex type situations for both sets to be the same,
636 in which case we can ignore this operation. */
637 if (superset
== subset
)
643 superset_entry
= get_alias_set_entry (superset
);
644 if (superset_entry
== 0)
646 /* Create an entry for the SUPERSET, so that we have a place to
647 attach the SUBSET. */
649 = (alias_set_entry
) xmalloc (sizeof (struct alias_set_entry
));
650 superset_entry
->alias_set
= superset
;
651 superset_entry
->children
652 = splay_tree_new (splay_tree_compare_ints
, 0, 0);
653 superset_entry
->has_zero_child
= 0;
654 splay_tree_insert (alias_sets
, (splay_tree_key
) superset
,
655 (splay_tree_value
) superset_entry
);
659 superset_entry
->has_zero_child
= 1;
662 subset_entry
= get_alias_set_entry (subset
);
663 /* If there is an entry for the subset, enter all of its children
664 (if they are not already present) as children of the SUPERSET. */
667 if (subset_entry
->has_zero_child
)
668 superset_entry
->has_zero_child
= 1;
670 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
671 superset_entry
->children
);
674 /* Enter the SUBSET itself as a child of the SUPERSET. */
675 splay_tree_insert (superset_entry
->children
,
676 (splay_tree_key
) subset
, 0);
680 /* Record that component types of TYPE, if any, are part of that type for
681 aliasing purposes. For record types, we only record component types
682 for fields that are marked addressable. For array types, we always
683 record the component types, so the front end should not call this
684 function if the individual component aren't addressable. */
687 record_component_aliases (type
)
690 HOST_WIDE_INT superset
= get_alias_set (type
);
696 switch (TREE_CODE (type
))
699 if (! TYPE_NONALIASED_COMPONENT (type
))
700 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
705 case QUAL_UNION_TYPE
:
706 /* Recursively record aliases for the base classes, if there are any */
707 if (TYPE_BINFO (type
) != NULL
&& TYPE_BINFO_BASETYPES (type
) != NULL
)
710 for (i
= 0; i
< TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type
)); i
++)
712 tree binfo
= TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type
), i
);
713 record_alias_subset (superset
,
714 get_alias_set (BINFO_TYPE (binfo
)));
717 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
718 if (TREE_CODE (field
) == FIELD_DECL
&& ! DECL_NONADDRESSABLE_P (field
))
719 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
723 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
731 /* Allocate an alias set for use in storing and reading from the varargs
735 get_varargs_alias_set ()
737 static HOST_WIDE_INT set
= -1;
740 set
= new_alias_set ();
745 /* Likewise, but used for the fixed portions of the frame, e.g., register
749 get_frame_alias_set ()
751 static HOST_WIDE_INT set
= -1;
754 set
= new_alias_set ();
759 /* Inside SRC, the source of a SET, find a base address. */
762 find_base_value (src
)
767 switch (GET_CODE (src
))
775 /* At the start of a function, argument registers have known base
776 values which may be lost later. Returning an ADDRESS
777 expression here allows optimization based on argument values
778 even when the argument registers are used for other purposes. */
779 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
780 return new_reg_base_value
[regno
];
782 /* If a pseudo has a known base value, return it. Do not do this
783 for non-fixed hard regs since it can result in a circular
784 dependency chain for registers which have values at function entry.
786 The test above is not sufficient because the scheduler may move
787 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
788 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
789 && regno
< reg_base_value_size
)
791 /* If we're inside init_alias_analysis, use new_reg_base_value
792 to reduce the number of relaxation iterations. */
793 if (new_reg_base_value
&& new_reg_base_value
[regno
]
794 && REG_N_SETS (regno
) == 1)
795 return new_reg_base_value
[regno
];
797 if (reg_base_value
[regno
])
798 return reg_base_value
[regno
];
804 /* Check for an argument passed in memory. Only record in the
805 copying-arguments block; it is too hard to track changes
807 if (copying_arguments
808 && (XEXP (src
, 0) == arg_pointer_rtx
809 || (GET_CODE (XEXP (src
, 0)) == PLUS
810 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
811 return gen_rtx_ADDRESS (VOIDmode
, src
);
816 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
819 /* ... fall through ... */
824 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
826 /* If either operand is a REG that is a known pointer, then it
828 if (REG_P (src_0
) && REG_POINTER (src_0
))
829 return find_base_value (src_0
);
830 if (REG_P (src_1
) && REG_POINTER (src_1
))
831 return find_base_value (src_1
);
833 /* If either operand is a REG, then see if we already have
834 a known value for it. */
837 temp
= find_base_value (src_0
);
844 temp
= find_base_value (src_1
);
849 /* If either base is named object or a special address
850 (like an argument or stack reference), then use it for the
853 && (GET_CODE (src_0
) == SYMBOL_REF
854 || GET_CODE (src_0
) == LABEL_REF
855 || (GET_CODE (src_0
) == ADDRESS
856 && GET_MODE (src_0
) != VOIDmode
)))
860 && (GET_CODE (src_1
) == SYMBOL_REF
861 || GET_CODE (src_1
) == LABEL_REF
862 || (GET_CODE (src_1
) == ADDRESS
863 && GET_MODE (src_1
) != VOIDmode
)))
866 /* Guess which operand is the base address:
867 If either operand is a symbol, then it is the base. If
868 either operand is a CONST_INT, then the other is the base. */
869 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
870 return find_base_value (src_0
);
871 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
872 return find_base_value (src_1
);
878 /* The standard form is (lo_sum reg sym) so look only at the
880 return find_base_value (XEXP (src
, 1));
883 /* If the second operand is constant set the base
884 address to the first operand. */
885 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
886 return find_base_value (XEXP (src
, 0));
890 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
900 return find_base_value (XEXP (src
, 0));
903 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
905 rtx temp
= find_base_value (XEXP (src
, 0));
907 #ifdef POINTERS_EXTEND_UNSIGNED
908 if (temp
!= 0 && CONSTANT_P (temp
) && GET_MODE (temp
) != Pmode
)
909 temp
= convert_memory_address (Pmode
, temp
);
922 /* Called from init_alias_analysis indirectly through note_stores. */
924 /* While scanning insns to find base values, reg_seen[N] is nonzero if
925 register N has been set in this function. */
926 static char *reg_seen
;
928 /* Addresses which are known not to alias anything else are identified
929 by a unique integer. */
930 static int unique_id
;
933 record_set (dest
, set
, data
)
935 void *data ATTRIBUTE_UNUSED
;
941 if (GET_CODE (dest
) != REG
)
944 regno
= REGNO (dest
);
946 if (regno
>= reg_base_value_size
)
949 /* If this spans multiple hard registers, then we must indicate that every
950 register has an unusable value. */
951 if (regno
< FIRST_PSEUDO_REGISTER
)
952 n
= HARD_REGNO_NREGS (regno
, GET_MODE (dest
));
959 reg_seen
[regno
+ n
] = 1;
960 new_reg_base_value
[regno
+ n
] = 0;
967 /* A CLOBBER wipes out any old value but does not prevent a previously
968 unset register from acquiring a base address (i.e. reg_seen is not
970 if (GET_CODE (set
) == CLOBBER
)
972 new_reg_base_value
[regno
] = 0;
981 new_reg_base_value
[regno
] = 0;
985 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
986 GEN_INT (unique_id
++));
990 /* This is not the first set. If the new value is not related to the
991 old value, forget the base value. Note that the following code is
993 extern int x, y; int *p = &x; p += (&y-&x);
994 ANSI C does not allow computing the difference of addresses
995 of distinct top level objects. */
996 if (new_reg_base_value
[regno
])
997 switch (GET_CODE (src
))
1001 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1002 new_reg_base_value
[regno
] = 0;
1005 /* If the value we add in the PLUS is also a valid base value,
1006 this might be the actual base value, and the original value
1009 rtx other
= NULL_RTX
;
1011 if (XEXP (src
, 0) == dest
)
1012 other
= XEXP (src
, 1);
1013 else if (XEXP (src
, 1) == dest
)
1014 other
= XEXP (src
, 0);
1016 if (! other
|| find_base_value (other
))
1017 new_reg_base_value
[regno
] = 0;
1021 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
1022 new_reg_base_value
[regno
] = 0;
1025 new_reg_base_value
[regno
] = 0;
1028 /* If this is the first set of a register, record the value. */
1029 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1030 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1031 new_reg_base_value
[regno
] = find_base_value (src
);
1033 reg_seen
[regno
] = 1;
1036 /* Called from loop optimization when a new pseudo-register is
1037 created. It indicates that REGNO is being set to VAL. f INVARIANT
1038 is true then this value also describes an invariant relationship
1039 which can be used to deduce that two registers with unknown values
1043 record_base_value (regno
, val
, invariant
)
1048 if (regno
>= reg_base_value_size
)
1051 if (invariant
&& alias_invariant
)
1052 alias_invariant
[regno
] = val
;
1054 if (GET_CODE (val
) == REG
)
1056 if (REGNO (val
) < reg_base_value_size
)
1057 reg_base_value
[regno
] = reg_base_value
[REGNO (val
)];
1062 reg_base_value
[regno
] = find_base_value (val
);
1065 /* Clear alias info for a register. This is used if an RTL transformation
1066 changes the value of a register. This is used in flow by AUTO_INC_DEC
1067 optimizations. We don't need to clear reg_base_value, since flow only
1068 changes the offset. */
1071 clear_reg_alias_info (reg
)
1074 unsigned int regno
= REGNO (reg
);
1076 if (regno
< reg_known_value_size
&& regno
>= FIRST_PSEUDO_REGISTER
)
1077 reg_known_value
[regno
] = reg
;
1080 /* Returns a canonical version of X, from the point of view alias
1081 analysis. (For example, if X is a MEM whose address is a register,
1082 and the register has a known value (say a SYMBOL_REF), then a MEM
1083 whose address is the SYMBOL_REF is returned.) */
1089 /* Recursively look for equivalences. */
1090 if (GET_CODE (x
) == REG
&& REGNO (x
) >= FIRST_PSEUDO_REGISTER
1091 && REGNO (x
) < reg_known_value_size
)
1092 return reg_known_value
[REGNO (x
)] == x
1093 ? x
: canon_rtx (reg_known_value
[REGNO (x
)]);
1094 else if (GET_CODE (x
) == PLUS
)
1096 rtx x0
= canon_rtx (XEXP (x
, 0));
1097 rtx x1
= canon_rtx (XEXP (x
, 1));
1099 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1101 if (GET_CODE (x0
) == CONST_INT
)
1102 return plus_constant (x1
, INTVAL (x0
));
1103 else if (GET_CODE (x1
) == CONST_INT
)
1104 return plus_constant (x0
, INTVAL (x1
));
1105 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1109 /* This gives us much better alias analysis when called from
1110 the loop optimizer. Note we want to leave the original
1111 MEM alone, but need to return the canonicalized MEM with
1112 all the flags with their original values. */
1113 else if (GET_CODE (x
) == MEM
)
1114 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1119 /* Return 1 if X and Y are identical-looking rtx's.
1120 Expect that X and Y has been already canonicalized.
1122 We use the data in reg_known_value above to see if two registers with
1123 different numbers are, in fact, equivalent. */
1126 rtx_equal_for_memref_p (x
, y
)
1134 if (x
== 0 && y
== 0)
1136 if (x
== 0 || y
== 0)
1142 code
= GET_CODE (x
);
1143 /* Rtx's of different codes cannot be equal. */
1144 if (code
!= GET_CODE (y
))
1147 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1148 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1150 if (GET_MODE (x
) != GET_MODE (y
))
1153 /* Some RTL can be compared without a recursive examination. */
1157 return CSELIB_VAL_PTR (x
) == CSELIB_VAL_PTR (y
);
1160 return REGNO (x
) == REGNO (y
);
1163 return XEXP (x
, 0) == XEXP (y
, 0);
1166 return XSTR (x
, 0) == XSTR (y
, 0);
1170 /* There's no need to compare the contents of CONST_DOUBLEs or
1171 CONST_INTs because pointer equality is a good enough
1172 comparison for these nodes. */
1176 return (XINT (x
, 1) == XINT (y
, 1)
1177 && rtx_equal_for_memref_p (XEXP (x
, 0),
1184 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1186 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1187 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1188 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1189 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1190 /* For commutative operations, the RTX match if the operand match in any
1191 order. Also handle the simple binary and unary cases without a loop. */
1192 if (code
== EQ
|| code
== NE
|| GET_RTX_CLASS (code
) == 'c')
1194 rtx xop0
= canon_rtx (XEXP (x
, 0));
1195 rtx yop0
= canon_rtx (XEXP (y
, 0));
1196 rtx yop1
= canon_rtx (XEXP (y
, 1));
1198 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1199 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1200 || (rtx_equal_for_memref_p (xop0
, yop1
)
1201 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1203 else if (GET_RTX_CLASS (code
) == '<' || GET_RTX_CLASS (code
) == '2')
1205 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1206 canon_rtx (XEXP (y
, 0)))
1207 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1208 canon_rtx (XEXP (y
, 1))));
1210 else if (GET_RTX_CLASS (code
) == '1')
1211 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1212 canon_rtx (XEXP (y
, 0)));
1214 /* Compare the elements. If any pair of corresponding elements
1215 fail to match, return 0 for the whole things.
1217 Limit cases to types which actually appear in addresses. */
1219 fmt
= GET_RTX_FORMAT (code
);
1220 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1225 if (XINT (x
, i
) != XINT (y
, i
))
1230 /* Two vectors must have the same length. */
1231 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1234 /* And the corresponding elements must match. */
1235 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1236 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1237 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1242 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1243 canon_rtx (XEXP (y
, i
))) == 0)
1247 /* This can happen for asm operands. */
1249 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1253 /* This can happen for an asm which clobbers memory. */
1257 /* It is believed that rtx's at this level will never
1258 contain anything but integers and other rtx's,
1259 except for within LABEL_REFs and SYMBOL_REFs. */
1267 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1268 X and return it, or return 0 if none found. */
1271 find_symbolic_term (x
)
1278 code
= GET_CODE (x
);
1279 if (code
== SYMBOL_REF
|| code
== LABEL_REF
)
1281 if (GET_RTX_CLASS (code
) == 'o')
1284 fmt
= GET_RTX_FORMAT (code
);
1285 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1291 t
= find_symbolic_term (XEXP (x
, i
));
1295 else if (fmt
[i
] == 'E')
1306 struct elt_loc_list
*l
;
1308 #if defined (FIND_BASE_TERM)
1309 /* Try machine-dependent ways to find the base term. */
1310 x
= FIND_BASE_TERM (x
);
1313 switch (GET_CODE (x
))
1316 return REG_BASE_VALUE (x
);
1319 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1329 return find_base_term (XEXP (x
, 0));
1332 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1334 rtx temp
= find_base_term (XEXP (x
, 0));
1336 #ifdef POINTERS_EXTEND_UNSIGNED
1337 if (temp
!= 0 && CONSTANT_P (temp
) && GET_MODE (temp
) != Pmode
)
1338 temp
= convert_memory_address (Pmode
, temp
);
1345 val
= CSELIB_VAL_PTR (x
);
1346 for (l
= val
->locs
; l
; l
= l
->next
)
1347 if ((x
= find_base_term (l
->loc
)) != 0)
1353 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1360 rtx tmp1
= XEXP (x
, 0);
1361 rtx tmp2
= XEXP (x
, 1);
1363 /* This is a little bit tricky since we have to determine which of
1364 the two operands represents the real base address. Otherwise this
1365 routine may return the index register instead of the base register.
1367 That may cause us to believe no aliasing was possible, when in
1368 fact aliasing is possible.
1370 We use a few simple tests to guess the base register. Additional
1371 tests can certainly be added. For example, if one of the operands
1372 is a shift or multiply, then it must be the index register and the
1373 other operand is the base register. */
1375 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1376 return find_base_term (tmp2
);
1378 /* If either operand is known to be a pointer, then use it
1379 to determine the base term. */
1380 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1381 return find_base_term (tmp1
);
1383 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1384 return find_base_term (tmp2
);
1386 /* Neither operand was known to be a pointer. Go ahead and find the
1387 base term for both operands. */
1388 tmp1
= find_base_term (tmp1
);
1389 tmp2
= find_base_term (tmp2
);
1391 /* If either base term is named object or a special address
1392 (like an argument or stack reference), then use it for the
1395 && (GET_CODE (tmp1
) == SYMBOL_REF
1396 || GET_CODE (tmp1
) == LABEL_REF
1397 || (GET_CODE (tmp1
) == ADDRESS
1398 && GET_MODE (tmp1
) != VOIDmode
)))
1402 && (GET_CODE (tmp2
) == SYMBOL_REF
1403 || GET_CODE (tmp2
) == LABEL_REF
1404 || (GET_CODE (tmp2
) == ADDRESS
1405 && GET_MODE (tmp2
) != VOIDmode
)))
1408 /* We could not determine which of the two operands was the
1409 base register and which was the index. So we can determine
1410 nothing from the base alias check. */
1415 if (GET_CODE (XEXP (x
, 1)) == CONST_INT
&& INTVAL (XEXP (x
, 1)) != 0)
1416 return find_base_term (XEXP (x
, 0));
1424 return REG_BASE_VALUE (frame_pointer_rtx
);
1431 /* Return 0 if the addresses X and Y are known to point to different
1432 objects, 1 if they might be pointers to the same object. */
1435 base_alias_check (x
, y
, x_mode
, y_mode
)
1437 enum machine_mode x_mode
, y_mode
;
1439 rtx x_base
= find_base_term (x
);
1440 rtx y_base
= find_base_term (y
);
1442 /* If the address itself has no known base see if a known equivalent
1443 value has one. If either address still has no known base, nothing
1444 is known about aliasing. */
1449 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1452 x_base
= find_base_term (x_c
);
1460 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1463 y_base
= find_base_term (y_c
);
1468 /* If the base addresses are equal nothing is known about aliasing. */
1469 if (rtx_equal_p (x_base
, y_base
))
1472 /* The base addresses of the read and write are different expressions.
1473 If they are both symbols and they are not accessed via AND, there is
1474 no conflict. We can bring knowledge of object alignment into play
1475 here. For example, on alpha, "char a, b;" can alias one another,
1476 though "char a; long b;" cannot. */
1477 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1479 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1481 if (GET_CODE (x
) == AND
1482 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1483 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1485 if (GET_CODE (y
) == AND
1486 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1487 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1489 /* Differing symbols never alias. */
1493 /* If one address is a stack reference there can be no alias:
1494 stack references using different base registers do not alias,
1495 a stack reference can not alias a parameter, and a stack reference
1496 can not alias a global. */
1497 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1498 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1501 if (! flag_argument_noalias
)
1504 if (flag_argument_noalias
> 1)
1507 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1508 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1511 /* Convert the address X into something we can use. This is done by returning
1512 it unchanged unless it is a value; in the latter case we call cselib to get
1513 a more useful rtx. */
1520 struct elt_loc_list
*l
;
1522 if (GET_CODE (x
) != VALUE
)
1524 v
= CSELIB_VAL_PTR (x
);
1525 for (l
= v
->locs
; l
; l
= l
->next
)
1526 if (CONSTANT_P (l
->loc
))
1528 for (l
= v
->locs
; l
; l
= l
->next
)
1529 if (GET_CODE (l
->loc
) != REG
&& GET_CODE (l
->loc
) != MEM
)
1532 return v
->locs
->loc
;
1536 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1537 where SIZE is the size in bytes of the memory reference. If ADDR
1538 is not modified by the memory reference then ADDR is returned. */
1541 addr_side_effect_eval (addr
, size
, n_refs
)
1548 switch (GET_CODE (addr
))
1551 offset
= (n_refs
+ 1) * size
;
1554 offset
= -(n_refs
+ 1) * size
;
1557 offset
= n_refs
* size
;
1560 offset
= -n_refs
* size
;
1568 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1571 addr
= XEXP (addr
, 0);
1572 addr
= canon_rtx (addr
);
1577 /* Return nonzero if X and Y (memory addresses) could reference the
1578 same location in memory. C is an offset accumulator. When
1579 C is nonzero, we are testing aliases between X and Y + C.
1580 XSIZE is the size in bytes of the X reference,
1581 similarly YSIZE is the size in bytes for Y.
1582 Expect that canon_rtx has been already called for X and Y.
1584 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1585 referenced (the reference was BLKmode), so make the most pessimistic
1588 If XSIZE or YSIZE is negative, we may access memory outside the object
1589 being referenced as a side effect. This can happen when using AND to
1590 align memory references, as is done on the Alpha.
1592 Nice to notice that varying addresses cannot conflict with fp if no
1593 local variables had their addresses taken, but that's too hard now. */
1596 memrefs_conflict_p (xsize
, x
, ysize
, y
, c
)
1601 if (GET_CODE (x
) == VALUE
)
1603 if (GET_CODE (y
) == VALUE
)
1605 if (GET_CODE (x
) == HIGH
)
1607 else if (GET_CODE (x
) == LO_SUM
)
1610 x
= addr_side_effect_eval (x
, xsize
, 0);
1611 if (GET_CODE (y
) == HIGH
)
1613 else if (GET_CODE (y
) == LO_SUM
)
1616 y
= addr_side_effect_eval (y
, ysize
, 0);
1618 if (rtx_equal_for_memref_p (x
, y
))
1620 if (xsize
<= 0 || ysize
<= 0)
1622 if (c
>= 0 && xsize
> c
)
1624 if (c
< 0 && ysize
+c
> 0)
1629 /* This code used to check for conflicts involving stack references and
1630 globals but the base address alias code now handles these cases. */
1632 if (GET_CODE (x
) == PLUS
)
1634 /* The fact that X is canonicalized means that this
1635 PLUS rtx is canonicalized. */
1636 rtx x0
= XEXP (x
, 0);
1637 rtx x1
= XEXP (x
, 1);
1639 if (GET_CODE (y
) == PLUS
)
1641 /* The fact that Y is canonicalized means that this
1642 PLUS rtx is canonicalized. */
1643 rtx y0
= XEXP (y
, 0);
1644 rtx y1
= XEXP (y
, 1);
1646 if (rtx_equal_for_memref_p (x1
, y1
))
1647 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1648 if (rtx_equal_for_memref_p (x0
, y0
))
1649 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1650 if (GET_CODE (x1
) == CONST_INT
)
1652 if (GET_CODE (y1
) == CONST_INT
)
1653 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1654 c
- INTVAL (x1
) + INTVAL (y1
));
1656 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1659 else if (GET_CODE (y1
) == CONST_INT
)
1660 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1664 else if (GET_CODE (x1
) == CONST_INT
)
1665 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1667 else if (GET_CODE (y
) == PLUS
)
1669 /* The fact that Y is canonicalized means that this
1670 PLUS rtx is canonicalized. */
1671 rtx y0
= XEXP (y
, 0);
1672 rtx y1
= XEXP (y
, 1);
1674 if (GET_CODE (y1
) == CONST_INT
)
1675 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1680 if (GET_CODE (x
) == GET_CODE (y
))
1681 switch (GET_CODE (x
))
1685 /* Handle cases where we expect the second operands to be the
1686 same, and check only whether the first operand would conflict
1689 rtx x1
= canon_rtx (XEXP (x
, 1));
1690 rtx y1
= canon_rtx (XEXP (y
, 1));
1691 if (! rtx_equal_for_memref_p (x1
, y1
))
1693 x0
= canon_rtx (XEXP (x
, 0));
1694 y0
= canon_rtx (XEXP (y
, 0));
1695 if (rtx_equal_for_memref_p (x0
, y0
))
1696 return (xsize
== 0 || ysize
== 0
1697 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1699 /* Can't properly adjust our sizes. */
1700 if (GET_CODE (x1
) != CONST_INT
)
1702 xsize
/= INTVAL (x1
);
1703 ysize
/= INTVAL (x1
);
1705 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1709 /* Are these registers known not to be equal? */
1710 if (alias_invariant
)
1712 unsigned int r_x
= REGNO (x
), r_y
= REGNO (y
);
1713 rtx i_x
, i_y
; /* invariant relationships of X and Y */
1715 i_x
= r_x
>= reg_base_value_size
? 0 : alias_invariant
[r_x
];
1716 i_y
= r_y
>= reg_base_value_size
? 0 : alias_invariant
[r_y
];
1718 if (i_x
== 0 && i_y
== 0)
1721 if (! memrefs_conflict_p (xsize
, i_x
? i_x
: x
,
1722 ysize
, i_y
? i_y
: y
, c
))
1731 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1732 as an access with indeterminate size. Assume that references
1733 besides AND are aligned, so if the size of the other reference is
1734 at least as large as the alignment, assume no other overlap. */
1735 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1737 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1739 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
1741 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1743 /* ??? If we are indexing far enough into the array/structure, we
1744 may yet be able to determine that we can not overlap. But we
1745 also need to that we are far enough from the end not to overlap
1746 a following reference, so we do nothing with that for now. */
1747 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1749 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
1752 if (GET_CODE (x
) == ADDRESSOF
)
1754 if (y
== frame_pointer_rtx
1755 || GET_CODE (y
) == ADDRESSOF
)
1756 return xsize
<= 0 || ysize
<= 0;
1758 if (GET_CODE (y
) == ADDRESSOF
)
1760 if (x
== frame_pointer_rtx
)
1761 return xsize
<= 0 || ysize
<= 0;
1766 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1768 c
+= (INTVAL (y
) - INTVAL (x
));
1769 return (xsize
<= 0 || ysize
<= 0
1770 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1773 if (GET_CODE (x
) == CONST
)
1775 if (GET_CODE (y
) == CONST
)
1776 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1777 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1779 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1782 if (GET_CODE (y
) == CONST
)
1783 return memrefs_conflict_p (xsize
, x
, ysize
,
1784 canon_rtx (XEXP (y
, 0)), c
);
1787 return (xsize
<= 0 || ysize
<= 0
1788 || (rtx_equal_for_memref_p (x
, y
)
1789 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1796 /* Functions to compute memory dependencies.
1798 Since we process the insns in execution order, we can build tables
1799 to keep track of what registers are fixed (and not aliased), what registers
1800 are varying in known ways, and what registers are varying in unknown
1803 If both memory references are volatile, then there must always be a
1804 dependence between the two references, since their order can not be
1805 changed. A volatile and non-volatile reference can be interchanged
1808 A MEM_IN_STRUCT reference at a non-AND varying address can never
1809 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1810 also must allow AND addresses, because they may generate accesses
1811 outside the object being referenced. This is used to generate
1812 aligned addresses from unaligned addresses, for instance, the alpha
1813 storeqi_unaligned pattern. */
1815 /* Read dependence: X is read after read in MEM takes place. There can
1816 only be a dependence here if both reads are volatile. */
1819 read_dependence (mem
, x
)
1823 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1826 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1827 MEM2 is a reference to a structure at a varying address, or returns
1828 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1829 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1830 to decide whether or not an address may vary; it should return
1831 nonzero whenever variation is possible.
1832 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1835 fixed_scalar_and_varying_struct_p (mem1
, mem2
, mem1_addr
, mem2_addr
, varies_p
)
1837 rtx mem1_addr
, mem2_addr
;
1838 int (*varies_p
) PARAMS ((rtx
, int));
1840 if (! flag_strict_aliasing
)
1843 if (MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1844 && !varies_p (mem1_addr
, 1) && varies_p (mem2_addr
, 1))
1845 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1849 if (MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1850 && varies_p (mem1_addr
, 1) && !varies_p (mem2_addr
, 1))
1851 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1858 /* Returns nonzero if something about the mode or address format MEM1
1859 indicates that it might well alias *anything*. */
1862 aliases_everything_p (mem
)
1865 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1866 /* If the address is an AND, its very hard to know at what it is
1867 actually pointing. */
1873 /* Return true if we can determine that the fields referenced cannot
1874 overlap for any pair of objects. */
1877 nonoverlapping_component_refs_p (x
, y
)
1880 tree fieldx
, fieldy
, typex
, typey
, orig_y
;
1884 /* The comparison has to be done at a common type, since we don't
1885 know how the inheritance hierarchy works. */
1889 fieldx
= TREE_OPERAND (x
, 1);
1890 typex
= DECL_FIELD_CONTEXT (fieldx
);
1895 fieldy
= TREE_OPERAND (y
, 1);
1896 typey
= DECL_FIELD_CONTEXT (fieldy
);
1901 y
= TREE_OPERAND (y
, 0);
1903 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
1905 x
= TREE_OPERAND (x
, 0);
1907 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1909 /* Never found a common type. */
1913 /* If we're left with accessing different fields of a structure,
1915 if (TREE_CODE (typex
) == RECORD_TYPE
1916 && fieldx
!= fieldy
)
1919 /* The comparison on the current field failed. If we're accessing
1920 a very nested structure, look at the next outer level. */
1921 x
= TREE_OPERAND (x
, 0);
1922 y
= TREE_OPERAND (y
, 0);
1925 && TREE_CODE (x
) == COMPONENT_REF
1926 && TREE_CODE (y
) == COMPONENT_REF
);
1931 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1934 decl_for_component_ref (x
)
1939 x
= TREE_OPERAND (x
, 0);
1941 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1943 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
1946 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1947 offset of the field reference. */
1950 adjust_offset_for_component_ref (x
, offset
)
1954 HOST_WIDE_INT ioffset
;
1959 ioffset
= INTVAL (offset
);
1962 tree field
= TREE_OPERAND (x
, 1);
1964 if (! host_integerp (DECL_FIELD_OFFSET (field
), 1))
1966 ioffset
+= (tree_low_cst (DECL_FIELD_OFFSET (field
), 1)
1967 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
1970 x
= TREE_OPERAND (x
, 0);
1972 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1974 return GEN_INT (ioffset
);
1977 /* Return nonzero if we can determine the exprs corresponding to memrefs
1978 X and Y and they do not overlap. */
1981 nonoverlapping_memrefs_p (x
, y
)
1984 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
1987 rtx moffsetx
, moffsety
;
1988 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
1990 /* Unless both have exprs, we can't tell anything. */
1991 if (exprx
== 0 || expry
== 0)
1994 /* If both are field references, we may be able to determine something. */
1995 if (TREE_CODE (exprx
) == COMPONENT_REF
1996 && TREE_CODE (expry
) == COMPONENT_REF
1997 && nonoverlapping_component_refs_p (exprx
, expry
))
2000 /* If the field reference test failed, look at the DECLs involved. */
2001 moffsetx
= MEM_OFFSET (x
);
2002 if (TREE_CODE (exprx
) == COMPONENT_REF
)
2004 tree t
= decl_for_component_ref (exprx
);
2007 moffsetx
= adjust_offset_for_component_ref (exprx
, moffsetx
);
2010 else if (TREE_CODE (exprx
) == INDIRECT_REF
)
2012 exprx
= TREE_OPERAND (exprx
, 0);
2013 if (flag_argument_noalias
< 2
2014 || TREE_CODE (exprx
) != PARM_DECL
)
2018 moffsety
= MEM_OFFSET (y
);
2019 if (TREE_CODE (expry
) == COMPONENT_REF
)
2021 tree t
= decl_for_component_ref (expry
);
2024 moffsety
= adjust_offset_for_component_ref (expry
, moffsety
);
2027 else if (TREE_CODE (expry
) == INDIRECT_REF
)
2029 expry
= TREE_OPERAND (expry
, 0);
2030 if (flag_argument_noalias
< 2
2031 || TREE_CODE (expry
) != PARM_DECL
)
2035 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2038 rtlx
= DECL_RTL (exprx
);
2039 rtly
= DECL_RTL (expry
);
2041 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2042 can't overlap unless they are the same because we never reuse that part
2043 of the stack frame used for locals for spilled pseudos. */
2044 if ((GET_CODE (rtlx
) != MEM
|| GET_CODE (rtly
) != MEM
)
2045 && ! rtx_equal_p (rtlx
, rtly
))
2048 /* Get the base and offsets of both decls. If either is a register, we
2049 know both are and are the same, so use that as the base. The only
2050 we can avoid overlap is if we can deduce that they are nonoverlapping
2051 pieces of that decl, which is very rare. */
2052 basex
= GET_CODE (rtlx
) == MEM
? XEXP (rtlx
, 0) : rtlx
;
2053 if (GET_CODE (basex
) == PLUS
&& GET_CODE (XEXP (basex
, 1)) == CONST_INT
)
2054 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2056 basey
= GET_CODE (rtly
) == MEM
? XEXP (rtly
, 0) : rtly
;
2057 if (GET_CODE (basey
) == PLUS
&& GET_CODE (XEXP (basey
, 1)) == CONST_INT
)
2058 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2060 /* If the bases are different, we know they do not overlap if both
2061 are constants or if one is a constant and the other a pointer into the
2062 stack frame. Otherwise a different base means we can't tell if they
2064 if (! rtx_equal_p (basex
, basey
))
2065 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2066 || (CONSTANT_P (basex
) && REG_P (basey
)
2067 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2068 || (CONSTANT_P (basey
) && REG_P (basex
)
2069 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2071 sizex
= (GET_CODE (rtlx
) != MEM
? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2072 : MEM_SIZE (rtlx
) ? INTVAL (MEM_SIZE (rtlx
))
2074 sizey
= (GET_CODE (rtly
) != MEM
? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2075 : MEM_SIZE (rtly
) ? INTVAL (MEM_SIZE (rtly
)) :
2078 /* If we have an offset for either memref, it can update the values computed
2081 offsetx
+= INTVAL (moffsetx
), sizex
-= INTVAL (moffsetx
);
2083 offsety
+= INTVAL (moffsety
), sizey
-= INTVAL (moffsety
);
2085 /* If a memref has both a size and an offset, we can use the smaller size.
2086 We can't do this if the offset isn't known because we must view this
2087 memref as being anywhere inside the DECL's MEM. */
2088 if (MEM_SIZE (x
) && moffsetx
)
2089 sizex
= INTVAL (MEM_SIZE (x
));
2090 if (MEM_SIZE (y
) && moffsety
)
2091 sizey
= INTVAL (MEM_SIZE (y
));
2093 /* Put the values of the memref with the lower offset in X's values. */
2094 if (offsetx
> offsety
)
2096 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2097 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2100 /* If we don't know the size of the lower-offset value, we can't tell
2101 if they conflict. Otherwise, we do the test. */
2102 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2105 /* True dependence: X is read after store in MEM takes place. */
2108 true_dependence (mem
, mem_mode
, x
, varies
)
2110 enum machine_mode mem_mode
;
2112 int (*varies
) PARAMS ((rtx
, int));
2114 rtx x_addr
, mem_addr
;
2117 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2120 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2121 This is used in epilogue deallocation functions. */
2122 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2124 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2127 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2130 /* Unchanging memory can't conflict with non-unchanging memory.
2131 A non-unchanging read can conflict with a non-unchanging write.
2132 An unchanging read can conflict with an unchanging write since
2133 there may be a single store to this address to initialize it.
2134 Note that an unchanging store can conflict with a non-unchanging read
2135 since we have to make conservative assumptions when we have a
2136 record with readonly fields and we are copying the whole thing.
2137 Just fall through to the code below to resolve potential conflicts.
2138 This won't handle all cases optimally, but the possible performance
2139 loss should be negligible. */
2140 if (RTX_UNCHANGING_P (x
) && ! RTX_UNCHANGING_P (mem
))
2143 if (nonoverlapping_memrefs_p (mem
, x
))
2146 if (mem_mode
== VOIDmode
)
2147 mem_mode
= GET_MODE (mem
);
2149 x_addr
= get_addr (XEXP (x
, 0));
2150 mem_addr
= get_addr (XEXP (mem
, 0));
2152 base
= find_base_term (x_addr
);
2153 if (base
&& (GET_CODE (base
) == LABEL_REF
2154 || (GET_CODE (base
) == SYMBOL_REF
2155 && CONSTANT_POOL_ADDRESS_P (base
))))
2158 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2161 x_addr
= canon_rtx (x_addr
);
2162 mem_addr
= canon_rtx (mem_addr
);
2164 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2165 SIZE_FOR_MODE (x
), x_addr
, 0))
2168 if (aliases_everything_p (x
))
2171 /* We cannot use aliases_everything_p to test MEM, since we must look
2172 at MEM_MODE, rather than GET_MODE (MEM). */
2173 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2176 /* In true_dependence we also allow BLKmode to alias anything. Why
2177 don't we do this in anti_dependence and output_dependence? */
2178 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2181 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2185 /* Canonical true dependence: X is read after store in MEM takes place.
2186 Variant of true_dependence which assumes MEM has already been
2187 canonicalized (hence we no longer do that here).
2188 The mem_addr argument has been added, since true_dependence computed
2189 this value prior to canonicalizing. */
2192 canon_true_dependence (mem
, mem_mode
, mem_addr
, x
, varies
)
2193 rtx mem
, mem_addr
, x
;
2194 enum machine_mode mem_mode
;
2195 int (*varies
) PARAMS ((rtx
, int));
2199 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2202 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2203 This is used in epilogue deallocation functions. */
2204 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2206 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2209 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2212 /* If X is an unchanging read, then it can't possibly conflict with any
2213 non-unchanging store. It may conflict with an unchanging write though,
2214 because there may be a single store to this address to initialize it.
2215 Just fall through to the code below to resolve the case where we have
2216 both an unchanging read and an unchanging write. This won't handle all
2217 cases optimally, but the possible performance loss should be
2219 if (RTX_UNCHANGING_P (x
) && ! RTX_UNCHANGING_P (mem
))
2222 if (nonoverlapping_memrefs_p (x
, mem
))
2225 x_addr
= get_addr (XEXP (x
, 0));
2227 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2230 x_addr
= canon_rtx (x_addr
);
2231 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2232 SIZE_FOR_MODE (x
), x_addr
, 0))
2235 if (aliases_everything_p (x
))
2238 /* We cannot use aliases_everything_p to test MEM, since we must look
2239 at MEM_MODE, rather than GET_MODE (MEM). */
2240 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2243 /* In true_dependence we also allow BLKmode to alias anything. Why
2244 don't we do this in anti_dependence and output_dependence? */
2245 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2248 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2252 /* Returns nonzero if a write to X might alias a previous read from
2253 (or, if WRITEP is nonzero, a write to) MEM. */
2256 write_dependence_p (mem
, x
, writep
)
2261 rtx x_addr
, mem_addr
;
2265 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2268 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2269 This is used in epilogue deallocation functions. */
2270 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2272 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2275 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2278 /* Unchanging memory can't conflict with non-unchanging memory. */
2279 if (RTX_UNCHANGING_P (x
) != RTX_UNCHANGING_P (mem
))
2282 /* If MEM is an unchanging read, then it can't possibly conflict with
2283 the store to X, because there is at most one store to MEM, and it must
2284 have occurred somewhere before MEM. */
2285 if (! writep
&& RTX_UNCHANGING_P (mem
))
2288 if (nonoverlapping_memrefs_p (x
, mem
))
2291 x_addr
= get_addr (XEXP (x
, 0));
2292 mem_addr
= get_addr (XEXP (mem
, 0));
2296 base
= find_base_term (mem_addr
);
2297 if (base
&& (GET_CODE (base
) == LABEL_REF
2298 || (GET_CODE (base
) == SYMBOL_REF
2299 && CONSTANT_POOL_ADDRESS_P (base
))))
2303 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2307 x_addr
= canon_rtx (x_addr
);
2308 mem_addr
= canon_rtx (mem_addr
);
2310 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2311 SIZE_FOR_MODE (x
), x_addr
, 0))
2315 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2318 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2319 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2322 /* Anti dependence: X is written after read in MEM takes place. */
2325 anti_dependence (mem
, x
)
2329 return write_dependence_p (mem
, x
, /*writep=*/0);
2332 /* Output dependence: X is written after store in MEM takes place. */
2335 output_dependence (mem
, x
)
2339 return write_dependence_p (mem
, x
, /*writep=*/1);
2342 /* A subroutine of nonlocal_mentioned_p, returns 1 if *LOC mentions
2343 something which is not local to the function and is not constant. */
2346 nonlocal_mentioned_p_1 (loc
, data
)
2348 void *data ATTRIBUTE_UNUSED
;
2357 switch (GET_CODE (x
))
2360 if (GET_CODE (SUBREG_REG (x
)) == REG
)
2362 /* Global registers are not local. */
2363 if (REGNO (SUBREG_REG (x
)) < FIRST_PSEUDO_REGISTER
2364 && global_regs
[subreg_regno (x
)])
2372 /* Global registers are not local. */
2373 if (regno
< FIRST_PSEUDO_REGISTER
&& global_regs
[regno
])
2388 /* Constants in the function's constants pool are constant. */
2389 if (CONSTANT_POOL_ADDRESS_P (x
))
2394 /* Non-constant calls and recursion are not local. */
2398 /* Be overly conservative and consider any volatile memory
2399 reference as not local. */
2400 if (MEM_VOLATILE_P (x
))
2402 base
= find_base_term (XEXP (x
, 0));
2405 /* A Pmode ADDRESS could be a reference via the structure value
2406 address or static chain. Such memory references are nonlocal.
2408 Thus, we have to examine the contents of the ADDRESS to find
2409 out if this is a local reference or not. */
2410 if (GET_CODE (base
) == ADDRESS
2411 && GET_MODE (base
) == Pmode
2412 && (XEXP (base
, 0) == stack_pointer_rtx
2413 || XEXP (base
, 0) == arg_pointer_rtx
2414 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2415 || XEXP (base
, 0) == hard_frame_pointer_rtx
2417 || XEXP (base
, 0) == frame_pointer_rtx
))
2419 /* Constants in the function's constant pool are constant. */
2420 if (GET_CODE (base
) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (base
))
2425 case UNSPEC_VOLATILE
:
2430 if (MEM_VOLATILE_P (x
))
2442 /* Returns nonzero if X might mention something which is not
2443 local to the function and is not constant. */
2446 nonlocal_mentioned_p (x
)
2451 if (GET_CODE (x
) == CALL_INSN
)
2453 if (! CONST_OR_PURE_CALL_P (x
))
2455 x
= CALL_INSN_FUNCTION_USAGE (x
);
2463 return for_each_rtx (&x
, nonlocal_mentioned_p_1
, NULL
);
2466 /* A subroutine of nonlocal_referenced_p, returns 1 if *LOC references
2467 something which is not local to the function and is not constant. */
2470 nonlocal_referenced_p_1 (loc
, data
)
2472 void *data ATTRIBUTE_UNUSED
;
2479 switch (GET_CODE (x
))
2485 return nonlocal_mentioned_p (x
);
2488 /* Non-constant calls and recursion are not local. */
2492 if (nonlocal_mentioned_p (SET_SRC (x
)))
2495 if (GET_CODE (SET_DEST (x
)) == MEM
)
2496 return nonlocal_mentioned_p (XEXP (SET_DEST (x
), 0));
2498 /* If the destination is anything other than a CC0, PC,
2499 MEM, REG, or a SUBREG of a REG that occupies all of
2500 the REG, then X references nonlocal memory if it is
2501 mentioned in the destination. */
2502 if (GET_CODE (SET_DEST (x
)) != CC0
2503 && GET_CODE (SET_DEST (x
)) != PC
2504 && GET_CODE (SET_DEST (x
)) != REG
2505 && ! (GET_CODE (SET_DEST (x
)) == SUBREG
2506 && GET_CODE (SUBREG_REG (SET_DEST (x
))) == REG
2507 && (((GET_MODE_SIZE (GET_MODE (SUBREG_REG (SET_DEST (x
))))
2508 + (UNITS_PER_WORD
- 1)) / UNITS_PER_WORD
)
2509 == ((GET_MODE_SIZE (GET_MODE (SET_DEST (x
)))
2510 + (UNITS_PER_WORD
- 1)) / UNITS_PER_WORD
))))
2511 return nonlocal_mentioned_p (SET_DEST (x
));
2515 if (GET_CODE (XEXP (x
, 0)) == MEM
)
2516 return nonlocal_mentioned_p (XEXP (XEXP (x
, 0), 0));
2520 return nonlocal_mentioned_p (XEXP (x
, 0));
2523 case UNSPEC_VOLATILE
:
2527 if (MEM_VOLATILE_P (x
))
2539 /* Returns nonzero if X might reference something which is not
2540 local to the function and is not constant. */
2543 nonlocal_referenced_p (x
)
2548 if (GET_CODE (x
) == CALL_INSN
)
2550 if (! CONST_OR_PURE_CALL_P (x
))
2552 x
= CALL_INSN_FUNCTION_USAGE (x
);
2560 return for_each_rtx (&x
, nonlocal_referenced_p_1
, NULL
);
2563 /* A subroutine of nonlocal_set_p, returns 1 if *LOC sets
2564 something which is not local to the function and is not constant. */
2567 nonlocal_set_p_1 (loc
, data
)
2569 void *data ATTRIBUTE_UNUSED
;
2576 switch (GET_CODE (x
))
2579 /* Non-constant calls and recursion are not local. */
2588 return nonlocal_mentioned_p (XEXP (x
, 0));
2591 if (nonlocal_mentioned_p (SET_DEST (x
)))
2593 return nonlocal_set_p (SET_SRC (x
));
2596 return nonlocal_mentioned_p (XEXP (x
, 0));
2602 case UNSPEC_VOLATILE
:
2606 if (MEM_VOLATILE_P (x
))
2618 /* Returns nonzero if X might set something which is not
2619 local to the function and is not constant. */
2627 if (GET_CODE (x
) == CALL_INSN
)
2629 if (! CONST_OR_PURE_CALL_P (x
))
2631 x
= CALL_INSN_FUNCTION_USAGE (x
);
2639 return for_each_rtx (&x
, nonlocal_set_p_1
, NULL
);
2642 /* Mark the function if it is pure or constant. */
2645 mark_constant_function ()
2648 int nonlocal_memory_referenced
;
2650 if (TREE_READONLY (current_function_decl
)
2651 || DECL_IS_PURE (current_function_decl
)
2652 || TREE_THIS_VOLATILE (current_function_decl
)
2653 || current_function_has_nonlocal_goto
2654 || !(*targetm
.binds_local_p
) (current_function_decl
))
2657 /* A loop might not return which counts as a side effect. */
2658 if (mark_dfs_back_edges ())
2661 nonlocal_memory_referenced
= 0;
2663 init_alias_analysis ();
2665 /* Determine if this is a constant or pure function. */
2667 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2669 if (! INSN_P (insn
))
2672 if (nonlocal_set_p (insn
) || global_reg_mentioned_p (insn
)
2673 || volatile_refs_p (PATTERN (insn
)))
2676 if (! nonlocal_memory_referenced
)
2677 nonlocal_memory_referenced
= nonlocal_referenced_p (insn
);
2680 end_alias_analysis ();
2682 /* Mark the function. */
2686 else if (nonlocal_memory_referenced
)
2688 cgraph_rtl_info (current_function_decl
)->pure_function
= 1;
2689 DECL_IS_PURE (current_function_decl
) = 1;
2693 cgraph_rtl_info (current_function_decl
)->const_function
= 1;
2694 TREE_READONLY (current_function_decl
) = 1;
2704 #ifndef OUTGOING_REGNO
2705 #define OUTGOING_REGNO(N) N
2707 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2708 /* Check whether this register can hold an incoming pointer
2709 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2710 numbers, so translate if necessary due to register windows. */
2711 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2712 && HARD_REGNO_MODE_OK (i
, Pmode
))
2713 static_reg_base_value
[i
]
2714 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2716 static_reg_base_value
[STACK_POINTER_REGNUM
]
2717 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2718 static_reg_base_value
[ARG_POINTER_REGNUM
]
2719 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2720 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2721 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2722 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2723 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2724 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2727 alias_sets
= splay_tree_new (splay_tree_compare_ints
, 0, 0);
2730 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2731 to be memory reference. */
2732 static bool memory_modified
;
2734 memory_modified_1 (x
, pat
, data
)
2735 rtx x
, pat ATTRIBUTE_UNUSED
;
2738 if (GET_CODE (x
) == MEM
)
2740 if (anti_dependence (x
, (rtx
)data
) || output_dependence (x
, (rtx
)data
))
2741 memory_modified
= true;
2746 /* Return true when INSN possibly modify memory contents of MEM
2747 (ie address can be modified). */
2749 memory_modified_in_insn_p (mem
, insn
)
2754 memory_modified
= false;
2755 note_stores (PATTERN (insn
), memory_modified_1
, mem
);
2756 return memory_modified
;
2759 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2763 init_alias_analysis ()
2765 int maxreg
= max_reg_num ();
2771 timevar_push (TV_ALIAS_ANALYSIS
);
2773 reg_known_value_size
= maxreg
;
2776 = (rtx
*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (rtx
))
2777 - FIRST_PSEUDO_REGISTER
;
2779 = (char*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (char))
2780 - FIRST_PSEUDO_REGISTER
;
2782 /* Overallocate reg_base_value to allow some growth during loop
2783 optimization. Loop unrolling can create a large number of
2785 reg_base_value_size
= maxreg
* 2;
2786 reg_base_value
= (rtx
*) ggc_alloc_cleared (reg_base_value_size
2789 new_reg_base_value
= (rtx
*) xmalloc (reg_base_value_size
* sizeof (rtx
));
2790 reg_seen
= (char *) xmalloc (reg_base_value_size
);
2791 if (! reload_completed
&& flag_old_unroll_loops
)
2793 /* ??? Why are we realloc'ing if we're just going to zero it? */
2794 alias_invariant
= (rtx
*)xrealloc (alias_invariant
,
2795 reg_base_value_size
* sizeof (rtx
));
2796 memset ((char *)alias_invariant
, 0, reg_base_value_size
* sizeof (rtx
));
2799 /* The basic idea is that each pass through this loop will use the
2800 "constant" information from the previous pass to propagate alias
2801 information through another level of assignments.
2803 This could get expensive if the assignment chains are long. Maybe
2804 we should throttle the number of iterations, possibly based on
2805 the optimization level or flag_expensive_optimizations.
2807 We could propagate more information in the first pass by making use
2808 of REG_N_SETS to determine immediately that the alias information
2809 for a pseudo is "constant".
2811 A program with an uninitialized variable can cause an infinite loop
2812 here. Instead of doing a full dataflow analysis to detect such problems
2813 we just cap the number of iterations for the loop.
2815 The state of the arrays for the set chain in question does not matter
2816 since the program has undefined behavior. */
2821 /* Assume nothing will change this iteration of the loop. */
2824 /* We want to assign the same IDs each iteration of this loop, so
2825 start counting from zero each iteration of the loop. */
2828 /* We're at the start of the function each iteration through the
2829 loop, so we're copying arguments. */
2830 copying_arguments
= true;
2832 /* Wipe the potential alias information clean for this pass. */
2833 memset ((char *) new_reg_base_value
, 0, reg_base_value_size
* sizeof (rtx
));
2835 /* Wipe the reg_seen array clean. */
2836 memset ((char *) reg_seen
, 0, reg_base_value_size
);
2838 /* Mark all hard registers which may contain an address.
2839 The stack, frame and argument pointers may contain an address.
2840 An argument register which can hold a Pmode value may contain
2841 an address even if it is not in BASE_REGS.
2843 The address expression is VOIDmode for an argument and
2844 Pmode for other registers. */
2846 memcpy (new_reg_base_value
, static_reg_base_value
,
2847 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2849 /* Walk the insns adding values to the new_reg_base_value array. */
2850 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2856 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2857 /* The prologue/epilogue insns are not threaded onto the
2858 insn chain until after reload has completed. Thus,
2859 there is no sense wasting time checking if INSN is in
2860 the prologue/epilogue until after reload has completed. */
2861 if (reload_completed
2862 && prologue_epilogue_contains (insn
))
2866 /* If this insn has a noalias note, process it, Otherwise,
2867 scan for sets. A simple set will have no side effects
2868 which could change the base value of any other register. */
2870 if (GET_CODE (PATTERN (insn
)) == SET
2871 && REG_NOTES (insn
) != 0
2872 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2873 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2875 note_stores (PATTERN (insn
), record_set
, NULL
);
2877 set
= single_set (insn
);
2880 && GET_CODE (SET_DEST (set
)) == REG
2881 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2883 unsigned int regno
= REGNO (SET_DEST (set
));
2884 rtx src
= SET_SRC (set
);
2886 if (REG_NOTES (insn
) != 0
2887 && (((note
= find_reg_note (insn
, REG_EQUAL
, 0)) != 0
2888 && REG_N_SETS (regno
) == 1)
2889 || (note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) != 0)
2890 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2891 && ! rtx_varies_p (XEXP (note
, 0), 1)
2892 && ! reg_overlap_mentioned_p (SET_DEST (set
), XEXP (note
, 0)))
2894 reg_known_value
[regno
] = XEXP (note
, 0);
2895 reg_known_equiv_p
[regno
] = REG_NOTE_KIND (note
) == REG_EQUIV
;
2897 else if (REG_N_SETS (regno
) == 1
2898 && GET_CODE (src
) == PLUS
2899 && GET_CODE (XEXP (src
, 0)) == REG
2900 && REGNO (XEXP (src
, 0)) >= FIRST_PSEUDO_REGISTER
2901 && (reg_known_value
[REGNO (XEXP (src
, 0))])
2902 && GET_CODE (XEXP (src
, 1)) == CONST_INT
)
2904 rtx op0
= XEXP (src
, 0);
2905 op0
= reg_known_value
[REGNO (op0
)];
2906 reg_known_value
[regno
]
2907 = plus_constant (op0
, INTVAL (XEXP (src
, 1)));
2908 reg_known_equiv_p
[regno
] = 0;
2910 else if (REG_N_SETS (regno
) == 1
2911 && ! rtx_varies_p (src
, 1))
2913 reg_known_value
[regno
] = src
;
2914 reg_known_equiv_p
[regno
] = 0;
2918 else if (GET_CODE (insn
) == NOTE
2919 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_FUNCTION_BEG
)
2920 copying_arguments
= false;
2923 /* Now propagate values from new_reg_base_value to reg_base_value. */
2924 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
2926 if (new_reg_base_value
[ui
]
2927 && new_reg_base_value
[ui
] != reg_base_value
[ui
]
2928 && ! rtx_equal_p (new_reg_base_value
[ui
], reg_base_value
[ui
]))
2930 reg_base_value
[ui
] = new_reg_base_value
[ui
];
2935 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2937 /* Fill in the remaining entries. */
2938 for (i
= FIRST_PSEUDO_REGISTER
; i
< maxreg
; i
++)
2939 if (reg_known_value
[i
] == 0)
2940 reg_known_value
[i
] = regno_reg_rtx
[i
];
2942 /* Simplify the reg_base_value array so that no register refers to
2943 another register, except to special registers indirectly through
2944 ADDRESS expressions.
2946 In theory this loop can take as long as O(registers^2), but unless
2947 there are very long dependency chains it will run in close to linear
2950 This loop may not be needed any longer now that the main loop does
2951 a better job at propagating alias information. */
2957 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
2959 rtx base
= reg_base_value
[ui
];
2960 if (base
&& GET_CODE (base
) == REG
)
2962 unsigned int base_regno
= REGNO (base
);
2963 if (base_regno
== ui
) /* register set from itself */
2964 reg_base_value
[ui
] = 0;
2966 reg_base_value
[ui
] = reg_base_value
[base_regno
];
2971 while (changed
&& pass
< MAX_ALIAS_LOOP_PASSES
);
2974 free (new_reg_base_value
);
2975 new_reg_base_value
= 0;
2978 timevar_pop (TV_ALIAS_ANALYSIS
);
2982 end_alias_analysis ()
2984 free (reg_known_value
+ FIRST_PSEUDO_REGISTER
);
2985 reg_known_value
= 0;
2986 reg_known_value_size
= 0;
2987 free (reg_known_equiv_p
+ FIRST_PSEUDO_REGISTER
);
2988 reg_known_equiv_p
= 0;
2990 reg_base_value_size
= 0;
2991 if (alias_invariant
)
2993 free (alias_invariant
);
2994 alias_invariant
= 0;
2998 #include "gt-alias.h"