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"
38 #include "langhooks.h"
40 /* The alias sets assigned to MEMs assist the back-end in determining
41 which MEMs can alias which other MEMs. In general, two MEMs in
42 different alias sets cannot alias each other, with one important
43 exception. Consider something like:
45 struct S {int i; double d; };
47 a store to an `S' can alias something of either type `int' or type
48 `double'. (However, a store to an `int' cannot alias a `double'
49 and vice versa.) We indicate this via a tree structure that looks
57 (The arrows are directed and point downwards.)
58 In this situation we say the alias set for `struct S' is the
59 `superset' and that those for `int' and `double' are `subsets'.
61 To see whether two alias sets can point to the same memory, we must
62 see if either alias set is a subset of the other. We need not trace
63 past immediate descendents, however, since we propagate all
64 grandchildren up one level.
66 Alias set zero is implicitly a superset of all other alias sets.
67 However, this is no actual entry for alias set zero. It is an
68 error to attempt to explicitly construct a subset of zero. */
70 typedef struct alias_set_entry
72 /* The alias set number, as stored in MEM_ALIAS_SET. */
73 HOST_WIDE_INT alias_set
;
75 /* The children of the alias set. These are not just the immediate
76 children, but, in fact, all descendents. So, if we have:
78 struct T { struct S s; float f; }
80 continuing our example above, the children here will be all of
81 `int', `double', `float', and `struct S'. */
84 /* Nonzero if would have a child of zero: this effectively makes this
85 alias set the same as alias set zero. */
89 static int rtx_equal_for_memref_p
PARAMS ((rtx
, rtx
));
90 static rtx find_symbolic_term
PARAMS ((rtx
));
91 rtx get_addr
PARAMS ((rtx
));
92 static int memrefs_conflict_p
PARAMS ((int, rtx
, int, rtx
,
94 static void record_set
PARAMS ((rtx
, rtx
, void *));
95 static rtx find_base_term
PARAMS ((rtx
));
96 static int base_alias_check
PARAMS ((rtx
, rtx
, enum machine_mode
,
98 static rtx find_base_value
PARAMS ((rtx
));
99 static int mems_in_disjoint_alias_sets_p
PARAMS ((rtx
, rtx
));
100 static int insert_subset_children
PARAMS ((splay_tree_node
, void*));
101 static tree find_base_decl
PARAMS ((tree
));
102 static alias_set_entry get_alias_set_entry
PARAMS ((HOST_WIDE_INT
));
103 static rtx fixed_scalar_and_varying_struct_p
PARAMS ((rtx
, rtx
, rtx
, rtx
,
104 int (*) (rtx
, int)));
105 static int aliases_everything_p
PARAMS ((rtx
));
106 static bool nonoverlapping_component_refs_p
PARAMS ((tree
, tree
));
107 static tree decl_for_component_ref
PARAMS ((tree
));
108 static rtx adjust_offset_for_component_ref
PARAMS ((tree
, rtx
));
109 static int nonoverlapping_memrefs_p
PARAMS ((rtx
, rtx
));
110 static int write_dependence_p
PARAMS ((rtx
, rtx
, int));
111 static int nonlocal_mentioned_p
PARAMS ((rtx
));
113 /* Set up all info needed to perform alias analysis on memory references. */
115 /* Returns the size in bytes of the mode of X. */
116 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
118 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
119 different alias sets. We ignore alias sets in functions making use
120 of variable arguments because the va_arg macros on some systems are
122 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
123 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
125 /* Cap the number of passes we make over the insns propagating alias
126 information through set chains. 10 is a completely arbitrary choice. */
127 #define MAX_ALIAS_LOOP_PASSES 10
129 /* reg_base_value[N] gives an address to which register N is related.
130 If all sets after the first add or subtract to the current value
131 or otherwise modify it so it does not point to a different top level
132 object, reg_base_value[N] is equal to the address part of the source
135 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
136 expressions represent certain special values: function arguments and
137 the stack, frame, and argument pointers.
139 The contents of an ADDRESS is not normally used, the mode of the
140 ADDRESS determines whether the ADDRESS is a function argument or some
141 other special value. Pointer equality, not rtx_equal_p, determines whether
142 two ADDRESS expressions refer to the same base address.
144 The only use of the contents of an ADDRESS is for determining if the
145 current function performs nonlocal memory memory references for the
146 purposes of marking the function as a constant function. */
148 static rtx
*reg_base_value
;
149 static rtx
*new_reg_base_value
;
150 static unsigned int reg_base_value_size
; /* size of reg_base_value array */
152 #define REG_BASE_VALUE(X) \
153 (REGNO (X) < reg_base_value_size \
154 ? reg_base_value[REGNO (X)] : 0)
156 /* Vector of known invariant relationships between registers. Set in
157 loop unrolling. Indexed by register number, if nonzero the value
158 is an expression describing this register in terms of another.
160 The length of this array is REG_BASE_VALUE_SIZE.
162 Because this array contains only pseudo registers it has no effect
164 static rtx
*alias_invariant
;
166 /* Vector indexed by N giving the initial (unchanging) value known for
167 pseudo-register N. This array is initialized in
168 init_alias_analysis, and does not change until end_alias_analysis
170 rtx
*reg_known_value
;
172 /* Indicates number of valid entries in reg_known_value. */
173 static unsigned int reg_known_value_size
;
175 /* Vector recording for each reg_known_value whether it is due to a
176 REG_EQUIV note. Future passes (viz., reload) may replace the
177 pseudo with the equivalent expression and so we account for the
178 dependences that would be introduced if that happens.
180 The REG_EQUIV notes created in assign_parms may mention the arg
181 pointer, and there are explicit insns in the RTL that modify the
182 arg pointer. Thus we must ensure that such insns don't get
183 scheduled across each other because that would invalidate the
184 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
185 wrong, but solving the problem in the scheduler will likely give
186 better code, so we do it here. */
187 char *reg_known_equiv_p
;
189 /* True when scanning insns from the start of the rtl to the
190 NOTE_INSN_FUNCTION_BEG note. */
191 static int copying_arguments
;
193 /* The splay-tree used to store the various alias set entries. */
194 static splay_tree alias_sets
;
196 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
197 such an entry, or NULL otherwise. */
199 static alias_set_entry
200 get_alias_set_entry (alias_set
)
201 HOST_WIDE_INT alias_set
;
204 = splay_tree_lookup (alias_sets
, (splay_tree_key
) alias_set
);
206 return sn
!= 0 ? ((alias_set_entry
) sn
->value
) : 0;
209 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
210 the two MEMs cannot alias each other. */
213 mems_in_disjoint_alias_sets_p (mem1
, mem2
)
217 #ifdef ENABLE_CHECKING
218 /* Perform a basic sanity check. Namely, that there are no alias sets
219 if we're not using strict aliasing. This helps to catch bugs
220 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
221 where a MEM is allocated in some way other than by the use of
222 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
223 use alias sets to indicate that spilled registers cannot alias each
224 other, we might need to remove this check. */
225 if (! flag_strict_aliasing
226 && (MEM_ALIAS_SET (mem1
) != 0 || MEM_ALIAS_SET (mem2
) != 0))
230 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
233 /* Insert the NODE into the splay tree given by DATA. Used by
234 record_alias_subset via splay_tree_foreach. */
237 insert_subset_children (node
, data
)
238 splay_tree_node node
;
241 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
246 /* Return 1 if the two specified alias sets may conflict. */
249 alias_sets_conflict_p (set1
, set2
)
250 HOST_WIDE_INT set1
, set2
;
254 /* If have no alias set information for one of the operands, we have
255 to assume it can alias anything. */
256 if (set1
== 0 || set2
== 0
257 /* If the two alias sets are the same, they may alias. */
261 /* See if the first alias set is a subset of the second. */
262 ase
= get_alias_set_entry (set1
);
264 && (ase
->has_zero_child
265 || splay_tree_lookup (ase
->children
,
266 (splay_tree_key
) set2
)))
269 /* Now do the same, but with the alias sets reversed. */
270 ase
= get_alias_set_entry (set2
);
272 && (ase
->has_zero_child
273 || splay_tree_lookup (ase
->children
,
274 (splay_tree_key
) set1
)))
277 /* The two alias sets are distinct and neither one is the
278 child of the other. Therefore, they cannot alias. */
282 /* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
283 has any readonly fields. If any of the fields have types that
284 contain readonly fields, return true as well. */
287 readonly_fields_p (type
)
292 if (TREE_CODE (type
) != RECORD_TYPE
&& TREE_CODE (type
) != UNION_TYPE
293 && TREE_CODE (type
) != QUAL_UNION_TYPE
)
296 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
297 if (TREE_CODE (field
) == FIELD_DECL
298 && (TREE_READONLY (field
)
299 || readonly_fields_p (TREE_TYPE (field
))))
305 /* Return 1 if any MEM object of type T1 will always conflict (using the
306 dependency routines in this file) with any MEM object of type T2.
307 This is used when allocating temporary storage. If T1 and/or T2 are
308 NULL_TREE, it means we know nothing about the storage. */
311 objects_must_conflict_p (t1
, t2
)
314 /* If neither has a type specified, we don't know if they'll conflict
315 because we may be using them to store objects of various types, for
316 example the argument and local variables areas of inlined functions. */
317 if (t1
== 0 && t2
== 0)
320 /* If one or the other has readonly fields or is readonly,
321 then they may not conflict. */
322 if ((t1
!= 0 && readonly_fields_p (t1
))
323 || (t2
!= 0 && readonly_fields_p (t2
))
324 || (t1
!= 0 && TYPE_READONLY (t1
))
325 || (t2
!= 0 && TYPE_READONLY (t2
)))
328 /* If they are the same type, they must conflict. */
330 /* Likewise if both are volatile. */
331 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
334 /* If one is aggregate and the other is scalar then they may not
336 if ((t1
!= 0 && AGGREGATE_TYPE_P (t1
))
337 != (t2
!= 0 && AGGREGATE_TYPE_P (t2
)))
340 /* Otherwise they conflict only if the alias sets conflict. */
341 return alias_sets_conflict_p (t1
? get_alias_set (t1
) : 0,
342 t2
? get_alias_set (t2
) : 0);
345 /* T is an expression with pointer type. Find the DECL on which this
346 expression is based. (For example, in `a[i]' this would be `a'.)
347 If there is no such DECL, or a unique decl cannot be determined,
348 NULL_TREE is returned. */
356 if (t
== 0 || t
== error_mark_node
|| ! POINTER_TYPE_P (TREE_TYPE (t
)))
359 /* If this is a declaration, return it. */
360 if (TREE_CODE_CLASS (TREE_CODE (t
)) == 'd')
363 /* Handle general expressions. It would be nice to deal with
364 COMPONENT_REFs here. If we could tell that `a' and `b' were the
365 same, then `a->f' and `b->f' are also the same. */
366 switch (TREE_CODE_CLASS (TREE_CODE (t
)))
369 return find_base_decl (TREE_OPERAND (t
, 0));
372 /* Return 0 if found in neither or both are the same. */
373 d0
= find_base_decl (TREE_OPERAND (t
, 0));
374 d1
= find_base_decl (TREE_OPERAND (t
, 1));
385 d0
= find_base_decl (TREE_OPERAND (t
, 0));
386 d1
= find_base_decl (TREE_OPERAND (t
, 1));
387 d2
= find_base_decl (TREE_OPERAND (t
, 2));
389 /* Set any nonzero values from the last, then from the first. */
390 if (d1
== 0) d1
= d2
;
391 if (d0
== 0) d0
= d1
;
392 if (d1
== 0) d1
= d0
;
393 if (d2
== 0) d2
= d1
;
395 /* At this point all are nonzero or all are zero. If all three are the
396 same, return it. Otherwise, return zero. */
397 return (d0
== d1
&& d1
== d2
) ? d0
: 0;
404 /* Return 1 if all the nested component references handled by
405 get_inner_reference in T are such that we can address the object in T. */
411 /* If we're at the end, it is vacuously addressable. */
412 if (! handled_component_p (t
))
415 /* Bitfields are never addressable. */
416 else if (TREE_CODE (t
) == BIT_FIELD_REF
)
419 /* Fields are addressable unless they are marked as nonaddressable or
420 the containing type has alias set 0. */
421 else if (TREE_CODE (t
) == COMPONENT_REF
422 && ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1))
423 && get_alias_set (TREE_TYPE (TREE_OPERAND (t
, 0))) != 0
424 && can_address_p (TREE_OPERAND (t
, 0)))
427 /* Likewise for arrays. */
428 else if ((TREE_CODE (t
) == ARRAY_REF
|| TREE_CODE (t
) == ARRAY_RANGE_REF
)
429 && ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0)))
430 && get_alias_set (TREE_TYPE (TREE_OPERAND (t
, 0))) != 0
431 && can_address_p (TREE_OPERAND (t
, 0)))
437 /* Return the alias set for T, which may be either a type or an
438 expression. Call language-specific routine for help, if needed. */
446 /* If we're not doing any alias analysis, just assume everything
447 aliases everything else. Also return 0 if this or its type is
449 if (! flag_strict_aliasing
|| t
== error_mark_node
451 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
454 /* We can be passed either an expression or a type. This and the
455 language-specific routine may make mutually-recursive calls to each other
456 to figure out what to do. At each juncture, we see if this is a tree
457 that the language may need to handle specially. First handle things that
462 tree placeholder_ptr
= 0;
464 /* Remove any nops, then give the language a chance to do
465 something with this tree before we look at it. */
467 set
= (*lang_hooks
.get_alias_set
) (t
);
471 /* First see if the actual object referenced is an INDIRECT_REF from a
472 restrict-qualified pointer or a "void *". Replace
473 PLACEHOLDER_EXPRs. */
474 while (TREE_CODE (inner
) == PLACEHOLDER_EXPR
475 || handled_component_p (inner
))
477 if (TREE_CODE (inner
) == PLACEHOLDER_EXPR
)
478 inner
= find_placeholder (inner
, &placeholder_ptr
);
480 inner
= TREE_OPERAND (inner
, 0);
485 /* Check for accesses through restrict-qualified pointers. */
486 if (TREE_CODE (inner
) == INDIRECT_REF
)
488 tree decl
= find_base_decl (TREE_OPERAND (inner
, 0));
490 if (decl
&& DECL_POINTER_ALIAS_SET_KNOWN_P (decl
))
492 /* If we haven't computed the actual alias set, do it now. */
493 if (DECL_POINTER_ALIAS_SET (decl
) == -2)
495 /* No two restricted pointers can point at the same thing.
496 However, a restricted pointer can point at the same thing
497 as an unrestricted pointer, if that unrestricted pointer
498 is based on the restricted pointer. So, we make the
499 alias set for the restricted pointer a subset of the
500 alias set for the type pointed to by the type of the
502 HOST_WIDE_INT pointed_to_alias_set
503 = get_alias_set (TREE_TYPE (TREE_TYPE (decl
)));
505 if (pointed_to_alias_set
== 0)
506 /* It's not legal to make a subset of alias set zero. */
510 DECL_POINTER_ALIAS_SET (decl
) = new_alias_set ();
511 record_alias_subset (pointed_to_alias_set
,
512 DECL_POINTER_ALIAS_SET (decl
));
516 /* We use the alias set indicated in the declaration. */
517 return DECL_POINTER_ALIAS_SET (decl
);
520 /* If we have an INDIRECT_REF via a void pointer, we don't
521 know anything about what that might alias. */
522 else if (TREE_CODE (TREE_TYPE (inner
)) == VOID_TYPE
)
526 /* Otherwise, pick up the outermost object that we could have a pointer
527 to, processing conversion and PLACEHOLDER_EXPR as above. */
529 while (TREE_CODE (t
) == PLACEHOLDER_EXPR
530 || (handled_component_p (t
) && ! can_address_p (t
)))
532 if (TREE_CODE (t
) == PLACEHOLDER_EXPR
)
533 t
= find_placeholder (t
, &placeholder_ptr
);
535 t
= TREE_OPERAND (t
, 0);
540 /* If we've already determined the alias set for a decl, just return
541 it. This is necessary for C++ anonymous unions, whose component
542 variables don't look like union members (boo!). */
543 if (TREE_CODE (t
) == VAR_DECL
544 && DECL_RTL_SET_P (t
) && GET_CODE (DECL_RTL (t
)) == MEM
)
545 return MEM_ALIAS_SET (DECL_RTL (t
));
547 /* Now all we care about is the type. */
551 /* Variant qualifiers don't affect the alias set, so get the main
552 variant. If this is a type with a known alias set, return it. */
553 t
= TYPE_MAIN_VARIANT (t
);
554 if (TYPE_ALIAS_SET_KNOWN_P (t
))
555 return TYPE_ALIAS_SET (t
);
557 /* See if the language has special handling for this type. */
558 set
= (*lang_hooks
.get_alias_set
) (t
);
562 /* There are no objects of FUNCTION_TYPE, so there's no point in
563 using up an alias set for them. (There are, of course, pointers
564 and references to functions, but that's different.) */
565 else if (TREE_CODE (t
) == FUNCTION_TYPE
)
568 /* Otherwise make a new alias set for this type. */
569 set
= new_alias_set ();
571 TYPE_ALIAS_SET (t
) = set
;
573 /* If this is an aggregate type, we must record any component aliasing
575 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
576 record_component_aliases (t
);
581 /* Return a brand-new alias set. */
586 static HOST_WIDE_INT last_alias_set
;
588 if (flag_strict_aliasing
)
589 return ++last_alias_set
;
594 /* Indicate that things in SUBSET can alias things in SUPERSET, but
595 not vice versa. For example, in C, a store to an `int' can alias a
596 structure containing an `int', but not vice versa. Here, the
597 structure would be the SUPERSET and `int' the SUBSET. This
598 function should be called only once per SUPERSET/SUBSET pair.
600 It is illegal for SUPERSET to be zero; everything is implicitly a
601 subset of alias set zero. */
604 record_alias_subset (superset
, subset
)
605 HOST_WIDE_INT superset
;
606 HOST_WIDE_INT subset
;
608 alias_set_entry superset_entry
;
609 alias_set_entry subset_entry
;
611 /* It is possible in complex type situations for both sets to be the same,
612 in which case we can ignore this operation. */
613 if (superset
== subset
)
619 superset_entry
= get_alias_set_entry (superset
);
620 if (superset_entry
== 0)
622 /* Create an entry for the SUPERSET, so that we have a place to
623 attach the SUBSET. */
625 = (alias_set_entry
) xmalloc (sizeof (struct alias_set_entry
));
626 superset_entry
->alias_set
= superset
;
627 superset_entry
->children
628 = splay_tree_new (splay_tree_compare_ints
, 0, 0);
629 superset_entry
->has_zero_child
= 0;
630 splay_tree_insert (alias_sets
, (splay_tree_key
) superset
,
631 (splay_tree_value
) superset_entry
);
635 superset_entry
->has_zero_child
= 1;
638 subset_entry
= get_alias_set_entry (subset
);
639 /* If there is an entry for the subset, enter all of its children
640 (if they are not already present) as children of the SUPERSET. */
643 if (subset_entry
->has_zero_child
)
644 superset_entry
->has_zero_child
= 1;
646 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
647 superset_entry
->children
);
650 /* Enter the SUBSET itself as a child of the SUPERSET. */
651 splay_tree_insert (superset_entry
->children
,
652 (splay_tree_key
) subset
, 0);
656 /* Record that component types of TYPE, if any, are part of that type for
657 aliasing purposes. For record types, we only record component types
658 for fields that are marked addressable. For array types, we always
659 record the component types, so the front end should not call this
660 function if the individual component aren't addressable. */
663 record_component_aliases (type
)
666 HOST_WIDE_INT superset
= get_alias_set (type
);
672 switch (TREE_CODE (type
))
675 if (! TYPE_NONALIASED_COMPONENT (type
))
676 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
681 case QUAL_UNION_TYPE
:
682 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
683 if (TREE_CODE (field
) == FIELD_DECL
&& ! DECL_NONADDRESSABLE_P (field
))
684 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
688 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
696 /* Allocate an alias set for use in storing and reading from the varargs
700 get_varargs_alias_set ()
702 static HOST_WIDE_INT set
= -1;
705 set
= new_alias_set ();
710 /* Likewise, but used for the fixed portions of the frame, e.g., register
714 get_frame_alias_set ()
716 static HOST_WIDE_INT set
= -1;
719 set
= new_alias_set ();
724 /* Inside SRC, the source of a SET, find a base address. */
727 find_base_value (src
)
732 switch (GET_CODE (src
))
740 /* At the start of a function, argument registers have known base
741 values which may be lost later. Returning an ADDRESS
742 expression here allows optimization based on argument values
743 even when the argument registers are used for other purposes. */
744 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
745 return new_reg_base_value
[regno
];
747 /* If a pseudo has a known base value, return it. Do not do this
748 for non-fixed hard regs since it can result in a circular
749 dependency chain for registers which have values at function entry.
751 The test above is not sufficient because the scheduler may move
752 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
753 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
754 && regno
< reg_base_value_size
755 && reg_base_value
[regno
])
756 return reg_base_value
[regno
];
761 /* Check for an argument passed in memory. Only record in the
762 copying-arguments block; it is too hard to track changes
764 if (copying_arguments
765 && (XEXP (src
, 0) == arg_pointer_rtx
766 || (GET_CODE (XEXP (src
, 0)) == PLUS
767 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
768 return gen_rtx_ADDRESS (VOIDmode
, src
);
773 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
776 /* ... fall through ... */
781 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
783 /* If either operand is a REG that is a known pointer, then it
785 if (REG_P (src_0
) && REG_POINTER (src_0
))
786 return find_base_value (src_0
);
787 if (REG_P (src_1
) && REG_POINTER (src_1
))
788 return find_base_value (src_1
);
790 /* If either operand is a REG, then see if we already have
791 a known value for it. */
794 temp
= find_base_value (src_0
);
801 temp
= find_base_value (src_1
);
806 /* If either base is named object or a special address
807 (like an argument or stack reference), then use it for the
810 && (GET_CODE (src_0
) == SYMBOL_REF
811 || GET_CODE (src_0
) == LABEL_REF
812 || (GET_CODE (src_0
) == ADDRESS
813 && GET_MODE (src_0
) != VOIDmode
)))
817 && (GET_CODE (src_1
) == SYMBOL_REF
818 || GET_CODE (src_1
) == LABEL_REF
819 || (GET_CODE (src_1
) == ADDRESS
820 && GET_MODE (src_1
) != VOIDmode
)))
823 /* Guess which operand is the base address:
824 If either operand is a symbol, then it is the base. If
825 either operand is a CONST_INT, then the other is the base. */
826 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
827 return find_base_value (src_0
);
828 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
829 return find_base_value (src_1
);
835 /* The standard form is (lo_sum reg sym) so look only at the
837 return find_base_value (XEXP (src
, 1));
840 /* If the second operand is constant set the base
841 address to the first operand. */
842 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
843 return find_base_value (XEXP (src
, 0));
847 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
857 return find_base_value (XEXP (src
, 0));
860 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
862 rtx temp
= find_base_value (XEXP (src
, 0));
864 #ifdef POINTERS_EXTEND_UNSIGNED
865 if (temp
!= 0 && CONSTANT_P (temp
) && GET_MODE (temp
) != Pmode
)
866 temp
= convert_memory_address (Pmode
, temp
);
879 /* Called from init_alias_analysis indirectly through note_stores. */
881 /* While scanning insns to find base values, reg_seen[N] is nonzero if
882 register N has been set in this function. */
883 static char *reg_seen
;
885 /* Addresses which are known not to alias anything else are identified
886 by a unique integer. */
887 static int unique_id
;
890 record_set (dest
, set
, data
)
892 void *data ATTRIBUTE_UNUSED
;
897 if (GET_CODE (dest
) != REG
)
900 regno
= REGNO (dest
);
902 if (regno
>= reg_base_value_size
)
907 /* A CLOBBER wipes out any old value but does not prevent a previously
908 unset register from acquiring a base address (i.e. reg_seen is not
910 if (GET_CODE (set
) == CLOBBER
)
912 new_reg_base_value
[regno
] = 0;
921 new_reg_base_value
[regno
] = 0;
925 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
926 GEN_INT (unique_id
++));
930 /* This is not the first set. If the new value is not related to the
931 old value, forget the base value. Note that the following code is
933 extern int x, y; int *p = &x; p += (&y-&x);
934 ANSI C does not allow computing the difference of addresses
935 of distinct top level objects. */
936 if (new_reg_base_value
[regno
])
937 switch (GET_CODE (src
))
941 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
942 new_reg_base_value
[regno
] = 0;
945 /* If the value we add in the PLUS is also a valid base value,
946 this might be the actual base value, and the original value
949 rtx other
= NULL_RTX
;
951 if (XEXP (src
, 0) == dest
)
952 other
= XEXP (src
, 1);
953 else if (XEXP (src
, 1) == dest
)
954 other
= XEXP (src
, 0);
956 if (! other
|| find_base_value (other
))
957 new_reg_base_value
[regno
] = 0;
961 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
962 new_reg_base_value
[regno
] = 0;
965 new_reg_base_value
[regno
] = 0;
968 /* If this is the first set of a register, record the value. */
969 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
970 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
971 new_reg_base_value
[regno
] = find_base_value (src
);
976 /* Called from loop optimization when a new pseudo-register is
977 created. It indicates that REGNO is being set to VAL. f INVARIANT
978 is true then this value also describes an invariant relationship
979 which can be used to deduce that two registers with unknown values
983 record_base_value (regno
, val
, invariant
)
988 if (regno
>= reg_base_value_size
)
991 if (invariant
&& alias_invariant
)
992 alias_invariant
[regno
] = val
;
994 if (GET_CODE (val
) == REG
)
996 if (REGNO (val
) < reg_base_value_size
)
997 reg_base_value
[regno
] = reg_base_value
[REGNO (val
)];
1002 reg_base_value
[regno
] = find_base_value (val
);
1005 /* Clear alias info for a register. This is used if an RTL transformation
1006 changes the value of a register. This is used in flow by AUTO_INC_DEC
1007 optimizations. We don't need to clear reg_base_value, since flow only
1008 changes the offset. */
1011 clear_reg_alias_info (reg
)
1014 unsigned int regno
= REGNO (reg
);
1016 if (regno
< reg_known_value_size
&& regno
>= FIRST_PSEUDO_REGISTER
)
1017 reg_known_value
[regno
] = reg
;
1020 /* Returns a canonical version of X, from the point of view alias
1021 analysis. (For example, if X is a MEM whose address is a register,
1022 and the register has a known value (say a SYMBOL_REF), then a MEM
1023 whose address is the SYMBOL_REF is returned.) */
1029 /* Recursively look for equivalences. */
1030 if (GET_CODE (x
) == REG
&& REGNO (x
) >= FIRST_PSEUDO_REGISTER
1031 && REGNO (x
) < reg_known_value_size
)
1032 return reg_known_value
[REGNO (x
)] == x
1033 ? x
: canon_rtx (reg_known_value
[REGNO (x
)]);
1034 else if (GET_CODE (x
) == PLUS
)
1036 rtx x0
= canon_rtx (XEXP (x
, 0));
1037 rtx x1
= canon_rtx (XEXP (x
, 1));
1039 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1041 if (GET_CODE (x0
) == CONST_INT
)
1042 return plus_constant (x1
, INTVAL (x0
));
1043 else if (GET_CODE (x1
) == CONST_INT
)
1044 return plus_constant (x0
, INTVAL (x1
));
1045 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1049 /* This gives us much better alias analysis when called from
1050 the loop optimizer. Note we want to leave the original
1051 MEM alone, but need to return the canonicalized MEM with
1052 all the flags with their original values. */
1053 else if (GET_CODE (x
) == MEM
)
1054 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1059 /* Return 1 if X and Y are identical-looking rtx's.
1061 We use the data in reg_known_value above to see if two registers with
1062 different numbers are, in fact, equivalent. */
1065 rtx_equal_for_memref_p (x
, y
)
1073 if (x
== 0 && y
== 0)
1075 if (x
== 0 || y
== 0)
1084 code
= GET_CODE (x
);
1085 /* Rtx's of different codes cannot be equal. */
1086 if (code
!= GET_CODE (y
))
1089 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1090 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1092 if (GET_MODE (x
) != GET_MODE (y
))
1095 /* Some RTL can be compared without a recursive examination. */
1099 return CSELIB_VAL_PTR (x
) == CSELIB_VAL_PTR (y
);
1102 return REGNO (x
) == REGNO (y
);
1105 return XEXP (x
, 0) == XEXP (y
, 0);
1108 return XSTR (x
, 0) == XSTR (y
, 0);
1112 /* There's no need to compare the contents of CONST_DOUBLEs or
1113 CONST_INTs because pointer equality is a good enough
1114 comparison for these nodes. */
1118 return (XINT (x
, 1) == XINT (y
, 1)
1119 && rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0)));
1125 /* For commutative operations, the RTX match if the operand match in any
1126 order. Also handle the simple binary and unary cases without a loop. */
1127 if (code
== EQ
|| code
== NE
|| GET_RTX_CLASS (code
) == 'c')
1128 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1129 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1130 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1131 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1132 else if (GET_RTX_CLASS (code
) == '<' || GET_RTX_CLASS (code
) == '2')
1133 return (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1134 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)));
1135 else if (GET_RTX_CLASS (code
) == '1')
1136 return rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0));
1138 /* Compare the elements. If any pair of corresponding elements
1139 fail to match, return 0 for the whole things.
1141 Limit cases to types which actually appear in addresses. */
1143 fmt
= GET_RTX_FORMAT (code
);
1144 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1149 if (XINT (x
, i
) != XINT (y
, i
))
1154 /* Two vectors must have the same length. */
1155 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1158 /* And the corresponding elements must match. */
1159 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1160 if (rtx_equal_for_memref_p (XVECEXP (x
, i
, j
),
1161 XVECEXP (y
, i
, j
)) == 0)
1166 if (rtx_equal_for_memref_p (XEXP (x
, i
), XEXP (y
, i
)) == 0)
1170 /* This can happen for asm operands. */
1172 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1176 /* This can happen for an asm which clobbers memory. */
1180 /* It is believed that rtx's at this level will never
1181 contain anything but integers and other rtx's,
1182 except for within LABEL_REFs and SYMBOL_REFs. */
1190 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
1191 X and return it, or return 0 if none found. */
1194 find_symbolic_term (x
)
1201 code
= GET_CODE (x
);
1202 if (code
== SYMBOL_REF
|| code
== LABEL_REF
)
1204 if (GET_RTX_CLASS (code
) == 'o')
1207 fmt
= GET_RTX_FORMAT (code
);
1208 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1214 t
= find_symbolic_term (XEXP (x
, i
));
1218 else if (fmt
[i
] == 'E')
1229 struct elt_loc_list
*l
;
1231 #if defined (FIND_BASE_TERM)
1232 /* Try machine-dependent ways to find the base term. */
1233 x
= FIND_BASE_TERM (x
);
1236 switch (GET_CODE (x
))
1239 return REG_BASE_VALUE (x
);
1242 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1252 return find_base_term (XEXP (x
, 0));
1255 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1257 rtx temp
= find_base_term (XEXP (x
, 0));
1259 #ifdef POINTERS_EXTEND_UNSIGNED
1260 if (temp
!= 0 && CONSTANT_P (temp
) && GET_MODE (temp
) != Pmode
)
1261 temp
= convert_memory_address (Pmode
, temp
);
1268 val
= CSELIB_VAL_PTR (x
);
1269 for (l
= val
->locs
; l
; l
= l
->next
)
1270 if ((x
= find_base_term (l
->loc
)) != 0)
1276 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1283 rtx tmp1
= XEXP (x
, 0);
1284 rtx tmp2
= XEXP (x
, 1);
1286 /* This is a little bit tricky since we have to determine which of
1287 the two operands represents the real base address. Otherwise this
1288 routine may return the index register instead of the base register.
1290 That may cause us to believe no aliasing was possible, when in
1291 fact aliasing is possible.
1293 We use a few simple tests to guess the base register. Additional
1294 tests can certainly be added. For example, if one of the operands
1295 is a shift or multiply, then it must be the index register and the
1296 other operand is the base register. */
1298 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1299 return find_base_term (tmp2
);
1301 /* If either operand is known to be a pointer, then use it
1302 to determine the base term. */
1303 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1304 return find_base_term (tmp1
);
1306 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1307 return find_base_term (tmp2
);
1309 /* Neither operand was known to be a pointer. Go ahead and find the
1310 base term for both operands. */
1311 tmp1
= find_base_term (tmp1
);
1312 tmp2
= find_base_term (tmp2
);
1314 /* If either base term is named object or a special address
1315 (like an argument or stack reference), then use it for the
1318 && (GET_CODE (tmp1
) == SYMBOL_REF
1319 || GET_CODE (tmp1
) == LABEL_REF
1320 || (GET_CODE (tmp1
) == ADDRESS
1321 && GET_MODE (tmp1
) != VOIDmode
)))
1325 && (GET_CODE (tmp2
) == SYMBOL_REF
1326 || GET_CODE (tmp2
) == LABEL_REF
1327 || (GET_CODE (tmp2
) == ADDRESS
1328 && GET_MODE (tmp2
) != VOIDmode
)))
1331 /* We could not determine which of the two operands was the
1332 base register and which was the index. So we can determine
1333 nothing from the base alias check. */
1338 if (GET_CODE (XEXP (x
, 1)) == CONST_INT
&& INTVAL (XEXP (x
, 1)) != 0)
1339 return find_base_term (XEXP (x
, 0));
1347 return REG_BASE_VALUE (frame_pointer_rtx
);
1354 /* Return 0 if the addresses X and Y are known to point to different
1355 objects, 1 if they might be pointers to the same object. */
1358 base_alias_check (x
, y
, x_mode
, y_mode
)
1360 enum machine_mode x_mode
, y_mode
;
1362 rtx x_base
= find_base_term (x
);
1363 rtx y_base
= find_base_term (y
);
1365 /* If the address itself has no known base see if a known equivalent
1366 value has one. If either address still has no known base, nothing
1367 is known about aliasing. */
1372 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1375 x_base
= find_base_term (x_c
);
1383 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1386 y_base
= find_base_term (y_c
);
1391 /* If the base addresses are equal nothing is known about aliasing. */
1392 if (rtx_equal_p (x_base
, y_base
))
1395 /* The base addresses of the read and write are different expressions.
1396 If they are both symbols and they are not accessed via AND, there is
1397 no conflict. We can bring knowledge of object alignment into play
1398 here. For example, on alpha, "char a, b;" can alias one another,
1399 though "char a; long b;" cannot. */
1400 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1402 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1404 if (GET_CODE (x
) == AND
1405 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1406 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1408 if (GET_CODE (y
) == AND
1409 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1410 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1412 /* Differing symbols never alias. */
1416 /* If one address is a stack reference there can be no alias:
1417 stack references using different base registers do not alias,
1418 a stack reference can not alias a parameter, and a stack reference
1419 can not alias a global. */
1420 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1421 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1424 if (! flag_argument_noalias
)
1427 if (flag_argument_noalias
> 1)
1430 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1431 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1434 /* Convert the address X into something we can use. This is done by returning
1435 it unchanged unless it is a value; in the latter case we call cselib to get
1436 a more useful rtx. */
1443 struct elt_loc_list
*l
;
1445 if (GET_CODE (x
) != VALUE
)
1447 v
= CSELIB_VAL_PTR (x
);
1448 for (l
= v
->locs
; l
; l
= l
->next
)
1449 if (CONSTANT_P (l
->loc
))
1451 for (l
= v
->locs
; l
; l
= l
->next
)
1452 if (GET_CODE (l
->loc
) != REG
&& GET_CODE (l
->loc
) != MEM
)
1455 return v
->locs
->loc
;
1459 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1460 where SIZE is the size in bytes of the memory reference. If ADDR
1461 is not modified by the memory reference then ADDR is returned. */
1464 addr_side_effect_eval (addr
, size
, n_refs
)
1471 switch (GET_CODE (addr
))
1474 offset
= (n_refs
+ 1) * size
;
1477 offset
= -(n_refs
+ 1) * size
;
1480 offset
= n_refs
* size
;
1483 offset
= -n_refs
* size
;
1491 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0), GEN_INT (offset
));
1493 addr
= XEXP (addr
, 0);
1498 /* Return nonzero if X and Y (memory addresses) could reference the
1499 same location in memory. C is an offset accumulator. When
1500 C is nonzero, we are testing aliases between X and Y + C.
1501 XSIZE is the size in bytes of the X reference,
1502 similarly YSIZE is the size in bytes for Y.
1504 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1505 referenced (the reference was BLKmode), so make the most pessimistic
1508 If XSIZE or YSIZE is negative, we may access memory outside the object
1509 being referenced as a side effect. This can happen when using AND to
1510 align memory references, as is done on the Alpha.
1512 Nice to notice that varying addresses cannot conflict with fp if no
1513 local variables had their addresses taken, but that's too hard now. */
1516 memrefs_conflict_p (xsize
, x
, ysize
, y
, c
)
1521 if (GET_CODE (x
) == VALUE
)
1523 if (GET_CODE (y
) == VALUE
)
1525 if (GET_CODE (x
) == HIGH
)
1527 else if (GET_CODE (x
) == LO_SUM
)
1530 x
= canon_rtx (addr_side_effect_eval (x
, xsize
, 0));
1531 if (GET_CODE (y
) == HIGH
)
1533 else if (GET_CODE (y
) == LO_SUM
)
1536 y
= canon_rtx (addr_side_effect_eval (y
, ysize
, 0));
1538 if (rtx_equal_for_memref_p (x
, y
))
1540 if (xsize
<= 0 || ysize
<= 0)
1542 if (c
>= 0 && xsize
> c
)
1544 if (c
< 0 && ysize
+c
> 0)
1549 /* This code used to check for conflicts involving stack references and
1550 globals but the base address alias code now handles these cases. */
1552 if (GET_CODE (x
) == PLUS
)
1554 /* The fact that X is canonicalized means that this
1555 PLUS rtx is canonicalized. */
1556 rtx x0
= XEXP (x
, 0);
1557 rtx x1
= XEXP (x
, 1);
1559 if (GET_CODE (y
) == PLUS
)
1561 /* The fact that Y is canonicalized means that this
1562 PLUS rtx is canonicalized. */
1563 rtx y0
= XEXP (y
, 0);
1564 rtx y1
= XEXP (y
, 1);
1566 if (rtx_equal_for_memref_p (x1
, y1
))
1567 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1568 if (rtx_equal_for_memref_p (x0
, y0
))
1569 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1570 if (GET_CODE (x1
) == CONST_INT
)
1572 if (GET_CODE (y1
) == CONST_INT
)
1573 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1574 c
- INTVAL (x1
) + INTVAL (y1
));
1576 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1579 else if (GET_CODE (y1
) == CONST_INT
)
1580 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1584 else if (GET_CODE (x1
) == CONST_INT
)
1585 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1587 else if (GET_CODE (y
) == PLUS
)
1589 /* The fact that Y is canonicalized means that this
1590 PLUS rtx is canonicalized. */
1591 rtx y0
= XEXP (y
, 0);
1592 rtx y1
= XEXP (y
, 1);
1594 if (GET_CODE (y1
) == CONST_INT
)
1595 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1600 if (GET_CODE (x
) == GET_CODE (y
))
1601 switch (GET_CODE (x
))
1605 /* Handle cases where we expect the second operands to be the
1606 same, and check only whether the first operand would conflict
1609 rtx x1
= canon_rtx (XEXP (x
, 1));
1610 rtx y1
= canon_rtx (XEXP (y
, 1));
1611 if (! rtx_equal_for_memref_p (x1
, y1
))
1613 x0
= canon_rtx (XEXP (x
, 0));
1614 y0
= canon_rtx (XEXP (y
, 0));
1615 if (rtx_equal_for_memref_p (x0
, y0
))
1616 return (xsize
== 0 || ysize
== 0
1617 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1619 /* Can't properly adjust our sizes. */
1620 if (GET_CODE (x1
) != CONST_INT
)
1622 xsize
/= INTVAL (x1
);
1623 ysize
/= INTVAL (x1
);
1625 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1629 /* Are these registers known not to be equal? */
1630 if (alias_invariant
)
1632 unsigned int r_x
= REGNO (x
), r_y
= REGNO (y
);
1633 rtx i_x
, i_y
; /* invariant relationships of X and Y */
1635 i_x
= r_x
>= reg_base_value_size
? 0 : alias_invariant
[r_x
];
1636 i_y
= r_y
>= reg_base_value_size
? 0 : alias_invariant
[r_y
];
1638 if (i_x
== 0 && i_y
== 0)
1641 if (! memrefs_conflict_p (xsize
, i_x
? i_x
: x
,
1642 ysize
, i_y
? i_y
: y
, c
))
1651 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1652 as an access with indeterminate size. Assume that references
1653 besides AND are aligned, so if the size of the other reference is
1654 at least as large as the alignment, assume no other overlap. */
1655 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1657 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1659 return memrefs_conflict_p (xsize
, XEXP (x
, 0), ysize
, y
, c
);
1661 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1663 /* ??? If we are indexing far enough into the array/structure, we
1664 may yet be able to determine that we can not overlap. But we
1665 also need to that we are far enough from the end not to overlap
1666 a following reference, so we do nothing with that for now. */
1667 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1669 return memrefs_conflict_p (xsize
, x
, ysize
, XEXP (y
, 0), c
);
1672 if (GET_CODE (x
) == ADDRESSOF
)
1674 if (y
== frame_pointer_rtx
1675 || GET_CODE (y
) == ADDRESSOF
)
1676 return xsize
<= 0 || ysize
<= 0;
1678 if (GET_CODE (y
) == ADDRESSOF
)
1680 if (x
== frame_pointer_rtx
)
1681 return xsize
<= 0 || ysize
<= 0;
1686 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1688 c
+= (INTVAL (y
) - INTVAL (x
));
1689 return (xsize
<= 0 || ysize
<= 0
1690 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1693 if (GET_CODE (x
) == CONST
)
1695 if (GET_CODE (y
) == CONST
)
1696 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1697 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1699 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1702 if (GET_CODE (y
) == CONST
)
1703 return memrefs_conflict_p (xsize
, x
, ysize
,
1704 canon_rtx (XEXP (y
, 0)), c
);
1707 return (xsize
<= 0 || ysize
<= 0
1708 || (rtx_equal_for_memref_p (x
, y
)
1709 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1716 /* Functions to compute memory dependencies.
1718 Since we process the insns in execution order, we can build tables
1719 to keep track of what registers are fixed (and not aliased), what registers
1720 are varying in known ways, and what registers are varying in unknown
1723 If both memory references are volatile, then there must always be a
1724 dependence between the two references, since their order can not be
1725 changed. A volatile and non-volatile reference can be interchanged
1728 A MEM_IN_STRUCT reference at a non-AND varying address can never
1729 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1730 also must allow AND addresses, because they may generate accesses
1731 outside the object being referenced. This is used to generate
1732 aligned addresses from unaligned addresses, for instance, the alpha
1733 storeqi_unaligned pattern. */
1735 /* Read dependence: X is read after read in MEM takes place. There can
1736 only be a dependence here if both reads are volatile. */
1739 read_dependence (mem
, x
)
1743 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1746 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1747 MEM2 is a reference to a structure at a varying address, or returns
1748 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1749 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1750 to decide whether or not an address may vary; it should return
1751 nonzero whenever variation is possible.
1752 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1755 fixed_scalar_and_varying_struct_p (mem1
, mem2
, mem1_addr
, mem2_addr
, varies_p
)
1757 rtx mem1_addr
, mem2_addr
;
1758 int (*varies_p
) PARAMS ((rtx
, int));
1760 if (! flag_strict_aliasing
)
1763 if (MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1764 && !varies_p (mem1_addr
, 1) && varies_p (mem2_addr
, 1))
1765 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1769 if (MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1770 && varies_p (mem1_addr
, 1) && !varies_p (mem2_addr
, 1))
1771 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1778 /* Returns nonzero if something about the mode or address format MEM1
1779 indicates that it might well alias *anything*. */
1782 aliases_everything_p (mem
)
1785 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1786 /* If the address is an AND, its very hard to know at what it is
1787 actually pointing. */
1793 /* Return true if we can determine that the fields referenced cannot
1794 overlap for any pair of objects. */
1797 nonoverlapping_component_refs_p (x
, y
)
1800 tree fieldx
, fieldy
, typex
, typey
, orig_y
;
1804 /* The comparison has to be done at a common type, since we don't
1805 know how the inheritance hierarchy works. */
1809 fieldx
= TREE_OPERAND (x
, 1);
1810 typex
= DECL_FIELD_CONTEXT (fieldx
);
1815 fieldy
= TREE_OPERAND (y
, 1);
1816 typey
= DECL_FIELD_CONTEXT (fieldy
);
1821 y
= TREE_OPERAND (y
, 0);
1823 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
1825 x
= TREE_OPERAND (x
, 0);
1827 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1829 /* Never found a common type. */
1833 /* If we're left with accessing different fields of a structure,
1835 if (TREE_CODE (typex
) == RECORD_TYPE
1836 && fieldx
!= fieldy
)
1839 /* The comparison on the current field failed. If we're accessing
1840 a very nested structure, look at the next outer level. */
1841 x
= TREE_OPERAND (x
, 0);
1842 y
= TREE_OPERAND (y
, 0);
1845 && TREE_CODE (x
) == COMPONENT_REF
1846 && TREE_CODE (y
) == COMPONENT_REF
);
1851 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
1854 decl_for_component_ref (x
)
1859 x
= TREE_OPERAND (x
, 0);
1861 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1863 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
1866 /* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
1867 offset of the field reference. */
1870 adjust_offset_for_component_ref (x
, offset
)
1874 HOST_WIDE_INT ioffset
;
1879 ioffset
= INTVAL (offset
);
1882 tree field
= TREE_OPERAND (x
, 1);
1884 if (! host_integerp (DECL_FIELD_OFFSET (field
), 1))
1886 ioffset
+= (tree_low_cst (DECL_FIELD_OFFSET (field
), 1)
1887 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
1890 x
= TREE_OPERAND (x
, 0);
1892 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
1894 return GEN_INT (ioffset
);
1897 /* Return nonzero if we can deterimine the exprs corresponding to memrefs
1898 X and Y and they do not overlap. */
1901 nonoverlapping_memrefs_p (x
, y
)
1904 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
1907 rtx moffsetx
, moffsety
;
1908 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
1910 /* Unless both have exprs, we can't tell anything. */
1911 if (exprx
== 0 || expry
== 0)
1914 /* If both are field references, we may be able to determine something. */
1915 if (TREE_CODE (exprx
) == COMPONENT_REF
1916 && TREE_CODE (expry
) == COMPONENT_REF
1917 && nonoverlapping_component_refs_p (exprx
, expry
))
1920 /* If the field reference test failed, look at the DECLs involved. */
1921 moffsetx
= MEM_OFFSET (x
);
1922 if (TREE_CODE (exprx
) == COMPONENT_REF
)
1924 tree t
= decl_for_component_ref (exprx
);
1927 moffsetx
= adjust_offset_for_component_ref (exprx
, moffsetx
);
1930 moffsety
= MEM_OFFSET (y
);
1931 if (TREE_CODE (expry
) == COMPONENT_REF
)
1933 tree t
= decl_for_component_ref (expry
);
1936 moffsety
= adjust_offset_for_component_ref (expry
, moffsety
);
1940 if (! DECL_P (exprx
) || ! DECL_P (expry
))
1943 rtlx
= DECL_RTL (exprx
);
1944 rtly
= DECL_RTL (expry
);
1946 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
1947 can't overlap unless they are the same because we never reuse that part
1948 of the stack frame used for locals for spilled pseudos. */
1949 if ((GET_CODE (rtlx
) != MEM
|| GET_CODE (rtly
) != MEM
)
1950 && ! rtx_equal_p (rtlx
, rtly
))
1953 /* Get the base and offsets of both decls. If either is a register, we
1954 know both are and are the same, so use that as the base. The only
1955 we can avoid overlap is if we can deduce that they are nonoverlapping
1956 pieces of that decl, which is very rare. */
1957 basex
= GET_CODE (rtlx
) == MEM
? XEXP (rtlx
, 0) : rtlx
;
1958 if (GET_CODE (basex
) == PLUS
&& GET_CODE (XEXP (basex
, 1)) == CONST_INT
)
1959 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
1961 basey
= GET_CODE (rtly
) == MEM
? XEXP (rtly
, 0) : rtly
;
1962 if (GET_CODE (basey
) == PLUS
&& GET_CODE (XEXP (basey
, 1)) == CONST_INT
)
1963 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
1965 /* If the bases are different, we know they do not overlap if both
1966 are constants or if one is a constant and the other a pointer into the
1967 stack frame. Otherwise a different base means we can't tell if they
1969 if (! rtx_equal_p (basex
, basey
))
1970 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
1971 || (CONSTANT_P (basex
) && REG_P (basey
)
1972 && REGNO_PTR_FRAME_P (REGNO (basey
)))
1973 || (CONSTANT_P (basey
) && REG_P (basex
)
1974 && REGNO_PTR_FRAME_P (REGNO (basex
))));
1976 sizex
= (GET_CODE (rtlx
) != MEM
? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
1977 : MEM_SIZE (rtlx
) ? INTVAL (MEM_SIZE (rtlx
))
1979 sizey
= (GET_CODE (rtly
) != MEM
? (int) GET_MODE_SIZE (GET_MODE (rtly
))
1980 : MEM_SIZE (rtly
) ? INTVAL (MEM_SIZE (rtly
)) :
1983 /* If we have an offset for either memref, it can update the values computed
1986 offsetx
+= INTVAL (moffsetx
), sizex
-= INTVAL (moffsetx
);
1988 offsety
+= INTVAL (moffsety
), sizey
-= INTVAL (moffsety
);
1990 /* If a memref has both a size and an offset, we can use the smaller size.
1991 We can't do this if the offset isn't known because we must view this
1992 memref as being anywhere inside the DECL's MEM. */
1993 if (MEM_SIZE (x
) && moffsetx
)
1994 sizex
= INTVAL (MEM_SIZE (x
));
1995 if (MEM_SIZE (y
) && moffsety
)
1996 sizey
= INTVAL (MEM_SIZE (y
));
1998 /* Put the values of the memref with the lower offset in X's values. */
1999 if (offsetx
> offsety
)
2001 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2002 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2005 /* If we don't know the size of the lower-offset value, we can't tell
2006 if they conflict. Otherwise, we do the test. */
2007 return sizex
>= 0 && offsety
> offsetx
+ sizex
;
2010 /* True dependence: X is read after store in MEM takes place. */
2013 true_dependence (mem
, mem_mode
, x
, varies
)
2015 enum machine_mode mem_mode
;
2017 int (*varies
) PARAMS ((rtx
, int));
2019 rtx x_addr
, mem_addr
;
2022 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2025 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2028 /* Unchanging memory can't conflict with non-unchanging memory.
2029 A non-unchanging read can conflict with a non-unchanging write.
2030 An unchanging read can conflict with an unchanging write since
2031 there may be a single store to this address to initialize it.
2032 Note that an unchanging store can conflict with a non-unchanging read
2033 since we have to make conservative assumptions when we have a
2034 record with readonly fields and we are copying the whole thing.
2035 Just fall through to the code below to resolve potential conflicts.
2036 This won't handle all cases optimally, but the possible performance
2037 loss should be negligible. */
2038 if (RTX_UNCHANGING_P (x
) && ! RTX_UNCHANGING_P (mem
))
2041 if (nonoverlapping_memrefs_p (mem
, x
))
2044 if (mem_mode
== VOIDmode
)
2045 mem_mode
= GET_MODE (mem
);
2047 x_addr
= get_addr (XEXP (x
, 0));
2048 mem_addr
= get_addr (XEXP (mem
, 0));
2050 base
= find_base_term (x_addr
);
2051 if (base
&& (GET_CODE (base
) == LABEL_REF
2052 || (GET_CODE (base
) == SYMBOL_REF
2053 && CONSTANT_POOL_ADDRESS_P (base
))))
2056 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2059 x_addr
= canon_rtx (x_addr
);
2060 mem_addr
= canon_rtx (mem_addr
);
2062 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2063 SIZE_FOR_MODE (x
), x_addr
, 0))
2066 if (aliases_everything_p (x
))
2069 /* We cannot use aliases_everything_p to test MEM, since we must look
2070 at MEM_MODE, rather than GET_MODE (MEM). */
2071 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2074 /* In true_dependence we also allow BLKmode to alias anything. Why
2075 don't we do this in anti_dependence and output_dependence? */
2076 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2079 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2083 /* Canonical true dependence: X is read after store in MEM takes place.
2084 Variant of true_dependence which assumes MEM has already been
2085 canonicalized (hence we no longer do that here).
2086 The mem_addr argument has been added, since true_dependence computed
2087 this value prior to canonicalizing. */
2090 canon_true_dependence (mem
, mem_mode
, mem_addr
, x
, varies
)
2091 rtx mem
, mem_addr
, x
;
2092 enum machine_mode mem_mode
;
2093 int (*varies
) PARAMS ((rtx
, int));
2097 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2100 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2103 /* If X is an unchanging read, then it can't possibly conflict with any
2104 non-unchanging store. It may conflict with an unchanging write though,
2105 because there may be a single store to this address to initialize it.
2106 Just fall through to the code below to resolve the case where we have
2107 both an unchanging read and an unchanging write. This won't handle all
2108 cases optimally, but the possible performance loss should be
2110 if (RTX_UNCHANGING_P (x
) && ! RTX_UNCHANGING_P (mem
))
2113 if (nonoverlapping_memrefs_p (x
, mem
))
2116 x_addr
= get_addr (XEXP (x
, 0));
2118 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2121 x_addr
= canon_rtx (x_addr
);
2122 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2123 SIZE_FOR_MODE (x
), x_addr
, 0))
2126 if (aliases_everything_p (x
))
2129 /* We cannot use aliases_everything_p to test MEM, since we must look
2130 at MEM_MODE, rather than GET_MODE (MEM). */
2131 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
2134 /* In true_dependence we also allow BLKmode to alias anything. Why
2135 don't we do this in anti_dependence and output_dependence? */
2136 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2139 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2143 /* Returns non-zero if a write to X might alias a previous read from
2144 (or, if WRITEP is non-zero, a write to) MEM. */
2147 write_dependence_p (mem
, x
, writep
)
2152 rtx x_addr
, mem_addr
;
2156 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2159 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2162 /* Unchanging memory can't conflict with non-unchanging memory. */
2163 if (RTX_UNCHANGING_P (x
) != RTX_UNCHANGING_P (mem
))
2166 /* If MEM is an unchanging read, then it can't possibly conflict with
2167 the store to X, because there is at most one store to MEM, and it must
2168 have occurred somewhere before MEM. */
2169 if (! writep
&& RTX_UNCHANGING_P (mem
))
2172 if (nonoverlapping_memrefs_p (x
, mem
))
2175 x_addr
= get_addr (XEXP (x
, 0));
2176 mem_addr
= get_addr (XEXP (mem
, 0));
2180 base
= find_base_term (mem_addr
);
2181 if (base
&& (GET_CODE (base
) == LABEL_REF
2182 || (GET_CODE (base
) == SYMBOL_REF
2183 && CONSTANT_POOL_ADDRESS_P (base
))))
2187 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2191 x_addr
= canon_rtx (x_addr
);
2192 mem_addr
= canon_rtx (mem_addr
);
2194 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2195 SIZE_FOR_MODE (x
), x_addr
, 0))
2199 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
2202 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
2203 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
2206 /* Anti dependence: X is written after read in MEM takes place. */
2209 anti_dependence (mem
, x
)
2213 return write_dependence_p (mem
, x
, /*writep=*/0);
2216 /* Output dependence: X is written after store in MEM takes place. */
2219 output_dependence (mem
, x
)
2223 return write_dependence_p (mem
, x
, /*writep=*/1);
2226 /* Returns non-zero if X mentions something which is not
2227 local to the function and is not constant. */
2230 nonlocal_mentioned_p (x
)
2237 code
= GET_CODE (x
);
2239 if (GET_RTX_CLASS (code
) == 'i')
2241 /* Constant functions can be constant if they don't use
2242 scratch memory used to mark function w/o side effects. */
2243 if (code
== CALL_INSN
&& CONST_OR_PURE_CALL_P (x
))
2245 x
= CALL_INSN_FUNCTION_USAGE (x
);
2251 code
= GET_CODE (x
);
2257 if (GET_CODE (SUBREG_REG (x
)) == REG
)
2259 /* Global registers are not local. */
2260 if (REGNO (SUBREG_REG (x
)) < FIRST_PSEUDO_REGISTER
2261 && global_regs
[subreg_regno (x
)])
2269 /* Global registers are not local. */
2270 if (regno
< FIRST_PSEUDO_REGISTER
&& global_regs
[regno
])
2284 /* Constants in the function's constants pool are constant. */
2285 if (CONSTANT_POOL_ADDRESS_P (x
))
2290 /* Non-constant calls and recursion are not local. */
2294 /* Be overly conservative and consider any volatile memory
2295 reference as not local. */
2296 if (MEM_VOLATILE_P (x
))
2298 base
= find_base_term (XEXP (x
, 0));
2301 /* A Pmode ADDRESS could be a reference via the structure value
2302 address or static chain. Such memory references are nonlocal.
2304 Thus, we have to examine the contents of the ADDRESS to find
2305 out if this is a local reference or not. */
2306 if (GET_CODE (base
) == ADDRESS
2307 && GET_MODE (base
) == Pmode
2308 && (XEXP (base
, 0) == stack_pointer_rtx
2309 || XEXP (base
, 0) == arg_pointer_rtx
2310 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2311 || XEXP (base
, 0) == hard_frame_pointer_rtx
2313 || XEXP (base
, 0) == frame_pointer_rtx
))
2315 /* Constants in the function's constant pool are constant. */
2316 if (GET_CODE (base
) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (base
))
2321 case UNSPEC_VOLATILE
:
2326 if (MEM_VOLATILE_P (x
))
2335 /* Recursively scan the operands of this expression. */
2338 const char *fmt
= GET_RTX_FORMAT (code
);
2341 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
2343 if (fmt
[i
] == 'e' && XEXP (x
, i
))
2345 if (nonlocal_mentioned_p (XEXP (x
, i
)))
2348 else if (fmt
[i
] == 'E')
2351 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2352 if (nonlocal_mentioned_p (XVECEXP (x
, i
, j
)))
2361 /* Mark the function if it is constant. */
2364 mark_constant_function ()
2367 int nonlocal_mentioned
;
2369 if (TREE_PUBLIC (current_function_decl
)
2370 || TREE_READONLY (current_function_decl
)
2371 || DECL_IS_PURE (current_function_decl
)
2372 || TREE_THIS_VOLATILE (current_function_decl
)
2373 || TYPE_MODE (TREE_TYPE (current_function_decl
)) == VOIDmode
)
2376 /* A loop might not return which counts as a side effect. */
2377 if (mark_dfs_back_edges ())
2380 nonlocal_mentioned
= 0;
2382 init_alias_analysis ();
2384 /* Determine if this is a constant function. */
2386 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2387 if (INSN_P (insn
) && nonlocal_mentioned_p (insn
))
2389 nonlocal_mentioned
= 1;
2393 end_alias_analysis ();
2395 /* Mark the function. */
2397 if (! nonlocal_mentioned
)
2398 TREE_READONLY (current_function_decl
) = 1;
2402 static HARD_REG_SET argument_registers
;
2409 #ifndef OUTGOING_REGNO
2410 #define OUTGOING_REGNO(N) N
2412 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2413 /* Check whether this register can hold an incoming pointer
2414 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2415 numbers, so translate if necessary due to register windows. */
2416 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2417 && HARD_REGNO_MODE_OK (i
, Pmode
))
2418 SET_HARD_REG_BIT (argument_registers
, i
);
2420 alias_sets
= splay_tree_new (splay_tree_compare_ints
, 0, 0);
2423 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2427 init_alias_analysis ()
2429 int maxreg
= max_reg_num ();
2435 reg_known_value_size
= maxreg
;
2438 = (rtx
*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (rtx
))
2439 - FIRST_PSEUDO_REGISTER
;
2441 = (char*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (char))
2442 - FIRST_PSEUDO_REGISTER
;
2444 /* Overallocate reg_base_value to allow some growth during loop
2445 optimization. Loop unrolling can create a large number of
2447 reg_base_value_size
= maxreg
* 2;
2448 reg_base_value
= (rtx
*) xcalloc (reg_base_value_size
, sizeof (rtx
));
2449 ggc_add_rtx_root (reg_base_value
, reg_base_value_size
);
2451 new_reg_base_value
= (rtx
*) xmalloc (reg_base_value_size
* sizeof (rtx
));
2452 reg_seen
= (char *) xmalloc (reg_base_value_size
);
2453 if (! reload_completed
&& flag_unroll_loops
)
2455 /* ??? Why are we realloc'ing if we're just going to zero it? */
2456 alias_invariant
= (rtx
*)xrealloc (alias_invariant
,
2457 reg_base_value_size
* sizeof (rtx
));
2458 memset ((char *)alias_invariant
, 0, reg_base_value_size
* sizeof (rtx
));
2461 /* The basic idea is that each pass through this loop will use the
2462 "constant" information from the previous pass to propagate alias
2463 information through another level of assignments.
2465 This could get expensive if the assignment chains are long. Maybe
2466 we should throttle the number of iterations, possibly based on
2467 the optimization level or flag_expensive_optimizations.
2469 We could propagate more information in the first pass by making use
2470 of REG_N_SETS to determine immediately that the alias information
2471 for a pseudo is "constant".
2473 A program with an uninitialized variable can cause an infinite loop
2474 here. Instead of doing a full dataflow analysis to detect such problems
2475 we just cap the number of iterations for the loop.
2477 The state of the arrays for the set chain in question does not matter
2478 since the program has undefined behavior. */
2483 /* Assume nothing will change this iteration of the loop. */
2486 /* We want to assign the same IDs each iteration of this loop, so
2487 start counting from zero each iteration of the loop. */
2490 /* We're at the start of the function each iteration through the
2491 loop, so we're copying arguments. */
2492 copying_arguments
= 1;
2494 /* Wipe the potential alias information clean for this pass. */
2495 memset ((char *) new_reg_base_value
, 0, reg_base_value_size
* sizeof (rtx
));
2497 /* Wipe the reg_seen array clean. */
2498 memset ((char *) reg_seen
, 0, reg_base_value_size
);
2500 /* Mark all hard registers which may contain an address.
2501 The stack, frame and argument pointers may contain an address.
2502 An argument register which can hold a Pmode value may contain
2503 an address even if it is not in BASE_REGS.
2505 The address expression is VOIDmode for an argument and
2506 Pmode for other registers. */
2508 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2509 if (TEST_HARD_REG_BIT (argument_registers
, i
))
2510 new_reg_base_value
[i
] = gen_rtx_ADDRESS (VOIDmode
,
2511 gen_rtx_REG (Pmode
, i
));
2513 new_reg_base_value
[STACK_POINTER_REGNUM
]
2514 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2515 new_reg_base_value
[ARG_POINTER_REGNUM
]
2516 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2517 new_reg_base_value
[FRAME_POINTER_REGNUM
]
2518 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2519 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2520 new_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2521 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2524 /* Walk the insns adding values to the new_reg_base_value array. */
2525 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2531 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2532 /* The prologue/epilogue insns are not threaded onto the
2533 insn chain until after reload has completed. Thus,
2534 there is no sense wasting time checking if INSN is in
2535 the prologue/epilogue until after reload has completed. */
2536 if (reload_completed
2537 && prologue_epilogue_contains (insn
))
2541 /* If this insn has a noalias note, process it, Otherwise,
2542 scan for sets. A simple set will have no side effects
2543 which could change the base value of any other register. */
2545 if (GET_CODE (PATTERN (insn
)) == SET
2546 && REG_NOTES (insn
) != 0
2547 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2548 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2550 note_stores (PATTERN (insn
), record_set
, NULL
);
2552 set
= single_set (insn
);
2555 && GET_CODE (SET_DEST (set
)) == REG
2556 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2558 unsigned int regno
= REGNO (SET_DEST (set
));
2559 rtx src
= SET_SRC (set
);
2561 if (REG_NOTES (insn
) != 0
2562 && (((note
= find_reg_note (insn
, REG_EQUAL
, 0)) != 0
2563 && REG_N_SETS (regno
) == 1)
2564 || (note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) != 0)
2565 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2566 && ! rtx_varies_p (XEXP (note
, 0), 1)
2567 && ! reg_overlap_mentioned_p (SET_DEST (set
), XEXP (note
, 0)))
2569 reg_known_value
[regno
] = XEXP (note
, 0);
2570 reg_known_equiv_p
[regno
] = REG_NOTE_KIND (note
) == REG_EQUIV
;
2572 else if (REG_N_SETS (regno
) == 1
2573 && GET_CODE (src
) == PLUS
2574 && GET_CODE (XEXP (src
, 0)) == REG
2575 && REGNO (XEXP (src
, 0)) >= FIRST_PSEUDO_REGISTER
2576 && (reg_known_value
[REGNO (XEXP (src
, 0))])
2577 && GET_CODE (XEXP (src
, 1)) == CONST_INT
)
2579 rtx op0
= XEXP (src
, 0);
2580 op0
= reg_known_value
[REGNO (op0
)];
2581 reg_known_value
[regno
]
2582 = plus_constant (op0
, INTVAL (XEXP (src
, 1)));
2583 reg_known_equiv_p
[regno
] = 0;
2585 else if (REG_N_SETS (regno
) == 1
2586 && ! rtx_varies_p (src
, 1))
2588 reg_known_value
[regno
] = src
;
2589 reg_known_equiv_p
[regno
] = 0;
2593 else if (GET_CODE (insn
) == NOTE
2594 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_FUNCTION_BEG
)
2595 copying_arguments
= 0;
2598 /* Now propagate values from new_reg_base_value to reg_base_value. */
2599 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
2601 if (new_reg_base_value
[ui
]
2602 && new_reg_base_value
[ui
] != reg_base_value
[ui
]
2603 && ! rtx_equal_p (new_reg_base_value
[ui
], reg_base_value
[ui
]))
2605 reg_base_value
[ui
] = new_reg_base_value
[ui
];
2610 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2612 /* Fill in the remaining entries. */
2613 for (i
= FIRST_PSEUDO_REGISTER
; i
< maxreg
; i
++)
2614 if (reg_known_value
[i
] == 0)
2615 reg_known_value
[i
] = regno_reg_rtx
[i
];
2617 /* Simplify the reg_base_value array so that no register refers to
2618 another register, except to special registers indirectly through
2619 ADDRESS expressions.
2621 In theory this loop can take as long as O(registers^2), but unless
2622 there are very long dependency chains it will run in close to linear
2625 This loop may not be needed any longer now that the main loop does
2626 a better job at propagating alias information. */
2632 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
2634 rtx base
= reg_base_value
[ui
];
2635 if (base
&& GET_CODE (base
) == REG
)
2637 unsigned int base_regno
= REGNO (base
);
2638 if (base_regno
== ui
) /* register set from itself */
2639 reg_base_value
[ui
] = 0;
2641 reg_base_value
[ui
] = reg_base_value
[base_regno
];
2646 while (changed
&& pass
< MAX_ALIAS_LOOP_PASSES
);
2649 free (new_reg_base_value
);
2650 new_reg_base_value
= 0;
2656 end_alias_analysis ()
2658 free (reg_known_value
+ FIRST_PSEUDO_REGISTER
);
2659 reg_known_value
= 0;
2660 reg_known_value_size
= 0;
2661 free (reg_known_equiv_p
+ FIRST_PSEUDO_REGISTER
);
2662 reg_known_equiv_p
= 0;
2665 ggc_del_root (reg_base_value
);
2666 free (reg_base_value
);
2669 reg_base_value_size
= 0;
2670 if (alias_invariant
)
2672 free (alias_invariant
);
2673 alias_invariant
= 0;