1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
3 Contributed by John Carr (jfc@mit.edu).
5 This file is part of GNU CC.
7 GNU CC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2, or (at your option)
12 GNU CC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU CC; see the file COPYING. If not, write to
19 the Free Software Foundation, 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
28 #include "insn-flags.h"
31 #include "hard-reg-set.h"
36 #include "splay-tree.h"
39 /* The alias sets assigned to MEMs assist the back-end in determining
40 which MEMs can alias which other MEMs. In general, two MEMs in
41 different alias sets cannot alias each other, with one important
42 exception. Consider something like:
44 struct S {int i; double d; };
46 a store to an `S' can alias something of either type `int' or type
47 `double'. (However, a store to an `int' cannot alias a `double'
48 and vice versa.) We indicate this via a tree structure that looks
56 (The arrows are directed and point downwards.)
57 In this situation we say the alias set for `struct S' is the
58 `superset' and that those for `int' and `double' are `subsets'.
60 To see whether two alias sets can point to the same memory, we must
61 see if either alias set is a subset of the other. We need not trace
62 past immediate decendents, however, since we propagate all
63 grandchildren up one level.
65 Alias set zero is implicitly a superset of all other alias sets.
66 However, this is no actual entry for alias set zero. It is an
67 error to attempt to explicitly construct a subset of zero. */
69 typedef struct alias_set_entry
71 /* The alias set number, as stored in MEM_ALIAS_SET. */
72 HOST_WIDE_INT alias_set
;
74 /* The children of the alias set. These are not just the immediate
75 children, but, in fact, all decendents. So, if we have:
77 struct T { struct S s; float f; }
79 continuing our example above, the children here will be all of
80 `int', `double', `float', and `struct S'. */
83 /* Nonzero if would have a child of zero: this effectively makes this
84 alias set the same as alias set zero. */
88 static int rtx_equal_for_memref_p
PARAMS ((rtx
, rtx
));
89 static rtx find_symbolic_term
PARAMS ((rtx
));
90 static rtx get_addr
PARAMS ((rtx
));
91 static int memrefs_conflict_p
PARAMS ((int, rtx
, int, rtx
,
93 static void record_set
PARAMS ((rtx
, rtx
, void *));
94 static rtx find_base_term
PARAMS ((rtx
));
95 static int base_alias_check
PARAMS ((rtx
, rtx
, enum machine_mode
,
97 static rtx find_base_value
PARAMS ((rtx
));
98 static int mems_in_disjoint_alias_sets_p
PARAMS ((rtx
, rtx
));
99 static int insert_subset_children
PARAMS ((splay_tree_node
, void*));
100 static tree find_base_decl
PARAMS ((tree
));
101 static alias_set_entry get_alias_set_entry
PARAMS ((HOST_WIDE_INT
));
102 static rtx fixed_scalar_and_varying_struct_p
PARAMS ((rtx
, rtx
, rtx
, rtx
,
104 static int aliases_everything_p
PARAMS ((rtx
));
105 static int write_dependence_p
PARAMS ((rtx
, rtx
, int));
106 static int nonlocal_reference_p
PARAMS ((rtx
));
108 /* Set up all info needed to perform alias analysis on memory references. */
110 /* Returns the size in bytes of the mode of X. */
111 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
113 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
114 different alias sets. We ignore alias sets in functions making use
115 of variable arguments because the va_arg macros on some systems are
117 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
118 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
120 /* Cap the number of passes we make over the insns propagating alias
121 information through set chains. 10 is a completely arbitrary choice. */
122 #define MAX_ALIAS_LOOP_PASSES 10
124 /* reg_base_value[N] gives an address to which register N is related.
125 If all sets after the first add or subtract to the current value
126 or otherwise modify it so it does not point to a different top level
127 object, reg_base_value[N] is equal to the address part of the source
130 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
131 expressions represent certain special values: function arguments and
132 the stack, frame, and argument pointers.
134 The contents of an ADDRESS is not normally used, the mode of the
135 ADDRESS determines whether the ADDRESS is a function argument or some
136 other special value. Pointer equality, not rtx_equal_p, determines whether
137 two ADDRESS expressions refer to the same base address.
139 The only use of the contents of an ADDRESS is for determining if the
140 current function performs nonlocal memory memory references for the
141 purposes of marking the function as a constant function. */
143 static rtx
*reg_base_value
;
144 static rtx
*new_reg_base_value
;
145 static unsigned int reg_base_value_size
; /* size of reg_base_value array */
147 #define REG_BASE_VALUE(X) \
148 (REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0)
150 /* Vector of known invariant relationships between registers. Set in
151 loop unrolling. Indexed by register number, if nonzero the value
152 is an expression describing this register in terms of another.
154 The length of this array is REG_BASE_VALUE_SIZE.
156 Because this array contains only pseudo registers it has no effect
158 static rtx
*alias_invariant
;
160 /* Vector indexed by N giving the initial (unchanging) value known for
161 pseudo-register N. This array is initialized in
162 init_alias_analysis, and does not change until end_alias_analysis
164 rtx
*reg_known_value
;
166 /* Indicates number of valid entries in reg_known_value. */
167 static unsigned int reg_known_value_size
;
169 /* Vector recording for each reg_known_value whether it is due to a
170 REG_EQUIV note. Future passes (viz., reload) may replace the
171 pseudo with the equivalent expression and so we account for the
172 dependences that would be introduced if that happens.
174 The REG_EQUIV notes created in assign_parms may mention the arg
175 pointer, and there are explicit insns in the RTL that modify the
176 arg pointer. Thus we must ensure that such insns don't get
177 scheduled across each other because that would invalidate the
178 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
179 wrong, but solving the problem in the scheduler will likely give
180 better code, so we do it here. */
181 char *reg_known_equiv_p
;
183 /* True when scanning insns from the start of the rtl to the
184 NOTE_INSN_FUNCTION_BEG note. */
185 static int copying_arguments
;
187 /* The splay-tree used to store the various alias set entries. */
188 static splay_tree alias_sets
;
190 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
191 such an entry, or NULL otherwise. */
193 static alias_set_entry
194 get_alias_set_entry (alias_set
)
195 HOST_WIDE_INT alias_set
;
198 = splay_tree_lookup (alias_sets
, (splay_tree_key
) alias_set
);
200 return sn
!= 0 ? ((alias_set_entry
) sn
->value
) : 0;
203 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
204 the two MEMs cannot alias each other. */
207 mems_in_disjoint_alias_sets_p (mem1
, mem2
)
213 #ifdef ENABLE_CHECKING
214 /* Perform a basic sanity check. Namely, that there are no alias sets
215 if we're not using strict aliasing. This helps to catch bugs
216 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
217 where a MEM is allocated in some way other than by the use of
218 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
219 use alias sets to indicate that spilled registers cannot alias each
220 other, we might need to remove this check. */
221 if (! flag_strict_aliasing
222 && (MEM_ALIAS_SET (mem1
) != 0 || MEM_ALIAS_SET (mem2
) != 0))
226 /* The code used in varargs macros are often not conforming ANSI C,
227 which can trick the compiler into making incorrect aliasing
228 assumptions in these functions. So, we don't use alias sets in
229 such a function. FIXME: This should be moved into the front-end;
230 it is a language-dependent notion, and there's no reason not to
231 still use these checks to handle globals. */
232 if (current_function_stdarg
|| current_function_varargs
)
235 /* If have no alias set information for one of the MEMs, we have to assume
236 it can alias anything. */
237 if (MEM_ALIAS_SET (mem1
) == 0 || MEM_ALIAS_SET (mem2
) == 0)
240 /* If the two alias sets are the same, they may alias. */
241 if (MEM_ALIAS_SET (mem1
) == MEM_ALIAS_SET (mem2
))
244 /* See if the first alias set is a subset of the second. */
245 ase
= get_alias_set_entry (MEM_ALIAS_SET (mem1
));
247 && (ase
->has_zero_child
248 || splay_tree_lookup (ase
->children
,
249 (splay_tree_key
) MEM_ALIAS_SET (mem2
))))
252 /* Now do the same, but with the alias sets reversed. */
253 ase
= get_alias_set_entry (MEM_ALIAS_SET (mem2
));
255 && (ase
->has_zero_child
256 || splay_tree_lookup (ase
->children
,
257 (splay_tree_key
) MEM_ALIAS_SET (mem1
))))
260 /* The two MEMs are in distinct alias sets, and neither one is the
261 child of the other. Therefore, they cannot alias. */
265 /* Insert the NODE into the splay tree given by DATA. Used by
266 record_alias_subset via splay_tree_foreach. */
269 insert_subset_children (node
, data
)
270 splay_tree_node node
;
273 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
278 /* T is an expression with pointer type. Find the DECL on which this
279 expression is based. (For example, in `a[i]' this would be `a'.)
280 If there is no such DECL, or a unique decl cannot be determined,
281 NULL_TREE is retured. */
289 if (t
== 0 || t
== error_mark_node
|| ! POINTER_TYPE_P (TREE_TYPE (t
)))
292 /* If this is a declaration, return it. */
293 if (TREE_CODE_CLASS (TREE_CODE (t
)) == 'd')
296 /* Handle general expressions. It would be nice to deal with
297 COMPONENT_REFs here. If we could tell that `a' and `b' were the
298 same, then `a->f' and `b->f' are also the same. */
299 switch (TREE_CODE_CLASS (TREE_CODE (t
)))
302 return find_base_decl (TREE_OPERAND (t
, 0));
305 /* Return 0 if found in neither or both are the same. */
306 d0
= find_base_decl (TREE_OPERAND (t
, 0));
307 d1
= find_base_decl (TREE_OPERAND (t
, 1));
318 d0
= find_base_decl (TREE_OPERAND (t
, 0));
319 d1
= find_base_decl (TREE_OPERAND (t
, 1));
320 d0
= find_base_decl (TREE_OPERAND (t
, 0));
321 d2
= find_base_decl (TREE_OPERAND (t
, 2));
323 /* Set any nonzero values from the last, then from the first. */
324 if (d1
== 0) d1
= d2
;
325 if (d0
== 0) d0
= d1
;
326 if (d1
== 0) d1
= d0
;
327 if (d2
== 0) d2
= d1
;
329 /* At this point all are nonzero or all are zero. If all three are the
330 same, return it. Otherwise, return zero. */
331 return (d0
== d1
&& d1
== d2
) ? d0
: 0;
338 /* Return the alias set for T, which may be either a type or an
339 expression. Call language-specific routine for help, if needed. */
347 HOST_WIDE_INT bitsize
, bitpos
;
349 enum machine_mode mode
;
350 int volatilep
, unsignedp
;
351 unsigned int alignment
;
353 /* If we're not doing any alias analysis, just assume everything
354 aliases everything else. Also return 0 if this or its type is
356 if (! flag_strict_aliasing
|| t
== error_mark_node
358 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
361 /* We can be passed either an expression or a type. This and the
362 language-specific routine may make mutually-recursive calls to
363 each other to figure out what to do. At each juncture, we see if
364 this is a tree that the language may need to handle specially.
365 First handle things that aren't types and start by removing nops
366 since we care only about the actual object. */
369 while (TREE_CODE (t
) == NOP_EXPR
|| TREE_CODE (t
) == CONVERT_EXPR
370 || TREE_CODE (t
) == NON_LVALUE_EXPR
)
371 t
= TREE_OPERAND (t
, 0);
373 /* Now give the language a chance to do something but record what we
374 gave it this time. */
376 if ((set
= lang_get_alias_set (t
)) != -1)
379 /* If this is a reference, go inside it and use the underlying
381 if (TREE_CODE_CLASS (TREE_CODE (t
)) == 'r')
382 t
= get_inner_reference (t
, &bitsize
, &bitpos
, &offset
, &mode
,
383 &unsignedp
, &volatilep
, &alignment
);
385 if (TREE_CODE (t
) == INDIRECT_REF
)
387 /* Check for accesses through restrict-qualified pointers. */
388 tree decl
= find_base_decl (TREE_OPERAND (t
, 0));
390 if (decl
&& DECL_POINTER_ALIAS_SET_KNOWN_P (decl
))
391 /* We use the alias set indicated in the declaration. */
392 return DECL_POINTER_ALIAS_SET (decl
);
394 /* If we have an INDIRECT_REF via a void pointer, we don't
395 know anything about what that might alias. */
396 if (TREE_CODE (TREE_TYPE (t
)) == VOID_TYPE
)
400 /* Give the language another chance to do something special. */
402 && (set
= lang_get_alias_set (t
)) != -1)
405 /* Now all we care about is the type. */
409 /* Variant qualifiers don't affect the alias set, so get the main
410 variant. If this is a type with a known alias set, return it. */
411 t
= TYPE_MAIN_VARIANT (t
);
412 if (TYPE_P (t
) && TYPE_ALIAS_SET_KNOWN_P (t
))
413 return TYPE_ALIAS_SET (t
);
415 /* See if the language has special handling for this type. */
416 if ((set
= lang_get_alias_set (t
)) != -1)
418 /* If the alias set is now known, we are done. */
419 if (TYPE_ALIAS_SET_KNOWN_P (t
))
420 return TYPE_ALIAS_SET (t
);
423 /* There are no objects of FUNCTION_TYPE, so there's no point in
424 using up an alias set for them. (There are, of course, pointers
425 and references to functions, but that's different.) */
426 else if (TREE_CODE (t
) == FUNCTION_TYPE
)
429 /* Otherwise make a new alias set for this type. */
430 set
= new_alias_set ();
432 TYPE_ALIAS_SET (t
) = set
;
434 /* If this is an aggregate type, we must record any component aliasing
436 if (AGGREGATE_TYPE_P (t
))
437 record_component_aliases (t
);
442 /* Return a brand-new alias set. */
447 static HOST_WIDE_INT last_alias_set
;
449 if (flag_strict_aliasing
)
450 return ++last_alias_set
;
455 /* Indicate that things in SUBSET can alias things in SUPERSET, but
456 not vice versa. For example, in C, a store to an `int' can alias a
457 structure containing an `int', but not vice versa. Here, the
458 structure would be the SUPERSET and `int' the SUBSET. This
459 function should be called only once per SUPERSET/SUBSET pair.
461 It is illegal for SUPERSET to be zero; everything is implicitly a
462 subset of alias set zero. */
465 record_alias_subset (superset
, subset
)
466 HOST_WIDE_INT superset
;
467 HOST_WIDE_INT subset
;
469 alias_set_entry superset_entry
;
470 alias_set_entry subset_entry
;
475 superset_entry
= get_alias_set_entry (superset
);
476 if (superset_entry
== 0)
478 /* Create an entry for the SUPERSET, so that we have a place to
479 attach the SUBSET. */
481 = (alias_set_entry
) xmalloc (sizeof (struct alias_set_entry
));
482 superset_entry
->alias_set
= superset
;
483 superset_entry
->children
484 = splay_tree_new (splay_tree_compare_ints
, 0, 0);
485 superset_entry
->has_zero_child
= 0;
486 splay_tree_insert (alias_sets
, (splay_tree_key
) superset
,
487 (splay_tree_value
) superset_entry
);
491 superset_entry
->has_zero_child
= 1;
494 subset_entry
= get_alias_set_entry (subset
);
495 /* If there is an entry for the subset, enter all of its children
496 (if they are not already present) as children of the SUPERSET. */
499 if (subset_entry
->has_zero_child
)
500 superset_entry
->has_zero_child
= 1;
502 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
503 superset_entry
->children
);
506 /* Enter the SUBSET itself as a child of the SUPERSET. */
507 splay_tree_insert (superset_entry
->children
,
508 (splay_tree_key
) subset
, 0);
512 /* Record that component types of TYPE, if any, are part of that type for
513 aliasing purposes. For record types, we only record component types
514 for fields that are marked addressable. For array types, we always
515 record the component types, so the front end should not call this
516 function if the individual component aren't addressable. */
519 record_component_aliases (type
)
522 HOST_WIDE_INT superset
= get_alias_set (type
);
528 switch (TREE_CODE (type
))
531 if (! TYPE_NONALIASED_COMPONENT (type
))
532 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
537 case QUAL_UNION_TYPE
:
538 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= TREE_CHAIN (field
))
539 if (! DECL_NONADDRESSABLE_P (field
))
540 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
548 /* Allocate an alias set for use in storing and reading from the varargs
552 get_varargs_alias_set ()
554 static HOST_WIDE_INT set
= -1;
557 set
= new_alias_set ();
562 /* Likewise, but used for the fixed portions of the frame, e.g., register
566 get_frame_alias_set ()
568 static HOST_WIDE_INT set
= -1;
571 set
= new_alias_set ();
576 /* Inside SRC, the source of a SET, find a base address. */
579 find_base_value (src
)
582 switch (GET_CODE (src
))
589 /* At the start of a function, argument registers have known base
590 values which may be lost later. Returning an ADDRESS
591 expression here allows optimization based on argument values
592 even when the argument registers are used for other purposes. */
593 if (REGNO (src
) < FIRST_PSEUDO_REGISTER
&& copying_arguments
)
594 return new_reg_base_value
[REGNO (src
)];
596 /* If a pseudo has a known base value, return it. Do not do this
597 for hard regs since it can result in a circular dependency
598 chain for registers which have values at function entry.
600 The test above is not sufficient because the scheduler may move
601 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
602 if (REGNO (src
) >= FIRST_PSEUDO_REGISTER
603 && (unsigned) REGNO (src
) < reg_base_value_size
604 && reg_base_value
[REGNO (src
)])
605 return reg_base_value
[REGNO (src
)];
610 /* Check for an argument passed in memory. Only record in the
611 copying-arguments block; it is too hard to track changes
613 if (copying_arguments
614 && (XEXP (src
, 0) == arg_pointer_rtx
615 || (GET_CODE (XEXP (src
, 0)) == PLUS
616 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
617 return gen_rtx_ADDRESS (VOIDmode
, src
);
622 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
625 /* ... fall through ... */
630 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
632 /* If either operand is a REG, then see if we already have
633 a known value for it. */
634 if (GET_CODE (src_0
) == REG
)
636 temp
= find_base_value (src_0
);
641 if (GET_CODE (src_1
) == REG
)
643 temp
= find_base_value (src_1
);
648 /* Guess which operand is the base address:
649 If either operand is a symbol, then it is the base. If
650 either operand is a CONST_INT, then the other is the base. */
651 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
652 return find_base_value (src_0
);
653 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
654 return find_base_value (src_1
);
656 /* This might not be necessary anymore:
657 If either operand is a REG that is a known pointer, then it
659 else if (GET_CODE (src_0
) == REG
&& REGNO_POINTER_FLAG (REGNO (src_0
)))
660 return find_base_value (src_0
);
661 else if (GET_CODE (src_1
) == REG
&& REGNO_POINTER_FLAG (REGNO (src_1
)))
662 return find_base_value (src_1
);
668 /* The standard form is (lo_sum reg sym) so look only at the
670 return find_base_value (XEXP (src
, 1));
673 /* If the second operand is constant set the base
674 address to the first operand. */
675 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
676 return find_base_value (XEXP (src
, 0));
680 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
682 return find_base_value (XEXP (src
, 0));
691 /* Called from init_alias_analysis indirectly through note_stores. */
693 /* While scanning insns to find base values, reg_seen[N] is nonzero if
694 register N has been set in this function. */
695 static char *reg_seen
;
697 /* Addresses which are known not to alias anything else are identified
698 by a unique integer. */
699 static int unique_id
;
702 record_set (dest
, set
, data
)
704 void *data ATTRIBUTE_UNUSED
;
706 register unsigned regno
;
709 if (GET_CODE (dest
) != REG
)
712 regno
= REGNO (dest
);
714 if (regno
>= reg_base_value_size
)
719 /* A CLOBBER wipes out any old value but does not prevent a previously
720 unset register from acquiring a base address (i.e. reg_seen is not
722 if (GET_CODE (set
) == CLOBBER
)
724 new_reg_base_value
[regno
] = 0;
733 new_reg_base_value
[regno
] = 0;
737 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
738 GEN_INT (unique_id
++));
742 /* This is not the first set. If the new value is not related to the
743 old value, forget the base value. Note that the following code is
745 extern int x, y; int *p = &x; p += (&y-&x);
746 ANSI C does not allow computing the difference of addresses
747 of distinct top level objects. */
748 if (new_reg_base_value
[regno
])
749 switch (GET_CODE (src
))
754 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
755 new_reg_base_value
[regno
] = 0;
758 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
759 new_reg_base_value
[regno
] = 0;
762 new_reg_base_value
[regno
] = 0;
765 /* If this is the first set of a register, record the value. */
766 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
767 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
768 new_reg_base_value
[regno
] = find_base_value (src
);
773 /* Called from loop optimization when a new pseudo-register is
774 created. It indicates that REGNO is being set to VAL. f INVARIANT
775 is true then this value also describes an invariant relationship
776 which can be used to deduce that two registers with unknown values
780 record_base_value (regno
, val
, invariant
)
785 if (regno
>= reg_base_value_size
)
788 if (invariant
&& alias_invariant
)
789 alias_invariant
[regno
] = val
;
791 if (GET_CODE (val
) == REG
)
793 if (REGNO (val
) < reg_base_value_size
)
794 reg_base_value
[regno
] = reg_base_value
[REGNO (val
)];
799 reg_base_value
[regno
] = find_base_value (val
);
802 /* Returns a canonical version of X, from the point of view alias
803 analysis. (For example, if X is a MEM whose address is a register,
804 and the register has a known value (say a SYMBOL_REF), then a MEM
805 whose address is the SYMBOL_REF is returned.) */
811 /* Recursively look for equivalences. */
812 if (GET_CODE (x
) == REG
&& REGNO (x
) >= FIRST_PSEUDO_REGISTER
813 && REGNO (x
) < reg_known_value_size
)
814 return reg_known_value
[REGNO (x
)] == x
815 ? x
: canon_rtx (reg_known_value
[REGNO (x
)]);
816 else if (GET_CODE (x
) == PLUS
)
818 rtx x0
= canon_rtx (XEXP (x
, 0));
819 rtx x1
= canon_rtx (XEXP (x
, 1));
821 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
823 /* We can tolerate LO_SUMs being offset here; these
824 rtl are used for nothing other than comparisons. */
825 if (GET_CODE (x0
) == CONST_INT
)
826 return plus_constant_for_output (x1
, INTVAL (x0
));
827 else if (GET_CODE (x1
) == CONST_INT
)
828 return plus_constant_for_output (x0
, INTVAL (x1
));
829 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
833 /* This gives us much better alias analysis when called from
834 the loop optimizer. Note we want to leave the original
835 MEM alone, but need to return the canonicalized MEM with
836 all the flags with their original values. */
837 else if (GET_CODE (x
) == MEM
)
839 rtx addr
= canon_rtx (XEXP (x
, 0));
841 if (addr
!= XEXP (x
, 0))
843 rtx
new = gen_rtx_MEM (GET_MODE (x
), addr
);
845 MEM_COPY_ATTRIBUTES (new, x
);
852 /* Return 1 if X and Y are identical-looking rtx's.
854 We use the data in reg_known_value above to see if two registers with
855 different numbers are, in fact, equivalent. */
858 rtx_equal_for_memref_p (x
, y
)
863 register enum rtx_code code
;
864 register const char *fmt
;
866 if (x
== 0 && y
== 0)
868 if (x
== 0 || y
== 0)
878 /* Rtx's of different codes cannot be equal. */
879 if (code
!= GET_CODE (y
))
882 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
883 (REG:SI x) and (REG:HI x) are NOT equivalent. */
885 if (GET_MODE (x
) != GET_MODE (y
))
888 /* Some RTL can be compared without a recursive examination. */
892 return REGNO (x
) == REGNO (y
);
895 return XEXP (x
, 0) == XEXP (y
, 0);
898 return XSTR (x
, 0) == XSTR (y
, 0);
902 /* There's no need to compare the contents of CONST_DOUBLEs or
903 CONST_INTs because pointer equality is a good enough
904 comparison for these nodes. */
908 return (REGNO (XEXP (x
, 0)) == REGNO (XEXP (y
, 0))
909 && XINT (x
, 1) == XINT (y
, 1));
915 /* For commutative operations, the RTX match if the operand match in any
916 order. Also handle the simple binary and unary cases without a loop. */
917 if (code
== EQ
|| code
== NE
|| GET_RTX_CLASS (code
) == 'c')
918 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
919 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
920 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
921 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
922 else if (GET_RTX_CLASS (code
) == '<' || GET_RTX_CLASS (code
) == '2')
923 return (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
924 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)));
925 else if (GET_RTX_CLASS (code
) == '1')
926 return rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0));
928 /* Compare the elements. If any pair of corresponding elements
929 fail to match, return 0 for the whole things.
931 Limit cases to types which actually appear in addresses. */
933 fmt
= GET_RTX_FORMAT (code
);
934 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
939 if (XINT (x
, i
) != XINT (y
, i
))
944 /* Two vectors must have the same length. */
945 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
948 /* And the corresponding elements must match. */
949 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
950 if (rtx_equal_for_memref_p (XVECEXP (x
, i
, j
),
951 XVECEXP (y
, i
, j
)) == 0)
956 if (rtx_equal_for_memref_p (XEXP (x
, i
), XEXP (y
, i
)) == 0)
960 /* This can happen for an asm which clobbers memory. */
964 /* It is believed that rtx's at this level will never
965 contain anything but integers and other rtx's,
966 except for within LABEL_REFs and SYMBOL_REFs. */
974 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
975 X and return it, or return 0 if none found. */
978 find_symbolic_term (x
)
982 register enum rtx_code code
;
983 register const char *fmt
;
986 if (code
== SYMBOL_REF
|| code
== LABEL_REF
)
988 if (GET_RTX_CLASS (code
) == 'o')
991 fmt
= GET_RTX_FORMAT (code
);
992 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
998 t
= find_symbolic_term (XEXP (x
, i
));
1002 else if (fmt
[i
] == 'E')
1013 struct elt_loc_list
*l
;
1015 switch (GET_CODE (x
))
1018 return REG_BASE_VALUE (x
);
1021 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1027 return find_base_term (XEXP (x
, 0));
1030 val
= CSELIB_VAL_PTR (x
);
1031 for (l
= val
->locs
; l
; l
= l
->next
)
1032 if ((x
= find_base_term (l
->loc
)) != 0)
1038 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1045 rtx tmp1
= XEXP (x
, 0);
1046 rtx tmp2
= XEXP (x
, 1);
1048 /* This is a litle bit tricky since we have to determine which of
1049 the two operands represents the real base address. Otherwise this
1050 routine may return the index register instead of the base register.
1052 That may cause us to believe no aliasing was possible, when in
1053 fact aliasing is possible.
1055 We use a few simple tests to guess the base register. Additional
1056 tests can certainly be added. For example, if one of the operands
1057 is a shift or multiply, then it must be the index register and the
1058 other operand is the base register. */
1060 /* If either operand is known to be a pointer, then use it
1061 to determine the base term. */
1062 if (REG_P (tmp1
) && REGNO_POINTER_FLAG (REGNO (tmp1
)))
1063 return find_base_term (tmp1
);
1065 if (REG_P (tmp2
) && REGNO_POINTER_FLAG (REGNO (tmp2
)))
1066 return find_base_term (tmp2
);
1068 /* Neither operand was known to be a pointer. Go ahead and find the
1069 base term for both operands. */
1070 tmp1
= find_base_term (tmp1
);
1071 tmp2
= find_base_term (tmp2
);
1073 /* If either base term is named object or a special address
1074 (like an argument or stack reference), then use it for the
1077 && (GET_CODE (tmp1
) == SYMBOL_REF
1078 || GET_CODE (tmp1
) == LABEL_REF
1079 || (GET_CODE (tmp1
) == ADDRESS
1080 && GET_MODE (tmp1
) != VOIDmode
)))
1084 && (GET_CODE (tmp2
) == SYMBOL_REF
1085 || GET_CODE (tmp2
) == LABEL_REF
1086 || (GET_CODE (tmp2
) == ADDRESS
1087 && GET_MODE (tmp2
) != VOIDmode
)))
1090 /* We could not determine which of the two operands was the
1091 base register and which was the index. So we can determine
1092 nothing from the base alias check. */
1097 if (GET_CODE (XEXP (x
, 0)) == REG
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1098 return REG_BASE_VALUE (XEXP (x
, 0));
1110 /* Return 0 if the addresses X and Y are known to point to different
1111 objects, 1 if they might be pointers to the same object. */
1114 base_alias_check (x
, y
, x_mode
, y_mode
)
1116 enum machine_mode x_mode
, y_mode
;
1118 rtx x_base
= find_base_term (x
);
1119 rtx y_base
= find_base_term (y
);
1121 /* If the address itself has no known base see if a known equivalent
1122 value has one. If either address still has no known base, nothing
1123 is known about aliasing. */
1128 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1131 x_base
= find_base_term (x_c
);
1139 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1142 y_base
= find_base_term (y_c
);
1147 /* If the base addresses are equal nothing is known about aliasing. */
1148 if (rtx_equal_p (x_base
, y_base
))
1151 /* The base addresses of the read and write are different expressions.
1152 If they are both symbols and they are not accessed via AND, there is
1153 no conflict. We can bring knowledge of object alignment into play
1154 here. For example, on alpha, "char a, b;" can alias one another,
1155 though "char a; long b;" cannot. */
1156 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1158 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1160 if (GET_CODE (x
) == AND
1161 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
1162 || GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1164 if (GET_CODE (y
) == AND
1165 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
1166 || GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1168 /* Differing symbols never alias. */
1172 /* If one address is a stack reference there can be no alias:
1173 stack references using different base registers do not alias,
1174 a stack reference can not alias a parameter, and a stack reference
1175 can not alias a global. */
1176 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1177 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1180 if (! flag_argument_noalias
)
1183 if (flag_argument_noalias
> 1)
1186 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1187 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
1190 /* Convert the address X into something we can use. This is done by returning
1191 it unchanged unless it is a value; in the latter case we call cselib to get
1192 a more useful rtx. */
1199 struct elt_loc_list
*l
;
1201 if (GET_CODE (x
) != VALUE
)
1203 v
= CSELIB_VAL_PTR (x
);
1204 for (l
= v
->locs
; l
; l
= l
->next
)
1205 if (CONSTANT_P (l
->loc
))
1207 for (l
= v
->locs
; l
; l
= l
->next
)
1208 if (GET_CODE (l
->loc
) != REG
&& GET_CODE (l
->loc
) != MEM
)
1211 return v
->locs
->loc
;
1215 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1216 where SIZE is the size in bytes of the memory reference. If ADDR
1217 is not modified by the memory reference then ADDR is returned. */
1220 addr_side_effect_eval (addr
, size
, n_refs
)
1227 switch (GET_CODE (addr
))
1230 offset
= (n_refs
+ 1) * size
;
1233 offset
= -(n_refs
+ 1) * size
;
1236 offset
= n_refs
* size
;
1239 offset
= -n_refs
* size
;
1247 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0), GEN_INT (offset
));
1249 addr
= XEXP (addr
, 0);
1254 /* Return nonzero if X and Y (memory addresses) could reference the
1255 same location in memory. C is an offset accumulator. When
1256 C is nonzero, we are testing aliases between X and Y + C.
1257 XSIZE is the size in bytes of the X reference,
1258 similarly YSIZE is the size in bytes for Y.
1260 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1261 referenced (the reference was BLKmode), so make the most pessimistic
1264 If XSIZE or YSIZE is negative, we may access memory outside the object
1265 being referenced as a side effect. This can happen when using AND to
1266 align memory references, as is done on the Alpha.
1268 Nice to notice that varying addresses cannot conflict with fp if no
1269 local variables had their addresses taken, but that's too hard now. */
1272 memrefs_conflict_p (xsize
, x
, ysize
, y
, c
)
1277 if (GET_CODE (x
) == VALUE
)
1279 if (GET_CODE (y
) == VALUE
)
1281 if (GET_CODE (x
) == HIGH
)
1283 else if (GET_CODE (x
) == LO_SUM
)
1286 x
= canon_rtx (addr_side_effect_eval (x
, xsize
, 0));
1287 if (GET_CODE (y
) == HIGH
)
1289 else if (GET_CODE (y
) == LO_SUM
)
1292 y
= canon_rtx (addr_side_effect_eval (y
, ysize
, 0));
1294 if (rtx_equal_for_memref_p (x
, y
))
1296 if (xsize
<= 0 || ysize
<= 0)
1298 if (c
>= 0 && xsize
> c
)
1300 if (c
< 0 && ysize
+c
> 0)
1305 /* This code used to check for conflicts involving stack references and
1306 globals but the base address alias code now handles these cases. */
1308 if (GET_CODE (x
) == PLUS
)
1310 /* The fact that X is canonicalized means that this
1311 PLUS rtx is canonicalized. */
1312 rtx x0
= XEXP (x
, 0);
1313 rtx x1
= XEXP (x
, 1);
1315 if (GET_CODE (y
) == PLUS
)
1317 /* The fact that Y is canonicalized means that this
1318 PLUS rtx is canonicalized. */
1319 rtx y0
= XEXP (y
, 0);
1320 rtx y1
= XEXP (y
, 1);
1322 if (rtx_equal_for_memref_p (x1
, y1
))
1323 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1324 if (rtx_equal_for_memref_p (x0
, y0
))
1325 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1326 if (GET_CODE (x1
) == CONST_INT
)
1328 if (GET_CODE (y1
) == CONST_INT
)
1329 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1330 c
- INTVAL (x1
) + INTVAL (y1
));
1332 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1335 else if (GET_CODE (y1
) == CONST_INT
)
1336 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1340 else if (GET_CODE (x1
) == CONST_INT
)
1341 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1343 else if (GET_CODE (y
) == PLUS
)
1345 /* The fact that Y is canonicalized means that this
1346 PLUS rtx is canonicalized. */
1347 rtx y0
= XEXP (y
, 0);
1348 rtx y1
= XEXP (y
, 1);
1350 if (GET_CODE (y1
) == CONST_INT
)
1351 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1356 if (GET_CODE (x
) == GET_CODE (y
))
1357 switch (GET_CODE (x
))
1361 /* Handle cases where we expect the second operands to be the
1362 same, and check only whether the first operand would conflict
1365 rtx x1
= canon_rtx (XEXP (x
, 1));
1366 rtx y1
= canon_rtx (XEXP (y
, 1));
1367 if (! rtx_equal_for_memref_p (x1
, y1
))
1369 x0
= canon_rtx (XEXP (x
, 0));
1370 y0
= canon_rtx (XEXP (y
, 0));
1371 if (rtx_equal_for_memref_p (x0
, y0
))
1372 return (xsize
== 0 || ysize
== 0
1373 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1375 /* Can't properly adjust our sizes. */
1376 if (GET_CODE (x1
) != CONST_INT
)
1378 xsize
/= INTVAL (x1
);
1379 ysize
/= INTVAL (x1
);
1381 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1385 /* Are these registers known not to be equal? */
1386 if (alias_invariant
)
1388 unsigned int r_x
= REGNO (x
), r_y
= REGNO (y
);
1389 rtx i_x
, i_y
; /* invariant relationships of X and Y */
1391 i_x
= r_x
>= reg_base_value_size
? 0 : alias_invariant
[r_x
];
1392 i_y
= r_y
>= reg_base_value_size
? 0 : alias_invariant
[r_y
];
1394 if (i_x
== 0 && i_y
== 0)
1397 if (! memrefs_conflict_p (xsize
, i_x
? i_x
: x
,
1398 ysize
, i_y
? i_y
: y
, c
))
1407 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1408 as an access with indeterminate size. Assume that references
1409 besides AND are aligned, so if the size of the other reference is
1410 at least as large as the alignment, assume no other overlap. */
1411 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1413 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1415 return memrefs_conflict_p (xsize
, XEXP (x
, 0), ysize
, y
, c
);
1417 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1419 /* ??? If we are indexing far enough into the array/structure, we
1420 may yet be able to determine that we can not overlap. But we
1421 also need to that we are far enough from the end not to overlap
1422 a following reference, so we do nothing with that for now. */
1423 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1425 return memrefs_conflict_p (xsize
, x
, ysize
, XEXP (y
, 0), c
);
1430 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1432 c
+= (INTVAL (y
) - INTVAL (x
));
1433 return (xsize
<= 0 || ysize
<= 0
1434 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1437 if (GET_CODE (x
) == CONST
)
1439 if (GET_CODE (y
) == CONST
)
1440 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1441 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1443 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1446 if (GET_CODE (y
) == CONST
)
1447 return memrefs_conflict_p (xsize
, x
, ysize
,
1448 canon_rtx (XEXP (y
, 0)), c
);
1451 return (xsize
< 0 || ysize
< 0
1452 || (rtx_equal_for_memref_p (x
, y
)
1453 && (xsize
== 0 || ysize
== 0
1454 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1461 /* Functions to compute memory dependencies.
1463 Since we process the insns in execution order, we can build tables
1464 to keep track of what registers are fixed (and not aliased), what registers
1465 are varying in known ways, and what registers are varying in unknown
1468 If both memory references are volatile, then there must always be a
1469 dependence between the two references, since their order can not be
1470 changed. A volatile and non-volatile reference can be interchanged
1473 A MEM_IN_STRUCT reference at a non-AND varying address can never
1474 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1475 also must allow AND addresses, because they may generate accesses
1476 outside the object being referenced. This is used to generate
1477 aligned addresses from unaligned addresses, for instance, the alpha
1478 storeqi_unaligned pattern. */
1480 /* Read dependence: X is read after read in MEM takes place. There can
1481 only be a dependence here if both reads are volatile. */
1484 read_dependence (mem
, x
)
1488 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1491 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1492 MEM2 is a reference to a structure at a varying address, or returns
1493 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1494 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1495 to decide whether or not an address may vary; it should return
1496 nonzero whenever variation is possible.
1497 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1500 fixed_scalar_and_varying_struct_p (mem1
, mem2
, mem1_addr
, mem2_addr
, varies_p
)
1502 rtx mem1_addr
, mem2_addr
;
1503 int (*varies_p
) PARAMS ((rtx
));
1505 if (MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1506 && !varies_p (mem1_addr
) && varies_p (mem2_addr
))
1507 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1511 if (MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1512 && varies_p (mem1_addr
) && !varies_p (mem2_addr
))
1513 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1520 /* Returns nonzero if something about the mode or address format MEM1
1521 indicates that it might well alias *anything*. */
1524 aliases_everything_p (mem
)
1527 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1528 /* If the address is an AND, its very hard to know at what it is
1529 actually pointing. */
1535 /* True dependence: X is read after store in MEM takes place. */
1538 true_dependence (mem
, mem_mode
, x
, varies
)
1540 enum machine_mode mem_mode
;
1542 int (*varies
) PARAMS ((rtx
));
1544 register rtx x_addr
, mem_addr
;
1546 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
1549 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
1552 /* If X is an unchanging read, then it can't possibly conflict with any
1553 non-unchanging store. It may conflict with an unchanging write though,
1554 because there may be a single store to this address to initialize it.
1555 Just fall through to the code below to resolve the case where we have
1556 both an unchanging read and an unchanging write. This won't handle all
1557 cases optimally, but the possible performance loss should be
1559 if (RTX_UNCHANGING_P (x
) && ! RTX_UNCHANGING_P (mem
))
1562 if (mem_mode
== VOIDmode
)
1563 mem_mode
= GET_MODE (mem
);
1565 x_addr
= get_addr (XEXP (x
, 0));
1566 mem_addr
= get_addr (XEXP (mem
, 0));
1568 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
1571 x_addr
= canon_rtx (x_addr
);
1572 mem_addr
= canon_rtx (mem_addr
);
1574 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
1575 SIZE_FOR_MODE (x
), x_addr
, 0))
1578 if (aliases_everything_p (x
))
1581 /* We cannot use aliases_everyting_p to test MEM, since we must look
1582 at MEM_MODE, rather than GET_MODE (MEM). */
1583 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
1586 /* In true_dependence we also allow BLKmode to alias anything. Why
1587 don't we do this in anti_dependence and output_dependence? */
1588 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
1591 return ! fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
1595 /* Returns non-zero if a write to X might alias a previous read from
1596 (or, if WRITEP is non-zero, a write to) MEM. */
1599 write_dependence_p (mem
, x
, writep
)
1604 rtx x_addr
, mem_addr
;
1607 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
1610 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
1613 /* If MEM is an unchanging read, then it can't possibly conflict with
1614 the store to X, because there is at most one store to MEM, and it must
1615 have occurred somewhere before MEM. */
1616 if (!writep
&& RTX_UNCHANGING_P (mem
))
1619 x_addr
= get_addr (XEXP (x
, 0));
1620 mem_addr
= get_addr (XEXP (mem
, 0));
1622 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
1626 x_addr
= canon_rtx (x_addr
);
1627 mem_addr
= canon_rtx (mem_addr
);
1629 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
1630 SIZE_FOR_MODE (x
), x_addr
, 0))
1634 = fixed_scalar_and_varying_struct_p (mem
, x
, mem_addr
, x_addr
,
1637 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
1638 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
1641 /* Anti dependence: X is written after read in MEM takes place. */
1644 anti_dependence (mem
, x
)
1648 return write_dependence_p (mem
, x
, /*writep=*/0);
1651 /* Output dependence: X is written after store in MEM takes place. */
1654 output_dependence (mem
, x
)
1658 return write_dependence_p (mem
, x
, /*writep=*/1);
1661 /* Returns non-zero if X might refer to something which is not
1662 local to the function and is not constant. */
1665 nonlocal_reference_p (x
)
1669 register RTX_CODE code
;
1672 code
= GET_CODE (x
);
1674 if (GET_RTX_CLASS (code
) == 'i')
1676 /* Constant functions can be constant if they don't use
1677 scratch memory used to mark function w/o side effects. */
1678 if (code
== CALL_INSN
&& CONST_CALL_P (x
))
1680 x
= CALL_INSN_FUNCTION_USAGE (x
);
1686 code
= GET_CODE (x
);
1692 if (GET_CODE (SUBREG_REG (x
)) == REG
)
1694 /* Global registers are not local. */
1695 if (REGNO (SUBREG_REG (x
)) < FIRST_PSEUDO_REGISTER
1696 && global_regs
[REGNO (SUBREG_REG (x
)) + SUBREG_WORD (x
)])
1704 /* Global registers are not local. */
1705 if (regno
< FIRST_PSEUDO_REGISTER
&& global_regs
[regno
])
1719 /* Constants in the function's constants pool are constant. */
1720 if (CONSTANT_POOL_ADDRESS_P (x
))
1725 /* Recursion introduces no additional considerations. */
1726 if (GET_CODE (XEXP (x
, 0)) == MEM
1727 && GET_CODE (XEXP (XEXP (x
, 0), 0)) == SYMBOL_REF
1728 && strcmp(XSTR (XEXP (XEXP (x
, 0), 0), 0),
1729 IDENTIFIER_POINTER (
1730 DECL_ASSEMBLER_NAME (current_function_decl
))) == 0)
1735 /* Be overly conservative and consider any volatile memory
1736 reference as not local. */
1737 if (MEM_VOLATILE_P (x
))
1739 base
= find_base_term (XEXP (x
, 0));
1742 /* A Pmode ADDRESS could be a reference via the structure value
1743 address or static chain. Such memory references are nonlocal.
1745 Thus, we have to examine the contents of the ADDRESS to find
1746 out if this is a local reference or not. */
1747 if (GET_CODE (base
) == ADDRESS
1748 && GET_MODE (base
) == Pmode
1749 && (XEXP (base
, 0) == stack_pointer_rtx
1750 || XEXP (base
, 0) == arg_pointer_rtx
1751 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1752 || XEXP (base
, 0) == hard_frame_pointer_rtx
1754 || XEXP (base
, 0) == frame_pointer_rtx
))
1756 /* Constants in the function's constant pool are constant. */
1757 if (GET_CODE (base
) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (base
))
1770 /* Recursively scan the operands of this expression. */
1773 register const char *fmt
= GET_RTX_FORMAT (code
);
1776 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1778 if (fmt
[i
] == 'e' && XEXP (x
, i
))
1780 if (nonlocal_reference_p (XEXP (x
, i
)))
1783 else if (fmt
[i
] == 'E')
1786 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1787 if (nonlocal_reference_p (XVECEXP (x
, i
, j
)))
1796 /* Mark the function if it is constant. */
1799 mark_constant_function ()
1803 if (TREE_PUBLIC (current_function_decl
)
1804 || TREE_READONLY (current_function_decl
)
1805 || TREE_THIS_VOLATILE (current_function_decl
)
1806 || TYPE_MODE (TREE_TYPE (current_function_decl
)) == VOIDmode
)
1809 /* Determine if this is a constant function. */
1811 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1812 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
1813 && nonlocal_reference_p (insn
))
1816 /* Mark the function. */
1818 TREE_READONLY (current_function_decl
) = 1;
1822 static HARD_REG_SET argument_registers
;
1829 #ifndef OUTGOING_REGNO
1830 #define OUTGOING_REGNO(N) N
1832 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1833 /* Check whether this register can hold an incoming pointer
1834 argument. FUNCTION_ARG_REGNO_P tests outgoing register
1835 numbers, so translate if necessary due to register windows. */
1836 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
1837 && HARD_REGNO_MODE_OK (i
, Pmode
))
1838 SET_HARD_REG_BIT (argument_registers
, i
);
1840 alias_sets
= splay_tree_new (splay_tree_compare_ints
, 0, 0);
1843 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
1847 init_alias_analysis ()
1849 int maxreg
= max_reg_num ();
1852 register unsigned int ui
;
1855 reg_known_value_size
= maxreg
;
1858 = (rtx
*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (rtx
))
1859 - FIRST_PSEUDO_REGISTER
;
1861 = (char*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (char))
1862 - FIRST_PSEUDO_REGISTER
;
1864 /* Overallocate reg_base_value to allow some growth during loop
1865 optimization. Loop unrolling can create a large number of
1867 reg_base_value_size
= maxreg
* 2;
1868 reg_base_value
= (rtx
*) xcalloc (reg_base_value_size
, sizeof (rtx
));
1870 ggc_add_rtx_root (reg_base_value
, reg_base_value_size
);
1872 new_reg_base_value
= (rtx
*) xmalloc (reg_base_value_size
* sizeof (rtx
));
1873 reg_seen
= (char *) xmalloc (reg_base_value_size
);
1874 if (! reload_completed
&& flag_unroll_loops
)
1876 /* ??? Why are we realloc'ing if we're just going to zero it? */
1877 alias_invariant
= (rtx
*)xrealloc (alias_invariant
,
1878 reg_base_value_size
* sizeof (rtx
));
1879 bzero ((char *)alias_invariant
, reg_base_value_size
* sizeof (rtx
));
1883 /* The basic idea is that each pass through this loop will use the
1884 "constant" information from the previous pass to propagate alias
1885 information through another level of assignments.
1887 This could get expensive if the assignment chains are long. Maybe
1888 we should throttle the number of iterations, possibly based on
1889 the optimization level or flag_expensive_optimizations.
1891 We could propagate more information in the first pass by making use
1892 of REG_N_SETS to determine immediately that the alias information
1893 for a pseudo is "constant".
1895 A program with an uninitialized variable can cause an infinite loop
1896 here. Instead of doing a full dataflow analysis to detect such problems
1897 we just cap the number of iterations for the loop.
1899 The state of the arrays for the set chain in question does not matter
1900 since the program has undefined behavior. */
1905 /* Assume nothing will change this iteration of the loop. */
1908 /* We want to assign the same IDs each iteration of this loop, so
1909 start counting from zero each iteration of the loop. */
1912 /* We're at the start of the funtion each iteration through the
1913 loop, so we're copying arguments. */
1914 copying_arguments
= 1;
1916 /* Wipe the potential alias information clean for this pass. */
1917 bzero ((char *) new_reg_base_value
, reg_base_value_size
* sizeof (rtx
));
1919 /* Wipe the reg_seen array clean. */
1920 bzero ((char *) reg_seen
, reg_base_value_size
);
1922 /* Mark all hard registers which may contain an address.
1923 The stack, frame and argument pointers may contain an address.
1924 An argument register which can hold a Pmode value may contain
1925 an address even if it is not in BASE_REGS.
1927 The address expression is VOIDmode for an argument and
1928 Pmode for other registers. */
1930 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1931 if (TEST_HARD_REG_BIT (argument_registers
, i
))
1932 new_reg_base_value
[i
] = gen_rtx_ADDRESS (VOIDmode
,
1933 gen_rtx_REG (Pmode
, i
));
1935 new_reg_base_value
[STACK_POINTER_REGNUM
]
1936 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
1937 new_reg_base_value
[ARG_POINTER_REGNUM
]
1938 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
1939 new_reg_base_value
[FRAME_POINTER_REGNUM
]
1940 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
1941 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1942 new_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
1943 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
1945 if (struct_value_incoming_rtx
1946 && GET_CODE (struct_value_incoming_rtx
) == REG
)
1947 new_reg_base_value
[REGNO (struct_value_incoming_rtx
)]
1948 = gen_rtx_ADDRESS (Pmode
, struct_value_incoming_rtx
);
1950 if (static_chain_rtx
1951 && GET_CODE (static_chain_rtx
) == REG
)
1952 new_reg_base_value
[REGNO (static_chain_rtx
)]
1953 = gen_rtx_ADDRESS (Pmode
, static_chain_rtx
);
1955 /* Walk the insns adding values to the new_reg_base_value array. */
1956 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1958 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
1962 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
1963 if (prologue_epilogue_contains (insn
))
1967 /* If this insn has a noalias note, process it, Otherwise,
1968 scan for sets. A simple set will have no side effects
1969 which could change the base value of any other register. */
1971 if (GET_CODE (PATTERN (insn
)) == SET
1972 && REG_NOTES (insn
) != 0
1973 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
1974 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
1976 note_stores (PATTERN (insn
), record_set
, NULL
);
1978 set
= single_set (insn
);
1981 && GET_CODE (SET_DEST (set
)) == REG
1982 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
1983 && REG_NOTES (insn
) != 0
1984 && (((note
= find_reg_note (insn
, REG_EQUAL
, 0)) != 0
1985 && REG_N_SETS (REGNO (SET_DEST (set
))) == 1)
1986 || (note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) != 0)
1987 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
1988 && ! reg_overlap_mentioned_p (SET_DEST (set
), XEXP (note
, 0)))
1990 int regno
= REGNO (SET_DEST (set
));
1991 reg_known_value
[regno
] = XEXP (note
, 0);
1992 reg_known_equiv_p
[regno
] = REG_NOTE_KIND (note
) == REG_EQUIV
;
1995 else if (GET_CODE (insn
) == NOTE
1996 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_FUNCTION_BEG
)
1997 copying_arguments
= 0;
2000 /* Now propagate values from new_reg_base_value to reg_base_value. */
2001 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
2003 if (new_reg_base_value
[ui
]
2004 && new_reg_base_value
[ui
] != reg_base_value
[ui
]
2005 && ! rtx_equal_p (new_reg_base_value
[ui
], reg_base_value
[ui
]))
2007 reg_base_value
[ui
] = new_reg_base_value
[ui
];
2012 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2014 /* Fill in the remaining entries. */
2015 for (i
= FIRST_PSEUDO_REGISTER
; i
< maxreg
; i
++)
2016 if (reg_known_value
[i
] == 0)
2017 reg_known_value
[i
] = regno_reg_rtx
[i
];
2019 /* Simplify the reg_base_value array so that no register refers to
2020 another register, except to special registers indirectly through
2021 ADDRESS expressions.
2023 In theory this loop can take as long as O(registers^2), but unless
2024 there are very long dependency chains it will run in close to linear
2027 This loop may not be needed any longer now that the main loop does
2028 a better job at propagating alias information. */
2034 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
2036 rtx base
= reg_base_value
[ui
];
2037 if (base
&& GET_CODE (base
) == REG
)
2039 unsigned int base_regno
= REGNO (base
);
2040 if (base_regno
== ui
) /* register set from itself */
2041 reg_base_value
[ui
] = 0;
2043 reg_base_value
[ui
] = reg_base_value
[base_regno
];
2048 while (changed
&& pass
< MAX_ALIAS_LOOP_PASSES
);
2051 free (new_reg_base_value
);
2052 new_reg_base_value
= 0;
2058 end_alias_analysis ()
2060 free (reg_known_value
+ FIRST_PSEUDO_REGISTER
);
2061 reg_known_value
= 0;
2062 reg_known_value_size
= 0;
2063 free (reg_known_equiv_p
+ FIRST_PSEUDO_REGISTER
);
2064 reg_known_equiv_p
= 0;
2068 ggc_del_root (reg_base_value
);
2069 free (reg_base_value
);
2072 reg_base_value_size
= 0;
2073 if (alias_invariant
)
2075 free (alias_invariant
);
2076 alias_invariant
= 0;