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"
35 #include "splay-tree.h"
38 /* The alias sets assigned to MEMs assist the back-end in determining
39 which MEMs can alias which other MEMs. In general, two MEMs in
40 different alias sets to not alias each other. There is one
41 exception, however. Consider something like:
43 struct S {int i; double d; };
45 a store to an `S' can alias something of either type `int' or type
46 `double'. (However, a store to an `int' cannot alias a `double'
47 and vice versa.) We indicate this via a tree structure that looks
55 (The arrows are directed and point downwards.) If, when comparing
56 two alias sets, we can hold one set fixed, trace the other set
57 downwards, and at some point find the first set, the two MEMs can
58 alias one another. In this situation we say the alias set for
59 `struct S' is the `superset' and that those for `int' and `double'
62 Alias set zero is implicitly a superset of all other alias sets.
63 However, this is no actual entry for alias set zero. It is an
64 error to attempt to explicitly construct a subset of zero. */
66 typedef struct alias_set_entry
68 /* The alias set number, as stored in MEM_ALIAS_SET. */
71 /* The children of the alias set. These are not just the immediate
72 children, but, in fact, all children. So, if we have:
74 struct T { struct S s; float f; }
76 continuing our example above, the children here will be all of
77 `int', `double', `float', and `struct S'. */
81 static rtx canon_rtx
PARAMS ((rtx
));
82 static int rtx_equal_for_memref_p
PARAMS ((rtx
, rtx
));
83 static rtx find_symbolic_term
PARAMS ((rtx
));
84 static int memrefs_conflict_p
PARAMS ((int, rtx
, int, rtx
,
86 static void record_set
PARAMS ((rtx
, rtx
, void *));
87 static rtx find_base_term
PARAMS ((rtx
));
88 static int base_alias_check
PARAMS ((rtx
, rtx
, enum machine_mode
,
90 static rtx find_base_value
PARAMS ((rtx
));
91 static int mems_in_disjoint_alias_sets_p
PARAMS ((rtx
, rtx
));
92 static int insert_subset_children
PARAMS ((splay_tree_node
, void*));
93 static alias_set_entry get_alias_set_entry
PARAMS ((int));
94 static rtx fixed_scalar_and_varying_struct_p
PARAMS ((rtx
, rtx
, int (*)(rtx
)));
95 static int aliases_everything_p
PARAMS ((rtx
));
96 static int write_dependence_p
PARAMS ((rtx
, rtx
, int));
97 static int nonlocal_reference_p
PARAMS ((rtx
));
99 /* Set up all info needed to perform alias analysis on memory references. */
101 /* Returns the size in bytes of the mode of X. */
102 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
104 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
105 different alias sets. We ignore alias sets in functions making use
106 of variable arguments because the va_arg macros on some systems are
108 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
109 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
111 /* Cap the number of passes we make over the insns propagating alias
112 information through set chains.
114 10 is a completely arbitrary choice. */
115 #define MAX_ALIAS_LOOP_PASSES 10
117 /* reg_base_value[N] gives an address to which register N is related.
118 If all sets after the first add or subtract to the current value
119 or otherwise modify it so it does not point to a different top level
120 object, reg_base_value[N] is equal to the address part of the source
123 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
124 expressions represent certain special values: function arguments and
125 the stack, frame, and argument pointers.
127 The contents of an ADDRESS is not normally used, the mode of the
128 ADDRESS determines whether the ADDRESS is a function argument or some
129 other special value. Pointer equality, not rtx_equal_p, determines whether
130 two ADDRESS expressions refer to the same base address.
132 The only use of the contents of an ADDRESS is for determining if the
133 current function performs nonlocal memory memory references for the
134 purposes of marking the function as a constant function. */
136 static rtx
*reg_base_value
;
137 static rtx
*new_reg_base_value
;
138 static unsigned int reg_base_value_size
; /* size of reg_base_value array */
140 #define REG_BASE_VALUE(X) \
141 ((unsigned) REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0)
143 /* Vector of known invariant relationships between registers. Set in
144 loop unrolling. Indexed by register number, if nonzero the value
145 is an expression describing this register in terms of another.
147 The length of this array is REG_BASE_VALUE_SIZE.
149 Because this array contains only pseudo registers it has no effect
151 static rtx
*alias_invariant
;
153 /* Vector indexed by N giving the initial (unchanging) value known
154 for pseudo-register N. */
155 rtx
*reg_known_value
;
157 /* Indicates number of valid entries in reg_known_value. */
158 static int reg_known_value_size
;
160 /* Vector recording for each reg_known_value whether it is due to a
161 REG_EQUIV note. Future passes (viz., reload) may replace the
162 pseudo with the equivalent expression and so we account for the
163 dependences that would be introduced if that happens. */
164 /* ??? This is a problem only on the Convex. The REG_EQUIV notes created in
165 assign_parms mention the arg pointer, and there are explicit insns in the
166 RTL that modify the arg pointer. Thus we must ensure that such insns don't
167 get scheduled across each other because that would invalidate the REG_EQUIV
168 notes. One could argue that the REG_EQUIV notes are wrong, but solving
169 the problem in the scheduler will likely give better code, so we do it
171 char *reg_known_equiv_p
;
173 /* True when scanning insns from the start of the rtl to the
174 NOTE_INSN_FUNCTION_BEG note. */
176 static int copying_arguments
;
178 /* The splay-tree used to store the various alias set entries. */
180 static splay_tree alias_sets
;
182 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
183 such an entry, or NULL otherwise. */
185 static alias_set_entry
186 get_alias_set_entry (alias_set
)
190 = splay_tree_lookup (alias_sets
, (splay_tree_key
) alias_set
);
192 return sn
!= 0 ? ((alias_set_entry
) sn
->value
) : 0;
195 /* Returns nonzero value if the alias sets for MEM1 and MEM2 are such
196 that the two MEMs cannot alias each other. */
199 mems_in_disjoint_alias_sets_p (mem1
, mem2
)
205 #ifdef ENABLE_CHECKING
206 /* Perform a basic sanity check. Namely, that there are no alias sets
207 if we're not using strict aliasing. This helps to catch bugs
208 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
209 where a MEM is allocated in some way other than by the use of
210 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
211 use alias sets to indicate that spilled registers cannot alias each
212 other, we might need to remove this check. */
213 if (! flag_strict_aliasing
214 && (MEM_ALIAS_SET (mem1
) != 0 || MEM_ALIAS_SET (mem2
) != 0))
218 /* The code used in varargs macros are often not conforming ANSI C,
219 which can trick the compiler into making incorrect aliasing
220 assumptions in these functions. So, we don't use alias sets in
221 such a function. FIXME: This should be moved into the front-end;
222 it is a language-dependent notion, and there's no reason not to
223 still use these checks to handle globals. */
224 if (current_function_stdarg
|| current_function_varargs
)
227 /* If have no alias set information for one of the MEMs, we have to assume
228 it can alias anything. */
229 if (MEM_ALIAS_SET (mem1
) == 0 || MEM_ALIAS_SET (mem2
) == 0)
232 /* If the two alias sets are the same, they may alias. */
233 if (MEM_ALIAS_SET (mem1
) == MEM_ALIAS_SET (mem2
))
236 /* Iterate through each of the children of the first alias set,
237 comparing it with the second alias set. */
238 ase
= get_alias_set_entry (MEM_ALIAS_SET (mem1
));
239 if (ase
!= 0 && splay_tree_lookup (ase
->children
,
240 (splay_tree_key
) MEM_ALIAS_SET (mem2
)))
243 /* Now do the same, but with the alias sets reversed. */
244 ase
= get_alias_set_entry (MEM_ALIAS_SET (mem2
));
245 if (ase
!= 0 && splay_tree_lookup (ase
->children
,
246 (splay_tree_key
) MEM_ALIAS_SET (mem1
)))
249 /* The two MEMs are in distinct alias sets, and neither one is the
250 child of the other. Therefore, they cannot alias. */
254 /* Insert the NODE into the splay tree given by DATA. Used by
255 record_alias_subset via splay_tree_foreach. */
258 insert_subset_children (node
, data
)
259 splay_tree_node node
;
262 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
267 /* Indicate that things in SUBSET can alias things in SUPERSET, but
268 not vice versa. For example, in C, a store to an `int' can alias a
269 structure containing an `int', but not vice versa. Here, the
270 structure would be the SUPERSET and `int' the SUBSET. This
271 function should be called only once per SUPERSET/SUBSET pair. At
272 present any given alias set may only be a subset of one superset.
274 It is illegal for SUPERSET to be zero; everything is implicitly a
275 subset of alias set zero. */
278 record_alias_subset (superset
, subset
)
282 alias_set_entry superset_entry
;
283 alias_set_entry subset_entry
;
288 superset_entry
= get_alias_set_entry (superset
);
289 if (superset_entry
== 0)
291 /* Create an entry for the SUPERSET, so that we have a place to
292 attach the SUBSET. */
294 = (alias_set_entry
) xmalloc (sizeof (struct alias_set_entry
));
295 superset_entry
->alias_set
= superset
;
296 superset_entry
->children
297 = splay_tree_new (splay_tree_compare_ints
, 0, 0);
298 splay_tree_insert (alias_sets
, (splay_tree_key
) superset
,
299 (splay_tree_value
) superset_entry
);
303 subset_entry
= get_alias_set_entry (subset
);
305 /* If there is an entry for the subset, enter all of its children
306 (if they are not already present) as children of the SUPERSET. */
308 splay_tree_foreach (subset_entry
->children
,
309 insert_subset_children
,
310 superset_entry
->children
);
312 /* Enter the SUBSET itself as a child of the SUPERSET. */
313 splay_tree_insert (superset_entry
->children
,
314 (splay_tree_key
) subset
, 0);
317 /* Inside SRC, the source of a SET, find a base address. */
320 find_base_value (src
)
323 switch (GET_CODE (src
))
330 /* At the start of a function, argument registers have known base
331 values which may be lost later. Returning an ADDRESS
332 expression here allows optimization based on argument values
333 even when the argument registers are used for other purposes. */
334 if (REGNO (src
) < FIRST_PSEUDO_REGISTER
&& copying_arguments
)
335 return new_reg_base_value
[REGNO (src
)];
337 /* If a pseudo has a known base value, return it. Do not do this
338 for hard regs since it can result in a circular dependency
339 chain for registers which have values at function entry.
341 The test above is not sufficient because the scheduler may move
342 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
343 if (REGNO (src
) >= FIRST_PSEUDO_REGISTER
344 && (unsigned) REGNO (src
) < reg_base_value_size
345 && reg_base_value
[REGNO (src
)])
346 return reg_base_value
[REGNO (src
)];
351 /* Check for an argument passed in memory. Only record in the
352 copying-arguments block; it is too hard to track changes
354 if (copying_arguments
355 && (XEXP (src
, 0) == arg_pointer_rtx
356 || (GET_CODE (XEXP (src
, 0)) == PLUS
357 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
358 return gen_rtx_ADDRESS (VOIDmode
, src
);
363 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
366 /* ... fall through ... */
371 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
373 /* If either operand is a REG, then see if we already have
374 a known value for it. */
375 if (GET_CODE (src_0
) == REG
)
377 temp
= find_base_value (src_0
);
382 if (GET_CODE (src_1
) == REG
)
384 temp
= find_base_value (src_1
);
389 /* Guess which operand is the base address:
390 If either operand is a symbol, then it is the base. If
391 either operand is a CONST_INT, then the other is the base. */
392 if (GET_CODE (src_1
) == CONST_INT
|| CONSTANT_P (src_0
))
393 return find_base_value (src_0
);
394 else if (GET_CODE (src_0
) == CONST_INT
|| CONSTANT_P (src_1
))
395 return find_base_value (src_1
);
397 /* This might not be necessary anymore:
398 If either operand is a REG that is a known pointer, then it
400 else if (GET_CODE (src_0
) == REG
&& REGNO_POINTER_FLAG (REGNO (src_0
)))
401 return find_base_value (src_0
);
402 else if (GET_CODE (src_1
) == REG
&& REGNO_POINTER_FLAG (REGNO (src_1
)))
403 return find_base_value (src_1
);
409 /* The standard form is (lo_sum reg sym) so look only at the
411 return find_base_value (XEXP (src
, 1));
414 /* If the second operand is constant set the base
415 address to the first operand. */
416 if (GET_CODE (XEXP (src
, 1)) == CONST_INT
&& INTVAL (XEXP (src
, 1)) != 0)
417 return find_base_value (XEXP (src
, 0));
421 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
423 return find_base_value (XEXP (src
, 0));
432 /* Called from init_alias_analysis indirectly through note_stores. */
434 /* While scanning insns to find base values, reg_seen[N] is nonzero if
435 register N has been set in this function. */
436 static char *reg_seen
;
438 /* Addresses which are known not to alias anything else are identified
439 by a unique integer. */
440 static int unique_id
;
443 record_set (dest
, set
, data
)
445 void *data ATTRIBUTE_UNUSED
;
447 register unsigned regno
;
450 if (GET_CODE (dest
) != REG
)
453 regno
= REGNO (dest
);
455 if (regno
>= reg_base_value_size
)
460 /* A CLOBBER wipes out any old value but does not prevent a previously
461 unset register from acquiring a base address (i.e. reg_seen is not
463 if (GET_CODE (set
) == CLOBBER
)
465 new_reg_base_value
[regno
] = 0;
474 new_reg_base_value
[regno
] = 0;
478 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
479 GEN_INT (unique_id
++));
483 /* This is not the first set. If the new value is not related to the
484 old value, forget the base value. Note that the following code is
486 extern int x, y; int *p = &x; p += (&y-&x);
487 ANSI C does not allow computing the difference of addresses
488 of distinct top level objects. */
489 if (new_reg_base_value
[regno
])
490 switch (GET_CODE (src
))
495 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
496 new_reg_base_value
[regno
] = 0;
499 if (XEXP (src
, 0) != dest
|| GET_CODE (XEXP (src
, 1)) != CONST_INT
)
500 new_reg_base_value
[regno
] = 0;
503 new_reg_base_value
[regno
] = 0;
506 /* If this is the first set of a register, record the value. */
507 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
508 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
509 new_reg_base_value
[regno
] = find_base_value (src
);
514 /* Called from loop optimization when a new pseudo-register is created. */
517 record_base_value (regno
, val
, invariant
)
522 if ((unsigned) regno
>= reg_base_value_size
)
525 /* If INVARIANT is true then this value also describes an invariant
526 relationship which can be used to deduce that two registers with
527 unknown values are different. */
528 if (invariant
&& alias_invariant
)
529 alias_invariant
[regno
] = val
;
531 if (GET_CODE (val
) == REG
)
533 if ((unsigned) REGNO (val
) < reg_base_value_size
)
534 reg_base_value
[regno
] = reg_base_value
[REGNO (val
)];
539 reg_base_value
[regno
] = find_base_value (val
);
546 /* Recursively look for equivalences. */
547 if (GET_CODE (x
) == REG
&& REGNO (x
) >= FIRST_PSEUDO_REGISTER
548 && REGNO (x
) < reg_known_value_size
)
549 return reg_known_value
[REGNO (x
)] == x
550 ? x
: canon_rtx (reg_known_value
[REGNO (x
)]);
551 else if (GET_CODE (x
) == PLUS
)
553 rtx x0
= canon_rtx (XEXP (x
, 0));
554 rtx x1
= canon_rtx (XEXP (x
, 1));
556 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
558 /* We can tolerate LO_SUMs being offset here; these
559 rtl are used for nothing other than comparisons. */
560 if (GET_CODE (x0
) == CONST_INT
)
561 return plus_constant_for_output (x1
, INTVAL (x0
));
562 else if (GET_CODE (x1
) == CONST_INT
)
563 return plus_constant_for_output (x0
, INTVAL (x1
));
564 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
568 /* This gives us much better alias analysis when called from
569 the loop optimizer. Note we want to leave the original
570 MEM alone, but need to return the canonicalized MEM with
571 all the flags with their original values. */
572 else if (GET_CODE (x
) == MEM
)
574 rtx addr
= canon_rtx (XEXP (x
, 0));
576 if (addr
!= XEXP (x
, 0))
578 rtx
new = gen_rtx_MEM (GET_MODE (x
), addr
);
580 RTX_UNCHANGING_P (new) = RTX_UNCHANGING_P (x
);
581 MEM_COPY_ATTRIBUTES (new, x
);
582 MEM_ALIAS_SET (new) = MEM_ALIAS_SET (x
);
589 /* Return 1 if X and Y are identical-looking rtx's.
591 We use the data in reg_known_value above to see if two registers with
592 different numbers are, in fact, equivalent. */
595 rtx_equal_for_memref_p (x
, y
)
600 register enum rtx_code code
;
601 register const char *fmt
;
603 if (x
== 0 && y
== 0)
605 if (x
== 0 || y
== 0)
615 /* Rtx's of different codes cannot be equal. */
616 if (code
!= GET_CODE (y
))
619 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
620 (REG:SI x) and (REG:HI x) are NOT equivalent. */
622 if (GET_MODE (x
) != GET_MODE (y
))
625 /* REG, LABEL_REF, and SYMBOL_REF can be compared nonrecursively. */
628 return REGNO (x
) == REGNO (y
);
629 if (code
== LABEL_REF
)
630 return XEXP (x
, 0) == XEXP (y
, 0);
631 if (code
== SYMBOL_REF
)
632 return XSTR (x
, 0) == XSTR (y
, 0);
633 if (code
== CONST_INT
)
634 return INTVAL (x
) == INTVAL (y
);
635 /* There's no need to compare the contents of CONST_DOUBLEs because
637 if (code
== CONST_DOUBLE
)
639 if (code
== ADDRESSOF
)
640 return (REGNO (XEXP (x
, 0)) == REGNO (XEXP (y
, 0))
641 && XINT (x
, 1) == XINT (y
, 1));
643 /* For commutative operations, the RTX match if the operand match in any
644 order. Also handle the simple binary and unary cases without a loop. */
645 if (code
== EQ
|| code
== NE
|| GET_RTX_CLASS (code
) == 'c')
646 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
647 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
648 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
649 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
650 else if (GET_RTX_CLASS (code
) == '<' || GET_RTX_CLASS (code
) == '2')
651 return (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
652 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)));
653 else if (GET_RTX_CLASS (code
) == '1')
654 return rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0));
656 /* Compare the elements. If any pair of corresponding elements
657 fail to match, return 0 for the whole things.
659 Limit cases to types which actually appear in addresses. */
661 fmt
= GET_RTX_FORMAT (code
);
662 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
667 if (XINT (x
, i
) != XINT (y
, i
))
672 /* Two vectors must have the same length. */
673 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
676 /* And the corresponding elements must match. */
677 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
678 if (rtx_equal_for_memref_p (XVECEXP (x
, i
, j
),
679 XVECEXP (y
, i
, j
)) == 0)
684 if (rtx_equal_for_memref_p (XEXP (x
, i
), XEXP (y
, i
)) == 0)
688 /* This can happen for an asm which clobbers memory. */
692 /* It is believed that rtx's at this level will never
693 contain anything but integers and other rtx's,
694 except for within LABEL_REFs and SYMBOL_REFs. */
702 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
703 X and return it, or return 0 if none found. */
706 find_symbolic_term (x
)
710 register enum rtx_code code
;
711 register const char *fmt
;
714 if (code
== SYMBOL_REF
|| code
== LABEL_REF
)
716 if (GET_RTX_CLASS (code
) == 'o')
719 fmt
= GET_RTX_FORMAT (code
);
720 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
726 t
= find_symbolic_term (XEXP (x
, i
));
730 else if (fmt
[i
] == 'E')
740 switch (GET_CODE (x
))
743 return REG_BASE_VALUE (x
);
746 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
752 return find_base_term (XEXP (x
, 0));
756 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
763 rtx tmp1
= XEXP (x
, 0);
764 rtx tmp2
= XEXP (x
, 1);
766 /* This is a litle bit tricky since we have to determine which of
767 the two operands represents the real base address. Otherwise this
768 routine may return the index register instead of the base register.
770 That may cause us to believe no aliasing was possible, when in
771 fact aliasing is possible.
773 We use a few simple tests to guess the base register. Additional
774 tests can certainly be added. For example, if one of the operands
775 is a shift or multiply, then it must be the index register and the
776 other operand is the base register. */
778 /* If either operand is known to be a pointer, then use it
779 to determine the base term. */
780 if (REG_P (tmp1
) && REGNO_POINTER_FLAG (REGNO (tmp1
)))
781 return find_base_term (tmp1
);
783 if (REG_P (tmp2
) && REGNO_POINTER_FLAG (REGNO (tmp2
)))
784 return find_base_term (tmp2
);
786 /* Neither operand was known to be a pointer. Go ahead and find the
787 base term for both operands. */
788 tmp1
= find_base_term (tmp1
);
789 tmp2
= find_base_term (tmp2
);
791 /* If either base term is named object or a special address
792 (like an argument or stack reference), then use it for the
795 && (GET_CODE (tmp1
) == SYMBOL_REF
796 || GET_CODE (tmp1
) == LABEL_REF
797 || (GET_CODE (tmp1
) == ADDRESS
798 && GET_MODE (tmp1
) != VOIDmode
)))
802 && (GET_CODE (tmp2
) == SYMBOL_REF
803 || GET_CODE (tmp2
) == LABEL_REF
804 || (GET_CODE (tmp2
) == ADDRESS
805 && GET_MODE (tmp2
) != VOIDmode
)))
808 /* We could not determine which of the two operands was the
809 base register and which was the index. So we can determine
810 nothing from the base alias check. */
815 if (GET_CODE (XEXP (x
, 0)) == REG
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
816 return REG_BASE_VALUE (XEXP (x
, 0));
828 /* Return 0 if the addresses X and Y are known to point to different
829 objects, 1 if they might be pointers to the same object. */
832 base_alias_check (x
, y
, x_mode
, y_mode
)
834 enum machine_mode x_mode
, y_mode
;
836 rtx x_base
= find_base_term (x
);
837 rtx y_base
= find_base_term (y
);
839 /* If the address itself has no known base see if a known equivalent
840 value has one. If either address still has no known base, nothing
841 is known about aliasing. */
846 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
849 x_base
= find_base_term (x_c
);
857 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
860 y_base
= find_base_term (y_c
);
865 /* If the base addresses are equal nothing is known about aliasing. */
866 if (rtx_equal_p (x_base
, y_base
))
869 /* The base addresses of the read and write are different expressions.
870 If they are both symbols and they are not accessed via AND, there is
871 no conflict. We can bring knowledge of object alignment into play
872 here. For example, on alpha, "char a, b;" can alias one another,
873 though "char a; long b;" cannot. */
874 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
876 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
878 if (GET_CODE (x
) == AND
879 && (GET_CODE (XEXP (x
, 1)) != CONST_INT
880 || GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
882 if (GET_CODE (y
) == AND
883 && (GET_CODE (XEXP (y
, 1)) != CONST_INT
884 || GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
886 /* Differing symbols never alias. */
890 /* If one address is a stack reference there can be no alias:
891 stack references using different base registers do not alias,
892 a stack reference can not alias a parameter, and a stack reference
893 can not alias a global. */
894 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
895 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
898 if (! flag_argument_noalias
)
901 if (flag_argument_noalias
> 1)
904 /* Weak noalias assertion (arguments are distinct, but may match globals). */
905 return ! (GET_MODE (x_base
) == VOIDmode
&& GET_MODE (y_base
) == VOIDmode
);
908 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
909 where SIZE is the size in bytes of the memory reference. If ADDR
910 is not modified by the memory reference then ADDR is returned. */
913 addr_side_effect_eval (addr
, size
, n_refs
)
920 switch (GET_CODE (addr
))
923 offset
= (n_refs
+ 1) * size
;
926 offset
= -(n_refs
+ 1) * size
;
929 offset
= n_refs
* size
;
932 offset
= -n_refs
* size
;
940 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0), GEN_INT (offset
));
942 addr
= XEXP (addr
, 0);
947 /* Return nonzero if X and Y (memory addresses) could reference the
948 same location in memory. C is an offset accumulator. When
949 C is nonzero, we are testing aliases between X and Y + C.
950 XSIZE is the size in bytes of the X reference,
951 similarly YSIZE is the size in bytes for Y.
953 If XSIZE or YSIZE is zero, we do not know the amount of memory being
954 referenced (the reference was BLKmode), so make the most pessimistic
957 If XSIZE or YSIZE is negative, we may access memory outside the object
958 being referenced as a side effect. This can happen when using AND to
959 align memory references, as is done on the Alpha.
961 Nice to notice that varying addresses cannot conflict with fp if no
962 local variables had their addresses taken, but that's too hard now. */
966 memrefs_conflict_p (xsize
, x
, ysize
, y
, c
)
971 if (GET_CODE (x
) == HIGH
)
973 else if (GET_CODE (x
) == LO_SUM
)
976 x
= canon_rtx (addr_side_effect_eval (x
, xsize
, 0));
977 if (GET_CODE (y
) == HIGH
)
979 else if (GET_CODE (y
) == LO_SUM
)
982 y
= canon_rtx (addr_side_effect_eval (y
, ysize
, 0));
984 if (rtx_equal_for_memref_p (x
, y
))
986 if (xsize
<= 0 || ysize
<= 0)
988 if (c
>= 0 && xsize
> c
)
990 if (c
< 0 && ysize
+c
> 0)
995 /* This code used to check for conflicts involving stack references and
996 globals but the base address alias code now handles these cases. */
998 if (GET_CODE (x
) == PLUS
)
1000 /* The fact that X is canonicalized means that this
1001 PLUS rtx is canonicalized. */
1002 rtx x0
= XEXP (x
, 0);
1003 rtx x1
= XEXP (x
, 1);
1005 if (GET_CODE (y
) == PLUS
)
1007 /* The fact that Y is canonicalized means that this
1008 PLUS rtx is canonicalized. */
1009 rtx y0
= XEXP (y
, 0);
1010 rtx y1
= XEXP (y
, 1);
1012 if (rtx_equal_for_memref_p (x1
, y1
))
1013 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1014 if (rtx_equal_for_memref_p (x0
, y0
))
1015 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1016 if (GET_CODE (x1
) == CONST_INT
)
1018 if (GET_CODE (y1
) == CONST_INT
)
1019 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1020 c
- INTVAL (x1
) + INTVAL (y1
));
1022 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1025 else if (GET_CODE (y1
) == CONST_INT
)
1026 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1030 else if (GET_CODE (x1
) == CONST_INT
)
1031 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1033 else if (GET_CODE (y
) == PLUS
)
1035 /* The fact that Y is canonicalized means that this
1036 PLUS rtx is canonicalized. */
1037 rtx y0
= XEXP (y
, 0);
1038 rtx y1
= XEXP (y
, 1);
1040 if (GET_CODE (y1
) == CONST_INT
)
1041 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1046 if (GET_CODE (x
) == GET_CODE (y
))
1047 switch (GET_CODE (x
))
1051 /* Handle cases where we expect the second operands to be the
1052 same, and check only whether the first operand would conflict
1055 rtx x1
= canon_rtx (XEXP (x
, 1));
1056 rtx y1
= canon_rtx (XEXP (y
, 1));
1057 if (! rtx_equal_for_memref_p (x1
, y1
))
1059 x0
= canon_rtx (XEXP (x
, 0));
1060 y0
= canon_rtx (XEXP (y
, 0));
1061 if (rtx_equal_for_memref_p (x0
, y0
))
1062 return (xsize
== 0 || ysize
== 0
1063 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1065 /* Can't properly adjust our sizes. */
1066 if (GET_CODE (x1
) != CONST_INT
)
1068 xsize
/= INTVAL (x1
);
1069 ysize
/= INTVAL (x1
);
1071 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1075 /* Are these registers known not to be equal? */
1076 if (alias_invariant
)
1078 unsigned int r_x
= REGNO (x
), r_y
= REGNO (y
);
1079 rtx i_x
, i_y
; /* invariant relationships of X and Y */
1081 i_x
= r_x
>= reg_base_value_size
? 0 : alias_invariant
[r_x
];
1082 i_y
= r_y
>= reg_base_value_size
? 0 : alias_invariant
[r_y
];
1084 if (i_x
== 0 && i_y
== 0)
1087 if (! memrefs_conflict_p (xsize
, i_x
? i_x
: x
,
1088 ysize
, i_y
? i_y
: y
, c
))
1097 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1098 as an access with indeterminate size. Assume that references
1099 besides AND are aligned, so if the size of the other reference is
1100 at least as large as the alignment, assume no other overlap. */
1101 if (GET_CODE (x
) == AND
&& GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1103 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
1105 return memrefs_conflict_p (xsize
, XEXP (x
, 0), ysize
, y
, c
);
1107 if (GET_CODE (y
) == AND
&& GET_CODE (XEXP (y
, 1)) == CONST_INT
)
1109 /* ??? If we are indexing far enough into the array/structure, we
1110 may yet be able to determine that we can not overlap. But we
1111 also need to that we are far enough from the end not to overlap
1112 a following reference, so we do nothing with that for now. */
1113 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
1115 return memrefs_conflict_p (xsize
, x
, ysize
, XEXP (y
, 0), c
);
1120 if (GET_CODE (x
) == CONST_INT
&& GET_CODE (y
) == CONST_INT
)
1122 c
+= (INTVAL (y
) - INTVAL (x
));
1123 return (xsize
<= 0 || ysize
<= 0
1124 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
1127 if (GET_CODE (x
) == CONST
)
1129 if (GET_CODE (y
) == CONST
)
1130 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1131 ysize
, canon_rtx (XEXP (y
, 0)), c
);
1133 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
1136 if (GET_CODE (y
) == CONST
)
1137 return memrefs_conflict_p (xsize
, x
, ysize
,
1138 canon_rtx (XEXP (y
, 0)), c
);
1141 return (xsize
< 0 || ysize
< 0
1142 || (rtx_equal_for_memref_p (x
, y
)
1143 && (xsize
== 0 || ysize
== 0
1144 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
1151 /* Functions to compute memory dependencies.
1153 Since we process the insns in execution order, we can build tables
1154 to keep track of what registers are fixed (and not aliased), what registers
1155 are varying in known ways, and what registers are varying in unknown
1158 If both memory references are volatile, then there must always be a
1159 dependence between the two references, since their order can not be
1160 changed. A volatile and non-volatile reference can be interchanged
1163 A MEM_IN_STRUCT reference at a non-QImode non-AND varying address can never
1164 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We must
1165 allow QImode aliasing because the ANSI C standard allows character
1166 pointers to alias anything. We are assuming that characters are
1167 always QImode here. We also must allow AND addresses, because they may
1168 generate accesses outside the object being referenced. This is used to
1169 generate aligned addresses from unaligned addresses, for instance, the
1170 alpha storeqi_unaligned pattern. */
1172 /* Read dependence: X is read after read in MEM takes place. There can
1173 only be a dependence here if both reads are volatile. */
1176 read_dependence (mem
, x
)
1180 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
1183 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1184 MEM2 is a reference to a structure at a varying address, or returns
1185 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1186 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1187 to decide whether or not an address may vary; it should return
1188 nonzero whenever variation is possible. */
1191 fixed_scalar_and_varying_struct_p (mem1
, mem2
, varies_p
)
1194 int (*varies_p
) PARAMS ((rtx
));
1196 rtx mem1_addr
= XEXP (mem1
, 0);
1197 rtx mem2_addr
= XEXP (mem2
, 0);
1199 if (MEM_SCALAR_P (mem1
) && MEM_IN_STRUCT_P (mem2
)
1200 && !varies_p (mem1_addr
) && varies_p (mem2_addr
))
1201 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1205 if (MEM_IN_STRUCT_P (mem1
) && MEM_SCALAR_P (mem2
)
1206 && varies_p (mem1_addr
) && !varies_p (mem2_addr
))
1207 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1214 /* Returns nonzero if something about the mode or address format MEM1
1215 indicates that it might well alias *anything*. */
1218 aliases_everything_p (mem
)
1221 if (GET_MODE (mem
) == QImode
)
1222 /* ANSI C says that a `char*' can point to anything. */
1225 if (GET_CODE (XEXP (mem
, 0)) == AND
)
1226 /* If the address is an AND, its very hard to know at what it is
1227 actually pointing. */
1233 /* True dependence: X is read after store in MEM takes place. */
1236 true_dependence (mem
, mem_mode
, x
, varies
)
1238 enum machine_mode mem_mode
;
1240 int (*varies
) PARAMS ((rtx
));
1242 register rtx x_addr
, mem_addr
;
1244 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
1247 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
1250 /* If X is an unchanging read, then it can't possibly conflict with any
1251 non-unchanging store. It may conflict with an unchanging write though,
1252 because there may be a single store to this address to initialize it.
1253 Just fall through to the code below to resolve the case where we have
1254 both an unchanging read and an unchanging write. This won't handle all
1255 cases optimally, but the possible performance loss should be
1257 if (RTX_UNCHANGING_P (x
) && ! RTX_UNCHANGING_P (mem
))
1260 if (mem_mode
== VOIDmode
)
1261 mem_mode
= GET_MODE (mem
);
1263 if (! base_alias_check (XEXP (x
, 0), XEXP (mem
, 0), GET_MODE (x
), mem_mode
))
1266 x_addr
= canon_rtx (XEXP (x
, 0));
1267 mem_addr
= canon_rtx (XEXP (mem
, 0));
1269 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
1270 SIZE_FOR_MODE (x
), x_addr
, 0))
1273 if (aliases_everything_p (x
))
1276 /* We cannot use aliases_everyting_p to test MEM, since we must look
1277 at MEM_MODE, rather than GET_MODE (MEM). */
1278 if (mem_mode
== QImode
|| GET_CODE (mem_addr
) == AND
)
1281 /* In true_dependence we also allow BLKmode to alias anything. Why
1282 don't we do this in anti_dependence and output_dependence? */
1283 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
1286 return !fixed_scalar_and_varying_struct_p (mem
, x
, varies
);
1289 /* Returns non-zero if a write to X might alias a previous read from
1290 (or, if WRITEP is non-zero, a write to) MEM. */
1293 write_dependence_p (mem
, x
, writep
)
1298 rtx x_addr
, mem_addr
;
1301 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
1304 /* If MEM is an unchanging read, then it can't possibly conflict with
1305 the store to X, because there is at most one store to MEM, and it must
1306 have occurred somewhere before MEM. */
1307 if (!writep
&& RTX_UNCHANGING_P (mem
))
1310 if (! base_alias_check (XEXP (x
, 0), XEXP (mem
, 0), GET_MODE (x
),
1315 mem
= canon_rtx (mem
);
1317 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
1320 x_addr
= XEXP (x
, 0);
1321 mem_addr
= XEXP (mem
, 0);
1323 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
1324 SIZE_FOR_MODE (x
), x_addr
, 0))
1328 = fixed_scalar_and_varying_struct_p (mem
, x
, rtx_addr_varies_p
);
1330 return (!(fixed_scalar
== mem
&& !aliases_everything_p (x
))
1331 && !(fixed_scalar
== x
&& !aliases_everything_p (mem
)));
1334 /* Anti dependence: X is written after read in MEM takes place. */
1337 anti_dependence (mem
, x
)
1341 return write_dependence_p (mem
, x
, /*writep=*/0);
1344 /* Output dependence: X is written after store in MEM takes place. */
1347 output_dependence (mem
, x
)
1351 return write_dependence_p (mem
, x
, /*writep=*/1);
1354 /* Returns non-zero if X might refer to something which is not
1355 local to the function and is not constant. */
1358 nonlocal_reference_p (x
)
1362 register RTX_CODE code
;
1365 code
= GET_CODE (x
);
1367 if (GET_RTX_CLASS (code
) == 'i')
1369 /* Constant functions are constant. */
1370 if (code
== CALL_INSN
&& CONST_CALL_P (x
))
1373 code
= GET_CODE (x
);
1379 if (GET_CODE (SUBREG_REG (x
)) == REG
)
1381 /* Global registers are not local. */
1382 if (REGNO (SUBREG_REG (x
)) < FIRST_PSEUDO_REGISTER
1383 && global_regs
[REGNO (SUBREG_REG (x
)) + SUBREG_WORD (x
)])
1391 /* Global registers are not local. */
1392 if (regno
< FIRST_PSEUDO_REGISTER
&& global_regs
[regno
])
1406 /* Constants in the function's constants pool are constant. */
1407 if (CONSTANT_POOL_ADDRESS_P (x
))
1412 /* Recursion introduces no additional considerations. */
1413 if (GET_CODE (XEXP (x
, 0)) == MEM
1414 && GET_CODE (XEXP (XEXP (x
, 0), 0)) == SYMBOL_REF
1415 && strcmp(XSTR (XEXP (XEXP (x
, 0), 0), 0),
1416 IDENTIFIER_POINTER (
1417 DECL_ASSEMBLER_NAME (current_function_decl
))) == 0)
1422 /* Be overly conservative and consider any volatile memory
1423 reference as not local. */
1424 if (MEM_VOLATILE_P (x
))
1426 base
= find_base_term (XEXP (x
, 0));
1429 /* A Pmode ADDRESS could be a reference via the structure value
1430 address or static chain. Such memory references are nonlocal.
1432 Thus, we have to examine the contents of the ADDRESS to find
1433 out if this is a local reference or not. */
1434 if (GET_CODE (base
) == ADDRESS
1435 && GET_MODE (base
) == Pmode
1436 && (XEXP (base
, 0) == stack_pointer_rtx
1437 || XEXP (base
, 0) == arg_pointer_rtx
1438 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1439 || XEXP (base
, 0) == hard_frame_pointer_rtx
1441 || XEXP (base
, 0) == frame_pointer_rtx
))
1443 /* Constants in the function's constant pool are constant. */
1444 if (GET_CODE (base
) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (base
))
1457 /* Recursively scan the operands of this expression. */
1460 register const char *fmt
= GET_RTX_FORMAT (code
);
1463 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1467 if (nonlocal_reference_p (XEXP (x
, i
)))
1470 else if (fmt
[i
] == 'E')
1473 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1474 if (nonlocal_reference_p (XVECEXP (x
, i
, j
)))
1483 /* Mark the function if it is constant. */
1486 mark_constant_function ()
1490 if (TREE_PUBLIC (current_function_decl
)
1491 || TREE_READONLY (current_function_decl
)
1492 || TREE_THIS_VOLATILE (current_function_decl
)
1493 || TYPE_MODE (TREE_TYPE (current_function_decl
)) == VOIDmode
)
1496 /* Determine if this is a constant function. */
1498 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1499 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i'
1500 && nonlocal_reference_p (insn
))
1503 /* Mark the function. */
1505 TREE_READONLY (current_function_decl
) = 1;
1509 static HARD_REG_SET argument_registers
;
1516 #ifndef OUTGOING_REGNO
1517 #define OUTGOING_REGNO(N) N
1519 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1520 /* Check whether this register can hold an incoming pointer
1521 argument. FUNCTION_ARG_REGNO_P tests outgoing register
1522 numbers, so translate if necessary due to register windows. */
1523 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
1524 && HARD_REGNO_MODE_OK (i
, Pmode
))
1525 SET_HARD_REG_BIT (argument_registers
, i
);
1527 alias_sets
= splay_tree_new (splay_tree_compare_ints
, 0, 0);
1531 init_alias_analysis ()
1533 int maxreg
= max_reg_num ();
1536 register unsigned int ui
;
1539 reg_known_value_size
= maxreg
;
1542 = (rtx
*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (rtx
))
1543 - FIRST_PSEUDO_REGISTER
;
1545 = (char*) xcalloc ((maxreg
- FIRST_PSEUDO_REGISTER
), sizeof (char))
1546 - FIRST_PSEUDO_REGISTER
;
1548 /* Overallocate reg_base_value to allow some growth during loop
1549 optimization. Loop unrolling can create a large number of
1551 reg_base_value_size
= maxreg
* 2;
1552 reg_base_value
= (rtx
*) xcalloc (reg_base_value_size
, sizeof (rtx
));
1554 ggc_add_rtx_root (reg_base_value
, reg_base_value_size
);
1556 new_reg_base_value
= (rtx
*) xmalloc (reg_base_value_size
* sizeof (rtx
));
1557 reg_seen
= (char *) xmalloc (reg_base_value_size
);
1558 if (! reload_completed
&& flag_unroll_loops
)
1560 /* ??? Why are we realloc'ing if we're just going to zero it? */
1561 alias_invariant
= (rtx
*)xrealloc (alias_invariant
,
1562 reg_base_value_size
* sizeof (rtx
));
1563 bzero ((char *)alias_invariant
, reg_base_value_size
* sizeof (rtx
));
1567 /* The basic idea is that each pass through this loop will use the
1568 "constant" information from the previous pass to propagate alias
1569 information through another level of assignments.
1571 This could get expensive if the assignment chains are long. Maybe
1572 we should throttle the number of iterations, possibly based on
1573 the optimization level or flag_expensive_optimizations.
1575 We could propagate more information in the first pass by making use
1576 of REG_N_SETS to determine immediately that the alias information
1577 for a pseudo is "constant".
1579 A program with an uninitialized variable can cause an infinite loop
1580 here. Instead of doing a full dataflow analysis to detect such problems
1581 we just cap the number of iterations for the loop.
1583 The state of the arrays for the set chain in question does not matter
1584 since the program has undefined behavior. */
1589 /* Assume nothing will change this iteration of the loop. */
1592 /* We want to assign the same IDs each iteration of this loop, so
1593 start counting from zero each iteration of the loop. */
1596 /* We're at the start of the funtion each iteration through the
1597 loop, so we're copying arguments. */
1598 copying_arguments
= 1;
1600 /* Wipe the potential alias information clean for this pass. */
1601 bzero ((char *) new_reg_base_value
, reg_base_value_size
* sizeof (rtx
));
1603 /* Wipe the reg_seen array clean. */
1604 bzero ((char *) reg_seen
, reg_base_value_size
);
1606 /* Mark all hard registers which may contain an address.
1607 The stack, frame and argument pointers may contain an address.
1608 An argument register which can hold a Pmode value may contain
1609 an address even if it is not in BASE_REGS.
1611 The address expression is VOIDmode for an argument and
1612 Pmode for other registers. */
1614 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
1615 if (TEST_HARD_REG_BIT (argument_registers
, i
))
1616 new_reg_base_value
[i
] = gen_rtx_ADDRESS (VOIDmode
,
1617 gen_rtx_REG (Pmode
, i
));
1619 new_reg_base_value
[STACK_POINTER_REGNUM
]
1620 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
1621 new_reg_base_value
[ARG_POINTER_REGNUM
]
1622 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
1623 new_reg_base_value
[FRAME_POINTER_REGNUM
]
1624 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
1625 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1626 new_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
1627 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
1629 if (struct_value_incoming_rtx
1630 && GET_CODE (struct_value_incoming_rtx
) == REG
)
1631 new_reg_base_value
[REGNO (struct_value_incoming_rtx
)]
1632 = gen_rtx_ADDRESS (Pmode
, struct_value_incoming_rtx
);
1634 if (static_chain_rtx
1635 && GET_CODE (static_chain_rtx
) == REG
)
1636 new_reg_base_value
[REGNO (static_chain_rtx
)]
1637 = gen_rtx_ADDRESS (Pmode
, static_chain_rtx
);
1639 /* Walk the insns adding values to the new_reg_base_value array. */
1640 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
1642 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
1643 if (prologue_epilogue_contains (insn
))
1646 if (GET_RTX_CLASS (GET_CODE (insn
)) == 'i')
1649 /* If this insn has a noalias note, process it, Otherwise,
1650 scan for sets. A simple set will have no side effects
1651 which could change the base value of any other register. */
1653 if (GET_CODE (PATTERN (insn
)) == SET
1654 && (find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
)))
1655 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
1657 note_stores (PATTERN (insn
), record_set
, NULL
);
1659 set
= single_set (insn
);
1662 && GET_CODE (SET_DEST (set
)) == REG
1663 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
1664 && (((note
= find_reg_note (insn
, REG_EQUAL
, 0)) != 0
1665 && REG_N_SETS (REGNO (SET_DEST (set
))) == 1)
1666 || (note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) != 0)
1667 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
1668 && ! reg_overlap_mentioned_p (SET_DEST (set
), XEXP (note
, 0)))
1670 int regno
= REGNO (SET_DEST (set
));
1671 reg_known_value
[regno
] = XEXP (note
, 0);
1672 reg_known_equiv_p
[regno
] = REG_NOTE_KIND (note
) == REG_EQUIV
;
1675 else if (GET_CODE (insn
) == NOTE
1676 && NOTE_LINE_NUMBER (insn
) == NOTE_INSN_FUNCTION_BEG
)
1677 copying_arguments
= 0;
1680 /* Now propagate values from new_reg_base_value to reg_base_value. */
1681 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
1683 if (new_reg_base_value
[ui
]
1684 && new_reg_base_value
[ui
] != reg_base_value
[ui
]
1685 && ! rtx_equal_p (new_reg_base_value
[ui
], reg_base_value
[ui
]))
1687 reg_base_value
[ui
] = new_reg_base_value
[ui
];
1692 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
1694 /* Fill in the remaining entries. */
1695 for (i
= FIRST_PSEUDO_REGISTER
; i
< maxreg
; i
++)
1696 if (reg_known_value
[i
] == 0)
1697 reg_known_value
[i
] = regno_reg_rtx
[i
];
1699 /* Simplify the reg_base_value array so that no register refers to
1700 another register, except to special registers indirectly through
1701 ADDRESS expressions.
1703 In theory this loop can take as long as O(registers^2), but unless
1704 there are very long dependency chains it will run in close to linear
1707 This loop may not be needed any longer now that the main loop does
1708 a better job at propagating alias information. */
1714 for (ui
= 0; ui
< reg_base_value_size
; ui
++)
1716 rtx base
= reg_base_value
[ui
];
1717 if (base
&& GET_CODE (base
) == REG
)
1719 unsigned int base_regno
= REGNO (base
);
1720 if (base_regno
== ui
) /* register set from itself */
1721 reg_base_value
[ui
] = 0;
1723 reg_base_value
[ui
] = reg_base_value
[base_regno
];
1728 while (changed
&& pass
< MAX_ALIAS_LOOP_PASSES
);
1731 free (new_reg_base_value
);
1732 new_reg_base_value
= 0;
1738 end_alias_analysis ()
1740 free (reg_known_value
+ FIRST_PSEUDO_REGISTER
);
1741 reg_known_value
= 0;
1742 reg_known_value_size
= 0;
1743 free (reg_known_equiv_p
+ FIRST_PSEUDO_REGISTER
);
1744 reg_known_equiv_p
= 0;
1748 ggc_del_root (reg_base_value
);
1749 free (reg_base_value
);
1752 reg_base_value_size
= 0;
1753 if (alias_invariant
)
1755 free (alias_invariant
);
1756 alias_invariant
= 0;