* optimize.c (initialize_inlined_parameters): Take FN to which the
[official-gcc.git] / gcc / alias.c
blobebb1e7c7efbe6c10d5893902bd9b2d4c93e923a1
1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999 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)
10 any later version.
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. */
22 #include "config.h"
23 #include "system.h"
24 #include "rtl.h"
25 #include "tree.h"
26 #include "tm_p.h"
27 #include "function.h"
28 #include "insn-flags.h"
29 #include "expr.h"
30 #include "regs.h"
31 #include "hard-reg-set.h"
32 #include "flags.h"
33 #include "output.h"
34 #include "toplev.h"
35 #include "splay-tree.h"
36 #include "ggc.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
48 like:
49 struct S
50 / \
51 / \
52 |/_ _\|
53 int double
55 (The arrows are directed and point downwards.) If, when comparing
56 two alias sets, we can hold one set fixed, and 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'
60 are `subsets'.
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 {
67 /* The alias set number, as stored in MEM_ALIAS_SET. */
68 int alias_set;
70 /* The children of the alias set. These are not just the immediate
71 children, but, in fact, all children. So, if we have:
73 struct T { struct S s; float f; }
75 continuing our example above, the children here will be all of
76 `int', `double', `float', and `struct S'. */
77 splay_tree children;
78 }* alias_set_entry;
80 static rtx canon_rtx PROTO((rtx));
81 static int rtx_equal_for_memref_p PROTO((rtx, rtx));
82 static rtx find_symbolic_term PROTO((rtx));
83 static int memrefs_conflict_p PROTO((int, rtx, int, rtx,
84 HOST_WIDE_INT));
85 static void record_set PROTO((rtx, rtx, void *));
86 static rtx find_base_term PROTO((rtx));
87 static int base_alias_check PROTO((rtx, rtx, enum machine_mode,
88 enum machine_mode));
89 static rtx find_base_value PROTO((rtx));
90 static int mems_in_disjoint_alias_sets_p PROTO((rtx, rtx));
91 static int insert_subset_children PROTO((splay_tree_node,
92 void*));
93 static alias_set_entry get_alias_set_entry PROTO((int));
94 static rtx fixed_scalar_and_varying_struct_p PROTO((rtx, rtx, int (*)(rtx)));
95 static int aliases_everything_p PROTO((rtx));
96 static int write_dependence_p PROTO((rtx, rtx, int));
97 static int nonlocal_reference_p PROTO((rtx));
99 /* Set up all info needed to perform alias analysis on memory references. */
101 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
103 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
104 different alias sets. We ignore alias sets in functions making use
105 of variable arguments because the va_arg macros on some systems are
106 not legal ANSI C. */
107 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
108 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
110 /* Cap the number of passes we make over the insns propagating alias
111 information through set chains.
113 10 is a completely arbitrary choice. */
114 #define MAX_ALIAS_LOOP_PASSES 10
116 /* reg_base_value[N] gives an address to which register N is related.
117 If all sets after the first add or subtract to the current value
118 or otherwise modify it so it does not point to a different top level
119 object, reg_base_value[N] is equal to the address part of the source
120 of the first set.
122 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
123 expressions represent certain special values: function arguments and
124 the stack, frame, and argument pointers.
126 The contents of an ADDRESS is not normally used, the mode of the
127 ADDRESS determines whether the ADDRESS is a function argument or some
128 other special value. Pointer equality, not rtx_equal_p, determines whether
129 two ADDRESS expressions refer to the same base address.
131 The only use of the contents of an ADDRESS is for determining if the
132 current function performs nonlocal memory memory references for the
133 purposes of marking the function as a constant function. */
135 static rtx *reg_base_value;
136 static rtx *new_reg_base_value;
137 static unsigned int reg_base_value_size; /* size of reg_base_value array */
138 #define REG_BASE_VALUE(X) \
139 ((unsigned) REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0)
141 /* Vector of known invariant relationships between registers. Set in
142 loop unrolling. Indexed by register number, if nonzero the value
143 is an expression describing this register in terms of another.
145 The length of this array is REG_BASE_VALUE_SIZE.
147 Because this array contains only pseudo registers it has no effect
148 after reload. */
149 static rtx *alias_invariant;
151 /* Vector indexed by N giving the initial (unchanging) value known
152 for pseudo-register N. */
153 rtx *reg_known_value;
155 /* Indicates number of valid entries in reg_known_value. */
156 static int reg_known_value_size;
158 /* Vector recording for each reg_known_value whether it is due to a
159 REG_EQUIV note. Future passes (viz., reload) may replace the
160 pseudo with the equivalent expression and so we account for the
161 dependences that would be introduced if that happens. */
162 /* ??? This is a problem only on the Convex. The REG_EQUIV notes created in
163 assign_parms mention the arg pointer, and there are explicit insns in the
164 RTL that modify the arg pointer. Thus we must ensure that such insns don't
165 get scheduled across each other because that would invalidate the REG_EQUIV
166 notes. One could argue that the REG_EQUIV notes are wrong, but solving
167 the problem in the scheduler will likely give better code, so we do it
168 here. */
169 char *reg_known_equiv_p;
171 /* True when scanning insns from the start of the rtl to the
172 NOTE_INSN_FUNCTION_BEG note. */
174 static int copying_arguments;
176 /* The splay-tree used to store the various alias set entries. */
178 static splay_tree alias_sets;
180 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
181 such an entry, or NULL otherwise. */
183 static alias_set_entry
184 get_alias_set_entry (alias_set)
185 int alias_set;
187 splay_tree_node sn =
188 splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
190 return sn ? ((alias_set_entry) sn->value) : ((alias_set_entry) 0);
193 /* Returns nonzero value if the alias sets for MEM1 and MEM2 are such
194 that the two MEMs cannot alias each other. */
196 static int
197 mems_in_disjoint_alias_sets_p (mem1, mem2)
198 rtx mem1;
199 rtx mem2;
201 alias_set_entry ase;
203 #ifdef ENABLE_CHECKING
204 /* Perform a basic sanity check. Namely, that there are no alias sets
205 if we're not using strict aliasing. This helps to catch bugs
206 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
207 where a MEM is allocated in some way other than by the use of
208 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
209 use alias sets to indicate that spilled registers cannot alias each
210 other, we might need to remove this check. */
211 if (!flag_strict_aliasing &&
212 (MEM_ALIAS_SET (mem1) || MEM_ALIAS_SET (mem2)))
213 abort ();
214 #endif
216 /* The code used in varargs macros are often not conforming ANSI C,
217 which can trick the compiler into making incorrect aliasing
218 assumptions in these functions. So, we don't use alias sets in
219 such a function. FIXME: This should be moved into the front-end;
220 it is a language-dependent notion, and there's no reason not to
221 still use these checks to handle globals. */
222 if (current_function_stdarg || current_function_varargs)
223 return 0;
225 if (!MEM_ALIAS_SET (mem1) || !MEM_ALIAS_SET (mem2))
226 /* We have no alias set information for one of the MEMs, so we
227 have to assume it can alias anything. */
228 return 0;
230 if (MEM_ALIAS_SET (mem1) == MEM_ALIAS_SET (mem2))
231 /* The two alias sets are the same, so they may alias. */
232 return 0;
234 /* Iterate through each of the children of the first alias set,
235 comparing it with the second alias set. */
236 ase = get_alias_set_entry (MEM_ALIAS_SET (mem1));
237 if (ase && splay_tree_lookup (ase->children,
238 (splay_tree_key) MEM_ALIAS_SET (mem2)))
239 return 0;
241 /* Now do the same, but with the alias sets reversed. */
242 ase = get_alias_set_entry (MEM_ALIAS_SET (mem2));
243 if (ase && splay_tree_lookup (ase->children,
244 (splay_tree_key) MEM_ALIAS_SET (mem1)))
245 return 0;
247 /* The two MEMs are in distinct alias sets, and neither one is the
248 child of the other. Therefore, they cannot alias. */
249 return 1;
252 /* Insert the NODE into the splay tree given by DATA. Used by
253 record_alias_subset via splay_tree_foreach. */
255 static int
256 insert_subset_children (node, data)
257 splay_tree_node node;
258 void *data;
260 splay_tree_insert ((splay_tree) data,
261 node->key,
262 node->value);
264 return 0;
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. */
277 void
278 record_alias_subset (superset, subset)
279 int superset;
280 int subset;
282 alias_set_entry superset_entry;
283 alias_set_entry subset_entry;
285 if (superset == 0)
286 abort ();
288 superset_entry = get_alias_set_entry (superset);
289 if (!superset_entry)
291 /* Create an entry for the SUPERSET, so that we have a place to
292 attach the SUBSET. */
293 superset_entry =
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,
299 (splay_tree_key) superset,
300 (splay_tree_value) superset_entry);
304 subset_entry = get_alias_set_entry (subset);
305 if (subset_entry)
306 /* There is an entry for the subset. Enter all of its children
307 (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,
315 /*value=*/0);
318 /* Inside SRC, the source of a SET, find a base address. */
320 static rtx
321 find_base_value (src)
322 register rtx src;
324 switch (GET_CODE (src))
326 case SYMBOL_REF:
327 case LABEL_REF:
328 return src;
330 case REG:
331 /* At the start of a function argument registers have known base
332 values which may be lost later. Returning an ADDRESS
333 expression here allows optimization based on argument values
334 even when the argument registers are used for other purposes. */
335 if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments)
336 return new_reg_base_value[REGNO (src)];
338 /* If a pseudo has a known base value, return it. Do not do this
339 for hard regs since it can result in a circular dependency
340 chain for registers which have values at function entry.
342 The test above is not sufficient because the scheduler may move
343 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
344 if (REGNO (src) >= FIRST_PSEUDO_REGISTER
345 && (unsigned) REGNO (src) < reg_base_value_size
346 && reg_base_value[REGNO (src)])
347 return reg_base_value[REGNO (src)];
349 return src;
351 case MEM:
352 /* Check for an argument passed in memory. Only record in the
353 copying-arguments block; it is too hard to track changes
354 otherwise. */
355 if (copying_arguments
356 && (XEXP (src, 0) == arg_pointer_rtx
357 || (GET_CODE (XEXP (src, 0)) == PLUS
358 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
359 return gen_rtx_ADDRESS (VOIDmode, src);
360 return 0;
362 case CONST:
363 src = XEXP (src, 0);
364 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
365 break;
366 /* fall through */
368 case PLUS:
369 case MINUS:
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);
378 if (temp)
379 src_0 = temp;
382 if (GET_CODE (src_1) == REG)
384 temp = find_base_value (src_1);
385 if (temp)
386 src_1 = temp;
389 /* Guess which operand is the base address.
391 If either operand is a symbol, then it is the base. If
392 either operand is a CONST_INT, then the other is the base. */
394 if (GET_CODE (src_1) == CONST_INT
395 || GET_CODE (src_0) == SYMBOL_REF
396 || GET_CODE (src_0) == LABEL_REF
397 || GET_CODE (src_0) == CONST)
398 return find_base_value (src_0);
400 if (GET_CODE (src_0) == CONST_INT
401 || GET_CODE (src_1) == SYMBOL_REF
402 || GET_CODE (src_1) == LABEL_REF
403 || GET_CODE (src_1) == CONST)
404 return find_base_value (src_1);
406 /* This might not be necessary anymore.
408 If either operand is a REG that is a known pointer, then it
409 is the base. */
410 if (GET_CODE (src_0) == REG && REGNO_POINTER_FLAG (REGNO (src_0)))
411 return find_base_value (src_0);
413 if (GET_CODE (src_1) == REG && REGNO_POINTER_FLAG (REGNO (src_1)))
414 return find_base_value (src_1);
416 return 0;
419 case LO_SUM:
420 /* The standard form is (lo_sum reg sym) so look only at the
421 second operand. */
422 return find_base_value (XEXP (src, 1));
424 case AND:
425 /* If the second operand is constant set the base
426 address to the first operand. */
427 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
428 return find_base_value (XEXP (src, 0));
429 return 0;
431 case ZERO_EXTEND:
432 case SIGN_EXTEND: /* used for NT/Alpha pointers */
433 case HIGH:
434 return find_base_value (XEXP (src, 0));
436 default:
437 break;
440 return 0;
443 /* Called from init_alias_analysis indirectly through note_stores. */
445 /* while scanning insns to find base values, reg_seen[N] is nonzero if
446 register N has been set in this function. */
447 static char *reg_seen;
449 /* Addresses which are known not to alias anything else are identified
450 by a unique integer. */
451 static int unique_id;
453 static void
454 record_set (dest, set, data)
455 rtx dest, set;
456 void *data ATTRIBUTE_UNUSED;
458 register unsigned regno;
459 rtx src;
461 if (GET_CODE (dest) != REG)
462 return;
464 regno = REGNO (dest);
466 if (regno >= reg_base_value_size)
467 abort ();
469 if (set)
471 /* A CLOBBER wipes out any old value but does not prevent a previously
472 unset register from acquiring a base address (i.e. reg_seen is not
473 set). */
474 if (GET_CODE (set) == CLOBBER)
476 new_reg_base_value[regno] = 0;
477 return;
479 src = SET_SRC (set);
481 else
483 if (reg_seen[regno])
485 new_reg_base_value[regno] = 0;
486 return;
488 reg_seen[regno] = 1;
489 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
490 GEN_INT (unique_id++));
491 return;
494 /* This is not the first set. If the new value is not related to the
495 old value, forget the base value. Note that the following code is
496 not detected:
497 extern int x, y; int *p = &x; p += (&y-&x);
498 ANSI C does not allow computing the difference of addresses
499 of distinct top level objects. */
500 if (new_reg_base_value[regno])
501 switch (GET_CODE (src))
503 case LO_SUM:
504 case PLUS:
505 case MINUS:
506 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
507 new_reg_base_value[regno] = 0;
508 break;
509 case AND:
510 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
511 new_reg_base_value[regno] = 0;
512 break;
513 default:
514 new_reg_base_value[regno] = 0;
515 break;
517 /* If this is the first set of a register, record the value. */
518 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
519 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
520 new_reg_base_value[regno] = find_base_value (src);
522 reg_seen[regno] = 1;
525 /* Called from loop optimization when a new pseudo-register is created. */
526 void
527 record_base_value (regno, val, invariant)
528 int regno;
529 rtx val;
530 int invariant;
532 if ((unsigned) regno >= reg_base_value_size)
533 return;
535 /* If INVARIANT is true then this value also describes an invariant
536 relationship which can be used to deduce that two registers with
537 unknown values are different. */
538 if (invariant && alias_invariant)
539 alias_invariant[regno] = val;
541 if (GET_CODE (val) == REG)
543 if ((unsigned) REGNO (val) < reg_base_value_size)
545 reg_base_value[regno] = reg_base_value[REGNO (val)];
547 return;
549 reg_base_value[regno] = find_base_value (val);
552 static rtx
553 canon_rtx (x)
554 rtx x;
556 /* Recursively look for equivalences. */
557 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
558 && REGNO (x) < reg_known_value_size)
559 return reg_known_value[REGNO (x)] == x
560 ? x : canon_rtx (reg_known_value[REGNO (x)]);
561 else if (GET_CODE (x) == PLUS)
563 rtx x0 = canon_rtx (XEXP (x, 0));
564 rtx x1 = canon_rtx (XEXP (x, 1));
566 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
568 /* We can tolerate LO_SUMs being offset here; these
569 rtl are used for nothing other than comparisons. */
570 if (GET_CODE (x0) == CONST_INT)
571 return plus_constant_for_output (x1, INTVAL (x0));
572 else if (GET_CODE (x1) == CONST_INT)
573 return plus_constant_for_output (x0, INTVAL (x1));
574 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
577 /* This gives us much better alias analysis when called from
578 the loop optimizer. Note we want to leave the original
579 MEM alone, but need to return the canonicalized MEM with
580 all the flags with their original values. */
581 else if (GET_CODE (x) == MEM)
583 rtx addr = canon_rtx (XEXP (x, 0));
584 if (addr != XEXP (x, 0))
586 rtx new = gen_rtx_MEM (GET_MODE (x), addr);
587 RTX_UNCHANGING_P (new) = RTX_UNCHANGING_P (x);
588 MEM_COPY_ATTRIBUTES (new, x);
589 MEM_ALIAS_SET (new) = MEM_ALIAS_SET (x);
590 x = new;
593 return x;
596 /* Return 1 if X and Y are identical-looking rtx's.
598 We use the data in reg_known_value above to see if two registers with
599 different numbers are, in fact, equivalent. */
601 static int
602 rtx_equal_for_memref_p (x, y)
603 rtx x, y;
605 register int i;
606 register int j;
607 register enum rtx_code code;
608 register const char *fmt;
610 if (x == 0 && y == 0)
611 return 1;
612 if (x == 0 || y == 0)
613 return 0;
614 x = canon_rtx (x);
615 y = canon_rtx (y);
617 if (x == y)
618 return 1;
620 code = GET_CODE (x);
621 /* Rtx's of different codes cannot be equal. */
622 if (code != GET_CODE (y))
623 return 0;
625 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
626 (REG:SI x) and (REG:HI x) are NOT equivalent. */
628 if (GET_MODE (x) != GET_MODE (y))
629 return 0;
631 /* REG, LABEL_REF, and SYMBOL_REF can be compared nonrecursively. */
633 if (code == REG)
634 return REGNO (x) == REGNO (y);
635 if (code == LABEL_REF)
636 return XEXP (x, 0) == XEXP (y, 0);
637 if (code == SYMBOL_REF)
638 return XSTR (x, 0) == XSTR (y, 0);
639 if (code == CONST_INT)
640 return INTVAL (x) == INTVAL (y);
641 /* There's no need to compare the contents of CONST_DOUBLEs because
642 they're unique. */
643 if (code == CONST_DOUBLE)
644 return 0;
645 if (code == ADDRESSOF)
646 return REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0)) && XINT (x, 1) == XINT (y, 1);
648 /* For commutative operations, the RTX match if the operand match in any
649 order. Also handle the simple binary and unary cases without a loop. */
650 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
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 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
654 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
655 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
656 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
657 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
658 else if (GET_RTX_CLASS (code) == '1')
659 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
661 /* Compare the elements. If any pair of corresponding elements
662 fail to match, return 0 for the whole things.
664 Limit cases to types which actually appear in addresses. */
666 fmt = GET_RTX_FORMAT (code);
667 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
669 switch (fmt[i])
671 case 'i':
672 if (XINT (x, i) != XINT (y, i))
673 return 0;
674 break;
676 case 'E':
677 /* Two vectors must have the same length. */
678 if (XVECLEN (x, i) != XVECLEN (y, i))
679 return 0;
681 /* And the corresponding elements must match. */
682 for (j = 0; j < XVECLEN (x, i); j++)
683 if (rtx_equal_for_memref_p (XVECEXP (x, i, j), XVECEXP (y, i, j)) == 0)
684 return 0;
685 break;
687 case 'e':
688 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
689 return 0;
690 break;
692 /* This can happen for an asm which clobbers memory. */
693 case '0':
694 break;
696 /* It is believed that rtx's at this level will never
697 contain anything but integers and other rtx's,
698 except for within LABEL_REFs and SYMBOL_REFs. */
699 default:
700 abort ();
703 return 1;
706 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
707 X and return it, or return 0 if none found. */
709 static rtx
710 find_symbolic_term (x)
711 rtx x;
713 register int i;
714 register enum rtx_code code;
715 register const char *fmt;
717 code = GET_CODE (x);
718 if (code == SYMBOL_REF || code == LABEL_REF)
719 return x;
720 if (GET_RTX_CLASS (code) == 'o')
721 return 0;
723 fmt = GET_RTX_FORMAT (code);
724 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
726 rtx t;
728 if (fmt[i] == 'e')
730 t = find_symbolic_term (XEXP (x, i));
731 if (t != 0)
732 return t;
734 else if (fmt[i] == 'E')
735 break;
737 return 0;
740 static rtx
741 find_base_term (x)
742 register rtx x;
744 switch (GET_CODE (x))
746 case REG:
747 return REG_BASE_VALUE (x);
749 case ZERO_EXTEND:
750 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
751 case HIGH:
752 case PRE_INC:
753 case PRE_DEC:
754 case POST_INC:
755 case POST_DEC:
756 return find_base_term (XEXP (x, 0));
758 case CONST:
759 x = XEXP (x, 0);
760 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
761 return 0;
762 /* fall through */
763 case LO_SUM:
764 case PLUS:
765 case MINUS:
767 rtx tmp1 = XEXP (x, 0);
768 rtx tmp2 = XEXP (x, 1);
770 /* This is a litle bit tricky since we have to determine which of
771 the two operands represents the real base address. Otherwise this
772 routine may return the index register instead of the base register.
774 That may cause us to believe no aliasing was possible, when in
775 fact aliasing is possible.
777 We use a few simple tests to guess the base register. Additional
778 tests can certainly be added. For example, if one of the operands
779 is a shift or multiply, then it must be the index register and the
780 other operand is the base register. */
782 /* If either operand is known to be a pointer, then use it
783 to determine the base term. */
784 if (REG_P (tmp1) && REGNO_POINTER_FLAG (REGNO (tmp1)))
785 return find_base_term (tmp1);
787 if (REG_P (tmp2) && REGNO_POINTER_FLAG (REGNO (tmp2)))
788 return find_base_term (tmp2);
790 /* Neither operand was known to be a pointer. Go ahead and find the
791 base term for both operands. */
792 tmp1 = find_base_term (tmp1);
793 tmp2 = find_base_term (tmp2);
795 /* If either base term is named object or a special address
796 (like an argument or stack reference), then use it for the
797 base term. */
798 if (tmp1
799 && (GET_CODE (tmp1) == SYMBOL_REF
800 || GET_CODE (tmp1) == LABEL_REF
801 || (GET_CODE (tmp1) == ADDRESS
802 && GET_MODE (tmp1) != VOIDmode)))
803 return tmp1;
805 if (tmp2
806 && (GET_CODE (tmp2) == SYMBOL_REF
807 || GET_CODE (tmp2) == LABEL_REF
808 || (GET_CODE (tmp2) == ADDRESS
809 && GET_MODE (tmp2) != VOIDmode)))
810 return tmp2;
812 /* We could not determine which of the two operands was the
813 base register and which was the index. So we can determine
814 nothing from the base alias check. */
815 return 0;
818 case AND:
819 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
820 return REG_BASE_VALUE (XEXP (x, 0));
821 return 0;
823 case SYMBOL_REF:
824 case LABEL_REF:
825 return x;
827 default:
828 return 0;
832 /* Return 0 if the addresses X and Y are known to point to different
833 objects, 1 if they might be pointers to the same object. */
835 static int
836 base_alias_check (x, y, x_mode, y_mode)
837 rtx x, y;
838 enum machine_mode x_mode, y_mode;
840 rtx x_base = find_base_term (x);
841 rtx y_base = find_base_term (y);
843 /* If the address itself has no known base see if a known equivalent
844 value has one. If either address still has no known base, nothing
845 is known about aliasing. */
846 if (x_base == 0)
848 rtx x_c;
849 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
850 return 1;
851 x_base = find_base_term (x_c);
852 if (x_base == 0)
853 return 1;
856 if (y_base == 0)
858 rtx y_c;
859 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
860 return 1;
861 y_base = find_base_term (y_c);
862 if (y_base == 0)
863 return 1;
866 /* If the base addresses are equal nothing is known about aliasing. */
867 if (rtx_equal_p (x_base, y_base))
868 return 1;
870 /* The base addresses of the read and write are different expressions.
871 If they are both symbols and they are not accessed via AND, there is
872 no conflict. We can bring knowledge of object alignment into play
873 here. For example, on alpha, "char a, b;" can alias one another,
874 though "char a; long b;" cannot. */
875 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
877 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
878 return 1;
879 if (GET_CODE (x) == AND
880 && (GET_CODE (XEXP (x, 1)) != CONST_INT
881 || GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
882 return 1;
883 if (GET_CODE (y) == AND
884 && (GET_CODE (XEXP (y, 1)) != CONST_INT
885 || GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
886 return 1;
887 /* Differing symbols never alias. */
888 return 0;
891 /* If one address is a stack reference there can be no alias:
892 stack references using different base registers do not alias,
893 a stack reference can not alias a parameter, and a stack reference
894 can not alias a global. */
895 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
896 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
897 return 0;
899 if (! flag_argument_noalias)
900 return 1;
902 if (flag_argument_noalias > 1)
903 return 0;
905 /* Weak noalias assertion (arguments are distinct, but may match globals). */
906 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
909 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
910 where SIZE is the size in bytes of the memory reference. If ADDR
911 is not modified by the memory reference then ADDR is returned. */
914 addr_side_effect_eval (addr, size, n_refs)
915 rtx addr;
916 int size;
917 int n_refs;
919 int offset = 0;
921 switch (GET_CODE (addr))
923 case PRE_INC:
924 offset = (n_refs + 1) * size;
925 break;
926 case PRE_DEC:
927 offset = -(n_refs + 1) * size;
928 break;
929 case POST_INC:
930 offset = n_refs * size;
931 break;
932 case POST_DEC:
933 offset = -n_refs * size;
934 break;
936 default:
937 return addr;
940 if (offset)
941 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
942 else
943 addr = XEXP (addr, 0);
945 return addr;
948 /* Return nonzero if X and Y (memory addresses) could reference the
949 same location in memory. C is an offset accumulator. When
950 C is nonzero, we are testing aliases between X and Y + C.
951 XSIZE is the size in bytes of the X reference,
952 similarly YSIZE is the size in bytes for Y.
954 If XSIZE or YSIZE is zero, we do not know the amount of memory being
955 referenced (the reference was BLKmode), so make the most pessimistic
956 assumptions.
958 If XSIZE or YSIZE is negative, we may access memory outside the object
959 being referenced as a side effect. This can happen when using AND to
960 align memory references, as is done on the Alpha.
962 Nice to notice that varying addresses cannot conflict with fp if no
963 local variables had their addresses taken, but that's too hard now. */
966 static int
967 memrefs_conflict_p (xsize, x, ysize, y, c)
968 register rtx x, y;
969 int xsize, ysize;
970 HOST_WIDE_INT c;
972 if (GET_CODE (x) == HIGH)
973 x = XEXP (x, 0);
974 else if (GET_CODE (x) == LO_SUM)
975 x = XEXP (x, 1);
976 else
977 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
978 if (GET_CODE (y) == HIGH)
979 y = XEXP (y, 0);
980 else if (GET_CODE (y) == LO_SUM)
981 y = XEXP (y, 1);
982 else
983 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
985 if (rtx_equal_for_memref_p (x, y))
987 if (xsize <= 0 || ysize <= 0)
988 return 1;
989 if (c >= 0 && xsize > c)
990 return 1;
991 if (c < 0 && ysize+c > 0)
992 return 1;
993 return 0;
996 /* This code used to check for conflicts involving stack references and
997 globals but the base address alias code now handles these cases. */
999 if (GET_CODE (x) == PLUS)
1001 /* The fact that X is canonicalized means that this
1002 PLUS rtx is canonicalized. */
1003 rtx x0 = XEXP (x, 0);
1004 rtx x1 = XEXP (x, 1);
1006 if (GET_CODE (y) == PLUS)
1008 /* The fact that Y is canonicalized means that this
1009 PLUS rtx is canonicalized. */
1010 rtx y0 = XEXP (y, 0);
1011 rtx y1 = XEXP (y, 1);
1013 if (rtx_equal_for_memref_p (x1, y1))
1014 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1015 if (rtx_equal_for_memref_p (x0, y0))
1016 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1017 if (GET_CODE (x1) == CONST_INT)
1019 if (GET_CODE (y1) == CONST_INT)
1020 return memrefs_conflict_p (xsize, x0, ysize, y0,
1021 c - INTVAL (x1) + INTVAL (y1));
1022 else
1023 return memrefs_conflict_p (xsize, x0, ysize, y,
1024 c - INTVAL (x1));
1026 else if (GET_CODE (y1) == CONST_INT)
1027 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1029 return 1;
1031 else if (GET_CODE (x1) == CONST_INT)
1032 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1034 else if (GET_CODE (y) == PLUS)
1036 /* The fact that Y is canonicalized means that this
1037 PLUS rtx is canonicalized. */
1038 rtx y0 = XEXP (y, 0);
1039 rtx y1 = XEXP (y, 1);
1041 if (GET_CODE (y1) == CONST_INT)
1042 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1043 else
1044 return 1;
1047 if (GET_CODE (x) == GET_CODE (y))
1048 switch (GET_CODE (x))
1050 case MULT:
1052 /* Handle cases where we expect the second operands to be the
1053 same, and check only whether the first operand would conflict
1054 or not. */
1055 rtx x0, y0;
1056 rtx x1 = canon_rtx (XEXP (x, 1));
1057 rtx y1 = canon_rtx (XEXP (y, 1));
1058 if (! rtx_equal_for_memref_p (x1, y1))
1059 return 1;
1060 x0 = canon_rtx (XEXP (x, 0));
1061 y0 = canon_rtx (XEXP (y, 0));
1062 if (rtx_equal_for_memref_p (x0, y0))
1063 return (xsize == 0 || ysize == 0
1064 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1066 /* Can't properly adjust our sizes. */
1067 if (GET_CODE (x1) != CONST_INT)
1068 return 1;
1069 xsize /= INTVAL (x1);
1070 ysize /= INTVAL (x1);
1071 c /= INTVAL (x1);
1072 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1075 case REG:
1076 /* Are these registers known not to be equal? */
1077 if (alias_invariant)
1079 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1080 rtx i_x, i_y; /* invariant relationships of X and Y */
1082 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1083 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1085 if (i_x == 0 && i_y == 0)
1086 break;
1088 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1089 ysize, i_y ? i_y : y, c))
1090 return 0;
1092 break;
1094 default:
1095 break;
1098 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1099 as an access with indeterminate size. Assume that references
1100 besides AND are aligned, so if the size of the other reference is
1101 at least as large as the alignment, assume no other overlap. */
1102 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1104 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1105 xsize = -1;
1106 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1108 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1110 /* ??? If we are indexing far enough into the array/structure, we
1111 may yet be able to determine that we can not overlap. But we
1112 also need to that we are far enough from the end not to overlap
1113 a following reference, so we do nothing with that for now. */
1114 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1115 ysize = -1;
1116 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1119 if (CONSTANT_P (x))
1121 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1123 c += (INTVAL (y) - INTVAL (x));
1124 return (xsize <= 0 || ysize <= 0
1125 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1128 if (GET_CODE (x) == CONST)
1130 if (GET_CODE (y) == CONST)
1131 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1132 ysize, canon_rtx (XEXP (y, 0)), c);
1133 else
1134 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1135 ysize, y, c);
1137 if (GET_CODE (y) == CONST)
1138 return memrefs_conflict_p (xsize, x, ysize,
1139 canon_rtx (XEXP (y, 0)), c);
1141 if (CONSTANT_P (y))
1142 return (xsize < 0 || ysize < 0
1143 || (rtx_equal_for_memref_p (x, y)
1144 && (xsize == 0 || ysize == 0
1145 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1147 return 1;
1149 return 1;
1152 /* Functions to compute memory dependencies.
1154 Since we process the insns in execution order, we can build tables
1155 to keep track of what registers are fixed (and not aliased), what registers
1156 are varying in known ways, and what registers are varying in unknown
1157 ways.
1159 If both memory references are volatile, then there must always be a
1160 dependence between the two references, since their order can not be
1161 changed. A volatile and non-volatile reference can be interchanged
1162 though.
1164 A MEM_IN_STRUCT reference at a non-QImode non-AND varying address can never
1165 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We must
1166 allow QImode aliasing because the ANSI C standard allows character
1167 pointers to alias anything. We are assuming that characters are
1168 always QImode here. We also must allow AND addresses, because they may
1169 generate accesses outside the object being referenced. This is used to
1170 generate aligned addresses from unaligned addresses, for instance, the
1171 alpha storeqi_unaligned pattern. */
1173 /* Read dependence: X is read after read in MEM takes place. There can
1174 only be a dependence here if both reads are volatile. */
1177 read_dependence (mem, x)
1178 rtx mem;
1179 rtx x;
1181 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1184 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1185 MEM2 is a reference to a structure at a varying address, or returns
1186 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1187 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1188 to decide whether or not an address may vary; it should return
1189 nozero whenever variation is possible. */
1191 static rtx
1192 fixed_scalar_and_varying_struct_p (mem1, mem2, varies_p)
1193 rtx mem1;
1194 rtx mem2;
1195 int (*varies_p) PROTO((rtx));
1197 rtx mem1_addr = XEXP (mem1, 0);
1198 rtx mem2_addr = XEXP (mem2, 0);
1200 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1201 && !varies_p (mem1_addr) && varies_p (mem2_addr))
1202 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1203 varying address. */
1204 return mem1;
1206 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1207 && varies_p (mem1_addr) && !varies_p (mem2_addr))
1208 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1209 varying address. */
1210 return mem2;
1212 return NULL_RTX;
1215 /* Returns nonzero if something about the mode or address format MEM1
1216 indicates that it might well alias *anything*. */
1218 static int
1219 aliases_everything_p (mem)
1220 rtx mem;
1222 if (GET_MODE (mem) == QImode)
1223 /* ANSI C says that a `char*' can point to anything. */
1224 return 1;
1226 if (GET_CODE (XEXP (mem, 0)) == AND)
1227 /* If the address is an AND, its very hard to know at what it is
1228 actually pointing. */
1229 return 1;
1231 return 0;
1234 /* True dependence: X is read after store in MEM takes place. */
1237 true_dependence (mem, mem_mode, x, varies)
1238 rtx mem;
1239 enum machine_mode mem_mode;
1240 rtx x;
1241 int (*varies) PROTO((rtx));
1243 register rtx x_addr, mem_addr;
1245 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1246 return 1;
1248 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1249 return 0;
1251 /* If X is an unchanging read, then it can't possibly conflict with any
1252 non-unchanging store. It may conflict with an unchanging write though,
1253 because there may be a single store to this address to initialize it.
1254 Just fall through to the code below to resolve the case where we have
1255 both an unchanging read and an unchanging write. This won't handle all
1256 cases optimally, but the possible performance loss should be
1257 negligible. */
1258 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1259 return 0;
1261 if (mem_mode == VOIDmode)
1262 mem_mode = GET_MODE (mem);
1264 if (! base_alias_check (XEXP (x, 0), XEXP (mem, 0), GET_MODE (x), mem_mode))
1265 return 0;
1267 x_addr = canon_rtx (XEXP (x, 0));
1268 mem_addr = canon_rtx (XEXP (mem, 0));
1270 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1271 SIZE_FOR_MODE (x), x_addr, 0))
1272 return 0;
1274 if (aliases_everything_p (x))
1275 return 1;
1277 /* We cannot use aliases_everyting_p to test MEM, since we must look
1278 at MEM_MODE, rather than GET_MODE (MEM). */
1279 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1280 return 1;
1282 /* In true_dependence we also allow BLKmode to alias anything. Why
1283 don't we do this in anti_dependence and output_dependence? */
1284 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1285 return 1;
1287 return !fixed_scalar_and_varying_struct_p (mem, x, varies);
1290 /* Returns non-zero if a write to X might alias a previous read from
1291 (or, if WRITEP is non-zero, a write to) MEM. */
1293 static int
1294 write_dependence_p (mem, x, writep)
1295 rtx mem;
1296 rtx x;
1297 int writep;
1299 rtx x_addr, mem_addr;
1300 rtx fixed_scalar;
1302 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1303 return 1;
1305 /* If MEM is an unchanging read, then it can't possibly conflict with
1306 the store to X, because there is at most one store to MEM, and it must
1307 have occurred somewhere before MEM. */
1308 if (!writep && RTX_UNCHANGING_P (mem))
1309 return 0;
1311 if (! base_alias_check (XEXP (x, 0), XEXP (mem, 0), GET_MODE (x),
1312 GET_MODE (mem)))
1313 return 0;
1315 x = canon_rtx (x);
1316 mem = canon_rtx (mem);
1318 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1319 return 0;
1321 x_addr = XEXP (x, 0);
1322 mem_addr = XEXP (mem, 0);
1324 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1325 SIZE_FOR_MODE (x), x_addr, 0))
1326 return 0;
1328 fixed_scalar
1329 = fixed_scalar_and_varying_struct_p (mem, x, rtx_addr_varies_p);
1331 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1332 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1335 /* Anti dependence: X is written after read in MEM takes place. */
1338 anti_dependence (mem, x)
1339 rtx mem;
1340 rtx x;
1342 return write_dependence_p (mem, x, /*writep=*/0);
1345 /* Output dependence: X is written after store in MEM takes place. */
1348 output_dependence (mem, x)
1349 register rtx mem;
1350 register rtx x;
1352 return write_dependence_p (mem, x, /*writep=*/1);
1355 /* Returns non-zero if X might refer to something which is not
1356 local to the function and is not constant. */
1358 static int
1359 nonlocal_reference_p (x)
1360 rtx x;
1362 rtx base;
1363 register RTX_CODE code;
1364 int regno;
1366 code = GET_CODE (x);
1368 if (GET_RTX_CLASS (code) == 'i')
1370 /* Constant functions are constant. */
1371 if (code == CALL_INSN && CONST_CALL_P (x))
1372 return 0;
1373 x = PATTERN (x);
1374 code = GET_CODE (x);
1377 switch (code)
1379 case SUBREG:
1380 if (GET_CODE (SUBREG_REG (x)) == REG)
1382 /* Global registers are not local. */
1383 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1384 && global_regs[REGNO (SUBREG_REG (x)) + SUBREG_WORD (x)])
1385 return 1;
1386 return 0;
1388 break;
1390 case REG:
1391 regno = REGNO (x);
1392 /* Global registers are not local. */
1393 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1394 return 1;
1395 return 0;
1397 case SCRATCH:
1398 case PC:
1399 case CC0:
1400 case CONST_INT:
1401 case CONST_DOUBLE:
1402 case CONST:
1403 case LABEL_REF:
1404 return 0;
1406 case SYMBOL_REF:
1407 /* Constants in the function's constants pool are constant. */
1408 if (CONSTANT_POOL_ADDRESS_P (x))
1409 return 0;
1410 return 1;
1412 case CALL:
1413 /* Recursion introduces no additional considerations. */
1414 if (GET_CODE (XEXP (x, 0)) == MEM
1415 && GET_CODE (XEXP (XEXP (x, 0), 0)) == SYMBOL_REF
1416 && strcmp(XSTR (XEXP (XEXP (x, 0), 0), 0),
1417 IDENTIFIER_POINTER (
1418 DECL_ASSEMBLER_NAME (current_function_decl))) == 0)
1419 return 0;
1420 return 1;
1422 case MEM:
1423 /* Be overly conservative and consider any volatile memory
1424 reference as not local. */
1425 if (MEM_VOLATILE_P (x))
1426 return 1;
1427 base = find_base_term (XEXP (x, 0));
1428 if (base)
1430 /* A Pmode ADDRESS could be a reference via the structure value
1431 address or static chain. Such memory references are nonlocal.
1433 Thus, we have to examine the contents of the ADDRESS to find
1434 out if this is a local reference or not. */
1435 if (GET_CODE (base) == ADDRESS
1436 && GET_MODE (base) == Pmode
1437 && (XEXP (base, 0) == stack_pointer_rtx
1438 || XEXP (base, 0) == arg_pointer_rtx
1439 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1440 || XEXP (base, 0) == hard_frame_pointer_rtx
1441 #endif
1442 || XEXP (base, 0) == frame_pointer_rtx))
1443 return 0;
1444 /* Constants in the function's constant pool are constant. */
1445 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
1446 return 0;
1448 return 1;
1450 case ASM_INPUT:
1451 case ASM_OPERANDS:
1452 return 1;
1454 default:
1455 break;
1458 /* Recursively scan the operands of this expression. */
1461 register const char *fmt = GET_RTX_FORMAT (code);
1462 register int i;
1464 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1466 if (fmt[i] == 'e')
1468 if (nonlocal_reference_p (XEXP (x, i)))
1469 return 1;
1471 if (fmt[i] == 'E')
1473 register int j;
1474 for (j = 0; j < XVECLEN (x, i); j++)
1475 if (nonlocal_reference_p (XVECEXP (x, i, j)))
1476 return 1;
1481 return 0;
1484 /* Mark the function if it is constant. */
1486 void
1487 mark_constant_function ()
1489 rtx insn;
1491 if (TREE_PUBLIC (current_function_decl)
1492 || TREE_READONLY (current_function_decl)
1493 || TREE_THIS_VOLATILE (current_function_decl)
1494 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
1495 return;
1497 /* Determine if this is a constant function. */
1499 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1500 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
1501 && nonlocal_reference_p (insn))
1502 return;
1504 /* Mark the function. */
1506 TREE_READONLY (current_function_decl) = 1;
1510 static HARD_REG_SET argument_registers;
1512 void
1513 init_alias_once ()
1515 register int i;
1517 #ifndef OUTGOING_REGNO
1518 #define OUTGOING_REGNO(N) N
1519 #endif
1520 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1521 /* Check whether this register can hold an incoming pointer
1522 argument. FUNCTION_ARG_REGNO_P tests outgoing register
1523 numbers, so translate if necessary due to register windows. */
1524 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
1525 && HARD_REGNO_MODE_OK (i, Pmode))
1526 SET_HARD_REG_BIT (argument_registers, i);
1528 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
1531 void
1532 init_alias_analysis ()
1534 int maxreg = max_reg_num ();
1535 int changed, pass;
1536 register int i;
1537 register unsigned int ui;
1538 register rtx insn;
1540 reg_known_value_size = maxreg;
1542 reg_known_value
1543 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
1544 - FIRST_PSEUDO_REGISTER;
1545 reg_known_equiv_p
1546 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
1547 - FIRST_PSEUDO_REGISTER;
1549 /* Overallocate reg_base_value to allow some growth during loop
1550 optimization. Loop unrolling can create a large number of
1551 registers. */
1552 reg_base_value_size = maxreg * 2;
1553 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
1554 if (ggc_p)
1555 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
1557 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
1558 reg_seen = (char *) xmalloc (reg_base_value_size);
1559 if (! reload_completed && flag_unroll_loops)
1561 /* ??? Why are we realloc'ing if we're just going to zero it? */
1562 alias_invariant = (rtx *)xrealloc (alias_invariant,
1563 reg_base_value_size * sizeof (rtx));
1564 bzero ((char *)alias_invariant, reg_base_value_size * sizeof (rtx));
1568 /* The basic idea is that each pass through this loop will use the
1569 "constant" information from the previous pass to propagate alias
1570 information through another level of assignments.
1572 This could get expensive if the assignment chains are long. Maybe
1573 we should throttle the number of iterations, possibly based on
1574 the optimization level or flag_expensive_optimizations.
1576 We could propagate more information in the first pass by making use
1577 of REG_N_SETS to determine immediately that the alias information
1578 for a pseudo is "constant".
1580 A program with an uninitialized variable can cause an infinite loop
1581 here. Instead of doing a full dataflow analysis to detect such problems
1582 we just cap the number of iterations for the loop.
1584 The state of the arrays for the set chain in question does not matter
1585 since the program has undefined behavior. */
1587 pass = 0;
1590 /* Assume nothing will change this iteration of the loop. */
1591 changed = 0;
1593 /* We want to assign the same IDs each iteration of this loop, so
1594 start counting from zero each iteration of the loop. */
1595 unique_id = 0;
1597 /* We're at the start of the funtion each iteration through the
1598 loop, so we're copying arguments. */
1599 copying_arguments = 1;
1601 /* Wipe the potential alias information clean for this pass. */
1602 bzero ((char *) new_reg_base_value, reg_base_value_size * sizeof (rtx));
1604 /* Wipe the reg_seen array clean. */
1605 bzero ((char *) reg_seen, reg_base_value_size);
1607 /* Mark all hard registers which may contain an address.
1608 The stack, frame and argument pointers may contain an address.
1609 An argument register which can hold a Pmode value may contain
1610 an address even if it is not in BASE_REGS.
1612 The address expression is VOIDmode for an argument and
1613 Pmode for other registers. */
1615 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1616 if (TEST_HARD_REG_BIT (argument_registers, i))
1617 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
1618 gen_rtx_REG (Pmode, i));
1620 new_reg_base_value[STACK_POINTER_REGNUM]
1621 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
1622 new_reg_base_value[ARG_POINTER_REGNUM]
1623 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
1624 new_reg_base_value[FRAME_POINTER_REGNUM]
1625 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
1626 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1627 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
1628 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
1629 #endif
1630 if (struct_value_incoming_rtx
1631 && GET_CODE (struct_value_incoming_rtx) == REG)
1632 new_reg_base_value[REGNO (struct_value_incoming_rtx)]
1633 = gen_rtx_ADDRESS (Pmode, struct_value_incoming_rtx);
1635 if (static_chain_rtx
1636 && GET_CODE (static_chain_rtx) == REG)
1637 new_reg_base_value[REGNO (static_chain_rtx)]
1638 = gen_rtx_ADDRESS (Pmode, static_chain_rtx);
1640 /* Walk the insns adding values to the new_reg_base_value array. */
1641 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1643 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
1644 if (prologue_epilogue_contains (insn))
1645 continue;
1646 #endif
1647 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1649 rtx note, set;
1650 /* If this insn has a noalias note, process it, Otherwise,
1651 scan for sets. A simple set will have no side effects
1652 which could change the base value of any other register. */
1654 if (GET_CODE (PATTERN (insn)) == SET
1655 && (find_reg_note (insn, REG_NOALIAS, NULL_RTX)))
1656 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
1657 else
1658 note_stores (PATTERN (insn), record_set, NULL);
1660 set = single_set (insn);
1662 if (set != 0
1663 && GET_CODE (SET_DEST (set)) == REG
1664 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
1665 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
1666 && REG_N_SETS (REGNO (SET_DEST (set))) == 1)
1667 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
1668 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
1669 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
1671 int regno = REGNO (SET_DEST (set));
1672 reg_known_value[regno] = XEXP (note, 0);
1673 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
1676 else if (GET_CODE (insn) == NOTE
1677 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
1678 copying_arguments = 0;
1681 /* Now propagate values from new_reg_base_value to reg_base_value. */
1682 for (ui = 0; ui < reg_base_value_size; ui++)
1684 if (new_reg_base_value[ui]
1685 && new_reg_base_value[ui] != reg_base_value[ui]
1686 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
1688 reg_base_value[ui] = new_reg_base_value[ui];
1689 changed = 1;
1693 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
1695 /* Fill in the remaining entries. */
1696 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
1697 if (reg_known_value[i] == 0)
1698 reg_known_value[i] = regno_reg_rtx[i];
1700 /* Simplify the reg_base_value array so that no register refers to
1701 another register, except to special registers indirectly through
1702 ADDRESS expressions.
1704 In theory this loop can take as long as O(registers^2), but unless
1705 there are very long dependency chains it will run in close to linear
1706 time.
1708 This loop may not be needed any longer now that the main loop does
1709 a better job at propagating alias information. */
1710 pass = 0;
1713 changed = 0;
1714 pass++;
1715 for (ui = 0; ui < reg_base_value_size; ui++)
1717 rtx base = reg_base_value[ui];
1718 if (base && GET_CODE (base) == REG)
1720 unsigned int base_regno = REGNO (base);
1721 if (base_regno == ui) /* register set from itself */
1722 reg_base_value[ui] = 0;
1723 else
1724 reg_base_value[ui] = reg_base_value[base_regno];
1725 changed = 1;
1729 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
1731 /* Clean up. */
1732 free (new_reg_base_value);
1733 new_reg_base_value = 0;
1734 free (reg_seen);
1735 reg_seen = 0;
1738 void
1739 end_alias_analysis ()
1741 free (reg_known_value + FIRST_PSEUDO_REGISTER);
1742 reg_known_value = 0;
1743 reg_known_value_size = 0;
1744 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
1745 reg_known_equiv_p = 0;
1746 if (reg_base_value)
1748 if (ggc_p)
1749 ggc_del_root (reg_base_value);
1750 free (reg_base_value);
1751 reg_base_value = 0;
1753 reg_base_value_size = 0;
1754 if (alias_invariant)
1756 free (alias_invariant);
1757 alias_invariant = 0;