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"
32 #include "basic-block.h"
37 #include "splay-tree.h"
40 /* The alias sets assigned to MEMs assist the back-end in determining
41 which MEMs can alias which other MEMs. In general, two MEMs in
42 different alias sets cannot alias each other, with one important
43 exception. Consider something like:
45 struct S {int i; double d; };
47 a store to an `S' can alias something of either type `int' or type
48 `double'. (However, a store to an `int' cannot alias a `double'
49 and vice versa.) We indicate this via a tree structure that looks
57 (The arrows are directed and point downwards.)
58 In this situation we say the alias set for `struct S' is the
59 `superset' and that those for `int' and `double' are `subsets'.
61 To see whether two alias sets can point to the same memory, we must
62 see if either alias set is a subset of the other. We need not trace
63 past immediate decendents, however, since we propagate all
64 grandchildren up one level.
66 Alias set zero is implicitly a superset of all other alias sets.
67 However, this is no actual entry for alias set zero. It is an
68 error to attempt to explicitly construct a subset of zero. */
70 typedef struct alias_set_entry
72 /* The alias set number, as stored in MEM_ALIAS_SET. */
73 HOST_WIDE_INT alias_set;
75 /* The children of the alias set. These are not just the immediate
76 children, but, in fact, all decendents. So, if we have:
78 struct T { struct S s; float f; }
80 continuing our example above, the children here will be all of
81 `int', `double', `float', and `struct S'. */
84 /* Nonzero if would have a child of zero: this effectively makes this
85 alias set the same as alias set zero. */
89 static int rtx_equal_for_memref_p PARAMS ((rtx, rtx));
90 static rtx find_symbolic_term PARAMS ((rtx));
91 static rtx get_addr PARAMS ((rtx));
92 static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx,
94 static void record_set PARAMS ((rtx, rtx, void *));
95 static rtx find_base_term PARAMS ((rtx));
96 static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode,
98 static rtx find_base_value PARAMS ((rtx));
99 static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx));
100 static int insert_subset_children PARAMS ((splay_tree_node, void*));
101 static tree find_base_decl PARAMS ((tree));
102 static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT));
103 static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx,
105 static int aliases_everything_p PARAMS ((rtx));
106 static int write_dependence_p PARAMS ((rtx, rtx, int));
107 static int nonlocal_mentioned_p PARAMS ((rtx));
109 static int loop_p PARAMS ((void));
111 /* Set up all info needed to perform alias analysis on memory references. */
113 /* Returns the size in bytes of the mode of X. */
114 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
116 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
117 different alias sets. We ignore alias sets in functions making use
118 of variable arguments because the va_arg macros on some systems are
120 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
121 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
123 /* Cap the number of passes we make over the insns propagating alias
124 information through set chains. 10 is a completely arbitrary choice. */
125 #define MAX_ALIAS_LOOP_PASSES 10
127 /* reg_base_value[N] gives an address to which register N is related.
128 If all sets after the first add or subtract to the current value
129 or otherwise modify it so it does not point to a different top level
130 object, reg_base_value[N] is equal to the address part of the source
133 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
134 expressions represent certain special values: function arguments and
135 the stack, frame, and argument pointers.
137 The contents of an ADDRESS is not normally used, the mode of the
138 ADDRESS determines whether the ADDRESS is a function argument or some
139 other special value. Pointer equality, not rtx_equal_p, determines whether
140 two ADDRESS expressions refer to the same base address.
142 The only use of the contents of an ADDRESS is for determining if the
143 current function performs nonlocal memory memory references for the
144 purposes of marking the function as a constant function. */
146 static rtx *reg_base_value;
147 static rtx *new_reg_base_value;
148 static unsigned int reg_base_value_size; /* size of reg_base_value array */
150 #define REG_BASE_VALUE(X) \
151 (REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0)
153 /* Vector of known invariant relationships between registers. Set in
154 loop unrolling. Indexed by register number, if nonzero the value
155 is an expression describing this register in terms of another.
157 The length of this array is REG_BASE_VALUE_SIZE.
159 Because this array contains only pseudo registers it has no effect
161 static rtx *alias_invariant;
163 /* Vector indexed by N giving the initial (unchanging) value known for
164 pseudo-register N. This array is initialized in
165 init_alias_analysis, and does not change until end_alias_analysis
167 rtx *reg_known_value;
169 /* Indicates number of valid entries in reg_known_value. */
170 static unsigned int reg_known_value_size;
172 /* Vector recording for each reg_known_value whether it is due to a
173 REG_EQUIV note. Future passes (viz., reload) may replace the
174 pseudo with the equivalent expression and so we account for the
175 dependences that would be introduced if that happens.
177 The REG_EQUIV notes created in assign_parms may mention the arg
178 pointer, and there are explicit insns in the RTL that modify the
179 arg pointer. Thus we must ensure that such insns don't get
180 scheduled across each other because that would invalidate the
181 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
182 wrong, but solving the problem in the scheduler will likely give
183 better code, so we do it here. */
184 char *reg_known_equiv_p;
186 /* True when scanning insns from the start of the rtl to the
187 NOTE_INSN_FUNCTION_BEG note. */
188 static int copying_arguments;
190 /* The splay-tree used to store the various alias set entries. */
191 static splay_tree alias_sets;
193 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
194 such an entry, or NULL otherwise. */
196 static alias_set_entry
197 get_alias_set_entry (alias_set)
198 HOST_WIDE_INT alias_set;
201 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
203 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
206 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
207 the two MEMs cannot alias each other. */
210 mems_in_disjoint_alias_sets_p (mem1, mem2)
216 #ifdef ENABLE_CHECKING
217 /* Perform a basic sanity check. Namely, that there are no alias sets
218 if we're not using strict aliasing. This helps to catch bugs
219 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
220 where a MEM is allocated in some way other than by the use of
221 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
222 use alias sets to indicate that spilled registers cannot alias each
223 other, we might need to remove this check. */
224 if (! flag_strict_aliasing
225 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
229 /* If have no alias set information for one of the MEMs, we have to assume
230 it can alias anything. */
231 if (MEM_ALIAS_SET (mem1) == 0 || MEM_ALIAS_SET (mem2) == 0)
234 /* If the two alias sets are the same, they may alias. */
235 if (MEM_ALIAS_SET (mem1) == MEM_ALIAS_SET (mem2))
238 /* See if the first alias set is a subset of the second. */
239 ase = get_alias_set_entry (MEM_ALIAS_SET (mem1));
241 && (ase->has_zero_child
242 || splay_tree_lookup (ase->children,
243 (splay_tree_key) MEM_ALIAS_SET (mem2))))
246 /* Now do the same, but with the alias sets reversed. */
247 ase = get_alias_set_entry (MEM_ALIAS_SET (mem2));
249 && (ase->has_zero_child
250 || splay_tree_lookup (ase->children,
251 (splay_tree_key) MEM_ALIAS_SET (mem1))))
254 /* The two MEMs are in distinct alias sets, and neither one is the
255 child of the other. Therefore, they cannot alias. */
259 /* Insert the NODE into the splay tree given by DATA. Used by
260 record_alias_subset via splay_tree_foreach. */
263 insert_subset_children (node, data)
264 splay_tree_node node;
267 splay_tree_insert ((splay_tree) data, node->key, node->value);
272 /* T is an expression with pointer type. Find the DECL on which this
273 expression is based. (For example, in `a[i]' this would be `a'.)
274 If there is no such DECL, or a unique decl cannot be determined,
275 NULL_TREE is retured. */
283 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
286 /* If this is a declaration, return it. */
287 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
290 /* Handle general expressions. It would be nice to deal with
291 COMPONENT_REFs here. If we could tell that `a' and `b' were the
292 same, then `a->f' and `b->f' are also the same. */
293 switch (TREE_CODE_CLASS (TREE_CODE (t)))
296 return find_base_decl (TREE_OPERAND (t, 0));
299 /* Return 0 if found in neither or both are the same. */
300 d0 = find_base_decl (TREE_OPERAND (t, 0));
301 d1 = find_base_decl (TREE_OPERAND (t, 1));
312 d0 = find_base_decl (TREE_OPERAND (t, 0));
313 d1 = find_base_decl (TREE_OPERAND (t, 1));
314 d0 = find_base_decl (TREE_OPERAND (t, 0));
315 d2 = find_base_decl (TREE_OPERAND (t, 2));
317 /* Set any nonzero values from the last, then from the first. */
318 if (d1 == 0) d1 = d2;
319 if (d0 == 0) d0 = d1;
320 if (d1 == 0) d1 = d0;
321 if (d2 == 0) d2 = d1;
323 /* At this point all are nonzero or all are zero. If all three are the
324 same, return it. Otherwise, return zero. */
325 return (d0 == d1 && d1 == d2) ? d0 : 0;
332 /* Return the alias set for T, which may be either a type or an
333 expression. Call language-specific routine for help, if needed. */
342 /* If we're not doing any alias analysis, just assume everything
343 aliases everything else. Also return 0 if this or its type is
345 if (! flag_strict_aliasing || t == error_mark_node
347 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
350 /* We can be passed either an expression or a type. This and the
351 language-specific routine may make mutually-recursive calls to
352 each other to figure out what to do. At each juncture, we see if
353 this is a tree that the language may need to handle specially.
354 First handle things that aren't types and start by removing nops
355 since we care only about the actual object. */
358 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
359 || TREE_CODE (t) == NON_LVALUE_EXPR)
360 t = TREE_OPERAND (t, 0);
362 /* Now give the language a chance to do something but record what we
363 gave it this time. */
365 if ((set = lang_get_alias_set (t)) != -1)
368 /* Now loop the same way as get_inner_reference and get the alias
369 set to use. Pick up the outermost object that we could have
373 /* Unnamed bitfields are not an addressable object. */
374 if (TREE_CODE (t) == BIT_FIELD_REF)
376 else if (TREE_CODE (t) == COMPONENT_REF)
378 if (! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
379 /* Stop at an adressable decl. */
382 else if (TREE_CODE (t) == ARRAY_REF)
384 if (! TYPE_NONALIASED_COMPONENT
385 (TREE_TYPE (TREE_OPERAND (t, 0))))
386 /* Stop at an addresssable array element. */
389 else if (TREE_CODE (t) != NON_LVALUE_EXPR
390 && ! ((TREE_CODE (t) == NOP_EXPR
391 || TREE_CODE (t) == CONVERT_EXPR)
392 && (TYPE_MODE (TREE_TYPE (t))
393 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))))))
394 /* Stop if not one of above and not mode-preserving conversion. */
397 t = TREE_OPERAND (t, 0);
400 if (TREE_CODE (t) == INDIRECT_REF)
402 /* Check for accesses through restrict-qualified pointers. */
403 tree decl = find_base_decl (TREE_OPERAND (t, 0));
405 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
406 /* We use the alias set indicated in the declaration. */
407 return DECL_POINTER_ALIAS_SET (decl);
409 /* If we have an INDIRECT_REF via a void pointer, we don't
410 know anything about what that might alias. */
411 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
415 /* Give the language another chance to do something special. */
417 && (set = lang_get_alias_set (t)) != -1)
420 /* Now all we care about is the type. */
424 /* Variant qualifiers don't affect the alias set, so get the main
425 variant. If this is a type with a known alias set, return it. */
426 t = TYPE_MAIN_VARIANT (t);
427 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
428 return TYPE_ALIAS_SET (t);
430 /* See if the language has special handling for this type. */
431 if ((set = lang_get_alias_set (t)) != -1)
433 /* If the alias set is now known, we are done. */
434 if (TYPE_ALIAS_SET_KNOWN_P (t))
435 return TYPE_ALIAS_SET (t);
438 /* There are no objects of FUNCTION_TYPE, so there's no point in
439 using up an alias set for them. (There are, of course, pointers
440 and references to functions, but that's different.) */
441 else if (TREE_CODE (t) == FUNCTION_TYPE)
444 /* Otherwise make a new alias set for this type. */
445 set = new_alias_set ();
447 TYPE_ALIAS_SET (t) = set;
449 /* If this is an aggregate type, we must record any component aliasing
451 if (AGGREGATE_TYPE_P (t))
452 record_component_aliases (t);
457 /* Return a brand-new alias set. */
462 static HOST_WIDE_INT last_alias_set;
464 if (flag_strict_aliasing)
465 return ++last_alias_set;
470 /* Indicate that things in SUBSET can alias things in SUPERSET, but
471 not vice versa. For example, in C, a store to an `int' can alias a
472 structure containing an `int', but not vice versa. Here, the
473 structure would be the SUPERSET and `int' the SUBSET. This
474 function should be called only once per SUPERSET/SUBSET pair.
476 It is illegal for SUPERSET to be zero; everything is implicitly a
477 subset of alias set zero. */
480 record_alias_subset (superset, subset)
481 HOST_WIDE_INT superset;
482 HOST_WIDE_INT subset;
484 alias_set_entry superset_entry;
485 alias_set_entry subset_entry;
490 superset_entry = get_alias_set_entry (superset);
491 if (superset_entry == 0)
493 /* Create an entry for the SUPERSET, so that we have a place to
494 attach the SUBSET. */
496 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
497 superset_entry->alias_set = superset;
498 superset_entry->children
499 = splay_tree_new (splay_tree_compare_ints, 0, 0);
500 superset_entry->has_zero_child = 0;
501 splay_tree_insert (alias_sets, (splay_tree_key) superset,
502 (splay_tree_value) superset_entry);
506 superset_entry->has_zero_child = 1;
509 subset_entry = get_alias_set_entry (subset);
510 /* If there is an entry for the subset, enter all of its children
511 (if they are not already present) as children of the SUPERSET. */
514 if (subset_entry->has_zero_child)
515 superset_entry->has_zero_child = 1;
517 splay_tree_foreach (subset_entry->children, insert_subset_children,
518 superset_entry->children);
521 /* Enter the SUBSET itself as a child of the SUPERSET. */
522 splay_tree_insert (superset_entry->children,
523 (splay_tree_key) subset, 0);
527 /* Record that component types of TYPE, if any, are part of that type for
528 aliasing purposes. For record types, we only record component types
529 for fields that are marked addressable. For array types, we always
530 record the component types, so the front end should not call this
531 function if the individual component aren't addressable. */
534 record_component_aliases (type)
537 HOST_WIDE_INT superset = get_alias_set (type);
543 switch (TREE_CODE (type))
546 if (! TYPE_NONALIASED_COMPONENT (type))
547 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
552 case QUAL_UNION_TYPE:
553 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
554 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
555 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
563 /* Allocate an alias set for use in storing and reading from the varargs
567 get_varargs_alias_set ()
569 static HOST_WIDE_INT set = -1;
572 set = new_alias_set ();
577 /* Likewise, but used for the fixed portions of the frame, e.g., register
581 get_frame_alias_set ()
583 static HOST_WIDE_INT set = -1;
586 set = new_alias_set ();
591 /* Inside SRC, the source of a SET, find a base address. */
594 find_base_value (src)
597 switch (GET_CODE (src))
604 /* At the start of a function, argument registers have known base
605 values which may be lost later. Returning an ADDRESS
606 expression here allows optimization based on argument values
607 even when the argument registers are used for other purposes. */
608 if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments)
609 return new_reg_base_value[REGNO (src)];
611 /* If a pseudo has a known base value, return it. Do not do this
612 for hard regs since it can result in a circular dependency
613 chain for registers which have values at function entry.
615 The test above is not sufficient because the scheduler may move
616 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
617 if (REGNO (src) >= FIRST_PSEUDO_REGISTER
618 && (unsigned) REGNO (src) < reg_base_value_size
619 && reg_base_value[REGNO (src)])
620 return reg_base_value[REGNO (src)];
625 /* Check for an argument passed in memory. Only record in the
626 copying-arguments block; it is too hard to track changes
628 if (copying_arguments
629 && (XEXP (src, 0) == arg_pointer_rtx
630 || (GET_CODE (XEXP (src, 0)) == PLUS
631 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
632 return gen_rtx_ADDRESS (VOIDmode, src);
637 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
640 /* ... fall through ... */
645 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
647 /* If either operand is a REG, then see if we already have
648 a known value for it. */
649 if (GET_CODE (src_0) == REG)
651 temp = find_base_value (src_0);
656 if (GET_CODE (src_1) == REG)
658 temp = find_base_value (src_1);
663 /* Guess which operand is the base address:
664 If either operand is a symbol, then it is the base. If
665 either operand is a CONST_INT, then the other is the base. */
666 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
667 return find_base_value (src_0);
668 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
669 return find_base_value (src_1);
671 /* This might not be necessary anymore:
672 If either operand is a REG that is a known pointer, then it
674 else if (GET_CODE (src_0) == REG && REG_POINTER (src_0))
675 return find_base_value (src_0);
676 else if (GET_CODE (src_1) == REG && REG_POINTER (src_1))
677 return find_base_value (src_1);
683 /* The standard form is (lo_sum reg sym) so look only at the
685 return find_base_value (XEXP (src, 1));
688 /* If the second operand is constant set the base
689 address to the first operand. */
690 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
691 return find_base_value (XEXP (src, 0));
695 case SIGN_EXTEND: /* used for NT/Alpha pointers */
697 return find_base_value (XEXP (src, 0));
706 /* Called from init_alias_analysis indirectly through note_stores. */
708 /* While scanning insns to find base values, reg_seen[N] is nonzero if
709 register N has been set in this function. */
710 static char *reg_seen;
712 /* Addresses which are known not to alias anything else are identified
713 by a unique integer. */
714 static int unique_id;
717 record_set (dest, set, data)
719 void *data ATTRIBUTE_UNUSED;
721 register unsigned regno;
724 if (GET_CODE (dest) != REG)
727 regno = REGNO (dest);
729 if (regno >= reg_base_value_size)
734 /* A CLOBBER wipes out any old value but does not prevent a previously
735 unset register from acquiring a base address (i.e. reg_seen is not
737 if (GET_CODE (set) == CLOBBER)
739 new_reg_base_value[regno] = 0;
748 new_reg_base_value[regno] = 0;
752 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
753 GEN_INT (unique_id++));
757 /* This is not the first set. If the new value is not related to the
758 old value, forget the base value. Note that the following code is
760 extern int x, y; int *p = &x; p += (&y-&x);
761 ANSI C does not allow computing the difference of addresses
762 of distinct top level objects. */
763 if (new_reg_base_value[regno])
764 switch (GET_CODE (src))
769 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
770 new_reg_base_value[regno] = 0;
773 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
774 new_reg_base_value[regno] = 0;
777 new_reg_base_value[regno] = 0;
780 /* If this is the first set of a register, record the value. */
781 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
782 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
783 new_reg_base_value[regno] = find_base_value (src);
788 /* Called from loop optimization when a new pseudo-register is
789 created. It indicates that REGNO is being set to VAL. f INVARIANT
790 is true then this value also describes an invariant relationship
791 which can be used to deduce that two registers with unknown values
795 record_base_value (regno, val, invariant)
800 if (regno >= reg_base_value_size)
803 if (invariant && alias_invariant)
804 alias_invariant[regno] = val;
806 if (GET_CODE (val) == REG)
808 if (REGNO (val) < reg_base_value_size)
809 reg_base_value[regno] = reg_base_value[REGNO (val)];
814 reg_base_value[regno] = find_base_value (val);
817 /* Returns a canonical version of X, from the point of view alias
818 analysis. (For example, if X is a MEM whose address is a register,
819 and the register has a known value (say a SYMBOL_REF), then a MEM
820 whose address is the SYMBOL_REF is returned.) */
826 /* Recursively look for equivalences. */
827 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
828 && REGNO (x) < reg_known_value_size)
829 return reg_known_value[REGNO (x)] == x
830 ? x : canon_rtx (reg_known_value[REGNO (x)]);
831 else if (GET_CODE (x) == PLUS)
833 rtx x0 = canon_rtx (XEXP (x, 0));
834 rtx x1 = canon_rtx (XEXP (x, 1));
836 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
838 /* We can tolerate LO_SUMs being offset here; these
839 rtl are used for nothing other than comparisons. */
840 if (GET_CODE (x0) == CONST_INT)
841 return plus_constant_for_output (x1, INTVAL (x0));
842 else if (GET_CODE (x1) == CONST_INT)
843 return plus_constant_for_output (x0, INTVAL (x1));
844 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
848 /* This gives us much better alias analysis when called from
849 the loop optimizer. Note we want to leave the original
850 MEM alone, but need to return the canonicalized MEM with
851 all the flags with their original values. */
852 else if (GET_CODE (x) == MEM)
854 rtx addr = canon_rtx (XEXP (x, 0));
856 if (addr != XEXP (x, 0))
858 rtx new = gen_rtx_MEM (GET_MODE (x), addr);
860 MEM_COPY_ATTRIBUTES (new, x);
867 /* Return 1 if X and Y are identical-looking rtx's.
869 We use the data in reg_known_value above to see if two registers with
870 different numbers are, in fact, equivalent. */
873 rtx_equal_for_memref_p (x, y)
878 register enum rtx_code code;
879 register const char *fmt;
881 if (x == 0 && y == 0)
883 if (x == 0 || y == 0)
893 /* Rtx's of different codes cannot be equal. */
894 if (code != GET_CODE (y))
897 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
898 (REG:SI x) and (REG:HI x) are NOT equivalent. */
900 if (GET_MODE (x) != GET_MODE (y))
903 /* Some RTL can be compared without a recursive examination. */
907 return REGNO (x) == REGNO (y);
910 return XEXP (x, 0) == XEXP (y, 0);
913 return XSTR (x, 0) == XSTR (y, 0);
917 /* There's no need to compare the contents of CONST_DOUBLEs or
918 CONST_INTs because pointer equality is a good enough
919 comparison for these nodes. */
923 return (REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0))
924 && XINT (x, 1) == XINT (y, 1));
930 /* For commutative operations, the RTX match if the operand match in any
931 order. Also handle the simple binary and unary cases without a loop. */
932 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
933 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
934 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
935 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
936 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
937 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
938 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
939 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
940 else if (GET_RTX_CLASS (code) == '1')
941 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
943 /* Compare the elements. If any pair of corresponding elements
944 fail to match, return 0 for the whole things.
946 Limit cases to types which actually appear in addresses. */
948 fmt = GET_RTX_FORMAT (code);
949 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
954 if (XINT (x, i) != XINT (y, i))
959 /* Two vectors must have the same length. */
960 if (XVECLEN (x, i) != XVECLEN (y, i))
963 /* And the corresponding elements must match. */
964 for (j = 0; j < XVECLEN (x, i); j++)
965 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
966 XVECEXP (y, i, j)) == 0)
971 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
975 /* This can happen for an asm which clobbers memory. */
979 /* It is believed that rtx's at this level will never
980 contain anything but integers and other rtx's,
981 except for within LABEL_REFs and SYMBOL_REFs. */
989 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
990 X and return it, or return 0 if none found. */
993 find_symbolic_term (x)
997 register enum rtx_code code;
998 register const char *fmt;
1000 code = GET_CODE (x);
1001 if (code == SYMBOL_REF || code == LABEL_REF)
1003 if (GET_RTX_CLASS (code) == 'o')
1006 fmt = GET_RTX_FORMAT (code);
1007 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1013 t = find_symbolic_term (XEXP (x, i));
1017 else if (fmt[i] == 'E')
1028 struct elt_loc_list *l;
1030 #if defined (FIND_BASE_TERM)
1031 /* Try machine-dependent ways to find the base term. */
1032 x = FIND_BASE_TERM (x);
1035 switch (GET_CODE (x))
1038 return REG_BASE_VALUE (x);
1041 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1047 return find_base_term (XEXP (x, 0));
1050 val = CSELIB_VAL_PTR (x);
1051 for (l = val->locs; l; l = l->next)
1052 if ((x = find_base_term (l->loc)) != 0)
1058 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1065 rtx tmp1 = XEXP (x, 0);
1066 rtx tmp2 = XEXP (x, 1);
1068 /* This is a litle bit tricky since we have to determine which of
1069 the two operands represents the real base address. Otherwise this
1070 routine may return the index register instead of the base register.
1072 That may cause us to believe no aliasing was possible, when in
1073 fact aliasing is possible.
1075 We use a few simple tests to guess the base register. Additional
1076 tests can certainly be added. For example, if one of the operands
1077 is a shift or multiply, then it must be the index register and the
1078 other operand is the base register. */
1080 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1081 return find_base_term (tmp2);
1083 /* If either operand is known to be a pointer, then use it
1084 to determine the base term. */
1085 if (REG_P (tmp1) && REG_POINTER (tmp1))
1086 return find_base_term (tmp1);
1088 if (REG_P (tmp2) && REG_POINTER (tmp2))
1089 return find_base_term (tmp2);
1091 /* Neither operand was known to be a pointer. Go ahead and find the
1092 base term for both operands. */
1093 tmp1 = find_base_term (tmp1);
1094 tmp2 = find_base_term (tmp2);
1096 /* If either base term is named object or a special address
1097 (like an argument or stack reference), then use it for the
1100 && (GET_CODE (tmp1) == SYMBOL_REF
1101 || GET_CODE (tmp1) == LABEL_REF
1102 || (GET_CODE (tmp1) == ADDRESS
1103 && GET_MODE (tmp1) != VOIDmode)))
1107 && (GET_CODE (tmp2) == SYMBOL_REF
1108 || GET_CODE (tmp2) == LABEL_REF
1109 || (GET_CODE (tmp2) == ADDRESS
1110 && GET_MODE (tmp2) != VOIDmode)))
1113 /* We could not determine which of the two operands was the
1114 base register and which was the index. So we can determine
1115 nothing from the base alias check. */
1120 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1121 return REG_BASE_VALUE (XEXP (x, 0));
1129 return REG_BASE_VALUE (frame_pointer_rtx);
1136 /* Return 0 if the addresses X and Y are known to point to different
1137 objects, 1 if they might be pointers to the same object. */
1140 base_alias_check (x, y, x_mode, y_mode)
1142 enum machine_mode x_mode, y_mode;
1144 rtx x_base = find_base_term (x);
1145 rtx y_base = find_base_term (y);
1147 /* If the address itself has no known base see if a known equivalent
1148 value has one. If either address still has no known base, nothing
1149 is known about aliasing. */
1154 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1157 x_base = find_base_term (x_c);
1165 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1168 y_base = find_base_term (y_c);
1173 /* If the base addresses are equal nothing is known about aliasing. */
1174 if (rtx_equal_p (x_base, y_base))
1177 /* The base addresses of the read and write are different expressions.
1178 If they are both symbols and they are not accessed via AND, there is
1179 no conflict. We can bring knowledge of object alignment into play
1180 here. For example, on alpha, "char a, b;" can alias one another,
1181 though "char a; long b;" cannot. */
1182 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1184 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1186 if (GET_CODE (x) == AND
1187 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1188 || GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1190 if (GET_CODE (y) == AND
1191 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1192 || GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1194 /* Differing symbols never alias. */
1198 /* If one address is a stack reference there can be no alias:
1199 stack references using different base registers do not alias,
1200 a stack reference can not alias a parameter, and a stack reference
1201 can not alias a global. */
1202 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1203 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1206 if (! flag_argument_noalias)
1209 if (flag_argument_noalias > 1)
1212 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1213 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1216 /* Convert the address X into something we can use. This is done by returning
1217 it unchanged unless it is a value; in the latter case we call cselib to get
1218 a more useful rtx. */
1225 struct elt_loc_list *l;
1227 if (GET_CODE (x) != VALUE)
1229 v = CSELIB_VAL_PTR (x);
1230 for (l = v->locs; l; l = l->next)
1231 if (CONSTANT_P (l->loc))
1233 for (l = v->locs; l; l = l->next)
1234 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1237 return v->locs->loc;
1241 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1242 where SIZE is the size in bytes of the memory reference. If ADDR
1243 is not modified by the memory reference then ADDR is returned. */
1246 addr_side_effect_eval (addr, size, n_refs)
1253 switch (GET_CODE (addr))
1256 offset = (n_refs + 1) * size;
1259 offset = -(n_refs + 1) * size;
1262 offset = n_refs * size;
1265 offset = -n_refs * size;
1273 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1275 addr = XEXP (addr, 0);
1280 /* Return nonzero if X and Y (memory addresses) could reference the
1281 same location in memory. C is an offset accumulator. When
1282 C is nonzero, we are testing aliases between X and Y + C.
1283 XSIZE is the size in bytes of the X reference,
1284 similarly YSIZE is the size in bytes for Y.
1286 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1287 referenced (the reference was BLKmode), so make the most pessimistic
1290 If XSIZE or YSIZE is negative, we may access memory outside the object
1291 being referenced as a side effect. This can happen when using AND to
1292 align memory references, as is done on the Alpha.
1294 Nice to notice that varying addresses cannot conflict with fp if no
1295 local variables had their addresses taken, but that's too hard now. */
1298 memrefs_conflict_p (xsize, x, ysize, y, c)
1303 if (GET_CODE (x) == VALUE)
1305 if (GET_CODE (y) == VALUE)
1307 if (GET_CODE (x) == HIGH)
1309 else if (GET_CODE (x) == LO_SUM)
1312 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1313 if (GET_CODE (y) == HIGH)
1315 else if (GET_CODE (y) == LO_SUM)
1318 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1320 if (rtx_equal_for_memref_p (x, y))
1322 if (xsize <= 0 || ysize <= 0)
1324 if (c >= 0 && xsize > c)
1326 if (c < 0 && ysize+c > 0)
1331 /* This code used to check for conflicts involving stack references and
1332 globals but the base address alias code now handles these cases. */
1334 if (GET_CODE (x) == PLUS)
1336 /* The fact that X is canonicalized means that this
1337 PLUS rtx is canonicalized. */
1338 rtx x0 = XEXP (x, 0);
1339 rtx x1 = XEXP (x, 1);
1341 if (GET_CODE (y) == PLUS)
1343 /* The fact that Y is canonicalized means that this
1344 PLUS rtx is canonicalized. */
1345 rtx y0 = XEXP (y, 0);
1346 rtx y1 = XEXP (y, 1);
1348 if (rtx_equal_for_memref_p (x1, y1))
1349 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1350 if (rtx_equal_for_memref_p (x0, y0))
1351 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1352 if (GET_CODE (x1) == CONST_INT)
1354 if (GET_CODE (y1) == CONST_INT)
1355 return memrefs_conflict_p (xsize, x0, ysize, y0,
1356 c - INTVAL (x1) + INTVAL (y1));
1358 return memrefs_conflict_p (xsize, x0, ysize, y,
1361 else if (GET_CODE (y1) == CONST_INT)
1362 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1366 else if (GET_CODE (x1) == CONST_INT)
1367 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1369 else if (GET_CODE (y) == PLUS)
1371 /* The fact that Y is canonicalized means that this
1372 PLUS rtx is canonicalized. */
1373 rtx y0 = XEXP (y, 0);
1374 rtx y1 = XEXP (y, 1);
1376 if (GET_CODE (y1) == CONST_INT)
1377 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1382 if (GET_CODE (x) == GET_CODE (y))
1383 switch (GET_CODE (x))
1387 /* Handle cases where we expect the second operands to be the
1388 same, and check only whether the first operand would conflict
1391 rtx x1 = canon_rtx (XEXP (x, 1));
1392 rtx y1 = canon_rtx (XEXP (y, 1));
1393 if (! rtx_equal_for_memref_p (x1, y1))
1395 x0 = canon_rtx (XEXP (x, 0));
1396 y0 = canon_rtx (XEXP (y, 0));
1397 if (rtx_equal_for_memref_p (x0, y0))
1398 return (xsize == 0 || ysize == 0
1399 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1401 /* Can't properly adjust our sizes. */
1402 if (GET_CODE (x1) != CONST_INT)
1404 xsize /= INTVAL (x1);
1405 ysize /= INTVAL (x1);
1407 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1411 /* Are these registers known not to be equal? */
1412 if (alias_invariant)
1414 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1415 rtx i_x, i_y; /* invariant relationships of X and Y */
1417 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1418 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1420 if (i_x == 0 && i_y == 0)
1423 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1424 ysize, i_y ? i_y : y, c))
1433 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1434 as an access with indeterminate size. Assume that references
1435 besides AND are aligned, so if the size of the other reference is
1436 at least as large as the alignment, assume no other overlap. */
1437 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1439 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1441 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1443 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1445 /* ??? If we are indexing far enough into the array/structure, we
1446 may yet be able to determine that we can not overlap. But we
1447 also need to that we are far enough from the end not to overlap
1448 a following reference, so we do nothing with that for now. */
1449 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1451 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1454 if (GET_CODE (x) == ADDRESSOF)
1456 if (y == frame_pointer_rtx
1457 || GET_CODE (y) == ADDRESSOF)
1458 return xsize <= 0 || ysize <= 0;
1460 if (GET_CODE (y) == ADDRESSOF)
1462 if (x == frame_pointer_rtx)
1463 return xsize <= 0 || ysize <= 0;
1468 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1470 c += (INTVAL (y) - INTVAL (x));
1471 return (xsize <= 0 || ysize <= 0
1472 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1475 if (GET_CODE (x) == CONST)
1477 if (GET_CODE (y) == CONST)
1478 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1479 ysize, canon_rtx (XEXP (y, 0)), c);
1481 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1484 if (GET_CODE (y) == CONST)
1485 return memrefs_conflict_p (xsize, x, ysize,
1486 canon_rtx (XEXP (y, 0)), c);
1489 return (xsize <= 0 || ysize <= 0
1490 || (rtx_equal_for_memref_p (x, y)
1491 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1498 /* Functions to compute memory dependencies.
1500 Since we process the insns in execution order, we can build tables
1501 to keep track of what registers are fixed (and not aliased), what registers
1502 are varying in known ways, and what registers are varying in unknown
1505 If both memory references are volatile, then there must always be a
1506 dependence between the two references, since their order can not be
1507 changed. A volatile and non-volatile reference can be interchanged
1510 A MEM_IN_STRUCT reference at a non-AND varying address can never
1511 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1512 also must allow AND addresses, because they may generate accesses
1513 outside the object being referenced. This is used to generate
1514 aligned addresses from unaligned addresses, for instance, the alpha
1515 storeqi_unaligned pattern. */
1517 /* Read dependence: X is read after read in MEM takes place. There can
1518 only be a dependence here if both reads are volatile. */
1521 read_dependence (mem, x)
1525 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1528 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1529 MEM2 is a reference to a structure at a varying address, or returns
1530 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1531 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1532 to decide whether or not an address may vary; it should return
1533 nonzero whenever variation is possible.
1534 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1537 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1539 rtx mem1_addr, mem2_addr;
1540 int (*varies_p) PARAMS ((rtx));
1542 if (! flag_strict_aliasing)
1545 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1546 && !varies_p (mem1_addr) && varies_p (mem2_addr))
1547 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1551 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1552 && varies_p (mem1_addr) && !varies_p (mem2_addr))
1553 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1560 /* Returns nonzero if something about the mode or address format MEM1
1561 indicates that it might well alias *anything*. */
1564 aliases_everything_p (mem)
1567 if (GET_CODE (XEXP (mem, 0)) == AND)
1568 /* If the address is an AND, its very hard to know at what it is
1569 actually pointing. */
1575 /* True dependence: X is read after store in MEM takes place. */
1578 true_dependence (mem, mem_mode, x, varies)
1580 enum machine_mode mem_mode;
1582 int (*varies) PARAMS ((rtx));
1584 register rtx x_addr, mem_addr;
1587 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1590 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1593 /* Unchanging memory can't conflict with non-unchanging memory.
1594 A non-unchanging read can conflict with a non-unchanging write.
1595 An unchanging read can conflict with an unchanging write since
1596 there may be a single store to this address to initialize it.
1597 Note that an unchanging store can conflict with a non-unchanging read
1598 since we have to make conservative assumptions when we have a
1599 record with readonly fields and we are copying the whole thing.
1600 Just fall through to the code below to resolve potential conflicts.
1601 This won't handle all cases optimally, but the possible performance
1602 loss should be negligible. */
1603 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1606 if (mem_mode == VOIDmode)
1607 mem_mode = GET_MODE (mem);
1609 x_addr = get_addr (XEXP (x, 0));
1610 mem_addr = get_addr (XEXP (mem, 0));
1612 base = find_base_term (x_addr);
1613 if (base && (GET_CODE (base) == LABEL_REF
1614 || (GET_CODE (base) == SYMBOL_REF
1615 && CONSTANT_POOL_ADDRESS_P (base))))
1618 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1621 x_addr = canon_rtx (x_addr);
1622 mem_addr = canon_rtx (mem_addr);
1624 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1625 SIZE_FOR_MODE (x), x_addr, 0))
1628 if (aliases_everything_p (x))
1631 /* We cannot use aliases_everyting_p to test MEM, since we must look
1632 at MEM_MODE, rather than GET_MODE (MEM). */
1633 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1636 /* In true_dependence we also allow BLKmode to alias anything. Why
1637 don't we do this in anti_dependence and output_dependence? */
1638 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1641 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1645 /* Returns non-zero if a write to X might alias a previous read from
1646 (or, if WRITEP is non-zero, a write to) MEM. */
1649 write_dependence_p (mem, x, writep)
1654 rtx x_addr, mem_addr;
1658 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1661 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1664 /* Unchanging memory can't conflict with non-unchanging memory. */
1665 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1668 /* If MEM is an unchanging read, then it can't possibly conflict with
1669 the store to X, because there is at most one store to MEM, and it must
1670 have occurred somewhere before MEM. */
1671 if (! writep && RTX_UNCHANGING_P (mem))
1674 x_addr = get_addr (XEXP (x, 0));
1675 mem_addr = get_addr (XEXP (mem, 0));
1679 base = find_base_term (mem_addr);
1680 if (base && (GET_CODE (base) == LABEL_REF
1681 || (GET_CODE (base) == SYMBOL_REF
1682 && CONSTANT_POOL_ADDRESS_P (base))))
1686 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1690 x_addr = canon_rtx (x_addr);
1691 mem_addr = canon_rtx (mem_addr);
1693 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1694 SIZE_FOR_MODE (x), x_addr, 0))
1698 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1701 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1702 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1705 /* Anti dependence: X is written after read in MEM takes place. */
1708 anti_dependence (mem, x)
1712 return write_dependence_p (mem, x, /*writep=*/0);
1715 /* Output dependence: X is written after store in MEM takes place. */
1718 output_dependence (mem, x)
1722 return write_dependence_p (mem, x, /*writep=*/1);
1725 /* Returns non-zero if X mentions something which is not
1726 local to the function and is not constant. */
1729 nonlocal_mentioned_p (x)
1733 register RTX_CODE code;
1736 code = GET_CODE (x);
1738 if (GET_RTX_CLASS (code) == 'i')
1740 /* Constant functions can be constant if they don't use
1741 scratch memory used to mark function w/o side effects. */
1742 if (code == CALL_INSN && CONST_CALL_P (x))
1744 x = CALL_INSN_FUNCTION_USAGE (x);
1750 code = GET_CODE (x);
1756 if (GET_CODE (SUBREG_REG (x)) == REG)
1758 /* Global registers are not local. */
1759 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1760 && global_regs[REGNO (SUBREG_REG (x)) + SUBREG_WORD (x)])
1768 /* Global registers are not local. */
1769 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1783 /* Constants in the function's constants pool are constant. */
1784 if (CONSTANT_POOL_ADDRESS_P (x))
1789 /* Non-constant calls and recursion are not local. */
1793 /* Be overly conservative and consider any volatile memory
1794 reference as not local. */
1795 if (MEM_VOLATILE_P (x))
1797 base = find_base_term (XEXP (x, 0));
1800 /* A Pmode ADDRESS could be a reference via the structure value
1801 address or static chain. Such memory references are nonlocal.
1803 Thus, we have to examine the contents of the ADDRESS to find
1804 out if this is a local reference or not. */
1805 if (GET_CODE (base) == ADDRESS
1806 && GET_MODE (base) == Pmode
1807 && (XEXP (base, 0) == stack_pointer_rtx
1808 || XEXP (base, 0) == arg_pointer_rtx
1809 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1810 || XEXP (base, 0) == hard_frame_pointer_rtx
1812 || XEXP (base, 0) == frame_pointer_rtx))
1814 /* Constants in the function's constant pool are constant. */
1815 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
1820 case UNSPEC_VOLATILE:
1825 if (MEM_VOLATILE_P (x))
1834 /* Recursively scan the operands of this expression. */
1837 register const char *fmt = GET_RTX_FORMAT (code);
1840 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1842 if (fmt[i] == 'e' && XEXP (x, i))
1844 if (nonlocal_mentioned_p (XEXP (x, i)))
1847 else if (fmt[i] == 'E')
1850 for (j = 0; j < XVECLEN (x, i); j++)
1851 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
1860 /* Return non-zero if a loop (natural or otherwise) is present.
1861 Inspired by Depth_First_Search_PP described in:
1863 Advanced Compiler Design and Implementation
1865 Morgan Kaufmann, 1997
1867 and heavily borrowed from flow_depth_first_order_compute. */
1880 /* Allocate the preorder and postorder number arrays. */
1881 pre = (int *) xcalloc (n_basic_blocks, sizeof (int));
1882 post = (int *) xcalloc (n_basic_blocks, sizeof (int));
1884 /* Allocate stack for back-tracking up CFG. */
1885 stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
1888 /* Allocate bitmap to track nodes that have been visited. */
1889 visited = sbitmap_alloc (n_basic_blocks);
1891 /* None of the nodes in the CFG have been visited yet. */
1892 sbitmap_zero (visited);
1894 /* Push the first edge on to the stack. */
1895 stack[sp++] = ENTRY_BLOCK_PTR->succ;
1903 /* Look at the edge on the top of the stack. */
1908 /* Check if the edge destination has been visited yet. */
1909 if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
1911 /* Mark that we have visited the destination. */
1912 SET_BIT (visited, dest->index);
1914 pre[dest->index] = prenum++;
1918 /* Since the DEST node has been visited for the first
1919 time, check its successors. */
1920 stack[sp++] = dest->succ;
1923 post[dest->index] = postnum++;
1927 if (dest != EXIT_BLOCK_PTR
1928 && pre[src->index] >= pre[dest->index]
1929 && post[dest->index] == 0)
1932 if (! e->succ_next && src != ENTRY_BLOCK_PTR)
1933 post[src->index] = postnum++;
1936 stack[sp - 1] = e->succ_next;
1945 sbitmap_free (visited);
1950 /* Mark the function if it is constant. */
1953 mark_constant_function ()
1956 int nonlocal_mentioned;
1958 if (TREE_PUBLIC (current_function_decl)
1959 || TREE_READONLY (current_function_decl)
1960 || DECL_IS_PURE (current_function_decl)
1961 || TREE_THIS_VOLATILE (current_function_decl)
1962 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
1965 /* A loop might not return which counts as a side effect. */
1969 nonlocal_mentioned = 0;
1971 init_alias_analysis ();
1973 /* Determine if this is a constant function. */
1975 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1976 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
1978 nonlocal_mentioned = 1;
1982 end_alias_analysis ();
1984 /* Mark the function. */
1986 if (! nonlocal_mentioned)
1987 TREE_READONLY (current_function_decl) = 1;
1991 static HARD_REG_SET argument_registers;
1998 #ifndef OUTGOING_REGNO
1999 #define OUTGOING_REGNO(N) N
2001 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2002 /* Check whether this register can hold an incoming pointer
2003 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2004 numbers, so translate if necessary due to register windows. */
2005 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2006 && HARD_REGNO_MODE_OK (i, Pmode))
2007 SET_HARD_REG_BIT (argument_registers, i);
2009 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2012 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2016 init_alias_analysis ()
2018 int maxreg = max_reg_num ();
2021 register unsigned int ui;
2024 reg_known_value_size = maxreg;
2027 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2028 - FIRST_PSEUDO_REGISTER;
2030 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2031 - FIRST_PSEUDO_REGISTER;
2033 /* Overallocate reg_base_value to allow some growth during loop
2034 optimization. Loop unrolling can create a large number of
2036 reg_base_value_size = maxreg * 2;
2037 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2038 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2040 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2041 reg_seen = (char *) xmalloc (reg_base_value_size);
2042 if (! reload_completed && flag_unroll_loops)
2044 /* ??? Why are we realloc'ing if we're just going to zero it? */
2045 alias_invariant = (rtx *)xrealloc (alias_invariant,
2046 reg_base_value_size * sizeof (rtx));
2047 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2051 /* The basic idea is that each pass through this loop will use the
2052 "constant" information from the previous pass to propagate alias
2053 information through another level of assignments.
2055 This could get expensive if the assignment chains are long. Maybe
2056 we should throttle the number of iterations, possibly based on
2057 the optimization level or flag_expensive_optimizations.
2059 We could propagate more information in the first pass by making use
2060 of REG_N_SETS to determine immediately that the alias information
2061 for a pseudo is "constant".
2063 A program with an uninitialized variable can cause an infinite loop
2064 here. Instead of doing a full dataflow analysis to detect such problems
2065 we just cap the number of iterations for the loop.
2067 The state of the arrays for the set chain in question does not matter
2068 since the program has undefined behavior. */
2073 /* Assume nothing will change this iteration of the loop. */
2076 /* We want to assign the same IDs each iteration of this loop, so
2077 start counting from zero each iteration of the loop. */
2080 /* We're at the start of the funtion each iteration through the
2081 loop, so we're copying arguments. */
2082 copying_arguments = 1;
2084 /* Wipe the potential alias information clean for this pass. */
2085 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2087 /* Wipe the reg_seen array clean. */
2088 memset ((char *) reg_seen, 0, reg_base_value_size);
2090 /* Mark all hard registers which may contain an address.
2091 The stack, frame and argument pointers may contain an address.
2092 An argument register which can hold a Pmode value may contain
2093 an address even if it is not in BASE_REGS.
2095 The address expression is VOIDmode for an argument and
2096 Pmode for other registers. */
2098 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2099 if (TEST_HARD_REG_BIT (argument_registers, i))
2100 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2101 gen_rtx_REG (Pmode, i));
2103 new_reg_base_value[STACK_POINTER_REGNUM]
2104 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2105 new_reg_base_value[ARG_POINTER_REGNUM]
2106 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2107 new_reg_base_value[FRAME_POINTER_REGNUM]
2108 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2109 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2110 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2111 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2114 /* Walk the insns adding values to the new_reg_base_value array. */
2115 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2121 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2122 /* The prologue/epilouge insns are not threaded onto the
2123 insn chain until after reload has completed. Thus,
2124 there is no sense wasting time checking if INSN is in
2125 the prologue/epilogue until after reload has completed. */
2126 if (reload_completed
2127 && prologue_epilogue_contains (insn))
2131 /* If this insn has a noalias note, process it, Otherwise,
2132 scan for sets. A simple set will have no side effects
2133 which could change the base value of any other register. */
2135 if (GET_CODE (PATTERN (insn)) == SET
2136 && REG_NOTES (insn) != 0
2137 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2138 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2140 note_stores (PATTERN (insn), record_set, NULL);
2142 set = single_set (insn);
2145 && GET_CODE (SET_DEST (set)) == REG
2146 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
2147 && REG_NOTES (insn) != 0
2148 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2149 && REG_N_SETS (REGNO (SET_DEST (set))) == 1)
2150 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2151 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2152 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2154 int regno = REGNO (SET_DEST (set));
2155 reg_known_value[regno] = XEXP (note, 0);
2156 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2159 else if (GET_CODE (insn) == NOTE
2160 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2161 copying_arguments = 0;
2164 /* Now propagate values from new_reg_base_value to reg_base_value. */
2165 for (ui = 0; ui < reg_base_value_size; ui++)
2167 if (new_reg_base_value[ui]
2168 && new_reg_base_value[ui] != reg_base_value[ui]
2169 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2171 reg_base_value[ui] = new_reg_base_value[ui];
2176 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2178 /* Fill in the remaining entries. */
2179 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2180 if (reg_known_value[i] == 0)
2181 reg_known_value[i] = regno_reg_rtx[i];
2183 /* Simplify the reg_base_value array so that no register refers to
2184 another register, except to special registers indirectly through
2185 ADDRESS expressions.
2187 In theory this loop can take as long as O(registers^2), but unless
2188 there are very long dependency chains it will run in close to linear
2191 This loop may not be needed any longer now that the main loop does
2192 a better job at propagating alias information. */
2198 for (ui = 0; ui < reg_base_value_size; ui++)
2200 rtx base = reg_base_value[ui];
2201 if (base && GET_CODE (base) == REG)
2203 unsigned int base_regno = REGNO (base);
2204 if (base_regno == ui) /* register set from itself */
2205 reg_base_value[ui] = 0;
2207 reg_base_value[ui] = reg_base_value[base_regno];
2212 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2215 free (new_reg_base_value);
2216 new_reg_base_value = 0;
2222 end_alias_analysis ()
2224 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2225 reg_known_value = 0;
2226 reg_known_value_size = 0;
2227 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2228 reg_known_equiv_p = 0;
2231 ggc_del_root (reg_base_value);
2232 free (reg_base_value);
2235 reg_base_value_size = 0;
2236 if (alias_invariant)
2238 free (alias_invariant);
2239 alias_invariant = 0;