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 /* The code used in varargs macros are often not conforming ANSI C,
230 which can trick the compiler into making incorrect aliasing
231 assumptions in these functions. So, we don't use alias sets in
232 such a function. FIXME: This should be moved into the front-end;
233 it is a language-dependent notion, and there's no reason not to
234 still use these checks to handle globals. */
235 if (current_function_stdarg || current_function_varargs)
238 /* If have no alias set information for one of the MEMs, we have to assume
239 it can alias anything. */
240 if (MEM_ALIAS_SET (mem1) == 0 || MEM_ALIAS_SET (mem2) == 0)
243 /* If the two alias sets are the same, they may alias. */
244 if (MEM_ALIAS_SET (mem1) == MEM_ALIAS_SET (mem2))
247 /* See if the first alias set is a subset of the second. */
248 ase = get_alias_set_entry (MEM_ALIAS_SET (mem1));
250 && (ase->has_zero_child
251 || splay_tree_lookup (ase->children,
252 (splay_tree_key) MEM_ALIAS_SET (mem2))))
255 /* Now do the same, but with the alias sets reversed. */
256 ase = get_alias_set_entry (MEM_ALIAS_SET (mem2));
258 && (ase->has_zero_child
259 || splay_tree_lookup (ase->children,
260 (splay_tree_key) MEM_ALIAS_SET (mem1))))
263 /* The two MEMs are in distinct alias sets, and neither one is the
264 child of the other. Therefore, they cannot alias. */
268 /* Insert the NODE into the splay tree given by DATA. Used by
269 record_alias_subset via splay_tree_foreach. */
272 insert_subset_children (node, data)
273 splay_tree_node node;
276 splay_tree_insert ((splay_tree) data, node->key, node->value);
281 /* T is an expression with pointer type. Find the DECL on which this
282 expression is based. (For example, in `a[i]' this would be `a'.)
283 If there is no such DECL, or a unique decl cannot be determined,
284 NULL_TREE is retured. */
292 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
295 /* If this is a declaration, return it. */
296 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
299 /* Handle general expressions. It would be nice to deal with
300 COMPONENT_REFs here. If we could tell that `a' and `b' were the
301 same, then `a->f' and `b->f' are also the same. */
302 switch (TREE_CODE_CLASS (TREE_CODE (t)))
305 return find_base_decl (TREE_OPERAND (t, 0));
308 /* Return 0 if found in neither or both are the same. */
309 d0 = find_base_decl (TREE_OPERAND (t, 0));
310 d1 = find_base_decl (TREE_OPERAND (t, 1));
321 d0 = find_base_decl (TREE_OPERAND (t, 0));
322 d1 = find_base_decl (TREE_OPERAND (t, 1));
323 d0 = find_base_decl (TREE_OPERAND (t, 0));
324 d2 = find_base_decl (TREE_OPERAND (t, 2));
326 /* Set any nonzero values from the last, then from the first. */
327 if (d1 == 0) d1 = d2;
328 if (d0 == 0) d0 = d1;
329 if (d1 == 0) d1 = d0;
330 if (d2 == 0) d2 = d1;
332 /* At this point all are nonzero or all are zero. If all three are the
333 same, return it. Otherwise, return zero. */
334 return (d0 == d1 && d1 == d2) ? d0 : 0;
341 /* Return the alias set for T, which may be either a type or an
342 expression. Call language-specific routine for help, if needed. */
351 /* If we're not doing any alias analysis, just assume everything
352 aliases everything else. Also return 0 if this or its type is
354 if (! flag_strict_aliasing || t == error_mark_node
356 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
359 /* We can be passed either an expression or a type. This and the
360 language-specific routine may make mutually-recursive calls to
361 each other to figure out what to do. At each juncture, we see if
362 this is a tree that the language may need to handle specially.
363 First handle things that aren't types and start by removing nops
364 since we care only about the actual object. */
367 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
368 || TREE_CODE (t) == NON_LVALUE_EXPR)
369 t = TREE_OPERAND (t, 0);
371 /* Now give the language a chance to do something but record what we
372 gave it this time. */
374 if ((set = lang_get_alias_set (t)) != -1)
377 /* Now loop the same way as get_inner_reference and get the alias
378 set to use. Pick up the outermost object that we could have
382 /* Unnamed bitfields are not an addressable object. */
383 if (TREE_CODE (t) == BIT_FIELD_REF)
385 else if (TREE_CODE (t) == COMPONENT_REF)
387 if (! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
388 /* Stop at an adressable decl. */
391 else if (TREE_CODE (t) == ARRAY_REF)
393 if (! TYPE_NONALIASED_COMPONENT
394 (TREE_TYPE (TREE_OPERAND (t, 0))))
395 /* Stop at an addresssable array element. */
398 else if (TREE_CODE (t) != NON_LVALUE_EXPR
399 && ! ((TREE_CODE (t) == NOP_EXPR
400 || TREE_CODE (t) == CONVERT_EXPR)
401 && (TYPE_MODE (TREE_TYPE (t))
402 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))))))
403 /* Stop if not one of above and not mode-preserving conversion. */
406 t = TREE_OPERAND (t, 0);
409 if (TREE_CODE (t) == INDIRECT_REF)
411 /* Check for accesses through restrict-qualified pointers. */
412 tree decl = find_base_decl (TREE_OPERAND (t, 0));
414 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
415 /* We use the alias set indicated in the declaration. */
416 return DECL_POINTER_ALIAS_SET (decl);
418 /* If we have an INDIRECT_REF via a void pointer, we don't
419 know anything about what that might alias. */
420 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
424 /* Give the language another chance to do something special. */
426 && (set = lang_get_alias_set (t)) != -1)
429 /* Now all we care about is the type. */
433 /* Variant qualifiers don't affect the alias set, so get the main
434 variant. If this is a type with a known alias set, return it. */
435 t = TYPE_MAIN_VARIANT (t);
436 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
437 return TYPE_ALIAS_SET (t);
439 /* See if the language has special handling for this type. */
440 if ((set = lang_get_alias_set (t)) != -1)
442 /* If the alias set is now known, we are done. */
443 if (TYPE_ALIAS_SET_KNOWN_P (t))
444 return TYPE_ALIAS_SET (t);
447 /* There are no objects of FUNCTION_TYPE, so there's no point in
448 using up an alias set for them. (There are, of course, pointers
449 and references to functions, but that's different.) */
450 else if (TREE_CODE (t) == FUNCTION_TYPE)
453 /* Otherwise make a new alias set for this type. */
454 set = new_alias_set ();
456 TYPE_ALIAS_SET (t) = set;
458 /* If this is an aggregate type, we must record any component aliasing
460 if (AGGREGATE_TYPE_P (t))
461 record_component_aliases (t);
466 /* Return a brand-new alias set. */
471 static HOST_WIDE_INT last_alias_set;
473 if (flag_strict_aliasing)
474 return ++last_alias_set;
479 /* Indicate that things in SUBSET can alias things in SUPERSET, but
480 not vice versa. For example, in C, a store to an `int' can alias a
481 structure containing an `int', but not vice versa. Here, the
482 structure would be the SUPERSET and `int' the SUBSET. This
483 function should be called only once per SUPERSET/SUBSET pair.
485 It is illegal for SUPERSET to be zero; everything is implicitly a
486 subset of alias set zero. */
489 record_alias_subset (superset, subset)
490 HOST_WIDE_INT superset;
491 HOST_WIDE_INT subset;
493 alias_set_entry superset_entry;
494 alias_set_entry subset_entry;
499 superset_entry = get_alias_set_entry (superset);
500 if (superset_entry == 0)
502 /* Create an entry for the SUPERSET, so that we have a place to
503 attach the SUBSET. */
505 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
506 superset_entry->alias_set = superset;
507 superset_entry->children
508 = splay_tree_new (splay_tree_compare_ints, 0, 0);
509 superset_entry->has_zero_child = 0;
510 splay_tree_insert (alias_sets, (splay_tree_key) superset,
511 (splay_tree_value) superset_entry);
515 superset_entry->has_zero_child = 1;
518 subset_entry = get_alias_set_entry (subset);
519 /* If there is an entry for the subset, enter all of its children
520 (if they are not already present) as children of the SUPERSET. */
523 if (subset_entry->has_zero_child)
524 superset_entry->has_zero_child = 1;
526 splay_tree_foreach (subset_entry->children, insert_subset_children,
527 superset_entry->children);
530 /* Enter the SUBSET itself as a child of the SUPERSET. */
531 splay_tree_insert (superset_entry->children,
532 (splay_tree_key) subset, 0);
536 /* Record that component types of TYPE, if any, are part of that type for
537 aliasing purposes. For record types, we only record component types
538 for fields that are marked addressable. For array types, we always
539 record the component types, so the front end should not call this
540 function if the individual component aren't addressable. */
543 record_component_aliases (type)
546 HOST_WIDE_INT superset = get_alias_set (type);
552 switch (TREE_CODE (type))
555 if (! TYPE_NONALIASED_COMPONENT (type))
556 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
561 case QUAL_UNION_TYPE:
562 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
563 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
564 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
572 /* Allocate an alias set for use in storing and reading from the varargs
576 get_varargs_alias_set ()
578 static HOST_WIDE_INT set = -1;
581 set = new_alias_set ();
586 /* Likewise, but used for the fixed portions of the frame, e.g., register
590 get_frame_alias_set ()
592 static HOST_WIDE_INT set = -1;
595 set = new_alias_set ();
600 /* Inside SRC, the source of a SET, find a base address. */
603 find_base_value (src)
606 switch (GET_CODE (src))
613 /* At the start of a function, argument registers have known base
614 values which may be lost later. Returning an ADDRESS
615 expression here allows optimization based on argument values
616 even when the argument registers are used for other purposes. */
617 if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments)
618 return new_reg_base_value[REGNO (src)];
620 /* If a pseudo has a known base value, return it. Do not do this
621 for hard regs since it can result in a circular dependency
622 chain for registers which have values at function entry.
624 The test above is not sufficient because the scheduler may move
625 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
626 if (REGNO (src) >= FIRST_PSEUDO_REGISTER
627 && (unsigned) REGNO (src) < reg_base_value_size
628 && reg_base_value[REGNO (src)])
629 return reg_base_value[REGNO (src)];
634 /* Check for an argument passed in memory. Only record in the
635 copying-arguments block; it is too hard to track changes
637 if (copying_arguments
638 && (XEXP (src, 0) == arg_pointer_rtx
639 || (GET_CODE (XEXP (src, 0)) == PLUS
640 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
641 return gen_rtx_ADDRESS (VOIDmode, src);
646 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
649 /* ... fall through ... */
654 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
656 /* If either operand is a REG, then see if we already have
657 a known value for it. */
658 if (GET_CODE (src_0) == REG)
660 temp = find_base_value (src_0);
665 if (GET_CODE (src_1) == REG)
667 temp = find_base_value (src_1);
672 /* Guess which operand is the base address:
673 If either operand is a symbol, then it is the base. If
674 either operand is a CONST_INT, then the other is the base. */
675 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
676 return find_base_value (src_0);
677 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
678 return find_base_value (src_1);
680 /* This might not be necessary anymore:
681 If either operand is a REG that is a known pointer, then it
683 else if (GET_CODE (src_0) == REG && REGNO_POINTER_FLAG (REGNO (src_0)))
684 return find_base_value (src_0);
685 else if (GET_CODE (src_1) == REG && REGNO_POINTER_FLAG (REGNO (src_1)))
686 return find_base_value (src_1);
692 /* The standard form is (lo_sum reg sym) so look only at the
694 return find_base_value (XEXP (src, 1));
697 /* If the second operand is constant set the base
698 address to the first operand. */
699 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
700 return find_base_value (XEXP (src, 0));
704 case SIGN_EXTEND: /* used for NT/Alpha pointers */
706 return find_base_value (XEXP (src, 0));
715 /* Called from init_alias_analysis indirectly through note_stores. */
717 /* While scanning insns to find base values, reg_seen[N] is nonzero if
718 register N has been set in this function. */
719 static char *reg_seen;
721 /* Addresses which are known not to alias anything else are identified
722 by a unique integer. */
723 static int unique_id;
726 record_set (dest, set, data)
728 void *data ATTRIBUTE_UNUSED;
730 register unsigned regno;
733 if (GET_CODE (dest) != REG)
736 regno = REGNO (dest);
738 if (regno >= reg_base_value_size)
743 /* A CLOBBER wipes out any old value but does not prevent a previously
744 unset register from acquiring a base address (i.e. reg_seen is not
746 if (GET_CODE (set) == CLOBBER)
748 new_reg_base_value[regno] = 0;
757 new_reg_base_value[regno] = 0;
761 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
762 GEN_INT (unique_id++));
766 /* This is not the first set. If the new value is not related to the
767 old value, forget the base value. Note that the following code is
769 extern int x, y; int *p = &x; p += (&y-&x);
770 ANSI C does not allow computing the difference of addresses
771 of distinct top level objects. */
772 if (new_reg_base_value[regno])
773 switch (GET_CODE (src))
778 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
779 new_reg_base_value[regno] = 0;
782 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
783 new_reg_base_value[regno] = 0;
786 new_reg_base_value[regno] = 0;
789 /* If this is the first set of a register, record the value. */
790 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
791 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
792 new_reg_base_value[regno] = find_base_value (src);
797 /* Called from loop optimization when a new pseudo-register is
798 created. It indicates that REGNO is being set to VAL. f INVARIANT
799 is true then this value also describes an invariant relationship
800 which can be used to deduce that two registers with unknown values
804 record_base_value (regno, val, invariant)
809 if (regno >= reg_base_value_size)
812 if (invariant && alias_invariant)
813 alias_invariant[regno] = val;
815 if (GET_CODE (val) == REG)
817 if (REGNO (val) < reg_base_value_size)
818 reg_base_value[regno] = reg_base_value[REGNO (val)];
823 reg_base_value[regno] = find_base_value (val);
826 /* Returns a canonical version of X, from the point of view alias
827 analysis. (For example, if X is a MEM whose address is a register,
828 and the register has a known value (say a SYMBOL_REF), then a MEM
829 whose address is the SYMBOL_REF is returned.) */
835 /* Recursively look for equivalences. */
836 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
837 && REGNO (x) < reg_known_value_size)
838 return reg_known_value[REGNO (x)] == x
839 ? x : canon_rtx (reg_known_value[REGNO (x)]);
840 else if (GET_CODE (x) == PLUS)
842 rtx x0 = canon_rtx (XEXP (x, 0));
843 rtx x1 = canon_rtx (XEXP (x, 1));
845 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
847 /* We can tolerate LO_SUMs being offset here; these
848 rtl are used for nothing other than comparisons. */
849 if (GET_CODE (x0) == CONST_INT)
850 return plus_constant_for_output (x1, INTVAL (x0));
851 else if (GET_CODE (x1) == CONST_INT)
852 return plus_constant_for_output (x0, INTVAL (x1));
853 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
857 /* This gives us much better alias analysis when called from
858 the loop optimizer. Note we want to leave the original
859 MEM alone, but need to return the canonicalized MEM with
860 all the flags with their original values. */
861 else if (GET_CODE (x) == MEM)
863 rtx addr = canon_rtx (XEXP (x, 0));
865 if (addr != XEXP (x, 0))
867 rtx new = gen_rtx_MEM (GET_MODE (x), addr);
869 MEM_COPY_ATTRIBUTES (new, x);
876 /* Return 1 if X and Y are identical-looking rtx's.
878 We use the data in reg_known_value above to see if two registers with
879 different numbers are, in fact, equivalent. */
882 rtx_equal_for_memref_p (x, y)
887 register enum rtx_code code;
888 register const char *fmt;
890 if (x == 0 && y == 0)
892 if (x == 0 || y == 0)
902 /* Rtx's of different codes cannot be equal. */
903 if (code != GET_CODE (y))
906 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
907 (REG:SI x) and (REG:HI x) are NOT equivalent. */
909 if (GET_MODE (x) != GET_MODE (y))
912 /* Some RTL can be compared without a recursive examination. */
916 return REGNO (x) == REGNO (y);
919 return XEXP (x, 0) == XEXP (y, 0);
922 return XSTR (x, 0) == XSTR (y, 0);
926 /* There's no need to compare the contents of CONST_DOUBLEs or
927 CONST_INTs because pointer equality is a good enough
928 comparison for these nodes. */
932 return (REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0))
933 && XINT (x, 1) == XINT (y, 1));
939 /* For commutative operations, the RTX match if the operand match in any
940 order. Also handle the simple binary and unary cases without a loop. */
941 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
942 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
943 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
944 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
945 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
946 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
947 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
948 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
949 else if (GET_RTX_CLASS (code) == '1')
950 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
952 /* Compare the elements. If any pair of corresponding elements
953 fail to match, return 0 for the whole things.
955 Limit cases to types which actually appear in addresses. */
957 fmt = GET_RTX_FORMAT (code);
958 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
963 if (XINT (x, i) != XINT (y, i))
968 /* Two vectors must have the same length. */
969 if (XVECLEN (x, i) != XVECLEN (y, i))
972 /* And the corresponding elements must match. */
973 for (j = 0; j < XVECLEN (x, i); j++)
974 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
975 XVECEXP (y, i, j)) == 0)
980 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
984 /* This can happen for an asm which clobbers memory. */
988 /* It is believed that rtx's at this level will never
989 contain anything but integers and other rtx's,
990 except for within LABEL_REFs and SYMBOL_REFs. */
998 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
999 X and return it, or return 0 if none found. */
1002 find_symbolic_term (x)
1006 register enum rtx_code code;
1007 register const char *fmt;
1009 code = GET_CODE (x);
1010 if (code == SYMBOL_REF || code == LABEL_REF)
1012 if (GET_RTX_CLASS (code) == 'o')
1015 fmt = GET_RTX_FORMAT (code);
1016 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1022 t = find_symbolic_term (XEXP (x, i));
1026 else if (fmt[i] == 'E')
1037 struct elt_loc_list *l;
1039 #if defined (FIND_BASE_TERM)
1040 /* Try machine-dependent ways to find the base term. */
1041 x = FIND_BASE_TERM (x);
1044 switch (GET_CODE (x))
1047 return REG_BASE_VALUE (x);
1050 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1056 return find_base_term (XEXP (x, 0));
1059 val = CSELIB_VAL_PTR (x);
1060 for (l = val->locs; l; l = l->next)
1061 if ((x = find_base_term (l->loc)) != 0)
1067 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1074 rtx tmp1 = XEXP (x, 0);
1075 rtx tmp2 = XEXP (x, 1);
1077 /* This is a litle bit tricky since we have to determine which of
1078 the two operands represents the real base address. Otherwise this
1079 routine may return the index register instead of the base register.
1081 That may cause us to believe no aliasing was possible, when in
1082 fact aliasing is possible.
1084 We use a few simple tests to guess the base register. Additional
1085 tests can certainly be added. For example, if one of the operands
1086 is a shift or multiply, then it must be the index register and the
1087 other operand is the base register. */
1089 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1090 return find_base_term (tmp2);
1092 /* If either operand is known to be a pointer, then use it
1093 to determine the base term. */
1094 if (REG_P (tmp1) && REGNO_POINTER_FLAG (REGNO (tmp1)))
1095 return find_base_term (tmp1);
1097 if (REG_P (tmp2) && REGNO_POINTER_FLAG (REGNO (tmp2)))
1098 return find_base_term (tmp2);
1100 /* Neither operand was known to be a pointer. Go ahead and find the
1101 base term for both operands. */
1102 tmp1 = find_base_term (tmp1);
1103 tmp2 = find_base_term (tmp2);
1105 /* If either base term is named object or a special address
1106 (like an argument or stack reference), then use it for the
1109 && (GET_CODE (tmp1) == SYMBOL_REF
1110 || GET_CODE (tmp1) == LABEL_REF
1111 || (GET_CODE (tmp1) == ADDRESS
1112 && GET_MODE (tmp1) != VOIDmode)))
1116 && (GET_CODE (tmp2) == SYMBOL_REF
1117 || GET_CODE (tmp2) == LABEL_REF
1118 || (GET_CODE (tmp2) == ADDRESS
1119 && GET_MODE (tmp2) != VOIDmode)))
1122 /* We could not determine which of the two operands was the
1123 base register and which was the index. So we can determine
1124 nothing from the base alias check. */
1129 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1130 return REG_BASE_VALUE (XEXP (x, 0));
1138 return REG_BASE_VALUE (frame_pointer_rtx);
1145 /* Return 0 if the addresses X and Y are known to point to different
1146 objects, 1 if they might be pointers to the same object. */
1149 base_alias_check (x, y, x_mode, y_mode)
1151 enum machine_mode x_mode, y_mode;
1153 rtx x_base = find_base_term (x);
1154 rtx y_base = find_base_term (y);
1156 /* If the address itself has no known base see if a known equivalent
1157 value has one. If either address still has no known base, nothing
1158 is known about aliasing. */
1163 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1166 x_base = find_base_term (x_c);
1174 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1177 y_base = find_base_term (y_c);
1182 /* If the base addresses are equal nothing is known about aliasing. */
1183 if (rtx_equal_p (x_base, y_base))
1186 /* The base addresses of the read and write are different expressions.
1187 If they are both symbols and they are not accessed via AND, there is
1188 no conflict. We can bring knowledge of object alignment into play
1189 here. For example, on alpha, "char a, b;" can alias one another,
1190 though "char a; long b;" cannot. */
1191 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1193 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1195 if (GET_CODE (x) == AND
1196 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1197 || GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1199 if (GET_CODE (y) == AND
1200 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1201 || GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1203 /* Differing symbols never alias. */
1207 /* If one address is a stack reference there can be no alias:
1208 stack references using different base registers do not alias,
1209 a stack reference can not alias a parameter, and a stack reference
1210 can not alias a global. */
1211 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1212 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1215 if (! flag_argument_noalias)
1218 if (flag_argument_noalias > 1)
1221 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1222 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1225 /* Convert the address X into something we can use. This is done by returning
1226 it unchanged unless it is a value; in the latter case we call cselib to get
1227 a more useful rtx. */
1234 struct elt_loc_list *l;
1236 if (GET_CODE (x) != VALUE)
1238 v = CSELIB_VAL_PTR (x);
1239 for (l = v->locs; l; l = l->next)
1240 if (CONSTANT_P (l->loc))
1242 for (l = v->locs; l; l = l->next)
1243 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1246 return v->locs->loc;
1250 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1251 where SIZE is the size in bytes of the memory reference. If ADDR
1252 is not modified by the memory reference then ADDR is returned. */
1255 addr_side_effect_eval (addr, size, n_refs)
1262 switch (GET_CODE (addr))
1265 offset = (n_refs + 1) * size;
1268 offset = -(n_refs + 1) * size;
1271 offset = n_refs * size;
1274 offset = -n_refs * size;
1282 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1284 addr = XEXP (addr, 0);
1289 /* Return nonzero if X and Y (memory addresses) could reference the
1290 same location in memory. C is an offset accumulator. When
1291 C is nonzero, we are testing aliases between X and Y + C.
1292 XSIZE is the size in bytes of the X reference,
1293 similarly YSIZE is the size in bytes for Y.
1295 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1296 referenced (the reference was BLKmode), so make the most pessimistic
1299 If XSIZE or YSIZE is negative, we may access memory outside the object
1300 being referenced as a side effect. This can happen when using AND to
1301 align memory references, as is done on the Alpha.
1303 Nice to notice that varying addresses cannot conflict with fp if no
1304 local variables had their addresses taken, but that's too hard now. */
1307 memrefs_conflict_p (xsize, x, ysize, y, c)
1312 if (GET_CODE (x) == VALUE)
1314 if (GET_CODE (y) == VALUE)
1316 if (GET_CODE (x) == HIGH)
1318 else if (GET_CODE (x) == LO_SUM)
1321 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1322 if (GET_CODE (y) == HIGH)
1324 else if (GET_CODE (y) == LO_SUM)
1327 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1329 if (rtx_equal_for_memref_p (x, y))
1331 if (xsize <= 0 || ysize <= 0)
1333 if (c >= 0 && xsize > c)
1335 if (c < 0 && ysize+c > 0)
1340 /* This code used to check for conflicts involving stack references and
1341 globals but the base address alias code now handles these cases. */
1343 if (GET_CODE (x) == PLUS)
1345 /* The fact that X is canonicalized means that this
1346 PLUS rtx is canonicalized. */
1347 rtx x0 = XEXP (x, 0);
1348 rtx x1 = XEXP (x, 1);
1350 if (GET_CODE (y) == PLUS)
1352 /* The fact that Y is canonicalized means that this
1353 PLUS rtx is canonicalized. */
1354 rtx y0 = XEXP (y, 0);
1355 rtx y1 = XEXP (y, 1);
1357 if (rtx_equal_for_memref_p (x1, y1))
1358 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1359 if (rtx_equal_for_memref_p (x0, y0))
1360 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1361 if (GET_CODE (x1) == CONST_INT)
1363 if (GET_CODE (y1) == CONST_INT)
1364 return memrefs_conflict_p (xsize, x0, ysize, y0,
1365 c - INTVAL (x1) + INTVAL (y1));
1367 return memrefs_conflict_p (xsize, x0, ysize, y,
1370 else if (GET_CODE (y1) == CONST_INT)
1371 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1375 else if (GET_CODE (x1) == CONST_INT)
1376 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1378 else if (GET_CODE (y) == PLUS)
1380 /* The fact that Y is canonicalized means that this
1381 PLUS rtx is canonicalized. */
1382 rtx y0 = XEXP (y, 0);
1383 rtx y1 = XEXP (y, 1);
1385 if (GET_CODE (y1) == CONST_INT)
1386 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1391 if (GET_CODE (x) == GET_CODE (y))
1392 switch (GET_CODE (x))
1396 /* Handle cases where we expect the second operands to be the
1397 same, and check only whether the first operand would conflict
1400 rtx x1 = canon_rtx (XEXP (x, 1));
1401 rtx y1 = canon_rtx (XEXP (y, 1));
1402 if (! rtx_equal_for_memref_p (x1, y1))
1404 x0 = canon_rtx (XEXP (x, 0));
1405 y0 = canon_rtx (XEXP (y, 0));
1406 if (rtx_equal_for_memref_p (x0, y0))
1407 return (xsize == 0 || ysize == 0
1408 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1410 /* Can't properly adjust our sizes. */
1411 if (GET_CODE (x1) != CONST_INT)
1413 xsize /= INTVAL (x1);
1414 ysize /= INTVAL (x1);
1416 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1420 /* Are these registers known not to be equal? */
1421 if (alias_invariant)
1423 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1424 rtx i_x, i_y; /* invariant relationships of X and Y */
1426 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1427 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1429 if (i_x == 0 && i_y == 0)
1432 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1433 ysize, i_y ? i_y : y, c))
1442 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1443 as an access with indeterminate size. Assume that references
1444 besides AND are aligned, so if the size of the other reference is
1445 at least as large as the alignment, assume no other overlap. */
1446 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1448 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1450 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1452 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1454 /* ??? If we are indexing far enough into the array/structure, we
1455 may yet be able to determine that we can not overlap. But we
1456 also need to that we are far enough from the end not to overlap
1457 a following reference, so we do nothing with that for now. */
1458 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1460 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1463 if (GET_CODE (x) == ADDRESSOF)
1465 if (y == frame_pointer_rtx
1466 || GET_CODE (y) == ADDRESSOF)
1467 return xsize <= 0 || ysize <= 0;
1469 if (GET_CODE (y) == ADDRESSOF)
1471 if (x == frame_pointer_rtx)
1472 return xsize <= 0 || ysize <= 0;
1477 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1479 c += (INTVAL (y) - INTVAL (x));
1480 return (xsize <= 0 || ysize <= 0
1481 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1484 if (GET_CODE (x) == CONST)
1486 if (GET_CODE (y) == CONST)
1487 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1488 ysize, canon_rtx (XEXP (y, 0)), c);
1490 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1493 if (GET_CODE (y) == CONST)
1494 return memrefs_conflict_p (xsize, x, ysize,
1495 canon_rtx (XEXP (y, 0)), c);
1498 return (xsize <= 0 || ysize <= 0
1499 || (rtx_equal_for_memref_p (x, y)
1500 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1507 /* Functions to compute memory dependencies.
1509 Since we process the insns in execution order, we can build tables
1510 to keep track of what registers are fixed (and not aliased), what registers
1511 are varying in known ways, and what registers are varying in unknown
1514 If both memory references are volatile, then there must always be a
1515 dependence between the two references, since their order can not be
1516 changed. A volatile and non-volatile reference can be interchanged
1519 A MEM_IN_STRUCT reference at a non-AND varying address can never
1520 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1521 also must allow AND addresses, because they may generate accesses
1522 outside the object being referenced. This is used to generate
1523 aligned addresses from unaligned addresses, for instance, the alpha
1524 storeqi_unaligned pattern. */
1526 /* Read dependence: X is read after read in MEM takes place. There can
1527 only be a dependence here if both reads are volatile. */
1530 read_dependence (mem, x)
1534 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1537 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1538 MEM2 is a reference to a structure at a varying address, or returns
1539 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1540 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1541 to decide whether or not an address may vary; it should return
1542 nonzero whenever variation is possible.
1543 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1546 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1548 rtx mem1_addr, mem2_addr;
1549 int (*varies_p) PARAMS ((rtx));
1551 if (! flag_strict_aliasing)
1554 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1555 && !varies_p (mem1_addr) && varies_p (mem2_addr))
1556 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1560 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1561 && varies_p (mem1_addr) && !varies_p (mem2_addr))
1562 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1569 /* Returns nonzero if something about the mode or address format MEM1
1570 indicates that it might well alias *anything*. */
1573 aliases_everything_p (mem)
1576 if (GET_CODE (XEXP (mem, 0)) == AND)
1577 /* If the address is an AND, its very hard to know at what it is
1578 actually pointing. */
1584 /* True dependence: X is read after store in MEM takes place. */
1587 true_dependence (mem, mem_mode, x, varies)
1589 enum machine_mode mem_mode;
1591 int (*varies) PARAMS ((rtx));
1593 register rtx x_addr, mem_addr;
1596 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1599 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1602 /* Unchanging memory can't conflict with non-unchanging memory.
1603 A non-unchanging read can conflict with a non-unchanging write.
1604 An unchanging read can conflict with an unchanging write since
1605 there may be a single store to this address to initialize it.
1606 Note that an unchanging store can conflict with a non-unchanging read
1607 since we have to make conservative assumptions when we have a
1608 record with readonly fields and we are copying the whole thing.
1609 Just fall through to the code below to resolve potential conflicts.
1610 This won't handle all cases optimally, but the possible performance
1611 loss should be negligible. */
1612 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1615 if (mem_mode == VOIDmode)
1616 mem_mode = GET_MODE (mem);
1618 x_addr = get_addr (XEXP (x, 0));
1619 mem_addr = get_addr (XEXP (mem, 0));
1621 base = find_base_term (x_addr);
1622 if (base && (GET_CODE (base) == LABEL_REF
1623 || (GET_CODE (base) == SYMBOL_REF
1624 && CONSTANT_POOL_ADDRESS_P (base))))
1627 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1630 x_addr = canon_rtx (x_addr);
1631 mem_addr = canon_rtx (mem_addr);
1633 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1634 SIZE_FOR_MODE (x), x_addr, 0))
1637 if (aliases_everything_p (x))
1640 /* We cannot use aliases_everyting_p to test MEM, since we must look
1641 at MEM_MODE, rather than GET_MODE (MEM). */
1642 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1645 /* In true_dependence we also allow BLKmode to alias anything. Why
1646 don't we do this in anti_dependence and output_dependence? */
1647 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1650 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1654 /* Returns non-zero if a write to X might alias a previous read from
1655 (or, if WRITEP is non-zero, a write to) MEM. */
1658 write_dependence_p (mem, x, writep)
1663 rtx x_addr, mem_addr;
1667 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1670 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1673 /* Unchanging memory can't conflict with non-unchanging memory. */
1674 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1677 /* If MEM is an unchanging read, then it can't possibly conflict with
1678 the store to X, because there is at most one store to MEM, and it must
1679 have occurred somewhere before MEM. */
1680 if (! writep && RTX_UNCHANGING_P (mem))
1683 x_addr = get_addr (XEXP (x, 0));
1684 mem_addr = get_addr (XEXP (mem, 0));
1688 base = find_base_term (mem_addr);
1689 if (base && (GET_CODE (base) == LABEL_REF
1690 || (GET_CODE (base) == SYMBOL_REF
1691 && CONSTANT_POOL_ADDRESS_P (base))))
1695 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1699 x_addr = canon_rtx (x_addr);
1700 mem_addr = canon_rtx (mem_addr);
1702 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1703 SIZE_FOR_MODE (x), x_addr, 0))
1707 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1710 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1711 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1714 /* Anti dependence: X is written after read in MEM takes place. */
1717 anti_dependence (mem, x)
1721 return write_dependence_p (mem, x, /*writep=*/0);
1724 /* Output dependence: X is written after store in MEM takes place. */
1727 output_dependence (mem, x)
1731 return write_dependence_p (mem, x, /*writep=*/1);
1734 /* Returns non-zero if X mentions something which is not
1735 local to the function and is not constant. */
1738 nonlocal_mentioned_p (x)
1742 register RTX_CODE code;
1745 code = GET_CODE (x);
1747 if (GET_RTX_CLASS (code) == 'i')
1749 /* Constant functions can be constant if they don't use
1750 scratch memory used to mark function w/o side effects. */
1751 if (code == CALL_INSN && CONST_CALL_P (x))
1753 x = CALL_INSN_FUNCTION_USAGE (x);
1759 code = GET_CODE (x);
1765 if (GET_CODE (SUBREG_REG (x)) == REG)
1767 /* Global registers are not local. */
1768 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1769 && global_regs[REGNO (SUBREG_REG (x)) + SUBREG_WORD (x)])
1777 /* Global registers are not local. */
1778 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1792 /* Constants in the function's constants pool are constant. */
1793 if (CONSTANT_POOL_ADDRESS_P (x))
1798 /* Non-constant calls and recursion are not local. */
1802 /* Be overly conservative and consider any volatile memory
1803 reference as not local. */
1804 if (MEM_VOLATILE_P (x))
1806 base = find_base_term (XEXP (x, 0));
1809 /* A Pmode ADDRESS could be a reference via the structure value
1810 address or static chain. Such memory references are nonlocal.
1812 Thus, we have to examine the contents of the ADDRESS to find
1813 out if this is a local reference or not. */
1814 if (GET_CODE (base) == ADDRESS
1815 && GET_MODE (base) == Pmode
1816 && (XEXP (base, 0) == stack_pointer_rtx
1817 || XEXP (base, 0) == arg_pointer_rtx
1818 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1819 || XEXP (base, 0) == hard_frame_pointer_rtx
1821 || XEXP (base, 0) == frame_pointer_rtx))
1823 /* Constants in the function's constant pool are constant. */
1824 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
1829 case UNSPEC_VOLATILE:
1834 if (MEM_VOLATILE_P (x))
1843 /* Recursively scan the operands of this expression. */
1846 register const char *fmt = GET_RTX_FORMAT (code);
1849 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1851 if (fmt[i] == 'e' && XEXP (x, i))
1853 if (nonlocal_mentioned_p (XEXP (x, i)))
1856 else if (fmt[i] == 'E')
1859 for (j = 0; j < XVECLEN (x, i); j++)
1860 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
1869 /* Return non-zero if a loop (natural or otherwise) is present.
1870 Inspired by Depth_First_Search_PP described in:
1872 Advanced Compiler Design and Implementation
1874 Morgan Kaufmann, 1997
1876 and heavily borrowed from flow_depth_first_order_compute. */
1889 /* Allocate the preorder and postorder number arrays. */
1890 pre = (int *) xcalloc (n_basic_blocks, sizeof (int));
1891 post = (int *) xcalloc (n_basic_blocks, sizeof (int));
1893 /* Allocate stack for back-tracking up CFG. */
1894 stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
1897 /* Allocate bitmap to track nodes that have been visited. */
1898 visited = sbitmap_alloc (n_basic_blocks);
1900 /* None of the nodes in the CFG have been visited yet. */
1901 sbitmap_zero (visited);
1903 /* Push the first edge on to the stack. */
1904 stack[sp++] = ENTRY_BLOCK_PTR->succ;
1912 /* Look at the edge on the top of the stack. */
1917 /* Check if the edge destination has been visited yet. */
1918 if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
1920 /* Mark that we have visited the destination. */
1921 SET_BIT (visited, dest->index);
1923 pre[dest->index] = prenum++;
1927 /* Since the DEST node has been visited for the first
1928 time, check its successors. */
1929 stack[sp++] = dest->succ;
1932 post[dest->index] = postnum++;
1936 if (dest != EXIT_BLOCK_PTR
1937 && pre[src->index] >= pre[dest->index]
1938 && post[dest->index] == 0)
1941 if (! e->succ_next && src != ENTRY_BLOCK_PTR)
1942 post[src->index] = postnum++;
1945 stack[sp - 1] = e->succ_next;
1954 sbitmap_free (visited);
1959 /* Mark the function if it is constant. */
1962 mark_constant_function ()
1965 int nonlocal_mentioned;
1967 if (TREE_PUBLIC (current_function_decl)
1968 || TREE_READONLY (current_function_decl)
1969 || DECL_IS_PURE (current_function_decl)
1970 || TREE_THIS_VOLATILE (current_function_decl)
1971 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
1974 /* A loop might not return which counts as a side effect. */
1978 nonlocal_mentioned = 0;
1980 init_alias_analysis ();
1982 /* Determine if this is a constant function. */
1984 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1985 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
1987 nonlocal_mentioned = 1;
1991 end_alias_analysis ();
1993 /* Mark the function. */
1995 if (! nonlocal_mentioned)
1996 TREE_READONLY (current_function_decl) = 1;
2000 static HARD_REG_SET argument_registers;
2007 #ifndef OUTGOING_REGNO
2008 #define OUTGOING_REGNO(N) N
2010 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2011 /* Check whether this register can hold an incoming pointer
2012 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2013 numbers, so translate if necessary due to register windows. */
2014 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2015 && HARD_REGNO_MODE_OK (i, Pmode))
2016 SET_HARD_REG_BIT (argument_registers, i);
2018 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2021 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2025 init_alias_analysis ()
2027 int maxreg = max_reg_num ();
2030 register unsigned int ui;
2033 reg_known_value_size = maxreg;
2036 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2037 - FIRST_PSEUDO_REGISTER;
2039 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2040 - FIRST_PSEUDO_REGISTER;
2042 /* Overallocate reg_base_value to allow some growth during loop
2043 optimization. Loop unrolling can create a large number of
2045 reg_base_value_size = maxreg * 2;
2046 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2047 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2049 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2050 reg_seen = (char *) xmalloc (reg_base_value_size);
2051 if (! reload_completed && flag_unroll_loops)
2053 /* ??? Why are we realloc'ing if we're just going to zero it? */
2054 alias_invariant = (rtx *)xrealloc (alias_invariant,
2055 reg_base_value_size * sizeof (rtx));
2056 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2060 /* The basic idea is that each pass through this loop will use the
2061 "constant" information from the previous pass to propagate alias
2062 information through another level of assignments.
2064 This could get expensive if the assignment chains are long. Maybe
2065 we should throttle the number of iterations, possibly based on
2066 the optimization level or flag_expensive_optimizations.
2068 We could propagate more information in the first pass by making use
2069 of REG_N_SETS to determine immediately that the alias information
2070 for a pseudo is "constant".
2072 A program with an uninitialized variable can cause an infinite loop
2073 here. Instead of doing a full dataflow analysis to detect such problems
2074 we just cap the number of iterations for the loop.
2076 The state of the arrays for the set chain in question does not matter
2077 since the program has undefined behavior. */
2082 /* Assume nothing will change this iteration of the loop. */
2085 /* We want to assign the same IDs each iteration of this loop, so
2086 start counting from zero each iteration of the loop. */
2089 /* We're at the start of the funtion each iteration through the
2090 loop, so we're copying arguments. */
2091 copying_arguments = 1;
2093 /* Wipe the potential alias information clean for this pass. */
2094 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2096 /* Wipe the reg_seen array clean. */
2097 memset ((char *) reg_seen, 0, reg_base_value_size);
2099 /* Mark all hard registers which may contain an address.
2100 The stack, frame and argument pointers may contain an address.
2101 An argument register which can hold a Pmode value may contain
2102 an address even if it is not in BASE_REGS.
2104 The address expression is VOIDmode for an argument and
2105 Pmode for other registers. */
2107 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2108 if (TEST_HARD_REG_BIT (argument_registers, i))
2109 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2110 gen_rtx_REG (Pmode, i));
2112 new_reg_base_value[STACK_POINTER_REGNUM]
2113 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2114 new_reg_base_value[ARG_POINTER_REGNUM]
2115 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2116 new_reg_base_value[FRAME_POINTER_REGNUM]
2117 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2118 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2119 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2120 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2123 /* Walk the insns adding values to the new_reg_base_value array. */
2124 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2130 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2131 /* The prologue/epilouge insns are not threaded onto the
2132 insn chain until after reload has completed. Thus,
2133 there is no sense wasting time checking if INSN is in
2134 the prologue/epilogue until after reload has completed. */
2135 if (reload_completed
2136 && prologue_epilogue_contains (insn))
2140 /* If this insn has a noalias note, process it, Otherwise,
2141 scan for sets. A simple set will have no side effects
2142 which could change the base value of any other register. */
2144 if (GET_CODE (PATTERN (insn)) == SET
2145 && REG_NOTES (insn) != 0
2146 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2147 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2149 note_stores (PATTERN (insn), record_set, NULL);
2151 set = single_set (insn);
2154 && GET_CODE (SET_DEST (set)) == REG
2155 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
2156 && REG_NOTES (insn) != 0
2157 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2158 && REG_N_SETS (REGNO (SET_DEST (set))) == 1)
2159 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2160 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2161 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2163 int regno = REGNO (SET_DEST (set));
2164 reg_known_value[regno] = XEXP (note, 0);
2165 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2168 else if (GET_CODE (insn) == NOTE
2169 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2170 copying_arguments = 0;
2173 /* Now propagate values from new_reg_base_value to reg_base_value. */
2174 for (ui = 0; ui < reg_base_value_size; ui++)
2176 if (new_reg_base_value[ui]
2177 && new_reg_base_value[ui] != reg_base_value[ui]
2178 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2180 reg_base_value[ui] = new_reg_base_value[ui];
2185 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2187 /* Fill in the remaining entries. */
2188 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2189 if (reg_known_value[i] == 0)
2190 reg_known_value[i] = regno_reg_rtx[i];
2192 /* Simplify the reg_base_value array so that no register refers to
2193 another register, except to special registers indirectly through
2194 ADDRESS expressions.
2196 In theory this loop can take as long as O(registers^2), but unless
2197 there are very long dependency chains it will run in close to linear
2200 This loop may not be needed any longer now that the main loop does
2201 a better job at propagating alias information. */
2207 for (ui = 0; ui < reg_base_value_size; ui++)
2209 rtx base = reg_base_value[ui];
2210 if (base && GET_CODE (base) == REG)
2212 unsigned int base_regno = REGNO (base);
2213 if (base_regno == ui) /* register set from itself */
2214 reg_base_value[ui] = 0;
2216 reg_base_value[ui] = reg_base_value[base_regno];
2221 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2224 free (new_reg_base_value);
2225 new_reg_base_value = 0;
2231 end_alias_analysis ()
2233 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2234 reg_known_value = 0;
2235 reg_known_value_size = 0;
2236 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2237 reg_known_equiv_p = 0;
2240 ggc_del_root (reg_base_value);
2241 free (reg_base_value);
2244 reg_base_value_size = 0;
2245 if (alias_invariant)
2247 free (alias_invariant);
2248 alias_invariant = 0;