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) || TREE_CODE (t) == COMPLEX_TYPE)
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)));
559 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
567 /* Allocate an alias set for use in storing and reading from the varargs
571 get_varargs_alias_set ()
573 static HOST_WIDE_INT set = -1;
576 set = new_alias_set ();
581 /* Likewise, but used for the fixed portions of the frame, e.g., register
585 get_frame_alias_set ()
587 static HOST_WIDE_INT set = -1;
590 set = new_alias_set ();
595 /* Inside SRC, the source of a SET, find a base address. */
598 find_base_value (src)
601 switch (GET_CODE (src))
608 /* At the start of a function, argument registers have known base
609 values which may be lost later. Returning an ADDRESS
610 expression here allows optimization based on argument values
611 even when the argument registers are used for other purposes. */
612 if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments)
613 return new_reg_base_value[REGNO (src)];
615 /* If a pseudo has a known base value, return it. Do not do this
616 for hard regs since it can result in a circular dependency
617 chain for registers which have values at function entry.
619 The test above is not sufficient because the scheduler may move
620 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
621 if (REGNO (src) >= FIRST_PSEUDO_REGISTER
622 && (unsigned) REGNO (src) < reg_base_value_size
623 && reg_base_value[REGNO (src)])
624 return reg_base_value[REGNO (src)];
629 /* Check for an argument passed in memory. Only record in the
630 copying-arguments block; it is too hard to track changes
632 if (copying_arguments
633 && (XEXP (src, 0) == arg_pointer_rtx
634 || (GET_CODE (XEXP (src, 0)) == PLUS
635 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
636 return gen_rtx_ADDRESS (VOIDmode, src);
641 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
644 /* ... fall through ... */
649 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
651 /* If either operand is a REG, then see if we already have
652 a known value for it. */
653 if (GET_CODE (src_0) == REG)
655 temp = find_base_value (src_0);
660 if (GET_CODE (src_1) == REG)
662 temp = find_base_value (src_1);
667 /* Guess which operand is the base address:
668 If either operand is a symbol, then it is the base. If
669 either operand is a CONST_INT, then the other is the base. */
670 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
671 return find_base_value (src_0);
672 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
673 return find_base_value (src_1);
675 /* This might not be necessary anymore:
676 If either operand is a REG that is a known pointer, then it
678 else if (GET_CODE (src_0) == REG && REG_POINTER (src_0))
679 return find_base_value (src_0);
680 else if (GET_CODE (src_1) == REG && REG_POINTER (src_1))
681 return find_base_value (src_1);
687 /* The standard form is (lo_sum reg sym) so look only at the
689 return find_base_value (XEXP (src, 1));
692 /* If the second operand is constant set the base
693 address to the first operand. */
694 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
695 return find_base_value (XEXP (src, 0));
699 case SIGN_EXTEND: /* used for NT/Alpha pointers */
701 return find_base_value (XEXP (src, 0));
710 /* Called from init_alias_analysis indirectly through note_stores. */
712 /* While scanning insns to find base values, reg_seen[N] is nonzero if
713 register N has been set in this function. */
714 static char *reg_seen;
716 /* Addresses which are known not to alias anything else are identified
717 by a unique integer. */
718 static int unique_id;
721 record_set (dest, set, data)
723 void *data ATTRIBUTE_UNUSED;
725 register unsigned regno;
728 if (GET_CODE (dest) != REG)
731 regno = REGNO (dest);
733 if (regno >= reg_base_value_size)
738 /* A CLOBBER wipes out any old value but does not prevent a previously
739 unset register from acquiring a base address (i.e. reg_seen is not
741 if (GET_CODE (set) == CLOBBER)
743 new_reg_base_value[regno] = 0;
752 new_reg_base_value[regno] = 0;
756 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
757 GEN_INT (unique_id++));
761 /* This is not the first set. If the new value is not related to the
762 old value, forget the base value. Note that the following code is
764 extern int x, y; int *p = &x; p += (&y-&x);
765 ANSI C does not allow computing the difference of addresses
766 of distinct top level objects. */
767 if (new_reg_base_value[regno])
768 switch (GET_CODE (src))
773 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
774 new_reg_base_value[regno] = 0;
777 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
778 new_reg_base_value[regno] = 0;
781 new_reg_base_value[regno] = 0;
784 /* If this is the first set of a register, record the value. */
785 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
786 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
787 new_reg_base_value[regno] = find_base_value (src);
792 /* Called from loop optimization when a new pseudo-register is
793 created. It indicates that REGNO is being set to VAL. f INVARIANT
794 is true then this value also describes an invariant relationship
795 which can be used to deduce that two registers with unknown values
799 record_base_value (regno, val, invariant)
804 if (regno >= reg_base_value_size)
807 if (invariant && alias_invariant)
808 alias_invariant[regno] = val;
810 if (GET_CODE (val) == REG)
812 if (REGNO (val) < reg_base_value_size)
813 reg_base_value[regno] = reg_base_value[REGNO (val)];
818 reg_base_value[regno] = find_base_value (val);
821 /* Returns a canonical version of X, from the point of view alias
822 analysis. (For example, if X is a MEM whose address is a register,
823 and the register has a known value (say a SYMBOL_REF), then a MEM
824 whose address is the SYMBOL_REF is returned.) */
830 /* Recursively look for equivalences. */
831 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
832 && REGNO (x) < reg_known_value_size)
833 return reg_known_value[REGNO (x)] == x
834 ? x : canon_rtx (reg_known_value[REGNO (x)]);
835 else if (GET_CODE (x) == PLUS)
837 rtx x0 = canon_rtx (XEXP (x, 0));
838 rtx x1 = canon_rtx (XEXP (x, 1));
840 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
842 /* We can tolerate LO_SUMs being offset here; these
843 rtl are used for nothing other than comparisons. */
844 if (GET_CODE (x0) == CONST_INT)
845 return plus_constant_for_output (x1, INTVAL (x0));
846 else if (GET_CODE (x1) == CONST_INT)
847 return plus_constant_for_output (x0, INTVAL (x1));
848 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
852 /* This gives us much better alias analysis when called from
853 the loop optimizer. Note we want to leave the original
854 MEM alone, but need to return the canonicalized MEM with
855 all the flags with their original values. */
856 else if (GET_CODE (x) == MEM)
858 rtx addr = canon_rtx (XEXP (x, 0));
860 if (addr != XEXP (x, 0))
862 rtx new = gen_rtx_MEM (GET_MODE (x), addr);
864 MEM_COPY_ATTRIBUTES (new, x);
871 /* Return 1 if X and Y are identical-looking rtx's.
873 We use the data in reg_known_value above to see if two registers with
874 different numbers are, in fact, equivalent. */
877 rtx_equal_for_memref_p (x, y)
882 register enum rtx_code code;
883 register const char *fmt;
885 if (x == 0 && y == 0)
887 if (x == 0 || y == 0)
897 /* Rtx's of different codes cannot be equal. */
898 if (code != GET_CODE (y))
901 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
902 (REG:SI x) and (REG:HI x) are NOT equivalent. */
904 if (GET_MODE (x) != GET_MODE (y))
907 /* Some RTL can be compared without a recursive examination. */
911 return REGNO (x) == REGNO (y);
914 return XEXP (x, 0) == XEXP (y, 0);
917 return XSTR (x, 0) == XSTR (y, 0);
921 /* There's no need to compare the contents of CONST_DOUBLEs or
922 CONST_INTs because pointer equality is a good enough
923 comparison for these nodes. */
927 return (REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0))
928 && XINT (x, 1) == XINT (y, 1));
934 /* For commutative operations, the RTX match if the operand match in any
935 order. Also handle the simple binary and unary cases without a loop. */
936 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
937 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
938 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
939 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
940 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
941 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
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 else if (GET_RTX_CLASS (code) == '1')
945 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
947 /* Compare the elements. If any pair of corresponding elements
948 fail to match, return 0 for the whole things.
950 Limit cases to types which actually appear in addresses. */
952 fmt = GET_RTX_FORMAT (code);
953 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
958 if (XINT (x, i) != XINT (y, i))
963 /* Two vectors must have the same length. */
964 if (XVECLEN (x, i) != XVECLEN (y, i))
967 /* And the corresponding elements must match. */
968 for (j = 0; j < XVECLEN (x, i); j++)
969 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
970 XVECEXP (y, i, j)) == 0)
975 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
979 /* This can happen for an asm which clobbers memory. */
983 /* It is believed that rtx's at this level will never
984 contain anything but integers and other rtx's,
985 except for within LABEL_REFs and SYMBOL_REFs. */
993 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
994 X and return it, or return 0 if none found. */
997 find_symbolic_term (x)
1001 register enum rtx_code code;
1002 register const char *fmt;
1004 code = GET_CODE (x);
1005 if (code == SYMBOL_REF || code == LABEL_REF)
1007 if (GET_RTX_CLASS (code) == 'o')
1010 fmt = GET_RTX_FORMAT (code);
1011 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1017 t = find_symbolic_term (XEXP (x, i));
1021 else if (fmt[i] == 'E')
1032 struct elt_loc_list *l;
1034 #if defined (FIND_BASE_TERM)
1035 /* Try machine-dependent ways to find the base term. */
1036 x = FIND_BASE_TERM (x);
1039 switch (GET_CODE (x))
1042 return REG_BASE_VALUE (x);
1045 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1051 return find_base_term (XEXP (x, 0));
1054 val = CSELIB_VAL_PTR (x);
1055 for (l = val->locs; l; l = l->next)
1056 if ((x = find_base_term (l->loc)) != 0)
1062 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1069 rtx tmp1 = XEXP (x, 0);
1070 rtx tmp2 = XEXP (x, 1);
1072 /* This is a litle bit tricky since we have to determine which of
1073 the two operands represents the real base address. Otherwise this
1074 routine may return the index register instead of the base register.
1076 That may cause us to believe no aliasing was possible, when in
1077 fact aliasing is possible.
1079 We use a few simple tests to guess the base register. Additional
1080 tests can certainly be added. For example, if one of the operands
1081 is a shift or multiply, then it must be the index register and the
1082 other operand is the base register. */
1084 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1085 return find_base_term (tmp2);
1087 /* If either operand is known to be a pointer, then use it
1088 to determine the base term. */
1089 if (REG_P (tmp1) && REG_POINTER (tmp1))
1090 return find_base_term (tmp1);
1092 if (REG_P (tmp2) && REG_POINTER (tmp2))
1093 return find_base_term (tmp2);
1095 /* Neither operand was known to be a pointer. Go ahead and find the
1096 base term for both operands. */
1097 tmp1 = find_base_term (tmp1);
1098 tmp2 = find_base_term (tmp2);
1100 /* If either base term is named object or a special address
1101 (like an argument or stack reference), then use it for the
1104 && (GET_CODE (tmp1) == SYMBOL_REF
1105 || GET_CODE (tmp1) == LABEL_REF
1106 || (GET_CODE (tmp1) == ADDRESS
1107 && GET_MODE (tmp1) != VOIDmode)))
1111 && (GET_CODE (tmp2) == SYMBOL_REF
1112 || GET_CODE (tmp2) == LABEL_REF
1113 || (GET_CODE (tmp2) == ADDRESS
1114 && GET_MODE (tmp2) != VOIDmode)))
1117 /* We could not determine which of the two operands was the
1118 base register and which was the index. So we can determine
1119 nothing from the base alias check. */
1124 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1125 return REG_BASE_VALUE (XEXP (x, 0));
1133 return REG_BASE_VALUE (frame_pointer_rtx);
1140 /* Return 0 if the addresses X and Y are known to point to different
1141 objects, 1 if they might be pointers to the same object. */
1144 base_alias_check (x, y, x_mode, y_mode)
1146 enum machine_mode x_mode, y_mode;
1148 rtx x_base = find_base_term (x);
1149 rtx y_base = find_base_term (y);
1151 /* If the address itself has no known base see if a known equivalent
1152 value has one. If either address still has no known base, nothing
1153 is known about aliasing. */
1158 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1161 x_base = find_base_term (x_c);
1169 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1172 y_base = find_base_term (y_c);
1177 /* If the base addresses are equal nothing is known about aliasing. */
1178 if (rtx_equal_p (x_base, y_base))
1181 /* The base addresses of the read and write are different expressions.
1182 If they are both symbols and they are not accessed via AND, there is
1183 no conflict. We can bring knowledge of object alignment into play
1184 here. For example, on alpha, "char a, b;" can alias one another,
1185 though "char a; long b;" cannot. */
1186 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1188 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1190 if (GET_CODE (x) == AND
1191 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1192 || GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1194 if (GET_CODE (y) == AND
1195 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1196 || GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1198 /* Differing symbols never alias. */
1202 /* If one address is a stack reference there can be no alias:
1203 stack references using different base registers do not alias,
1204 a stack reference can not alias a parameter, and a stack reference
1205 can not alias a global. */
1206 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1207 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1210 if (! flag_argument_noalias)
1213 if (flag_argument_noalias > 1)
1216 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1217 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1220 /* Convert the address X into something we can use. This is done by returning
1221 it unchanged unless it is a value; in the latter case we call cselib to get
1222 a more useful rtx. */
1229 struct elt_loc_list *l;
1231 if (GET_CODE (x) != VALUE)
1233 v = CSELIB_VAL_PTR (x);
1234 for (l = v->locs; l; l = l->next)
1235 if (CONSTANT_P (l->loc))
1237 for (l = v->locs; l; l = l->next)
1238 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1241 return v->locs->loc;
1245 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1246 where SIZE is the size in bytes of the memory reference. If ADDR
1247 is not modified by the memory reference then ADDR is returned. */
1250 addr_side_effect_eval (addr, size, n_refs)
1257 switch (GET_CODE (addr))
1260 offset = (n_refs + 1) * size;
1263 offset = -(n_refs + 1) * size;
1266 offset = n_refs * size;
1269 offset = -n_refs * size;
1277 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1279 addr = XEXP (addr, 0);
1284 /* Return nonzero if X and Y (memory addresses) could reference the
1285 same location in memory. C is an offset accumulator. When
1286 C is nonzero, we are testing aliases between X and Y + C.
1287 XSIZE is the size in bytes of the X reference,
1288 similarly YSIZE is the size in bytes for Y.
1290 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1291 referenced (the reference was BLKmode), so make the most pessimistic
1294 If XSIZE or YSIZE is negative, we may access memory outside the object
1295 being referenced as a side effect. This can happen when using AND to
1296 align memory references, as is done on the Alpha.
1298 Nice to notice that varying addresses cannot conflict with fp if no
1299 local variables had their addresses taken, but that's too hard now. */
1302 memrefs_conflict_p (xsize, x, ysize, y, c)
1307 if (GET_CODE (x) == VALUE)
1309 if (GET_CODE (y) == VALUE)
1311 if (GET_CODE (x) == HIGH)
1313 else if (GET_CODE (x) == LO_SUM)
1316 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1317 if (GET_CODE (y) == HIGH)
1319 else if (GET_CODE (y) == LO_SUM)
1322 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1324 if (rtx_equal_for_memref_p (x, y))
1326 if (xsize <= 0 || ysize <= 0)
1328 if (c >= 0 && xsize > c)
1330 if (c < 0 && ysize+c > 0)
1335 /* This code used to check for conflicts involving stack references and
1336 globals but the base address alias code now handles these cases. */
1338 if (GET_CODE (x) == PLUS)
1340 /* The fact that X is canonicalized means that this
1341 PLUS rtx is canonicalized. */
1342 rtx x0 = XEXP (x, 0);
1343 rtx x1 = XEXP (x, 1);
1345 if (GET_CODE (y) == PLUS)
1347 /* The fact that Y is canonicalized means that this
1348 PLUS rtx is canonicalized. */
1349 rtx y0 = XEXP (y, 0);
1350 rtx y1 = XEXP (y, 1);
1352 if (rtx_equal_for_memref_p (x1, y1))
1353 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1354 if (rtx_equal_for_memref_p (x0, y0))
1355 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1356 if (GET_CODE (x1) == CONST_INT)
1358 if (GET_CODE (y1) == CONST_INT)
1359 return memrefs_conflict_p (xsize, x0, ysize, y0,
1360 c - INTVAL (x1) + INTVAL (y1));
1362 return memrefs_conflict_p (xsize, x0, ysize, y,
1365 else if (GET_CODE (y1) == CONST_INT)
1366 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1370 else if (GET_CODE (x1) == CONST_INT)
1371 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1373 else if (GET_CODE (y) == PLUS)
1375 /* The fact that Y is canonicalized means that this
1376 PLUS rtx is canonicalized. */
1377 rtx y0 = XEXP (y, 0);
1378 rtx y1 = XEXP (y, 1);
1380 if (GET_CODE (y1) == CONST_INT)
1381 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1386 if (GET_CODE (x) == GET_CODE (y))
1387 switch (GET_CODE (x))
1391 /* Handle cases where we expect the second operands to be the
1392 same, and check only whether the first operand would conflict
1395 rtx x1 = canon_rtx (XEXP (x, 1));
1396 rtx y1 = canon_rtx (XEXP (y, 1));
1397 if (! rtx_equal_for_memref_p (x1, y1))
1399 x0 = canon_rtx (XEXP (x, 0));
1400 y0 = canon_rtx (XEXP (y, 0));
1401 if (rtx_equal_for_memref_p (x0, y0))
1402 return (xsize == 0 || ysize == 0
1403 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1405 /* Can't properly adjust our sizes. */
1406 if (GET_CODE (x1) != CONST_INT)
1408 xsize /= INTVAL (x1);
1409 ysize /= INTVAL (x1);
1411 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1415 /* Are these registers known not to be equal? */
1416 if (alias_invariant)
1418 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1419 rtx i_x, i_y; /* invariant relationships of X and Y */
1421 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1422 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1424 if (i_x == 0 && i_y == 0)
1427 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1428 ysize, i_y ? i_y : y, c))
1437 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1438 as an access with indeterminate size. Assume that references
1439 besides AND are aligned, so if the size of the other reference is
1440 at least as large as the alignment, assume no other overlap. */
1441 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1443 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1445 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1447 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1449 /* ??? If we are indexing far enough into the array/structure, we
1450 may yet be able to determine that we can not overlap. But we
1451 also need to that we are far enough from the end not to overlap
1452 a following reference, so we do nothing with that for now. */
1453 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1455 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1458 if (GET_CODE (x) == ADDRESSOF)
1460 if (y == frame_pointer_rtx
1461 || GET_CODE (y) == ADDRESSOF)
1462 return xsize <= 0 || ysize <= 0;
1464 if (GET_CODE (y) == ADDRESSOF)
1466 if (x == frame_pointer_rtx)
1467 return xsize <= 0 || ysize <= 0;
1472 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1474 c += (INTVAL (y) - INTVAL (x));
1475 return (xsize <= 0 || ysize <= 0
1476 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1479 if (GET_CODE (x) == CONST)
1481 if (GET_CODE (y) == CONST)
1482 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1483 ysize, canon_rtx (XEXP (y, 0)), c);
1485 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1488 if (GET_CODE (y) == CONST)
1489 return memrefs_conflict_p (xsize, x, ysize,
1490 canon_rtx (XEXP (y, 0)), c);
1493 return (xsize <= 0 || ysize <= 0
1494 || (rtx_equal_for_memref_p (x, y)
1495 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1502 /* Functions to compute memory dependencies.
1504 Since we process the insns in execution order, we can build tables
1505 to keep track of what registers are fixed (and not aliased), what registers
1506 are varying in known ways, and what registers are varying in unknown
1509 If both memory references are volatile, then there must always be a
1510 dependence between the two references, since their order can not be
1511 changed. A volatile and non-volatile reference can be interchanged
1514 A MEM_IN_STRUCT reference at a non-AND varying address can never
1515 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1516 also must allow AND addresses, because they may generate accesses
1517 outside the object being referenced. This is used to generate
1518 aligned addresses from unaligned addresses, for instance, the alpha
1519 storeqi_unaligned pattern. */
1521 /* Read dependence: X is read after read in MEM takes place. There can
1522 only be a dependence here if both reads are volatile. */
1525 read_dependence (mem, x)
1529 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1532 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1533 MEM2 is a reference to a structure at a varying address, or returns
1534 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1535 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1536 to decide whether or not an address may vary; it should return
1537 nonzero whenever variation is possible.
1538 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1541 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1543 rtx mem1_addr, mem2_addr;
1544 int (*varies_p) PARAMS ((rtx));
1546 if (! flag_strict_aliasing)
1549 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1550 && !varies_p (mem1_addr) && varies_p (mem2_addr))
1551 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1555 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1556 && varies_p (mem1_addr) && !varies_p (mem2_addr))
1557 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1564 /* Returns nonzero if something about the mode or address format MEM1
1565 indicates that it might well alias *anything*. */
1568 aliases_everything_p (mem)
1571 if (GET_CODE (XEXP (mem, 0)) == AND)
1572 /* If the address is an AND, its very hard to know at what it is
1573 actually pointing. */
1579 /* True dependence: X is read after store in MEM takes place. */
1582 true_dependence (mem, mem_mode, x, varies)
1584 enum machine_mode mem_mode;
1586 int (*varies) PARAMS ((rtx));
1588 register rtx x_addr, mem_addr;
1591 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1594 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1597 /* Unchanging memory can't conflict with non-unchanging memory.
1598 A non-unchanging read can conflict with a non-unchanging write.
1599 An unchanging read can conflict with an unchanging write since
1600 there may be a single store to this address to initialize it.
1601 Note that an unchanging store can conflict with a non-unchanging read
1602 since we have to make conservative assumptions when we have a
1603 record with readonly fields and we are copying the whole thing.
1604 Just fall through to the code below to resolve potential conflicts.
1605 This won't handle all cases optimally, but the possible performance
1606 loss should be negligible. */
1607 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1610 if (mem_mode == VOIDmode)
1611 mem_mode = GET_MODE (mem);
1613 x_addr = get_addr (XEXP (x, 0));
1614 mem_addr = get_addr (XEXP (mem, 0));
1616 base = find_base_term (x_addr);
1617 if (base && (GET_CODE (base) == LABEL_REF
1618 || (GET_CODE (base) == SYMBOL_REF
1619 && CONSTANT_POOL_ADDRESS_P (base))))
1622 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1625 x_addr = canon_rtx (x_addr);
1626 mem_addr = canon_rtx (mem_addr);
1628 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1629 SIZE_FOR_MODE (x), x_addr, 0))
1632 if (aliases_everything_p (x))
1635 /* We cannot use aliases_everyting_p to test MEM, since we must look
1636 at MEM_MODE, rather than GET_MODE (MEM). */
1637 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1640 /* In true_dependence we also allow BLKmode to alias anything. Why
1641 don't we do this in anti_dependence and output_dependence? */
1642 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1645 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1649 /* Returns non-zero if a write to X might alias a previous read from
1650 (or, if WRITEP is non-zero, a write to) MEM. */
1653 write_dependence_p (mem, x, writep)
1658 rtx x_addr, mem_addr;
1662 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1665 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1668 /* Unchanging memory can't conflict with non-unchanging memory. */
1669 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1672 /* If MEM is an unchanging read, then it can't possibly conflict with
1673 the store to X, because there is at most one store to MEM, and it must
1674 have occurred somewhere before MEM. */
1675 if (! writep && RTX_UNCHANGING_P (mem))
1678 x_addr = get_addr (XEXP (x, 0));
1679 mem_addr = get_addr (XEXP (mem, 0));
1683 base = find_base_term (mem_addr);
1684 if (base && (GET_CODE (base) == LABEL_REF
1685 || (GET_CODE (base) == SYMBOL_REF
1686 && CONSTANT_POOL_ADDRESS_P (base))))
1690 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1694 x_addr = canon_rtx (x_addr);
1695 mem_addr = canon_rtx (mem_addr);
1697 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1698 SIZE_FOR_MODE (x), x_addr, 0))
1702 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1705 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1706 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1709 /* Anti dependence: X is written after read in MEM takes place. */
1712 anti_dependence (mem, x)
1716 return write_dependence_p (mem, x, /*writep=*/0);
1719 /* Output dependence: X is written after store in MEM takes place. */
1722 output_dependence (mem, x)
1726 return write_dependence_p (mem, x, /*writep=*/1);
1729 /* Returns non-zero if X mentions something which is not
1730 local to the function and is not constant. */
1733 nonlocal_mentioned_p (x)
1737 register RTX_CODE code;
1740 code = GET_CODE (x);
1742 if (GET_RTX_CLASS (code) == 'i')
1744 /* Constant functions can be constant if they don't use
1745 scratch memory used to mark function w/o side effects. */
1746 if (code == CALL_INSN && CONST_CALL_P (x))
1748 x = CALL_INSN_FUNCTION_USAGE (x);
1754 code = GET_CODE (x);
1760 if (GET_CODE (SUBREG_REG (x)) == REG)
1762 /* Global registers are not local. */
1763 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1764 && global_regs[REGNO (SUBREG_REG (x)) + SUBREG_WORD (x)])
1772 /* Global registers are not local. */
1773 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1787 /* Constants in the function's constants pool are constant. */
1788 if (CONSTANT_POOL_ADDRESS_P (x))
1793 /* Non-constant calls and recursion are not local. */
1797 /* Be overly conservative and consider any volatile memory
1798 reference as not local. */
1799 if (MEM_VOLATILE_P (x))
1801 base = find_base_term (XEXP (x, 0));
1804 /* A Pmode ADDRESS could be a reference via the structure value
1805 address or static chain. Such memory references are nonlocal.
1807 Thus, we have to examine the contents of the ADDRESS to find
1808 out if this is a local reference or not. */
1809 if (GET_CODE (base) == ADDRESS
1810 && GET_MODE (base) == Pmode
1811 && (XEXP (base, 0) == stack_pointer_rtx
1812 || XEXP (base, 0) == arg_pointer_rtx
1813 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1814 || XEXP (base, 0) == hard_frame_pointer_rtx
1816 || XEXP (base, 0) == frame_pointer_rtx))
1818 /* Constants in the function's constant pool are constant. */
1819 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
1824 case UNSPEC_VOLATILE:
1829 if (MEM_VOLATILE_P (x))
1838 /* Recursively scan the operands of this expression. */
1841 register const char *fmt = GET_RTX_FORMAT (code);
1844 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1846 if (fmt[i] == 'e' && XEXP (x, i))
1848 if (nonlocal_mentioned_p (XEXP (x, i)))
1851 else if (fmt[i] == 'E')
1854 for (j = 0; j < XVECLEN (x, i); j++)
1855 if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
1864 /* Return non-zero if a loop (natural or otherwise) is present.
1865 Inspired by Depth_First_Search_PP described in:
1867 Advanced Compiler Design and Implementation
1869 Morgan Kaufmann, 1997
1871 and heavily borrowed from flow_depth_first_order_compute. */
1884 /* Allocate the preorder and postorder number arrays. */
1885 pre = (int *) xcalloc (n_basic_blocks, sizeof (int));
1886 post = (int *) xcalloc (n_basic_blocks, sizeof (int));
1888 /* Allocate stack for back-tracking up CFG. */
1889 stack = (edge *) xmalloc ((n_basic_blocks + 1) * sizeof (edge));
1892 /* Allocate bitmap to track nodes that have been visited. */
1893 visited = sbitmap_alloc (n_basic_blocks);
1895 /* None of the nodes in the CFG have been visited yet. */
1896 sbitmap_zero (visited);
1898 /* Push the first edge on to the stack. */
1899 stack[sp++] = ENTRY_BLOCK_PTR->succ;
1907 /* Look at the edge on the top of the stack. */
1912 /* Check if the edge destination has been visited yet. */
1913 if (dest != EXIT_BLOCK_PTR && ! TEST_BIT (visited, dest->index))
1915 /* Mark that we have visited the destination. */
1916 SET_BIT (visited, dest->index);
1918 pre[dest->index] = prenum++;
1922 /* Since the DEST node has been visited for the first
1923 time, check its successors. */
1924 stack[sp++] = dest->succ;
1927 post[dest->index] = postnum++;
1931 if (dest != EXIT_BLOCK_PTR
1932 && pre[src->index] >= pre[dest->index]
1933 && post[dest->index] == 0)
1936 if (! e->succ_next && src != ENTRY_BLOCK_PTR)
1937 post[src->index] = postnum++;
1940 stack[sp - 1] = e->succ_next;
1949 sbitmap_free (visited);
1954 /* Mark the function if it is constant. */
1957 mark_constant_function ()
1960 int nonlocal_mentioned;
1962 if (TREE_PUBLIC (current_function_decl)
1963 || TREE_READONLY (current_function_decl)
1964 || DECL_IS_PURE (current_function_decl)
1965 || TREE_THIS_VOLATILE (current_function_decl)
1966 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
1969 /* A loop might not return which counts as a side effect. */
1973 nonlocal_mentioned = 0;
1975 init_alias_analysis ();
1977 /* Determine if this is a constant function. */
1979 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1980 if (INSN_P (insn) && nonlocal_mentioned_p (insn))
1982 nonlocal_mentioned = 1;
1986 end_alias_analysis ();
1988 /* Mark the function. */
1990 if (! nonlocal_mentioned)
1991 TREE_READONLY (current_function_decl) = 1;
1995 static HARD_REG_SET argument_registers;
2002 #ifndef OUTGOING_REGNO
2003 #define OUTGOING_REGNO(N) N
2005 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2006 /* Check whether this register can hold an incoming pointer
2007 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2008 numbers, so translate if necessary due to register windows. */
2009 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
2010 && HARD_REGNO_MODE_OK (i, Pmode))
2011 SET_HARD_REG_BIT (argument_registers, i);
2013 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
2016 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2020 init_alias_analysis ()
2022 int maxreg = max_reg_num ();
2025 register unsigned int ui;
2028 reg_known_value_size = maxreg;
2031 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
2032 - FIRST_PSEUDO_REGISTER;
2034 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
2035 - FIRST_PSEUDO_REGISTER;
2037 /* Overallocate reg_base_value to allow some growth during loop
2038 optimization. Loop unrolling can create a large number of
2040 reg_base_value_size = maxreg * 2;
2041 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
2042 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
2044 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
2045 reg_seen = (char *) xmalloc (reg_base_value_size);
2046 if (! reload_completed && flag_unroll_loops)
2048 /* ??? Why are we realloc'ing if we're just going to zero it? */
2049 alias_invariant = (rtx *)xrealloc (alias_invariant,
2050 reg_base_value_size * sizeof (rtx));
2051 memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
2055 /* The basic idea is that each pass through this loop will use the
2056 "constant" information from the previous pass to propagate alias
2057 information through another level of assignments.
2059 This could get expensive if the assignment chains are long. Maybe
2060 we should throttle the number of iterations, possibly based on
2061 the optimization level or flag_expensive_optimizations.
2063 We could propagate more information in the first pass by making use
2064 of REG_N_SETS to determine immediately that the alias information
2065 for a pseudo is "constant".
2067 A program with an uninitialized variable can cause an infinite loop
2068 here. Instead of doing a full dataflow analysis to detect such problems
2069 we just cap the number of iterations for the loop.
2071 The state of the arrays for the set chain in question does not matter
2072 since the program has undefined behavior. */
2077 /* Assume nothing will change this iteration of the loop. */
2080 /* We want to assign the same IDs each iteration of this loop, so
2081 start counting from zero each iteration of the loop. */
2084 /* We're at the start of the funtion each iteration through the
2085 loop, so we're copying arguments. */
2086 copying_arguments = 1;
2088 /* Wipe the potential alias information clean for this pass. */
2089 memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
2091 /* Wipe the reg_seen array clean. */
2092 memset ((char *) reg_seen, 0, reg_base_value_size);
2094 /* Mark all hard registers which may contain an address.
2095 The stack, frame and argument pointers may contain an address.
2096 An argument register which can hold a Pmode value may contain
2097 an address even if it is not in BASE_REGS.
2099 The address expression is VOIDmode for an argument and
2100 Pmode for other registers. */
2102 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
2103 if (TEST_HARD_REG_BIT (argument_registers, i))
2104 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
2105 gen_rtx_REG (Pmode, i));
2107 new_reg_base_value[STACK_POINTER_REGNUM]
2108 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
2109 new_reg_base_value[ARG_POINTER_REGNUM]
2110 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
2111 new_reg_base_value[FRAME_POINTER_REGNUM]
2112 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
2113 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
2114 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2115 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2118 /* Walk the insns adding values to the new_reg_base_value array. */
2119 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2125 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2126 /* The prologue/epilouge insns are not threaded onto the
2127 insn chain until after reload has completed. Thus,
2128 there is no sense wasting time checking if INSN is in
2129 the prologue/epilogue until after reload has completed. */
2130 if (reload_completed
2131 && prologue_epilogue_contains (insn))
2135 /* If this insn has a noalias note, process it, Otherwise,
2136 scan for sets. A simple set will have no side effects
2137 which could change the base value of any other register. */
2139 if (GET_CODE (PATTERN (insn)) == SET
2140 && REG_NOTES (insn) != 0
2141 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2142 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2144 note_stores (PATTERN (insn), record_set, NULL);
2146 set = single_set (insn);
2149 && GET_CODE (SET_DEST (set)) == REG
2150 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
2151 && REG_NOTES (insn) != 0
2152 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2153 && REG_N_SETS (REGNO (SET_DEST (set))) == 1)
2154 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2155 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2156 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2158 int regno = REGNO (SET_DEST (set));
2159 reg_known_value[regno] = XEXP (note, 0);
2160 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2163 else if (GET_CODE (insn) == NOTE
2164 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2165 copying_arguments = 0;
2168 /* Now propagate values from new_reg_base_value to reg_base_value. */
2169 for (ui = 0; ui < reg_base_value_size; ui++)
2171 if (new_reg_base_value[ui]
2172 && new_reg_base_value[ui] != reg_base_value[ui]
2173 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2175 reg_base_value[ui] = new_reg_base_value[ui];
2180 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2182 /* Fill in the remaining entries. */
2183 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2184 if (reg_known_value[i] == 0)
2185 reg_known_value[i] = regno_reg_rtx[i];
2187 /* Simplify the reg_base_value array so that no register refers to
2188 another register, except to special registers indirectly through
2189 ADDRESS expressions.
2191 In theory this loop can take as long as O(registers^2), but unless
2192 there are very long dependency chains it will run in close to linear
2195 This loop may not be needed any longer now that the main loop does
2196 a better job at propagating alias information. */
2202 for (ui = 0; ui < reg_base_value_size; ui++)
2204 rtx base = reg_base_value[ui];
2205 if (base && GET_CODE (base) == REG)
2207 unsigned int base_regno = REGNO (base);
2208 if (base_regno == ui) /* register set from itself */
2209 reg_base_value[ui] = 0;
2211 reg_base_value[ui] = reg_base_value[base_regno];
2216 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2219 free (new_reg_base_value);
2220 new_reg_base_value = 0;
2226 end_alias_analysis ()
2228 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2229 reg_known_value = 0;
2230 reg_known_value_size = 0;
2231 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2232 reg_known_equiv_p = 0;
2235 ggc_del_root (reg_base_value);
2236 free (reg_base_value);
2239 reg_base_value_size = 0;
2240 if (alias_invariant)
2242 free (alias_invariant);
2243 alias_invariant = 0;