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"
36 #include "splay-tree.h"
39 /* The alias sets assigned to MEMs assist the back-end in determining
40 which MEMs can alias which other MEMs. In general, two MEMs in
41 different alias sets cannot alias each other, with one important
42 exception. Consider something like:
44 struct S {int i; double d; };
46 a store to an `S' can alias something of either type `int' or type
47 `double'. (However, a store to an `int' cannot alias a `double'
48 and vice versa.) We indicate this via a tree structure that looks
56 (The arrows are directed and point downwards.)
57 In this situation we say the alias set for `struct S' is the
58 `superset' and that those for `int' and `double' are `subsets'.
60 To see whether two alias sets can point to the same memory, we must
61 see if either alias set is a subset of the other. We need not trace
62 past immediate decendents, however, since we propagate all
63 grandchildren up one level.
65 Alias set zero is implicitly a superset of all other alias sets.
66 However, this is no actual entry for alias set zero. It is an
67 error to attempt to explicitly construct a subset of zero. */
69 typedef struct alias_set_entry
71 /* The alias set number, as stored in MEM_ALIAS_SET. */
72 HOST_WIDE_INT alias_set;
74 /* The children of the alias set. These are not just the immediate
75 children, but, in fact, all decendents. So, if we have:
77 struct T { struct S s; float f; }
79 continuing our example above, the children here will be all of
80 `int', `double', `float', and `struct S'. */
83 /* Nonzero if would have a child of zero: this effectively makes this
84 alias set the same as alias set zero. */
88 static int rtx_equal_for_memref_p PARAMS ((rtx, rtx));
89 static rtx find_symbolic_term PARAMS ((rtx));
90 static rtx get_addr PARAMS ((rtx));
91 static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx,
93 static void record_set PARAMS ((rtx, rtx, void *));
94 static rtx find_base_term PARAMS ((rtx));
95 static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode,
97 static rtx find_base_value PARAMS ((rtx));
98 static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx));
99 static int insert_subset_children PARAMS ((splay_tree_node, void*));
100 static tree find_base_decl PARAMS ((tree));
101 static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT));
102 static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx,
104 static int aliases_everything_p PARAMS ((rtx));
105 static int write_dependence_p PARAMS ((rtx, rtx, int));
106 static int nonlocal_reference_p PARAMS ((rtx));
108 /* Set up all info needed to perform alias analysis on memory references. */
110 /* Returns the size in bytes of the mode of X. */
111 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
113 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
114 different alias sets. We ignore alias sets in functions making use
115 of variable arguments because the va_arg macros on some systems are
117 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
118 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
120 /* Cap the number of passes we make over the insns propagating alias
121 information through set chains. 10 is a completely arbitrary choice. */
122 #define MAX_ALIAS_LOOP_PASSES 10
124 /* reg_base_value[N] gives an address to which register N is related.
125 If all sets after the first add or subtract to the current value
126 or otherwise modify it so it does not point to a different top level
127 object, reg_base_value[N] is equal to the address part of the source
130 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
131 expressions represent certain special values: function arguments and
132 the stack, frame, and argument pointers.
134 The contents of an ADDRESS is not normally used, the mode of the
135 ADDRESS determines whether the ADDRESS is a function argument or some
136 other special value. Pointer equality, not rtx_equal_p, determines whether
137 two ADDRESS expressions refer to the same base address.
139 The only use of the contents of an ADDRESS is for determining if the
140 current function performs nonlocal memory memory references for the
141 purposes of marking the function as a constant function. */
143 static rtx *reg_base_value;
144 static rtx *new_reg_base_value;
145 static unsigned int reg_base_value_size; /* size of reg_base_value array */
147 #define REG_BASE_VALUE(X) \
148 (REGNO (X) < reg_base_value_size ? reg_base_value[REGNO (X)] : 0)
150 /* Vector of known invariant relationships between registers. Set in
151 loop unrolling. Indexed by register number, if nonzero the value
152 is an expression describing this register in terms of another.
154 The length of this array is REG_BASE_VALUE_SIZE.
156 Because this array contains only pseudo registers it has no effect
158 static rtx *alias_invariant;
160 /* Vector indexed by N giving the initial (unchanging) value known for
161 pseudo-register N. This array is initialized in
162 init_alias_analysis, and does not change until end_alias_analysis
164 rtx *reg_known_value;
166 /* Indicates number of valid entries in reg_known_value. */
167 static unsigned int reg_known_value_size;
169 /* Vector recording for each reg_known_value whether it is due to a
170 REG_EQUIV note. Future passes (viz., reload) may replace the
171 pseudo with the equivalent expression and so we account for the
172 dependences that would be introduced if that happens.
174 The REG_EQUIV notes created in assign_parms may mention the arg
175 pointer, and there are explicit insns in the RTL that modify the
176 arg pointer. Thus we must ensure that such insns don't get
177 scheduled across each other because that would invalidate the
178 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
179 wrong, but solving the problem in the scheduler will likely give
180 better code, so we do it here. */
181 char *reg_known_equiv_p;
183 /* True when scanning insns from the start of the rtl to the
184 NOTE_INSN_FUNCTION_BEG note. */
185 static int copying_arguments;
187 /* The splay-tree used to store the various alias set entries. */
188 static splay_tree alias_sets;
190 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
191 such an entry, or NULL otherwise. */
193 static alias_set_entry
194 get_alias_set_entry (alias_set)
195 HOST_WIDE_INT alias_set;
198 = splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
200 return sn != 0 ? ((alias_set_entry) sn->value) : 0;
203 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
204 the two MEMs cannot alias each other. */
207 mems_in_disjoint_alias_sets_p (mem1, mem2)
213 #ifdef ENABLE_CHECKING
214 /* Perform a basic sanity check. Namely, that there are no alias sets
215 if we're not using strict aliasing. This helps to catch bugs
216 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
217 where a MEM is allocated in some way other than by the use of
218 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
219 use alias sets to indicate that spilled registers cannot alias each
220 other, we might need to remove this check. */
221 if (! flag_strict_aliasing
222 && (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
226 /* The code used in varargs macros are often not conforming ANSI C,
227 which can trick the compiler into making incorrect aliasing
228 assumptions in these functions. So, we don't use alias sets in
229 such a function. FIXME: This should be moved into the front-end;
230 it is a language-dependent notion, and there's no reason not to
231 still use these checks to handle globals. */
232 if (current_function_stdarg || current_function_varargs)
235 /* If have no alias set information for one of the MEMs, we have to assume
236 it can alias anything. */
237 if (MEM_ALIAS_SET (mem1) == 0 || MEM_ALIAS_SET (mem2) == 0)
240 /* If the two alias sets are the same, they may alias. */
241 if (MEM_ALIAS_SET (mem1) == MEM_ALIAS_SET (mem2))
244 /* See if the first alias set is a subset of the second. */
245 ase = get_alias_set_entry (MEM_ALIAS_SET (mem1));
247 && (ase->has_zero_child
248 || splay_tree_lookup (ase->children,
249 (splay_tree_key) MEM_ALIAS_SET (mem2))))
252 /* Now do the same, but with the alias sets reversed. */
253 ase = get_alias_set_entry (MEM_ALIAS_SET (mem2));
255 && (ase->has_zero_child
256 || splay_tree_lookup (ase->children,
257 (splay_tree_key) MEM_ALIAS_SET (mem1))))
260 /* The two MEMs are in distinct alias sets, and neither one is the
261 child of the other. Therefore, they cannot alias. */
265 /* Insert the NODE into the splay tree given by DATA. Used by
266 record_alias_subset via splay_tree_foreach. */
269 insert_subset_children (node, data)
270 splay_tree_node node;
273 splay_tree_insert ((splay_tree) data, node->key, node->value);
278 /* T is an expression with pointer type. Find the DECL on which this
279 expression is based. (For example, in `a[i]' this would be `a'.)
280 If there is no such DECL, or a unique decl cannot be determined,
281 NULL_TREE is retured. */
289 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
292 /* If this is a declaration, return it. */
293 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
296 /* Handle general expressions. It would be nice to deal with
297 COMPONENT_REFs here. If we could tell that `a' and `b' were the
298 same, then `a->f' and `b->f' are also the same. */
299 switch (TREE_CODE_CLASS (TREE_CODE (t)))
302 return find_base_decl (TREE_OPERAND (t, 0));
305 /* Return 0 if found in neither or both are the same. */
306 d0 = find_base_decl (TREE_OPERAND (t, 0));
307 d1 = find_base_decl (TREE_OPERAND (t, 1));
318 d0 = find_base_decl (TREE_OPERAND (t, 0));
319 d1 = find_base_decl (TREE_OPERAND (t, 1));
320 d0 = find_base_decl (TREE_OPERAND (t, 0));
321 d2 = find_base_decl (TREE_OPERAND (t, 2));
323 /* Set any nonzero values from the last, then from the first. */
324 if (d1 == 0) d1 = d2;
325 if (d0 == 0) d0 = d1;
326 if (d1 == 0) d1 = d0;
327 if (d2 == 0) d2 = d1;
329 /* At this point all are nonzero or all are zero. If all three are the
330 same, return it. Otherwise, return zero. */
331 return (d0 == d1 && d1 == d2) ? d0 : 0;
338 /* Return the alias set for T, which may be either a type or an
339 expression. Call language-specific routine for help, if needed. */
348 /* If we're not doing any alias analysis, just assume everything
349 aliases everything else. Also return 0 if this or its type is
351 if (! flag_strict_aliasing || t == error_mark_node
353 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
356 /* We can be passed either an expression or a type. This and the
357 language-specific routine may make mutually-recursive calls to
358 each other to figure out what to do. At each juncture, we see if
359 this is a tree that the language may need to handle specially.
360 First handle things that aren't types and start by removing nops
361 since we care only about the actual object. */
364 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
365 || TREE_CODE (t) == NON_LVALUE_EXPR)
366 t = TREE_OPERAND (t, 0);
368 /* Now give the language a chance to do something but record what we
369 gave it this time. */
371 if ((set = lang_get_alias_set (t)) != -1)
374 /* Now loop the same way as get_inner_reference and get the alias
375 set to use. Pick up the outermost object that we could have
379 /* Unnamed bitfields are not an addressable object. */
380 if (TREE_CODE (t) == BIT_FIELD_REF)
382 else if (TREE_CODE (t) == COMPONENT_REF)
384 if (! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
385 /* Stop at an adressable decl. */
388 else if (TREE_CODE (t) == ARRAY_REF)
390 if (! TYPE_NONALIASED_COMPONENT
391 (TREE_TYPE (TREE_OPERAND (t, 0))))
392 /* Stop at an addresssable array element. */
395 else if (TREE_CODE (t) != NON_LVALUE_EXPR
396 && ! ((TREE_CODE (t) == NOP_EXPR
397 || TREE_CODE (t) == CONVERT_EXPR)
398 && (TYPE_MODE (TREE_TYPE (t))
399 == TYPE_MODE (TREE_TYPE (TREE_OPERAND (t, 0))))))
400 /* Stop if not one of above and not mode-preserving conversion. */
403 t = TREE_OPERAND (t, 0);
406 if (TREE_CODE (t) == INDIRECT_REF)
408 /* Check for accesses through restrict-qualified pointers. */
409 tree decl = find_base_decl (TREE_OPERAND (t, 0));
411 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
412 /* We use the alias set indicated in the declaration. */
413 return DECL_POINTER_ALIAS_SET (decl);
415 /* If we have an INDIRECT_REF via a void pointer, we don't
416 know anything about what that might alias. */
417 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
421 /* Give the language another chance to do something special. */
423 && (set = lang_get_alias_set (t)) != -1)
426 /* Now all we care about is the type. */
430 /* Variant qualifiers don't affect the alias set, so get the main
431 variant. If this is a type with a known alias set, return it. */
432 t = TYPE_MAIN_VARIANT (t);
433 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
434 return TYPE_ALIAS_SET (t);
436 /* See if the language has special handling for this type. */
437 if ((set = lang_get_alias_set (t)) != -1)
439 /* If the alias set is now known, we are done. */
440 if (TYPE_ALIAS_SET_KNOWN_P (t))
441 return TYPE_ALIAS_SET (t);
444 /* There are no objects of FUNCTION_TYPE, so there's no point in
445 using up an alias set for them. (There are, of course, pointers
446 and references to functions, but that's different.) */
447 else if (TREE_CODE (t) == FUNCTION_TYPE)
450 /* Otherwise make a new alias set for this type. */
451 set = new_alias_set ();
453 TYPE_ALIAS_SET (t) = set;
455 /* If this is an aggregate type, we must record any component aliasing
457 if (AGGREGATE_TYPE_P (t))
458 record_component_aliases (t);
463 /* Return a brand-new alias set. */
468 static HOST_WIDE_INT last_alias_set;
470 if (flag_strict_aliasing)
471 return ++last_alias_set;
476 /* Indicate that things in SUBSET can alias things in SUPERSET, but
477 not vice versa. For example, in C, a store to an `int' can alias a
478 structure containing an `int', but not vice versa. Here, the
479 structure would be the SUPERSET and `int' the SUBSET. This
480 function should be called only once per SUPERSET/SUBSET pair.
482 It is illegal for SUPERSET to be zero; everything is implicitly a
483 subset of alias set zero. */
486 record_alias_subset (superset, subset)
487 HOST_WIDE_INT superset;
488 HOST_WIDE_INT subset;
490 alias_set_entry superset_entry;
491 alias_set_entry subset_entry;
496 superset_entry = get_alias_set_entry (superset);
497 if (superset_entry == 0)
499 /* Create an entry for the SUPERSET, so that we have a place to
500 attach the SUBSET. */
502 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
503 superset_entry->alias_set = superset;
504 superset_entry->children
505 = splay_tree_new (splay_tree_compare_ints, 0, 0);
506 superset_entry->has_zero_child = 0;
507 splay_tree_insert (alias_sets, (splay_tree_key) superset,
508 (splay_tree_value) superset_entry);
512 superset_entry->has_zero_child = 1;
515 subset_entry = get_alias_set_entry (subset);
516 /* If there is an entry for the subset, enter all of its children
517 (if they are not already present) as children of the SUPERSET. */
520 if (subset_entry->has_zero_child)
521 superset_entry->has_zero_child = 1;
523 splay_tree_foreach (subset_entry->children, insert_subset_children,
524 superset_entry->children);
527 /* Enter the SUBSET itself as a child of the SUPERSET. */
528 splay_tree_insert (superset_entry->children,
529 (splay_tree_key) subset, 0);
533 /* Record that component types of TYPE, if any, are part of that type for
534 aliasing purposes. For record types, we only record component types
535 for fields that are marked addressable. For array types, we always
536 record the component types, so the front end should not call this
537 function if the individual component aren't addressable. */
540 record_component_aliases (type)
543 HOST_WIDE_INT superset = get_alias_set (type);
549 switch (TREE_CODE (type))
552 if (! TYPE_NONALIASED_COMPONENT (type))
553 record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
558 case QUAL_UNION_TYPE:
559 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
560 if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
561 record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
569 /* Allocate an alias set for use in storing and reading from the varargs
573 get_varargs_alias_set ()
575 static HOST_WIDE_INT set = -1;
578 set = new_alias_set ();
583 /* Likewise, but used for the fixed portions of the frame, e.g., register
587 get_frame_alias_set ()
589 static HOST_WIDE_INT set = -1;
592 set = new_alias_set ();
597 /* Inside SRC, the source of a SET, find a base address. */
600 find_base_value (src)
603 switch (GET_CODE (src))
610 /* At the start of a function, argument registers have known base
611 values which may be lost later. Returning an ADDRESS
612 expression here allows optimization based on argument values
613 even when the argument registers are used for other purposes. */
614 if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments)
615 return new_reg_base_value[REGNO (src)];
617 /* If a pseudo has a known base value, return it. Do not do this
618 for hard regs since it can result in a circular dependency
619 chain for registers which have values at function entry.
621 The test above is not sufficient because the scheduler may move
622 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
623 if (REGNO (src) >= FIRST_PSEUDO_REGISTER
624 && (unsigned) REGNO (src) < reg_base_value_size
625 && reg_base_value[REGNO (src)])
626 return reg_base_value[REGNO (src)];
631 /* Check for an argument passed in memory. Only record in the
632 copying-arguments block; it is too hard to track changes
634 if (copying_arguments
635 && (XEXP (src, 0) == arg_pointer_rtx
636 || (GET_CODE (XEXP (src, 0)) == PLUS
637 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
638 return gen_rtx_ADDRESS (VOIDmode, src);
643 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
646 /* ... fall through ... */
651 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
653 /* If either operand is a REG, then see if we already have
654 a known value for it. */
655 if (GET_CODE (src_0) == REG)
657 temp = find_base_value (src_0);
662 if (GET_CODE (src_1) == REG)
664 temp = find_base_value (src_1);
669 /* Guess which operand is the base address:
670 If either operand is a symbol, then it is the base. If
671 either operand is a CONST_INT, then the other is the base. */
672 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
673 return find_base_value (src_0);
674 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
675 return find_base_value (src_1);
677 /* This might not be necessary anymore:
678 If either operand is a REG that is a known pointer, then it
680 else if (GET_CODE (src_0) == REG && REGNO_POINTER_FLAG (REGNO (src_0)))
681 return find_base_value (src_0);
682 else if (GET_CODE (src_1) == REG && REGNO_POINTER_FLAG (REGNO (src_1)))
683 return find_base_value (src_1);
689 /* The standard form is (lo_sum reg sym) so look only at the
691 return find_base_value (XEXP (src, 1));
694 /* If the second operand is constant set the base
695 address to the first operand. */
696 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
697 return find_base_value (XEXP (src, 0));
701 case SIGN_EXTEND: /* used for NT/Alpha pointers */
703 return find_base_value (XEXP (src, 0));
712 /* Called from init_alias_analysis indirectly through note_stores. */
714 /* While scanning insns to find base values, reg_seen[N] is nonzero if
715 register N has been set in this function. */
716 static char *reg_seen;
718 /* Addresses which are known not to alias anything else are identified
719 by a unique integer. */
720 static int unique_id;
723 record_set (dest, set, data)
725 void *data ATTRIBUTE_UNUSED;
727 register unsigned regno;
730 if (GET_CODE (dest) != REG)
733 regno = REGNO (dest);
735 if (regno >= reg_base_value_size)
740 /* A CLOBBER wipes out any old value but does not prevent a previously
741 unset register from acquiring a base address (i.e. reg_seen is not
743 if (GET_CODE (set) == CLOBBER)
745 new_reg_base_value[regno] = 0;
754 new_reg_base_value[regno] = 0;
758 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
759 GEN_INT (unique_id++));
763 /* This is not the first set. If the new value is not related to the
764 old value, forget the base value. Note that the following code is
766 extern int x, y; int *p = &x; p += (&y-&x);
767 ANSI C does not allow computing the difference of addresses
768 of distinct top level objects. */
769 if (new_reg_base_value[regno])
770 switch (GET_CODE (src))
775 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
776 new_reg_base_value[regno] = 0;
779 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
780 new_reg_base_value[regno] = 0;
783 new_reg_base_value[regno] = 0;
786 /* If this is the first set of a register, record the value. */
787 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
788 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
789 new_reg_base_value[regno] = find_base_value (src);
794 /* Called from loop optimization when a new pseudo-register is
795 created. It indicates that REGNO is being set to VAL. f INVARIANT
796 is true then this value also describes an invariant relationship
797 which can be used to deduce that two registers with unknown values
801 record_base_value (regno, val, invariant)
806 if (regno >= reg_base_value_size)
809 if (invariant && alias_invariant)
810 alias_invariant[regno] = val;
812 if (GET_CODE (val) == REG)
814 if (REGNO (val) < reg_base_value_size)
815 reg_base_value[regno] = reg_base_value[REGNO (val)];
820 reg_base_value[regno] = find_base_value (val);
823 /* Returns a canonical version of X, from the point of view alias
824 analysis. (For example, if X is a MEM whose address is a register,
825 and the register has a known value (say a SYMBOL_REF), then a MEM
826 whose address is the SYMBOL_REF is returned.) */
832 /* Recursively look for equivalences. */
833 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
834 && REGNO (x) < reg_known_value_size)
835 return reg_known_value[REGNO (x)] == x
836 ? x : canon_rtx (reg_known_value[REGNO (x)]);
837 else if (GET_CODE (x) == PLUS)
839 rtx x0 = canon_rtx (XEXP (x, 0));
840 rtx x1 = canon_rtx (XEXP (x, 1));
842 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
844 /* We can tolerate LO_SUMs being offset here; these
845 rtl are used for nothing other than comparisons. */
846 if (GET_CODE (x0) == CONST_INT)
847 return plus_constant_for_output (x1, INTVAL (x0));
848 else if (GET_CODE (x1) == CONST_INT)
849 return plus_constant_for_output (x0, INTVAL (x1));
850 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
854 /* This gives us much better alias analysis when called from
855 the loop optimizer. Note we want to leave the original
856 MEM alone, but need to return the canonicalized MEM with
857 all the flags with their original values. */
858 else if (GET_CODE (x) == MEM)
860 rtx addr = canon_rtx (XEXP (x, 0));
862 if (addr != XEXP (x, 0))
864 rtx new = gen_rtx_MEM (GET_MODE (x), addr);
866 MEM_COPY_ATTRIBUTES (new, x);
873 /* Return 1 if X and Y are identical-looking rtx's.
875 We use the data in reg_known_value above to see if two registers with
876 different numbers are, in fact, equivalent. */
879 rtx_equal_for_memref_p (x, y)
884 register enum rtx_code code;
885 register const char *fmt;
887 if (x == 0 && y == 0)
889 if (x == 0 || y == 0)
899 /* Rtx's of different codes cannot be equal. */
900 if (code != GET_CODE (y))
903 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
904 (REG:SI x) and (REG:HI x) are NOT equivalent. */
906 if (GET_MODE (x) != GET_MODE (y))
909 /* Some RTL can be compared without a recursive examination. */
913 return REGNO (x) == REGNO (y);
916 return XEXP (x, 0) == XEXP (y, 0);
919 return XSTR (x, 0) == XSTR (y, 0);
923 /* There's no need to compare the contents of CONST_DOUBLEs or
924 CONST_INTs because pointer equality is a good enough
925 comparison for these nodes. */
929 return (REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0))
930 && XINT (x, 1) == XINT (y, 1));
936 /* For commutative operations, the RTX match if the operand match in any
937 order. Also handle the simple binary and unary cases without a loop. */
938 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
939 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
940 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
941 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
942 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
943 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
944 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
945 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
946 else if (GET_RTX_CLASS (code) == '1')
947 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
949 /* Compare the elements. If any pair of corresponding elements
950 fail to match, return 0 for the whole things.
952 Limit cases to types which actually appear in addresses. */
954 fmt = GET_RTX_FORMAT (code);
955 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
960 if (XINT (x, i) != XINT (y, i))
965 /* Two vectors must have the same length. */
966 if (XVECLEN (x, i) != XVECLEN (y, i))
969 /* And the corresponding elements must match. */
970 for (j = 0; j < XVECLEN (x, i); j++)
971 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
972 XVECEXP (y, i, j)) == 0)
977 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
981 /* This can happen for an asm which clobbers memory. */
985 /* It is believed that rtx's at this level will never
986 contain anything but integers and other rtx's,
987 except for within LABEL_REFs and SYMBOL_REFs. */
995 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
996 X and return it, or return 0 if none found. */
999 find_symbolic_term (x)
1003 register enum rtx_code code;
1004 register const char *fmt;
1006 code = GET_CODE (x);
1007 if (code == SYMBOL_REF || code == LABEL_REF)
1009 if (GET_RTX_CLASS (code) == 'o')
1012 fmt = GET_RTX_FORMAT (code);
1013 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1019 t = find_symbolic_term (XEXP (x, i));
1023 else if (fmt[i] == 'E')
1034 struct elt_loc_list *l;
1036 #if defined (FIND_BASE_TERM)
1037 /* Try machine-dependent ways to find the base term. */
1038 x = FIND_BASE_TERM (x);
1041 switch (GET_CODE (x))
1044 return REG_BASE_VALUE (x);
1047 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1053 return find_base_term (XEXP (x, 0));
1056 val = CSELIB_VAL_PTR (x);
1057 for (l = val->locs; l; l = l->next)
1058 if ((x = find_base_term (l->loc)) != 0)
1064 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1071 rtx tmp1 = XEXP (x, 0);
1072 rtx tmp2 = XEXP (x, 1);
1074 /* This is a litle bit tricky since we have to determine which of
1075 the two operands represents the real base address. Otherwise this
1076 routine may return the index register instead of the base register.
1078 That may cause us to believe no aliasing was possible, when in
1079 fact aliasing is possible.
1081 We use a few simple tests to guess the base register. Additional
1082 tests can certainly be added. For example, if one of the operands
1083 is a shift or multiply, then it must be the index register and the
1084 other operand is the base register. */
1086 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
1087 return find_base_term (tmp2);
1089 /* If either operand is known to be a pointer, then use it
1090 to determine the base term. */
1091 if (REG_P (tmp1) && REGNO_POINTER_FLAG (REGNO (tmp1)))
1092 return find_base_term (tmp1);
1094 if (REG_P (tmp2) && REGNO_POINTER_FLAG (REGNO (tmp2)))
1095 return find_base_term (tmp2);
1097 /* Neither operand was known to be a pointer. Go ahead and find the
1098 base term for both operands. */
1099 tmp1 = find_base_term (tmp1);
1100 tmp2 = find_base_term (tmp2);
1102 /* If either base term is named object or a special address
1103 (like an argument or stack reference), then use it for the
1106 && (GET_CODE (tmp1) == SYMBOL_REF
1107 || GET_CODE (tmp1) == LABEL_REF
1108 || (GET_CODE (tmp1) == ADDRESS
1109 && GET_MODE (tmp1) != VOIDmode)))
1113 && (GET_CODE (tmp2) == SYMBOL_REF
1114 || GET_CODE (tmp2) == LABEL_REF
1115 || (GET_CODE (tmp2) == ADDRESS
1116 && GET_MODE (tmp2) != VOIDmode)))
1119 /* We could not determine which of the two operands was the
1120 base register and which was the index. So we can determine
1121 nothing from the base alias check. */
1126 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1127 return REG_BASE_VALUE (XEXP (x, 0));
1135 return REG_BASE_VALUE (stack_pointer_rtx);
1142 /* Return 0 if the addresses X and Y are known to point to different
1143 objects, 1 if they might be pointers to the same object. */
1146 base_alias_check (x, y, x_mode, y_mode)
1148 enum machine_mode x_mode, y_mode;
1150 rtx x_base = find_base_term (x);
1151 rtx y_base = find_base_term (y);
1153 /* If the address itself has no known base see if a known equivalent
1154 value has one. If either address still has no known base, nothing
1155 is known about aliasing. */
1160 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1163 x_base = find_base_term (x_c);
1171 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1174 y_base = find_base_term (y_c);
1179 /* If the base addresses are equal nothing is known about aliasing. */
1180 if (rtx_equal_p (x_base, y_base))
1183 /* The base addresses of the read and write are different expressions.
1184 If they are both symbols and they are not accessed via AND, there is
1185 no conflict. We can bring knowledge of object alignment into play
1186 here. For example, on alpha, "char a, b;" can alias one another,
1187 though "char a; long b;" cannot. */
1188 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1190 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1192 if (GET_CODE (x) == AND
1193 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1194 || GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1196 if (GET_CODE (y) == AND
1197 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1198 || GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1200 /* Differing symbols never alias. */
1204 /* If one address is a stack reference there can be no alias:
1205 stack references using different base registers do not alias,
1206 a stack reference can not alias a parameter, and a stack reference
1207 can not alias a global. */
1208 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1209 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1212 if (! flag_argument_noalias)
1215 if (flag_argument_noalias > 1)
1218 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1219 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1222 /* Convert the address X into something we can use. This is done by returning
1223 it unchanged unless it is a value; in the latter case we call cselib to get
1224 a more useful rtx. */
1231 struct elt_loc_list *l;
1233 if (GET_CODE (x) != VALUE)
1235 v = CSELIB_VAL_PTR (x);
1236 for (l = v->locs; l; l = l->next)
1237 if (CONSTANT_P (l->loc))
1239 for (l = v->locs; l; l = l->next)
1240 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1243 return v->locs->loc;
1247 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1248 where SIZE is the size in bytes of the memory reference. If ADDR
1249 is not modified by the memory reference then ADDR is returned. */
1252 addr_side_effect_eval (addr, size, n_refs)
1259 switch (GET_CODE (addr))
1262 offset = (n_refs + 1) * size;
1265 offset = -(n_refs + 1) * size;
1268 offset = n_refs * size;
1271 offset = -n_refs * size;
1279 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1281 addr = XEXP (addr, 0);
1286 /* Return nonzero if X and Y (memory addresses) could reference the
1287 same location in memory. C is an offset accumulator. When
1288 C is nonzero, we are testing aliases between X and Y + C.
1289 XSIZE is the size in bytes of the X reference,
1290 similarly YSIZE is the size in bytes for Y.
1292 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1293 referenced (the reference was BLKmode), so make the most pessimistic
1296 If XSIZE or YSIZE is negative, we may access memory outside the object
1297 being referenced as a side effect. This can happen when using AND to
1298 align memory references, as is done on the Alpha.
1300 Nice to notice that varying addresses cannot conflict with fp if no
1301 local variables had their addresses taken, but that's too hard now. */
1304 memrefs_conflict_p (xsize, x, ysize, y, c)
1309 if (GET_CODE (x) == VALUE)
1311 if (GET_CODE (y) == VALUE)
1313 if (GET_CODE (x) == HIGH)
1315 else if (GET_CODE (x) == LO_SUM)
1318 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1319 if (GET_CODE (y) == HIGH)
1321 else if (GET_CODE (y) == LO_SUM)
1324 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1326 if (rtx_equal_for_memref_p (x, y))
1328 if (xsize <= 0 || ysize <= 0)
1330 if (c >= 0 && xsize > c)
1332 if (c < 0 && ysize+c > 0)
1337 /* This code used to check for conflicts involving stack references and
1338 globals but the base address alias code now handles these cases. */
1340 if (GET_CODE (x) == PLUS)
1342 /* The fact that X is canonicalized means that this
1343 PLUS rtx is canonicalized. */
1344 rtx x0 = XEXP (x, 0);
1345 rtx x1 = XEXP (x, 1);
1347 if (GET_CODE (y) == PLUS)
1349 /* The fact that Y is canonicalized means that this
1350 PLUS rtx is canonicalized. */
1351 rtx y0 = XEXP (y, 0);
1352 rtx y1 = XEXP (y, 1);
1354 if (rtx_equal_for_memref_p (x1, y1))
1355 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1356 if (rtx_equal_for_memref_p (x0, y0))
1357 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1358 if (GET_CODE (x1) == CONST_INT)
1360 if (GET_CODE (y1) == CONST_INT)
1361 return memrefs_conflict_p (xsize, x0, ysize, y0,
1362 c - INTVAL (x1) + INTVAL (y1));
1364 return memrefs_conflict_p (xsize, x0, ysize, y,
1367 else if (GET_CODE (y1) == CONST_INT)
1368 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1372 else if (GET_CODE (x1) == CONST_INT)
1373 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1375 else if (GET_CODE (y) == PLUS)
1377 /* The fact that Y is canonicalized means that this
1378 PLUS rtx is canonicalized. */
1379 rtx y0 = XEXP (y, 0);
1380 rtx y1 = XEXP (y, 1);
1382 if (GET_CODE (y1) == CONST_INT)
1383 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1388 if (GET_CODE (x) == GET_CODE (y))
1389 switch (GET_CODE (x))
1393 /* Handle cases where we expect the second operands to be the
1394 same, and check only whether the first operand would conflict
1397 rtx x1 = canon_rtx (XEXP (x, 1));
1398 rtx y1 = canon_rtx (XEXP (y, 1));
1399 if (! rtx_equal_for_memref_p (x1, y1))
1401 x0 = canon_rtx (XEXP (x, 0));
1402 y0 = canon_rtx (XEXP (y, 0));
1403 if (rtx_equal_for_memref_p (x0, y0))
1404 return (xsize == 0 || ysize == 0
1405 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1407 /* Can't properly adjust our sizes. */
1408 if (GET_CODE (x1) != CONST_INT)
1410 xsize /= INTVAL (x1);
1411 ysize /= INTVAL (x1);
1413 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1417 /* Are these registers known not to be equal? */
1418 if (alias_invariant)
1420 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1421 rtx i_x, i_y; /* invariant relationships of X and Y */
1423 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1424 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1426 if (i_x == 0 && i_y == 0)
1429 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1430 ysize, i_y ? i_y : y, c))
1439 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1440 as an access with indeterminate size. Assume that references
1441 besides AND are aligned, so if the size of the other reference is
1442 at least as large as the alignment, assume no other overlap. */
1443 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1445 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1447 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1449 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1451 /* ??? If we are indexing far enough into the array/structure, we
1452 may yet be able to determine that we can not overlap. But we
1453 also need to that we are far enough from the end not to overlap
1454 a following reference, so we do nothing with that for now. */
1455 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1457 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1460 if (GET_CODE (x) == ADDRESSOF && GET_CODE (y) == ADDRESSOF)
1461 return xsize < 0 || ysize < 0;
1465 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1467 c += (INTVAL (y) - INTVAL (x));
1468 return (xsize <= 0 || ysize <= 0
1469 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1472 if (GET_CODE (x) == CONST)
1474 if (GET_CODE (y) == CONST)
1475 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1476 ysize, canon_rtx (XEXP (y, 0)), c);
1478 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1481 if (GET_CODE (y) == CONST)
1482 return memrefs_conflict_p (xsize, x, ysize,
1483 canon_rtx (XEXP (y, 0)), c);
1486 return (xsize <= 0 || ysize <= 0
1487 || (rtx_equal_for_memref_p (x, y)
1488 && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1495 /* Functions to compute memory dependencies.
1497 Since we process the insns in execution order, we can build tables
1498 to keep track of what registers are fixed (and not aliased), what registers
1499 are varying in known ways, and what registers are varying in unknown
1502 If both memory references are volatile, then there must always be a
1503 dependence between the two references, since their order can not be
1504 changed. A volatile and non-volatile reference can be interchanged
1507 A MEM_IN_STRUCT reference at a non-AND varying address can never
1508 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1509 also must allow AND addresses, because they may generate accesses
1510 outside the object being referenced. This is used to generate
1511 aligned addresses from unaligned addresses, for instance, the alpha
1512 storeqi_unaligned pattern. */
1514 /* Read dependence: X is read after read in MEM takes place. There can
1515 only be a dependence here if both reads are volatile. */
1518 read_dependence (mem, x)
1522 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1525 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1526 MEM2 is a reference to a structure at a varying address, or returns
1527 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1528 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1529 to decide whether or not an address may vary; it should return
1530 nonzero whenever variation is possible.
1531 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1534 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1536 rtx mem1_addr, mem2_addr;
1537 int (*varies_p) PARAMS ((rtx));
1539 if (! flag_strict_aliasing)
1542 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1543 && !varies_p (mem1_addr) && varies_p (mem2_addr))
1544 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1548 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1549 && varies_p (mem1_addr) && !varies_p (mem2_addr))
1550 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1557 /* Returns nonzero if something about the mode or address format MEM1
1558 indicates that it might well alias *anything*. */
1561 aliases_everything_p (mem)
1564 if (GET_CODE (XEXP (mem, 0)) == AND)
1565 /* If the address is an AND, its very hard to know at what it is
1566 actually pointing. */
1572 /* True dependence: X is read after store in MEM takes place. */
1575 true_dependence (mem, mem_mode, x, varies)
1577 enum machine_mode mem_mode;
1579 int (*varies) PARAMS ((rtx));
1581 register rtx x_addr, mem_addr;
1584 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1587 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1590 /* Unchanging memory can't conflict with non-unchanging memory.
1591 A non-unchanging read can conflict with a non-unchanging write.
1592 An unchanging read can conflict with an unchanging write since
1593 there may be a single store to this address to initialize it.
1594 Just fall through to the code below to resolve potential conflicts.
1595 This won't handle all cases optimally, but the possible performance
1596 loss should be negligible. */
1597 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1600 if (mem_mode == VOIDmode)
1601 mem_mode = GET_MODE (mem);
1603 x_addr = get_addr (XEXP (x, 0));
1604 mem_addr = get_addr (XEXP (mem, 0));
1606 base = find_base_term (x_addr);
1607 if (base && (GET_CODE (base) == LABEL_REF
1608 || (GET_CODE (base) == SYMBOL_REF
1609 && CONSTANT_POOL_ADDRESS_P (base))))
1612 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1615 x_addr = canon_rtx (x_addr);
1616 mem_addr = canon_rtx (mem_addr);
1618 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1619 SIZE_FOR_MODE (x), x_addr, 0))
1622 if (aliases_everything_p (x))
1625 /* We cannot use aliases_everyting_p to test MEM, since we must look
1626 at MEM_MODE, rather than GET_MODE (MEM). */
1627 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1630 /* In true_dependence we also allow BLKmode to alias anything. Why
1631 don't we do this in anti_dependence and output_dependence? */
1632 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1635 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1639 /* Returns non-zero if a write to X might alias a previous read from
1640 (or, if WRITEP is non-zero, a write to) MEM. */
1643 write_dependence_p (mem, x, writep)
1648 rtx x_addr, mem_addr;
1652 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1655 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1658 /* Unchanging memory can't conflict with non-unchanging memory. */
1659 if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
1662 /* If MEM is an unchanging read, then it can't possibly conflict with
1663 the store to X, because there is at most one store to MEM, and it must
1664 have occurred somewhere before MEM. */
1665 if (! writep && RTX_UNCHANGING_P (mem))
1668 x_addr = get_addr (XEXP (x, 0));
1669 mem_addr = get_addr (XEXP (mem, 0));
1673 base = find_base_term (mem_addr);
1674 if (base && (GET_CODE (base) == LABEL_REF
1675 || (GET_CODE (base) == SYMBOL_REF
1676 && CONSTANT_POOL_ADDRESS_P (base))))
1680 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1684 x_addr = canon_rtx (x_addr);
1685 mem_addr = canon_rtx (mem_addr);
1687 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1688 SIZE_FOR_MODE (x), x_addr, 0))
1692 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1695 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1696 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1699 /* Anti dependence: X is written after read in MEM takes place. */
1702 anti_dependence (mem, x)
1706 return write_dependence_p (mem, x, /*writep=*/0);
1709 /* Output dependence: X is written after store in MEM takes place. */
1712 output_dependence (mem, x)
1716 return write_dependence_p (mem, x, /*writep=*/1);
1719 /* Returns non-zero if X might refer to something which is not
1720 local to the function and is not constant. */
1723 nonlocal_reference_p (x)
1727 register RTX_CODE code;
1730 code = GET_CODE (x);
1732 if (GET_RTX_CLASS (code) == 'i')
1734 /* Constant functions can be constant if they don't use
1735 scratch memory used to mark function w/o side effects. */
1736 if (code == CALL_INSN && CONST_CALL_P (x))
1738 x = CALL_INSN_FUNCTION_USAGE (x);
1744 code = GET_CODE (x);
1750 if (GET_CODE (SUBREG_REG (x)) == REG)
1752 /* Global registers are not local. */
1753 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1754 && global_regs[REGNO (SUBREG_REG (x)) + SUBREG_WORD (x)])
1762 /* Global registers are not local. */
1763 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1777 /* Constants in the function's constants pool are constant. */
1778 if (CONSTANT_POOL_ADDRESS_P (x))
1783 /* Recursion introduces no additional considerations. */
1784 if (GET_CODE (XEXP (x, 0)) == MEM
1785 && GET_CODE (XEXP (XEXP (x, 0), 0)) == SYMBOL_REF
1786 && strcmp(XSTR (XEXP (XEXP (x, 0), 0), 0),
1787 IDENTIFIER_POINTER (
1788 DECL_ASSEMBLER_NAME (current_function_decl))) == 0)
1793 /* Be overly conservative and consider any volatile memory
1794 reference as not local. */
1795 if (MEM_VOLATILE_P (x))
1797 base = find_base_term (XEXP (x, 0));
1800 /* A Pmode ADDRESS could be a reference via the structure value
1801 address or static chain. Such memory references are nonlocal.
1803 Thus, we have to examine the contents of the ADDRESS to find
1804 out if this is a local reference or not. */
1805 if (GET_CODE (base) == ADDRESS
1806 && GET_MODE (base) == Pmode
1807 && (XEXP (base, 0) == stack_pointer_rtx
1808 || XEXP (base, 0) == arg_pointer_rtx
1809 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1810 || XEXP (base, 0) == hard_frame_pointer_rtx
1812 || XEXP (base, 0) == frame_pointer_rtx))
1814 /* Constants in the function's constant pool are constant. */
1815 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
1828 /* Recursively scan the operands of this expression. */
1831 register const char *fmt = GET_RTX_FORMAT (code);
1834 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1836 if (fmt[i] == 'e' && XEXP (x, i))
1838 if (nonlocal_reference_p (XEXP (x, i)))
1841 else if (fmt[i] == 'E')
1844 for (j = 0; j < XVECLEN (x, i); j++)
1845 if (nonlocal_reference_p (XVECEXP (x, i, j)))
1854 /* Mark the function if it is constant. */
1857 mark_constant_function ()
1861 if (TREE_PUBLIC (current_function_decl)
1862 || TREE_READONLY (current_function_decl)
1863 || TREE_THIS_VOLATILE (current_function_decl)
1864 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
1867 /* Determine if this is a constant function. */
1869 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1870 if (INSN_P (insn) && nonlocal_reference_p (insn))
1873 /* Mark the function. */
1875 TREE_READONLY (current_function_decl) = 1;
1879 static HARD_REG_SET argument_registers;
1886 #ifndef OUTGOING_REGNO
1887 #define OUTGOING_REGNO(N) N
1889 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1890 /* Check whether this register can hold an incoming pointer
1891 argument. FUNCTION_ARG_REGNO_P tests outgoing register
1892 numbers, so translate if necessary due to register windows. */
1893 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
1894 && HARD_REGNO_MODE_OK (i, Pmode))
1895 SET_HARD_REG_BIT (argument_registers, i);
1897 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
1900 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
1904 init_alias_analysis ()
1906 int maxreg = max_reg_num ();
1909 register unsigned int ui;
1912 reg_known_value_size = maxreg;
1915 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
1916 - FIRST_PSEUDO_REGISTER;
1918 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
1919 - FIRST_PSEUDO_REGISTER;
1921 /* Overallocate reg_base_value to allow some growth during loop
1922 optimization. Loop unrolling can create a large number of
1924 reg_base_value_size = maxreg * 2;
1925 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
1927 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
1929 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
1930 reg_seen = (char *) xmalloc (reg_base_value_size);
1931 if (! reload_completed && flag_unroll_loops)
1933 /* ??? Why are we realloc'ing if we're just going to zero it? */
1934 alias_invariant = (rtx *)xrealloc (alias_invariant,
1935 reg_base_value_size * sizeof (rtx));
1936 bzero ((char *)alias_invariant, reg_base_value_size * sizeof (rtx));
1940 /* The basic idea is that each pass through this loop will use the
1941 "constant" information from the previous pass to propagate alias
1942 information through another level of assignments.
1944 This could get expensive if the assignment chains are long. Maybe
1945 we should throttle the number of iterations, possibly based on
1946 the optimization level or flag_expensive_optimizations.
1948 We could propagate more information in the first pass by making use
1949 of REG_N_SETS to determine immediately that the alias information
1950 for a pseudo is "constant".
1952 A program with an uninitialized variable can cause an infinite loop
1953 here. Instead of doing a full dataflow analysis to detect such problems
1954 we just cap the number of iterations for the loop.
1956 The state of the arrays for the set chain in question does not matter
1957 since the program has undefined behavior. */
1962 /* Assume nothing will change this iteration of the loop. */
1965 /* We want to assign the same IDs each iteration of this loop, so
1966 start counting from zero each iteration of the loop. */
1969 /* We're at the start of the funtion each iteration through the
1970 loop, so we're copying arguments. */
1971 copying_arguments = 1;
1973 /* Wipe the potential alias information clean for this pass. */
1974 bzero ((char *) new_reg_base_value, reg_base_value_size * sizeof (rtx));
1976 /* Wipe the reg_seen array clean. */
1977 bzero ((char *) reg_seen, reg_base_value_size);
1979 /* Mark all hard registers which may contain an address.
1980 The stack, frame and argument pointers may contain an address.
1981 An argument register which can hold a Pmode value may contain
1982 an address even if it is not in BASE_REGS.
1984 The address expression is VOIDmode for an argument and
1985 Pmode for other registers. */
1987 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1988 if (TEST_HARD_REG_BIT (argument_registers, i))
1989 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
1990 gen_rtx_REG (Pmode, i));
1992 new_reg_base_value[STACK_POINTER_REGNUM]
1993 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
1994 new_reg_base_value[ARG_POINTER_REGNUM]
1995 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
1996 new_reg_base_value[FRAME_POINTER_REGNUM]
1997 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
1998 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1999 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
2000 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
2003 /* Walk the insns adding values to the new_reg_base_value array. */
2004 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
2010 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2011 /* The prologue/epilouge insns are not threaded onto the
2012 insn chain until after reload has completed. Thus,
2013 there is no sense wasting time checking if INSN is in
2014 the prologue/epilogue until after reload has completed. */
2015 if (reload_completed
2016 && prologue_epilogue_contains (insn))
2020 /* If this insn has a noalias note, process it, Otherwise,
2021 scan for sets. A simple set will have no side effects
2022 which could change the base value of any other register. */
2024 if (GET_CODE (PATTERN (insn)) == SET
2025 && REG_NOTES (insn) != 0
2026 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
2027 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
2029 note_stores (PATTERN (insn), record_set, NULL);
2031 set = single_set (insn);
2034 && GET_CODE (SET_DEST (set)) == REG
2035 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
2036 && REG_NOTES (insn) != 0
2037 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
2038 && REG_N_SETS (REGNO (SET_DEST (set))) == 1)
2039 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
2040 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
2041 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
2043 int regno = REGNO (SET_DEST (set));
2044 reg_known_value[regno] = XEXP (note, 0);
2045 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
2048 else if (GET_CODE (insn) == NOTE
2049 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
2050 copying_arguments = 0;
2053 /* Now propagate values from new_reg_base_value to reg_base_value. */
2054 for (ui = 0; ui < reg_base_value_size; ui++)
2056 if (new_reg_base_value[ui]
2057 && new_reg_base_value[ui] != reg_base_value[ui]
2058 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
2060 reg_base_value[ui] = new_reg_base_value[ui];
2065 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
2067 /* Fill in the remaining entries. */
2068 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
2069 if (reg_known_value[i] == 0)
2070 reg_known_value[i] = regno_reg_rtx[i];
2072 /* Simplify the reg_base_value array so that no register refers to
2073 another register, except to special registers indirectly through
2074 ADDRESS expressions.
2076 In theory this loop can take as long as O(registers^2), but unless
2077 there are very long dependency chains it will run in close to linear
2080 This loop may not be needed any longer now that the main loop does
2081 a better job at propagating alias information. */
2087 for (ui = 0; ui < reg_base_value_size; ui++)
2089 rtx base = reg_base_value[ui];
2090 if (base && GET_CODE (base) == REG)
2092 unsigned int base_regno = REGNO (base);
2093 if (base_regno == ui) /* register set from itself */
2094 reg_base_value[ui] = 0;
2096 reg_base_value[ui] = reg_base_value[base_regno];
2101 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2104 free (new_reg_base_value);
2105 new_reg_base_value = 0;
2111 end_alias_analysis ()
2113 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2114 reg_known_value = 0;
2115 reg_known_value_size = 0;
2116 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2117 reg_known_equiv_p = 0;
2121 ggc_del_root (reg_base_value);
2122 free (reg_base_value);
2125 reg_base_value_size = 0;
2126 if (alias_invariant)
2128 free (alias_invariant);
2129 alias_invariant = 0;