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'. */
84 /* The language-specific function for alias analysis. If NULL, the
85 language does not do any special alias analysis. */
86 HOST_WIDE_INT (*lang_get_alias_set) PARAMS ((tree));
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));
246 if (ase != 0 && splay_tree_lookup (ase->children,
247 (splay_tree_key) MEM_ALIAS_SET (mem2)))
250 /* Now do the same, but with the alias sets reversed. */
251 ase = get_alias_set_entry (MEM_ALIAS_SET (mem2));
252 if (ase != 0 && splay_tree_lookup (ase->children,
253 (splay_tree_key) MEM_ALIAS_SET (mem1)))
256 /* The two MEMs are in distinct alias sets, and neither one is the
257 child of the other. Therefore, they cannot alias. */
261 /* Insert the NODE into the splay tree given by DATA. Used by
262 record_alias_subset via splay_tree_foreach. */
265 insert_subset_children (node, data)
266 splay_tree_node node;
269 splay_tree_insert ((splay_tree) data, node->key, node->value);
274 /* T is an expression with pointer type. Find the DECL on which this
275 expression is based. (For example, in `a[i]' this would be `a'.)
276 If there is no such DECL, or a unique decl cannot be determined,
277 NULL_TREE is retured. */
285 if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
288 /* If this is a declaration, return it. */
289 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
292 /* Handle general expressions. It would be nice to deal with
293 COMPONENT_REFs here. If we could tell that `a' and `b' were the
294 same, then `a->f' and `b->f' are also the same. */
295 switch (TREE_CODE_CLASS (TREE_CODE (t)))
298 return find_base_decl (TREE_OPERAND (t, 0));
301 /* Return 0 if found in neither or both are the same. */
302 d0 = find_base_decl (TREE_OPERAND (t, 0));
303 d1 = find_base_decl (TREE_OPERAND (t, 1));
314 d0 = find_base_decl (TREE_OPERAND (t, 0));
315 d1 = find_base_decl (TREE_OPERAND (t, 1));
316 d0 = find_base_decl (TREE_OPERAND (t, 0));
317 d2 = find_base_decl (TREE_OPERAND (t, 2));
319 /* Set any nonzero values from the last, then from the first. */
320 if (d1 == 0) d1 = d2;
321 if (d0 == 0) d0 = d1;
322 if (d1 == 0) d1 = d0;
323 if (d2 == 0) d2 = d1;
325 /* At this point all are nonzero or all are zero. If all three are the
326 same, return it. Otherwise, return zero. */
327 return (d0 == d1 && d1 == d2) ? d0 : 0;
334 /* Return the alias set for T, which may be either a type or an
335 expression. Call language-specific routine for help, if needed. */
342 HOST_WIDE_INT bitsize, bitpos;
344 enum machine_mode mode;
345 int volatilep, unsignedp;
346 unsigned int alignment;
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 But first remove nops since we care only about the actual object. */
361 while (TREE_CODE (t) == NOP_EXPR || TREE_CODE (t) == CONVERT_EXPR
362 || TREE_CODE (t) == NON_LVALUE_EXPR)
363 t = TREE_OPERAND (t, 0);
365 /* Now give the language a chance to do something. */
366 if (lang_get_alias_set != 0
367 && (set = (*lang_get_alias_set) (t)) != -1)
370 /* If this is a reference, go inside it and use the underlying object. */
371 if (TREE_CODE_CLASS (TREE_CODE (t)) == 'r')
372 t = get_inner_reference (t, &bitsize, &bitpos, &offset, &mode,
373 &unsignedp, &volatilep, &alignment);
375 if (TREE_CODE (t) == INDIRECT_REF)
377 /* Check for accesses through restrict-qualified pointers. */
378 tree decl = find_base_decl (TREE_OPERAND (t, 0));
380 if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
381 /* We use the alias set indicated in the declaration. */
382 return DECL_POINTER_ALIAS_SET (decl);
384 /* If we have an INDIRECT_REF via a void pointer, we don't know anything
385 about what that might alias. */
386 if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE)
390 /* Give the language another chance to do something special. */
391 if (lang_get_alias_set != 0
392 && (set = (*lang_get_alias_set) (t)) != -1)
395 /* Now we are done with expressions, so get the type if this isn't
400 /* Variant qualifiers don't affect the alias set, so get the main
401 variant. If this is a type with a known alias set, return it. */
402 t = TYPE_MAIN_VARIANT (t);
403 if (TYPE_P (t) && TYPE_ALIAS_SET_KNOWN_P (t))
404 return TYPE_ALIAS_SET (t);
406 /* See if the language has special handling for this type. */
407 if (lang_get_alias_set != 0
408 && (set = (*lang_get_alias_set) (t)) != -1)
410 /* There are no objects of FUNCTION_TYPE, so there's no point in
411 using up an alias set for them. (There are, of course, pointers
412 and references to functions, but that's different.) */
413 else if (TREE_CODE (t) == FUNCTION_TYPE)
416 /* Otherwise make a new alias set for this type. */
417 set = new_alias_set ();
419 TYPE_ALIAS_SET (t) = set;
423 /* Return a brand-new alias set. */
428 static HOST_WIDE_INT last_alias_set;
430 if (flag_strict_aliasing)
431 return ++last_alias_set;
436 /* Indicate that things in SUBSET can alias things in SUPERSET, but
437 not vice versa. For example, in C, a store to an `int' can alias a
438 structure containing an `int', but not vice versa. Here, the
439 structure would be the SUPERSET and `int' the SUBSET. This
440 function should be called only once per SUPERSET/SUBSET pair.
442 It is illegal for SUPERSET to be zero; everything is implicitly a
443 subset of alias set zero. */
446 record_alias_subset (superset, subset)
447 HOST_WIDE_INT superset;
448 HOST_WIDE_INT subset;
450 alias_set_entry superset_entry;
451 alias_set_entry subset_entry;
456 superset_entry = get_alias_set_entry (superset);
457 if (superset_entry == 0)
459 /* Create an entry for the SUPERSET, so that we have a place to
460 attach the SUBSET. */
462 = (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
463 superset_entry->alias_set = superset;
464 superset_entry->children
465 = splay_tree_new (splay_tree_compare_ints, 0, 0);
466 splay_tree_insert (alias_sets, (splay_tree_key) superset,
467 (splay_tree_value) superset_entry);
471 subset_entry = get_alias_set_entry (subset);
473 /* If there is an entry for the subset, enter all of its children
474 (if they are not already present) as children of the SUPERSET. */
476 splay_tree_foreach (subset_entry->children,
477 insert_subset_children,
478 superset_entry->children);
480 /* Enter the SUBSET itself as a child of the SUPERSET. */
481 splay_tree_insert (superset_entry->children,
482 (splay_tree_key) subset, 0);
485 /* Record that component types of TYPE, if any, are part of that type for
486 aliasing purposes. For record types, we only record component types
487 for fields that are marked addressable. For array types, we always
488 record the component types, so the front end should not call this
489 function if the individual component aren't addressable. */
492 record_component_aliases (type)
495 HOST_WIDE_INT superset = get_alias_set (type);
496 HOST_WIDE_INT subset;
502 switch (TREE_CODE (type))
505 subset = get_alias_set (TREE_TYPE (type));
507 record_alias_subset (superset, subset);
512 case QUAL_UNION_TYPE:
513 for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
515 subset = get_alias_set (TREE_TYPE (field));
516 if (TREE_ADDRESSABLE (field) && subset != 0 && subset != superset)
517 record_alias_subset (superset, subset);
526 /* Allocate an alias set for use in storing and reading from the varargs
530 get_varargs_alias_set ()
532 static HOST_WIDE_INT set = -1;
535 set = new_alias_set ();
540 /* Likewise, but used for the fixed portions of the frame, e.g., register
544 get_frame_alias_set ()
546 static HOST_WIDE_INT set = -1;
549 set = new_alias_set ();
554 /* Inside SRC, the source of a SET, find a base address. */
557 find_base_value (src)
560 switch (GET_CODE (src))
567 /* At the start of a function, argument registers have known base
568 values which may be lost later. Returning an ADDRESS
569 expression here allows optimization based on argument values
570 even when the argument registers are used for other purposes. */
571 if (REGNO (src) < FIRST_PSEUDO_REGISTER && copying_arguments)
572 return new_reg_base_value[REGNO (src)];
574 /* If a pseudo has a known base value, return it. Do not do this
575 for hard regs since it can result in a circular dependency
576 chain for registers which have values at function entry.
578 The test above is not sufficient because the scheduler may move
579 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
580 if (REGNO (src) >= FIRST_PSEUDO_REGISTER
581 && (unsigned) REGNO (src) < reg_base_value_size
582 && reg_base_value[REGNO (src)])
583 return reg_base_value[REGNO (src)];
588 /* Check for an argument passed in memory. Only record in the
589 copying-arguments block; it is too hard to track changes
591 if (copying_arguments
592 && (XEXP (src, 0) == arg_pointer_rtx
593 || (GET_CODE (XEXP (src, 0)) == PLUS
594 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
595 return gen_rtx_ADDRESS (VOIDmode, src);
600 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
603 /* ... fall through ... */
608 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
610 /* If either operand is a REG, then see if we already have
611 a known value for it. */
612 if (GET_CODE (src_0) == REG)
614 temp = find_base_value (src_0);
619 if (GET_CODE (src_1) == REG)
621 temp = find_base_value (src_1);
626 /* Guess which operand is the base address:
627 If either operand is a symbol, then it is the base. If
628 either operand is a CONST_INT, then the other is the base. */
629 if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
630 return find_base_value (src_0);
631 else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
632 return find_base_value (src_1);
634 /* This might not be necessary anymore:
635 If either operand is a REG that is a known pointer, then it
637 else if (GET_CODE (src_0) == REG && REGNO_POINTER_FLAG (REGNO (src_0)))
638 return find_base_value (src_0);
639 else if (GET_CODE (src_1) == REG && REGNO_POINTER_FLAG (REGNO (src_1)))
640 return find_base_value (src_1);
646 /* The standard form is (lo_sum reg sym) so look only at the
648 return find_base_value (XEXP (src, 1));
651 /* If the second operand is constant set the base
652 address to the first operand. */
653 if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
654 return find_base_value (XEXP (src, 0));
658 case SIGN_EXTEND: /* used for NT/Alpha pointers */
660 return find_base_value (XEXP (src, 0));
669 /* Called from init_alias_analysis indirectly through note_stores. */
671 /* While scanning insns to find base values, reg_seen[N] is nonzero if
672 register N has been set in this function. */
673 static char *reg_seen;
675 /* Addresses which are known not to alias anything else are identified
676 by a unique integer. */
677 static int unique_id;
680 record_set (dest, set, data)
682 void *data ATTRIBUTE_UNUSED;
684 register unsigned regno;
687 if (GET_CODE (dest) != REG)
690 regno = REGNO (dest);
692 if (regno >= reg_base_value_size)
697 /* A CLOBBER wipes out any old value but does not prevent a previously
698 unset register from acquiring a base address (i.e. reg_seen is not
700 if (GET_CODE (set) == CLOBBER)
702 new_reg_base_value[regno] = 0;
711 new_reg_base_value[regno] = 0;
715 new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
716 GEN_INT (unique_id++));
720 /* This is not the first set. If the new value is not related to the
721 old value, forget the base value. Note that the following code is
723 extern int x, y; int *p = &x; p += (&y-&x);
724 ANSI C does not allow computing the difference of addresses
725 of distinct top level objects. */
726 if (new_reg_base_value[regno])
727 switch (GET_CODE (src))
732 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
733 new_reg_base_value[regno] = 0;
736 if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
737 new_reg_base_value[regno] = 0;
740 new_reg_base_value[regno] = 0;
743 /* If this is the first set of a register, record the value. */
744 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
745 && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
746 new_reg_base_value[regno] = find_base_value (src);
751 /* Called from loop optimization when a new pseudo-register is
752 created. It indicates that REGNO is being set to VAL. f INVARIANT
753 is true then this value also describes an invariant relationship
754 which can be used to deduce that two registers with unknown values
758 record_base_value (regno, val, invariant)
763 if (regno >= reg_base_value_size)
766 if (invariant && alias_invariant)
767 alias_invariant[regno] = val;
769 if (GET_CODE (val) == REG)
771 if (REGNO (val) < reg_base_value_size)
772 reg_base_value[regno] = reg_base_value[REGNO (val)];
777 reg_base_value[regno] = find_base_value (val);
780 /* Returns a canonical version of X, from the point of view alias
781 analysis. (For example, if X is a MEM whose address is a register,
782 and the register has a known value (say a SYMBOL_REF), then a MEM
783 whose address is the SYMBOL_REF is returned.) */
789 /* Recursively look for equivalences. */
790 if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
791 && REGNO (x) < reg_known_value_size)
792 return reg_known_value[REGNO (x)] == x
793 ? x : canon_rtx (reg_known_value[REGNO (x)]);
794 else if (GET_CODE (x) == PLUS)
796 rtx x0 = canon_rtx (XEXP (x, 0));
797 rtx x1 = canon_rtx (XEXP (x, 1));
799 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
801 /* We can tolerate LO_SUMs being offset here; these
802 rtl are used for nothing other than comparisons. */
803 if (GET_CODE (x0) == CONST_INT)
804 return plus_constant_for_output (x1, INTVAL (x0));
805 else if (GET_CODE (x1) == CONST_INT)
806 return plus_constant_for_output (x0, INTVAL (x1));
807 return gen_rtx_PLUS (GET_MODE (x), x0, x1);
811 /* This gives us much better alias analysis when called from
812 the loop optimizer. Note we want to leave the original
813 MEM alone, but need to return the canonicalized MEM with
814 all the flags with their original values. */
815 else if (GET_CODE (x) == MEM)
817 rtx addr = canon_rtx (XEXP (x, 0));
819 if (addr != XEXP (x, 0))
821 rtx new = gen_rtx_MEM (GET_MODE (x), addr);
823 MEM_COPY_ATTRIBUTES (new, x);
830 /* Return 1 if X and Y are identical-looking rtx's.
832 We use the data in reg_known_value above to see if two registers with
833 different numbers are, in fact, equivalent. */
836 rtx_equal_for_memref_p (x, y)
841 register enum rtx_code code;
842 register const char *fmt;
844 if (x == 0 && y == 0)
846 if (x == 0 || y == 0)
856 /* Rtx's of different codes cannot be equal. */
857 if (code != GET_CODE (y))
860 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
861 (REG:SI x) and (REG:HI x) are NOT equivalent. */
863 if (GET_MODE (x) != GET_MODE (y))
866 /* Some RTL can be compared without a recursive examination. */
870 return REGNO (x) == REGNO (y);
873 return XEXP (x, 0) == XEXP (y, 0);
876 return XSTR (x, 0) == XSTR (y, 0);
880 /* There's no need to compare the contents of CONST_DOUBLEs or
881 CONST_INTs because pointer equality is a good enough
882 comparison for these nodes. */
886 return (REGNO (XEXP (x, 0)) == REGNO (XEXP (y, 0))
887 && XINT (x, 1) == XINT (y, 1));
893 /* For commutative operations, the RTX match if the operand match in any
894 order. Also handle the simple binary and unary cases without a loop. */
895 if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
896 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
897 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
898 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
899 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
900 else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
901 return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
902 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
903 else if (GET_RTX_CLASS (code) == '1')
904 return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
906 /* Compare the elements. If any pair of corresponding elements
907 fail to match, return 0 for the whole things.
909 Limit cases to types which actually appear in addresses. */
911 fmt = GET_RTX_FORMAT (code);
912 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
917 if (XINT (x, i) != XINT (y, i))
922 /* Two vectors must have the same length. */
923 if (XVECLEN (x, i) != XVECLEN (y, i))
926 /* And the corresponding elements must match. */
927 for (j = 0; j < XVECLEN (x, i); j++)
928 if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
929 XVECEXP (y, i, j)) == 0)
934 if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
938 /* This can happen for an asm which clobbers memory. */
942 /* It is believed that rtx's at this level will never
943 contain anything but integers and other rtx's,
944 except for within LABEL_REFs and SYMBOL_REFs. */
952 /* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
953 X and return it, or return 0 if none found. */
956 find_symbolic_term (x)
960 register enum rtx_code code;
961 register const char *fmt;
964 if (code == SYMBOL_REF || code == LABEL_REF)
966 if (GET_RTX_CLASS (code) == 'o')
969 fmt = GET_RTX_FORMAT (code);
970 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
976 t = find_symbolic_term (XEXP (x, i));
980 else if (fmt[i] == 'E')
991 struct elt_loc_list *l;
993 switch (GET_CODE (x))
996 return REG_BASE_VALUE (x);
999 case SIGN_EXTEND: /* Used for Alpha/NT pointers */
1005 return find_base_term (XEXP (x, 0));
1008 val = CSELIB_VAL_PTR (x);
1009 for (l = val->locs; l; l = l->next)
1010 if ((x = find_base_term (l->loc)) != 0)
1016 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
1023 rtx tmp1 = XEXP (x, 0);
1024 rtx tmp2 = XEXP (x, 1);
1026 /* This is a litle bit tricky since we have to determine which of
1027 the two operands represents the real base address. Otherwise this
1028 routine may return the index register instead of the base register.
1030 That may cause us to believe no aliasing was possible, when in
1031 fact aliasing is possible.
1033 We use a few simple tests to guess the base register. Additional
1034 tests can certainly be added. For example, if one of the operands
1035 is a shift or multiply, then it must be the index register and the
1036 other operand is the base register. */
1038 /* If either operand is known to be a pointer, then use it
1039 to determine the base term. */
1040 if (REG_P (tmp1) && REGNO_POINTER_FLAG (REGNO (tmp1)))
1041 return find_base_term (tmp1);
1043 if (REG_P (tmp2) && REGNO_POINTER_FLAG (REGNO (tmp2)))
1044 return find_base_term (tmp2);
1046 /* Neither operand was known to be a pointer. Go ahead and find the
1047 base term for both operands. */
1048 tmp1 = find_base_term (tmp1);
1049 tmp2 = find_base_term (tmp2);
1051 /* If either base term is named object or a special address
1052 (like an argument or stack reference), then use it for the
1055 && (GET_CODE (tmp1) == SYMBOL_REF
1056 || GET_CODE (tmp1) == LABEL_REF
1057 || (GET_CODE (tmp1) == ADDRESS
1058 && GET_MODE (tmp1) != VOIDmode)))
1062 && (GET_CODE (tmp2) == SYMBOL_REF
1063 || GET_CODE (tmp2) == LABEL_REF
1064 || (GET_CODE (tmp2) == ADDRESS
1065 && GET_MODE (tmp2) != VOIDmode)))
1068 /* We could not determine which of the two operands was the
1069 base register and which was the index. So we can determine
1070 nothing from the base alias check. */
1075 if (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (XEXP (x, 1)) == CONST_INT)
1076 return REG_BASE_VALUE (XEXP (x, 0));
1088 /* Return 0 if the addresses X and Y are known to point to different
1089 objects, 1 if they might be pointers to the same object. */
1092 base_alias_check (x, y, x_mode, y_mode)
1094 enum machine_mode x_mode, y_mode;
1096 rtx x_base = find_base_term (x);
1097 rtx y_base = find_base_term (y);
1099 /* If the address itself has no known base see if a known equivalent
1100 value has one. If either address still has no known base, nothing
1101 is known about aliasing. */
1106 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
1109 x_base = find_base_term (x_c);
1117 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
1120 y_base = find_base_term (y_c);
1125 /* If the base addresses are equal nothing is known about aliasing. */
1126 if (rtx_equal_p (x_base, y_base))
1129 /* The base addresses of the read and write are different expressions.
1130 If they are both symbols and they are not accessed via AND, there is
1131 no conflict. We can bring knowledge of object alignment into play
1132 here. For example, on alpha, "char a, b;" can alias one another,
1133 though "char a; long b;" cannot. */
1134 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
1136 if (GET_CODE (x) == AND && GET_CODE (y) == AND)
1138 if (GET_CODE (x) == AND
1139 && (GET_CODE (XEXP (x, 1)) != CONST_INT
1140 || GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
1142 if (GET_CODE (y) == AND
1143 && (GET_CODE (XEXP (y, 1)) != CONST_INT
1144 || GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
1146 /* Differing symbols never alias. */
1150 /* If one address is a stack reference there can be no alias:
1151 stack references using different base registers do not alias,
1152 a stack reference can not alias a parameter, and a stack reference
1153 can not alias a global. */
1154 if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
1155 || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
1158 if (! flag_argument_noalias)
1161 if (flag_argument_noalias > 1)
1164 /* Weak noalias assertion (arguments are distinct, but may match globals). */
1165 return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
1168 /* Convert the address X into something we can use. This is done by returning
1169 it unchanged unless it is a value; in the latter case we call cselib to get
1170 a more useful rtx. */
1177 struct elt_loc_list *l;
1179 if (GET_CODE (x) != VALUE)
1181 v = CSELIB_VAL_PTR (x);
1182 for (l = v->locs; l; l = l->next)
1183 if (CONSTANT_P (l->loc))
1185 for (l = v->locs; l; l = l->next)
1186 if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
1189 return v->locs->loc;
1193 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1194 where SIZE is the size in bytes of the memory reference. If ADDR
1195 is not modified by the memory reference then ADDR is returned. */
1198 addr_side_effect_eval (addr, size, n_refs)
1205 switch (GET_CODE (addr))
1208 offset = (n_refs + 1) * size;
1211 offset = -(n_refs + 1) * size;
1214 offset = n_refs * size;
1217 offset = -n_refs * size;
1225 addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
1227 addr = XEXP (addr, 0);
1232 /* Return nonzero if X and Y (memory addresses) could reference the
1233 same location in memory. C is an offset accumulator. When
1234 C is nonzero, we are testing aliases between X and Y + C.
1235 XSIZE is the size in bytes of the X reference,
1236 similarly YSIZE is the size in bytes for Y.
1238 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1239 referenced (the reference was BLKmode), so make the most pessimistic
1242 If XSIZE or YSIZE is negative, we may access memory outside the object
1243 being referenced as a side effect. This can happen when using AND to
1244 align memory references, as is done on the Alpha.
1246 Nice to notice that varying addresses cannot conflict with fp if no
1247 local variables had their addresses taken, but that's too hard now. */
1250 memrefs_conflict_p (xsize, x, ysize, y, c)
1255 if (GET_CODE (x) == VALUE)
1257 if (GET_CODE (y) == VALUE)
1259 if (GET_CODE (x) == HIGH)
1261 else if (GET_CODE (x) == LO_SUM)
1264 x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
1265 if (GET_CODE (y) == HIGH)
1267 else if (GET_CODE (y) == LO_SUM)
1270 y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
1272 if (rtx_equal_for_memref_p (x, y))
1274 if (xsize <= 0 || ysize <= 0)
1276 if (c >= 0 && xsize > c)
1278 if (c < 0 && ysize+c > 0)
1283 /* This code used to check for conflicts involving stack references and
1284 globals but the base address alias code now handles these cases. */
1286 if (GET_CODE (x) == PLUS)
1288 /* The fact that X is canonicalized means that this
1289 PLUS rtx is canonicalized. */
1290 rtx x0 = XEXP (x, 0);
1291 rtx x1 = XEXP (x, 1);
1293 if (GET_CODE (y) == PLUS)
1295 /* The fact that Y is canonicalized means that this
1296 PLUS rtx is canonicalized. */
1297 rtx y0 = XEXP (y, 0);
1298 rtx y1 = XEXP (y, 1);
1300 if (rtx_equal_for_memref_p (x1, y1))
1301 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1302 if (rtx_equal_for_memref_p (x0, y0))
1303 return memrefs_conflict_p (xsize, x1, ysize, y1, c);
1304 if (GET_CODE (x1) == CONST_INT)
1306 if (GET_CODE (y1) == CONST_INT)
1307 return memrefs_conflict_p (xsize, x0, ysize, y0,
1308 c - INTVAL (x1) + INTVAL (y1));
1310 return memrefs_conflict_p (xsize, x0, ysize, y,
1313 else if (GET_CODE (y1) == CONST_INT)
1314 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1318 else if (GET_CODE (x1) == CONST_INT)
1319 return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
1321 else if (GET_CODE (y) == PLUS)
1323 /* The fact that Y is canonicalized means that this
1324 PLUS rtx is canonicalized. */
1325 rtx y0 = XEXP (y, 0);
1326 rtx y1 = XEXP (y, 1);
1328 if (GET_CODE (y1) == CONST_INT)
1329 return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
1334 if (GET_CODE (x) == GET_CODE (y))
1335 switch (GET_CODE (x))
1339 /* Handle cases where we expect the second operands to be the
1340 same, and check only whether the first operand would conflict
1343 rtx x1 = canon_rtx (XEXP (x, 1));
1344 rtx y1 = canon_rtx (XEXP (y, 1));
1345 if (! rtx_equal_for_memref_p (x1, y1))
1347 x0 = canon_rtx (XEXP (x, 0));
1348 y0 = canon_rtx (XEXP (y, 0));
1349 if (rtx_equal_for_memref_p (x0, y0))
1350 return (xsize == 0 || ysize == 0
1351 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1353 /* Can't properly adjust our sizes. */
1354 if (GET_CODE (x1) != CONST_INT)
1356 xsize /= INTVAL (x1);
1357 ysize /= INTVAL (x1);
1359 return memrefs_conflict_p (xsize, x0, ysize, y0, c);
1363 /* Are these registers known not to be equal? */
1364 if (alias_invariant)
1366 unsigned int r_x = REGNO (x), r_y = REGNO (y);
1367 rtx i_x, i_y; /* invariant relationships of X and Y */
1369 i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
1370 i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
1372 if (i_x == 0 && i_y == 0)
1375 if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
1376 ysize, i_y ? i_y : y, c))
1385 /* Treat an access through an AND (e.g. a subword access on an Alpha)
1386 as an access with indeterminate size. Assume that references
1387 besides AND are aligned, so if the size of the other reference is
1388 at least as large as the alignment, assume no other overlap. */
1389 if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
1391 if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
1393 return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
1395 if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
1397 /* ??? If we are indexing far enough into the array/structure, we
1398 may yet be able to determine that we can not overlap. But we
1399 also need to that we are far enough from the end not to overlap
1400 a following reference, so we do nothing with that for now. */
1401 if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
1403 return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
1408 if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
1410 c += (INTVAL (y) - INTVAL (x));
1411 return (xsize <= 0 || ysize <= 0
1412 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
1415 if (GET_CODE (x) == CONST)
1417 if (GET_CODE (y) == CONST)
1418 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1419 ysize, canon_rtx (XEXP (y, 0)), c);
1421 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
1424 if (GET_CODE (y) == CONST)
1425 return memrefs_conflict_p (xsize, x, ysize,
1426 canon_rtx (XEXP (y, 0)), c);
1429 return (xsize < 0 || ysize < 0
1430 || (rtx_equal_for_memref_p (x, y)
1431 && (xsize == 0 || ysize == 0
1432 || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
1439 /* Functions to compute memory dependencies.
1441 Since we process the insns in execution order, we can build tables
1442 to keep track of what registers are fixed (and not aliased), what registers
1443 are varying in known ways, and what registers are varying in unknown
1446 If both memory references are volatile, then there must always be a
1447 dependence between the two references, since their order can not be
1448 changed. A volatile and non-volatile reference can be interchanged
1451 A MEM_IN_STRUCT reference at a non-AND varying address can never
1452 conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
1453 also must allow AND addresses, because they may generate accesses
1454 outside the object being referenced. This is used to generate
1455 aligned addresses from unaligned addresses, for instance, the alpha
1456 storeqi_unaligned pattern. */
1458 /* Read dependence: X is read after read in MEM takes place. There can
1459 only be a dependence here if both reads are volatile. */
1462 read_dependence (mem, x)
1466 return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
1469 /* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
1470 MEM2 is a reference to a structure at a varying address, or returns
1471 MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
1472 value is returned MEM1 and MEM2 can never alias. VARIES_P is used
1473 to decide whether or not an address may vary; it should return
1474 nonzero whenever variation is possible.
1475 MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
1478 fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
1480 rtx mem1_addr, mem2_addr;
1481 int (*varies_p) PARAMS ((rtx));
1483 if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
1484 && !varies_p (mem1_addr) && varies_p (mem2_addr))
1485 /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
1489 if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
1490 && varies_p (mem1_addr) && !varies_p (mem2_addr))
1491 /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
1498 /* Returns nonzero if something about the mode or address format MEM1
1499 indicates that it might well alias *anything*. */
1502 aliases_everything_p (mem)
1505 if (GET_CODE (XEXP (mem, 0)) == AND)
1506 /* If the address is an AND, its very hard to know at what it is
1507 actually pointing. */
1513 /* True dependence: X is read after store in MEM takes place. */
1516 true_dependence (mem, mem_mode, x, varies)
1518 enum machine_mode mem_mode;
1520 int (*varies) PARAMS ((rtx));
1522 register rtx x_addr, mem_addr;
1524 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1527 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1530 /* If X is an unchanging read, then it can't possibly conflict with any
1531 non-unchanging store. It may conflict with an unchanging write though,
1532 because there may be a single store to this address to initialize it.
1533 Just fall through to the code below to resolve the case where we have
1534 both an unchanging read and an unchanging write. This won't handle all
1535 cases optimally, but the possible performance loss should be
1537 if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
1540 if (mem_mode == VOIDmode)
1541 mem_mode = GET_MODE (mem);
1543 x_addr = get_addr (XEXP (x, 0));
1544 mem_addr = get_addr (XEXP (mem, 0));
1546 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
1549 x_addr = canon_rtx (x_addr);
1550 mem_addr = canon_rtx (mem_addr);
1552 if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
1553 SIZE_FOR_MODE (x), x_addr, 0))
1556 if (aliases_everything_p (x))
1559 /* We cannot use aliases_everyting_p to test MEM, since we must look
1560 at MEM_MODE, rather than GET_MODE (MEM). */
1561 if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
1564 /* In true_dependence we also allow BLKmode to alias anything. Why
1565 don't we do this in anti_dependence and output_dependence? */
1566 if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
1569 return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1573 /* Returns non-zero if a write to X might alias a previous read from
1574 (or, if WRITEP is non-zero, a write to) MEM. */
1577 write_dependence_p (mem, x, writep)
1582 rtx x_addr, mem_addr;
1585 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
1588 if (DIFFERENT_ALIAS_SETS_P (x, mem))
1591 /* If MEM is an unchanging read, then it can't possibly conflict with
1592 the store to X, because there is at most one store to MEM, and it must
1593 have occurred somewhere before MEM. */
1594 if (!writep && RTX_UNCHANGING_P (mem))
1597 x_addr = get_addr (XEXP (x, 0));
1598 mem_addr = get_addr (XEXP (mem, 0));
1600 if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
1604 x_addr = canon_rtx (x_addr);
1605 mem_addr = canon_rtx (mem_addr);
1607 if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
1608 SIZE_FOR_MODE (x), x_addr, 0))
1612 = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
1615 return (!(fixed_scalar == mem && !aliases_everything_p (x))
1616 && !(fixed_scalar == x && !aliases_everything_p (mem)));
1619 /* Anti dependence: X is written after read in MEM takes place. */
1622 anti_dependence (mem, x)
1626 return write_dependence_p (mem, x, /*writep=*/0);
1629 /* Output dependence: X is written after store in MEM takes place. */
1632 output_dependence (mem, x)
1636 return write_dependence_p (mem, x, /*writep=*/1);
1639 /* Returns non-zero if X might refer to something which is not
1640 local to the function and is not constant. */
1643 nonlocal_reference_p (x)
1647 register RTX_CODE code;
1650 code = GET_CODE (x);
1652 if (GET_RTX_CLASS (code) == 'i')
1654 /* Constant functions can be constant if they don't use
1655 scratch memory used to mark function w/o side effects. */
1656 if (code == CALL_INSN && CONST_CALL_P (x))
1658 x = CALL_INSN_FUNCTION_USAGE (x);
1664 code = GET_CODE (x);
1670 if (GET_CODE (SUBREG_REG (x)) == REG)
1672 /* Global registers are not local. */
1673 if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
1674 && global_regs[REGNO (SUBREG_REG (x)) + SUBREG_WORD (x)])
1682 /* Global registers are not local. */
1683 if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
1697 /* Constants in the function's constants pool are constant. */
1698 if (CONSTANT_POOL_ADDRESS_P (x))
1703 /* Recursion introduces no additional considerations. */
1704 if (GET_CODE (XEXP (x, 0)) == MEM
1705 && GET_CODE (XEXP (XEXP (x, 0), 0)) == SYMBOL_REF
1706 && strcmp(XSTR (XEXP (XEXP (x, 0), 0), 0),
1707 IDENTIFIER_POINTER (
1708 DECL_ASSEMBLER_NAME (current_function_decl))) == 0)
1713 /* Be overly conservative and consider any volatile memory
1714 reference as not local. */
1715 if (MEM_VOLATILE_P (x))
1717 base = find_base_term (XEXP (x, 0));
1720 /* A Pmode ADDRESS could be a reference via the structure value
1721 address or static chain. Such memory references are nonlocal.
1723 Thus, we have to examine the contents of the ADDRESS to find
1724 out if this is a local reference or not. */
1725 if (GET_CODE (base) == ADDRESS
1726 && GET_MODE (base) == Pmode
1727 && (XEXP (base, 0) == stack_pointer_rtx
1728 || XEXP (base, 0) == arg_pointer_rtx
1729 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1730 || XEXP (base, 0) == hard_frame_pointer_rtx
1732 || XEXP (base, 0) == frame_pointer_rtx))
1734 /* Constants in the function's constant pool are constant. */
1735 if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
1748 /* Recursively scan the operands of this expression. */
1751 register const char *fmt = GET_RTX_FORMAT (code);
1754 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
1756 if (fmt[i] == 'e' && XEXP (x, i))
1758 if (nonlocal_reference_p (XEXP (x, i)))
1761 else if (fmt[i] == 'E')
1764 for (j = 0; j < XVECLEN (x, i); j++)
1765 if (nonlocal_reference_p (XVECEXP (x, i, j)))
1774 /* Mark the function if it is constant. */
1777 mark_constant_function ()
1781 if (TREE_PUBLIC (current_function_decl)
1782 || TREE_READONLY (current_function_decl)
1783 || TREE_THIS_VOLATILE (current_function_decl)
1784 || TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
1787 /* Determine if this is a constant function. */
1789 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1790 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i'
1791 && nonlocal_reference_p (insn))
1794 /* Mark the function. */
1796 TREE_READONLY (current_function_decl) = 1;
1800 static HARD_REG_SET argument_registers;
1807 #ifndef OUTGOING_REGNO
1808 #define OUTGOING_REGNO(N) N
1810 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1811 /* Check whether this register can hold an incoming pointer
1812 argument. FUNCTION_ARG_REGNO_P tests outgoing register
1813 numbers, so translate if necessary due to register windows. */
1814 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
1815 && HARD_REGNO_MODE_OK (i, Pmode))
1816 SET_HARD_REG_BIT (argument_registers, i);
1818 alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
1821 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
1825 init_alias_analysis ()
1827 int maxreg = max_reg_num ();
1830 register unsigned int ui;
1833 reg_known_value_size = maxreg;
1836 = (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
1837 - FIRST_PSEUDO_REGISTER;
1839 = (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
1840 - FIRST_PSEUDO_REGISTER;
1842 /* Overallocate reg_base_value to allow some growth during loop
1843 optimization. Loop unrolling can create a large number of
1845 reg_base_value_size = maxreg * 2;
1846 reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
1848 ggc_add_rtx_root (reg_base_value, reg_base_value_size);
1850 new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
1851 reg_seen = (char *) xmalloc (reg_base_value_size);
1852 if (! reload_completed && flag_unroll_loops)
1854 /* ??? Why are we realloc'ing if we're just going to zero it? */
1855 alias_invariant = (rtx *)xrealloc (alias_invariant,
1856 reg_base_value_size * sizeof (rtx));
1857 bzero ((char *)alias_invariant, reg_base_value_size * sizeof (rtx));
1861 /* The basic idea is that each pass through this loop will use the
1862 "constant" information from the previous pass to propagate alias
1863 information through another level of assignments.
1865 This could get expensive if the assignment chains are long. Maybe
1866 we should throttle the number of iterations, possibly based on
1867 the optimization level or flag_expensive_optimizations.
1869 We could propagate more information in the first pass by making use
1870 of REG_N_SETS to determine immediately that the alias information
1871 for a pseudo is "constant".
1873 A program with an uninitialized variable can cause an infinite loop
1874 here. Instead of doing a full dataflow analysis to detect such problems
1875 we just cap the number of iterations for the loop.
1877 The state of the arrays for the set chain in question does not matter
1878 since the program has undefined behavior. */
1883 /* Assume nothing will change this iteration of the loop. */
1886 /* We want to assign the same IDs each iteration of this loop, so
1887 start counting from zero each iteration of the loop. */
1890 /* We're at the start of the funtion each iteration through the
1891 loop, so we're copying arguments. */
1892 copying_arguments = 1;
1894 /* Wipe the potential alias information clean for this pass. */
1895 bzero ((char *) new_reg_base_value, reg_base_value_size * sizeof (rtx));
1897 /* Wipe the reg_seen array clean. */
1898 bzero ((char *) reg_seen, reg_base_value_size);
1900 /* Mark all hard registers which may contain an address.
1901 The stack, frame and argument pointers may contain an address.
1902 An argument register which can hold a Pmode value may contain
1903 an address even if it is not in BASE_REGS.
1905 The address expression is VOIDmode for an argument and
1906 Pmode for other registers. */
1908 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
1909 if (TEST_HARD_REG_BIT (argument_registers, i))
1910 new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
1911 gen_rtx_REG (Pmode, i));
1913 new_reg_base_value[STACK_POINTER_REGNUM]
1914 = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
1915 new_reg_base_value[ARG_POINTER_REGNUM]
1916 = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
1917 new_reg_base_value[FRAME_POINTER_REGNUM]
1918 = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
1919 #if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
1920 new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
1921 = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
1923 if (struct_value_incoming_rtx
1924 && GET_CODE (struct_value_incoming_rtx) == REG)
1925 new_reg_base_value[REGNO (struct_value_incoming_rtx)]
1926 = gen_rtx_ADDRESS (Pmode, struct_value_incoming_rtx);
1928 if (static_chain_rtx
1929 && GET_CODE (static_chain_rtx) == REG)
1930 new_reg_base_value[REGNO (static_chain_rtx)]
1931 = gen_rtx_ADDRESS (Pmode, static_chain_rtx);
1933 /* Walk the insns adding values to the new_reg_base_value array. */
1934 for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
1936 if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
1940 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
1941 if (prologue_epilogue_contains (insn))
1945 /* If this insn has a noalias note, process it, Otherwise,
1946 scan for sets. A simple set will have no side effects
1947 which could change the base value of any other register. */
1949 if (GET_CODE (PATTERN (insn)) == SET
1950 && REG_NOTES (insn) != 0
1951 && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
1952 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
1954 note_stores (PATTERN (insn), record_set, NULL);
1956 set = single_set (insn);
1959 && GET_CODE (SET_DEST (set)) == REG
1960 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER
1961 && REG_NOTES (insn) != 0
1962 && (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
1963 && REG_N_SETS (REGNO (SET_DEST (set))) == 1)
1964 || (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
1965 && GET_CODE (XEXP (note, 0)) != EXPR_LIST
1966 && ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
1968 int regno = REGNO (SET_DEST (set));
1969 reg_known_value[regno] = XEXP (note, 0);
1970 reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
1973 else if (GET_CODE (insn) == NOTE
1974 && NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
1975 copying_arguments = 0;
1978 /* Now propagate values from new_reg_base_value to reg_base_value. */
1979 for (ui = 0; ui < reg_base_value_size; ui++)
1981 if (new_reg_base_value[ui]
1982 && new_reg_base_value[ui] != reg_base_value[ui]
1983 && ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
1985 reg_base_value[ui] = new_reg_base_value[ui];
1990 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
1992 /* Fill in the remaining entries. */
1993 for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
1994 if (reg_known_value[i] == 0)
1995 reg_known_value[i] = regno_reg_rtx[i];
1997 /* Simplify the reg_base_value array so that no register refers to
1998 another register, except to special registers indirectly through
1999 ADDRESS expressions.
2001 In theory this loop can take as long as O(registers^2), but unless
2002 there are very long dependency chains it will run in close to linear
2005 This loop may not be needed any longer now that the main loop does
2006 a better job at propagating alias information. */
2012 for (ui = 0; ui < reg_base_value_size; ui++)
2014 rtx base = reg_base_value[ui];
2015 if (base && GET_CODE (base) == REG)
2017 unsigned int base_regno = REGNO (base);
2018 if (base_regno == ui) /* register set from itself */
2019 reg_base_value[ui] = 0;
2021 reg_base_value[ui] = reg_base_value[base_regno];
2026 while (changed && pass < MAX_ALIAS_LOOP_PASSES);
2029 free (new_reg_base_value);
2030 new_reg_base_value = 0;
2036 end_alias_analysis ()
2038 free (reg_known_value + FIRST_PSEUDO_REGISTER);
2039 reg_known_value = 0;
2040 reg_known_value_size = 0;
2041 free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
2042 reg_known_equiv_p = 0;
2046 ggc_del_root (reg_base_value);
2047 free (reg_base_value);
2050 reg_base_value_size = 0;
2051 if (alias_invariant)
2053 free (alias_invariant);
2054 alias_invariant = 0;