1 /* Alias analysis for GNU C
2 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
3 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
4 Contributed by John Carr (jfc@mit.edu).
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
33 #include "hard-reg-set.h"
34 #include "basic-block.h"
37 #include "diagnostic-core.h"
39 #include "splay-tree.h"
41 #include "langhooks.h"
45 #include "tree-pass.h"
47 #include "tree-ssa-alias.h"
48 #include "pointer-set.h"
49 #include "tree-flow.h"
51 /* The aliasing API provided here solves related but different problems:
53 Say there exists (in c)
67 Consider the four questions:
69 Can a store to x1 interfere with px2->y1?
70 Can a store to x1 interfere with px2->z2?
72 Can a store to x1 change the value pointed to by with py?
73 Can a store to x1 change the value pointed to by with pz?
75 The answer to these questions can be yes, yes, yes, and maybe.
77 The first two questions can be answered with a simple examination
78 of the type system. If structure X contains a field of type Y then
79 a store thru a pointer to an X can overwrite any field that is
80 contained (recursively) in an X (unless we know that px1 != px2).
82 The last two of the questions can be solved in the same way as the
83 first two questions but this is too conservative. The observation
84 is that in some cases analysis we can know if which (if any) fields
85 are addressed and if those addresses are used in bad ways. This
86 analysis may be language specific. In C, arbitrary operations may
87 be applied to pointers. However, there is some indication that
88 this may be too conservative for some C++ types.
90 The pass ipa-type-escape does this analysis for the types whose
91 instances do not escape across the compilation boundary.
93 Historically in GCC, these two problems were combined and a single
94 data structure was used to represent the solution to these
95 problems. We now have two similar but different data structures,
96 The data structure to solve the last two question is similar to the
97 first, but does not contain have the fields in it whose address are
98 never taken. For types that do escape the compilation unit, the
99 data structures will have identical information.
102 /* The alias sets assigned to MEMs assist the back-end in determining
103 which MEMs can alias which other MEMs. In general, two MEMs in
104 different alias sets cannot alias each other, with one important
105 exception. Consider something like:
107 struct S { int i; double d; };
109 a store to an `S' can alias something of either type `int' or type
110 `double'. (However, a store to an `int' cannot alias a `double'
111 and vice versa.) We indicate this via a tree structure that looks
119 (The arrows are directed and point downwards.)
120 In this situation we say the alias set for `struct S' is the
121 `superset' and that those for `int' and `double' are `subsets'.
123 To see whether two alias sets can point to the same memory, we must
124 see if either alias set is a subset of the other. We need not trace
125 past immediate descendants, however, since we propagate all
126 grandchildren up one level.
128 Alias set zero is implicitly a superset of all other alias sets.
129 However, this is no actual entry for alias set zero. It is an
130 error to attempt to explicitly construct a subset of zero. */
132 struct GTY(()) alias_set_entry_d
{
133 /* The alias set number, as stored in MEM_ALIAS_SET. */
134 alias_set_type alias_set
;
136 /* Nonzero if would have a child of zero: this effectively makes this
137 alias set the same as alias set zero. */
140 /* The children of the alias set. These are not just the immediate
141 children, but, in fact, all descendants. So, if we have:
143 struct T { struct S s; float f; }
145 continuing our example above, the children here will be all of
146 `int', `double', `float', and `struct S'. */
147 splay_tree
GTY((param1_is (int), param2_is (int))) children
;
149 typedef struct alias_set_entry_d
*alias_set_entry
;
151 static int rtx_equal_for_memref_p (const_rtx
, const_rtx
);
152 static int memrefs_conflict_p (int, rtx
, int, rtx
, HOST_WIDE_INT
);
153 static void record_set (rtx
, const_rtx
, void *);
154 static int base_alias_check (rtx
, rtx
, enum machine_mode
,
156 static rtx
find_base_value (rtx
);
157 static int mems_in_disjoint_alias_sets_p (const_rtx
, const_rtx
);
158 static int insert_subset_children (splay_tree_node
, void*);
159 static alias_set_entry
get_alias_set_entry (alias_set_type
);
160 static int aliases_everything_p (const_rtx
);
161 static bool nonoverlapping_component_refs_p (const_tree
, const_tree
);
162 static tree
decl_for_component_ref (tree
);
163 static int write_dependence_p (const_rtx
, const_rtx
, int);
165 static void memory_modified_1 (rtx
, const_rtx
, void *);
167 /* Set up all info needed to perform alias analysis on memory references. */
169 /* Returns the size in bytes of the mode of X. */
170 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
172 /* Returns nonzero if MEM1 and MEM2 do not alias because they are in
173 different alias sets. We ignore alias sets in functions making use
174 of variable arguments because the va_arg macros on some systems are
176 #define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
177 mems_in_disjoint_alias_sets_p (MEM1, MEM2)
179 /* Cap the number of passes we make over the insns propagating alias
180 information through set chains. 10 is a completely arbitrary choice. */
181 #define MAX_ALIAS_LOOP_PASSES 10
183 /* reg_base_value[N] gives an address to which register N is related.
184 If all sets after the first add or subtract to the current value
185 or otherwise modify it so it does not point to a different top level
186 object, reg_base_value[N] is equal to the address part of the source
189 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
190 expressions represent certain special values: function arguments and
191 the stack, frame, and argument pointers.
193 The contents of an ADDRESS is not normally used, the mode of the
194 ADDRESS determines whether the ADDRESS is a function argument or some
195 other special value. Pointer equality, not rtx_equal_p, determines whether
196 two ADDRESS expressions refer to the same base address.
198 The only use of the contents of an ADDRESS is for determining if the
199 current function performs nonlocal memory memory references for the
200 purposes of marking the function as a constant function. */
202 static GTY(()) VEC(rtx
,gc
) *reg_base_value
;
203 static rtx
*new_reg_base_value
;
205 /* We preserve the copy of old array around to avoid amount of garbage
206 produced. About 8% of garbage produced were attributed to this
208 static GTY((deletable
)) VEC(rtx
,gc
) *old_reg_base_value
;
210 #define static_reg_base_value \
211 (this_target_rtl->x_static_reg_base_value)
213 #define REG_BASE_VALUE(X) \
214 (REGNO (X) < VEC_length (rtx, reg_base_value) \
215 ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)
217 /* Vector indexed by N giving the initial (unchanging) value known for
218 pseudo-register N. This array is initialized in init_alias_analysis,
219 and does not change until end_alias_analysis is called. */
220 static GTY((length("reg_known_value_size"))) rtx
*reg_known_value
;
222 /* Indicates number of valid entries in reg_known_value. */
223 static GTY(()) unsigned int reg_known_value_size
;
225 /* Vector recording for each reg_known_value whether it is due to a
226 REG_EQUIV note. Future passes (viz., reload) may replace the
227 pseudo with the equivalent expression and so we account for the
228 dependences that would be introduced if that happens.
230 The REG_EQUIV notes created in assign_parms may mention the arg
231 pointer, and there are explicit insns in the RTL that modify the
232 arg pointer. Thus we must ensure that such insns don't get
233 scheduled across each other because that would invalidate the
234 REG_EQUIV notes. One could argue that the REG_EQUIV notes are
235 wrong, but solving the problem in the scheduler will likely give
236 better code, so we do it here. */
237 static bool *reg_known_equiv_p
;
239 /* True when scanning insns from the start of the rtl to the
240 NOTE_INSN_FUNCTION_BEG note. */
241 static bool copying_arguments
;
243 DEF_VEC_P(alias_set_entry
);
244 DEF_VEC_ALLOC_P(alias_set_entry
,gc
);
246 /* The splay-tree used to store the various alias set entries. */
247 static GTY (()) VEC(alias_set_entry
,gc
) *alias_sets
;
249 /* Build a decomposed reference object for querying the alias-oracle
250 from the MEM rtx and store it in *REF.
251 Returns false if MEM is not suitable for the alias-oracle. */
254 ao_ref_from_mem (ao_ref
*ref
, const_rtx mem
)
256 tree expr
= MEM_EXPR (mem
);
262 ao_ref_init (ref
, expr
);
264 /* Get the base of the reference and see if we have to reject or
266 base
= ao_ref_base (ref
);
267 if (base
== NULL_TREE
)
270 /* The tree oracle doesn't like to have these. */
271 if (TREE_CODE (base
) == FUNCTION_DECL
272 || TREE_CODE (base
) == LABEL_DECL
)
275 /* If this is a pointer dereference of a non-SSA_NAME punt.
276 ??? We could replace it with a pointer to anything. */
277 if ((INDIRECT_REF_P (base
)
278 || TREE_CODE (base
) == MEM_REF
)
279 && TREE_CODE (TREE_OPERAND (base
, 0)) != SSA_NAME
)
281 if (TREE_CODE (base
) == TARGET_MEM_REF
283 && TREE_CODE (TMR_BASE (base
)) != SSA_NAME
)
286 /* If this is a reference based on a partitioned decl replace the
287 base with an INDIRECT_REF of the pointer representative we
288 created during stack slot partitioning. */
289 if (TREE_CODE (base
) == VAR_DECL
290 && ! TREE_STATIC (base
)
291 && cfun
->gimple_df
->decls_to_pointers
!= NULL
)
294 namep
= pointer_map_contains (cfun
->gimple_df
->decls_to_pointers
, base
);
296 ref
->base
= build_simple_mem_ref (*(tree
*)namep
);
298 else if (TREE_CODE (base
) == TARGET_MEM_REF
299 && TREE_CODE (TMR_BASE (base
)) == ADDR_EXPR
300 && TREE_CODE (TREE_OPERAND (TMR_BASE (base
), 0)) == VAR_DECL
301 && ! TREE_STATIC (TREE_OPERAND (TMR_BASE (base
), 0))
302 && cfun
->gimple_df
->decls_to_pointers
!= NULL
)
305 namep
= pointer_map_contains (cfun
->gimple_df
->decls_to_pointers
,
306 TREE_OPERAND (TMR_BASE (base
), 0));
308 ref
->base
= build_simple_mem_ref (*(tree
*)namep
);
311 ref
->ref_alias_set
= MEM_ALIAS_SET (mem
);
313 /* If MEM_OFFSET or MEM_SIZE are unknown we have to punt.
314 Keep points-to related information though. */
315 if (!MEM_OFFSET_KNOWN_P (mem
)
316 || !MEM_SIZE_KNOWN_P (mem
))
318 ref
->ref
= NULL_TREE
;
325 /* If the base decl is a parameter we can have negative MEM_OFFSET in
326 case of promoted subregs on bigendian targets. Trust the MEM_EXPR
328 if (MEM_OFFSET (mem
) < 0
329 && (MEM_SIZE (mem
) + MEM_OFFSET (mem
)) * BITS_PER_UNIT
== ref
->size
)
332 ref
->offset
+= MEM_OFFSET (mem
) * BITS_PER_UNIT
;
333 ref
->size
= MEM_SIZE (mem
) * BITS_PER_UNIT
;
335 /* The MEM may extend into adjacent fields, so adjust max_size if
337 if (ref
->max_size
!= -1
338 && ref
->size
> ref
->max_size
)
339 ref
->max_size
= ref
->size
;
341 /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of
342 the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */
343 if (MEM_EXPR (mem
) != get_spill_slot_decl (false)
345 || (DECL_P (ref
->base
)
346 && (!host_integerp (DECL_SIZE (ref
->base
), 1)
347 || (TREE_INT_CST_LOW (DECL_SIZE ((ref
->base
)))
348 < (unsigned HOST_WIDE_INT
)(ref
->offset
+ ref
->size
))))))
354 /* Query the alias-oracle on whether the two memory rtx X and MEM may
355 alias. If TBAA_P is set also apply TBAA. Returns true if the
356 two rtxen may alias, false otherwise. */
359 rtx_refs_may_alias_p (const_rtx x
, const_rtx mem
, bool tbaa_p
)
363 if (!ao_ref_from_mem (&ref1
, x
)
364 || !ao_ref_from_mem (&ref2
, mem
))
367 return refs_may_alias_p_1 (&ref1
, &ref2
,
369 && MEM_ALIAS_SET (x
) != 0
370 && MEM_ALIAS_SET (mem
) != 0);
373 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is
374 such an entry, or NULL otherwise. */
376 static inline alias_set_entry
377 get_alias_set_entry (alias_set_type alias_set
)
379 return VEC_index (alias_set_entry
, alias_sets
, alias_set
);
382 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
383 the two MEMs cannot alias each other. */
386 mems_in_disjoint_alias_sets_p (const_rtx mem1
, const_rtx mem2
)
388 /* Perform a basic sanity check. Namely, that there are no alias sets
389 if we're not using strict aliasing. This helps to catch bugs
390 whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
391 where a MEM is allocated in some way other than by the use of
392 gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
393 use alias sets to indicate that spilled registers cannot alias each
394 other, we might need to remove this check. */
395 gcc_assert (flag_strict_aliasing
396 || (!MEM_ALIAS_SET (mem1
) && !MEM_ALIAS_SET (mem2
)));
398 return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1
), MEM_ALIAS_SET (mem2
));
401 /* Insert the NODE into the splay tree given by DATA. Used by
402 record_alias_subset via splay_tree_foreach. */
405 insert_subset_children (splay_tree_node node
, void *data
)
407 splay_tree_insert ((splay_tree
) data
, node
->key
, node
->value
);
412 /* Return true if the first alias set is a subset of the second. */
415 alias_set_subset_of (alias_set_type set1
, alias_set_type set2
)
419 /* Everything is a subset of the "aliases everything" set. */
423 /* Otherwise, check if set1 is a subset of set2. */
424 ase
= get_alias_set_entry (set2
);
426 && (ase
->has_zero_child
427 || splay_tree_lookup (ase
->children
,
428 (splay_tree_key
) set1
)))
433 /* Return 1 if the two specified alias sets may conflict. */
436 alias_sets_conflict_p (alias_set_type set1
, alias_set_type set2
)
441 if (alias_sets_must_conflict_p (set1
, set2
))
444 /* See if the first alias set is a subset of the second. */
445 ase
= get_alias_set_entry (set1
);
447 && (ase
->has_zero_child
448 || splay_tree_lookup (ase
->children
,
449 (splay_tree_key
) set2
)))
452 /* Now do the same, but with the alias sets reversed. */
453 ase
= get_alias_set_entry (set2
);
455 && (ase
->has_zero_child
456 || splay_tree_lookup (ase
->children
,
457 (splay_tree_key
) set1
)))
460 /* The two alias sets are distinct and neither one is the
461 child of the other. Therefore, they cannot conflict. */
465 /* Return 1 if the two specified alias sets will always conflict. */
468 alias_sets_must_conflict_p (alias_set_type set1
, alias_set_type set2
)
470 if (set1
== 0 || set2
== 0 || set1
== set2
)
476 /* Return 1 if any MEM object of type T1 will always conflict (using the
477 dependency routines in this file) with any MEM object of type T2.
478 This is used when allocating temporary storage. If T1 and/or T2 are
479 NULL_TREE, it means we know nothing about the storage. */
482 objects_must_conflict_p (tree t1
, tree t2
)
484 alias_set_type set1
, set2
;
486 /* If neither has a type specified, we don't know if they'll conflict
487 because we may be using them to store objects of various types, for
488 example the argument and local variables areas of inlined functions. */
489 if (t1
== 0 && t2
== 0)
492 /* If they are the same type, they must conflict. */
494 /* Likewise if both are volatile. */
495 || (t1
!= 0 && TYPE_VOLATILE (t1
) && t2
!= 0 && TYPE_VOLATILE (t2
)))
498 set1
= t1
? get_alias_set (t1
) : 0;
499 set2
= t2
? get_alias_set (t2
) : 0;
501 /* We can't use alias_sets_conflict_p because we must make sure
502 that every subtype of t1 will conflict with every subtype of
503 t2 for which a pair of subobjects of these respective subtypes
504 overlaps on the stack. */
505 return alias_sets_must_conflict_p (set1
, set2
);
508 /* Return true if all nested component references handled by
509 get_inner_reference in T are such that we should use the alias set
510 provided by the object at the heart of T.
512 This is true for non-addressable components (which don't have their
513 own alias set), as well as components of objects in alias set zero.
514 This later point is a special case wherein we wish to override the
515 alias set used by the component, but we don't have per-FIELD_DECL
516 assignable alias sets. */
519 component_uses_parent_alias_set (const_tree t
)
523 /* If we're at the end, it vacuously uses its own alias set. */
524 if (!handled_component_p (t
))
527 switch (TREE_CODE (t
))
530 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t
, 1)))
535 case ARRAY_RANGE_REF
:
536 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t
, 0))))
545 /* Bitfields and casts are never addressable. */
549 t
= TREE_OPERAND (t
, 0);
550 if (get_alias_set (TREE_TYPE (t
)) == 0)
555 /* Return the alias set for the memory pointed to by T, which may be
556 either a type or an expression. Return -1 if there is nothing
557 special about dereferencing T. */
559 static alias_set_type
560 get_deref_alias_set_1 (tree t
)
562 /* If we're not doing any alias analysis, just assume everything
563 aliases everything else. */
564 if (!flag_strict_aliasing
)
567 /* All we care about is the type. */
571 /* If we have an INDIRECT_REF via a void pointer, we don't
572 know anything about what that might alias. Likewise if the
573 pointer is marked that way. */
574 if (TREE_CODE (TREE_TYPE (t
)) == VOID_TYPE
575 || TYPE_REF_CAN_ALIAS_ALL (t
))
581 /* Return the alias set for the memory pointed to by T, which may be
582 either a type or an expression. */
585 get_deref_alias_set (tree t
)
587 alias_set_type set
= get_deref_alias_set_1 (t
);
589 /* Fall back to the alias-set of the pointed-to type. */
594 set
= get_alias_set (TREE_TYPE (t
));
600 /* Return the alias set for T, which may be either a type or an
601 expression. Call language-specific routine for help, if needed. */
604 get_alias_set (tree t
)
608 /* If we're not doing any alias analysis, just assume everything
609 aliases everything else. Also return 0 if this or its type is
611 if (! flag_strict_aliasing
|| t
== error_mark_node
613 && (TREE_TYPE (t
) == 0 || TREE_TYPE (t
) == error_mark_node
)))
616 /* We can be passed either an expression or a type. This and the
617 language-specific routine may make mutually-recursive calls to each other
618 to figure out what to do. At each juncture, we see if this is a tree
619 that the language may need to handle specially. First handle things that
625 /* Give the language a chance to do something with this tree
626 before we look at it. */
628 set
= lang_hooks
.get_alias_set (t
);
632 /* Get the base object of the reference. */
634 while (handled_component_p (inner
))
636 /* If there is a VIEW_CONVERT_EXPR in the chain we cannot use
637 the type of any component references that wrap it to
638 determine the alias-set. */
639 if (TREE_CODE (inner
) == VIEW_CONVERT_EXPR
)
640 t
= TREE_OPERAND (inner
, 0);
641 inner
= TREE_OPERAND (inner
, 0);
644 /* Handle pointer dereferences here, they can override the
646 if (INDIRECT_REF_P (inner
))
648 set
= get_deref_alias_set_1 (TREE_OPERAND (inner
, 0));
652 else if (TREE_CODE (inner
) == TARGET_MEM_REF
)
653 return get_deref_alias_set (TMR_OFFSET (inner
));
654 else if (TREE_CODE (inner
) == MEM_REF
)
656 set
= get_deref_alias_set_1 (TREE_OPERAND (inner
, 1));
661 /* If the innermost reference is a MEM_REF that has a
662 conversion embedded treat it like a VIEW_CONVERT_EXPR above,
663 using the memory access type for determining the alias-set. */
664 if (TREE_CODE (inner
) == MEM_REF
665 && TYPE_MAIN_VARIANT (TREE_TYPE (inner
))
667 (TREE_TYPE (TREE_TYPE (TREE_OPERAND (inner
, 1)))))
668 return get_deref_alias_set (TREE_OPERAND (inner
, 1));
670 /* Otherwise, pick up the outermost object that we could have a pointer
671 to, processing conversions as above. */
672 while (component_uses_parent_alias_set (t
))
674 t
= TREE_OPERAND (t
, 0);
678 /* If we've already determined the alias set for a decl, just return
679 it. This is necessary for C++ anonymous unions, whose component
680 variables don't look like union members (boo!). */
681 if (TREE_CODE (t
) == VAR_DECL
682 && DECL_RTL_SET_P (t
) && MEM_P (DECL_RTL (t
)))
683 return MEM_ALIAS_SET (DECL_RTL (t
));
685 /* Now all we care about is the type. */
689 /* Variant qualifiers don't affect the alias set, so get the main
691 t
= TYPE_MAIN_VARIANT (t
);
693 /* Always use the canonical type as well. If this is a type that
694 requires structural comparisons to identify compatible types
695 use alias set zero. */
696 if (TYPE_STRUCTURAL_EQUALITY_P (t
))
698 /* Allow the language to specify another alias set for this
700 set
= lang_hooks
.get_alias_set (t
);
706 t
= TYPE_CANONICAL (t
);
708 /* The canonical type should not require structural equality checks. */
709 gcc_checking_assert (!TYPE_STRUCTURAL_EQUALITY_P (t
));
711 /* If this is a type with a known alias set, return it. */
712 if (TYPE_ALIAS_SET_KNOWN_P (t
))
713 return TYPE_ALIAS_SET (t
);
715 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */
716 if (!COMPLETE_TYPE_P (t
))
718 /* For arrays with unknown size the conservative answer is the
719 alias set of the element type. */
720 if (TREE_CODE (t
) == ARRAY_TYPE
)
721 return get_alias_set (TREE_TYPE (t
));
723 /* But return zero as a conservative answer for incomplete types. */
727 /* See if the language has special handling for this type. */
728 set
= lang_hooks
.get_alias_set (t
);
732 /* There are no objects of FUNCTION_TYPE, so there's no point in
733 using up an alias set for them. (There are, of course, pointers
734 and references to functions, but that's different.) */
735 else if (TREE_CODE (t
) == FUNCTION_TYPE
|| TREE_CODE (t
) == METHOD_TYPE
)
738 /* Unless the language specifies otherwise, let vector types alias
739 their components. This avoids some nasty type punning issues in
740 normal usage. And indeed lets vectors be treated more like an
742 else if (TREE_CODE (t
) == VECTOR_TYPE
)
743 set
= get_alias_set (TREE_TYPE (t
));
745 /* Unless the language specifies otherwise, treat array types the
746 same as their components. This avoids the asymmetry we get
747 through recording the components. Consider accessing a
748 character(kind=1) through a reference to a character(kind=1)[1:1].
749 Or consider if we want to assign integer(kind=4)[0:D.1387] and
750 integer(kind=4)[4] the same alias set or not.
751 Just be pragmatic here and make sure the array and its element
752 type get the same alias set assigned. */
753 else if (TREE_CODE (t
) == ARRAY_TYPE
&& !TYPE_NONALIASED_COMPONENT (t
))
754 set
= get_alias_set (TREE_TYPE (t
));
756 /* From the former common C and C++ langhook implementation:
758 Unfortunately, there is no canonical form of a pointer type.
759 In particular, if we have `typedef int I', then `int *', and
760 `I *' are different types. So, we have to pick a canonical
761 representative. We do this below.
763 Technically, this approach is actually more conservative that
764 it needs to be. In particular, `const int *' and `int *'
765 should be in different alias sets, according to the C and C++
766 standard, since their types are not the same, and so,
767 technically, an `int **' and `const int **' cannot point at
770 But, the standard is wrong. In particular, this code is
775 const int* const* cipp = ipp;
776 And, it doesn't make sense for that to be legal unless you
777 can dereference IPP and CIPP. So, we ignore cv-qualifiers on
778 the pointed-to types. This issue has been reported to the
781 In addition to the above canonicalization issue, with LTO
782 we should also canonicalize `T (*)[]' to `T *' avoiding
783 alias issues with pointer-to element types and pointer-to
786 Likewise we need to deal with the situation of incomplete
787 pointed-to types and make `*(struct X **)&a' and
788 `*(struct X {} **)&a' alias. Otherwise we will have to
789 guarantee that all pointer-to incomplete type variants
790 will be replaced by pointer-to complete type variants if
793 With LTO the convenient situation of using `void *' to
794 access and store any pointer type will also become
795 more apparent (and `void *' is just another pointer-to
796 incomplete type). Assigning alias-set zero to `void *'
797 and all pointer-to incomplete types is a not appealing
798 solution. Assigning an effective alias-set zero only
799 affecting pointers might be - by recording proper subset
800 relationships of all pointer alias-sets.
802 Pointer-to function types are another grey area which
803 needs caution. Globbing them all into one alias-set
804 or the above effective zero set would work.
806 For now just assign the same alias-set to all pointers.
807 That's simple and avoids all the above problems. */
808 else if (POINTER_TYPE_P (t
)
809 && t
!= ptr_type_node
)
810 set
= get_alias_set (ptr_type_node
);
812 /* Otherwise make a new alias set for this type. */
815 /* Each canonical type gets its own alias set, so canonical types
816 shouldn't form a tree. It doesn't really matter for types
817 we handle specially above, so only check it where it possibly
818 would result in a bogus alias set. */
819 gcc_checking_assert (TYPE_CANONICAL (t
) == t
);
821 set
= new_alias_set ();
824 TYPE_ALIAS_SET (t
) = set
;
826 /* If this is an aggregate type or a complex type, we must record any
827 component aliasing information. */
828 if (AGGREGATE_TYPE_P (t
) || TREE_CODE (t
) == COMPLEX_TYPE
)
829 record_component_aliases (t
);
834 /* Return a brand-new alias set. */
839 if (flag_strict_aliasing
)
842 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
843 VEC_safe_push (alias_set_entry
, gc
, alias_sets
, 0);
844 return VEC_length (alias_set_entry
, alias_sets
) - 1;
850 /* Indicate that things in SUBSET can alias things in SUPERSET, but that
851 not everything that aliases SUPERSET also aliases SUBSET. For example,
852 in C, a store to an `int' can alias a load of a structure containing an
853 `int', and vice versa. But it can't alias a load of a 'double' member
854 of the same structure. Here, the structure would be the SUPERSET and
855 `int' the SUBSET. This relationship is also described in the comment at
856 the beginning of this file.
858 This function should be called only once per SUPERSET/SUBSET pair.
860 It is illegal for SUPERSET to be zero; everything is implicitly a
861 subset of alias set zero. */
864 record_alias_subset (alias_set_type superset
, alias_set_type subset
)
866 alias_set_entry superset_entry
;
867 alias_set_entry subset_entry
;
869 /* It is possible in complex type situations for both sets to be the same,
870 in which case we can ignore this operation. */
871 if (superset
== subset
)
874 gcc_assert (superset
);
876 superset_entry
= get_alias_set_entry (superset
);
877 if (superset_entry
== 0)
879 /* Create an entry for the SUPERSET, so that we have a place to
880 attach the SUBSET. */
881 superset_entry
= ggc_alloc_cleared_alias_set_entry_d ();
882 superset_entry
->alias_set
= superset
;
883 superset_entry
->children
884 = splay_tree_new_ggc (splay_tree_compare_ints
,
885 ggc_alloc_splay_tree_scalar_scalar_splay_tree_s
,
886 ggc_alloc_splay_tree_scalar_scalar_splay_tree_node_s
);
887 superset_entry
->has_zero_child
= 0;
888 VEC_replace (alias_set_entry
, alias_sets
, superset
, superset_entry
);
892 superset_entry
->has_zero_child
= 1;
895 subset_entry
= get_alias_set_entry (subset
);
896 /* If there is an entry for the subset, enter all of its children
897 (if they are not already present) as children of the SUPERSET. */
900 if (subset_entry
->has_zero_child
)
901 superset_entry
->has_zero_child
= 1;
903 splay_tree_foreach (subset_entry
->children
, insert_subset_children
,
904 superset_entry
->children
);
907 /* Enter the SUBSET itself as a child of the SUPERSET. */
908 splay_tree_insert (superset_entry
->children
,
909 (splay_tree_key
) subset
, 0);
913 /* Record that component types of TYPE, if any, are part of that type for
914 aliasing purposes. For record types, we only record component types
915 for fields that are not marked non-addressable. For array types, we
916 only record the component type if it is not marked non-aliased. */
919 record_component_aliases (tree type
)
921 alias_set_type superset
= get_alias_set (type
);
927 switch (TREE_CODE (type
))
931 case QUAL_UNION_TYPE
:
932 /* Recursively record aliases for the base classes, if there are any. */
933 if (TYPE_BINFO (type
))
936 tree binfo
, base_binfo
;
938 for (binfo
= TYPE_BINFO (type
), i
= 0;
939 BINFO_BASE_ITERATE (binfo
, i
, base_binfo
); i
++)
940 record_alias_subset (superset
,
941 get_alias_set (BINFO_TYPE (base_binfo
)));
943 for (field
= TYPE_FIELDS (type
); field
!= 0; field
= DECL_CHAIN (field
))
944 if (TREE_CODE (field
) == FIELD_DECL
&& !DECL_NONADDRESSABLE_P (field
))
945 record_alias_subset (superset
, get_alias_set (TREE_TYPE (field
)));
949 record_alias_subset (superset
, get_alias_set (TREE_TYPE (type
)));
952 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
960 /* Allocate an alias set for use in storing and reading from the varargs
963 static GTY(()) alias_set_type varargs_set
= -1;
966 get_varargs_alias_set (void)
969 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
970 varargs alias set to an INDIRECT_REF (FIXME!), so we can't
971 consistently use the varargs alias set for loads from the varargs
972 area. So don't use it anywhere. */
975 if (varargs_set
== -1)
976 varargs_set
= new_alias_set ();
982 /* Likewise, but used for the fixed portions of the frame, e.g., register
985 static GTY(()) alias_set_type frame_set
= -1;
988 get_frame_alias_set (void)
991 frame_set
= new_alias_set ();
996 /* Inside SRC, the source of a SET, find a base address. */
999 find_base_value (rtx src
)
1003 #if defined (FIND_BASE_TERM)
1004 /* Try machine-dependent ways to find the base term. */
1005 src
= FIND_BASE_TERM (src
);
1008 switch (GET_CODE (src
))
1015 regno
= REGNO (src
);
1016 /* At the start of a function, argument registers have known base
1017 values which may be lost later. Returning an ADDRESS
1018 expression here allows optimization based on argument values
1019 even when the argument registers are used for other purposes. */
1020 if (regno
< FIRST_PSEUDO_REGISTER
&& copying_arguments
)
1021 return new_reg_base_value
[regno
];
1023 /* If a pseudo has a known base value, return it. Do not do this
1024 for non-fixed hard regs since it can result in a circular
1025 dependency chain for registers which have values at function entry.
1027 The test above is not sufficient because the scheduler may move
1028 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
1029 if ((regno
>= FIRST_PSEUDO_REGISTER
|| fixed_regs
[regno
])
1030 && regno
< VEC_length (rtx
, reg_base_value
))
1032 /* If we're inside init_alias_analysis, use new_reg_base_value
1033 to reduce the number of relaxation iterations. */
1034 if (new_reg_base_value
&& new_reg_base_value
[regno
]
1035 && DF_REG_DEF_COUNT (regno
) == 1)
1036 return new_reg_base_value
[regno
];
1038 if (VEC_index (rtx
, reg_base_value
, regno
))
1039 return VEC_index (rtx
, reg_base_value
, regno
);
1045 /* Check for an argument passed in memory. Only record in the
1046 copying-arguments block; it is too hard to track changes
1048 if (copying_arguments
1049 && (XEXP (src
, 0) == arg_pointer_rtx
1050 || (GET_CODE (XEXP (src
, 0)) == PLUS
1051 && XEXP (XEXP (src
, 0), 0) == arg_pointer_rtx
)))
1052 return gen_rtx_ADDRESS (VOIDmode
, src
);
1056 src
= XEXP (src
, 0);
1057 if (GET_CODE (src
) != PLUS
&& GET_CODE (src
) != MINUS
)
1060 /* ... fall through ... */
1065 rtx temp
, src_0
= XEXP (src
, 0), src_1
= XEXP (src
, 1);
1067 /* If either operand is a REG that is a known pointer, then it
1069 if (REG_P (src_0
) && REG_POINTER (src_0
))
1070 return find_base_value (src_0
);
1071 if (REG_P (src_1
) && REG_POINTER (src_1
))
1072 return find_base_value (src_1
);
1074 /* If either operand is a REG, then see if we already have
1075 a known value for it. */
1078 temp
= find_base_value (src_0
);
1085 temp
= find_base_value (src_1
);
1090 /* If either base is named object or a special address
1091 (like an argument or stack reference), then use it for the
1094 && (GET_CODE (src_0
) == SYMBOL_REF
1095 || GET_CODE (src_0
) == LABEL_REF
1096 || (GET_CODE (src_0
) == ADDRESS
1097 && GET_MODE (src_0
) != VOIDmode
)))
1101 && (GET_CODE (src_1
) == SYMBOL_REF
1102 || GET_CODE (src_1
) == LABEL_REF
1103 || (GET_CODE (src_1
) == ADDRESS
1104 && GET_MODE (src_1
) != VOIDmode
)))
1107 /* Guess which operand is the base address:
1108 If either operand is a symbol, then it is the base. If
1109 either operand is a CONST_INT, then the other is the base. */
1110 if (CONST_INT_P (src_1
) || CONSTANT_P (src_0
))
1111 return find_base_value (src_0
);
1112 else if (CONST_INT_P (src_0
) || CONSTANT_P (src_1
))
1113 return find_base_value (src_1
);
1119 /* The standard form is (lo_sum reg sym) so look only at the
1121 return find_base_value (XEXP (src
, 1));
1124 /* If the second operand is constant set the base
1125 address to the first operand. */
1126 if (CONST_INT_P (XEXP (src
, 1)) && INTVAL (XEXP (src
, 1)) != 0)
1127 return find_base_value (XEXP (src
, 0));
1131 /* As we do not know which address space the pointer is refering to, we can
1132 handle this only if the target does not support different pointer or
1133 address modes depending on the address space. */
1134 if (!target_default_pointer_address_modes_p ())
1136 if (GET_MODE_SIZE (GET_MODE (src
)) < GET_MODE_SIZE (Pmode
))
1146 return find_base_value (XEXP (src
, 0));
1149 case SIGN_EXTEND
: /* used for NT/Alpha pointers */
1150 /* As we do not know which address space the pointer is refering to, we can
1151 handle this only if the target does not support different pointer or
1152 address modes depending on the address space. */
1153 if (!target_default_pointer_address_modes_p ())
1157 rtx temp
= find_base_value (XEXP (src
, 0));
1159 if (temp
!= 0 && CONSTANT_P (temp
))
1160 temp
= convert_memory_address (Pmode
, temp
);
1172 /* Called from init_alias_analysis indirectly through note_stores. */
1174 /* While scanning insns to find base values, reg_seen[N] is nonzero if
1175 register N has been set in this function. */
1176 static char *reg_seen
;
1178 /* Addresses which are known not to alias anything else are identified
1179 by a unique integer. */
1180 static int unique_id
;
1183 record_set (rtx dest
, const_rtx set
, void *data ATTRIBUTE_UNUSED
)
1192 regno
= REGNO (dest
);
1194 gcc_checking_assert (regno
< VEC_length (rtx
, reg_base_value
));
1196 /* If this spans multiple hard registers, then we must indicate that every
1197 register has an unusable value. */
1198 if (regno
< FIRST_PSEUDO_REGISTER
)
1199 n
= hard_regno_nregs
[regno
][GET_MODE (dest
)];
1206 reg_seen
[regno
+ n
] = 1;
1207 new_reg_base_value
[regno
+ n
] = 0;
1214 /* A CLOBBER wipes out any old value but does not prevent a previously
1215 unset register from acquiring a base address (i.e. reg_seen is not
1217 if (GET_CODE (set
) == CLOBBER
)
1219 new_reg_base_value
[regno
] = 0;
1222 src
= SET_SRC (set
);
1226 if (reg_seen
[regno
])
1228 new_reg_base_value
[regno
] = 0;
1231 reg_seen
[regno
] = 1;
1232 new_reg_base_value
[regno
] = gen_rtx_ADDRESS (Pmode
,
1233 GEN_INT (unique_id
++));
1237 /* If this is not the first set of REGNO, see whether the new value
1238 is related to the old one. There are two cases of interest:
1240 (1) The register might be assigned an entirely new value
1241 that has the same base term as the original set.
1243 (2) The set might be a simple self-modification that
1244 cannot change REGNO's base value.
1246 If neither case holds, reject the original base value as invalid.
1247 Note that the following situation is not detected:
1249 extern int x, y; int *p = &x; p += (&y-&x);
1251 ANSI C does not allow computing the difference of addresses
1252 of distinct top level objects. */
1253 if (new_reg_base_value
[regno
] != 0
1254 && find_base_value (src
) != new_reg_base_value
[regno
])
1255 switch (GET_CODE (src
))
1259 if (XEXP (src
, 0) != dest
&& XEXP (src
, 1) != dest
)
1260 new_reg_base_value
[regno
] = 0;
1263 /* If the value we add in the PLUS is also a valid base value,
1264 this might be the actual base value, and the original value
1267 rtx other
= NULL_RTX
;
1269 if (XEXP (src
, 0) == dest
)
1270 other
= XEXP (src
, 1);
1271 else if (XEXP (src
, 1) == dest
)
1272 other
= XEXP (src
, 0);
1274 if (! other
|| find_base_value (other
))
1275 new_reg_base_value
[regno
] = 0;
1279 if (XEXP (src
, 0) != dest
|| !CONST_INT_P (XEXP (src
, 1)))
1280 new_reg_base_value
[regno
] = 0;
1283 new_reg_base_value
[regno
] = 0;
1286 /* If this is the first set of a register, record the value. */
1287 else if ((regno
>= FIRST_PSEUDO_REGISTER
|| ! fixed_regs
[regno
])
1288 && ! reg_seen
[regno
] && new_reg_base_value
[regno
] == 0)
1289 new_reg_base_value
[regno
] = find_base_value (src
);
1291 reg_seen
[regno
] = 1;
1294 /* Return REG_BASE_VALUE for REGNO. Selective scheduler uses this to avoid
1295 using hard registers with non-null REG_BASE_VALUE for renaming. */
1297 get_reg_base_value (unsigned int regno
)
1299 return VEC_index (rtx
, reg_base_value
, regno
);
1302 /* If a value is known for REGNO, return it. */
1305 get_reg_known_value (unsigned int regno
)
1307 if (regno
>= FIRST_PSEUDO_REGISTER
)
1309 regno
-= FIRST_PSEUDO_REGISTER
;
1310 if (regno
< reg_known_value_size
)
1311 return reg_known_value
[regno
];
1319 set_reg_known_value (unsigned int regno
, rtx val
)
1321 if (regno
>= FIRST_PSEUDO_REGISTER
)
1323 regno
-= FIRST_PSEUDO_REGISTER
;
1324 if (regno
< reg_known_value_size
)
1325 reg_known_value
[regno
] = val
;
1329 /* Similarly for reg_known_equiv_p. */
1332 get_reg_known_equiv_p (unsigned int regno
)
1334 if (regno
>= FIRST_PSEUDO_REGISTER
)
1336 regno
-= FIRST_PSEUDO_REGISTER
;
1337 if (regno
< reg_known_value_size
)
1338 return reg_known_equiv_p
[regno
];
1344 set_reg_known_equiv_p (unsigned int regno
, bool val
)
1346 if (regno
>= FIRST_PSEUDO_REGISTER
)
1348 regno
-= FIRST_PSEUDO_REGISTER
;
1349 if (regno
< reg_known_value_size
)
1350 reg_known_equiv_p
[regno
] = val
;
1355 /* Returns a canonical version of X, from the point of view alias
1356 analysis. (For example, if X is a MEM whose address is a register,
1357 and the register has a known value (say a SYMBOL_REF), then a MEM
1358 whose address is the SYMBOL_REF is returned.) */
1363 /* Recursively look for equivalences. */
1364 if (REG_P (x
) && REGNO (x
) >= FIRST_PSEUDO_REGISTER
)
1366 rtx t
= get_reg_known_value (REGNO (x
));
1370 return canon_rtx (t
);
1373 if (GET_CODE (x
) == PLUS
)
1375 rtx x0
= canon_rtx (XEXP (x
, 0));
1376 rtx x1
= canon_rtx (XEXP (x
, 1));
1378 if (x0
!= XEXP (x
, 0) || x1
!= XEXP (x
, 1))
1380 if (CONST_INT_P (x0
))
1381 return plus_constant (x1
, INTVAL (x0
));
1382 else if (CONST_INT_P (x1
))
1383 return plus_constant (x0
, INTVAL (x1
));
1384 return gen_rtx_PLUS (GET_MODE (x
), x0
, x1
);
1388 /* This gives us much better alias analysis when called from
1389 the loop optimizer. Note we want to leave the original
1390 MEM alone, but need to return the canonicalized MEM with
1391 all the flags with their original values. */
1393 x
= replace_equiv_address_nv (x
, canon_rtx (XEXP (x
, 0)));
1398 /* Return 1 if X and Y are identical-looking rtx's.
1399 Expect that X and Y has been already canonicalized.
1401 We use the data in reg_known_value above to see if two registers with
1402 different numbers are, in fact, equivalent. */
1405 rtx_equal_for_memref_p (const_rtx x
, const_rtx y
)
1412 if (x
== 0 && y
== 0)
1414 if (x
== 0 || y
== 0)
1420 code
= GET_CODE (x
);
1421 /* Rtx's of different codes cannot be equal. */
1422 if (code
!= GET_CODE (y
))
1425 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
1426 (REG:SI x) and (REG:HI x) are NOT equivalent. */
1428 if (GET_MODE (x
) != GET_MODE (y
))
1431 /* Some RTL can be compared without a recursive examination. */
1435 return REGNO (x
) == REGNO (y
);
1438 return XEXP (x
, 0) == XEXP (y
, 0);
1441 return XSTR (x
, 0) == XSTR (y
, 0);
1447 /* There's no need to compare the contents of CONST_DOUBLEs or
1448 CONST_INTs because pointer equality is a good enough
1449 comparison for these nodes. */
1456 /* canon_rtx knows how to handle plus. No need to canonicalize. */
1458 return ((rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 0))
1459 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 1)))
1460 || (rtx_equal_for_memref_p (XEXP (x
, 0), XEXP (y
, 1))
1461 && rtx_equal_for_memref_p (XEXP (x
, 1), XEXP (y
, 0))));
1462 /* For commutative operations, the RTX match if the operand match in any
1463 order. Also handle the simple binary and unary cases without a loop. */
1464 if (COMMUTATIVE_P (x
))
1466 rtx xop0
= canon_rtx (XEXP (x
, 0));
1467 rtx yop0
= canon_rtx (XEXP (y
, 0));
1468 rtx yop1
= canon_rtx (XEXP (y
, 1));
1470 return ((rtx_equal_for_memref_p (xop0
, yop0
)
1471 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop1
))
1472 || (rtx_equal_for_memref_p (xop0
, yop1
)
1473 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)), yop0
)));
1475 else if (NON_COMMUTATIVE_P (x
))
1477 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1478 canon_rtx (XEXP (y
, 0)))
1479 && rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 1)),
1480 canon_rtx (XEXP (y
, 1))));
1482 else if (UNARY_P (x
))
1483 return rtx_equal_for_memref_p (canon_rtx (XEXP (x
, 0)),
1484 canon_rtx (XEXP (y
, 0)));
1486 /* Compare the elements. If any pair of corresponding elements
1487 fail to match, return 0 for the whole things.
1489 Limit cases to types which actually appear in addresses. */
1491 fmt
= GET_RTX_FORMAT (code
);
1492 for (i
= GET_RTX_LENGTH (code
) - 1; i
>= 0; i
--)
1497 if (XINT (x
, i
) != XINT (y
, i
))
1502 /* Two vectors must have the same length. */
1503 if (XVECLEN (x
, i
) != XVECLEN (y
, i
))
1506 /* And the corresponding elements must match. */
1507 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1508 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x
, i
, j
)),
1509 canon_rtx (XVECEXP (y
, i
, j
))) == 0)
1514 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x
, i
)),
1515 canon_rtx (XEXP (y
, i
))) == 0)
1519 /* This can happen for asm operands. */
1521 if (strcmp (XSTR (x
, i
), XSTR (y
, i
)))
1525 /* This can happen for an asm which clobbers memory. */
1529 /* It is believed that rtx's at this level will never
1530 contain anything but integers and other rtx's,
1531 except for within LABEL_REFs and SYMBOL_REFs. */
1540 find_base_term (rtx x
)
1543 struct elt_loc_list
*l
, *f
;
1546 #if defined (FIND_BASE_TERM)
1547 /* Try machine-dependent ways to find the base term. */
1548 x
= FIND_BASE_TERM (x
);
1551 switch (GET_CODE (x
))
1554 return REG_BASE_VALUE (x
);
1557 /* As we do not know which address space the pointer is refering to, we can
1558 handle this only if the target does not support different pointer or
1559 address modes depending on the address space. */
1560 if (!target_default_pointer_address_modes_p ())
1562 if (GET_MODE_SIZE (GET_MODE (x
)) < GET_MODE_SIZE (Pmode
))
1572 return find_base_term (XEXP (x
, 0));
1575 case SIGN_EXTEND
: /* Used for Alpha/NT pointers */
1576 /* As we do not know which address space the pointer is refering to, we can
1577 handle this only if the target does not support different pointer or
1578 address modes depending on the address space. */
1579 if (!target_default_pointer_address_modes_p ())
1583 rtx temp
= find_base_term (XEXP (x
, 0));
1585 if (temp
!= 0 && CONSTANT_P (temp
))
1586 temp
= convert_memory_address (Pmode
, temp
);
1592 val
= CSELIB_VAL_PTR (x
);
1599 /* Temporarily reset val->locs to avoid infinite recursion. */
1602 for (l
= f
; l
; l
= l
->next
)
1603 if (GET_CODE (l
->loc
) == VALUE
1604 && CSELIB_VAL_PTR (l
->loc
)->locs
1605 && !CSELIB_VAL_PTR (l
->loc
)->locs
->next
1606 && CSELIB_VAL_PTR (l
->loc
)->locs
->loc
== x
)
1608 else if ((ret
= find_base_term (l
->loc
)) != 0)
1615 /* The standard form is (lo_sum reg sym) so look only at the
1617 return find_base_term (XEXP (x
, 1));
1621 if (GET_CODE (x
) != PLUS
&& GET_CODE (x
) != MINUS
)
1627 rtx tmp1
= XEXP (x
, 0);
1628 rtx tmp2
= XEXP (x
, 1);
1630 /* This is a little bit tricky since we have to determine which of
1631 the two operands represents the real base address. Otherwise this
1632 routine may return the index register instead of the base register.
1634 That may cause us to believe no aliasing was possible, when in
1635 fact aliasing is possible.
1637 We use a few simple tests to guess the base register. Additional
1638 tests can certainly be added. For example, if one of the operands
1639 is a shift or multiply, then it must be the index register and the
1640 other operand is the base register. */
1642 if (tmp1
== pic_offset_table_rtx
&& CONSTANT_P (tmp2
))
1643 return find_base_term (tmp2
);
1645 /* If either operand is known to be a pointer, then use it
1646 to determine the base term. */
1647 if (REG_P (tmp1
) && REG_POINTER (tmp1
))
1649 rtx base
= find_base_term (tmp1
);
1654 if (REG_P (tmp2
) && REG_POINTER (tmp2
))
1656 rtx base
= find_base_term (tmp2
);
1661 /* Neither operand was known to be a pointer. Go ahead and find the
1662 base term for both operands. */
1663 tmp1
= find_base_term (tmp1
);
1664 tmp2
= find_base_term (tmp2
);
1666 /* If either base term is named object or a special address
1667 (like an argument or stack reference), then use it for the
1670 && (GET_CODE (tmp1
) == SYMBOL_REF
1671 || GET_CODE (tmp1
) == LABEL_REF
1672 || (GET_CODE (tmp1
) == ADDRESS
1673 && GET_MODE (tmp1
) != VOIDmode
)))
1677 && (GET_CODE (tmp2
) == SYMBOL_REF
1678 || GET_CODE (tmp2
) == LABEL_REF
1679 || (GET_CODE (tmp2
) == ADDRESS
1680 && GET_MODE (tmp2
) != VOIDmode
)))
1683 /* We could not determine which of the two operands was the
1684 base register and which was the index. So we can determine
1685 nothing from the base alias check. */
1690 if (CONST_INT_P (XEXP (x
, 1)) && INTVAL (XEXP (x
, 1)) != 0)
1691 return find_base_term (XEXP (x
, 0));
1703 /* Return 0 if the addresses X and Y are known to point to different
1704 objects, 1 if they might be pointers to the same object. */
1707 base_alias_check (rtx x
, rtx y
, enum machine_mode x_mode
,
1708 enum machine_mode y_mode
)
1710 rtx x_base
= find_base_term (x
);
1711 rtx y_base
= find_base_term (y
);
1713 /* If the address itself has no known base see if a known equivalent
1714 value has one. If either address still has no known base, nothing
1715 is known about aliasing. */
1720 if (! flag_expensive_optimizations
|| (x_c
= canon_rtx (x
)) == x
)
1723 x_base
= find_base_term (x_c
);
1731 if (! flag_expensive_optimizations
|| (y_c
= canon_rtx (y
)) == y
)
1734 y_base
= find_base_term (y_c
);
1739 /* If the base addresses are equal nothing is known about aliasing. */
1740 if (rtx_equal_p (x_base
, y_base
))
1743 /* The base addresses are different expressions. If they are not accessed
1744 via AND, there is no conflict. We can bring knowledge of object
1745 alignment into play here. For example, on alpha, "char a, b;" can
1746 alias one another, though "char a; long b;" cannot. AND addesses may
1747 implicitly alias surrounding objects; i.e. unaligned access in DImode
1748 via AND address can alias all surrounding object types except those
1749 with aligment 8 or higher. */
1750 if (GET_CODE (x
) == AND
&& GET_CODE (y
) == AND
)
1752 if (GET_CODE (x
) == AND
1753 && (!CONST_INT_P (XEXP (x
, 1))
1754 || (int) GET_MODE_UNIT_SIZE (y_mode
) < -INTVAL (XEXP (x
, 1))))
1756 if (GET_CODE (y
) == AND
1757 && (!CONST_INT_P (XEXP (y
, 1))
1758 || (int) GET_MODE_UNIT_SIZE (x_mode
) < -INTVAL (XEXP (y
, 1))))
1761 /* Differing symbols not accessed via AND never alias. */
1762 if (GET_CODE (x_base
) != ADDRESS
&& GET_CODE (y_base
) != ADDRESS
)
1765 /* If one address is a stack reference there can be no alias:
1766 stack references using different base registers do not alias,
1767 a stack reference can not alias a parameter, and a stack reference
1768 can not alias a global. */
1769 if ((GET_CODE (x_base
) == ADDRESS
&& GET_MODE (x_base
) == Pmode
)
1770 || (GET_CODE (y_base
) == ADDRESS
&& GET_MODE (y_base
) == Pmode
))
1776 /* Convert the address X into something we can use. This is done by returning
1777 it unchanged unless it is a value; in the latter case we call cselib to get
1778 a more useful rtx. */
1784 struct elt_loc_list
*l
;
1786 if (GET_CODE (x
) != VALUE
)
1788 v
= CSELIB_VAL_PTR (x
);
1791 for (l
= v
->locs
; l
; l
= l
->next
)
1792 if (CONSTANT_P (l
->loc
))
1794 for (l
= v
->locs
; l
; l
= l
->next
)
1795 if (!REG_P (l
->loc
) && !MEM_P (l
->loc
))
1798 return v
->locs
->loc
;
1803 /* Return the address of the (N_REFS + 1)th memory reference to ADDR
1804 where SIZE is the size in bytes of the memory reference. If ADDR
1805 is not modified by the memory reference then ADDR is returned. */
1808 addr_side_effect_eval (rtx addr
, int size
, int n_refs
)
1812 switch (GET_CODE (addr
))
1815 offset
= (n_refs
+ 1) * size
;
1818 offset
= -(n_refs
+ 1) * size
;
1821 offset
= n_refs
* size
;
1824 offset
= -n_refs
* size
;
1832 addr
= gen_rtx_PLUS (GET_MODE (addr
), XEXP (addr
, 0),
1835 addr
= XEXP (addr
, 0);
1836 addr
= canon_rtx (addr
);
1841 /* Return one if X and Y (memory addresses) reference the
1842 same location in memory or if the references overlap.
1843 Return zero if they do not overlap, else return
1844 minus one in which case they still might reference the same location.
1846 C is an offset accumulator. When
1847 C is nonzero, we are testing aliases between X and Y + C.
1848 XSIZE is the size in bytes of the X reference,
1849 similarly YSIZE is the size in bytes for Y.
1850 Expect that canon_rtx has been already called for X and Y.
1852 If XSIZE or YSIZE is zero, we do not know the amount of memory being
1853 referenced (the reference was BLKmode), so make the most pessimistic
1856 If XSIZE or YSIZE is negative, we may access memory outside the object
1857 being referenced as a side effect. This can happen when using AND to
1858 align memory references, as is done on the Alpha.
1860 Nice to notice that varying addresses cannot conflict with fp if no
1861 local variables had their addresses taken, but that's too hard now.
1863 ??? Contrary to the tree alias oracle this does not return
1864 one for X + non-constant and Y + non-constant when X and Y are equal.
1865 If that is fixed the TBAA hack for union type-punning can be removed. */
1868 memrefs_conflict_p (int xsize
, rtx x
, int ysize
, rtx y
, HOST_WIDE_INT c
)
1870 if (GET_CODE (x
) == VALUE
)
1874 struct elt_loc_list
*l
= NULL
;
1875 if (CSELIB_VAL_PTR (x
))
1876 for (l
= CSELIB_VAL_PTR (x
)->locs
; l
; l
= l
->next
)
1877 if (REG_P (l
->loc
) && rtx_equal_for_memref_p (l
->loc
, y
))
1884 /* Don't call get_addr if y is the same VALUE. */
1888 if (GET_CODE (y
) == VALUE
)
1892 struct elt_loc_list
*l
= NULL
;
1893 if (CSELIB_VAL_PTR (y
))
1894 for (l
= CSELIB_VAL_PTR (y
)->locs
; l
; l
= l
->next
)
1895 if (REG_P (l
->loc
) && rtx_equal_for_memref_p (l
->loc
, x
))
1902 /* Don't call get_addr if x is the same VALUE. */
1906 if (GET_CODE (x
) == HIGH
)
1908 else if (GET_CODE (x
) == LO_SUM
)
1911 x
= addr_side_effect_eval (x
, xsize
, 0);
1912 if (GET_CODE (y
) == HIGH
)
1914 else if (GET_CODE (y
) == LO_SUM
)
1917 y
= addr_side_effect_eval (y
, ysize
, 0);
1919 if (rtx_equal_for_memref_p (x
, y
))
1921 if (xsize
<= 0 || ysize
<= 0)
1923 if (c
>= 0 && xsize
> c
)
1925 if (c
< 0 && ysize
+c
> 0)
1930 /* This code used to check for conflicts involving stack references and
1931 globals but the base address alias code now handles these cases. */
1933 if (GET_CODE (x
) == PLUS
)
1935 /* The fact that X is canonicalized means that this
1936 PLUS rtx is canonicalized. */
1937 rtx x0
= XEXP (x
, 0);
1938 rtx x1
= XEXP (x
, 1);
1940 if (GET_CODE (y
) == PLUS
)
1942 /* The fact that Y is canonicalized means that this
1943 PLUS rtx is canonicalized. */
1944 rtx y0
= XEXP (y
, 0);
1945 rtx y1
= XEXP (y
, 1);
1947 if (rtx_equal_for_memref_p (x1
, y1
))
1948 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
1949 if (rtx_equal_for_memref_p (x0
, y0
))
1950 return memrefs_conflict_p (xsize
, x1
, ysize
, y1
, c
);
1951 if (CONST_INT_P (x1
))
1953 if (CONST_INT_P (y1
))
1954 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
,
1955 c
- INTVAL (x1
) + INTVAL (y1
));
1957 return memrefs_conflict_p (xsize
, x0
, ysize
, y
,
1960 else if (CONST_INT_P (y1
))
1961 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1965 else if (CONST_INT_P (x1
))
1966 return memrefs_conflict_p (xsize
, x0
, ysize
, y
, c
- INTVAL (x1
));
1968 else if (GET_CODE (y
) == PLUS
)
1970 /* The fact that Y is canonicalized means that this
1971 PLUS rtx is canonicalized. */
1972 rtx y0
= XEXP (y
, 0);
1973 rtx y1
= XEXP (y
, 1);
1975 if (CONST_INT_P (y1
))
1976 return memrefs_conflict_p (xsize
, x
, ysize
, y0
, c
+ INTVAL (y1
));
1981 if (GET_CODE (x
) == GET_CODE (y
))
1982 switch (GET_CODE (x
))
1986 /* Handle cases where we expect the second operands to be the
1987 same, and check only whether the first operand would conflict
1990 rtx x1
= canon_rtx (XEXP (x
, 1));
1991 rtx y1
= canon_rtx (XEXP (y
, 1));
1992 if (! rtx_equal_for_memref_p (x1
, y1
))
1994 x0
= canon_rtx (XEXP (x
, 0));
1995 y0
= canon_rtx (XEXP (y
, 0));
1996 if (rtx_equal_for_memref_p (x0
, y0
))
1997 return (xsize
== 0 || ysize
== 0
1998 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
2000 /* Can't properly adjust our sizes. */
2001 if (!CONST_INT_P (x1
))
2003 xsize
/= INTVAL (x1
);
2004 ysize
/= INTVAL (x1
);
2006 return memrefs_conflict_p (xsize
, x0
, ysize
, y0
, c
);
2013 /* Treat an access through an AND (e.g. a subword access on an Alpha)
2014 as an access with indeterminate size. Assume that references
2015 besides AND are aligned, so if the size of the other reference is
2016 at least as large as the alignment, assume no other overlap. */
2017 if (GET_CODE (x
) == AND
&& CONST_INT_P (XEXP (x
, 1)))
2019 if (GET_CODE (y
) == AND
|| ysize
< -INTVAL (XEXP (x
, 1)))
2021 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)), ysize
, y
, c
);
2023 if (GET_CODE (y
) == AND
&& CONST_INT_P (XEXP (y
, 1)))
2025 /* ??? If we are indexing far enough into the array/structure, we
2026 may yet be able to determine that we can not overlap. But we
2027 also need to that we are far enough from the end not to overlap
2028 a following reference, so we do nothing with that for now. */
2029 if (GET_CODE (x
) == AND
|| xsize
< -INTVAL (XEXP (y
, 1)))
2031 return memrefs_conflict_p (xsize
, x
, ysize
, canon_rtx (XEXP (y
, 0)), c
);
2036 if (CONST_INT_P (x
) && CONST_INT_P (y
))
2038 c
+= (INTVAL (y
) - INTVAL (x
));
2039 return (xsize
<= 0 || ysize
<= 0
2040 || (c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0));
2043 if (GET_CODE (x
) == CONST
)
2045 if (GET_CODE (y
) == CONST
)
2046 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2047 ysize
, canon_rtx (XEXP (y
, 0)), c
);
2049 return memrefs_conflict_p (xsize
, canon_rtx (XEXP (x
, 0)),
2052 if (GET_CODE (y
) == CONST
)
2053 return memrefs_conflict_p (xsize
, x
, ysize
,
2054 canon_rtx (XEXP (y
, 0)), c
);
2057 return (xsize
<= 0 || ysize
<= 0
2058 || (rtx_equal_for_memref_p (x
, y
)
2059 && ((c
>= 0 && xsize
> c
) || (c
< 0 && ysize
+c
> 0))));
2067 /* Functions to compute memory dependencies.
2069 Since we process the insns in execution order, we can build tables
2070 to keep track of what registers are fixed (and not aliased), what registers
2071 are varying in known ways, and what registers are varying in unknown
2074 If both memory references are volatile, then there must always be a
2075 dependence between the two references, since their order can not be
2076 changed. A volatile and non-volatile reference can be interchanged
2079 We also must allow AND addresses, because they may generate accesses
2080 outside the object being referenced. This is used to generate aligned
2081 addresses from unaligned addresses, for instance, the alpha
2082 storeqi_unaligned pattern. */
2084 /* Read dependence: X is read after read in MEM takes place. There can
2085 only be a dependence here if both reads are volatile. */
2088 read_dependence (const_rtx mem
, const_rtx x
)
2090 return MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
);
2093 /* Returns nonzero if something about the mode or address format MEM1
2094 indicates that it might well alias *anything*. */
2097 aliases_everything_p (const_rtx mem
)
2099 if (GET_CODE (XEXP (mem
, 0)) == AND
)
2100 /* If the address is an AND, it's very hard to know at what it is
2101 actually pointing. */
2107 /* Return true if we can determine that the fields referenced cannot
2108 overlap for any pair of objects. */
2111 nonoverlapping_component_refs_p (const_tree x
, const_tree y
)
2113 const_tree fieldx
, fieldy
, typex
, typey
, orig_y
;
2115 if (!flag_strict_aliasing
)
2120 /* The comparison has to be done at a common type, since we don't
2121 know how the inheritance hierarchy works. */
2125 fieldx
= TREE_OPERAND (x
, 1);
2126 typex
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx
));
2131 fieldy
= TREE_OPERAND (y
, 1);
2132 typey
= TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy
));
2137 y
= TREE_OPERAND (y
, 0);
2139 while (y
&& TREE_CODE (y
) == COMPONENT_REF
);
2141 x
= TREE_OPERAND (x
, 0);
2143 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2144 /* Never found a common type. */
2148 /* If we're left with accessing different fields of a structure,
2150 if (TREE_CODE (typex
) == RECORD_TYPE
2151 && fieldx
!= fieldy
)
2154 /* The comparison on the current field failed. If we're accessing
2155 a very nested structure, look at the next outer level. */
2156 x
= TREE_OPERAND (x
, 0);
2157 y
= TREE_OPERAND (y
, 0);
2160 && TREE_CODE (x
) == COMPONENT_REF
2161 && TREE_CODE (y
) == COMPONENT_REF
);
2166 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
2169 decl_for_component_ref (tree x
)
2173 x
= TREE_OPERAND (x
, 0);
2175 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2177 return x
&& DECL_P (x
) ? x
: NULL_TREE
;
2180 /* Walk up the COMPONENT_REF list in X and adjust *OFFSET to compensate
2181 for the offset of the field reference. *KNOWN_P says whether the
2185 adjust_offset_for_component_ref (tree x
, bool *known_p
,
2186 HOST_WIDE_INT
*offset
)
2192 tree xoffset
= component_ref_field_offset (x
);
2193 tree field
= TREE_OPERAND (x
, 1);
2195 if (! host_integerp (xoffset
, 1))
2200 *offset
+= (tree_low_cst (xoffset
, 1)
2201 + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field
), 1)
2204 x
= TREE_OPERAND (x
, 0);
2206 while (x
&& TREE_CODE (x
) == COMPONENT_REF
);
2209 /* Return nonzero if we can determine the exprs corresponding to memrefs
2210 X and Y and they do not overlap.
2211 If LOOP_VARIANT is set, skip offset-based disambiguation */
2214 nonoverlapping_memrefs_p (const_rtx x
, const_rtx y
, bool loop_invariant
)
2216 tree exprx
= MEM_EXPR (x
), expry
= MEM_EXPR (y
);
2219 bool moffsetx_known_p
, moffsety_known_p
;
2220 HOST_WIDE_INT moffsetx
= 0, moffsety
= 0;
2221 HOST_WIDE_INT offsetx
= 0, offsety
= 0, sizex
, sizey
, tem
;
2223 /* Unless both have exprs, we can't tell anything. */
2224 if (exprx
== 0 || expry
== 0)
2227 /* For spill-slot accesses make sure we have valid offsets. */
2228 if ((exprx
== get_spill_slot_decl (false)
2229 && ! MEM_OFFSET_KNOWN_P (x
))
2230 || (expry
== get_spill_slot_decl (false)
2231 && ! MEM_OFFSET_KNOWN_P (y
)))
2234 /* If both are field references, we may be able to determine something. */
2235 if (TREE_CODE (exprx
) == COMPONENT_REF
2236 && TREE_CODE (expry
) == COMPONENT_REF
2237 && nonoverlapping_component_refs_p (exprx
, expry
))
2241 /* If the field reference test failed, look at the DECLs involved. */
2242 moffsetx_known_p
= MEM_OFFSET_KNOWN_P (x
);
2243 if (moffsetx_known_p
)
2244 moffsetx
= MEM_OFFSET (x
);
2245 if (TREE_CODE (exprx
) == COMPONENT_REF
)
2247 tree t
= decl_for_component_ref (exprx
);
2250 adjust_offset_for_component_ref (exprx
, &moffsetx_known_p
, &moffsetx
);
2254 moffsety_known_p
= MEM_OFFSET_KNOWN_P (y
);
2255 if (moffsety_known_p
)
2256 moffsety
= MEM_OFFSET (y
);
2257 if (TREE_CODE (expry
) == COMPONENT_REF
)
2259 tree t
= decl_for_component_ref (expry
);
2262 adjust_offset_for_component_ref (expry
, &moffsety_known_p
, &moffsety
);
2266 if (! DECL_P (exprx
) || ! DECL_P (expry
))
2269 /* With invalid code we can end up storing into the constant pool.
2270 Bail out to avoid ICEing when creating RTL for this.
2271 See gfortran.dg/lto/20091028-2_0.f90. */
2272 if (TREE_CODE (exprx
) == CONST_DECL
2273 || TREE_CODE (expry
) == CONST_DECL
)
2276 rtlx
= DECL_RTL (exprx
);
2277 rtly
= DECL_RTL (expry
);
2279 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
2280 can't overlap unless they are the same because we never reuse that part
2281 of the stack frame used for locals for spilled pseudos. */
2282 if ((!MEM_P (rtlx
) || !MEM_P (rtly
))
2283 && ! rtx_equal_p (rtlx
, rtly
))
2286 /* If we have MEMs refering to different address spaces (which can
2287 potentially overlap), we cannot easily tell from the addresses
2288 whether the references overlap. */
2289 if (MEM_P (rtlx
) && MEM_P (rtly
)
2290 && MEM_ADDR_SPACE (rtlx
) != MEM_ADDR_SPACE (rtly
))
2293 /* Get the base and offsets of both decls. If either is a register, we
2294 know both are and are the same, so use that as the base. The only
2295 we can avoid overlap is if we can deduce that they are nonoverlapping
2296 pieces of that decl, which is very rare. */
2297 basex
= MEM_P (rtlx
) ? XEXP (rtlx
, 0) : rtlx
;
2298 if (GET_CODE (basex
) == PLUS
&& CONST_INT_P (XEXP (basex
, 1)))
2299 offsetx
= INTVAL (XEXP (basex
, 1)), basex
= XEXP (basex
, 0);
2301 basey
= MEM_P (rtly
) ? XEXP (rtly
, 0) : rtly
;
2302 if (GET_CODE (basey
) == PLUS
&& CONST_INT_P (XEXP (basey
, 1)))
2303 offsety
= INTVAL (XEXP (basey
, 1)), basey
= XEXP (basey
, 0);
2305 /* If the bases are different, we know they do not overlap if both
2306 are constants or if one is a constant and the other a pointer into the
2307 stack frame. Otherwise a different base means we can't tell if they
2309 if (! rtx_equal_p (basex
, basey
))
2310 return ((CONSTANT_P (basex
) && CONSTANT_P (basey
))
2311 || (CONSTANT_P (basex
) && REG_P (basey
)
2312 && REGNO_PTR_FRAME_P (REGNO (basey
)))
2313 || (CONSTANT_P (basey
) && REG_P (basex
)
2314 && REGNO_PTR_FRAME_P (REGNO (basex
))));
2316 /* Offset based disambiguation not appropriate for loop invariant */
2320 sizex
= (!MEM_P (rtlx
) ? (int) GET_MODE_SIZE (GET_MODE (rtlx
))
2321 : MEM_SIZE_KNOWN_P (rtlx
) ? MEM_SIZE (rtlx
)
2323 sizey
= (!MEM_P (rtly
) ? (int) GET_MODE_SIZE (GET_MODE (rtly
))
2324 : MEM_SIZE_KNOWN_P (rtly
) ? MEM_SIZE (rtly
)
2327 /* If we have an offset for either memref, it can update the values computed
2329 if (moffsetx_known_p
)
2330 offsetx
+= moffsetx
, sizex
-= moffsetx
;
2331 if (moffsety_known_p
)
2332 offsety
+= moffsety
, sizey
-= moffsety
;
2334 /* If a memref has both a size and an offset, we can use the smaller size.
2335 We can't do this if the offset isn't known because we must view this
2336 memref as being anywhere inside the DECL's MEM. */
2337 if (MEM_SIZE_KNOWN_P (x
) && moffsetx_known_p
)
2338 sizex
= MEM_SIZE (x
);
2339 if (MEM_SIZE_KNOWN_P (y
) && moffsety_known_p
)
2340 sizey
= MEM_SIZE (y
);
2342 /* Put the values of the memref with the lower offset in X's values. */
2343 if (offsetx
> offsety
)
2345 tem
= offsetx
, offsetx
= offsety
, offsety
= tem
;
2346 tem
= sizex
, sizex
= sizey
, sizey
= tem
;
2349 /* If we don't know the size of the lower-offset value, we can't tell
2350 if they conflict. Otherwise, we do the test. */
2351 return sizex
>= 0 && offsety
>= offsetx
+ sizex
;
2354 /* Helper for true_dependence and canon_true_dependence.
2355 Checks for true dependence: X is read after store in MEM takes place.
2357 If MEM_CANONICALIZED is FALSE, then X_ADDR and MEM_ADDR should be
2358 NULL_RTX, and the canonical addresses of MEM and X are both computed
2359 here. If MEM_CANONICALIZED, then MEM must be already canonicalized.
2361 If X_ADDR is non-NULL, it is used in preference of XEXP (x, 0).
2363 Returns 1 if there is a true dependence, 0 otherwise. */
2366 true_dependence_1 (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2367 const_rtx x
, rtx x_addr
, bool mem_canonicalized
)
2372 gcc_checking_assert (mem_canonicalized
? (mem_addr
!= NULL_RTX
)
2373 : (mem_addr
== NULL_RTX
&& x_addr
== NULL_RTX
));
2375 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2378 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2379 This is used in epilogue deallocation functions, and in cselib. */
2380 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2382 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2384 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2385 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2388 /* Read-only memory is by definition never modified, and therefore can't
2389 conflict with anything. We don't expect to find read-only set on MEM,
2390 but stupid user tricks can produce them, so don't die. */
2391 if (MEM_READONLY_P (x
))
2394 /* If we have MEMs refering to different address spaces (which can
2395 potentially overlap), we cannot easily tell from the addresses
2396 whether the references overlap. */
2397 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2402 mem_addr
= XEXP (mem
, 0);
2403 if (mem_mode
== VOIDmode
)
2404 mem_mode
= GET_MODE (mem
);
2409 x_addr
= XEXP (x
, 0);
2410 if (!((GET_CODE (x_addr
) == VALUE
2411 && GET_CODE (mem_addr
) != VALUE
2412 && reg_mentioned_p (x_addr
, mem_addr
))
2413 || (GET_CODE (x_addr
) != VALUE
2414 && GET_CODE (mem_addr
) == VALUE
2415 && reg_mentioned_p (mem_addr
, x_addr
))))
2417 x_addr
= get_addr (x_addr
);
2418 if (! mem_canonicalized
)
2419 mem_addr
= get_addr (mem_addr
);
2423 base
= find_base_term (x_addr
);
2424 if (base
&& (GET_CODE (base
) == LABEL_REF
2425 || (GET_CODE (base
) == SYMBOL_REF
2426 && CONSTANT_POOL_ADDRESS_P (base
))))
2429 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), mem_mode
))
2432 x_addr
= canon_rtx (x_addr
);
2433 if (!mem_canonicalized
)
2434 mem_addr
= canon_rtx (mem_addr
);
2436 if ((ret
= memrefs_conflict_p (GET_MODE_SIZE (mem_mode
), mem_addr
,
2437 SIZE_FOR_MODE (x
), x_addr
, 0)) != -1)
2440 if (DIFFERENT_ALIAS_SETS_P (x
, mem
))
2443 if (nonoverlapping_memrefs_p (mem
, x
, false))
2446 if (aliases_everything_p (x
))
2449 /* We cannot use aliases_everything_p to test MEM, since we must look
2450 at MEM_ADDR, rather than XEXP (mem, 0). */
2451 if (GET_CODE (mem_addr
) == AND
)
2454 /* ??? In true_dependence we also allow BLKmode to alias anything. Why
2455 don't we do this in anti_dependence and output_dependence? */
2456 if (mem_mode
== BLKmode
|| GET_MODE (x
) == BLKmode
)
2459 return rtx_refs_may_alias_p (x
, mem
, true);
2462 /* True dependence: X is read after store in MEM takes place. */
2465 true_dependence (const_rtx mem
, enum machine_mode mem_mode
, const_rtx x
)
2467 return true_dependence_1 (mem
, mem_mode
, NULL_RTX
,
2468 x
, NULL_RTX
, /*mem_canonicalized=*/false);
2471 /* Canonical true dependence: X is read after store in MEM takes place.
2472 Variant of true_dependence which assumes MEM has already been
2473 canonicalized (hence we no longer do that here).
2474 The mem_addr argument has been added, since true_dependence_1 computed
2475 this value prior to canonicalizing. */
2478 canon_true_dependence (const_rtx mem
, enum machine_mode mem_mode
, rtx mem_addr
,
2479 const_rtx x
, rtx x_addr
)
2481 return true_dependence_1 (mem
, mem_mode
, mem_addr
,
2482 x
, x_addr
, /*mem_canonicalized=*/true);
2485 /* Returns nonzero if a write to X might alias a previous read from
2486 (or, if WRITEP is nonzero, a write to) MEM. */
2489 write_dependence_p (const_rtx mem
, const_rtx x
, int writep
)
2491 rtx x_addr
, mem_addr
;
2495 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2498 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
2499 This is used in epilogue deallocation functions. */
2500 if (GET_MODE (x
) == BLKmode
&& GET_CODE (XEXP (x
, 0)) == SCRATCH
)
2502 if (GET_MODE (mem
) == BLKmode
&& GET_CODE (XEXP (mem
, 0)) == SCRATCH
)
2504 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2505 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2508 /* A read from read-only memory can't conflict with read-write memory. */
2509 if (!writep
&& MEM_READONLY_P (mem
))
2512 /* If we have MEMs refering to different address spaces (which can
2513 potentially overlap), we cannot easily tell from the addresses
2514 whether the references overlap. */
2515 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2518 x_addr
= XEXP (x
, 0);
2519 mem_addr
= XEXP (mem
, 0);
2520 if (!((GET_CODE (x_addr
) == VALUE
2521 && GET_CODE (mem_addr
) != VALUE
2522 && reg_mentioned_p (x_addr
, mem_addr
))
2523 || (GET_CODE (x_addr
) != VALUE
2524 && GET_CODE (mem_addr
) == VALUE
2525 && reg_mentioned_p (mem_addr
, x_addr
))))
2527 x_addr
= get_addr (x_addr
);
2528 mem_addr
= get_addr (mem_addr
);
2533 base
= find_base_term (mem_addr
);
2534 if (base
&& (GET_CODE (base
) == LABEL_REF
2535 || (GET_CODE (base
) == SYMBOL_REF
2536 && CONSTANT_POOL_ADDRESS_P (base
))))
2540 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
),
2544 x_addr
= canon_rtx (x_addr
);
2545 mem_addr
= canon_rtx (mem_addr
);
2547 if ((ret
= memrefs_conflict_p (SIZE_FOR_MODE (mem
), mem_addr
,
2548 SIZE_FOR_MODE (x
), x_addr
, 0)) != -1)
2551 if (nonoverlapping_memrefs_p (x
, mem
, false))
2554 return rtx_refs_may_alias_p (x
, mem
, false);
2557 /* Anti dependence: X is written after read in MEM takes place. */
2560 anti_dependence (const_rtx mem
, const_rtx x
)
2562 return write_dependence_p (mem
, x
, /*writep=*/0);
2565 /* Output dependence: X is written after store in MEM takes place. */
2568 output_dependence (const_rtx mem
, const_rtx x
)
2570 return write_dependence_p (mem
, x
, /*writep=*/1);
2575 /* Check whether X may be aliased with MEM. Don't do offset-based
2576 memory disambiguation & TBAA. */
2578 may_alias_p (const_rtx mem
, const_rtx x
)
2580 rtx x_addr
, mem_addr
;
2582 if (MEM_VOLATILE_P (x
) && MEM_VOLATILE_P (mem
))
2585 /* ??? In true_dependence we also allow BLKmode to alias anything. */
2586 if (GET_MODE (mem
) == BLKmode
|| GET_MODE (x
) == BLKmode
)
2589 if (MEM_ALIAS_SET (x
) == ALIAS_SET_MEMORY_BARRIER
2590 || MEM_ALIAS_SET (mem
) == ALIAS_SET_MEMORY_BARRIER
)
2593 /* Read-only memory is by definition never modified, and therefore can't
2594 conflict with anything. We don't expect to find read-only set on MEM,
2595 but stupid user tricks can produce them, so don't die. */
2596 if (MEM_READONLY_P (x
))
2599 /* If we have MEMs refering to different address spaces (which can
2600 potentially overlap), we cannot easily tell from the addresses
2601 whether the references overlap. */
2602 if (MEM_ADDR_SPACE (mem
) != MEM_ADDR_SPACE (x
))
2605 x_addr
= XEXP (x
, 0);
2606 mem_addr
= XEXP (mem
, 0);
2607 if (!((GET_CODE (x_addr
) == VALUE
2608 && GET_CODE (mem_addr
) != VALUE
2609 && reg_mentioned_p (x_addr
, mem_addr
))
2610 || (GET_CODE (x_addr
) != VALUE
2611 && GET_CODE (mem_addr
) == VALUE
2612 && reg_mentioned_p (mem_addr
, x_addr
))))
2614 x_addr
= get_addr (x_addr
);
2615 mem_addr
= get_addr (mem_addr
);
2618 if (! base_alias_check (x_addr
, mem_addr
, GET_MODE (x
), GET_MODE (mem_addr
)))
2621 x_addr
= canon_rtx (x_addr
);
2622 mem_addr
= canon_rtx (mem_addr
);
2624 if (nonoverlapping_memrefs_p (mem
, x
, true))
2627 if (aliases_everything_p (x
))
2630 /* We cannot use aliases_everything_p to test MEM, since we must look
2631 at MEM_ADDR, rather than XEXP (mem, 0). */
2632 if (GET_CODE (mem_addr
) == AND
)
2635 /* TBAA not valid for loop_invarint */
2636 return rtx_refs_may_alias_p (x
, mem
, false);
2640 init_alias_target (void)
2644 memset (static_reg_base_value
, 0, sizeof static_reg_base_value
);
2646 for (i
= 0; i
< FIRST_PSEUDO_REGISTER
; i
++)
2647 /* Check whether this register can hold an incoming pointer
2648 argument. FUNCTION_ARG_REGNO_P tests outgoing register
2649 numbers, so translate if necessary due to register windows. */
2650 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i
))
2651 && HARD_REGNO_MODE_OK (i
, Pmode
))
2652 static_reg_base_value
[i
]
2653 = gen_rtx_ADDRESS (VOIDmode
, gen_rtx_REG (Pmode
, i
));
2655 static_reg_base_value
[STACK_POINTER_REGNUM
]
2656 = gen_rtx_ADDRESS (Pmode
, stack_pointer_rtx
);
2657 static_reg_base_value
[ARG_POINTER_REGNUM
]
2658 = gen_rtx_ADDRESS (Pmode
, arg_pointer_rtx
);
2659 static_reg_base_value
[FRAME_POINTER_REGNUM
]
2660 = gen_rtx_ADDRESS (Pmode
, frame_pointer_rtx
);
2661 #if !HARD_FRAME_POINTER_IS_FRAME_POINTER
2662 static_reg_base_value
[HARD_FRAME_POINTER_REGNUM
]
2663 = gen_rtx_ADDRESS (Pmode
, hard_frame_pointer_rtx
);
2667 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
2668 to be memory reference. */
2669 static bool memory_modified
;
2671 memory_modified_1 (rtx x
, const_rtx pat ATTRIBUTE_UNUSED
, void *data
)
2675 if (anti_dependence (x
, (const_rtx
)data
) || output_dependence (x
, (const_rtx
)data
))
2676 memory_modified
= true;
2681 /* Return true when INSN possibly modify memory contents of MEM
2682 (i.e. address can be modified). */
2684 memory_modified_in_insn_p (const_rtx mem
, const_rtx insn
)
2688 memory_modified
= false;
2689 note_stores (PATTERN (insn
), memory_modified_1
, CONST_CAST_RTX(mem
));
2690 return memory_modified
;
2693 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
2697 init_alias_analysis (void)
2699 unsigned int maxreg
= max_reg_num ();
2705 timevar_push (TV_ALIAS_ANALYSIS
);
2707 reg_known_value_size
= maxreg
- FIRST_PSEUDO_REGISTER
;
2708 reg_known_value
= ggc_alloc_cleared_vec_rtx (reg_known_value_size
);
2709 reg_known_equiv_p
= XCNEWVEC (bool, reg_known_value_size
);
2711 /* If we have memory allocated from the previous run, use it. */
2712 if (old_reg_base_value
)
2713 reg_base_value
= old_reg_base_value
;
2716 VEC_truncate (rtx
, reg_base_value
, 0);
2718 VEC_safe_grow_cleared (rtx
, gc
, reg_base_value
, maxreg
);
2720 new_reg_base_value
= XNEWVEC (rtx
, maxreg
);
2721 reg_seen
= XNEWVEC (char, maxreg
);
2723 /* The basic idea is that each pass through this loop will use the
2724 "constant" information from the previous pass to propagate alias
2725 information through another level of assignments.
2727 This could get expensive if the assignment chains are long. Maybe
2728 we should throttle the number of iterations, possibly based on
2729 the optimization level or flag_expensive_optimizations.
2731 We could propagate more information in the first pass by making use
2732 of DF_REG_DEF_COUNT to determine immediately that the alias information
2733 for a pseudo is "constant".
2735 A program with an uninitialized variable can cause an infinite loop
2736 here. Instead of doing a full dataflow analysis to detect such problems
2737 we just cap the number of iterations for the loop.
2739 The state of the arrays for the set chain in question does not matter
2740 since the program has undefined behavior. */
2745 /* Assume nothing will change this iteration of the loop. */
2748 /* We want to assign the same IDs each iteration of this loop, so
2749 start counting from zero each iteration of the loop. */
2752 /* We're at the start of the function each iteration through the
2753 loop, so we're copying arguments. */
2754 copying_arguments
= true;
2756 /* Wipe the potential alias information clean for this pass. */
2757 memset (new_reg_base_value
, 0, maxreg
* sizeof (rtx
));
2759 /* Wipe the reg_seen array clean. */
2760 memset (reg_seen
, 0, maxreg
);
2762 /* Mark all hard registers which may contain an address.
2763 The stack, frame and argument pointers may contain an address.
2764 An argument register which can hold a Pmode value may contain
2765 an address even if it is not in BASE_REGS.
2767 The address expression is VOIDmode for an argument and
2768 Pmode for other registers. */
2770 memcpy (new_reg_base_value
, static_reg_base_value
,
2771 FIRST_PSEUDO_REGISTER
* sizeof (rtx
));
2773 /* Walk the insns adding values to the new_reg_base_value array. */
2774 for (insn
= get_insns (); insn
; insn
= NEXT_INSN (insn
))
2780 #if defined (HAVE_prologue) || defined (HAVE_epilogue)
2781 /* The prologue/epilogue insns are not threaded onto the
2782 insn chain until after reload has completed. Thus,
2783 there is no sense wasting time checking if INSN is in
2784 the prologue/epilogue until after reload has completed. */
2785 if (reload_completed
2786 && prologue_epilogue_contains (insn
))
2790 /* If this insn has a noalias note, process it, Otherwise,
2791 scan for sets. A simple set will have no side effects
2792 which could change the base value of any other register. */
2794 if (GET_CODE (PATTERN (insn
)) == SET
2795 && REG_NOTES (insn
) != 0
2796 && find_reg_note (insn
, REG_NOALIAS
, NULL_RTX
))
2797 record_set (SET_DEST (PATTERN (insn
)), NULL_RTX
, NULL
);
2799 note_stores (PATTERN (insn
), record_set
, NULL
);
2801 set
= single_set (insn
);
2804 && REG_P (SET_DEST (set
))
2805 && REGNO (SET_DEST (set
)) >= FIRST_PSEUDO_REGISTER
)
2807 unsigned int regno
= REGNO (SET_DEST (set
));
2808 rtx src
= SET_SRC (set
);
2811 note
= find_reg_equal_equiv_note (insn
);
2812 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
2813 && DF_REG_DEF_COUNT (regno
) != 1)
2816 if (note
!= NULL_RTX
2817 && GET_CODE (XEXP (note
, 0)) != EXPR_LIST
2818 && ! rtx_varies_p (XEXP (note
, 0), 1)
2819 && ! reg_overlap_mentioned_p (SET_DEST (set
),
2822 set_reg_known_value (regno
, XEXP (note
, 0));
2823 set_reg_known_equiv_p (regno
,
2824 REG_NOTE_KIND (note
) == REG_EQUIV
);
2826 else if (DF_REG_DEF_COUNT (regno
) == 1
2827 && GET_CODE (src
) == PLUS
2828 && REG_P (XEXP (src
, 0))
2829 && (t
= get_reg_known_value (REGNO (XEXP (src
, 0))))
2830 && CONST_INT_P (XEXP (src
, 1)))
2832 t
= plus_constant (t
, INTVAL (XEXP (src
, 1)));
2833 set_reg_known_value (regno
, t
);
2834 set_reg_known_equiv_p (regno
, 0);
2836 else if (DF_REG_DEF_COUNT (regno
) == 1
2837 && ! rtx_varies_p (src
, 1))
2839 set_reg_known_value (regno
, src
);
2840 set_reg_known_equiv_p (regno
, 0);
2844 else if (NOTE_P (insn
)
2845 && NOTE_KIND (insn
) == NOTE_INSN_FUNCTION_BEG
)
2846 copying_arguments
= false;
2849 /* Now propagate values from new_reg_base_value to reg_base_value. */
2850 gcc_assert (maxreg
== (unsigned int) max_reg_num ());
2852 for (ui
= 0; ui
< maxreg
; ui
++)
2854 if (new_reg_base_value
[ui
]
2855 && new_reg_base_value
[ui
] != VEC_index (rtx
, reg_base_value
, ui
)
2856 && ! rtx_equal_p (new_reg_base_value
[ui
],
2857 VEC_index (rtx
, reg_base_value
, ui
)))
2859 VEC_replace (rtx
, reg_base_value
, ui
, new_reg_base_value
[ui
]);
2864 while (changed
&& ++pass
< MAX_ALIAS_LOOP_PASSES
);
2866 /* Fill in the remaining entries. */
2867 for (i
= 0; i
< (int)reg_known_value_size
; i
++)
2868 if (reg_known_value
[i
] == 0)
2869 reg_known_value
[i
] = regno_reg_rtx
[i
+ FIRST_PSEUDO_REGISTER
];
2872 free (new_reg_base_value
);
2873 new_reg_base_value
= 0;
2876 timevar_pop (TV_ALIAS_ANALYSIS
);
2879 /* Equate REG_BASE_VALUE (reg1) to REG_BASE_VALUE (reg2).
2880 Special API for var-tracking pass purposes. */
2883 vt_equate_reg_base_value (const_rtx reg1
, const_rtx reg2
)
2885 VEC_replace (rtx
, reg_base_value
, REGNO (reg1
), REG_BASE_VALUE (reg2
));
2889 end_alias_analysis (void)
2891 old_reg_base_value
= reg_base_value
;
2892 ggc_free (reg_known_value
);
2893 reg_known_value
= 0;
2894 reg_known_value_size
= 0;
2895 free (reg_known_equiv_p
);
2896 reg_known_equiv_p
= 0;
2899 #include "gt-alias.h"