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freebsd/contrib/gcc/alias.c

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/* Alias analysis for GNU C
Copyright (C) 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
Contributed by John Carr (jfc@mit.edu).
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA. */
#include "config.h"
#include "system.h"
#include "rtl.h"
#include "tree.h"
#include "tm_p.h"
#include "function.h"
#include "expr.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "flags.h"
#include "output.h"
#include "toplev.h"
#include "cselib.h"
#include "splay-tree.h"
#include "ggc.h"
#include "langhooks.h"
/* The alias sets assigned to MEMs assist the back-end in determining
which MEMs can alias which other MEMs. In general, two MEMs in
different alias sets cannot alias each other, with one important
exception. Consider something like:
struct S {int i; double d; };
a store to an `S' can alias something of either type `int' or type
`double'. (However, a store to an `int' cannot alias a `double'
and vice versa.) We indicate this via a tree structure that looks
like:
struct S
/ \
/ \
|/_ _\|
int double
(The arrows are directed and point downwards.)
In this situation we say the alias set for `struct S' is the
`superset' and that those for `int' and `double' are `subsets'.
To see whether two alias sets can point to the same memory, we must
see if either alias set is a subset of the other. We need not trace
past immediate descendents, however, since we propagate all
grandchildren up one level.
Alias set zero is implicitly a superset of all other alias sets.
However, this is no actual entry for alias set zero. It is an
error to attempt to explicitly construct a subset of zero. */
typedef struct alias_set_entry
{
/* The alias set number, as stored in MEM_ALIAS_SET. */
HOST_WIDE_INT alias_set;
/* The children of the alias set. These are not just the immediate
children, but, in fact, all descendents. So, if we have:
struct T { struct S s; float f; }
continuing our example above, the children here will be all of
`int', `double', `float', and `struct S'. */
splay_tree children;
/* Nonzero if would have a child of zero: this effectively makes this
alias set the same as alias set zero. */
int has_zero_child;
} *alias_set_entry;
static int rtx_equal_for_memref_p PARAMS ((rtx, rtx));
static rtx find_symbolic_term PARAMS ((rtx));
rtx get_addr PARAMS ((rtx));
static int memrefs_conflict_p PARAMS ((int, rtx, int, rtx,
HOST_WIDE_INT));
static void record_set PARAMS ((rtx, rtx, void *));
static rtx find_base_term PARAMS ((rtx));
static int base_alias_check PARAMS ((rtx, rtx, enum machine_mode,
enum machine_mode));
static rtx find_base_value PARAMS ((rtx));
static int mems_in_disjoint_alias_sets_p PARAMS ((rtx, rtx));
static int insert_subset_children PARAMS ((splay_tree_node, void*));
static tree find_base_decl PARAMS ((tree));
static alias_set_entry get_alias_set_entry PARAMS ((HOST_WIDE_INT));
static rtx fixed_scalar_and_varying_struct_p PARAMS ((rtx, rtx, rtx, rtx,
int (*) (rtx, int)));
static int aliases_everything_p PARAMS ((rtx));
static bool nonoverlapping_component_refs_p PARAMS ((tree, tree));
static tree decl_for_component_ref PARAMS ((tree));
static rtx adjust_offset_for_component_ref PARAMS ((tree, rtx));
static int nonoverlapping_memrefs_p PARAMS ((rtx, rtx));
static int write_dependence_p PARAMS ((rtx, rtx, int));
static int nonlocal_mentioned_p PARAMS ((rtx));
/* Set up all info needed to perform alias analysis on memory references. */
/* Returns the size in bytes of the mode of X. */
#define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))
/* Returns nonzero if MEM1 and MEM2 do not alias because they are in
different alias sets. We ignore alias sets in functions making use
of variable arguments because the va_arg macros on some systems are
not legal ANSI C. */
#define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2) \
mems_in_disjoint_alias_sets_p (MEM1, MEM2)
/* Cap the number of passes we make over the insns propagating alias
information through set chains. 10 is a completely arbitrary choice. */
#define MAX_ALIAS_LOOP_PASSES 10
/* reg_base_value[N] gives an address to which register N is related.
If all sets after the first add or subtract to the current value
or otherwise modify it so it does not point to a different top level
object, reg_base_value[N] is equal to the address part of the source
of the first set.
A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS
expressions represent certain special values: function arguments and
the stack, frame, and argument pointers.
The contents of an ADDRESS is not normally used, the mode of the
ADDRESS determines whether the ADDRESS is a function argument or some
other special value. Pointer equality, not rtx_equal_p, determines whether
two ADDRESS expressions refer to the same base address.
The only use of the contents of an ADDRESS is for determining if the
current function performs nonlocal memory memory references for the
purposes of marking the function as a constant function. */
static rtx *reg_base_value;
static rtx *new_reg_base_value;
static unsigned int reg_base_value_size; /* size of reg_base_value array */
#define REG_BASE_VALUE(X) \
(REGNO (X) < reg_base_value_size \
? reg_base_value[REGNO (X)] : 0)
/* Vector of known invariant relationships between registers. Set in
loop unrolling. Indexed by register number, if nonzero the value
is an expression describing this register in terms of another.
The length of this array is REG_BASE_VALUE_SIZE.
Because this array contains only pseudo registers it has no effect
after reload. */
static rtx *alias_invariant;
/* Vector indexed by N giving the initial (unchanging) value known for
pseudo-register N. This array is initialized in
init_alias_analysis, and does not change until end_alias_analysis
is called. */
rtx *reg_known_value;
/* Indicates number of valid entries in reg_known_value. */
static unsigned int reg_known_value_size;
/* Vector recording for each reg_known_value whether it is due to a
REG_EQUIV note. Future passes (viz., reload) may replace the
pseudo with the equivalent expression and so we account for the
dependences that would be introduced if that happens.
The REG_EQUIV notes created in assign_parms may mention the arg
pointer, and there are explicit insns in the RTL that modify the
arg pointer. Thus we must ensure that such insns don't get
scheduled across each other because that would invalidate the
REG_EQUIV notes. One could argue that the REG_EQUIV notes are
wrong, but solving the problem in the scheduler will likely give
better code, so we do it here. */
char *reg_known_equiv_p;
/* True when scanning insns from the start of the rtl to the
NOTE_INSN_FUNCTION_BEG note. */
static int copying_arguments;
/* The splay-tree used to store the various alias set entries. */
static splay_tree alias_sets;
/* Returns a pointer to the alias set entry for ALIAS_SET, if there is
such an entry, or NULL otherwise. */
static alias_set_entry
get_alias_set_entry (alias_set)
HOST_WIDE_INT alias_set;
{
splay_tree_node sn
= splay_tree_lookup (alias_sets, (splay_tree_key) alias_set);
return sn != 0 ? ((alias_set_entry) sn->value) : 0;
}
/* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
the two MEMs cannot alias each other. */
static int
mems_in_disjoint_alias_sets_p (mem1, mem2)
rtx mem1;
rtx mem2;
{
#ifdef ENABLE_CHECKING
/* Perform a basic sanity check. Namely, that there are no alias sets
if we're not using strict aliasing. This helps to catch bugs
whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
where a MEM is allocated in some way other than by the use of
gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared. If we begin to
use alias sets to indicate that spilled registers cannot alias each
other, we might need to remove this check. */
if (! flag_strict_aliasing
&& (MEM_ALIAS_SET (mem1) != 0 || MEM_ALIAS_SET (mem2) != 0))
abort ();
#endif
return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
}
/* Insert the NODE into the splay tree given by DATA. Used by
record_alias_subset via splay_tree_foreach. */
static int
insert_subset_children (node, data)
splay_tree_node node;
void *data;
{
splay_tree_insert ((splay_tree) data, node->key, node->value);
return 0;
}
/* Return 1 if the two specified alias sets may conflict. */
int
alias_sets_conflict_p (set1, set2)
HOST_WIDE_INT set1, set2;
{
alias_set_entry ase;
/* If have no alias set information for one of the operands, we have
to assume it can alias anything. */
if (set1 == 0 || set2 == 0
/* If the two alias sets are the same, they may alias. */
|| set1 == set2)
return 1;
/* See if the first alias set is a subset of the second. */
ase = get_alias_set_entry (set1);
if (ase != 0
&& (ase->has_zero_child
|| splay_tree_lookup (ase->children,
(splay_tree_key) set2)))
return 1;
/* Now do the same, but with the alias sets reversed. */
ase = get_alias_set_entry (set2);
if (ase != 0
&& (ase->has_zero_child
|| splay_tree_lookup (ase->children,
(splay_tree_key) set1)))
return 1;
/* The two alias sets are distinct and neither one is the
child of the other. Therefore, they cannot alias. */
return 0;
}
/* Return 1 if TYPE is a RECORD_TYPE, UNION_TYPE, or QUAL_UNION_TYPE and has
has any readonly fields. If any of the fields have types that
contain readonly fields, return true as well. */
int
readonly_fields_p (type)
tree type;
{
tree field;
if (TREE_CODE (type) != RECORD_TYPE && TREE_CODE (type) != UNION_TYPE
&& TREE_CODE (type) != QUAL_UNION_TYPE)
return 0;
for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL
&& (TREE_READONLY (field)
|| readonly_fields_p (TREE_TYPE (field))))
return 1;
return 0;
}
/* Return 1 if any MEM object of type T1 will always conflict (using the
dependency routines in this file) with any MEM object of type T2.
This is used when allocating temporary storage. If T1 and/or T2 are
NULL_TREE, it means we know nothing about the storage. */
int
objects_must_conflict_p (t1, t2)
tree t1, t2;
{
/* If neither has a type specified, we don't know if they'll conflict
because we may be using them to store objects of various types, for
example the argument and local variables areas of inlined functions. */
if (t1 == 0 && t2 == 0)
return 0;
/* If one or the other has readonly fields or is readonly,
then they may not conflict. */
if ((t1 != 0 && readonly_fields_p (t1))
|| (t2 != 0 && readonly_fields_p (t2))
|| (t1 != 0 && TYPE_READONLY (t1))
|| (t2 != 0 && TYPE_READONLY (t2)))
return 0;
/* If they are the same type, they must conflict. */
if (t1 == t2
/* Likewise if both are volatile. */
|| (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
return 1;
/* If one is aggregate and the other is scalar then they may not
conflict. */
if ((t1 != 0 && AGGREGATE_TYPE_P (t1))
!= (t2 != 0 && AGGREGATE_TYPE_P (t2)))
return 0;
/* Otherwise they conflict only if the alias sets conflict. */
return alias_sets_conflict_p (t1 ? get_alias_set (t1) : 0,
t2 ? get_alias_set (t2) : 0);
}
/* T is an expression with pointer type. Find the DECL on which this
expression is based. (For example, in `a[i]' this would be `a'.)
If there is no such DECL, or a unique decl cannot be determined,
NULL_TREE is returned. */
static tree
find_base_decl (t)
tree t;
{
tree d0, d1, d2;
if (t == 0 || t == error_mark_node || ! POINTER_TYPE_P (TREE_TYPE (t)))
return 0;
/* If this is a declaration, return it. */
if (TREE_CODE_CLASS (TREE_CODE (t)) == 'd')
return t;
/* Handle general expressions. It would be nice to deal with
COMPONENT_REFs here. If we could tell that `a' and `b' were the
same, then `a->f' and `b->f' are also the same. */
switch (TREE_CODE_CLASS (TREE_CODE (t)))
{
case '1':
return find_base_decl (TREE_OPERAND (t, 0));
case '2':
/* Return 0 if found in neither or both are the same. */
d0 = find_base_decl (TREE_OPERAND (t, 0));
d1 = find_base_decl (TREE_OPERAND (t, 1));
if (d0 == d1)
return d0;
else if (d0 == 0)
return d1;
else if (d1 == 0)
return d0;
else
return 0;
case '3':
d0 = find_base_decl (TREE_OPERAND (t, 0));
d1 = find_base_decl (TREE_OPERAND (t, 1));
d2 = find_base_decl (TREE_OPERAND (t, 2));
/* Set any nonzero values from the last, then from the first. */
if (d1 == 0) d1 = d2;
if (d0 == 0) d0 = d1;
if (d1 == 0) d1 = d0;
if (d2 == 0) d2 = d1;
/* At this point all are nonzero or all are zero. If all three are the
same, return it. Otherwise, return zero. */
return (d0 == d1 && d1 == d2) ? d0 : 0;
default:
return 0;
}
}
/* Return 1 if all the nested component references handled by
get_inner_reference in T are such that we can address the object in T. */
int
can_address_p (t)
tree t;
{
/* If we're at the end, it is vacuously addressable. */
if (! handled_component_p (t))
return 1;
/* Bitfields are never addressable. */
else if (TREE_CODE (t) == BIT_FIELD_REF)
return 0;
/* Fields are addressable unless they are marked as nonaddressable or
the containing type has alias set 0. */
else if (TREE_CODE (t) == COMPONENT_REF
&& ! DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))
&& get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
&& can_address_p (TREE_OPERAND (t, 0)))
return 1;
/* Likewise for arrays. */
else if ((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
&& ! TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))
&& get_alias_set (TREE_TYPE (TREE_OPERAND (t, 0))) != 0
&& can_address_p (TREE_OPERAND (t, 0)))
return 1;
return 0;
}
/* Return the alias set for T, which may be either a type or an
expression. Call language-specific routine for help, if needed. */
HOST_WIDE_INT
get_alias_set (t)
tree t;
{
HOST_WIDE_INT set;
/* If we're not doing any alias analysis, just assume everything
aliases everything else. Also return 0 if this or its type is
an error. */
if (! flag_strict_aliasing || t == error_mark_node
|| (! TYPE_P (t)
&& (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
return 0;
/* We can be passed either an expression or a type. This and the
language-specific routine may make mutually-recursive calls to each other
to figure out what to do. At each juncture, we see if this is a tree
that the language may need to handle specially. First handle things that
aren't types. */
if (! TYPE_P (t))
{
tree inner = t;
tree placeholder_ptr = 0;
/* Remove any nops, then give the language a chance to do
something with this tree before we look at it. */
STRIP_NOPS (t);
set = (*lang_hooks.get_alias_set) (t);
if (set != -1)
return set;
/* First see if the actual object referenced is an INDIRECT_REF from a
restrict-qualified pointer or a "void *". Replace
PLACEHOLDER_EXPRs. */
while (TREE_CODE (inner) == PLACEHOLDER_EXPR
|| handled_component_p (inner))
{
if (TREE_CODE (inner) == PLACEHOLDER_EXPR)
inner = find_placeholder (inner, &placeholder_ptr);
else
inner = TREE_OPERAND (inner, 0);
STRIP_NOPS (inner);
}
/* Check for accesses through restrict-qualified pointers. */
if (TREE_CODE (inner) == INDIRECT_REF)
{
tree decl = find_base_decl (TREE_OPERAND (inner, 0));
if (decl && DECL_POINTER_ALIAS_SET_KNOWN_P (decl))
{
/* If we haven't computed the actual alias set, do it now. */
if (DECL_POINTER_ALIAS_SET (decl) == -2)
{
/* No two restricted pointers can point at the same thing.
However, a restricted pointer can point at the same thing
as an unrestricted pointer, if that unrestricted pointer
is based on the restricted pointer. So, we make the
alias set for the restricted pointer a subset of the
alias set for the type pointed to by the type of the
decl. */
HOST_WIDE_INT pointed_to_alias_set
= get_alias_set (TREE_TYPE (TREE_TYPE (decl)));
if (pointed_to_alias_set == 0)
/* It's not legal to make a subset of alias set zero. */
;
else
{
DECL_POINTER_ALIAS_SET (decl) = new_alias_set ();
record_alias_subset (pointed_to_alias_set,
DECL_POINTER_ALIAS_SET (decl));
}
}
/* We use the alias set indicated in the declaration. */
return DECL_POINTER_ALIAS_SET (decl);
}
/* If we have an INDIRECT_REF via a void pointer, we don't
know anything about what that might alias. */
else if (TREE_CODE (TREE_TYPE (inner)) == VOID_TYPE)
return 0;
}
/* Otherwise, pick up the outermost object that we could have a pointer
to, processing conversion and PLACEHOLDER_EXPR as above. */
placeholder_ptr = 0;
while (TREE_CODE (t) == PLACEHOLDER_EXPR
|| (handled_component_p (t) && ! can_address_p (t)))
{
if (TREE_CODE (t) == PLACEHOLDER_EXPR)
t = find_placeholder (t, &placeholder_ptr);
else
t = TREE_OPERAND (t, 0);
STRIP_NOPS (t);
}
/* If we've already determined the alias set for a decl, just return
it. This is necessary for C++ anonymous unions, whose component
variables don't look like union members (boo!). */
if (TREE_CODE (t) == VAR_DECL
&& DECL_RTL_SET_P (t) && GET_CODE (DECL_RTL (t)) == MEM)
return MEM_ALIAS_SET (DECL_RTL (t));
/* Now all we care about is the type. */
t = TREE_TYPE (t);
}
/* Variant qualifiers don't affect the alias set, so get the main
variant. If this is a type with a known alias set, return it. */
t = TYPE_MAIN_VARIANT (t);
if (TYPE_ALIAS_SET_KNOWN_P (t))
return TYPE_ALIAS_SET (t);
/* See if the language has special handling for this type. */
set = (*lang_hooks.get_alias_set) (t);
if (set != -1)
return set;
/* There are no objects of FUNCTION_TYPE, so there's no point in
using up an alias set for them. (There are, of course, pointers
and references to functions, but that's different.) */
else if (TREE_CODE (t) == FUNCTION_TYPE)
set = 0;
else
/* Otherwise make a new alias set for this type. */
set = new_alias_set ();
TYPE_ALIAS_SET (t) = set;
/* If this is an aggregate type, we must record any component aliasing
information. */
if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
record_component_aliases (t);
return set;
}
/* Return a brand-new alias set. */
HOST_WIDE_INT
new_alias_set ()
{
static HOST_WIDE_INT last_alias_set;
if (flag_strict_aliasing)
return ++last_alias_set;
else
return 0;
}
/* Indicate that things in SUBSET can alias things in SUPERSET, but
not vice versa. For example, in C, a store to an `int' can alias a
structure containing an `int', but not vice versa. Here, the
structure would be the SUPERSET and `int' the SUBSET. This
function should be called only once per SUPERSET/SUBSET pair.
It is illegal for SUPERSET to be zero; everything is implicitly a
subset of alias set zero. */
void
record_alias_subset (superset, subset)
HOST_WIDE_INT superset;
HOST_WIDE_INT subset;
{
alias_set_entry superset_entry;
alias_set_entry subset_entry;
/* It is possible in complex type situations for both sets to be the same,
in which case we can ignore this operation. */
if (superset == subset)
return;
if (superset == 0)
abort ();
superset_entry = get_alias_set_entry (superset);
if (superset_entry == 0)
{
/* Create an entry for the SUPERSET, so that we have a place to
attach the SUBSET. */
superset_entry
= (alias_set_entry) xmalloc (sizeof (struct alias_set_entry));
superset_entry->alias_set = superset;
superset_entry->children
= splay_tree_new (splay_tree_compare_ints, 0, 0);
superset_entry->has_zero_child = 0;
splay_tree_insert (alias_sets, (splay_tree_key) superset,
(splay_tree_value) superset_entry);
}
if (subset == 0)
superset_entry->has_zero_child = 1;
else
{
subset_entry = get_alias_set_entry (subset);
/* If there is an entry for the subset, enter all of its children
(if they are not already present) as children of the SUPERSET. */
if (subset_entry)
{
if (subset_entry->has_zero_child)
superset_entry->has_zero_child = 1;
splay_tree_foreach (subset_entry->children, insert_subset_children,
superset_entry->children);
}
/* Enter the SUBSET itself as a child of the SUPERSET. */
splay_tree_insert (superset_entry->children,
(splay_tree_key) subset, 0);
}
}
/* Record that component types of TYPE, if any, are part of that type for
aliasing purposes. For record types, we only record component types
for fields that are marked addressable. For array types, we always
record the component types, so the front end should not call this
function if the individual component aren't addressable. */
void
record_component_aliases (type)
tree type;
{
HOST_WIDE_INT superset = get_alias_set (type);
tree field;
if (superset == 0)
return;
switch (TREE_CODE (type))
{
case ARRAY_TYPE:
if (! TYPE_NONALIASED_COMPONENT (type))
record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
break;
case RECORD_TYPE:
case UNION_TYPE:
case QUAL_UNION_TYPE:
for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
break;
case COMPLEX_TYPE:
record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
break;
default:
break;
}
}
/* Allocate an alias set for use in storing and reading from the varargs
spill area. */
HOST_WIDE_INT
get_varargs_alias_set ()
{
static HOST_WIDE_INT set = -1;
if (set == -1)
set = new_alias_set ();
return set;
}
/* Likewise, but used for the fixed portions of the frame, e.g., register
save areas. */
HOST_WIDE_INT
get_frame_alias_set ()
{
static HOST_WIDE_INT set = -1;
if (set == -1)
set = new_alias_set ();
return set;
}
/* Inside SRC, the source of a SET, find a base address. */
static rtx
find_base_value (src)
rtx src;
{
unsigned int regno;
switch (GET_CODE (src))
{
case SYMBOL_REF:
case LABEL_REF:
return src;
case REG:
regno = REGNO (src);
/* At the start of a function, argument registers have known base
values which may be lost later. Returning an ADDRESS
expression here allows optimization based on argument values
even when the argument registers are used for other purposes. */
if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
return new_reg_base_value[regno];
/* If a pseudo has a known base value, return it. Do not do this
for non-fixed hard regs since it can result in a circular
dependency chain for registers which have values at function entry.
The test above is not sufficient because the scheduler may move
a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */
if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
&& regno < reg_base_value_size
&& reg_base_value[regno])
return reg_base_value[regno];
return src;
case MEM:
/* Check for an argument passed in memory. Only record in the
copying-arguments block; it is too hard to track changes
otherwise. */
if (copying_arguments
&& (XEXP (src, 0) == arg_pointer_rtx
|| (GET_CODE (XEXP (src, 0)) == PLUS
&& XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
return gen_rtx_ADDRESS (VOIDmode, src);
return 0;
case CONST:
src = XEXP (src, 0);
if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
break;
/* ... fall through ... */
case PLUS:
case MINUS:
{
rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);
/* If either operand is a REG that is a known pointer, then it
is the base. */
if (REG_P (src_0) && REG_POINTER (src_0))
return find_base_value (src_0);
if (REG_P (src_1) && REG_POINTER (src_1))
return find_base_value (src_1);
/* If either operand is a REG, then see if we already have
a known value for it. */
if (REG_P (src_0))
{
temp = find_base_value (src_0);
if (temp != 0)
src_0 = temp;
}
if (REG_P (src_1))
{
temp = find_base_value (src_1);
if (temp!= 0)
src_1 = temp;
}
/* If either base is named object or a special address
(like an argument or stack reference), then use it for the
base term. */
if (src_0 != 0
&& (GET_CODE (src_0) == SYMBOL_REF
|| GET_CODE (src_0) == LABEL_REF
|| (GET_CODE (src_0) == ADDRESS
&& GET_MODE (src_0) != VOIDmode)))
return src_0;
if (src_1 != 0
&& (GET_CODE (src_1) == SYMBOL_REF
|| GET_CODE (src_1) == LABEL_REF
|| (GET_CODE (src_1) == ADDRESS
&& GET_MODE (src_1) != VOIDmode)))
return src_1;
/* Guess which operand is the base address:
If either operand is a symbol, then it is the base. If
either operand is a CONST_INT, then the other is the base. */
if (GET_CODE (src_1) == CONST_INT || CONSTANT_P (src_0))
return find_base_value (src_0);
else if (GET_CODE (src_0) == CONST_INT || CONSTANT_P (src_1))
return find_base_value (src_1);
return 0;
}
case LO_SUM:
/* The standard form is (lo_sum reg sym) so look only at the
second operand. */
return find_base_value (XEXP (src, 1));
case AND:
/* If the second operand is constant set the base
address to the first operand. */
if (GET_CODE (XEXP (src, 1)) == CONST_INT && INTVAL (XEXP (src, 1)) != 0)
return find_base_value (XEXP (src, 0));
return 0;
case TRUNCATE:
if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
break;
/* Fall through. */
case HIGH:
case PRE_INC:
case PRE_DEC:
case POST_INC:
case POST_DEC:
case PRE_MODIFY:
case POST_MODIFY:
return find_base_value (XEXP (src, 0));
case ZERO_EXTEND:
case SIGN_EXTEND: /* used for NT/Alpha pointers */
{
rtx temp = find_base_value (XEXP (src, 0));
#ifdef POINTERS_EXTEND_UNSIGNED
if (temp != 0 && CONSTANT_P (temp) && GET_MODE (temp) != Pmode)
temp = convert_memory_address (Pmode, temp);
#endif
return temp;
}
default:
break;
}
return 0;
}
/* Called from init_alias_analysis indirectly through note_stores. */
/* While scanning insns to find base values, reg_seen[N] is nonzero if
register N has been set in this function. */
static char *reg_seen;
/* Addresses which are known not to alias anything else are identified
by a unique integer. */
static int unique_id;
static void
record_set (dest, set, data)
rtx dest, set;
void *data ATTRIBUTE_UNUSED;
{
unsigned regno;
rtx src;
if (GET_CODE (dest) != REG)
return;
regno = REGNO (dest);
if (regno >= reg_base_value_size)
abort ();
if (set)
{
/* A CLOBBER wipes out any old value but does not prevent a previously
unset register from acquiring a base address (i.e. reg_seen is not
set). */
if (GET_CODE (set) == CLOBBER)
{
new_reg_base_value[regno] = 0;
return;
}
src = SET_SRC (set);
}
else
{
if (reg_seen[regno])
{
new_reg_base_value[regno] = 0;
return;
}
reg_seen[regno] = 1;
new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
GEN_INT (unique_id++));
return;
}
/* This is not the first set. If the new value is not related to the
old value, forget the base value. Note that the following code is
not detected:
extern int x, y; int *p = &x; p += (&y-&x);
ANSI C does not allow computing the difference of addresses
of distinct top level objects. */
if (new_reg_base_value[regno])
switch (GET_CODE (src))
{
case LO_SUM:
case MINUS:
if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
new_reg_base_value[regno] = 0;
break;
case PLUS:
/* If the value we add in the PLUS is also a valid base value,
this might be the actual base value, and the original value
an index. */
{
rtx other = NULL_RTX;
if (XEXP (src, 0) == dest)
other = XEXP (src, 1);
else if (XEXP (src, 1) == dest)
other = XEXP (src, 0);
if (! other || find_base_value (other))
new_reg_base_value[regno] = 0;
break;
}
case AND:
if (XEXP (src, 0) != dest || GET_CODE (XEXP (src, 1)) != CONST_INT)
new_reg_base_value[regno] = 0;
break;
default:
new_reg_base_value[regno] = 0;
break;
}
/* If this is the first set of a register, record the value. */
else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
&& ! reg_seen[regno] && new_reg_base_value[regno] == 0)
new_reg_base_value[regno] = find_base_value (src);
reg_seen[regno] = 1;
}
/* Called from loop optimization when a new pseudo-register is
created. It indicates that REGNO is being set to VAL. f INVARIANT
is true then this value also describes an invariant relationship
which can be used to deduce that two registers with unknown values
are different. */
void
record_base_value (regno, val, invariant)
unsigned int regno;
rtx val;
int invariant;
{
if (regno >= reg_base_value_size)
return;
if (invariant && alias_invariant)
alias_invariant[regno] = val;
if (GET_CODE (val) == REG)
{
if (REGNO (val) < reg_base_value_size)
reg_base_value[regno] = reg_base_value[REGNO (val)];
return;
}
reg_base_value[regno] = find_base_value (val);
}
/* Clear alias info for a register. This is used if an RTL transformation
changes the value of a register. This is used in flow by AUTO_INC_DEC
optimizations. We don't need to clear reg_base_value, since flow only
changes the offset. */
void
clear_reg_alias_info (reg)
rtx reg;
{
unsigned int regno = REGNO (reg);
if (regno < reg_known_value_size && regno >= FIRST_PSEUDO_REGISTER)
reg_known_value[regno] = reg;
}
/* Returns a canonical version of X, from the point of view alias
analysis. (For example, if X is a MEM whose address is a register,
and the register has a known value (say a SYMBOL_REF), then a MEM
whose address is the SYMBOL_REF is returned.) */
rtx
canon_rtx (x)
rtx x;
{
/* Recursively look for equivalences. */
if (GET_CODE (x) == REG && REGNO (x) >= FIRST_PSEUDO_REGISTER
&& REGNO (x) < reg_known_value_size)
return reg_known_value[REGNO (x)] == x
? x : canon_rtx (reg_known_value[REGNO (x)]);
else if (GET_CODE (x) == PLUS)
{
rtx x0 = canon_rtx (XEXP (x, 0));
rtx x1 = canon_rtx (XEXP (x, 1));
if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
{
if (GET_CODE (x0) == CONST_INT)
return plus_constant (x1, INTVAL (x0));
else if (GET_CODE (x1) == CONST_INT)
return plus_constant (x0, INTVAL (x1));
return gen_rtx_PLUS (GET_MODE (x), x0, x1);
}
}
/* This gives us much better alias analysis when called from
the loop optimizer. Note we want to leave the original
MEM alone, but need to return the canonicalized MEM with
all the flags with their original values. */
else if (GET_CODE (x) == MEM)
x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));
return x;
}
/* Return 1 if X and Y are identical-looking rtx's.
We use the data in reg_known_value above to see if two registers with
different numbers are, in fact, equivalent. */
static int
rtx_equal_for_memref_p (x, y)
rtx x, y;
{
int i;
int j;
enum rtx_code code;
const char *fmt;
if (x == 0 && y == 0)
return 1;
if (x == 0 || y == 0)
return 0;
x = canon_rtx (x);
y = canon_rtx (y);
if (x == y)
return 1;
code = GET_CODE (x);
/* Rtx's of different codes cannot be equal. */
if (code != GET_CODE (y))
return 0;
/* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
(REG:SI x) and (REG:HI x) are NOT equivalent. */
if (GET_MODE (x) != GET_MODE (y))
return 0;
/* Some RTL can be compared without a recursive examination. */
switch (code)
{
case VALUE:
return CSELIB_VAL_PTR (x) == CSELIB_VAL_PTR (y);
case REG:
return REGNO (x) == REGNO (y);
case LABEL_REF:
return XEXP (x, 0) == XEXP (y, 0);
case SYMBOL_REF:
return XSTR (x, 0) == XSTR (y, 0);
case CONST_INT:
case CONST_DOUBLE:
/* There's no need to compare the contents of CONST_DOUBLEs or
CONST_INTs because pointer equality is a good enough
comparison for these nodes. */
return 0;
case ADDRESSOF:
return (XINT (x, 1) == XINT (y, 1)
&& rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)));
default:
break;
}
/* For commutative operations, the RTX match if the operand match in any
order. Also handle the simple binary and unary cases without a loop. */
if (code == EQ || code == NE || GET_RTX_CLASS (code) == 'c')
return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
&& rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
|| (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
&& rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
else if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == '2')
return (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
&& rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)));
else if (GET_RTX_CLASS (code) == '1')
return rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0));
/* Compare the elements. If any pair of corresponding elements
fail to match, return 0 for the whole things.
Limit cases to types which actually appear in addresses. */
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
switch (fmt[i])
{
case 'i':
if (XINT (x, i) != XINT (y, i))
return 0;
break;
case 'E':
/* Two vectors must have the same length. */
if (XVECLEN (x, i) != XVECLEN (y, i))
return 0;
/* And the corresponding elements must match. */
for (j = 0; j < XVECLEN (x, i); j++)
if (rtx_equal_for_memref_p (XVECEXP (x, i, j),
XVECEXP (y, i, j)) == 0)
return 0;
break;
case 'e':
if (rtx_equal_for_memref_p (XEXP (x, i), XEXP (y, i)) == 0)
return 0;
break;
/* This can happen for asm operands. */
case 's':
if (strcmp (XSTR (x, i), XSTR (y, i)))
return 0;
break;
/* This can happen for an asm which clobbers memory. */
case '0':
break;
/* It is believed that rtx's at this level will never
contain anything but integers and other rtx's,
except for within LABEL_REFs and SYMBOL_REFs. */
default:
abort ();
}
}
return 1;
}
/* Given an rtx X, find a SYMBOL_REF or LABEL_REF within
X and return it, or return 0 if none found. */
static rtx
find_symbolic_term (x)
rtx x;
{
int i;
enum rtx_code code;
const char *fmt;
code = GET_CODE (x);
if (code == SYMBOL_REF || code == LABEL_REF)
return x;
if (GET_RTX_CLASS (code) == 'o')
return 0;
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
rtx t;
if (fmt[i] == 'e')
{
t = find_symbolic_term (XEXP (x, i));
if (t != 0)
return t;
}
else if (fmt[i] == 'E')
break;
}
return 0;
}
static rtx
find_base_term (x)
rtx x;
{
cselib_val *val;
struct elt_loc_list *l;
#if defined (FIND_BASE_TERM)
/* Try machine-dependent ways to find the base term. */
x = FIND_BASE_TERM (x);
#endif
switch (GET_CODE (x))
{
case REG:
return REG_BASE_VALUE (x);
case TRUNCATE:
if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
return 0;
/* Fall through. */
case HIGH:
case PRE_INC:
case PRE_DEC:
case POST_INC:
case POST_DEC:
case PRE_MODIFY:
case POST_MODIFY:
return find_base_term (XEXP (x, 0));
case ZERO_EXTEND:
case SIGN_EXTEND: /* Used for Alpha/NT pointers */
{
rtx temp = find_base_term (XEXP (x, 0));
#ifdef POINTERS_EXTEND_UNSIGNED
if (temp != 0 && CONSTANT_P (temp) && GET_MODE (temp) != Pmode)
temp = convert_memory_address (Pmode, temp);
#endif
return temp;
}
case VALUE:
val = CSELIB_VAL_PTR (x);
for (l = val->locs; l; l = l->next)
if ((x = find_base_term (l->loc)) != 0)
return x;
return 0;
case CONST:
x = XEXP (x, 0);
if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
return 0;
/* fall through */
case LO_SUM:
case PLUS:
case MINUS:
{
rtx tmp1 = XEXP (x, 0);
rtx tmp2 = XEXP (x, 1);
/* This is a little bit tricky since we have to determine which of
the two operands represents the real base address. Otherwise this
routine may return the index register instead of the base register.
That may cause us to believe no aliasing was possible, when in
fact aliasing is possible.
We use a few simple tests to guess the base register. Additional
tests can certainly be added. For example, if one of the operands
is a shift or multiply, then it must be the index register and the
other operand is the base register. */
if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
return find_base_term (tmp2);
/* If either operand is known to be a pointer, then use it
to determine the base term. */
if (REG_P (tmp1) && REG_POINTER (tmp1))
return find_base_term (tmp1);
if (REG_P (tmp2) && REG_POINTER (tmp2))
return find_base_term (tmp2);
/* Neither operand was known to be a pointer. Go ahead and find the
base term for both operands. */
tmp1 = find_base_term (tmp1);
tmp2 = find_base_term (tmp2);
/* If either base term is named object or a special address
(like an argument or stack reference), then use it for the
base term. */
if (tmp1 != 0
&& (GET_CODE (tmp1) == SYMBOL_REF
|| GET_CODE (tmp1) == LABEL_REF
|| (GET_CODE (tmp1) == ADDRESS
&& GET_MODE (tmp1) != VOIDmode)))
return tmp1;
if (tmp2 != 0
&& (GET_CODE (tmp2) == SYMBOL_REF
|| GET_CODE (tmp2) == LABEL_REF
|| (GET_CODE (tmp2) == ADDRESS
&& GET_MODE (tmp2) != VOIDmode)))
return tmp2;
/* We could not determine which of the two operands was the
base register and which was the index. So we can determine
nothing from the base alias check. */
return 0;
}
case AND:
if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) != 0)
return find_base_term (XEXP (x, 0));
return 0;
case SYMBOL_REF:
case LABEL_REF:
return x;
case ADDRESSOF:
return REG_BASE_VALUE (frame_pointer_rtx);
default:
return 0;
}
}
/* Return 0 if the addresses X and Y are known to point to different
objects, 1 if they might be pointers to the same object. */
static int
base_alias_check (x, y, x_mode, y_mode)
rtx x, y;
enum machine_mode x_mode, y_mode;
{
rtx x_base = find_base_term (x);
rtx y_base = find_base_term (y);
/* If the address itself has no known base see if a known equivalent
value has one. If either address still has no known base, nothing
is known about aliasing. */
if (x_base == 0)
{
rtx x_c;
if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
return 1;
x_base = find_base_term (x_c);
if (x_base == 0)
return 1;
}
if (y_base == 0)
{
rtx y_c;
if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
return 1;
y_base = find_base_term (y_c);
if (y_base == 0)
return 1;
}
/* If the base addresses are equal nothing is known about aliasing. */
if (rtx_equal_p (x_base, y_base))
return 1;
/* The base addresses of the read and write are different expressions.
If they are both symbols and they are not accessed via AND, there is
no conflict. We can bring knowledge of object alignment into play
here. For example, on alpha, "char a, b;" can alias one another,
though "char a; long b;" cannot. */
if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
{
if (GET_CODE (x) == AND && GET_CODE (y) == AND)
return 1;
if (GET_CODE (x) == AND
&& (GET_CODE (XEXP (x, 1)) != CONST_INT
|| (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
return 1;
if (GET_CODE (y) == AND
&& (GET_CODE (XEXP (y, 1)) != CONST_INT
|| (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
return 1;
/* Differing symbols never alias. */
return 0;
}
/* If one address is a stack reference there can be no alias:
stack references using different base registers do not alias,
a stack reference can not alias a parameter, and a stack reference
can not alias a global. */
if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
|| (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
return 0;
if (! flag_argument_noalias)
return 1;
if (flag_argument_noalias > 1)
return 0;
/* Weak noalias assertion (arguments are distinct, but may match globals). */
return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
}
/* Convert the address X into something we can use. This is done by returning
it unchanged unless it is a value; in the latter case we call cselib to get
a more useful rtx. */
rtx
get_addr (x)
rtx x;
{
cselib_val *v;
struct elt_loc_list *l;
if (GET_CODE (x) != VALUE)
return x;
v = CSELIB_VAL_PTR (x);
for (l = v->locs; l; l = l->next)
if (CONSTANT_P (l->loc))
return l->loc;
for (l = v->locs; l; l = l->next)
if (GET_CODE (l->loc) != REG && GET_CODE (l->loc) != MEM)
return l->loc;
if (v->locs)
return v->locs->loc;
return x;
}
/* Return the address of the (N_REFS + 1)th memory reference to ADDR
where SIZE is the size in bytes of the memory reference. If ADDR
is not modified by the memory reference then ADDR is returned. */
rtx
addr_side_effect_eval (addr, size, n_refs)
rtx addr;
int size;
int n_refs;
{
int offset = 0;
switch (GET_CODE (addr))
{
case PRE_INC:
offset = (n_refs + 1) * size;
break;
case PRE_DEC:
offset = -(n_refs + 1) * size;
break;
case POST_INC:
offset = n_refs * size;
break;
case POST_DEC:
offset = -n_refs * size;
break;
default:
return addr;
}
if (offset)
addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0), GEN_INT (offset));
else
addr = XEXP (addr, 0);
return addr;
}
/* Return nonzero if X and Y (memory addresses) could reference the
same location in memory. C is an offset accumulator. When
C is nonzero, we are testing aliases between X and Y + C.
XSIZE is the size in bytes of the X reference,
similarly YSIZE is the size in bytes for Y.
If XSIZE or YSIZE is zero, we do not know the amount of memory being
referenced (the reference was BLKmode), so make the most pessimistic
assumptions.
If XSIZE or YSIZE is negative, we may access memory outside the object
being referenced as a side effect. This can happen when using AND to
align memory references, as is done on the Alpha.
Nice to notice that varying addresses cannot conflict with fp if no
local variables had their addresses taken, but that's too hard now. */
static int
memrefs_conflict_p (xsize, x, ysize, y, c)
rtx x, y;
int xsize, ysize;
HOST_WIDE_INT c;
{
if (GET_CODE (x) == VALUE)
x = get_addr (x);
if (GET_CODE (y) == VALUE)
y = get_addr (y);
if (GET_CODE (x) == HIGH)
x = XEXP (x, 0);
else if (GET_CODE (x) == LO_SUM)
x = XEXP (x, 1);
else
x = canon_rtx (addr_side_effect_eval (x, xsize, 0));
if (GET_CODE (y) == HIGH)
y = XEXP (y, 0);
else if (GET_CODE (y) == LO_SUM)
y = XEXP (y, 1);
else
y = canon_rtx (addr_side_effect_eval (y, ysize, 0));
if (rtx_equal_for_memref_p (x, y))
{
if (xsize <= 0 || ysize <= 0)
return 1;
if (c >= 0 && xsize > c)
return 1;
if (c < 0 && ysize+c > 0)
return 1;
return 0;
}
/* This code used to check for conflicts involving stack references and
globals but the base address alias code now handles these cases. */
if (GET_CODE (x) == PLUS)
{
/* The fact that X is canonicalized means that this
PLUS rtx is canonicalized. */
rtx x0 = XEXP (x, 0);
rtx x1 = XEXP (x, 1);
if (GET_CODE (y) == PLUS)
{
/* The fact that Y is canonicalized means that this
PLUS rtx is canonicalized. */
rtx y0 = XEXP (y, 0);
rtx y1 = XEXP (y, 1);
if (rtx_equal_for_memref_p (x1, y1))
return memrefs_conflict_p (xsize, x0, ysize, y0, c);
if (rtx_equal_for_memref_p (x0, y0))
return memrefs_conflict_p (xsize, x1, ysize, y1, c);
if (GET_CODE (x1) == CONST_INT)
{
if (GET_CODE (y1) == CONST_INT)
return memrefs_conflict_p (xsize, x0, ysize, y0,
c - INTVAL (x1) + INTVAL (y1));
else
return memrefs_conflict_p (xsize, x0, ysize, y,
c - INTVAL (x1));
}
else if (GET_CODE (y1) == CONST_INT)
return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
return 1;
}
else if (GET_CODE (x1) == CONST_INT)
return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
}
else if (GET_CODE (y) == PLUS)
{
/* The fact that Y is canonicalized means that this
PLUS rtx is canonicalized. */
rtx y0 = XEXP (y, 0);
rtx y1 = XEXP (y, 1);
if (GET_CODE (y1) == CONST_INT)
return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
else
return 1;
}
if (GET_CODE (x) == GET_CODE (y))
switch (GET_CODE (x))
{
case MULT:
{
/* Handle cases where we expect the second operands to be the
same, and check only whether the first operand would conflict
or not. */
rtx x0, y0;
rtx x1 = canon_rtx (XEXP (x, 1));
rtx y1 = canon_rtx (XEXP (y, 1));
if (! rtx_equal_for_memref_p (x1, y1))
return 1;
x0 = canon_rtx (XEXP (x, 0));
y0 = canon_rtx (XEXP (y, 0));
if (rtx_equal_for_memref_p (x0, y0))
return (xsize == 0 || ysize == 0
|| (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
/* Can't properly adjust our sizes. */
if (GET_CODE (x1) != CONST_INT)
return 1;
xsize /= INTVAL (x1);
ysize /= INTVAL (x1);
c /= INTVAL (x1);
return memrefs_conflict_p (xsize, x0, ysize, y0, c);
}
case REG:
/* Are these registers known not to be equal? */
if (alias_invariant)
{
unsigned int r_x = REGNO (x), r_y = REGNO (y);
rtx i_x, i_y; /* invariant relationships of X and Y */
i_x = r_x >= reg_base_value_size ? 0 : alias_invariant[r_x];
i_y = r_y >= reg_base_value_size ? 0 : alias_invariant[r_y];
if (i_x == 0 && i_y == 0)
break;
if (! memrefs_conflict_p (xsize, i_x ? i_x : x,
ysize, i_y ? i_y : y, c))
return 0;
}
break;
default:
break;
}
/* Treat an access through an AND (e.g. a subword access on an Alpha)
as an access with indeterminate size. Assume that references
besides AND are aligned, so if the size of the other reference is
at least as large as the alignment, assume no other overlap. */
if (GET_CODE (x) == AND && GET_CODE (XEXP (x, 1)) == CONST_INT)
{
if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
xsize = -1;
return memrefs_conflict_p (xsize, XEXP (x, 0), ysize, y, c);
}
if (GET_CODE (y) == AND && GET_CODE (XEXP (y, 1)) == CONST_INT)
{
/* ??? If we are indexing far enough into the array/structure, we
may yet be able to determine that we can not overlap. But we
also need to that we are far enough from the end not to overlap
a following reference, so we do nothing with that for now. */
if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
ysize = -1;
return memrefs_conflict_p (xsize, x, ysize, XEXP (y, 0), c);
}
if (GET_CODE (x) == ADDRESSOF)
{
if (y == frame_pointer_rtx
|| GET_CODE (y) == ADDRESSOF)
return xsize <= 0 || ysize <= 0;
}
if (GET_CODE (y) == ADDRESSOF)
{
if (x == frame_pointer_rtx)
return xsize <= 0 || ysize <= 0;
}
if (CONSTANT_P (x))
{
if (GET_CODE (x) == CONST_INT && GET_CODE (y) == CONST_INT)
{
c += (INTVAL (y) - INTVAL (x));
return (xsize <= 0 || ysize <= 0
|| (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
}
if (GET_CODE (x) == CONST)
{
if (GET_CODE (y) == CONST)
return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
ysize, canon_rtx (XEXP (y, 0)), c);
else
return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
ysize, y, c);
}
if (GET_CODE (y) == CONST)
return memrefs_conflict_p (xsize, x, ysize,
canon_rtx (XEXP (y, 0)), c);
if (CONSTANT_P (y))
return (xsize <= 0 || ysize <= 0
|| (rtx_equal_for_memref_p (x, y)
&& ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));
return 1;
}
return 1;
}
/* Functions to compute memory dependencies.
Since we process the insns in execution order, we can build tables
to keep track of what registers are fixed (and not aliased), what registers
are varying in known ways, and what registers are varying in unknown
ways.
If both memory references are volatile, then there must always be a
dependence between the two references, since their order can not be
changed. A volatile and non-volatile reference can be interchanged
though.
A MEM_IN_STRUCT reference at a non-AND varying address can never
conflict with a non-MEM_IN_STRUCT reference at a fixed address. We
also must allow AND addresses, because they may generate accesses
outside the object being referenced. This is used to generate
aligned addresses from unaligned addresses, for instance, the alpha
storeqi_unaligned pattern. */
/* Read dependence: X is read after read in MEM takes place. There can
only be a dependence here if both reads are volatile. */
int
read_dependence (mem, x)
rtx mem;
rtx x;
{
return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
}
/* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
MEM2 is a reference to a structure at a varying address, or returns
MEM2 if vice versa. Otherwise, returns NULL_RTX. If a non-NULL
value is returned MEM1 and MEM2 can never alias. VARIES_P is used
to decide whether or not an address may vary; it should return
nonzero whenever variation is possible.
MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2. */
static rtx
fixed_scalar_and_varying_struct_p (mem1, mem2, mem1_addr, mem2_addr, varies_p)
rtx mem1, mem2;
rtx mem1_addr, mem2_addr;
int (*varies_p) PARAMS ((rtx, int));
{
if (! flag_strict_aliasing)
return NULL_RTX;
if (MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
&& !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
/* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
varying address. */
return mem1;
if (MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
&& varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
/* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
varying address. */
return mem2;
return NULL_RTX;
}
/* Returns nonzero if something about the mode or address format MEM1
indicates that it might well alias *anything*. */
static int
aliases_everything_p (mem)
rtx mem;
{
if (GET_CODE (XEXP (mem, 0)) == AND)
/* If the address is an AND, its very hard to know at what it is
actually pointing. */
return 1;
return 0;
}
/* Return true if we can determine that the fields referenced cannot
overlap for any pair of objects. */
static bool
nonoverlapping_component_refs_p (x, y)
tree x, y;
{
tree fieldx, fieldy, typex, typey, orig_y;
do
{
/* The comparison has to be done at a common type, since we don't
know how the inheritance hierarchy works. */
orig_y = y;
do
{
fieldx = TREE_OPERAND (x, 1);
typex = DECL_FIELD_CONTEXT (fieldx);
y = orig_y;
do
{
fieldy = TREE_OPERAND (y, 1);
typey = DECL_FIELD_CONTEXT (fieldy);
if (typex == typey)
goto found;
y = TREE_OPERAND (y, 0);
}
while (y && TREE_CODE (y) == COMPONENT_REF);
x = TREE_OPERAND (x, 0);
}
while (x && TREE_CODE (x) == COMPONENT_REF);
/* Never found a common type. */
return false;
found:
/* If we're left with accessing different fields of a structure,
then no overlap. */
if (TREE_CODE (typex) == RECORD_TYPE
&& fieldx != fieldy)
return true;
/* The comparison on the current field failed. If we're accessing
a very nested structure, look at the next outer level. */
x = TREE_OPERAND (x, 0);
y = TREE_OPERAND (y, 0);
}
while (x && y
&& TREE_CODE (x) == COMPONENT_REF
&& TREE_CODE (y) == COMPONENT_REF);
return false;
}
/* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */
static tree
decl_for_component_ref (x)
tree x;
{
do
{
x = TREE_OPERAND (x, 0);
}
while (x && TREE_CODE (x) == COMPONENT_REF);
return x && DECL_P (x) ? x : NULL_TREE;
}
/* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
offset of the field reference. */
static rtx
adjust_offset_for_component_ref (x, offset)
tree x;
rtx offset;
{
HOST_WIDE_INT ioffset;
if (! offset)
return NULL_RTX;
ioffset = INTVAL (offset);
do
{
tree field = TREE_OPERAND (x, 1);
if (! host_integerp (DECL_FIELD_OFFSET (field), 1))
return NULL_RTX;
ioffset += (tree_low_cst (DECL_FIELD_OFFSET (field), 1)
+ (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
/ BITS_PER_UNIT));
x = TREE_OPERAND (x, 0);
}
while (x && TREE_CODE (x) == COMPONENT_REF);
return GEN_INT (ioffset);
}
/* Return nonzero if we can deterimine the exprs corresponding to memrefs
X and Y and they do not overlap. */
static int
nonoverlapping_memrefs_p (x, y)
rtx x, y;
{
tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
rtx rtlx, rtly;
rtx basex, basey;
rtx moffsetx, moffsety;
HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;
/* Unless both have exprs, we can't tell anything. */
if (exprx == 0 || expry == 0)
return 0;
/* If both are field references, we may be able to determine something. */
if (TREE_CODE (exprx) == COMPONENT_REF
&& TREE_CODE (expry) == COMPONENT_REF
&& nonoverlapping_component_refs_p (exprx, expry))
return 1;
/* If the field reference test failed, look at the DECLs involved. */
moffsetx = MEM_OFFSET (x);
if (TREE_CODE (exprx) == COMPONENT_REF)
{
tree t = decl_for_component_ref (exprx);
if (! t)
return 0;
moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
exprx = t;
}
moffsety = MEM_OFFSET (y);
if (TREE_CODE (expry) == COMPONENT_REF)
{
tree t = decl_for_component_ref (expry);
if (! t)
return 0;
moffsety = adjust_offset_for_component_ref (expry, moffsety);
expry = t;
}
if (! DECL_P (exprx) || ! DECL_P (expry))
return 0;
rtlx = DECL_RTL (exprx);
rtly = DECL_RTL (expry);
/* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
can't overlap unless they are the same because we never reuse that part
of the stack frame used for locals for spilled pseudos. */
if ((GET_CODE (rtlx) != MEM || GET_CODE (rtly) != MEM)
&& ! rtx_equal_p (rtlx, rtly))
return 1;
/* Get the base and offsets of both decls. If either is a register, we
know both are and are the same, so use that as the base. The only
we can avoid overlap is if we can deduce that they are nonoverlapping
pieces of that decl, which is very rare. */
basex = GET_CODE (rtlx) == MEM ? XEXP (rtlx, 0) : rtlx;
if (GET_CODE (basex) == PLUS && GET_CODE (XEXP (basex, 1)) == CONST_INT)
offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);
basey = GET_CODE (rtly) == MEM ? XEXP (rtly, 0) : rtly;
if (GET_CODE (basey) == PLUS && GET_CODE (XEXP (basey, 1)) == CONST_INT)
offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);
/* If the bases are different, we know they do not overlap if both
are constants or if one is a constant and the other a pointer into the
stack frame. Otherwise a different base means we can't tell if they
overlap or not. */
if (! rtx_equal_p (basex, basey))
return ((CONSTANT_P (basex) && CONSTANT_P (basey))
|| (CONSTANT_P (basex) && REG_P (basey)
&& REGNO_PTR_FRAME_P (REGNO (basey)))
|| (CONSTANT_P (basey) && REG_P (basex)
&& REGNO_PTR_FRAME_P (REGNO (basex))));
sizex = (GET_CODE (rtlx) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
: MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
: -1);
sizey = (GET_CODE (rtly) != MEM ? (int) GET_MODE_SIZE (GET_MODE (rtly))
: MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
-1);
/* If we have an offset for either memref, it can update the values computed
above. */
if (moffsetx)
offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
if (moffsety)
offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);
/* If a memref has both a size and an offset, we can use the smaller size.
We can't do this if the offset isn't known because we must view this
memref as being anywhere inside the DECL's MEM. */
if (MEM_SIZE (x) && moffsetx)
sizex = INTVAL (MEM_SIZE (x));
if (MEM_SIZE (y) && moffsety)
sizey = INTVAL (MEM_SIZE (y));
/* Put the values of the memref with the lower offset in X's values. */
if (offsetx > offsety)
{
tem = offsetx, offsetx = offsety, offsety = tem;
tem = sizex, sizex = sizey, sizey = tem;
}
/* If we don't know the size of the lower-offset value, we can't tell
if they conflict. Otherwise, we do the test. */
return sizex >= 0 && offsety > offsetx + sizex;
}
/* True dependence: X is read after store in MEM takes place. */
int
true_dependence (mem, mem_mode, x, varies)
rtx mem;
enum machine_mode mem_mode;
rtx x;
int (*varies) PARAMS ((rtx, int));
{
rtx x_addr, mem_addr;
rtx base;
if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
return 1;
/* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
This is used in epilogue deallocation functions. */
if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
return 1;
if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
return 1;
if (DIFFERENT_ALIAS_SETS_P (x, mem))
return 0;
/* Unchanging memory can't conflict with non-unchanging memory.
A non-unchanging read can conflict with a non-unchanging write.
An unchanging read can conflict with an unchanging write since
there may be a single store to this address to initialize it.
Note that an unchanging store can conflict with a non-unchanging read
since we have to make conservative assumptions when we have a
record with readonly fields and we are copying the whole thing.
Just fall through to the code below to resolve potential conflicts.
This won't handle all cases optimally, but the possible performance
loss should be negligible. */
if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
return 0;
if (nonoverlapping_memrefs_p (mem, x))
return 0;
if (mem_mode == VOIDmode)
mem_mode = GET_MODE (mem);
x_addr = get_addr (XEXP (x, 0));
mem_addr = get_addr (XEXP (mem, 0));
base = find_base_term (x_addr);
if (base && (GET_CODE (base) == LABEL_REF
|| (GET_CODE (base) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (base))))
return 0;
if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
return 0;
x_addr = canon_rtx (x_addr);
mem_addr = canon_rtx (mem_addr);
if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
SIZE_FOR_MODE (x), x_addr, 0))
return 0;
if (aliases_everything_p (x))
return 1;
/* We cannot use aliases_everything_p to test MEM, since we must look
at MEM_MODE, rather than GET_MODE (MEM). */
if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
return 1;
/* In true_dependence we also allow BLKmode to alias anything. Why
don't we do this in anti_dependence and output_dependence? */
if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
return 1;
return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
varies);
}
/* Canonical true dependence: X is read after store in MEM takes place.
Variant of true_dependence which assumes MEM has already been
canonicalized (hence we no longer do that here).
The mem_addr argument has been added, since true_dependence computed
this value prior to canonicalizing. */
int
canon_true_dependence (mem, mem_mode, mem_addr, x, varies)
rtx mem, mem_addr, x;
enum machine_mode mem_mode;
int (*varies) PARAMS ((rtx, int));
{
rtx x_addr;
if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
return 1;
/* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
This is used in epilogue deallocation functions. */
if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
return 1;
if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
return 1;
if (DIFFERENT_ALIAS_SETS_P (x, mem))
return 0;
/* If X is an unchanging read, then it can't possibly conflict with any
non-unchanging store. It may conflict with an unchanging write though,
because there may be a single store to this address to initialize it.
Just fall through to the code below to resolve the case where we have
both an unchanging read and an unchanging write. This won't handle all
cases optimally, but the possible performance loss should be
negligible. */
if (RTX_UNCHANGING_P (x) && ! RTX_UNCHANGING_P (mem))
return 0;
if (nonoverlapping_memrefs_p (x, mem))
return 0;
x_addr = get_addr (XEXP (x, 0));
if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
return 0;
x_addr = canon_rtx (x_addr);
if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
SIZE_FOR_MODE (x), x_addr, 0))
return 0;
if (aliases_everything_p (x))
return 1;
/* We cannot use aliases_everything_p to test MEM, since we must look
at MEM_MODE, rather than GET_MODE (MEM). */
if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
return 1;
/* In true_dependence we also allow BLKmode to alias anything. Why
don't we do this in anti_dependence and output_dependence? */
if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
return 1;
return ! fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
varies);
}
/* Returns non-zero if a write to X might alias a previous read from
(or, if WRITEP is non-zero, a write to) MEM. */
static int
write_dependence_p (mem, x, writep)
rtx mem;
rtx x;
int writep;
{
rtx x_addr, mem_addr;
rtx fixed_scalar;
rtx base;
if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
return 1;
/* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
This is used in epilogue deallocation functions. */
if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
return 1;
if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
return 1;
if (DIFFERENT_ALIAS_SETS_P (x, mem))
return 0;
/* Unchanging memory can't conflict with non-unchanging memory. */
if (RTX_UNCHANGING_P (x) != RTX_UNCHANGING_P (mem))
return 0;
/* If MEM is an unchanging read, then it can't possibly conflict with
the store to X, because there is at most one store to MEM, and it must
have occurred somewhere before MEM. */
if (! writep && RTX_UNCHANGING_P (mem))
return 0;
if (nonoverlapping_memrefs_p (x, mem))
return 0;
x_addr = get_addr (XEXP (x, 0));
mem_addr = get_addr (XEXP (mem, 0));
if (! writep)
{
base = find_base_term (mem_addr);
if (base && (GET_CODE (base) == LABEL_REF
|| (GET_CODE (base) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (base))))
return 0;
}
if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
GET_MODE (mem)))
return 0;
x_addr = canon_rtx (x_addr);
mem_addr = canon_rtx (mem_addr);
if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
SIZE_FOR_MODE (x), x_addr, 0))
return 0;
fixed_scalar
= fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
rtx_addr_varies_p);
return (!(fixed_scalar == mem && !aliases_everything_p (x))
&& !(fixed_scalar == x && !aliases_everything_p (mem)));
}
/* Anti dependence: X is written after read in MEM takes place. */
int
anti_dependence (mem, x)
rtx mem;
rtx x;
{
return write_dependence_p (mem, x, /*writep=*/0);
}
/* Output dependence: X is written after store in MEM takes place. */
int
output_dependence (mem, x)
rtx mem;
rtx x;
{
return write_dependence_p (mem, x, /*writep=*/1);
}
/* Returns non-zero if X mentions something which is not
local to the function and is not constant. */
static int
nonlocal_mentioned_p (x)
rtx x;
{
rtx base;
RTX_CODE code;
int regno;
code = GET_CODE (x);
if (GET_RTX_CLASS (code) == 'i')
{
/* Constant functions can be constant if they don't use
scratch memory used to mark function w/o side effects. */
if (code == CALL_INSN && CONST_OR_PURE_CALL_P (x))
{
x = CALL_INSN_FUNCTION_USAGE (x);
if (x == 0)
return 0;
}
else
x = PATTERN (x);
code = GET_CODE (x);
}
switch (code)
{
case SUBREG:
if (GET_CODE (SUBREG_REG (x)) == REG)
{
/* Global registers are not local. */
if (REGNO (SUBREG_REG (x)) < FIRST_PSEUDO_REGISTER
&& global_regs[subreg_regno (x)])
return 1;
return 0;
}
break;
case REG:
regno = REGNO (x);
/* Global registers are not local. */
if (regno < FIRST_PSEUDO_REGISTER && global_regs[regno])
return 1;
return 0;
case SCRATCH:
case PC:
case CC0:
case CONST_INT:
case CONST_DOUBLE:
case CONST_VECTOR:
case CONST:
case LABEL_REF:
return 0;
case SYMBOL_REF:
/* Constants in the function's constants pool are constant. */
if (CONSTANT_POOL_ADDRESS_P (x))
return 0;
return 1;
case CALL:
/* Non-constant calls and recursion are not local. */
return 1;
case MEM:
/* Be overly conservative and consider any volatile memory
reference as not local. */
if (MEM_VOLATILE_P (x))
return 1;
base = find_base_term (XEXP (x, 0));
if (base)
{
/* A Pmode ADDRESS could be a reference via the structure value
address or static chain. Such memory references are nonlocal.
Thus, we have to examine the contents of the ADDRESS to find
out if this is a local reference or not. */
if (GET_CODE (base) == ADDRESS
&& GET_MODE (base) == Pmode
&& (XEXP (base, 0) == stack_pointer_rtx
|| XEXP (base, 0) == arg_pointer_rtx
#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
|| XEXP (base, 0) == hard_frame_pointer_rtx
#endif
|| XEXP (base, 0) == frame_pointer_rtx))
return 0;
/* Constants in the function's constant pool are constant. */
if (GET_CODE (base) == SYMBOL_REF && CONSTANT_POOL_ADDRESS_P (base))
return 0;
}
return 1;
case UNSPEC_VOLATILE:
case ASM_INPUT:
return 1;
case ASM_OPERANDS:
if (MEM_VOLATILE_P (x))
return 1;
/* FALLTHROUGH */
default:
break;
}
/* Recursively scan the operands of this expression. */
{
const char *fmt = GET_RTX_FORMAT (code);
int i;
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
if (fmt[i] == 'e' && XEXP (x, i))
{
if (nonlocal_mentioned_p (XEXP (x, i)))
return 1;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
if (nonlocal_mentioned_p (XVECEXP (x, i, j)))
return 1;
}
}
}
return 0;
}
/* Mark the function if it is constant. */
void
mark_constant_function ()
{
rtx insn;
int nonlocal_mentioned;
if (TREE_PUBLIC (current_function_decl)
|| TREE_READONLY (current_function_decl)
|| DECL_IS_PURE (current_function_decl)
|| TREE_THIS_VOLATILE (current_function_decl)
|| TYPE_MODE (TREE_TYPE (current_function_decl)) == VOIDmode)
return;
/* A loop might not return which counts as a side effect. */
if (mark_dfs_back_edges ())
return;
nonlocal_mentioned = 0;
init_alias_analysis ();
/* Determine if this is a constant function. */
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
if (INSN_P (insn) && nonlocal_mentioned_p (insn))
{
nonlocal_mentioned = 1;
break;
}
end_alias_analysis ();
/* Mark the function. */
if (! nonlocal_mentioned)
TREE_READONLY (current_function_decl) = 1;
}
static HARD_REG_SET argument_registers;
void
init_alias_once ()
{
int i;
#ifndef OUTGOING_REGNO
#define OUTGOING_REGNO(N) N
#endif
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
/* Check whether this register can hold an incoming pointer
argument. FUNCTION_ARG_REGNO_P tests outgoing register
numbers, so translate if necessary due to register windows. */
if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
&& HARD_REGNO_MODE_OK (i, Pmode))
SET_HARD_REG_BIT (argument_registers, i);
alias_sets = splay_tree_new (splay_tree_compare_ints, 0, 0);
}
/* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE
array. */
void
init_alias_analysis ()
{
int maxreg = max_reg_num ();
int changed, pass;
int i;
unsigned int ui;
rtx insn;
reg_known_value_size = maxreg;
reg_known_value
= (rtx *) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (rtx))
- FIRST_PSEUDO_REGISTER;
reg_known_equiv_p
= (char*) xcalloc ((maxreg - FIRST_PSEUDO_REGISTER), sizeof (char))
- FIRST_PSEUDO_REGISTER;
/* Overallocate reg_base_value to allow some growth during loop
optimization. Loop unrolling can create a large number of
registers. */
reg_base_value_size = maxreg * 2;
reg_base_value = (rtx *) xcalloc (reg_base_value_size, sizeof (rtx));
ggc_add_rtx_root (reg_base_value, reg_base_value_size);
new_reg_base_value = (rtx *) xmalloc (reg_base_value_size * sizeof (rtx));
reg_seen = (char *) xmalloc (reg_base_value_size);
if (! reload_completed && flag_unroll_loops)
{
/* ??? Why are we realloc'ing if we're just going to zero it? */
alias_invariant = (rtx *)xrealloc (alias_invariant,
reg_base_value_size * sizeof (rtx));
memset ((char *)alias_invariant, 0, reg_base_value_size * sizeof (rtx));
}
/* The basic idea is that each pass through this loop will use the
"constant" information from the previous pass to propagate alias
information through another level of assignments.
This could get expensive if the assignment chains are long. Maybe
we should throttle the number of iterations, possibly based on
the optimization level or flag_expensive_optimizations.
We could propagate more information in the first pass by making use
of REG_N_SETS to determine immediately that the alias information
for a pseudo is "constant".
A program with an uninitialized variable can cause an infinite loop
here. Instead of doing a full dataflow analysis to detect such problems
we just cap the number of iterations for the loop.
The state of the arrays for the set chain in question does not matter
since the program has undefined behavior. */
pass = 0;
do
{
/* Assume nothing will change this iteration of the loop. */
changed = 0;
/* We want to assign the same IDs each iteration of this loop, so
start counting from zero each iteration of the loop. */
unique_id = 0;
/* We're at the start of the function each iteration through the
loop, so we're copying arguments. */
copying_arguments = 1;
/* Wipe the potential alias information clean for this pass. */
memset ((char *) new_reg_base_value, 0, reg_base_value_size * sizeof (rtx));
/* Wipe the reg_seen array clean. */
memset ((char *) reg_seen, 0, reg_base_value_size);
/* Mark all hard registers which may contain an address.
The stack, frame and argument pointers may contain an address.
An argument register which can hold a Pmode value may contain
an address even if it is not in BASE_REGS.
The address expression is VOIDmode for an argument and
Pmode for other registers. */
for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
if (TEST_HARD_REG_BIT (argument_registers, i))
new_reg_base_value[i] = gen_rtx_ADDRESS (VOIDmode,
gen_rtx_REG (Pmode, i));
new_reg_base_value[STACK_POINTER_REGNUM]
= gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
new_reg_base_value[ARG_POINTER_REGNUM]
= gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
new_reg_base_value[FRAME_POINTER_REGNUM]
= gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
new_reg_base_value[HARD_FRAME_POINTER_REGNUM]
= gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
#endif
/* Walk the insns adding values to the new_reg_base_value array. */
for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
{
if (INSN_P (insn))
{
rtx note, set;
#if defined (HAVE_prologue) || defined (HAVE_epilogue)
/* The prologue/epilogue insns are not threaded onto the
insn chain until after reload has completed. Thus,
there is no sense wasting time checking if INSN is in
the prologue/epilogue until after reload has completed. */
if (reload_completed
&& prologue_epilogue_contains (insn))
continue;
#endif
/* If this insn has a noalias note, process it, Otherwise,
scan for sets. A simple set will have no side effects
which could change the base value of any other register. */
if (GET_CODE (PATTERN (insn)) == SET
&& REG_NOTES (insn) != 0
&& find_reg_note (insn, REG_NOALIAS, NULL_RTX))
record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
else
note_stores (PATTERN (insn), record_set, NULL);
set = single_set (insn);
if (set != 0
&& GET_CODE (SET_DEST (set)) == REG
&& REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
{
unsigned int regno = REGNO (SET_DEST (set));
rtx src = SET_SRC (set);
if (REG_NOTES (insn) != 0
&& (((note = find_reg_note (insn, REG_EQUAL, 0)) != 0
&& REG_N_SETS (regno) == 1)
|| (note = find_reg_note (insn, REG_EQUIV, NULL_RTX)) != 0)
&& GET_CODE (XEXP (note, 0)) != EXPR_LIST
&& ! rtx_varies_p (XEXP (note, 0), 1)
&& ! reg_overlap_mentioned_p (SET_DEST (set), XEXP (note, 0)))
{
reg_known_value[regno] = XEXP (note, 0);
reg_known_equiv_p[regno] = REG_NOTE_KIND (note) == REG_EQUIV;
}
else if (REG_N_SETS (regno) == 1
&& GET_CODE (src) == PLUS
&& GET_CODE (XEXP (src, 0)) == REG
&& REGNO (XEXP (src, 0)) >= FIRST_PSEUDO_REGISTER
&& (reg_known_value[REGNO (XEXP (src, 0))])
&& GET_CODE (XEXP (src, 1)) == CONST_INT)
{
rtx op0 = XEXP (src, 0);
op0 = reg_known_value[REGNO (op0)];
reg_known_value[regno]
= plus_constant (op0, INTVAL (XEXP (src, 1)));
reg_known_equiv_p[regno] = 0;
}
else if (REG_N_SETS (regno) == 1
&& ! rtx_varies_p (src, 1))
{
reg_known_value[regno] = src;
reg_known_equiv_p[regno] = 0;
}
}
}
else if (GET_CODE (insn) == NOTE
&& NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
copying_arguments = 0;
}
/* Now propagate values from new_reg_base_value to reg_base_value. */
for (ui = 0; ui < reg_base_value_size; ui++)
{
if (new_reg_base_value[ui]
&& new_reg_base_value[ui] != reg_base_value[ui]
&& ! rtx_equal_p (new_reg_base_value[ui], reg_base_value[ui]))
{
reg_base_value[ui] = new_reg_base_value[ui];
changed = 1;
}
}
}
while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);
/* Fill in the remaining entries. */
for (i = FIRST_PSEUDO_REGISTER; i < maxreg; i++)
if (reg_known_value[i] == 0)
reg_known_value[i] = regno_reg_rtx[i];
/* Simplify the reg_base_value array so that no register refers to
another register, except to special registers indirectly through
ADDRESS expressions.
In theory this loop can take as long as O(registers^2), but unless
there are very long dependency chains it will run in close to linear
time.
This loop may not be needed any longer now that the main loop does
a better job at propagating alias information. */
pass = 0;
do
{
changed = 0;
pass++;
for (ui = 0; ui < reg_base_value_size; ui++)
{
rtx base = reg_base_value[ui];
if (base && GET_CODE (base) == REG)
{
unsigned int base_regno = REGNO (base);
if (base_regno == ui) /* register set from itself */
reg_base_value[ui] = 0;
else
reg_base_value[ui] = reg_base_value[base_regno];
changed = 1;
}
}
}
while (changed && pass < MAX_ALIAS_LOOP_PASSES);
/* Clean up. */
free (new_reg_base_value);
new_reg_base_value = 0;
free (reg_seen);
reg_seen = 0;
}
void
end_alias_analysis ()
{
free (reg_known_value + FIRST_PSEUDO_REGISTER);
reg_known_value = 0;
reg_known_value_size = 0;
free (reg_known_equiv_p + FIRST_PSEUDO_REGISTER);
reg_known_equiv_p = 0;
if (reg_base_value)
{
ggc_del_root (reg_base_value);
free (reg_base_value);
reg_base_value = 0;
}
reg_base_value_size = 0;
if (alias_invariant)
{
free (alias_invariant);
alias_invariant = 0;
}
}
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