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/* Incremential hashing for jhash.
Copyright (C) 2014 Free Software Foundation, Inc.
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 3, 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 COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "hashtab.h"
#include "inchash.h"
/* Borrowed from hashtab.c iterative_hash implementation. */
#define mix(a,b,c) \
{ \
a -= b; a -= c; a ^= (c>>13); \
b -= c; b -= a; b ^= (a<< 8); \
c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
}
/* Produce good hash value combining VAL and VAL2. */
hashval_t
iterative_hash_hashval_t (hashval_t val, hashval_t val2)
{
/* the golden ratio; an arbitrary value. */
hashval_t a = 0x9e3779b9;
mix (a, val, val2);
return val2;
}
/* Produce good hash value combining VAL and VAL2. */
hashval_t
iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2)
{
if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t))
return iterative_hash_hashval_t (val, val2);
else
{
hashval_t a = (hashval_t) val;
/* Avoid warnings about shifting of more than the width of the type on
hosts that won't execute this path. */
int zero = 0;
hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero));
mix (a, b, val2);
if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t))
{
hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero));
hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero));
mix (a, b, val2);
}
return val2;
}
}
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