76 lines
2.3 KiB
C
76 lines
2.3 KiB
C
/* Incremential hashing for jhash.
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Copyright (C) 2014 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "hashtab.h"
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#include "inchash.h"
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/* Borrowed from hashtab.c iterative_hash implementation. */
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#define mix(a,b,c) \
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{ \
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a -= b; a -= c; a ^= (c>>13); \
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b -= c; b -= a; b ^= (a<< 8); \
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c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
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a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
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b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
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c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
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a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
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b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
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c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
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}
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/* Produce good hash value combining VAL and VAL2. */
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hashval_t
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iterative_hash_hashval_t (hashval_t val, hashval_t val2)
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{
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/* the golden ratio; an arbitrary value. */
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hashval_t a = 0x9e3779b9;
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mix (a, val, val2);
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return val2;
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}
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/* Produce good hash value combining VAL and VAL2. */
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hashval_t
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iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2)
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{
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if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t))
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return iterative_hash_hashval_t (val, val2);
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else
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{
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hashval_t a = (hashval_t) val;
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/* Avoid warnings about shifting of more than the width of the type on
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hosts that won't execute this path. */
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int zero = 0;
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hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero));
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mix (a, b, val2);
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if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t))
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{
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hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero));
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hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero));
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mix (a, b, val2);
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}
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return val2;
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}
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}
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