1 /* An incremental hash abstract data type.
2 Copyright (C) 2014-2015 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
24 /* This file implements an incremential hash function ADT, to be used
25 by code that incrementially hashes a lot of unrelated data
26 (not in a single memory block) into a single value. The goal
27 is to make it easy to plug in efficient hash algorithms.
28 Currently it just implements the plain old jhash based
29 incremental hash from gcc's tree.c. */
31 hashval_t
iterative_hash_host_wide_int (HOST_WIDE_INT
, hashval_t
);
32 hashval_t
iterative_hash_hashval_t (hashval_t
, hashval_t
);
41 /* Start incremential hashing, optionally with SEED. */
42 hash (hashval_t seed
= 0)
48 /* End incremential hashing and provide the final value. */
54 /* Add unsigned value V. */
55 void add_int (unsigned v
)
57 val
= iterative_hash_hashval_t (v
, val
);
60 /* Add HOST_WIDE_INT value V. */
61 void add_wide_int (HOST_WIDE_INT v
)
63 val
= iterative_hash_host_wide_int (v
, val
);
66 /* Hash in pointer PTR. */
67 void add_ptr (const void *ptr
)
69 add (&ptr
, sizeof (ptr
));
72 /* Add a memory block DATA with size LEN. */
73 void add (const void *data
, size_t len
)
75 val
= iterative_hash (data
, len
, val
);
78 /* Merge hash value OTHER. */
79 void merge_hash (hashval_t other
)
81 val
= iterative_hash_hashval_t (other
, val
);
84 /* Hash in state from other inchash OTHER. */
85 void merge (hash
&other
)
87 merge_hash (other
.val
);
90 template<class T
> void add_object(T
&obj
)
92 add (&obj
, sizeof(T
));
95 /* Support for accumulating boolean flags */
97 void add_flag (bool flag
)
99 bits
= (bits
<< 1) | flag
;
108 /* Support for commutative hashing. Add A and B in a defined order
109 based on their value. This is useful for hashing commutative
110 expressions, so that A+B and B+A get the same hash. */
112 void add_commutative (hash
&a
, hash
&b
)
114 if (a
.end() > b
.end())
133 /* Borrowed from hashtab.c iterative_hash implementation. */
136 a -= b; a -= c; a ^= (c>>13); \
137 b -= c; b -= a; b ^= (a<< 8); \
138 c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
139 a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
140 b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
141 c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
142 a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
143 b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
144 c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
148 /* Produce good hash value combining VAL and VAL2. */
151 iterative_hash_hashval_t (hashval_t val
, hashval_t val2
)
153 /* the golden ratio; an arbitrary value. */
154 hashval_t a
= 0x9e3779b9;
160 /* Produce good hash value combining VAL and VAL2. */
164 iterative_hash_host_wide_int (HOST_WIDE_INT val
, hashval_t val2
)
166 if (sizeof (HOST_WIDE_INT
) == sizeof (hashval_t
))
167 return iterative_hash_hashval_t (val
, val2
);
170 hashval_t a
= (hashval_t
) val
;
171 /* Avoid warnings about shifting of more than the width of the type on
172 hosts that won't execute this path. */
174 hashval_t b
= (hashval_t
) (val
>> (sizeof (hashval_t
) * 8 + zero
));
176 if (sizeof (HOST_WIDE_INT
) > 2 * sizeof (hashval_t
))
178 hashval_t a
= (hashval_t
) (val
>> (sizeof (hashval_t
) * 16 + zero
));
179 hashval_t b
= (hashval_t
) (val
>> (sizeof (hashval_t
) * 24 + zero
));