1/* An incremental hash abstract data type.
2 Copyright (C) 2014-2017 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING3. If not see
18<http://www.gnu.org/licenses/>. */
19
20#ifndef INCHASH_H
21#define INCHASH_H 1
22
23
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. */
30
31hashval_t iterative_hash_host_wide_int (HOST_WIDE_INT, hashval_t);
32hashval_t iterative_hash_hashval_t (hashval_t, hashval_t);
33
34namespace inchash
35{
36
37class hash
38{
39 public:
40
41 /* Start incremential hashing, optionally with SEED. */
42 hash (hashval_t seed = 0)
43 {
44 val = seed;
45 bits = 0;
46 }
47
48 /* End incremential hashing and provide the final value. */
49 hashval_t end ()
50 {
51 return val;
52 }
53
54 /* Add unsigned value V. */
55 void add_int (unsigned v)
56 {
57 val = iterative_hash_hashval_t (v, val);
58 }
59
60 /* Add HOST_WIDE_INT value V. */
61 void add_hwi (HOST_WIDE_INT v)
62 {
63 val = iterative_hash_host_wide_int (v, val);
64 }
65
66 /* Add wide_int-based value V. */
67 template<typename T>
68 void add_wide_int (const generic_wide_int<T> &x)
69 {
70 add_int (x.get_len ());
71 for (unsigned i = 0; i < x.get_len (); i++)
72 add_hwi (x.elt (i));
73 }
74
75 /* Hash in pointer PTR. */
76 void add_ptr (const void *ptr)
77 {
78 add (&ptr, sizeof (ptr));
79 }
80
81 /* Add a memory block DATA with size LEN. */
82 void add (const void *data, size_t len)
83 {
84 val = iterative_hash (data, len, val);
85 }
86
87 /* Merge hash value OTHER. */
88 void merge_hash (hashval_t other)
89 {
90 val = iterative_hash_hashval_t (other, val);
91 }
92
93 /* Hash in state from other inchash OTHER. */
94 void merge (hash &other)
95 {
96 merge_hash (other.val);
97 }
98
99 template<class T> void add_object(T &obj)
100 {
101 add (&obj, sizeof(T));
102 }
103
104 /* Support for accumulating boolean flags */
105
106 void add_flag (bool flag)
107 {
108 bits = (bits << 1) | flag;
109 }
110
111 void commit_flag ()
112 {
113 add_int (bits);
114 bits = 0;
115 }
116
117 /* Support for commutative hashing. Add A and B in a defined order
118 based on their value. This is useful for hashing commutative
119 expressions, so that A+B and B+A get the same hash. */
120
121 void add_commutative (hash &a, hash &b)
122 {
123 if (a.end() > b.end())
124 {
125 merge (b);
126 merge (a);
127 }
128 else
129 {
130 merge (a);
131 merge (b);
132 }
133 }
134
135 private:
136 hashval_t val;
137 unsigned bits;
138};
139
140}
141
142/* Borrowed from hashtab.c iterative_hash implementation. */
143#define mix(a,b,c) \
144{ \
145 a -= b; a -= c; a ^= (c>>13); \
146 b -= c; b -= a; b ^= (a<< 8); \
147 c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
148 a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
149 b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
150 c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
151 a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
152 b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
153 c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
154}
155
156
157/* Produce good hash value combining VAL and VAL2. */
158inline
159hashval_t
160iterative_hash_hashval_t (hashval_t val, hashval_t val2)
161{
162 /* the golden ratio; an arbitrary value. */
163 hashval_t a = 0x9e3779b9;
164
165 mix (a, val, val2);
166 return val2;
167}
168
169/* Produce good hash value combining VAL and VAL2. */
170
171inline
172hashval_t
173iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2)
174{
175 if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t))
176 return iterative_hash_hashval_t (val, val2);
177 else
178 {
179 hashval_t a = (hashval_t) val;
180 /* Avoid warnings about shifting of more than the width of the type on
181 hosts that won't execute this path. */
182 int zero = 0;
183 hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero));
184 mix (a, b, val2);
185 if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t))
186 {
187 hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero));
188 hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero));
189 mix (a, b, val2);
190 }
191 return val2;
192 }
193}
194
195#endif
196