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6b214d09 | 1 | /* An incremental hash abstract data type. |
d353bf18 | 2 | Copyright (C) 2014-2015 Free Software Foundation, Inc. |
6b214d09 | 3 | |
4 | This file is part of GCC. | |
5 | ||
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 | |
9 | version. | |
10 | ||
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 | |
14 | for more details. | |
15 | ||
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/>. */ | |
19 | ||
20 | #ifndef INCHASH_H | |
21 | #define INCHASH_H 1 | |
22 | ||
6b214d09 | 23 | #include "hashtab.h" |
24 | ||
25 | /* This file implements an incremential hash function ADT, to be used | |
26 | by code that incrementially hashes a lot of unrelated data | |
27 | (not in a single memory block) into a single value. The goal | |
28 | is to make it easy to plug in efficient hash algorithms. | |
29 | Currently it just implements the plain old jhash based | |
30 | incremental hash from gcc's tree.c. */ | |
31 | ||
0ff42de5 | 32 | hashval_t iterative_hash_host_wide_int (HOST_WIDE_INT, hashval_t); |
33 | hashval_t iterative_hash_hashval_t (hashval_t, hashval_t); | |
6b214d09 | 34 | |
7fdbd1ec | 35 | namespace inchash |
36 | { | |
37 | ||
38 | class hash | |
6b214d09 | 39 | { |
40 | public: | |
41 | ||
42 | /* Start incremential hashing, optionally with SEED. */ | |
7fdbd1ec | 43 | hash (hashval_t seed = 0) |
6b214d09 | 44 | { |
45 | val = seed; | |
46 | bits = 0; | |
47 | } | |
48 | ||
49 | /* End incremential hashing and provide the final value. */ | |
50 | hashval_t end () | |
51 | { | |
52 | return val; | |
53 | } | |
54 | ||
55 | /* Add unsigned value V. */ | |
56 | void add_int (unsigned v) | |
57 | { | |
58 | val = iterative_hash_hashval_t (v, val); | |
59 | } | |
60 | ||
61 | /* Add HOST_WIDE_INT value V. */ | |
62 | void add_wide_int (HOST_WIDE_INT v) | |
63 | { | |
64 | val = iterative_hash_host_wide_int (v, val); | |
65 | } | |
66 | ||
67 | /* Hash in pointer PTR. */ | |
0ff42de5 | 68 | void add_ptr (const void *ptr) |
6b214d09 | 69 | { |
70 | add (&ptr, sizeof (ptr)); | |
71 | } | |
72 | ||
73 | /* Add a memory block DATA with size LEN. */ | |
74 | void add (const void *data, size_t len) | |
75 | { | |
76 | val = iterative_hash (data, len, val); | |
77 | } | |
78 | ||
79 | /* Merge hash value OTHER. */ | |
80 | void merge_hash (hashval_t other) | |
81 | { | |
82 | val = iterative_hash_hashval_t (other, val); | |
83 | } | |
84 | ||
85 | /* Hash in state from other inchash OTHER. */ | |
7fdbd1ec | 86 | void merge (hash &other) |
6b214d09 | 87 | { |
88 | merge_hash (other.val); | |
89 | } | |
90 | ||
7fdbd1ec | 91 | template<class T> void add_object(T &obj) |
92 | { | |
93 | add (&obj, sizeof(T)); | |
94 | } | |
95 | ||
6b214d09 | 96 | /* Support for accumulating boolean flags */ |
97 | ||
98 | void add_flag (bool flag) | |
99 | { | |
100 | bits = (bits << 1) | flag; | |
101 | } | |
102 | ||
103 | void commit_flag () | |
104 | { | |
105 | add_int (bits); | |
106 | bits = 0; | |
107 | } | |
108 | ||
109 | /* Support for commutative hashing. Add A and B in a defined order | |
110 | based on their value. This is useful for hashing commutative | |
111 | expressions, so that A+B and B+A get the same hash. */ | |
112 | ||
7fdbd1ec | 113 | void add_commutative (hash &a, hash &b) |
6b214d09 | 114 | { |
115 | if (a.end() > b.end()) | |
116 | { | |
0ff42de5 | 117 | merge (b); |
6b214d09 | 118 | merge (a); |
119 | } | |
120 | else | |
121 | { | |
0ff42de5 | 122 | merge (a); |
123 | merge (b); | |
6b214d09 | 124 | } |
125 | } | |
126 | ||
127 | private: | |
128 | hashval_t val; | |
129 | unsigned bits; | |
130 | }; | |
131 | ||
7fdbd1ec | 132 | } |
6b214d09 | 133 | |
0ff42de5 | 134 | /* Borrowed from hashtab.c iterative_hash implementation. */ |
135 | #define mix(a,b,c) \ | |
136 | { \ | |
137 | a -= b; a -= c; a ^= (c>>13); \ | |
138 | b -= c; b -= a; b ^= (a<< 8); \ | |
139 | c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \ | |
140 | a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \ | |
141 | b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \ | |
142 | c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \ | |
143 | a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \ | |
144 | b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \ | |
145 | c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \ | |
146 | } | |
147 | ||
148 | ||
149 | /* Produce good hash value combining VAL and VAL2. */ | |
150 | inline | |
151 | hashval_t | |
152 | iterative_hash_hashval_t (hashval_t val, hashval_t val2) | |
153 | { | |
154 | /* the golden ratio; an arbitrary value. */ | |
155 | hashval_t a = 0x9e3779b9; | |
156 | ||
157 | mix (a, val, val2); | |
158 | return val2; | |
159 | } | |
160 | ||
161 | /* Produce good hash value combining VAL and VAL2. */ | |
162 | ||
163 | inline | |
164 | hashval_t | |
165 | iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2) | |
166 | { | |
167 | if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t)) | |
168 | return iterative_hash_hashval_t (val, val2); | |
169 | else | |
170 | { | |
171 | hashval_t a = (hashval_t) val; | |
172 | /* Avoid warnings about shifting of more than the width of the type on | |
173 | hosts that won't execute this path. */ | |
174 | int zero = 0; | |
175 | hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero)); | |
176 | mix (a, b, val2); | |
177 | if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t)) | |
178 | { | |
179 | hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero)); | |
180 | hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero)); | |
181 | mix (a, b, val2); | |
182 | } | |
183 | return val2; | |
184 | } | |
185 | } | |
186 | ||
6b214d09 | 187 | #endif |