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6d8eb96b | 1 | /* An incremental hash abstract data type. |
cbe34bb5 | 2 | Copyright (C) 2014-2017 Free Software Foundation, Inc. |
6d8eb96b AK |
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 | ||
6d8eb96b AK |
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 | ||
2d44c7de ML |
31 | hashval_t iterative_hash_host_wide_int (HOST_WIDE_INT, hashval_t); |
32 | hashval_t iterative_hash_hashval_t (hashval_t, hashval_t); | |
6d8eb96b | 33 | |
50de5793 AK |
34 | namespace inchash |
35 | { | |
36 | ||
37 | class hash | |
6d8eb96b AK |
38 | { |
39 | public: | |
40 | ||
41 | /* Start incremential hashing, optionally with SEED. */ | |
50de5793 | 42 | hash (hashval_t seed = 0) |
6d8eb96b AK |
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_wide_int (HOST_WIDE_INT v) | |
62 | { | |
63 | val = iterative_hash_host_wide_int (v, val); | |
64 | } | |
65 | ||
66 | /* Hash in pointer PTR. */ | |
2d44c7de | 67 | void add_ptr (const void *ptr) |
6d8eb96b AK |
68 | { |
69 | add (&ptr, sizeof (ptr)); | |
70 | } | |
71 | ||
72 | /* Add a memory block DATA with size LEN. */ | |
73 | void add (const void *data, size_t len) | |
74 | { | |
75 | val = iterative_hash (data, len, val); | |
76 | } | |
77 | ||
78 | /* Merge hash value OTHER. */ | |
79 | void merge_hash (hashval_t other) | |
80 | { | |
81 | val = iterative_hash_hashval_t (other, val); | |
82 | } | |
83 | ||
84 | /* Hash in state from other inchash OTHER. */ | |
50de5793 | 85 | void merge (hash &other) |
6d8eb96b AK |
86 | { |
87 | merge_hash (other.val); | |
88 | } | |
89 | ||
50de5793 AK |
90 | template<class T> void add_object(T &obj) |
91 | { | |
92 | add (&obj, sizeof(T)); | |
93 | } | |
94 | ||
6d8eb96b AK |
95 | /* Support for accumulating boolean flags */ |
96 | ||
97 | void add_flag (bool flag) | |
98 | { | |
99 | bits = (bits << 1) | flag; | |
100 | } | |
101 | ||
102 | void commit_flag () | |
103 | { | |
104 | add_int (bits); | |
105 | bits = 0; | |
106 | } | |
107 | ||
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. */ | |
111 | ||
50de5793 | 112 | void add_commutative (hash &a, hash &b) |
6d8eb96b AK |
113 | { |
114 | if (a.end() > b.end()) | |
115 | { | |
2d44c7de | 116 | merge (b); |
6d8eb96b AK |
117 | merge (a); |
118 | } | |
119 | else | |
120 | { | |
2d44c7de ML |
121 | merge (a); |
122 | merge (b); | |
6d8eb96b AK |
123 | } |
124 | } | |
125 | ||
126 | private: | |
127 | hashval_t val; | |
128 | unsigned bits; | |
129 | }; | |
130 | ||
50de5793 | 131 | } |
6d8eb96b | 132 | |
2d44c7de ML |
133 | /* Borrowed from hashtab.c iterative_hash implementation. */ |
134 | #define mix(a,b,c) \ | |
135 | { \ | |
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; \ | |
145 | } | |
146 | ||
147 | ||
148 | /* Produce good hash value combining VAL and VAL2. */ | |
149 | inline | |
150 | hashval_t | |
151 | iterative_hash_hashval_t (hashval_t val, hashval_t val2) | |
152 | { | |
153 | /* the golden ratio; an arbitrary value. */ | |
154 | hashval_t a = 0x9e3779b9; | |
155 | ||
156 | mix (a, val, val2); | |
157 | return val2; | |
158 | } | |
159 | ||
160 | /* Produce good hash value combining VAL and VAL2. */ | |
161 | ||
162 | inline | |
163 | hashval_t | |
164 | iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2) | |
165 | { | |
166 | if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t)) | |
167 | return iterative_hash_hashval_t (val, val2); | |
168 | else | |
169 | { | |
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. */ | |
173 | int zero = 0; | |
174 | hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero)); | |
175 | mix (a, b, val2); | |
176 | if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t)) | |
177 | { | |
178 | hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero)); | |
179 | hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero)); | |
180 | mix (a, b, val2); | |
181 | } | |
182 | return val2; | |
183 | } | |
184 | } | |
185 | ||
6d8eb96b | 186 | #endif |