1/* An incremental hash abstract data type.
2 Copyright (C) 2014-2026 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.cc. */
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 () const
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 polynomial value V, treating each element as an unsigned int. */
61 template<unsigned int N, typename T>
62 void add_poly_int (const poly_int<N, T> &v)
63 {
64 for (unsigned int i = 0; i < N; ++i)
65 add_int (v: v.coeffs[i]);
66 }
67
68 /* Add HOST_WIDE_INT value V. */
69 void add_hwi (HOST_WIDE_INT v)
70 {
71 val = iterative_hash_host_wide_int (v, val);
72 }
73
74 /* Add polynomial value V, treating each element as a HOST_WIDE_INT. */
75 template<unsigned int N, typename T>
76 void add_poly_hwi (const poly_int<N, T> &v)
77 {
78 for (unsigned int i = 0; i < N; ++i)
79 add_hwi (v: v.coeffs[i]);
80 }
81
82 /* Add wide_int-based value V. */
83 template<typename T>
84 void add_wide_int (const generic_wide_int<T> &x)
85 {
86 add_int (v: x.get_len ());
87 for (unsigned i = 0; i < x.get_len (); i++)
88 add_hwi (v: x.sext_elt (i));
89 }
90
91 void add_real_value (const class real_value &v);
92
93 /* Hash in pointer PTR. */
94 void add_ptr (const void *ptr)
95 {
96 add (data: &ptr, len: sizeof (ptr));
97 }
98
99 /* Add a memory block DATA with size LEN. */
100 void add (const void *data, size_t len)
101 {
102 val = iterative_hash (data, len, val);
103 }
104
105 /* Merge hash value OTHER. */
106 void merge_hash (hashval_t other)
107 {
108 val = iterative_hash_hashval_t (other, val);
109 }
110
111 /* Hash in state from other inchash OTHER. */
112 void merge (const hash &other)
113 {
114 merge_hash (other: other.val);
115 }
116
117 template<class T> void add_object(T &obj)
118 {
119 add (data: &obj, len: sizeof(T));
120 }
121
122 /* Support for accumulating boolean flags */
123
124 void add_flag (bool flag)
125 {
126 bits = (bits << 1) | flag;
127 }
128
129 void commit_flag ()
130 {
131 add_int (v: bits);
132 bits = 0;
133 }
134
135 /* Support for commutative hashing. Add A and B in a defined order
136 based on their value. This is useful for hashing commutative
137 expressions, so that A+B and B+A get the same hash. */
138
139 void add_commutative (const hash &a, const hash &b)
140 {
141 if (a.end() > b.end())
142 {
143 merge (other: b);
144 merge (other: a);
145 }
146 else
147 {
148 merge (other: a);
149 merge (other: b);
150 }
151 }
152
153 private:
154 hashval_t val;
155 unsigned bits;
156};
157
158}
159
160/* Borrowed from hashtab.c iterative_hash implementation. */
161#define mix(a,b,c) \
162{ \
163 a -= b; a -= c; a ^= (c>>13); \
164 b -= c; b -= a; b ^= (a<< 8); \
165 c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
166 a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
167 b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
168 c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
169 a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
170 b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
171 c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
172}
173
174
175/* Produce good hash value combining VAL and VAL2. */
176inline
177hashval_t
178iterative_hash_hashval_t (hashval_t val, hashval_t val2)
179{
180 /* the golden ratio; an arbitrary value. */
181 hashval_t a = 0x9e3779b9;
182
183 mix (a, val, val2);
184 return val2;
185}
186
187/* Produce good hash value combining VAL and VAL2. */
188
189inline
190hashval_t
191iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2)
192{
193 if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t))
194 return iterative_hash_hashval_t (val, val2);
195 else
196 {
197 hashval_t a = (hashval_t) val;
198 /* Avoid warnings about shifting of more than the width of the type on
199 hosts that won't execute this path. */
200 int zero = 0;
201 hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero));
202 mix (a, b, val2);
203 if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t))
204 {
205 hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero));
206 hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero));
207 mix (a, b, val2);
208 }
209 return val2;
210 }
211}
212
213#endif
214

source code of gcc/inchash.h