summaryrefslogtreecommitdiff
path: root/gcc/inchash.h
blob: e0dfdffa85b0b1b616261b284d7f6e5a0c1deda4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
/* An incremental hash abstract data type.
   Copyright (C) 2014-2015 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#ifndef INCHASH_H
#define INCHASH_H 1


/* This file implements an incremential hash function ADT, to be used
   by code that incrementially hashes a lot of unrelated data
   (not in a single memory block) into a single value. The goal
   is to make it easy to plug in efficient hash algorithms.
   Currently it just implements the plain old jhash based
   incremental hash from gcc's tree.c.  */

hashval_t iterative_hash_host_wide_int (HOST_WIDE_INT, hashval_t);
hashval_t iterative_hash_hashval_t (hashval_t, hashval_t);

namespace inchash
{

class hash
{
 public:

  /* Start incremential hashing, optionally with SEED.  */
  hash (hashval_t seed = 0)
  {
    val = seed;
    bits = 0;
  }

  /* End incremential hashing and provide the final value.  */
  hashval_t end ()
  {
    return val;
  }

  /* Add unsigned value V.  */
  void add_int (unsigned v)
  {
    val = iterative_hash_hashval_t (v, val);
  }

  /* Add HOST_WIDE_INT value V.  */
  void add_wide_int (HOST_WIDE_INT v)
  {
    val = iterative_hash_host_wide_int (v, val);
  }

  /* Hash in pointer PTR.  */
  void add_ptr (const void *ptr)
  {
    add (&ptr, sizeof (ptr));
  }

  /* Add a memory block DATA with size LEN.  */
  void add (const void *data, size_t len)
  {
    val = iterative_hash (data, len, val);
  }

  /* Merge hash value OTHER.  */
  void merge_hash (hashval_t other)
  {
    val = iterative_hash_hashval_t (other, val);
  }

  /* Hash in state from other inchash OTHER.  */
  void merge (hash &other)
  {
    merge_hash (other.val);
  }

  template<class T> void add_object(T &obj)
  {
    add (&obj, sizeof(T));
  }

  /* Support for accumulating boolean flags */

  void add_flag (bool flag)
  {
    bits = (bits << 1) | flag;
  }

  void commit_flag ()
  {
    add_int (bits);
    bits = 0;
  }

  /* Support for commutative hashing. Add A and B in a defined order
     based on their value. This is useful for hashing commutative
     expressions, so that A+B and B+A get the same hash.  */

  void add_commutative (hash &a, hash &b)
  {
    if (a.end() > b.end())
      {
	merge (b);
	merge (a);
      }
    else
      {
	merge (a);
	merge (b);
      }
  }

 private:
  hashval_t val;
  unsigned bits;
};

}

/* Borrowed from hashtab.c iterative_hash implementation.  */
#define mix(a,b,c) \
{ \
  a -= b; a -= c; a ^= (c>>13); \
  b -= c; b -= a; b ^= (a<< 8); \
  c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
  a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
  b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
  c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
  a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
  b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
  c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
}


/* Produce good hash value combining VAL and VAL2.  */
inline
hashval_t
iterative_hash_hashval_t (hashval_t val, hashval_t val2)
{
  /* the golden ratio; an arbitrary value.  */
  hashval_t a = 0x9e3779b9;

  mix (a, val, val2);
  return val2;
}

/* Produce good hash value combining VAL and VAL2.  */

inline
hashval_t
iterative_hash_host_wide_int (HOST_WIDE_INT val, hashval_t val2)
{
  if (sizeof (HOST_WIDE_INT) == sizeof (hashval_t))
    return iterative_hash_hashval_t (val, val2);
  else
    {
      hashval_t a = (hashval_t) val;
      /* Avoid warnings about shifting of more than the width of the type on
         hosts that won't execute this path.  */
      int zero = 0;
      hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 8 + zero));
      mix (a, b, val2);
      if (sizeof (HOST_WIDE_INT) > 2 * sizeof (hashval_t))
	{
	  hashval_t a = (hashval_t) (val >> (sizeof (hashval_t) * 16 + zero));
	  hashval_t b = (hashval_t) (val >> (sizeof (hashval_t) * 24 + zero));
	  mix (a, b, val2);
	}
      return val2;
    }
}

#endif