1 /* mpn_popcount, mpn_hamdist -- mpn bit population count/hamming distance.
2
3 Copyright 1994, 1996, 2000-2002, 2005, 2011, 2012 Free Software Foundation,
4 Inc.
5
6 This file is part of the GNU MP Library.
7
8 The GNU MP Library is free software; you can redistribute it and/or modify
9 it under the terms of either:
10
11 * the GNU Lesser General Public License as published by the Free
12 Software Foundation; either version 3 of the License, or (at your
13 option) any later version.
14
15 or
16
17 * the GNU General Public License as published by the Free Software
18 Foundation; either version 2 of the License, or (at your option) any
19 later version.
20
21 or both in parallel, as here.
22
23 The GNU MP Library is distributed in the hope that it will be useful, but
24 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
26 for more details.
27
28 You should have received copies of the GNU General Public License and the
29 GNU Lesser General Public License along with the GNU MP Library. If not,
30 see https://www.gnu.org/licenses/. */
31
32 #include "gmp-impl.h"
33
34 #if OPERATION_popcount
35 #define FNAME mpn_popcount
36 #define POPHAM(u,v) u
37 #endif
38
39 #if OPERATION_hamdist
40 #define FNAME mpn_hamdist
41 #define POPHAM(u,v) u ^ v
42 #endif
43
44 mp_bitcnt_t
FNAME(mp_srcptr up,mp_srcptr vp,mp_size_t n)45 FNAME (mp_srcptr up,
46 #if OPERATION_hamdist
47 mp_srcptr vp,
48 #endif
49 mp_size_t n) __GMP_NOTHROW
50 {
51 mp_bitcnt_t result = 0;
52 mp_limb_t p0, p1, p2, p3, x, p01, p23;
53 mp_size_t i;
54
55 ASSERT (n >= 1); /* Actually, this code handles any n, but some
56 assembly implementations do not. */
57
58 for (i = n >> 2; i != 0; i--)
59 {
60 p0 = POPHAM (up[0], vp[0]);
61 p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
62 p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5); /* 4 0-4 */
63
64 p1 = POPHAM (up[1], vp[1]);
65 p1 -= (p1 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
66 p1 = ((p1 >> 2) & MP_LIMB_T_MAX/5) + (p1 & MP_LIMB_T_MAX/5); /* 4 0-4 */
67
68 p01 = p0 + p1; /* 8 0-8 */
69 p01 = ((p01 >> 4) & MP_LIMB_T_MAX/17) + (p01 & MP_LIMB_T_MAX/17); /* 8 0-16 */
70
71 p2 = POPHAM (up[2], vp[2]);
72 p2 -= (p2 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
73 p2 = ((p2 >> 2) & MP_LIMB_T_MAX/5) + (p2 & MP_LIMB_T_MAX/5); /* 4 0-4 */
74
75 p3 = POPHAM (up[3], vp[3]);
76 p3 -= (p3 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
77 p3 = ((p3 >> 2) & MP_LIMB_T_MAX/5) + (p3 & MP_LIMB_T_MAX/5); /* 4 0-4 */
78
79 p23 = p2 + p3; /* 8 0-8 */
80 p23 = ((p23 >> 4) & MP_LIMB_T_MAX/17) + (p23 & MP_LIMB_T_MAX/17); /* 8 0-16 */
81
82 x = p01 + p23; /* 8 0-32 */
83 x = (x >> 8) + x; /* 8 0-64 */
84 x = (x >> 16) + x; /* 8 0-128 */
85 #if GMP_LIMB_BITS > 32
86 x = ((x >> 32) & 0xff) + (x & 0xff); /* 8 0-256 */
87 result += x;
88 #else
89 result += x & 0xff;
90 #endif
91 up += 4;
92 #if OPERATION_hamdist
93 vp += 4;
94 #endif
95 }
96
97 n &= 3;
98 if (n != 0)
99 {
100 x = 0;
101 do
102 {
103 p0 = POPHAM (up[0], vp[0]);
104 p0 -= (p0 >> 1) & MP_LIMB_T_MAX/3; /* 2 0-2 */
105 p0 = ((p0 >> 2) & MP_LIMB_T_MAX/5) + (p0 & MP_LIMB_T_MAX/5); /* 4 0-4 */
106 p0 = ((p0 >> 4) + p0) & MP_LIMB_T_MAX/17; /* 8 0-8 */
107
108 x += p0;
109 up += 1;
110 #if OPERATION_hamdist
111 vp += 1;
112 #endif
113 }
114 while (--n);
115
116 x = (x >> 8) + x;
117 x = (x >> 16) + x;
118 #if GMP_LIMB_BITS > 32
119 x = (x >> 32) + x;
120 #endif
121 result += x & 0xff;
122 }
123
124 return result;
125 }
126