2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
22 #if !defined(BITCOUNT_H_INCLUDED)
23 #define BITCOUNT_H_INCLUDED
27 // Select type of intrinsic bit count instruction to use, see
28 // README.txt on how to pgo compile with POPCNT support.
30 #if defined(__INTEL_COMPILER) && defined(USE_POPCNT) // Intel compiler
32 #include <nmmintrin.h>
34 inline bool cpu_has_popcnt() {
36 int CPUInfo[4] = {-1};
37 __cpuid(CPUInfo, 0x00000001);
38 return (CPUInfo[2] >> 23) & 1;
41 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
43 #elif defined(_MSC_VER) && defined(USE_POPCNT) // Microsoft compiler
47 inline bool cpu_has_popcnt() {
49 int CPUInfo[4] = {-1};
50 __cpuid(CPUInfo, 0x00000001);
51 return (CPUInfo[2] >> 23) & 1;
54 #define POPCNT_INTRINSIC(x) __popcnt64(x)
56 #else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled
58 inline bool cpu_has_popcnt() { return false; }
60 #define POPCNT_INTRINSIC(x) 0
62 #endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions
65 /// Software implementation of bit count functions
69 inline int count_1s(Bitboard b) {
70 b -= ((b>>1) & 0x5555555555555555ULL);
71 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
72 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
73 b *= 0x0101010101010101ULL;
77 inline int count_1s_max_15(Bitboard b) {
78 b -= (b>>1) & 0x5555555555555555ULL;
79 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
80 b *= 0x1111111111111111ULL;
84 #else // if !defined(IS_64BIT)
86 inline int count_1s(Bitboard b) {
87 unsigned w = unsigned(b >> 32), v = unsigned(b);
88 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
89 w -= (w >> 1) & 0x55555555;
90 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
91 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
92 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
93 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
94 v *= 0x01010101; // mul is fast on amd procs
98 inline int count_1s_max_15(Bitboard b) {
99 unsigned w = unsigned(b >> 32), v = unsigned(b);
100 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
101 w -= (w >> 1) & 0x55555555;
102 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
103 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
104 v += w; // 0-8 in 4 bits
112 /// count_1s() counts the number of nonzero bits in a bitboard.
113 /// If template parameter is true an intrinsic is called, otherwise
114 /// we fallback on a software implementation.
116 template<bool UseIntrinsic>
117 inline int count_1s(Bitboard b) {
119 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
122 template<bool UseIntrinsic>
123 inline int count_1s_max_15(Bitboard b) {
125 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
129 // Global constant initialized at startup that is set to true if
130 // CPU on which application runs supports POPCNT intrinsic. Unless
131 // USE_POPCNT is not defined.
132 const bool CpuHasPOPCNT = cpu_has_popcnt();
135 // Global constant used to print info about the use of 64 optimized
136 // functions to verify that a 64 bit compile has been correctly built.
137 #if defined(IS_64BIT)
138 const bool CpuHas64BitPath = true;
140 const bool CpuHas64BitPath = false;
143 #endif // !defined(BITCOUNT_H_INCLUDED)