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
28 // Select type of software bit count function to use
30 #if !defined(AUTO_CONFIGURATION) || defined(IS_64BIT)
32 //#define USE_COMPACT_ROOK_ATTACKS
33 //#define USE_32BIT_ATTACKS
34 #define USE_FOLDED_BITSCAN
36 #define BITCOUNT_SWAR_64
37 //#define BITCOUNT_SWAR_32
38 //#define BITCOUNT_LOOP
42 #define USE_32BIT_ATTACKS
43 #define USE_FOLDED_BITSCAN
44 #define BITCOUNT_SWAR_32
49 // Select type of intrinsic bit count instruction to use
51 #if defined(_MSC_VER) // Microsoft compiler
55 inline bool cpu_has_popcnt() {
57 int CPUInfo[4] = {-1};
58 __cpuid(CPUInfo, 0x00000001);
59 return (CPUInfo[2] >> 23) & 1;
62 #define POPCNT_INTRINSIC(x) __popcnt64(x)
64 #elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
66 #include <nmmintrin.h>
68 inline bool cpu_has_popcnt() {
70 int CPUInfo[4] = {-1};
71 __cpuid(CPUInfo, 0x00000001);
72 return (CPUInfo[2] >> 23) & 1;
75 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
77 #else // Safe fallback for unsupported compilers
79 inline bool cpu_has_popcnt() { return false; }
81 #define POPCNT_INTRINSIC(x) sw_count_1s(x)
86 /// Software implementation of bit count functions
88 #if defined(BITCOUNT_LOOP)
90 inline int sw_count_1s(Bitboard b) {
92 for(r = 0; b; r++, b &= b - 1);
96 inline int sw_count_1s_max_15(Bitboard b) {
100 #elif defined(BITCOUNT_SWAR_32)
102 inline int sw_count_1s(Bitboard b) {
103 unsigned w = unsigned(b >> 32), v = unsigned(b);
104 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
105 w -= (w >> 1) & 0x55555555;
106 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
107 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
108 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
109 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
110 v *= 0x01010101; // mul is fast on amd procs
114 inline int sw_count_1s_max_15(Bitboard b) {
115 unsigned w = unsigned(b >> 32), v = unsigned(b);
116 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
117 w -= (w >> 1) & 0x55555555;
118 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
119 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
120 v += w; // 0-8 in 4 bits
125 #elif defined(BITCOUNT_SWAR_64)
127 inline int sw_count_1s(Bitboard b) {
128 b -= ((b>>1) & 0x5555555555555555ULL);
129 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
130 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
131 b *= 0x0101010101010101ULL;
135 inline int sw_count_1s_max_15(Bitboard b) {
136 b -= (b>>1) & 0x5555555555555555ULL;
137 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
138 b *= 0x1111111111111111ULL;
145 /// count_1s() counts the number of nonzero bits in a bitboard.
146 /// If template parameter is true an intrinsic is called, otherwise
147 /// we fallback on a software implementation.
149 template<bool UseIntrinsic>
150 inline int count_1s(Bitboard b) {
152 return UseIntrinsic ? POPCNT_INTRINSIC(b) : sw_count_1s(b);
155 template<bool UseIntrinsic>
156 inline int count_1s_max_15(Bitboard b) {
158 return UseIntrinsic ? POPCNT_INTRINSIC(b) : sw_count_1s_max_15(b);
162 // Global variable initialized at startup that is set to true if
163 // CPU on which application runs support POPCNT intrinsic.
165 const bool CpuHasPOPCNT = cpu_has_popcnt();
167 #endif // !defined(BITCOUNT_H_INCLUDED)