2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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.
29 #if !defined(USE_POPCNT)
30 #define POPCNT_INTRINSIC(x) 0
31 #elif defined(_MSC_VER)
32 #define POPCNT_INTRINSIC(x) (int)__popcnt64(x)
33 #elif defined(__GNUC__)
35 #define POPCNT_INTRINSIC(x) ({ \
36 unsigned long __ret; \
37 __asm__("popcnt %1, %0" : "=r" (__ret) : "r" (x)); \
43 /// Software implementation of bit count functions
47 inline int count_1s(Bitboard b) {
48 b -= ((b>>1) & 0x5555555555555555ULL);
49 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
50 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
51 b *= 0x0101010101010101ULL;
55 inline int count_1s_max_15(Bitboard b) {
56 b -= (b>>1) & 0x5555555555555555ULL;
57 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
58 b *= 0x1111111111111111ULL;
62 #else // if !defined(IS_64BIT)
64 inline int count_1s(Bitboard b) {
65 unsigned w = unsigned(b >> 32), v = unsigned(b);
66 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
67 w -= (w >> 1) & 0x55555555;
68 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
69 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
70 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
71 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
72 v *= 0x01010101; // mul is fast on amd procs
76 inline int count_1s_max_15(Bitboard b) {
77 unsigned w = unsigned(b >> 32), v = unsigned(b);
78 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
79 w -= (w >> 1) & 0x55555555;
80 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
81 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
82 v += w; // 0-8 in 4 bits
90 /// count_1s() counts the number of nonzero bits in a bitboard.
91 /// If template parameter is true an intrinsic is called, otherwise
92 /// we fallback on a software implementation.
94 template<bool UseIntrinsic>
95 inline int count_1s(Bitboard b) {
97 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
100 template<bool UseIntrinsic>
101 inline int count_1s_max_15(Bitboard b) {
103 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
107 // Detect hardware POPCNT support
108 inline bool cpu_has_popcnt() {
110 int CPUInfo[4] = {-1};
111 __cpuid(CPUInfo, 0x00000001);
112 return (CPUInfo[2] >> 23) & 1;
116 // Global constant initialized at startup that is set to true if
117 // CPU on which application runs supports POPCNT intrinsic. Unless
118 // USE_POPCNT is not defined.
119 #if defined(USE_POPCNT)
120 const bool CpuHasPOPCNT = cpu_has_popcnt();
122 const bool CpuHasPOPCNT = false;
126 // Global constant used to print info about the use of 64 optimized
127 // functions to verify that a 64 bit compile has been correctly built.
128 #if defined(IS_64BIT)
129 const bool CpuHas64BitPath = true;
131 const bool CpuHas64BitPath = false;
134 #endif // !defined(BITCOUNT_H_INCLUDED)