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 inline bool cpu_has_popcnt() {
34 int CPUInfo[4] = {-1};
35 __cpuid(CPUInfo, 0x00000001);
36 return (CPUInfo[2] >> 23) & 1;
39 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
41 #elif defined(_MSC_VER) && defined(USE_POPCNT) // Microsoft compiler
43 inline bool cpu_has_popcnt() {
45 int CPUInfo[4] = {-1};
46 __cpuid(CPUInfo, 0x00000001);
47 return (CPUInfo[2] >> 23) & 1;
50 #define POPCNT_INTRINSIC(x) (int)__popcnt64(x)
52 #elif defined(__GNUC__) && defined(USE_POPCNT) // Gcc compiler
54 inline bool cpu_has_popcnt() {
56 unsigned int eax, ebx, ecx, edx;
57 __cpuid(1, &eax, &ebx, &ecx, &edx);
58 return (ecx >> 23) & 1;
61 #define POPCNT_INTRINSIC(x) ({ \
62 unsigned long __ret; \
63 __asm__("popcnt %1, %0" : "=r" (__ret) : "r" (x)); \
66 #else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled
68 inline bool cpu_has_popcnt() { return false; }
70 #define POPCNT_INTRINSIC(x) 0
72 #endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions
75 /// Software implementation of bit count functions
79 inline int count_1s(Bitboard b) {
80 b -= ((b>>1) & 0x5555555555555555ULL);
81 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
82 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
83 b *= 0x0101010101010101ULL;
87 inline int count_1s_max_15(Bitboard b) {
88 b -= (b>>1) & 0x5555555555555555ULL;
89 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
90 b *= 0x1111111111111111ULL;
94 #else // if !defined(IS_64BIT)
96 inline int count_1s(Bitboard b) {
97 unsigned w = unsigned(b >> 32), v = unsigned(b);
98 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
99 w -= (w >> 1) & 0x55555555;
100 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
101 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
102 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
103 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
104 v *= 0x01010101; // mul is fast on amd procs
108 inline int count_1s_max_15(Bitboard b) {
109 unsigned w = unsigned(b >> 32), v = unsigned(b);
110 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
111 w -= (w >> 1) & 0x55555555;
112 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
113 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
114 v += w; // 0-8 in 4 bits
122 /// count_1s() counts the number of nonzero bits in a bitboard.
123 /// If template parameter is true an intrinsic is called, otherwise
124 /// we fallback on a software implementation.
126 template<bool UseIntrinsic>
127 inline int count_1s(Bitboard b) {
129 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
132 template<bool UseIntrinsic>
133 inline int count_1s_max_15(Bitboard b) {
135 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
139 // Global constant initialized at startup that is set to true if
140 // CPU on which application runs supports POPCNT intrinsic. Unless
141 // USE_POPCNT is not defined.
142 const bool CpuHasPOPCNT = cpu_has_popcnt();
145 // Global constant used to print info about the use of 64 optimized
146 // functions to verify that a 64 bit compile has been correctly built.
147 #if defined(IS_64BIT)
148 const bool CpuHas64BitPath = true;
150 const bool CpuHas64BitPath = false;
153 #endif // !defined(BITCOUNT_H_INCLUDED)