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) (int)__popcnt64(x)
56 #elif defined(__GNUC__) && defined(USE_POPCNT) // Gcc compiler
58 inline void __cpuid(unsigned int op,
59 unsigned int *eax, unsigned int *ebx,
60 unsigned int *ecx, unsigned int *edx)
64 __asm__("cpuid" : "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=d" (*edx)
65 : "0" (*eax), "2" (*ecx));
68 inline bool cpu_has_popcnt() {
70 unsigned int eax, ebx, ecx, edx;
71 __cpuid(1, &eax, &ebx, &ecx, &edx);
72 return (ecx >> 23) & 1;
75 #define POPCNT_INTRINSIC(x) ({ \
76 unsigned long __ret; \
77 __asm__("popcnt %1, %0" : "=r" (__ret) : "r" (x)); \
80 #else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled
82 inline bool cpu_has_popcnt() { return false; }
84 #define POPCNT_INTRINSIC(x) 0
86 #endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions
89 /// Software implementation of bit count functions
93 inline int count_1s(Bitboard b) {
94 b -= ((b>>1) & 0x5555555555555555ULL);
95 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
96 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
97 b *= 0x0101010101010101ULL;
101 inline int count_1s_max_15(Bitboard b) {
102 b -= (b>>1) & 0x5555555555555555ULL;
103 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
104 b *= 0x1111111111111111ULL;
108 #else // if !defined(IS_64BIT)
110 inline int count_1s(Bitboard b) {
111 unsigned w = unsigned(b >> 32), v = unsigned(b);
112 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
113 w -= (w >> 1) & 0x55555555;
114 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
115 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
116 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
117 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
118 v *= 0x01010101; // mul is fast on amd procs
122 inline int count_1s_max_15(Bitboard b) {
123 unsigned w = unsigned(b >> 32), v = unsigned(b);
124 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
125 w -= (w >> 1) & 0x55555555;
126 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
127 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
128 v += w; // 0-8 in 4 bits
136 /// count_1s() counts the number of nonzero bits in a bitboard.
137 /// If template parameter is true an intrinsic is called, otherwise
138 /// we fallback on a software implementation.
140 template<bool UseIntrinsic>
141 inline int count_1s(Bitboard b) {
143 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
146 template<bool UseIntrinsic>
147 inline int count_1s_max_15(Bitboard b) {
149 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
153 // Global constant initialized at startup that is set to true if
154 // CPU on which application runs supports POPCNT intrinsic. Unless
155 // USE_POPCNT is not defined.
156 const bool CpuHasPOPCNT = cpu_has_popcnt();
159 // Global constant used to print info about the use of 64 optimized
160 // functions to verify that a 64 bit compile has been correctly built.
161 #if defined(IS_64BIT)
162 const bool CpuHas64BitPath = true;
164 const bool CpuHas64BitPath = false;
167 #endif // !defined(BITCOUNT_H_INCLUDED)