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
25 // To disable POPCNT support uncomment NO_POPCNT define. You should do it only
26 // in PGO compiling to exercise the default fallback path. Don't forget to
27 // re-comment the line for the final optimized compile though ;-)
34 // Select type of intrinsic bit count instruction to use
36 #if defined(_MSC_VER) && defined(IS_64BIT) && !defined(NO_POPCNT) // Microsoft compiler
40 inline bool cpu_has_popcnt() {
42 int CPUInfo[4] = {-1};
43 __cpuid(CPUInfo, 0x00000001);
44 return (CPUInfo[2] >> 23) & 1;
47 // Define a dummy template to workaround a compile error if __popcnt64() is not defined.
49 // If __popcnt64() is defined in <intrin.h> it will be choosen first due to
50 // C++ overload rules that always prefer a function to a template with the same name.
51 // If not, we avoid a compile error and because cpu_has_popcnt() should return false,
52 // our templetized __popcnt64() is never called anyway.
53 template<typename T> unsigned __popcnt64(T) { return 0; } // Is never called
55 #define POPCNT_INTRINSIC(x) __popcnt64(x)
57 #elif defined(__INTEL_COMPILER) && defined(IS_64BIT) && !defined(NO_POPCNT) // Intel compiler
59 #include <nmmintrin.h>
61 inline bool cpu_has_popcnt() {
63 int CPUInfo[4] = {-1};
64 __cpuid(CPUInfo, 0x00000001);
65 return (CPUInfo[2] >> 23) & 1;
68 // See comment of __popcnt64<>() few lines above for an explanation.
69 template<typename T> unsigned _mm_popcnt_u64(T) { return 0; } // Is never called
71 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
73 #else // Safe fallback for unsupported compilers or when NO_POPCNT is defined
75 inline bool cpu_has_popcnt() { return false; }
77 #define POPCNT_INTRINSIC(x) 0
79 #endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions
82 /// Software implementation of bit count functions
86 inline int count_1s(Bitboard b) {
87 b -= ((b>>1) & 0x5555555555555555ULL);
88 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
89 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
90 b *= 0x0101010101010101ULL;
94 inline int count_1s_max_15(Bitboard b) {
95 b -= (b>>1) & 0x5555555555555555ULL;
96 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
97 b *= 0x1111111111111111ULL;
101 #else // if !defined(IS_64BIT)
103 inline int count_1s(Bitboard b) {
104 unsigned w = unsigned(b >> 32), v = unsigned(b);
105 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
106 w -= (w >> 1) & 0x55555555;
107 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
108 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
109 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
110 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
111 v *= 0x01010101; // mul is fast on amd procs
115 inline int count_1s_max_15(Bitboard b) {
116 unsigned w = unsigned(b >> 32), v = unsigned(b);
117 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
118 w -= (w >> 1) & 0x55555555;
119 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
120 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
121 v += w; // 0-8 in 4 bits
129 /// count_1s() counts the number of nonzero bits in a bitboard.
130 /// If template parameter is true an intrinsic is called, otherwise
131 /// we fallback on a software implementation.
133 template<bool UseIntrinsic>
134 inline int count_1s(Bitboard b) {
136 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
139 template<bool UseIntrinsic>
140 inline int count_1s_max_15(Bitboard b) {
142 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
146 // Global constant initialized at startup that is set to true if
147 // CPU on which application runs supports POPCNT intrinsic. Unless
148 // NO_POPCNT is defined.
149 #if defined(NO_POPCNT)
150 const bool CpuHasPOPCNT = false;
152 const bool CpuHasPOPCNT = cpu_has_popcnt();
156 // Global constant used to print info about the use of 64 optimized
157 // functions to verify that a 64 bit compile has been correctly built.
158 #if defined(IS_64BIT)
159 const bool CpuHas64BitPath = true;
161 const bool CpuHas64BitPath = false;
164 #endif // !defined(BITCOUNT_H_INCLUDED)