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 following line. 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 ;-)
28 //#define DISABLE_POPCNT_SUPPORT
33 // Select type of intrinsic bit count instruction to use
35 #if defined(_MSC_VER) && defined(_WIN64) // Microsoft compiler
39 inline bool cpu_has_popcnt() {
41 int CPUInfo[4] = {-1};
42 __cpuid(CPUInfo, 0x00000001);
43 return (CPUInfo[2] >> 23) & 1;
46 #define POPCNT_INTRINSIC(x) __popcnt64(x)
48 #elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
50 #include <nmmintrin.h>
52 inline bool cpu_has_popcnt() {
54 int CPUInfo[4] = {-1};
55 __cpuid(CPUInfo, 0x00000001);
56 return (CPUInfo[2] >> 23) & 1;
59 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
61 #else // Safe fallback for unsupported compilers
63 inline bool cpu_has_popcnt() { return false; }
65 #define POPCNT_INTRINSIC(x) count_1s(x)
67 #endif // cpu_has_popcnt() selection
70 /// Software implementation of bit count functions
74 inline int count_1s(Bitboard b) {
75 b -= ((b>>1) & 0x5555555555555555ULL);
76 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
77 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
78 b *= 0x0101010101010101ULL;
82 inline int count_1s_max_15(Bitboard b) {
83 b -= (b>>1) & 0x5555555555555555ULL;
84 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
85 b *= 0x1111111111111111ULL;
89 #else // if !defined(IS_64BIT)
91 inline int count_1s(Bitboard b) {
92 unsigned w = unsigned(b >> 32), v = unsigned(b);
93 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
94 w -= (w >> 1) & 0x55555555;
95 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
96 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
97 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
98 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
99 v *= 0x01010101; // mul is fast on amd procs
103 inline int count_1s_max_15(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 += w; // 0-8 in 4 bits
117 /// count_1s() counts the number of nonzero bits in a bitboard.
118 /// If template parameter is true an intrinsic is called, otherwise
119 /// we fallback on a software implementation.
121 template<bool UseIntrinsic>
122 inline int count_1s(Bitboard b) {
124 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s(b);
127 template<bool UseIntrinsic>
128 inline int count_1s_max_15(Bitboard b) {
130 return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
134 // Global variable initialized at startup that is set to true if
135 // CPU on which application runs supports POPCNT intrinsic. Unless
136 // DISABLE_POPCNT_SUPPORT is defined.
137 #if defined(DISABLE_POPCNT_SUPPORT)
138 const bool CpuHasPOPCNT = false;
140 const bool CpuHasPOPCNT = cpu_has_popcnt();
144 // Global variable used to print info about the use of 64 optimized
145 // functions to verify that a 64bit compile has been correctly built.
146 #if defined(IS_64BIT)
147 const bool CpuHas64BitPath = true;
149 const bool CpuHas64BitPath = false;
152 #endif // !defined(BITCOUNT_H_INCLUDED)