Introduce bitcount.h

It will be used for POPCNT intrinsics.

For now no bianry and functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

src/bitcount.h

@@ -0,0 +1,162 @@
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2009 Marco Costalba
+
+  Stockfish is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+
+  Stockfish is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#if !defined(BITCOUNT_H_INCLUDED)
+#define BITCOUNT_H_INCLUDED
+
+#include "bitboard.h"
+
+
+// Select type of software bit count function to use
+
+#if !defined(AUTO_CONFIGURATION) || defined(IS_64BIT)
+
+//#define USE_COMPACT_ROOK_ATTACKS
+//#define USE_32BIT_ATTACKS
+#define USE_FOLDED_BITSCAN
+
+#define BITCOUNT_SWAR_64
+//#define BITCOUNT_SWAR_32
+//#define BITCOUNT_LOOP
+
+#else
+
+#define USE_32BIT_ATTACKS
+#define USE_FOLDED_BITSCAN
+#define BITCOUNT_SWAR_32
+
+#endif
+
+
+// Select type of intrinsic bit count instruction to use
+
+#if defined(_MSC_VER) // Microsoft compiler
+
+#include <intrin.h>
+
+inline bool cpu_has_popcnt() {
+
+  int CPUInfo[4] = {-1};
+  __cpuid(CPUInfo, 0x00000001);
+  return (CPUInfo[2] >> 23) & 1;
+}
+
+#define POPCNT_INTRINSIC(x) __popcnt64(x)
+
+#elif defined(__INTEL_COMPILER) && (defined(__x86_64) || defined(_M_X64)) // Intel compiler
+
+#include <nmmintrin.h>
+
+inline bool cpu_has_popcnt() {
+
+  int CPUInfo[4] = {-1};
+  __cpuid(CPUInfo, 0x00000001);
+  return (CPUInfo[2] >> 23) & 1;
+}
+
+#define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
+
+#else // Safe fallback for unsupported compilers
+
+inline bool cpu_has_popcnt() { return false; }
+
+#define POPCNT_INTRINSIC(x) sw_count_1s(x)
+
+#endif
+
+
+/// Software implementation of bit count functions
+
+#if defined(BITCOUNT_LOOP)
+
+inline int sw_count_1s(Bitboard b) {
+  int r;
+  for(r = 0; b; r++, b &= b - 1);
+  return r;
+}
+
+inline int sw_count_1s_max_15(Bitboard b) {
+  return count_1s(b);
+}
+
+#elif defined(BITCOUNT_SWAR_32)
+
+inline int sw_count_1s(Bitboard b) {
+  unsigned w = unsigned(b >> 32), v = unsigned(b);
+  v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
+  w -= (w >> 1) & 0x55555555;
+  v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
+  w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
+  v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
+  v += (((w >> 4) + w) & 0x0F0F0F0F);  // 0-16 in 8 bits
+  v *= 0x01010101; // mul is fast on amd procs
+  return int(v >> 24);
+}
+
+inline int sw_count_1s_max_15(Bitboard b) {
+  unsigned w = unsigned(b >> 32), v = unsigned(b);
+  v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
+  w -= (w >> 1) & 0x55555555;
+  v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
+  w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
+  v += w; // 0-8 in 4 bits
+  v *= 0x11111111;
+  return int(v >> 28);
+}
+
+#elif defined(BITCOUNT_SWAR_64)
+
+inline int sw_count_1s(Bitboard b) {
+  b -= ((b>>1) & 0x5555555555555555ULL);
+  b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
+  b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
+  b *= 0x0101010101010101ULL;
+  return int(b >> 56);
+}
+
+inline int sw_count_1s_max_15(Bitboard b) {
+  b -= (b>>1) & 0x5555555555555555ULL;
+  b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
+  b *= 0x1111111111111111ULL;
+  return int(b >> 60);
+}
+
+#endif // BITCOUNT
+
+
+/// count_1s() counts the number of nonzero bits in a bitboard.
+/// If template parameter is true an intrinsic is called, otherwise
+/// we fallback on a software implementation.
+
+template<bool UseIntrinsic>
+inline int count_1s(Bitboard b) {
+
+  return UseIntrinsic ? POPCNT_INTRINSIC(b) : sw_count_1s(b);
+}
+
+template<bool UseIntrinsic>
+inline int count_1s_max_15(Bitboard b) {
+
+  return UseIntrinsic ? POPCNT_INTRINSIC(b) : sw_count_1s_max_15(b);
+}
+
+
+#endif // !defined(BITCOUNT_H_INCLUDED)