/*
  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

// To enable POPCNT support uncomment USE_POPCNT define. For PGO compile on a Core i7
// you may want to collect profile data first with USE_POPCNT disabled and then, in a
// second profiling session, with USE_POPCNT enabled so to exercise both paths. Don't
// forget to leave USE_POPCNT enabled for the final optimized compile though ;-)

//#define USE_POPCNT


#include "types.h"

// Select type of intrinsic bit count instruction to use

#if defined(__INTEL_COMPILER) && defined(IS_64BIT) && defined(USE_POPCNT) // Intel compiler

#include <nmmintrin.h>

inline bool cpu_has_popcnt() {

  int CPUInfo[4] = {-1};
  __cpuid(CPUInfo, 0x00000001);
  return (CPUInfo[2] >> 23) & 1;
}

// Define a dummy template to workaround a compile error if _mm_popcnt_u64() is not defined.
//
// If _mm_popcnt_u64() is defined in <nmmintrin.h> it will be choosen first due to
// C++ overload rules that always prefer a function to a template with the same name.
// If not, we avoid a compile error and because cpu_has_popcnt() should return false,
// our templetized _mm_popcnt_u64() is never called anyway.
template<typename T> inline unsigned _mm_popcnt_u64(T) { return 0; } // Is never called

#define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)

#elif defined(_MSC_VER) && defined(IS_64BIT) && defined(USE_POPCNT) // Microsoft compiler

#include <intrin.h>

inline bool cpu_has_popcnt() {

  int CPUInfo[4] = {-1};
  __cpuid(CPUInfo, 0x00000001);
  return (CPUInfo[2] >> 23) & 1;
}

// See comment of _mm_popcnt_u64<>() few lines above for an explanation.
template<typename T> inline unsigned __popcnt64(T) { return 0; } // Is never called

#define POPCNT_INTRINSIC(x) __popcnt64(x)

#else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled

inline bool cpu_has_popcnt() { return false; }

#define POPCNT_INTRINSIC(x) 0

#endif // cpu_has_popcnt() and POPCNT_INTRINSIC() definitions


/// Software implementation of bit count functions

#if defined(IS_64BIT)

inline int 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 count_1s_max_15(Bitboard b) {
  b -= (b>>1) & 0x5555555555555555ULL;
  b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
  b *= 0x1111111111111111ULL;
  return int(b >> 60);
}

#else // if !defined(IS_64BIT)

inline int 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 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);
}

#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) : count_1s(b);
}

template<bool UseIntrinsic>
inline int count_1s_max_15(Bitboard b) {

  return UseIntrinsic ? POPCNT_INTRINSIC(b) : count_1s_max_15(b);
}


// Global constant initialized at startup that is set to true if
// CPU on which application runs supports POPCNT intrinsic. Unless
// USE_POPCNT is not defined.
const bool CpuHasPOPCNT = cpu_has_popcnt();


// Global constant used to print info about the use of 64 optimized
// functions to verify that a 64 bit compile has been correctly built.
#if defined(IS_64BIT)
const bool CpuHas64BitPath = true;
#else
const bool CpuHas64BitPath = false;
#endif

#endif // !defined(BITCOUNT_H_INCLUDED)