/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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
#ifndef BITBOARD_H_INCLUDED
#define BITBOARD_H_INCLUDED
-#include "types.h"
+#include <string>
-extern Bitboard pext(Bitboard b, Bitboard mask);
+#include "types.h"
-namespace Bitboards {
+namespace Bitbases {
void init();
-const std::string pretty(Bitboard b);
+bool probe(Square wksq, Square wpsq, Square bksq, Color us);
}
-namespace Bitbases {
+namespace Bitboards {
-void init_kpk();
-bool probe_kpk(Square wksq, Square wpsq, Square bksq, Color us);
+void init();
+const std::string pretty(Bitboard b);
}
-const Bitboard FileABB = 0x0101010101010101ULL;
-const Bitboard FileBBB = FileABB << 1;
-const Bitboard FileCBB = FileABB << 2;
-const Bitboard FileDBB = FileABB << 3;
-const Bitboard FileEBB = FileABB << 4;
-const Bitboard FileFBB = FileABB << 5;
-const Bitboard FileGBB = FileABB << 6;
-const Bitboard FileHBB = FileABB << 7;
+constexpr Bitboard AllSquares = ~Bitboard(0);
+constexpr Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
+
+constexpr Bitboard FileABB = 0x0101010101010101ULL;
+constexpr Bitboard FileBBB = FileABB << 1;
+constexpr Bitboard FileCBB = FileABB << 2;
+constexpr Bitboard FileDBB = FileABB << 3;
+constexpr Bitboard FileEBB = FileABB << 4;
+constexpr Bitboard FileFBB = FileABB << 5;
+constexpr Bitboard FileGBB = FileABB << 6;
+constexpr Bitboard FileHBB = FileABB << 7;
-const Bitboard Rank1BB = 0xFF;
-const Bitboard Rank2BB = Rank1BB << (8 * 1);
-const Bitboard Rank3BB = Rank1BB << (8 * 2);
-const Bitboard Rank4BB = Rank1BB << (8 * 3);
-const Bitboard Rank5BB = Rank1BB << (8 * 4);
-const Bitboard Rank6BB = Rank1BB << (8 * 5);
-const Bitboard Rank7BB = Rank1BB << (8 * 6);
-const Bitboard Rank8BB = Rank1BB << (8 * 7);
+constexpr Bitboard Rank1BB = 0xFF;
+constexpr Bitboard Rank2BB = Rank1BB << (8 * 1);
+constexpr Bitboard Rank3BB = Rank1BB << (8 * 2);
+constexpr Bitboard Rank4BB = Rank1BB << (8 * 3);
+constexpr Bitboard Rank5BB = Rank1BB << (8 * 4);
+constexpr Bitboard Rank6BB = Rank1BB << (8 * 5);
+constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);
+constexpr Bitboard Rank8BB = Rank1BB << (8 * 7);
-CACHE_LINE_ALIGNMENT
+constexpr Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
+constexpr Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
+constexpr Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
+constexpr Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
-extern Bitboard RMasks[SQUARE_NB];
-extern Bitboard RMagics[SQUARE_NB];
-extern Bitboard* RAttacks[SQUARE_NB];
-extern unsigned RShifts[SQUARE_NB];
+constexpr Bitboard KingFlank[FILE_NB] = {
+ QueenSide ^ FileDBB, QueenSide, QueenSide,
+ CenterFiles, CenterFiles,
+ KingSide, KingSide, KingSide ^ FileEBB
+};
-extern Bitboard BMasks[SQUARE_NB];
-extern Bitboard BMagics[SQUARE_NB];
-extern Bitboard* BAttacks[SQUARE_NB];
-extern unsigned BShifts[SQUARE_NB];
+extern uint8_t PopCnt16[1 << 16];
+extern uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
extern Bitboard SquareBB[SQUARE_NB];
-extern Bitboard FileBB[FILE_NB];
-extern Bitboard RankBB[RANK_NB];
-extern Bitboard AdjacentFilesBB[FILE_NB];
-extern Bitboard InFrontBB[COLOR_NB][RANK_NB];
-extern Bitboard StepAttacksBB[PIECE_NB][SQUARE_NB];
-extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
-extern Bitboard DistanceRingsBB[SQUARE_NB][8];
-extern Bitboard ForwardBB[COLOR_NB][SQUARE_NB];
-extern Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
-extern Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
+extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];
-extern int SquareDistance[SQUARE_NB][SQUARE_NB];
-const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
+/// Magic holds all magic bitboards relevant data for a single square
+struct Magic {
+ Bitboard mask;
+ Bitboard magic;
+ Bitboard* attacks;
+ unsigned shift;
+
+ // Compute the attack's index using the 'magic bitboards' approach
+ unsigned index(Bitboard occupied) const {
+
+ if (HasPext)
+ return unsigned(pext(occupied, mask));
+
+ if (Is64Bit)
+ return unsigned(((occupied & mask) * magic) >> shift);
+
+ unsigned lo = unsigned(occupied) & unsigned(mask);
+ unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
+ return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
+ }
+};
+
+extern Magic RookMagics[SQUARE_NB];
+extern Magic BishopMagics[SQUARE_NB];
+
+inline Bitboard square_bb(Square s) {
+ assert(is_ok(s));
+ return SquareBB[s];
+}
+
/// Overloads of bitwise operators between a Bitboard and a Square for testing
/// whether a given bit is set in a bitboard, and for setting and clearing bits.
-inline Bitboard operator&(Bitboard b, Square s) {
- return b & SquareBB[s];
-}
+inline Bitboard operator&( Bitboard b, Square s) { return b & square_bb(s); }
+inline Bitboard operator|( Bitboard b, Square s) { return b | square_bb(s); }
+inline Bitboard operator^( Bitboard b, Square s) { return b ^ square_bb(s); }
+inline Bitboard& operator|=(Bitboard& b, Square s) { return b |= square_bb(s); }
+inline Bitboard& operator^=(Bitboard& b, Square s) { return b ^= square_bb(s); }
-inline Bitboard& operator|=(Bitboard& b, Square s) {
- return b |= SquareBB[s];
-}
+inline Bitboard operator&(Square s, Bitboard b) { return b & s; }
+inline Bitboard operator|(Square s, Bitboard b) { return b | s; }
+inline Bitboard operator^(Square s, Bitboard b) { return b ^ s; }
-inline Bitboard& operator^=(Bitboard& b, Square s) {
- return b ^= SquareBB[s];
-}
+inline Bitboard operator|(Square s1, Square s2) { return square_bb(s1) | s2; }
-inline Bitboard operator|(Bitboard b, Square s) {
- return b | SquareBB[s];
+constexpr bool more_than_one(Bitboard b) {
+ return b & (b - 1);
}
-inline Bitboard operator^(Bitboard b, Square s) {
- return b ^ SquareBB[s];
+/// Counts the occupation of the bitboard depending on the occupation of SQ_A1
+/// as in `b & (1ULL << SQ_A1) ? more_than_two(b) : more_than_one(b)`
+
+constexpr bool conditional_more_than_two(Bitboard b) {
+ return b & (b - 1) & (b - 2);
}
-inline bool more_than_one(Bitboard b) {
- return b & (b - 1);
+constexpr bool opposite_colors(Square s1, Square s2) {
+ return (s1 + rank_of(s1) + s2 + rank_of(s2)) & 1;
}
-inline int square_distance(Square s1, Square s2) {
- return SquareDistance[s1][s2];
+
+/// rank_bb() and file_bb() return a bitboard representing all the squares on
+/// the given file or rank.
+
+constexpr Bitboard rank_bb(Rank r) {
+ return Rank1BB << (8 * r);
}
-inline int file_distance(Square s1, Square s2) {
- return abs(file_of(s1) - file_of(s2));
+constexpr Bitboard rank_bb(Square s) {
+ return rank_bb(rank_of(s));
}
-inline int rank_distance(Square s1, Square s2) {
- return abs(rank_of(s1) - rank_of(s2));
+constexpr Bitboard file_bb(File f) {
+ return FileABB << f;
}
+constexpr Bitboard file_bb(Square s) {
+ return file_bb(file_of(s));
+}
-/// shift_bb() moves bitboard one step along direction Delta. Mainly for pawns.
-template<Square Delta>
-inline Bitboard shift_bb(Bitboard b) {
+/// shift() moves a bitboard one or two steps as specified by the direction D
- return Delta == DELTA_N ? b << 8 : Delta == DELTA_S ? b >> 8
- : Delta == DELTA_NE ? (b & ~FileHBB) << 9 : Delta == DELTA_SE ? (b & ~FileHBB) >> 7
- : Delta == DELTA_NW ? (b & ~FileABB) << 7 : Delta == DELTA_SW ? (b & ~FileABB) >> 9
+template<Direction D>
+constexpr Bitboard shift(Bitboard b) {
+ return D == NORTH ? b << 8 : D == SOUTH ? b >> 8
+ : D == NORTH+NORTH? b <<16 : D == SOUTH+SOUTH? b >>16
+ : D == EAST ? (b & ~FileHBB) << 1 : D == WEST ? (b & ~FileABB) >> 1
+ : D == NORTH_EAST ? (b & ~FileHBB) << 9 : D == NORTH_WEST ? (b & ~FileABB) << 7
+ : D == SOUTH_EAST ? (b & ~FileHBB) >> 7 : D == SOUTH_WEST ? (b & ~FileABB) >> 9
: 0;
}
-/// rank_bb() and file_bb() take a file or a square as input and return
-/// a bitboard representing all squares on the given file or rank.
+/// pawn_attacks_bb() returns the squares attacked by pawns of the given color
+/// from the squares in the given bitboard.
-inline Bitboard rank_bb(Rank r) {
- return RankBB[r];
+template<Color C>
+constexpr Bitboard pawn_attacks_bb(Bitboard b) {
+ return C == WHITE ? shift<NORTH_WEST>(b) | shift<NORTH_EAST>(b)
+ : shift<SOUTH_WEST>(b) | shift<SOUTH_EAST>(b);
}
-inline Bitboard rank_bb(Square s) {
- return RankBB[rank_of(s)];
-}
+inline Bitboard pawn_attacks_bb(Color c, Square s) {
-inline Bitboard file_bb(File f) {
- return FileBB[f];
+ assert(is_ok(s));
+ return PawnAttacks[c][s];
}
-inline Bitboard file_bb(Square s) {
- return FileBB[file_of(s)];
+
+/// pawn_double_attacks_bb() returns the squares doubly attacked by pawns of the
+/// given color from the squares in the given bitboard.
+
+template<Color C>
+constexpr Bitboard pawn_double_attacks_bb(Bitboard b) {
+ return C == WHITE ? shift<NORTH_WEST>(b) & shift<NORTH_EAST>(b)
+ : shift<SOUTH_WEST>(b) & shift<SOUTH_EAST>(b);
}
-/// adjacent_files_bb() takes a file as input and returns a bitboard representing
-/// all squares on the adjacent files.
+/// adjacent_files_bb() returns a bitboard representing all the squares on the
+/// adjacent files of a given square.
-inline Bitboard adjacent_files_bb(File f) {
- return AdjacentFilesBB[f];
+constexpr Bitboard adjacent_files_bb(Square s) {
+ return shift<EAST>(file_bb(s)) | shift<WEST>(file_bb(s));
}
-/// in_front_bb() takes a color and a rank as input, and returns a bitboard
-/// representing all the squares on all ranks in front of the rank, from the
-/// given color's point of view. For instance, in_front_bb(BLACK, RANK_3) will
-/// give all squares on ranks 1 and 2.
+/// line_bb() returns a bitboard representing an entire line (from board edge
+/// to board edge) that intersects the two given squares. If the given squares
+/// are not on a same file/rank/diagonal, the function returns 0. For instance,
+/// line_bb(SQ_C4, SQ_F7) will return a bitboard with the A2-G8 diagonal.
+
+inline Bitboard line_bb(Square s1, Square s2) {
-inline Bitboard in_front_bb(Color c, Rank r) {
- return InFrontBB[c][r];
+ assert(is_ok(s1) && is_ok(s2));
+ return LineBB[s1][s2];
}
-/// between_bb() returns a bitboard representing all squares between two squares.
-/// For instance, between_bb(SQ_C4, SQ_F7) returns a bitboard with the bits for
-/// square d5 and e6 set. If s1 and s2 are not on the same rank, file or diagonal,
-/// 0 is returned.
+/// between_bb() returns a bitboard representing squares that are linearly
+/// between the two given squares (excluding the given squares). If the given
+/// squares are not on a same file/rank/diagonal, we return 0. For instance,
+/// between_bb(SQ_C4, SQ_F7) will return a bitboard with squares D5 and E6.
inline Bitboard between_bb(Square s1, Square s2) {
- return BetweenBB[s1][s2];
+ Bitboard b = line_bb(s1, s2) & ((AllSquares << s1) ^ (AllSquares << s2));
+ return b & (b - 1); //exclude lsb
}
-/// forward_bb() takes a color and a square as input, and returns a bitboard
-/// representing all squares along the line in front of the square, from the
-/// point of view of the given color. Definition of the table is:
-/// ForwardBB[c][s] = in_front_bb(c, s) & file_bb(s)
+/// forward_ranks_bb() returns a bitboard representing the squares on the ranks
+/// in front of the given one, from the point of view of the given color. For instance,
+/// forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
-inline Bitboard forward_bb(Color c, Square s) {
- return ForwardBB[c][s];
+constexpr Bitboard forward_ranks_bb(Color c, Square s) {
+ return c == WHITE ? ~Rank1BB << 8 * relative_rank(WHITE, s)
+ : ~Rank8BB >> 8 * relative_rank(BLACK, s);
}
-/// pawn_attack_span() takes a color and a square as input, and returns a bitboard
-/// representing all squares that can be attacked by a pawn of the given color
-/// when it moves along its file starting from the given square. Definition is:
-/// PawnAttackSpan[c][s] = in_front_bb(c, s) & adjacent_files_bb(s);
+/// forward_file_bb() returns a bitboard representing all the squares along the
+/// line in front of the given one, from the point of view of the given color.
-inline Bitboard pawn_attack_span(Color c, Square s) {
- return PawnAttackSpan[c][s];
+constexpr Bitboard forward_file_bb(Color c, Square s) {
+ return forward_ranks_bb(c, s) & file_bb(s);
}
-/// passed_pawn_mask() takes a color and a square as input, and returns a
-/// bitboard mask which can be used to test if a pawn of the given color on
-/// the given square is a passed pawn. Definition of the table is:
-/// PassedPawnMask[c][s] = pawn_attack_span(c, s) | forward_bb(c, s)
+/// pawn_attack_span() returns a bitboard representing all the squares that can
+/// be attacked by a pawn of the given color when it moves along its file, starting
+/// from the given square.
-inline Bitboard passed_pawn_mask(Color c, Square s) {
- return PassedPawnMask[c][s];
+constexpr Bitboard pawn_attack_span(Color c, Square s) {
+ return forward_ranks_bb(c, s) & adjacent_files_bb(s);
}
-/// squares_of_color() returns a bitboard representing all squares with the same
-/// color of the given square.
+/// passed_pawn_span() returns a bitboard which can be used to test if a pawn of
+/// the given color and on the given square is a passed pawn.
-inline Bitboard squares_of_color(Square s) {
- return DarkSquares & s ? DarkSquares : ~DarkSquares;
+constexpr Bitboard passed_pawn_span(Color c, Square s) {
+ return pawn_attack_span(c, s) | forward_file_bb(c, s);
}
-/// aligned() returns true if the squares s1, s2 and s3 are aligned
-/// either on a straight or on a diagonal line.
+/// aligned() returns true if the squares s1, s2 and s3 are aligned either on a
+/// straight or on a diagonal line.
inline bool aligned(Square s1, Square s2, Square s3) {
- return LineBB[s1][s2] & s3;
+ return line_bb(s1, s2) & s3;
}
-/// Functions for computing sliding attack bitboards. Function attacks_bb() takes
-/// a square and a bitboard of occupied squares as input, and returns a bitboard
-/// representing all squares attacked by Pt (bishop or rook) on the given square.
-template<PieceType Pt>
-FORCE_INLINE unsigned magic_index(Square s, Bitboard occ) {
+/// distance() functions return the distance between x and y, defined as the
+/// number of steps for a king in x to reach y.
+
+template<typename T1 = Square> inline int distance(Square x, Square y);
+template<> inline int distance<File>(Square x, Square y) { return std::abs(file_of(x) - file_of(y)); }
+template<> inline int distance<Rank>(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); }
+template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
+
+inline int edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
+inline int edge_distance(Rank r) { return std::min(r, Rank(RANK_8 - r)); }
- Bitboard* const Masks = Pt == ROOK ? RMasks : BMasks;
- Bitboard* const Magics = Pt == ROOK ? RMagics : BMagics;
- unsigned* const Shifts = Pt == ROOK ? RShifts : BShifts;
- if (Is64Bit)
- return unsigned(((occ & Masks[s]) * Magics[s]) >> Shifts[s]);
+/// safe_destination() returns the bitboard of target square for the given step
+/// from the given square. If the step is off the board, returns empty bitboard.
- unsigned lo = unsigned(occ) & unsigned(Masks[s]);
- unsigned hi = unsigned(occ >> 32) & unsigned(Masks[s] >> 32);
- return (lo * unsigned(Magics[s]) ^ hi * unsigned(Magics[s] >> 32)) >> Shifts[s];
+inline Bitboard safe_destination(Square s, int step)
+{
+ Square to = Square(s + step);
+ return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
}
+
+/// attacks_bb(Square) returns the pseudo attacks of the give piece type
+/// assuming an empty board.
+
template<PieceType Pt>
-inline Bitboard attacks_bb(Square s, Bitboard occ) {
- return (Pt == ROOK ? RAttacks : BAttacks)[s][magic_index<Pt>(s, occ)];
+inline Bitboard attacks_bb(Square s) {
+
+ assert((Pt != PAWN) && (is_ok(s)));
+
+ return PseudoAttacks[Pt][s];
}
-inline Bitboard attacks_bb(Piece pc, Square s, Bitboard occ) {
- switch (type_of(pc))
+/// attacks_bb(Square, Bitboard) returns the attacks by the given piece
+/// assuming the board is occupied according to the passed Bitboard.
+/// Sliding piece attacks do not continue passed an occupied square.
+
+template<PieceType Pt>
+inline Bitboard attacks_bb(Square s, Bitboard occupied) {
+
+ assert((Pt != PAWN) && (is_ok(s)));
+
+ switch (Pt)
{
- case BISHOP: return attacks_bb<BISHOP>(s, occ);
- case ROOK : return attacks_bb<ROOK>(s, occ);
- case QUEEN : return attacks_bb<BISHOP>(s, occ) | attacks_bb<ROOK>(s, occ);
- default : return StepAttacksBB[pc][s];
+ case BISHOP: return BishopMagics[s].attacks[BishopMagics[s].index(occupied)];
+ case ROOK : return RookMagics[s].attacks[ RookMagics[s].index(occupied)];
+ case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
+ default : return PseudoAttacks[Pt][s];
}
}
-/// lsb()/msb() finds the least/most significant bit in a non-zero bitboard.
-/// pop_lsb() finds and clears the least significant bit in a non-zero bitboard.
+inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
-#ifdef USE_BSFQ
+ assert((pt != PAWN) && (is_ok(s)));
-# if defined(_MSC_VER) && !defined(__INTEL_COMPILER)
+ switch (pt)
+ {
+ case BISHOP: return attacks_bb<BISHOP>(s, occupied);
+ case ROOK : return attacks_bb< ROOK>(s, occupied);
+ case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
+ default : return PseudoAttacks[pt][s];
+ }
+}
+
+
+/// popcount() counts the number of non-zero bits in a bitboard
+
+inline int popcount(Bitboard b) {
+
+#ifndef USE_POPCNT
+
+ union { Bitboard bb; uint16_t u[4]; } v = { b };
+ return PopCnt16[v.u[0]] + PopCnt16[v.u[1]] + PopCnt16[v.u[2]] + PopCnt16[v.u[3]];
+
+#elif defined(_MSC_VER) || defined(__INTEL_COMPILER)
+
+ return (int)_mm_popcnt_u64(b);
+
+#else // Assumed gcc or compatible compiler
+
+ return __builtin_popcountll(b);
+
+#endif
+}
+
+
+/// lsb() and msb() return the least/most significant bit in a non-zero bitboard
+
+#if defined(__GNUC__) // GCC, Clang, ICC
+
+inline Square lsb(Bitboard b) {
+ assert(b);
+ return Square(__builtin_ctzll(b));
+}
+
+inline Square msb(Bitboard b) {
+ assert(b);
+ return Square(63 ^ __builtin_clzll(b));
+}
-FORCE_INLINE Square lsb(Bitboard b) {
+#elif defined(_MSC_VER) // MSVC
+
+#ifdef _WIN64 // MSVC, WIN64
+
+inline Square lsb(Bitboard b) {
+ assert(b);
unsigned long idx;
_BitScanForward64(&idx, b);
return (Square) idx;
}
-FORCE_INLINE Square msb(Bitboard b) {
+inline Square msb(Bitboard b) {
+ assert(b);
unsigned long idx;
_BitScanReverse64(&idx, b);
return (Square) idx;
}
-# elif defined(__arm__)
+#else // MSVC, WIN32
-FORCE_INLINE int lsb32(uint32_t v) {
- __asm__("rbit %0, %1" : "=r"(v) : "r"(v));
- return __builtin_clz(v);
-}
+inline Square lsb(Bitboard b) {
+ assert(b);
+ unsigned long idx;
-FORCE_INLINE Square msb(Bitboard b) {
- return (Square) (63 - __builtin_clzll(b));
+ if (b & 0xffffffff) {
+ _BitScanForward(&idx, int32_t(b));
+ return Square(idx);
+ } else {
+ _BitScanForward(&idx, int32_t(b >> 32));
+ return Square(idx + 32);
+ }
}
-FORCE_INLINE Square lsb(Bitboard b) {
- return (Square) (uint32_t(b) ? lsb32(uint32_t(b)) : 32 + lsb32(uint32_t(b >> 32)));
+inline Square msb(Bitboard b) {
+ assert(b);
+ unsigned long idx;
+
+ if (b >> 32) {
+ _BitScanReverse(&idx, int32_t(b >> 32));
+ return Square(idx + 32);
+ } else {
+ _BitScanReverse(&idx, int32_t(b));
+ return Square(idx);
+ }
}
-# else
+#endif
-FORCE_INLINE Square lsb(Bitboard b) { // Assembly code by Heinz van Saanen
- Bitboard idx;
- __asm__("bsfq %1, %0": "=r"(idx): "rm"(b) );
- return (Square) idx;
-}
+#else // Compiler is neither GCC nor MSVC compatible
+
+#error "Compiler not supported."
+
+#endif
-FORCE_INLINE Square msb(Bitboard b) {
- Bitboard idx;
- __asm__("bsrq %1, %0": "=r"(idx): "rm"(b) );
- return (Square) idx;
-}
-# endif
+/// pop_lsb() finds and clears the least significant bit in a non-zero bitboard
-FORCE_INLINE Square pop_lsb(Bitboard* b) {
+inline Square pop_lsb(Bitboard* b) {
+ assert(*b);
const Square s = lsb(*b);
*b &= *b - 1;
return s;
}
-#else // if defined(USE_BSFQ)
-extern Square msb(Bitboard b);
-extern Square lsb(Bitboard b);
-extern Square pop_lsb(Bitboard* b);
-
-#endif
-
-/// frontmost_sq() and backmost_sq() find the square corresponding to the
-/// most/least advanced bit relative to the given color.
-
-inline Square frontmost_sq(Color c, Bitboard b) { return c == WHITE ? msb(b) : lsb(b); }
-inline Square backmost_sq(Color c, Bitboard b) { return c == WHITE ? lsb(b) : msb(b); }
+/// frontmost_sq() returns the most advanced square for the given color,
+/// requires a non-zero bitboard.
+inline Square frontmost_sq(Color c, Bitboard b) {
+ assert(b);
+ return c == WHITE ? msb(b) : lsb(b);
+}
#endif // #ifndef BITBOARD_H_INCLUDED
projects / stockfish / blobdiff