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Small micro optimization in generate_evasions()

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No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-09-21 07:55:26 +01:00
parent a7cb05b1eb
commit 746bcb348f
1 changed files with 10 additions and 11 deletions
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21
src/movegen.cpp
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@ -225,6 +225,8 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
Color us = pos.side_to_move(); Color us = pos.side_to_move();
Color them = opposite_color(us); Color them = opposite_color(us);
Square ksq = pos.king_square(us); Square ksq = pos.king_square(us);
Bitboard sliderAttacks = EmptyBoardBB;
Bitboard checkers = pos.checkers();
assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING)); assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
@ -236,30 +238,28 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
// remove them from king evasions set so to avoid a couple // remove them from king evasions set so to avoid a couple
// of cycles in the slow king evasions legality check loop // of cycles in the slow king evasions legality check loop
// and to be able to use attackers_to(). // and to be able to use attackers_to().
Bitboard checkers = pos.checkers();
Bitboard checkersAttacks = EmptyBoardBB;
Bitboard b = checkers & pos.pieces(BISHOP, QUEEN); Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
while (b) while (b)
{ {
from = pop_1st_bit(&b); from = pop_1st_bit(&b);
checkersAttacks |= bishop_attacks_bb(from, b_noKing); sliderAttacks |= bishop_attacks_bb(from, b_noKing);
} }
b = checkers & pos.pieces(ROOK, QUEEN); b = checkers & pos.pieces(ROOK, QUEEN);
while (b) while (b)
{ {
from = pop_1st_bit(&b); from = pop_1st_bit(&b);
checkersAttacks |= rook_attacks_bb(from, b_noKing); sliderAttacks |= rook_attacks_bb(from, b_noKing);
} }
// Generate evasions for king // Generate evasions for king, both captures and non captures
Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~checkersAttacks; Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
Bitboard enemy = pos.pieces_of_color(them); Bitboard enemy = pos.pieces_of_color(them);
while (b1) while (b1)
{ {
to = pop_1st_bit(&b1); to = pop_1st_bit(&b1);
// Note that we can use attackers_to() only because we // Note that we can use attackers_to() only because we
// have already removed slider checkers. // have already removed slider checkers attacked squares.
if (!(pos.attackers_to(to) & enemy)) if (!(pos.attackers_to(to) & enemy))
(*mlist++).move = make_move(ksq, to); (*mlist++).move = make_move(ksq, to);
} }
@ -301,15 +301,14 @@ MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pin
(*mlist++).move = make_move(from, checksq); (*mlist++).move = make_move(from, checksq);
} }
// Blocking check evasions are possible only if the checking piece is // Blocking check evasions are possible only if the checking piece is a slider
// a slider. if (sliderAttacks)
if (checkers & (pos.pieces(BISHOP) | pos.pieces(ROOK) | pos.pieces(QUEEN)))
{ {
Bitboard blockSquares = squares_between(checksq, ksq); Bitboard blockSquares = squares_between(checksq, ksq);
assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB); assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
if (blockSquares != EmptyBoardBB) if (blockSquares)
{ {
mlist = generate_piece_moves<PAWN>(pos, mlist, us, blockSquares, pinned); mlist = generate_piece_moves<PAWN>(pos, mlist, us, blockSquares, pinned);
mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, blockSquares, pinned); mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, blockSquares, pinned);