- // Blocking check evasions are possible only if the checking piece is
- // a slider
- if (checkers & pos.sliders())
- {
- Bitboard blockSquares = squares_between(checksq, ksq);
-
- assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
-
- // Pawn moves. Because a blocking evasion can never be a capture, we
- // only generate pawn pushes. As so often, the code for pawns is a bit
- // ugly, and uses separate clauses for white and black pawns. :-(
- if (us == WHITE)
- {
- // Find non-pinned pawns
- b1 = pos.pawns(WHITE) & not_pinned;
-
- // Single pawn pushes. We don't have to AND with empty squares here,
- // because the blocking squares will always be empty.
- b2 = (b1 << 8) & blockSquares;
- while(b2)
- {
- to = pop_1st_bit(&b2);
-
- assert(pos.piece_on(to) == EMPTY);
-
- if (square_rank(to) == RANK_8)
- {
- mlist[n++].move = make_promotion_move(to - DELTA_N, to, QUEEN);
- mlist[n++].move = make_promotion_move(to - DELTA_N, to, ROOK);
- mlist[n++].move = make_promotion_move(to - DELTA_N, to, BISHOP);
- mlist[n++].move = make_promotion_move(to - DELTA_N, to, KNIGHT);
- } else
- mlist[n++].move = make_move(to - DELTA_N, to);
- }
-
- // Double pawn pushes
- b2 = (((b1 << 8) & pos.empty_squares() & Rank3BB) << 8) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
-
- assert(pos.piece_on(to) == EMPTY);
- assert(square_rank(to) == RANK_4);
-
- mlist[n++].move = make_move(to - DELTA_N - DELTA_N, to);
- }
- } else { // (us == BLACK)
-
- // Find non-pinned pawns
- b1 = pos.pawns(BLACK) & not_pinned;
-
- // Single pawn pushes. We don't have to AND with empty squares here,
- // because the blocking squares will always be empty.
- b2 = (b1 >> 8) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
-
- assert(pos.piece_on(to) == EMPTY);
-
- if (square_rank(to) == RANK_1)
- {
- mlist[n++].move = make_promotion_move(to - DELTA_S, to, QUEEN);
- mlist[n++].move = make_promotion_move(to - DELTA_S, to, ROOK);
- mlist[n++].move = make_promotion_move(to - DELTA_S, to, BISHOP);
- mlist[n++].move = make_promotion_move(to - DELTA_S, to, KNIGHT);
- } else
- mlist[n++].move = make_move(to - DELTA_S, to);
- }
-
- // Double pawn pushes
- b2 = (((b1 >> 8) & pos.empty_squares() & Rank6BB) >> 8) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
-
- assert(pos.piece_on(to) == EMPTY);
- assert(square_rank(to) == RANK_5);
-
- mlist[n++].move = make_move(to - DELTA_S - DELTA_S, to);
- }
- }
-
- // Knight moves
- b1 = pos.knights(us) & not_pinned;
- while (b1)
- {
- from = pop_1st_bit(&b1);
- b2 = pos.knight_attacks(from) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
- mlist[n++].move = make_move(from, to);
- }
- }
-
- // Bishop moves
- b1 = pos.bishops(us) & not_pinned;
- while (b1)
- {
- from = pop_1st_bit(&b1);
- b2 = pos.bishop_attacks(from) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
- mlist[n++].move = make_move(from, to);
- }
- }
-
- // Rook moves
- b1 = pos.rooks(us) & not_pinned;
- while (b1)
- {
- from = pop_1st_bit(&b1);
- b2 = pos.rook_attacks(from) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
- mlist[n++].move = make_move(from, to);
- }
- }
-
- // Queen moves
- b1 = pos.queens(us) & not_pinned;
- while (b1)
- {
- from = pop_1st_bit(&b1);
- b2 = pos.queen_attacks(from) & blockSquares;
- while (b2)
- {
- to = pop_1st_bit(&b2);
- mlist[n++].move = make_move(from, to);
- }
- }
- }