/// generate_evasions() generates all check evasions when the side to move is
-/// in check. Unlike the other move generation functions, this one generates
-/// only legal moves. It returns the number of generated moves. This
-/// function is very ugly, and needs cleaning up some time later. FIXME
+/// in check. Unlike the other move generation functions, this one generates
+/// only legal moves. It returns the number of generated moves.
int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
assert(pos.piece_on(ksq) == king_of_color(us));
// The bitboard of occupied pieces without our king
- Bitboard b2 = pos.occupied_squares();
- clear_bit(&b2, ksq);
+ Bitboard b_noKing = pos.occupied_squares();
+ clear_bit(&b_noKing, ksq);
// Find squares attacked by slider checkers, we will
// remove them from king evasions set so to avoid a couple
while (b)
{
from = pop_1st_bit(&b);
- checkersAttacks |= bishop_attacks_bb(from, b2);
+ checkersAttacks |= bishop_attacks_bb(from, b_noKing);
}
b = checkers & (pos.queens() | pos.rooks());
while (b)
{
from = pop_1st_bit(&b);
- checkersAttacks |= rook_attacks_bb(from, b2);
+ checkersAttacks |= rook_attacks_bb(from, b_noKing);
}
// Generate evasions for king
{
to = pop_1st_bit(&b1);
// Note that we can use square_is_attacked() only because we
- // have already removed sliders checkers.
+ // have already removed slider checkers.
if (!pos.square_is_attacked(to, them))
(*mlist++).move = make_move(ksq, to);
}
assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
- // Pieces moves
- mlist = generate_piece_blocking_evasions<PAWN>(pos, mlist, us, pinned, blockSquares);
- mlist = generate_piece_blocking_evasions<KNIGHT>(pos, mlist, us, pinned, blockSquares);
- mlist = generate_piece_blocking_evasions<BISHOP>(pos, mlist, us, pinned, blockSquares);
- mlist = generate_piece_blocking_evasions<ROOK>(pos, mlist, us, pinned, blockSquares);
- mlist = generate_piece_blocking_evasions<QUEEN>(pos, mlist, us, pinned, blockSquares);
- }
+ if (blockSquares != EmptyBoardBB)
+ {
+ // Pieces moves
+ mlist = generate_piece_blocking_evasions<PAWN>(pos, mlist, us, pinned, blockSquares);
+ mlist = generate_piece_blocking_evasions<KNIGHT>(pos, mlist, us, pinned, blockSquares);
+ mlist = generate_piece_blocking_evasions<BISHOP>(pos, mlist, us, pinned, blockSquares);
+ mlist = generate_piece_blocking_evasions<ROOK>(pos, mlist, us, pinned, blockSquares);
+ mlist = generate_piece_blocking_evasions<QUEEN>(pos, mlist, us, pinned, blockSquares);
+ }
+ }
- // Finally, the ugly special case of en passant captures. An en passant
- // capture can only be a check evasion if the check is not a discovered
- // check. If pos.ep_square() is set, the last move made must have been
- // a double pawn push. If, furthermore, the checking piece is a pawn,
- // an en passant check evasion may be possible.
- if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them)))
- {
- to = pos.ep_square();
- b1 = pos.pawn_attacks(them, to) & pos.pawns(us);
+ // Finally, the special case of en passant captures. An en passant
+ // capture can only be a check evasion if the check is not a discovered
+ // check. If pos.ep_square() is set, the last move made must have been
+ // a double pawn push. If, furthermore, the checking piece is a pawn,
+ // an en passant check evasion may be possible.
+ if (pos.ep_square() != SQ_NONE && (checkers & pos.pawns(them)))
+ {
+ to = pos.ep_square();
+ b1 = pos.pawn_attacks(them, to) & pos.pawns(us);
- // The checking pawn cannot be a discovered (bishop) check candidate
- // otherwise we were in check also before last double push move.
- assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
- assert(count_1s(b1) == 1 || count_1s(b1) == 2);
+ // The checking pawn cannot be a discovered (bishop) check candidate
+ // otherwise we were in check also before last double push move.
+ assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
+ assert(count_1s(b1) == 1 || count_1s(b1) == 2);
- b1 &= ~pinned;
- while (b1)
- {
- from = pop_1st_bit(&b1);
- // Move is always legal because checking pawn is not a discovered
- // check candidate and our capturing pawn has been already tested
- // against pinned pieces.
- (*mlist++).move = make_ep_move(from, to);
- }
- }
+ b1 &= ~pinned;
+ while (b1)
+ {
+ from = pop_1st_bit(&b1);
+ // Move is always legal because checking pawn is not a discovered
+ // check candidate and our capturing pawn has been already tested
+ // against pinned pieces.
+ (*mlist++).move = make_ep_move(from, to);
+ }
+ }
}
return int(mlist - mlist_start);
}