- // Find squares attacked by slider checkers, we will remove them from the king
- // evasions so to skip known illegal moves avoiding useless legality check later.
- do
- {
- ++checkersCnt;
- checksq = pop_lsb(&b);
-
- assert(color_of(pos.piece_on(checksq)) == ~us);
-
- switch (type_of(pos.piece_on(checksq)))
- {
- case BISHOP: sliderAttacks |= PseudoAttacks[BISHOP][checksq]; break;
- case ROOK: sliderAttacks |= PseudoAttacks[ROOK][checksq]; break;
- case QUEEN:
- // If queen and king are far or not on a diagonal line we can safely
- // remove all the squares attacked in the other direction becuase are
- // not reachable by the king anyway.
- if (between_bb(ksq, checksq) || !(PseudoAttacks[BISHOP][checksq] & ksq))
- sliderAttacks |= PseudoAttacks[QUEEN][checksq];
-
- // Otherwise we need to use real rook attacks to check if king is safe
- // to move in the other direction. For example: king in B2, queen in A1
- // a knight in B1, and we can safely move to C1.
- else
- sliderAttacks |= PseudoAttacks[BISHOP][checksq] | pos.attacks_from<ROOK>(checksq);
-
- default:
- break;
- }
- } while (b);
-
- // Generate evasions for king, capture and non capture moves
- b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;
- SERIALIZE(b);
-
- if (checkersCnt > 1)
- return mlist; // Double check, only a king move can save the day
-
- // Generate blocking evasions or captures of the checking piece
- Bitboard target = between_bb(checksq, ksq) | checksq;
-
- return us == WHITE ? generate_all<WHITE, EVASIONS>(pos, mlist, target)
- : generate_all<BLACK, EVASIONS>(pos, mlist, target);
+ if (more_than_one(pos.checkers()))
+ return moveList; // Double check, only a king move can save the day
+
+ // Generate blocking interpositions or captures of the checking piece
+ return us == WHITE ? generate_all<WHITE, EVASIONS>(pos, moveList)
+ : generate_all<BLACK, EVASIONS>(pos, moveList);