- // Knight moves
- b1 = pos.knights(us) & ~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) & ~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) & ~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) & ~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);
- }
- }
- }
-
- // 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);
- assert(b1 != EmptyBoardBB);
- b1 &= ~pinned;
- while(b1) {
- from = pop_1st_bit(&b1);
-
- // Before generating the move, we have to make sure it is legal.
- // This is somewhat tricky, because the two disappearing pawns may
- // cause new "discovered checks". We test this by removing the
- // two relevant bits from the occupied squares bitboard, and using
- // the low-level bitboard functions for bishop and rook attacks.
- b2 = pos.occupied_squares();
- clear_bit(&b2, from);
- clear_bit(&b2, checksq);
- if(((bishop_attacks_bb(ksq, b2) & pos.bishops_and_queens(them))
- == EmptyBoardBB) &&
- ((rook_attacks_bb(ksq, b2) & pos.rooks_and_queens(them))
- == EmptyBoardBB))
- mlist[n++].move = make_ep_move(from, to);
+ // 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);
+
+ 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);
+ }