constexpr Direction UpLeft = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
const Square ksq = pos.square<KING>(Them);
- Bitboard emptySquares;
+ const Bitboard emptySquares = Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces();
+ const Bitboard enemies = Type == EVASIONS ? pos.checkers()
+ : Type == CAPTURES ? target : pos.pieces(Them);
Bitboard pawnsOn7 = pos.pieces(Us, PAWN) & TRank7BB;
Bitboard pawnsNotOn7 = pos.pieces(Us, PAWN) & ~TRank7BB;
- Bitboard enemies = (Type == EVASIONS ? pos.checkers()
- : Type == CAPTURES ? target : pos.pieces(Them));
-
// Single and double pawn pushes, no promotions
if (Type != CAPTURES)
{
- emptySquares = (Type == QUIETS || Type == QUIET_CHECKS ? target : ~pos.pieces());
-
Bitboard b1 = shift<Up>(pawnsNotOn7) & emptySquares;
Bitboard b2 = shift<Up>(b1 & TRank3BB) & emptySquares;
if (Type == QUIET_CHECKS)
{
- b1 &= pawn_attacks_bb(Them, ksq);
- b2 &= pawn_attacks_bb(Them, ksq);
-
- // Add pawn pushes which give discovered check. This is possible only
- // if the pawn is not on the same file as the enemy king, because we
- // don't generate captures. Note that a possible discovered check
- // promotion has been already generated amongst the captures.
- Bitboard dcCandidateQuiets = pos.blockers_for_king(Them) & pawnsNotOn7;
- if (dcCandidateQuiets)
- {
- Bitboard dc1 = shift<Up>(dcCandidateQuiets) & emptySquares & ~file_bb(ksq);
- Bitboard dc2 = shift<Up>(dc1 & TRank3BB) & emptySquares;
-
- b1 |= dc1;
- b2 |= dc2;
- }
+ // To make a quiet check, you either make a direct check by pushing a pawn
+ // or push a blocker pawn that is not on the same file as the enemy king.
+ // Discovered check promotion has been already generated amongst the captures.
+ Bitboard dcCandidatePawns = pos.blockers_for_king(Them) & ~file_bb(ksq);
+ b1 &= pawn_attacks_bb(Them, ksq) | shift< Up>(dcCandidatePawns);
+ b2 &= pawn_attacks_bb(Them, ksq) | shift<Up+Up>(dcCandidatePawns);
}
while (b1)
// Promotions and underpromotions
if (pawnsOn7)
{
- if (Type == CAPTURES)
- emptySquares = ~pos.pieces();
-
- if (Type == EVASIONS)
- emptySquares &= target;
-
Bitboard b1 = shift<UpRight>(pawnsOn7) & enemies;
Bitboard b2 = shift<UpLeft >(pawnsOn7) & enemies;
Bitboard b3 = shift<Up >(pawnsOn7) & emptySquares;
+ if (Type == EVASIONS)
+ b3 &= target;
+
while (b1)
moveList = make_promotions<Type, UpRight>(moveList, pop_lsb(b1), ksq);
while (bb)
{
Square from = pop_lsb(bb);
-
Bitboard b = attacks_bb<Pt>(from, pos.pieces()) & target;
+
+ // To check, you either move freely a blocker or make a direct check.
if (Checks && (Pt == QUEEN || !(pos.blockers_for_king(~Us) & from)))
b &= pos.check_squares(Pt);