Consolidate some threats code (#894)

No functional change.

Bench: 3142485

Author: protonspring

src/board.rs

@@ -430,7 +430,6 @@ impl Board {
         // This "hack" is used to speed up the implementation of `Board::is_legal`.
         let stm = self.side_to_move();
         let occupancies = self.occupancies() ^ self.colored_pieces(stm, PieceType::King);
-
         let mut threats = pawn_attacks_setwise(self.colored_pieces(!stm, PieceType::Pawn), !stm);
         self.state.piece_threats[PieceType::Pawn] = threats;
 
@@ -466,25 +465,28 @@ impl Board {
             | self.piece_threats(PieceType::Rook)
             | self.piece_threats(PieceType::Queen)
             | self.piece_threats(PieceType::King);
-    }
 
-    /// Updates the checkers bitboard to mark opponent pieces currently threatening our king,
-    /// and our pinned pieces that cannot move without leaving the king in check.
-    pub fn update_king_threats(&mut self) {
-        let stm = self.side_to_move();
-        let our_king = self.king_square(stm);
+        let diagonal = self.pieces2(PieceType::Bishop, PieceType::Queen);
+        let orthogonal = self.pieces2(PieceType::Rook, PieceType::Queen);
 
         self.state.pinned = [Bitboard::default(); 2];
         self.state.pinners = [Bitboard::default(); 2];
-        self.state.checkers = (pawn_attacks(our_king, stm) & self.colored_pieces(!stm, PieceType::Pawn))
-            | (knight_attacks(our_king) & self.colored_pieces(!stm, PieceType::Knight));
-
-        let diagonal = self.pieces2(PieceType::Bishop, PieceType::Queen);
-        let orthogonal = self.pieces2(PieceType::Rook, PieceType::Queen);
 
         for color in [Color::White, Color::Black] {
             let king = self.king_square(color);
 
+            if color == stm {
+                self.state.checkers = (pawn_attacks(king, stm) & self.colored_pieces(!stm, PieceType::Pawn))
+                    | (knight_attacks(king) & self.colored_pieces(!stm, PieceType::Knight));
+            } else {
+                self.state.checking_squares[PieceType::Pawn] = pawn_attacks(king, !stm);
+                self.state.checking_squares[PieceType::Knight] = knight_attacks(king);
+                self.state.checking_squares[PieceType::Bishop] = bishop_attacks(king, self.occupancies());
+                self.state.checking_squares[PieceType::Rook] = rook_attacks(king, self.occupancies());
+                self.state.checking_squares[PieceType::Queen] =
+                    self.checking_squares(PieceType::Bishop) | self.checking_squares(PieceType::Rook);
+            }
+
             let diagonal = diagonal & bishop_attacks(king, self.colors(!color)) & self.colors(!color);
             let orthogonal = orthogonal & rook_attacks(king, self.colors(!color)) & self.colors(!color);
 
@@ -503,14 +505,6 @@ impl Board {
                 }
             }
         }
-
-        let their_king = self.king_square(!stm);
-        self.state.checking_squares[PieceType::Pawn] = pawn_attacks(their_king, !stm);
-        self.state.checking_squares[PieceType::Knight] = knight_attacks(their_king);
-        self.state.checking_squares[PieceType::Bishop] = bishop_attacks(their_king, self.occupancies());
-        self.state.checking_squares[PieceType::Rook] = rook_attacks(their_king, self.occupancies());
-        self.state.checking_squares[PieceType::Queen] =
-            self.checking_squares(PieceType::Bishop) | self.checking_squares(PieceType::Rook);
     }
 
     pub fn update_hash_keys(&mut self) {

src/board/makemove.rs

@@ -13,7 +13,6 @@ impl Board {
         self.state.recapture_square = Square::None;
 
         self.update_threats();
-        self.update_king_threats();
 
         if self.en_passant() != Square::None {
             self.state.key ^= ZOBRIST.en_passant[self.en_passant()];
@@ -131,7 +130,6 @@ impl Board {
         self.state.key ^= ZOBRIST.castling[self.state.castling];
 
         self.update_threats();
-        self.update_king_threats();
         self.update_en_passant();
 
         self.state.repetition = 0;

src/board/parser.rs

@@ -58,7 +58,6 @@ impl Board {
         board.fullmove_number = parts.next().unwrap_or_default().parse().unwrap_or_default();
 
         board.update_threats();
-        board.update_king_threats();
         board.update_hash_keys();
         board.update_en_passant();