Micro optimize Position::move_is_check()

More then optimization it is worth a bit of better
code self documenting.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/direction.h b/src/direction.h
index 4ca264a0291ae5ed59deb21a7170444fcadab32b..f2ba6ec339e407edca596632cb925befcba9ede6 100644 (file)
--- a/src/direction.h
+++ b/src/direction.h
@@ -74,6 +74,13 @@ inline SignedDirection signed_direction_between_squares(Square s1, Square s2) {
   return SignedDirection(SignedDirectionTable[s1][s2]);
 }
 
+inline bool direction_is_diagonal(Square s1, Square s2) {
+  return DirectionTable[s1][s2] & 2;
+}
+
+inline bool direction_is_straight(Square s1, Square s2) {
+  return DirectionTable[s1][s2] < 2;
+}
 
 ////
 //// Prototypes

diff --git a/src/position.cpp b/src/position.cpp
index 2ede62feecd8d7b201baaa9044bf3c59d5241f1a..5a42792eb8a97bc105883a0436cf6cc42f903de5 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -599,19 +599,17 @@ bool Position::move_is_check(Move m, Bitboard dcCandidates) const {
 
   case BISHOP:
     return   (dcCandidates && bit_is_set(dcCandidates, from))
-          || (   direction_between_squares(ksq, to) != DIR_NONE
-              && bit_is_set(piece_attacks<BISHOP>(ksq), to));
+          || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to));
 
   case ROOK:
     return   (dcCandidates && bit_is_set(dcCandidates, from))
-          || (   direction_between_squares(ksq, to) != DIR_NONE
-              && bit_is_set(piece_attacks<ROOK>(ksq), to));
+          || (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to));
 
   case QUEEN:
       // Discovered checks are impossible!
       assert(!bit_is_set(dcCandidates, from));
-      return (   direction_between_squares(ksq, to) != DIR_NONE
-              && bit_is_set(piece_attacks<QUEEN>(ksq), to));
+      return (   (direction_is_straight(ksq, to) && bit_is_set(piece_attacks<ROOK>(ksq), to))
+              || (direction_is_diagonal(ksq, to) && bit_is_set(piece_attacks<BISHOP>(ksq), to)));
 
   case KING:
       // Discovered check?