Use 16 bits to store a move instead of 17

Shrink of 1 bit so to fit a move in an uint_16 and
possibly a MoveStack in an uint_32.

No functional change.

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

src/move.h

@@ -40,13 +40,12 @@ const int MOVES_MAX = 256;
 
 class Position;
 
-/// A move needs 17 bits to be stored
+/// A move needs 16 bits to be stored
 ///
 /// bit  0- 5: destination square (from 0 to 63)
 /// bit  6-11: origin square (from 0 to 63)
-/// bit 12-14: promotion piece type
-/// bit    15: en passant flag
-/// bit    16: castle flag
+/// bit 12-13: promotion piece type - 2 (from KNIGHT-2 to QUEEN-2)
+/// bit 14-15: special move flag: promotion (1), en passant (2), castle (3)
 ///
 /// Special cases are MOVE_NONE and MOVE_NULL. We can sneak these in
 /// because in any normal move destination square is always different
@@ -153,24 +152,20 @@ inline Square move_to(Move m) {
   return Square(m & 0x3F);
 }
 
-inline PieceType move_promotion_piece(Move m) {
-  return PieceType((int(m) >> 12) & 7);
+inline bool move_is_special(Move m) {
+  return m & (3 << 14);
 }
 
-inline int move_is_special(Move m) {
-  return m & (0x1F << 12);
-}
-
-inline int move_is_promotion(Move m) {
-  return m & (7 << 12);
+inline bool move_is_promotion(Move m) {
+  return (m & (3 << 14)) == (1 << 14);
 }
 
 inline int move_is_ep(Move m) {
-  return m & (1 << 15);
+  return (m & (3 << 14)) == (2 << 14);
 }
 
 inline int move_is_castle(Move m) {
-  return m & (1 << 16);
+  return (m & (3 << 14)) == (3 << 14);
 }
 
 inline bool move_is_short_castle(Move m) {
@@ -181,20 +176,24 @@ inline bool move_is_long_castle(Move m) {
   return move_is_castle(m) && (move_to(m) < move_from(m));
 }
 
-inline Move make_promotion_move(Square from, Square to, PieceType promotion) {
-  return Move(int(to) | (int(from) << 6) | (int(promotion) << 12));
+inline PieceType move_promotion_piece(Move m) {
+  return move_is_promotion(m) ? PieceType(((int(m) >> 12) & 3) + 2) : PIECE_TYPE_NONE;
 }
 
 inline Move make_move(Square from, Square to) {
   return Move(int(to) | (int(from) << 6));
 }
 
-inline Move make_castle_move(Square from, Square to) {
-  return Move(int(to) | (int(from) << 6) | (1 << 16));
+inline Move make_promotion_move(Square from, Square to, PieceType promotion) {
+  return Move(int(to) | (int(from) << 6) | ((int(promotion) - 2) << 12) | (1 << 14));
 }
 
 inline Move make_ep_move(Square from, Square to) {
-  return Move(int(to) | (int(from) << 6) | (1 << 15));
+  return Move(int(to) | (int(from) << 6) | (2 << 14));
+}
+
+inline Move make_castle_move(Square from, Square to) {
+  return Move(int(to) | (int(from) << 6) | (3 << 14));
 }
 
 

src/tt.h

@@ -80,8 +80,8 @@ protected:
 ///
 /// the 32 bits of the data field are so defined
 ///
-/// bit  0-16: move
-/// bit 17-20: not used
+/// bit  0-15: move
+/// bit 16-20: not used
 /// bit 21-22: value type
 /// bit 23-31: generation
 
@@ -91,7 +91,7 @@ public:
   void save(uint32_t k, Value v, ValueType t, Depth d, Move m, int g, Value statV, Value kd) {
 
       key32 = k;
-      data = (m & 0x1FFFF) | (t << 21) | (g << 23);
+      data = (m & 0xFFFF) | (t << 21) | (g << 23);
       value16     = (int16_t)v;
       depth16     = (int16_t)d;
       staticValue = (int16_t)statV;
@@ -101,7 +101,7 @@ public:
 
   uint32_t key() const { return key32; }
   Depth depth() const { return Depth(depth16); }
-  Move move() const { return Move(data & 0x1FFFF); }
+  Move move() const { return Move(data & 0xFFFF); }
   Value value() const { return Value(value16); }
   ValueType type() const { return ValueType((data >> 21) & 3); }
   int generation() const { return data >> 23; }