Make enums unsigned

Speed up by using unsigned enums.

Passed STC:
LLR: 2.98 (-2.94,2.94) <0.00,2.00>
Total: 49248 W: 12894 L: 12568 D: 23786
Ptnml(0-2): 119, 5353, 13397, 5593, 16
https://tests.stockfishchess.org/tests/view/695e3e5002d0182a589fe965

closes https://github.com/official-stockfish/Stockfish/pull/6532

No functional change

src/bitboard.cpp

@@ -49,12 +49,15 @@ std::string Bitboards::pretty(Bitboard b) {
 
     std::string s = "+---+---+---+---+---+---+---+---+\n";
 
-    for (Rank r = RANK_8; r >= RANK_1; --r)
+    for (Rank r = RANK_8;; --r)
     {
         for (File f = FILE_A; f <= FILE_H; ++f)
             s += b & make_square(f, r) ? "| X " : "|   ";
 
         s += "| " + std::to_string(1 + r) + "\n+---+---+---+---+---+---+---+---+\n";
+
+        if (r == RANK_1)
+            break;
     }
     s += "  a   b   c   d   e   f   g   h\n";
 

src/movegen.cpp

@@ -47,10 +47,10 @@ template<Direction offset>
 inline Move* splat_pawn_moves(Move* moveList, Bitboard to_bb) {
     alignas(64) static constexpr auto SPLAT_TABLE = [] {
         std::array<Move, 64> table{};
-        for (int8_t i = 0; i < 64; i++)
+        for (int i = 0; i < 64; i++)
         {
-            Square from{std::clamp<int8_t>(i - offset, 0, 63)};
-            table[i] = {Move(from, Square{i})};
+            Square from{uint8_t(std::clamp(i - offset, 0, 63))};
+            table[i] = {Move(from, Square{uint8_t(i)})};
         }
         return table;
     }();
@@ -68,7 +68,7 @@ inline Move* splat_pawn_moves(Move* moveList, Bitboard to_bb) {
 inline Move* splat_moves(Move* moveList, Square from, Bitboard to_bb) {
     alignas(64) static constexpr auto SPLAT_TABLE = [] {
         std::array<Move, 64> table{};
-        for (int8_t i = 0; i < 64; i++)
+        for (uint8_t i = 0; i < 64; i++)
             table[i] = {Move(SQUARE_ZERO, Square{i})};
         return table;
     }();

src/position.cpp

@@ -66,12 +66,15 @@ std::ostream& operator<<(std::ostream& os, const Position& pos) {
 
     os << "\n +---+---+---+---+---+---+---+---+\n";
 
-    for (Rank r = RANK_8; r >= RANK_1; --r)
+    for (Rank r = RANK_8;; --r)
     {
         for (File f = FILE_A; f <= FILE_H; ++f)
             os << " | " << PieceToChar[pos.piece_on(make_square(f, r))];
 
         os << " | " << (1 + r) << "\n +---+---+---+---+---+---+---+---+\n";
+
+        if (r == RANK_1)
+            break;
     }
 
     os << "   a   b   c   d   e   f   g   h\n"
@@ -416,7 +419,7 @@ string Position::fen() const {
     int                emptyCnt;
     std::ostringstream ss;
 
-    for (Rank r = RANK_8; r >= RANK_1; --r)
+    for (Rank r = RANK_8;; --r)
     {
         for (File f = FILE_A; f <= FILE_H; ++f)
         {
@@ -430,8 +433,9 @@ string Position::fen() const {
                 ss << PieceToChar[piece_on(make_square(f, r))];
         }
 
-        if (r > RANK_1)
-            ss << '/';
+        if (r == RANK_1)
+            break;
+        ss << '/';
     }
 
     ss << (sideToMove == WHITE ? " w " : " b ");
@@ -1477,10 +1481,13 @@ void Position::flip() {
     string            f, token;
     std::stringstream ss(fen());
 
-    for (Rank r = RANK_8; r >= RANK_1; --r)  // Piece placement
+    for (Rank r = RANK_8;; --r)  // Piece placement
     {
         std::getline(ss, token, r > RANK_1 ? '/' : ' ');
         f.insert(0, token + (f.empty() ? " " : "/"));
+
+        if (r == RANK_1)
+            break;
     }
 
     ss >> token;                        // Active color

src/timeman.h

@@ -26,7 +26,7 @@
 namespace Stockfish {
 
 class OptionsMap;
-enum Color : int8_t;
+enum Color : uint8_t;
 
 namespace Search {
 struct LimitsType;

src/types.h

@@ -117,13 +117,13 @@ using Bitboard = uint64_t;
 constexpr int MAX_MOVES = 256;
 constexpr int MAX_PLY   = 246;
 
-enum Color : int8_t {
+enum Color : uint8_t {
     WHITE,
     BLACK,
     COLOR_NB = 2
 };
 
-enum CastlingRights : int8_t {
+enum CastlingRights : uint8_t {
     NO_CASTLING,
     WHITE_OO,
     WHITE_OOO = WHITE_OO << 1,
@@ -139,7 +139,7 @@ enum CastlingRights : int8_t {
     CASTLING_RIGHT_NB = 16
 };
 
-enum Bound : int8_t {
+enum Bound : uint8_t {
     BOUND_NONE,
     BOUND_UPPER,
     BOUND_LOWER,
@@ -190,13 +190,13 @@ constexpr Value QueenValue  = 2538;
 
 
 // clang-format off
-enum PieceType : std::int8_t {
+enum PieceType : std::uint8_t {
     NO_PIECE_TYPE, PAWN, KNIGHT, BISHOP, ROOK, QUEEN, KING,
     ALL_PIECES = 0,
     PIECE_TYPE_NB = 8
 };
 
-enum Piece : std::int8_t {
+enum Piece : std::uint8_t {
     NO_PIECE,
     W_PAWN = PAWN,     W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
     B_PAWN = PAWN + 8, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING,
@@ -227,7 +227,7 @@ constexpr Depth DEPTH_UNSEARCHED   = -2;
 constexpr Depth DEPTH_ENTRY_OFFSET = -3;
 
 // clang-format off
-enum Square : int8_t {
+enum Square : uint8_t {
     SQ_A1, SQ_B1, SQ_C1, SQ_D1, SQ_E1, SQ_F1, SQ_G1, SQ_H1,
     SQ_A2, SQ_B2, SQ_C2, SQ_D2, SQ_E2, SQ_F2, SQ_G2, SQ_H2,
     SQ_A3, SQ_B3, SQ_C3, SQ_D3, SQ_E3, SQ_F3, SQ_G3, SQ_H3,
@@ -255,7 +255,7 @@ enum Direction : int8_t {
     NORTH_WEST = NORTH + WEST
 };
 
-enum File : int8_t {
+enum File : uint8_t {
     FILE_A,
     FILE_B,
     FILE_C,
@@ -267,7 +267,7 @@ enum File : int8_t {
     FILE_NB
 };
 
-enum Rank : int8_t {
+enum Rank : uint8_t {
     RANK_1,
     RANK_2,
     RANK_3,
@@ -406,7 +406,7 @@ constexpr Key make_key(uint64_t seed) {
 }
 
 
-enum MoveType {
+enum MoveType : uint16_t {
     NORMAL,
     PROMOTION  = 1 << 14,
     EN_PASSANT = 2 << 14,

src/uci.h

@@ -33,7 +33,7 @@ namespace Stockfish {
 class Position;
 class Move;
 class Score;
-enum Square : int8_t;
+enum Square : uint8_t;
 using Value = int;
 
 class UCIEngine {