Optimize generate_moves

[stockfish] / src / movegen.cpp

diff --git a/src/movegen.cpp b/src/movegen.cpp
index 5ce2de7c6baa789ed335bc21de24d1ae03249e90..88c31cfa4856643e60ca45c64cfa53706aff1d97 100644 (file)
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -156,10 +156,8 @@ namespace {
         {
             assert(rank_of(pos.ep_square()) == relative_rank(Us, RANK_6));
 
-            // An en passant capture can be an evasion only if the checking piece
-            // is the double pushed pawn and so is in the target. Otherwise this
-            // is a discovery check and we are forced to do otherwise.
-            if (Type == EVASIONS && !(target & (pos.ep_square() - Up)))
+            // An en passant capture cannot resolve a discovered check.
+            if (Type == EVASIONS && (target & (pos.ep_square() + Up)))
                 return moveList;
 
             b1 = pawnsNotOn7 & pawn_attacks_bb(Them, pos.ep_square());
@@ -182,17 +180,17 @@ namespace {
 
     Bitboard bb = piecesToMove & pos.pieces(Pt);
 
+    if (!bb)
+        return moveList;
+
+    [[maybe_unused]] const Bitboard checkSquares = pos.check_squares(Pt);
+
     while (bb) {
         Square from = pop_lsb(&bb);
 
-        if (Checks && (Pt == BISHOP || Pt == ROOK || Pt == QUEEN)
-            && !(attacks_bb<Pt>(from) & target & pos.check_squares(Pt)))
-            continue;
-
         Bitboard b = attacks_bb<Pt>(from, pos.pieces()) & target;
-
-        if (Checks)
-            b &= pos.check_squares(Pt);
+        if constexpr (Checks)
+            b &= checkSquares;
 
         while (b)
             *moveList++ = make_move(from, pop_lsb(&b));
@@ -204,6 +202,9 @@ namespace {
 
   template<Color Us, GenType Type>
   ExtMove* generate_all(const Position& pos, ExtMove* moveList) {
+
+    static_assert(Type != LEGAL, "Unsupported type in generate_all()");
+
     constexpr bool Checks = Type == QUIET_CHECKS; // Reduce template instantations
     Bitboard target, piecesToMove = pos.pieces(Us);
 
@@ -228,8 +229,6 @@ namespace {
         case NON_EVASIONS:
             target = ~pos.pieces(Us);
             break;
-        default:
-            static_assert(true, "Unsupported type in generate_all()");
     }
 
     moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);