Reduce amount of branching and work duplication in generate_moves.

BM123499 · Sopel97 · commit 22a8c4be06fe · 2021-01-11T21:43:05.000+01:00
diff --git a/src/movegen.cpp b/src/movegen.cpp
@@ -180,17 +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));
