Changes

If we think about to the occupancy lookup, we may recognize that the outer squares don't matter. There are no more squares behind. The outer squares are either attacked or not - independent from their occupancy state. We can use the '''six inner bits''' only as lookup-index with two additional cheap instructions.

occ unsigned int rankOccX2 = (occ >> rkx8) & 2*63;// 2 times the inner six bit rank occupancy used as index U64 attacks = arrFirstRankAttacks64x8[4*occ rankOccX2 + file];// 8 * rank occupancy + file