I think this is beyond simply making the variable static/constant. It is the specific value of the constant that is allowing the division to be substituted wit

I think this is beyond simply making the variable static/constant. It is the specific value of the constant that is allowing the division to be substituted with bitwise AND, which then makes it so much faster. I wonder how much the speedup would be if some other near-random value is there for the constant (which is likely beyond the purpose at hand).