[dheera]

Same point; divide by power of 2 is a fast subtraction operation in float world, while divide by 255 shits all over the whole float

[yongjik]

If your input is an arbitrary float, you need to check for denormals (and maybe NaNs). You can do bitmasking trick to avoid conditional jumps but I'm skeptical you can do it faster than SIMD multiply instruction.