[onan_barbarian]

It is your comment that is (mildly) misleading.

The SSE version is 16x faster than the x87 FPU version and almost 4x faster than the marvelous method. Further, the marvelous method is a loop and is much more resource-hungry than an instruction that goes away for 5-10 cycles (reciprocal throughput is now 1 cycle) but leaves you with most of your execution resources to do other useful work.

Vectorizing the marvelous method is very likely to be painful, as it has the treatment of a value as both a float and an int - while the xmm registers are dual-purpose operating on one successively as a int and a float causes some extra latency. The use of bit shifts and float operations require these cross-domain transfers...