Hacking around with SIMD extensions

Just want to get your feedback on this before I do any more on it. I was just trying to improve the performance of some of the commonly used functions that I was encountering. gcc with the flags modified below DOES pick up these loops and vectorizes them nicely into some small SSE instructions (well, certainly while using -DNUMBER_IS_SINGLE=true anyway, it should work with doubles too). 

FWIW, the Steam hardware survey says almost everything (99.96%) supports SSE2 these days anyway, so I reckon it's reasonable to enable it in release mode. http://store.steampowered.com/hwsurvey/ (click on "Other Settings" at the bottom).