These files provide a lot of usefull SSE stuff
1.) very fast SSE versions of log/exp/sin/cos/sincos/atan2 …
2.) some highly optimized convinient functions (for example load and store from raw data where only every second value is used LC2VFU and STC2VFU)
3.) selection functions to avoid branches in SSE code (also optimized for machines with SSE4)
I picked up that code some years ago and optimized it further for speedups used in RawTherapee