In my experience writing high end VFX software for three platforms, Linux's libc is the slowest with normal maths functions, and Windows is the fastest.
Intel's math libs are often 4-5x times faster - if you do a microbenchmark of a loop of powf() or sin() functions, it'll be that much faster using the Intel libs.
If building with fmath=fast for fast floating point math, Intel's fast versions are also quite a bit more accurate, and done't produce nans or infs as much.
> Linux's libc is the slowest with normal maths functions
Do you happen to remember which one? There have been a few "sporks" of glibc in the last few years and, if memory serves me correctly, Debian now use eglibc.
I think the sporks were done to address bloat, but I'm also curious if they address speed.
If this includes OS X, I would love to see a source.