[xmcqdpt2]

From the example in the article (exp) it sounds like they are implementing highly optimized versions of transcendental functions. This is great! One of the reason gfortran is so much slower than the intel fortran compiler is the slow special functions it uses. However those tricks appear to degrade badly under some LLVM optimizations that are enabled with fastmath.

It makes sense to optimize for the non-fast math case because that's the recommended setting, and I guess having two implementations of all the (very important, easy to mess up, core) special functions + all the testing infra to check that they work correctly on all platforms was probably deemed too much work for marginal benefits.