I added it to Digital Mars C and C++ in the early 1990s. Also full NaN support in all the math.h functions. AFAIK it was the first C compiler to do it.
It was based on a specification worked out by NCEG (Numerical C Extensions Group), a long forgotten group that tried to modernize C numerics support.
> the fast math is as good as the accurate math
I was more interested in correct results than fast wrong answers.