using fma makes it possible to write faster libm functions, but going back to a 1 ulp world with the same fma optimizations would give you another 20% speedup a

using fma makes it possible to write faster libm functions, but going back to a 1 ulp world with the same fma optimizations would give you another 20% speedup at least. the other issue is that these functions tend to have much larger code size which tends not to be a significant problem in micro benchmarks, but means that in real applications you increase cache pressure allowing things down in aggregate