No. Changing the rounding behavior of floating point code is not generally OK. Numerical algorithms are often extremely carefully written and it is totally unpredictable what adding more precision can do. For example, adding more precision can actually make some algorithms diverge, or take many more iterations to converge, because when designing an algorithm with higher-level knowledge, the rounding behavior can be exploited on purpose.

Automatic FMA is absolutely an unsafe optimization. Don't do it unless software requests it.