Did you mean -fbroken-and-not-necessarily-fast-math? [1]

[1] But really, if -ffast-math does turn -funsafe-math-optimizations on, it should have been named similarly. There is a possibility of much safer -ffast-math with almost zero breakage (by assuming a subset of IEEE 754, like the fixed rounding mode). The current -ffast-math is so reckless [2].

[2] https://simonbyrne.github.io/notes/fastmath/#flushing_subnor...

I find that -ffast-math is not so bad, so long as I develop and test with it from the beginning. It's much like any of the other more aggressive optimizations in that sense.

Plus, comparing against strict math as I go tends to highlight where I might have been about to do something dodgy anyway.