Another PSA is that dynamic libraries compiled with fast-math will also introduce inaccuracies in unrelated libraries in the same executable, as they introduce dynamic initialization that globally changes the floating point environment.
I would think practically all modern FPU code on x86-64 would be using the SIMD registers which have explicit widths.
Actually, no, the x87 FPU instructions are the only ones that won't be affected.
It sets the FTZ/DAZ bits, which exist for SSE instructions but not x87 instructions.