@pervognsen FYI tininess detection before/after isn’t just FMA. It’s also FMUL and conversions between FP formats.

On the upside, it only affects the underflow flag unless the program has unmasked that exception (which isn’t portable anyway), or is flushing subnormals (widely supported, but non-standard). So if underflow is already set in your modeled FPSR, and you’re in default IEEE 754 mode (the norm for most programs), you can safely ignore it.

@pervognsen NaN propagation bit is slightly wrong too—754 not only doesn’t specify “which” NaN propagates, but some HW will propagate a NaN result that is not either NaN input (eg ARM with the DN bit set in FPCR).

And only generating one NaN generally won’t save you anyway, unless you have no mechanism to load binary data/reinterpret bit patterns.