https://github.com/tgrysztar/fasm2/blob/master/include/iset/avx.inc#L2650
https://github.com/tgrysztar/fasm2/blob/master/include/iset/avx.inc#L4142

The first set looks more in line with, for example, vadd{pd|ps|sd|ss}, but the first set is missing vfmadd. What happens when a macro is redefined like this for the others?

These are AVX+FMA and AVX512 cases, I needed to combine them into a single set of macros, but apparently I forgot.
As usual, when a macro is redefined, it overwrites the previous version (but may also call the previous version if it does so explicitly).

https://github.com/tgrysztar/fasm2/blob/92be28b09658b94fc128ea602c27256f4ec4cbc1/include/iset/avx.inc#L2649
OK, now there is no fmadd instruction, and, given the redefinition behavior, now vfmaddsub gets assembled as fmadd.

I was convinced I was leaving the other line around, I honestly don't know how this happened.
I redid the commit.