About 60 weeks ago I had to apply a mailing list patch on top of the most recent GCC master prior to the patch, so GCC would know -mnative for them. It was on the branch that is becoming GCC9.
If it wasn't backported, I'll wish you luck getting decent perf out of them. I recall a double-digit boost in CPU perf compared to GCC7 at -O3 when only allowing the vectoe instructions of Avoton, but not being able to get full instruction scheduling optimization.
They are not slow though, I use them for e.g. irssi/toxic bouncers and such. Uptime is sufficient, if you have backups as you should have.