https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89853
--- Comment #5 from Peter Bergner <bergner at gcc dot gnu.org> --- (In reply to Martin Liška from comment #4) > Just for the record, my Ryzen machine periodic tester probably improved due > to the revision: > https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=158.377.0&plot.1=41. > 377.0&plot.2=70.377.0&plot.3=31.377.0 > > As seen, it's now about 5% faster than GCC8 branch. Very interesting, thanks for that! Since the two of you both used -O2 and generic tuning (ie, same code), that would tend to agree with my speculation that this is an AMD EPYC specific pipeline issue/hazard/... we're unluckily hitting. Agreed? If so, I'm not sure we can really blame my patch, but if someone could narrow down what the exact issue is that is causing the slowdown, maybe we can mitigate it somehow.
