[Bug target/84490] New: 436.cactusADM regressed by 6-8% percent with -Ofast on Zen, compared to gcc 7.2

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84490

            Bug ID: 84490
           Summary: 436.cactusADM regressed by 6-8% percent with -Ofast on
                    Zen, compared to gcc 7.2
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
  Target Milestone: ---

Compared to gcc 7.2, 436.cactusADM is about 8% and 6% slower when run
on an AND Ryzen and an AMD EPYC respectively after compiling it on
trunk with -Ofast (and generic march and tuning).

So far I have not done any bisecting, only verified that this is most
probably unrelated to PR 82362 because r251713 does not seem to have
any effect on the benchmark (the benchmark is already slow with that
revision).