https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120941

--- Comment #11 from Filip Kastl <pheeck at gcc dot gnu.org> ---
(In reply to H.J. Lu from comment #9)
> Created attachment 61803 [details]
> A patch
> 
> Please try this.

Tried applying this on top of r16-1644-gaba3b9d3a48a07.
With r16-1644-gaba3b9d3a48a07 ... 224s
With r16-1644-gaba3b9d3a48a07 and the patch ... 161s
(this is on the machine where I originally measured 24% slowdown)

Looks like this patch gets us the original speed and even a bit more.  Nice.

(In reply to H.J. Lu from comment #10)
> (In reply to Filip Kastl from comment #8)
> > The same commit (r16-1644-gaba3b9d3a48a07) causes ~20% slowdown of 470lbm
> > from 2006 SPEC on Zen5 with -Ofast -march=native -flto -fprofile-use.
> > 
> > https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=1283.240.0
> 
> Can you extra a small testcase to show the issue?

I could try.  But we already have a patch.  So I think we don't have to search
for a smaller testcase.  What do you think?

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