[Bug middle-end/90056] 548.exchange2_r regressions on AMD Zen

[jamborm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90056

Martin Jambor <jamborm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |MOVED

--- Comment #2 from Martin Jambor <jamborm at gcc dot gnu.org> ---
(In reply to Martin Jambor from comment #0)
> As of revision 270053, the 548.exchange2_r benchmark from SPEC 2017
> INTrate suite suffered a number of smaller regressions on AMD Zen
> CPUs:
> 
>   - At -O2, it is 4.5% slower than when compiled with GCC 7

I am about to file a specific bug about exchange at -O2.

>   - At -Ofast, it is 4.7% slower than when compiled with GCC 8

This is no longer true.

>   - At -Ofast -march=native -mutine=native, this difference is 6.9%

Again, I will file a more specific bug about -Ofast -march=native in a
little while.

>   - At -Ofast and native tuning, it is 6% slower with PGO than
>     without it.

I can still see this in my measurements on Zen1-based CPU but not in
those done on AMD Zen2 or Intel Cascade Lake.  So I am not sure if we
care.  I'll e happy to file a specific bug if we do.