[Bug target/94373] 548.exchange2_r run time is 7-12% worse than GCC 9 at -O2 and generic march/mtune

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94373

--- Comment #4 from Richard Biener  ---
Note the cited commit simply caused more complete unrolling to happen.  Too
much actually which is why I reverted it.  Note GCC 9.2 does not have that more
unrolling so the difference must be something else in the end.

[Bug target/94373] 548.exchange2_r run time is 7-12% worse than GCC 9 at -O2 and generic march/mtune

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94373

--- Comment #3 from Hongtao.liu  ---
(In reply to Hongtao.liu from comment #2)
> I think
> Change lea_cost from 2 --> 1 in skylake can fix this regressions.
> 
> Since it's stage4 now, i hold my patch.

Classify: it's for -O2 -mtune=skylake-avx512

not sure the what cause the regression for -O2 -mtune=generic.

[Bug target/94373] 548.exchange2_r run time is 7-12% worse than GCC 9 at -O2 and generic march/mtune

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94373

--- Comment #2 from Hongtao.liu  ---
I think
Change lea_cost from 2 --> 1 in skylake can fix this regressions.

Since it's stage4 now, i hold my patch.

[Bug target/94373] 548.exchange2_r run time is 7-12% worse than GCC 9 at -O2 and generic march/mtune

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94373

Andrew Pinski  changed:

   What|Removed |Added

   Keywords||missed-optimization
  Component|tree-optimization   |target

--- Comment #1 from Andrew Pinski  ---
Seems IV related and most likely a target cost model issue too.