[Bug target/81614] Should -mtune-ctrl=partial_reg_stall be turned by default?

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81614

--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Cody Gray from comment #3)

> > Also, it is hard to confirm tuning PRs without hard benchmark data.
> 
> No, it really isn't. I know that's a canned response, likely brought about
> by hard-won experience with a lot of dubious "tuning" feature requests, but
> it's just a cop-out in this case, if not outright dismissive. Partial
> register stalls are a well-documented phenomenon, confirmed by multiple
> sources, and have been a significant source of performance degradation since
> the Pentium Pro was released circa 1995.

Well, then please find some representative benchmark suite and test the effect
of -mtune-ctrl=partial_reg_stall on your target. There are plenty of benchmarks
listed at [1].

It is an one-line change in the compiler source to set the new default then.

[1] https://gcc.opensuse.org/specs/cxx_groups