Enable the vectorizer at -O2 for GCC 12

[Bill Schmidt]

On 8/30/21 8:04 AM, Florian Weimer wrote:
> There has been a discussion, both off-list and on the gcc-help mailing
> list (“Why vectorization didn't turn on by -O2”, spread across several
> months), about enabling the auto-vectorizer at -O2, similar to what
> Clang does.
>
> I think the review concluded that the very cheap cost model should be
> used for that.
>
> Are there any remaining blockers?

Hi Florian,

I don't think I'd characterize it as having blockers, but we are 
continuing to investigate small performance issues that arise with 
very-cheap, including some things that regressed in GCC 12.  Kewen Lin 
is leading that effort.  Kewen, do you feel we have any major remaining 
concerns with this plan?

Thanks,
Bill

>
> Thanks,
> Florian
>