[llvm-dev] [RFC] NewGVN

[Michael Spencer via llvm-dev]

On Tue, Nov 22, 2016 at 10:27 AM, Jack Howarth via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> >>On Fri, Nov 18, 2016 at 8:43 AM, Philip Reames via llvm-dev
> ><llvm-dev at lists.llvm.org> wrote:
> >> Glad to see this landing!  It's been a long time coming.
> >>
> >> Once this is in, please do not turn it on by default immediately.  Let's
> >> call for volunteers to find some of the most egregious miscompiles, fix
> >> them, and then turn this on by default.
> >>
> >There are no immediate plans to enable NewGVN by default (at least,
> >not in the near future). In fact, the mail that I originally wrote
> >doesn't at all mention the switch, neither any follow-ups from me or
> >Daniel, so, I'm not entirely sure where you got that idea from. If you
> >take a look more closely (at the mail, or a the patch), you'll realize
> >that "key" pieces that are in old GVN are still missing. The most
> >noticeable are PRE and load coercion. In other words, the patch
> >proposed is not (yet) on par with what the current GVN does (although
> >all the missing pieces are already implemented out-of-tree).
> >Also, let me try to clarify one point. This is already a call for
> >volunteers. If you feel adventurous, you can download the
> >patch/apply/test/report issues. I can and I will spend time
> i>ntegrating the rest of the work and fix all the reported
> >bugs/miscompiles. If there's something that can we do in a cleaner
> >way, a discussion will happen on the mailing list/on the review thread
> >and everybody will have a chance to comment, as it's happening for the
> >initial patch (and as I always try to do).
> >Once the first patch lands, I'll commit a temporary cl::opt to enable
> >NewGVN for those interested in testing and send another CFT e-mail.
> >FWIW, The patch had already a round of light testing internally. Of
> >course, this is not enough or indicative of its maturity/robustness. I
> >plan to have it tested more carefully inside my organization in
> >parallel.
> >That said, thanks for you input.
>
> Why even commit the patch to enable the pass into trunk. Just leave it
> up on Phabricator for testers to apply locally to their tree?
>              Jack
>
>
Because that increase friction to testing it. Asking people to pass -mllvm
-newgvn will end up with a lot more testing than "please apply this patch
and recompile everything".

- Michael Spencer


>
> >--
> >Davide
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