[cfe-dev] [LLVMdev] [3.6 Release] RC3 has been tagged

[Hayden Livingston]

In the interest of educating others, can someone explain what the
regression is? Is it understood?

I'm new to this area and would love to understand how we identified what is
causing this regression? An optimization gone rogue? Some optimization
missing, etc.

On Tue, Feb 17, 2015 at 11:12 AM, Hans Wennborg <hans at chromium.org> wrote:

> Hi Jack,
>
> On Sun, Feb 15, 2015 at 6:05 AM, Jack Howarth
> <howarth.mailing.lists at gmail.com> wrote:
> >    What are the acceptable performance regressions in the generated
> > code for a llvm release? We seem to be badly regressed in some
> > benchmarks (which I first noticed from the review of 3.6-rc1 at
> >
> http://www.phoronix.com/scan.php?page=article&item=llvm-clang-3.5-3.6-rc1
> ).
> > This same issue has also been reported in
> > http://llvm.org/bugs/show_bug.cgi?id=22058. In the case of the 22%
> > performance degradation in SciMark2's Sparse matmult benchmark, I have
> > identified both commits that contribute equally to this regression in
> > http://llvm.org/bugs/show_bug.cgi?id=22589...
>
> Thank you very much for trying out the release candidate.
>
> I asked a few of the other developers, and the consensus was that
> while unfortunate, we won't block the release on a perf regression
> like this, at least not at this stage in the release process.
>
> Having said that, we will be doing an rc4, and Hal said that he or
> Sanjoy might be able to squeeze in a patch for the issue you pointed
> out before that. Otherwise, it will have to wait to 3.6.1 or 3.7.
>
> Thanks,
> Hans
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