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

[Renato Golin]

On 18 February 2015 at 18:54, Jack Howarth
<howarth.mailing.lists at gmail.com> wrote:
> http://www.phoronix.com/scan.php?page=article&item=llvm-clang-3.5-3.6-rc1&num=2

First, I have to say, I was saddened by that post, since the new
release regress in a lot of the benchmarks, but not enough to stop the
world and fix all of those regressions.

I have seen other similar regressions in my internal benchmarks, but
again, not enough to stop everything. My focus now is to make it work
well. I'll only focus on performance when the whole toolchain is
working as I expect, or when I have more people to look at performance
in parallel. I assume other people feel in the same way.

Second, how many benchmarks are there, and which of them classify as
"important"? Should we stop for 20% regressions on any benchmark on
the Internet? SciMark is a well known benchmark, I give you that, but
to be honest, it means nothing to me. Maybe it will, one day, but not
today, and probably not for another year or two.

It seems that others in the community feel in the same way, or we
would have seen a lot of people jumping up and down until the
regression got fixed. Hal and others seem to be on top of the issue,
and I assume they're the ones most interested in getting that fixed.
If they're happy with it going to 3.6.1, an no one else is trying to
get that fixed, I'm happy with that outcome.

As Hans said, we'll probably have an RC4. If you're so worried with
this specific regression, can you try to fix it? It seems two commits
are responsible in equal measure, so it shouldn't be too hard to see
what they do, produce the code with and without each one of them, and
see why things go slower. I'm not an expert on x86, and I didn't even
run that benchmark on ARM/AArch64, so I can't possibly help.

cheers,
--renato