[llvm] r285296 - [DAGCombiner] Add vector demanded elements support to computeKnownBits

[Davide Italiano via llvm-commits]

On Thu, Oct 27, 2016 at 3:36 PM, Juergen Ributzka via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Hi Simon,
>
> I think this commit is causing timeouts on our LTO builds on green dragon:
> http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto/10676/
>
> A build usually takes 45min and we kill them if they last more than 90min.
>

Out of curiosity, why is the timeout so high? I understand that false
positives are not great, but 2x seems a little bit excessive.
Have you already tried with 1.5x (or something around that value)?

P.S. Ideally we {sh,c}ould have a decent infrastructure for tracking
compile-time regressions (at least this is what I'm more concerned
about because of LTO, others might care about runtime performance as
well), but this is not a hill I want to die on (at least not today),
and I still think lowering the timeout threshold could help finding
regressions.

--
Davide