[llvm-dev] Enable vectorizer-maximize-bandwidth by default?

[Chandler Carruth via llvm-dev]

On Tue, May 30, 2017 at 1:40 AM Agabaria, Mohammed via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> We’re seeing nice improvements but also significant degradations on IA,
> which we would like to investigate before the patch is committed.
>
>
>
> Major degradations we see:
>
>
>
> networking
>
>    ip_pktcheckb1m          -6.80 %
>
>    ip_pktcheckb2m          -6.74 %
>
>    ip_pktcheckb4m          -7.57 %
>
>    ip_pktcheckb512k       -6.58 %
>
> Telecom
>
>    autcor00data_1          -78.02 %
>
>    autcor00data_2          -76.80 %
>
>    autcor00data_3          -77.00 %
>
> (on Atom)
>
>
>
> We still working on creating reproducers.
>
> In general we support this patch, just want to have a chance to
> investigate the issues. We need a few days for that.
>

I mean, OK... but keep in mind that Dehao's original email went out over a
week ago, so this patch has already been held up a while. As these
benchmarks aren't readily available, we also can't do anything to help
until a test case is posted.

Have you considered contributing these benchmarks to the LLVM test suite?


>
>
>
>
>
>
> *From:* llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org
> <llvm-dev-bounces at lists.llvm.org>] *On Behalf Of *Chandler Carruth via
> llvm-dev
> *Sent:* Tuesday, May 30, 2017 11:27
> *To:* Flamedoge <code.kchoi at gmail.com>; Dehao Chen <dehao at google.com>
> *Cc:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* Re: [llvm-dev] Enable vectorizer-maximize-bandwidth by default?
>
>
>
> If you care about such hardware, please run benchmarks with the flag?
>
>
>
> Dehao has made this flag available. It is important that those who care
> about particular hardware provid ebenchmark results. Not everyone in the
> community will have access to particular hardware variants.
>
>
>
> On Tue, May 30, 2017 at 1:14 AM Flamedoge <code.kchoi at gmail.com> wrote:
>
> Thank you for running these.
>
>
>
> May I suggest testing on AVX2 capable hardware? That would be Intel
> Haswell, AMD Carrizo and up.
>
> I'm not sure what "vectorizer-maximize-bandwidth" implies, but doubling
> the vector lanes may help light up parallel regions.
>
>
>
> Kevin
>
>
>
> On Tue, May 30, 2017 at 12:58 AM, Chandler Carruth via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> On Fri, May 19, 2017 at 4:01 PM Adam Nemet via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> I will run it on Cyclone/AArch64 next week.
>
>
>
> FYI, we're still waiting on these Adam...
>
>
>
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