[llvm-dev] [GlobalISel][AArch64] Toward flipping the switch for O0: Please give it a try!

[Diana Picus via llvm-dev]

On 17 June 2017 at 01:43, Quentin Colombet <qcolombet at apple.com> wrote:
> *** Your Help Is Needed ***
>
> - Please share your experience in using the GISel APIs and how we can make
> them better. Moving forward we’ll have those conversations on open source
> instead of internally/with a narrower audience.
> - Report any performance problem you identify
> - Propose patches!

While we're at it, these patches could use some review:
* [GlobalISel] combine not symmetric merge/unmerge nodes [1]
* [GlobalISel] Make multi-step legalization work [2]
* [GlobalISel] Enable specifying how to legalize non-power-of-2 size
types. [NFC-ish] [3]

Note that [2] is a spin-off from [3], which has been in review for a
long, long time.

[1] https://reviews.llvm.org/D33626
[2] https://reviews.llvm.org/D32529
[3] https://reviews.llvm.org/D30529

Cheers,
Diana

>
> Cheers,
> -Quentin
>
>
>
> On Jun 16, 2017, at 3:06 PM, Quentin Colombet via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>
>
> On Jun 14, 2017, at 7:27 AM, Diana Picus <diana.picus at linaro.org> wrote:
>
> On 12 June 2017 at 18:54, Diana Picus <diana.picus at linaro.org> wrote:
>>
>> Hi all,
>>
>> I added a buildbot [1] running the test-suite with -O0 -global-isel. It
>> runs into the same 2 timeouts that I reported previously on this thread
>> (paq8p and scimark2). It would be nice to make it green before flipping the
>> switch.
>>
>
> I did some more investigations on a machine similar to the one running the
> buildbot. For paq8p and scimark2, I get these results for O0:
>
> PAQ8p:
> Fast isel: 666.344
> Global isel: 731.384
>
> SciMark2-C:
> Fast isel: 463.908
> Global isel: 496.22
>
> The current timeout is 500s (so in this particular case we didn't hit it for
> scimark2, and it ran successfully to completion). I don't think the
> difference between FastISel and GlobalISel is too atrocious, so I would
> propose increasing the timeout for these 2 benchmarks. I'm not sure if we
> can do this on a per-bot basis, but I see some precedent for setting custom
> timeout thresholds for various benchmarks on different architectures
> (sometimes with comments that it's done so we can run O0 on that particular
> benchmark).
>
> Something along these lines works:
> https://reviews.llvm.org/differential/diff/102547/
>
> What do you guys think about this approach?
>
>
> Looks reasonable to me.
>
>
> Thanks,
> Diana
>
> PS: The buildbot is using the Makefiles because that's what our other
> AArch64 test-suite bots use. Moving all of them to CMake is a transition for
> another time.