llvm dev - Jul 2020 - NPM and code-size

(NPM: new pass manager;  LPM: legacy pass manager)

In a first quick experiment today I compared code-size of the LMP vs. the NMP
for the CSiBE benchmark (and some other), and this shows code-size increases
with the NPM that would probably be unacceptable for us. So, now I am wondering
how/if we need to mitigate this, and have a bunch of questions.

As I've noticed quite some activity around the NPM recently, I am first of
all curious if there's an idea or estimate when the NPM will be enabled? And
sorry if I missed this. That would give us an idea how much time we have to tune
the NMP and the pipeline for code-size, which I think would be the obvious
mitigation. Other questions would be if the NPM is mostly tuned for performance
at the moment, if others have observed code-size increases too, and if flipping
the switch from the LPM to NPM would be for all optimisation levels at the same
time, or if we e.g. will fall back to the old one for some?

Thanks,
Sjoerd.
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There's no official timeline for switching to the NPM, but I am trying to
get it ready ASAP.
What flags are you using for code size? I'm not familiar with the internals
of the NPM optimization passes especially in regards to code size, adding
some people who may be more familiar.

On Wed, Jul 22, 2020 at 7:51 AM Sjoerd Meijer via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> (NPM: new pass manager;  LPM: legacy pass manager)
>
> In a first quick experiment today I compared code-size of the LMP vs. the
> NMP for the CSiBE benchmark (and some other), and this shows code-size
> increases with the NPM that would probably be unacceptable for us. So, now
> I am wondering how/if we need to mitigate this, and have a bunch of
> questions.
>
> As I've noticed quite some activity around the NPM recently, I am first
of
> all curious if there's an idea or estimate when the NPM will be
enabled?
> And sorry if I missed this. That would give us an idea how much time we
> have to tune the NMP and the pipeline for code-size, which I think would be
> the obvious mitigation. Other questions would be if the NPM is mostly tuned
> for performance at the moment, if others have observed code-size increases
> too, and if flipping the switch from the LPM to NPM would be for all
> optimisation levels at the same time, or if we e.g. will fall back to the
> old one for some?
>
> Thanks,
> Sjoerd.
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Extracting some test cases to demonstrate the issue would be helpful for
triaging purposes.

David

On Wed, Jul 22, 2020 at 9:00 AM Arthur Eubanks <aeubanks at google.com>
wrote:
> There's no official timeline for switching to the NPM, but I am trying
to
> get it ready ASAP.
> What flags are you using for code size? I'm not familiar with the
> internals of the NPM optimization passes especially in regards to code
> size, adding some people who may be more familiar.
>
> On Wed, Jul 22, 2020 at 7:51 AM Sjoerd Meijer via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> (NPM: new pass manager;  LPM: legacy pass manager)
>>
>> In a first quick experiment today I compared code-size of the LMP vs.
the
>> NMP for the CSiBE benchmark (and some other), and this shows code-size
>> increases with the NPM that would probably be unacceptable for us. So,
now
>> I am wondering how/if we need to mitigate this, and have a bunch of
>> questions.
>>
>> As I've noticed quite some activity around the NPM recently, I am
first
>> of all curious if there's an idea or estimate when the NPM will be
enabled?
>> And sorry if I missed this. That would give us an idea how much time we
>> have to tune the NMP and the pipeline for code-size, which I think
would be
>> the obvious mitigation. Other questions would be if the NPM is mostly
tuned
>> for performance at the moment, if others have observed code-size
increases
>> too, and if flipping the switch from the LPM to NPM would be for all
>> optimisation levels at the same time, or if we e.g. will fall back to
the
>> old one for some?
>>
>> Thanks,
>> Sjoerd.
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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