[llvm-dev] Switching to the New Pass Manager by Default

[Jordan Rupprecht via llvm-dev]

Hi Leonard,
Is the new pass manager expected to work with sanitizers now?

On Fri, Aug 2, 2019 at 1:25 PM Leonard Chan via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> I think so far most individual projects have their own statistics on build
> time/performance impact on switching to the new PM, but I agree that there
> should at least be one place that people can reference on the impact.
>
> On Fri, Aug 2, 2019 at 1:14 PM Philip Reames <listmail at philipreames.com>
> wrote:
>
>> Thanks for all the hard work that went into getting it here.
>>
>> +1
>>
>> Can you spell out what performance validation has been done?  Informally,
>> I know there's been quite a bit, but getting a summary in one place for
>> later reference would be super helpful.
>>
>> Philip
>> On 8/2/19 10:25 AM, Leonard Chan via llvm-dev wrote:
>>
>> Hello all,
>>
>> As of now, all LLVM and Clang tests have been updated/addressed to run
>> under the new/experimental pass manager (at least the ones that failed when
>> using the new PM).
>>
>> For those who aren't aware of what the new pass manager (PM) is, the
>> tl;dr is that this will serve as a replacement for the legacy PM, and
>> promises faster build times by restructuring how passes are run over IR
>> units. For some time, when someone wants to create a new pass, they may
>> need to implement it for both pass managers since the legacy one is what is
>> enabled by default. Passes that were initially made under the new PM have
>> also slowly been ported over time.
>>
>> Now that LLVM 9.0.0 has branched, we have about 6 months before the next
>> release. We think it would be a good idea to take this opportunity and make
>> the new PM the default one which gives us enough time to work out any kinks
>> that might come out of this switch before LLVM 10.0.0 branch point. We
>> suspect that there may be other LLVM projects that will be affected by
>> this, probably from unported passes.
>>
>> Does anyone have any opinions on this?
>>
>> Off the top of my head, the next immediate work would be to update the
>> docs with instructions on how to write or port a new PM pass, and address
>> any breakages for other LLVM projects.
>>
>> Thanks,
>> Leonard
>>
>> _______________________________________________
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>>
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