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

Leonard Chan via llvm-dev llvm-dev at lists.llvm.org
Fri Aug 2 14:28:47 PDT 2019

I believe a good amount of them (if not most of them) have already been
ported! Off the top of my head, I remember that asan, tsan, msan, hwasan,
the kernel santizers, and sancov have been ported. I don't think ubsan has
been ported yet though.

You can also check if other passes you need run under the new PM by
checking PassRegistry.def.

On Fri, Aug 2, 2019, 14:20 Jordan Rupprecht <rupprecht at google.com> wrote:

> 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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