[llvm-dev] [RFC] Introduce an LLVM "Incubator" Process

Tue Jun 30 11:47:34 PDT 2020

Thanks all for the great points - Stella and I wrote up a specific draft to answer the questions here.  I just sent an email to start a new llvm-dev thread with a specific draft we can iterate on - drawing in a bunch of the feedback from this thread.  Thank you for the great feedback!

-Chris

> On Jun 23, 2020, at 11:54 AM, Stella Laurenzo <stellaraccident at gmail.com> wrote:
> 
> 
> 
> On Tue, Jun 23, 2020 at 11:22 AM Philip Reames via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
> Generally +1 on the idea.
> 
> This does sound like an extension of the existing "experimental backend" idea.  At least at first, it sounds like the two are separate - experimental backends live in monorepo, incubation projects don't - but there's definitely some experience we can learn from and adapt.
> 
> One concern I have is about fragmentation and branding.  Specifically, I'm not sure an end state with a bunch of incubator projects under the LLVM umbrella with distinct developer communities is something we'd want to encourage.  This might need some discussion more broadly, but a few specific ideas:
> 
> Maybe we should require each incubator proposal to have a sponsor from within the existing community?  This doesn't have to be the lead or proposal author, but someone who already contributes who stands up and says they think this is beneficial to LLVM long term, and are willing to put some level (tbd) of supervision and steering into it.
> Maybe we should be careful on the wording we require for describing such a project?  Perception matters, and I'm hesitant to see discussions about "bugs in LLVM" if one incubator has quality issues.  Maybe specifically require READMEs to be explicit about incubation status and strong discourage the use of "an LLVM project" and related phrases for incubators?  (e.g. Recommend "X, an LLVM incubator" instead?)
> 
> Fwiw, the ASF Incubator has guidelines to similar ends: http://incubator.apache.org/guides/branding.html <http://incubator.apache.org/guides/branding.html> (see specifically the "Disclaimers").
>  
> If we're going to have looser standards for incubators, I think we need to be very explicit about eventual "promotion".  It needs to be very clear in our definition of incubator which items must be fixed for inclusion in mono-repo, and which items must be fixed to be non-experimental.  (If experimental is a distinct we maintain at least.)
> 
> Philip
> 
> On 6/20/20 3:42 PM, Chris Lattner via llvm-dev wrote:
>> Hi all,
>> 
>> Today, we maintain a high bar for getting a new subproject into LLVM: first a subproject has to be built far enough along to “prove its worth” to be part of the LLVM monorepo (e.g. demonstrate community, etc).  Once conceptually approved, it needs to follow all of the policies and practices expected by an LLVM subproject.
>> 
>> This is problematic for a couple reasons: it implicitly means that projects have to start *somewhere else* but proactively decide to follow LLVM design methodology and principles in the hope of being accepted.  It is sometimes socially difficult to get these projects going because there are many other forces that could encourage other practices.  For example, I personally encountered this at Google with MLIR - “why aren’t you using Google coding standards?”, several of us are currently discussing this in a new skunkworks project in the “compilers for hardware” world, and the Flang and other projects have found this challenging in the past.  Once the project gets to a point of critical mass with the “wrong” approach, it is very difficult and expensive to convert to the LLVM style, and from a social perspective, inertia sometimes leads to forking off to separate projects instead of folding back in to LLVM.
>> 
>> A former colleague recently suggested the idea of introducing an incubator process of some sort (e.g. xref the Apache version of this idea <https://incubator.apache.org/>).  I think this is a really interesting idea, and it is much easier now that the majority of the “official” code is in the LLVM monorepo.
>> 
>> Here is a sketch of how this could work:
>> 
>>  - We maintain the same high bar to get into the LLVM monorepo, LLVM CI etc.  No change here.
>> 
>>  - We have a very light-weight proposal process that allows people to create incubator projects in the LLVM organization, with no code up front.  The project would be required to have e.g. a charter document and README.
>> 
>>  - Such projects are required to follow the LLVM developer policy, coding standards, CoC, etc, but can define their own stability and evolution process, code owners, etc.
>> 
>>  - When the project is ready to graduate, it would follow the existing process for becoming a first-class part of the mono repo.
>> 
>>  - We have some policy on when to retire/delete projects, which can be ironed out the first time it comes up (e.g. start with a nomination).
>> 
>>  - We could even try to help encourage new projects to include a ‘mentor’ that has experience with the LLVM project to help nudge things in the right direction and encourage proper development approach.
>> 
>> What do you think?  Is anyone interested in helping to write up a more detailed proposal?
>> 
>> -Chris
>> 
>> 
>> 
>> 
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