[llvm-dev] [RFC] AAP Backend

[Robinson, Paul via llvm-dev]

Re-reading the thread, it looks like there is a difference of opinion
what "an active community behind the target" means: an active community
of LLVM-target-maintainers, and/or an active community of end-users.

I'd think the immediate practical concern is that there is an active
community of LLVM-target-maintainers, so that the maintenance burden
does not fall unduly on the rest of the LLVM community.  Beyond that
is the broader and vaguer question of whether there is anybody *else*
who would benefit from the in-tree target, other than the maintainers.
You could think of the former as a "cost" (to the LLVM community)
question, and the latter as a "benefit" (beyond the community) question.
Or even more succinctly:
- does is hurt "us" to have this?
- does it help "them" to have this?
A secondary point to having an end-user community is that if the
initial maintainers drop out for any reason, there is likely to be
somebody to take their place, preserving the low-hurt characteristic.

As a straw man, if some of us ex-DEC folks wanted to resurrect the
Alpha target, I'd think that would be pretty cool, but it's hard to
point to anybody that could actually make use of an Alpha-target Clang.
So while I suspect there are enough of us around that the "hurt" part
could be low to nothing, there's really nobody on the "help" side.
And after the Alpha fans die off, well, that's that.

I didn't pay enough attention to the Lanai debate to know whether
Google has much of an end-user community there.  It seems likely the
hurt side would not be a problem, even if the current maintainers
rotate out for whatever reason then Google seems likely to rotate in
somebody else to take their place.  That capacity would seem to make
it less necessary to identify an end-user community of its own.

Regarding AAP, we've got a few target-maintainers, who say they do
have target-users who could benefit.  Alex asked if the maintainers
could better quantify their user base, which seems like a reasonable
question.  Who is on the "help" side?  Would they be able to take
over from the initial target-maintainers if necessary?

--paulr


> -----Original Message-----
> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Mehdi
> Amini via llvm-dev
> Sent: Friday, August 26, 2016 10:05 AM
> To: Renato Golin
> Cc: LLVM Dev; Alex Rosenberg
> Subject: Re: [llvm-dev] [RFC] AAP Backend
> 
> 
> > On Aug 26, 2016, at 9:55 AM, Renato Golin <renato.golin at linaro.org>
> wrote:
> >
> > On 26 August 2016 at 17:45, Mehdi Amini <mehdi.amini at apple.com> wrote:
> >> “Major corporation” does not mean size to me, I read it as “having a
> major involvement in the project”.
> >
> > Still, you're rejecting new developers because they haven't
> > contributed much before.
> 
> Can you quote exactly where *I*  *rejected* anything?
> 
> 
> > But if their back-end is upstream, than they'll contribute code
> > upstream for their changes on their back-end.
> >
> > However, if we don't allow their back-end to be upstream, they won't
> > contribute to the project.
> >
> > Looks like a self-defeating argument, and one that still doesn't agree
> > with the open source philosophy.
> >
> > Not to mention that it's an argument that is not required by the
> > policy in any way.
> 
> The policy you quote says *must be an active community behind the target”.
> The question is *only* about this, so it seems right on point to me.
> 
> 
> >> “the question is about who will use/develop/maintain this backend
> upstream in LLVM?"
> >
> > They have answered that question. Ed and Simon will be the active
> > maintainers. I imagine they have other developers around to help.
> > I don't see *any* concern here, nor any violation of the policy. Like
> > the Lanai back-end, the community is the maintainers. LGTM.
> 
> See above quote from the policy.
> 
> 
> >
> >> "is there already an open-source community around this backend
> somewhere?"
> >
> > This is not a requirement of the policy, nor was a requirement to any
> > other back-end, so not a valid argument.
> 
> Asking a question is not an argument.
> 
> 
> >
> > If we were to reject changes for not having an open source community
> > elsewhere, we'd be chopping a very large parts of LLVM off.
> 
> I didn’t write that, and *I* didn’t ask any rejection. In short my only
> question is “what is the community around this”? (And I didn’t even start
> the question but found it interesting).
> 
> —
> Mehdi
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