llvm dev - May 2016 - LLVM Releases: Upstream vs. Downstream / Distros

On 12 May 2016 at 16:57, Daniel Berlin <dberlin at dberlin.org>
wrote:
> Errr, Stephen has spoken up here, but my folks are in contact with android
> folks pretty much every week, and I don't think what you are stating is
> correct on a lot of fronts.
I obviously don't speak for Android and have already apologised to
Steve about my choice of words.

> So if android is your particular concern here, i can pretty much state that
> android LLVM is on a release process close to the rest of Google, which is
> 'follow TOT very closely'.
Isn't this what I said?

Following ToT very closely is only good for groups that have high
involvement in LLVM, like Google and Android.

And for that reason (and others), Android doesn't use the upstream
releases. I was wondering if we could make anything so they would.

The major benefit wouldn't be, as I explained, specifically for
Google/Android, but for Android users, Linux users, Linux distros,
LLVM library users (including Renderscript), etc.

--renato

On Thu, May 12, 2016 at 9:07 AM, Renato Golin <renato.golin at linaro.org>
wrote:
> On 12 May 2016 at 16:57, Daniel Berlin <dberlin at dberlin.org>
wrote:
> > Errr, Stephen has spoken up here, but my folks are in contact with
> android
> > folks pretty much every week, and I don't think what you are
stating is
> > correct on a lot of fronts.
>
> I obviously don't speak for Android and have already apologised to
> Steve about my choice of words.
>
>
> > So if android is your particular concern here, i can pretty much state
> that
> > android LLVM is on a release process close to the rest of Google,
which
> is
> > 'follow TOT very closely'.
>
> Isn't this what I said?
>
But your position seems to be "this is a bad thing for folks", and the
position we take is that it's explicitly a good thing.

>
> Following ToT very closely is only good for groups that have high
> involvement in LLVM, like Google and Android.
>
> And for that reason (and others), Android doesn't use the upstream
> releases. I was wondering if we could make anything so they would.
>
>
> The major benefit wouldn't be, as I explained, specifically for
> Google/Android, but for Android users, Linux users, Linux distros,
> LLVM library users (including Renderscript), etc.
>
There is a strong implicit assumption here that the current model they use
is better for users than the model LLVM uses, and that aligning these
models in *that* direction ends up better from usings than aligning models
in the other direction.

IE make ToT more appealing to follow, have folks follow that.
Maybe that's true, maybe it's not, but it needs a lot more evidence :)

The evidence i see so far is that they spend time trying to get disparate
projects to use a single version of LLVM, but i also have seen no evidence
that any of the projects using stable releases would ever align their
policies *anyway*, so they still have that problem no matter what you do to
stable releases.

If that is the real concern,  i think the entire discussion is misplaced.
Because that problem is solely one of API compatibility between releases.

If there are other concerns, it'd be good to catalogue them :)


>
> --renato
>
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On 12 May 2016 at 17:15, Daniel Berlin <dberlin at dberlin.org>
wrote:
> But your position seems to be "this is a bad thing for folks",
and the
> position we take is that it's explicitly a good thing.
Then I apologise again! :)

My point was that following ToT is perfect for developer teams working
*on* LLVM. Everyone should be doing that, and most people are. Check.

But for some people, including library users, LTS distributions and
some downstream releases (citation needed), having an up-to-date and
stable release *may* (citation needed) be the only stable way to
progress into newer LLVM technology.

> IE make ToT more appealing to follow, have folks follow that.
> Maybe that's true, maybe it's not, but it needs a lot more evidence
:)
There were responses on this thread that said it's possible and
desirable to test ToT better, than only validate releases, and I think
this is great. Mostly because ultimately this will eventually benefit
the releases anyway.

Maybe, the solution to the always-too-old-release problem is to get
better trunk and give up at all on releases, like Arch Linux rolling
releases (which I use), so I'm ok with it, too.

As long as we make it a clear and simple process, so upstream users
can benefit too, whatever works. :)

cheers,
--renato