[cfe-dev] moving the clang-omp merge along

[Chandler Carruth]

On Thu, May 29, 2014 at 6:46 AM, Andrey Bokhanko
<andreybokhanko at gmail.com>wrote:

> While we are on the topic, let me update on some other things happening in
> responce to other issues highlighted by Chandler:
>

I just wanted to say, I am very happy to see progress starting here. =] All
of my comments below are meant to help the effort move faster and deal
better with the LLVM project.


> - This library is not being developed as an active part of the LLVM
> community, even if it is checked into SVN as part of the LLVM project and
> under its license. See r197914 where there is a code drop of many months
> worth of development with *no* change log, attribution, information, or
> other participation in any part of the community.
>
> This is changing, and many developers joining the whole OpenMP in clang
> support effort. I can say that Michael Wong and many of his colleagues from
> IBM are involved; Eric Stotzer and his colleagues from TI are involved;
> Barbara Chapman and her group from UofHouston is involved; Guansong Zhang
> from AMD is involved. Obviously, Hal Finkel, Chris Bergstrom, Steve Noonan
> and many others continue to be actively involved as well.
>
> Take a look at the recent activity in openmp-dev mailing list. More to
> come.
>

Pretty happy about this, and looking forward to more. Some things that
would be helpful (IMO, others may disagree) to start looking into how/when
to adopt or integrate:

- Start more closely following the LLVM developer policy around code review
and small, incremental patches and development.
  - Maybe use code review tools like Phabricator? Dunno what would be
needed to make this work well, probably some stuff...
- Check that the codebase compiles with the same host toolchain baseline as
the rest of the LLVM project[1]
- Maybe work out a plan toward generally conforming with the coding
standards[2] where applicable?


>
> It is buildable with clang now. Moreover, regular buildbots, with both gcc
> and clang, are running:
>
> http://lab.llvm.org:8011/builders/libiomp5-gcc-x86_64-linux-debian
> http://lab.llvm.org:8011/builders/libiomp5-clang-x86_64-linux-debian
>

Just want to say, this in particular is fantastic.


> - The build system is totally disjoint from LLVM's, in fact it is an
> entirely custom Perl build system that is unlike anything in use by the
> LLVM project.
>
> We started to work on improving build system. Stay tuned.
>

Very cool. I would look closely at the compiler-rt and libc++ CMake builds.
Hopefully useful.


> - There are *zero tests* in the open source repository!!!! This is even
> called out in the original submission and on the primary website. We simply
> *cannot* ship and link against a runtime library which has no tests!
>
> University of Houston contributed OpenUH test suite:
> http://lists.cs.uiuc.edu/pipermail/openmp-commits/2014-May/000019.html.
> Sunita Chandrasekaran from the University works on integrating this suite
> into LLVM test system.
>
> BTW, any advice with how to approach this would be *much* appreciated!
>

I think the right way to go is something along the lines of the ASan (in
compiler-rt) lit tests, but maybe others have a better idea. I agree that
testing here is hard.


> - No part of this library has gone through an LLVM release process either,
> not even as a "new" or "beta" project.
>
> Aha! So, you support inclusion of openmp (library, not compiler) in 3.5 as
> well? :-)
>

Hehe, I see what you did there.

I do genuinely support it going through the release process, but I think
that there are two things that need to be pretty solid first:

1) the build system work probably needs to be pretty solid. i'd be happy
with support on par with compiler-rt or libc++ in CMake...
2) the test suite needs to be at least reasonably well integrated so
release testers actually hit it and exercise the code
3) we need a good switch in Clang to use iomp (I know you or someone on the
patch thread worked on this, did it land? if so, done!)

Maybe others have other thoughts, but I think those three are my key ones.

Anyways, thanks for the clarification and all the hard work on this stuff.
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