[PATCH] [OPENMP] Replace libgomp by libiomp5 in driver

[Andrey Bokhanko]

Hi Chandler,

I agree with most of your libiomp concerns. However, I wonder why they
haven't been raised before? Also, I guess openmp-dev mailing list (
http://lists.cs.uiuc.edu/mailman/listinfo/openmp-dev) is the proper place
to raise them.

As for

- 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.
> - There has been essentially *zero* discussion with the rest of the clang
> or llvm community about this library. There are separate mailing lists
> which have nearly no traffic since the code drop.
>

the answer is very simple: apparently, very few people in the community
care for OpenMP in clang and are willing to contribute their time and
efforts into further development.

You are welcome to join at any point! -- and make openmp-dev list
non-empty. Again, your concerns is a good start -- I'm actually they glad
that you posted them.

As for

Today, when users get Clang on Linux, they likely already have libgomp
> installed much as they have libstdc++ installed. We don't even vaguely
> document how to build or install libiomp5, much less is that common
> practice when installing a Clang and LLVM based toolchain. As such, this
> essentially regresses every user if -fopenmp on Linux.
>

This is really bizarre.

libgomp dependency was introduced with no code review whatsoever (
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130114/072077.html),
serves very limited set of users (those who use clang on Linux *and* use a
compiler with no OpenMP support for OpenMP programs *and* directly call
libgomp API *and* started to do all this staff since clang 3.3, not
before), uses a library not readily available on Darwin, uses a
GPL-licensed library while a BSD-licensed one is available and interferes
with OpenMP support development (as it relies on Intel OMP API that libgomp
doesn't support).

IMHO, the sooner this dependency will be eliminated, the better.

Alternatively, Hal's suggestion (
http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20140217/099500.html)
makes sense for me.

Yours,
Andrey
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