I think this is a great idea. My understanding from the wiki page is that the full plan involves:

  1. We need to fix compatibility with recent LLVM versions. This really sucks for users. Ben Gamari is working on this, see #9142 and ​Phab:D155
  2. We need to fix up the LLVM IR generation in GHC, and fix the compiler driver to invoke the tools with a better set of optimizations. Nathan Howell has been wrangled into looking into this.
  3. We need to ship a pre-built version of LLVM for developers and users, and put them in binary distributions for major platforms. Austin Seipp could handle this.
  4. We can fix other bugs, like LLVM -split-obj support, which opens the way to shipping GHC with LLVM-optimized base libraries. Reid Barton expressed some interest in this.
I assume that 1. will come with 7.10.1. Is there any way we could do 3. in one of the 7.10 releases before 7.12.1?

Basing this question on Austin's words "we only need opt and llc, so the distributions can be tiny. " and "it's not actually very complicated to implement or support, I think." :) I guess it might be more difficult than I think but I thought it was worth asking the question as I believe 3. on its own is worthwhile and would hopefully simplify support for LLVM in GHC.

Thanks
George

On Fri, Oct 24, 2014 at 8:52 PM, Austin Seipp <austin@well-typed.com> wrote:
Hi *,

A few days ago a discussion on IRC occurred about the LLVM backend,
its current status, and what we could do to make it a rock solid part
of GHC for all our users.

Needless to say, the situation right now isn't so hot: we have no
commitment to version support, two major versions are busted, others
are seriously buggy, and yet there are lots of things we could improve
on.

So I give you a proposal, from a few of us to you all, about improving it:

https://ghc.haskell.org/trac/ghc/wiki/ImprovedLLVMBackend

I won't repeat what's on the wiki page too much, but the TL;DR version
is: we should start packaging a version of LLVM, and shipping it with
e.g. binary distributions of GHC. It's just a lot better for everyone.

I know we're normally fairly hesitant about things like this (shipping
external dependencies), but I think it's the only sane thing to do
here, and the situation is fairly unique in that it's not actually
very complicated to implement or support, I think.

We'd like to do this for 7.12. I've also wrangled some people to help.
Those people know who they are (because they're CC'd), and I will now
badger them into submission until it is fixed for 7.12.

Please let me know what you think.

PS. Joachim, I would be particularly interested in upstream needs for
Debian, as I know of their standard packaging policy to not duplicate
things.

--
Regards,

Austin Seipp, Haskell Consultant
Well-Typed LLP, http://www.well-typed.com/
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