Proposal: Improving the LLVM backend by packaging it

[Herbert Valerio Riedel]

On 2014-11-01 at 17:26:26 +0100, Austin Seipp wrote:

[...]

>> How long does building those two llvm binaries take? If it is
>> sufficiently quick, maybe that would be a suitable distribution for
>> developers as well, and avoids having to separately build, distribute,
>> download, and install the binaries.
>
> In practice it takes a while... I haven't timed it, but I'd guess on
> average it adds about 30-40 minutes for most people just to build
> llvm. I'm not sure how many things we can disable to make the build
> faster, but I'd ballpark it at half an hour at best (it's a few
> thousand source files, after all).
>
> This would mostly hurt if you cleaned up the tree later (e.g. 'make
> distclean'), which I do rather frequently in order to get a pristine
> build tree.

This also hurts buildbots as 30+ minutes is even more than a validate
run takes... :-/

Otoh, we don't have to force everyone to build GHC's bundled LLVM, and
could allow to use the system-wide installed LLVM binaries if a matching
version is provided by the system. As an example, I currently have
llvm-3.4 and llvm-3.5 installed, and could easily have a llvm-3.6
snapshot installed via the package manager (e.g. via
http://llvm.org/apt/).

Cheers,
  hvr