[Mesa-dev] [RFC PATCH 00/16] A new IR for Mesa

[Stéphane Marchesin]

On Wed, Aug 20, 2014 at 11:56 AM, Matt Turner <mattst88 at gmail.com> wrote:
> On Wed, Aug 20, 2014 at 11:13 AM, Kenneth Graunke <kenneth at whitecape.org> wrote:
>> Gentoo has also had trouble updating for similar reasons; Matt (the Gentoo Mesa package mantainer) can probably comment more.
>
> Yes, at one point we were stuck two releases behind current Mesa (and
> this is Gentoo!) because we couldn't get the appropriate version of
> LLVM stabilized because a number of reverse dependencies didn't work
> with the new LLVM version.
>
> Having multiple versions installed in parallel breaks down pretty
> easily. Where do the headers go? Where do all the executables go? Do
> you version all of them and install one for each version? Do other
> distros allow multiple versions of LLVM to be installed in parallel?
> How do they manage?

For Chrome OS we have multiple versions of LLVM, basically one for
each consumer, and each consumer (except for the clang family) links
to its version statically. It is tedious but less painful than having
to change all the consumers at once (I certainly don't want to update
our ASan tools because I upgraded mesa). It's wasteful and by no means
ideal, but it's a pragmatic solution to a problem over which I have no
control :)

Stéphane

>
>> I've also heard stories from friends of mine who use radeonsi that they couldn't get new GL features or compiler fixes unless they upgrade both Mesa /and/ LLVM, and that LLVM was usually either not released or not available in their distribution for a few months.
>
> I get the sense that this is a problem that a backend in LLVM would
> cause, but maybe not so if we just used LLVM IR for the GLSL compiler.
> I think the C API is suitable for this kind of thing as well. Tom?
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