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

[Rob Clark]

On Wed, Aug 27, 2014 at 2:26 PM, John Kessenich <johnk at lunarg.com> wrote:
> Hi,
>
> If Mesa used an LLVM IR for it's shader compiler stack, it would most likely
>
> Pick a specific shipped version.  Shipped versions are stable and
> unchanging.  Upgrading to a newer version would be done only by choice, on
> Mesa's schedule.
> Not bring the source into mesa: it works perfectly well sitting next to
> Mesa.
> Link it in statically so there are no distro/versioning issues and no
> interactions with other components of the system that independently use LLVM
> however they wish.  This is also quite small compared to other uses of LLVM
> people sometimes discuss.
>
> Externally, no one could even tell some helper functions within the compiler
> stack came from LLVM or a specific version of LLVM.
>
>> Packaging and ABI stability...
>
> These don't even exist with linking statically to a chosen version.

So, I don't suppose it is possible to have multiple side-by-side
llvm's?  Ie. I wonder what happens when I'm switching back and forth
between latest stable mesa branch, vs master which has moved on to
llvm n+1?

I guess that is less of packaging issue.. but I don't really look
forward to having to recompile llvm when switching between branches.

BR,
-R


> JohnK
>
>
>
> On Tue, Aug 26, 2014 at 10:25 PM, Greg Fischer <greg at lunarg.com> wrote:
>>
>> My apologies for a too-brief response to this question.
>>
>> GlassyMesa links LLVM statically into Mesa. I believe that previous
>> posters to this thread have already done a pretty good job of arguing that
>> this is at least a workable approach.
>>
>> Best regards,
>> Greg
>>
>>
>>
>> On Tue, Aug 26, 2014 at 7:14 PM, Kenneth Graunke <kenneth at whitecape.org>
>> wrote:
>>>
>>> On Tuesday, August 26, 2014 06:45:42 PM Greg Fischer wrote:
>>> > The GlassyMesa effort is ongoing despite the lack of recent activity.
>>> > We
>>> > continue to embrace LLVM as a basis for shader compilation in Mesa and
>>> > elsewhere.
>>> >
>>> > We agree that translating from LLVM back "up" to GLSL IR is problematic
>>> > and
>>> > that an architecture that supports LLVM backends would be desirable.
>>> >
>>> > The current published code is a work-in-progress. We are currently
>>> > working
>>> > on tuning of compilation time and code generation quality, and some of
>>> > that
>>> > work will likely be appearing soon. There have also been recent
>>> > improvements in glslang, the parser for this stack.
>>> >
>>> > Packaging and ABI stability have not been an issue for us.
>>>
>>> As far as I know, you haven't actually shipped your software in any Linux
>>> distribution yet, so a lack of packaging problems sort of goes without
>>> saying...
>>>
>>> --Ken
>>
>>
>>
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>
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