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

[Ian Romanick]

On 08/27/2014 02:55 PM, Marek Olšák wrote:
> Our plan is to always require the latest released version of LLVM
> because of new features in our LLVM backend that the radeonsi driver
> depends on to advertise all GL features. Some new features listed for
> the radeonsi driver in Mesa release notes are only enabled if you have
> latest LLVM from git/svn.

I think this underscores the fundamental problem have having such a
critical, core piece of project infrastructure being completely out of
the control of the project.  For me, trying to ship a product on which
people rely, this is an absolute non-starter.

At least with the other components on which Mesa relies (e.g., libdrm,
2D drivers, etc.) it's largely the same group of people with the same
set of goals.

> Marek
> 
> On Wed, Aug 27, 2014 at 8:39 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>> 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.
>>
>> So... what happens when some backend, say radeonsi, requires a newer
>> version? That would become linked to moving the rest of mesa up to a
>> newer version, or linking in 2 different versions of llvm (not sure if
>> that'd be possible...)
>>
>>   -ilia
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