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

[Dave Airlie]

On 21 August 2014 19:10, Henri Verbeet <hverbeet at gmail.com> wrote:
> On 21 August 2014 04:56, Michel Dänzer <michel at daenzer.net> wrote:
>> On 21.08.2014 04:29, Henri Verbeet wrote:
>>> For whatever it's worth, I have been avoiding radeonsi in part because
>>> of the LLVM dependency. Some of the other issues already mentioned
>>> aside, I also think it makes it just painful to do bisects over
>>> moderate/longer periods of time.
>>
>> More painful, sure, but not too bad IME. In particular, if you know the
>> regression is in Mesa, you can always use a stable release of LLVM for
>> the bisect. You only need to change the --with-llvm-prefix= parameter to
>> Mesa's configure for that. Of course, it could still be mildly painful
>> if you need to go so far back that the current stable LLVM release
>> wasn't supported yet. But how often does that happen? Very rarely for me.
>>
> Sure, it's not impossible, but is that really the kind of process you
> want users to go through when bisecting a regression? Perhaps throw in
> building 32-bit versions of both Mesa and LLVM on 64-bit as well if
> they want to run 32-bit applications.
>
>> Without LLVM, I'm not sure there would be a driver you could avoid. :)
>>
> R600g didn't really exist either, and that one seems to have worked
> out fine. I think in a large part because of work done by Jerome and
> Dave in the early days, but regardless. From what I've seen from SI, I
> don't think radeonsi needed to be a separate driver to start with, and
> while its ISA is certainly different from R600-Cayman, it doesn't
> particularly strike me as much harder to work with.
>
> Back to the more immediate topic though, I think think that on
> occasion the discussion is framed as "Is there any reason using LLVM
> IR wouldn't work?", while it would perhaps be more appropriate to
> think of as "Would using LLVM IR provide enough advantages to justify
> adding a LLVM dependency to core Mesa?".

Could we use an llvm compatible IR? is also a question I'd like to see answered.

Dave.