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

[Dave Airlie]

On 22 August 2014 12:46, Jason Ekstrand <jason at jlekstrand.net> wrote:
> On Thu, Aug 21, 2014 at 7:36 PM, Dave Airlie <airlied at gmail.com> wrote:
>>
>> 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.
>
>
> What do you mean by llvm compatible?  Do you mean forking their IR inside
> mesa or just something that's easy to translate back and forth?
>

Importing/forking the llvm IR code with a different symbol set, and
trying to not intentionally
be incompatible with their llvm.

Dave.