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

[Christian König]

Am 22.08.2014 um 17:13 schrieb Connor Abbott:
> On Thu, Aug 21, 2014 at 11:08 PM, Dave Airlie <airlied at gmail.com> wrote:
>> 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.
> That sounds like a huge amount of work, possibly even more work than
> going it on our own because the LLVM project moves really quickly and
> we'd have to import all of the changes. Also, it seems pretty ugly and
> I'm sure distro maintainers would just looooooove a solution like that
> /s. Just look at the situation with Chromium and Fedora now (or at
> least last I checked).

Actually the LLVM IR is considered stable and as Dave explained we 
wouldn't depend on LLVM, but rather just use the same concept for the IR.

This actually sounds like a pretty good idea to me. And I would say we 
should just continue moving the GLSL IR towards SSA and all the 
specialized GL opcodes into something similar to LLVM intrinsics.

Christian.

>
> Connor
>
>> Dave.
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev