[Mesa-dev] [r600g] Is LLVM-compiler (--enable-r600-llvm-compiler) usable, now?

Michel Dänzer michel at daenzer.net
Wed Oct 22 19:34:57 PDT 2014

On 23.10.2014 02:24, Alex Deucher wrote:
> On Wed, Oct 22, 2014 at 12:49 PM, Dieter Nützel <Dieter at nuetzel-hh.de> wrote:
>> subject say it all ;-)
> The llvm support for r600g is for compute (OpenCL).  The fact that is
> it somewhat usable for graphics is mainly for testing purposes.  There
> are no plans to expand it to handle additional graphics features,
> although any interested parties are welcome to contribute to improving
> it.  IIRC, even when you enable it, it currently only gets applied to
> compute shaders.

The LLVM compiler is used automatically for OpenCL, even without 
--enable-r600-llvm-compiler. That option allows using LLVM for graphics 
as well, but it's currently disabled by default at runtime, the user 
needs to explicitly enable it via the environment variable 
R600_DEBUG=llvm or R600_LLVM=1. Due to the limitations of that (no 
geometry shader support and other missing functionality, lots of bugs), 
I'd currently recommend against enabling it unless you want to work on 
fixing its problems.

>> Second, we are now nearly on par with 3.16 on RV730 (AGP) with all your
>> latest work, but I think about what we could get if we find the right commit
>> between 3.16 (.4 here) and 3.17-rc1 (the transition from 3.16 to 3.17-next).
>> I do not have 3.16.x around (it is not any longer in the openSUSE kernel
>> current tree) but with latest 3.16.4 I was faster then with all 3.17.x and
>> 3.18/3.19-next kernels.

Faster doing what?

>> WC helped on RV730 (AGP) with some apps, here:

What exactly do you mean by 'WC helped'? CPU mappings of GTT have always 
used write-combining with AGP, so unless you disable AGP, the changes 
related to that shouldn't change anything.

Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer

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