[Mesa-dev] Testing optimizer

[Paul Berry]

On 17 December 2013 11:07, Patrick Baggett <baggett.patrick at gmail.com>wrote:

>
>
>
> On Tue, Dec 17, 2013 at 10:59 AM, Paul Berry <stereotype441 at gmail.com>wrote:
>
>> On 17 December 2013 08:46, Tom Stellard <tom at stellard.net> wrote:
>>
>>> On Tue, Dec 17, 2013 at 09:57:31AM -0600, Patrick Baggett wrote:
>>> > Hi all,
>>> >
>>> > Is there a way to see the machine code that is generated by the GLSL
>>> > compiler for all GPU instruction sets? For example, I would like to
>>> know if
>>> > the optimizer optimizes certain (equivalent) constructs (or not), and
>>> avoid
>>> > them if possible. I know there is a lot to optimization on GPUs that I
>>> > don't know, but I'd still like to get some ballpark estimates. For
>>> example,
>>> > I'm curious whether:
>>>
>>> Each driver has its own environment variable for dumping machine code.
>>>
>>> llvmpipe: GALLIVM_DEBUG=asm (I think you need to build mesa
>>>                              with --enable-debug for this to work)
>>> r300g: RADEON_DEBUG=fp,vp
>>> r600g, radeonsi: R600_DEBUG=ps,vs
>>>
>>> I'm not sure what the other drivers use.
>>>
>>> -Tom
>>>
>>
>> I believe every driver also supports MESA_GLSL=dump, which prints out the
>> IR both before and after linking (you'll want to look at the version after
>> linking to see what optimizations have been applied, since some
>> optimizations happen at link time).  Looking at the IR rather than the
>> machine code is more likely to give you the information you need, since
>> Mesa performs the same IR-level optimizations on all architectures, whereas
>> the optimizations that happen at machine code level are vastly different
>> from one driver to the next.
>>
>>
> I do want to see both, actually. For example, if a driver implements a
> specific optimization (machine code level) and another driver clearly does
> not, then that would be considered "interesting" to me.
>

Ok, in that case the environment variable you want for seeing the generated
assembly code for Intel is:

INTEL_DEBUG=vs,fs,gs


>
>
>
>> Another thing which might be useful to you is Aras Pranckevičius's
>> "glsl-optimizer" project (https://github.com/aras-p/glsl-optimizer),
>> which performs Mesa's IR-level optimizations on a shader and then
>> translates it from IR back to GLSL.
>>
>> Paul
>>
>>
> Thanks to everyone for the great tips!
>
>
>>
>>> >
>>> >     //let p1, p2, p3 be vec2 uniforms
>>> >
>>> >     vec4(p1, 0, 0) + vec4(p2, 0, 0) + vec4(p3, 0, 1)
>>> >
>>> > produces identical machine code as:
>>> >
>>> >     vec4(p1+p2+p3, 0, 1);
>>> >
>>> > for all architectures supported by Mesa.
>>>
>>> > _______________________________________________
>>> > 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
>>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20131217/1a6d58b3/attachment-0001.html>