[Mesa-dev] [PATCH 7/8] glsl: Optimize "if (cond) discard; " to a conditional discard.

[Connor Abbott]

On Tue, Feb 24, 2015 at 11:39 AM, Matt Turner <mattst88 at gmail.com> wrote:
> On Tue, Feb 24, 2015 at 7:53 AM, Jason Ekstrand <jason at jlekstrand.net> wrote:
>> On Tue, Feb 24, 2015 at 2:19 AM, Kenneth Graunke <kenneth at whitecape.org>
>> wrote:
>>>
>>> st_glsl_to_tgsi and ir_to_mesa have handled conditional discards for a
>>> long time; the previous patch added that capability to i965.
>>>
>>> i965 (Haswell) shader-db stats:
>>>
>>> Without NIR:
>>> total instructions in shared programs: 5792133 -> 5776360 (-0.27%)
>>> instructions in affected programs:     737585 -> 721812 (-2.14%)
>>> helped:                                6300
>>> HURT:                                  68
>>> GAINED:                                2
>>>
>>> With NIR:
>>> total instructions in shared programs: 5787538 -> 5769569 (-0.31%)
>>> instructions in affected programs:     767843 -> 749874 (-2.34%)
>>> helped:                                6522
>>> HURT:                                  35
>>> GAINED:                                6
>>
>>
>> What all do you have in that branch?  Last I checked (10 minutes ago), NIR
>> wasn't beating GLSL IR yet.
>> --Jason
>
> I think you misread. Those stats are just for this patch, and they
> show NIR generating more instructions than non-NIR.

> Without NIR:
> total instructions in shared programs: 5792133 -> 5776360 (-0.27%)

> With NIR:
> total instructions in shared programs: 5787538 -> 5769569 (-0.31%)

So either I fail at reading comprehension, or the stats show us
generating more instructions with non-NIR than with NIR. Maybe Ken ran
the comparison on top of his Mesa IR -> NIR series? We get some
*serious* improvements in the ARB shaders when we run them through
NIR, so I wouldn't be too surprised if NIR starts beating non-NIR
after we start using the NIR path for those.

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