[Mesa-dev] [PATCH 0/8] i965: gl_TessLevel rescrambling in NIR

[Mark Janes]

Eero Tamminen <eero.t.tamminen at intel.com> writes:

> Hi,
>
> On 04.01.2017 13:07, Kenneth Graunke wrote:
>> This series reworks i965's handling of gl_TessLevelInner/Outer[] arrays.
>> Instead of using lower_tess_levels to turn them into vec4/vec2s, we pass
>> them through to NIR and make them compact arrays (where array indexing
>> translates to enhanced layouts components).
>>
>> This has some nice benefits.  In the last patch, we're able to drop
>> reswizzling and writemask-munging for load_output and store_output
>> in both the scalar TCS and vec4 TCS backends, as well as code to do
>> the same for TES system values.  That's 5 copies of backend code
>> replaced by a small amount of extra code in remap_patch_urb_offsets.
>>
>> It also means we can drop TES handling entirely - the ordinary input
>> handling code will handle it just fine.
>
> Have you tried whether this makes any perf difference in GpuTest v0.7 
> TessMark, GfxBench v4 tessellation, or in SynMark2 v7.0 terrain 
> tessellation tests?
>
>
>
>> This is the first step toward tessellation support in Vulkan (anv).
>> (lower_tess_levels is written in GLSL IR, so we need a replacement.)
>
> Are there yet other use-cases for Vulkan tessellation besides Sacha 
> Willems' three tests here:
> 	https://github.com/SaschaWillems/Vulkan
> ?

There are tessellation tests in the vulkancts, is that what you mean?

> 	 - Eero
>
>> This has an impact on shader-db's TCS shaders (but not a single TES):
>>
>> With scalar TCS/TES:
>>
>>    total instructions in shared programs: 13388151 -> 13387794 (-0.00%)
>>    instructions in affected programs: 31920 -> 31563 (-1.12%)
>>    helped: 75
>>    HURT: 0
>>
>>    total cycles in shared programs: 257010676 -> 257008504 (-0.00%)
>>    cycles in affected programs: 165632 -> 163460 (-1.31%)
>>    helped: 75
>>    HURT: 0
>>
>> With vec4 TCS/TES:
>>
>>    total instructions in shared programs: 13345621 -> 13345681 (0.00%)
>>    instructions in affected programs: 18593 -> 18653 (0.32%)
>>    helped: 36
>>    HURT: 25
>>
>>    total cycles in shared programs: 256761898 -> 256759952 (-0.00%)
>>    cycles in affected programs: 266644 -> 264698 (-0.73%)
>>    helped: 172
>>    HURT: 44
>>
>> The vec4 stats are not great, but I don't expect it to make much of a
>> performance difference - TCS isn't usually the bottleneck (TES is).
>> They could be improved by writing a peephole pass to detect load/stores
>> to the same base+offset with consecutive scalar components and turn them
>> into vec2/vec4 load/stores.
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev