[Mesa-dev] V2 radeonsi use STD430 packing of UBOs by default
Timothy Arceri
tarceri at itsqueeze.com
Wed Aug 30 07:18:19 UTC 2017
On 30/08/17 10:25, Marek Olšák wrote:
> I have to conclude that I don't see a way to use LOAD with CONSTBUF
> and keep the same performance as before. It looks like there are some
> deficiencies in our compiler stack that are unfixable in Mesa alone.
Well that's frustrating :( Pretty much makes finishing off uniform
packing [1] pointless. Besides an issue with matrices and some tidy ups
it was mostly done.
[1] https://github.com/tarceri/Mesa/compare/uniform_packing5
>
> Marek
>
> On Wed, Aug 30, 2017 at 2:11 AM, Marek Olšák <maraeo at gmail.com> wrote:
>> Related IRC discussion:
>>
>> 00:01 < mareko> arsenm: what are the chances I can convince you to
>> allow me to set mayLoad = 0 on s_buffer_load_dword? :) the instruction
>> always reads from read-only memory with Mesa
>> 00:02 < mareko> apparently, readnone doesn't get through
>> 00:02 < arsenm> mareko: you should get the same effect by having
>> invariant on the MMO
>> 00:03 < mareko> arsenm: and how would I set invariant on SI.load.const?
>> 00:04 < arsenm> mareko: we create MMOs for a few other intrinsics
>> already, it should be the same
>> 00:05 < mareko> if only I had time to play with LLVM
>> 00:05 < arsenm> mareko: it looks like that is already done so it might
>> be a more specific problem
>> 00:05 < arsenm> that rematerializable scalar loads patch is probably
>> OK now though
>> 00:07 < arsenm> https://reviews.llvm.org/D11621
>>
>> Marek
>>
>>
>> On Wed, Aug 30, 2017 at 1:58 AM, Marek Olšák <maraeo at gmail.com> wrote:
>>> Interesting. It may be that glsl_to_tgsi uses copy propagation to fold
>>> those CONST loads into operands, which puts them next to their uses in LLVM.
>>>
>>> I guess LLVM doesn't understand that s_buffer_load_dword loads from
>>> immutable dereferenceable memory. It would benefit from mayLoad = 0 in
>>> this case I think.
>>>
>>> Marek
>>>
>>> On Thu, Aug 24, 2017 at 11:48 AM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
>>>>
>>>>
>>>> On 24/08/17 18:12, Nicolai Hähnle wrote:
>>>>>
>>>>> On 24.08.2017 09:45, Timothy Arceri wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 22/08/17 22:14, Timothy Arceri wrote:
>>>>>>>
>>>>>>> I'm a little unsure what to do with this now. Below is my shader-db
>>>>>>> results, the majority of negative changes are from Natural Selection
>>>>>>> 2.
>>>>>>>
>>>>>>> I looked at some dumps of the worst Natural Selection 2 shaders and
>>>>>>> it seems to just be scheduling differences causing the regressions.
>>>>>>>
>>>>>>> I tested with sisched but that just made things even worse.
>>>>>>>
>>>>>>> Obviously we should be aiming to improve the schedulare, but since
>>>>>>> this regresses things and I have no evidence of it helping anything
>>>>>>> it makes the case for adding it pretty weak.
>>>>>>>
>>>>>>> Thoughts??
>>>>>>>
>>>>>>> PERCENTAGE DELTAS Shaders SGPRs VGPRs SpillSGPR MaxWaves
>>>>>>> --------------------------------------------------------------------
>>>>>>> All affected 5797 2.92 3.05 % 5.04 % -2.94
>>>>>>> -------------------------------------------------------------------
>>>>>>> Total 72287 0.28 % 0.34 % 0.33 % -0.21 %
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> mesa-dev mailing list
>>>>>>> mesa-dev at lists.freedesktop.org
>>>>>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
>>>>>>>
>>>>>>
>>>>>>
>>>>>> As far as I can tell this is because after this chnage we end up with
>>>>>> large sections of consecutive loads. Any thoughts on avoid this?
>>>>>
>>>>>
>>>>> Odd. Do you see the same change in TGSI?
>>>>>
>>>>> This is one of those things that ideally LLVM would be smart about, but
>>>>> unfortunately it isn't really.
>>>>
>>>>
>>>> Yeah I assume it's very doable since SSA makes this stuff reasonably easy to
>>>> deal with. However I'm not really sure where to begin, or how welcome a pass
>>>> to do this sorting would be. We have a similar pass in nir for moving
>>>> comparisons to where they are first used.
>>>>
>>>> The TGSI is introduces an extra temp to store the value of the LOAD, this is
>>>> probably what triggers the difference in LLVM.
>>>>
>>>> eg.
>>>>
>>>> LOAD TEMP[61], UBO[2], IMM[2].yyyy
>>>> LOAD TEMP[62], UBO[2], IMM[1].zzzz
>>>> LOAD TEMP[63], UBO[2], IMM[1].wwww
>>>> LOAD TEMP[64], UBO[2], IMM[2].xxxx
>>>> DP4 TEMP[65].x, TEMP[60], TEMP[61]
>>>> DP4 TEMP[66].x, TEMP[60], TEMP[62]
>>>> MOV TEMP[65].y, TEMP[66].xxxx
>>>> DP4 TEMP[67].x, TEMP[60], TEMP[63]
>>>> MOV TEMP[65].z, TEMP[67].xxxx
>>>> DP4 TEMP[68].x, TEMP[60], TEMP[64]
>>>> MOV TEMP[69].w, TEMP[68].xxxx
>>>> MOV TEMP[69].xyz, TEMP[65].xyzx
>>>> LOAD TEMP[70], UBO[1], IMM[6].yyyy
>>>> LOAD TEMP[71], UBO[1], IMM[6].zzzz
>>>> DP4 TEMP[72].x, TEMP[69], TEMP[70]
>>>> DP4 TEMP[73].x, TEMP[69], TEMP[71]
>>>> LOAD TEMP[74], UBO[1], IMM[6].wwww
>>>> LOAD TEMP[75], UBO[1], IMM[7].xxxx
>>>> LOAD TEMP[76], UBO[1], IMM[7].yyyy
>>>> LOAD TEMP[77], UBO[1], IMM[7].zzzz
>>>> DP4 TEMP[78].x, TEMP[69], TEMP[74]
>>>> DP4 TEMP[79].x, TEMP[69], TEMP[75]
>>>> MOV TEMP[78].y, TEMP[79].xxxx
>>>> DP4 TEMP[80].x, TEMP[69], TEMP[76]
>>>> MOV TEMP[78].z, TEMP[80].xxxx
>>>> DP4 TEMP[81].x, TEMP[69], TEMP[77]
>>>> MOV TEMP[78].w, TEMP[81].xxxx
>>>>
>>>> vs
>>>>
>>>> DP4 TEMP[63].x, TEMP[62], CONST[2][0]
>>>> DP4 TEMP[64].x, TEMP[62], CONST[2][1]
>>>> MOV TEMP[63].y, TEMP[64].xxxx
>>>> DP4 TEMP[65].x, TEMP[62], CONST[2][2]
>>>> MOV TEMP[63].z, TEMP[65].xxxx
>>>> DP4 TEMP[66].x, TEMP[62], CONST[2][3]
>>>> MOV TEMP[67].w, TEMP[66].xxxx
>>>> MOV TEMP[67].xyz, TEMP[63].xyzx
>>>> DP4 TEMP[68].x, TEMP[67], CONST[1][14]
>>>> DP4 TEMP[69].x, TEMP[67], CONST[1][15]
>>>> DP4 TEMP[70].x, TEMP[67], CONST[1][8]
>>>> DP4 TEMP[71].x, TEMP[67], CONST[1][9]
>>>> MOV TEMP[70].y, TEMP[71].xxxx
>>>> DP4 TEMP[72].x, TEMP[67], CONST[1][10]
>>>> MOV TEMP[70].z, TEMP[72].xxxx
>>>> DP4 TEMP[73].x, TEMP[67], CONST[1][11]
>>>> MOV TEMP[70].w, TEMP[73].xxxx
>>>> MOV TEMP[74].xyw, TEMP[70].xyxw
>>>>
>>>>>
>>>>> Cheers,
>>>>> Nicolai
>>>>>
>>>> _______________________________________________
>>>> mesa-dev mailing list
>>>> mesa-dev at lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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