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 %
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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
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