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 <tarc...@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@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@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
