On Sat, May 16, 2015 at 12:12 PM, Matt Turner <matts...@gmail.com> wrote: > On Fri, May 8, 2015 at 3:27 AM, Kenneth Graunke <kenn...@whitecape.org> wrote: >> Looking at a couple of the shaders that are still worse off...it looks >> like a ton of Source shaders used to do MUL/ADD with an attribute and >> two immediates, and now are doing MOV/MOV/MAD. > > I just looked, and thought that too for a minute, but it actually > shouldn't be doing that. Take for instance: > > shaders/closed/steam/dota-2/498.shader_test VS SIMD8: 47 -> 53 (12.77%) > > It indeed replaces 6x MUL/ADD pairs with MOV/MAD (introducing 6 extra > MOVs), but.... > > Without NIR we have > > mul(8) g15<1>F g6<8,8,1>F 6F > ... > add(8) g16<1>F g15<8,8,1>F 2.1F > add(8) g35<1>F g15<8,8,1>F 3.1F > add(8) g42<1>F g15<8,8,1>F 4.1F > add(8) g45<1>F g15<8,8,1>F 5.1F > add(8) g48<1>F g15<8,8,1>F 0.1F > add(8) g51<1>F g15<8,8,1>F 1.1F > > That is, one multiply is consumed by 6 adds. > > With NIR we have > > mov(1) g22<1>F 2.1F > mov(1) g22.1<1>F 6F > mad(8) g16<1>F g22<0,1,0>.xF g22.1<0,1,0>.xF g6<4,4,1>F > mov(1) g22.2<1>F 3.1F > mad(8) g23<1>F g22.2<0,1,0>.xF g22.1<0,1,0>.xF g6<4,4,1>F > mov(1) g22.3<1>F 4.1F > mad(8) g30<1>F g22.3<0,1,0>.xF g22.1<0,1,0>.xF g6<4,4,1>F > mov(1) g22.4<1>F 5.1F > mad(8) g33<1>F g22.4<0,1,0>.xF g22.1<0,1,0>.xF g6<4,4,1>F > mov(1) g22.5<1>F 0.1F > mad(8) g36<1>F g22.5<0,1,0>.xF g22.1<0,1,0>.xF g6<4,4,1>F > mov(1) g22.6<1>F 1.1F > mad(8) g39<1>F g22.6<0,1,0>.xF g22.1<0,1,0>.xF g6<4,4,1>F > > So we're doing the g6 * 6F operation 6 times! We see this in the NIR as well: > > vec1 ssa_419 = ffma ssa_384, ssa_132, ssa_133 > vec1 ssa_423 = ffma ssa_384, ssa_132, ssa_135 > vec1 ssa_427 = ffma ssa_384, ssa_132, ssa_137 > vec1 ssa_428 = ffma ssa_384, ssa_132, ssa_139 > vec1 ssa_429 = ffma ssa_384, ssa_132, ssa_141 > vec1 ssa_430 = ffma ssa_384, ssa_132, ssa_144 > > Whoops. Ideas for fixing that? I'm guessing that this accounts for > nearly all of the remaining 1120 hurt programs.
Ugh... We've been tacitly assuming that your constant combine stuff will magically make immediates not a problem. In this case, they are a problem. I guess we could do something different for 1 vs. 2 immediates. --Jason _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
