On Fri, May 8, 2015 at 10:08 AM, Jason Ekstrand <ja...@jlekstrand.net> wrote: > On Fri, May 8, 2015 at 3:27 AM, Kenneth Graunke <kenn...@whitecape.org> wrote: >> On Thursday, May 07, 2015 06:17:46 PM Matt Turner wrote: >>> On Thu, May 7, 2015 at 4:50 PM, Jason Ekstrand <ja...@jlekstrand.net> wrote: >>> > GLSL IR vs. NIR shader-db results for SIMD8 vertex shaders on Broadwell: >>> > >>> > total instructions in shared programs: 2724483 -> 2711790 (-0.47%) >>> > instructions in affected programs: 1860859 -> 1848166 (-0.68%) >>> > helped: 4387 >>> > HURT: 4758 >>> > GAINED: 1499 >>> > >>> > The gained programs are ARB vertext programs that were previously going >>> > through the vec4 backend. Now that we have prog_to_nir, ARB vertex >>> > programs can go through the scalar backend so they show up as "gained" in >>> > the shader-db results. >>> >>> Again, I'm kind of confused and disappointed that we're just okay with >>> hurting 4700 programs without more analysis. I guess I'll go do >>> that... >> >> I took a stab at that tonight. The good news is, the majority of the >> hurt is pretty stupid. Indirect uniform address calculations involve >> a lot of integer multiplication by 4. >> >> For whatever reason, we're getting 4*x instead of x*4, which doesn't >> support immediates. So we get: >> >> MOV tmp 4 >> MUL dst tmp x >> >> Normally, constant propagation would commute the operands, giving us >> "MUL dst x 4" like we want. But it sees integer multiplication and >> chickens out, due to the asymmetry on some platforms. > > Right. I just sent out a patch that puts immediates in src1 for > commutative ALU ops at the emit stage. We probably still want to do > something in constant propagation in case we can fold something, but > it fixes the problem for now. It also helps even more than the > shifting patch. > > I don't know. Maybe we just want to make constant propagation do the > right thing on BDW+. Matt?
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