[Mesa-dev] [PATCH 00/23] Handle Booleans and things better
Jason Ekstrand
jason at jlekstrand.net
Fri Mar 20 15:10:42 PDT 2015
On Fri, Mar 20, 2015 at 1:58 PM, Ian Romanick <idr at freedesktop.org> wrote:
> This is a series that I've been working on for quite some time. Some of
> these patches data from as long ago as July 2014. It's finally time to
> just send it out. I have felt like I have been shaving an infinite yak,
> and I have some additional patchs in-progress that will go on top of
> this series.
>
> Overall results for the without NIR:
>
> GM45 (0x2A42):
> total instructions in shared programs: 3550788 -> 3544141 (-0.19%)
> instructions in affected programs: 513721 -> 507074 (-1.29%)
> helped: 1409
> HURT: 269
>
> Iron Lake (0x0046):
> total instructions in shared programs: 4980593 -> 4973020 (-0.15%)
> instructions in affected programs: 572150 -> 564577 (-1.32%)
> helped: 1649
> HURT: 386
> GAINED: 5
> LOST: 24
>
> Sandy Bridge (0x0116):
> total instructions in shared programs: 6817068 -> 6797680 (-0.28%)
> instructions in affected programs: 1388229 -> 1368841 (-1.40%)
> helped: 5343
> HURT: 319
> GAINED: 4
> LOST: 11
>
> Ivy Bridge (0x0166):
> total instructions in shared programs: 6290138 -> 6273022 (-0.27%)
> instructions in affected programs: 1204828 -> 1187712 (-1.42%)
> helped: 4558
> HURT: 825
> GAINED: 1
> LOST: 3
>
> Haswell (0x0426):
> total instructions in shared programs: 5777876 -> 5759525 (-0.32%)
> instructions in affected programs: 1130638 -> 1112287 (-1.62%)
> helped: 4830
> HURT: 606
> GAINED: 1
> LOST: 3
>
> Broadwell (0x162E):
> total instructions in shared programs: 6821191 -> 6806526 (-0.21%)
> instructions in affected programs: 1252081 -> 1237416 (-1.17%)
> helped: 5090
> HURT: 608
> GAINED: 4
> LOST: 4
FYI: I added a "-p" for platform option to Matt's fancy new
shader-runner so you can do "./run -p bdw shaders" and it does the
INTEL_DEVID_OVERRIDE for you. I was doing similar experiments this
week (running shader-db on everything) and found it useful. Thought
you might like to know.
> In some ways the results with NIR are even better (if you ignore Sandy
> Bridge):
>
> Sandy Bridge (0x0116) NIR:
> total instructions in shared programs: 6820689 -> 6785869 (-0.51%)
> instructions in affected programs: 1858575 -> 1823755 (-1.87%)
> helped: 4559
> HURT: 3320
> GAINED: 3
> LOST: 29
>
> Ivy Bridge (0x0166) NIR:
> total instructions in shared programs: 6309309 -> 6276897 (-0.51%)
> instructions in affected programs: 1639688 -> 1607276 (-1.98%)
> helped: 4053
> HURT: 3496
> GAINED: 34
> LOST: 3
>
> Haswell (0x0426) NIR:
> total instructions in shared programs: 5790261 -> 5751689 (-0.67%)
> instructions in affected programs: 1506127 -> 1467555 (-2.56%)
> helped: 5407
> HURT: 1957
> GAINED: 28
> LOST: 3
>
> Broadwell (0x162E) NIR:
> total instructions in shared programs: 7012929 -> 6977716 (-0.50%)
> instructions in affected programs: 1604094 -> 1568881 (-2.20%)
> helped: 5626
> HURT: 2029
> GAINED: 20
> LOST: 3
>
> In that there are 12 shaders that are hurt (by ~40 instructions) because
> we are now able to unroll a loop. This is noted in the commit message
> of "glsl: Optimize certain if-statements to just casts from the
> condition".
>
> There are a couple commits that hurt a fair number of shaders with NIR.
> It doesn't seem like this should be the case, and it seems like there is
> probably work that can be done in brw_fs_nir.cpp to account for this.
What commits were those? In particular, what was needed to avoid
regressions from later commits?
> Without some of the initial changes to brw_fs_visitor.cpp, there were
> also regressions without NIR. All of the changes in this series at the
> GLSL IR level are things that could have been written in the shader
> source.
As the local defender of NIR, I feel the need to say that it would be
good if someone threw together a few patches to try and mirror the
algebraic optimizations here in NIR. Patches 8, 9, 11, 12, 13, 14,
16, and 23 could be implemented with a line or two each in
nir_opt_algebraic.py.
There are a couple of reasons I'm asking for this. One is that NIR
may be able to CSE something that results in one of these patterns and
we wouldn't get the optimization. Another reason is that with Ken's
work to run ARB programs through NIR, we would like those to get as
many optimizations as the can and they b2f the universe. As an aside,
it would also be nice to get shader-db numbers for just the NIR
versions without the glsl versions optimizing ahead of it. That will
be much easier to do *before* this series lands.
> At the end of the day on Broadwell with NIR, there are a bunch of
> shaders (some as small as ~22 instructions) hurt by 1 to 4 instructions.
> Only one shader is really hurt (119 -> 139). This shader is noted in
> patch "glsl: Distribute multiply over b2f". At the same time, over 250
> shaders with more than 100 instructions are helped by more than 20%.
> Oh, and we gained 20 SIMD16 shaders. :)
>
> This series is also available as the bool-optimizations-v6 branch in my
> fd.o Mesa repo.
>
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