On 13.09.2016 19:13, Marek Olšák wrote:
This is quite easy because we just have to get rid of all of
the preloading at the beginning of shaders.
I also removed preloading of PS inputs with literal indexing, which
has almost the same effect as sinking interp instructions.
I'm slightly concerned that LICM won't move interps because they are
not considered speculatively-executable (=movable) by LLVM, but
the shader-db stats show that it doesn't matter.
LLVM is smart enough to do CSE where needed for both descriptor loads
and interps. In fact, it's the CSE which is responsible for some of
the remaining SGPR spills. (It makes sense if you think about it)
The compile time increased by 6% because CSE has a lot more work,
but it's certainly worth it.
shader-db stats:
[PATCH 4/6] radeonsi: get rid of img/buf/sampler descriptor
https://people.freedesktop.org/~mareko/no_preload1.html
[PATCH 5/6] radeonsi: get rid of constant buffer preloading
https://people.freedesktop.org/~mareko/no_preload2.html
[PATCH 6/6] radeonsi: reload PS inputs with direct indexing at each
https://people.freedesktop.org/~mareko/no_preload3_ps.html
Total diff:
https://people.freedesktop.org/~mareko/no_preload_total.html
Those numbers are impressive.
We do have to be slightly careful, I noticed that LLVM didn't lift some
constant loads out of loops with the earlier preload removal, in shaders
where SGPR pressure wasn't an issue at all.
I think the right way to deal with this is to improve heuristics in
LLVM, so I'm fine with changing Mesa in this way.
Some comments sent in reply to the respective patches. Patches 2, 3, and
5 are
Reviewed-by: Nicolai Hähnle <nicolai.haeh...@amd.com>
Please review.
Marek
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