On Tue, Sep 13, 2016 at 8:16 PM, Nicolai Hähnle <nhaeh...@gmail.com> wrote: > > 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.
Yeah. The problem is the LICM (moving stuff out of loops) and Sink (moving stuff forward) passes are no-ops with intrinsics, because intrinsics fail the "isSafeToSpeculativelyExecute" function. The trivial fix would be to add a new "movable" flag for intrinsics and process it in that function. Marek _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
