[PATCH] D124387: AMDGPU: Fold out readfirstlane between vgpr to vgpr copies
Jay Foad via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Apr 25 07:27:30 PDT 2022
foad added inline comments.
================
Comment at: llvm/lib/Target/AMDGPU/SIFoldOperands.cpp:1858
+ //
+ // => %2 = COPY %0
+ //
----------------
This transformation only makes sense if you know that %0 is uniform. I think @nhaehnle has suggested introducing a "readanylane" pseudo and/or intrinsic for that kind of use case.
I'm not sure if there is any existing code that deliberately uses readfirstlane on a non-uniform argument, but if there is then this will break it.
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https://reviews.llvm.org/D124387/new/
https://reviews.llvm.org/D124387
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