[PATCH] D143731: [AMDGPU] Break-up large PHIs for DAGISel

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Target/AMDGPU/AMDGPUCodeGenPrepare.cpp:1415
+
+  return B.CreateExtractVector(SubVecTy, Val, B.getInt64(Idx));
+}
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Pierre-vh wrote:
> arsenm wrote:
> > This must be a new intrinsic, I didn't know it existed. Usually you would do a shufflevector to get the reduced elements
> If shufflevector has better handling and gets folded out for sure then it might be simpler to use it.
> Do I just do a shufflevector with the same operand twice + the mask of the indexes I want?
You can use poison for the second operand 


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  https://reviews.llvm.org/D143731/new/

https://reviews.llvm.org/D143731