[PATCH] D87174: [GlobalISel] Add `X,Y<dead> = G_UNMERGE Z` -> X = G_TRUNC Z

[Quentin Colombet via Phabricator via llvm-commits]

qcolombet created this revision.
qcolombet added reviewers: aemerson, paquette, arsenm, volkan.
Herald added subscribers: kerbowa, hiraditya, rovka, nhaehnle, jvesely.
Herald added a project: LLVM.
qcolombet requested review of this revision.
Herald added a subscriber: wdng.

Add a combiner helper that replaces G_UNMERGE where all the destination lanes
are dead expect the first one with a G_TRUNC.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D87174

Files:
  llvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h
  llvm/include/llvm/Target/GlobalISel/Combine.td
  llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/combine-unmerge.mir
  llvm/test/CodeGen/AMDGPU/GlobalISel/combine-shl-narrow.mir
  llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-llvm.amdgcn.image.store.2d.d16.ll
  llvm/test/CodeGen/AMDGPU/GlobalISel/llvm.amdgcn.s.buffer.load.ll
  llvm/test/CodeGen/AMDGPU/GlobalISel/postlegalizercombiner-select.mir
  llvm/test/CodeGen/AMDGPU/GlobalISel/regbankselect-amdgcn.s.buffer.load.ll

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