[PATCH] D97731: [AArch64][GlobalISel] Lower G_BUILD_VECTOR -> G_DUP for non-constant splats

[Jessica Paquette via Phabricator via llvm-commits]

paquette created this revision.
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If we have

  %vec = G_BUILD_VECTOR %reg, %reg, ..., %reg

Then lower it to

  %vec = G_DUP %reg

Only do this when `%reg` is not a constant. In the case of a constant, we should prefer MOV.

Minor code size improvements on CTMark at -Os.


https://reviews.llvm.org/D97731

Files:
  llvm/lib/Target/AArch64/AArch64Combine.td
  llvm/lib/Target/AArch64/GISel/AArch64PostLegalizerLowering.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/postlegalizer-lowering-build-vector-to-dup.mir

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