[PATCH] D140289: [AArch64] Combine Trunc(DUP) -> DUP

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: SjoerdMeijer, samtebbs, bipmis, fhahn.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: All.
dmgreen requested review of this revision.
Herald added a project: LLVM.

This adds a simple fold of `TRUNCATE(AArch64ISD::DUP)` -> `AArch64ISD::DUP`, which can help generate more optimal UMULL sequences, and seems useful in general.


https://reviews.llvm.org/D140289

Files:
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/test/CodeGen/AArch64/aarch64-dup-ext.ll
  llvm/test/CodeGen/AArch64/aarch64-smull.ll
  llvm/test/CodeGen/AArch64/dag-combine-trunc-build-vec.ll

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