[PATCH] D69510: [ARM] MVE reverse shuffles.

[Dave Green via Phabricator via llvm-commits]

dmgreen created this revision.
dmgreen added reviewers: t.p.northover, samparker, SjoerdMeijer, ostannard, simon_tatham.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: LLVM.

The vectorizer can sometimes make reverse shuffles from indices that count down. In MVE, we don't have a 128bit rev instruction, but we can select this to a VREV64 with some lane movs to swap the two halfs.

Ideally this would use VMOVD's, but only gets as far as VMOVS's at the moment.


https://reviews.llvm.org/D69510

Files:
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/test/CodeGen/Thumb2/mve-shuffle.ll
  llvm/test/CodeGen/Thumb2/mve-shufflemov.ll

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