[all-commits] [llvm/llvm-project] 3f90df: [ARM] MVE reverse shuffles.

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3f90df22f1b72932016102daf8e92e99252e5589
      https://github.com/llvm/llvm-project/commit/3f90df22f1b72932016102daf8e92e99252e5589
  Author: David Green <david.green at arm.com>
  Date:   2021-09-20 (Mon, 20 Sep 2021)

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

  Log Message:
  -----------
  [ARM] MVE reverse shuffles.

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.

Differential Revision: https://reviews.llvm.org/D69510