[all-commits] [llvm/llvm-project] ba78ca: [AArch64] Use DUP for BUILD_VECTOR with few differ...

[Florian Hahn via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: ba78cae20f1467ebba6bd1005ef3e48e1fd96dee
      https://github.com/llvm/llvm-project/commit/ba78cae20f1467ebba6bd1005ef3e48e1fd96dee
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2020-10-28 (Wed, 28 Oct 2020)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/test/CodeGen/AArch64/arm64-vector-insertion.ll

  Log Message:
  -----------
  [AArch64] Use DUP for BUILD_VECTOR with few different elements.

If most elements of BUILD_VECTOR are the same, with a few different
elements, it is better to use DUP  for the common elements and
INSERT_VECTOR_ELT for the different elements.

Currently this transform is guarded quite restrictively to only trigger
in clearly beneficial cases.

With D90176, the lowering for patterns originating from code like
` float32x4_t y = {a,a,a,0};` (common in 3D apps) are lowered even
better (unnecessary fmov is removed).

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D90233