[all-commits] [llvm/llvm-project] 31ed36: [X86] SimplifyDemandedVectorElts - attempt to reco...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 31ed36d0447def348af7b1d27daceb57d063382f
      https://github.com/llvm/llvm-project/commit/31ed36d0447def348af7b1d27daceb57d063382f
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2019-11-04 (Mon, 04 Nov 2019)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/avx512-intrinsics-fast-isel.ll
    M llvm/test/CodeGen/X86/shrink_vmul.ll
    M llvm/test/CodeGen/X86/vec_smulo.ll
    M llvm/test/CodeGen/X86/vec_umulo.ll

  Log Message:
  -----------
  [X86] SimplifyDemandedVectorElts - attempt to recombine target shuffle using DemandedElts mask (REAPPLIED)

If we don't demand all elements, then attempt to combine to a simpler shuffle.

At the moment we can only do this if Depth == 0 as combineX86ShufflesRecursively uses Depth to track whether the shuffle has really changed or not - we'll need to change this before we can properly start merging combineX86ShufflesRecursively into SimplifyDemandedVectorElts (see D66004).

This reapplies rL368307 (reverted at rL369167) after the fix for the infinite loop reported at PR43024 was applied at rG3f087e38a2e7b87a5adaaac1c1b61e51220e7ff3