Add code for lowering v32i8 shifts by a splat to AVX2 immediate shift instructions. Remove 256-bit splat handling from LowerShift as it was already handled by PerformShiftCombine.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145005 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed