[X86][SSE] Lower v8i16 general shifts to SSE shifts directly. NFCI.

We don't gain anything from forcing another round of generic shift lowering - we know these are legal constant splat shifts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340302 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed