[X86][SSE] Attempt to combine 64-bit and 16-bit shuffles to unary shuffles before...

[X86][SSE] Attempt to combine 64-bit and 16-bit shuffles to unary shuffles before bit shifts

We are combining shuffles to bit shifts before unary permutes, which means we can't fold loads plus the destination register is destructive

The 32-bit shuffles are a bit tricky and will be dealt with in a later patch

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306977 91177308-0d34-0410-b5e6-96231b3b80d8