[InstCombine] add rotate narrowing tests with odd types; NFC
[InstCombine] add rotate narrowing tests with odd types; NFC

There's a potential miscompile here. It's unlikely in the real 
world because this transform is guarded with shouldChangeType(), 
but this test file doesn't include a standard data-layout for
some reason (despite including a custom 1), so we can see the bug. 


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@346966 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm