[X86][SSE] Move VSRAI sign extend in reg fold into SimplifyDemandedBits
[X86][SSE] Move VSRAI sign extend in reg fold into SimplifyDemandedBits

(VSRAI (VSHLI X, C1), C1) --> X iff NumSignBits(X) > C1

This works better as part of SimplifyDemandedBits than part of the general combine.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@349462 91177308-0d34-0410-b5e6-96231b3b80d8

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