[X86] Convert ==/!= comparisons with -1 for checking undef in shuffle lowering to comparisons of <0 or >=0. While there do the same for other kinds of index checks that can just check for greater than 0. No functional change intended.
[X86] Convert ==/!= comparisons with -1 for checking undef in shuffle lowering to comparisons of <0 or >=0. While there do the same for other kinds of index checks that can just check for greater than 0. No functional change intended.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@273788 91177308-0d34-0410-b5e6-96231b3b80d8

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