[X86] Rewrite the zero vector checks in lowerV2X128VectorShuffle to use the Zeroable APInt
[X86] Rewrite the zero vector checks in lowerV2X128VectorShuffle to use the Zeroable APInt

We already have zeroable bits in an APInt. We might as well use that instead of checking for an all zero BUILD_VECTOR.

Differential Revision: https://reviews.llvm.org/D37950

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@314332 91177308-0d34-0410-b5e6-96231b3b80d8

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