CodeGen: Fix a use-after-free in TailDuplication
CodeGen: Fix a use-after-free in TailDuplication

The call to processPHI already erased MI from its parent, so MI isn't
even valid here, making the getParent() call a use-after-free in
addition to being redundant.

Found by ASan with the ArrayRecycler changes in llvm.org/pr26808.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@266008 91177308-0d34-0410-b5e6-96231b3b80d8

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