[X86] Simplify early-exit check. NFC.
[X86] Simplify early-exit check. NFC.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@265447 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 90af9e70145ed233a4e63abf51021cebc2e56a05)

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm