[NFC] Better encapsulation of llvm::Optional Storage
[NFC] Better encapsulation of llvm::Optional Storage

Second attempt, trying to navigate out of the UB zone using
union for storage instead of raw bytes.

I'm prepared to revert that commit as soon as validation breaks,
which is likely to happen.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@354238 91177308-0d34-0410-b5e6-96231b3b80d8

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