[LICM] Restructure implicit exit handling to be more clear [NFCI]
[LICM] Restructure implicit exit handling to be more clear [NFCI]

When going to explain this to someone else, I got tripped up by the complicated meaning of IsKnownNonEscapingObject in load-store promotion.  Extract a helper routine and clarify naming/scopes to make this a bit more obvious.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@316699 91177308-0d34-0410-b5e6-96231b3b80d8

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