[Tests] Add tests for D62939 (miscompiles around dead pointer IVs)
[Tests] Add tests for D62939 (miscompiles around dead pointer IVs)

Flesh out a collection of tests for switching to a dead IV within LFTR, both for the current miscompile, and for some cases which we should be able to handle via simple reasoning.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@362976 91177308-0d34-0410-b5e6-96231b3b80d8

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