[PRE] Add a bunch of test cases for LICM-like PRE patterns
[PRE] Add a bunch of test cases for LICM-like PRE patterns

These were inspired by a very old review I'm about to abandon (https://reviews.llvm.org/D7061).  Several of the test cases from that worked without modification and expanding test coverage of such cases is always worthwhile.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@321764 91177308-0d34-0410-b5e6-96231b3b80d8

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