[NewGVN] Add a test for non most dominating leader.
[NewGVN] Add a test for non most dominating leader.

Taken from PR32845. Dan removed the most dominating leader check
in r303443, but we check this test anyway to make sure things
don't regress.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@303515 91177308-0d34-0410-b5e6-96231b3b80d8

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