Optimize a common case in the Lengauer-Tarjan dominators algorithm. This gives a 9.7% speedup running domtree on test-suite.
Optimize a common case in the Lengauer-Tarjan dominators algorithm. This gives a
9.7% speedup running domtree on test-suite.

Reviewed by Chris Lattner.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@120003 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,dslab-epfl/asap,llvm-mirror/llvm,chubbymaggie/asap,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,dslab-epfl/asap,apple/swift-llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,dslab-epfl/asap,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,chubbymaggie/asap,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,llvm-mirror/llvm,chubbymaggie/asap,chubbymaggie/asap,llvm-mirror/llvm,chubbymaggie/asap,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,llvm-mirror/llvm,chubbymaggie/asap