Make the 'shrink global to bool' optimization more self contained, and thus  easier to show that its safe.  No functionality change.
Make the 'shrink global to bool' optimization more self contained, and thus 
easier to show that its safe.  No functionality change.


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@45946 91177308-0d34-0410-b5e6-96231b3b80d8

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