Extend SimplifyCFG's common-destination folding heuristic to allow a single "bonus" instruction to be speculatively executed.  Add a heuristic to ensure we're not tripping up out-of-order execution by checking that this bonus instruction only uses values that were already guaranteed to be available.
Extend SimplifyCFG's common-destination folding heuristic to allow a single
"bonus" instruction to be speculatively executed.  Add a heuristic to
ensure we're not tripping up out-of-order execution by checking that this bonus
instruction only uses values that were already guaranteed to be available.

This allows us to eliminate the short circuit in (x&1)&&(x&2).


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@108351 91177308-0d34-0410-b5e6-96231b3b80d8

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