BBVectorize: Remove the linear searches from pair connection searching
BBVectorize: Remove the linear searches from pair connection searching

This removes the last of the linear searches over ranges of std::multimap
iterators, giving a 7% speedup on the doduc.bc input from PR15222.

No functionality change intended.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@174859 91177308-0d34-0410-b5e6-96231b3b80d8

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