Implement Transforms/SimplifyCFG/switch_thread.ll

This does a simple form of "jump threading", which eliminates CFG edges that
are provably dead.  This triggers 90 times in the external tests, and
eliminating CFG edges is always always a good thing! :)

llvm-svn: 20300
1 file changed
tree: ba5cd04505f6110ed11865e0e0ffa4c9c377909e
  1. llvm/