[PATCH] Remove dangling BlockAddresses in GlobalDCE

[Bruno Cardoso Lopes]

Without this patch, GlobalDCE won't properly clean up blockaddress references, leaving BBs ref counts without proper update. One way to test that such ref counts are updated is to expose the module to further optimizations that actually use this refcount; simplifycfg in this example.
Other passes need to be executed before GlobalDCE to trigger the removal of @foo.addrs.

http://reviews.llvm.org/D4932