Followup to r191252.

Make sure that the code that handles the constant addresses is run for the
GEPs. This just refactors that code and then calls it for the GEPs that are
collected during the iteration.

<rdar://problem/12445434>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191281 91177308-0d34-0410-b5e6-96231b3b80d8