If the NVPTX backend is used with relocation model 'static', DAGCombiner will have global addresses combined with any add instruction that adds a constant offset to it. However, lowering is not prepared to deal with the offset that is added in GlobalAddress nodes. This issue can be replicated if llc is called with relocation-model=static or if the backend is invoked directly from clang.
This patch fixes the issue by undoing what DAGCombiner does, which looks to me as the less disruptive solution. Next to the fix, a comment is added explaining other alternatives to tackle this issue.