d4df3825bd
LLVM IR allows globals with external linkage to have initializers, including undef. The translation was incorrectly using undef as a indicator that the initializer should be ignored in translation, leading to the impossibility to create an external global with an explicit undef initializer. Fix this and use nullptr as a marker instead. Reviewed By: wsmoses Differential Revision: https://reviews.llvm.org/D105631