even if the underlying operand is NULL. This may happen in debugging context
within opt with partial loop unrolling (see test/Transforms/LoopUnroll/partial.ll).
After this fix I can resubmit the (backed out) r63459:
* lib/VMCore/AsmWriter.cpp: use precise accessors.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64142 91177308-0d34-0410-b5e6-96231b3b80d8