Fix a crash when emitting debug info for multi-reg function arguments
by reusing more of the existing machinery

This is a follow-up to r312169.
Thanks to Björn Pettersson for the testcase!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312773 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed