Debug info: Tighten up uses of plain MDNode pointers which don't survive replaceOperandWith.

TrackingVH notices when it gets RAUW'd. Fixes PR12305 and PR12315.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153115 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed