Utils: Resolve cycles under distinct MDNodes

Track unresolved nodes under distinct `MDNode`s during `MapMetadata()`,
and resolve them at the end.  Previously, these cycles wouldn't get
resolved.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228180 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed