MapMetadata: Allow unresolved metadata if it won't change

Allow unresolved nodes through the `MapMetadata()` if
`RF_NoModuleLevelChanges`, since there's no remapping to do anyway.

This fixes PR22929.  I'll add a clang test as a follow-up.

llvm-svn: 232449

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Utils/ValueMapper.cpp b/llvm/lib/Transforms/Utils/ValueMapper.cpp
index 49c0902addb..54c76887234 100644
--- a/llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ b/llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -291,14 +291,18 @@ static Metadata *MapMetadataImpl(const Metadata *MD,
     return nullptr;
   }
 
+  // Note: this cast precedes the Flags check so we always get its associated
+  // assertion.
   const MDNode *Node = cast<MDNode>(MD);
-  assert(Node->isResolved() && "Unexpected unresolved node");
 
   // If this is a module-level metadata and we know that nothing at the
   // module level is changing, then use an identity mapping.
   if (Flags & RF_NoModuleLevelChanges)
     return mapToSelf(VM, MD);
 
+  // Require resolved nodes whenever metadata might be remapped.
+  assert(Node->isResolved() && "Unexpected unresolved node");
+
   if (Node->isDistinct())
     return mapDistinctNode(Node, Cycles, VM, Flags, TypeMapper, Materializer);