+ return AnyChanged;
+}
+
+/// Map a distinct MDNode.
+///
+/// Whether distinct nodes change is independent of their operands. If \a
+/// RF_MoveDistinctMDs, then they are reused, and their operands remapped in
+/// place; effectively, they're moved from one graph to another. Otherwise,
+/// they're cloned/duplicated, and the new copy's operands are remapped.
+static Metadata *mapDistinctNode(const MDNode *Node,
+ SmallVectorImpl<MDNode *> &DistinctWorklist,
+ ValueToValueMapTy &VM, RemapFlags Flags,
+ ValueMapTypeRemapper *TypeMapper,
+ ValueMaterializer *Materializer) {
+ assert(Node->isDistinct() && "Expected distinct node");
+
+ MDNode *NewMD;
+ if (Flags & RF_MoveDistinctMDs)
+ NewMD = const_cast<MDNode *>(Node);
+ else
+ NewMD = MDNode::replaceWithDistinct(Node->clone());
+
+ // Remap operands later.
+ DistinctWorklist.push_back(NewMD);
+ return mapToMetadata(VM, Node, NewMD);
+}
+
+/// \brief Map a uniqued MDNode.
+///
+/// Uniqued nodes may not need to be recreated (they may map to themselves).
+static Metadata *mapUniquedNode(const MDNode *Node,
+ SmallVectorImpl<MDNode *> &DistinctWorklist,
+ ValueToValueMapTy &VM, RemapFlags Flags,
+ ValueMapTypeRemapper *TypeMapper,
+ ValueMaterializer *Materializer) {
+ assert(Node->isUniqued() && "Expected uniqued node");
+
+ // Create a temporary node and map it upfront in case we have a uniquing
+ // cycle. If necessary, this mapping will get updated by RAUW logic before
+ // returning.
+ auto ClonedMD = Node->clone();
+ mapToMetadata(VM, Node, ClonedMD.get());
+ if (!remapOperands(*ClonedMD, DistinctWorklist, VM, Flags, TypeMapper,
+ Materializer)) {
+ // No operands changed, so use the original.
+ ClonedMD->replaceAllUsesWith(const_cast<MDNode *>(Node));
+ return const_cast<MDNode *>(Node);
+ }
+
+ // Uniquify the cloned node.
+ return MDNode::replaceWithUniqued(std::move(ClonedMD));
+}
+
+static Metadata *MapMetadataImpl(const Metadata *MD,
+ SmallVectorImpl<MDNode *> &DistinctWorklist,
+ ValueToValueMapTy &VM, RemapFlags Flags,
+ ValueMapTypeRemapper *TypeMapper,
+ ValueMaterializer *Materializer) {
+ // If the value already exists in the map, use it.
+ if (Metadata *NewMD = VM.MD().lookup(MD).get())
+ return NewMD;
+
+ if (isa<MDString>(MD))
+ return mapToSelf(VM, MD);
+
+ if (isa<ConstantAsMetadata>(MD))
+ if ((Flags & RF_NoModuleLevelChanges))
+ return mapToSelf(VM, MD);
+
+ if (const auto *VMD = dyn_cast<ValueAsMetadata>(MD)) {
+ Value *MappedV =
+ MapValue(VMD->getValue(), VM, Flags, TypeMapper, Materializer);
+ if (VMD->getValue() == MappedV ||
+ (!MappedV && (Flags & RF_IgnoreMissingEntries)))
+ return mapToSelf(VM, MD);
+
+ // FIXME: This assert crashes during bootstrap, but I think it should be
+ // correct. For now, just match behaviour from before the metadata/value
+ // split.
+ //
+ // assert((MappedV || (Flags & RF_NullMapMissingGlobalValues)) &&
+ // "Referenced metadata not in value map!");
+ if (MappedV)
+ return mapToMetadata(VM, MD, ValueAsMetadata::get(MappedV));
+ return nullptr;
+ }
+
+ // Note: this cast precedes the Flags check so we always get its associated
+ // assertion.
+ const MDNode *Node = cast<MDNode>(MD);
+
+ // 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, DistinctWorklist, VM, Flags, TypeMapper,
+ Materializer);
+
+ return mapUniquedNode(Node, DistinctWorklist, VM, Flags, TypeMapper,
+ Materializer);
+}
+
+Metadata *llvm::MapMetadata(const Metadata *MD, ValueToValueMapTy &VM,
+ RemapFlags Flags, ValueMapTypeRemapper *TypeMapper,
+ ValueMaterializer *Materializer) {
+ SmallVector<MDNode *, 8> DistinctWorklist;
+ Metadata *NewMD = MapMetadataImpl(MD, DistinctWorklist, VM, Flags, TypeMapper,
+ Materializer);
+
+ // When there are no module-level changes, it's possible that the metadata
+ // graph has temporaries. Skip the logic to resolve cycles, since it's
+ // unnecessary (and invalid) in that case.
+ if (Flags & RF_NoModuleLevelChanges)
+ return NewMD;
+
+ // Resolve cycles involving the entry metadata.
+ resolveCycles(NewMD);
+
+ // Remap the operands of distinct MDNodes.
+ while (!DistinctWorklist.empty())
+ remapOperands(*DistinctWorklist.pop_back_val(), DistinctWorklist, VM, Flags,
+ TypeMapper, Materializer);
+
+ return NewMD;
+}
+
+MDNode *llvm::MapMetadata(const MDNode *MD, ValueToValueMapTy &VM,
+ RemapFlags Flags, ValueMapTypeRemapper *TypeMapper,
+ ValueMaterializer *Materializer) {
+ return cast<MDNode>(MapMetadata(static_cast<const Metadata *>(MD), VM, Flags,
+ TypeMapper, Materializer));