Index: llvm/include/llvm/DWARFLinker/DWARFLinkerCompileUnit.h
===================================================================
--- llvm/include/llvm/DWARFLinker/DWARFLinkerCompileUnit.h
+++ llvm/include/llvm/DWARFLinker/DWARFLinkerCompileUnit.h
@@ -77,6 +77,9 @@
 
     /// Is ODR marking done?
     bool ODRMarkingDone : 1;
+
+    /// Is this a reference to a DIE that hasn't been cloned yet?
+    bool Reference : 1;
   };
 
   CompileUnit(DWARFUnit &OrigUnit, unsigned ID, bool CanUseODR,
@@ -160,15 +163,15 @@
   /// current debug_info section size).
   uint64_t computeNextUnitOffset(uint16_t DwarfVersion);
 
-  /// Keep track of a forward reference to DIE \p Die in \p RefUnit by \p
-  /// Attr. The attribute should be fixed up later to point to the absolute
-  /// offset of \p Die in the debug_info section or to the canonical offset of
-  /// \p Ctxt if it is non-null.
-  void noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
-                            DeclContext *Ctxt, PatchLocation Attr);
+  /// Keep track of a forward or backward reference to DIE \p Die in \p RefUnit
+  /// by \p Attr. The attribute should be fixed up later to point to the
+  /// absolute offset of \p Die in the debug_info section or to the canonical
+  /// offset of \p Ctxt if it is non-null.
+  void noteReference(DIE *Die, const CompileUnit *RefUnit, DeclContext *Ctxt,
+                     PatchLocation Attr);
 
-  /// Apply all fixups recorded by noteForwardReference().
-  void fixupForwardReferences();
+  /// Apply all fixups recorded by noteReference().
+  void fixupReferences();
 
   /// Add the low_pc of a label that is relocated by applying
   /// offset \p PCOffset.
@@ -260,7 +263,7 @@
   /// isn't known you emit the reference attribute.
   std::vector<
       std::tuple<DIE *, const CompileUnit *, DeclContext *, PatchLocation>>
-      ForwardDIEReferences;
+      DIEReferences;
 
   /// The ranges in that map are the PC ranges for functions in this unit,
   /// associated with the PC offset to apply to the addresses to get
Index: llvm/lib/DWARFLinker/DWARFLinker.cpp
===================================================================
--- llvm/lib/DWARFLinker/DWARFLinker.cpp
+++ llvm/lib/DWARFLinker/DWARFLinker.cpp
@@ -934,9 +934,9 @@
   }
 
   if (!RefInfo.Clone) {
-    assert(Ref > InputDIE.getOffset());
     // We haven't cloned this DIE yet. Just create an empty one and
     // store it. It'll get really cloned when we process it.
+    RefInfo.Reference = true;
     RefInfo.Clone = DIE::get(DIEAlloc, dwarf::Tag(RefDie.getTag()));
   }
   NewRefDie = RefInfo.Clone;
@@ -949,7 +949,7 @@
     // FIXME: we should be able to design DIEEntry reliance on
     // DwarfDebug away.
     uint64_t Attr;
-    if (Ref < InputDIE.getOffset()) {
+    if (Ref < InputDIE.getOffset() && !RefInfo.Reference) {
       // We must have already cloned that DIE.
       uint32_t NewRefOffset =
           RefUnit->getStartOffset() + NewRefDie->getOffset();
@@ -957,12 +957,12 @@
       Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
                    dwarf::DW_FORM_ref_addr, DIEInteger(Attr));
     } else {
-      // A forward reference. Note and fixup later.
+      // A forward or backward reference. Note and fixup later.
       Attr = 0xBADDEF;
-      Unit.noteForwardReference(
-          NewRefDie, RefUnit, RefInfo.Ctxt,
-          Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
-                       dwarf::DW_FORM_ref_addr, DIEInteger(Attr)));
+      Unit.noteReference(NewRefDie, RefUnit, RefInfo.Ctxt,
+                         Die.addValue(DIEAlloc, dwarf::Attribute(AttrSpec.Attr),
+                                      dwarf::DW_FORM_ref_addr,
+                                      DIEInteger(Attr)));
     }
     return U.getRefAddrByteSize();
   }
@@ -2237,7 +2237,7 @@
       if (LLVM_LIKELY(!Linker.Options.Update))
         Linker.generateUnitRanges(*CurrentUnit);
 
-      CurrentUnit->fixupForwardReferences();
+      CurrentUnit->fixupReferences();
 
       if (!CurrentUnit->getOutputUnitDIE())
         continue;
Index: llvm/lib/DWARFLinker/DWARFLinkerCompileUnit.cpp
===================================================================
--- llvm/lib/DWARFLinker/DWARFLinkerCompileUnit.cpp
+++ llvm/lib/DWARFLinker/DWARFLinkerCompileUnit.cpp
@@ -78,13 +78,13 @@
 
 /// Keep track of a forward cross-cu reference from this unit
 /// to \p Die that lives in \p RefUnit.
-void CompileUnit::noteForwardReference(DIE *Die, const CompileUnit *RefUnit,
-                                       DeclContext *Ctxt, PatchLocation Attr) {
-  ForwardDIEReferences.emplace_back(Die, RefUnit, Ctxt, Attr);
+void CompileUnit::noteReference(DIE *Die, const CompileUnit *RefUnit,
+                                DeclContext *Ctxt, PatchLocation Attr) {
+  DIEReferences.emplace_back(Die, RefUnit, Ctxt, Attr);
 }
 
-void CompileUnit::fixupForwardReferences() {
-  for (const auto &Ref : ForwardDIEReferences) {
+void CompileUnit::fixupReferences() {
+  for (const auto &Ref : DIEReferences) {
     DIE *RefDie;
     const CompileUnit *RefUnit;
     PatchLocation Attr;