Index: llvm/include/llvm/Linker/IRMover.h
===================================================================
--- llvm/include/llvm/Linker/IRMover.h
+++ llvm/include/llvm/Linker/IRMover.h
@@ -71,15 +71,11 @@
   ///   not present in ValuesToLink. The GlobalValue and a ValueAdder callback
   ///   are passed as an argument, and the callback is expected to be called
   ///   if the GlobalValue needs to be added to the \p ValuesToLink and linked.
-  /// - \p LinkModuleInlineAsm is true if the ModuleInlineAsm string in Src
-  ///   should be linked with (concatenated into) the ModuleInlineAsm string
-  ///   for the destination module. It should be true for full LTO, but not
-  ///   when importing for ThinLTO, otherwise we can have duplicate symbols.
   /// - \p IsPerformingImport is true when this IR link is to perform ThinLTO
   ///   function importing from Src.
   Error move(std::unique_ptr<Module> Src, ArrayRef<GlobalValue *> ValuesToLink,
              std::function<void(GlobalValue &GV, ValueAdder Add)> AddLazyFor,
-             bool LinkModuleInlineAsm, bool IsPerformingImport);
+             bool IsPerformingImport);
   Module &getModule() { return Composite; }
 
 private:
Index: llvm/lib/LTO/LTO.cpp
===================================================================
--- llvm/lib/LTO/LTO.cpp
+++ llvm/lib/LTO/LTO.cpp
@@ -510,7 +510,6 @@
 
   return RegularLTO.Mover->move(std::move(*MOrErr), Keep,
                                 [](GlobalValue &, IRMover::ValueAdder) {},
-                                /* LinkModuleInlineAsm */ true,
                                 /* IsPerformingImport */ false);
 }
 
Index: llvm/lib/Linker/IRMover.cpp
===================================================================
--- llvm/lib/Linker/IRMover.cpp
+++ llvm/lib/Linker/IRMover.cpp
@@ -395,11 +395,12 @@
       Worklist.push_back(GV);
   }
 
-  /// Flag whether the ModuleInlineAsm string in Src should be linked with
-  /// (concatenated into) the ModuleInlineAsm string for the destination
-  /// module. It should be true for full LTO, but not when importing for
-  /// ThinLTO, otherwise we can have duplicate symbols.
-  bool LinkModuleInlineAsm;
+  /// Whether we are importing globals for ThinLTO, as opposed to linking the
+  /// source module. If this flag is set, it means that we can rely on some
+  /// other object file to define any non-GlobalValue entities defined by the
+  /// source module. This currently causes us to not link retained types in
+  /// debug info metadata and module inline asm.
+  bool IsPerformingImport;
 
   /// Set to true when all global value body linking is complete (including
   /// lazy linking). Used to prevent metadata linking from creating new
@@ -491,10 +492,10 @@
            IRMover::IdentifiedStructTypeSet &Set, std::unique_ptr<Module> SrcM,
            ArrayRef<GlobalValue *> ValuesToLink,
            std::function<void(GlobalValue &, IRMover::ValueAdder)> AddLazyFor,
-           bool LinkModuleInlineAsm, bool IsPerformingImport)
+           bool IsPerformingImport)
       : DstM(DstM), SrcM(std::move(SrcM)), AddLazyFor(std::move(AddLazyFor)),
         TypeMap(Set), GValMaterializer(*this), LValMaterializer(*this),
-        SharedMDs(SharedMDs), LinkModuleInlineAsm(LinkModuleInlineAsm),
+        SharedMDs(SharedMDs), IsPerformingImport(IsPerformingImport),
         Mapper(ValueMap, RF_MoveDistinctMDs | RF_IgnoreMissingLocals, &TypeMap,
                &GValMaterializer),
         AliasMCID(Mapper.registerAlternateMappingContext(AliasValueMap,
@@ -1294,7 +1295,7 @@
   DstM.setTargetTriple(mergeTriples(SrcTriple, DstTriple));
 
   // Append the module inline asm string.
-  if (LinkModuleInlineAsm && !SrcM->getModuleInlineAsm().empty()) {
+  if (!IsPerformingImport && !SrcM->getModuleInlineAsm().empty()) {
     if (DstM.getModuleInlineAsm().empty())
       DstM.setModuleInlineAsm(SrcM->getModuleInlineAsm());
     else
@@ -1433,10 +1434,10 @@
 Error IRMover::move(
     std::unique_ptr<Module> Src, ArrayRef<GlobalValue *> ValuesToLink,
     std::function<void(GlobalValue &, ValueAdder Add)> AddLazyFor,
-    bool LinkModuleInlineAsm, bool IsPerformingImport) {
+    bool IsPerformingImport) {
   IRLinker TheIRLinker(Composite, SharedMDs, IdentifiedStructTypes,
                        std::move(Src), ValuesToLink, std::move(AddLazyFor),
-                       LinkModuleInlineAsm, IsPerformingImport);
+                       IsPerformingImport);
   Error E = TheIRLinker.run();
   Composite.dropTriviallyDeadConstantArrays();
   return E;
Index: llvm/lib/Linker/LinkModules.cpp
===================================================================
--- llvm/lib/Linker/LinkModules.cpp
+++ llvm/lib/Linker/LinkModules.cpp
@@ -538,7 +538,6 @@
                            [this](GlobalValue &GV, IRMover::ValueAdder Add) {
                              addLazyFor(GV, Add);
                            },
-                           /* LinkModuleInlineAsm */ true,
                            /* IsPerformingImport */ false)) {
     handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
       DstM.getContext().diagnose(LinkDiagnosticInfo(DS_Error, EIB.message()));
Index: llvm/lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -773,7 +773,7 @@
 
     if (Mover.move(std::move(SrcModule), GlobalsToImport.getArrayRef(),
                    [](GlobalValue &, IRMover::ValueAdder) {},
-                   /*LinkModuleInlineAsm=*/false, /*IsPerformingImport=*/true))
+                   /*IsPerformingImport=*/true))
       report_fatal_error("Function Import: link error");
 
     ImportedCount += GlobalsToImport.size();