[ThinLTO] Enable AutoHide on symbols with local_unnamed_addr

[steven_wu]

Summary

Teach thinLTO to analyze and auto hide local_unnamed_addr symbols if
possible.

[steven_wu]

Generated by mistake. Abandon and I will reformat the patch.

include/llvm/IR/ModuleSummaryIndex.h

void setWithGlobalValueDeadStripping() {
     WithGlobalValueDeadStripping = true;
   }
 
   bool isGlobalValueLive(const GlobalValueSummary *GVS) const {
     return !WithGlobalValueDeadStripping || GVS->isLive();
   }
   bool isGUIDLive(GlobalValue::GUID GUID) const;
 
+  bool canGlobalValueAutoHide(const GlobalValue *GV) const {
+    return canGUIDAutoHide(GV->getGUID());
+  }
+  bool canGUIDAutoHide(GlobalValue::GUID GUID) const;
+
   /// Return a ValueInfo for GUID if it exists, otherwise return ValueInfo().
   ValueInfo getValueInfo(GlobalValue::GUID GUID) const {
     auto I = GlobalValueMap.find(GUID);
     return ValueInfo(IsAnalysis, I == GlobalValueMap.end() ? nullptr : &*I);
   }
 
   /// Return a ValueInfo for \p GUID.
   ValueInfo getOrInsertValueInfo(GlobalValue::GUID GUID) {

include/llvm/LTO/LTO.h

 ///
 /// This is done for correctness (if value exported, ensure we always
 /// emit a copy), and compile-time optimization (allow drop of duplicates).
 void thinLTOResolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing,
     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
-        recordNewLinkage);
+        recordNewLinkage,
+    function_ref<void(GlobalValue::GUID)> recordAutoHide);
 
 /// Update the linkages in the given \p Index to mark exported values
 /// as external and non-exported values as internal. The ThinLTO backends
 /// must apply the changes to the Module via thinLTOInternalizeModule.
 void thinLTOInternalizeAndPromoteInIndex(
     ModuleSummaryIndex &Index,
     function_ref<bool(StringRef, GlobalValue::GUID)> isExported);
 

include/llvm/LTO/LTOBackend.h

Error backend(Config &C, AddStreamFn AddStream,
               unsigned ParallelCodeGenParallelismLevel,
               std::unique_ptr<Module> M, ModuleSummaryIndex &CombinedIndex);
 
 /// Runs a ThinLTO backend.
 Error thinBackend(Config &C, unsigned Task, AddStreamFn AddStream, Module &M,
                   const ModuleSummaryIndex &CombinedIndex,
                   const FunctionImporter::ImportMapTy &ImportList,
                   const GVSummaryMapTy &DefinedGlobals,
-                  MapVector<StringRef, BitcodeModule> &ModuleMap);
+                  MapVector<StringRef, BitcodeModule> &ModuleMap,
+                  const DenseSet<GlobalValue::GUID> &AutoHideCandidates);
 }
 }
 
 #endif

include/llvm/Transforms/IPO/FunctionImport.h

 
 /// Emit into \p OutputFilename the files module \p ModulePath will import from.
 std::error_code
 EmitImportsFiles(StringRef ModulePath, StringRef OutputFilename,
                  const FunctionImporter::ImportMapTy &ModuleImports);
 
 /// Resolve WeakForLinker values in \p TheModule based on the information
 /// recorded in the summaries during global summary-based analysis.
-void thinLTOResolveWeakForLinkerModule(Module &TheModule,
-                                       const GVSummaryMapTy &DefinedGlobals);
+void thinLTOResolveWeakForLinkerModule(
+    Module &TheModule, const GVSummaryMapTy &DefinedGlobals,
+    const DenseSet<GlobalValue::GUID> &AutoHideCandidates);
 
 /// Internalize \p TheModule based on the information recorded in the summaries
 /// during global summary-based analysis.
 void thinLTOInternalizeModule(Module &TheModule,
                               const GVSummaryMapTy &DefinedGlobals);
 
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_IPO_FUNCTIONIMPORT_H

lib/Analysis/ModuleSummaryAnalysis.cpp

computeFunctionSummary(ModuleSummaryIndex &Index, const Module &M,
   bool NonRenamableLocal = isNonRenamableLocal(F);
   bool NotEligibleForImport =
       NonRenamableLocal || HasInlineAsmMaybeReferencingInternal ||
       // Inliner doesn't handle variadic functions.
       // FIXME: refactor this to use the same code that inliner is using.
       F.isVarArg() ||
       // Don't try to import functions with noinline attribute.
       F.getAttributes().hasFnAttribute(Attribute::NoInline);
-  GlobalValueSummary::GVFlags Flags(F.getLinkage(), NotEligibleForImport,
-                                    /* Live = */ false, F.isDSOLocal(),
-                                    /* UnnamedAddr= */false);
+  GlobalValueSummary::GVFlags Flags(
+      F.getLinkage(), NotEligibleForImport,
+      /* UnnamedAddr= */ F.hasAtLeastLocalUnnamedAddr());
   FunctionSummary::FFlags FunFlags{
       F.hasFnAttribute(Attribute::ReadNone),
       F.hasFnAttribute(Attribute::ReadOnly),
       F.hasFnAttribute(Attribute::NoRecurse),
       F.returnDoesNotAlias(),
   };
   auto FuncSummary = llvm::make_unique<FunctionSummary>(
       Flags, NumInsts, FunFlags, RefEdges.takeVector(),
       CallGraphEdges.takeVector(), TypeTests.takeVector(),
       TypeTestAssumeVCalls.takeVector(), TypeCheckedLoadVCalls.takeVector(),
       TypeTestAssumeConstVCalls.takeVector(),
       TypeCheckedLoadConstVCalls.takeVector());
   if (NonRenamableLocal)
     CantBePromoted.insert(F.getGUID());
   Index.addGlobalValueSummary(F.getName(), std::move(FuncSummary));
 }
 
 static void
 computeVariableSummary(ModuleSummaryIndex &Index, const GlobalVariable &V,
                        DenseSet<GlobalValue::GUID> &CantBePromoted) {
   SetVector<ValueInfo> RefEdges;
   SmallPtrSet<const User *, 8> Visited;
   findRefEdges(Index, &V, RefEdges, Visited);
   bool NonRenamableLocal = isNonRenamableLocal(V);
-  GlobalValueSummary::GVFlags Flags(V.getLinkage(), NonRenamableLocal,
-                                    /* Live = */ false, V.isDSOLocal(),
-                                    /* UnnamedAddr= */false);
+  GlobalValueSummary::GVFlags Flags(
+      V.getLinkage(), NonRenamableLocal,
+      /* UnnamedAddr= */ V.hasAtLeastLocalUnnamedAddr());
   auto GVarSummary =
       llvm::make_unique<GlobalVarSummary>(Flags, RefEdges.takeVector());
   if (NonRenamableLocal)
     CantBePromoted.insert(V.getGUID());
   Index.addGlobalValueSummary(V.getName(), std::move(GVarSummary));
 }
 
 static void
 computeAliasSummary(ModuleSummaryIndex &Index, const GlobalAlias &A,
                     DenseSet<GlobalValue::GUID> &CantBePromoted) {
   bool NonRenamableLocal = isNonRenamableLocal(A);
-  GlobalValueSummary::GVFlags Flags(A.getLinkage(), NonRenamableLocal,
-                                    /* Live = */ false, A.isDSOLocal(),
-                                    /* UnnamedAddr= */false);
+  GlobalValueSummary::GVFlags Flags(
+      A.getLinkage(), NonRenamableLocal,
+      /* UnnamedAddr= */ A.hasAtLeastLocalUnnamedAddr());
   auto AS = llvm::make_unique<AliasSummary>(Flags);
   auto *Aliasee = A.getBaseObject();
   auto *AliaseeSummary = Index.getGlobalValueSummary(*Aliasee);
   assert(AliaseeSummary && "Alias expects aliasee summary to be parsed");
   AS->setAliasee(AliaseeSummary);
   if (NonRenamableLocal)
     CantBePromoted.insert(A.getGUID());
   Index.addGlobalValueSummary(A.getName(), std::move(AS));
ModuleSymbolTable::CollectAsmSymbols(
           if (Flags & (object::BasicSymbolRef::SF_Weak |
                        object::BasicSymbolRef::SF_Global))
             return;
           HasLocalInlineAsmSymbol = true;
           GlobalValue *GV = M.getNamedValue(Name);
           if (!GV)
             return;
           assert(GV->isDeclaration() && "Def in module asm already has definition");
-          GlobalValueSummary::GVFlags GVFlags(GlobalValue::InternalLinkage,
-                                              /* NotEligibleToImport = */ true,
-                                              /* Live = */ true,
-                                              /* Local */ GV->isDSOLocal(),
-                                              /* UnnamedAddr= */ false);
+          GlobalValueSummary::GVFlags GVFlags(
+              GlobalValue::InternalLinkage,
+              /* UnnamedAddr= */ GV->hasAtLeastLocalUnnamedAddr());
           CantBePromoted.insert(GlobalValue::getGUID(Name));
           // Create the appropriate summary type.
           if (Function *F = dyn_cast<Function>(GV)) {
             std::unique_ptr<FunctionSummary> Summary =
                 llvm::make_unique<FunctionSummary>(
                     GVFlags, 0,
                     FunctionSummary::FFlags{
                         F->hasFnAttribute(Attribute::ReadNone),

lib/IR/ModuleSummaryIndex.cpp

bool ModuleSummaryIndex::isGUIDLive(GlobalValue::GUID GUID) const {
   if (SummaryList.empty())
     return true;
   for (auto &I : SummaryList)
     if (isGlobalValueLive(I.get()))
       return true;
   return false;
 }
 
+bool ModuleSummaryIndex::canGUIDAutoHide(GlobalValue::GUID GUID) const {
+  auto VI = getValueInfo(GUID);
+  if (!VI)
+    return false;
+  const auto &SummaryList = VI.getSummaryList();
+  if (SummaryList.empty())
+    return false;
+  bool canBeAutoHide = true;
+  for (auto &I : SummaryList)
+    canBeAutoHide &= I->flags().UnnamedAddr &&
+                     I->linkage() == GlobalValue::LinkOnceODRLinkage;
+  return canBeAutoHide;
+}
+
 namespace {
 struct Attributes {
   void add(const Twine &Name, const Twine &Value,
            const Twine &Comment = Twine());
   std::string getAsString() const;
 
   std::vector<std::string> Attrs;
   std::string Comments;

lib/LTO/LTO.cpp

 // current module. However there is a chance that another module is still
 // referencing them because of the import. We make sure we always emit at least
 // one copy.
 void llvm::thinLTOResolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing,
     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
-        recordNewLinkage) {
+        recordNewLinkage,
+    function_ref<void(GlobalValue::GUID)> recordAutoHide) {
   // We won't optimize the globals that are referenced by an alias for now
   // Ideally we should turn the alias into a global and duplicate the definition
   // when needed.
   DenseSet<GlobalValueSummary *> GlobalInvolvedWithAlias;
   for (auto &I : Index)
     for (auto &S : I.second.SummaryList)
       if (auto AS = dyn_cast<AliasSummary>(S.get()))
         GlobalInvolvedWithAlias.insert(&AS->getAliasee());
 
+  // Record the symbols that can be auto hide. This needs to be completed
+  // before resolve linkage.
+  for (auto &I : Index) {
+    if (Index.canGUIDAutoHide(I.first))
+      recordAutoHide(I.first);
+  }
+
   for (auto &I : Index)
     thinLTOResolveWeakForLinkerGUID(I.second.SummaryList, I.first,
                                     GlobalInvolvedWithAlias, isPrevailing,
                                     recordNewLinkage);
 }
 
 static void thinLTOInternalizeAndPromoteGUID(
     GlobalValueSummaryList &GVSummaryList, GlobalValue::GUID GUID,
ThinBackendProc(Config &Conf, ModuleSummaryIndex &CombinedIndex,
         ModuleToDefinedGVSummaries(ModuleToDefinedGVSummaries) {}
 
   virtual ~ThinBackendProc() {}
   virtual Error start(
       unsigned Task, BitcodeModule BM,
       const FunctionImporter::ImportMapTy &ImportList,
       const FunctionImporter::ExportSetTy &ExportList,
       const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
-      MapVector<StringRef, BitcodeModule> &ModuleMap) = 0;
+      MapVector<StringRef, BitcodeModule> &ModuleMap,
+      const DenseSet<GlobalValue::GUID> &AutoHideCandidates) = 0;
   virtual Error wait() = 0;
 };
 
 namespace {
 class InProcessThinBackend : public ThinBackendProc {
   ThreadPool BackendThreadPool;
   AddStreamFn AddStream;
   NativeObjectCache Cache;
public:
   Error runThinLTOBackendThread(
       AddStreamFn AddStream, NativeObjectCache Cache, unsigned Task,
       BitcodeModule BM, ModuleSummaryIndex &CombinedIndex,
       const FunctionImporter::ImportMapTy &ImportList,
       const FunctionImporter::ExportSetTy &ExportList,
       const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
       const GVSummaryMapTy &DefinedGlobals,
       MapVector<StringRef, BitcodeModule> &ModuleMap,
-      const TypeIdSummariesByGuidTy &TypeIdSummariesByGuid) {
+      const TypeIdSummariesByGuidTy &TypeIdSummariesByGuid,
+      const DenseSet<GlobalValue::GUID> &AutoHideCandidates) {
     auto RunThinBackend = [&](AddStreamFn AddStream) {
       LTOLLVMContext BackendContext(Conf);
       Expected<std::unique_ptr<Module>> MOrErr = BM.parseModule(BackendContext);
       if (!MOrErr)
         return MOrErr.takeError();
 
       return thinBackend(Conf, Task, AddStream, **MOrErr, CombinedIndex,
-                         ImportList, DefinedGlobals, ModuleMap);
+                         ImportList, DefinedGlobals, ModuleMap,
+                         AutoHideCandidates);
     };
 
     auto ModuleID = BM.getModuleIdentifier();
 
     if (!Cache || !CombinedIndex.modulePaths().count(ModuleID) ||
         all_of(CombinedIndex.getModuleHash(ModuleID),
                [](uint32_t V) { return V == 0; }))
       // Cache disabled or no entry for this module in the combined index or
Error runThinLTOBackendThread(
     return Error::success();
   }
 
   Error start(
       unsigned Task, BitcodeModule BM,
       const FunctionImporter::ImportMapTy &ImportList,
       const FunctionImporter::ExportSetTy &ExportList,
       const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
-      MapVector<StringRef, BitcodeModule> &ModuleMap) override {
+      MapVector<StringRef, BitcodeModule> &ModuleMap,
+      const DenseSet<GlobalValue::GUID> &AutoHideCandidates) override {
     StringRef ModulePath = BM.getModuleIdentifier();
     assert(ModuleToDefinedGVSummaries.count(ModulePath));
     const GVSummaryMapTy &DefinedGlobals =
         ModuleToDefinedGVSummaries.find(ModulePath)->second;
     BackendThreadPool.async(
         [=](BitcodeModule BM, ModuleSummaryIndex &CombinedIndex,
             const FunctionImporter::ImportMapTy &ImportList,
             const FunctionImporter::ExportSetTy &ExportList,
             const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>
                 &ResolvedODR,
             const GVSummaryMapTy &DefinedGlobals,
             MapVector<StringRef, BitcodeModule> &ModuleMap,
             const TypeIdSummariesByGuidTy &TypeIdSummariesByGuid) {
           Error E = runThinLTOBackendThread(
               AddStream, Cache, Task, BM, CombinedIndex, ImportList, ExportList,
-              ResolvedODR, DefinedGlobals, ModuleMap, TypeIdSummariesByGuid);
+              ResolvedODR, DefinedGlobals, ModuleMap, TypeIdSummariesByGuid,
+              AutoHideCandidates);
           if (E) {
             std::unique_lock<std::mutex> L(ErrMu);
             if (Err)
               Err = joinErrors(std::move(*Err), std::move(E));
             else
               Err = std::move(E);
           }
         },
WriteIndexesThinBackend(
         ShouldEmitImportsFiles(ShouldEmitImportsFiles),
         LinkedObjectsFileName(LinkedObjectsFileName), OnWrite(OnWrite) {}
 
   Error start(
       unsigned Task, BitcodeModule BM,
       const FunctionImporter::ImportMapTy &ImportList,
       const FunctionImporter::ExportSetTy &ExportList,
       const std::map<GlobalValue::GUID, GlobalValue::LinkageTypes> &ResolvedODR,
-      MapVector<StringRef, BitcodeModule> &ModuleMap) override {
+      MapVector<StringRef, BitcodeModule> &ModuleMap,
+      const DenseSet<GlobalValue::GUID> &AutoHideCandidates) override {
     StringRef ModulePath = BM.getModuleIdentifier();
     std::string NewModulePath =
         getThinLTOOutputFile(ModulePath, OldPrefix, NewPrefix);
 
     std::error_code EC;
     if (!LinkedObjectsFileName.empty()) {
       if (!LinkedObjectsFile) {
         LinkedObjectsFile = llvm::make_unique<raw_fd_ostream>(
auto isPrevailing = [&](GlobalValue::GUID GUID,
                           const GlobalValueSummary *S) {
     return ThinLTO.PrevailingModuleForGUID[GUID] == S->modulePath();
   };
   auto recordNewLinkage = [&](StringRef ModuleIdentifier,
                               GlobalValue::GUID GUID,
                               GlobalValue::LinkageTypes NewLinkage) {
     ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
   };
+  DenseSet<GlobalValue::GUID> AutoHideCandidates;
+  auto recordAutoHide = [&](GlobalValue::GUID GUID) {
+    AutoHideCandidates.insert(GUID);
+  };
+
   thinLTOResolveWeakForLinkerInIndex(ThinLTO.CombinedIndex, isPrevailing,
-                                     recordNewLinkage);
+                                     recordNewLinkage, recordAutoHide);
 
   std::unique_ptr<ThinBackendProc> BackendProc =
       ThinLTO.Backend(Conf, ThinLTO.CombinedIndex, ModuleToDefinedGVSummaries,
                       AddStream, Cache);
 
   // Tasks 0 through ParallelCodeGenParallelismLevel-1 are reserved for combined
   // module and parallel code generation partitions.
   unsigned Task = RegularLTO.ParallelCodeGenParallelismLevel;
   for (auto &Mod : ThinLTO.ModuleMap) {
-    if (Error E = BackendProc->start(Task, Mod.second, ImportLists[Mod.first],
-                                     ExportLists[Mod.first],
-                                     ResolvedODR[Mod.first], ThinLTO.ModuleMap))
+    if (Error E = BackendProc->start(
+            Task, Mod.second, ImportLists[Mod.first], ExportLists[Mod.first],
+            ResolvedODR[Mod.first], ThinLTO.ModuleMap, AutoHideCandidates))
       return E;
     ++Task;
   }
 
   return BackendProc->wait();
 }
 
 Expected<std::unique_ptr<ToolOutputFile>>

lib/LTO/LTOBackend.cpp

if (GV->use_empty())
       GV->eraseFromParent();
   }
 }
 
 Error lto::thinBackend(Config &Conf, unsigned Task, AddStreamFn AddStream,
                        Module &Mod, const ModuleSummaryIndex &CombinedIndex,
                        const FunctionImporter::ImportMapTy &ImportList,
                        const GVSummaryMapTy &DefinedGlobals,
-                       MapVector<StringRef, BitcodeModule> &ModuleMap) {
+                       MapVector<StringRef, BitcodeModule> &ModuleMap,
+                       const DenseSet<GlobalValue::GUID> &AutoHideCandidates) {
   Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
   if (!TOrErr)
     return TOrErr.takeError();
 
   std::unique_ptr<TargetMachine> TM = createTargetMachine(Conf, *TOrErr, Mod);
 
   if (Conf.CodeGenOnly) {
     codegen(Conf, TM.get(), AddStream, Task, Mod);
     return Error::success();
   }
 
   if (Conf.PreOptModuleHook && !Conf.PreOptModuleHook(Task, Mod))
     return Error::success();
 
   renameModuleForThinLTO(Mod, CombinedIndex);
 
   dropDeadSymbols(Mod, DefinedGlobals, CombinedIndex);
 
-  thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals);
+  thinLTOResolveWeakForLinkerModule(Mod, DefinedGlobals, AutoHideCandidates);
 
   if (Conf.PostPromoteModuleHook && !Conf.PostPromoteModuleHook(Task, Mod))
     return Error::success();
 
   if (!DefinedGlobals.empty())
     thinLTOInternalizeModule(Mod, DefinedGlobals);
 
   if (Conf.PostInternalizeModuleHook &&

lib/LTO/ThinLTOCodeGenerator.cpp

 };
 
 static std::unique_ptr<MemoryBuffer>
 ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
                      StringMap<MemoryBufferRef> &ModuleMap, TargetMachine &TM,
                      const FunctionImporter::ImportMapTy &ImportList,
                      const FunctionImporter::ExportSetTy &ExportList,
                      const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
+                     const DenseSet<GlobalValue::GUID> &AutoHideCandidates,
                      const GVSummaryMapTy &DefinedGlobals,
                      const ThinLTOCodeGenerator::CachingOptions &CacheOptions,
                      bool DisableCodeGen, StringRef SaveTempsDir,
                      bool Freestanding, unsigned OptLevel, unsigned count) {
 
   // "Benchmark"-like optimization: single-source case
   bool SingleModule = (ModuleMap.size() == 1);
 
   if (!SingleModule) {
     promoteModule(TheModule, Index);
 
     // Apply summary-based LinkOnce/Weak resolution decisions.
-    thinLTOResolveWeakForLinkerModule(TheModule, DefinedGlobals);
+    thinLTOResolveWeakForLinkerModule(TheModule, DefinedGlobals,
+                                      AutoHideCandidates);
 
     // Save temps: after promotion.
     saveTempBitcode(TheModule, SaveTempsDir, count, ".1.promoted.bc");
   }
 
   // Be friendly and don't nuke totally the module when the client didn't
   // supply anything to preserve.
   if (!ExportList.empty() || !GUIDPreservedSymbols.empty()) {

 /// Resolve LinkOnce/Weak symbols. Record resolutions in the \p ResolvedODR map
 /// for caching, and in the \p Index for application during the ThinLTO
 /// backends. This is needed for correctness for exported symbols (ensure
 /// at least one copy kept) and a compile-time optimization (to drop duplicate
 /// copies when possible).
 static void resolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,
     StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>>
-        &ResolvedODR) {
-
+        &ResolvedODR,
+    DenseSet<GlobalValue::GUID> &AutoHideCandidates) {
   DenseMap<GlobalValue::GUID, const GlobalValueSummary *> PrevailingCopy;
   computePrevailingCopies(Index, PrevailingCopy);
 
   auto isPrevailing = [&](GlobalValue::GUID GUID, const GlobalValueSummary *S) {
     const auto &Prevailing = PrevailingCopy.find(GUID);
     // Not in map means that there was only one copy, which must be prevailing.
     if (Prevailing == PrevailingCopy.end())
       return true;
     return Prevailing->second == S;
   };
 
   auto recordNewLinkage = [&](StringRef ModuleIdentifier,
                               GlobalValue::GUID GUID,
                               GlobalValue::LinkageTypes NewLinkage) {
     ResolvedODR[ModuleIdentifier][GUID] = NewLinkage;
   };
 
-  thinLTOResolveWeakForLinkerInIndex(Index, isPrevailing, recordNewLinkage);
+  auto recordAutoHide = [&](GlobalValue::GUID GUID) {
+    AutoHideCandidates.insert(GUID);
+  };
+
+  thinLTOResolveWeakForLinkerInIndex(Index, isPrevailing, recordNewLinkage,
+                                     recordAutoHide);
 }
 
 // Initialize the TargetMachine builder for a given Triple
 static void initTMBuilder(TargetMachineBuilder &TMBuilder,
                           const Triple &TheTriple) {
   // Set a default CPU for Darwin triples (copied from LTOCodeGenerator).
   // FIXME this looks pretty terrible...
   if (TMBuilder.MCpu.empty() && TheTriple.isOSDarwin()) {
void ThinLTOCodeGenerator::promote(Module &TheModule,
   // Generate import/export list
   StringMap<FunctionImporter::ImportMapTy> ImportLists(ModuleCount);
   StringMap<FunctionImporter::ExportSetTy> ExportLists(ModuleCount);
   ComputeCrossModuleImport(Index, ModuleToDefinedGVSummaries, ImportLists,
                            ExportLists);
 
   // Resolve LinkOnce/Weak symbols.
   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
-  resolveWeakForLinkerInIndex(Index, ResolvedODR);
+  DenseSet<GlobalValue::GUID> AutoHideCandidates;
+  resolveWeakForLinkerInIndex(Index, ResolvedODR, AutoHideCandidates);
 
   thinLTOResolveWeakForLinkerModule(
-      TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
+      TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier],
+      AutoHideCandidates);
 
   // Promote the exported values in the index, so that they are promoted
   // in the module.
   internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, Index);
 
   promoteModule(TheModule, Index);
 }
 
void ThinLTOCodeGenerator::run() {
   // We use a std::map here to be able to have a defined ordering when
   // producing a hash for the cache entry.
   // FIXME: we should be able to compute the caching hash for the entry based
   // on the index, and nuke this map.
   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
 
   // Resolve LinkOnce/Weak symbols, this has to be computed early because it
   // impacts the caching.
-  resolveWeakForLinkerInIndex(*Index, ResolvedODR);
+  DenseSet<GlobalValue::GUID> AutoHideCandidates;
+  resolveWeakForLinkerInIndex(*Index, ResolvedODR, AutoHideCandidates);
 
   // Use global summary-based analysis to identify symbols that can be
   // internalized (because they aren't exported or preserved as per callback).
   // Changes are made in the index, consumed in the ThinLTO backends.
   internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, *Index);
 
   // Make sure that every module has an entry in the ExportLists and
   // ResolvedODR maps to enable threaded access to these maps below.
for (auto IndexCount : ModulesOrdering) {
 
         // Save temps: original file.
         saveTempBitcode(*TheModule, SaveTempsDir, count, ".0.original.bc");
 
         auto &ImportList = ImportLists[ModuleIdentifier];
         // Run the main process now, and generates a binary
         auto OutputBuffer = ProcessThinLTOModule(
             *TheModule, *Index, ModuleMap, *TMBuilder.create(), ImportList,
-            ExportList, GUIDPreservedSymbols,
+            ExportList, GUIDPreservedSymbols, AutoHideCandidates,
             ModuleToDefinedGVSummaries[ModuleIdentifier], CacheOptions,
             DisableCodeGen, SaveTempsDir, Freestanding, OptLevel, count);
 
         // Commit to the cache (if enabled)
         CacheEntry.write(*OutputBuffer);
 
         if (SavedObjectsDirectoryPath.empty()) {
           // We need to generated a memory buffer for the linker.

lib/Transforms/IPO/FunctionImport.cpp

if (Function *F = dyn_cast<Function>(&GV)) {
     GV.replaceAllUsesWith(NewGV);
     return false;
   }
   return true;
 }
 
 /// Fixup WeakForLinker linkages in \p TheModule based on summary analysis.
 void llvm::thinLTOResolveWeakForLinkerModule(
-    Module &TheModule, const GVSummaryMapTy &DefinedGlobals) {
+    Module &TheModule, const GVSummaryMapTy &DefinedGlobals,
+    const DenseSet<GlobalValue::GUID> &AutoHideCandidates) {
   auto updateLinkage = [&](GlobalValue &GV) {
     // See if the global summary analysis computed a new resolved linkage.
     const auto &GS = DefinedGlobals.find(GV.getGUID());
     if (GS == DefinedGlobals.end())
       return;
     auto NewLinkage = GS->second->linkage();
     if (NewLinkage == GV.getLinkage())
       return;
auto updateLinkage = [&](GlobalValue &GV) {
     if (GlobalValue::isAvailableExternallyLinkage(NewLinkage) &&
         GlobalValue::isInterposableLinkage(GV.getLinkage())) {
       if (!convertToDeclaration(GV))
         // FIXME: Change this to collect replaced GVs and later erase
         // them from the parent module once thinLTOResolveWeakForLinkerGUID is
         // changed to enable this for aliases.
         llvm_unreachable("Expected GV to be converted");
     } else {
-      // If the original symbols has global unnamed addr and linkonce_odr linkage,
-      // it should be an auto hide symbol. Add hidden visibility to the symbol to
-      // preserve the property.
-      if (GV.hasLinkOnceODRLinkage() && GV.hasGlobalUnnamedAddr() &&
-          NewLinkage == GlobalValue::WeakODRLinkage)
+      // If linkonce_odr symbols are promoted to weak_odr, make sure we don't
+      // lose the auto hide property. If linkonce_odr symbols has unnamed_addr
+      // or it is a candidate of auto hide, add hidden visibility to the symbol.
+      if ((GV.hasLinkOnceODRLinkage() &&
+           NewLinkage == GlobalValue::WeakODRLinkage) && // Is promote to weak.
+          (GV.hasGlobalUnnamedAddr() || AutoHideCandidates.count(GV.getGUID())))
         GV.setVisibility(GlobalValue::HiddenVisibility);
 
       DEBUG(dbgs() << "ODR fixing up linkage for `" << GV.getName() << "` from "
                    << GV.getLinkage() << " to " << NewLinkage << "\n");
       GV.setLinkage(NewLinkage);
     }
     // Remove declarations from comdats, including available_externally
     // as this is a declaration for the linker, and will be dropped eventually.

test/ThinLTO/X86/Inputs/linkonce_odr_unnamed_addr.ll

+@linkonceodrunnamed = linkonce_odr unnamed_addr constant i32 0
+
+@linkonceodrunnamed_local = linkonce_odr local_unnamed_addr constant i32 0
+
+@linkonceodrunnamed_m = linkonce_odr constant i32 0
+
+@linkonceodrunnamed_n = linkonce_odr unnamed_addr constant i32 0

test/ThinLTO/X86/linkonce_odr_unnamed_addr.ll

 ; This test ensures that when linkonce_odr + unnamed_addr symbols promoted to
 ; weak symbols, it preserves the auto hide property.
 
 ; RUN: opt -module-summary %s -o %t.bc
-; RUN: opt -module-summary %s -o %t2.bc
+; RUN: opt -module-summary %p/Inputs/linkonce_odr_unnamed_addr.ll -o %t2.bc
 ; RUN: llvm-lto -thinlto-action=thinlink -o %t3.bc %t.bc %t2.bc
 ; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc -o - | llvm-dis -o - | FileCheck %s
 
 ; CHECK: @linkonceodrunnamed = weak_odr hidden unnamed_addr constant i32 0
 @linkonceodrunnamed = linkonce_odr unnamed_addr constant i32 0
+
+; CHECK: @linkonceodrunnamed_local = weak_odr hidden local_unnamed_addr constant i32 0
+@linkonceodrunnamed_local = linkonce_odr local_unnamed_addr constant i32 0
+
+; CHECK: @linkonceodrunnamed_m = weak_odr local_unnamed_addr constant i32 0
+@linkonceodrunnamed_m = linkonce_odr local_unnamed_addr constant i32 0
+
+; CHECK: @linkonceodrunnamed_n = weak_odr hidden local_unnamed_addr constant i32 0
+@linkonceodrunnamed_n = linkonce_odr local_unnamed_addr constant i32 0