2 files changed, 20 insertions, 63 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 34eced3f4b1..3da1c74bc12 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -888,74 +888,18 @@ void ASTContext::mergeDefinitionIntoModule(NamedDecl *ND, Module *M,
     if (auto *Listener = getASTMutationListener())
       Listener->RedefinedHiddenDefinition(ND, M);
 
-  auto *Merged = &MergedDefModules[ND];
-  if (auto *CanonDef = Merged->CanonicalDef) {
-    ND = CanonDef;
-    Merged = &MergedDefModules[ND];
-  }
-  assert(!Merged->CanonicalDef && "canonical def not canonical");
-
-  Merged->MergedModules.push_back(M);
-
-  if (!getLangOpts().ModulesLocalVisibility)
+  if (getLangOpts().ModulesLocalVisibility)
+    MergedDefModules[ND].push_back(M);
+  else
     ND->setHidden(false);
 }
 
-void ASTContext::mergeDefinitionIntoModulesOf(NamedDecl *Def,
-                                              NamedDecl *Other) {
-  // We need to know the owning module of the merge source.
-  assert(Other->isFromASTFile() && "merge of non-imported decl not supported");
-  assert(Def != Other && "merging definition into itself");
-
-  if (!Other->isHidden()) {
-    Def->setHidden(false);
-    return;
-  }
-
-  assert(Other->getImportedOwningModule() &&
-         "hidden, imported declaration has no owning module");
-
-  // Mark Def as the canonical definition of merged definition Other.
-  {
-    auto &OtherMerged = MergedDefModules[Other];
-    assert((!OtherMerged.CanonicalDef || OtherMerged.CanonicalDef == Def) &&
-           "mismatched canonical definitions for declaration");
-    OtherMerged.CanonicalDef = Def;
-  }
-
-  auto &Merged = MergedDefModules[Def];
-  // Grab this again, we potentially just invalidated our reference.
-  auto &OtherMerged = MergedDefModules[Other];
-
-  if (Module *M = Other->getImportedOwningModule())
-    Merged.MergedModules.push_back(M);
-
-  // If this definition had any others merged into it, they're now merged into
-  // the canonical definition instead.
-  if (!OtherMerged.MergedModules.empty()) {
-    assert(!Merged.CanonicalDef && "canonical definition not canonical");
-    if (Merged.MergedModules.empty())
-      Merged.MergedModules = std::move(OtherMerged.MergedModules);
-    else
-      Merged.MergedModules.insert(Merged.MergedModules.end(),
-                                  OtherMerged.MergedModules.begin(),
-                                  OtherMerged.MergedModules.end());
-    OtherMerged.MergedModules.clear();
-  }
-}
-
 void ASTContext::deduplicateMergedDefinitonsFor(NamedDecl *ND) {
   auto It = MergedDefModules.find(ND);
   if (It == MergedDefModules.end())
     return;
 
-  if (auto *CanonDef = It->second.CanonicalDef) {
-    It = MergedDefModules.find(CanonDef);
-    if (It == MergedDefModules.end())
-      return;
-  }
-
-  auto &Merged = It->second.MergedModules;
+  auto &Merged = It->second;
   llvm::DenseSet<Module*> Found;
   for (Module *&M : Merged)
     if (!Found.insert(M).second)
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index ac136e95b4e..8ce118ce710 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -3481,10 +3481,23 @@ void ASTReader::makeModuleVisible(Module *Mod,
 /// visible.
 void ASTReader::mergeDefinitionVisibility(NamedDecl *Def,
                                           NamedDecl *MergedDef) {
+  // FIXME: This doesn't correctly handle the case where MergedDef is visible
+  // in modules other than its owning module. We should instead give the
+  // ASTContext a list of merged definitions for Def.
   if (Def->isHidden()) {
     // If MergedDef is visible or becomes visible, make the definition visible.
-    getContext().mergeDefinitionIntoModulesOf(Def, MergedDef);
-    PendingMergedDefinitionsToDeduplicate.insert(Def);
+    if (!MergedDef->isHidden())
+      Def->Hidden = false;
+    else if (getContext().getLangOpts().ModulesLocalVisibility) {
+      getContext().mergeDefinitionIntoModule(
+          Def, MergedDef->getImportedOwningModule(),
+          /*NotifyListeners*/ false);
+      PendingMergedDefinitionsToDeduplicate.insert(Def);
+    } else {
+      auto SubmoduleID = MergedDef->getOwningModuleID();
+      assert(SubmoduleID && "hidden definition in no module");
+      HiddenNamesMap[getSubmodule(SubmoduleID)].push_back(Def);
+    }
   }
 }
 
@@ -8619,7 +8632,7 @@ void ASTReader::finishPendingActions() {
       const FunctionDecl *Defn = nullptr;
       if (!getContext().getLangOpts().Modules || !FD->hasBody(Defn))
         FD->setLazyBody(PB->second);
-      else if (FD != Defn)
+      else
         mergeDefinitionVisibility(const_cast<FunctionDecl*>(Defn), FD);
       continue;
     }