[modules] Remove redundant import of lexical decls when building a lookup table

for a DeclContext, and fix propagation of exception specifications along
redeclaration chains.

This reverts r232905, r232907, and r232907, which reverted r232793, r232853,
and r232853.

One additional change is present here to resolve issues with LLDB: distinguish
between whether lexical decls missing from the lookup table are local or are
provided by the external AST source, and still look in the external source if
that's where they came from.

llvm-svn: 232928

8 files changed, 176 insertions, 138 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 89e1d52c643..57621a7b1f6 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -7946,7 +7946,7 @@ static GVALinkage basicGVALinkageForVariable(const ASTContext &Context,
     while (LexicalContext && !isa<FunctionDecl>(LexicalContext))
       LexicalContext = LexicalContext->getLexicalParent();
 
-    // Let the static local variable inherit it's linkage from the nearest
+    // Let the static local variable inherit its linkage from the nearest
     // enclosing function.
     if (LexicalContext)
       StaticLocalLinkage =
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index a8e151cc937..1f08a64d3ab 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -1011,10 +1011,10 @@ DeclContext::BuildDeclChain(ArrayRef<Decl*> Decls,
 /// built a lookup map. For every name in the map, pull in the new names from
 /// the external storage.
 void DeclContext::reconcileExternalVisibleStorage() const {
-  assert(NeedToReconcileExternalVisibleStorage && LookupPtr.getPointer());
+  assert(NeedToReconcileExternalVisibleStorage && LookupPtr);
   NeedToReconcileExternalVisibleStorage = false;
 
-  for (auto &Lookup : *LookupPtr.getPointer())
+  for (auto &Lookup : *LookupPtr)
     Lookup.second.setHasExternalDecls();
 }
 
@@ -1027,10 +1027,13 @@ DeclContext::LoadLexicalDeclsFromExternalStorage() const {
 
   // Notify that we have a DeclContext that is initializing.
   ExternalASTSource::Deserializing ADeclContext(Source);
-  
+
+  ExternalLexicalStorage = false;
+  bool HadLazyExternalLexicalLookups = HasLazyExternalLexicalLookups;
+  HasLazyExternalLexicalLookups = false;
+
   // Load the external declarations, if any.
   SmallVector<Decl*, 64> Decls;
-  ExternalLexicalStorage = false;
   switch (Source->FindExternalLexicalDecls(this, Decls)) {
   case ELR_Success:
     break;
@@ -1043,6 +1046,9 @@ DeclContext::LoadLexicalDeclsFromExternalStorage() const {
   if (Decls.empty())
     return;
 
+  if (HadLazyExternalLexicalLookups)
+    HasLazyLocalLexicalLookups = true;
+
   // We may have already loaded just the fields of this record, in which case
   // we need to ignore them.
   bool FieldsAlreadyLoaded = false;
@@ -1065,7 +1071,7 @@ ExternalASTSource::SetNoExternalVisibleDeclsForName(const DeclContext *DC,
                                                     DeclarationName Name) {
   ASTContext &Context = DC->getParentASTContext();
   StoredDeclsMap *Map;
-  if (!(Map = DC->LookupPtr.getPointer()))
+  if (!(Map = DC->LookupPtr))
     Map = DC->CreateStoredDeclsMap(Context);
   if (DC->NeedToReconcileExternalVisibleStorage)
     DC->reconcileExternalVisibleStorage();
@@ -1081,7 +1087,7 @@ ExternalASTSource::SetExternalVisibleDeclsForName(const DeclContext *DC,
                                                   ArrayRef<NamedDecl*> Decls) {
   ASTContext &Context = DC->getParentASTContext();
   StoredDeclsMap *Map;
-  if (!(Map = DC->LookupPtr.getPointer()))
+  if (!(Map = DC->LookupPtr))
     Map = DC->CreateStoredDeclsMap(Context);
   if (DC->NeedToReconcileExternalVisibleStorage)
     DC->reconcileExternalVisibleStorage();
@@ -1175,7 +1181,7 @@ void DeclContext::removeDecl(Decl *D) {
     // Remove only decls that have a name
     if (!ND->getDeclName()) return;
 
-    StoredDeclsMap *Map = getPrimaryContext()->LookupPtr.getPointer();
+    StoredDeclsMap *Map = getPrimaryContext()->LookupPtr;
     if (!Map) return;
 
     StoredDeclsMap::iterator Pos = Map->find(ND->getDeclName());
@@ -1263,32 +1269,28 @@ static bool shouldBeHidden(NamedDecl *D) {
 StoredDeclsMap *DeclContext::buildLookup() {
   assert(this == getPrimaryContext() && "buildLookup called on non-primary DC");
 
-  // FIXME: Should we keep going if hasExternalVisibleStorage?
-  if (!LookupPtr.getInt())
-    return LookupPtr.getPointer();
+  if (!HasLazyLocalLexicalLookups && !HasLazyExternalLexicalLookups)
+    return LookupPtr;
+
+  if (HasLazyExternalLexicalLookups)
+    LoadLexicalDeclsFromExternalStorage();
 
   SmallVector<DeclContext *, 2> Contexts;
   collectAllContexts(Contexts);
   for (unsigned I = 0, N = Contexts.size(); I != N; ++I)
-    buildLookupImpl<&DeclContext::decls_begin,
-                    &DeclContext::decls_end>(Contexts[I], false);
+    buildLookupImpl(Contexts[I], hasExternalVisibleStorage());
 
   // We no longer have any lazy decls.
-  LookupPtr.setInt(false);
-  return LookupPtr.getPointer();
+  HasLazyLocalLexicalLookups = false;
+  return LookupPtr;
 }
 
 /// buildLookupImpl - Build part of the lookup data structure for the
 /// declarations contained within DCtx, which will either be this
 /// DeclContext, a DeclContext linked to it, or a transparent context
 /// nested within it.
-template<DeclContext::decl_iterator (DeclContext::*Begin)() const,
-         DeclContext::decl_iterator (DeclContext::*End)() const>
 void DeclContext::buildLookupImpl(DeclContext *DCtx, bool Internal) {
-  for (decl_iterator I = (DCtx->*Begin)(), E = (DCtx->*End)();
-       I != E; ++I) {
-    Decl *D = *I;
-
+  for (Decl *D : DCtx->noload_decls()) {
     // Insert this declaration into the lookup structure, but only if
     // it's semantically within its decl context. Any other decls which
     // should be found in this context are added eagerly.
@@ -1309,7 +1311,7 @@ void DeclContext::buildLookupImpl(DeclContext *DCtx, bool Internal) {
     // context (recursively).
     if (DeclContext *InnerCtx = dyn_cast<DeclContext>(D))
       if (InnerCtx->isTransparentContext() || InnerCtx->isInlineNamespace())
-        buildLookupImpl<Begin, End>(InnerCtx, Internal);
+        buildLookupImpl(InnerCtx, Internal);
   }
 }
 
@@ -1337,9 +1339,9 @@ DeclContext::lookup(DeclarationName Name) const {
     if (NeedToReconcileExternalVisibleStorage)
       reconcileExternalVisibleStorage();
 
-    StoredDeclsMap *Map = LookupPtr.getPointer();
+    StoredDeclsMap *Map = LookupPtr;
 
-    if (LookupPtr.getInt())
+    if (HasLazyLocalLexicalLookups || HasLazyExternalLexicalLookups)
       // FIXME: Make buildLookup const?
       Map = const_cast<DeclContext*>(this)->buildLookup();
 
@@ -1353,7 +1355,7 @@ DeclContext::lookup(DeclarationName Name) const {
       return R.first->second.getLookupResult();
 
     if (Source->FindExternalVisibleDeclsByName(this, Name) || !R.second) {
-      if (StoredDeclsMap *Map = LookupPtr.getPointer()) {
+      if (StoredDeclsMap *Map = LookupPtr) {
         StoredDeclsMap::iterator I = Map->find(Name);
         if (I != Map->end())
           return I->second.getLookupResult();
@@ -1363,8 +1365,8 @@ DeclContext::lookup(DeclarationName Name) const {
     return lookup_result();
   }
 
-  StoredDeclsMap *Map = LookupPtr.getPointer();
-  if (LookupPtr.getInt())
+  StoredDeclsMap *Map = LookupPtr;
+  if (HasLazyLocalLexicalLookups || HasLazyExternalLexicalLookups)
     Map = const_cast<DeclContext*>(this)->buildLookup();
 
   if (!Map)
@@ -1388,26 +1390,18 @@ DeclContext::noload_lookup(DeclarationName Name) {
   if (PrimaryContext != this)
     return PrimaryContext->noload_lookup(Name);
 
-  StoredDeclsMap *Map = LookupPtr.getPointer();
-  if (LookupPtr.getInt()) {
-    // Carefully build the lookup map, without deserializing anything.
+  // If we have any lazy lexical declarations not in our lookup map, add them
+  // now. Don't import any external declarations, not even if we know we have
+  // some missing from the external visible lookups.
+  if (HasLazyLocalLexicalLookups) {
     SmallVector<DeclContext *, 2> Contexts;
     collectAllContexts(Contexts);
     for (unsigned I = 0, N = Contexts.size(); I != N; ++I)
-      buildLookupImpl<&DeclContext::noload_decls_begin,
-                      &DeclContext::noload_decls_end>(Contexts[I], true);
-
-    // We no longer have any lazy decls.
-    LookupPtr.setInt(false);
-
-    // There may now be names for which we have local decls but are
-    // missing the external decls. FIXME: Just set the hasExternalDecls
-    // flag on those names that have external decls.
-    NeedToReconcileExternalVisibleStorage = true;
-
-    Map = LookupPtr.getPointer();
+      buildLookupImpl(Contexts[I], hasExternalVisibleStorage());
+    HasLazyLocalLexicalLookups = false;
   }
 
+  StoredDeclsMap *Map = LookupPtr;
   if (!Map)
     return lookup_result();
 
@@ -1429,8 +1423,9 @@ void DeclContext::localUncachedLookup(DeclarationName Name,
   }
 
   // If we have a lookup table, check there first. Maybe we'll get lucky.
-  if (Name && !LookupPtr.getInt()) {
-    if (StoredDeclsMap *Map = LookupPtr.getPointer()) {
+  // FIXME: Should we be checking these flags on the primary context?
+  if (Name && !HasLazyLocalLexicalLookups && !HasLazyExternalLexicalLookups) {
+    if (StoredDeclsMap *Map = LookupPtr) {
       StoredDeclsMap::iterator Pos = Map->find(Name);
       if (Pos != Map->end()) {
         Results.insert(Results.end(),
@@ -1443,6 +1438,8 @@ void DeclContext::localUncachedLookup(DeclarationName Name,
 
   // Slow case: grovel through the declarations in our chain looking for 
   // matches.
+  // FIXME: If we have lazy external declarations, this will not find them!
+  // FIXME: Should we CollectAllContexts and walk them all here?
   for (Decl *D = FirstDecl; D; D = D->getNextDeclInContext()) {
     if (NamedDecl *ND = dyn_cast<NamedDecl>(D))
       if (ND->getDeclName() == Name)
@@ -1523,7 +1520,7 @@ void DeclContext::makeDeclVisibleInContextWithFlags(NamedDecl *D, bool Internal,
   // FIXME: As a performance hack, don't add such decls into the translation
   // unit unless we're in C++, since qualified lookup into the TU is never
   // performed.
-  if (LookupPtr.getPointer() || hasExternalVisibleStorage() ||
+  if (LookupPtr || hasExternalVisibleStorage() ||
       ((!Recoverable || D->getDeclContext() != D->getLexicalDeclContext()) &&
        (getParentASTContext().getLangOpts().CPlusPlus ||
         !isTranslationUnit()))) {
@@ -1533,7 +1530,7 @@ void DeclContext::makeDeclVisibleInContextWithFlags(NamedDecl *D, bool Internal,
     buildLookup();
     makeDeclVisibleInContextImpl(D, Internal);
   } else {
-    LookupPtr.setInt(true);
+    HasLazyLocalLexicalLookups = true;
   }
 
   // If we are a transparent context or inline namespace, insert into our
@@ -1551,7 +1548,7 @@ void DeclContext::makeDeclVisibleInContextWithFlags(NamedDecl *D, bool Internal,
 
 void DeclContext::makeDeclVisibleInContextImpl(NamedDecl *D, bool Internal) {
   // Find or create the stored declaration map.
-  StoredDeclsMap *Map = LookupPtr.getPointer();
+  StoredDeclsMap *Map = LookupPtr;
   if (!Map) {
     ASTContext *C = &getParentASTContext();
     Map = CreateStoredDeclsMap(*C);
@@ -1613,7 +1610,7 @@ DeclContext::udir_range DeclContext::using_directives() const {
 //===----------------------------------------------------------------------===//
 
 StoredDeclsMap *DeclContext::CreateStoredDeclsMap(ASTContext &C) const {
-  assert(!LookupPtr.getPointer() && "context already has a decls map");
+  assert(!LookupPtr && "context already has a decls map");
   assert(getPrimaryContext() == this &&
          "creating decls map on non-primary context");
 
@@ -1625,7 +1622,7 @@ StoredDeclsMap *DeclContext::CreateStoredDeclsMap(ASTContext &C) const {
     M = new StoredDeclsMap();
   M->Previous = C.LastSDM;
   C.LastSDM = llvm::PointerIntPair<StoredDeclsMap*,1>(M, Dependent);
-  LookupPtr.setPointer(M);
+  LookupPtr = M;
   return M;
 }
 
@@ -1657,11 +1654,11 @@ DependentDiagnostic *DependentDiagnostic::Create(ASTContext &C,
   assert(Parent->isDependentContext()
          && "cannot iterate dependent diagnostics of non-dependent context");
   Parent = Parent->getPrimaryContext();
-  if (!Parent->LookupPtr.getPointer())
+  if (!Parent->LookupPtr)
     Parent->CreateStoredDeclsMap(C);
 
-  DependentStoredDeclsMap *Map
-    = static_cast<DependentStoredDeclsMap*>(Parent->LookupPtr.getPointer());
+  DependentStoredDeclsMap *Map =
+      static_cast<DependentStoredDeclsMap *>(Parent->LookupPtr);
 
   // Allocate the copy of the PartialDiagnostic via the ASTContext's
   // BumpPtrAllocator, rather than the ASTContext itself.
diff --git a/clang/lib/Sema/IdentifierResolver.cpp b/clang/lib/Sema/IdentifierResolver.cpp
index a6efe96573a..53263bac546 100644
--- a/clang/lib/Sema/IdentifierResolver.cpp
+++ b/clang/lib/Sema/IdentifierResolver.cpp
@@ -98,7 +98,7 @@ bool IdentifierResolver::isDeclInScope(Decl *D, DeclContext *Ctx, Scope *S,
                                        bool AllowInlineNamespace) const {
   Ctx = Ctx->getRedeclContext();
 
-  if (Ctx->isFunctionOrMethod() || S->isFunctionPrototypeScope()) {
+  if (Ctx->isFunctionOrMethod() || (S && S->isFunctionPrototypeScope())) {
     // Ignore the scopes associated within transparent declaration contexts.
     while (S->getEntity() && S->getEntity()->isTransparentContext())
       S = S->getParent();
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index 41abd49627b..51d6acebada 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -167,13 +167,13 @@ Sema::ResolveExceptionSpec(SourceLocation Loc, const FunctionProtoType *FPT) {
 void
 Sema::UpdateExceptionSpec(FunctionDecl *FD,
                           const FunctionProtoType::ExceptionSpecInfo &ESI) {
-  for (auto *Redecl : FD->redecls())
-    Context.adjustExceptionSpec(cast<FunctionDecl>(Redecl), ESI);
-
   // If we've fully resolved the exception specification, notify listeners.
   if (!isUnresolvedExceptionSpec(ESI.Type))
     if (auto *Listener = getASTMutationListener())
       Listener->ResolvedExceptionSpec(FD);
+
+  for (auto *Redecl : FD->redecls())
+    Context.adjustExceptionSpec(cast<FunctionDecl>(Redecl), ESI);
 }
 
 /// Determine whether a function has an implicitly-generated exception
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index e15e532be19..0b406184058 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -3021,17 +3021,45 @@ static void LookupVisibleDecls(DeclContext *Ctx, LookupResult &Result,
   if (Visited.visitedContext(Ctx->getPrimaryContext()))
     return;
 
+  // Outside C++, lookup results for the TU live on identifiers.
+  if (isa<TranslationUnitDecl>(Ctx) &&
+      !Result.getSema().getLangOpts().CPlusPlus) {
+    auto &S = Result.getSema();
+    auto &Idents = S.Context.Idents;
+
+    // Ensure all external identifiers are in the identifier table.
+    if (IdentifierInfoLookup *External = Idents.getExternalIdentifierLookup()) {
+      std::unique_ptr<IdentifierIterator> Iter(External->getIdentifiers());
+      for (StringRef Name = Iter->Next(); !Name.empty(); Name = Iter->Next())
+        Idents.get(Name);
+    }
+
+    // Walk all lookup results in the TU for each identifier.
+    for (const auto &Ident : Idents) {
+      for (auto I = S.IdResolver.begin(Ident.getValue()),
+                E = S.IdResolver.end();
+           I != E; ++I) {
+        if (S.IdResolver.isDeclInScope(*I, Ctx)) {
+          if (NamedDecl *ND = Result.getAcceptableDecl(*I)) {
+            Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
+            Visited.add(ND);
+          }
+        }
+      }
+    }
+
+    return;
+  }
+
   if (CXXRecordDecl *Class = dyn_cast<CXXRecordDecl>(Ctx))
     Result.getSema().ForceDeclarationOfImplicitMembers(Class);
 
   // Enumerate all of the results in this context.
   for (const auto &R : Ctx->lookups()) {
-    for (auto *I : R) {
-      if (NamedDecl *ND = dyn_cast<NamedDecl>(I)) {
-        if ((ND = Result.getAcceptableDecl(ND))) {
-          Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
-          Visited.add(ND);
-        }
+    for (auto *D : R) {
+      if (auto *ND = Result.getAcceptableDecl(D)) {
+        Consumer.FoundDecl(ND, Visited.checkHidden(ND), Ctx, InBaseClass);
+        Visited.add(ND);
       }
     }
   }
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index f4b4c4b9879..a26f251cbdb 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -1,4 +1,4 @@
-//===--- ASTReader.cpp - AST File Reader ----------------------------------===//
+//===-- ASTReader.cpp - AST File Reader ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -2835,6 +2835,8 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
     }
 
     case EAGERLY_DESERIALIZED_DECLS:
+      // FIXME: Skip reading this record if our ASTConsumer doesn't care
+      // about "interesting" decls (for instance, if we're building a module).
       for (unsigned I = 0, N = Record.size(); I != N; ++I)
         EagerlyDeserializedDecls.push_back(getGlobalDeclID(F, Record[I]));
       break;
@@ -6832,6 +6834,12 @@ void ASTReader::PassInterestingDeclsToConsumer() {
   SaveAndRestore<bool> GuardPassingDeclsToConsumer(PassingDeclsToConsumer,
                                                    true);
 
+  // Ensure that we've loaded all potentially-interesting declarations
+  // that need to be eagerly loaded.
+  for (auto ID : EagerlyDeserializedDecls)
+    GetDecl(ID);
+  EagerlyDeserializedDecls.clear();
+
   while (!InterestingDecls.empty()) {
     Decl *D = InterestingDecls.front();
     InterestingDecls.pop_front();
@@ -6850,17 +6858,8 @@ void ASTReader::PassInterestingDeclToConsumer(Decl *D) {
 void ASTReader::StartTranslationUnit(ASTConsumer *Consumer) {
   this->Consumer = Consumer;
 
-  if (!Consumer)
-    return;
-
-  for (unsigned I = 0, N = EagerlyDeserializedDecls.size(); I != N; ++I) {
-    // Force deserialization of this decl, which will cause it to be queued for
-    // passing to the consumer.
-    GetDecl(EagerlyDeserializedDecls[I]);
-  }
-  EagerlyDeserializedDecls.clear();
-
-  PassInterestingDeclsToConsumer();
+  if (Consumer)
+    PassInterestingDeclsToConsumer();
 
   if (DeserializationListener)
     DeserializationListener->ReaderInitialized(this);
@@ -8618,6 +8617,13 @@ void ASTReader::FinishedDeserializing() {
   --NumCurrentElementsDeserializing;
 
   if (NumCurrentElementsDeserializing == 0) {
+    // Propagate exception specification updates along redeclaration chains.
+    for (auto Update : PendingExceptionSpecUpdates) {
+      auto *FPT = Update.second->getType()->castAs<FunctionProtoType>();
+      SemaObj->UpdateExceptionSpec(Update.second,
+                                   FPT->getExtProtoInfo().ExceptionSpec);
+    }
+
     diagnoseOdrViolations();
 
     // We are not in recursive loading, so it's safe to pass the "interesting"
@@ -8628,7 +8634,15 @@ void ASTReader::FinishedDeserializing() {
 }
 
 void ASTReader::pushExternalDeclIntoScope(NamedDecl *D, DeclarationName Name) {
-  D = D->getMostRecentDecl();
+  if (IdentifierInfo *II = Name.getAsIdentifierInfo()) {
+    // Remove any fake results before adding any real ones.
+    auto It = PendingFakeLookupResults.find(II);
+    if (It != PendingFakeLookupResults.end()) {
+      for (auto *ND : PendingFakeLookupResults[II])
+        SemaObj->IdResolver.RemoveDecl(ND);
+      PendingFakeLookupResults.erase(It);
+    }
+  }
 
   if (SemaObj->IdResolver.tryAddTopLevelDecl(D, Name) && SemaObj->TUScope) {
     SemaObj->TUScope->AddDecl(D);
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 83882a83693..5c6820f4834 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -228,9 +228,11 @@ namespace clang {
 
     template <typename DeclT>
     static void attachPreviousDeclImpl(ASTReader &Reader,
-                                       Redeclarable<DeclT> *D, Decl *Previous);
+                                       Redeclarable<DeclT> *D, Decl *Previous,
+                                       Decl *Canon);
     static void attachPreviousDeclImpl(ASTReader &Reader, ...);
-    static void attachPreviousDecl(ASTReader &Reader, Decl *D, Decl *Previous);
+    static void attachPreviousDecl(ASTReader &Reader, Decl *D, Decl *Previous,
+                                   Decl *Canon);
 
     template <typename DeclT>
     static void attachLatestDeclImpl(Redeclarable<DeclT> *D, Decl *Latest);
@@ -2621,8 +2623,11 @@ ASTDeclReader::FindExistingResult::~FindExistingResult() {
   if (needsAnonymousDeclarationNumber(New)) {
     setAnonymousDeclForMerging(Reader, New->getLexicalDeclContext(),
                                AnonymousDeclNumber, New);
-  } else if (DC->isTranslationUnit() && Reader.SemaObj) {
-    Reader.SemaObj->IdResolver.tryAddTopLevelDecl(New, Name);
+  } else if (DC->isTranslationUnit() && Reader.SemaObj &&
+             !Reader.getContext().getLangOpts().CPlusPlus) {
+    if (Reader.SemaObj->IdResolver.tryAddTopLevelDecl(New, Name))
+      Reader.PendingFakeLookupResults[Name.getAsIdentifierInfo()]
+            .push_back(New);
   } else if (DeclContext *MergeDC = getPrimaryContextForMerging(Reader, DC)) {
     // Add the declaration to its redeclaration context so later merging
     // lookups will find it.
@@ -2727,7 +2732,8 @@ ASTDeclReader::FindExistingResult ASTDeclReader::findExisting(NamedDecl *D) {
       if (isSameEntity(Existing, D))
         return FindExistingResult(Reader, D, Existing, AnonymousDeclNumber,
                                   TypedefNameForLinkage);
-  } else if (DC->isTranslationUnit() && Reader.SemaObj) {
+  } else if (DC->isTranslationUnit() && Reader.SemaObj &&
+             !Reader.getContext().getLangOpts().CPlusPlus) {
     IdentifierResolver &IdResolver = Reader.SemaObj->IdResolver;
 
     // Temporarily consider the identifier to be up-to-date. We don't want to
@@ -2816,14 +2822,14 @@ Decl *ASTReader::getMostRecentExistingDecl(Decl *D) {
 template<typename DeclT>
 void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
                                            Redeclarable<DeclT> *D,
-                                           Decl *Previous) {
+                                           Decl *Previous, Decl *Canon) {
   D->RedeclLink.setPrevious(cast<DeclT>(Previous));
 }
 namespace clang {
 template<>
 void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
                                            Redeclarable<FunctionDecl> *D,
-                                           Decl *Previous) {
+                                           Decl *Previous, Decl *Canon) {
   FunctionDecl *FD = static_cast<FunctionDecl*>(D);
   FunctionDecl *PrevFD = cast<FunctionDecl>(Previous);
 
@@ -2850,25 +2856,17 @@ void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader,
     FD->IsInline = true;
   }
 
-  // If this declaration has an unresolved exception specification but the
-  // previous declaration had a resolved one, resolve the exception
-  // specification now. If this declaration has a resolved exception
-  // specification but the previous declarations did not, apply our exception
-  // specification to all prior ones now.
+  // If we need to propagate an exception specification along the redecl
+  // chain, make a note of that so that we can do so later.
   auto *FPT = FD->getType()->getAs<FunctionProtoType>();
   auto *PrevFPT = PrevFD->getType()->getAs<FunctionProtoType>();
   if (FPT && PrevFPT) {
-    bool WasUnresolved = isUnresolvedExceptionSpec(FPT->getExceptionSpecType());
-    bool IsUnresolved = isUnresolvedExceptionSpec(PrevFPT->getExceptionSpecType());
-    if (WasUnresolved && !IsUnresolved) {
-      Reader.Context.adjustExceptionSpec(
-          FD, PrevFPT->getExtProtoInfo().ExceptionSpec);
-    } else if (!WasUnresolved && IsUnresolved) {
-      FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
-      for (FunctionDecl *PrevFDToUpdate = PrevFD; PrevFDToUpdate;
-           PrevFDToUpdate = PrevFDToUpdate->getPreviousDecl())
-         Reader.Context.adjustExceptionSpec(PrevFDToUpdate, EPI.ExceptionSpec);
-    }
+    bool IsUnresolved = isUnresolvedExceptionSpec(FPT->getExceptionSpecType());
+    bool WasUnresolved =
+        isUnresolvedExceptionSpec(PrevFPT->getExceptionSpecType());
+    if (IsUnresolved != WasUnresolved)
+      Reader.PendingExceptionSpecUpdates.insert(
+          std::make_pair(Canon, IsUnresolved ? PrevFD : FD));
   }
 }
 }
@@ -2877,14 +2875,14 @@ void ASTDeclReader::attachPreviousDeclImpl(ASTReader &Reader, ...) {
 }
 
 void ASTDeclReader::attachPreviousDecl(ASTReader &Reader, Decl *D,
-                                       Decl *Previous) {
+                                       Decl *Previous, Decl *Canon) {
   assert(D && Previous);
 
   switch (D->getKind()) {
 #define ABSTRACT_DECL(TYPE)
-#define DECL(TYPE, BASE)                                           \
-  case Decl::TYPE:                                                 \
-    attachPreviousDeclImpl(Reader, cast<TYPE##Decl>(D), Previous); \
+#define DECL(TYPE, BASE)                                                  \
+  case Decl::TYPE:                                                        \
+    attachPreviousDeclImpl(Reader, cast<TYPE##Decl>(D), Previous, Canon); \
     break;
 #include "clang/AST/DeclNodes.inc"
   }
@@ -3388,7 +3386,7 @@ void ASTReader::loadPendingDeclChain(Decl *CanonDecl) {
     if (Chain[I] == CanonDecl)
       continue;
 
-    ASTDeclReader::attachPreviousDecl(*this, Chain[I], MostRecent);
+    ASTDeclReader::attachPreviousDecl(*this, Chain[I], MostRecent, CanonDecl);
     MostRecent = Chain[I];
   }
   ASTDeclReader::attachLatestDecl(CanonDecl, MostRecent);
@@ -3732,23 +3730,24 @@ void ASTDeclReader::UpdateDecl(Decl *D, ModuleFile &ModuleFile,
     }
 
     case UPD_CXX_RESOLVED_EXCEPTION_SPEC: {
-      // FIXME: This doesn't send the right notifications if there are
-      // ASTMutationListeners other than an ASTWriter.
       FunctionProtoType::ExceptionSpecInfo ESI;
       SmallVector<QualType, 8> ExceptionStorage;
       Reader.readExceptionSpec(ModuleFile, ExceptionStorage, ESI, Record, Idx);
-      for (auto *Redecl : merged_redecls(D)) {
-        auto *FD = cast<FunctionDecl>(Redecl);
-        auto *FPT = FD->getType()->castAs<FunctionProtoType>();
-        if (!isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
-          // AST invariant: if any exception spec in the redecl chain is
-          // resolved, all are resolved. We don't need to go any further.
-          // FIXME: If the exception spec is resolved, check that it matches.
-          break;
-        }
+
+      // Update this declaration's exception specification, if needed.
+      auto *FD = cast<FunctionDecl>(D);
+      auto *FPT = FD->getType()->castAs<FunctionProtoType>();
+      // FIXME: If the exception specification is already present, check that it
+      // matches.
+      if (isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
         FD->setType(Reader.Context.getFunctionType(
             FPT->getReturnType(), FPT->getParamTypes(),
             FPT->getExtProtoInfo().withExceptionSpec(ESI)));
+
+        // When we get to the end of deserializing, see if there are other decls
+        // that we need to propagate this exception specification onto.
+        Reader.PendingExceptionSpecUpdates.insert(
+            std::make_pair(FD->getCanonicalDecl(), FD));
       }
       break;
     }
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index a8e92b8151c..e992685a83d 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3731,7 +3731,9 @@ void ASTWriter::AddUpdatedDeclContext(const DeclContext *DC) {
 uint32_t
 ASTWriter::GenerateNameLookupTable(const DeclContext *DC,
                                    llvm::SmallVectorImpl<char> &LookupTable) {
-  assert(!DC->LookupPtr.getInt() && "must call buildLookups first");
+  assert(!DC->HasLazyLocalLexicalLookups &&
+         !DC->HasLazyExternalLexicalLookups &&
+         "must call buildLookups first");
 
   llvm::OnDiskChainedHashTableGenerator<ASTDeclContextNameLookupTrait>
       Generator;
@@ -5804,37 +5806,36 @@ void ASTWriter::AddedCXXTemplateSpecialization(const FunctionTemplateDecl *TD,
 }
 
 void ASTWriter::ResolvedExceptionSpec(const FunctionDecl *FD) {
-  assert(!WritingAST && "Already writing the AST!");
-  FD = FD->getCanonicalDecl();
-  if (!FD->isFromASTFile())
-    return; // Not a function declared in PCH and defined outside.
-
-  DeclUpdates[FD].push_back(UPD_CXX_RESOLVED_EXCEPTION_SPEC);
+  assert(!DoneWritingDeclsAndTypes && "Already done writing updates!");
+  if (!Chain) return;
+  Chain->forEachFormerlyCanonicalImportedDecl(FD, [&](const Decl *D) {
+    // If we don't already know the exception specification for this redecl
+    // chain, add an update record for it.
+    if (isUnresolvedExceptionSpec(cast<FunctionDecl>(D)
+                                      ->getType()
+                                      ->castAs<FunctionProtoType>()
+                                      ->getExceptionSpecType()))
+      DeclUpdates[D].push_back(UPD_CXX_RESOLVED_EXCEPTION_SPEC);
+  });
 }
 
 void ASTWriter::DeducedReturnType(const FunctionDecl *FD, QualType ReturnType) {
   assert(!WritingAST && "Already writing the AST!");
-  FD = FD->getCanonicalDecl();
-  if (!FD->isFromASTFile())
-    return; // Not a function declared in PCH and defined outside.
-
-  DeclUpdates[FD].push_back(DeclUpdate(UPD_CXX_DEDUCED_RETURN_TYPE, ReturnType));
+  if (!Chain) return;
+  Chain->forEachFormerlyCanonicalImportedDecl(FD, [&](const Decl *D) {
+    DeclUpdates[D].push_back(
+        DeclUpdate(UPD_CXX_DEDUCED_RETURN_TYPE, ReturnType));
+  });
 }
 
 void ASTWriter::ResolvedOperatorDelete(const CXXDestructorDecl *DD,
                                        const FunctionDecl *Delete) {
   assert(!WritingAST && "Already writing the AST!");
   assert(Delete && "Not given an operator delete");
-  for (auto *D : DD->redecls()) {
-    if (D->isFromASTFile()) {
-      // We added an operator delete that some imported destructor didn't
-      // know about. Add an update record to let importers of us and that
-      // declaration know about it.
-      DeclUpdates[DD].push_back(
-          DeclUpdate(UPD_CXX_RESOLVED_DTOR_DELETE, Delete));
-      return;
-    }
-  }
+  if (!Chain) return;
+  Chain->forEachFormerlyCanonicalImportedDecl(DD, [&](const Decl *D) {
+    DeclUpdates[D].push_back(DeclUpdate(UPD_CXX_RESOLVED_DTOR_DELETE, Delete));
+  });
 }
 
 void ASTWriter::CompletedImplicitDefinition(const FunctionDecl *D) {
@@ -5851,8 +5852,7 @@ void ASTWriter::FunctionDefinitionInstantiated(const FunctionDecl *D) {
   if (!D->isFromASTFile())
     return;
 
-  DeclUpdates[D].push_back(
-      DeclUpdate(UPD_CXX_ADDED_FUNCTION_DEFINITION));
+  DeclUpdates[D].push_back(DeclUpdate(UPD_CXX_ADDED_FUNCTION_DEFINITION));
 }
 
 void ASTWriter::StaticDataMemberInstantiated(const VarDecl *D) {