Replace Sema's map of locally-scoped extern "C" declarations with a DeclContext

of extern "C" declarations. This is simpler and vastly more efficient for
modules builds (we no longer need to load *all* extern "C" declarations to
determine if we have a redeclaration).

No functionality change intended.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@231538 91177308-0d34-0410-b5e6-96231b3b80d8

10 files changed, 43 insertions, 62 deletions

diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 9cfc97b926..20d2aa6818 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -738,7 +738,8 @@ ASTContext::ASTContext(LangOptions &LOpts, SourceManager &SM,
       FILEDecl(nullptr), jmp_bufDecl(nullptr), sigjmp_bufDecl(nullptr),
       ucontext_tDecl(nullptr), BlockDescriptorType(nullptr),
       BlockDescriptorExtendedType(nullptr), cudaConfigureCallDecl(nullptr),
-      FirstLocalImport(), LastLocalImport(), SourceMgr(SM), LangOpts(LOpts),
+      FirstLocalImport(), LastLocalImport(), ExternCContext(nullptr),
+      SourceMgr(SM), LangOpts(LOpts),
       SanitizerBL(new SanitizerBlacklist(LangOpts.SanitizerBlacklistFiles, SM)),
       AddrSpaceMap(nullptr), Target(nullptr), PrintingPolicy(LOpts),
       Idents(idents), Selectors(sels), BuiltinInfo(builtins),
@@ -865,6 +866,13 @@ void ASTContext::PrintStats() const {
   BumpAlloc.PrintStats();
 }
 
+ExternCContextDecl *ASTContext::getExternCContextDecl() const {
+  if (!ExternCContext)
+    ExternCContext = ExternCContextDecl::Create(*this, getTranslationUnitDecl());
+
+  return ExternCContext;
+}
+
 RecordDecl *ASTContext::buildImplicitRecord(StringRef Name,
                                             RecordDecl::TagKind TK) const {
   SourceLocation Loc;
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index c7aac37524..bd0e503d38 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -3799,6 +3799,13 @@ TranslationUnitDecl *TranslationUnitDecl::Create(ASTContext &C) {
   return new (C, (DeclContext *)nullptr) TranslationUnitDecl(C);
 }
 
+void ExternCContextDecl::anchor() { }
+
+ExternCContextDecl *ExternCContextDecl::Create(const ASTContext &C,
+                                               TranslationUnitDecl *DC) {
+  return new (C, DC) ExternCContextDecl(DC);
+}
+
 void LabelDecl::anchor() { }
 
 LabelDecl *LabelDecl::Create(ASTContext &C, DeclContext *DC,
diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index 0390d81263..a8e151cc93 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -597,6 +597,7 @@ unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
     case Block:
     case Captured:
     case TranslationUnit:
+    case ExternCContext:
 
     case UsingDirective:
     case ClassTemplateSpecialization:
@@ -907,6 +908,7 @@ bool DeclContext::Encloses(const DeclContext *DC) const {
 DeclContext *DeclContext::getPrimaryContext() {
   switch (DeclKind) {
   case Decl::TranslationUnit:
+  case Decl::ExternCContext:
   case Decl::LinkageSpec:
   case Decl::Block:
   case Decl::Captured:
diff --git a/lib/CodeGen/CGDecl.cpp b/lib/CodeGen/CGDecl.cpp
index fb72a9a543..f79d1373d4 100644
--- a/lib/CodeGen/CGDecl.cpp
+++ b/lib/CodeGen/CGDecl.cpp
@@ -34,6 +34,7 @@ using namespace CodeGen;
 void CodeGenFunction::EmitDecl(const Decl &D) {
   switch (D.getKind()) {
   case Decl::TranslationUnit:
+  case Decl::ExternCContext:
   case Decl::Namespace:
   case Decl::UnresolvedUsingTypename:
   case Decl::ClassTemplateSpecialization:
diff --git a/lib/Sema/MultiplexExternalSemaSource.cpp b/lib/Sema/MultiplexExternalSemaSource.cpp
index a031577767..194c3693c1 100644
--- a/lib/Sema/MultiplexExternalSemaSource.cpp
+++ b/lib/Sema/MultiplexExternalSemaSource.cpp
@@ -242,12 +242,6 @@ void MultiplexExternalSemaSource::ReadUnusedLocalTypedefNameCandidates(
     Sources[i]->ReadUnusedLocalTypedefNameCandidates(Decls);
 }
 
-void MultiplexExternalSemaSource::ReadLocallyScopedExternCDecls(
-                                           SmallVectorImpl<NamedDecl*> &Decls) {
-  for(size_t i = 0; i < Sources.size(); ++i)
-    Sources[i]->ReadLocallyScopedExternCDecls(Decls);
-}
-
 void MultiplexExternalSemaSource::ReadReferencedSelectors(
                   SmallVectorImpl<std::pair<Selector, SourceLocation> > &Sels) {
   for(size_t i = 0; i < Sources.size(); ++i)
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 462854417e..778b617628 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -4864,27 +4864,13 @@ Sema::RegisterLocallyScopedExternCDecl(NamedDecl *ND, Scope *S) {
     return;
 
   // Note that we have a locally-scoped external with this name.
-  // FIXME: There can be multiple such declarations if they are functions marked
-  // __attribute__((overloadable)) declared in function scope in C.
-  LocallyScopedExternCDecls[ND->getDeclName()] = ND;
+  Context.getExternCContextDecl()->makeDeclVisibleInContext(ND);
 }
 
 NamedDecl *Sema::findLocallyScopedExternCDecl(DeclarationName Name) {
-  if (ExternalSource) {
-    // Load locally-scoped external decls from the external source.
-    // FIXME: This is inefficient. Maybe add a DeclContext for extern "C" decls?
-    SmallVector<NamedDecl *, 4> Decls;
-    ExternalSource->ReadLocallyScopedExternCDecls(Decls);
-    for (unsigned I = 0, N = Decls.size(); I != N; ++I) {
-      llvm::DenseMap<DeclarationName, NamedDecl *>::iterator Pos
-        = LocallyScopedExternCDecls.find(Decls[I]->getDeclName());
-      if (Pos == LocallyScopedExternCDecls.end())
-        LocallyScopedExternCDecls[Decls[I]->getDeclName()] = Decls[I];
-    }
-  }
-
-  NamedDecl *D = LocallyScopedExternCDecls.lookup(Name);
-  return D ? D->getMostRecentDecl() : nullptr;
+  // FIXME: We can have multiple results via __attribute__((overloadable)).
+  auto Result = Context.getExternCContextDecl()->lookup(Name);
+  return Result.empty() ? nullptr : *Result.begin();
 }
 
 /// \brief Diagnose function specifiers on a declaration of an identifier that
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 1df0701ee9..6936539f1c 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -289,6 +289,11 @@ TemplateDeclInstantiator::VisitTranslationUnitDecl(TranslationUnitDecl *D) {
 }
 
 Decl *
+TemplateDeclInstantiator::VisitExternCContextDecl(ExternCContextDecl *D) {
+  llvm_unreachable("extern \"C\" context cannot be instantiated");
+}
+
+Decl *
 TemplateDeclInstantiator::VisitLabelDecl(LabelDecl *D) {
   LabelDecl *Inst = LabelDecl::Create(SemaRef.Context, Owner, D->getLocation(),
                                       D->getIdentifier());
diff --git a/lib/Serialization/ASTCommon.cpp b/lib/Serialization/ASTCommon.cpp
index 04425acb4c..85c574c202 100644
--- a/lib/Serialization/ASTCommon.cpp
+++ b/lib/Serialization/ASTCommon.cpp
@@ -94,6 +94,7 @@ serialization::getDefinitiveDeclContext(const DeclContext *DC) {
   switch (DC->getDeclKind()) {
   // These entities may have multiple definitions.
   case Decl::TranslationUnit:
+  case Decl::ExternCContext:
   case Decl::Namespace:
   case Decl::LinkageSpec:
     return nullptr;
@@ -149,7 +150,11 @@ serialization::getDefinitiveDeclContext(const DeclContext *DC) {
 
 bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   switch (static_cast<Decl::Kind>(Kind)) {
-  case Decl::TranslationUnit: // Special case of a "merged" declaration.
+  case Decl::TranslationUnit:
+  case Decl::ExternCContext:
+    // Special case of a "merged" declaration.
+    return true;
+
   case Decl::Namespace:
   case Decl::NamespaceAlias:
   case Decl::Typedef:
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index d3721bbe34..7e3a779b07 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -2892,11 +2892,6 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       }
       break;
 
-    case LOCALLY_SCOPED_EXTERN_C_DECLS:
-      for (unsigned I = 0, N = Record.size(); I != N; ++I)
-        LocallyScopedExternCDecls.push_back(getGlobalDeclID(F, Record[I]));
-      break;
-
     case SELECTOR_OFFSETS: {
       F.SelectorOffsets = (const uint32_t *)Blob.data();
       F.LocalNumSelectors = Record[0];
@@ -6284,6 +6279,9 @@ static Decl *getPredefinedDecl(ASTContext &Context, PredefinedDeclIDs ID) {
 
   case PREDEF_DECL_BUILTIN_VA_LIST_ID:
     return Context.getBuiltinVaListDecl();
+
+  case PREDEF_DECL_EXTERN_C_CONTEXT_ID:
+    return Context.getExternCContextDecl();
   }
   llvm_unreachable("PredefinedDeclIDs unknown enum value");
 }
@@ -7326,17 +7324,6 @@ void ASTReader::ReadUnusedLocalTypedefNameCandidates(
   UnusedLocalTypedefNameCandidates.clear();
 }
 
-void 
-ASTReader::ReadLocallyScopedExternCDecls(SmallVectorImpl<NamedDecl *> &Decls) {
-  for (unsigned I = 0, N = LocallyScopedExternCDecls.size(); I != N; ++I) {
-    NamedDecl *D
-      = dyn_cast_or_null<NamedDecl>(GetDecl(LocallyScopedExternCDecls[I]));
-    if (D)
-      Decls.push_back(D);
-  }
-  LocallyScopedExternCDecls.clear();
-}
-
 void ASTReader::ReadReferencedSelectors(
        SmallVectorImpl<std::pair<Selector, SourceLocation> > &Sels) {
   if (ReferencedSelectorsData.empty())
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 19c7a96625..f92848ad21 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -892,7 +892,6 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(STATISTICS);
   RECORD(TENTATIVE_DEFINITIONS);
   RECORD(UNUSED_FILESCOPED_DECLS);
-  RECORD(LOCALLY_SCOPED_EXTERN_C_DECLS);
   RECORD(SELECTOR_OFFSETS);
   RECORD(METHOD_POOL);
   RECORD(PP_COUNTER_VALUE);
@@ -4231,6 +4230,8 @@ void ASTWriter::WriteASTCore(Sema &SemaRef,
     DeclIDs[Context.ObjCInstanceTypeDecl] = PREDEF_DECL_OBJC_INSTANCETYPE_ID;
   if (Context.BuiltinVaListDecl)
     DeclIDs[Context.getBuiltinVaListDecl()] = PREDEF_DECL_BUILTIN_VA_LIST_ID;
+  if (Context.ExternCContext)
+    DeclIDs[Context.ExternCContext] = PREDEF_DECL_EXTERN_C_CONTEXT_ID;
 
   if (!Chain) {
     // Make sure that we emit IdentifierInfos (and any attached
@@ -4289,20 +4290,6 @@ void ASTWriter::WriteASTCore(Sema &SemaRef,
     }
   }
 
-  // Build a record containing all of the locally-scoped extern "C"
-  // declarations in this header file. Generally, this record will be
-  // empty.
-  RecordData LocallyScopedExternCDecls;
-  // FIXME: This is filling in the AST file in densemap order which is
-  // nondeterminstic!
-  for (llvm::DenseMap<DeclarationName, NamedDecl *>::iterator
-         TD = SemaRef.LocallyScopedExternCDecls.begin(),
-         TDEnd = SemaRef.LocallyScopedExternCDecls.end();
-       TD != TDEnd; ++TD) {
-    if (!TD->second->isFromASTFile())
-      AddDeclRef(TD->second, LocallyScopedExternCDecls);
-  }
-  
   // Build a record containing all of the ext_vector declarations.
   RecordData ExtVectorDecls;
   AddLazyVectorDecls(*this, SemaRef.ExtVectorDecls, ExtVectorDecls);
@@ -4405,6 +4392,10 @@ void ASTWriter::WriteASTCore(Sema &SemaRef,
   Abv->Add(llvm::BitCodeAbbrevOp(llvm::BitCodeAbbrevOp::Blob));
   UpdateVisibleAbbrev = Stream.EmitAbbrev(Abv);
   WriteDeclContextVisibleUpdate(TU);
+
+  // If we have any extern "C" names, write out a visible update for them.
+  if (Context.ExternCContext)
+    WriteDeclContextVisibleUpdate(Context.ExternCContext);
   
   // If the translation unit has an anonymous namespace, and we don't already
   // have an update block for it, write it as an update block.
@@ -4589,11 +4580,6 @@ void ASTWriter::WriteASTCore(Sema &SemaRef,
     Stream.EmitRecord(WEAK_UNDECLARED_IDENTIFIERS,
                       WeakUndeclaredIdentifiers);
 
-  // Write the record containing locally-scoped extern "C" definitions.
-  if (!LocallyScopedExternCDecls.empty())
-    Stream.EmitRecord(LOCALLY_SCOPED_EXTERN_C_DECLS,
-                      LocallyScopedExternCDecls);
-
   // Write the record containing ext_vector type names.
   if (!ExtVectorDecls.empty())
     Stream.EmitRecord(EXT_VECTOR_DECLS, ExtVectorDecls);