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.

llvm-svn: 231538

1 files changed, 6 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTCommon.cpp b/clang/lib/Serialization/ASTCommon.cpp
index 04425acb4c5..85c574c2021 100644
--- a/clang/lib/Serialization/ASTCommon.cpp
+++ b/clang/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: