4 files changed, 21 insertions, 2 deletions
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index 9e6f7216e5f..86219d24667 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -1377,6 +1377,10 @@ void TextNodeDumper::VisitCapturedDecl(const CapturedDecl *D) {
 
 void TextNodeDumper::VisitImportDecl(const ImportDecl *D) {
   OS << ' ' << D->getImportedModule()->getFullModuleName();
+
+  for (Decl *InitD :
+       D->getASTContext().getModuleInitializers(D->getImportedModule()))
+    dumpDeclRef(InitD, "initializer");
 }
 
 void TextNodeDumper::VisitPragmaCommentDecl(const PragmaCommentDecl *D) {
diff --git a/clang/lib/Serialization/ASTCommon.h b/clang/lib/Serialization/ASTCommon.h
index 298b4714904..2678103ac9a 100644
--- a/clang/lib/Serialization/ASTCommon.h
+++ b/clang/lib/Serialization/ASTCommon.h
@@ -108,6 +108,21 @@ template<typename Fn> void numberAnonymousDeclsWithin(const DeclContext *DC,
   }
 }
 
+/// Determine whether the given declaration will be included in the per-module
+/// initializer if it needs to be eagerly handed to the AST consumer. If so, we
+/// should not hand it to the consumer when deserializing it, nor include it in
+/// the list of eagerly deserialized declarations.
+inline bool isPartOfPerModuleInitializer(const Decl *D) {
+  if (isa<ImportDecl>(D))
+    return true;
+  // Template instantiations are notionally in an "instantiation unit" rather
+  // than in any particular translation unit, so they need not be part of any
+  // particular (sub)module's per-module initializer.
+  if (auto *VD = dyn_cast<VarDecl>(D))
+    return !isTemplateInstantiation(VD->getTemplateSpecializationKind());
+  return false;
+}
+
 } // namespace serialization
 
 } // namespace clang
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 1c56cdbf948..6d02f4d1121 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2779,7 +2779,7 @@ static bool isConsumerInterestedIn(ASTContext &Ctx, Decl *D, bool HasBody) {
 
   // An ImportDecl or VarDecl imported from a module map module will get
   // emitted when we import the relevant module.
-  if (isa<ImportDecl>(D) || isa<VarDecl>(D)) {
+  if (isPartOfPerModuleInitializer(D)) {
     auto *M = D->getImportedOwningModule();
     if (M && M->Kind == Module::ModuleMapModule &&
         Ctx.DeclMustBeEmitted(D))
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index bd5191dcb91..ff0c56b9ed4 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -2272,7 +2272,7 @@ static bool isRequiredDecl(const Decl *D, ASTContext &Context,
   if (isa<FileScopeAsmDecl>(D) || isa<ObjCImplDecl>(D))
     return true;
 
-  if (WritingModule && (isa<VarDecl>(D) || isa<ImportDecl>(D))) {
+  if (WritingModule && isPartOfPerModuleInitializer(D)) {
     // These declarations are part of the module initializer, and are emitted
     // if and when the module is imported, rather than being emitted eagerly.
     return false;