2 files changed, 26 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGVtable.cpp b/clang/lib/CodeGen/CGVtable.cpp
index 841281cdc42..bae588ab9b8 100644
--- a/clang/lib/CodeGen/CGVtable.cpp
+++ b/clang/lib/CodeGen/CGVtable.cpp
@@ -3138,19 +3138,28 @@ void CodeGenVTables::EmitVTableRelatedData(GlobalDecl GD) {
   // Get the key function.
   const CXXMethodDecl *KeyFunction = CGM.getContext().getKeyFunction(RD);
   
+  TemplateSpecializationKind RDKind = RD->getTemplateSpecializationKind();
+  TemplateSpecializationKind MDKind = MD->getTemplateSpecializationKind();
+
   if (KeyFunction) {
     // We don't have the right key function.
     if (KeyFunction->getCanonicalDecl() != MD->getCanonicalDecl())
       return;
+  } else {
+    // If this is an explicit instantiation of a method, we don't need a vtable.
+    // Since we have no key function, we will emit the vtable when we see
+    // a use, and just defining a function is not an use.
+    if ((RDKind == TSK_ImplicitInstantiation ||
+         RDKind == TSK_ExplicitInstantiationDeclaration) &&
+        MDKind == TSK_ExplicitInstantiationDefinition)
+      return;
   }
 
   if (Vtables.count(RD))
     return;
 
-  TemplateSpecializationKind kind = RD->getTemplateSpecializationKind();
-  if (kind == TSK_ImplicitInstantiation)
+  if (RDKind == TSK_ImplicitInstantiation)
     CGM.DeferredVtables.push_back(RD);
   else
     GenerateClassData(CGM.getVtableLinkage(RD), RD);
 }
-
diff --git a/clang/test/CodeGenCXX/template-instantiation.cpp b/clang/test/CodeGenCXX/template-instantiation.cpp
index 9e0593998bb..416c0a1a207 100644
--- a/clang/test/CodeGenCXX/template-instantiation.cpp
+++ b/clang/test/CodeGenCXX/template-instantiation.cpp
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
 
 // CHECK-NOT: @_ZTVN5test118stdio_sync_filebufIwEE = constant
+// CHECK-NOT: _ZTVN5test315basic_fstreamXXIcEE
 // CHECK: @_ZTVN5test018stdio_sync_filebufIwEE = constant
 
 // CHECK: define linkonce_odr void @_ZN5test21CIiEC1Ev(
@@ -60,3 +61,16 @@ namespace test2 {
     a.zedbar(0.0);
   }
 }
+
+namespace test3 {
+  template<typename T>
+  class basic_fstreamXX  {
+    virtual void foo(){}
+    virtual void is_open() const  { }
+  };
+
+  extern template class basic_fstreamXX<char>;
+  // This template instantiation should not cause us to produce a vtable.
+  // (test at the top).
+  template void basic_fstreamXX<char>::is_open() const;
+}