Revert "[MS] Don't expect vftables to be provided for extern template instantiations"

This reverts commit r273296, it broke the Windows self-host.

llvm-svn: 273305

1 files changed, 7 insertions, 6 deletions

diff --git a/clang/lib/AST/VTableBuilder.cpp b/clang/lib/AST/VTableBuilder.cpp
index 640fbf47aea..e43acc4de78 100644
--- a/clang/lib/AST/VTableBuilder.cpp
+++ b/clang/lib/AST/VTableBuilder.cpp
@@ -2545,13 +2545,14 @@ public:
         MostDerivedClassLayout(Context.getASTRecordLayout(MostDerivedClass)),
         WhichVFPtr(*Which),
         Overriders(MostDerivedClass, CharUnits(), MostDerivedClass) {
-    // Provide the RTTI component if RTTIData is enabled. If the vftable would
-    // be available externally, we should not provide the RTTI componenent. It
-    // is currently impossible to get available externally vftables with either
-    // dllimport or extern template instantiations, but eventually we may add a
-    // flag to support additional devirtualization that needs this.
+    // Only include the RTTI component if we know that we will provide a
+    // definition of the vftable.  We always provide the definition of
+    // dllimported classes.
     if (Context.getLangOpts().RTTIData)
-      HasRTTIComponent = true;
+      if (MostDerivedClass->hasAttr<DLLImportAttr>() ||
+          MostDerivedClass->getTemplateSpecializationKind() !=
+              TSK_ExplicitInstantiationDeclaration)
+        HasRTTIComponent = true;
 
     LayoutVFTable();