Don't try to emit the vtable for a class just because we're emitting a
virtual function from it.

Fixes PR7241.

llvm-svn: 105345
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 81e80cc..1aa9a11 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -2745,7 +2745,7 @@
   const CXXRecordDecl *RD = MD->getParent();
   
   // Compute VTable related info for this class.
-  ComputeVTableRelatedInformation(RD);
+  ComputeVTableRelatedInformation(RD, false);
   
   ThunksMapTy::const_iterator I = Thunks.find(MD);
   if (I == Thunks.end()) {
@@ -2758,24 +2758,30 @@
     EmitThunk(GD, ThunkInfoVector[I]);
 }
 
-void CodeGenVTables::ComputeVTableRelatedInformation(const CXXRecordDecl *RD) {
-  uint64_t *&LayoutData = VTableLayoutMap[RD];
-  
-  // Check if we've computed this information before.
-  if (LayoutData)
-    return;
+void CodeGenVTables::ComputeVTableRelatedInformation(const CXXRecordDecl *RD,
+                                                     bool RequireVTable) {
+  VTableLayoutData &Entry = VTableLayoutMap[RD];
 
   // We may need to generate a definition for this vtable.
-  if (!isKeyFunctionInAnotherTU(CGM.getContext(), RD) &&
-      RD->getTemplateSpecializationKind()
-                                      != TSK_ExplicitInstantiationDeclaration)
-    CGM.DeferredVTables.push_back(RD);
+  if (RequireVTable && !Entry.getInt()) {
+    if (!isKeyFunctionInAnotherTU(CGM.getContext(), RD) &&
+        RD->getTemplateSpecializationKind()
+          != TSK_ExplicitInstantiationDeclaration)
+      CGM.DeferredVTables.push_back(RD);
+
+    Entry.setInt(true);
+  }
+  
+  // Check if we've computed this information before.
+  if (Entry.getPointer())
+    return;
 
   VTableBuilder Builder(*this, RD, 0, /*MostDerivedClassIsVirtual=*/0, RD);
 
   // Add the VTable layout.
   uint64_t NumVTableComponents = Builder.getNumVTableComponents();
-  LayoutData = new uint64_t[NumVTableComponents + 1];
+  uint64_t *LayoutData = new uint64_t[NumVTableComponents + 1];
+  Entry.setPointer(LayoutData);
 
   // Store the number of components.
   LayoutData[0] = NumVTableComponents;
@@ -2990,7 +2996,7 @@
   CGM.getMangleContext().mangleCXXVTable(RD, OutName);
   llvm::StringRef Name = OutName.str();
 
-  ComputeVTableRelatedInformation(RD);
+  ComputeVTableRelatedInformation(RD, true);
   
   const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
   llvm::ArrayType *ArrayType = 
diff --git a/clang/lib/CodeGen/CGVTables.h b/clang/lib/CodeGen/CGVTables.h
index e55377f..4c790f9 100644
--- a/clang/lib/CodeGen/CGVTables.h
+++ b/clang/lib/CodeGen/CGVTables.h
@@ -207,8 +207,12 @@
   
   /// Thunks - Contains all thunks that a given method decl will need.
   ThunksMapTy Thunks;
-  
-  typedef llvm::DenseMap<const CXXRecordDecl *, uint64_t *> VTableLayoutMapTy;
+
+  // The layout entry and a bool indicating whether we've actually emitted
+  // the vtable.
+  typedef llvm::PointerIntPair<uint64_t *, 1, bool> VTableLayoutData;
+  typedef llvm::DenseMap<const CXXRecordDecl *, VTableLayoutData>
+    VTableLayoutMapTy;
   
   /// VTableLayoutMap - Stores the vtable layout for all record decls.
   /// The layout is stored as an array of 64-bit integers, where the first
@@ -237,13 +241,13 @@
   uint64_t getNumVTableComponents(const CXXRecordDecl *RD) const {
     assert(VTableLayoutMap.count(RD) && "No vtable layout for this class!");
     
-    return VTableLayoutMap.lookup(RD)[0];
+    return VTableLayoutMap.lookup(RD).getPointer()[0];
   }
 
   const uint64_t *getVTableComponentsData(const CXXRecordDecl *RD) const {
     assert(VTableLayoutMap.count(RD) && "No vtable layout for this class!");
 
-    uint64_t *Components = VTableLayoutMap.lookup(RD);
+    uint64_t *Components = VTableLayoutMap.lookup(RD).getPointer();
     return &Components[1];
   }
 
@@ -275,7 +279,8 @@
   /// ComputeVTableRelatedInformation - Compute and store all vtable related
   /// information (vtable layout, vbase offset offsets, thunks etc) for the
   /// given record decl.
-  void ComputeVTableRelatedInformation(const CXXRecordDecl *RD);
+  void ComputeVTableRelatedInformation(const CXXRecordDecl *RD,
+                                       bool VTableRequired);
 
   /// CreateVTableInitializer - Create a vtable initializer for the given record
   /// decl.