Improve name mangling for dependently-scoped declaration references.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97422 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/Mangle.cpp

@@ -1369,7 +1369,18 @@ void CXXNameMangler::mangleExpression(const Expr *E) {
 
   case Expr::DependentScopeDeclRefExprClass: {
     const DependentScopeDeclRefExpr *DRE = cast<DependentScopeDeclRefExpr>(E);
-    const Type *QTy = DRE->getQualifier()->getAsType();
+    NestedNameSpecifier *NNS = DRE->getQualifier();
+    const Type *QTy = NNS->getAsType();
+
+    // When we're dealing with a nested-name-specifier that has just a
+    // dependent identifier in it, mangle that as a typename.  FIXME:
+    // It isn't clear that we ever actually want to have such a
+    // nested-name-specifier; why not just represent it as a typename type?
+    if (!QTy && NNS->getAsIdentifier() && NNS->getPrefix()) {
+      QTy = getASTContext().getTypenameType(NNS->getPrefix(),
+                                            NNS->getAsIdentifier())
+              .getTypePtr();
+    }
     assert(QTy && "Qualifier was not type!");
 
     // ::= sr <type> <unqualified-name>                   # dependent name

test/CodeGenCXX/mangle-template.cpp

@@ -85,3 +85,22 @@ namespace test7 {
   // CHECK: define void @_ZN5test71XIiEC1IdEEPT_PNS_5int_cIXplL_ZNS_4metaIiE5valueEEsrNS6_IS3_EE5valueEE4typeE
   template X<int>::X(double*, float*);
 }
+
+namespace test8 {
+  template<typename T>
+  struct meta {
+    struct type {
+      static const unsigned value = sizeof(T);
+    };
+  };
+
+  template<unsigned> struct int_c { 
+    typedef float type;
+  };
+
+  template<typename T>
+  void f(int_c<meta<T>::type::value>) { }
+
+  // CHECK: define void @_ZN5test81fIiEEvNS_5int_cIXsrNS_4metaIT_E4typeE5valueEEE
+  template void f<int>(int_c<sizeof(int)>);
+}