Improve key-function computation for templates. In particular:

  - All classes can have a key function; templates don't change that.
  non-template classes when computing the key function.
  - We always mark all of the virtual member functions of class
  template instantiations. 
  - The vtable for an instantiation of a class template has weak
  linkage. 

We could probably use available_externally linkage for vtables of
classes instantiated by explicit instantiation declarations (extern
templates), but GCC doesn't do this and I'm not 100% that the ABI
permits it.

llvm-svn: 92753

2 files changed, 64 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/vtable-key-function.cpp b/clang/test/CodeGenCXX/vtable-key-function.cpp
index 90e8ea66f76..97a546f8c93 100644
--- a/clang/test/CodeGenCXX/vtable-key-function.cpp
+++ b/clang/test/CodeGenCXX/vtable-key-function.cpp
@@ -13,3 +13,21 @@ struct A {
 A::A() { }
 A::A(int) { }
 }
+
+// Make sure that we don't assert when building the vtable for a class
+// template specialization or explicit instantiation with a key
+// function.
+template<typename T>
+struct Base {
+  virtual ~Base();
+};
+
+template<typename T>
+struct Derived : public Base<T> { };
+
+template<>
+struct Derived<char> : public Base<char> {
+  virtual void anchor();
+};
+
+void Derived<char>::anchor() { }
diff --git a/clang/test/CodeGenCXX/vtable-linkage.cpp b/clang/test/CodeGenCXX/vtable-linkage.cpp
index 6d3cf240096..23d78aadf7e 100644
--- a/clang/test/CodeGenCXX/vtable-linkage.cpp
+++ b/clang/test/CodeGenCXX/vtable-linkage.cpp
@@ -30,6 +30,30 @@ void D::f() { }
 
 static struct : D { } e;
 
+template<typename T>
+struct E {
+  virtual ~E();
+};
+
+template<typename T> E<T>::~E() { }
+
+template<>
+struct E<char> {
+  virtual void anchor();
+};
+
+void E<char>::anchor() { }
+
+template struct E<short>;
+extern template struct E<int>;
+
+void use_E() {
+  E<int> ei;
+  (void)ei;
+  E<long> el;
+  (void)el;
+}
+
 // B has a key function that is not defined in this translation unit so its vtable
 // has external linkage.
 // CHECK: @_ZTV1B = external constant
@@ -45,14 +69,36 @@ static struct : D { } e;
 // CHECK: @_ZTI1D = constant
 // CHECK: @_ZTV1D = constant
 
+// E<char> is an explicit specialization with a key function defined
+// in this translation unit, so its vtable should have external
+// linkage.
+// CHECK: @_ZTV1EIcE = constant
+
+// E<short> is an explicit template instantiation with a key function
+// defined in this translation unit, so its vtable should have
+// weak_odr linkage.
+// CHECK: @_ZTV1EIsE = weak_odr constant
+
+// E<long> is an implicit template instantiation with a key function
+// defined in this translation unit, so its vtable should have
+// weak_odr linkage.
+// CHECK: @_ZTV1EIlE = weak_odr constant
+
 // The anonymous struct for e has no linkage, so the vtable should have
 // internal linkage.
 // CHECK: @"_ZTS3$_0" = internal constant
 // CHECK: @"_ZTI3$_0" = internal constant
 // CHECK: @"_ZTV3$_0" = internal constant
 
+// E<int> is an explicit template instantiation declaration. It has a
+// key function that is not instantiation, so we should only reference
+// its vtable, not define it.
+// CHECK: @_ZTV1EIiE = external constant
+
 // The A vtable should have internal linkage since it is inside an anonymous 
 // namespace.
 // CHECK: @_ZTSN12_GLOBAL__N_11AE = internal constant
 // CHECK: @_ZTIN12_GLOBAL__N_11AE = internal constant
 // CHECK: @_ZTVN12_GLOBAL__N_11AE = internal constant
+
+