Improve name mangling for instantiation-dependent types that are not

dependent. This covers an odd class of types such as

  int (&)[sizeof(sizeof(T() + T()))];

which involve template parameters but, because of some trick typically
involving a form of expression that is never type-dependent, resolve
down to a non-dependent type. Such types need to be mangled
essentially as they were written in the source code (involving
template parameters), rather than via their canonical type.

In general, instantiation-dependent types should be mangled as
they were written in the source. However, since we can't do that now
without non-trivial refactoring of the AST (see the new FIXME), I've
gone for this partial solution: only use the as-written-in-the-source
mangling for these strange types that are instantiation-dependent but
not dependent. This provides better compatibility with previous
incarnations of Clang and with GCC. In the future, we'd like to get
this right.

Fixes <rdar://problem/9663282>.

llvm-svn: 134984

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/mangle.cpp b/clang/test/CodeGenCXX/mangle.cpp
index 0b3ba639afd..453b7b713ac 100644
--- a/clang/test/CodeGenCXX/mangle.cpp
+++ b/clang/test/CodeGenCXX/mangle.cpp
@@ -825,6 +825,15 @@ namespace test34 {
 
   // CHECK: define weak_odr void @_ZN6test342f3ILy4EEEvRAplT_Ly8E_i
   template void f3<4>(int (&)[4 + sizeof(int*)]);
+
+  // Mangling for instantiation-dependent sizeof() expressions as
+  // template arguments.
+  template<unsigned> struct A { };
+
+  template<typename T> void f4(::test34::A<sizeof(sizeof(decltype(T() + T())))>) { }
+
+  // CHECK: define weak_odr void @_ZN6test342f4IiEEvNS_1AIXszstDTplcvT__EcvS2__EEEEE
+  template void f4<int>(A<sizeof(sizeof(int))>);
 }
 
 namespace test35 {