Make all virtual member pointers use variadic musttail calls

This avoids encoding information about the function prototype into the
thunk at the cost of some function prototype bitcast gymnastics.

Fixes PR20653.

llvm-svn: 216782

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/microsoft-abi-vmemptr-fastcall.cpp b/clang/test/CodeGenCXX/microsoft-abi-vmemptr-fastcall.cpp
new file mode 100644
index 00000000000..9d55383d656
--- /dev/null
+++ b/clang/test/CodeGenCXX/microsoft-abi-vmemptr-fastcall.cpp
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -triple i686-pc-windows-msvc %s -emit-llvm-only -verify
+
+// We reject this because LLVM doesn't forward the second regparm through the
+// thunk.
+
+struct A {
+  virtual void __fastcall f(int a, int b);
+};
+void (__fastcall A::*doit())(int, int) {
+  return &A::f; // expected-error {{cannot compile this pointer to fastcall virtual member function yet}}
+}