2 files changed, 71 insertions, 0 deletions
diff --git a/clang/test/CodeGenCXX/ms-thunks-unprototyped-return.cpp b/clang/test/CodeGenCXX/ms-thunks-unprototyped-return.cpp
new file mode 100644
index 00000000000..ef39fd70607
--- /dev/null
+++ b/clang/test/CodeGenCXX/ms-thunks-unprototyped-return.cpp
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fno-rtti-data -triple x86_64-windows-msvc -emit-llvm-only %s -verify
+
+// Verify that we error out on this return adjusting thunk that we can't emit.
+
+struct Incomplete;
+
+struct A {
+  virtual A * clone(Incomplete p) = 0;
+};
+struct B : virtual A {
+  // expected-error@+1 2 {{cannot compile this return-adjusting thunk with incomplete parameter type yet}}
+  B * clone(Incomplete p) override;
+};
+struct C : B { int c; };
+C c;
diff --git a/clang/test/CodeGenCXX/ms-thunks-unprototyped.cpp b/clang/test/CodeGenCXX/ms-thunks-unprototyped.cpp
new file mode 100644
index 00000000000..b2ca5cb0d13
--- /dev/null
+++ b/clang/test/CodeGenCXX/ms-thunks-unprototyped.cpp
@@ -0,0 +1,56 @@
+// RUN: %clang_cc1 -fno-rtti-data -triple x86_64-windows-msvc -emit-llvm %s -o - | FileCheck %s
+
+// In this example, C does not override B::foo, but it needs to emit a thunk to
+// adjust for the relative difference of position between A-in-B and A-in-C.
+
+struct Incomplete;
+template <typename T>
+struct DoNotInstantiate {
+  typename T::does_not_exist field;
+};
+template <typename T>
+struct InstantiateLater;
+
+struct A {
+  virtual void foo(Incomplete p) = 0;
+  virtual void bar(DoNotInstantiate<int> p) = 0;
+  virtual int baz(InstantiateLater<int> p) = 0;
+};
+struct B : virtual A {
+  void foo(Incomplete p) override;
+  void bar(DoNotInstantiate<int> p) override;
+  inline int baz(InstantiateLater<int> p) override;
+};
+struct C : B { int c; };
+C c;
+
+// CHECK: @"??_7C@@6B@" = linkonce_odr unnamed_addr constant
+// CHECK-SAME: void (%struct.B*, ...)* @"?foo@B@@W7EAAXUIncomplete@@@Z"
+// CHECK-SAME: void (%struct.B*, ...)* @"?bar@B@@W7EAAXU?$DoNotInstantiate@H@@@Z"
+// CHECK-SAME: i32 (i8*, i32)* @"?baz@B@@W7EAAHU?$InstantiateLater@H@@@Z"
+
+// The thunks should have a -8 adjustment.
+
+// CHECK-LABEL: define linkonce_odr dso_local void @"?foo@B@@W7EAAXUIncomplete@@@Z"(%struct.B* %this, ...)
+// CHECK: %[[THIS_ADJ_i8:[^ ]*]] = getelementptr i8, i8* {{.*}}, i32 -8
+// CHECK: %[[THIS_ADJ:[^ ]*]] = bitcast i8* %[[THIS_ADJ_i8]] to %struct.B*
+// CHECK: musttail call void (%struct.B*, ...) {{.*}}@"?foo@B@@UEAAXUIncomplete@@@Z"
+// CHECK-SAME: (%struct.B* %[[THIS_ADJ]], ...)
+// CHECK-NEXT: ret void
+
+// CHECK-LABEL: define linkonce_odr dso_local void @"?bar@B@@W7EAAXU?$DoNotInstantiate@H@@@Z"(%struct.B* %this, ...)
+// CHECK: %[[THIS_ADJ_i8:[^ ]*]] = getelementptr i8, i8* {{.*}}, i32 -8
+// CHECK: %[[THIS_ADJ:[^ ]*]] = bitcast i8* %[[THIS_ADJ_i8]] to %struct.B*
+// CHECK: musttail call void (%struct.B*, ...) {{.*}}@"?bar@B@@UEAAXU?$DoNotInstantiate@H@@@Z"
+// CHECK-SAME: (%struct.B* %[[THIS_ADJ]], ...)
+// CHECK-NEXT: ret void
+
+// If we complete the definition later, things work out.
+template <typename T> struct InstantiateLater { T x; };
+inline int B::baz(InstantiateLater<int> p) { return p.x; }
+
+// CHECK-LABEL: define linkonce_odr dso_local i32 @"?baz@B@@W7EAAHU?$InstantiateLater@H@@@Z"(i8* %this.coerce, i32 %p.coerce)
+// CHECK: = getelementptr i8, i8* {{.*}}, i32 -8
+// CHECK: tail call i32 @"?baz@B@@UEAAHU?$InstantiateLater@H@@@Z"(i8* {{[^,]*}}, i32 {{.*}})
+
+// CHECK-LABEL: define linkonce_odr dso_local i32 @"?baz@B@@UEAAHU?$InstantiateLater@H@@@Z"(i8* %this.coerce, i32 %p.coerce)