Index: test/Verifier/musttail-valid.ll
===================================================================
--- test/Verifier/musttail-valid.ll
+++ test/Verifier/musttail-valid.ll
@@ -14,3 +14,21 @@
   %w = bitcast i8* %v to i32*
   ret i32* %w
 }
+
+declare x86_thiscallcc void @varargs_thiscall(i8*, ...)
+define x86_thiscallcc void @varargs_thiscall_thunk(i8* %this, ...) {
+  musttail call x86_thiscallcc void (i8*, ...)* @varargs_thiscall(i8* %this, ...)
+  ret void
+}
+
+declare x86_fastcallcc void @varargs_fastcall(i8*, ...)
+define x86_fastcallcc void @varargs_fastcall_thunk(i8* %this, ...) {
+  musttail call x86_fastcallcc void (i8*, ...)* @varargs_fastcall(i8* %this, ...)
+  ret void
+}
+
+; The verifier checks shouldn't be looking for musttail in the function. The
+; function might just abort. Doing a normal return is just UB.
+define x86_thiscallcc void @varargs_thiscall_unreachable(i8* %this, ...) {
+  unreachable
+}