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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@216782 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 101 insertions, 0 deletions

diff --git a/test/CodeGenCXX/microsoft-abi-vmemptr-conflicts.cpp b/test/CodeGenCXX/microsoft-abi-vmemptr-conflicts.cpp
new file mode 100644
index 0000000000..35ff4f3beb
--- /dev/null
+++ b/test/CodeGenCXX/microsoft-abi-vmemptr-conflicts.cpp
@@ -0,0 +1,101 @@
+// RUN: %clang_cc1 -fno-rtti -emit-llvm -triple=i386-pc-win32 %s -o - | FileCheck %s
+
+// In each test case, we have two member pointers whose thunks have the same
+// vtable offset and same mangling, but their prototypes conflict.  The
+// arguments and return type may differ.  Therefore, we have to bitcast the
+// function prototype.  Unfortunately, if the return types differ, LLVM's
+// optimizers can get upset.
+
+namespace num_params {
+struct A { virtual void a(int); };
+struct B { virtual void b(int, int); };
+struct C : A, B {
+  virtual void a(int);
+  virtual void b(int, int);
+};
+void f(C *c) {
+  (c->*(&C::a))(0);
+  (c->*(&C::b))(0, 0);
+}
+}
+
+// CHECK-LABEL: define void @"\01?f@num_params@@YAXPAUC@1@@Z"(%"struct.num_params::C"* %c)
+// CHECK: call x86_thiscallcc void bitcast (void (%"struct.num_params::C"*, ...)* @"\01??_9C@num_params@@$BA@AE" to void (%"struct.num_params::C"*, i32)*)(%"struct.num_params::C"* %{{.*}}, i32 0)
+// CHECK: call x86_thiscallcc void bitcast (void (%"struct.num_params::C"*, ...)* @"\01??_9C@num_params@@$BA@AE" to void (%"struct.num_params::C"*, i32, i32)*)(%"struct.num_params::C"* %{{.*}}, i32 0, i32 0)
+
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_9C@num_params@@$BA@AE"(%"struct.num_params::C"* %this, ...)
+// CHECK: musttail call x86_thiscallcc void (%"struct.num_params::C"*, ...)* %{{.*}}(%"struct.num_params::C"* %{{.*}}, ...)
+// CHECK-NEXT: ret void
+
+namespace i64_return {
+struct A { virtual int a(); };
+struct B { virtual long long b(); };
+struct C : A, B {
+  virtual int a();
+  virtual long long b();
+};
+long long f(C *c) {
+  int x = (c->*(&C::a))();
+  long long y = (c->*(&C::b))();
+  return x + y;
+}
+}
+
+// CHECK-LABEL: define i64 @"\01?f@i64_return@@YA_JPAUC@1@@Z"(%"struct.i64_return::C"* %c)
+// CHECK: call x86_thiscallcc i32 bitcast (void (%"struct.i64_return::C"*, ...)* @"\01??_9C@i64_return@@$BA@AE" to i32 (%"struct.i64_return::C"*)*)(%"struct.i64_return::C"* %{{.*}})
+// CHECK: call x86_thiscallcc i64 bitcast (void (%"struct.i64_return::C"*, ...)* @"\01??_9C@i64_return@@$BA@AE" to i64 (%"struct.i64_return::C"*)*)(%"struct.i64_return::C"* %{{.*}})
+
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_9C@i64_return@@$BA@AE"(%"struct.i64_return::C"* %this, ...)
+// CHECK: musttail call x86_thiscallcc void (%"struct.i64_return::C"*, ...)* %{{.*}}(%"struct.i64_return::C"* %{{.*}}, ...)
+// CHECK-NEXT: ret void
+
+namespace sret {
+struct Big { int big[32]; };
+struct A { virtual int a(); };
+struct B { virtual Big b(); };
+struct C : A, B {
+  virtual int a();
+  virtual Big b();
+};
+void f(C *c) {
+  (c->*(&C::a))();
+  Big b((c->*(&C::b))());
+}
+}
+
+// CHECK-LABEL: define void @"\01?f@sret@@YAXPAUC@1@@Z"(%"struct.sret::C"* %c)
+// CHECK: call x86_thiscallcc i32 bitcast (void (%"struct.sret::C"*, ...)* @"\01??_9C@sret@@$BA@AE" to i32 (%"struct.sret::C"*)*)(%"struct.sret::C"* %{{.*}})
+// CHECK: call x86_thiscallcc void bitcast (void (%"struct.sret::C"*, ...)* @"\01??_9C@sret@@$BA@AE" to void (%"struct.sret::C"*, %"struct.sret::Big"*)*)(%"struct.sret::C"* %{{.*}}, %"struct.sret::Big"* sret %{{.*}})
+
+// CHECK-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_9C@sret@@$BA@AE"(%"struct.sret::C"* %this, ...)
+// CHECK: musttail call x86_thiscallcc void (%"struct.sret::C"*, ...)* %{{.*}}(%"struct.sret::C"* %{{.*}}, ...)
+// CHECK-NEXT: ret void
+
+namespace cdecl_inalloca {
+// Fairly evil, since now we end up doing an inalloca-style call through a
+// thunk that doesn't use inalloca.  Hopefully the stacks line up?
+struct Big {
+  Big();
+  ~Big();
+  int big[32];
+};
+struct A { virtual void __cdecl a(); };
+struct B { virtual void __cdecl b(Big); };
+struct C : A, B {
+  virtual void __cdecl a();
+  virtual void __cdecl b(Big);
+};
+void f(C *c) {
+  Big b;
+  (c->*(&C::a))();
+  ((c->*(&C::b))(b));
+}
+}
+
+// CHECK-LABEL: define void @"\01?f@cdecl_inalloca@@YAXPAUC@1@@Z"(%"struct.cdecl_inalloca::C"* %c)
+// CHECK: call void bitcast (void (%"struct.cdecl_inalloca::C"*, ...)* @"\01??_9C@cdecl_inalloca@@$BA@AE" to void (%"struct.cdecl_inalloca::C"*)*)(%"struct.cdecl_inalloca::C"* %{{.*}})
+// CHECK: call void bitcast (void (%"struct.cdecl_inalloca::C"*, ...)* @"\01??_9C@cdecl_inalloca@@$BA@AE" to void (<{ %"struct.cdecl_inalloca::C"*, %"struct.cdecl_inalloca::Big" }>*)*)(<{ %"struct.cdecl_inalloca::C"*, %"struct.cdecl_inalloca::Big" }>* inalloca %{{.*}})
+
+// CHECK-LABEL: define linkonce_odr void @"\01??_9C@cdecl_inalloca@@$BA@AE"(%"struct.cdecl_inalloca::C"* %this, ...)
+// CHECK: musttail call void (%"struct.cdecl_inalloca::C"*, ...)* %{{.*}}(%"struct.cdecl_inalloca::C"* %{{.*}}, ...)
+// CHECK-NEXT: ret void