[-cxx-abi microsoft] Emit thunks for pointers to virtual member functions

Instead of storing the vtable offset directly in the function pointer and
doing a branch to check for virtualness at each call site, the MS ABI
generates a thunk for calling the function at a specific vtable offset,
and puts that in the function pointer.

This patch adds support for emitting such thunks. However, it doesn't support
pointers to virtual member functions that are variadic, have an incomplete
aggregate return type or parameter, or are overriding a function in a virtual
base class.

Differential Revision: http://llvm-reviews.chandlerc.com/D2104

llvm-svn: 194827

1 files changed, 108 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/microsoft-abi-virtual-member-pointers.cpp b/clang/test/CodeGenCXX/microsoft-abi-virtual-member-pointers.cpp
new file mode 100644
index 00000000000..51a04c89dcb
--- /dev/null
+++ b/clang/test/CodeGenCXX/microsoft-abi-virtual-member-pointers.cpp
@@ -0,0 +1,108 @@
+// RUN: %clang_cc1 -fno-rtti -emit-llvm -cxx-abi microsoft -triple=i386-pc-win32 %s -o - | FileCheck %s --check-prefix=CHECK32
+// RUN: %clang_cc1 -fno-rtti -emit-llvm -cxx-abi microsoft -triple=x86_64-pc-win32 %s -o - | FileCheck %s --check-prefix=CHECK64
+
+struct S {
+  int x, y, z;
+};
+
+struct C {
+  virtual void foo();
+  virtual int bar(int, double);
+  virtual S baz(int);
+};
+
+namespace {
+struct D {
+  virtual void foo();
+};
+}
+
+void f() {
+  void (C::*ptr)();
+  ptr = &C::foo;
+  ptr = &C::foo; // Don't crash trying to define the thunk twice :)
+
+  int (C::*ptr2)(int, double);
+  ptr2 = &C::bar;
+
+  S (C::*ptr3)(int);
+  ptr3 = &C::baz;
+
+  void (D::*ptr4)();
+  ptr4 = &D::foo;
+
+// CHECK32-LABEL: define void @"\01?f@@YAXXZ"()
+// CHECK32: store i8* bitcast (void (%struct.C*)* @"\01??_9C@@$BA@AE" to i8*), i8** %ptr
+// CHECK32: store i8* bitcast (i32 (%struct.C*, i32, double)* @"\01??_9C@@$B3AE" to i8*), i8** %ptr2
+// CHECK32: store i8* bitcast (void (%struct.S*, %struct.C*, i32)* @"\01??_9C@@$B7AE" to i8*), i8** %ptr3
+// CHECK32: store i8* bitcast (void (%"struct.<anonymous namespace>::D"*)* @"\01??_9D@?A@@$BA@AE" to i8*), i8** %ptr4
+// CHECK32: }
+//
+// CHECK64-LABEL: define void @"\01?f@@YAXXZ"()
+// CHECK64: store i8* bitcast (void (%struct.C*)* @"\01??_9C@@$BA@AA" to i8*), i8** %ptr
+// CHECK64: store i8* bitcast (i32 (%struct.C*, i32, double)* @"\01??_9C@@$B7AA" to i8*), i8** %ptr2
+// CHECK64: store i8* bitcast (void (%struct.S*, %struct.C*, i32)* @"\01??_9C@@$BBA@AA" to i8*), i8** %ptr3
+// CHECK64: store i8* bitcast (void (%"struct.<anonymous namespace>::D"*)* @"\01??_9D@?A@@$BA@AA" to i8*), i8** %ptr
+// CHECK64: }
+}
+
+
+// Thunk for calling the 1st virtual function in C with no parameters.
+// CHECK32-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_9C@@$BA@AE"(%struct.C* %this) unnamed_addr
+// CHECK32: [[VPTR:%.*]] = getelementptr inbounds void (%struct.C*)** %{{.*}}, i64 0
+// CHECK32: [[CALLEE:%.*]] = load void (%struct.C*)** [[VPTR]]
+// CHECK32: call x86_thiscallcc void [[CALLEE]](%struct.C* %{{.*}})
+// CHECK32: ret void
+// CHECK32: }
+//
+// CHECK64-LABEL: define linkonce_odr void @"\01??_9C@@$BA@AA"(%struct.C* %this) unnamed_addr
+// CHECK64: [[VPTR:%.*]] = getelementptr inbounds void (%struct.C*)** %{{.*}}, i64 0
+// CHECK64: [[CALLEE:%.*]] = load void (%struct.C*)** [[VPTR]]
+// CHECK64: call void [[CALLEE]](%struct.C* %{{.*}})
+// CHECK64: ret void
+// CHECK64: }
+
+// Thunk for calling the 2nd virtual function in C, taking int and double as parameters, returning int.
+// CHECK32-LABEL: define linkonce_odr x86_thiscallcc i32 @"\01??_9C@@$B3AE"(%struct.C* %this, i32, double) unnamed_addr
+// CHECK32: [[VPTR:%.*]] = getelementptr inbounds i32 (%struct.C*, i32, double)** %{{.*}}, i64 1
+// CHECK32: [[CALLEE:%.*]] = load i32 (%struct.C*, i32, double)** [[VPTR]]
+// CHECK32: [[CALL:%.*]] = call x86_thiscallcc i32 [[CALLEE]](%struct.C* %{{.*}}, i32 %{{.*}}, double %{{.*}})
+// CHECK32: ret i32 [[CALL]]
+// CHECK32: }
+//
+// CHECK64-LABEL: define linkonce_odr i32 @"\01??_9C@@$B7AA"(%struct.C* %this, i32, double) unnamed_addr
+// CHECK64: [[VPTR:%.*]] = getelementptr inbounds i32 (%struct.C*, i32, double)** %{{.*}}, i64 1
+// CHECK64: [[CALLEE:%.*]] = load i32 (%struct.C*, i32, double)** [[VPTR]]
+// CHECK64: [[CALL:%.*]] = call i32 [[CALLEE]](%struct.C* %{{.*}}, i32 %{{.*}}, double %{{.*}})
+// CHECK64: ret i32 [[CALL]]
+// CHECK64: }
+
+// Thunk for calling the 3rd virtual function in C, taking an int parameter, returning a struct.
+// CHECK32-LABEL: define linkonce_odr x86_thiscallcc void @"\01??_9C@@$B7AE"(%struct.S* noalias sret %agg.result, %struct.C* %this, i32) unnamed_addr
+// CHECK32: [[VPTR:%.*]] = getelementptr inbounds void (%struct.S*, %struct.C*, i32)** %{{.*}}, i64 2
+// CHECK32: [[CALLEE:%.*]] = load void (%struct.S*, %struct.C*, i32)** [[VPTR]]
+// CHECK32: call x86_thiscallcc void [[CALLEE]](%struct.S* sret %agg.result, %struct.C* %{{.*}}, i32 %{{.*}})
+// CHECK32: ret void
+// CHECK32: }
+//
+// CHECK64-LABEL: define linkonce_odr void @"\01??_9C@@$BBA@AA"(%struct.S* noalias sret %agg.result, %struct.C* %this, i32) unnamed_addr
+// CHECK64: [[VPTR:%.*]] = getelementptr inbounds void (%struct.S*, %struct.C*, i32)** %{{.*}}, i64 2
+// CHECK64: [[CALLEE:%.*]] = load void (%struct.S*, %struct.C*, i32)** [[VPTR]]
+// CHECK64: call void [[CALLEE]](%struct.S* sret %agg.result, %struct.C* %{{.*}}, i32 %{{.*}})
+// CHECK64: ret void
+// CHECK64: }
+
+// Thunk for calling the virtual function in internal class D.
+// CHECK32-LABEL: define internal x86_thiscallcc void @"\01??_9D@?A@@$BA@AE"(%"struct.<anonymous namespace>::D"* %this) unnamed_addr
+// CHECK32: [[VPTR:%.*]] = getelementptr inbounds void (%"struct.<anonymous namespace>::D"*)** %{{.*}}, i64 0
+// CHECK32: [[CALLEE:%.*]] = load void (%"struct.<anonymous namespace>::D"*)** [[VPTR]]
+// CHECK32: call x86_thiscallcc void [[CALLEE]](%"struct.<anonymous namespace>::D"* %{{.*}})
+// CHECK32: ret void
+// CHECK32: }
+//
+// CHECK64-LABEL: define internal void @"\01??_9D@?A@@$BA@AA"(%"struct.<anonymous namespace>::D"* %this) unnamed_addr
+// CHECK64: [[VPTR:%.*]] = getelementptr inbounds void (%"struct.<anonymous namespace>::D"*)** %{{.*}}, i64 0
+// CHECK64: [[CALLEE:%.*]] = load void (%"struct.<anonymous namespace>::D"*)** [[VPTR]]
+// CHECK64: call void [[CALLEE]](%"struct.<anonymous namespace>::D"* %{{.*}})
+// CHECK64: ret void
+// CHECK64: }