TheRock/compiler/amd-llvm/clang/test/CodeGenCXX/RelativeVTablesABI/multiple-inheritance.cpp

// Multiple inheritance.

// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -o - -emit-llvm -fhalf-no-semantic-interposition | FileCheck %s

// VTable for C contains 2 sub-vtables (represented as 2 structs). The first contains the components for B and the second contains the components for C. The RTTI ptr in both arrays still point to the RTTI struct for C.
// The component for bar() instead points to a thunk which redirects to C::bar() which overrides B::bar().
// Now that we have a class with 2 parents, the offset to top in the second array is non-zero.
// CHECK: @_ZTV1C.local = internal constant { [4 x i32], [3 x i32] } { [4 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1C.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1C3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1C3barEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 0, i32 2) to i64)) to i32)], [3 x i32] [i32 -8, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1C.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 1, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZThn8_N1C3barEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 1, i32 2) to i64)) to i32)] }, align 4

// CHECK: @_ZTV1C ={{.*}}alias { [4 x i32], [3 x i32] }, ptr @_ZTV1C.local

// CHECK:      define{{.*}} void @_Z8C_foobarP1C(ptr noundef %c) local_unnamed_addr
// CHECK-NEXT: entry:
// CHECK-NEXT:   [[vtable:%[a-z0-9]+]] = load ptr, ptr %c, align 8

// Offset 0 to get first method
// CHECK-NEXT:   [[ptr1:%[0-9]+]] = tail call ptr @llvm.load.relative.i32(ptr [[vtable]], i32 0)
// CHECK-NEXT:   call void [[ptr1]](ptr {{[^,]*}} %c)
// CHECK-NEXT:   [[vtable:%[a-z0-9]+]] = load ptr, ptr %c, align 8

// Offset by 4 to get the next bar()
// CHECK-NEXT:   [[ptr2:%[0-9]+]] = tail call ptr @llvm.load.relative.i32(ptr [[vtable]], i32 4)
// CHECK-NEXT:   call void [[ptr2]](ptr {{[^,]*}} %c)
// CHECK-NEXT:   ret void
// CHECK-NEXT: }

class A {
public:
  virtual void foo();
};

class B {
  virtual void bar();
};

class C : public A, public B {
public:
  void foo() override;
  void bar() override;
};

void C::foo() {}
void C::bar() {}

void C_foobar(C *c) {
  c->foo();
  c->bar();
}