710d647586
This functionality is described in the Itanium C++ABI 2.5.2 (and is also where the test comes from). See also VTableBuilder.cpp's documentation on the declaration of IsOverriderUsed for further details. However, the explaination is: When B and C are declared, A is a primary base in each case, so although vcall offsets are allocated in the A-in-B and A-in-C vtables, no this adjustment is required and no thunk is generated. However, inside D objects, A is no longer a primary base of C, so if we allowed calls to C::f() to use the copy of A's vtable in the C subobject, we would need to adjust this from C* to B::A*, which would require a third-party thunk. Since we require that a call to C::f() first convert to A*, C-in-D's copy of A's vtable is never referenced, so this is not necessary. The short of that is: there is no way to call these, so we just emit a nullptr rather than the required thunk.
31 lines
2.9 KiB
C++
31 lines
2.9 KiB
C++
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -fclangir -emit-cir -mmlir -mlir-print-ir-before=cir-cxxabi-lowering %s -o %t.cir 2> %t-before.cir
|
|
// RUN: FileCheck --input-file=%t-before.cir -check-prefix=CIR %s
|
|
// RUN: FileCheck --input-file=%t.cir --check-prefix=CIR %s
|
|
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -fclangir -emit-llvm %s -o %t-cir.ll
|
|
// RUN: FileCheck --input-file=%t-cir.ll --check-prefix=LLVM %s
|
|
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -emit-llvm %s -o %t.ll
|
|
// RUN: FileCheck --input-file=%t.ll --check-prefix=LLVM %s
|
|
|
|
|
|
// This is an example right out of the itanium ABI for a 'null' function
|
|
// pointer.
|
|
struct A { virtual void f(); };
|
|
struct B : virtual public A { int i; };
|
|
struct C : virtual public A { int j; };
|
|
struct D : public B, public C {
|
|
virtual void d();
|
|
};
|
|
void D::d() {}
|
|
|
|
// CIR: cir.global {{.*}}@_ZTV1D = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI1D> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1A1fEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1D1dEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 6>, #cir.const_array<[#cir.ptr<-16 : i64> : !cir.ptr<!u8i>, #cir.ptr<-16 : i64> : !cir.ptr<!u8i>, #cir.ptr<-16 : i64> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI1D> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 5>}>
|
|
//
|
|
// LLVM: @_ZTV1D = {{.*}}{ [6 x ptr], [5 x ptr] } { [6 x ptr] [ptr null, ptr null, ptr null, ptr @_ZTI1D, ptr @_ZN1A1fEv, ptr @_ZN1D1dEv], [5 x ptr] [ptr inttoptr (i64 -16 to ptr), ptr inttoptr (i64 -16 to ptr), ptr inttoptr (i64 -16 to ptr), ptr @_ZTI1D, ptr null] }, align 8
|
|
//
|
|
// CIR: cir.global {{.*}}@_ZTC1D0_1B = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI1B> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1A1fEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 5>}>
|
|
|
|
// LLVM: @_ZTC1D0_1B = {{.*}}{ [5 x ptr] } { [5 x ptr] [ptr null, ptr null, ptr null, ptr @_ZTI1B, ptr @_ZN1A1fEv] }, align 8
|
|
//
|
|
// CIR: cir.global {{.*}}@_ZTC1D16_1C = #cir.vtable<{#cir.const_array<[#cir.ptr<-16 : i64> : !cir.ptr<!u8i>, #cir.ptr<-16 : i64> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI1C> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 5>, #cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<16 : i64> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI1C> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1A1fEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}>
|
|
//
|
|
// LLVM: @_ZTC1D16_1C = {{.*}}{ [5 x ptr], [4 x ptr] } { [5 x ptr] [ptr inttoptr (i64 -16 to ptr), ptr inttoptr (i64 -16 to ptr), ptr null, ptr @_ZTI1C, ptr null], [4 x ptr] [ptr null, ptr inttoptr (i64 16 to ptr), ptr @_ZTI1C, ptr @_ZN1A1fEv] }, align 8
|