| //! Codegen vtables and vtable accesses. |
| //! |
| //! See `rustc_codegen_ssa/src/meth.rs` for reference. |
| |
| use crate::constant::data_id_for_vtable; |
| use crate::prelude::*; |
| |
| pub(crate) fn vtable_memflags() -> MemFlags { |
| let mut flags = MemFlags::trusted(); // A vtable access is always aligned and will never trap. |
| flags.set_readonly(); // A vtable is always read-only. |
| flags |
| } |
| |
| pub(crate) fn drop_fn_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value { |
| let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize; |
| fx.bcx.ins().load( |
| fx.pointer_type, |
| vtable_memflags(), |
| vtable, |
| (ty::COMMON_VTABLE_ENTRIES_DROPINPLACE * usize_size) as i32, |
| ) |
| } |
| |
| pub(crate) fn size_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value { |
| let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize; |
| fx.bcx.ins().load( |
| fx.pointer_type, |
| vtable_memflags(), |
| vtable, |
| (ty::COMMON_VTABLE_ENTRIES_SIZE * usize_size) as i32, |
| ) |
| } |
| |
| pub(crate) fn min_align_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value { |
| let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize; |
| fx.bcx.ins().load( |
| fx.pointer_type, |
| vtable_memflags(), |
| vtable, |
| (ty::COMMON_VTABLE_ENTRIES_ALIGN * usize_size) as i32, |
| ) |
| } |
| |
| pub(crate) fn get_ptr_and_method_ref<'tcx>( |
| fx: &mut FunctionCx<'_, '_, 'tcx>, |
| mut arg: CValue<'tcx>, |
| idx: usize, |
| ) -> (Pointer, Value) { |
| let (ptr, vtable) = 'block: { |
| if let Abi::Scalar(_) = arg.layout().abi { |
| while !arg.layout().ty.is_unsafe_ptr() && !arg.layout().ty.is_ref() { |
| let (idx, _) = arg |
| .layout() |
| .non_1zst_field(fx) |
| .expect("not exactly one non-1-ZST field in a `DispatchFromDyn` type"); |
| arg = arg.value_field(fx, FieldIdx::new(idx)); |
| } |
| } |
| |
| if let ty::Ref(_, ty, _) = arg.layout().ty.kind() { |
| if ty.is_dyn_star() { |
| let inner_layout = fx.layout_of(arg.layout().ty.builtin_deref(true).unwrap().ty); |
| let dyn_star = CPlace::for_ptr(Pointer::new(arg.load_scalar(fx)), inner_layout); |
| let ptr = dyn_star.place_field(fx, FieldIdx::ZERO).to_ptr(); |
| let vtable = |
| dyn_star.place_field(fx, FieldIdx::new(1)).to_cvalue(fx).load_scalar(fx); |
| break 'block (ptr, vtable); |
| } |
| } |
| |
| if let Abi::ScalarPair(_, _) = arg.layout().abi { |
| let (ptr, vtable) = arg.load_scalar_pair(fx); |
| (Pointer::new(ptr), vtable) |
| } else { |
| let (ptr, vtable) = arg.try_to_ptr().unwrap(); |
| (ptr, vtable.unwrap()) |
| } |
| }; |
| |
| let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes(); |
| let func_ref = fx.bcx.ins().load( |
| fx.pointer_type, |
| vtable_memflags(), |
| vtable, |
| (idx * usize_size as usize) as i32, |
| ); |
| (ptr, func_ref) |
| } |
| |
| pub(crate) fn get_vtable<'tcx>( |
| fx: &mut FunctionCx<'_, '_, 'tcx>, |
| ty: Ty<'tcx>, |
| trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>, |
| ) -> Value { |
| let data_id = data_id_for_vtable(fx.tcx, &mut fx.constants_cx, fx.module, ty, trait_ref); |
| let local_data_id = fx.module.declare_data_in_func(data_id, fx.bcx.func); |
| if fx.clif_comments.enabled() { |
| fx.add_comment(local_data_id, "vtable"); |
| } |
| fx.bcx.ins().global_value(fx.pointer_type, local_data_id) |
| } |