1 //! Codegen vtables and vtable accesses.
3 //! See `rustc_codegen_ssa/src/meth.rs` for reference.
4 // FIXME dedup this logic between miri, cg_llvm and cg_clif
9 fn vtable_memflags() -> MemFlags {
10 let mut flags = MemFlags::trusted(); // A vtable access is always aligned and will never trap.
11 flags.set_readonly(); // A vtable is always read-only.
15 pub(crate) fn drop_fn_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value {
16 let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
21 (ty::COMMON_VTABLE_ENTRIES_DROPINPLACE * usize_size) as i32,
25 pub(crate) fn size_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value {
26 let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
31 (ty::COMMON_VTABLE_ENTRIES_SIZE * usize_size) as i32,
35 pub(crate) fn min_align_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value {
36 let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
41 (ty::COMMON_VTABLE_ENTRIES_SIZE * usize_size) as i32,
45 pub(crate) fn get_ptr_and_method_ref<'tcx>(
46 fx: &mut FunctionCx<'_, '_, 'tcx>,
50 let (ptr, vtable) = if let Abi::ScalarPair(_, _) = arg.layout().abi {
51 arg.load_scalar_pair(fx)
53 let (ptr, vtable) = arg.try_to_ptr().unwrap();
54 (ptr.get_addr(fx), vtable.unwrap())
57 let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes();
58 let func_ref = fx.bcx.ins().load(
62 (idx * usize_size as usize) as i32,
67 pub(crate) fn get_vtable<'tcx>(
68 fx: &mut FunctionCx<'_, '_, 'tcx>,
69 layout: TyAndLayout<'tcx>,
70 trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
72 let data_id = if let Some(data_id) = fx.vtables.get(&(layout.ty, trait_ref)) {
75 let data_id = build_vtable(fx, layout, trait_ref);
76 fx.vtables.insert((layout.ty, trait_ref), data_id);
80 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
81 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
84 fn build_vtable<'tcx>(
85 fx: &mut FunctionCx<'_, '_, 'tcx>,
86 layout: TyAndLayout<'tcx>,
87 trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
90 let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
92 let drop_in_place_fn = import_function(
95 Instance::resolve_drop_in_place(tcx, layout.ty).polymorphize(fx.tcx),
98 let vtable_entries = if let Some(trait_ref) = trait_ref {
99 tcx.vtable_entries(trait_ref.with_self_ty(tcx, layout.ty))
101 ty::COMMON_VTABLE_ENTRIES
104 let mut data_ctx = DataContext::new();
105 let mut data = ::std::iter::repeat(0u8)
106 .take(vtable_entries.len() * usize_size)
107 .collect::<Vec<u8>>()
110 for (idx, entry) in vtable_entries.iter().enumerate() {
112 VtblEntry::MetadataSize => {
113 write_usize(fx.tcx, &mut data, idx, layout.size.bytes());
115 VtblEntry::MetadataAlign => {
116 write_usize(fx.tcx, &mut data, idx, layout.align.abi.bytes());
118 VtblEntry::MetadataDropInPlace | VtblEntry::Vacant | VtblEntry::Method(_, _) => {}
121 data_ctx.define(data);
123 for (idx, entry) in vtable_entries.iter().enumerate() {
125 VtblEntry::MetadataDropInPlace => {
126 let func_ref = fx.module.declare_func_in_data(drop_in_place_fn, &mut data_ctx);
127 data_ctx.write_function_addr((idx * usize_size) as u32, func_ref);
129 VtblEntry::Method(def_id, substs) => {
130 let func_id = import_function(
133 Instance::resolve_for_vtable(tcx, ParamEnv::reveal_all(), *def_id, substs)
135 .polymorphize(fx.tcx),
137 let func_ref = fx.module.declare_func_in_data(func_id, &mut data_ctx);
138 data_ctx.write_function_addr((idx * usize_size) as u32, func_ref);
140 VtblEntry::MetadataSize | VtblEntry::MetadataAlign | VtblEntry::Vacant => {}
144 data_ctx.set_align(fx.tcx.data_layout.pointer_align.pref.bytes());
146 let data_id = fx.module.declare_anonymous_data(false, false).unwrap();
148 fx.module.define_data(data_id, &data_ctx).unwrap();
153 fn write_usize(tcx: TyCtxt<'_>, buf: &mut [u8], idx: usize, num: u64) {
155 tcx.layout_of(ParamEnv::reveal_all().and(tcx.types.usize)).unwrap().size.bytes() as usize;
156 let target = &mut buf[idx * pointer_size..(idx + 1) * pointer_size];
158 match tcx.data_layout.endian {
159 rustc_target::abi::Endian::Little => match pointer_size {
160 4 => target.copy_from_slice(&(num as u32).to_le_bytes()),
161 8 => target.copy_from_slice(&(num as u64).to_le_bytes()),
162 _ => todo!("pointer size {} is not yet supported", pointer_size),
164 rustc_target::abi::Endian::Big => match pointer_size {
165 4 => target.copy_from_slice(&(num as u32).to_be_bytes()),
166 8 => target.copy_from_slice(&(num as u64).to_be_bytes()),
167 _ => todo!("pointer size {} is not yet supported", pointer_size),