compiler/rustc_codegen_cranelift/src/vtable.rs

   1 //! Codegen vtables and vtable accesses.
   2 //!
   3 //! See `rustc_codegen_ssa/src/meth.rs` for reference.
   4
   5 use crate::constant::data_id_for_alloc_id;
   6 use crate::prelude::*;
   7
   8 pub(crate) fn vtable_memflags() -> MemFlags {
   9     let mut flags = MemFlags::trusted(); // A vtable access is always aligned and will never trap.
  10     flags.set_readonly(); // A vtable is always read-only.
  11     flags
  12 }
  13
  14 pub(crate) fn drop_fn_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value {
  15     let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
  16     fx.bcx.ins().load(
  17         fx.pointer_type,
  18         vtable_memflags(),
  19         vtable,
  20         (ty::COMMON_VTABLE_ENTRIES_DROPINPLACE * usize_size) as i32,
  21     )
  22 }
  23
  24 pub(crate) fn size_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value {
  25     let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
  26     fx.bcx.ins().load(
  27         fx.pointer_type,
  28         vtable_memflags(),
  29         vtable,
  30         (ty::COMMON_VTABLE_ENTRIES_SIZE * usize_size) as i32,
  31     )
  32 }
  33
  34 pub(crate) fn min_align_of_obj(fx: &mut FunctionCx<'_, '_, '_>, vtable: Value) -> Value {
  35     let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes() as usize;
  36     fx.bcx.ins().load(
  37         fx.pointer_type,
  38         vtable_memflags(),
  39         vtable,
  40         (ty::COMMON_VTABLE_ENTRIES_ALIGN * usize_size) as i32,
  41     )
  42 }
  43
  44 pub(crate) fn get_ptr_and_method_ref<'tcx>(
  45     fx: &mut FunctionCx<'_, '_, 'tcx>,
  46     arg: CValue<'tcx>,
  47     idx: usize,
  48 ) -> (Value, Value) {
  49     let (ptr, vtable) = if let Abi::ScalarPair(_, _) = arg.layout().abi {
  50         arg.load_scalar_pair(fx)
  51     } else {
  52         let (ptr, vtable) = arg.try_to_ptr().unwrap();
  53         (ptr.get_addr(fx), vtable.unwrap())
  54     };
  55
  56     let usize_size = fx.layout_of(fx.tcx.types.usize).size.bytes();
  57     let func_ref = fx.bcx.ins().load(
  58         fx.pointer_type,
  59         vtable_memflags(),
  60         vtable,
  61         (idx * usize_size as usize) as i32,
  62     );
  63     (ptr, func_ref)
  64 }
  65
  66 pub(crate) fn get_vtable<'tcx>(
  67     fx: &mut FunctionCx<'_, '_, 'tcx>,
  68     ty: Ty<'tcx>,
  69     trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
  70 ) -> Value {
  71     let alloc_id = fx.tcx.vtable_allocation((ty, trait_ref));
  72     let data_id =
  73         data_id_for_alloc_id(&mut fx.constants_cx, &mut *fx.module, alloc_id, Mutability::Not);
  74     let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
  75     if fx.clif_comments.enabled() {
  76         fx.add_comment(local_data_id, format!("vtable: {:?}", alloc_id));
  77     }
  78     fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
  79 }