1 use rustc_data_structures::sync::Lrc;
2 use rustc::ty::{self, Ty};
3 use rustc::ty::layout::{Size, Align, LayoutOf};
4 use rustc::mir::interpret::{Scalar, Pointer, EvalResult, PointerArithmetic};
6 use super::{EvalContext, Machine, MemoryKind};
8 impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M> {
9 /// Creates a dynamic vtable for the given type and vtable origin. This is used only for
12 /// The `trait_ref` encodes the erased self type. Hence if we are
13 /// making an object `Foo<Trait>` from a value of type `Foo<T>`, then
14 /// `trait_ref` would map `T:Trait`.
18 poly_trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
19 ) -> EvalResult<'tcx, Pointer<M::PointerTag>> {
20 trace!("get_vtable(trait_ref={:?})", poly_trait_ref);
22 let (ty, poly_trait_ref) = self.tcx.erase_regions(&(ty, poly_trait_ref));
24 if let Some(&vtable) = self.vtables.get(&(ty, poly_trait_ref)) {
25 return Ok(Pointer::from(vtable).with_default_tag());
28 let methods = if let Some(poly_trait_ref) = poly_trait_ref {
29 let trait_ref = poly_trait_ref.with_self_ty(*self.tcx, ty);
30 let trait_ref = self.tcx.erase_regions(&trait_ref);
32 self.tcx.vtable_methods(trait_ref)
37 let layout = self.layout_of(ty)?;
38 assert!(!layout.is_unsized(), "can't create a vtable for an unsized type");
39 let size = layout.size.bytes();
40 let align = layout.align.abi.bytes();
42 let ptr_size = self.pointer_size();
43 let ptr_align = self.tcx.data_layout.pointer_align.abi;
44 // /////////////////////////////////////////////////////////////////////////////////////////
45 // If you touch this code, be sure to also make the corresponding changes to
46 // `get_vtable` in rust_codegen_llvm/meth.rs
47 // /////////////////////////////////////////////////////////////////////////////////////////
48 let vtable = self.memory.allocate(
49 ptr_size * (3 + methods.len() as u64),
55 let drop = crate::monomorphize::resolve_drop_in_place(*tcx, ty);
56 let drop = self.memory.create_fn_alloc(drop).with_default_tag();
57 // no need to do any alignment checks on the memory accesses below, because we know the
58 // allocation is correctly aligned as we created it above. Also we're only offsetting by
59 // multiples of `ptr_align`, which means that it will stay aligned to `ptr_align`.
61 .get_mut(vtable.alloc_id)?
62 .write_ptr_sized(tcx, vtable, Scalar::Ptr(drop).into())?;
64 let size_ptr = vtable.offset(ptr_size, self)?;
66 .get_mut(size_ptr.alloc_id)?
67 .write_ptr_sized(tcx, size_ptr, Scalar::from_uint(size, ptr_size).into())?;
68 let align_ptr = vtable.offset(ptr_size * 2, self)?;
70 .get_mut(align_ptr.alloc_id)?
71 .write_ptr_sized(tcx, align_ptr, Scalar::from_uint(align, ptr_size).into())?;
73 for (i, method) in methods.iter().enumerate() {
74 if let Some((def_id, substs)) = *method {
75 let instance = self.resolve(def_id, substs)?;
76 let fn_ptr = self.memory.create_fn_alloc(instance).with_default_tag();
77 let method_ptr = vtable.offset(ptr_size * (3 + i as u64), self)?;
79 .get_mut(method_ptr.alloc_id)?
80 .write_ptr_sized(tcx, method_ptr, Scalar::Ptr(fn_ptr).into())?;
84 self.memory.mark_immutable(vtable.alloc_id)?;
85 assert!(self.vtables.insert((ty, poly_trait_ref), vtable.alloc_id).is_none());
90 /// Return the drop fn instance as well as the actual dynamic type
91 pub fn read_drop_type_from_vtable(
93 vtable: Pointer<M::PointerTag>,
94 ) -> EvalResult<'tcx, (ty::Instance<'tcx>, ty::Ty<'tcx>)> {
95 // we don't care about the pointee type, we just want a pointer
96 self.memory.check_align(vtable.into(), self.tcx.data_layout.pointer_align.abi)?;
97 let drop_fn = self.memory
98 .get(vtable.alloc_id)?
99 .read_ptr_sized(self, vtable)?
101 let drop_instance = self.memory.get_fn(drop_fn)?;
102 trace!("Found drop fn: {:?}", drop_instance);
103 let fn_sig = drop_instance.ty(*self.tcx).fn_sig(*self.tcx);
104 let fn_sig = self.tcx.normalize_erasing_late_bound_regions(self.param_env, &fn_sig);
105 // the drop function takes *mut T where T is the type being dropped, so get that
106 let ty = fn_sig.inputs()[0].builtin_deref(true).unwrap().ty;
107 Ok((drop_instance, ty))
110 pub fn read_size_and_align_from_vtable(
112 vtable: Pointer<M::PointerTag>,
113 ) -> EvalResult<'tcx, (Size, Align)> {
114 let pointer_size = self.pointer_size();
115 self.memory.check_align(vtable.into(), self.tcx.data_layout.pointer_align.abi)?;
116 let alloc = self.memory.get(vtable.alloc_id)?;
117 let size = alloc.read_ptr_sized(self, vtable.offset(pointer_size, self)?)?
118 .to_bits(pointer_size)? as u64;
119 let align = alloc.read_ptr_sized(
121 vtable.offset(pointer_size * 2, self)?,
122 )?.to_bits(pointer_size)? as u64;
123 Ok((Size::from_bytes(size), Align::from_bytes(align).unwrap()))