bjoernager/rust
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make use of symbolic vtables in interpreter

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This commit is contained in:
Ralf Jung 2022-07-17 16:02:49 -04:00
parent a10d8e4581
commit fe00573324
23 changed files with 282 additions and 376 deletions
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32
compiler/rustc_const_eval/src/interpret/cast.rs
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@ -299,29 +299,35 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
(&ty::Dynamic(ref data_a, ..), &ty::Dynamic(ref data_b, ..)) => {
let val = self.read_immediate(src)?;
let (old_data, old_vptr) = val.to_scalar_pair()?;
let old_vptr = self.scalar_to_ptr(old_vptr)?;
if data_a.principal_def_id() == data_b.principal_def_id() {
return self.write_immediate(*val, dest);
}
// trait upcasting coercion
let vptr_entry_idx = self.tcx.vtable_trait_upcasting_coercion_new_vptr_slot((
let Some(vptr_entry_idx) = self.tcx.vtable_trait_upcasting_coercion_new_vptr_slot((
src_pointee_ty,
dest_pointee_ty,
));
)) else {
return self.write_immediate(*val, dest);
};
if let Some(entry_idx) = vptr_entry_idx {
let entry_idx = u64::try_from(entry_idx).unwrap();
let (old_data, old_vptr) = val.to_scalar_pair()?;
let old_vptr = self.scalar_to_ptr(old_vptr)?;
let new_vptr = self
.read_new_vtable_after_trait_upcasting_from_vtable(old_vptr, entry_idx)?;
self.write_immediate(Immediate::new_dyn_trait(old_data, new_vptr, self), dest)
} else {
self.write_immediate(*val, dest)
}
let (ty, _) = self.get_ptr_vtable(old_vptr)?;
let Some(ty::VtblEntry::TraitVPtr(new_trait)) = self.get_vtable_entries(old_vptr)?.get(vptr_entry_idx) else {
throw_ub_format!(
"upcasting to index {vptr_entry_idx} of vtable {old_vptr} but \
that vtable is too small or does not have an upcast-vtable at that index"
)
};
let new_trait = new_trait.map_bound(|trait_ref| {
ty::ExistentialTraitRef::erase_self_ty(*self.tcx, trait_ref)
});
let new_vptr = self.get_vtable_ptr(ty, Some(new_trait))?;
self.write_immediate(Immediate::new_dyn_trait(old_data, new_vptr, self), dest)
}
(_, &ty::Dynamic(ref data, _)) => {
// Initial cast from sized to dyn trait
let vtable = self.get_vtable(src_pointee_ty, data.principal())?;
let vtable = self.get_vtable_ptr(src_pointee_ty, data.principal())?;
let ptr = self.read_immediate(src)?.to_scalar()?;
let val = Immediate::new_dyn_trait(ptr, vtable, &*self.tcx);
self.write_immediate(val, dest)