CFI: Remove trait function encoding hack

Author: maurer

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -1136,44 +1136,5 @@ pub fn typeid_for_instance<'tcx>(
             bug!("typeid_for_instance: couldn't get fn_abi of instance {:?}", instance)
         });
 
-    // If this instance is a method and self is a reference, get the impl it belongs to
-    let impl_def_id = tcx.impl_of_method(instance.def_id());
-    if impl_def_id.is_some() && !fn_abi.args.is_empty() && fn_abi.args[0].layout.ty.is_ref() {
-        // If this impl is not an inherent impl, get the trait it implements
-        if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id.unwrap()) {
-            // Transform the concrete self into a reference to a trait object
-            let existential_predicate = trait_ref.map_bound(|trait_ref| {
-                ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef::erase_self_ty(
-                    tcx, trait_ref,
-                ))
-            });
-            let existential_predicates = tcx.mk_poly_existential_predicates(&[ty::Binder::dummy(
-                existential_predicate.skip_binder(),
-            )]);
-            // Is the concrete self mutable?
-            let self_ty = if fn_abi.args[0].layout.ty.is_mutable_ptr() {
-                Ty::new_mut_ref(
-                    tcx,
-                    tcx.lifetimes.re_erased,
-                    Ty::new_dynamic(tcx, existential_predicates, tcx.lifetimes.re_erased, ty::Dyn),
-                )
-            } else {
-                Ty::new_imm_ref(
-                    tcx,
-                    tcx.lifetimes.re_erased,
-                    Ty::new_dynamic(tcx, existential_predicates, tcx.lifetimes.re_erased, ty::Dyn),
-                )
-            };
-
-            // Replace the concrete self in an fn_abi clone by the reference to a trait object
-            let mut fn_abi = fn_abi.clone();
-            // HACK(rcvalle): It is okay to not replace or update the entire ArgAbi here because the
-            //   other fields are never used.
-            fn_abi.args[0].layout.ty = self_ty;
-
-            return typeid_for_fnabi(tcx, &fn_abi, options);
-        }
-    }
-
     typeid_for_fnabi(tcx, fn_abi, options)
 }

tests/ui/sanitizer/cfi-address-taken.rs

@@ -0,0 +1,30 @@
+// Check that the type of trait methods on a concrete type are not abstracted
+
+//@ needs-sanitizer-cfi
+//@ compile-flags: --crate-type=bin -Cprefer-dynamic=off -Clto -Zsanitizer=cfi
+//@ compile-flags: -C codegen-units=1 -C opt-level=0
+//@ run-pass
+
+trait Foo {
+    fn foo(&self);
+}
+
+struct S;
+
+impl Foo for S {
+    fn foo(&self) {}
+}
+
+struct S2 {
+    f: fn(&S)
+}
+
+impl S2 {
+    fn foo(&self, s: &S) {
+        (self.f)(s)
+    }
+}
+
+fn main() {
+    S2 { f: <S as Foo>::foo }.foo(&S)
+}