Account for diamond inheritance in vtable layout.

Author: Alexander Regueiro

src/librustc_codegen_ssa/base.rs

@@ -38,8 +38,8 @@ use rustc_middle::middle::cstore::EncodedMetadata;
 use rustc_middle::middle::cstore::{self, LinkagePreference};
 use rustc_middle::middle::lang_items;
 use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem};
+use rustc_middle::traits::Vtable;
 use rustc_middle::ty::layout::{self, HasTyCtxt, TyAndLayout};
-use rustc_middle::ty::layout::{FAT_PTR_ADDR, FAT_PTR_EXTRA};
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
 use rustc_session::cgu_reuse_tracker::CguReuse;
@@ -166,7 +166,8 @@ pub fn unsized_info<'tcx, 'a, Bx: BuilderMethods<'a, 'tcx>>(
             let target_ptr = if let Some(target_trait_ref) = target_data.principal() {
                 // Find the offset of the supertrait's vtable within the subtrait (parent) vtable.
                 let trait_ref = target_trait_ref.with_self_ty(tcx, source);
-                let vtable = tcx.codegen_fulfill_obligation((ty::ParamEnv::reveal_all(), trait_ref));
+                let vtable = tcx.codegen_fulfill_obligation((ty::ParamEnv::reveal_all(), trait_ref))
+                    .unwrap_or_else(|| bug!("unsized_info: no vtable found"));
                 let offset = match vtable {
                     Vtable::VtableObject(ref data) => data.vtable_base,
                     // HACK(alexreg): slightly dubious solution to ICE in
@@ -257,7 +258,7 @@ pub fn unsize_thin_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 pub fn coerce_ptr_unsized<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx: &mut Bx,
     op: OperandRef<'tcx, Bx::Value>,
-    dst: TyLayout<'tcx>,
+    dst: TyAndLayout<'tcx>,
 ) -> OperandValue<Bx::Value> {
     assert!(bx.cx().is_backend_scalar_pair(dst));
     let src = op.layout;
@@ -341,7 +342,7 @@ pub fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         (&ty::Ref(..), &ty::Ref(..) | &ty::RawPtr(..)) | (&ty::RawPtr(..), &ty::RawPtr(..)) => {
             let src_op = bx.load_operand(src);
             let dst_op = coerce_ptr_unsized(bx, src_op, dst.layout);
-            dst_op.store(bx, dst);s
+            dst_op.store(bx, dst);
         }
         (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) => {
             assert_eq!(def_a, def_b);

src/librustc_infer/infer/error_reporting/mod.rs

@@ -1681,10 +1681,10 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         exp_found: &ty::error::ExpectedFound<DefId>,
         diag: &mut DiagnosticBuilder<'tcx>,
     ) {
-        use rustc::ty::{Binder, TraitRef};
+        use ty::{Binder, TraitRef};
 
         let trait_ref = Binder::bind(TraitRef::identity(self.tcx, exp_found.found));
-        let supertraits = crate::traits::supertraits(self.tcx, trait_ref);
+        let supertraits = crate::traits::util::supertraits(self.tcx, trait_ref);
         if supertraits.into_iter().any(|trait_ref| trait_ref.def_id() == exp_found.expected) {
             diag.note("add `#![feature(trait_upcasting)]` to the crate attributes to enable");
         }

src/librustc_infer/traits/util.rs

@@ -91,6 +91,8 @@ impl<T: AsRef<ty::Predicate<'tcx>>> Extend<T> for PredicateSet<'tcx> {
 pub struct Elaborator<'tcx> {
     stack: Vec<PredicateObligation<'tcx>>,
     visited: PredicateSet<'tcx>,
+    /// `true` to allow the same predicate to appear more than once within the sequence.
+    allow_repetitions: bool,
 }
 
 pub fn elaborate_trait_ref<'tcx>(
@@ -108,6 +110,17 @@ pub fn elaborate_trait_refs<'tcx>(
     elaborate_predicates(tcx, predicates)
 }
 
+pub fn elaborate_trait_ref_with_repetitions<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    trait_ref: ty::PolyTraitRef<'tcx>,
+) -> Elaborator<'tcx> {
+    Elaborator {
+        stack: vec![predicate_obligation(trait_ref.without_const().to_predicate(), None)],
+        visited: PredicateSet::new(tcx),
+        allow_repetitions: true,
+    }
+}
+
 pub fn elaborate_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
     predicates: impl Iterator<Item = ty::Predicate<'tcx>>,
@@ -123,7 +136,11 @@ pub fn elaborate_obligations<'tcx>(
 ) -> Elaborator<'tcx> {
     let mut visited = PredicateSet::new(tcx);
     obligations.retain(|obligation| visited.insert(&obligation.predicate));
-    Elaborator { stack: obligations, visited }
+    Elaborator {
+        stack: obligations,
+        visited,
+        allow_repetitions: false,
+    }
 }
 
 fn predicate_obligation<'tcx>(
@@ -134,7 +151,12 @@ fn predicate_obligation<'tcx>(
     if let Some(span) = span {
         cause.span = span;
     }
-    Obligation { cause, param_env: ty::ParamEnv::empty(), recursion_depth: 0, predicate }
+    Obligation {
+        cause,
+        param_env: ty::ParamEnv::empty(),
+        recursion_depth: 0,
+        predicate,
+    }
 }
 
 impl Elaborator<'tcx> {
@@ -144,6 +166,7 @@ impl Elaborator<'tcx> {
 
     fn elaborate(&mut self, obligation: &PredicateObligation<'tcx>) {
         let tcx = self.visited.tcx;
+        let allow_repetitions = self.allow_repetitions;
         match obligation.predicate {
             ty::Predicate::Trait(ref data, _) => {
                 // Get predicates declared on the trait.
@@ -162,7 +185,7 @@ impl Elaborator<'tcx> {
                 // cases. One common case is when people define
                 // `trait Sized: Sized { }` rather than `trait Sized { }`.
                 let visited = &mut self.visited;
-                let obligations = obligations.filter(|o| visited.insert(&o.predicate));
+                let obligations = obligations.filter(|o| allow_repetitions || visited.insert(&o.predicate));
 
                 self.stack.extend(obligations);
             }
@@ -245,7 +268,7 @@ impl Elaborator<'tcx> {
                                 None
                             }
                         })
-                        .filter(|p| visited.insert(p))
+                        .filter(|p| allow_repetitions || visited.insert(p))
                         .map(|p| predicate_obligation(p, None)),
                 );
             }
@@ -284,6 +307,13 @@ pub fn supertraits<'tcx>(
     elaborate_trait_ref(tcx, trait_ref).filter_to_traits()
 }
 
+pub fn supertraits_with_repetitions<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    trait_ref: ty::PolyTraitRef<'tcx>,
+) -> Supertraits<'tcx> {
+    elaborate_trait_ref_with_repetitions(tcx, trait_ref).filter_to_traits()
+}
+
 pub fn transitive_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
     bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,

src/librustc_mir/interpret/traits.rs

@@ -61,7 +61,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             ptr_size * (
                 methods
                     .iter()
-                    .map(|l| u64::try_from(methods.len()).unwrap().checked_add(3).unwrap())
+                    .map(|l| u64::try_from(l.len()).unwrap().checked_add(3).unwrap())
                     .sum()
             ),
             ptr_align,

src/librustc_mir/monomorphize/collector.rs

@@ -889,6 +889,8 @@ fn create_mono_items_for_vtable_methods<'tcx>(
             // Walk all methods of the trait, including those of its supertraits.
             let methods = tcx.vtable_methods(poly_trait_ref);
             let methods = methods
+                .into_iter()
+                .flat_map(|s| *s)
                 .cloned()
                 .filter_map(|method| method)
                 .map(|(def_id, substs)| {

src/librustc_session/session.rs

@@ -474,9 +474,7 @@ impl Session {
         self.opts.debugging_opts.asm_comments
     }
     pub fn verify_llvm_ir(&self) -> bool {
-        (self.opts.debugging_opts.verify_llvm_ir
-         || cfg!(always_verify_llvm_ir))
-            && !self.opts.debugging_opts.no_verify_llvm_ir
+        self.opts.debugging_opts.verify_llvm_ir || cfg!(always_verify_llvm_ir)
     }
     pub fn borrowck_stats(&self) -> bool {
         self.opts.debugging_opts.borrowck_stats

src/librustc_trait_selection/traits/mod.rs

@@ -66,7 +66,8 @@ pub use self::util::{
     get_vtable_index_of_object_method, impl_item_is_final, predicate_for_trait_def, upcast_choices,
 };
 pub use self::util::{
-    supertrait_def_ids, supertraits, transitive_bounds, SupertraitDefIds, Supertraits,
+    supertraits, supertraits_with_repetitions, supertrait_def_ids, transitive_bounds, Supertraits,
+    SupertraitDefIds,
 };
 
 pub use rustc_infer::traits::*;
@@ -471,51 +472,52 @@ fn vtable_methods<'tcx>(
 ) -> &'tcx [&'tcx [Option<(DefId, SubstsRef<'tcx>)>]] {
     debug!("vtable_methods({:?})", trait_ref);
 
-    tcx.arena.alloc_from_iter(supertraits(tcx, trait_ref).map(move |trait_ref| {
-        let trait_methods = tcx
-            .associated_items(trait_ref.def_id())
-            .in_definition_order()
-            .filter(|item| item.kind == ty::AssocKind::Fn);
-
-        // Now, list each method's `DefId` and `InternalSubsts` (for within its trait).
-        // If the method can never be called from this object, produce `None`.
-        &*tcx.arena.alloc_from_iter(trait_methods.map(move |trait_method| {
-            debug!("vtable_methods: trait_method={:?}", trait_method);
-            let def_id = trait_method.def_id;
-
-            // Some methods cannot be called on an object; skip those.
-            if !is_vtable_safe_method(tcx, trait_ref.def_id(), &trait_method) {
-                debug!("vtable_methods: not vtable safe");
-                return None;
-            }
+    tcx.arena.alloc_from_iter(supertraits_with_repetitions(tcx, trait_ref)
+        .map(move |trait_ref| {
+            let trait_methods = tcx
+                .associated_items(trait_ref.def_id())
+                .in_definition_order()
+                .filter(|item| item.kind == ty::AssocKind::Fn);
+
+            // Now, list each method's `DefId` and `InternalSubsts` (for within its trait).
+            // If the method can never be called from this object, produce `None`.
+            &*tcx.arena.alloc_from_iter(trait_methods.map(move |trait_method| {
+                debug!("vtable_methods: trait_method={:?}", trait_method);
+                let def_id = trait_method.def_id;
+
+                // Some methods cannot be called on an object; skip those.
+                if !is_vtable_safe_method(tcx, trait_ref.def_id(), &trait_method) {
+                    debug!("vtable_methods: not vtable safe");
+                    return None;
+                }
 
-            // The method may have some early-bound lifetimes; add regions for those.
-            let substs = trait_ref.map_bound(|trait_ref| {
-                InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
-                    GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
-                    GenericParamDefKind::Type { .. } | GenericParamDefKind::Const => {
-                        trait_ref.substs[param.index as usize]
-                    }
-                })
-            });
-
-            // The trait type may have higher-ranked lifetimes in it;
-            // erase them if they appear, so that we get the type
-            // at some particular call site.
-            let substs =
-                tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &substs);
-
-            // It's possible that the method relies on where-clauses that
-            // do not hold for this particular set of type parameters.
-            // Note that this method could then never be called, so we
-            // do not want to try and codegen it, in that case (see #23435).
-            let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
-            if !normalize_and_test_predicates(tcx, predicates.predicates) {
-                debug!("vtable_methods: predicates do not hold");
-                return None;
-            }
+                // The method may have some early-bound lifetimes; add regions for those.
+                let substs = trait_ref.map_bound(|trait_ref| {
+                    InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
+                        GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
+                        GenericParamDefKind::Type { .. } | GenericParamDefKind::Const => {
+                            trait_ref.substs[param.index as usize]
+                        }
+                    })
+                });
+
+                // The trait type may have higher-ranked lifetimes in it;
+                // erase them if they appear, so that we get the type
+                // at some particular call site.
+                let substs =
+                    tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), &substs);
+
+                // It's possible that the method relies on where-clauses that
+                // do not hold for this particular set of type parameters.
+                // Note that this method could then never be called, so we
+                // do not want to try and codegen it, in that case (see #23435).
+                let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
+                if !normalize_and_test_predicates(tcx, predicates.predicates) {
+                    debug!("vtable_methods: predicates do not hold");
+                    return None;
+                }
 
-            Some((def_id, substs))
+                Some((def_id, substs))
         }))
     }))
 }

src/librustc_trait_selection/traits/select.rs

@@ -2696,26 +2696,27 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // where we can unify, because otherwise select would have
             // reported an ambiguity. (When we do find a match, also
             // record it for later.)
-            let nonmatching = util::supertraits(tcx, poly_trait_ref).take_while(|&t| {
-                match self.infcx.commit_if_ok(|_| self.match_poly_trait_ref(obligation, t)) {
-                    Ok(obligations) => {
-                        upcast_trait_ref = Some(t);
-                        nested.extend(obligations);
-                        false
-                    }
-                    Err(_) => true,
-                }
-            });
+            let nonmatching = util::supertraits_with_repetitions(tcx, poly_trait_ref)
+                .take_while(
+                    |&trait_ref| match self.infcx.commit_if_ok(
+                        |_| self.match_poly_trait_ref(obligation, trait_ref)
+                    ) {
+                        Ok(obligations) => {
+                            upcast_trait_ref = Some(trait_ref);
+                            nested.extend(obligations);
+                            false
+                        }
+                        Err(_) => true,
+                    },
+                );
 
             // Additionally, for each of the non-matching predicates that
             // we pass over, we sum up the set of number of vtable
             // entries, so that we can compute the offset for the selected
             // trait.
             vtable_base = nonmatching
                 // Skip 3 entries in vtable per supertrait for `(drop, size, align)` metadata.
-                .map(|trait_ref|
-                    u64::try_from(tcx.count_own_vtable_entries(trait_ref)).unwrap().checked_add(3).unwrap()
-                )
+                .map(|trait_ref| util::count_own_vtable_entries(tcx, trait_ref).checked_add(3).unwrap())
                 .sum();
         }