[experimental] Rvalue::InitBox prototype

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -104,7 +104,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
             }
             sym::pref_align_of
-            | sym::min_align_of
             | sym::needs_drop
             | sym::type_id
             | sym::type_name

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -501,6 +501,20 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 )
             }
 
+            mir::Rvalue::NullaryOp(mir::NullOp::AlignOf, ty) => {
+                let ty = self.monomorphize(ty);
+                assert!(bx.cx().type_is_sized(ty));
+                let val = bx.cx().const_usize(bx.cx().layout_of(ty).align.abi.bytes());
+                let tcx = self.cx.tcx();
+                (
+                    bx,
+                    OperandRef {
+                        val: OperandValue::Immediate(val),
+                        layout: self.cx.layout_of(tcx.types.usize),
+                    },
+                )
+            }
+
             mir::Rvalue::NullaryOp(mir::NullOp::Box, content_ty) => {
                 let content_ty = self.monomorphize(content_ty);
                 let content_layout = bx.cx().layout_of(content_ty);
@@ -544,6 +558,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     OperandRef::new_zst(&mut bx, self.cx.layout_of(self.monomorphize(ty)));
                 (bx, operand)
             }
+            mir::Rvalue::InitBox(ref operand, content_ty) => {
+                let operand = self.codegen_operand(&mut bx, operand);
+                let lloperand = operand.immediate();
+
+                let content_ty = self.monomorphize(content_ty);
+                let box_layout = bx.cx().layout_of(bx.tcx().mk_box(content_ty));
+                let llty_ptr = bx.cx().backend_type(box_layout);
+
+                let val = bx.pointercast(lloperand, llty_ptr);
+                let operand = OperandRef { val: OperandValue::Immediate(val), layout: box_layout };
+                (bx, operand)
+            }
         }
     }
 
@@ -757,6 +783,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             mir::Rvalue::AddressOf(..) |
             mir::Rvalue::Len(..) |
             mir::Rvalue::Cast(..) | // (*)
+            mir::Rvalue::InitBox(..) | // (*)
             mir::Rvalue::BinaryOp(..) |
             mir::Rvalue::CheckedBinaryOp(..) |
             mir::Rvalue::UnaryOp(..) |

compiler/rustc_hir/src/lang_items.rs

@@ -294,6 +294,7 @@ language_item_table! {
     BeginPanicFmt,           sym::begin_panic_fmt,     begin_panic_fmt,            Target::Fn,             GenericRequirement::None;
 
     ExchangeMalloc,          sym::exchange_malloc,     exchange_malloc_fn,         Target::Fn,             GenericRequirement::None;
+    BoxNew,                  sym::box_new,             box_new_fn,                 Target::Fn,             GenericRequirement::Minimum(1);
     BoxFree,                 sym::box_free,            box_free_fn,                Target::Fn,             GenericRequirement::Minimum(1);
     DropInPlace,             sym::drop_in_place,       drop_in_place_fn,           Target::Fn,             GenericRequirement::Minimum(1);
     Oom,                     sym::oom,                 oom,                        Target::Fn,             GenericRequirement::None;

compiler/rustc_middle/src/mir/mod.rs

@@ -2170,6 +2170,8 @@ pub enum Rvalue<'tcx> {
     /// that `Foo` has a destructor. These rvalues can be optimized
     /// away after type-checking and before lowering.
     Aggregate(Box<AggregateKind<'tcx>>, Vec<Operand<'tcx>>),
+
+    InitBox(Operand<'tcx>, Ty<'tcx>),
 }
 
 #[cfg(target_arch = "x86_64")]
@@ -2250,6 +2252,8 @@ impl BinOp {
 pub enum NullOp {
     /// Returns the size of a value of that type
     SizeOf,
+    /// Returns the minimum alignment of a type
+    AlignOf,
     /// Creates a new uninitialized box for a value of that type
     Box,
 }
@@ -2418,6 +2422,10 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                     }),
                 }
             }
+
+            InitBox(ref place, ref ty) => {
+                write!(fmt, "{:?} as box {:?}", place, ty)
+            }
         }
     }
 }

compiler/rustc_middle/src/mir/tcx.rs

@@ -196,7 +196,7 @@ impl<'tcx> Rvalue<'tcx> {
             Rvalue::UnaryOp(UnOp::Not | UnOp::Neg, ref operand) => operand.ty(local_decls, tcx),
             Rvalue::Discriminant(ref place) => place.ty(local_decls, tcx).ty.discriminant_ty(tcx),
             Rvalue::NullaryOp(NullOp::Box, t) => tcx.mk_box(t),
-            Rvalue::NullaryOp(NullOp::SizeOf, _) => tcx.types.usize,
+            Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => tcx.types.usize,
             Rvalue::Aggregate(ref ak, ref ops) => match **ak {
                 AggregateKind::Array(ty) => tcx.mk_array(ty, ops.len() as u64),
                 AggregateKind::Tuple => tcx.mk_tup(ops.iter().map(|op| op.ty(local_decls, tcx))),
@@ -206,6 +206,7 @@ impl<'tcx> Rvalue<'tcx> {
                     tcx.mk_generator(did, substs, movability)
                 }
             },
+            Rvalue::InitBox(_, ty) => tcx.mk_box(ty),
         }
     }
 
@@ -215,6 +216,7 @@ impl<'tcx> Rvalue<'tcx> {
     pub fn initialization_state(&self) -> RvalueInitializationState {
         match *self {
             Rvalue::NullaryOp(NullOp::Box, _) => RvalueInitializationState::Shallow,
+            Rvalue::InitBox(_, _) => RvalueInitializationState::Shallow,
             _ => RvalueInitializationState::Deep,
         }
     }

compiler/rustc_middle/src/mir/type_foldable.rs

@@ -210,6 +210,7 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
                 });
                 Aggregate(kind, fields.fold_with(folder))
             }
+            InitBox(op, ty) => InitBox(op.fold_with(folder), ty.fold_with(folder)),
         }
     }
 
@@ -255,6 +256,10 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
                 }
                 fields.visit_with(visitor)
             }
+            InitBox(ref op, ty) => {
+                op.visit_with(visitor)?;
+                ty.visit_with(visitor)
+            }
         }
     }
 }

compiler/rustc_middle/src/mir/visit.rs

@@ -753,6 +753,11 @@ macro_rules! make_mir_visitor {
                             self.visit_operand(operand, location);
                         }
                     }
+
+                    Rvalue::InitBox(operand, ty) => {
+                        self.visit_operand(operand, location);
+                        self.visit_ty(ty, TyContext::Location(location));
+                    }
                 }
             }
 

compiler/rustc_mir/src/borrow_check/invalidation.rs

@@ -318,9 +318,8 @@ impl<'cx, 'tcx> InvalidationGenerator<'cx, 'tcx> {
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)
-            | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/) => {
-                self.consume_operand(location, operand)
-            }
+            | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/)
+            | Rvalue::InitBox(ref operand, _ /*ty*/) => self.consume_operand(location, operand),
 
             Rvalue::Len(place) | Rvalue::Discriminant(place) => {
                 let af = match *rvalue {

compiler/rustc_mir/src/borrow_check/mod.rs

@@ -1341,7 +1341,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)
-            | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/) => {
+            | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/)
+            | Rvalue::InitBox(ref operand, _ /*ty*/) => {
                 self.consume_operand(location, (operand, span), flow_state)
             }
 

compiler/rustc_mir/src/borrow_check/type_check/mod.rs

@@ -2320,6 +2320,25 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
 
+            Rvalue::InitBox(_, ty) => {
+                // Even with unsized locals cannot box an unsized value.
+                if self.unsized_feature_enabled() {
+                    let span = body.source_info(location).span;
+                    self.ensure_place_sized(ty, span);
+                }
+
+                let trait_ref = ty::TraitRef {
+                    def_id: tcx.require_lang_item(LangItem::Sized, Some(self.last_span)),
+                    substs: tcx.mk_substs_trait(ty, &[]),
+                };
+
+                self.prove_trait_ref(
+                    trait_ref,
+                    location.to_locations(),
+                    ConstraintCategory::SizedBound,
+                );
+            }
+
             Rvalue::AddressOf(..)
             | Rvalue::ThreadLocalRef(..)
             | Rvalue::Use(..)
@@ -2343,6 +2362,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             | Rvalue::AddressOf(..)
             | Rvalue::Len(..)
             | Rvalue::Cast(..)
+            | Rvalue::InitBox(..)
             | Rvalue::BinaryOp(..)
             | Rvalue::CheckedBinaryOp(..)
             | Rvalue::NullaryOp(..)

compiler/rustc_mir/src/dataflow/impls/borrowed_locals.rs

@@ -169,6 +169,7 @@ where
             }
 
             mir::Rvalue::Cast(..)
+            | mir::Rvalue::InitBox(..)
             | mir::Rvalue::Use(..)
             | mir::Rvalue::ThreadLocalRef(..)
             | mir::Rvalue::Repeat(..)

compiler/rustc_mir/src/dataflow/move_paths/builder.rs

@@ -327,6 +327,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::Cast(_, ref operand, _)
+            | Rvalue::InitBox(ref operand, _)
             | Rvalue::UnaryOp(_, ref operand) => self.gather_operand(operand),
             Rvalue::BinaryOp(ref _binop, box (ref lhs, ref rhs))
             | Rvalue::CheckedBinaryOp(ref _binop, box (ref lhs, ref rhs)) => {
@@ -342,7 +343,7 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             | Rvalue::AddressOf(..)
             | Rvalue::Discriminant(..)
             | Rvalue::Len(..)
-            | Rvalue::NullaryOp(NullOp::SizeOf, _)
+            | Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _)
             | Rvalue::NullaryOp(NullOp::Box, _) => {
                 // This returns an rvalue with uninitialized contents. We can't
                 // move out of it here because it is an rvalue - assignments always

compiler/rustc_mir/src/interpret/intrinsics.rs

@@ -160,17 +160,14 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.write_scalar(Scalar::from_machine_usize(result, self), dest)?;
             }
 
-            sym::min_align_of
-            | sym::pref_align_of
+            sym::pref_align_of
             | sym::needs_drop
             | sym::type_id
             | sym::type_name
             | sym::variant_count => {
                 let gid = GlobalId { instance, promoted: None };
                 let ty = match intrinsic_name {
-                    sym::min_align_of | sym::pref_align_of | sym::variant_count => {
-                        self.tcx.types.usize
-                    }
+                    sym::pref_align_of | sym::variant_count => self.tcx.types.usize,
                     sym::needs_drop => self.tcx.types.bool,
                     sym::type_id => self.tcx.types.u64,
                     sym::type_name => self.tcx.mk_static_str(),

compiler/rustc_mir/src/interpret/step.rs

@@ -284,6 +284,29 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.write_scalar(Scalar::from_machine_usize(layout.size.bytes(), self), &dest)?;
             }
 
+            NullaryOp(mir::NullOp::AlignOf, ty) => {
+                let ty = self.subst_from_current_frame_and_normalize_erasing_regions(ty);
+                let layout = self.layout_of(ty)?;
+                if layout.is_unsized() {
+                    // FIXME: This should be a span_bug (#80742)
+                    self.tcx.sess.delay_span_bug(
+                        self.frame().current_span(),
+                        &format!("SizeOf nullary MIR operator called for unsized type {}", ty),
+                    );
+                    throw_inval!(SizeOfUnsizedType(ty));
+                }
+                self.write_scalar(
+                    Scalar::from_machine_usize(layout.align.abi.bytes(), self),
+                    &dest,
+                )?;
+            }
+
+            InitBox(ref operand, _) => {
+                let src = self.eval_operand(operand, None)?;
+                let v = self.read_immediate(&src)?;
+                self.write_immediate(*v, &dest)?;
+            }
+
             Cast(cast_kind, ref operand, cast_ty) => {
                 let src = self.eval_operand(operand, None)?;
                 let cast_ty = self.subst_from_current_frame_and_normalize_erasing_regions(cast_ty);

compiler/rustc_mir/src/transform/check_consts/check.rs

@@ -648,8 +648,9 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
                 }
             }
 
-            Rvalue::NullaryOp(NullOp::SizeOf, _) => {}
+            Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, _) => {}
             Rvalue::NullaryOp(NullOp::Box, _) => self.check_op(ops::HeapAllocation),
+            Rvalue::InitBox(_, _) => {}
 
             Rvalue::UnaryOp(_, ref operand) => {
                 let ty = operand.ty(self.body, self.tcx);
@@ -899,6 +900,12 @@ impl Visitor<'tcx> for Checker<'mir, 'tcx> {
                     return;
                 }
 
+                let is_box_new = Some(callee) == tcx.lang_items().box_new_fn();
+                if is_box_new {
+                    self.check_op(ops::HeapAllocation);
+                    return;
+                }
+
                 // `async` blocks get lowered to `std::future::from_generator(/* a closure */)`.
                 let is_async_block = Some(callee) == tcx.lang_items().from_generator_fn();
                 if is_async_block {

compiler/rustc_mir/src/transform/check_consts/qualifs.rs

@@ -166,7 +166,8 @@ where
         Rvalue::Use(operand)
         | Rvalue::Repeat(operand, _)
         | Rvalue::UnaryOp(_, operand)
-        | Rvalue::Cast(_, operand, _) => in_operand::<Q, _>(cx, in_local, operand),
+        | Rvalue::Cast(_, operand, _)
+        | Rvalue::InitBox(operand, _) => in_operand::<Q, _>(cx, in_local, operand),
 
         Rvalue::BinaryOp(_, box (lhs, rhs)) | Rvalue::CheckedBinaryOp(_, box (lhs, rhs)) => {
             in_operand::<Q, _>(cx, in_local, lhs) || in_operand::<Q, _>(cx, in_local, rhs)

compiler/rustc_mir/src/transform/const_prop.rs

@@ -723,6 +723,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             | Rvalue::Repeat(..)
             | Rvalue::Len(..)
             | Rvalue::Cast(..)
+            | Rvalue::InitBox(..)
             | Rvalue::Discriminant(..)
             | Rvalue::NullaryOp(..) => {}
         }

compiler/rustc_mir/src/transform/dest_prop.rs

@@ -969,6 +969,7 @@ impl<'tcx> Visitor<'tcx> for BorrowCollector {
             }
 
             Rvalue::Cast(..)
+            | Rvalue::InitBox(..)
             | Rvalue::Use(..)
             | Rvalue::Repeat(..)
             | Rvalue::Len(..)

compiler/rustc_mir/src/transform/lower_intrinsics.rs

@@ -105,6 +105,19 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                             terminator.kind = TerminatorKind::Goto { target };
                         }
                     }
+                    sym::min_align_of => {
+                        if let Some((destination, target)) = *destination {
+                            let tp_ty = substs.type_at(0);
+                            block.statements.push(Statement {
+                                source_info: terminator.source_info,
+                                kind: StatementKind::Assign(Box::new((
+                                    destination,
+                                    Rvalue::NullaryOp(NullOp::AlignOf, tp_ty),
+                                ))),
+                            });
+                            terminator.kind = TerminatorKind::Goto { target };
+                        }
+                    }
                     sym::discriminant_value => {
                         if let (Some((destination, target)), Some(arg)) =
                             (*destination, args[0].place())

compiler/rustc_mir/src/transform/promote_consts.rs

@@ -520,8 +520,11 @@ impl<'tcx> Validator<'_, 'tcx> {
             Rvalue::NullaryOp(op, _) => match op {
                 NullOp::Box => return Err(Unpromotable),
                 NullOp::SizeOf => {}
+                NullOp::AlignOf => {}
             },
 
+            Rvalue::InitBox(_, _) => return Err(Unpromotable),
+
             Rvalue::UnaryOp(op, operand) => {
                 match op {
                     // These operations can never fail.

compiler/rustc_mir/src/transform/separate_const_switch.rs

@@ -204,6 +204,7 @@ fn is_likely_const<'tcx>(mut tracked_place: Place<'tcx>, block: &BasicBlockData<
                         | Rvalue::AddressOf(_, _)
                         | Rvalue::Cast(_, Operand::Constant(_), _)
                         | Rvalue::NullaryOp(_, _)
+                        | Rvalue::InitBox(_, _)
                         | Rvalue::UnaryOp(_, Operand::Constant(_)) => return true,
 
                         // These rvalues make things ambiguous
@@ -301,6 +302,7 @@ fn find_determining_place<'tcx>(
                     | Rvalue::ThreadLocalRef(_)
                     | Rvalue::AddressOf(_, _)
                     | Rvalue::NullaryOp(_, _)
+                    | Rvalue::InitBox(_, _)
                     | Rvalue::UnaryOp(_, Operand::Constant(_))
                     | Rvalue::Cast(_, Operand::Constant(_), _)
                     => return None,