Add `AggregateKind::RawPtr` and enough support to compile

compiler/rustc_borrowck/src/lib.rs

@@ -1315,7 +1315,8 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     }
                     AggregateKind::Adt(..)
                     | AggregateKind::Array(..)
-                    | AggregateKind::Tuple { .. } => (),
+                    | AggregateKind::Tuple { .. }
+                    | AggregateKind::RawPtr(..) => (),
                 }
 
                 for operand in operands {

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1921,7 +1921,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
             AggregateKind::Array(ty) => Ok(ty),
-            AggregateKind::Tuple => {
+            AggregateKind::Tuple | AggregateKind::RawPtr(..) => {
                 unreachable!("This should have been covered in check_rvalues");
             }
         }
@@ -2518,6 +2518,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 AggregateKind::Closure(_, _) => None,
                 AggregateKind::Coroutine(_, _) => None,
                 AggregateKind::CoroutineClosure(_, _) => None,
+                AggregateKind::RawPtr(_, _) => None,
             },
         }
     }
@@ -2539,6 +2540,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             return;
         }
 
+        if let AggregateKind::RawPtr(..) = aggregate_kind {
+            bug!("RawPtr should only be in runtime MIR");
+        }
+
         for (i, operand) in operands.iter_enumerated() {
             let field_ty = match self.aggregate_field_ty(aggregate_kind, i, location) {
                 Ok(field_ty) => field_ty,
@@ -2757,7 +2762,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 ),
             ),
 
-            AggregateKind::Array(_) | AggregateKind::Tuple => {
+            AggregateKind::Array(_) | AggregateKind::Tuple | AggregateKind::RawPtr(..) => {
                 (CRATE_DEF_ID.to_def_id(), ty::InstantiatedPredicates::empty())
             }
         };

compiler/rustc_const_eval/src/transform/validate.rs

@@ -923,6 +923,44 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         }
                     }
                 }
+                AggregateKind::RawPtr(pointee_ty, mutability) => {
+                    if !matches!(self.mir_phase, MirPhase::Runtime(_)) {
+                        // It would probably be fine to support this in earlier phases,
+                        // but at the time of writing it's only ever introduced from intrinsic lowering,
+                        // so earlier things just `bug!` on it.
+                        self.fail(location, "RawPtr should be in runtime MIR only");
+                    }
+
+                    if fields.len() != 2 {
+                        self.fail(location, "raw pointer aggregate must have 2 fields");
+                    } else {
+                        let data_ptr_ty = fields.raw[0].ty(self.body, self.tcx);
+                        let metadata_ty = fields.raw[1].ty(self.body, self.tcx);
+                        if let ty::RawPtr(in_pointee, in_mut) = data_ptr_ty.kind() {
+                            if *in_mut != mutability {
+                                self.fail(location, "input and output mutability must match");
+                            }
+
+                            // FIXME: check `Thin` instead of `Sized`
+                            if !in_pointee.is_sized(self.tcx, self.param_env) {
+                                self.fail(location, "input pointer must be thin");
+                            }
+                        } else {
+                            self.fail(location, "first operand to raw pointer aggregate must be a raw pointer");
+                        }
+
+                        // FIXME: Check metadata more generally
+                        if pointee_ty.is_slice() {
+                            if !self.mir_assign_valid_types(metadata_ty, self.tcx.types.usize) {
+                                self.fail(location, "slice metadata must be usize");
+                            }
+                        } else if pointee_ty.is_sized(self.tcx, self.param_env) {
+                            if metadata_ty != self.tcx.types.unit {
+                                self.fail(location, "metadata for pointer-to-thin must be unit");
+                            }
+                        }
+                    }
+                }
             },
             Rvalue::Ref(_, BorrowKind::Fake, _) => {
                 if self.mir_phase >= MirPhase::Runtime(RuntimePhase::Initial) {

compiler/rustc_middle/src/mir/pretty.rs

@@ -1094,6 +1094,15 @@ impl<'tcx> Debug for Rvalue<'tcx> {
 
                         struct_fmt.finish()
                     }),
+
+                    AggregateKind::RawPtr(pointee_ty, mutability) => {
+                        let kind_str = match mutability {
+                            Mutability::Mut => "mut",
+                            Mutability::Not => "const",
+                        };
+                        with_no_trimmed_paths!(write!(fmt, "*{kind_str} {pointee_ty} from "))?;
+                        fmt_tuple(fmt, "")
+                    }
                 }
             }
 

compiler/rustc_middle/src/mir/syntax.rs

@@ -1351,6 +1351,21 @@ pub enum AggregateKind<'tcx> {
     Closure(DefId, GenericArgsRef<'tcx>),
     Coroutine(DefId, GenericArgsRef<'tcx>),
     CoroutineClosure(DefId, GenericArgsRef<'tcx>),
+
+    /// Construct a raw pointer from the data pointer and metadata.
+    ///
+    /// The `Ty` here is the type of the *pointee*, not the pointer itself.
+    /// The `Mutability` indicates whether this produces a `*const` or `*mut`.
+    ///
+    /// The [`Rvalue::Aggregate`] operands for thus must be
+    ///
+    /// 0. A raw pointer of matching mutability with any [`core::ptr::Thin`] pointee
+    /// 1. A value of the appropriate [`core::ptr::Pointee::Metadata`] type
+    ///
+    /// *Both* operands must always be included, even the unit value if this is
+    /// creating a thin pointer. If you're just converting between thin pointers,
+    /// you may want an [`Rvalue::Cast`] with [`CastKind::PtrToPtr`] instead.
+    RawPtr(Ty<'tcx>, Mutability),
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]

compiler/rustc_middle/src/mir/tcx.rs

@@ -206,6 +206,7 @@ impl<'tcx> Rvalue<'tcx> {
                 AggregateKind::CoroutineClosure(did, args) => {
                     Ty::new_coroutine_closure(tcx, did, args)
                 }
+                AggregateKind::RawPtr(ty, mutability) => Ty::new_ptr(tcx, ty, mutability),
             },
             Rvalue::ShallowInitBox(_, ty) => Ty::new_box(tcx, ty),
             Rvalue::CopyForDeref(ref place) => place.ty(local_decls, tcx).ty,

compiler/rustc_middle/src/mir/visit.rs

@@ -751,6 +751,9 @@ macro_rules! make_mir_visitor {
                             ) => {
                                 self.visit_args(coroutine_closure_args, location);
                             }
+                            AggregateKind::RawPtr(ty, _) => {
+                                self.visit_ty($(& $mutability)? *ty, TyContext::Location(location));
+                            }
                         }
 
                         for operand in operands {

compiler/rustc_mir_transform/src/gvn.rs

@@ -885,6 +885,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                 AggregateKind::Adt(did, ..) => tcx.def_kind(did) != DefKind::Enum,
                 // Coroutines are never ZST, as they at least contain the implicit states.
                 AggregateKind::Coroutine(..) => false,
+                AggregateKind::RawPtr(..) => bug!("MIR for RawPtr aggregate must have 2 fields"),
             };
 
             if is_zst {
@@ -910,6 +911,8 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             }
             // Do not track unions.
             AggregateKind::Adt(_, _, _, _, Some(_)) => return None,
+            // FIXME: Do the extra work to GVN `from_raw_parts`
+            AggregateKind::RawPtr(..) => return None,
         };
 
         let fields: Option<Vec<_>> = fields

compiler/rustc_mir_transform/src/known_panics_lint.rs

@@ -603,6 +603,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         AggregateKind::Adt(_, variant, _, _, _) => variant,
                         AggregateKind::Array(_)
                         | AggregateKind::Tuple
+                        | AggregateKind::RawPtr(_, _)
                         | AggregateKind::Closure(_, _)
                         | AggregateKind::Coroutine(_, _)
                         | AggregateKind::CoroutineClosure(_, _) => VariantIdx::ZERO,

compiler/rustc_smir/src/rustc_smir/convert/mir.rs

@@ -543,6 +543,9 @@ impl<'tcx> Stable<'tcx> for mir::AggregateKind<'tcx> {
             mir::AggregateKind::CoroutineClosure(..) => {
                 todo!("FIXME(async_closures): Lower these to SMIR")
             }
+            mir::AggregateKind::RawPtr(ty, mutability) => {
+                stable_mir::mir::AggregateKind::RawPtr(ty.stable(tables), mutability.stable(tables))
+            }
         }
     }
 }

compiler/stable_mir/src/mir/body.rs

@@ -602,6 +602,7 @@ impl Rvalue {
                 AggregateKind::Coroutine(def, ref args, mov) => {
                     Ok(Ty::new_coroutine(def, args.clone(), mov))
                 }
+                AggregateKind::RawPtr(ty, mutability) => Ok(Ty::new_ptr(ty, mutability)),
             },
             Rvalue::ShallowInitBox(_, ty) => Ok(Ty::new_box(*ty)),
             Rvalue::CopyForDeref(place) => place.ty(locals),
@@ -617,6 +618,7 @@ pub enum AggregateKind {
     Closure(ClosureDef, GenericArgs),
     // FIXME(stable_mir): Movability here is redundant
     Coroutine(CoroutineDef, GenericArgs, Movability),
+    RawPtr(Ty, Mutability),
 }
 
 #[derive(Clone, Debug, Eq, PartialEq)]