Rollup merge of #64588 - matthewjasper:mir-address-of, r=oli-obk

Add a raw "address of" operator

* Parse and feature gate `&raw [const | mut] expr` (feature gate name is `raw_address_of`)
* Add `mir::Rvalue::AddressOf`
* Use the new `Rvalue` for:
    * the new syntax
    * reference to pointer casts
    * drop shims for slices and arrays
* Stop using `mir::Rvalue::Cast` with a reference as the operand
* Correctly evaluate `mir::Rvalue::{Ref, AddressOf}` in constant propagation

cc @Centril @RalfJung @oli-obk @eddyb
cc #64490

src/librustc/mir/mod.rs

@@ -2060,6 +2060,11 @@ pub enum Rvalue<'tcx> {
     /// &x or &mut x
     Ref(Region<'tcx>, BorrowKind, Place<'tcx>),
 
+    /// Create a raw pointer to the given place
+    /// Can be generated by raw address of expressions (`&raw const x`),
+    /// or when casting a reference to a raw pointer.
+    AddressOf(Mutability, Place<'tcx>),
+
     /// length of a [X] or [X;n] value
     Len(Place<'tcx>),
 
@@ -2214,6 +2219,15 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                 write!(fmt, "&{}{}{:?}", region, kind_str, place)
             }
 
+            AddressOf(mutability, ref place) => {
+                let kind_str = match mutability {
+                    Mutability::Mut => "mut",
+                    Mutability::Not => "const",
+                };
+
+                write!(fmt, "&raw {} {:?}", kind_str, place)
+            }
+
             Aggregate(ref kind, ref places) => {
                 fn fmt_tuple(fmt: &mut Formatter<'_>, places: &[Operand<'_>]) -> fmt::Result {
                     let mut tuple_fmt = fmt.debug_tuple("");
@@ -3085,6 +3099,9 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
             Ref(region, bk, ref place) => {
                 Ref(region.fold_with(folder), bk, place.fold_with(folder))
             }
+            AddressOf(mutability, ref place) => {
+                AddressOf(mutability, place.fold_with(folder))
+            }
             Len(ref place) => Len(place.fold_with(folder)),
             Cast(kind, ref op, ty) => Cast(kind, op.fold_with(folder), ty.fold_with(folder)),
             BinaryOp(op, ref rhs, ref lhs) => {
@@ -3125,6 +3142,7 @@ impl<'tcx> TypeFoldable<'tcx> for Rvalue<'tcx> {
             Use(ref op) => op.visit_with(visitor),
             Repeat(ref op, _) => op.visit_with(visitor),
             Ref(region, _, ref place) => region.visit_with(visitor) || place.visit_with(visitor),
+            AddressOf(_, ref place) => place.visit_with(visitor),
             Len(ref place) => place.visit_with(visitor),
             Cast(_, ref op, ty) => op.visit_with(visitor) || ty.visit_with(visitor),
             BinaryOp(_, ref rhs, ref lhs) | CheckedBinaryOp(_, ref rhs, ref lhs) => {

src/librustc/mir/tcx.rs

@@ -172,6 +172,13 @@ impl<'tcx> Rvalue<'tcx> {
                     }
                 )
             }
+            Rvalue::AddressOf(mutability, ref place) => {
+                let place_ty = place.ty(local_decls, tcx).ty;
+                tcx.mk_ptr(ty::TypeAndMut {
+                    ty: place_ty,
+                    mutbl: mutability.into(),
+                })
+            }
             Rvalue::Len(..) => tcx.types.usize,
             Rvalue::Cast(.., ty) => ty,
             Rvalue::BinaryOp(op, ref lhs, ref rhs) => {

src/librustc/mir/visit.rs

@@ -570,6 +570,18 @@ macro_rules! make_mir_visitor {
                         self.visit_place(path, ctx, location);
                     }
 
+                    Rvalue::AddressOf(m, path) => {
+                        let ctx = match m {
+                            Mutability::Mut => PlaceContext::MutatingUse(
+                                MutatingUseContext::AddressOf
+                            ),
+                            Mutability::Not => PlaceContext::NonMutatingUse(
+                                NonMutatingUseContext::AddressOf
+                            ),
+                        };
+                        self.visit_place(path, ctx, location);
+                    }
+
                     Rvalue::Len(path) => {
                         self.visit_place(
                             path,
@@ -1031,6 +1043,8 @@ pub enum NonMutatingUseContext {
     ShallowBorrow,
     /// Unique borrow.
     UniqueBorrow,
+    /// AddressOf for *const pointer.
+    AddressOf,
     /// Used as base for another place, e.g., `x` in `x.y`. Will not mutate the place.
     /// For example, the projection `x.y` is not marked as a mutation in these cases:
     ///
@@ -1054,6 +1068,8 @@ pub enum MutatingUseContext {
     Drop,
     /// Mutable borrow.
     Borrow,
+    /// AddressOf for *mut pointer.
+    AddressOf,
     /// Used as base for another place, e.g., `x` in `x.y`. Could potentially mutate the place.
     /// For example, the projection `x.y` is marked as a mutation in these cases:
     ///

src/librustc/ty/cast.rs

@@ -28,8 +28,6 @@ pub enum CastTy<'tcx> {
     FnPtr,
     /// Raw pointers
     Ptr(ty::TypeAndMut<'tcx>),
-    /// References
-    RPtr(ty::TypeAndMut<'tcx>),
 }
 
 /// Cast Kind. See RFC 401 (or librustc_typeck/check/cast.rs)
@@ -63,7 +61,6 @@ impl<'tcx> CastTy<'tcx> {
             ty::Adt(d,_) if d.is_enum() && d.is_payloadfree() =>
                 Some(CastTy::Int(IntTy::CEnum)),
             ty::RawPtr(mt) => Some(CastTy::Ptr(mt)),
-            ty::Ref(_, ty, mutbl) => Some(CastTy::RPtr(ty::TypeAndMut { ty, mutbl })),
             ty::FnPtr(..) => Some(CastTy::FnPtr),
             _ => None,
         }

src/librustc_codegen_ssa/mir/analyze.rs

@@ -340,10 +340,12 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
             PlaceContext::MutatingUse(MutatingUseContext::Store) |
             PlaceContext::MutatingUse(MutatingUseContext::AsmOutput) |
             PlaceContext::MutatingUse(MutatingUseContext::Borrow) |
+            PlaceContext::MutatingUse(MutatingUseContext::AddressOf) |
             PlaceContext::MutatingUse(MutatingUseContext::Projection) |
             PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow) |
             PlaceContext::NonMutatingUse(NonMutatingUseContext::UniqueBorrow) |
             PlaceContext::NonMutatingUse(NonMutatingUseContext::ShallowBorrow) |
+            PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) |
             PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => {
                 self.not_ssa(local);
             }

src/librustc_codegen_ssa/mir/place.rs

@@ -448,7 +448,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let cx = self.cx;
         let tcx = self.cx.tcx();
 
-        let result = match &place_ref {
+        let result = match place_ref {
             mir::PlaceRef {
                 base: mir::PlaceBase::Local(index),
                 projection: [],

src/librustc_codegen_ssa/mir/rvalue.rs

@@ -7,7 +7,7 @@ use crate::MemFlags;
 use crate::common::{self, RealPredicate, IntPredicate};
 use crate::traits::*;
 
-use rustc::ty::{self, Ty, adjustment::{PointerCast}, Instance};
+use rustc::ty::{self, Ty, TyCtxt, adjustment::{PointerCast}, Instance};
 use rustc::ty::cast::{CastTy, IntTy};
 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt};
 use rustc::mir;
@@ -349,8 +349,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 }
                             }
                             (CastTy::Ptr(_), CastTy::Ptr(_)) |
-                            (CastTy::FnPtr, CastTy::Ptr(_)) |
-                            (CastTy::RPtr(_), CastTy::Ptr(_)) =>
+                            (CastTy::FnPtr, CastTy::Ptr(_)) =>
                                 bx.pointercast(llval, ll_t_out),
                             (CastTy::Ptr(_), CastTy::Int(_)) |
                             (CastTy::FnPtr, CastTy::Int(_)) =>
@@ -375,24 +374,18 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             mir::Rvalue::Ref(_, bk, ref place) => {
-                let cg_place = self.codegen_place(&mut bx, &place.as_ref());
-
-                let ty = cg_place.layout.ty;
+                let mk_ref = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| tcx.mk_ref(
+                    tcx.lifetimes.re_erased,
+                    ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() }
+                );
+                self.codegen_place_to_pointer(bx, place, mk_ref)
+            }
 
-                // Note: places are indirect, so storing the `llval` into the
-                // destination effectively creates a reference.
-                let val = if !bx.cx().type_has_metadata(ty) {
-                    OperandValue::Immediate(cg_place.llval)
-                } else {
-                    OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
-                };
-                (bx, OperandRef {
-                    val,
-                    layout: self.cx.layout_of(self.cx.tcx().mk_ref(
-                        self.cx.tcx().lifetimes.re_erased,
-                        ty::TypeAndMut { ty, mutbl: bk.to_mutbl_lossy() }
-                    )),
-                })
+            mir::Rvalue::AddressOf(mutability, ref place) => {
+                let mk_ptr = move |tcx: TyCtxt<'tcx>, ty: Ty<'tcx>| tcx.mk_ptr(
+                    ty::TypeAndMut { ty, mutbl: mutability.into() }
+                );
+                self.codegen_place_to_pointer(bx, place, mk_ptr)
             }
 
             mir::Rvalue::Len(ref place) => {
@@ -548,6 +541,30 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         cg_value.len(bx.cx())
     }
 
+    /// Codegen an `Rvalue::AddressOf` or `Rvalue::Ref`
+    fn codegen_place_to_pointer(
+        &mut self,
+        mut bx: Bx,
+        place: &mir::Place<'tcx>,
+        mk_ptr_ty: impl FnOnce(TyCtxt<'tcx>, Ty<'tcx>) -> Ty<'tcx>,
+    ) -> (Bx, OperandRef<'tcx, Bx::Value>) {
+        let cg_place = self.codegen_place(&mut bx, &place.as_ref());
+
+        let ty = cg_place.layout.ty;
+
+        // Note: places are indirect, so storing the `llval` into the
+        // destination effectively creates a reference.
+        let val = if !bx.cx().type_has_metadata(ty) {
+            OperandValue::Immediate(cg_place.llval)
+        } else {
+            OperandValue::Pair(cg_place.llval, cg_place.llextra.unwrap())
+        };
+        (bx, OperandRef {
+            val,
+            layout: self.cx.layout_of(mk_ptr_ty(self.cx.tcx(), ty)),
+        })
+    }
+
     pub fn codegen_scalar_binop(
         &mut self,
         bx: &mut Bx,
@@ -704,6 +721,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>, span: Span) -> bool {
         match *rvalue {
             mir::Rvalue::Ref(..) |
+            mir::Rvalue::AddressOf(..) |
             mir::Rvalue::Len(..) |
             mir::Rvalue::Cast(..) | // (*)
             mir::Rvalue::BinaryOp(..) |

src/librustc_error_codes/error_codes/E0745.md

@@ -11,7 +11,7 @@ fn temp_address() {
 
 To avoid the error, first bind the temporary to a named local variable.
 
-```ignore (not yet implemented)
+```
 # #![feature(raw_ref_op)]
 fn temp_address() {
     let val = 2;

src/librustc_mir/borrow_check/invalidation.rs

@@ -3,7 +3,7 @@ use rustc::mir::visit::Visitor;
 use rustc::mir::{BasicBlock, Location, Body, Place, ReadOnlyBodyAndCache, Rvalue};
 use rustc::mir::{Statement, StatementKind};
 use rustc::mir::TerminatorKind;
-use rustc::mir::{Operand, BorrowKind};
+use rustc::mir::{Operand, BorrowKind, Mutability};
 use rustc_data_structures::graph::dominators::Dominators;
 
 use crate::dataflow::indexes::BorrowIndex;
@@ -337,6 +337,22 @@ impl<'cx, 'tcx> InvalidationGenerator<'cx, 'tcx> {
                 );
             }
 
+            Rvalue::AddressOf(mutability, ref place) => {
+                let access_kind = match mutability {
+                    Mutability::Mut => (Deep, Write(WriteKind::MutableBorrow(BorrowKind::Mut {
+                        allow_two_phase_borrow: false,
+                    }))),
+                    Mutability::Not => (Deep, Read(ReadKind::Borrow(BorrowKind::Shared))),
+                };
+
+                self.access_place(
+                    location,
+                    place,
+                    access_kind,
+                    LocalMutationIsAllowed::No,
+                );
+            }
+
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)

src/librustc_mir/borrow_check/mod.rs

@@ -1233,6 +1233,31 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 );
             }
 
+
+            Rvalue::AddressOf(mutability, ref place) => {
+                let access_kind = match mutability {
+                    Mutability::Mut => (Deep, Write(WriteKind::MutableBorrow(BorrowKind::Mut {
+                        allow_two_phase_borrow: false,
+                    }))),
+                    Mutability::Not => (Deep, Read(ReadKind::Borrow(BorrowKind::Shared))),
+                };
+
+                self.access_place(
+                    location,
+                    (place, span),
+                    access_kind,
+                    LocalMutationIsAllowed::No,
+                    flow_state,
+                );
+
+                self.check_if_path_or_subpath_is_moved(
+                    location,
+                    InitializationRequiringAction::Borrow,
+                    (place.as_ref(), span),
+                    flow_state,
+                );
+            }
+
             Rvalue::Use(ref operand)
             | Rvalue::Repeat(ref operand, _)
             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)

src/librustc_mir/borrow_check/type_check/mod.rs

@@ -2273,41 +2273,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         let cast_ty_from = CastTy::from_ty(ty_from);
                         let cast_ty_to = CastTy::from_ty(ty);
                         match (cast_ty_from, cast_ty_to) {
-                            (Some(CastTy::RPtr(ref_tm)), Some(CastTy::Ptr(ptr_tm))) => {
-                                if let hir::Mutability::Mutable = ptr_tm.mutbl {
-                                    if let Err(terr) = self.eq_types(
-                                        ref_tm.ty,
-                                        ptr_tm.ty,
-                                        location.to_locations(),
-                                        ConstraintCategory::Cast,
-                                    ) {
-                                        span_mirbug!(
-                                            self,
-                                            rvalue,
-                                            "equating {:?} with {:?} yields {:?}",
-                                            ref_tm.ty,
-                                            ptr_tm.ty,
-                                            terr
-                                        )
-                                    }
-                                } else {
-                                    if let Err(terr) = self.sub_types(
-                                        ref_tm.ty,
-                                        ptr_tm.ty,
-                                        location.to_locations(),
-                                        ConstraintCategory::Cast,
-                                    ) {
-                                        span_mirbug!(
-                                            self,
-                                            rvalue,
-                                            "relating {:?} with {:?} yields {:?}",
-                                            ref_tm.ty,
-                                            ptr_tm.ty,
-                                            terr
-                                        )
-                                    }
-                                }
-                            },
                             (None, _)
                             | (_, None)
                             | (_, Some(CastTy::FnPtr))
@@ -2320,7 +2285,15 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                 ty_from,
                                 ty,
                             ),
-                            _ => (),
+                            (Some(CastTy::Int(_)), Some(CastTy::Int(_)))
+                            | (Some(CastTy::Float), Some(CastTy::Int(_)))
+                            | (Some(CastTy::Int(_)), Some(CastTy::Float))
+                            | (Some(CastTy::Float), Some(CastTy::Float))
+                            | (Some(CastTy::Ptr(_)), Some(CastTy::Int(_)))
+                            | (Some(CastTy::FnPtr), Some(CastTy::Int(_)))
+                            | (Some(CastTy::Int(_)), Some(CastTy::Ptr(_)))
+                            | (Some(CastTy::Ptr(_)), Some(CastTy::Ptr(_)))
+                            | (Some(CastTy::FnPtr), Some(CastTy::Ptr(_))) => (),
                         }
                     }
                 }
@@ -2371,7 +2344,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
             }
 
-            Rvalue::Use(..)
+            Rvalue::AddressOf(..)
+            | Rvalue::Use(..)
             | Rvalue::Len(..)
             | Rvalue::BinaryOp(..)
             | Rvalue::CheckedBinaryOp(..)
@@ -2388,6 +2362,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             Rvalue::Use(_)
             | Rvalue::Repeat(..)
             | Rvalue::Ref(..)
+            | Rvalue::AddressOf(..)
             | Rvalue::Len(..)
             | Rvalue::Cast(..)
             | Rvalue::BinaryOp(..)

src/librustc_mir/build/expr/as_place.rs

@@ -276,6 +276,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | ExprKind::Pointer { .. }
             | ExprKind::Repeat { .. }
             | ExprKind::Borrow { .. }
+            | ExprKind::AddressOf { .. }
             | ExprKind::Match { .. }
             | ExprKind::Loop { .. }
             | ExprKind::Block { .. }

src/librustc_mir/build/expr/as_rvalue.rs

@@ -276,6 +276,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             | ExprKind::NeverToAny { .. }
             | ExprKind::Use { .. }
             | ExprKind::Borrow { .. }
+            | ExprKind::AddressOf { .. }
             | ExprKind::Adt { .. }
             | ExprKind::Loop { .. }
             | ExprKind::LogicalOp { .. }