Remove Rvalue::Len again.

compiler/rustc_borrowck/src/lib.rs

@@ -1557,9 +1557,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                 );
             }
 
-            &(Rvalue::Len(place) | Rvalue::Discriminant(place)) => {
+            &Rvalue::Discriminant(place) => {
                 let af = match *rvalue {
-                    Rvalue::Len(..) => Some(ArtificialField::ArrayLength),
                     Rvalue::Discriminant(..) => None,
                     _ => unreachable!(),
                 };

compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs

@@ -306,16 +306,11 @@ impl<'a, 'tcx> LoanInvalidationsGenerator<'a, 'tcx> {
                 self.consume_operand(location, op);
             }
 
-            &(Rvalue::Len(place) | Rvalue::Discriminant(place)) => {
-                let af = match rvalue {
-                    Rvalue::Len(..) => Some(ArtificialField::ArrayLength),
-                    Rvalue::Discriminant(..) => None,
-                    _ => unreachable!(),
-                };
+            &Rvalue::Discriminant(place) => {
                 self.access_place(
                     location,
                     place,
-                    (Shallow(af), Read(ReadKind::Copy)),
+                    (Shallow(None), Read(ReadKind::Copy)),
                     LocalMutationIsAllowed::No,
                 );
             }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1631,7 +1631,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             | Rvalue::BinaryOp(..)
             | Rvalue::RawPtr(..)
             | Rvalue::ThreadLocalRef(..)
-            | Rvalue::Len(..)
             | Rvalue::Discriminant(..)
             | Rvalue::NullaryOp(NullOp::OffsetOf(..), _) => {}
         }
@@ -2201,7 +2200,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             | Rvalue::Repeat(..)
             | Rvalue::Ref(..)
             | Rvalue::RawPtr(..)
-            | Rvalue::Len(..)
             | Rvalue::Cast(..)
             | Rvalue::ShallowInitBox(..)
             | Rvalue::BinaryOp(..)

compiler/rustc_codegen_cranelift/src/base.rs

@@ -834,12 +834,6 @@ fn codegen_stmt<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, cur_block: Block, stmt:
                         fx.bcx.ins().nop();
                     }
                 }
-                Rvalue::Len(place) => {
-                    let place = codegen_place(fx, place);
-                    let usize_layout = fx.layout_of(fx.tcx.types.usize);
-                    let len = codegen_array_len(fx, place);
-                    lval.write_cvalue(fx, CValue::by_val(len, usize_layout));
-                }
                 Rvalue::ShallowInitBox(ref operand, content_ty) => {
                     let content_ty = fx.monomorphize(content_ty);
                     let box_layout = fx.layout_of(Ty::new_box(fx.tcx, content_ty));

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -7,9 +7,9 @@ use rustc_middle::{bug, mir, span_bug};
 use rustc_session::config::OptLevel;
 use tracing::{debug, instrument};
 
+use super::FunctionCx;
 use super::operand::{OperandRef, OperandRefBuilder, OperandValue};
 use super::place::{PlaceRef, PlaceValue, codegen_tag_value};
-use super::{FunctionCx, LocalRef};
 use crate::common::{IntPredicate, TypeKind};
 use crate::traits::*;
 use crate::{MemFlags, base};
@@ -510,14 +510,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 self.codegen_place_to_pointer(bx, place, mk_ptr)
             }
 
-            mir::Rvalue::Len(place) => {
-                let size = self.evaluate_array_len(bx, place);
-                OperandRef {
-                    val: OperandValue::Immediate(size),
-                    layout: bx.cx().layout_of(bx.tcx().types.usize),
-                }
-            }
-
             mir::Rvalue::BinaryOp(op_with_overflow, box (ref lhs, ref rhs))
                 if let Some(op) = op_with_overflow.overflowing_to_wrapping() =>
             {
@@ -749,21 +741,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         }
     }
 
-    fn evaluate_array_len(&mut self, bx: &mut Bx, place: mir::Place<'tcx>) -> Bx::Value {
-        // ZST are passed as operands and require special handling
-        // because codegen_place() panics if Local is operand.
-        if let Some(index) = place.as_local()
-            && let LocalRef::Operand(op) = self.locals[index]
-            && let ty::Array(_, n) = op.layout.ty.kind()
-        {
-            let n = n.try_to_target_usize(bx.tcx()).expect("expected monomorphic const in codegen");
-            return bx.cx().const_usize(n);
-        }
-        // use common size calculation for non zero-sized types
-        let cg_value = self.codegen_place(bx, place.as_ref());
-        cg_value.len(bx.cx())
-    }
-
     /// Codegen an `Rvalue::RawPtr` or `Rvalue::Ref`
     fn codegen_place_to_pointer(
         &mut self,

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -573,8 +573,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             Rvalue::Use(_)
             | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
-            | Rvalue::Discriminant(..)
-            | Rvalue::Len(_) => {}
+            | Rvalue::Discriminant(..) => {}
 
             Rvalue::Aggregate(kind, ..) => {
                 if let AggregateKind::Coroutine(def_id, ..) = kind.as_ref()

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -232,9 +232,7 @@ where
             Q::in_any_value_of_ty(cx, rvalue.ty(cx.body, cx.tcx))
         }
 
-        Rvalue::Discriminant(place) | Rvalue::Len(place) => {
-            in_place::<Q, _>(cx, in_local, place.as_ref())
-        }
+        Rvalue::Discriminant(place) => in_place::<Q, _>(cx, in_local, place.as_ref()),
 
         Rvalue::CopyForDeref(place) => in_place::<Q, _>(cx, in_local, place.as_ref()),
 

compiler/rustc_const_eval/src/check_consts/resolver.rs

@@ -197,7 +197,6 @@ where
             | mir::Rvalue::CopyForDeref(..)
             | mir::Rvalue::ThreadLocalRef(..)
             | mir::Rvalue::Repeat(..)
-            | mir::Rvalue::Len(..)
             | mir::Rvalue::BinaryOp(..)
             | mir::Rvalue::NullaryOp(..)
             | mir::Rvalue::UnaryOp(..)

compiler/rustc_const_eval/src/interpret/step.rs

@@ -17,7 +17,7 @@ use tracing::{info, instrument, trace};
 
 use super::{
     FnArg, FnVal, ImmTy, Immediate, InterpCx, InterpResult, Machine, MemPlaceMeta, PlaceTy,
-    Projectable, Scalar, interp_ok, throw_ub, throw_unsup_format,
+    Projectable, interp_ok, throw_ub, throw_unsup_format,
 };
 use crate::interpret::EnteredTraceSpan;
 use crate::{enter_trace_span, util};
@@ -225,12 +225,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 self.write_repeat(operand, &dest)?;
             }
 
-            Len(place) => {
-                let src = self.eval_place(place)?;
-                let len = src.len(self)?;
-                self.write_scalar(Scalar::from_target_usize(len, self), &dest)?;
-            }
-
             Ref(_, borrow_kind, place) => {
                 let src = self.eval_place(place)?;
                 let place = self.force_allocation(&src)?;

compiler/rustc_middle/src/mir/pretty.rs

@@ -1062,7 +1062,6 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                 pretty_print_const(b, fmt, false)?;
                 write!(fmt, "]")
             }
-            Len(ref a) => write!(fmt, "Len({a:?})"),
             Cast(ref kind, ref place, ref ty) => {
                 with_no_trimmed_paths!(write!(fmt, "{place:?} as {ty} ({kind:?})"))
             }

compiler/rustc_middle/src/mir/statement.rs

@@ -697,7 +697,6 @@ impl<'tcx> Rvalue<'tcx> {
             | Rvalue::Ref(_, _, _)
             | Rvalue::ThreadLocalRef(_)
             | Rvalue::RawPtr(_, _)
-            | Rvalue::Len(_)
             | Rvalue::Cast(
                 CastKind::IntToInt
                 | CastKind::FloatToInt
@@ -739,7 +738,6 @@ impl<'tcx> Rvalue<'tcx> {
                 let place_ty = place.ty(local_decls, tcx).ty;
                 Ty::new_ptr(tcx, place_ty, kind.to_mutbl_lossy())
             }
-            Rvalue::Len(..) => tcx.types.usize,
             Rvalue::Cast(.., ty) => ty,
             Rvalue::BinaryOp(op, box (ref lhs, ref rhs)) => {
                 let lhs_ty = lhs.ty(local_decls, tcx);

compiler/rustc_middle/src/mir/syntax.rs

@@ -1407,16 +1407,6 @@ pub enum Rvalue<'tcx> {
     /// model.
     RawPtr(RawPtrKind, Place<'tcx>),
 
-    /// Yields the length of the place, as a `usize`.
-    ///
-    /// If the type of the place is an array, this is the array length. For slices (`[T]`, not
-    /// `&[T]`) this accesses the place's metadata to determine the length. This rvalue is
-    /// ill-formed for places of other types.
-    ///
-    /// This cannot be a `UnOp(PtrMetadata, _)` because that expects a value, and we only
-    /// have a place, and `UnOp(PtrMetadata, RawPtr(place))` is not a thing.
-    Len(Place<'tcx>),
-
     /// Performs essentially all of the casts that can be performed via `as`.
     ///
     /// This allows for casts from/to a variety of types.

compiler/rustc_middle/src/mir/visit.rs

@@ -717,14 +717,6 @@ macro_rules! make_mir_visitor {
                         self.visit_place(path, ctx, location);
                     }
 
-                    Rvalue::Len(path) => {
-                        self.visit_place(
-                            path,
-                            PlaceContext::NonMutatingUse(NonMutatingUseContext::Inspect),
-                            location
-                        );
-                    }
-
                     Rvalue::Cast(_cast_kind, operand, ty) => {
                         self.visit_operand(operand, location);
                         self.visit_ty($(& $mutability)? *ty, TyContext::Location(location));

compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs

@@ -229,6 +229,11 @@ impl<'a, 'tcx> ParseCtxt<'a, 'tcx> {
                 let source = self.parse_operand(args[0])?;
                 Ok(Rvalue::Cast(CastKind::PtrToPtr, source, expr.ty))
             },
+            @call(mir_cast_unsize, args) => {
+                let source = self.parse_operand(args[0])?;
+                let kind = CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, CoercionSource::AsCast);
+                Ok(Rvalue::Cast(kind, source, expr.ty))
+            },
             @call(mir_checked, args) => {
                 parse_by_kind!(self, args[0], _, "binary op",
                     ExprKind::Binary { op, lhs, rhs } => {
@@ -247,7 +252,6 @@ impl<'a, 'tcx> ParseCtxt<'a, 'tcx> {
                 let offset = self.parse_operand(args[1])?;
                 Ok(Rvalue::BinaryOp(BinOp::Offset, Box::new((ptr, offset))))
             },
-            @call(mir_len, args) => Ok(Rvalue::Len(self.parse_place(args[0])?)),
             @call(mir_ptr_metadata, args) => Ok(Rvalue::UnaryOp(UnOp::PtrMetadata, self.parse_operand(args[0])?)),
             @call(mir_copy_for_deref, args) => Ok(Rvalue::CopyForDeref(self.parse_place(args[0])?)),
             ExprKind::Borrow { borrow_kind, arg } => Ok(

compiler/rustc_mir_build/src/builder/expr/as_place.rs

@@ -663,7 +663,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     ///
     /// For arrays it'll be `Operand::Constant` with the actual length;
     /// For slices it'll be `Operand::Move` of a local using `PtrMetadata`.
-    fn len_of_slice_or_array(
+    pub(in crate::builder) fn len_of_slice_or_array(
         &mut self,
         block: BasicBlock,
         place: Place<'tcx>,

compiler/rustc_mir_build/src/builder/matches/test.rs

@@ -309,7 +309,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let actual = self.temp(usize_ty, test.span);
 
                 // actual = len(place)
-                self.cfg.push_assign(block, source_info, actual, Rvalue::Len(place));
+                let length_op = self.len_of_slice_or_array(block, place, test.span, source_info);
+                self.cfg.push_assign(block, source_info, actual, Rvalue::Use(length_op));
 
                 // expected = <N>
                 let expected = self.push_usize(block, source_info, len);

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -91,7 +91,6 @@ where
             | Rvalue::Use(..)
             | Rvalue::ThreadLocalRef(..)
             | Rvalue::Repeat(..)
-            | Rvalue::Len(..)
             | Rvalue::BinaryOp(..)
             | Rvalue::NullaryOp(..)
             | Rvalue::UnaryOp(..)

compiler/rustc_mir_dataflow/src/move_paths/builder.rs

@@ -413,7 +413,6 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             Rvalue::Ref(..)
             | Rvalue::RawPtr(..)
             | Rvalue::Discriminant(..)
-            | Rvalue::Len(..)
             | Rvalue::NullaryOp(
                 NullOp::SizeOf
                 | NullOp::AlignOf

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -412,18 +412,6 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
         state: &mut State<FlatSet<Scalar>>,
     ) -> ValueOrPlace<FlatSet<Scalar>> {
         let val = match rvalue {
-            Rvalue::Len(place) => {
-                let place_ty = place.ty(self.local_decls, self.tcx);
-                if let ty::Array(_, len) = place_ty.ty.kind() {
-                    Const::Ty(self.tcx.types.usize, *len)
-                        .try_eval_scalar(self.tcx, self.typing_env)
-                        .map_or(FlatSet::Top, FlatSet::Elem)
-                } else if let [ProjectionElem::Deref] = place.projection[..] {
-                    state.get_len(place.local.into(), &self.map)
-                } else {
-                    FlatSet::Top
-                }
-            }
             Rvalue::Cast(CastKind::IntToInt | CastKind::IntToFloat, operand, ty) => {
                 let Ok(layout) = self.tcx.layout_of(self.typing_env.as_query_input(*ty)) else {
                     return ValueOrPlace::Value(FlatSet::Top);
@@ -465,15 +453,23 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
                 let (val, _overflow) = self.binary_op(state, *op, left, right);
                 val
             }
-            Rvalue::UnaryOp(op, operand) => match self.eval_operand(operand, state) {
-                FlatSet::Elem(value) => self
-                    .ecx
-                    .unary_op(*op, &value)
-                    .discard_err()
-                    .map_or(FlatSet::Top, |val| self.wrap_immediate(*val)),
-                FlatSet::Bottom => FlatSet::Bottom,
-                FlatSet::Top => FlatSet::Top,
-            },
+            Rvalue::UnaryOp(op, operand) => {
+                if let UnOp::PtrMetadata = op
+                    && let Some(place) = operand.place()
+                    && let Some(len) = self.map.find_len(place.as_ref())
+                {
+                    return ValueOrPlace::Place(len);
+                }
+                match self.eval_operand(operand, state) {
+                    FlatSet::Elem(value) => self
+                        .ecx
+                        .unary_op(*op, &value)
+                        .discard_err()
+                        .map_or(FlatSet::Top, |val| self.wrap_immediate(*val)),
+                    FlatSet::Bottom => FlatSet::Bottom,
+                    FlatSet::Top => FlatSet::Top,
+                }
+            }
             Rvalue::NullaryOp(null_op, ty) => {
                 let Ok(layout) = self.tcx.layout_of(self.typing_env.as_query_input(*ty)) else {
                     return ValueOrPlace::Value(FlatSet::Top);