Remove Rvalue::Len.

46 files changed, 656 insertions, 291 deletions

diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 5d2dda8b0e7..f196bd04d0e 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/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!(),
                 };
diff --git a/compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs b/compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs
index 99dd0b2dd46..c2ad6fcb4b7 100644
--- a/compiler/rustc_borrowck/src/polonius/legacy/loan_invalidations.rs
+++ b/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,
                 );
             }
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 8c5447fe1e9..dcedf0b1532 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/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(..)
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index 3a28dd7e73c..41e11e1de61 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/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));
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index f8755874014..c30e6a50505 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/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,
diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index ca707b50d50..3397bd9a68e 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/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()
diff --git a/compiler/rustc_const_eval/src/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/check_consts/qualifs.rs
index faf41f1658b..34d1fdd8c86 100644
--- a/compiler/rustc_const_eval/src/check_consts/qualifs.rs
+++ b/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()),
 
diff --git a/compiler/rustc_const_eval/src/check_consts/resolver.rs b/compiler/rustc_const_eval/src/check_consts/resolver.rs
index d98e5027e4d..664dda8701a 100644
--- a/compiler/rustc_const_eval/src/check_consts/resolver.rs
+++ b/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(..)
diff --git a/compiler/rustc_const_eval/src/interpret/step.rs b/compiler/rustc_const_eval/src/interpret/step.rs
index 46950d60f8c..923e00ad4cf 100644
--- a/compiler/rustc_const_eval/src/interpret/step.rs
+++ b/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)?;
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index f9d0a5f0a3b..96148fd5b92 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/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:?})"))
             }
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
index ec2a8e86077..28294b47e90 100644
--- a/compiler/rustc_middle/src/mir/statement.rs
+++ b/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);
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index d402ea4b04f..e6c8512564e 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/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.
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index b498b7b8912..07a15b3cd18 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/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));
diff --git a/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs
index 41d3aefcbe6..54490e00509 100644
--- a/compiler/rustc_mir_build/src/builder/custom/parse/instruction.rs
+++ b/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(
diff --git a/compiler/rustc_mir_build/src/builder/expr/as_place.rs b/compiler/rustc_mir_build/src/builder/expr/as_place.rs
index 7c851ec465b..5a6bd2f413c 100644
--- a/compiler/rustc_mir_build/src/builder/expr/as_place.rs
+++ b/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>,
diff --git a/compiler/rustc_mir_build/src/builder/matches/test.rs b/compiler/rustc_mir_build/src/builder/matches/test.rs
index d03794fe2d5..1b6d96e49f0 100644
--- a/compiler/rustc_mir_build/src/builder/matches/test.rs
+++ b/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);
diff --git a/compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs b/compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs
index 9abb8343432..a4e4e30a8bb 100644
--- a/compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs
+++ b/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(..)
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs b/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
index 48718cad597..f38bb445824 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/builder.rs
+++ b/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
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index fe53de31f75..5c984984d3c 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/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);
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index bf6aa800d20..30e68a3f650 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -200,8 +200,6 @@ enum Value<'tcx> {
     Projection(VnIndex, ProjectionElem<VnIndex, ()>),
     /// Discriminant of the given value.
     Discriminant(VnIndex),
-    /// Length of an array or slice.
-    Len(VnIndex),
 
     // Operations.
     NullaryOp(NullOp<'tcx>, Ty<'tcx>),
@@ -477,11 +475,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                     self.ecx.discriminant_for_variant(base.layout.ty, variant).discard_err()?;
                 discr_value.into()
             }
-            Len(slice) => {
-                let slice = self.evaluated[slice].as_ref()?;
-                let len = slice.len(&self.ecx).discard_err()?;
-                ImmTy::from_uint(len, ty).into()
-            }
             NullaryOp(null_op, arg_ty) => {
                 let arg_layout = self.ecx.layout_of(arg_ty).ok()?;
                 if let NullOp::SizeOf | NullOp::AlignOf = null_op
@@ -841,7 +834,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             }
 
             // Operations.
-            Rvalue::Len(ref mut place) => return self.simplify_len(place, location),
             Rvalue::Cast(ref mut kind, ref mut value, to) => {
                 return self.simplify_cast(kind, value, to, location);
             }
@@ -1049,7 +1041,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
         if op == UnOp::PtrMetadata {
             let mut was_updated = false;
             loop {
-                match self.get(arg_index) {
+                arg_index = match self.get(arg_index) {
                     // Pointer casts that preserve metadata, such as
                     // `*const [i32]` <-> `*mut [i32]` <-> `*mut [f32]`.
                     // It's critical that this not eliminate cases like
@@ -1061,9 +1053,19 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                     Value::Cast { kind: CastKind::PtrToPtr, value: inner }
                         if self.pointers_have_same_metadata(self.ty(*inner), arg_ty) =>
                     {
-                        arg_index = *inner;
-                        was_updated = true;
-                        continue;
+                        *inner
+                    }
+
+                    // We have an unsizing cast, which assigns the length to wide pointer metadata.
+                    Value::Cast {
+                        kind: CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _),
+                        value: from,
+                    } if let Some(from) = self.ty(*from).builtin_deref(true)
+                        && let ty::Array(_, len) = from.kind()
+                        && let Some(to) = self.ty(arg_index).builtin_deref(true)
+                        && let ty::Slice(..) = to.kind() =>
+                    {
+                        return Some(self.insert_constant(Const::Ty(self.tcx.types.usize, *len)));
                     }
 
                     // `&mut *p`, `&raw *p`, etc don't change metadata.
@@ -1072,18 +1074,16 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                             place.as_ref()
                             && let Some(local_index) = self.locals[local] =>
                     {
-                        arg_index = local_index;
-                        was_updated = true;
-                        continue;
+                        local_index
                     }
 
-                    _ => {
-                        if was_updated && let Some(op) = self.try_as_operand(arg_index, location) {
-                            *arg_op = op;
-                        }
-                        break;
-                    }
-                }
+                    _ => break,
+                };
+                was_updated = true;
+            }
+
+            if was_updated && let Some(op) = self.try_as_operand(arg_index, location) {
+                *arg_op = op;
             }
         }
 
@@ -1407,39 +1407,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
         Some(self.insert(to, Value::Cast { kind, value }))
     }
 
-    fn simplify_len(&mut self, place: &mut Place<'tcx>, location: Location) -> Option<VnIndex> {
-        // Trivial case: we are fetching a statically known length.
-        let place_ty = place.ty(self.local_decls, self.tcx).ty;
-        if let ty::Array(_, len) = place_ty.kind() {
-            return Some(self.insert_constant(Const::Ty(self.tcx.types.usize, *len)));
-        }
-
-        let mut inner = self.simplify_place_value(place, location)?;
-
-        // The length information is stored in the wide pointer.
-        // Reborrowing copies length information from one pointer to the other.
-        while let Value::Address { place: borrowed, .. } = self.get(inner)
-            && let [PlaceElem::Deref] = borrowed.projection[..]
-            && let Some(borrowed) = self.locals[borrowed.local]
-        {
-            inner = borrowed;
-        }
-
-        // We have an unsizing cast, which assigns the length to wide pointer metadata.
-        if let Value::Cast { kind, value: from } = self.get(inner)
-            && let CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _) = kind
-            && let Some(from) = self.ty(*from).builtin_deref(true)
-            && let ty::Array(_, len) = from.kind()
-            && let Some(to) = self.ty(inner).builtin_deref(true)
-            && let ty::Slice(..) = to.kind()
-        {
-            return Some(self.insert_constant(Const::Ty(self.tcx.types.usize, *len)));
-        }
-
-        // Fallback: a symbolic `Len`.
-        Some(self.insert(self.tcx.types.usize, Value::Len(inner)))
-    }
-
     fn pointers_have_same_metadata(&self, left_ptr_ty: Ty<'tcx>, right_ptr_ty: Ty<'tcx>) -> bool {
         let left_meta_ty = left_ptr_ty.pointee_metadata_ty_or_projection(self.tcx);
         let right_meta_ty = right_ptr_ty.pointee_metadata_ty_or_projection(self.tcx);
diff --git a/compiler/rustc_mir_transform/src/known_panics_lint.rs b/compiler/rustc_mir_transform/src/known_panics_lint.rs
index 481c7941909..aaacc5866a2 100644
--- a/compiler/rustc_mir_transform/src/known_panics_lint.rs
+++ b/compiler/rustc_mir_transform/src/known_panics_lint.rs
@@ -441,7 +441,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             | Rvalue::Use(..)
             | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
-            | Rvalue::Len(..)
             | Rvalue::Cast(..)
             | Rvalue::ShallowInitBox(..)
             | Rvalue::Discriminant(..)
@@ -604,20 +603,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 return None;
             }
 
-            Len(place) => {
-                let len = if let ty::Array(_, n) = place.ty(self.local_decls(), self.tcx).ty.kind()
-                {
-                    n.try_to_target_usize(self.tcx)?
-                } else {
-                    match self.get_const(place)? {
-                        Value::Immediate(src) => src.len(&self.ecx).discard_err()?,
-                        Value::Aggregate { fields, .. } => fields.len() as u64,
-                        Value::Uninit => return None,
-                    }
-                };
-                ImmTy::from_scalar(Scalar::from_target_usize(len, self), layout).into()
-            }
-
             Ref(..) | RawPtr(..) => return None,
 
             NullaryOp(ref null_op, ty) => {
diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs
index 9ea2eb4f25d..a0b0c8c990f 100644
--- a/compiler/rustc_mir_transform/src/promote_consts.rs
+++ b/compiler/rustc_mir_transform/src/promote_consts.rs
@@ -437,9 +437,7 @@ impl<'tcx> Validator<'_, 'tcx> {
                 self.validate_operand(op)?
             }
 
-            Rvalue::Discriminant(place) | Rvalue::Len(place) => {
-                self.validate_place(place.as_ref())?
-            }
+            Rvalue::Discriminant(place) => self.validate_place(place.as_ref())?,
 
             Rvalue::ThreadLocalRef(_) => return Err(Unpromotable),
 
diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs
index 99e4782e470..c8a9a88dc3f 100644
--- a/compiler/rustc_mir_transform/src/validate.rs
+++ b/compiler/rustc_mir_transform/src/validate.rs
@@ -1064,14 +1064,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 }
             }
             Rvalue::Ref(..) => {}
-            Rvalue::Len(p) => {
-                let pty = p.ty(&self.body.local_decls, self.tcx).ty;
-                check_kinds!(
-                    pty,
-                    "Cannot compute length of non-array type {:?}",
-                    ty::Array(..) | ty::Slice(..)
-                );
-            }
             Rvalue::BinaryOp(op, vals) => {
                 use BinOp::*;
                 let a = vals.0.ty(&self.body.local_decls, self.tcx);
diff --git a/compiler/rustc_public/src/unstable/convert/stable/mir.rs b/compiler/rustc_public/src/unstable/convert/stable/mir.rs
index be8ee80bed3..b10af6526ea 100644
--- a/compiler/rustc_public/src/unstable/convert/stable/mir.rs
+++ b/compiler/rustc_public/src/unstable/convert/stable/mir.rs
@@ -215,7 +215,6 @@ impl<'tcx> Stable<'tcx> for mir::Rvalue<'tcx> {
                 mutability.stable(tables, cx),
                 place.stable(tables, cx),
             ),
-            Len(place) => crate::mir::Rvalue::Len(place.stable(tables, cx)),
             Cast(cast_kind, op, ty) => crate::mir::Rvalue::Cast(
                 cast_kind.stable(tables, cx),
                 op.stable(tables, cx),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index cdb0b5b58da..16b8b46f97c 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1413,6 +1413,7 @@ symbols! {
         mir_call,
         mir_cast_ptr_to_ptr,
         mir_cast_transmute,
+        mir_cast_unsize,
         mir_checked,
         mir_copy_for_deref,
         mir_debuginfo,
diff --git a/library/core/src/intrinsics/mir.rs b/library/core/src/intrinsics/mir.rs
index 55dcf7cd47e..c4bd10e606a 100644
--- a/library/core/src/intrinsics/mir.rs
+++ b/library/core/src/intrinsics/mir.rs
@@ -401,7 +401,6 @@ define!("mir_storage_dead", fn StorageDead<T>(local: T));
 define!("mir_assume", fn Assume(operand: bool));
 define!("mir_deinit", fn Deinit<T>(place: T));
 define!("mir_checked", fn Checked<T>(binop: T) -> (T, bool));
-define!("mir_len", fn Len<T>(place: T) -> usize);
 define!(
     "mir_ptr_metadata",
     fn PtrMetadata<P: ?Sized>(place: *const P) -> <P as ::core::ptr::Pointee>::Metadata
@@ -492,6 +491,13 @@ define!(
     fn CastPtrToPtr<T, U>(operand: T) -> U
 );
 define!(
+    "mir_cast_unsize",
+    /// Emits a `CastKind::PointerCoercion(Unsize)` cast.
+    ///
+    /// This allows bypassing normal validation to generate strange casts.
+    fn CastUnsize<T, U>(operand: T) -> U
+);
+define!(
     "mir_make_place",
     #[doc(hidden)]
     fn __internal_make_place<T>(place: T) -> *mut T
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index 68f0b5ea255..40fd2cdeb86 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -126,7 +126,7 @@ fn check_rvalue<'tcx>(
 ) -> McfResult {
     match rvalue {
         Rvalue::ThreadLocalRef(_) => Err((span, "cannot access thread local storage in const fn".into())),
-        Rvalue::Len(place) | Rvalue::Discriminant(place) | Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) => {
+        Rvalue::Discriminant(place) | Rvalue::Ref(_, _, place) | Rvalue::RawPtr(_, place) => {
             check_place(cx, *place, span, body, msrv)
         },
         Rvalue::CopyForDeref(place) => check_place(cx, *place, span, body, msrv),
diff --git a/tests/mir-opt/building/custom/arrays.arrays.built.after.mir b/tests/mir-opt/building/custom/arrays.arrays.built.after.mir
index 30d11e31e4d..f9f24c8eabe 100644
--- a/tests/mir-opt/building/custom/arrays.arrays.built.after.mir
+++ b/tests/mir-opt/building/custom/arrays.arrays.built.after.mir
@@ -3,12 +3,16 @@
 fn arrays() -> usize {
     let mut _0: usize;
     let mut _1: [i32; C];
-    let mut _2: usize;
+    let mut _2: *const [i32; C];
+    let mut _3: *const [i32];
+    let mut _4: usize;
 
     bb0: {
         _1 = [const 5_i32; C];
-        _2 = Len(_1);
-        _0 = copy _2;
+        _2 = &raw const _1;
+        _3 = copy _2 as *const [i32] (PointerCoercion(Unsize, AsCast));
+        _4 = PtrMetadata(copy _3);
+        _0 = copy _4;
         return;
     }
 }
diff --git a/tests/mir-opt/building/custom/arrays.rs b/tests/mir-opt/building/custom/arrays.rs
index 4bd6f93e113..e9cdded4a0e 100644
--- a/tests/mir-opt/building/custom/arrays.rs
+++ b/tests/mir-opt/building/custom/arrays.rs
@@ -10,7 +10,9 @@ fn arrays<const C: usize>() -> usize {
     mir! {
         {
             let x = [5_i32; C];
-            let c = Len(x);
+            let y = &raw const x;
+            let z = CastUnsize::<_, *const [i32]>(y);
+            let c = PtrMetadata(z);
             RET = c;
             Return()
         }
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff
new file mode 100644
index 00000000000..fd9ef54fe77
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-abort.diff
@@ -0,0 +1,77 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: u32;
+      let mut _2: &[u32];
+      let mut _3: &[u32; 3];
+      let _4: &[u32; 3];
+      let _5: [u32; 3];
+      let _6: usize;
+      let mut _7: usize;
+      let mut _8: bool;
+      let mut _10: &[u32];
+      let _11: usize;
+      let mut _12: usize;
+      let mut _13: bool;
+      let mut _14: &[u32; 3];
+      scope 1 {
+          debug local => _1;
+          let _9: u32;
+          scope 2 {
+              debug constant => _9;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          _14 = const main::promoted[0];
+          _4 = copy _14;
+          _3 = copy _4;
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
+          StorageDead(_3);
+          StorageLive(_6);
+          _6 = const 1_usize;
+-         _7 = PtrMetadata(copy _2);
+-         _8 = Lt(copy _6, copy _7);
+-         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, copy _6) -> [success: bb1, unwind unreachable];
++         _7 = const 3_usize;
++         _8 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+-         _1 = copy (*_2)[_6];
++         _1 = copy (*_2)[1 of 2];
+          StorageDead(_6);
+          StorageDead(_4);
+          StorageDead(_2);
+          StorageLive(_9);
+          StorageLive(_10);
+          _10 = const main::SLICE;
+          StorageLive(_11);
+          _11 = const 1_usize;
+-         _12 = PtrMetadata(copy _10);
+-         _13 = Lt(copy _11, copy _12);
+-         assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, copy _11) -> [success: bb2, unwind unreachable];
++         _12 = const 3_usize;
++         _13 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb2, unwind unreachable];
+      }
+  
+      bb2: {
+-         _9 = copy (*_10)[_11];
++         _9 = copy (*_10)[1 of 2];
+          StorageDead(_11);
+          StorageDead(_10);
+          _0 = const ();
+          StorageDead(_9);
+          StorageDead(_1);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff
new file mode 100644
index 00000000000..1fec08c2562
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.32bit.panic-unwind.diff
@@ -0,0 +1,77 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: u32;
+      let mut _2: &[u32];
+      let mut _3: &[u32; 3];
+      let _4: &[u32; 3];
+      let _5: [u32; 3];
+      let _6: usize;
+      let mut _7: usize;
+      let mut _8: bool;
+      let mut _10: &[u32];
+      let _11: usize;
+      let mut _12: usize;
+      let mut _13: bool;
+      let mut _14: &[u32; 3];
+      scope 1 {
+          debug local => _1;
+          let _9: u32;
+          scope 2 {
+              debug constant => _9;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          _14 = const main::promoted[0];
+          _4 = copy _14;
+          _3 = copy _4;
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
+          StorageDead(_3);
+          StorageLive(_6);
+          _6 = const 1_usize;
+-         _7 = PtrMetadata(copy _2);
+-         _8 = Lt(copy _6, copy _7);
+-         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, copy _6) -> [success: bb1, unwind continue];
++         _7 = const 3_usize;
++         _8 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb1, unwind continue];
+      }
+  
+      bb1: {
+-         _1 = copy (*_2)[_6];
++         _1 = copy (*_2)[1 of 2];
+          StorageDead(_6);
+          StorageDead(_4);
+          StorageDead(_2);
+          StorageLive(_9);
+          StorageLive(_10);
+          _10 = const main::SLICE;
+          StorageLive(_11);
+          _11 = const 1_usize;
+-         _12 = PtrMetadata(copy _10);
+-         _13 = Lt(copy _11, copy _12);
+-         assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, copy _11) -> [success: bb2, unwind continue];
++         _12 = const 3_usize;
++         _13 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb2, unwind continue];
+      }
+  
+      bb2: {
+-         _9 = copy (*_10)[_11];
++         _9 = copy (*_10)[1 of 2];
+          StorageDead(_11);
+          StorageDead(_10);
+          _0 = const ();
+          StorageDead(_9);
+          StorageDead(_1);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff
new file mode 100644
index 00000000000..fd9ef54fe77
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-abort.diff
@@ -0,0 +1,77 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: u32;
+      let mut _2: &[u32];
+      let mut _3: &[u32; 3];
+      let _4: &[u32; 3];
+      let _5: [u32; 3];
+      let _6: usize;
+      let mut _7: usize;
+      let mut _8: bool;
+      let mut _10: &[u32];
+      let _11: usize;
+      let mut _12: usize;
+      let mut _13: bool;
+      let mut _14: &[u32; 3];
+      scope 1 {
+          debug local => _1;
+          let _9: u32;
+          scope 2 {
+              debug constant => _9;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          _14 = const main::promoted[0];
+          _4 = copy _14;
+          _3 = copy _4;
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
+          StorageDead(_3);
+          StorageLive(_6);
+          _6 = const 1_usize;
+-         _7 = PtrMetadata(copy _2);
+-         _8 = Lt(copy _6, copy _7);
+-         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, copy _6) -> [success: bb1, unwind unreachable];
++         _7 = const 3_usize;
++         _8 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+-         _1 = copy (*_2)[_6];
++         _1 = copy (*_2)[1 of 2];
+          StorageDead(_6);
+          StorageDead(_4);
+          StorageDead(_2);
+          StorageLive(_9);
+          StorageLive(_10);
+          _10 = const main::SLICE;
+          StorageLive(_11);
+          _11 = const 1_usize;
+-         _12 = PtrMetadata(copy _10);
+-         _13 = Lt(copy _11, copy _12);
+-         assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, copy _11) -> [success: bb2, unwind unreachable];
++         _12 = const 3_usize;
++         _13 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb2, unwind unreachable];
+      }
+  
+      bb2: {
+-         _9 = copy (*_10)[_11];
++         _9 = copy (*_10)[1 of 2];
+          StorageDead(_11);
+          StorageDead(_10);
+          _0 = const ();
+          StorageDead(_9);
+          StorageDead(_1);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff
new file mode 100644
index 00000000000..1fec08c2562
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.main.DataflowConstProp.64bit.panic-unwind.diff
@@ -0,0 +1,77 @@
+- // MIR for `main` before DataflowConstProp
++ // MIR for `main` after DataflowConstProp
+  
+  fn main() -> () {
+      let mut _0: ();
+      let _1: u32;
+      let mut _2: &[u32];
+      let mut _3: &[u32; 3];
+      let _4: &[u32; 3];
+      let _5: [u32; 3];
+      let _6: usize;
+      let mut _7: usize;
+      let mut _8: bool;
+      let mut _10: &[u32];
+      let _11: usize;
+      let mut _12: usize;
+      let mut _13: bool;
+      let mut _14: &[u32; 3];
+      scope 1 {
+          debug local => _1;
+          let _9: u32;
+          scope 2 {
+              debug constant => _9;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_1);
+          StorageLive(_2);
+          StorageLive(_3);
+          StorageLive(_4);
+          _14 = const main::promoted[0];
+          _4 = copy _14;
+          _3 = copy _4;
+          _2 = move _3 as &[u32] (PointerCoercion(Unsize, AsCast));
+          StorageDead(_3);
+          StorageLive(_6);
+          _6 = const 1_usize;
+-         _7 = PtrMetadata(copy _2);
+-         _8 = Lt(copy _6, copy _7);
+-         assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, copy _6) -> [success: bb1, unwind continue];
++         _7 = const 3_usize;
++         _8 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb1, unwind continue];
+      }
+  
+      bb1: {
+-         _1 = copy (*_2)[_6];
++         _1 = copy (*_2)[1 of 2];
+          StorageDead(_6);
+          StorageDead(_4);
+          StorageDead(_2);
+          StorageLive(_9);
+          StorageLive(_10);
+          _10 = const main::SLICE;
+          StorageLive(_11);
+          _11 = const 1_usize;
+-         _12 = PtrMetadata(copy _10);
+-         _13 = Lt(copy _11, copy _12);
+-         assert(move _13, "index out of bounds: the length is {} but the index is {}", move _12, copy _11) -> [success: bb2, unwind continue];
++         _12 = const 3_usize;
++         _13 = const true;
++         assert(const true, "index out of bounds: the length is {} but the index is {}", const 3_usize, const 1_usize) -> [success: bb2, unwind continue];
+      }
+  
+      bb2: {
+-         _9 = copy (*_10)[_11];
++         _9 = copy (*_10)[1 of 2];
+          StorageDead(_11);
+          StorageDead(_10);
+          _0 = const ();
+          StorageDead(_9);
+          StorageDead(_1);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/dataflow-const-prop/slice_len.rs b/tests/mir-opt/dataflow-const-prop/slice_len.rs
new file mode 100644
index 00000000000..e0e68f9fde5
--- /dev/null
+++ b/tests/mir-opt/dataflow-const-prop/slice_len.rs
@@ -0,0 +1,34 @@
+// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
+//@ test-mir-pass: DataflowConstProp
+//@ compile-flags: -Zmir-enable-passes=+InstSimplify-after-simplifycfg
+// EMIT_MIR_FOR_EACH_BIT_WIDTH
+
+// EMIT_MIR slice_len.main.DataflowConstProp.diff
+
+// CHECK-LABEL: fn main(
+fn main() {
+    // CHECK: debug local => [[local:_.*]];
+    // CHECK: debug constant => [[constant:_.*]];
+
+    // CHECK-NOT: {{_.*}} = Len(
+    // CHECK-NOT: {{_.*}} = Lt(
+    // CHECK-NOT: assert(move _
+    // CHECK: {{_.*}} = const 3_usize;
+    // CHECK: {{_.*}} = const true;
+    // CHECK: assert(const true,
+
+    // CHECK: [[local]] = copy (*{{_.*}})[1 of 2];
+    let local = (&[1u32, 2, 3] as &[u32])[1];
+
+    // CHECK-NOT: {{_.*}} = Len(
+    // CHECK-NOT: {{_.*}} = Lt(
+    // CHECK-NOT: assert(move _
+    const SLICE: &[u32] = &[1, 2, 3];
+    // CHECK: {{_.*}} = const 3_usize;
+    // CHECK: {{_.*}} = const true;
+    // CHECK: assert(const true,
+
+    // CHECK-NOT: [[constant]] = {{copy|move}} (*{{_.*}})[_
+    // CHECK: [[constant]] = copy (*{{_.*}})[1 of 2];
+    let constant = SLICE[1];
+}
diff --git a/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff b/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff
index 0d0477fe772..59b65a52f4e 100644
--- a/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff
+++ b/tests/mir-opt/gvn.array_len.GVN.panic-abort.diff
@@ -12,8 +12,7 @@
       }
   
       bb0: {
--         StorageLive(_2);
-+         nop;
+          StorageLive(_2);
           StorageLive(_3);
           _3 = &(*_1);
           _2 = move _3 as &[i32] (PointerCoercion(Unsize, Implicit));
@@ -23,8 +22,7 @@
 -         _0 = PtrMetadata(move _4);
 +         _0 = const 42_usize;
           StorageDead(_4);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           return;
       }
   }
diff --git a/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff b/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff
index 0d0477fe772..59b65a52f4e 100644
--- a/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff
+++ b/tests/mir-opt/gvn.array_len.GVN.panic-unwind.diff
@@ -12,8 +12,7 @@
       }
   
       bb0: {
--         StorageLive(_2);
-+         nop;
+          StorageLive(_2);
           StorageLive(_3);
           _3 = &(*_1);
           _2 = move _3 as &[i32] (PointerCoercion(Unsize, Implicit));
@@ -23,8 +22,7 @@
 -         _0 = PtrMetadata(move _4);
 +         _0 = const 42_usize;
           StorageDead(_4);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           return;
       }
   }
diff --git a/tests/mir-opt/instsimplify/combine_array_len.norm2.InstSimplify-after-simplifycfg.panic-abort.diff b/tests/mir-opt/instsimplify/combine_array_len.norm2.InstSimplify-after-simplifycfg.panic-abort.diff
new file mode 100644
index 00000000000..feba0fe7c4a
--- /dev/null
+++ b/tests/mir-opt/instsimplify/combine_array_len.norm2.InstSimplify-after-simplifycfg.panic-abort.diff
@@ -0,0 +1,71 @@
+- // MIR for `norm2` before InstSimplify-after-simplifycfg
++ // MIR for `norm2` after InstSimplify-after-simplifycfg
+  
+  fn norm2(_1: [f32; 2]) -> f32 {
+      debug x => _1;
+      let mut _0: f32;
+      let _2: f32;
+      let _3: usize;
+      let mut _4: bool;
+      let _6: usize;
+      let mut _7: bool;
+      let mut _8: f32;
+      let mut _9: f32;
+      let mut _10: f32;
+      let mut _11: f32;
+      let mut _12: f32;
+      let mut _13: f32;
+      scope 1 {
+          debug a => _2;
+          let _5: f32;
+          scope 2 {
+              debug b => _5;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          StorageLive(_3);
+          _3 = const 0_usize;
+          _4 = Lt(copy _3, const 2_usize);
+          assert(move _4, "index out of bounds: the length is {} but the index is {}", const 2_usize, copy _3) -> [success: bb1, unwind unreachable];
+      }
+  
+      bb1: {
+          _2 = copy _1[_3];
+          StorageDead(_3);
+          StorageLive(_5);
+          StorageLive(_6);
+          _6 = const 1_usize;
+          _7 = Lt(copy _6, const 2_usize);
+          assert(move _7, "index out of bounds: the length is {} but the index is {}", const 2_usize, copy _6) -> [success: bb2, unwind unreachable];
+      }
+  
+      bb2: {
+          _5 = copy _1[_6];
+          StorageDead(_6);
+          StorageLive(_8);
+          StorageLive(_9);
+          _9 = copy _2;
+          StorageLive(_10);
+          _10 = copy _2;
+          _8 = Mul(move _9, move _10);
+          StorageDead(_10);
+          StorageDead(_9);
+          StorageLive(_11);
+          StorageLive(_12);
+          _12 = copy _5;
+          StorageLive(_13);
+          _13 = copy _5;
+          _11 = Mul(move _12, move _13);
+          StorageDead(_13);
+          StorageDead(_12);
+          _0 = Add(move _8, move _11);
+          StorageDead(_11);
+          StorageDead(_8);
+          StorageDead(_5);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/combine_array_len.norm2.InstSimplify-after-simplifycfg.panic-unwind.diff b/tests/mir-opt/instsimplify/combine_array_len.norm2.InstSimplify-after-simplifycfg.panic-unwind.diff
new file mode 100644
index 00000000000..0ccf6a825c4
--- /dev/null
+++ b/tests/mir-opt/instsimplify/combine_array_len.norm2.InstSimplify-after-simplifycfg.panic-unwind.diff
@@ -0,0 +1,71 @@
+- // MIR for `norm2` before InstSimplify-after-simplifycfg
++ // MIR for `norm2` after InstSimplify-after-simplifycfg
+  
+  fn norm2(_1: [f32; 2]) -> f32 {
+      debug x => _1;
+      let mut _0: f32;
+      let _2: f32;
+      let _3: usize;
+      let mut _4: bool;
+      let _6: usize;
+      let mut _7: bool;
+      let mut _8: f32;
+      let mut _9: f32;
+      let mut _10: f32;
+      let mut _11: f32;
+      let mut _12: f32;
+      let mut _13: f32;
+      scope 1 {
+          debug a => _2;
+          let _5: f32;
+          scope 2 {
+              debug b => _5;
+          }
+      }
+  
+      bb0: {
+          StorageLive(_2);
+          StorageLive(_3);
+          _3 = const 0_usize;
+          _4 = Lt(copy _3, const 2_usize);
+          assert(move _4, "index out of bounds: the length is {} but the index is {}", const 2_usize, copy _3) -> [success: bb1, unwind continue];
+      }
+  
+      bb1: {
+          _2 = copy _1[_3];
+          StorageDead(_3);
+          StorageLive(_5);
+          StorageLive(_6);
+          _6 = const 1_usize;
+          _7 = Lt(copy _6, const 2_usize);
+          assert(move _7, "index out of bounds: the length is {} but the index is {}", const 2_usize, copy _6) -> [success: bb2, unwind continue];
+      }
+  
+      bb2: {
+          _5 = copy _1[_6];
+          StorageDead(_6);
+          StorageLive(_8);
+          StorageLive(_9);
+          _9 = copy _2;
+          StorageLive(_10);
+          _10 = copy _2;
+          _8 = Mul(move _9, move _10);
+          StorageDead(_10);
+          StorageDead(_9);
+          StorageLive(_11);
+          StorageLive(_12);
+          _12 = copy _5;
+          StorageLive(_13);
+          _13 = copy _5;
+          _11 = Mul(move _12, move _13);
+          StorageDead(_13);
+          StorageDead(_12);
+          _0 = Add(move _8, move _11);
+          StorageDead(_11);
+          StorageDead(_8);
+          StorageDead(_5);
+          StorageDead(_2);
+          return;
+      }
+  }
+  
diff --git a/tests/mir-opt/instsimplify/combine_array_len.rs b/tests/mir-opt/instsimplify/combine_array_len.rs
new file mode 100644
index 00000000000..91f43f75689
--- /dev/null
+++ b/tests/mir-opt/instsimplify/combine_array_len.rs
@@ -0,0 +1,15 @@
+// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
+//@ test-mir-pass: InstSimplify-after-simplifycfg
+
+// EMIT_MIR combine_array_len.norm2.InstSimplify-after-simplifycfg.diff
+fn norm2(x: [f32; 2]) -> f32 {
+    // CHECK-LABEL: fn norm2(
+    // CHECK-NOT: Len(
+    let a = x[0];
+    let b = x[1];
+    a * a + b * b
+}
+
+fn main() {
+    assert_eq!(norm2([3.0, 4.0]), 5.0 * 5.0);
+}
diff --git a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff
index 08dee3697e0..5cf36b9aebf 100644
--- a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff
+++ b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-abort.diff
@@ -7,18 +7,16 @@
       let _2: &[T];
       let _3: &[T; 3];
       let _4: [T; 3];
-      let mut _5: usize;
-      let mut _6: bool;
-      let mut _10: !;
+      let mut _8: !;
       scope 1 {
           debug v => _2;
+          let _5: &T;
+          let _6: &T;
           let _7: &T;
-          let _8: &T;
-          let _9: &T;
           scope 2 {
-              debug v1 => _7;
-              debug v2 => _8;
-              debug v3 => _9;
+              debug v1 => _5;
+              debug v2 => _6;
+              debug v3 => _7;
           }
       }
   
@@ -27,25 +25,23 @@
           _4 = [copy _1, copy _1, copy _1];
           _3 = &_4;
           _2 = copy _3 as &[T] (PointerCoercion(Unsize, Implicit));
-          nop;
-          nop;
           goto -> bb2;
       }
   
       bb1: {
-          _10 = core::panicking::panic(const "internal error: entered unreachable code") -> unwind unreachable;
+          _8 = core::panicking::panic(const "internal error: entered unreachable code") -> unwind unreachable;
       }
   
       bb2: {
+          StorageLive(_5);
+          _5 = &(*_2)[0 of 3];
+          StorageLive(_6);
+          _6 = &(*_2)[1 of 3];
           StorageLive(_7);
-          _7 = &(*_2)[0 of 3];
-          StorageLive(_8);
-          _8 = &(*_2)[1 of 3];
-          StorageLive(_9);
-          _9 = &(*_2)[2 of 3];
-          StorageDead(_9);
-          StorageDead(_8);
+          _7 = &(*_2)[2 of 3];
           StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
           StorageDead(_4);
           return;
       }
diff --git a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff
index aa44a2ad532..0598a3aa3f1 100644
--- a/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff
+++ b/tests/mir-opt/issue_76432.test.SimplifyComparisonIntegral.panic-unwind.diff
@@ -7,18 +7,16 @@
       let _2: &[T];
       let _3: &[T; 3];
       let _4: [T; 3];
-      let mut _5: usize;
-      let mut _6: bool;
-      let mut _10: !;
+      let mut _8: !;
       scope 1 {
           debug v => _2;
+          let _5: &T;
+          let _6: &T;
           let _7: &T;
-          let _8: &T;
-          let _9: &T;
           scope 2 {
-              debug v1 => _7;
-              debug v2 => _8;
-              debug v3 => _9;
+              debug v1 => _5;
+              debug v2 => _6;
+              debug v3 => _7;
           }
       }
   
@@ -27,25 +25,23 @@
           _4 = [copy _1, copy _1, copy _1];
           _3 = &_4;
           _2 = copy _3 as &[T] (PointerCoercion(Unsize, Implicit));
-          nop;
-          nop;
           goto -> bb2;
       }
   
       bb1: {
-          _10 = core::panicking::panic(const "internal error: entered unreachable code") -> unwind continue;
+          _8 = core::panicking::panic(const "internal error: entered unreachable code") -> unwind continue;
       }
   
       bb2: {
+          StorageLive(_5);
+          _5 = &(*_2)[0 of 3];
+          StorageLive(_6);
+          _6 = &(*_2)[1 of 3];
           StorageLive(_7);
-          _7 = &(*_2)[0 of 3];
-          StorageLive(_8);
-          _8 = &(*_2)[1 of 3];
-          StorageLive(_9);
-          _9 = &(*_2)[2 of 3];
-          StorageDead(_9);
-          StorageDead(_8);
+          _7 = &(*_2)[2 of 3];
           StorageDead(_7);
+          StorageDead(_6);
+          StorageDead(_5);
           StorageDead(_4);
           return;
       }
diff --git a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff
index 180a7db0297..714a12804e6 100644
--- a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-abort.diff
@@ -18,8 +18,7 @@
       }
   
       bb0: {
--         StorageLive(_2);
-+         nop;
+          StorageLive(_2);
           StorageLive(_3);
           StorageLive(_4);
           _4 = &_1;
@@ -41,8 +40,7 @@
       bb1: {
           StorageDead(_6);
           StorageDead(_5);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           StorageDead(_7);
           return;
       }
diff --git a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff
index 180a7db0297..714a12804e6 100644
--- a/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_len_raw.GVN.panic-unwind.diff
@@ -18,8 +18,7 @@
       }
   
       bb0: {
--         StorageLive(_2);
-+         nop;
+          StorageLive(_2);
           StorageLive(_3);
           StorageLive(_4);
           _4 = &_1;
@@ -41,8 +40,7 @@
       bb1: {
           StorageDead(_6);
           StorageDead(_5);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           StorageDead(_7);
           return;
       }
diff --git a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff
index 49964f8b49e..b236b22f067 100644
--- a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff
+++ b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-abort.diff
@@ -17,8 +17,7 @@
       }
   
       bb0: {
--         StorageLive(_2);
-+         nop;
+          StorageLive(_2);
           StorageLive(_3);
           StorageLive(_4);
           _4 = &mut _1;
@@ -38,8 +37,7 @@
       bb1: {
           StorageDead(_6);
           StorageDead(_5);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           return;
       }
   }
diff --git a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff
index 49964f8b49e..b236b22f067 100644
--- a/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff
+++ b/tests/mir-opt/lower_array_len.array_len_reborrow.GVN.panic-unwind.diff
@@ -17,8 +17,7 @@
       }
   
       bb0: {
--         StorageLive(_2);
-+         nop;
+          StorageLive(_2);
           StorageLive(_3);
           StorageLive(_4);
           _4 = &mut _1;
@@ -38,8 +37,7 @@
       bb1: {
           StorageDead(_6);
           StorageDead(_5);
--         StorageDead(_2);
-+         nop;
+          StorageDead(_2);
           return;
       }
   }
diff --git a/tests/mir-opt/reference_prop.debuginfo.ReferencePropagation.diff b/tests/mir-opt/reference_prop.debuginfo.ReferencePropagation.diff
index 3da795b61f9..375b6096d88 100644
--- a/tests/mir-opt/reference_prop.debuginfo.ReferencePropagation.diff
+++ b/tests/mir-opt/reference_prop.debuginfo.ReferencePropagation.diff
@@ -17,14 +17,15 @@
       let mut _15: std::ops::RangeFull;
       let mut _16: usize;
       let mut _17: usize;
-      let mut _18: bool;
-      let _23: &&mut u8;
-      let _24: &mut u8;
-      let mut _25: debuginfo::T;
+      let mut _18: usize;
+      let mut _19: bool;
+      let _24: &&mut u8;
+      let _25: &mut u8;
+      let mut _26: debuginfo::T;
       scope 1 {
           debug ref_mut_u8 => _1;
           let _3: &u8;
-          let mut _28: &debuginfo::T;
+          let mut _29: &debuginfo::T;
           scope 2 {
               debug field => _3;
               let _5: &u8;
@@ -32,22 +33,22 @@
 -                 debug reborrow => _5;
 +                 debug reborrow => _1;
                   let _9: &i32;
-                  let _22: &&&mut u8;
-                  let mut _27: &std::option::Option<i32>;
+                  let _23: &&&mut u8;
+                  let mut _28: &std::option::Option<i32>;
                   scope 4 {
                       debug variant_field => _9;
                   }
                   scope 5 {
-                      debug constant_index => _19;
-                      debug subslice => _20;
-                      debug constant_index_from_end => _21;
-                      let _19: &i32;
-                      let _20: &[i32];
-                      let _21: &i32;
-                      let mut _26: &[i32; 10];
+                      debug constant_index => _20;
+                      debug subslice => _21;
+                      debug constant_index_from_end => _22;
+                      let _20: &i32;
+                      let _21: &[i32];
+                      let _22: &i32;
+                      let mut _27: &[i32; 10];
                   }
                   scope 6 {
-                      debug multiple_borrow => _22;
+                      debug multiple_borrow => _23;
                   }
               }
           }
@@ -59,8 +60,8 @@
           _2 = const 5_u8;
           _1 = &mut _2;
           StorageLive(_3);
-          _28 = const debuginfo::promoted[2];
-          _3 = &((*_28).0: u8);
+          _29 = const debuginfo::promoted[2];
+          _3 = &((*_29).0: u8);
 -         StorageLive(_5);
 -         _5 = &(*_1);
 -         StorageLive(_6);
@@ -76,8 +77,8 @@
   
       bb2: {
           StorageLive(_9);
-          _27 = const debuginfo::promoted[1];
-          _9 = &(((*_27) as Some).0: i32);
+          _28 = const debuginfo::promoted[1];
+          _9 = &(((*_28) as Some).0: i32);
 -         _6 = const ();
           StorageDead(_9);
           goto -> bb4;
@@ -92,11 +93,11 @@
           StorageDead(_7);
 -         StorageDead(_6);
 -         StorageLive(_10);
--         StorageLive(_11);
+          StorageLive(_11);
 -         StorageLive(_12);
           StorageLive(_13);
-          _26 = const debuginfo::promoted[0];
-          _13 = &(*_26);
+          _27 = const debuginfo::promoted[0];
+          _13 = &(*_27);
           StorageLive(_15);
           _15 = RangeFull;
 -         _12 = <[i32; 10] as Index<RangeFull>>::index(move _13, move _15) -> [return: bb5, unwind continue];
@@ -106,28 +107,28 @@
       bb5: {
           StorageDead(_15);
           StorageDead(_13);
--         _11 = &(*_12);
--         _16 = Len((*_11));
-+         _16 = Len((*_12));
-          _17 = const 3_usize;
-          _18 = Ge(move _16, move _17);
-          switchInt(move _18) -> [0: bb7, otherwise: bb6];
+          _11 = &(*_12);
+          _17 = PtrMetadata(copy _11);
+          _16 = move _17;
+          _18 = const 3_usize;
+          _19 = Ge(move _16, move _18);
+          switchInt(move _19) -> [0: bb7, otherwise: bb6];
       }
   
       bb6: {
-          StorageLive(_19);
--         _19 = &(*_11)[1 of 3];
-+         _19 = &(*_12)[1 of 3];
           StorageLive(_20);
--         _20 = &(*_11)[2:-1];
-+         _20 = &(*_12)[2:-1];
+-         _20 = &(*_11)[1 of 3];
++         _20 = &(*_12)[1 of 3];
           StorageLive(_21);
--         _21 = &(*_11)[-1 of 3];
+-         _21 = &(*_11)[2:-1];
++         _21 = &(*_12)[2:-1];
+          StorageLive(_22);
+-         _22 = &(*_11)[-1 of 3];
 -         _10 = const ();
-+         _21 = &(*_12)[-1 of 3];
++         _22 = &(*_12)[-1 of 3];
+          StorageDead(_22);
           StorageDead(_21);
           StorageDead(_20);
-          StorageDead(_19);
           goto -> bb8;
       }
   
@@ -138,21 +139,21 @@
   
       bb8: {
 -         StorageDead(_12);
--         StorageDead(_11);
+          StorageDead(_11);
 -         StorageDead(_10);
-          StorageLive(_22);
           StorageLive(_23);
           StorageLive(_24);
           StorageLive(_25);
-          _25 = T(const 6_u8);
-          _24 = &mut (_25.0: u8);
+          StorageLive(_26);
+          _26 = T(const 6_u8);
+          _25 = &mut (_26.0: u8);
+          _24 = &_25;
           _23 = &_24;
-          _22 = &_23;
           _0 = const ();
+          StorageDead(_26);
           StorageDead(_25);
           StorageDead(_24);
           StorageDead(_23);
-          StorageDead(_22);
 -         StorageDead(_5);
           StorageDead(_3);
           StorageDead(_2);