Auto merge of #134330 - scottmcm:no-more-rvalue-len, r=matthewjasper

Delete `Rvalue::Len` 🎉

Everything's moved to `PtrMetadata`, so we can get rid of the `Len` variant now.

~~Depends on #134326, so draft until that lands~~ Ready!

r? mir

Author: bors

compiler/rustc_borrowck/src/lib.rs

@@ -820,7 +820,6 @@ use self::ReadOrWrite::{Activation, Read, Reservation, Write};
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 enum ArtificialField {
-    ArrayLength,
     FakeBorrow,
 }
 
@@ -1268,16 +1267,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                 );
             }
 
-            &(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, span),
-                    (Shallow(af), Read(ReadKind::Copy)),
+                    (Shallow(None), Read(ReadKind::Copy)),
                     LocalMutationIsAllowed::No,
                     state,
                 );

compiler/rustc_borrowck/src/places_conflict.rs

@@ -203,8 +203,7 @@ fn place_components_conflict<'tcx>(
             let base_ty = base.ty(body, tcx).ty;
 
             match (elem, base_ty.kind(), access) {
-                (_, _, Shallow(Some(ArtificialField::ArrayLength)))
-                | (_, _, Shallow(Some(ArtificialField::FakeBorrow))) => {
+                (_, _, Shallow(Some(ArtificialField::FakeBorrow))) => {
                     // The array length is like additional fields on the
                     // type; it does not overlap any existing data there.
                     // Furthermore, if cannot actually be a prefix of any

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

@@ -299,16 +299,11 @@ 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

@@ -2427,7 +2427,6 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
             Rvalue::RawPtr(..)
             | Rvalue::ThreadLocalRef(..)
-            | Rvalue::Len(..)
             | Rvalue::Discriminant(..)
             | Rvalue::NullaryOp(NullOp::OffsetOf(..), _) => {}
         }
@@ -2443,7 +2442,6 @@ 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

@@ -828,12 +828,6 @@ fn codegen_stmt<'tcx>(
                         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

@@ -10,9 +10,9 @@ use rustc_session::config::OptLevel;
 use rustc_span::{DUMMY_SP, Span};
 use tracing::{debug, instrument};
 
+use super::FunctionCx;
 use super::operand::{OperandRef, OperandValue};
 use super::place::PlaceRef;
-use super::{FunctionCx, LocalRef};
 use crate::common::IntPredicate;
 use crate::traits::*;
 use crate::{MemFlags, base};
@@ -593,14 +593,6 @@ 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() =>
             {
@@ -800,24 +792,6 @@ 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() {
-            if let LocalRef::Operand(op) = self.locals[index] {
-                if 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,
@@ -1089,7 +1063,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             mir::Rvalue::Ref(..) |
             mir::Rvalue::CopyForDeref(..) |
             mir::Rvalue::RawPtr(..) |
-            mir::Rvalue::Len(..) |
             mir::Rvalue::Cast(..) | // (*)
             mir::Rvalue::ShallowInitBox(..) | // (*)
             mir::Rvalue::BinaryOp(..) |

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -488,8 +488,7 @@ 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

@@ -230,9 +230,7 @@ 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

@@ -15,7 +15,7 @@ use tracing::{info, instrument, trace};
 
 use super::{
     FnArg, FnVal, ImmTy, Immediate, InterpCx, InterpResult, Machine, MemPlaceMeta, PlaceTy,
-    Projectable, Scalar, interp_ok, throw_ub,
+    Projectable, interp_ok, throw_ub,
 };
 use crate::util;
 
@@ -218,12 +218,6 @@ 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

@@ -1068,7 +1068,6 @@ 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

@@ -424,7 +424,6 @@ impl<'tcx> Rvalue<'tcx> {
             | Rvalue::Ref(_, _, _)
             | Rvalue::ThreadLocalRef(_)
             | Rvalue::RawPtr(_, _)
-            | Rvalue::Len(_)
             | Rvalue::Cast(
                 CastKind::IntToInt
                 | CastKind::FloatToInt

compiler/rustc_middle/src/mir/syntax.rs

@@ -1351,16 +1351,6 @@ pub enum Rvalue<'tcx> {
     /// model.
     RawPtr(Mutability, 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/tcx.rs

@@ -175,7 +175,6 @@ impl<'tcx> Rvalue<'tcx> {
                 let place_ty = place.ty(local_decls, tcx).ty;
                 Ty::new_ptr(tcx, place_ty, mutability)
             }
-            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/visit.rs

@@ -695,14 +695,6 @@ 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

@@ -246,7 +246,6 @@ 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

@@ -635,7 +635,7 @@ 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

@@ -243,11 +243,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
 
             TestKind::Len { len, op } => {
-                let usize_ty = self.tcx.types.usize;
-                let actual = self.temp(usize_ty, test.span);
-
                 // actual = len(place)
-                self.cfg.push_assign(block, source_info, actual, Rvalue::Len(place));
+                let actual = self.len_of_slice_or_array(block, place, test.span, source_info);
 
                 // expected = <N>
                 let expected = self.push_usize(block, source_info, len);
@@ -262,7 +259,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     fail_block,
                     source_info,
                     op,
-                    Operand::Move(actual),
+                    actual,
                     Operand::Move(expected),
                 );
             }

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

@@ -411,7 +411,6 @@ 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 | NullOp::OffsetOf(..) | NullOp::UbChecks,
                 _,

compiler/rustc_mir_transform/src/dataflow_const_prop.rs

@@ -408,18 +408,6 @@ 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);

compiler/rustc_mir_transform/src/dest_prop.rs

@@ -574,7 +574,6 @@ impl WriteInfo {
                     | Rvalue::NullaryOp(_, _)
                     | Rvalue::Ref(_, _, _)
                     | Rvalue::RawPtr(_, _)
-                    | Rvalue::Len(_)
                     | Rvalue::Discriminant(_)
                     | Rvalue::CopyForDeref(_) => {}
                 }