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

This reverts commit e108481, reversing
changes made to 303e8bd.

(cherry picked from commit ca1c17c)

Author: lqd

compiler/rustc_borrowck/src/lib.rs

@@ -828,6 +828,7 @@ use self::ReadOrWrite::{Activation, Read, Reservation, Write};
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 enum ArtificialField {
+    ArrayLength,
     FakeBorrow,
 }
 
@@ -1345,11 +1346,16 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
                 );
             }
 
-            &Rvalue::Discriminant(place) => {
+            &(Rvalue::Len(place) | Rvalue::Discriminant(place)) => {
+                let af = match *rvalue {
+                    Rvalue::Len(..) => Some(ArtificialField::ArrayLength),
+                    Rvalue::Discriminant(..) => None,
+                    _ => unreachable!(),
+                };
                 self.access_place(
                     location,
                     (place, span),
-                    (Shallow(None), Read(ReadKind::Copy)),
+                    (Shallow(af), Read(ReadKind::Copy)),
                     LocalMutationIsAllowed::No,
                     state,
                 );

compiler/rustc_borrowck/src/places_conflict.rs

@@ -203,7 +203,8 @@ fn place_components_conflict<'tcx>(
             let base_ty = base.ty(body, tcx).ty;
 
             match (elem, base_ty.kind(), access) {
-                (_, _, Shallow(Some(ArtificialField::FakeBorrow))) => {
+                (_, _, Shallow(Some(ArtificialField::ArrayLength)))
+                | (_, _, 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

@@ -298,11 +298,16 @@ impl<'a, 'tcx> LoanInvalidationsGenerator<'a, 'tcx> {
                 self.consume_operand(location, op);
             }
 
-            &Rvalue::Discriminant(place) => {
+            &(Rvalue::Len(place) | Rvalue::Discriminant(place)) => {
+                let af = match rvalue {
+                    Rvalue::Len(..) => Some(ArtificialField::ArrayLength),
+                    Rvalue::Discriminant(..) => None,
+                    _ => unreachable!(),
+                };
                 self.access_place(
                     location,
                     place,
-                    (Shallow(None), Read(ReadKind::Copy)),
+                    (Shallow(af), Read(ReadKind::Copy)),
                     LocalMutationIsAllowed::No,
                 );
             }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -2221,6 +2221,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
             Rvalue::RawPtr(..)
             | Rvalue::ThreadLocalRef(..)
+            | Rvalue::Len(..)
             | Rvalue::Discriminant(..)
             | Rvalue::NullaryOp(NullOp::OffsetOf(..), _) => {}
         }
@@ -2236,6 +2237,7 @@ 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

@@ -828,6 +828,12 @@ 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};
@@ -593,6 +593,14 @@ 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() =>
             {
@@ -792,6 +800,24 @@ 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,
@@ -1063,6 +1089,7 @@ 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

@@ -488,7 +488,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
             Rvalue::Use(_)
             | Rvalue::CopyForDeref(..)
             | Rvalue::Repeat(..)
-            | Rvalue::Discriminant(..) => {}
+            | Rvalue::Discriminant(..)
+            | Rvalue::Len(_) => {}
 
             Rvalue::Aggregate(kind, ..) => {
                 if let AggregateKind::Coroutine(def_id, ..) = kind.as_ref()

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -230,7 +230,9 @@ where
             Q::in_any_value_of_ty(cx, rvalue.ty(cx.body, cx.tcx))
         }
 
-        Rvalue::Discriminant(place) => in_place::<Q, _>(cx, in_local, place.as_ref()),
+        Rvalue::Discriminant(place) | Rvalue::Len(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

@@ -197,6 +197,7 @@ 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, interp_ok, throw_ub,
+    Projectable, Scalar, interp_ok, throw_ub,
 };
 use crate::util;
 
@@ -218,6 +218,12 @@ 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)?;