Rollup merge of #98688 - RalfJung:from-mplace, r=oli-obk

interpret: add From<&MplaceTy> for PlaceTy

We have a similar instance for `&MPlaceTy` to `OpTy`. Also add the same for `&mut`.

This avoids having to write `&(*place).into()`, which we have a few times here and at least twice in Miri (and it comes up again in my current patch).

r? ```@oli-obk```

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -346,7 +346,7 @@ fn valtree_into_mplace<'tcx>(
         ty::FnDef(_, _) => {
             ecx.write_immediate(
                 Immediate::Scalar(ScalarMaybeUninit::Scalar(Scalar::ZST)),
-                &(*place).into(),
+                &place.into(),
             )
             .unwrap();
         }
@@ -355,7 +355,7 @@ fn valtree_into_mplace<'tcx>(
             debug!("writing trivial valtree {:?} to place {:?}", scalar_int, place);
             ecx.write_immediate(
                 Immediate::Scalar(ScalarMaybeUninit::Scalar(scalar_int.into())),
-                &(*place).into(),
+                &place.into(),
             )
             .unwrap();
         }
@@ -382,7 +382,7 @@ fn valtree_into_mplace<'tcx>(
             };
             debug!(?imm);
 
-            ecx.write_immediate(imm, &(*place).into()).unwrap();
+            ecx.write_immediate(imm, &place.into()).unwrap();
         }
         ty::Adt(_, _) | ty::Tuple(_) | ty::Array(_, _) | ty::Str | ty::Slice(_) => {
             let branches = valtree.unwrap_branch();
@@ -464,11 +464,11 @@ fn valtree_into_mplace<'tcx>(
 
             if let Some(variant_idx) = variant_idx {
                 // don't forget filling the place with the discriminant of the enum
-                ecx.write_discriminant(variant_idx, &(*place).into()).unwrap();
+                ecx.write_discriminant(variant_idx, &place.into()).unwrap();
             }
 
             debug!("dump of place after writing discriminant:");
-            dump_place(ecx, (*place).into());
+            dump_place(ecx, place.into());
         }
         _ => bug!("shouldn't have created a ValTree for {:?}", ty),
     }

compiler/rustc_const_eval/src/interpret/intern.rs

@@ -195,7 +195,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: CompileTimeMachine<'mir, 'tcx, const_eval::Memory
         let tcx = self.ecx.tcx;
         let ty = mplace.layout.ty;
         if let ty::Ref(_, referenced_ty, ref_mutability) = *ty.kind() {
-            let value = self.ecx.read_immediate(&(*mplace).into())?;
+            let value = self.ecx.read_immediate(&mplace.into())?;
             let mplace = self.ecx.ref_to_mplace(&value)?;
             assert_eq!(mplace.layout.ty, referenced_ty);
             // Handle trait object vtables.

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -204,6 +204,13 @@ impl<'tcx, Tag: Provenance> From<&'_ MPlaceTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
     }
 }
 
+impl<'tcx, Tag: Provenance> From<&'_ mut MPlaceTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
+    #[inline(always)]
+    fn from(mplace: &mut MPlaceTy<'tcx, Tag>) -> Self {
+        OpTy { op: Operand::Indirect(**mplace), layout: mplace.layout }
+    }
+}
+
 impl<'tcx, Tag: Provenance> From<ImmTy<'tcx, Tag>> for OpTy<'tcx, Tag> {
     #[inline(always)]
     fn from(val: ImmTy<'tcx, Tag>) -> Self {

compiler/rustc_const_eval/src/interpret/place.rs

@@ -118,7 +118,21 @@ impl<'tcx, Tag: Provenance> std::ops::Deref for MPlaceTy<'tcx, Tag> {
 impl<'tcx, Tag: Provenance> From<MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
     #[inline(always)]
     fn from(mplace: MPlaceTy<'tcx, Tag>) -> Self {
-        PlaceTy { place: Place::Ptr(mplace.mplace), layout: mplace.layout }
+        PlaceTy { place: Place::Ptr(*mplace), layout: mplace.layout }
+    }
+}
+
+impl<'tcx, Tag: Provenance> From<&'_ MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
+    #[inline(always)]
+    fn from(mplace: &MPlaceTy<'tcx, Tag>) -> Self {
+        PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout }
+    }
+}
+
+impl<'tcx, Tag: Provenance> From<&'_ mut MPlaceTy<'tcx, Tag>> for PlaceTy<'tcx, Tag> {
+    #[inline(always)]
+    fn from(mplace: &mut MPlaceTy<'tcx, Tag>) -> Self {
+        PlaceTy { place: Place::Ptr(**mplace), layout: mplace.layout }
     }
 }
 

compiler/rustc_const_eval/src/interpret/visitor.rs

@@ -92,7 +92,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> Value<'mir, 'tcx, M>
         &self,
         _ecx: &InterpCx<'mir, 'tcx, M>,
     ) -> InterpResult<'tcx, OpTy<'tcx, M::PointerTag>> {
-        Ok((*self).into())
+        Ok(self.into())
     }
 
     #[inline(always)]