Skip reinterning if nothing changed

Author: oli-obk

compiler/rustc_codegen_cranelift/src/value_and_place.rs

@@ -674,14 +674,6 @@ impl<'tcx> CPlace<'tcx> {
         }
     }
 
-    pub(crate) fn place_opaque_cast(
-        self,
-        fx: &mut FunctionCx<'_, '_, 'tcx>,
-        ty: Ty<'tcx>,
-    ) -> CPlace<'tcx> {
-        CPlace { inner: self.inner, layout: fx.layout_of(ty) }
-    }
-
     pub(crate) fn place_field(
         self,
         fx: &mut FunctionCx<'_, '_, 'tcx>,

compiler/rustc_const_eval/src/interpret/projection.rs

@@ -316,7 +316,9 @@ where
     {
         use rustc_middle::mir::ProjectionElem::*;
         Ok(match proj_elem {
-            OpaqueCast(ty) => bug!("OpaqueCast({ty}) encountered after borrowck"),
+            OpaqueCast(ty) => {
+                span_bug!(self.cur_span(), "OpaqueCast({ty}) encountered after borrowck")
+            }
             Field(field, _) => self.project_field(base, field.index())?,
             Downcast(_, variant) => self.project_downcast(base, variant)?,
             Deref => self.deref_pointer(&base.to_op(self)?)?.into(),

compiler/rustc_mir_transform/src/reveal_all.rs

@@ -32,6 +32,10 @@ impl<'tcx> MutVisitor<'tcx> for RevealAllVisitor<'tcx> {
         _context: PlaceContext,
         _location: Location,
     ) {
+        // Performance optimization: don't reintern if there is no `OpaqueCast` to remove.
+        if place.projection.iter().all(|elem| !matches!(elem, ProjectionElem::OpaqueCast(_))) {
+            return;
+        }
         // `OpaqueCast` projections are only needed if there are opaque types on which projections are performed.
         // After the `RevealAll` pass, all opaque types are replaced with their hidden types, so we don't need these
         // projections anymore.