mir-opt: Replace clone on primitives with copy

We can't do it for everything, but it would be nice to at least stop making calls to clone methods in debug from things like derived-clones.

compiler/rustc_middle/src/mir/mod.rs

@@ -1915,6 +1915,27 @@ impl<'tcx> Place<'tcx> {
             (base, proj)
         })
     }
+
+    /// Generates a new place by appending `more_projections` to the existing ones
+    /// and interning the result.
+    pub fn project_deeper(self, more_projections: &[PlaceElem<'tcx>], tcx: TyCtxt<'tcx>) -> Self {
+        if more_projections.is_empty() {
+            return self;
+        }
+
+        let mut v: Vec<PlaceElem<'tcx>>;
+
+        let new_projections = if self.projection.is_empty() {
+            more_projections
+        } else {
+            v = Vec::with_capacity(self.projection.len() + more_projections.len());
+            v.extend(self.projection);
+            v.extend(more_projections);
+            &v
+        };
+
+        Place { local: self.local, projection: tcx.intern_place_elems(new_projections) }
+    }
 }
 
 impl From<Local> for Place<'_> {
@@ -2187,6 +2208,15 @@ impl<'tcx> Operand<'tcx> {
             Operand::Copy(_) | Operand::Move(_) => None,
         }
     }
+
+    /// Gets the `ty::FnDef` from an operand if it's a constant function item.
+    ///
+    /// While this is unlikely in general, it's the normal case of what you'll
+    /// find as the `func` in a [`TerminatorKind::Call`].
+    pub fn const_fn_def(&self) -> Option<(DefId, SubstsRef<'tcx>)> {
+        let const_ty = self.constant()?.literal.const_for_ty()?.ty();
+        if let ty::FnDef(def_id, substs) = *const_ty.kind() { Some((def_id, substs)) } else { None }
+    }
 }
 
 ///////////////////////////////////////////////////////////////////////////