Add+Use mir::BinOp::Cmp

compiler/rustc_middle/src/mir/syntax.rs

@@ -1444,6 +1444,8 @@ pub enum BinOp {
     Ge,
     /// The `>` operator (greater than)
     Gt,
+    /// The `<=>` operator (three-way comparison, like `Ord::cmp`)
+    Cmp,
     /// The `ptr.offset` operator
     Offset,
 }

compiler/rustc_middle/src/mir/tcx.rs

@@ -276,6 +276,11 @@ impl<'tcx> BinOp {
             &BinOp::Eq | &BinOp::Lt | &BinOp::Le | &BinOp::Ne | &BinOp::Ge | &BinOp::Gt => {
                 tcx.types.bool
             }
+            &BinOp::Cmp => {
+                // these should be integer-like types of the same size.
+                assert_eq!(lhs_ty, rhs_ty);
+                tcx.ty_ordering_enum(None)
+            }
         }
     }
 }
@@ -312,7 +317,8 @@ impl BinOp {
             BinOp::Gt => hir::BinOpKind::Gt,
             BinOp::Le => hir::BinOpKind::Le,
             BinOp::Ge => hir::BinOpKind::Ge,
-            BinOp::AddUnchecked
+            BinOp::Cmp
+            | BinOp::AddUnchecked
             | BinOp::SubUnchecked
             | BinOp::MulUnchecked
             | BinOp::ShlUnchecked

compiler/rustc_middle/src/ty/context.rs

@@ -905,6 +905,13 @@ impl<'tcx> TyCtxt<'tcx> {
         self.get_lang_items(())
     }
 
+    /// Gets a `Ty` representing the [`LangItem::OrderingEnum`]
+    #[track_caller]
+    pub fn ty_ordering_enum(self, span: Option<Span>) -> Ty<'tcx> {
+        let ordering_enum = self.require_lang_item(hir::LangItem::OrderingEnum, span);
+        self.type_of(ordering_enum).no_bound_vars().unwrap()
+    }
+
     /// Obtain the given diagnostic item's `DefId`. Use `is_diagnostic_item` if you just want to
     /// compare against another `DefId`, since `is_diagnostic_item` is cheaper.
     pub fn get_diagnostic_item(self, name: Symbol) -> Option<DefId> {