@@ 119,6 119,28 @@ struct Reduce
                                 continue;
 
                     switch row.op
+                    case 'case
+                        a := getarg 0 Const
+                        b := getarg 1 Const
+                        aptr asz := 'data ('constof builder a)
+                        bptr bsz := 'data ('constof builder b)
+                        updates += 1
+                        value := if
+                            and (asz == bsz)
+                                (memcmp (aptr as rawstring) (bptr as rawstring) asz) == 0
+                            imply
+                                'wrap Module.Id.ConstEmpty 0
+                                Module.Id.Value
+                        else
+                            imply
+                                'wrap Module.Id.ConstUndef 0
+                                Module.Id.Value
+                        row := getrow& ()
+                        if (empty? row.deps)
+                            row.op = Operation.ALIAS
+                        else
+                            row.op = Operation.pass
+                        row.operands = typeinit value
                     pass 'iadd
                     pass 'isub
                     pass 'imul