          ELSE
                         IF OperandSize = 16
                              THEN
                                    IF second word on stack is not within stack limits
                                         THEN #SS(0); FI;
                                    IF first or second word on stack is not in canonical space
                                         THEN #SS(0); FI;
                              ELSE (* OperandSize = 64 *)
                                    IF first or second quadwo