ABS/XY: [ R1, R2 -> R0 ] [/ R3, R4 /]

        DEC     R3, R1, R2, DT_SIGNED;                               /* R3 = (- R2), R1, +-;     */
        CR      R0, R3, 0, CR_GE, DT_SIGNED;                         /* R0 = [>= 0], R3, +-;     */

IF:     BZ R0 ->.ELSE;                                               /* if (![= 0], R0) {        */
                SELECT R0, R3;                                       /*     R0 = R3;             */
        FWD ->.END;                                                  /* } else {                 */
ELSE:           LD R4, -1;                                           /*     R4 = -1;             */
                MUL R0, R3, R4, DT_SIGNED;                           /*     R0 = (* R4), R3, +-; */
END:    ;                                                            /* }                        */

RET
