emit_movn_r
emit_movn_r(ctx, rd, MIPS_R_ZERO, hi(rs)); /* rd = 0 if rsh */
emit_movn_r(ctx, rd, MIPS_R_ZERO, tmp); /* rd = 0 if tmp != 0 */
emit_movn_r(ctx, t1, t2, rd); /* t1 = rd ? t2 : t1 */
emit_movn_r(ctx, t1, MIPS_R_ZERO, cmp); /* t1 = 0 if cmp != 0 */
emit_movn_r(ctx, t1, t2, rd); /* t1 = rd ? t2 : t1 */
emit_movn_r(ctx, t1, MIPS_R_ZERO, t3); /* t1 = 0 if t3 != 0 */