add $t1,$t2,$t3
lw $s1,3($s3)
addu $t1,$t2,$t2
jr $t3
andi $t2,$t3,3
sb $t3,3($t2)
sll $t1,$t2,3
or $t3,$t1,$s0
sll $s0,$s0,3
add $t1,$t2,$t3
jr $t0