addi $t0,$0,0 # $t0 = 0
addi $t1,$0,1 # $t1 = 1
add  $t2,$t1,$t0 # $t2 = $t1 + $t0 = 1 + 0 = 1
add  $t3,$t2,$t1 # $t3 = $t2 + $t1 = 1 + 1 = 2