Question

The MIPS assembly program given here is expected to find the sum of elements in array "myArr. Even though the code is syntactically correct, there are four bugs because of which the program is not glving the required output. With the help of the line numbers given identify the bug. Write the line number where you find the bug and give how the correct statement to eliminate the corresponding logical error (10 points partial points given for partial correct answers) 1 .data 2 myArr: .word 4,3,6,12,24,3,7,15 3 sum: word o 4 .bext 5 main: 6 li $t1,5 7 li $t3,0 8 9 loopi: 10 sw $a1, myArt(513) 11 add st4,514,5a1 12 sub st1,$t1,1 13 addi $t3,513,4 14 bitz sti, loopi jal Disp jal Exit 17 Disp: 18 li $v0,1 19 move sa 2,5t4 20 syscall 21 Ir sra 22 Exit: 23 li svo, 10 24 syscall 15 16

Answer 1

In this program, the value in $t1 is being used as a reference to the size of the array. I can tell this because, it is being decremented at every iteration in loop1, and it is the variable that is used in deciding whether to loop again or break out of the loop.

I find two logical errors:

1.)line 5: the intial content of $t1 is 5. But there are 8 elements in myArr. So, change this line to load 8 into $t1. The altered code will be : li $t1, 8

2.)line 14: The condition specified in this line is that to loop again if $t1 is less than zero. This is wrong, the loop will terminate after the first iteration. We have to loop again only if $t1 is greater than zero. Change this line to : bgtz $t1, loop1