Question

In MIPS assembly, write an assembly language version of the following C code segment:

int A[100], B[100];

for (i=1; i < 100; i++) {

A[i] = A[i-1] + B[i];

}

Answer 1

C code
int A[100], B[100];
for (i=1; i < 100; i++) {
   A[i] = A[i-1] + B[i];
}

Let the Base address of array A[] is stored in Register $s1
the Base address of array B[] is stored in Register $s2

MIPS code

   addi $t0, $0,100   //$t0 = 100
   addi $t1, $0, 1       //i = 1

Loop:
   slt $t2, $t1, $t0    //if(i<100) set $t2 = 1
   beq $t2, $0, Exit   //if($t2 = 0) branch to Exit
   sll $t2, $t1, 2       //$t2 = 4*i
   add $t3, $t2, $s1   //$t3 = address of A[i]
   add $t4, $t2, $s2   //$t4 = address of B[i]
   lw $t2, -4($t3)       //$t2 = A[i-1]
   lw $t4, 0($t4)       //$t4 = B[i]
   add $t2, $t2, $t4   //$t2 = A[i-1] + B[i]
   sw $t2, 0($t3)       //A[i] = A[i-1] + B[i]
   addi $t1, $t1, 1   // i = i + 1
   j Loop           //Jump to Loop
Exit: