Question

Translate these loops into C. Assume that the C level integer i is held in register $t1,$s2 holds the c level integer called result, and $s0 holds the base address of the integer MemArray.

addi $t1, $s0, 400

loop: lw $s1, 0($s0)

add $s2, $s2, $s1

lw $s1, 4($s0)

add $s2, $s2, $s1

addi $s0, $s0, 8

bne $t1, $s0, Loop

Answer 1

addi $t1, $s0, 400  # $t1 = &MemArray[100]
loop:
    lw $s1, 0($s0)  # $s1 = MemArray[0]
    add $s2, $s2, $s1   # result = result + MemArray[0]
    lw $s1, 4($s0)      # $s1 = MemArray[1]
    add $s2, $s2, $s1   # result = result + MemArray[1]
    addi $s0, $s0, 8    # MemArray += 2
    bne $t1, $s0, Loop  #

C code:
--------
int i = 0;
while (i < 100) {
    result += MemArray[i] + MemArray[i+1];
    i += 2;
}