C to MIPS Conversion Practice Set 1

Full MIPS solutions are provided below so you can blank out fields as needed.

Assumptions:

• Calling convention: arguments in $a0, $a1, $a2, return with jr $ra
• 32-bit MIPS
• short is 16 bits, int is 32 bits

1) Function f1

C code:

/* ptr: $a0, i: $a1, val: $a2 */
void f1(short *ptr, int i, unsigned val)
{
    int tmp = val / 32;
    ptr[tmp] = 5;
    ptr[i] = val % 4;
}

MIPS solution:

f1:
    s____     $t0, $__, 5
    sll       $t1, $t0, ___
    add       $t1, ____, $t1
    addi      $t2, $zero, ___
    ___       $t2, 0($t1)
    andi      $t3, $a2, ___
    sll       $t4, $a1, ___
    add       $t4, ___, $t4
    ___       $t3, 0($t4)
    jr        $ra

2) Function f2

C code:

/* data: $a0, val: $a1 */
void f2(int *data, int val)
{
    if (val > 0 && val < 8) {
        data[val] = data[0];
    }
    else {
        data[1] = 0x55AAAA55;
    }
}

MIPS solution:

f2:
    slt       $t0, $zero, $a1
    b__       $t0, $zero, L_else
    ____      $t1, $a1, 8
    b__       $t1, $zero, L_else
    sll       $t2, $a1, ___
    add       $t3, ___, $t2
    l__       $t4, ______
    s__       $t4, ______
    b         L_done
L_else:
    ___       $t5, 0x55AA
    ori       $t5, $t5, 0xAA55
    sw        $t5, 4($a0)
L_done:
    jr        $ra

f1 Solutions

f1:
    srl       $t0, $a2, 5
    sll       $t1, $t0, 1
    add       $t1, $a0, $t1
    addi      $t2, $zero, 5
    sh        $t2, 0($t1)
    andi      $t3, $a2, 3
    sll       $t4, $a1, 1
    add       $t4, $a0, $t4
    sh        $t3, 0($t4)
    jr        $ra

f2 Solutions

f2:
    slt       $t0, $zero, $a1
    beq       $t0, $zero, L_else
    slti      $t1, $a1, 8
    beq       $t1, $zero, L_else
    sll       $t2, $a1, 2
    add       $t3, $a0, $t2
    lw        $t4, 0($a0)
    sw        $t4, 0($t3)
    b         L_done
L_else:
    lui       $t5, 0x55AA
    ori       $t5, $t5, 0xAA55
    sw        $t5, 4($a0)
L_done:
    jr        $ra