Quiz #1 Solution

Name:__________________ Quiz #2

1) Registers and Stack Conventions:
A) What rules/precautions must the Caller of a function follow for the s-registers:

Nothing. The caller assumes that the callee will not change the s-registers.

B) What rules/precautions must a Callee of a function follow for the s-registers:

The Callee has agreed not to change/contaminate the s-registers,
so, in order to use them, they must be backed up and restored before
the function completes.

2) Write a valid MIPS function to sum the elements of an array of integers:
(Use pointer indexing)

       int sum(int *data, int size)

sum:

    move $t0,$a0     # Copy pointer to the array
    move $t1,$0      # Init a counter
    move $v0,$0      # Init a running total

sum_for:
    bge $t0,$a1,sum_end  # For loop condition check
        lw $t3,0($t0)    # Load the current word
        add $v0,$v0,$t3  # Add it to the running total
        add $t0,$t0,4    # Advance the pointer to the next element of the array
        add $t1,$t1,1    # Advance the for loop counter
    j sum_for            # Return to top of for loop

sum_end:
    jr $ra           # Return to the caller