Computer Organization Test 2

Question 1. (18 points) Translate the following high-level language code segment to MIPS assembly language. Use the registers indicated in the code.

a)  for $4 = 0 to 100 by steps of size 10 do
	   if ($3 < $4) OR ($2 >= 50) then
	       $2 = $2 + $3
	   end if 
    end for          

b) while ($8 > 20) do

if ($8 > 100) AND ($8 < 200) then

$7 = $8

$8 = $8 - 10


$8 = $8 - $7

end if

$7 = $6 + 4

end while

Question 2. (12 points) Suppose you have the following .data area in MIPS assembly language:


array: .word 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25

For each of the following assembly language segments, what value is loaded into register $t2?

a) li $t0, 5

la $t1, array

mul $t3, $t0, 4

add $t1, $t1, $t3

lw $t2, 0($t1)

b) la $t1, array

lw $t2, 8($t1)

c) li $t0, 5

la $t1, array

sll $t3, $t0, 2 # shift left logical

add $t1, $t1, $t3

lw $t2, 0($t1)

Question 3. (8 points) For the .data area in question 2, complete the translation of the following high-level code segment to MIPS assembly language.

for i = 0 to 14 do la $t1, array
array[i+1] = array[i] for:
end for li $t0, 0
  li $t2, 14
  bgt $t0, $t2, end_for
  j for_compare

Question 4. (8 points) Assume that a two-dimensional array A is stored in memory using column-major order, i.e., column 0 is followed by column 1, etc. Write a formula to calculate the address of element A[i][j].

Question 5. Consider the following selection sort subprogram that utilizes a function Max to search for the largest element in the unsorted part of the array.

a) (6 points) Using the MIPS register conventions ($a0-$a3, $t0-$t9, $s0-$s7, $v0-$v1, $sp, $ra), what registers would be used to pass each of the following parameters to selectionSort:

base address of "numbers" array count

b) (6 points) Using the MIPS register conventions, which of these parameters ("numbers", "count", or both of them) should be moved into $s-registers?

c) (6 points) Using the MIPS register conventions, what registers should be used for each of the local variables:
lastUnsortedIndex maxIndex temp

d) (4 points) In addition to the above registers, the value of "numbers[maxIndex]" will need to be stored into a register. Using the MIPS register conventions, what register should be used to hold this value?

e) (6 points) For the registers indicated above, write the MIPS instructions to set up the selectionSort call-frame on the run-time stack (i.e., move the stack pointer and save registers, etc.).

f) (8 points) For the registers indicated above, write the assemble language code to call the Max function ("maxIndex = Max(numbers, 0, lastUnsortedIndex)"). Include the MIPS instructions to setup the parameters to Max and assigning "maxIndex" the value returned. (You do not need to write the Max function code just the code to call it)

g) (8 points) Using the registers you indicated, write the MIPS assembly language statements to perform the statements:

Question 6. (10 points) In the last lab, we used bit strings to represent sets of letters stored in a 32-bit word. Suppose we have two bitStrings in $a0 and $a1. Write the MIPS assembly language code to check if $a0 is a subset of $a1. (Recall that $a0 is a subset of $a1 if every element of $a0 is also in $a1)