Write complete MIPS32 assembly language program fro this exercise. Name your ass

Question

Write complete MIPS32 assembly language program fro this exercise.

Name your assembly language source code file hw3-4-s. The greatest common divisor (GCD) of two integers a and b is the largest (most positive) integer g that divides both a and b. We say that a number n divides m if the remainder after dividing m by n is zero. Euclid's algorithm^1 is an elegant way to calculate the GCD of two integers. Here is the algorithm in pseudocode, --a and b can be negative integers and one, but not both, of them can be zero. Since GCD(a, b) is the largest (most -- positive) integer that divides both a and b, it will be a positive integer. It is true that GCD(a, b) = GCD(|a|, |b|) so -- we start by setting x to be the larger (by absolute value) of a and b, and y to the smaller. x leftarrow max(|a|, |b|) y leftarrow min(|a|, |b|) -- GCD(a, 0) = a when a 0 (GCD(0, 0) is undefined). So, if y is 0, our gcd is x. For this exercise, you are to write a complete MIPS32 assembly language program that displays prompts asking the user to enter values for a and b. The program shall compute and display GCD(a, b). Here is a sample run; make your program work similarly,

Explanation / Answer

   .text # assembly directive that indicates what follows are instructions
   .globl main # assembly directive that makes the symbol main global
main: # assembly label
   sub   $sp,$sp,8   # push stack to save registers needed by the system code that called main
   sw   $ra,0($sp)   # save return address

   li   $v0,4 # Ready for string output
   la   $a0,pow # Load address of pow
   syscall # Print string
  
   li $v0,5 # Ready for integer input
   syscall # Read integer from console
   move $t2,$v0 # Move into to $t2 temporarily
      
   li   $v0,4 # Ready for string output
   la   $a0,bas # Load address of bas
   syscall # Print string
  
   li $v0,5 # Ready for integer input
   syscall # Read integer from console
   move $a0,$t2 # Move into to $a0
   move $a1,$v0 # Move power integer to $a1
  
  
   jal   euc       # call subroutine power to compute the exponent
   sw   $v0,4($sp) # result returned in $v0 and stored on the stack

# print the result
  
   li   $v0,4 # the argument to a system call is placed in register $v0
# The value 4 tells syscall to print a string
   la   $a0,str # pseudo-instruction to load the address of the label str
# The address of the string must be placed in register $a0
   syscall # system call to print the string at address str

   li   $v0,1 # The value 1 tells syscall to print an integer
   lw   $a0,4($sp) # Load the sum from the stack to register $a0
   syscall # System call to print the integer in register $a0
  
   lw   $ra,0($sp)   # restore return address used to jump back to system
   add   $sp,$sp,8   # pop stack to prepare for the return to the system
   jr   $ra # [jump register] return to the system

   .data # Assembly directive indicating what follows is data
str: # label of address containing a string
   .asciiz "value = " # Assembly directive used to create a null terminated ASCII string
bas: # label of address containing a string
   .asciiz "second integer = " # Assembly directive used to create a null terminated ASCII string
pow: # label of address containing a string
   .asciiz "first integer = " # Assembly directive used to create a null terminated ASCII string

   .text
euc:
   sub   $sp,$sp,4 # Push stack to create room to save register $s0
   sw   $s0,0($sp) # save $s0 on stack
                          
   bne $a1,$zero,L1 # if (b == 0), if not go to L1
       j EXIT # jump to EXIT
  
   L1:   
       beq $a1, $zero, EXIT # branch loop
       move $t4,$a1 # set up c = b
       rem $a1,$a0,$a1 # b = a % b
       move $a0,$t4 # a = c
       j L1 # jump back to top of loop
   EXIT:

   move $v0,$a0 # Move a to $v0

   lw   $s0,0($sp) # restore $s0 to value prior to function call
   add   $sp,$sp,4 # pop stack
   jr   $ra # return to calling procedure

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