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HW10 solution

1. (20 points) Consider the following C code:

   // Find m that is relatively prime to n.
   int relPrime(int n)
   {
    int m;
   
    m = 2;
   
    while (gcd(n, m) != 1) {  // n is the input from the outside world
      m = m + 1;
    }
   
    return m;
   }

    

   // The following method determines the Greatest Common Divisor of a and b 
   // using Euclid's algorithm.
   int gcd(int a, int b)
   {
   if (a == 0) {
     return b;
   }
   
   while (b != 0) {
     if (a > b) {
       a = a - b;
     } else {
       b = b - a;
     }
   }
   
   return a;
   }

a. Download this template file, relPrime.asm.

• PUT YOUR NAME IN THIS FILE!

b. Also download the tests for this homework here.

c. In relPrime.asm, create a RISC-V procedure that is equivalent to the gcd() function above. Important notes:

• You only the core RISC-V instructions on our class RISC-V green sheet. This is so you can put this code through your own assembler from Practical 1 and 2 later.
• Follow the RISC-V Procedure Calling conventions.
• Even though the C code is inefficient, DO NOT CHANGE THE LOGIC OF THE CODE. Your job is to translate this code directly.
• To test your code for gcd, set the value of TEST_GCD to 1 in your relPrime.asm file. That will tell runtests to test your gcd() procedure.

d. In the same file, add a RISC-V procedure equivalent to the C function relPrime() above.

• Test your relPrime implementation the same way: Set the value of TEST_RELPRIME to 1 in your file to enable the tests.

e. Upload your completed relPrime.asm code to gradescope as a pdf, just like the other homeworks, you are not uploading an asm file directly.

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