The following code is used to derive Fibonacci algorithm with this sequence: (0, 1, 1, 2, 3, 5, 8, 13, 21, …) where each number is “add” of two previous ones. int fib(int n){ if (n==0) return 0; else if (n == 1) return 1; else return fib(n−1) + fib(n−2); } Explain why the following RISC-V assembly code works, you need to explain all the details using the comments as hints? # IMPORTANT! Stack pointer must remain a multiple of 16!!!! 1. addi x10,x10,8 # fib(8), you can change it 2. fib: 3. beq x10, x0, done # If n==0, return 0 4. addi x5, x0, 1 5. beq x10, x5, done # If n==1, return 1 6. addi x2, x2, -16 # Allocate 2 words of stack space 7. sd x1, 0(x2) # Save the return address 8. sd x10, 8(x2) # Save the current n 9. addi x10, x10, -1 # x10 = n-1 10. jal x1, fib # fib(n-1) 11. ld x5, 8(x2) # Load old n from the stack 12. sd x10, 8(x2) # Push fib(n-1) onto the stack 13. addi x10, x5, -2 # x10 = n-2 14. jal x1, fib # Call fib(n-2) 15. ld x5, 8(x2) # x5 = fib(n-1) 16. add x10, x10, x5 # x10 = fib(n-1)+fib(n-2) 17. # Clean up: 18. ld x1, 0(x2) # Load saved return address 19. addi x2, x2, 16 # Pop two words from the stack 20. done: 21. jalr x0, 0(x1)

The following code is used to derive Fibonacci algorithm with this sequence:

(0, 1, 1, 2, 3, 5, 8, 13, 21, …) where each number is “add” of two previous ones.

int fib(int n){

if (n==0)

return 0;

else if (n == 1)

return 1;

else

return fib(n−1) + fib(n−2);

}

Explain why the following RISC-V assembly code works, you need to explain all the

details using the comments as hints?

# IMPORTANT! Stack pointer must remain a multiple of 16!!!!

1. addi x10,x10,8 # fib(8), you can change it

2. fib:

3. beq x10, x0, done # If n==0, return 0

4. addi x5, x0, 1

5. beq x10, x5, done # If n==1, return 1

6. addi x2, x2, -16 # Allocate 2 words of stack space

7. sd x1, 0(x2) # Save the return address

8. sd x10, 8(x2) # Save the current n

9. addi x10, x10, -1 # x10 = n-1

10. jal x1, fib # fib(n-1)

11. ld x5, 8(x2) # Load old n from the stack

12. sd x10, 8(x2) # Push fib(n-1) onto the stack

13. addi x10, x5, -2 # x10 = n-2

14. jal x1, fib # Call fib(n-2)

15. ld x5, 8(x2) # x5 = fib(n-1)

16. add x10, x10, x5 # x10 = fib(n-1)+fib(n-2)

17. # Clean up:

18. ld x1, 0(x2) # Load saved return address

19. addi x2, x2, 16 # Pop two words from the stack

20. done:

21. jalr x0, 0(x1)