Recursive Fibonacci in ARM - recursion

Question

I'm trying to convert this recursive Fibonacci code to arm assembly language. I'm new to this and not really sure how to do it. I have some code snippets of things that I've played with below.
Fib (n) {
if (n == 0 || n == 1) return 1;
else return Fib(n-2) + Fib(n-1);
}
Here is my attempt so far:
RO = 1
CMP RO #1
BGT P2
MOV R7 #1
B END
P2:
END LDR LR [SO,#0]
ADD SP SP, #8
MOV PC, LR
Help would be much appreciated

Answer 1

For the sake of avoiding spoon-feeding, I wrote a LEGv8 program that finds Fibonacci sequence using recursion. LEGv8 is slightly different than ARMv8, however the algorithm remains.
Please review the code, and change the commands / registers to their corresponding values in ARMv8.
I assumed that n (the range of the Fibonacci sequence) is stored in register X19.
I also assumed that we ought to store the Fibonacci sequence in an array, which has its base address stored in X20.
MOV X17, XZR // keep (previous) 0 in X17 for further use
ADDI X18, XZR, #1 // keep (Current) 1 in X18 for further use
ADDI X9, XZR, #0 // Assuming i = 0 is in register X9
fibo:
SUBI SP, SP, #24 // Adjust stack pointer for 3 items
STUR LR, [SP, #16] // save the return address
STUR X17, [SP, #8] //save content of X17 on the stack
STUR X18, [SP, #0] //save content of X18 on the stack
SUBS X10, X9, X19 // test for i==n
CBNZ X10, L1 // If i not equal to n, go to L1
MOV X6, XZR // keep 0 on X6
ADDI X5, XZR, #1 // keep 1 on X5
ADDI X2, X9, #1 //X9 increased by 1 for further use
STUR X6, [X20,#0] //store 0 in the array
STUR X5, [X20, #8] //store 1 in the array
ADDI SP, SP, #24 // pop 3 items from the stack
BR LR // return to the caller
L1:
ADD X16, X17, X18 // Next_Num = previous + Current
MOV X17, X18 // Previous = Current
MOV X18, X16 // Current= Next_Num
ADDI X9, X9, #1 // i++
BL fibo // call fibo
LDUR X18, [SP, #0] // return from BL; restore previous
LDUR X17, [SP, #8] // restore current
LDUR LR, [SP, #16] // restore the return address
ADDI SP, SP, #24 // adjust stack pointer to pop 3 items
ADD X7, X18, X17 // keep (previous + current) value on register X7
LSL X2, X2, #3 // Multiplying by 8 for offset
ADD X12, X20, X2 // address of the array increase by 8
STUR X7, [X12, #0] // store (previous + current) value on the array
SUBI X2, X2, #1 // X9 decreased by 1
BR LR // return