segmentiaon fault in x86 assembly implementation of collatz conjecture - recursion

Question

I'm trying to write a subroutine that takes in a positive integer and returns the number of steps required for that integer to reach 1 by following the Collatz conjecture. If the input is 1, the output should be zero.
My psudeocode for this is, which is implenting it recursively(we can only use recursion)
int threexplusone(int x){
if(x == 1){
return 0;
}else{
if(x % 2 == 0){
return (threexplusone(x/2)+1);
}else{
return (threexplusone(3*x+1)+1);
}
}
}
My code is like this
threexplusone:
push rbx ;store the rbx to stack
mov rax, 0 ;store the base case
cmp rdi, 1 ;compare the input with 1
je done ;finished the loop if equal to 1
jmp threexplusone_recursive ;jump to the recursion
threexplusone_recursive:
mov rbx, rdi ;move rdi's value to rbx
sar rbx, 1 ;divide x by 2
sub rbx, rdi ;substitute to get the remainder
cmp rbx, 0 ;compare to check if the remainder is 0
je even ;start the even instruction
jne odd ;start the odd insturction
even:
sar rdi,1 ;divided the input by 2
xor rax,rax
call threexplusone ;do the recursion
inc rax ;add the result by one
jmp done ;
odd:
imul rdi,3 ;multiply x by 3
add rdi, 1 ;add x by 1
xor rax, rax
call threexplusone ;do the recursion
inc rax ;add the result by one
jmp done ;
done:
pop rbx
ret
I'm testing it in a cpp file, which
1.Ask for an input value, x, which is the positive integer to pass to the subroutin,
2.Ask for an input value, n, which is the number of times to call the subroutine
3.Run the subroutine once and store the result
4.Run the subroutine n times with the parameter x as the input
5.Print out the number of iterations it took for the integer to converge to 1.
int main(){
int x;
cout << "Enter a number: " << endl;
cin >> x;
int n;
cout << "Enter iterations of subroutine: " << endl;
cin >> n;
int result = threexplusone(x);
for(int i = 0; i < n; i++){
result = threexplusone(x);
}
cout << result << endl;
return 0;
}
The expected result should be
Enter a number:
100
Enter iterations of subroutine:
30
Steps take: 25
Insetead, I have a segmentaiotn fault
Enter a number:
100
Enter iterations of subroutine:
30
Segmentation fault (core dumped)
I step through the debugger, this is what it tells me
Program received signal SIGSEGV, Segmentation fault.
0x000000000040133a in odd ()
So it seems like the problem is in the odd insturction part
odd:
imul rdi,3 ;multiply x by 3
add rdi, 1 ;add x by 1
xor rax, rax
call threexplusone ;do the recursion
inc rax ;add the result by one
jmp done
I'm wondering which part of my assembly could be the cause? Thanks