# Recursive Fibonnaci
# %rdi is the number for iterations.

fib:    push %rbp          # push previous base pointer
        movq %rsp,%rbp     # setup new base pointer

if:     cmpq $1, %rdi      # if (a-1) > 0: goto long
        jg long

quick:  movq %rdi, %rax
        jmp return

long:   pushq %rdi         # Push a onto the stack
        subq $1, %rdi
        call fib           # Call fib(a-1)
        pushq %rax         # Push fib(a-1) onto the stack
        subq $1, %rdi
        call fib           # Call fib(a-2)
        popq %rdi          # pop fib(a-1) into rdi
        addq %rdi, %rax    # rax = fib(a-1)+fib(a-2)
        popq %rdi          # Guarantee that a lies in rdi.

return: leave              # Clean up (stack pointers?)
        ret                # return m (rax)