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; By considering the terms in the Fibonacci sequence whose values do not exceed four million,
; find the sum of the even-valued terms.
extern printf
SECTION .data
flag: db "%d",10,0 ; "%d\n\0"
SECTION .text
global main
main:
push rbp ; set up stack
mov rbp, rsp
mov rax, 1 ; start at fib_1 = 1
push rax ; push first term of fib onto stack
mov r11, 0 ; sum = 0
mov r12, 0x3D0900 ; max = 4000000, this is < 2^64
; so we only need one register
.loop xor rdx, rdx ; clear rdx (remainder)
push rax ; push current term on the stack
mov rcx, 2 ; divisible by 2
div rcx ; divide rdx:rax/rcx
cmp rdx, 0 ; compare only remainder
jz .sum ; if r = 0 , add to sum
jmp .next ; else skip
.sum add r11, QWORD [rsp] ; add latest term to sum register
.next mov rax, QWORD [rsp] ; reload rax to current term
add rax, QWORD [rsp+8] ; add last term to current term
cmp rax, r12 ; while rax < r12 (4 mil)
jl .loop
mov rdi, flag ; arg 1 (format)
mov rsi, r11 ; arg 2 (value)
mov rax, 0 ; no xmm registers
call printf wrt ..plt
mov rsp, rbp ; reset to the top of the stack
pop rbp
mov rax, 0
ret
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