sum.asm

;; nasm -f elf64 prog.asm && gcc -o prog prog.o

%define under 1000

	section .data
output:
	db "Result: %lu",10,0

	section .text
	extern printf
	global main

main:	
	mov rsi, 0

	mov rcx, 3
_mult_3:			; Add multiples of 3
	add rsi, rcx
	add rcx, 3
	cmp rcx, under
	jl _mult_3

	mov rcx, 5
_mult_5:			; Add multiples of 5
	add rsi, rcx
	add rcx, 5
	cmp rcx, under
	jl _mult_5

 	mov rcx, 15
_mult_15:			; Remove multiples of 15 because they've
	sub rsi, rcx		; been counted twice
	add rcx, 15
	cmp rcx, under
	jl _mult_15

	xor rax, rax
	mov rdi, output
	call printf

	mov rax, 0
	ret