fibo_printf.asm

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; Im starting to play with nasm on 64bits linux
; this is just a working code which will compute the 
; 100 firsts round of fibonaci starting with (1,1)
; The main difficulties is not to compute the number
; its about displaying them 
; I find an elegant way there : 
; http://tuttlem.github.io/2013/01/08/printing-a-register-s-value-in-hex.html
; also a dude (tefter) from #asm@freenode 
; provided a nice version to print in decimal way !
; 
; this code is for linux x86_64 only: 
; how to compile :  
; nasm -f elf64 -g -F stabs -o fibo.o fibo.asm
; gcc -o fibo fibo.o
;./fibo 
; 
; Courtesy of Netmonk, netmonk at netmonk dot org 
; http://www.netmonk.org



; Defining syswrite macro
%macro sys_write 3
    mov eax,1
    mov rdi, %1
    mov rsi, %2
    mov rdx, %3
    syscall
%endmacro


section .data
    Stmsg: db "Starting computation",10  ;  Starting msg 
    StmsgLen equ $-Stmsg   ; length of Stmsg 
    Edmsg: db "Ending computation",10   ; Ending msg
    EdmsgLen equ $-Edmsg ; length of Edmsg
    fmt: db "%ld", 10,0

extern printf

global main 
main: 
    nop
    sys_write 1,Stmsg,StmsgLen; writing starting msg 

    xor r14,r14 ; r14 = 0
    xor r12,r12 ; r12 = 0
    inc r12; r12=0+1=1    

Fibo: 
    add r14,r12 ; r14=r14+r12
    jc Done; if overflow (CF=1) then jump to end
    push rbp 
    mov rsi,r14
    mov rdi,fmt
    xor rax,rax
    call printf
    add r12,r14; r12=r14+r12 (r14 already have the new value from last add)
    jc Done; if overflow (CF=1) then jump to end
    push rbp	
    mov rsi,r12
    mov rdi,fmt
    xor rax,rax
    call printf
    jmp Fibo;
Done: 
    sys_write 1,Edmsg,EdmsgLen; printing end msg
    mov rax,60 ; load the 60 (exit) syscall value into rax
    mov rdi,0 ; load into rdi the return value of exit code
    syscall; call the kernel syscall