; div_test.asm       print a string using printf
; Assemble:	  nasm -f elf64 -l div_test.lst  div_test.asm
; Link:		  gcc -m64 -o div_test  div_test.o
; Run:		  ./div_test > div_test.out
; Output:	  cat div_test.out
;
;                rax  quotient
;           ________
;  divisor / rdx rax  128 bit 2's complement dividend
;                rdx  remainder
;

        extern	printf		; the C function, to be called

%macro	pabcd 1			; a print macro
	section .text
        mov     rdi, fmt4	; first arg, format
	mov	[trax], rax	; second arg  save users registers
	mov     [trbx], rbx     ; third arg
	mov     [trcx], rcx     ; fourth arg
	mov     [trdx], rdx     ; fifth arg
	mov	rsi, [trax]	; second arg
	mov     rdx, [trbx]     ; third arg
	mov     rcx, [trcx]     ; fourth arg
	mov     r8,  [trdx]     ; fifth arg
	mov     rax, 0	        ; no xmm used
	call    printf		; Call C function
	mov	rax, [trax]	; second arg      restore users registers
	mov     rbx, [trbx]     ; third arg       being overly cautious
	mov     rcx, [trcx]     ; fourth arg
	mov     rdx, [trdx]     ; fifth arg
%endmacro

        section .data		; Data section, initialized variables
msg:	db "Div_Test running", 0
msge:	db "Div_Test finished", 0
fmt:	db "%s", 10, 0
fmt4:   db "rax=%ld, %rbx=%ld, rcx=%ld, rdx=%ld", 10, 0
i31:	dq 31
i2:	dq 2
	
	section .bss
trax:	resq	1
trbx:	resq	1
trcx:	resq	1
trdx:	resq	1
	
        section .text           ; Code section.
	
        global main		; the standard gcc entry point
main:				; the program label for the entry point
        push    rbp		; set up stack frame, must be aligned
	
	mov	rdi, fmt
	mov	rsi, msg
	mov	rax, 0
        call    printf

	mov	rax, [i31] 	; low 64 bits of dividend
	mov	rdx, 0		; high 64 bits of dividend
	mov	rcx, 0 	
	mov	rbx, 0	
	idiv	qword [i2]	; divisor
	pabcd	" "		; quotient in rax, remainder in rdx

	mov	rax, [i31]
	mov	rdx, 0
	div	qword [i2]
	pabcd	" "

	mov	rax, [i31]
	mov	rdx, 0
;	div	2               ; error
;	div	qword 2         ; error
;	div	rax, [i2]       ; error
;	idiv	rax, [i2]       ; error
	mov	rbx, 2
	idiv	rbx		; divisor OK
	pabcd	" "

	
	mov	rdi, fmt
	mov	rsi, msge
	mov	rax, 0
        call    printf
	
        pop     rbp		; restore stack 
	mov	rax,0		; normal, no error, return value
	ret			; return