; exnl5.asm  example  if then else
	extern printf
        section .data		; Data section, initialized variables
msg:	db "nasm  exnl5.asm running", 0	; C string needs 0
msg2:	db "exnl5.asm finished", 0
msg3:	db "if then else on integers", 0
msg4:	db "if then else on floats", 0
fmt:    db "%s", 10, 0
	
a:	dq 1
b:	dq 2
c:	dq 3
xyz:	dq 4
fmt1:   db "true a < b ",10,0
fmt2:   db "wrong on a < b ",10,0
fmt3:   db "wrong on b > c ",10,0
fmt4:   db "false b > c ",10,0
fmt5:	db "failed 4==xyz ",10,0
fmt6:	db "passed 4==xyz ",10,0
fmt7:	db "failed 5>xyz ",10,0
fmt8:	db "passed 5>xyz ",10,0
fmt9:	db "failed 3<xyz ",10,0
fmt10:	db "passed 3<xyz ",10,0
af:	dt 1.0
bf:	dt 2.0
cf:	dt 3.0
fmt1f:	db "true af < bf ",10,0
fmt2f:	db "wrong on af < bf ",10,0
fmt3f:	db "wrong on bf > cf ",10,0
fmt4f:	db "false bf > cf ",10,0

	section .bss		; unused, except to pop
t:	rest 1			; reserve one space for dt


        section .text           ; Code section.
        global main
main:
        push    rbp		; set up stack frame, must be aligned
	
	mov	rdi,fmt         ; address of format, required register rdi
	mov	rsi,msg         ; address of data
	mov	rax,0		; or can be  xor  rax,rax
        call    printf		; Call C function

	mov	rdi,fmt         ; address of format, required register rdi
	mov	rsi,msg3        ;
	mov	rax,0		;
        call    printf		;

; code ifint_64.c for nasm 
; /* ifint_64.c an 'if' statement that will be coded for nasm */
; #include <stdio.h>
; int main()
; {
;   long int a=1;
;   long int b=2;
;   long int c=3;
;   long int xyz=4;
;   if(a<b)
;     printf("true a < b \n");
;   else
;     printf("wrong on a < b \n");
;   if(b>c)
;     printf("wrong on b > c \n");
;   else
;     printf("false b > c \n");
;
;   if(4==xyz) goto label1e;
;   printf("failed 4==xyz\n");
;label1e: printf("passed 4==xyz\n");
;
;   if(5>xyz) goto label1g;
;   printf("failed 5>xyz\n");
;label1g: printf("passed 5>xyz\n");
;
;   if(3<xyz) goto label1l;
;   printf("failed 3<xyz\n");
;label1l: printf("passed 3<xyz\n");
;
;   return 0;
;}
; result of executing both "C" and assembly is:
; true a < b
; false b > c 
	
	mov	rax,[a]		; a
	cmp	rax,[b]		; compare a to b
	jge	false1		; choose jump to false part
	; a < b sign is set
        mov	rdi, fmt1	; printf("true a < b \n");
	mov	rax,0
        call    printf	
        jmp	exit1		; jump over false part
false1:	;  a < b is false 
        mov	rdi, fmt2	; printf("wrong on a < b \n");
	mov	rax,0
        call    printf
exit1:				; finished 'if' statement

	mov	rax,[b]		; b
	cmp	rax,[c]		; compare b to c
	jle	false2		; choose jump to false part
	; b > c sign is not set
        mov	rdi, fmt3	; printf("wrong on b > c \n");
	mov	rax,0
        call    printf	
        jmp	exit2		; jump over false part
false2:	;  b > c is false 
        mov	rdi, fmt4	; printf("false b > c \n");
	mov	rax,0
        call    printf
exit2:				; finished 'if' statement

	mov	rax,4
	cmp	rax,[xyz]	; if(4==xyz) goto label1e;
	je	label1e
	mov	rdi, fmt5
	mov	rax,0
	call	printf
label1e:mov	rdi, fmt6
	mov	rax,0
	call	printf

	mov	rax,5
	cmp	rax,[xyz]	; if(5>xyz) goto label1g;
	jg	label1g
	mov	rdi, fmt7
	mov	rax,0
	call	printf
label1g:mov	rdi, fmt8
	mov	rax,0
	call	printf

	mov	rax,3
	cmp	rax,[xyz]	; if(3<xyz) goto label1l;
	jl	label1l
	mov	rdi, fmt9
	mov	rax,0
	call	printf
label1l:mov	rdi, fmt10
	mov	rax,0
	call	printf
	
	mov	rdi,fmt         ; address of format, required register rdi
	mov	rsi,msg4        ;
	mov	rax,0		;
        call    printf		;

; code ifflt_64.c for nasm 
; /* ifflt_64.c an 'if' statement that will be coded for nasm */
; #include <stdio.h>
; int main()
; {
;   double af=1.0;
;   double bf=2.0;
;   double cf=3.0;
;   if(af<bf)
;     printf("true af < bf \n");
;   else
;     printf("wrong on af < bf \n");
;   if(b>c)
;     printf("wrong on bf > cf \n");
;   else
;     printf("false bf > cf \n");
;   return 0;
;}
; result of executing both "C" and assembly is:
; true af < bf
; false bf > cf 
	


	fld	tword [bf]	; bf into st0
	fld	tword [af]	; af into st0, pushes b into st1
	fcompp			; compare and pop both
;	fcomip	st0,st1		; compare af to bf, pop af
;	fstp	tword [t]	; just to pop bf
	jl	false1f		; choose jump to false part
	; af < bf sign is set
        mov	rdi, fmt1f	; printf("true af < bf \n");
	mov	rax, 0
        call    printf	
        jmp	exit1f		; jump over false part
false1f: ;  af < bf is false 
        mov	rdi, fmt2f	; printf("wrong on af < bf \n");
	mov	rax, 0
        call    printf
exit1f:				; finished 'if' statement

	fld	tword [cf]	; cf into st0
	fld	tword [bf]	; bf into st0, pushes cf into st1
	fcompp			; compare and pop both
;	fcomip	st0,st1		; compare bf to cf, pop bf
;	fstp	tword [t]	; just to pop cf
	jg	false2f		; choose jump to false part
	; bf > cf sign is not set
        mov	rdi, fmt3f	; printf("wrong on bf > cf \n");
	mov	rax, 0
        call    printf	
        jmp	exit2f		; jump over false part
false2f: ;  bf > cf is false 
        mov	rdi, fmt4f	; printf("false bf > cf \n");
	mov	rax, 0
        call    printf
exit2f:				; finished 'if' statement

	mov	rdi,fmt		; print finished
	mov	rsi,msg2
	mov	rax,0
	call	printf
        pop     rbp		; restore stack 
	mov	rax,0		; normal, no error, return value
	ret			; return