;;
;; funcdemo3.asm
;;
;; Demonstrates writing a function to mimic the following code:
;;
;; long calc(long a, long b, long c, long d, long e, long f, long g, long h)
;; {
;;    return (a+b*c+d) - (e+f*g+h);
;; }
;;
;; We demonstrate stack-based and register-based calling conventions.
;;
;; by Terry Sergeant
;; For AL
;;
%include "../iomacros.asm"
%include "../dumpregs.asm"

		section .data
enternum:		db	"Enter X: ",0
sumis:		db	"Sum is : ",0
endl		db	0AH,0


		section .text
		global 		main
main:
		align_stack

		; register-based parameters
		xor	rax,rax
		mov	rdi, 1
		mov	rsi, 2
		mov	rdx, 3
		mov	rcx, 4
		mov	r8, 5
		mov	r9, 6

		push	qword 8
		push	qword 7
		call	calc2
		add	rsp,16


		put_str	sumis	; print "sum is: ",RAX
		put_i	eax
		put_str	endl



		; stack-based parameters
;		push	r13
;		push	r12
;		push	r9
;		push	r8
;		push	rcx
;		push	rdx
;		push	rsi
;		push	rdi
;		call	calc
;		add	rsp,64
;
;		put_str	sumis	; print "sum is: ",RAX
;		put_i	eax
;		put_str	endl



theend:		mov     eax, 60
		xor     rdi, rdi
		syscall


	; long calc(long a, long b, long c, long d, long e, long f, long g, long h)
	;    return (a+b*c+d) - (e+f*g+h);
	; we destroy R12 and put answer in RAX
;calc:
;		push	rbp
;		mov	rbp,rsp
;		push	r12		; we use r12 for temp value
;
;		mov	rax,[rbp+24]	; rax= b
;		imul	rax,[rbp+32]	; rax= b*c
;		add	rax,[rbp+16]	; rax= a+b*c
;		add	rax,[rbp+40]	; rax= a+b*c+d
;		mov	r12,[rbp+56]	; r12= f
;		imul	r12,[rbp+64]	; r12= f*g
;		add	r12,[rbp+48]	; r12= e+f*g
;		add	r12,[rbp+72]	; r12= e+f*g+h
;		sub	rax,r12		; rax= rax-r12
;
;		pop	r12		; restore r12
;		pop	rbp		; restore rbp
;		ret
;

	; long calc(long a, long b, long c, long d, long e, long f, long g, long h)
	;    return (a+b*c+d) - (e+f*g+h);
	; we destroy R12 and put answer in RAX
calc2:
		mov	rax,rsi		; rax= b
		imul	rax,rdx		; rax= b*c
		add	rax,rdi		; rax= a+b*c
		add	rax,rcx		; rax= a+b*c+d
		mov	r12,r9		; r12= f
		imul	r12,[rsp+8]	; r12= f*g
		add	r12,r8		; r12= e+f*g
		add	r12,[rsp+16]	; r12= e+f*g+h
		sub	rax,r12		; rax= rax-r12
		ret