hi,

here is week puzzle from me.


I have made two subroutines.
First subroutine saves registers R0..R7, DPH, DPL and accuculator into stack area and the second subroutine restores their values back.
Both subroutines work perfect. I use them like:

A_SUBROUTINE:
	CALL	SAVE_CONTEXT
; a task
	CALL	RESTORE_CONTEXT
	RET

The questions is: what important care should I keep in mind when use these subroutines?

Some more details:
- the question is not about stack size; assume it is enough.
- the question is not about registers` banks; assume I use only one register bank over the whole program.
- the question is related to optimization of assembler code.


Here are the subroutines (wrote under Keil):

	USING	0

;-------------------------------------------------------------------------------;
; Preserve registers								;
;-------------------------------------------------------------------------------;
SAVE_CONTEXT:
	PUSH	ACC
	PUSH	AR0
	MOV	R0,SP
	PUSH	AR1
	PUSH	AR2
	PUSH	AR3
	PUSH	AR4
	PUSH	AR5
	PUSH	AR6
	PUSH	AR7
	DEC	R0
	DEC	R0
	DEC	R0
	MOV	A,DPH
	XCH	A,@R0
	PUSH	ACC
	INC	R0
	MOV	A,DPL
	XCH	A,@R0
	PUSH	ACC
	INC	R0
	MOV	A,@R0
	INC	R0
	MOV	AR0,@R0
	RET

;-------------------------------------------------------------------------------;
; Restore registers								;
;-------------------------------------------------------------------------------;
RESTORE_CONTEXT:
	POP	DPL
	POP	DPH
	POP	AR7
	POP	AR6
	POP	AR5
	POP	AR4
	POP	AR3
	POP	AR2
	POP	AR1
	MOV	R0,SP
	DEC	R0
	DEC	R0
	DEC	R0
	MOV	A,DPH
	XCH	A,@R0
	MOV	DPH,A
	INC	R0
	MOV	A,DPL
	XCH	A,@R0
	MOV	DPL,A
	POP	AR0
	POP	ACC
	RET

I`m waiting for your questions, ideas etc.

Regards,
Oleg