Panasonic MN1030 user manual Optimization of function calls

Chapter 4 Optimization

Optimization of function calls

This section describes the optimization of function calls by the linker.

The assembler provides advanced processing for function calls. This processing uses a combination of the call and ret instructions and the global and funcinfo directives. The following is an example.

	global	_0func
_TEXT	section	CODE, PUBLIC, 1
	:
	call	_0func	(1)
	:
	global	_0func, _func
_TEXT	section	CODE, PUBLIC, 1
_func	movm	[D2], (SP)	(2)
	add	-4, SP
_0func	funcinfo	_func, 8, [D2]
	:
	:		(3)
	ret

(1)gives the call to the function _0func. (3) is the body of the function. (2) the section between the labels _func and _0func, saves a register and sets up the stack frame.

When this source file is assembled and linked, the linker eliminates section (2). This section is preserved when the symbol _func is referred.

For further details on machine instructions and directives, see the Instruction Manual and Section 9.4 "Writing Directives."

NOTE:	This optimization of function calls is always carried out regardless of the state of
	the optimization option (-O). It is suppressed throughout if even one of the source
	files to be linked contains a calls instruction with the operand (An).

Usage Example 51