Panasonic PanaXSeries MN1030 Series - Page 63

Chapter 4 Optimization
Usage Example 51
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.
(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).
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