Apcs

(Project Properties window)

*.prj\ASSEMBLE\Assembly\
APCS\Apcs

Set to enabled by default.

Select enabled if your assembly language code is expected to conform to one of the APCS variants. You should select enabled if you are writing assembly language routines that are called from C or C++, or from other assembly language routines that expect your code to follow APCS calling conventions.

Select disabled if you are writing standalone assembly language routines that are not called from other routines that expect APCS calling conventions to be followed.

See –-apcs in the documentation for your toolchain.