You can specify the name to be used in the assembler code for a C function or variable by writing the asm (or __asm__) keyword after the declarator as follows:
int foo asm ("myfoo") = 2;
This specifies that the name to be used for the variable foo in the assembler code should be “myfoo” rather than the usual “_foo”.
On systems where an underscore is normally prepended to the name of a C function or variable, this feature allows you to define names for the linker that do not start with an underscore.
You cannot use asm in this way in a function definition; but you can get the same effect by writing a declaration for the function before its definition and putting asm there, like this:
extern func () asm ("FUNC");
func (x, y)
int x, y;
...
It is up to you to make sure that the assembler names you choose do not conflict with any other assembler symbols. Also, you must not use a register name; that would produce completely invalid assembler code. The compiler does not as yet have the ability to store static variables in registers. Perhaps that will be added.