o  Using the .MCALL directive is optional unless the macro name
       is the same as an opcode or assembler directive. The assembler
       automatically searches for a library macro when it encounters
       an identifier that is not an opcode or directive in the
       opcode field. If your macro name is the same as an opcode or
       directive, you must use the .MCALL directive. You can also use
       the .MCALL directive in your program to document which macros
       are used by your program.