-Org
The -Org option enables allocation of local variables and addresses of global variables and functions to processor registers for the lifetime of a function. This form of register allocation will always reduce code size but may reduce execution speed for some paths through the function.
To enable allocation of local variables and addresses of global variables and functions to processor registers for a project:
To enable allocation of local variables and addresses of global variables and functions to processor registers for a particular file:
-Or- (Disable register allocation), -Orl (Register allocation of locals)