1. A method of changing a status of a run-time determined software routine between activated and deactivated, comprising: employing an invariant flag to evaluate a conditional statement associated with said run-time determined software routine to determine the status as one of activated or deactivated, said invariant flag being selected to cause said conditional statement to always evaluate to a known result; and during run-time, utilising a run-time code replacement facility to change said invariant flag to a second invariant flag that causes said conditional statement to always evaluate to a different known result; and optimizing said run-time determined software routine by excluding from compiled native machine code the run-time determined software routine when the invariant flag is selected to cause the conditional statement associated with said routine to evaluate to the different know result.