1. A method of facilitating processing in a computing environment, said method comprising: generating, by an optimizer executing in a processor, modified code of an application, wherein the application comprises unmodified code and modified code; and based on generating the modified code, setting by the optimizer one or more controls to selectively enable use of extended mode features by the application, the extended mode features comprising one or more features at an instruction set level different from an instruction set level available to the application.