1. A method for executing instructions in a processor having a polymorphic execution unit, comprising: reloading a state associated with a first instruction class and reconfiguring the polymorphic execution unit to operate in accordance with the first instruction class, directly responsive to an instruction of the first instruction class being encountered and the polymorphic execution unit being configured to operate in accordance with a second instruction class; and reloading a state associated with a second instruction class and reconfiguring the polymorphic execution unit to operate in accordance with the second instruction class, directly responsive to an instruction of the second instruction class being encountered and the polymorphic execution unit being configured to operate in accordance with the first instruction class.