1. A system comprising: one or more processors; one or more memories; and a virtual machine that generates and stores executable processor instructions in one or more of the one or more memories that implement a program initially compiled to a first set of intermediate instructions, the virtual machine generating and including additional sets of executable instructions at defined positions in the executable processor instructions that implement the program, the additional sets of executable instructions and defined positions specified in a first specification initially compiled to a second set of intermediate instructions; and generating and including, in one or more of the additional sets of executable instructions, switches that control execution of the additional sets of executable instructions and that are defined in a third specification.