1. A computer-implemented method for executing a target program in a computer system, comprising: compiling code of said target program for execution on a computer system processor to produce an executable target program, said processor having a set of N registers available for use by programs executed by the processor, each register of said set of N registers being assignable during compilation of said programs to program variables used by said programs; reserving, during said compiling code of said target program, at least one register of said set of N registers for later use by a dynamic binary optimizer during execution of said target program, wherein the number of registers of said set of N registers assignable by compiling code of said target program to program variables used by said target program is no more than N less the number of registers of said set of N registers which are reserved; and executing said executable target program with a dynamic binary optimizer, said dynamic binary optimizer using said at least one register of said set of N registers which is reserved during execution of said target program.