In a method for the optimisation of compiler-generated program code, the compiler-generated program code is searched for program code fragments which correspond, at least in their effect, to respectively one library code fragment contained in a predefined library. The program code fragments found thereby are replaced by respectively one call of the corresponding library code fragment. A computer program product comprises program instructions for the execution of this method. A portable data carrier contains both the program code optimised according to this method and the library.