1. A computer-implemented method for converting an original program to a modified program, comprising: identifying a plurality of original function calls in the original program, wherein the original program is targeted to a first platform, and wherein the plurality of original function calls comprise invocations of a plurality of functions implemented on the first platform; determining whether individual ones of the original function calls correspond to alternative function calls in an index; and for individual ones of the original function calls that correspond to the alternative function calls in the index, replacing the individual ones of the original function calls with corresponding ones of the alternative function calls in the modified program, wherein the modified program is targeted to a second platform, and wherein the alternative function calls comprise invocations of a plurality of functions implemented on the second platform.