1. A system comprising: one or more memories that, during operation, store instructions; and one or more processors that, during operation, retrieve instructions from the one or more memories and execute the instructions to cause the system to perform operations comprising: identifying, within source code of a called function, a dependency of the called function on a variable that is not defined by the called function's programming interface as a parameter of the called function; generating a persistent dependency database associated with the called function, wherein the persistent dependency database stores an indication of the dependency; identifying a call to the called function within source code of a calling function; in response to identifying the call, accessing the persistent dependency database; generating a determination of whether the calling function interacts with the called function based, at least in part, upon an expressed dependency of the called function indicated in the persistent dependency database; and vectorizing code within the calling function based at least in part on the determination.