1. A computing method comprising: executing a program of instructions stored in computer-readable storage media, said instructions including both branch-prediction hints for predicting the occurrence of a speculative branch or the address of a speculative branch target, and hint-performance data for distinguishing among plural likelihoods that a prediction based on a given hint will be fulfilled; tracking performances of said hints so as to generate updated hint-performance data; storing said updated hint-performance data in said program instructions without modifying an associated hint; and modifying said associated hint at a time determined at least in part as a function of said performance data.