1. A method for executing an anti-prefetch instruction, comprising: decoding instructions in a decode unit in a processor to prepare the instructions for execution; upon decoding an anti-prefetch instruction, stalling the decode unit to prevent the decoding of subsequent instructions; executing the anti-prefetch instruction, wherein executing the anti-prefetch instruction involves: sending a prefetch request for a cache line in an L1 cache; determining if the prefetch request misses in the L1 cache; if the prefetch request hits in the L1 cache, determining if the cache line contains a predetermined value; and conditionally performing subsequent operations based on whether the prefetch request missed in the L1 cache or the value of the data in the cache line.