Study And Implement On Code Reordering Technology Of I-Cache Optimization

With the development of architecture, especially of multi-issue architecture, the demands for efficiently instruction fetching on modern microprocessors is increasing. So, how to improve i-cache hit rate and enhance processor's performance became a significant issue.Code reordering is an important technology of i-cache optimization, which can position closely together those codes that switch their control to each other frequently, such that the size of the working set can be reduced and i-cache hit rate can be increased. In this paper we studied the code reordering technology from several aspects, and get following achievement:First, we discussed two methods of gathering the information for code reordering such as profile-based prediction, program-based branch prediction, and analyzed the algorithms of them.Second, we studied and compared three main methods of code reordering, including procedure reordering, basic block reordering and procedure splitting.Third, we analyzed in detail the implement method of code reordering in GCC and pointed out its deficiencies.Last, we give an approach of code reordering at abstract tree level based on the frame of GCC4.1. Our method obtains procedures calling frequency information based on static branch prediction, and reorders the procedures by HP algorithm. The experiment result shows that this approach can obtain considerable optimization effect.