Accurate simulation and evaluation of code reordering

The need for bridging the ever growing gap between memory and processor performance has motivated research for exploiting the memory hierarchy effectively. An important software solution called code reordering produces a new program layout to better utilize the available memory hierarchy. Many algorithms have been proposed. They differ based on: 1) the code granularity assumed by the reordering algorithm, and 2) the models used to guide code placement. In this paper we present a framework that provides accurate simulation and evaluation of code reordering algorithms on an out-of-order superscalar processor. Our approach allows both profile-guided and compile-time approaches to be simulated. Using a single simulation pass, different graph models are constructed and utilized during code placement. Various combinations of basic block/procedure reordering algorithms can be employed. We discuss the necessary modifications made to a detailed simulator of a processor in order to accurately simulate the optimized code layout