Enhancing Compiler Techniques for Memory Energy Optimizations

As both chip densities and clock frequencies steadily rise in modern microprocessors, energy consumption is quickly joining performance as a key design constraint. Power issues are increasingly important in embedded systems, especially those found in portable devices. Much research has focused on the memory subsystems of these devices since they are a leading energy consumer. Compiler optimizations that are traditionally used to increase performance have shown much promise in also reducing cache energy consumption. In this paper we study the interaction between performance-oriented compiler optimizations and memory energy consumption and demonstrate that the best performance optimizations do not necessarily generate the best energy behavior in memory. We also show a simple metric that a power-optimizing compiler can utilize in order to capture the energy impact of potential optimizations. Next, we present heuristic algorithms that determine a suitable optimization strategy given a memory energy upper bound. Finally, we demonstrate that our strategies will gain even more importance in the future when leakage energy is expected to play an even larger role in the total energy consumption equation.