Compiler optimization on instruction scheduling for low power

In this paper, we investigate the compiler transformation techniques to the problem of scheduling VLIW instructions aimed to reduce the power consumption on the instruction bus. It can be categorized into two types: horizontal and vertical scheduling. For the horizontal case, we propose a bipartite-matching scheme. We prove that our greedy algorithm always gives the optimal switching activities of the instruction bus. In the vertical case, we prove that the problem is NP-hard, and propose a heuristic algorithm. Experimental results show average 13% improvements with 4-way issue architecture and average 20% improvement with 8-way issue architecture for power consumptions of instruction bus as compared with conventional list scheduling for an extensive set of benchmarks.