Maximum Loop Distribution and Fusion for Two-level Loops Considering Code Size

In this paper, we propose a technique combining loop distribution with loop fusion to improve the timing performance without increasing the code size of the transformed loops. We first develop the loop distribution theorems that state the conditions distributing any two-level nested loop in the maximum way. Based on the loop distribution theorems, we design an algorithm to conduct maximum loop distribution. Then we propose a technique of maximum loop distribution with direct loop fusion, which performs maximum loop distribution followed by direct loop fusion. The experimental results show that the execution time of the transformed loops by our technique is reduced 41.9% on average compared to the original loops without the increase of the code size.