Statement Re-ordering for DOACROSS Loops

In this paper, we propose a new statement re-ordering algorithm for DOACROSS loops that overcomes some of the problems in the previous schemes. The new algorithm uses a hierarchical approach to locate strongly dependent statement groups and to order these groups considering critical dependences. A new optimization problem, dependence covering maximization, which was not discussed before is also introduced. It is shown that this optimization problem is NP-complete, and a heuristic algorithm is incorporated in our algorithm. Run-time complexity analysis is given for both algorithms. This new statement re-ordering scheme, combined with the dependence covering maximization, can be an important compiler optimization to parallelize loop structures for large scale coarse and fine grain parallelism.