弹性数据相关与软件流水

Flexible Data Dependence and Software Pipelining

最差路径是有分支循环软件流水的一大障碍 .对于有分支循环 ,某些数据相关 (称为弹性相关 )在循环的动态执行中可能产生、也可能不产生实例 .据此 ,可将严重限制并行性的弹性相关用限制较松的虚构相关代替 ,再进行软件流水 .若调度没有遵守原来的弹性相关 ,则使用下推变换修正 .从而缓解或者完全解除了最差路径的限制 .该方法与经典的控制猜测互补 ,特点是允许调度含错 。

For software pipelining of loops with conditional statements, the worst-case path is a great obstacle. In such a loop, some data dependencies called flexible dependencies, may or may not have instances during execution of the loop. From this fact, flexible dependencies that severely limit parallelization of the loop are identified and replaced with less tight virtual dependencies. Then software pipelining is applied. If the schedule does not satisfy the original flexible dependencies, downpush transform is used to rectify. The resulting schedule is partly or completely free of the worst-case effects. This approach is a complement to the classical control speculation. It is characterized by a try-and-catch way: errors are first allowed to be present in the schedule, and then rectified.