多媒体程序中消除控制相关的技术研究

Optimizations for Eliminating Control Dependence in Multimedia Programs

随着多媒体应用的快速发展,最大程度地提升多媒体程序的性能逐渐变为计算机领域研究的热点。硬件平台和多媒体程序的特点是该领域研究需要关注的两个主要方面,当前的主流桌面处理器在提升主频的同时也增大了分支预测失误的开销,而多媒体应用程序中分支语句的大量使用进一步增大了分支预测失误的概率。我们在优化多媒体程序测试包BMW(BerkeleyMultimediaWorkload)过程中发现,通过消除程序中的控制相关,尽量减少程序中的分支指令可以显著地提升程序的性能。本文首先讨论了多媒体程序中消除控制相关的一些基本优化方法。针对当前主流处理器引入多媒体扩展指令集来优化程序的趋势,本文进一步总结了在SIMD架构下使用多媒体扩展指令集消除控制相关的方法。这两方面的优化方法应用到实际程序中,得到的平均性能提升分别为7%和26%。

With the rapid development of multimedia applications, many researches have focused on how to accelerate such workload. During the optimization of Berkeley Multimedia Workload, we find that heavy utilization of branch instructions in programs often increases the misprediction of processors with deep pipelines Therefore, it is very important to eliminate the branch instructions as many as possible. This paper proposes some methods to eliminate conditional branches on the hasis of conditional move instructions Furthermore, it ＂also makes a survey on the methods to rid the oontrol dependence with the support of MiME （Multimedia Extensions）. These methods are applied to BMW （Berkeley Multimedia Workload） and a satisfactory speedup is obtained.