基于申威GCC编译器的间接预取算法

Indirect Prefetching Algorithm Based on Shenwei GCC Compiler

对间接存储器的访问延迟往往会影响应用程序的执行性能,一种有效的解决方案是使用预取技术.国产申威平台中支持常规访问模式的软件预取和硬件预取机制,但是其GCC编译器中缺少为间接存储器访问模式自动插入预取的方法.为了解决这个问题,基于申威GCC开发了一个完整间接预取优化遍,它利用深度优先搜索算法查找引用循环归纳变量的间接内存引用并为之生成合适的软件预取.在一组内存受限的基准测试中,自动预取遍对SW1621处理器的平均加速比达到1.16倍.

The delayed access to indirect memory often affects the execution performance of applications.An effective solution is to resort to the prefetching technology.Although the Shenwei platform developed in China supports the software and hardware prefetching mechanisms for conventional access modes,the compilers in its GNU compiler collection(GCC)lack the method of automatically inserting prefetches for indirect memory access.A complete indirect prefetching optimization pass is developed on the basis of the Shenwei GCC to solve this problem,and it uses a depthfirst search algorithm to find indirect memory references that refer to loop induction variables and generate appropriate software prefetches for them.In a set of memory-bound benchmark tests,the average speed-up ratio of the automatic prefetching pass on the SW1621 processor reaches 1.16 times.