一种寄存器压力敏感的指令投机调度技术  

A Register Pressure Sensitive Instruction Speculative Scheduling Technology

作　　者：黄磊[1] 冯晓兵[2] 吕方[3] 

机构地区：[1]中国科学院计算机系统结构重点实验室,北京100190 [2]中国科学院计算技术研究所,北京100190 [3]中国科学院研究生院,北京100049

出　　处：《计算机研究与发展》2009年第3期485-491,共7页Journal of Computer Research and Development

基　　金：国家"九七三"重点基础研究发展计划基金项目(2005CB321602)~~

摘　　要：投机是指令调度克服指令间控制依赖的一种重要手段.投机一方面可以提高指令级并行带来性能改善,另一方面,它也可能拉长变量活跃区间,增大寄存器压力,导致变量溢出,从而恶化性能.前人的寄存器压力敏感的指令调度的方法,往往当调度区域内活跃变量个数超过阈值时一味保守地调度.考虑到每调度一条指令的收益和代价是不同的,通过具体分析一次投机调度的性能收益和溢出代价来有选择地投机指令,而不是仅仅考虑活跃变量的数目.实验表明,该方法能有效提高程序性能,对SPEC2000的整数例子,比不考虑寄存器压力的投机调度平均性能提高1.44%.Speculation is an important method to overcome control flow constraints during instruction scheduling. On the one hand, speculation can exploit more instruction-level parallelism and improve performance. However, on the other hand, it may also lengthen the live range of variables and increase the register pressure, which in turn results in spilling some variables to memory and deteriorating the performance. Previous work on register pressure sensitive instruction scheduling generally scheduled instructions conservatively when there were too many live variables in the scheduling region. But actually different variables have different spilling costs and different impacts on performance. Here a register pressure sensitive speculative instruction scheduling technology is presented, which not only considers the count of live variables, but also analyzes the benefits and the spilling costs brought by instructions＇ speculative motions. The decrement of cycles in critical path is calculated as benefit, while the spilled variables are predicted and their spilling cost is used as cost. Only the speculative motion with benefit greater than the cost is permitted in our method. This algorithm has been implemented in Godson Compiler for MIPS architecture. Experiment result shows that the method in this paper can obtain 1.44% speedup on average relative to its register pressure insensitive counterpart on SPEC CPU2000INT benchmarks.

关 键 词：投机 指令调度 寄存器压力 活跃区间溢出 超标量 

分 类 号：TP314[自动化与计算机技术—计算机软件与理论]