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| Optimization of data forwarding based on early write-back strategy |
| CAI Wei-guang, YAO Qing-dong, LIU Peng, ZHANG Qi, ZHANG Yi-xiong |
| (Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China) |
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Abstract For deep pipeline and complex instruction set architecture, a data forwarding model based on operand access order was introduced, which utilized five parameters to describe the instruction execution process. Employing this model, a processor prototype MediaDSP64 of RISC/DSP architecture was analyzed, and a data forwarding optimization method based on distributed bypassing unit was introduced. The number of data forwarding source was reduced without instruction execution efficiency degradation, by earlier writing back the result of auxiliary register in DSP instructions. For the out of order execution caused by this method, a shadow register structure was designed to deal with precise exception handling. Experimental results showed that the hardware resource of data forwarding circuit was reduced by 43.8%, and the timing delay of critical path was reduced by 19.8%．
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Published: 26 February 2010
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基于提前写回策略的数据转发优化方法
针对深度流水线和复杂指令集结构,给出一种基于操作数访问时序的数据转发模型,使用5个参数描述指令执行过程,并以一种RISC/DSP结构MediaDSP64原型机为例进行分析.在分布式转发电路的基础上,提出一种基于提前写回策略的转发优化方法.该策略在不影响指令执行效率的前提下,通过将DSP指令中辅助寄存器的结果提前写回寄存器文件减少了转发源的数量.针对该方法造成的指令乱序执行情况,设计一种影子寄存器结构,保证了精确异常处理的实现.实验结果表明,转发电路的硬件资源占用减少了43.8%,关键路径延时下降了19.8%.
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