BOOM处理器采用的Store指令回查策略虽然解决了访存指令乱序执行引发的数据冲突问题,但是该策略会导致流水线的大量冲刷,降低了处理器的性能.对此,提出了一种访存指令的相关性预测方法.该方法取消了Load指令访存前的查询操作,增加了Load指令相关性预测表,只有预测为无相关性的Load指令才可以乱序执行.这种方法在保证程序逻辑正确的前提下避免了大量冲刷流水线.测试程序采用SPEC CPU 2006下的7个子程序,实验结果表明,改进后的处理器执行程序的性能平均提升了3.5％.
Optimization of memory access logic in BOOM processor
Although the Store instruction backtracking strategy adopted by BOOM processors solves the problem of data conflicts caused by out-of-order execution of memory access instructions,this strat-egy can lead to a large amount of pipeline flushing and reduce the processor performance.To address this,a correlation prediction method for memory access instructions is proposed.This method cancels the query operation before the Load instruction accesses memory and adds a Load instruction correlation prediction table.Only Load instructions that are predicted to be uncorrelated can be executed in disor-der.This method avoids a large amount of pipeline flushing while ensuring the correctness of program logic.The test program uses 7 subroutines under SPEC CPU 2006,and the experimental results show that the improved processor's execution performance is improved by 3.5％on average.
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