【摘要】 在嵌入式系统的应用中,程序代码中存在着相当多的局部变量,这些局部变量的使用范围(生存期)通常都很小。相关指令在流水中需要局部变量的值可以直接从旁路逻辑中得到,并在流水中完成局部变量值的全部使用。对这种局部变量就没有必要将流水输出结果写回寄存器文件,以减少对寄存器文件(RF)的读写操作次数,从而降低对寄存器文件端口的读写要求。决定是否将结果写回寄存器文件的关键的是要确定寄存器的生存期以及流水中旁路逻辑的情况,本文根据所设计的媒体处理器提出了一种确定程序代码中寄存器生存期的算法,并通过指令编码实现对硬件结构的使能控制,即对流水输出结果写回寄存器文件的控制。软件仿真结果表明,对DSP中不同的应用程序平均可以减少94%的寄存器文件写次数。更多还原

【Abstract】 In the application programs of embedded system,there exist many local variables,whose lifetimes usually are ephemeral,and replaced by registers in assembler codes.This means that their lifetimes only span few instructions.In pipeline the values of local variables needed by dependent instructions may be directly gotten from bypassing logic,and some of them can complete all usage.In this case,it is not necessary to write their values back into register file(RF).Thus the requirement of read/write operation on RF is reduced.Whether to write the results back is dependent on register lifetime(or variable lifetime) and actual bypassing logic in pipeline.Based on the media processor designed by the authors,this paper proposes an algorithm to calculate register lifetime in programs,and the control of writing results back into RF is implemented through an enable control signal provided by instruction encoding at compile time.The results of simulation show that the average number of write operation on RF is reduced by 94% for various application programs.更多还原