龙芯链接后优化器设计与分析

GLTO Design and Analysis

链接后优化技术是在编译链接后对整个程序再进行优化的一种技术·它克服了传统编译器优化局限于一个函数、一个模块的缺点,将优化范围扩展到整个程序,并且充分利用了链接后确定的信息·参照Arizona大学为Alpha处理器设计的链接后优化器ALTO,针对龙芯2号处理器的微体系结构和指令集的特征,设计了龙芯上的链接后优化器GLTO(Godsonlinktimeoptimizer)·GLTO使得龙芯处理器SPEC2000定点程序ref分值提高了9·4%,具有显著的优化效果·分析了主要优化策略的效果和产生的原因,提出了处理器的结构设计中的改进设想,并将GLTO与ALTO做了对比分析·

Link time optimization is a technique which optimizes the whole program after compilation. It overcomes the limitations of traditional compilers by enlarging the optimizing scope from a single function or a module to the whole program, and fully utilizes the information only available at link time. Guided by the link time optimizer ALTO developed by Arizona University for the Compag Alpha, the GLTO （Godson link time optimizer） is designed with the consideration of the features of the microarchitecture and the instruction set of the Godson-2 processor. GLTO can achieve a 9.4% performance improvement of the SPEC2000 integer benchmark with ref input on average. In this paper, the effect and the cause of several major optimizing methods are explored, some improvements in the processor architecture design are proposed, and the differences between GLTO and ALTO are analyzed.