GLTO Design and Analysis

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.