Value Speculation for VLIW and EPIC Architectures

这个项目致力于打破水平（EPIC，VLIW）微架构的纯依赖性的新技术。调度长度的最终限制是通过计算的最长链。这项研究提出了依赖链分裂技术，使用先前提出的超标量微体系结构的方法攻击纯依赖链。超标量处理器的技术不能直接应用于VLIW或EPIC架构，因为这样的架构没有或几乎没有动态推测机制。本质上，它们执行编译器静态推测的代码。这项工作的核心思想是在一个有利的分裂点打破一个链条，然后投机地执行链条的后半部分。这个项目开发的技术，以找到一个区域的代码的最佳分割点（S），开发基于硬件的非常低的开销值剖析，研究VLIW/EPIC特定的值预测器设计，调查的算法来解决惩罚分支修补代码，寻找到的方法，为VLIW/EPIC值投机增加信心预测，并研究软件的潜力，只有价值投机。诸如寄存器压力影响和跨控制流的值推测的分支插入等问题也正在探索中。

This project addresses new techniques to break pure dependencies for horizontal (EPIC, VLIW) microarchitectures. The ultimate limit to schedule length is the longest chain through the computation. The research presents techniques for dependence chain splitting, which attack pure dependence chains using methods presented earlier for superscalar microarchitectures. The techniques for superscalar processors are not directly applicable to VLIW or EPIC architectures, since such architectures have no or little dynamic speculation mechanisms. Essentially, they execute code that is statically speculated by the compiler. The core idea of this work is to break a chain at a beneficial split point, and then speculatively execute the second half of the chain. This project develops techniques to find the best split point(s) of a region of code, develop hardware-based very low overhead value profiling, study VLIW/EPIC-specific value predictor designs, investigate heuristics to address the penalty branches to patch-up code, look into methods for adding confidence prediction for VLIW/EPIC value speculation, and study the potential of software-only value speculation. Issues such as register pressure impact and branch insertion for value speculation across control flow are also being explored.