FoMR: Collaborative Research: Dependent ILP: Dynamic Hoisting and Eager Scheduling of Dependent Instructions

计算中的指令级并行(ILP)允许应用程序中的不同机器级指令在微处理器内并行执行。ILP的开发在计算方面提供了显著的性能优势，但近年来ILP的性能几乎没有改善。该项目提出了一种名为“急切执行”的新方法，可以显著提高ILP。许多应用程序的成功取决于它们的执行效率。拟议的急切执行技术将使在移动设备上运行的应用程序和在不断增长的数据中心上运行的大型数据应用程序受益。该项目的方法包括以下优点：(1)直接相关的消费者指令可以更快地传送到功能单元以供执行；(2)可以检测到其源寄存器值自上次执行以来没有改变的指令的执行，并且可以避免冗余计算；(3)生产者/消费者对指令之间的依赖性有时可以被折叠，以便它们可以同时被调度用于执行；(4)来自多个路径的消费者指令可以推测性地执行，其结果可以自然地保留在范例中，以避免在分支误预测之后重新执行；以及(5)关键指令可以被急切地执行以提高性能，包括加载到预取高速缓存线和预计计算分支结果以避免分支误预测延迟。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Instruction-level parallelism (ILP) in computing allows different machine-level instructions within an application to execute in parallel within a micro-processor. Exploitation of ILP has provided significant performance benefits in computing, but there has been little improvement in ILP in recent years. This project proposes a new approach called "eager execution" that could significantly increase ILP. The success of many applications depends on how efficiently they can be executed. The proposed eager execution technique will benefit applications that span those running on mobile devices to large data applications running on the ever-growing number of data centers. Enabling better systems at all scales will further enable the ubiquitous computing that continues to pervade lives.The project's approach includes the following advantages: (1) immediately-dependent consumer instructions can be more quickly delivered to functional units for execution; (2) the execution of instructions whose source register values have not changed since its last execution can be detected and redundant computation can be avoided; (3) the dependency between a producer/consumer pair of instructions can sometimes be collapsed so they can be simultaneously dispatched for execution; (4) consumer instructions from multiple paths may be speculatively executed and their results can be naturally retained in the paradigm to avoid re-execution after a branch misprediction; and (5) critical instructions can be eagerly executed to improve performance, which include loads to prefetch cache lines and pre-computation of branch results to avoid branch misprediction delays.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.