Recent work in the field of value prediction (VP) has shown that given an efficient confidence estimation mechanism, prediction validation could be removed from the out-of-order engine and delayed until commit time. As a result, a simple recovery mechanism—pipeline squashing—can be used, whereas the out-of-order engine remains mostly unmodified. Yet, VP and validation at commit time require additional ports on the physical register file, potentially rendering the overall number of ports unbearable. Fortunately, VP also implies that many single-cycle ALU instructions have their operands predicted in the front-end and can be executed in-place, in-order. Similarly, the execution of single-cycle instructions whose result has been predicted can be delayed until commit time since predictions are validated at commit time. Consequently, a significant number of instructions—10% to 70% in our experiments—can bypass the out-of-order engine, allowing for a reduction of the issue width. This reduction paves the way for a truly practical implementation of VP. Furthermore, since VP in itself usually increases performance, our resulting {Early—Out-of-Order—Late} Execution architecture, EOLE, is often more efficient than a baseline VP-augmented 6-issue superscalar while having a significantly narrower 4-issue out-of-order engine.

中文翻译：

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EOLE

价值预测 (VP) 领域的最新工作表明，给定有效的置信度估计机制，可以将预测验证从无序引擎中移除并延迟到提交时间。因此，可以使用简单的恢复机制——管道挤压——而无序引擎大部分保持不变。然而，提交时的 VP 和验证需要物理寄存器文件上的额外端口，这可能会使端口的总数难以承受。幸运的是，VP 还意味着许多单周期 ALU 指令的操作数都在前端进行了预测，并且可以按顺序就地执行。类似地，其结果已被预测的单周期指令的执行可以延迟到提交时间，因为预测在提交时得到验证。所以，大量指令（在我们的实验中占 10% 到 70%）可以绕过乱序引擎，从而减少问题宽度。这种减少为真正实际实施 VP 铺平了道路。此外，由于 VP 本身通常会提高性能，因此我们得到的 {Early-Out-of-Order-Late} 执行架构 EOLE 通常比基线 VP-augmented 6-issue superscalar 更有效，同时具有明显更窄的 4-issue无序引擎。