Register sharing for equality prediction
Register sharing for equality prediction
复制标题
寄存器共享以进行相等预测
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
André Seznec
中科院分区：
文献类型：
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作者：
Arthur Perais;F. A. Endo;André Seznec
最近，价值预测（VP）在研究界已获得了新的牵引力。 VP猜测指令的结果增加了指令水平并行性（ILP）。在大多数实施例中，VP需要大表格跟踪许多静态说明的预测。但是，在许多情况下，可以检测到指令的结果是由较旧的机上指令产生的，但不能预测结果本身。因此，有可能依靠预测寄存器平等并通过重命友处理投机。为此，我们建议使用距离预测，该技术以前用于执行投机性存储器绕过（短路def-商店载荷链）。距离预测试图确定有多少个说明将感兴趣的指令和产生相同结果的最新旧指令分开。有了这些信息，可以从ROB中检索旧说明的物理寄存器标识符并提供给Renamer。在本文中，我们首先量化了基于重命名的寄存器平等预测和规范基准标准的常规副总裁带来的性能提高。其次，我们研究了两种不同方案之间的重叠，并表明这些机制通常捕获不同的行为。
Recently, Value Prediction (VP) has been gaining renewed traction in the research community. VP speculates on the result of instructions to increase Instruction Level Parallelism (ILP). In most embodiments, VP requires large tables to track predictions for many static instructions. However, in many cases, it is possible to detect that the result of an instruction is produced by an older inflight instruction, but not to predict the result itself. Consequently it is possible to rely on predicting register equality and handle speculation through the renamer. To do so, we propose to use Distance Prediction, a technique that was previously used to perform Speculative Memory Bypassing (short-circuiting def-store-load-use chains). Distance Prediction attempts to determine how many instructions separate the instruction of interest and the most recent older instruction that produced the same result. With this information, the physical register identifier of the older instruction can be retrieved from the ROB and provided to the renamer. In this paper, we first quantify the performance gains brought by renaming-based register equality prediction and regular VP on SPEC benchmarks. Second, we study the overlap between the two different schemes and show that those mechanisms often capture different behavior.