arXiv:2506.17247cs.LGcs.AI2025-06被引 4

用递归学习预测布缓冲位置,提升物理综合时序收敛效率。

Recursive Learning-Based Virtual Buffering for Analytical Global Placement

  • 递归学习生成缓冲布局,动态优化位置与类型。
  • 开源测试中时序松弛改善达31%~56%,功耗基本不变。
  • 适配真实设计流程,解决电气规则违规问题。

由于现代工艺节点下互连延迟与单元延迟的非线性缩放,物理综合流程中需考虑缓冲密度感知的布局以实现时序收敛。现有方法面临两大挑战:(i) 传统 van Ginneken-Lillis 类缓冲策略在全局布局阶段计算开销大;(ii) 基于机器学习的方法(如 BufFormer)未充分考虑电气规则检查(ERC)违规,且无法闭环反馈至物理设计流程。本文提出 MLBuf-RePlAce,首个基于 OpenROAD 开源框架的可学习虚拟缓冲感知分析式全局布局框架。该方法采用高效的递归学习生成式缓冲策略,在全局布局阶段预测缓冲类型与位置,有效缓解 ERC 违规。我们在 TILOS MacroPlacement 与 OpenROAD-flow-scripts 的开源测试用例上进行对比,结果表明:在不增加后布线功耗的前提下,相较于 OpenROAD 默认的虚拟缓冲时序驱动全局布局器,MLBuf-RePlAce 在开源流程中实现总负松弛(TNS)最大/平均改进 56%/31%;在商业流程中则实现最大/平均改进 53%/28%,后布线功耗平均仅提升 0.2%。

原文摘要 · Abstract (English)

Due to the skewed scaling of interconnect versus cell delay in modern technology nodes, placement with buffer porosity (i.e., cell density) awareness is essential for timing closure in physical synthesis flows. However, existing approaches face two key challenges: (i) traditional van Ginneken-Lillis-style buffering approaches are computationally expensive during global placement; and (ii) machine learning-based approaches, such as BufFormer, lack a thorough consideration of Electrical Rule Check (ERC) violations and fail to "close the loop" back into the physical design flow. In this work, we propose MLBuf-RePlAce, the first open-source learning-driven virtual buffering-aware analytical global placement framework, built on top of the OpenROAD infrastructure. MLBuf-RePlAce adopts an efficient recursive learning-based generative buffering approach to predict buffer types and locations, addressing ERC violations during global placement. We compare MLBuf-RePlAce against the default virtual buffering-based timing-driven global placer in OpenROAD, using open-source testcases from the TILOS MacroPlacement and OpenROAD-flow-scripts repositories. Without degradation of post-route power, MLBuf-RePlAce achieves (maximum, average) improvements of (56%, 31%) in total negative slack (TNS) within the open-source OpenROAD flow. When evaluated by completion in a commercial flow, MLBuf-RePlAce achieves (maximum, average) improvements of (53%, 28%) in TNS with an average of 0.2% improvement in post-route power.

布局优化机器学习时序收敛物理设计

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