January 2026 performance summary for the OpenXiangShan project family. The month focused on delivering targeted performance improvements, reliability fixes, and maintainability enhancements across three repositories, with a strong emphasis on critical-path optimizations and robust timing controls.

Month 2025-12 — Summary of delivered features and fixes across OpenXiangShan/XiangShan and OpenXiangShan/NEMU. Key outcomes include improved execution performance and decoding stability, alongside enhanced CSR configurability and maintainability. Key features delivered and major fixes: TopDown Execution Model Optimizations (XiangShan) introducing TopDownGen to aggregate uop information and manage stall conditions, refining load/store timing; commits 64d438dad20e56ae0a27696f51275909ec4f78a7 and aab516f66c00f990e2656605657421ec03ee1fdf; DecodeUnit CSR Handling Stability for vl/vlenb fixed CSR read prioritization to prevent EX_II (commit f1e32921ec06f990b854234d689df029554a5c0e); Macro-based CSR Handling via Macros in NEMU to improve configurability and maintainability (commit 13c6398421040a45234e3a24d6062a8533c34b2c). Overall impact: improved performance, stability, and maintainability; technologies demonstrated: performance optimization, CSR handling, macro-based configuration, cross-repo collaboration.

OpenXiangShan - 2025-11 monthly summary: Delivered core feature enhancements across NEMU, Ready-to-Run, and YunSuan, driving stronger memory security, readiness, and vector compute capabilities. Emphasized business value through improved configurability, collaboration, and maintainability.

Monthly work summary for Oct 2025 focused on OpenXiangShan/XiangShan delivery, stability improvements, and capability enhancements that drive system reliability and performance. Highlights include ALU-level control-flow enhancements, submodule floating-point improvements, and CSR read-order correctness corrections that strengthen OoO execution behavior and ISA robustness.

September 2025 monthly summary focusing on key accomplishments across OpenXiangShan NEMU and XiangShan. Key features delivered and bugs fixed improved interrupt handling, instruction fetch correctness, and trap management. The work delivered increased reliability of RISC-V interrupt processing, correctness of metadata in the fetch path, and stability of NMI/trap flows, enabling safer production deployments and easier validation.

August 2025 monthly summary focused on stabilizing RISC-V CSR interrupt handling and interoperability across OpenXiangShan/NEMU and OpenXiangShan/ready-to-run. Key fixes improve simulation correctness and interpreter integration, directly reducing debugging time and accelerating verification cycles.

July 2025 highlights for OpenXiangShan/XiangShan: Delivered the Vector Move Unit (vmove) to accelerate vector data movement and processing. The changes enhance vector throughput, provide a foundation for future vector features, and demonstrate end-to-end integration across the vector path. This work supports performance objectives and broader workloads requiring vector acceleration.

June 2025 monthly summary for OpenXiangShan projects focused on modularity improvements and vector data handling across XiangShan and YunSuan. Delivered two key features that strengthen reuse, maintainability, and vector processing capabilities. In XiangShan, the multiplication wrapper was modularized by moving MulFuOpType and Mul implementations to YunSuan, reducing coupling and enabling cross-repo reuse. In YunSuan, a new Vector Move Unit (VMove) was introduced, providing a suite of vector move operations and opcodes to enable efficient data manipulation within vector registers for integer and floating-point workloads. These efforts lay groundwork for faster feature integration and more robust vectorized processing. Technologies/skills demonstrated include modular refactoring, cross-repo architectural alignment, and vector architecture design, all contributing to higher-quality code, easier maintenance, and stronger business value.

May 2025 monthly summary for OpenXiangShan/NEMU: Delivered a correctness-focused diff-testing improvement by fixing CSR old value synchronization for xtopei and xtopi. Ensured the old CSR values are read during diff comparisons between RTL and NEMU, preventing stale values from skewing CSR-related diffs. This reduces false positives in diff reports and strengthens CSR semantics in the diff-testing loop. Key commits include the fixes for xtopei (csrrw read old value) and xtopi (csrr xtopi read old value).

April 2025 monthly summary for OpenXiangShan development across three repositories. Focused on delivering robust NEMU integration, expanding RISC-V architecture support, strengthening interrupt handling and stability, and improving testing fidelity through difftest alignment. Business value centers on runtime stability, broader target support, and clearer error handling across PMP/PMA checks.

Month: 2025-03 summary focusing on key accomplishments across three OpenXiangShan repositories. Key features delivered include NEMU interpreter reference integration into ready-to-run; major bugs fixed in difftest reset handling and RVV FP status bits; overall impact: improved simulation fidelity, stability, and testing reliability; technologies demonstrated: NEMU integration, difftest verification hardening, RVV/vector semantics, FP status handling, and cross-repo coordination.

February 2025 monthly summary for OpenXiangShan/NEMU: Delivered RISC-V 64-bit memory subsystem optimization and clean code cleanup to improve performance and maintainability. Key changes include prefetch control enhancements via SPFCTL and removal of unused CUSTOM_CSR_SFETCHCTL, reinforcing code quality and future upgrade readiness.

January 2025 monthly summary focusing on key accomplishments across OpenXiangShan projects. Delivered observable improvements in cache observability (L2 Miss IO signaling), submodule reliability (Huancun upgrade), interrupt correctness (external source differentiation and priority handling), and testing fidelity (difftest/harness corrections and NEMU reference updates). The work spans four repositories and includes submodule upgrades, CSR/interrupt enhancements, and ready-to-run/NEMU synchronization, delivering measurable business value in reliability, debuggability, and performance insight.

December 2024 monthly summary for OpenXiangShan/XiangShan. The month focused on CSR module performance optimization and interrupt handling simplification, delivering measurable improvements in latency and resource usage. Key changes consolidated the CSR interrupt vector from 64 bits to 8 bits, simplifying prioritization and reducing interrupt handling complexity. A redundant cycle in the CSR write path was removed, further lowering latency. No separate major bug fixes were reported this month; the work emphasized performance improvements, maintainability, and scalability of the CSR subsystem to support future features. Overall impact: improved CSR throughput and lower latency, enabling faster CSR operations and a more scalable interrupt architecture that supports upcoming workload growth. This work demonstrates strong RTL/CSR optimization skills and disciplined commit-driven development. Technologies/skills demonstrated: RTL/CSR architecture optimization, Verilog/SystemVerilog, timing optimization, interrupt design simplification, performance-focused debugging, and careful code maintenance.

November 2024 performance summary: Delivered robust interrupt architecture, CSR correctness, and emulation/testing enhancements across XiangShan and its tooling. Key outcomes include hardened interrupt routing across NMI/M/HS/VS with updated STOPI behavior and filtering; CSR module enhancements adding interrupt numbers 14 and 15; correctness fixes for CSR aliasing and IP status handling; refactored iprios handling for safer maintenance; submodule updates to align ready-to-run and difftest payloads with AIA CSR support; and NEMU/Spike integration improvements including 64-bit RISC-V readiness and a timer fix for mip.mtip in spike.

Month: 2024-10 — OpenXiangShan performance and stability-focused monthly summary. This period prioritized reliability, correctness, and test fidelity across two repositories: OpenXiangShan/XiangShan and OpenXiangShan/riscv-isa-sim. Key work delivered includes critical bug fixes in CSR interrupt handling, FP instruction corrections in the yunsuan submodule, and enhanced Difftest MIP update support. The changes reduced interrupt misbehavior, improved floating-point correctness, and strengthened difftest coverage, delivering measurable business value through more stable simulations, faster CI feedback, and higher confidence in product-grade behavior.

Month: 2024-09 — OpenXiangShan/riscv-isa-sim monthly summary. Delivered RISC-V Zicbom and Zicboz extensions support with enhanced environment control register configuration. This work increases ISA completeness and testing readiness for Zicbom/Zicboz workloads, while improving configurability of environment control registers. No major bugs fixed this month; focus remained on feature integration, code quality, and alignment with the roadmap. Technologies demonstrated include low-level ISA simulation, C/C++ development, and version control discipline.