XiangShan

XiangShan (香山) is an open-source high-performance RISC-V processor project.

Detailed documents will be released in the near future.

Copyright 2020-2021 by Institute of Computing Technology, Chinese Academy of Sciences.

=== Tutorial is Comming! ===

A tutorial on XiangShan is held at RISC-V World Conference China 2021 in June. Multiple technical reports will be included in the conference as well. Stay tuned!

For more information, please refer to this link.

Architecture

The first stable micro-architecture of XiangShan is called Yanqihu (雁栖湖) on this branch, which has been developed since June, 2020. The current version of XiangShan, also known as Nanhu (南湖), is still under development on master branch.

The micro-architecture overview is shown below.

Sub-directories Overview

Some of the key directories are shown below.

.
├── fpga                   # supported FPGA boards and files to build a Vivado project
├── read-to-run            # pre-built simulation images
├── scripts                # scripts for agile development
└── src
    ├── test               # test files (including diff-test, module-test, etc.)
    └── main/scala         # design files
        ├── bus/tilelink   # tilelink utils
        ├── device         # virtual device for simulation
        ├── difftest       # diff-test chisel interface
        ├── system         # SoC wrapper
        ├── top            # top module
        ├── utils          # utilization code
        ├── xiangshan      # main design code
        └── xstransforms   # some useful firrtl transforms

Generate Verilog

• Run make verilog to generate verilog code. The output file is build/XSTop.v.
• Refer to Makefile for more information.

Run Programs by Simulation

Prepare environment

• Set environment variable NEMU_HOME to the absolute path of the NEMU project.
• Set environment variable NOOP_HOME to the absolute path of the XiangShan project.
• Set environment variable AM_HOME to the absolute path of the AM project.
• Install mill. Refer to the Manual section in this guide.
• Clone this project and run make init to initialize submodules.

Run with simulator

• Install Verilator, the open-source Verilog simulator.
• Run make emu to build the C++ simulator ./build/emu with Verilator.
• Refer to ./build/emu --help for run-time arguments of the simulator.
• Refer to Makefile and verilator.mk for more information.

Example:

make emu CONFIG=MinimalConfig SIM_ARGS=--disable-log EMU_THREADS=2 -j10
./build/emu -b 0 -e 0 -i ./ready-to-run/coremark-2-iteration.bin --diff ./ready-to-run/riscv64-nemu-interpreter-so

Acknowledgement

In the development of XiangShan, some sub-modules from open source community are employed. All relavant usage is listed below.

Sub-module	Source	Detail
L2 Cache/LLC	Sifive block-inclusivecache	We enhance the function and the timing of the original module, finally turning it into a Cache generator that can be configured as L2/LLC.
Diplomacy/TileLink	Rocket-chip	We reused the diplomacy framework and TileLink utility that exist in rocket-chip to negotiate bus.
FPU	Berkeley hardfloat	We use Berkeley-hardfloat as our FPU and implement a SRT-4 div/sqrt unit for it. Additionally, we split the FMA pipeline to optimize the timing.

We are grateful for the support of the open source community and encourage other open source projects to reuse our code within the scope of the license.