yosys-slang is a Yosys plugin providing a new command (read_slang) for loading SystemVerilog designs.
yosys-slang builds on top of the slang library to provide comprehensive SystemVerilog support. The plugin supports an (informally defined) synthesizable subset of SystemVerilog in version IEEE 1800-2017 or IEEE 1800-2023.
Please open GitHub issues for missing features and/or confusing error messages.
The plugin is available prebuilt as part of
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OSS CAD Suite from YosysHQ, and
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IIC-OSIC-TOOLS from Johannes Kepler University
2025/05: Koopa taped out using yosys-slang.
2024/12: ETH Zürich have used yosys-slang for a chip tapeout. Meet MLEM.
yosys-slang can parse a number of open-source IPs, including:
For details see the compat suite repository which documents sample command lines.
Prerequisities:
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Yosys installed: supported versions are 0.44 0.45 0.46 0.47 0.48 0.49 0.50 0.51 0.52 0.53
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C++ compiler: GCC 11 and clang 17 are minimum supported versions
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Usual toolchains, CMake
Check out the repository including the submodule, e.g. with
git clone --recursive https://github.com/povik/yosys-slang
Then build both slang and the build/slang.so plugin for Yosys:
make -j$(nproc)
Use a custom -jN switch to build with N concurrent processes instead of matching the number of cores.
The built plugin is placed at build/slang.so. Copy this file into the Yosys plugin directory, which can be achieved through make install, or use a full path to this file (instead of the slang shorthand) when loading the plugin.
You load the plugin into Yosys on startup by passing the -m argument:
$ yosys -m slang
Or, alternatively, you load the plugin at runtime with the plugin command:
plugin -i slang
After the plugin has been loaded, the frontend is invoked with the read_slang command.
For a full documentation of the command options, see help read_slang. The command understands standard slang options.
Sample usage:
read_slang picorv32.v --top picorv32 -D DEBUG
Contributions are welcome! If you intent to develop a particular feature, feel free to get in touch and consult on the appropriate approach.
The following organizations have supported the project and contributed to yosys-slang development:
The bulk of yosys-slang source code is is distributed under the ISC license, see LICENSE. An exception is src/initial_eval.cc which contains modified portions of Slang and is distributed under the terms of the MIT license, see the file header.
In addition, yosys-slang embeds
- slang, Copyright (c) Michael Popoloski, see
third_party/slang/for license information - {fmt}, Copyright (c) Victor Zverovich and {fmt} contributors, see
third_party/fmt/for license information