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Instead of using copies of primitives from OpenTitan, vendor the files in directly from OpenTitan, and use them. Benefits: - Less potential for diverging code between OpenTitan and Ibex, causing problems when importing Ibex into OT. - Use of the abstract primitives instead of the generic ones. The abstract primitives are replaced during synthesis time with target-dependent implementations. For simulation, nothing changes. For synthesis for a given target technology (e.g. a specific ASIC or FPGA technology), the primitives system can be instructed to choose optimized versions (if available). This is most relevant for the icache, which hard-coded the generic SRAM primitive before. This primitive is always implemented as registers. By using the abstract primitive (prim_ram_1p) instead, the RAMs can be replaced with memory-compiler-generated ones if necessary. There are no real draw-backs, but a couple points to be aware of: - Our ram_1p and ram_2p implementations are kept as wrapper around the primitives, since their interface deviates slightly from the one in prim_ram*. This also includes a rather unfortunate naming confusion around rvalid, which means "read data valid" in the OpenTitan advanced RAM primitives (prim_ram_1p_adv for example), but means "ack" in PULP-derived IP and in our bus implementation. - The core_ibex UVM DV doesn't use FuseSoC to generate its file list, but uses a hard-coded list in `ibex_files.f` instead. Since the dynamic primitives system requires the use of FuseSoC we need to provide a stop-gap until this file is removed. Issue #893 tracks progress on that. - Dynamic primitives depend no a not-yet-merged feature of FuseSoC (https://github.com/olofk/fusesoc/pull/391). We depend on the same functionality in OpenTitan and have instructed users to use a patched branch of FuseSoC for a long time through `python-requirements.txt`, so no action is needed for users which are either successfully interacting with the OpenTitan source code, or have followed our instructions. All other users will see a reasonably descriptive error message during a FuseSoC run. - This commit is massive, but there are no good ways to split it into bisectable, yet small, chunks. I'm sorry. Reviewers can safely ignore all code in `vendor/lowrisc_ip`, it's an import from OpenTitan. - The check_tool_requirements tooling isn't easily vendor-able from OpenTitan at the moment. I've filed https://github.com/lowRISC/opentitan/issues/2309 to get that sorted. - The LFSR primitive doesn't have a own core file, forcing us to include the catch-all `lowrisc:prim:all` core. I've filed https://github.com/lowRISC/opentitan/issues/2310 to get that sorted. |
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| ci | ||
| doc | ||
| dv | ||
| examples | ||
| formal | ||
| lint | ||
| rtl | ||
| shared | ||
| syn | ||
| util | ||
| vendor | ||
| .clang-format | ||
| .gitignore | ||
| azure-pipelines.yml | ||
| check_tool_requirements.core | ||
| CONTRIBUTING.md | ||
| CREDITS.md | ||
| ibex_configs.yaml | ||
| ibex_core.core | ||
| ibex_core_tracing.core | ||
| ibex_icache.core | ||
| ibex_pkg.core | ||
| ibex_tracer.core | ||
| LICENSE | ||
| Makefile | ||
| python-requirements.txt | ||
| README.md | ||
| src_files.yml | ||
| tool_requirements.py | ||
Ibex RISC-V Core
Ibex is a small and efficient, 32-bit, in-order RISC-V core with a 2-stage pipeline that implements the RV32IMC instruction set architecture.
Ibex offers several configuration parameters to meet the needs of various application scenarios. The options include two different choices for the architecture of the multiplier and divider unit, as well as the possibility to drop the support for the "M" extension completely. In addition, the "E" extension can be enabled when opting for a minimum-area configuration.
This core was initially developed as part of the PULP platform under the name "Zero-riscy" [1], and has been contributed to lowRISC who maintains it and develops it further. It is under active development, with further code cleanups, feature additions, and test and verification planned for the future.
Documentation
The Ibex user manual can be
read online at ReadTheDocs. It is also contained in
the doc folder of this repository.
Contributing
We highly appreciate community contributions. To ease our work of reviewing your contributions, please:
- Create your own branch to commit your changes and then open a Pull Request.
- Split large contributions into smaller commits addressing individual changes or bug fixes. Do not mix unrelated changes into the same commit!
- Write meaningful commit messages. For more information, please check out the contribution guide.
- If asked to modify your changes, do fixup your commits and rebase your branch to maintain a clean history.
When contributing SystemVerilog source code, please try to be consistent and adhere to our Verilog coding style guide.
When contributing C or C++ source code, please try to adhere to the OpenTitan C++ coding style
guide.
All C and C++ code should be formatted with clang-format before committing.
Either run clang-format -i filename.cc or git clang-format on added files.
To get started, please check out the "Good First Issue" list.
Issues and Troubleshooting
If you find any problems or issues with Ibex or the documentation, please check out the issue tracker and create a new issue if your problem is not yet tracked.
Questions?
Do not hesitate to contact us, e.g., on our public Ibex channel on Zulip!
License
Unless otherwise noted, everything in this repository is covered by the Apache License, Version 2.0 (see LICENSE for full text).
Credits
Many people have contributed to Ibex through the years. Please have a look at the credits file and the commit history for more information.