816ef46c78
According to the RISC-V spec [1]. Any float-point instructions
accumulate FFLAGS register rather than write it to reflect the CSR
behavior.
In the previous implementation. We read the FFLAGS, set the exception
flags, and write the result back to the FFLAGS. This works in the gem5
simple and minor CPU model as they are actually written to `regFile`
after executing the instructions. However, in the gem5 O3 CPU model, it
will record in the `destMiscReg` buffer until the commit stage when
writing to the `miscReg` in the execution stage. The next instruction
will get the old FFLAGS and cause the incorrect result.
The CL introduced the `MISCREG_FFLAGS_EXE` and used the same size of
`miscRegFile` because the `MISCREG_FFLAGS_EXE` and `MISCREG_FFLAGS`
shared the same space. When executing the float-pointing instruction,
any exception flags should be updated via `MISCREG_FFLAGS_EXE` to
accumulate the FFLAGS in `setMiscReg` method. For the MISCREG_FFLAGS, it
should only be called in the CSROp.
[1] Syntactic Dependencies: Appendix A
c80ecada1c/src/mm-eplan.adoc (syntactic-dependencies-rules-9-11)
gem5 issue: https://github.com/gem5/gem5/issues/755
Change-Id: Ib7f13d95b8a921c37766a54a217a5a4b1ef17c6f
The gem5 Simulator
This is the repository for the gem5 simulator. It contains the full source code for the simulator and all tests and regressions.
The gem5 simulator is a modular platform for computer-system architecture research, encompassing system-level architecture as well as processor microarchitecture. It is primarily used to evaluate new hardware designs, system software changes, and compile-time and run-time system optimizations.
The main website can be found at http://www.gem5.org.
Testing status
Note: These regard tests run on the develop branch of gem5: https://github.com/gem5/gem5/tree/develop.
Getting started
A good starting point is http://www.gem5.org/about, and for more information about building the simulator and getting started please see http://www.gem5.org/documentation and http://www.gem5.org/documentation/learning_gem5/introduction.
Building gem5
To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/documentation/general_docs/building for more details concerning the minimum versions of these tools.
Once you have all dependencies resolved, execute
scons build/ALL/gem5.opt to build an optimized version of the gem5 binary
(gem5.opt) containing all gem5 ISAs. If you only wish to compile gem5 to
include a single ISA, you can replace ALL with the name of the ISA. Valid
options include ARM, NULL, MIPS, POWER, RISCV, SPARC, and X86
The complete list of options can be found in the build_opts directory.
See https://www.gem5.org/documentation/general_docs/building for more information on building gem5.
The Source Tree
The main source tree includes these subdirectories:
- build_opts: pre-made default configurations for gem5
- build_tools: tools used internally by gem5's build process.
- configs: example simulation configuration scripts
- ext: less-common external packages needed to build gem5
- include: include files for use in other programs
- site_scons: modular components of the build system
- src: source code of the gem5 simulator. The C++ source, Python wrappers, and Python standard library are found in this directory.
- system: source for some optional system software for simulated systems
- tests: regression tests
- util: useful utility programs and files
gem5 Resources
To run full-system simulations, you may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of these resources can be obtained from https://resources.gem5.org.
More information on gem5 Resources can be found at https://www.gem5.org/documentation/general_docs/gem5_resources/.
Getting Help, Reporting bugs, and Requesting Features
We provide a variety of channels for users and developers to get help, report bugs, requests features, or engage in community discussions. Below are a few of the most common we recommend using.
- GitHub Discussions: A GitHub Discussions page. This can be used to start discussions or ask questions. Available at https://github.com/orgs/gem5/discussions.
- GitHub Issues: A GitHub Issues page for reporting bugs or requesting features. Available at https://github.com/gem5/gem5/issues.
- Jira Issue Tracker: A Jira Issue Tracker for reporting bugs or requesting features. Available at https://gem5.atlassian.net/.
- Slack: A Slack server with a variety of channels for the gem5 community to engage in a variety of discussions. Please visit https://www.gem5.org/join-slack to join.
- gem5-users@gem5.org: A mailing list for users of gem5 to ask questions or start discussions. To join the mailing list please visit https://www.gem5.org/mailing_lists.
- gem5-dev@gem5.org: A mailing list for developers of gem5 to ask questions or start discussions. To join the mailing list please visit https://www.gem5.org/mailing_lists.
Contributing to gem5
We hope you enjoy using gem5. When appropriate we advise charing your contributions to the project. https://www.gem5.org/contributing can help you get started. Additional information can be found in the CONTRIBUTING.md file.