This is an attempt to a full VFPU documentation for Sony's MIPS Allegrex CPU, the main CPU of Sony's PSP.
Latest docs revision can be found here:
Current documentation is incomplete, scattered all over the internet (in some forums, personal websites, github repos and projects, etc) and, in many cases, contradictory. As opposed to other devices (like the PS2 console) Sony did not release any public documentation (nor SDK/toolchain) for the Sony PSP. For this reason we've attempted to collect all these documents and distil a usable set of documents that can be used by coders, hombrew devs, and anyone interested in writing VFPU assembly.
Since there's some gaps in knowledge as well as contradictions, this
documentation is designed so that it can be verified. All instructions are
described in inst-vfpu-desc.yaml: encoding, operands, valid prefixes,
precision, register collisions and, most importantly, functional description.
For each of these statements there's a test that can be executed on a PSP
device to validate it. Some tests are manually crafted whereas the majority are
autogenerated from the YAML description. Major tests exist for:
- Functional description (pseudo C code)
- Prefix compatibility
- Register overlap restrictions
- Calculation accuracy
- Performance (throughput and latency)
With these tests in place, we can be reasonably sure of the statements described in the docs. For convenience and consistency we also generate most of the actual documentation from this YAML description, so that any change in the formal description is reflected both in the human-readable docs and the tests.
The main assets created by this repo are the tests (which are mostly for internal consumption) and the documentation itself, in HTML and PDF format.
You can generate the docs in HTML and PDF format by running make docs. This
requires weasyprint as well as a few python modules such as mako, pyyaml,
markdown and tatsu.
To build the tests a recent PSP toolchain
is required. You will need to follow the SDK instructions (that is, set PSPDEV
and PATH environment variables before running any make rules). You can just
run make psptests to get EBOOT.PBP binaries (or, as usual, run
make psptests BUILD_PRX=1 to get .prx modules). We recommend running build
parallel (-jN) since tests are pretty big and take a while to build.
Some tests are autogenerated (but also checked-in in the repo), you might
re-generate them (ie. if you want to update the instruction description) by
running make tests. It is recommended to install clang-format to produce
readable test files. Tests are generally deterministic to avoid random data
changing on every build.
All sources and documentation are placed under the GPL 3 license unless explicitely indicated in the file header. If there's any issue or you would like to use certain parts in your project but have some licensing issues, feel free to reach out to the original author(s) and contributor(s).