The stdarch crate is more than willing to accept contributions! First you'll probably want to check out the repository and make sure that tests pass for you:
$ git clone https://github.com/rust-lang/stdarch $ cd stdarch $ TARGET="<your-target-arch>" ci/run.sh
Where <your-target-arch> is the target triple as used by rustup, e.g. x86_64-unknown-linux-gnu (without any preceding nightly- or similar). Also remember that this repository requires the nightly channel of Rust! The above tests do in fact require nightly rust to be the default on your system, to set that use rustup default nightly (and rustup default stable to revert).
If any of the above steps don't work, please let us know!
Next up you can find an issue to help out on, we‘ve selected a few with the help wanted and impl-period tags which could particularly use some help. You may be most interested in #40, implementing all vendor intrinsics on x86. That issue’s got some good pointers about where to get started!
If you've got general questions feel free to join us on gitter and ask around! Feel free to ping either @BurntSushi or @alexcrichton with questions.
There are a few features that must be enabled for the given intrinsic to work properly and the example must only be run by cargo test --doc when the feature is supported by the CPU. As a result, the default fn main that is generated by rustdoc will not work (in most cases). Consider using the following as a guide to ensure your example works as expected.
/// # // We need cfg_target_feature to ensure the example is only /// # // run by `cargo test --doc` when the CPU supports the feature /// # #![feature(cfg_target_feature)] /// # // We need target_feature for the intrinsic to work /// # #![feature(target_feature)] /// # /// # // rustdoc by default uses `extern crate stdarch`, but we need the /// # // `#[macro_use]` /// # #[macro_use] extern crate stdarch; /// # /// # // The real main function /// # fn main() { /// # // Only run this if `<target feature>` is supported /// # if cfg_feature_enabled!("<target feature>") { /// # // Create a `worker` function that will only be run if the target feature /// # // is supported and ensure that `target_feature` is enabled for your worker /// # // function /// # #[target_feature(enable = "<target feature>")] /// # unsafe fn worker() { /// /// // Write your example here. Feature specific intrinsics will work here! Go wild! /// /// # } /// # unsafe { worker(); } /// # } /// # }
If some of the above syntax does not look familiar, the Documentation as tests section of the Rust Book describes the rustdoc syntax quite well. As always, feel free to join us on gitter and ask us if you hit any snags, and thank you for helping to improve the documentation of stdarch!
It is generally recommended that you use ci/run.sh to run the tests. However this might not work for you, e.g. if you are on Windows.
In that case you can fall back to running cargo +nightly test and cargo +nightly test --release -p core_arch for testing the code generation. Note that these require the nightly toolchain to be installed and for rustc to know about your target triple and its CPU. In particular you need to set the TARGET environment variable as you would for ci/run.sh. In addition you need to set RUSTCFLAGS (need the C) to indicate target features, e.g. RUSTCFLAGS="-C -target-features=+avx2". You can also set -C -target-cpu=native if you're “just” developing against your current CPU.
Be warned that when you use these alternative instructions, things may go less smoothly than they would with ci/run.sh, e.g. instruction generation tests may fail because the disassembler named them differently, e.g. it may generate vaesenc instead of aesenc instructions despite them behaving the same. Also these instructions execute less tests than would normally be done, so don't be surprised that when you eventually pull-request some errors may show up for tests not covered here.