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diff --git a/library/portable-simd/README.md b/library/portable-simd/README.md new file mode 100644 index 000000000..db0af2da6 --- /dev/null +++ b/library/portable-simd/README.md @@ -0,0 +1,69 @@ +# The Rust standard library's portable SIMD API + + +Code repository for the [Portable SIMD Project Group](https://github.com/rust-lang/project-portable-simd). +Please refer to [CONTRIBUTING.md](./CONTRIBUTING.md) for our contributing guidelines. + +The docs for this crate are published from the main branch. +You can [read them here][docs]. + +If you have questions about SIMD, we have begun writing a [guide][simd-guide]. +We can also be found on [Zulip][zulip-project-portable-simd]. + +If you are interested in support for a specific architecture, you may want [stdarch] instead. + +## Hello World + +Now we're gonna dip our toes into this world with a small SIMD "Hello, World!" example. Make sure your compiler is up to date and using `nightly`. We can do that by running + +```bash +rustup update -- nightly +``` + +or by setting up `rustup default nightly` or else with `cargo +nightly {build,test,run}`. After updating, run +```bash +cargo new hellosimd +``` +to create a new crate. Edit `hellosimd/Cargo.toml` to be +```toml +[package] +name = "hellosimd" +version = "0.1.0" +edition = "2018" +[dependencies] +core_simd = { git = "https://github.com/rust-lang/portable-simd" } +``` + +and finally write this in `src/main.rs`: +```rust +use core_simd::*; +fn main() { + let a = f32x4::splat(10.0); + let b = f32x4::from_array([1.0, 2.0, 3.0, 4.0]); + println!("{:?}", a + b); +} +``` + +Explanation: We import all the bindings from the crate with the first line. Then, we construct our SIMD vectors with methods like `splat` or `from_array`. Finally, we can use operators on them like `+` and the appropriate SIMD instructions will be carried out. When we run `cargo run` you should get `[11.0, 12.0, 13.0, 14.0]`. + +## Code Organization + +Currently the crate is organized so that each element type is a file, and then the 64-bit, 128-bit, 256-bit, and 512-bit vectors using those types are contained in said file. + +All types are then exported as a single, flat module. + +Depending on the size of the primitive type, the number of lanes the vector will have varies. For example, 128-bit vectors have four `f32` lanes and two `f64` lanes. + +The supported element types are as follows: +* **Floating Point:** `f32`, `f64` +* **Signed Integers:** `i8`, `i16`, `i32`, `i64`, `i128`, `isize` +* **Unsigned Integers:** `u8`, `u16`, `u32`, `u64`, `u128`, `usize` +* **Masks:** `mask8`, `mask16`, `mask32`, `mask64`, `mask128`, `masksize` + +Floating point, signed integers, and unsigned integers are the [primitive types](https://doc.rust-lang.org/core/primitive/index.html) you're already used to. +The `mask` types are "truthy" values, but they use the number of bits in their name instead of just 1 bit like a normal `bool` uses. + +[simd-guide]: ./beginners-guide.md +[zulip-project-portable-simd]: https://rust-lang.zulipchat.com/#narrow/stream/257879-project-portable-simd +[stdarch]: https://github.com/rust-lang/stdarch +[docs]: https://rust-lang.github.io/portable-simd/core_simd |