A crate to help you go wide.

Specifically, this has portable "wide" data types that do their best to be SIMD when possible.

On x86, x86_64, wasm32 and aarch64 neon this is done with explicit intrinsic usage (via safe_arch), and on other architectures this is done by carefully writing functions so that LLVM hopefully does the right thing. When Rust stabilizes more explicit intrinsics then they can go into safe_arch and then they can get used here.

Aarch64 always enables the NEON extension, so wide can always take advantage of SIMD on this platform.

SIMD is an optional extension for WASM, but it is supported by all modern browsers.

To enable SIMD in your build you need to set RUSTFLAGS="-C target-feature=+simd128", e.g.:

RUSTFLAGS="-C target-feature=+simd128" cargo build --target wasm32-unknown-unknown

Rust i686 and x86_64 targets guarantee only the presence of basic operations on 128-bit vectors (SSE2). If you need anything else, you need to explicitly enable the relevant SIMD extensions at build time. For example, this will use all SIMD extensions available on your CPU:

RUSTFLAGS='-C target-cpu=native' cargo build --release

However, attempting to use an instruction that is not supported by the CPU will crash the program or lead to undefined behavior. Therefore distributing binaries built with SIMD extensions enabled is not recommended.

Note: wide only supports detecting the available SIMD extensions at build time. Runtime feature detection via is_x86_feature_detected! or crates like multiversion do not work with wide.

• The rust-version entry of the crate's Cargo.toml will be kept accurate to the required Rust compiler version.
• The rust-version entry may increase in any new release (major, minor, or patch).
• If your build uses Resolver 3 (or later) this will be fine. If you're using a Resolver earlier than 3 then you are responsible for pinning a maximum crate version when you're using an old Rust version.