The private std::detect module implements run-time feature detection in Rust's standard library. This allows detecting whether the CPU the binary runs on supports certain features, like SIMD instructions.

Usage

std::detect APIs are available as part of libstd. Prefer using it via the standard library than through this crate. Unstable features of std::detect are available on nightly Rust behind the feature(stdsimd) feature-gate.

If you need run-time feature detection in #[no_std] environments, Rust core library cannot help you. By design, Rust core is platform independent, but performing run-time feature detection requires a certain level of cooperation from the platform.

You can then manually include std_detect as a dependency to get similar run-time feature detection support than the one offered by Rust's standard library. We intend to make std_detect more flexible and configurable in this regard to better serve the needs of #[no_std] targets.

Features

std_detect_dlsym_getauxval (enabled by default, requires libc): Enable to use libc::dlsym to query whether getauxval is linked into the binary. When this is not the case, this feature allows other fallback methods to perform run-time feature detection. When this feature is disabled, std_detect assumes that getauxval is linked to the binary. If that is not the case the behavior is undefined.
std_detect_file_io (enabled by default, requires std): Enable to perform run-time feature detection using file APIs (e.g. /proc/cpuinfo, etc.) if other more performant methods fail. This feature requires libstd as a dependency, preventing the crate from working on applications in which std is not available.

Platform support

All x86/x86_64 targets are supported on all platforms by querying the cpuid instruction directly for the features supported by the hardware and the operating system. std_detect assumes that the binary is an user-space application. If you need raw support for querying cpuid, consider using the cupid crate.
Linux:
- arm{32, 64}, mips{32,64}{,el}, powerpc{32,64}{,le}: std_detect supports these on Linux by querying ELF auxiliary vectors (using getauxval when available), and if that fails, by querying /proc/cpuinfo.
- arm64: partial support for doing run-time feature detection by directly querying mrs is implemented for Linux >= 4.11, but not enabled by default.
FreeBSD:
- arm64: run-time feature detection is implemented by directly querying mrs.

License

This project is licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in std_detect by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

[azure]: https://dev.azure.com/rust-lang2/stdarch/_apis/build/status/rust-lang.stdarch?branchName=auto)](https://dev.azure.com/rust-lang2/stdarch/_build/latest?definitionId=2&branchName=auto [Azure Pipelines Status]: https://dev.azure.com/rust-lang2/stdarch/_apis/build/status/rust-lang.stdarch?branchName=auto [std_detect_crate_badge]: https://img.shields.io/crates/v/std_detect.svg [std_detect_crate_link]: https://crates.io/crates/std_detect [std_detect_docs_badge]: https://docs.rs/std_detect/badge.svg [std_detect_docs_link]: https://docs.rs/std_detect/

README.md

std::detect - Rust's standard library run-time CPU feature detection

Usage

Features

Platform support

License

Contribution

`std::detect` - Rust's standard library run-time CPU feature detection