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|
//! This crate provides macros for runtime CPU feature detection. It's intended
//! as a stopgap until Rust [RFC 2725] adding first-class target feature detection
//! macros to `libcore` is implemented.
//!
//! Supported target architectures:
//! - `aarch64`: Linux and macOS/M4 only (ARM64 does not support OS-independent feature detection)
//! - Target features: `aes`, `sha2`, `sha3`
//! - `x86`/`x86_64`: OS independent and `no_std`-friendly
//! - Target features: `adx`, `aes`, `avx`, `avx2`, `bmi1`, `bmi2`, `fma`,
//! `mmx`, `pclmulqdq`, `popcnt`, `rdrand`, `rdseed`, `sgx`, `sha`, `sse`,
//! `sse2`, `sse3`, `sse4.1`, `sse4.2`, `ssse3`
//!
//! If you would like detection support for a target feature which is not on
//! this list, please [open a GitHub issue][gh].
//!
//! # Example
//! ```
//! # #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
//! # {
//! // This macro creates `cpuid_aes_sha` module
//! cpufeatures::new!(cpuid_aes_sha, "aes", "sha");
//!
//! // `token` is a Zero Sized Type (ZST) value, which guarantees
//! // that underlying static storage got properly initialized,
//! // which allows to omit initialization branch
//! let token: cpuid_aes_sha::InitToken = cpuid_aes_sha::init();
//!
//! if token.get() {
//! println!("CPU supports both SHA and AES extensions");
//! } else {
//! println!("SHA and AES extensions are not supported");
//! }
//!
//! // If stored value needed only once you can get stored value
//! // omitting the token
//! let val = cpuid_aes_sha::get();
//! assert_eq!(val, token.get());
//!
//! // Additionally you can get both token and value
//! let (token, val) = cpuid_aes_sha::init_get();
//! assert_eq!(val, token.get());
//! # }
//! ```
//!
//! Note that if all tested target features are enabled via compiler options
//! (e.g. by using `RUSTFLAGS`), the `get` method will always return `true`
//! and `init` will not use CPUID instruction. Such behavior allows
//! compiler to completely eliminate fallback code.
//!
//! After first call macro caches result and returns it in subsequent
//! calls, thus runtime overhead for them is minimal.
//!
//! [RFC 2725]: https://github.com/rust-lang/rfcs/pull/2725
//! [gh]: https://github.com/RustCrypto/utils/issues/new?title=cpufeatures:%20requesting%20support%20for%20CHANGEME%20target%20feature
#![no_std]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg",
html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg"
)]
#[cfg(not(miri))]
#[cfg(all(target_arch = "aarch64"))]
#[doc(hidden)]
pub mod aarch64;
#[cfg(not(miri))]
#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
mod x86;
#[cfg(miri)]
mod miri;
#[cfg(not(any(target_arch = "aarch64", target_arch = "x86", target_arch = "x86_64")))]
compile_error!("This crate works only on `aarch64`, `x86`, and `x86-64` targets.");
/// Create module with CPU feature detection code.
#[macro_export]
macro_rules! new {
($mod_name:ident, $($tf:tt),+ $(,)?) => {
mod $mod_name {
use core::sync::atomic::{AtomicU8, Ordering::Relaxed};
const UNINIT: u8 = u8::max_value();
static STORAGE: AtomicU8 = AtomicU8::new(UNINIT);
/// Initialization token
#[derive(Copy, Clone, Debug)]
pub struct InitToken(());
impl InitToken {
/// Get initialized value
#[inline(always)]
pub fn get(&self) -> bool {
$crate::__unless_target_features! {
$($tf),+ => {
STORAGE.load(Relaxed) == 1
}
}
}
}
/// Initialize underlying storage if needed and get
/// stored value and initialization token.
#[inline]
pub fn init_get() -> (InitToken, bool) {
let res = $crate::__unless_target_features! {
$($tf),+ => {
// Relaxed ordering is fine, as we only have a single atomic variable.
let val = STORAGE.load(Relaxed);
if val == UNINIT {
let res = $crate::__detect_target_features!($($tf),+);
STORAGE.store(res as u8, Relaxed);
res
} else {
val == 1
}
}
};
(InitToken(()), res)
}
/// Initialize underlying storage if needed and get
/// initialization token.
#[inline]
pub fn init() -> InitToken {
init_get().0
}
/// Initialize underlying storage if needed and get
/// stored value.
#[inline]
pub fn get() -> bool {
init_get().1
}
}
};
}
|
