1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136

//! 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/meta/master/logo.svg",
    html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
    html_root_url = "https://docs.rs/cpufeatures/0.2.1"
)]

#[cfg(all(target_arch = "aarch64"))]
#[doc(hidden)]
pub mod aarch64;

#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
mod x86;

#[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
            }
        }
    };
}