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    //! Run-time feature detection on ARM Aarch32.

    #[macro_export]
    #[unstable(feature = "stdsimd", issue = "27731")]
    #[allow_internal_unstable]
    macro_rules! is_arm_feature_detected {
        ("neon") => {
            cfg!(target_feature = "neon") ||
                $crate::arch::detect::check_for($crate::arch::detect::Feature::neon)
        };
        ("pmull") => {
            cfg!(target_feature = "pmull") ||
                $crate::arch::detect::check_for($crate::arch::detect::Feature::pmull)
        };
        ("v7") => { compile_error!("\"v7\" feature cannot be detected at run-time") };
        ("vfp2") => { compile_error!("\"vfp2\" feature cannot be detected at run-time") };
        ("vfp3") => { compile_error!("\"vfp3\" feature cannot be detected at run-time") };
        ("vfp4") => { compile_error!("\"vfp4\" feature cannot be detected at run-time") };
        ($t:tt) => { compile_error!(concat!("unknown arm target feature: ", $t)) };
    }

    /// ARM CPU Feature enum. Each variant denotes a position in a bitset for a
    /// particular feature.
    ///
    /// PLEASE: do not use this, it is an implementation detail subject to change.
    #[doc(hidden)]
    #[allow(non_camel_case_types)]
    #[repr(u8)]
    #[unstable(feature = "stdsimd_internal", issue = "0")]
    pub enum Feature {
        /// ARM Advanced SIMD (NEON) - Aarch32
        neon,
        /// Polynomial Multiply
        pmull,
    }

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