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    //! RDRAND and RDSEED instructions for returning random numbers from an Intel
    //! on-chip hardware random number generator which has been seeded by an
    //! on-chip entropy source.

    #![cfg_attr(feature = "cargo-clippy", allow(clippy::module_name_repetitions))]

    #[allow(improper_ctypes)]
    extern "unadjusted" {
        #[link_name = "llvm.x86.rdrand.64"]
        fn x86_rdrand64_step() -> (u64, i32);
        #[link_name = "llvm.x86.rdseed.64"]
        fn x86_rdseed64_step() -> (u64, i32);
    }

    #[cfg(test)]
    use stdsimd_test::assert_instr;

    /// Read a hardware generated 64-bit random value and store the result in val.
    /// Returns 1 if a random value was generated, and 0 otherwise.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_rdrand64_step)
    #[inline]
    #[target_feature(enable = "rdrand")]
    #[cfg_attr(test, assert_instr(rdrand))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _rdrand64_step(val: &mut u64) -> i32 {
        let (v, flag) = x86_rdrand64_step();
        *val = v;
        flag
    }

    /// Read a 64-bit NIST SP800-90B and SP800-90C compliant random value and store
    /// in val. Return 1 if a random value was generated, and 0 otherwise.
    ///
    /// [Intel's documentation](https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_rdseed64_step)
    #[inline]
    #[target_feature(enable = "rdseed")]
    #[cfg_attr(test, assert_instr(rdseed))]
    #[stable(feature = "simd_x86", since = "1.27.0")]
    pub unsafe fn _rdseed64_step(val: &mut u64) -> i32 {
        let (v, flag) = x86_rdseed64_step();
        *val = v;
        flag
    }

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