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    //! Run-time feature detection for PowerPC on Linux.

    use arch::detect::Feature;
    use arch::detect::cache;
    use super::auxvec;
    use super::cpuinfo;

    /// Performs run-time feature detection.
    #[inline]
    pub fn check_for(x: Feature) -> bool {
        cache::test(x as u32, detect_features)
    }

    /// Try to read the features from the auxiliary vector, and if that fails, try
    /// to read them from /proc/cpuinfo.
    fn detect_features() -> cache::Initializer {
        let mut value = cache::Initializer::default();
        let enable_feature = |value: &mut cache::Initializer, f, enable| {
            if enable {
                value.set(f as u32);
            }
        };

        // The values are part of the platform-specific [asm/cputable.h][cputable]
        //
        // [cputable]: https://github.com/torvalds/linux/blob/master/arch/powerpc/include/uapi/asm/cputable.h
        if let Ok(auxv) = auxvec::auxv() {
            // note: the PowerPC values are the mask to do the test (instead of the
            // index of the bit to test like in ARM and Aarch64)
            enable_feature(&mut value, Feature::altivec, auxv.hwcap & 0x10000000 != 0);
            enable_feature(&mut value, Feature::vsx, auxv.hwcap & 0x00000080 != 0);
            enable_feature(&mut value, Feature::power8, auxv.hwcap & 0x80000000 != 0);
            return value;
        }

        // PowerPC's /proc/cpuinfo lacks a proper Feature field,
        // but `altivec` support is indicated in the `cpu` field.
        if let Ok(c) = cpuinfo::CpuInfo::new() {
            enable_feature(&mut value, Feature::altivec, c.field("cpu").has("altivec"));
            return value;
        }
        value
    }

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