src/memmem/vector.rs

/// A trait for describing vector operations used by vectorized searchers.
///
/// The trait is highly constrained to low level vector operations needed. In
/// general, it was invented mostly to be generic over x86's __m128i and
/// __m256i types. It's likely that once std::simd becomes a thing, we can
/// migrate to that since the operations required are quite simple.
///
/// TODO: Consider moving this trait up a level and using it to implement
/// memchr as well. The trait might need to grow one or two methods, but
/// otherwise should be close to sufficient already.
///
/// # Safety
///
/// All methods are not safe since they are intended to be implemented using
/// vendor intrinsics, which are also not safe. Callers must ensure that the
/// appropriate target features are enabled in the calling function, and that
/// the current CPU supports them. All implementations should avoid marking the
/// routines with #[target_feature] and instead mark them as #[inline(always)]
/// to ensure they get appropriately inlined. (inline(always) cannot be used
/// with target_feature.)
pub(crate) trait Vector: Copy + core::fmt::Debug {
    /// _mm_set1_epi8 or _mm256_set1_epi8
    unsafe fn splat(byte: u8) -> Self;
    /// _mm_loadu_si128 or _mm256_loadu_si256
    unsafe fn load_unaligned(data: *const u8) -> Self;
    /// _mm_movemask_epi8 or _mm256_movemask_epi8
    unsafe fn movemask(self) -> u32;
    /// _mm_cmpeq_epi8 or _mm256_cmpeq_epi8
    unsafe fn cmpeq(self, vector2: Self) -> Self;
    /// _mm_and_si128 or _mm256_and_si256
    unsafe fn and(self, vector2: Self) -> Self;
}

#[cfg(target_arch = "x86_64")]
mod x86sse {
    use super::Vector;
    use core::arch::x86_64::*;

    impl Vector for __m128i {
        #[inline(always)]
        unsafe fn splat(byte: u8) -> __m128i {
            _mm_set1_epi8(byte as i8)
        }

        #[inline(always)]
        unsafe fn load_unaligned(data: *const u8) -> __m128i {
            _mm_loadu_si128(data as *const __m128i)
        }

        #[inline(always)]
        unsafe fn movemask(self) -> u32 {
            _mm_movemask_epi8(self) as u32
        }

        #[inline(always)]
        unsafe fn cmpeq(self, vector2: Self) -> __m128i {
            _mm_cmpeq_epi8(self, vector2)
        }

        #[inline(always)]
        unsafe fn and(self, vector2: Self) -> __m128i {
            _mm_and_si128(self, vector2)
        }
    }
}

#[cfg(all(feature = "std", target_arch = "x86_64"))]
mod x86avx {
    use super::Vector;
    use core::arch::x86_64::*;

    impl Vector for __m256i {
        #[inline(always)]
        unsafe fn splat(byte: u8) -> __m256i {
            _mm256_set1_epi8(byte as i8)
        }

        #[inline(always)]
        unsafe fn load_unaligned(data: *const u8) -> __m256i {
            _mm256_loadu_si256(data as *const __m256i)
        }

        #[inline(always)]
        unsafe fn movemask(self) -> u32 {
            _mm256_movemask_epi8(self) as u32
        }

        #[inline(always)]
        unsafe fn cmpeq(self, vector2: Self) -> __m256i {
            _mm256_cmpeq_epi8(self, vector2)
        }

        #[inline(always)]
        unsafe fn and(self, vector2: Self) -> __m256i {
            _mm256_and_si256(self, vector2)
        }
    }
}