fast_image_resize 6.0.0

Library for fast image resizing with using of SIMD instructions
Documentation 
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use core::arch::aarch64::*;

use crate::convolution::optimisations::{CoefficientsI32Chunk, Normalizer32};
use crate::pixels::U16;
use crate::{neon_utils, ImageView, ImageViewMut};

#[inline]
pub(crate) fn horiz_convolution(
    src_view: &impl ImageView<Pixel = U16>,
    dst_view: &mut impl ImageViewMut<Pixel = U16>,
    offset: u32,
    normalizer: &Normalizer32,
) {
    let precision = normalizer.precision();

    macro_rules! call {
        ($imm8:expr) => {{
            horiz_convolution_p::<$imm8>(src_view, dst_view, offset, normalizer);
        }};
    }
    constify_64_imm8!(precision, call);
}

fn horiz_convolution_p<const PRECISION: i32>(
    src_view: &impl ImageView<Pixel = U16>,
    dst_view: &mut impl ImageViewMut<Pixel = U16>,
    offset: u32,
    normalizer: &Normalizer32,
) {
    let coefficients_chunks = normalizer.chunks();
    let dst_height = dst_view.height();

    let src_iter = src_view.iter_4_rows(offset, dst_height + offset);
    let dst_iter = dst_view.iter_4_rows_mut();
    for (src_rows, dst_rows) in src_iter.zip(dst_iter) {
        unsafe {
            horiz_convolution_four_rows::<PRECISION>(src_rows, dst_rows, coefficients_chunks);
        }
    }

    let yy = dst_height - dst_height % 4;
    let src_rows = src_view.iter_rows(yy + offset);
    let dst_rows = dst_view.iter_rows_mut(yy);
    for (src_row, dst_row) in src_rows.zip(dst_rows) {
        unsafe {
            horiz_convolution_one_row::<PRECISION>(src_row, dst_row, coefficients_chunks);
        }
    }
}

/// For safety, it is necessary to ensure the following conditions:
/// - length of all rows in src_rows must be equal
/// - length of all rows in dst_rows must be equal
/// - coefficients_chunks.len() == dst_rows.0.len()
/// - max(chunk.start + chunk.values.len() for chunk in coefficients_chunks) <= src_row.0.len()
/// - precision <= MAX_COEFS_PRECISION
#[target_feature(enable = "neon")]
unsafe fn horiz_convolution_four_rows<const PRECISION: i32>(
    src_rows: [&[U16]; 4],
    dst_rows: [&mut [U16]; 4],
    coefficients_chunks: &[CoefficientsI32Chunk],
) {
    let initial = vdupq_n_s64(1i64 << (PRECISION - 2));
    let zero_u16x4 = vdup_n_u16(0);

    for (dst_x, coeffs_chunk) in coefficients_chunks.iter().enumerate() {
        let mut x: usize = coeffs_chunk.start as usize;
        let mut sss_a = [initial; 4];
        let mut coeffs = coeffs_chunk.values();

        let coeffs_by_4 = coeffs.chunks_exact(4);
        coeffs = coeffs_by_4.remainder();
        for k in coeffs_by_4 {
            let coeffs_i32x4 = neon_utils::load_i32x4(k, 0);
            let coeff0 = vget_low_s32(coeffs_i32x4);
            let coeff1 = vget_high_s32(coeffs_i32x4);

            for i in 0..4 {
                let source = neon_utils::load_u16x4(src_rows[i], x);
                let mut sss = sss_a[i];

                let pix_i32 = vreinterpret_s32_u16(vzip1_u16(source, zero_u16x4));
                sss = vmlal_s32(sss, pix_i32, coeff0);
                let pix_i32 = vreinterpret_s32_u16(vzip2_u16(source, zero_u16x4));
                sss = vmlal_s32(sss, pix_i32, coeff1);

                sss_a[i] = sss;
            }
            x += 4;
        }

        let mut coeffs_by_2 = coeffs.chunks_exact(2);
        coeffs = coeffs_by_2.remainder();
        if let Some(k) = coeffs_by_2.next() {
            let coeffs_i32x2 = neon_utils::load_i32x2(k, 0);

            for i in 0..4 {
                let source = neon_utils::load_u16x2(src_rows[i], x);
                let pix_i32 = vreinterpret_s32_u16(vzip1_u16(source, zero_u16x4));
                sss_a[i] = vmlal_s32(sss_a[i], pix_i32, coeffs_i32x2);
            }
            x += 2;
        }

        if !coeffs.is_empty() {
            let coeffs_i32x2 = neon_utils::load_i32x1(coeffs, 0);
            for i in 0..4 {
                let source = neon_utils::load_u16x1(src_rows[i], x);
                let pix_i32 = vreinterpret_s32_u16(vzip1_u16(source, zero_u16x4));
                sss_a[i] = vmlal_s32(sss_a[i], pix_i32, coeffs_i32x2);
            }
        }

        let mut sss_a_i64 = [
            vadd_s64(vget_low_s64(sss_a[0]), vget_high_s64(sss_a[0])),
            vadd_s64(vget_low_s64(sss_a[1]), vget_high_s64(sss_a[1])),
            vadd_s64(vget_low_s64(sss_a[2]), vget_high_s64(sss_a[2])),
            vadd_s64(vget_low_s64(sss_a[3]), vget_high_s64(sss_a[3])),
        ];
        sss_a_i64[0] = vshr_n_s64::<PRECISION>(sss_a_i64[0]);
        sss_a_i64[1] = vshr_n_s64::<PRECISION>(sss_a_i64[1]);
        sss_a_i64[2] = vshr_n_s64::<PRECISION>(sss_a_i64[2]);
        sss_a_i64[3] = vshr_n_s64::<PRECISION>(sss_a_i64[3]);

        for i in 0..4 {
            let res = vdupd_lane_s64::<0>(sss_a_i64[i]);
            dst_rows[i].get_unchecked_mut(dst_x).0 = vqmovns_u32(vqmovund_s64(res));
        }
    }
}

/// For safety, it is necessary to ensure the following conditions:
/// - bounds.len() == dst_row.len()
/// - coefficients_chunks.len() == dst_row.len()
/// - max(chunk.start + chunk.values.len() for chunk in coefficients_chunks) <= src_row.len()
/// - precision <= MAX_COEFS_PRECISION
#[target_feature(enable = "neon")]
unsafe fn horiz_convolution_one_row<const PRECISION: i32>(
    src_row: &[U16],
    dst_row: &mut [U16],
    coefficients_chunks: &[CoefficientsI32Chunk],
) {
    let initial = vdupq_n_s64(1i64 << (PRECISION - 2));
    let zero_u16x8 = vdupq_n_u16(0);
    let zero_u16x4 = vdup_n_u16(0);

    for (dst_x, coeffs_chunk) in coefficients_chunks.iter().enumerate() {
        let mut x: usize = coeffs_chunk.start as usize;
        let mut sss = initial;
        let mut coeffs = coeffs_chunk.values();

        let coeffs_by_8 = coeffs.chunks_exact(8);
        coeffs = coeffs_by_8.remainder();
        for k in coeffs_by_8 {
            let coeffs_i32x4x2 = neon_utils::load_i32x4x2(k, 0);
            let source = neon_utils::load_u16x8(src_row, x);

            let pix_i32 = vreinterpretq_s32_u16(vzip1q_u16(source, zero_u16x8));
            sss = vmlal_s32(sss, vget_low_s32(pix_i32), vget_low_s32(coeffs_i32x4x2.0));
            sss = vmlal_s32(sss, vget_high_s32(pix_i32), vget_high_s32(coeffs_i32x4x2.0));

            let pix_i32 = vreinterpretq_s32_u16(vzip2q_u16(source, zero_u16x8));
            sss = vmlal_s32(sss, vget_low_s32(pix_i32), vget_low_s32(coeffs_i32x4x2.1));
            sss = vmlal_s32(sss, vget_high_s32(pix_i32), vget_high_s32(coeffs_i32x4x2.1));

            x += 8;
        }

        let mut coeffs_by_4 = coeffs.chunks_exact(4);
        coeffs = coeffs_by_4.remainder();
        if let Some(k) = coeffs_by_4.next() {
            let coeffs_i32x4 = neon_utils::load_i32x4(k, 0);
            let source = neon_utils::load_u16x4(src_row, x);

            let pix_i32 = vreinterpret_s32_u16(vzip1_u16(source, zero_u16x4));
            sss = vmlal_s32(sss, pix_i32, vget_low_s32(coeffs_i32x4));
            let pix_i32 = vreinterpret_s32_u16(vzip2_u16(source, zero_u16x4));
            sss = vmlal_s32(sss, pix_i32, vget_high_s32(coeffs_i32x4));

            x += 4;
        }

        let mut coeffs_by_2 = coeffs.chunks_exact(2);
        coeffs = coeffs_by_2.remainder();
        if let Some(k) = coeffs_by_2.next() {
            let coeffs_i32x2 = neon_utils::load_i32x2(k, 0);
            let source = neon_utils::load_u16x2(src_row, x);
            let pix_i32 = vreinterpret_s32_u16(vzip1_u16(source, zero_u16x4));
            sss = vmlal_s32(sss, pix_i32, coeffs_i32x2);
            x += 2;
        }

        if !coeffs.is_empty() {
            let coeffs_i32x2 = neon_utils::load_i32x1(coeffs, 0);
            let source = neon_utils::load_u16x1(src_row, x);
            let pix_i32 = vreinterpret_s32_u16(vzip1_u16(source, zero_u16x4));
            sss = vmlal_s32(sss, pix_i32, coeffs_i32x2);
        }

        let mut sss_i64 = vadd_s64(vget_low_s64(sss), vget_high_s64(sss));
        sss_i64 = vshr_n_s64::<PRECISION>(sss_i64);

        let res = vdupd_lane_s64::<0>(sss_i64);
        dst_row.get_unchecked_mut(dst_x).0 = vqmovns_u32(vqmovund_s64(res));
    }
}