fast_image_resize 6.0.0

Library for fast image resizing with using of SIMD instructions
Documentation 
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use core::arch::x86_64::*;

use crate::convolution::optimisations::Normalizer32;
use crate::pixels::U16x4;
use crate::{simd_utils, ImageView, ImageViewMut};

#[inline]
pub(crate) fn horiz_convolution(
    src_view: &impl ImageView<Pixel = U16x4>,
    dst_view: &mut impl ImageViewMut<Pixel = U16x4>,
    offset: u32,
    normalizer: &Normalizer32,
) {
    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(src_rows, dst_rows, normalizer);
        }
    }

    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(src_row, dst_row, normalizer);
        }
    }
}

/// 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 = "sse4.1")]
unsafe fn horiz_convolution_four_rows(
    src_rows: [&[U16x4]; 4],
    dst_rows: [&mut [U16x4]; 4],
    normalizer: &Normalizer32,
) {
    let precision = normalizer.precision();
    let half_error = 1i64 << (precision - 1);
    let mut rg_buf = [0i64; 2];
    let mut ba_buf = [0i64; 2];

    /*
       |R0   G0   B0   A0  | |R1   G1   B1   A1  |
       |0001 0203 0405 0607| |0809 1011 1213 1415|

        Shuffle to extract R0 and G0 as i64:
        -1, -1, -1, -1, -1, -1, 3, 2, -1, -1, -1, -1, -1, -1, 1, 0

        Shuffle to extract R1 and G1 as i64:
        -1, -1, -1, -1, -1, -1, 11, 10, -1, -1, -1, -1, -1, -1, 9, 8

        Shuffle to extract B0 and A0 as i64:
        -1, -1, -1, -1, -1, -1, 7, 6, -1, -1, -1, -1, -1, -1, 5, 4

        Shuffle to extract B1 and A1 as i64:
        -1, -1, -1, -1, -1, -1, 15, 14, -1, -1, -1, -1, -1, -1, 13, 12
    */

    let rg0_shuffle = _mm_set_epi8(-1, -1, -1, -1, -1, -1, 3, 2, -1, -1, -1, -1, -1, -1, 1, 0);
    let rg1_shuffle = _mm_set_epi8(-1, -1, -1, -1, -1, -1, 11, 10, -1, -1, -1, -1, -1, -1, 9, 8);
    let ba0_shuffle = _mm_set_epi8(-1, -1, -1, -1, -1, -1, 7, 6, -1, -1, -1, -1, -1, -1, 5, 4);
    let ba1_shuffle = _mm_set_epi8(
        -1, -1, -1, -1, -1, -1, 15, 14, -1, -1, -1, -1, -1, -1, 13, 12,
    );

    for (dst_x, chunk) in normalizer.chunks().iter().enumerate() {
        let mut x = chunk.start as usize;
        let mut coeffs = chunk.values();
        let mut rg_sum = [_mm_set1_epi64x(half_error); 4];
        let mut ba_sum = [_mm_set1_epi64x(half_error); 4];

        let coeffs_by_2 = coeffs.chunks_exact(2);
        coeffs = coeffs_by_2.remainder();

        for k in coeffs_by_2 {
            let coeff0_i64x2 = _mm_set1_epi64x(k[0] as i64);
            let coeff1_i64x2 = _mm_set1_epi64x(k[1] as i64);

            for i in 0..4 {
                let source = simd_utils::loadu_si128(src_rows[i], x);
                let mut sum = rg_sum[i];
                let rg_i64x2 = _mm_shuffle_epi8(source, rg0_shuffle);
                sum = _mm_add_epi64(sum, _mm_mul_epi32(rg_i64x2, coeff0_i64x2));
                let rg_i64x2 = _mm_shuffle_epi8(source, rg1_shuffle);
                sum = _mm_add_epi64(sum, _mm_mul_epi32(rg_i64x2, coeff1_i64x2));
                rg_sum[i] = sum;

                let mut sum = ba_sum[i];
                let ba_i64x2 = _mm_shuffle_epi8(source, ba0_shuffle);
                sum = _mm_add_epi64(sum, _mm_mul_epi32(ba_i64x2, coeff0_i64x2));
                let ba_i64x2 = _mm_shuffle_epi8(source, ba1_shuffle);
                sum = _mm_add_epi64(sum, _mm_mul_epi32(ba_i64x2, coeff1_i64x2));
                ba_sum[i] = sum;
            }
            x += 2;
        }

        if let Some(&k) = coeffs.first() {
            let coeff0_i64x2 = _mm_set1_epi64x(k as i64);
            for i in 0..4 {
                let source = simd_utils::loadl_epi64(src_rows[i], x);
                let rg_i64x2 = _mm_shuffle_epi8(source, rg0_shuffle);
                rg_sum[i] = _mm_add_epi64(rg_sum[i], _mm_mul_epi32(rg_i64x2, coeff0_i64x2));
                let ba_i64x2 = _mm_shuffle_epi8(source, ba0_shuffle);
                ba_sum[i] = _mm_add_epi64(ba_sum[i], _mm_mul_epi32(ba_i64x2, coeff0_i64x2));
            }
        }

        for i in 0..4 {
            _mm_storeu_si128(rg_buf.as_mut_ptr() as *mut __m128i, rg_sum[i]);
            _mm_storeu_si128(ba_buf.as_mut_ptr() as *mut __m128i, ba_sum[i]);
            let dst_pixel = dst_rows[i].get_unchecked_mut(dst_x);
            dst_pixel.0 = [
                normalizer.clip(rg_buf[0]),
                normalizer.clip(rg_buf[1]),
                normalizer.clip(ba_buf[0]),
                normalizer.clip(ba_buf[1]),
            ];
        }
    }
}

/// For safety, it is necessary to ensure the following conditions:
/// - bounds.len() == dst_row.len()
/// - coeffs.len() == dst_rows.0.len() * window_size
/// - max(bound.start + bound.size for bound in bounds) <= src_row.len()
/// - precision <= MAX_COEFS_PRECISION
#[inline]
#[target_feature(enable = "sse4.1")]
unsafe fn horiz_convolution_one_row(
    src_row: &[U16x4],
    dst_row: &mut [U16x4],
    normalizer: &Normalizer32,
) {
    let precision = normalizer.precision();
    let half_error = 1i64 << (precision - 1);
    let mut rg_buf = [0i64; 2];
    let mut ba_buf = [0i64; 2];

    /*
       |R0   G0   B0   A0  | |R1   G1   B1   A1  |
       |0001 0203 0405 0607| |0809 1011 1213 1415|

        Shuffle to extract R0 and G0 as i64:
        -1, -1, -1, -1, -1, -1, 3, 2, -1, -1, -1, -1, -1, -1, 1, 0

        Shuffle to extract R1 and G1 as i64:
        -1, -1, -1, -1, -1, -1, 11, 10, -1, -1, -1, -1, -1, -1, 9, 8

        Shuffle to extract B0 and A0 as i64:
        -1, -1, -1, -1, -1, -1, 7, 6, -1, -1, -1, -1, -1, -1, 5, 4

        Shuffle to extract B1 and A1 as i64:
        -1, -1, -1, -1, -1, -1, 15, 14, -1, -1, -1, -1, -1, -1, 13, 12
    */

    let rg0_shuffle = _mm_set_epi8(-1, -1, -1, -1, -1, -1, 3, 2, -1, -1, -1, -1, -1, -1, 1, 0);
    let rg1_shuffle = _mm_set_epi8(-1, -1, -1, -1, -1, -1, 11, 10, -1, -1, -1, -1, -1, -1, 9, 8);
    let ba0_shuffle = _mm_set_epi8(-1, -1, -1, -1, -1, -1, 7, 6, -1, -1, -1, -1, -1, -1, 5, 4);
    let ba1_shuffle = _mm_set_epi8(
        -1, -1, -1, -1, -1, -1, 15, 14, -1, -1, -1, -1, -1, -1, 13, 12,
    );

    for (dst_x, chunk) in normalizer.chunks().iter().enumerate() {
        let mut x = chunk.start as usize;
        let mut coeffs = chunk.values();
        let mut rg_sum = _mm_set1_epi64x(half_error);
        let mut ba_sum = _mm_set1_epi64x(half_error);

        let coeffs_by_2 = coeffs.chunks_exact(2);
        coeffs = coeffs_by_2.remainder();

        for k in coeffs_by_2 {
            let coeff0_i64x2 = _mm_set1_epi64x(k[0] as i64);
            let coeff1_i64x2 = _mm_set1_epi64x(k[1] as i64);

            let source = simd_utils::loadu_si128(src_row, x);

            let rg_i64x2 = _mm_shuffle_epi8(source, rg0_shuffle);
            rg_sum = _mm_add_epi64(rg_sum, _mm_mul_epi32(rg_i64x2, coeff0_i64x2));
            let rg_i64x2 = _mm_shuffle_epi8(source, rg1_shuffle);
            rg_sum = _mm_add_epi64(rg_sum, _mm_mul_epi32(rg_i64x2, coeff1_i64x2));

            let ba_i64x2 = _mm_shuffle_epi8(source, ba0_shuffle);
            ba_sum = _mm_add_epi64(ba_sum, _mm_mul_epi32(ba_i64x2, coeff0_i64x2));
            let ba_i64x2 = _mm_shuffle_epi8(source, ba1_shuffle);
            ba_sum = _mm_add_epi64(ba_sum, _mm_mul_epi32(ba_i64x2, coeff1_i64x2));

            x += 2;
        }

        if let Some(&k) = coeffs.first() {
            let coeff0_i64x2 = _mm_set1_epi64x(k as i64);
            let source = simd_utils::loadl_epi64(src_row, x);
            let rg_i64x2 = _mm_shuffle_epi8(source, rg0_shuffle);
            rg_sum = _mm_add_epi64(rg_sum, _mm_mul_epi32(rg_i64x2, coeff0_i64x2));
            let ba_i64x2 = _mm_shuffle_epi8(source, ba0_shuffle);
            ba_sum = _mm_add_epi64(ba_sum, _mm_mul_epi32(ba_i64x2, coeff0_i64x2));
        }

        _mm_storeu_si128(rg_buf.as_mut_ptr() as *mut __m128i, rg_sum);
        _mm_storeu_si128(ba_buf.as_mut_ptr() as *mut __m128i, ba_sum);
        let dst_pixel = dst_row.get_unchecked_mut(dst_x);
        dst_pixel.0 = [
            normalizer.clip(rg_buf[0]),
            normalizer.clip(rg_buf[1]),
            normalizer.clip(ba_buf[0]),
            normalizer.clip(ba_buf[1]),
        ];
    }
}