fast_image_resize 6.0.0

Library for fast image resizing with using of SIMD instructions
Documentation 
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use core::arch::wasm32::*;

use crate::convolution::optimisations::{CoefficientsI32Chunk, Normalizer32};
use crate::convolution::vertical_u16::native::convolution_by_u16;
use crate::pixels::InnerPixel;
use crate::{wasm32_utils, ImageView, ImageViewMut};

pub(crate) fn vert_convolution<T: InnerPixel<Component = u16>>(
    src_view: &impl ImageView<Pixel = T>,
    dst_view: &mut impl ImageViewMut<Pixel = T>,
    offset: u32,
    normalizer: &Normalizer32,
) {
    let coefficients_chunks = normalizer.chunks();
    let src_x = offset as usize * T::count_of_components();

    let dst_rows = dst_view.iter_rows_mut(0);
    for (dst_row, coeffs_chunk) in dst_rows.zip(coefficients_chunks) {
        unsafe {
            vert_convolution_into_one_row_u16(src_view, dst_row, src_x, coeffs_chunk, normalizer);
        }
    }
}

#[target_feature(enable = "simd128")]
unsafe fn vert_convolution_into_one_row_u16<T: InnerPixel<Component = u16>>(
    src_view: &impl ImageView<Pixel = T>,
    dst_row: &mut [T],
    mut src_x: usize,
    coeffs_chunk: &CoefficientsI32Chunk,
    normalizer: &Normalizer32,
) {
    let y_start = coeffs_chunk.start;
    let coeffs = coeffs_chunk.values();
    let max_rows = coeffs.len() as u32;
    let mut dst_u16 = T::components_mut(dst_row);

    /*
        |0    1    2    3    4    5    6    7   |
        |0001 0203 0405 0607 0809 1011 1213 1415|

        Shuffle to extract 0-1 components as i64:
        0, 1, -1, -1, -1, -1, -1, -1, 2, 3, -1, -1, -1, -1, -1, -1

        Shuffle to extract 2-3 components as i64:
        4, 5, -1, -1, -1, -1, -1, -1, 6, 7, -1, -1, -1, -1, -1, -1

        Shuffle to extract 4-5 components as i64:
        8, 9, -1, -1, -1, -1, -1, -1, 10, 11, -1, -1, -1, -1, -1, -1

        Shuffle to extract 6-7 components as i64:
        12, 13, -1, -1, -1, -1, -1, -1, 14, 15, -1, -1, -1, -1, -1, -1

    */

    let c_shuffles = [
        i8x16(0, 1, -1, -1, -1, -1, -1, -1, 2, 3, -1, -1, -1, -1, -1, -1),
        i8x16(4, 5, -1, -1, -1, -1, -1, -1, 6, 7, -1, -1, -1, -1, -1, -1),
        i8x16(8, 9, -1, -1, -1, -1, -1, -1, 10, 11, -1, -1, -1, -1, -1, -1),
        i8x16(
            12, 13, -1, -1, -1, -1, -1, -1, 14, 15, -1, -1, -1, -1, -1, -1,
        ),
    ];

    let precision = normalizer.precision();
    let initial = i64x2_splat(1 << (precision - 1));
    let mut c_buf = [0i64; 2];

    let mut dst_chunks_16 = dst_u16.chunks_exact_mut(16);
    for dst_chunk in &mut dst_chunks_16 {
        let mut sums = [[initial; 2], [initial; 2], [initial; 2], [initial; 2]];

        let mut y: u32 = 0;
        let coeffs_2 = coeffs.chunks_exact(2);
        let coeffs_reminder = coeffs_2.remainder();

        for (src_rows, two_coeffs) in src_view.iter_2_rows(y_start, max_rows).zip(coeffs_2) {
            let src_rows = src_rows.map(|row| T::components(row));

            for r in 0..2 {
                let coeff_i64x2 = i64x2_splat(two_coeffs[r] as i64);
                for x in 0..2 {
                    let source = wasm32_utils::load_v128(src_rows[r], src_x + x * 8);
                    for i in 0..4 {
                        let c_i64x2 = i8x16_swizzle(source, c_shuffles[i]);
                        sums[i][x] =
                            i64x2_add(sums[i][x], wasm32_utils::i64x2_mul_lo(c_i64x2, coeff_i64x2));
                    }
                }
            }
            y += 2;
        }

        if let Some(&k) = coeffs_reminder.first() {
            if let Some(s_row) = src_view.iter_rows(y_start + y).next() {
                let components = T::components(s_row);
                let coeff_i64x2 = i64x2_splat(k as i64);

                for x in 0..2 {
                    let source = wasm32_utils::load_v128(components, src_x + x * 8);
                    for i in 0..4 {
                        let c_i64x2 = i8x16_swizzle(source, c_shuffles[i]);
                        sums[i][x] =
                            i64x2_add(sums[i][x], wasm32_utils::i64x2_mul_lo(c_i64x2, coeff_i64x2));
                    }
                }
            }
        }

        let mut dst_ptr = dst_chunk.as_mut_ptr();
        for x in 0..2 {
            for sum in sums {
                v128_store(c_buf.as_mut_ptr() as *mut v128, sum[x]);
                *dst_ptr = normalizer.clip(c_buf[0]);
                dst_ptr = dst_ptr.add(1);
                *dst_ptr = normalizer.clip(c_buf[1]);
                dst_ptr = dst_ptr.add(1);
            }
        }

        src_x += 16;
    }

    dst_u16 = dst_chunks_16.into_remainder();
    let mut dst_chunks_8 = dst_u16.chunks_exact_mut(8);
    if let Some(dst_chunk) = dst_chunks_8.next() {
        let mut sums = [initial, initial, initial, initial];

        let mut y: u32 = 0;
        let coeffs_2 = coeffs.chunks_exact(2);
        let coeffs_reminder = coeffs_2.remainder();

        for (src_rows, two_coeffs) in src_view.iter_2_rows(y_start, max_rows).zip(coeffs_2) {
            let src_rows = src_rows.map(|row| T::components(row));
            let coeffs_i64 = [
                i64x2_splat(two_coeffs[0] as i64),
                i64x2_splat(two_coeffs[1] as i64),
            ];

            for r in 0..2 {
                let source = wasm32_utils::load_v128(src_rows[r], src_x);
                for i in 0..4 {
                    let c_i64x2 = i8x16_swizzle(source, c_shuffles[i]);
                    sums[i] =
                        i64x2_add(sums[i], wasm32_utils::i64x2_mul_lo(c_i64x2, coeffs_i64[r]));
                }
            }
            y += 2;
        }

        if let Some(&k) = coeffs_reminder.first() {
            if let Some(s_row) = src_view.iter_rows(y_start + y).next() {
                let components = T::components(s_row);
                let coeff_i64x2 = i64x2_splat(k as i64);
                let source = wasm32_utils::load_v128(components, src_x);
                for i in 0..4 {
                    let c_i64x2 = i8x16_swizzle(source, c_shuffles[i]);
                    sums[i] = i64x2_add(sums[i], wasm32_utils::i64x2_mul_lo(c_i64x2, coeff_i64x2));
                }
            }
        }

        let mut dst_ptr = dst_chunk.as_mut_ptr();
        for sum in sums {
            // let mask = _mm_cmpgt_epi64(sums[i], zero);
            // sums[i] = _mm_and_si128(sums[i] , mask);
            // sums[i] = _mm_srl_epi64(sums[i] , precision_i64);
            // _mm_packus_epi32(sums[i] , sums[i] );
            v128_store(c_buf.as_mut_ptr() as *mut v128, sum);
            *dst_ptr = normalizer.clip(c_buf[0]);
            dst_ptr = dst_ptr.add(1);
            *dst_ptr = normalizer.clip(c_buf[1]);
            dst_ptr = dst_ptr.add(1);
        }

        src_x += 8;
    }

    dst_u16 = dst_chunks_8.into_remainder();
    let mut dst_chunks_4 = dst_u16.chunks_exact_mut(4);
    if let Some(dst_chunk) = dst_chunks_4.next() {
        let mut c01 = initial;
        let mut c23 = initial;
        let mut y: u32 = 0;
        let coeffs_2 = coeffs.chunks_exact(2);
        let coeffs_reminder = coeffs_2.remainder();

        for (src_rows, two_coeffs) in src_view.iter_2_rows(y_start, max_rows).zip(coeffs_2) {
            let src_rows = src_rows.map(|row| T::components(row));
            let coeffs_i64 = [
                i64x2_splat(two_coeffs[0] as i64),
                i64x2_splat(two_coeffs[1] as i64),
            ];
            for r in 0..2 {
                let comp_x4 = src_rows[r].get_unchecked(src_x..src_x + 4);
                let c_i64x2 = i64x2(comp_x4[0] as i64, comp_x4[1] as i64);
                c01 = i64x2_add(c01, wasm32_utils::i64x2_mul_lo(c_i64x2, coeffs_i64[r]));
                let c_i64x2 = i64x2(comp_x4[2] as i64, comp_x4[3] as i64);
                c23 = i64x2_add(c23, wasm32_utils::i64x2_mul_lo(c_i64x2, coeffs_i64[r]));
            }
            y += 2;
        }

        if let Some(&k) = coeffs_reminder.first() {
            if let Some(s_row) = src_view.iter_rows(y_start + y).next() {
                let components = T::components(s_row);
                let coeff_i64x2 = i64x2_splat(k as i64);

                let comp_x4 = components.get_unchecked(src_x..src_x + 4);
                let c_i64x2 = i64x2(comp_x4[0] as i64, comp_x4[1] as i64);
                c01 = i64x2_add(c01, wasm32_utils::i64x2_mul_lo(c_i64x2, coeff_i64x2));
                let c_i64x2 = i64x2(comp_x4[2] as i64, comp_x4[3] as i64);
                c23 = i64x2_add(c23, wasm32_utils::i64x2_mul_lo(c_i64x2, coeff_i64x2));
            }
        }

        let mut dst_ptr = dst_chunk.as_mut_ptr();
        v128_store(c_buf.as_mut_ptr() as *mut v128, c01);
        *dst_ptr = normalizer.clip(c_buf[0]);
        dst_ptr = dst_ptr.add(1);
        *dst_ptr = normalizer.clip(c_buf[1]);
        dst_ptr = dst_ptr.add(1);
        v128_store(c_buf.as_mut_ptr() as *mut v128, c23);
        *dst_ptr = normalizer.clip(c_buf[0]);
        dst_ptr = dst_ptr.add(1);
        *dst_ptr = normalizer.clip(c_buf[1]);

        src_x += 4;
    }

    dst_u16 = dst_chunks_4.into_remainder();
    if !dst_u16.is_empty() {
        let initial = 1 << (precision - 1);
        convolution_by_u16(
            src_view, normalizer, initial, dst_u16, src_x, y_start, coeffs,
        );
    }
}