FFmpeg/libswscale/aarch64/swscale_unscaled_neon.S

/*
 * Copyright (c) 2024 Ramiro Polla
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/aarch64/asm.S"

function ff_nv24_to_yuv420p_chroma_neon, export=1
// x0  uint8_t *dst1
// x1  int dstStride1
// x2  uint8_t *dst2
// x3  int dstStride2
// x4  const uint8_t *src
// x5  int srcStride
// w6  int w
// w7  int h

        add             x9, x4, w5, sxtw            // x9 = src + srcStride
        lsl             w5, w5, #1                  // srcStride *= 2
        sub             w5, w5, w6, lsl #2          // srcPadding = (2 * srcStride) - (4 * w)
        sub             w1, w1, w6                  // dstPadding1 = dstStride1 - w
        sub             w3, w3, w6                  // dstPadding2 = dstStride2 - w

1:
        mov             w10, w6                     // w10 = w

2:
        ld2             {v0.16b, v1.16b}, [x4], #32 // v0 = U1, v1 = V1
        ld2             {v2.16b, v3.16b}, [x9], #32 // v2 = U2, v3 = V2

        uaddlp          v0.8h, v0.16b               // pairwise add U1 into v0
        uaddlp          v1.8h, v1.16b               // pairwise add V1 into v1
        uadalp          v0.8h, v2.16b               // pairwise add U2, accumulate into v0
        uadalp          v1.8h, v3.16b               // pairwise add V2, accumulate into v1

        shrn            v0.8b, v0.8h, #2            // divide by 4
        shrn            v1.8b, v1.8h, #2            // divide by 4

        st1             {v0.8b}, [x0], #8           // store U into dst1
        st1             {v1.8b}, [x2], #8           // store V into dst2

        subs            w10, w10, #8
        b.gt            2b

        // next row
        add             x4, x4, w5, sxtw            // src1 += srcPadding
        add             x9, x9, w5, sxtw            // src2 += srcPadding
        add             x0, x0, w1, sxtw            // dst1 += dstPadding1
        add             x2, x2, w3, sxtw            // dst2 += dstPadding2

        subs            w7, w7, #2
        b.gt            1b

        ret
endfunc