path: root/simd/arm/arm64/jsimd_neon.S

/*
 * ARMv8 NEON optimizations for libjpeg-turbo
 *
 * Copyright (C) 2009-2011, Nokia Corporation and/or its subsidiary(-ies).
 *                          All Rights Reserved.
 * Author:  Siarhei Siamashka <siarhei.siamashka@nokia.com>
 * Copyright (C) 2013-2014, Linaro Limited.  All Rights Reserved.
 * Author:  Ragesh Radhakrishnan <ragesh.r@linaro.org>
 * Copyright (C) 2014-2016, D. R. Commander.  All Rights Reserved.
 * Copyright (C) 2015-2016, 2018, Matthieu Darbois.  All Rights Reserved.
 * Copyright (C) 2016, Siarhei Siamashka.  All Rights Reserved.
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

#if defined(__linux__) && defined(__ELF__)
.section .note.GNU-stack, "", %progbits  /* mark stack as non-executable */
#endif

.text


#define RESPECT_STRICT_ALIGNMENT  1


/*****************************************************************************/

/* Supplementary macro for setting function attributes */
.macro asm_function fname
#ifdef __APPLE__
    .private_extern _\fname
    .globl _\fname
_\fname:
#else
    .global \fname
#ifdef __ELF__
    .hidden \fname
    .type \fname, %function
#endif
\fname:
#endif
.endm

.macro transpose_8x8 l0, l1, l2, l3, l4, l5, l6, l7, t0, t1, t2, t3
    trn1            \t0\().8h, \l0\().8h, \l1\().8h
    trn1            \t1\().8h, \l2\().8h, \l3\().8h
    trn1            \t2\().8h, \l4\().8h, \l5\().8h
    trn1            \t3\().8h, \l6\().8h, \l7\().8h
    trn2            \l1\().8h, \l0\().8h, \l1\().8h
    trn2            \l3\().8h, \l2\().8h, \l3\().8h
    trn2            \l5\().8h, \l4\().8h, \l5\().8h
    trn2            \l7\().8h, \l6\().8h, \l7\().8h

    trn1            \l4\().4s, \t2\().4s, \t3\().4s
    trn2            \t3\().4s, \t2\().4s, \t3\().4s
    trn1            \t2\().4s, \t0\().4s, \t1\().4s
    trn2            \l2\().4s, \t0\().4s, \t1\().4s
    trn1            \t0\().4s, \l1\().4s, \l3\().4s
    trn2            \l3\().4s, \l1\().4s, \l3\().4s
    trn2            \t1\().4s, \l5\().4s, \l7\().4s
    trn1            \l5\().4s, \l5\().4s, \l7\().4s

    trn2            \l6\().2d, \l2\().2d, \t3\().2d
    trn1            \l0\().2d, \t2\().2d, \l4\().2d
    trn1            \l1\().2d, \t0\().2d, \l5\().2d
    trn2            \l7\().2d, \l3\().2d, \t1\().2d
    trn1            \l2\().2d, \l2\().2d, \t3\().2d
    trn2            \l4\().2d, \t2\().2d, \l4\().2d
    trn1            \l3\().2d, \l3\().2d, \t1\().2d
    trn2            \l5\().2d, \t0\().2d, \l5\().2d
.endm


#define CENTERJSAMPLE  128

/*****************************************************************************/

/*
 * jsimd_idct_ifast_neon
 *
 * This function contains a fast, not so accurate integer implementation of
 * the inverse DCT (Discrete Cosine Transform). It uses the same calculations
 * and produces exactly the same output as IJG's original 'jpeg_idct_ifast'
 * function from jidctfst.c
 *
 * Normally 1-D AAN DCT needs 5 multiplications and 29 additions.
 * But in ARM NEON case some extra additions are required because VQDMULH
 * instruction can't handle the constants larger than 1. So the expressions
 * like "x * 1.082392200" have to be converted to "x * 0.082392200 + x",
 * which introduces an extra addition. Overall, there are 6 extra additions
 * per 1-D IDCT pass, totalling to 5 VQDMULH and 35 VADD/VSUB instructions.
 */

#define XFIX_1_082392200  v0.h[0]
#define XFIX_1_414213562  v0.h[1]
#define XFIX_1_847759065  v0.h[2]
#define XFIX_2_613125930  v0.h[3]

.balign 16
Ljsimd_idct_ifast_neon_consts:
  .short (277 * 128 - 256 * 128)  /* XFIX_1_082392200 */
  .short (362 * 128 - 256 * 128)  /* XFIX_1_414213562 */
  .short (473 * 128 - 256 * 128)  /* XFIX_1_847759065 */
  .short (669 * 128 - 512 * 128)  /* XFIX_2_613125930 */

asm_function jsimd_idct_ifast_neon

    DCT_TABLE       .req x0
    COEF_BLOCK      .req x1
    OUTPUT_BUF      .req x2
    OUTPUT_COL      .req x3
    TMP1            .req x0
    TMP2            .req x1
    TMP3            .req x9
    TMP4            .req x10
    TMP5            .req x11
    TMP6            .req x12
    TMP7            .req x13
    TMP8            .req x14

    /* OUTPUT_COL is a JDIMENSION (unsigned int) argument, so the ABI doesn't
       guarantee that the upper (unused) 32 bits of x3 are valid.  This
       instruction ensures that those bits are set to zero. */
    uxtw x3, w3

    /* Load and dequantize coefficients into NEON registers
     * with the following allocation:
     *       0 1 2 3 | 4 5 6 7
     *      ---------+--------
     *   0 | d16     | d17     ( v16.8h )
     *   1 | d18     | d19     ( v17.8h )
     *   2 | d20     | d21     ( v18.8h )
     *   3 | d22     | d23     ( v19.8h )
     *   4 | d24     | d25     ( v20.8h )
     *   5 | d26     | d27     ( v21.8h )
     *   6 | d28     | d29     ( v22.8h )
     *   7 | d30     | d31     ( v23.8h )
     */
    /* Save NEON registers used in fast IDCT */
    adr             TMP5, Ljsimd_idct_ifast_neon_consts
    ld1             {v16.8h, v17.8h}, [COEF_BLOCK], 32
    ld1             {v0.8h, v1.8h}, [DCT_TABLE], 32
    ld1             {v18.8h, v19.8h}, [COEF_BLOCK], 32
    mul             v16.8h, v16.8h, v0.8h
    ld1             {v2.8h, v3.8h}, [DCT_TABLE], 32
    mul             v17.8h, v17.8h, v1.8h
    ld1             {v20.8h, v21.8h}, [COEF_BLOCK], 32
    mul             v18.8h, v18.8h, v2.8h
    ld1             {v0.8h, v1.8h}, [DCT_TABLE], 32
    mul             v19.8h, v19.8h, v3.8h
    ld1             {v22.8h, v23.8h}, [COEF_BLOCK], 32
    mul             v20.8h, v20.8h, v0.8h
    ld1             {v2.8h, v3.8h}, [DCT_TABLE], 32
    mul             v22.8h, v22.8h, v2.8h
    mul             v21.8h, v21.8h, v1.8h
    ld1             {v0.4h}, [TMP5]        /* load constants */
    mul             v23.8h, v23.8h, v3.8h

    /* 1-D IDCT, pass 1 */
    sub             v2.8h, v18.8h, v22.8h
    add             v22.8h, v18.8h, v22.8h
    sub             v1.8h, v19.8h, v21.8h
    add             v21.8h, v19.8h, v21.8h
    sub             v5.8h, v17.8h, v23.8h
    add             v23.8h, v17.8h, v23.8h
    sqdmulh         v4.8h, v2.8h, XFIX_1_414213562
    sqdmulh         v6.8h, v1.8h, XFIX_2_613125930
    add             v3.8h, v1.8h, v1.8h
    sub             v1.8h, v5.8h, v1.8h
    add             v18.8h, v2.8h, v4.8h
    sqdmulh         v4.8h, v1.8h, XFIX_1_847759065
    sub             v2.8h, v23.8h, v21.8h
    add             v3.8h, v3.8h, v6.8h
    sqdmulh         v6.8h, v2.8h, XFIX_1_414213562
    add             v1.8h, v1.8h, v4.8h
    sqdmulh         v4.8h, v5.8h, XFIX_1_082392200
    sub             v18.8h, v18.8h, v22.8h
    add             v2.8h, v2.8h, v6.8h
    sub             v6.8h, v16.8h, v20.8h
    add             v20.8h, v16.8h, v20.8h
    add             v17.8h, v5.8h, v4.8h
    add             v5.8h, v6.8h, v18.8h
    sub             v18.8h, v6.8h, v18.8h
    add             v6.8h, v23.8h, v21.8h
    add             v16.8h, v20.8h, v22.8h
    sub             v3.8h, v6.8h, v3.8h
    sub             v20.8h, v20.8h, v22.8h
    sub             v3.8h, v3.8h, v1.8h
    sub             v1.8h, v17.8h, v1.8h
    add             v2.8h, v3.8h, v2.8h
    sub             v23.8h, v16.8h, v6.8h
    add             v1.8h, v1.8h, v2.8h
    add             v16.8h, v16.8h, v6.8h
    add             v22.8h, v5.8h, v3.8h
    sub             v17.8h, v5.8h, v3.8h
    sub             v21.8h, v18.8h, v2.8h
    add             v18.8h, v18.8h, v2.8h
    sub             v19.8h, v20.8h, v1.8h
    add             v20.8h, v20.8h, v1.8h
    transpose_8x8   v16, v17, v18, v19, v20, v21, v22, v23, v28, v29, v30, v31
    /* 1-D IDCT, pass 2 */
    sub             v2.8h, v18.8h, v22.8h
    add             v22.8h, v18.8h, v22.8h
    sub             v1.8h, v19.8h, v21.8h
    add             v21.8h, v19.8h, v21.8h
    sub             v5.8h, v17.8h, v23.8h
    add             v23.8h, v17.8h, v23.8h
    sqdmulh         v4.8h, v2.8h, XFIX_1_414213562
    sqdmulh         v6.8h, v1.8h, XFIX_2_613125930
    add             v3.8h, v1.8h, v1.8h
    sub             v1.8h, v5.8h, v1.8h
    add             v18.8h, v2.8h, v4.8h
    sqdmulh         v4.8h, v1.8h, XFIX_1_847759065
    sub             v2.8h, v23.8h, v21.8h
    add             v3.8h, v3.8h, v6.8h
    sqdmulh         v6.8h, v2.8h, XFIX_1_414213562
    add             v1.8h, v1.8h, v4.8h
    sqdmulh         v4.8h, v5.8h, XFIX_1_082392200
    sub             v18.8h, v18.8h, v22.8h
    add             v2.8h, v2.8h, v6.8h
    sub             v6.8h, v16.8h, v20.8h
    add             v20.8h, v16.8h, v20.8h
    add             v17.8h, v5.8h, v4.8h
    add             v5.8h, v6.8h, v18.8h
    sub             v18.8h, v6.8h, v18.8h
    add             v6.8h, v23.8h, v21.8h
    add             v16.8h, v20.8h, v22.8h
    sub             v3.8h, v6.8h, v3.8h
    sub             v20.8h, v20.8h, v22.8h
    sub             v3.8h, v3.8h, v1.8h
    sub             v1.8h, v17.8h, v1.8h
    add             v2.8h, v3.8h, v2.8h
    sub             v23.8h, v16.8h, v6.8h
    add             v1.8h, v1.8h, v2.8h
    add             v16.8h, v16.8h, v6.8h
    add             v22.8h, v5.8h, v3.8h
    sub             v17.8h, v5.8h, v3.8h
    sub             v21.8h, v18.8h, v2.8h
    add             v18.8h, v18.8h, v2.8h
    sub             v19.8h, v20.8h, v1.8h
    add             v20.8h, v20.8h, v1.8h
    /* Descale to 8-bit and range limit */
    movi            v0.16b, #0x80
      /* Prepare pointers (dual-issue with NEON instructions) */
      ldp             TMP1, TMP2, [OUTPUT_BUF], 16
    sqshrn          v28.8b, v16.8h, #5
      ldp             TMP3, TMP4, [OUTPUT_BUF], 16
    sqshrn          v29.8b, v17.8h, #5
      add             TMP1, TMP1, OUTPUT_COL
    sqshrn          v30.8b, v18.8h, #5
      add             TMP2, TMP2, OUTPUT_COL
    sqshrn          v31.8b, v19.8h, #5
      add             TMP3, TMP3, OUTPUT_COL
    sqshrn2         v28.16b, v20.8h, #5
      add             TMP4, TMP4, OUTPUT_COL
    sqshrn2         v29.16b, v21.8h, #5
      ldp             TMP5, TMP6, [OUTPUT_BUF], 16
    sqshrn2         v30.16b, v22.8h, #5
      ldp             TMP7, TMP8, [OUTPUT_BUF], 16
    sqshrn2         v31.16b, v23.8h, #5
      add             TMP5, TMP5, OUTPUT_COL
    add             v16.16b, v28.16b, v0.16b
      add             TMP6, TMP6, OUTPUT_COL
    add             v18.16b, v29.16b, v0.16b
      add             TMP7, TMP7, OUTPUT_COL
    add             v20.16b, v30.16b, v0.16b
      add             TMP8, TMP8, OUTPUT_COL
    add             v22.16b, v31.16b, v0.16b

    /* Transpose the final 8-bit samples */
    trn1            v28.16b, v16.16b, v18.16b
    trn1            v30.16b, v20.16b, v22.16b
    trn2            v29.16b, v16.16b, v18.16b
    trn2            v31.16b, v20.16b, v22.16b

    trn1            v16.8h, v28.8h, v30.8h
    trn2            v18.8h, v28.8h, v30.8h
    trn1            v20.8h, v29.8h, v31.8h
    trn2            v22.8h, v29.8h, v31.8h

    uzp1            v28.4s, v16.4s, v18.4s
    uzp2            v30.4s, v16.4s, v18.4s
    uzp1            v29.4s, v20.4s, v22.4s
    uzp2            v31.4s, v20.4s, v22.4s

    /* Store results to the output buffer */
    st1             {v28.d}[0], [TMP1]
    st1             {v29.d}[0], [TMP2]
    st1             {v28.d}[1], [TMP3]
    st1             {v29.d}[1], [TMP4]
    st1             {v30.d}[0], [TMP5]
    st1             {v31.d}[0], [TMP6]
    st1             {v30.d}[1], [TMP7]
    st1             {v31.d}[1], [TMP8]
    blr             x30

    .unreq          DCT_TABLE
    .unreq          COEF_BLOCK
    .unreq          OUTPUT_BUF
    .unreq          OUTPUT_COL
    .unreq          TMP1
    .unreq          TMP2
    .unreq          TMP3
    .unreq          TMP4
    .unreq          TMP5
    .unreq          TMP6
    .unreq          TMP7
    .unreq          TMP8


/*****************************************************************************/

/*
 * jsimd_extrgb_ycc_convert_neon
 * jsimd_extbgr_ycc_convert_neon
 * jsimd_extrgbx_ycc_convert_neon
 * jsimd_extbgrx_ycc_convert_neon
 * jsimd_extxbgr_ycc_convert_neon
 * jsimd_extxrgb_ycc_convert_neon
 *
 * Colorspace conversion RGB -> YCbCr
 */

.macro do_store size
  .if \size == 8
    st1             {v20.8b}, [Y], #8
    st1             {v21.8b}, [U], #8
    st1             {v22.8b}, [V], #8
  .elseif \size == 4
    st1             {v20.b}[0], [Y], #1
    st1             {v20.b}[1], [Y], #1
    st1             {v20.b}[2], [Y], #1
    st1             {v20.b}[3], [Y], #1
    st1             {v21.b}[0], [U], #1
    st1             {v21.b}[1], [U], #1
    st1             {v21.b}[2], [U], #1
    st1             {v21.b}[3], [U], #1
    st1             {v22.b}[0], [V], #1
    st1             {v22.b}[1], [V], #1
    st1             {v22.b}[2], [V], #1
    st1             {v22.b}[3], [V], #1
  .elseif \size == 2
    st1             {v20.b}[4], [Y], #1
    st1             {v20.b}[5], [Y], #1
    st1             {v21.b}[4], [U], #1
    st1             {v21.b}[5], [U], #1
    st1             {v22.b}[4], [V], #1
    st1             {v22.b}[5], [V], #1
  .elseif \size == 1
    st1             {v20.b}[6], [Y], #1
    st1             {v21.b}[6], [U], #1
    st1             {v22.b}[6], [V], #1
  .else
    .error unsupported macroblock size
  .endif
.endm

.macro do_load bpp, size, fast_ld3
  .if \bpp == 24
    .if \size == 8
      .if \fast_ld3 == 1
        ld3         {v10.8b, v11.8b, v12.8b}, [RGB], #24
      .else
        ld1         {v10.b}[0], [RGB], #1
        ld1         {v11.b}[0], [RGB], #1
        ld1         {v12.b}[0], [RGB], #1

        ld1         {v10.b}[1], [RGB], #1
        ld1         {v11.b}[1], [RGB], #1
        ld1         {v12.b}[1], [RGB], #1

        ld1         {v10.b}[2], [RGB], #1
        ld1         {v11.b}[2], [RGB], #1
        ld1         {v12.b}[2], [RGB], #1

        ld1         {v10.b}[3], [RGB], #1
        ld1         {v11.b}[3], [RGB], #1
        ld1         {v12.b}[3], [RGB], #1

        ld1         {v10.b}[4], [RGB], #1
        ld1         {v11.b}[4], [RGB], #1
        ld1         {v12.b}[4], [RGB], #1

        ld1         {v10.b}[5], [RGB], #1
        ld1         {v11.b}[5], [RGB], #1
        ld1         {v12.b}[5], [RGB], #1

        ld1         {v10.b}[6], [RGB], #1
        ld1         {v11.b}[6], [RGB], #1
        ld1         {v12.b}[6], [RGB], #1

        ld1         {v10.b}[7], [RGB], #1
        ld1         {v11.b}[7], [RGB], #1
        ld1         {v12.b}[7], [RGB], #1
      .endif
      prfm          pldl1keep, [RGB, #128]
    .elseif \size == 4
      ld3           {v10.b, v11.b, v12.b}[0], [RGB], #3
      ld3           {v10.b, v11.b, v12.b}[1], [RGB], #3
      ld3           {v10.b, v11.b, v12.b}[2], [RGB], #3
      ld3           {v10.b, v11.b, v12.b}[3], [RGB], #3
    .elseif \size == 2
      ld3           {v10.b, v11.b, v12.b}[4], [RGB], #3
      ld3           {v10.b, v11.b, v12.b}[5], [RGB], #3
    .elseif \size == 1
      ld3           {v10.b, v11.b, v12.b}[6], [RGB], #3
    .else
      .error unsupported macroblock size
    .endif
  .elseif \bpp == 32
    .if \size == 8
      ld4           {v10.8b, v11.8b, v12.8b, v13.8b}, [RGB], #32
      prfm          pldl1keep, [RGB, #128]
    .elseif \size == 4
      ld4           {v10.b, v11.b, v12.b, v13.b}[0], [RGB], #4
      ld4           {v10.b, v11.b, v12.b, v13.b}[1], [RGB], #4
      ld4           {v10.b, v11.b, v12.b, v13.b}[2], [RGB], #4
      ld4           {v10.b, v11.b, v12.b, v13.b}[3], [RGB], #4
    .elseif \size == 2
      ld4           {v10.b, v11.b, v12.b, v13.b}[4], [RGB], #4
      ld4           {v10.b, v11.b, v12.b, v13.b}[5], [RGB], #4
    .elseif \size == 1
      ld4           {v10.b, v11.b, v12.b, v13.b}[6], [RGB], #4
    .else
      .error unsupported macroblock size
    .endif
  .else
    .error unsupported bpp
  .endif
.endm

.macro generate_jsimd_rgb_ycc_convert_neon colorid, bpp, r_offs, g_offs, \
                                           b_offs, fast_ld3

/*
 * 2-stage pipelined RGB->YCbCr conversion
 */

.macro do_rgb_to_yuv_stage1
    ushll           v4.8h, v1\r_offs\().8b, #0  /* r = v4 */
    ushll           v6.8h, v1\g_offs\().8b, #0  /* g = v6 */
    ushll           v8.8h, v1\b_offs\().8b, #0  /* b = v8 */
    rev64           v18.4s, v1.4s
    rev64           v26.4s, v1.4s
    rev64           v28.4s, v1.4s
    rev64           v30.4s, v1.4s
    umull           v14.4s, v4.4h, v0.h[0]
    umull2          v16.4s, v4.8h, v0.h[0]
    umlsl           v18.4s, v4.4h, v0.h[3]
    umlsl2          v26.4s, v4.8h, v0.h[3]
    umlal           v28.4s, v4.4h, v0.h[5]
    umlal2          v30.4s, v4.8h, v0.h[5]
    umlal           v14.4s, v6.4h, v0.h[1]
    umlal2          v16.4s, v6.8h, v0.h[1]
    umlsl           v18.4s, v6.4h, v0.h[4]
    umlsl2          v26.4s, v6.8h, v0.h[4]
    umlsl           v28.4s, v6.4h, v0.h[6]
    umlsl2          v30.4s, v6.8h, v0.h[6]
    umlal           v14.4s, v8.4h, v0.h[2]
    umlal2          v16.4s, v8.8h, v0.h[2]
    umlal           v18.4s, v8.4h, v0.h[5]
    umlal2          v26.4s, v8.8h, v0.h[5]
    umlsl           v28.4s, v8.4h, v0.h[7]
    umlsl2          v30.4s, v8.8h, v0.h[7]
.endm

.macro do_rgb_to_yuv_stage2
    rshrn           v20.4h, v14.4s, #16
    shrn            v22.4h, v18.4s, #16
    shrn            v24.4h, v28.4s, #16
    rshrn2          v20.8h, v16.4s, #16
    shrn2           v22.8h, v26.4s, #16
    shrn2           v24.8h, v30.4s, #16
    xtn             v20.8b, v20.8h       /* v20 = y */
    xtn             v21.8b, v22.8h       /* v21 = u */
    xtn             v22.8b, v24.8h       /* v22 = v */
.endm

.macro do_rgb_to_yuv
    do_rgb_to_yuv_stage1
    do_rgb_to_yuv_stage2
.endm

/* TODO: expand macros and interleave instructions if some in-order
 *       ARM64 processor actually can dual-issue LOAD/STORE with ALU */
.macro do_rgb_to_yuv_stage2_store_load_stage1 fast_ld3
    do_rgb_to_yuv_stage2
    do_load         \bpp, 8, \fast_ld3
    st1             {v20.8b}, [Y], #8
    st1             {v21.8b}, [U], #8
    st1             {v22.8b}, [V], #8
    do_rgb_to_yuv_stage1
.endm

.balign 16
.if \fast_ld3 == 1
Ljsimd_\colorid\()_ycc_neon_consts:
.else
Ljsimd_\colorid\()_ycc_neon_slowld3_consts:
.endif
  .short 19595, 38470, 7471, 11059
  .short 21709, 32768, 27439, 5329
  .short 32767, 128, 32767, 128
  .short 32767, 128, 32767, 128

.if \fast_ld3 == 1
asm_function jsimd_\colorid\()_ycc_convert_neon
.else
asm_function jsimd_\colorid\()_ycc_convert_neon_slowld3
.endif
    OUTPUT_WIDTH    .req w0
    INPUT_BUF       .req x1
    OUTPUT_BUF      .req x2
    OUTPUT_ROW      .req w3
    NUM_ROWS        .req w4

    OUTPUT_BUF0     .req x5
    OUTPUT_BUF1     .req x6
    OUTPUT_BUF2     .req x2  /* OUTPUT_BUF */

    RGB             .req x7
    Y               .req x9
    U               .req x10
    V               .req x11
    N               .req w12

    /* Load constants to d0, d1, d2, d3 */
    .if \fast_ld3 == 1
      adr           x13, Ljsimd_\colorid\()_ycc_neon_consts
    .else
      adr           x13, Ljsimd_\colorid\()_ycc_neon_slowld3_consts
    .endif
    ld1             {v0.8h, v1.8h}, [x13]

    ldr             OUTPUT_BUF0, [OUTPUT_BUF]
    ldr             OUTPUT_BUF1, [OUTPUT_BUF, #8]
    ldr             OUTPUT_BUF2, [OUTPUT_BUF, #16]
    .unreq          OUTPUT_BUF

    /* Save NEON registers */
    sub             sp, sp, #64
    mov             x9, sp
    st1             {v8.8b, v9.8b, v10.8b, v11.8b}, [x9], 32
    st1             {v12.8b, v13.8b, v14.8b, v15.8b}, [x9], 32

    /* Outer loop over scanlines */
    cmp             NUM_ROWS, #1
    b.lt            9f
0:
    ldr             Y, [OUTPUT_BUF0, OUTPUT_ROW, uxtw #3]
    ldr             U, [OUTPUT_BUF1, OUTPUT_ROW, uxtw #3]
    mov             N, OUTPUT_WIDTH
    ldr             V, [OUTPUT_BUF2, OUTPUT_ROW, uxtw #3]
    add             OUTPUT_ROW, OUTPUT_ROW, #1
    ldr             RGB, [INPUT_BUF], #8

    /* Inner loop over pixels */
    subs            N, N, #8
    b.lt            3f
    do_load         \bpp, 8, \fast_ld3
    do_rgb_to_yuv_stage1
    subs            N, N, #8
    b.lt            2f
1:
    do_rgb_to_yuv_stage2_store_load_stage1 \fast_ld3
    subs            N, N, #8
    b.ge            1b
2:
    do_rgb_to_yuv_stage2
    do_store        8
    tst             N, #7
    b.eq            8f
3:
    tbz             N, #2, 3f
    do_load         \bpp, 4, \fast_ld3
3:
    tbz             N, #1, 4f
    do_load         \bpp, 2, \fast_ld3
4:
    tbz             N, #0, 5f
    do_load         \bpp, 1, \fast_ld3
5:
    do_rgb_to_yuv
    tbz             N, #2, 6f
    do_store        4
6:
    tbz             N, #1, 7f
    do_store        2
7:
    tbz             N, #0, 8f
    do_store        1
8:
    subs            NUM_ROWS, NUM_ROWS, #1
    b.gt            0b
9:
    /* Restore all registers and return */
    ld1             {v8.8b, v9.8b, v10.8b, v11.8b}, [sp], 32
    ld1             {v12.8b, v13.8b, v14.8b, v15.8b}, [sp], 32
    br              x30

    .unreq          OUTPUT_WIDTH
    .unreq          OUTPUT_ROW
    .unreq          INPUT_BUF
    .unreq          NUM_ROWS
    .unreq          OUTPUT_BUF0
    .unreq          OUTPUT_BUF1
    .unreq          OUTPUT_BUF2
    .unreq          RGB
    .unreq          Y
    .unreq          U
    .unreq          V
    .unreq          N

.purgem do_rgb_to_yuv
.purgem do_rgb_to_yuv_stage1
.purgem do_rgb_to_yuv_stage2
.purgem do_rgb_to_yuv_stage2_store_load_stage1

.endm

/*--------------------------------- id ----- bpp R  G  B  Fast LD3 */
generate_jsimd_rgb_ycc_convert_neon extrgb,  24, 0, 1, 2, 1
generate_jsimd_rgb_ycc_convert_neon extbgr,  24, 2, 1, 0, 1
generate_jsimd_rgb_ycc_convert_neon extrgbx, 32, 0, 1, 2, 1
generate_jsimd_rgb_ycc_convert_neon extbgrx, 32, 2, 1, 0, 1
generate_jsimd_rgb_ycc_convert_neon extxbgr, 32, 3, 2, 1, 1
generate_jsimd_rgb_ycc_convert_neon extxrgb, 32, 1, 2, 3, 1

generate_jsimd_rgb_ycc_convert_neon extrgb,  24, 0, 1, 2, 0
generate_jsimd_rgb_ycc_convert_neon extbgr,  24, 2, 1, 0, 0

.purgem do_load
.purgem do_store


/*****************************************************************************/

/*
 * Load data into workspace, applying unsigned->signed conversion
 *
 * TODO: can be combined with 'jsimd_fdct_ifast_neon' to get
 *       rid of VST1.16 instructions
 */

asm_function jsimd_convsamp_neon
    SAMPLE_DATA     .req x0
    START_COL       .req x1
    WORKSPACE       .req x2
    TMP1            .req x9
    TMP2            .req x10
    TMP3            .req x11
    TMP4            .req x12
    TMP5            .req x13
    TMP6            .req x14
    TMP7            .req x15
    TMP8            .req x4
    TMPDUP          .req w3

    /* START_COL is a JDIMENSION (unsigned int) argument, so the ABI doesn't
       guarantee that the upper (unused) 32 bits of x1 are valid.  This
       instruction ensures that those bits are set to zero. */
    uxtw x1, w1

    mov             TMPDUP, #128
    ldp             TMP1, TMP2, [SAMPLE_DATA], 16
    ldp             TMP3, TMP4, [SAMPLE_DATA], 16
    dup             v0.8b, TMPDUP
    add             TMP1, TMP1, START_COL
    add             TMP2, TMP2, START_COL
    ldp             TMP5, TMP6, [SAMPLE_DATA], 16
    add             TMP3, TMP3, START_COL
    add             TMP4, TMP4, START_COL
    ldp             TMP7, TMP8, [SAMPLE_DATA], 16
    add             TMP5, TMP5, START_COL
    add             TMP6, TMP6, START_COL
    ld1             {v16.8b}, [TMP1]
    add             TMP7, TMP7, START_COL
    add             TMP8, TMP8, START_COL
    ld1             {v17.8b}, [TMP2]
    usubl           v16.8h, v16.8b, v0.8b
    ld1             {v18.8b}, [TMP3]
    usubl           v17.8h, v17.8b, v0.8b
    ld1             {v19.8b}, [TMP4]
    usubl           v18.8h, v18.8b, v0.8b
    ld1             {v20.8b}, [TMP5]
    usubl           v19.8h, v19.8b, v0.8b
    ld1             {v21.8b}, [TMP6]
    st1             {v16.8h, v17.8h, v18.8h, v19.8h}, [WORKSPACE], 64
    usubl           v20.8h, v20.8b, v0.8b
    ld1             {v22.8b}, [TMP7]
    usubl           v21.8h, v21.8b, v0.8b
    ld1             {v23.8b}, [TMP8]
    usubl           v22.8h, v22.8b, v0.8b
    usubl           v23.8h, v23.8b, v0.8b
    st1             {v20.8h, v21.8h, v22.8h, v23.8h}, [WORKSPACE], 64

    br              x30

    .unreq          SAMPLE_DATA
    .unreq          START_COL
    .unreq          WORKSPACE
    .unreq          TMP1
    .unreq          TMP2
    .unreq          TMP3
    .unreq          TMP4
    .unreq          TMP5
    .unreq          TMP6
    .unreq          TMP7
    .unreq          TMP8
    .unreq          TMPDUP

/*****************************************************************************/

/*
 * jsimd_fdct_islow_neon
 *
 * This file contains a slow-but-accurate integer implementation of the
 * forward DCT (Discrete Cosine Transform). The following code is based
 * directly on the IJG''s original jfdctint.c; see the jfdctint.c for
 * more details.
 *
 * TODO: can be combined with 'jsimd_convsamp_neon' to get
 *       rid of a bunch of VLD1.16 instructions
 */

#define CONST_BITS  13
#define PASS1_BITS  2

#define DESCALE_P1  (CONST_BITS - PASS1_BITS)
#define DESCALE_P2  (CONST_BITS + PASS1_BITS)

#define F_0_298   2446  /* FIX(0.298631336) */
#define F_0_390   3196  /* FIX(0.390180644) */
#define F_0_541   4433  /* FIX(0.541196100) */
#define F_0_765   6270  /* FIX(0.765366865) */
#define F_0_899   7373  /* FIX(0.899976223) */
#define F_1_175   9633  /* FIX(1.175875602) */
#define F_1_501  12299  /* FIX(1.501321110) */
#define F_1_847  15137  /* FIX(1.847759065) */
#define F_1_961  16069  /* FIX(1.961570560) */
#define F_2_053  16819  /* FIX(2.053119869) */
#define F_2_562  20995  /* FIX(2.562915447) */
#define F_3_072  25172  /* FIX(3.072711026) */

.balign 16
Ljsimd_fdct_islow_neon_consts:
  .short F_0_298
  .short -F_0_390
  .short F_0_541
  .short F_0_765
  .short - F_0_899
  .short F_1_175
  .short F_1_501
  .short - F_1_847
  .short - F_1_961
  .short F_2_053
  .short - F_2_562
  .short F_3_072
  .short 0          /* padding */
  .short 0
  .short 0
  .short 0

#undef F_0_298
#undef F_0_390
#undef F_0_541
#undef F_0_765
#undef F_0_899
#undef F_1_175
#undef F_1_501
#undef F_1_847
#undef F_1_961
#undef F_2_053
#undef F_2_562
#undef F_3_072
#define XFIX_P_0_298  v0.h[0]
#define XFIX_N_0_390  v0.h[1]
#define XFIX_P_0_541  v0.h[2]
#define XFIX_P_0_765  v0.h[3]
#define XFIX_N_0_899  v0.h[4]
#define XFIX_P_1_175  v0.h[5]
#define XFIX_P_1_501  v0.h[6]
#define XFIX_N_1_847  v0.h[7]
#define XFIX_N_1_961  v1.h[0]
#define XFIX_P_2_053  v1.h[1]
#define XFIX_N_2_562  v1.h[2]
#define XFIX_P_3_072  v1.h[3]

asm_function jsimd_fdct_islow_neon

    DATA            .req x0
    TMP             .req x9

    /* Load constants */
    adr             TMP, Ljsimd_fdct_islow_neon_consts
    ld1             {v0.8h, v1.8h}, [TMP]

    /* Save NEON registers */
    sub             sp, sp, #64
    mov             x10, sp
    st1             {v8.8b, v9.8b, v10.8b, v11.8b}, [x10], 32
    st1             {v12.8b, v13.8b, v14.8b, v15.8b}, [x10], 32

    /* Load all DATA into NEON registers with the following allocation:
     *       0 1 2 3 | 4 5 6 7
     *      ---------+--------
     *   0 | d16     | d17    | v16.8h
     *   1 | d18     | d19    | v17.8h
     *   2 | d20     | d21    | v18.8h
     *   3 | d22     | d23    | v19.8h
     *   4 | d24     | d25    | v20.8h
     *   5 | d26     | d27    | v21.8h
     *   6 | d28     | d29    | v22.8h
     *   7 | d30     | d31    | v23.8h
     */

    ld1             {v16.8h, v17.8h, v18.8h, v19.8h}, [DATA], 64
    ld1             {v20.8h, v21.8h, v22.8h, v23.8h}, [DATA]
    sub             DATA, DATA, #64

    /* Transpose */
    transpose_8x8   v16, v17, v18, v19, v20, v21, v22, v23, v31, v2, v3, v4
    /* 1-D FDCT */
    add             v24.8h, v16.8h, v23.8h  /* tmp0 = dataptr[0] + dataptr[7]; */
    sub             v31.8h, v16.8h, v23.8h  /* tmp7 = dataptr[0] - dataptr[7]; */
    add             v25.8h, v17.8h, v22.8h  /* tmp1 = dataptr[1] + dataptr[6]; */
    sub             v30.8h, v17.8h, v22.8h  /* tmp6 = dataptr[1] - dataptr[6]; */
    add             v26.8h, v18.8h, v21.8h  /* tmp2 = dataptr[2] + dataptr[5]; */
    sub             v29.8h, v18.8h, v21.8h  /* tmp5 = dataptr[2] - dataptr[5]; */
    add             v27.8h, v19.8h, v20.8h  /* tmp3 = dataptr[3] + dataptr[4]; */
    sub             v28.8h, v19.8h, v20.8h  /* tmp4 = dataptr[3] - dataptr[4]; */

    /* even part */

    add             v8.8h, v24.8h, v27.8h   /* tmp10 = tmp0 + tmp3; */
    sub             v9.8h, v24.8h, v27.8h   /* tmp13 = tmp0 - tmp3; */
    add             v10.8h, v25.8h, v26.8h  /* tmp11 = tmp1 + tmp2; */
    sub             v11.8h, v25.8h, v26.8h  /* tmp12 = tmp1 - tmp2; */

    add             v16.8h, v8.8h, v10.8h  /* tmp10 + tmp11 */
    sub             v20.8h, v8.8h, v10.8h  /* tmp10 - tmp11 */

    add             v18.8h, v11.8h, v9.8h  /* tmp12 + tmp13 */

    shl             v16.8h, v16.8h, #PASS1_BITS  /* dataptr[0] = (DCTELEM)LEFT_SHIFT(tmp10 + tmp11, PASS1_BITS); */
    shl             v20.8h, v20.8h, #PASS1_BITS  /* dataptr[4] = (DCTELEM)LEFT_SHIFT(tmp10 - tmp11, PASS1_BITS); */

    smull2          v24.4s, v18.8h, XFIX_P_0_541  /* z1 hi = MULTIPLY(tmp12 + tmp13, XFIX_P_0_541); */
    smull           v18.4s, v18.4h, XFIX_P_0_541  /* z1 lo = MULTIPLY(tmp12 + tmp13, XFIX_P_0_541); */
    mov             v22.16b, v18.16b
    mov             v25.16b, v24.16b

    smlal           v18.4s, v9.4h, XFIX_P_0_765   /* lo z1 + MULTIPLY(tmp13, XFIX_P_0_765) */
    smlal2          v24.4s, v9.8h, XFIX_P_0_765   /* hi z1 + MULTIPLY(tmp13, XFIX_P_0_765) */
    smlal           v22.4s, v11.4h, XFIX_N_1_847  /* lo z1 + MULTIPLY(tmp12, XFIX_N_1_847) */
    smlal2          v25.4s, v11.8h, XFIX_N_1_847  /* hi z1 + MULTIPLY(tmp12, XFIX_N_1_847) */

    rshrn           v18.4h, v18.4s, #DESCALE_P1
    rshrn           v22.4h, v22.4s, #DESCALE_P1
    rshrn2          v18.8h, v24.4s, #DESCALE_P1  /* dataptr[2] = (DCTELEM)DESCALE(z1 + MULTIPLY(tmp13, XFIX_P_0_765), CONST_BITS-PASS1_BITS); */
    rshrn2          v22.8h, v25.4s, #DESCALE_P1  /* dataptr[6] = (DCTELEM)DESCALE(z1 + MULTIPLY(tmp12, XFIX_N_1_847), CONST_BITS-PASS1_BITS); */

    /* Odd part */

    add             v8.8h, v28.8h, v31.8h        /* z1 = tmp4 + tmp7; */
    add             v9.8h, v29.8h, v30.8h        /* z2 = tmp5 + tmp6; */
    add             v10.8h, v28.8h, v30.8h       /* z3 = tmp4 + tmp6; */
    add             v11.8h, v29.8h, v31.8h       /* z4 = tmp5 + tmp7; */
    smull           v4.4s, v10.4h, XFIX_P_1_175  /* z5 lo = z3 lo * XFIX_P_1_175 */
    smull2          v5.4s, v10.8h, XFIX_P_1_175
    smlal           v4.4s, v11.4h, XFIX_P_1_175  /* z5 = MULTIPLY(z3 + z4, FIX_1_175875602); */
    smlal2          v5.4s, v11.8h, XFIX_P_1_175

    smull2          v24.4s, v28.8h, XFIX_P_0_298
    smull2          v25.4s, v29.8h, XFIX_P_2_053
    smull2          v26.4s, v30.8h, XFIX_P_3_072
    smull2          v27.4s, v31.8h, XFIX_P_1_501
    smull           v28.4s, v28.4h, XFIX_P_0_298  /* tmp4 = MULTIPLY(tmp4, FIX_0_298631336); */
    smull           v29.4s, v29.4h, XFIX_P_2_053  /* tmp5 = MULTIPLY(tmp5, FIX_2_053119869); */
    smull           v30.4s, v30.4h, XFIX_P_3_072  /* tmp6 = MULTIPLY(tmp6, FIX_3_072711026); */
    smull           v31.4s, v31.4h, XFIX_P_1_501  /* tmp7 = MULTIPLY(tmp7, FIX_1_501321110); */

    smull2          v12.4s, v8.8h, XFIX_N_0_899
    smull2          v13.4s, v9.8h, XFIX_N_2_562
    smull2          v14.4s, v10.8h, XFIX_N_1_961
    smull2          v15.4s, v11.8h, XFIX_N_0_390
    smull           v8.4s, v8.4h, XFIX_N_0_899    /* z1 = MULTIPLY(z1, -FIX_0_899976223); */
    smull           v9.4s, v9.4h, XFIX_N_2_562    /* z2 = MULTIPLY(z2, -FIX_2_562915447); */
    smull           v10.4s, v10.4h, XFIX_N_1_961  /* z3 = MULTIPLY(z3, -FIX_1_961570560); */
    smull           v11.4s, v11.4h, XFIX_N_0_390  /* z4 = MULTIPLY(z4, -FIX_0_390180644); */

    add             v10.4s, v10.4s, v4.4s  /* z3 += z5 */
    add             v14.4s, v14.4s, v5.4s
    add             v11.4s, v11.4s, v4.4s  /* z4 += z5 */
    add             v15.4s, v15.4s, v5.4s

    add             v28.4s, v28.4s, v8.4s   /* tmp4 += z1 */
    add             v24.4s, v24.4s, v12.4s
    add             v29.4s, v29.4s, v9.4s   /* tmp5 += z2 */
    add             v25.4s, v25.4s, v13.4s
    add             v30.4s, v30.4s, v10.4s  /* tmp6 += z3 */
    add             v26.4s, v26.4s, v14.4s
    add             v31.4s, v31.4s, v11.4s  /* tmp7 += z4 */
    add             v27.4s, v27.4s, v15.4s

    add             v28.4s, v28.4s, v10.4s  /* tmp4 += z3 */
    add             v24.4s, v24.4s, v14.4s
    add             v29.4s, v29.4s, v11.4s  /* tmp5 += z4 */
    add             v25.4s, v25.4s, v15.4s
    add             v30.4s, v30.4s, v9.4s   /* tmp6 += z2 */
    add             v26.4s, v26.4s, v13.4s
    add             v31.4s, v31.4s, v8.4s   /* tmp7 += z1 */
    add             v27.4s, v27.4s, v12.4s

    rshrn           v23.4h, v28.4s, #DESCALE_P1
    rshrn           v21.4h, v29.4s, #DESCALE_P1
    rshrn           v19.4h, v30.4s, #DESCALE_P1
    rshrn           v17.4h, v31.4s, #DESCALE_P1
    rshrn2          v23.8h, v24.4s, #DESCALE_P1  /* dataptr[7] = (DCTELEM)DESCALE(tmp4 + z1 + z3, CONST_BITS-PASS1_BITS); */
    rshrn2          v21.8h, v25.4s, #DESCALE_P1  /* dataptr[5] = (DCTELEM)DESCALE(tmp5 + z2 + z4, CONST_BITS-PASS1_BITS); */
    rshrn2          v19.8h, v26.4s, #DESCALE_P1  /* dataptr[3] = (DCTELEM)DESCALE(tmp6 + z2 + z3, CONST_BITS-PASS1_BITS); */
    rshrn2          v17.8h, v27.4s, #DESCALE_P1  /* dataptr[1] = (DCTELEM)DESCALE(tmp7 + z1 + z4, CONST_BITS-PASS1_BITS); */

    /* Transpose */
    transpose_8x8   v16, v17, v18, v19, v20, v21, v22, v23, v31, v2, v3, v4

    /* 1-D FDCT */
    add             v24.8h, v16.8h, v23.8h  /* tmp0 = dataptr[0] + dataptr[7]; */
    sub             v31.8h, v16.8h, v23.8h  /* tmp7 = dataptr[0] - dataptr[7]; */
    add             v25.8h, v17.8h, v22.8h  /* tmp1 = dataptr[1] + dataptr[6]; */
    sub             v30.8h, v17.8h, v22.8h  /* tmp6 = dataptr[1] - dataptr[6]; */
    add             v26.8h, v18.8h, v21.8h  /* tmp2 = dataptr[2] + dataptr[5]; */
    sub             v29.8h, v18.8h, v21.8h  /* tmp5 = dataptr[2] - dataptr[5]; */
    add             v27.8h, v19.8h, v20.8h  /* tmp3 = dataptr[3] + dataptr[4]; */
    sub             v28.8h, v19.8h, v20.8h  /* tmp4 = dataptr[3] - dataptr[4]; */

    /* even part */
    add             v8.8h, v24.8h, v27.8h   /* tmp10 = tmp0 + tmp3; */
    sub             v9.8h, v24.8h, v27.8h   /* tmp13 = tmp0 - tmp3; */
    add             v10.8h, v25.8h, v26.8h  /* tmp11 = tmp1 + tmp2; */
    sub             v11.8h, v25.8h, v26.8h  /* tmp12 = tmp1 - tmp2; */

    add             v16.8h, v8.8h, v10.8h  /* tmp10 + tmp11 */
    sub             v20.8h, v8.8h, v10.8h  /* tmp10 - tmp11 */

    add             v18.8h, v11.8h, v9.8h  /* tmp12 + tmp13 */

    srshr           v16.8h, v16.8h, #PASS1_BITS  /* dataptr[0] = (DCTELEM)DESCALE(tmp10 + tmp11, PASS1_BITS); */
    srshr           v20.8h, v20.8h, #PASS1_BITS  /* dataptr[4] = (DCTELEM)DESCALE(tmp10 - tmp11, PASS1_BITS); */

    smull2          v24.4s, v18.8h, XFIX_P_0_541  /* z1 hi = MULTIPLY(tmp12 + tmp13, XFIX_P_0_541); */
    smull           v18.4s, v18.4h, XFIX_P_0_541  /* z1 lo = MULTIPLY(tmp12 + tmp13, XFIX_P_0_541); */
    mov             v22.16b, v18.16b
    mov             v25.16b, v24.16b

    smlal           v18.4s, v9.4h, XFIX_P_0_765   /* lo z1 + MULTIPLY(tmp13, XFIX_P_0_765) */
    smlal2          v24.4s, v9.8h, XFIX_P_0_765   /* hi z1 + MULTIPLY(tmp13, XFIX_P_0_765) */
    smlal           v22.4s, v11.4h, XFIX_N_1_847  /* lo z1 + MULTIPLY(tmp12, XFIX_N_1_847) */
    smlal2          v25.4s, v11.8h, XFIX_N_1_847  /* hi z1 + MULTIPLY(tmp12, XFIX_N_1_847) */

    rshrn           v18.4h, v18.4s, #DESCALE_P2
    rshrn           v22.4h, v22.4s, #DESCALE_P2
    rshrn2          v18.8h, v24.4s, #DESCALE_P2  /* dataptr[2] = (DCTELEM)DESCALE(z1 + MULTIPLY(tmp13, XFIX_P_0_765), CONST_BITS-PASS1_BITS); */
    rshrn2          v22.8h, v25.4s, #DESCALE_P2  /* dataptr[6] = (DCTELEM)DESCALE(z1 + MULTIPLY(tmp12, XFIX_N_1_847), CONST_BITS-PASS1_BITS); */

    /* Odd part */
    add             v8.8h, v28.8h, v31.8h   /* z1 = tmp4 + tmp7; */
    add             v9.8h, v29.8h, v30.8h   /* z2 = tmp5 + tmp6; */
    add             v10.8h, v28.8h, v30.8h  /* z3 = tmp4 + tmp6; */
    add             v11.8h, v29.8h, v31.8h  /* z4 = tmp5 + tmp7; */

    smull           v4.4s, v10.4h, XFIX_P_1_175  /* z5 lo = z3 lo * XFIX_P_1_175 */
    smull2          v5.4s, v10.8h, XFIX_P_1_175
    smlal           v4.4s, v11.4h, XFIX_P_1_175  /* z5 = MULTIPLY(z3 + z4, FIX_1_175875602); */
    smlal2          v5.4s, v11.8h, XFIX_P_1_175

    smull2          v24.4s, v28.8h, XFIX_P_0_298
    smull2          v25.4s, v29.8h, XFIX_P_2_053
    smull2          v26.4s, v30.8h, XFIX_P_3_072
    smull2          v27.4s, v31.8h, XFIX_P_1_501
    smull           v28.4s, v28.4h, XFIX_P_0_298  /* tmp4 = MULTIPLY(tmp4, FIX_0_298631336); */
    smull           v29.4s, v29.4h, XFIX_P_2_053  /* tmp5 = MULTIPLY(tmp5, FIX_2_053119869); */
    smull           v30.4s, v30.4h, XFIX_P_3_072  /* tmp6 = MULTIPLY(tmp6, FIX_3_072711026); */
    smull           v31.4s, v31.4h, XFIX_P_1_501  /* tmp7 = MULTIPLY(tmp7, FIX_1_501321110); */

    smull2          v12.4s, v8.8h, XFIX_N_0_899
    smull2          v13.4s, v9.8h, XFIX_N_2_562
    smull2          v14.4s, v10.8h, XFIX_N_1_961
    smull2          v15.4s, v11.8h, XFIX_N_0_390
    smull           v8.4s, v8.4h, XFIX_N_0_899    /* z1 = MULTIPLY(z1, -FIX_0_899976223); */
    smull           v9.4s, v9.4h, XFIX_N_2_562    /* z2 = MULTIPLY(z2, -FIX_2_562915447); */
    smull           v10.4s, v10.4h, XFIX_N_1_961  /* z3 = MULTIPLY(z3, -FIX_1_961570560); */
    smull           v11.4s, v11.4h, XFIX_N_0_390  /* z4 = MULTIPLY(z4, -FIX_0_390180644); */

    add             v10.4s, v10.4s, v4.4s
    add             v14.4s, v14.4s, v5.4s
    add             v11.4s, v11.4s, v4.4s
    add             v15.4s, v15.4s, v5.4s

    add             v28.4s, v28.4s, v8.4s   /* tmp4 += z1 */
    add             v24.4s, v24.4s, v12.4s
    add             v29.4s, v29.4s, v9.4s   /* tmp5 += z2 */
    add             v25.4s, v25.4s, v13.4s
    add             v30.4s, v30.4s, v10.4s  /* tmp6 += z3 */
    add             v26.4s, v26.4s, v14.4s
    add             v31.4s, v31.4s, v11.4s  /* tmp7 += z4 */
    add             v27.4s, v27.4s, v15.4s

    add             v28.4s, v28.4s, v10.4s  /* tmp4 += z3 */
    add             v24.4s, v24.4s, v14.4s
    add             v29.4s, v29.4s, v11.4s  /* tmp5 += z4 */
    add             v25.4s, v25.4s, v15.4s
    add             v30.4s, v30.4s, v9.4s   /* tmp6 += z2 */
    add             v26.4s, v26.4s, v13.4s
    add             v31.4s, v31.4s, v8.4s   /* tmp7 += z1 */
    add             v27.4s, v27.4s, v12.4s

    rshrn           v23.4h, v28.4s, #DESCALE_P2
    rshrn           v21.4h, v29.4s, #DESCALE_P2
    rshrn           v19.4h, v30.4s, #DESCALE_P2
    rshrn           v17.4h, v31.4s, #DESCALE_P2
    rshrn2          v23.8h, v24.4s, #DESCALE_P2  /* dataptr[7] = (DCTELEM)DESCALE(tmp4 + z1 + z3, CONST_BITS-PASS1_BITS); */
    rshrn2          v21.8h, v25.4s, #DESCALE_P2  /* dataptr[5] = (DCTELEM)DESCALE(tmp5 + z2 + z4, CONST_BITS-PASS1_BITS); */
    rshrn2          v19.8h, v26.4s, #DESCALE_P2  /* dataptr[3] = (DCTELEM)DESCALE(tmp6 + z2 + z3, CONST_BITS-PASS1_BITS); */
    rshrn2          v17.8h, v27.4s, #DESCALE_P2  /* dataptr[1] = (DCTELEM)DESCALE(tmp7 + z1 + z4, CONST_BITS-PASS1_BITS); */

    /* store results */
    st1             {v16.8h, v17.8h, v18.8h, v19.8h}, [DATA], 64
    st1             {v20.8h, v21.8h, v22.8h, v23.8h}, [DATA]

    /* Restore NEON registers */
    ld1             {v8.8b, v9.8b, v10.8b, v11.8b}, [sp], 32
    ld1             {v12.8b, v13.8b, v14.8b, v15.8b}, [sp], 32

    br              x30

    .unreq          DATA
    .unreq          TMP

#undef XFIX_P_0_298
#undef XFIX_N_0_390
#undef XFIX_P_0_541
#undef XFIX_P_0_765
#undef XFIX_N_0_899
#undef XFIX_P_1_175
#undef XFIX_P_1_501
#undef XFIX_N_1_847
#undef XFIX_N_1_961
#undef XFIX_P_2_053
#undef XFIX_N_2_562
#undef XFIX_P_3_072


/*****************************************************************************/

/*
 * jsimd_fdct_ifast_neon
 *
 * This function contains a fast, not so accurate integer implementation of
 * the forward DCT (Discrete Cosine Transform). It uses the same calculations
 * and produces exactly the same output as IJG's original 'jpeg_fdct_ifast'
 * function from jfdctfst.c
 *
 * TODO: can be combined with 'jsimd_convsamp_neon' to get
 *       rid of a bunch of VLD1.16 instructions
 */

#undef XFIX_0_541196100
#define XFIX_0_382683433  v0.h[0]
#define XFIX_0_541196100  v0.h[1]
#define XFIX_0_707106781  v0.h[2]
#define XFIX_1_306562965  v0.h[3]

.balign 16
Ljsimd_fdct_ifast_neon_consts:
  .short (98 * 128)               /* XFIX_0_382683433 */
  .short (139 * 128)              /* XFIX_0_541196100 */
  .short (181 * 128)              /* XFIX_0_707106781 */
  .short (334 * 128 - 256 * 128)  /* XFIX_1_306562965 */

asm_function jsimd_fdct_ifast_neon

    DATA            .req x0
    TMP             .req x9

    /* Load constants */
    adr             TMP, Ljsimd_fdct_ifast_neon_consts
    ld1             {v0.4h}, [TMP]

    /* Load all DATA into NEON registers with the following allocation:
     *       0 1 2 3 | 4 5 6 7
     *      ---------+--------
     *   0 | d16     | d17    | v0.8h
     *   1 | d18     | d19    | q9
     *   2 | d20     | d21    | q10
     *   3 | d22     | d23    | q11
     *   4 | d24     | d25    | q12
     *   5 | d26     | d27    | q13
     *   6 | d28     | d29    | q14
     *   7 | d30     | d31    | q15
     */

    ld1             {v16.8h, v17.8h, v18.8h, v19.8h}, [DATA], 64
    ld1             {v20.8h, v21.8h, v22.8h, v23.8h}, [DATA]
    mov             TMP, #2
    sub             DATA, DATA, #64
1:
    /* Transpose */
    transpose_8x8   v16, v17, v18, v19, v20, v21, v22, v23, v1, v2, v3, v4
    subs            TMP, TMP, #1
    /* 1-D FDCT */
    add             v4.8h, v19.8h, v20.8h
    sub             v20.8h, v19.8h, v20.8h
    sub             v28.8h, v18.8h, v21.8h
    add             v18.8h, v18.8h, v21.8h
    sub             v29.8h, v17.8h, v22.8h
    add             v17.8h, v17.8h, v22.8h
    sub             v21.8h, v16.8h, v23.8h
    add             v16.8h, v16.8h, v23.8h
    sub             v6.8h, v17.8h, v18.8h
    sub             v7.8h, v16.8h, v4.8h
    add             v5.8h, v17.8h, v18.8h
    add             v6.8h, v6.8h, v7.8h
    add             v4.8h, v16.8h, v4.8h
    sqdmulh         v6.8h, v6.8h, XFIX_0_707106781
    add             v19.8h, v20.8h, v28.8h
    add             v16.8h, v4.8h, v5.8h
    sub             v20.8h, v4.8h, v5.8h
    add             v5.8h, v28.8h, v29.8h
    add             v29.8h, v29.8h, v21.8h
    sqdmulh         v5.8h, v5.8h, XFIX_0_707106781
    sub             v28.8h, v19.8h, v29.8h
    add             v18.8h, v7.8h, v6.8h
    sqdmulh         v28.8h, v28.8h, XFIX_0_382683433
    sub             v22.8h, v7.8h, v6.8h
    sqdmulh         v19.8h, v19.8h, XFIX_0_541196100
    sqdmulh         v7.8h, v29.8h, XFIX_1_306562965
    add             v6.8h, v21.8h, v5.8h
    sub             v5.8h, v21.8h, v5.8h
    add             v29.8h, v29.8h, v28.8h
    add             v19.8h, v19.8h, v28.8h
    add             v29.8h, v29.8h, v7.8h
    add             v21.8h, v5.8h, v19.8h
    sub             v19.8h, v5.8h, v19.8h
    add             v17.8h, v6.8h, v29.8h
    sub             v23.8h, v6.8h, v29.8h

    b.ne            1b

    /* store results */
    st1             {v16.8h, v17.8h, v18.8h, v19.8h}, [DATA], 64
    st1             {v20.8h, v21.8h, v22.8h, v23.8h}, [DATA]

    br              x30

    .unreq          DATA
    .unreq          TMP
#undef XFIX_0_382683433
#undef XFIX_0_541196100
#undef XFIX_0_707106781
#undef XFIX_1_306562965


/*****************************************************************************/

/*
 * GLOBAL(void)
 * jsimd_quantize_neon(JCOEFPTR coef_block, DCTELEM *divisors,
 *                     DCTELEM *workspace);
 *
 */
asm_function jsimd_quantize_neon

    COEF_BLOCK      .req x0
    DIVISORS        .req x1
    WORKSPACE       .req x2

    RECIPROCAL      .req DIVISORS
    CORRECTION      .req x9
    SHIFT           .req x10
    LOOP_COUNT      .req x11

    mov             LOOP_COUNT, #2
    add             CORRECTION, DIVISORS, #(64 * 2)
    add             SHIFT, DIVISORS, #(64 * 6)
1:
    subs            LOOP_COUNT, LOOP_COUNT, #1
    ld1             {v0.8h, v1.8h, v2.8h, v3.8h}, [WORKSPACE], 64
    ld1             {v4.8h, v5.8h, v6.8h, v7.8h}, [CORRECTION], 64
    abs             v20.8h, v0.8h
    abs             v21.8h, v1.8h
    abs             v22.8h, v2.8h
    abs             v23.8h, v3.8h
    ld1             {v28.8h, v29.8h, v30.8h, v31.8h}, [RECIPROCAL], 64
    add             v20.8h, v20.8h, v4.8h  /* add correction */
    add             v21.8h, v21.8h, v5.8h
    add             v22.8h, v22.8h, v6.8h
    add             v23.8h, v23.8h, v7.8h
    umull           v4.4s, v20.4h, v28.4h  /* multiply by reciprocal */
    umull2          v16.4s, v20.8h, v28.8h
    umull           v5.4s, v21.4h, v29.4h
    umull2          v17.4s, v21.8h, v29.8h
    umull           v6.4s, v22.4h, v30.4h  /* multiply by reciprocal */
    umull2          v18.4s, v22.8h, v30.8h
    umull           v7.4s, v23.4h, v31.4h
    umull2          v19.4s, v23.8h, v31.8h
    ld1             {v24.8h, v25.8h, v26.8h, v27.8h}, [SHIFT], 64
    shrn            v4.4h, v4.4s, #16
    shrn            v5.4h, v5.4s, #16
    shrn            v6.4h, v6.4s, #16
    shrn            v7.4h, v7.4s, #16
    shrn2           v4.8h, v16.4s, #16
    shrn2           v5.8h, v17.4s, #16
    shrn2           v6.8h, v18.4s, #16
    shrn2           v7.8h, v19.4s, #16
    neg             v24.8h, v24.8h
    neg             v25.8h, v25.8h
    neg             v26.8h, v26.8h
    neg             v27.8h, v27.8h
    sshr            v0.8h, v0.8h, #15  /* extract sign */
    sshr            v1.8h, v1.8h, #15
    sshr            v2.8h, v2.8h, #15
    sshr            v3.8h, v3.8h, #15
    ushl            v4.8h, v4.8h, v24.8h  /* shift */
    ushl            v5.8h, v5.8h, v25.8h
    ushl            v6.8h, v6.8h, v26.8h
    ushl            v7.8h, v7.8h, v27.8h

    eor             v4.16b, v4.16b, v0.16b  /* restore sign */
    eor             v5.16b, v5.16b, v1.16b
    eor             v6.16b, v6.16b, v2.16b
    eor             v7.16b, v7.16b, v3.16b
    sub             v4.8h, v4.8h, v0.8h
    sub             v5.8h, v5.8h, v1.8h
    sub             v6.8h, v6.8h, v2.8h
    sub             v7.8h, v7.8h, v3.8h
    st1             {v4.8h, v5.8h, v6.8h, v7.8h}, [COEF_BLOCK], 64

    b.ne            1b

    br              x30  /* return */

    .unreq          COEF_BLOCK
    .unreq          DIVISORS
    .unreq          WORKSPACE
    .unreq          RECIPROCAL
    .unreq          CORRECTION
    .unreq          SHIFT
    .unreq          LOOP_COUNT


/*****************************************************************************/

/*
 * Downsample pixel values of a single component.
 * This version handles the common case of 2:1 horizontal and 1:1 vertical,
 * without smoothing.
 *
 * GLOBAL(void)
 * jsimd_h2v1_downsample_neon(JDIMENSION image_width, int max_v_samp_factor,
 *                            JDIMENSION v_samp_factor,
 *                            JDIMENSION width_in_blocks,
 *                            JSAMPARRAY input_data, JSAMPARRAY output_data);
 */

.balign 16
Ljsimd_h2_downsample_neon_consts:
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F  /* diff 0 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0E  /* diff 1 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0D, 0x0D  /* diff 2 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0C, 0x0C, 0x0C  /* diff 3 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x0A, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B  /* diff 4 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A  /* diff 5 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09  /* diff 6 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08  /* diff 7 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, \
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07  /* diff 8 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x06, \
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06  /* diff 9 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x05, 0x05, \
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05  /* diff 10 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x04, 0x04, 0x04, 0x04, \
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04  /* diff 11 */
  .byte 0x00, 0x01, 0x02, 0x03, 0x03, 0x03, 0x03, 0x03, \
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03  /* diff 12 */
  .byte 0x00, 0x01, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, \
        0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02  /* diff 13 */
  .byte 0x00, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, \
        0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01  /* diff 14 */
  .byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00  /* diff 15 */

asm_function jsimd_h2v1_downsample_neon
    IMAGE_WIDTH     .req x0
    MAX_V_SAMP      .req x1
    V_SAMP          .req x2
    BLOCK_WIDTH     .req x3
    INPUT_DATA      .req x4
    OUTPUT_DATA     .req x5
    OUTPTR          .req x9
    INPTR           .req x10
    TMP1            .req x11
    TMP2            .req x12
    TMP3            .req x13
    TMPDUP          .req w15

    mov             TMPDUP, #0x10000
    lsl             TMP2, BLOCK_WIDTH, #4
    sub             TMP2, TMP2, IMAGE_WIDTH
    adr             TMP3, Ljsimd_h2_downsample_neon_consts
    add             TMP3, TMP3, TMP2, lsl #4
    dup             v16.4s, TMPDUP
    ld1             {v18.16b}, [TMP3]

1:  /* row loop */
    ldr             INPTR, [INPUT_DATA], #8
    ldr             OUTPTR, [OUTPUT_DATA], #8
    subs            TMP1, BLOCK_WIDTH, #1
    b.eq            3f
2:  /* columns */
    ld1             {v0.16b}, [INPTR], #16
    mov             v4.16b, v16.16b
    subs            TMP1, TMP1, #1
    uadalp          v4.8h, v0.16b
    shrn            v6.8b, v4.8h, #1
    st1             {v6.8b}, [OUTPTR], #8
    b.ne            2b
3:  /* last columns */
    ld1             {v0.16b}, [INPTR]
    mov             v4.16b, v16.16b
    subs            V_SAMP, V_SAMP, #1
    /* expand right */
    tbl             v2.16b, {v0.16b}, v18.16b
    uadalp          v4.8h, v2.16b
    shrn            v6.8b, v4.8h, #1
    st1             {v6.8b}, [OUTPTR], #8
    b.ne            1b

    br              x30

    .unreq          IMAGE_WIDTH
    .unreq          MAX_V_SAMP
    .unreq          V_SAMP
    .unreq          BLOCK_WIDTH
    .unreq          INPUT_DATA
    .unreq          OUTPUT_DATA
    .unreq          OUTPTR
    .unreq          INPTR
    .unreq          TMP1
    .unreq          TMP2
    .unreq          TMP3
    .unreq          TMPDUP


/*****************************************************************************/

/*
 * Downsample pixel values of a single component.
 * This version handles the common case of 2:1 horizontal and 2:1 vertical,
 * without smoothing.
 *
 * GLOBAL(void)
 * jsimd_h2v2_downsample_neon(JDIMENSION image_width, int max_v_samp_factor,
 *                            JDIMENSION v_samp_factor,
 *                            JDIMENSION width_in_blocks,
 *                            JSAMPARRAY input_data, JSAMPARRAY output_data);
 */

.balign 16
asm_function jsimd_h2v2_downsample_neon
    IMAGE_WIDTH     .req x0
    MAX_V_SAMP      .req x1
    V_SAMP          .req x2
    BLOCK_WIDTH     .req x3
    INPUT_DATA      .req x4
    OUTPUT_DATA     .req x5
    OUTPTR          .req x9
    INPTR0          .req x10
    INPTR1          .req x14
    TMP1            .req x11
    TMP2            .req x12
    TMP3            .req x13
    TMPDUP          .req w15

    mov             TMPDUP, #1
    lsl             TMP2, BLOCK_WIDTH, #4
    lsl             TMPDUP, TMPDUP, #17
    sub             TMP2, TMP2, IMAGE_WIDTH
    adr             TMP3, Ljsimd_h2_downsample_neon_consts
    orr             TMPDUP, TMPDUP, #1
    add             TMP3, TMP3, TMP2, lsl #4
    dup             v16.4s, TMPDUP
    ld1             {v18.16b}, [TMP3]

1:  /* row loop */
    ldr             INPTR0, [INPUT_DATA], #8
    ldr             OUTPTR, [OUTPUT_DATA], #8
    ldr             INPTR1, [INPUT_DATA], #8
    subs            TMP1, BLOCK_WIDTH, #1
    b.eq            3f
2:  /* columns */
    ld1             {v0.16b}, [INPTR0], #16
    ld1             {v1.16b}, [INPTR1], #16
    mov             v4.16b, v16.16b
    subs            TMP1, TMP1, #1
    uadalp          v4.8h, v0.16b
    uadalp          v4.8h, v1.16b
    shrn            v6.8b, v4.8h, #2
    st1             {v6.8b}, [OUTPTR], #8
    b.ne            2b
3:  /* last columns */
    ld1             {v0.16b}, [INPTR0], #16
    ld1             {v1.16b}, [INPTR1], #16
    mov             v4.16b, v16.16b
    subs            V_SAMP, V_SAMP, #1
    /* expand right */
    tbl             v2.16b, {v0.16b}, v18.16b
    tbl             v3.16b, {v1.16b}, v18.16b
    uadalp          v4.8h, v2.16b
    uadalp          v4.8h, v3.16b
    shrn            v6.8b, v4.8h, #2
    st1             {v6.8b}, [OUTPTR], #8
    b.ne            1b

    br              x30

    .unreq          IMAGE_WIDTH
    .unreq          MAX_V_SAMP
    .unreq          V_SAMP
    .unreq          BLOCK_WIDTH
    .unreq          INPUT_DATA
    .unreq          OUTPUT_DATA
    .unreq          OUTPTR
    .unreq          INPTR0
    .unreq          INPTR1
    .unreq          TMP1
    .unreq          TMP2
    .unreq          TMP3
    .unreq          TMPDUP


/*****************************************************************************/

/*
 * GLOBAL(JOCTET *)
 * jsimd_huff_encode_one_block(working_state *state, JOCTET *buffer,
 *                             JCOEFPTR block, int last_dc_val,
 *                             c_derived_tbl *dctbl, c_derived_tbl *actbl)
 *
 */

    BUFFER          .req x1
    PUT_BUFFER      .req x6
    PUT_BITS        .req x7
    PUT_BITSw       .req w7

.macro emit_byte
    sub             PUT_BITS, PUT_BITS, #0x8
    lsr             x19, PUT_BUFFER, PUT_BITS
    uxtb            w19, w19
    strb            w19, [BUFFER, #1]!
    cmp             w19, #0xff
    b.ne            14f
    strb            wzr, [BUFFER, #1]!
14:
.endm
.macro put_bits CODE, SIZE
    lsl             PUT_BUFFER, PUT_BUFFER, \SIZE
    add             PUT_BITS, PUT_BITS, \SIZE
    orr             PUT_BUFFER, PUT_BUFFER, \CODE
.endm
.macro checkbuf31
    cmp             PUT_BITS, #0x20
    b.lt            31f
    emit_byte
    emit_byte
    emit_byte
    emit_byte
31:
.endm
.macro checkbuf47
    cmp             PUT_BITS, #0x30
    b.lt            47f
    emit_byte
    emit_byte
    emit_byte
    emit_byte
    emit_byte
    emit_byte
47:
.endm

.macro generate_jsimd_huff_encode_one_block fast_tbl

.balign 16
.if \fast_tbl == 1
Ljsimd_huff_encode_one_block_neon_consts:
.else
Ljsimd_huff_encode_one_block_neon_slowtbl_consts:
.endif
    .byte 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, \
          0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80
.if \fast_tbl == 1
    .byte    0,   1,   2,   3,  16,  17,  32,  33, \
            18,  19,   4,   5,   6,   7,  20,  21  /* L0 => L3 : 4 lines OK */
    .byte   34,  35,  48,  49, 255, 255,  50,  51, \
            36,  37,  22,  23,   8,   9,  10,  11  /* L0 => L3 : 4 lines OK */
    .byte    8,   9,  22,  23,  36,  37,  50,  51, \
           255, 255, 255, 255, 255, 255,  52,  53  /* L1 => L4 : 4 lines OK */
    .byte   54,  55,  40,  41,  26,  27,  12,  13, \
            14,  15,  28,  29,  42,  43,  56,  57  /* L0 => L3 : 4 lines OK */
    .byte    6,   7,  20,  21,  34,  35,  48,  49, \
            50,  51,  36,  37,  22,  23,   8,   9  /* L4 => L7 : 4 lines OK */
    .byte   42,  43,  28,  29,  14,  15,  30,  31, \
            44,  45,  58,  59, 255, 255, 255, 255  /* L1 => L4 : 4 lines OK */
    .byte  255, 255, 255, 255,  56,  57,  42,  43, \
            28,  29,  14,  15,  30,  31,  44,  45  /* L3 => L6 : 4 lines OK */
    .byte   26,  27,  40,  41,  42,  43,  28,  29, \
            14,  15,  30,  31,  44,  45,  46,  47  /* L5 => L7 : 3 lines OK */
    .byte  255, 255, 255, 255,   0,   1, 255, 255, \
           255, 255, 255, 255, 255, 255, 255, 255  /* L4 : 1 lines OK */
    .byte  255, 255, 255, 255, 255, 255, 255, 255, \
             0,   1,  16,  17,   2,   3, 255, 255  /* L5 => L6 : 2 lines OK */
    .byte  255, 255, 255, 255, 255, 255, 255, 255, \
           255, 255, 255, 255,   8,   9,  22,  23  /* L5 => L6 : 2 lines OK */
    .byte    4,   5,   6,   7, 255, 255, 255, 255, \
           255, 255, 255, 255, 255, 255, 255, 255  /* L7 : 1 line OK */
.endif

.if \fast_tbl == 1
asm_function jsimd_huff_encode_one_block_neon
.else
asm_function jsimd_huff_encode_one_block_neon_slowtbl
.endif
    sub             sp, sp, 272
    sub             BUFFER, BUFFER, #0x1    /* BUFFER=buffer-- */
    /* Save ARM registers */
    stp             x19, x20, [sp]
.if \fast_tbl == 1
    adr             x15, Ljsimd_huff_encode_one_block_neon_consts
.else
    adr             x15, Ljsimd_huff_encode_one_block_neon_slowtbl_consts
.endif
    ldr             PUT_BUFFER, [x0, #0x10]
    ldr             PUT_BITSw, [x0, #0x18]
    ldrsh           w12, [x2]               /* load DC coeff in w12 */
    /* prepare data */
.if \fast_tbl == 1
    ld1             {v23.16b}, [x15], #16
    ld1             {v0.16b, v1.16b, v2.16b, v3.16b}, [x15], #64
    ld1             {v4.16b, v5.16b, v6.16b, v7.16b}, [x15], #64
    ld1             {v16.16b, v17.16b, v18.16b, v19.16b}, [x15], #64
    ld1             {v24.16b, v25.16b, v26.16b, v27.16b}, [x2], #64
    ld1             {v28.16b, v29.16b, v30.16b, v31.16b}, [x2], #64
    sub             w12, w12, w3      /* last_dc_val, not used afterwards */
    /* ZigZag 8x8 */
    tbl             v0.16b, {v24.16b, v25.16b, v26.16b, v27.16b}, v0.16b
    tbl             v1.16b, {v24.16b, v25.16b, v26.16b, v27.16b}, v1.16b
    tbl             v2.16b, {v25.16b, v26.16b, v27.16b, v28.16b}, v2.16b
    tbl             v3.16b, {v24.16b, v25.16b, v26.16b, v27.16b}, v3.16b
    tbl             v4.16b, {v28.16b, v29.16b, v30.16b, v31.16b}, v4.16b
    tbl             v5.16b, {v25.16b, v26.16b, v27.16b, v28.16b}, v5.16b
    tbl             v6.16b, {v27.16b, v28.16b, v29.16b, v30.16b}, v6.16b
    tbl             v7.16b, {v29.16b, v30.16b, v31.16b}, v7.16b
    ins             v0.h[0], w12
    tbx             v1.16b, {v28.16b}, v16.16b
    tbx             v2.16b, {v29.16b, v30.16b}, v17.16b
    tbx             v5.16b, {v29.16b, v30.16b}, v18.16b
    tbx             v6.16b, {v31.16b}, v19.16b
.else
      add             x13, x2, #0x22
      sub             w12, w12, w3    /* last_dc_val, not used afterwards */
    ld1             {v23.16b}, [x15]
      add             x14, x2, #0x18
      add             x3, x2, #0x36
    ins             v0.h[0], w12
      add             x9, x2, #0x2
    ld1             {v1.h}[0], [x13]
      add             x15, x2, #0x30
    ld1             {v2.h}[0], [x14]
      add             x19, x2, #0x26
    ld1             {v3.h}[0], [x3]
      add             x20, x2, #0x28
    ld1             {v0.h}[1], [x9]
      add             x12, x2, #0x10
    ld1             {v1.h}[1], [x15]
      add             x13, x2, #0x40
    ld1             {v2.h}[1], [x19]
      add             x14, x2, #0x34
    ld1             {v3.h}[1], [x20]
      add             x3, x2, #0x1a
    ld1             {v0.h}[2], [x12]
      add             x9, x2, #0x20
    ld1             {v1.h}[2], [x13]
      add             x15, x2, #0x32
    ld1             {v2.h}[2], [x14]
      add             x19, x2, #0x42
    ld1             {v3.h}[2], [x3]
      add             x20, x2, #0xc
    ld1             {v0.h}[3], [x9]
      add             x12, x2, #0x12
    ld1             {v1.h}[3], [x15]
      add             x13, x2, #0x24
    ld1             {v2.h}[3], [x19]
      add             x14, x2, #0x50
    ld1             {v3.h}[3], [x20]
      add             x3, x2, #0xe
    ld1             {v0.h}[4], [x12]
      add             x9, x2, #0x4
    ld1             {v1.h}[4], [x13]
      add             x15, x2, #0x16
    ld1             {v2.h}[4], [x14]
      add             x19, x2, #0x60
    ld1             {v3.h}[4], [x3]
      add             x20, x2, #0x1c
    ld1             {v0.h}[5], [x9]
      add             x12, x2, #0x6
    ld1             {v1.h}[5], [x15]
      add             x13, x2, #0x8
    ld1             {v2.h}[5], [x19]
      add             x14, x2, #0x52
    ld1             {v3.h}[5], [x20]
      add             x3, x2, #0x2a
    ld1             {v0.h}[6], [x12]
      add             x9, x2, #0x14
    ld1             {v1.h}[6], [x13]
      add             x15, x2, #0xa
    ld1             {v2.h}[6], [x14]
      add             x19, x2, #0x44
    ld1             {v3.h}[6], [x3]
      add             x20, x2, #0x38
    ld1             {v0.h}[7], [x9]
      add             x12, x2, #0x46
    ld1             {v1.h}[7], [x15]
      add             x13, x2, #0x3a
    ld1             {v2.h}[7], [x19]
      add             x14, x2, #0x74
    ld1             {v3.h}[7], [x20]
      add             x3, x2, #0x6a
    ld1             {v4.h}[0], [x12]
      add             x9, x2, #0x54
    ld1             {v5.h}[0], [x13]
      add             x15, x2, #0x2c
    ld1             {v6.h}[0], [x14]
      add             x19, x2, #0x76
    ld1             {v7.h}[0], [x3]
      add             x20, x2, #0x78
    ld1             {v4.h}[1], [x9]
      add             x12, x2, #0x62
    ld1             {v5.h}[1], [x15]
      add             x13, x2, #0x1e
    ld1             {v6.h}[1], [x19]
      add             x14, x2, #0x68
    ld1             {v7.h}[1], [x20]
      add             x3, x2, #0x7a
    ld1             {v4.h}[2], [x12]
      add             x9, x2, #0x70
    ld1             {v5.h}[2], [x13]
      add             x15, x2, #0x2e
    ld1             {v6.h}[2], [x14]
      add             x19, x2, #0x5a
    ld1             {v7.h}[2], [x3]
      add             x20, x2, #0x6c
    ld1             {v4.h}[3], [x9]
      add             x12, x2, #0x72
    ld1             {v5.h}[3], [x15]
      add             x13, x2, #0x3c
    ld1             {v6.h}[3], [x19]
      add             x14, x2, #0x4c
    ld1             {v7.h}[3], [x20]
      add             x3, x2, #0x5e
    ld1             {v4.h}[4], [x12]
      add             x9, x2, #0x64
    ld1             {v5.h}[4], [x13]
      add             x15, x2, #0x4a
    ld1             {v6.h}[4], [x14]
      add             x19, x2, #0x3e
    ld1             {v7.h}[4], [x3]
      add             x20, x2, #0x6e
    ld1             {v4.h}[5], [x9]
      add             x12, x2, #0x56
    ld1             {v5.h}[5], [x15]
      add             x13, x2, #0x58
    ld1             {v6.h}[5], [x19]
      add             x14, x2, #0x4e
    ld1             {v7.h}[5], [x20]
      add             x3, x2, #0x7c
    ld1             {v4.h}[6], [x12]
      add             x9, x2, #0x48
    ld1             {v5.h}[6], [x13]
      add             x15, x2, #0x66
    ld1             {v6.h}[6], [x14]
      add             x19, x2, #0x5c
    ld1             {v7.h}[6], [x3]
      add             x20, x2, #0x7e
    ld1             {v4.h}[7], [x9]
    ld1             {v5.h}[7], [x15]
    ld1             {v6.h}[7], [x19]
    ld1             {v7.h}[7], [x20]
.endif
    cmlt            v24.8h, v0.8h, #0
    cmlt            v25.8h, v1.8h, #0
    cmlt            v26.8h, v2.8h, #0
    cmlt            v27.8h, v3.8h, #0
    cmlt            v28.8h, v4.8h, #0
    cmlt            v29.8h, v5.8h, #0
    cmlt            v30.8h, v6.8h, #0
    cmlt            v31.8h, v7.8h, #0
    abs             v0.8h, v0.8h
    abs             v1.8h, v1.8h
    abs             v2.8h, v2.8h
    abs             v3.8h, v3.8h
    abs             v4.8h, v4.8h
    abs             v5.8h, v5.8h
    abs             v6.8h, v6.8h
    abs             v7.8h, v7.8h
    eor             v24.16b, v24.16b, v0.16b
    eor             v25.16b, v25.16b, v1.16b
    eor             v26.16b, v26.16b, v2.16b
    eor             v27.16b, v27.16b, v3.16b
    eor             v28.16b, v28.16b, v4.16b
    eor             v29.16b, v29.16b, v5.16b
    eor             v30.16b, v30.16b, v6.16b
    eor             v31.16b, v31.16b, v7.16b
    cmeq            v16.8h, v0.8h, #0
    cmeq            v17.8h, v1.8h, #0
    cmeq            v18.8h, v2.8h, #0
    cmeq            v19.8h, v3.8h, #0
    cmeq            v20.8h, v4.8h, #0
    cmeq            v21.8h, v5.8h, #0
    cmeq            v22.8h, v6.8h, #0
    xtn             v16.8b, v16.8h
    xtn             v18.8b, v18.8h
    xtn             v20.8b, v20.8h
    xtn             v22.8b, v22.8h
      umov            w14, v0.h[0]
    xtn2            v16.16b, v17.8h
      umov            w13, v24.h[0]
    xtn2            v18.16b, v19.8h
      clz             w14, w14
    xtn2            v20.16b, v21.8h
      lsl             w13, w13, w14
    cmeq            v17.8h, v7.8h, #0
      sub             w12, w14, #32
    xtn2            v22.16b, v17.8h
      lsr             w13, w13, w14
    and             v16.16b, v16.16b, v23.16b
      neg             w12, w12
    and             v18.16b, v18.16b, v23.16b
      add             x3, x4, #0x400           /* r1 = dctbl->ehufsi */
    and             v20.16b, v20.16b, v23.16b
      add             x15, sp, #0x90           /* x15 = t2 */
    and             v22.16b, v22.16b, v23.16b
      ldr             w10, [x4, x12, lsl #2]
    addp            v16.16b, v16.16b, v18.16b
      ldrb            w11, [x3, x12]
    addp            v20.16b, v20.16b, v22.16b
      checkbuf47
    addp            v16.16b, v16.16b, v20.16b
      put_bits        x10, x11
    addp            v16.16b, v16.16b, v18.16b
      checkbuf47
    umov            x9, v16.D[0]
      put_bits        x13, x12
    cnt             v17.8b, v16.8b
      mvn             x9, x9
    addv            B18, v17.8b
      add             x4, x5, #0x400   /* x4 = actbl->ehufsi */
    umov            w12, v18.b[0]
      lsr             x9, x9, #0x1     /* clear AC coeff */
    ldr             w13, [x5, #0x3c0]  /* x13 = actbl->ehufco[0xf0] */
    rbit            x9, x9             /* x9 = index0 */
    ldrb            w14, [x4, #0xf0]   /* x14 = actbl->ehufsi[0xf0] */
    cmp             w12, #(64-8)
    add             x11, sp, #16
    b.lt            4f
    cbz             x9, 6f
    st1             {v0.8h, v1.8h, v2.8h, v3.8h}, [x11], #64
    st1             {v4.8h, v5.8h, v6.8h, v7.8h}, [x11], #64
    st1             {v24.8h, v25.8h, v26.8h, v27.8h}, [x11], #64
    st1             {v28.8h, v29.8h, v30.8h, v31.8h}, [x11], #64
1:
    clz             x2, x9
    add             x15, x15, x2, lsl #1
    lsl             x9, x9, x2
    ldrh            w20, [x15, #-126]
2:
    cmp             x2, #0x10
    b.lt            3f
    sub             x2, x2, #0x10
    checkbuf47
    put_bits        x13, x14
    b               2b
3:
    clz             w20, w20
    ldrh            w3, [x15, #2]!
    sub             w11, w20, #32
    lsl             w3, w3, w20
    neg             w11, w11
    lsr             w3, w3, w20
    add             x2, x11, x2, lsl #4
    lsl             x9, x9, #0x1
    ldr             w12, [x5, x2, lsl #2]
    ldrb            w10, [x4, x2]
    checkbuf31
    put_bits        x12, x10
    put_bits        x3, x11
    cbnz            x9, 1b
    b               6f
4:
    movi            v21.8h, #0x0010
    clz             v0.8h, v0.8h
    clz             v1.8h, v1.8h
    clz             v2.8h, v2.8h
    clz             v3.8h, v3.8h
    clz             v4.8h, v4.8h
    clz             v5.8h, v5.8h
    clz             v6.8h, v6.8h
    clz             v7.8h, v7.8h
    ushl            v24.8h, v24.8h, v0.8h
    ushl            v25.8h, v25.8h, v1.8h
    ushl            v26.8h, v26.8h, v2.8h
    ushl            v27.8h, v27.8h, v3.8h
    ushl            v28.8h, v28.8h, v4.8h
    ushl            v29.8h, v29.8h, v5.8h
    ushl            v30.8h, v30.8h, v6.8h
    ushl            v31.8h, v31.8h, v7.8h
    neg             v0.8h, v0.8h
    neg             v1.8h, v1.8h
    neg             v2.8h, v2.8h
    neg             v3.8h, v3.8h
    neg             v4.8h, v4.8h
    neg             v5.8h, v5.8h
    neg             v6.8h, v6.8h
    neg             v7.8h, v7.8h
    ushl            v24.8h, v24.8h, v0.8h
    ushl            v25.8h, v25.8h, v1.8h
    ushl            v26.8h, v26.8h, v2.8h
    ushl            v27.8h, v27.8h, v3.8h
    ushl            v28.8h, v28.8h, v4.8h
    ushl            v29.8h, v29.8h, v5.8h
    ushl            v30.8h, v30.8h, v6.8h
    ushl            v31.8h, v31.8h, v7.8h
    add             v0.8h, v21.8h, v0.8h
    add             v1.8h, v21.8h, v1.8h
    add             v2.8h, v21.8h, v2.8h
    add             v3.8h, v21.8h, v3.8h
    add             v4.8h, v21.8h, v4.8h
    add             v5.8h, v21.8h, v5.8h
    add             v6.8h, v21.8h, v6.8h
    add             v7.8h, v21.8h, v7.8h
    st1             {v0.8h, v1.8h, v2.8h, v3.8h}, [x11], #64
    st1             {v4.8h, v5.8h, v6.8h, v7.8h}, [x11], #64
    st1             {v24.8h, v25.8h, v26.8h, v27.8h}, [x11], #64
    st1             {v28.8h, v29.8h, v30.8h, v31.8h}, [x11], #64
1:
    clz             x2, x9
    add             x15, x15, x2, lsl #1
    lsl             x9, x9, x2
    ldrh            w11, [x15, #-126]
2:
    cmp             x2, #0x10
    b.lt            3f
    sub             x2, x2, #0x10
    checkbuf47
    put_bits        x13, x14
    b               2b
3:
    ldrh            w3, [x15, #2]!
    add             x2, x11, x2, lsl #4
    lsl             x9, x9, #0x1
    ldr             w12, [x5, x2, lsl #2]
    ldrb            w10, [x4, x2]
    checkbuf31
    put_bits        x12, x10
    put_bits        x3, x11
    cbnz            x9, 1b
6:
    add             x13, sp, #0x10e
    cmp             x15, x13
    b.hs            1f
    ldr             w12, [x5]
    ldrb            w14, [x4]
    checkbuf47
    put_bits        x12, x14
1:
    str             PUT_BUFFER, [x0, #0x10]
    str             PUT_BITSw, [x0, #0x18]
    ldp             x19, x20, [sp], 16
    add             x0, BUFFER, #0x1
    add             sp, sp, 256
    br              x30

.endm

generate_jsimd_huff_encode_one_block 1
generate_jsimd_huff_encode_one_block 0

    .unreq          BUFFER
    .unreq          PUT_BUFFER
    .unreq          PUT_BITS
    .unreq          PUT_BITSw

.purgem emit_byte
.purgem put_bits
.purgem checkbuf31
.purgem checkbuf47