/*

 * AltiVec optimizations for libjpeg-turbo

 *

 * Copyright (C) 2014-2015, D. R. Commander.  All Rights Reserved.

 * Copyright (C) 2014, Jay Foad.  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.

 */

/* This file is included by jcgray-altivec.c */

void jsimd_rgb_gray_convert_altivec(JDIMENSION img_width, JSAMPARRAY input_buf,

                                    JSAMPIMAGE output_buf,

                                    JDIMENSION output_row, int num_rows)

{

  JSAMPROW inptr, outptr;

  int pitch = img_width * RGB_PIXELSIZE, num_cols;

#if __BIG_ENDIAN__

  int offset;

  unsigned char __attribute__((aligned(16))) tmpbuf[RGB_PIXELSIZE * 16];

#endif

  __vector unsigned char rgb0, rgb1 = { 0 }, rgb2 = { 0 },

    rgbg0, rgbg1, rgbg2, rgbg3, y;

#if __BIG_ENDIAN__ || RGB_PIXELSIZE == 4

  __vector unsigned char rgb3 = { 0 };

#endif

#if __BIG_ENDIAN__ && RGB_PIXELSIZE == 4

  __vector unsigned char rgb4 = { 0 };

#endif

  __vector short rg0, rg1, rg2, rg3, bg0, bg1, bg2, bg3;

  __vector unsigned short yl, yh;

  __vector int y0, y1, y2, y3;

  /* Constants */

  __vector short pw_f0299_f0337 = { __4X2(F_0_299, F_0_337) },

    pw_f0114_f0250 = { __4X2(F_0_114, F_0_250) };

  __vector int pd_onehalf = { __4X(ONE_HALF) };

  __vector unsigned char pb_zero = { __16X(0) },

#if __BIG_ENDIAN__

    shift_pack_index =

      { 0, 1, 4, 5,  8,  9, 12, 13, 16, 17, 20, 21, 24, 25, 28, 29 };

#else

    shift_pack_index =

      { 2, 3, 6, 7, 10, 11, 14, 15, 18, 19, 22, 23, 26, 27, 30, 31 };

#endif

  while (--num_rows >= 0) {

    inptr = *input_buf++;

    outptr = output_buf[0][output_row];

    output_row++;

    for (num_cols = pitch; num_cols > 0;

         num_cols -= RGB_PIXELSIZE * 16, inptr += RGB_PIXELSIZE * 16,

         outptr += 16) {

#if __BIG_ENDIAN__

      /* Load 16 pixels == 48 or 64 bytes */

      offset = (size_t)inptr & 15;

      if (offset) {

        __vector unsigned char unaligned_shift_index;

        int bytes = num_cols + offset;

        if (bytes < (RGB_PIXELSIZE + 1) * 16 && (bytes & 15)) {

          /* Slow path to prevent buffer overread.  Since there is no way to

           * read a partial AltiVec register, overread would occur on the last

           * chunk of the last image row if the right edge is not on a 16-byte

           * boundary.  It could also occur on other rows if the bytes per row

           * is low enough.  Since we can't determine whether we're on the last

           * image row, we have to assume every row is the last.

           */

          memcpy(tmpbuf, inptr, min(num_cols, RGB_PIXELSIZE * 16));

          rgb0 = vec_ld(0, tmpbuf);

          rgb1 = vec_ld(16, tmpbuf);

          rgb2 = vec_ld(32, tmpbuf);

#if RGB_PIXELSIZE == 4

          rgb3 = vec_ld(48, tmpbuf);

#endif

        } else {

          /* Fast path */

          rgb0 = vec_ld(0, inptr);

          if (bytes > 16)

            rgb1 = vec_ld(16, inptr);

          if (bytes > 32)

            rgb2 = vec_ld(32, inptr);

          if (bytes > 48)

            rgb3 = vec_ld(48, inptr);

#if RGB_PIXELSIZE == 4

          if (bytes > 64)

            rgb4 = vec_ld(64, inptr);

#endif

          unaligned_shift_index = vec_lvsl(0, inptr);

          rgb0 = vec_perm(rgb0, rgb1, unaligned_shift_index);

          rgb1 = vec_perm(rgb1, rgb2, unaligned_shift_index);

          rgb2 = vec_perm(rgb2, rgb3, unaligned_shift_index);

#if RGB_PIXELSIZE == 4

          rgb3 = vec_perm(rgb3, rgb4, unaligned_shift_index);

#endif

        }

      } else {

        if (num_cols < RGB_PIXELSIZE * 16 && (num_cols & 15)) {

          /* Slow path */

          memcpy(tmpbuf, inptr, min(num_cols, RGB_PIXELSIZE * 16));

          rgb0 = vec_ld(0, tmpbuf);

          rgb1 = vec_ld(16, tmpbuf);

          rgb2 = vec_ld(32, tmpbuf);

#if RGB_PIXELSIZE == 4

          rgb3 = vec_ld(48, tmpbuf);

#endif

        } else {

          /* Fast path */

          rgb0 = vec_ld(0, inptr);

          if (num_cols > 16)

            rgb1 = vec_ld(16, inptr);

          if (num_cols > 32)

            rgb2 = vec_ld(32, inptr);

#if RGB_PIXELSIZE == 4

          if (num_cols > 48)

            rgb3 = vec_ld(48, inptr);

#endif

        }

      }

#else

      /* Little endian */

      rgb0 = vec_vsx_ld(0, inptr);

      if (num_cols > 16)

        rgb1 = vec_vsx_ld(16, inptr);

      if (num_cols > 32)

        rgb2 = vec_vsx_ld(32, inptr);

#if RGB_PIXELSIZE == 4

      if (num_cols > 48)

        rgb3 = vec_vsx_ld(48, inptr);

#endif

#endif

#if RGB_PIXELSIZE == 3

      /* rgb0 = R0 G0 B0 R1 G1 B1 R2 G2 B2 R3 G3 B3 R4 G4 B4 R5

       * rgb1 = G5 B5 R6 G6 B6 R7 G7 B7 R8 G8 B8 R9 G9 B9 Ra Ga

       * rgb2 = Ba Rb Gb Bb Rc Gc Bc Rd Gd Bd Re Ge Be Rf Gf Bf

       *

       * rgbg0 = R0 G0 R1 G1 R2 G2 R3 G3 B0 G0 B1 G1 B2 G2 B3 G3

       * rgbg1 = R4 G4 R5 G5 R6 G6 R7 G7 B4 G4 B5 G5 B6 G6 B7 G7

       * rgbg2 = R8 G8 R9 G9 Ra Ga Rb Gb B8 G8 B9 G9 Ba Ga Bb Gb

       * rgbg3 = Rc Gc Rd Gd Re Ge Rf Gf Bc Gc Bd Gd Be Ge Bf Gf

       */

      rgbg0 = vec_perm(rgb0, rgb0, (__vector unsigned char)RGBG_INDEX0);

      rgbg1 = vec_perm(rgb0, rgb1, (__vector unsigned char)RGBG_INDEX1);

      rgbg2 = vec_perm(rgb1, rgb2, (__vector unsigned char)RGBG_INDEX2);

      rgbg3 = vec_perm(rgb2, rgb2, (__vector unsigned char)RGBG_INDEX3);

#else

      /* rgb0 = R0 G0 B0 X0 R1 G1 B1 X1 R2 G2 B2 X2 R3 G3 B3 X3

       * rgb1 = R4 G4 B4 X4 R5 G5 B5 X5 R6 G6 B6 X6 R7 G7 B7 X7

       * rgb2 = R8 G8 B8 X8 R9 G9 B9 X9 Ra Ga Ba Xa Rb Gb Bb Xb

       * rgb3 = Rc Gc Bc Xc Rd Gd Bd Xd Re Ge Be Xe Rf Gf Bf Xf

       *

       * rgbg0 = R0 G0 R1 G1 R2 G2 R3 G3 B0 G0 B1 G1 B2 G2 B3 G3

       * rgbg1 = R4 G4 R5 G5 R6 G6 R7 G7 B4 G4 B5 G5 B6 G6 B7 G7

       * rgbg2 = R8 G8 R9 G9 Ra Ga Rb Gb B8 G8 B9 G9 Ba Ga Bb Gb

       * rgbg3 = Rc Gc Rd Gd Re Ge Rf Gf Bc Gc Bd Gd Be Ge Bf Gf

       */

      rgbg0 = vec_perm(rgb0, rgb0, (__vector unsigned char)RGBG_INDEX);

      rgbg1 = vec_perm(rgb1, rgb1, (__vector unsigned char)RGBG_INDEX);

      rgbg2 = vec_perm(rgb2, rgb2, (__vector unsigned char)RGBG_INDEX);

      rgbg3 = vec_perm(rgb3, rgb3, (__vector unsigned char)RGBG_INDEX);

#endif

      /* rg0 = R0 G0 R1 G1 R2 G2 R3 G3

       * bg0 = B0 G0 B1 G1 B2 G2 B3 G3

       * ...

       *

       * NOTE: We have to use vec_merge*() here because vec_unpack*() doesn't

       * support unsigned vectors.

       */

      rg0 = (__vector signed short)VEC_UNPACKHU(rgbg0);

      bg0 = (__vector signed short)VEC_UNPACKLU(rgbg0);

      rg1 = (__vector signed short)VEC_UNPACKHU(rgbg1);

      bg1 = (__vector signed short)VEC_UNPACKLU(rgbg1);

      rg2 = (__vector signed short)VEC_UNPACKHU(rgbg2);

      bg2 = (__vector signed short)VEC_UNPACKLU(rgbg2);

      rg3 = (__vector signed short)VEC_UNPACKHU(rgbg3);

      bg3 = (__vector signed short)VEC_UNPACKLU(rgbg3);

      /* (Original)

       * Y  =  0.29900 * R + 0.58700 * G + 0.11400 * B

       *

       * (This implementation)

       * Y  =  0.29900 * R + 0.33700 * G + 0.11400 * B + 0.25000 * G

       */

      /* Calculate Y values */

      y0 = vec_msums(rg0, pw_f0299_f0337, pd_onehalf);

      y1 = vec_msums(rg1, pw_f0299_f0337, pd_onehalf);

      y2 = vec_msums(rg2, pw_f0299_f0337, pd_onehalf);

      y3 = vec_msums(rg3, pw_f0299_f0337, pd_onehalf);

      y0 = vec_msums(bg0, pw_f0114_f0250, y0);

      y1 = vec_msums(bg1, pw_f0114_f0250, y1);

      y2 = vec_msums(bg2, pw_f0114_f0250, y2);

      y3 = vec_msums(bg3, pw_f0114_f0250, y3);

      /* Clever way to avoid 4 shifts + 2 packs.  This packs the high word from

       * each dword into a new 16-bit vector, which is the equivalent of

       * descaling the 32-bit results (right-shifting by 16 bits) and then

       * packing them.

       */

      yl = vec_perm((__vector unsigned short)y0, (__vector unsigned short)y1,

                    shift_pack_index);

      yh = vec_perm((__vector unsigned short)y2, (__vector unsigned short)y3,

                    shift_pack_index);

      y = vec_pack(yl, yh);

      vec_st(y, 0, outptr);

    }

  }

}