kc3-lang/libjpeg-turbo/simd/arm/jquanti-neon.c

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• Hash : e69dd40c
  Author :
  Date : 2024-01-23T13:26:41
  

  Reorganize source to make things easier to find
  
  - Move all libjpeg documentation, except for README.ijg, into the doc/
    subdirectory.
  
  - Move the TurboJPEG C API documentation from doc/html/ into
    doc/turbojpeg/.
  
  - Move all C source code and headers into a src/ subdirectory.
  
  - Move turbojpeg-jni.c into the java/ subdirectory.
  
  Referring to #226, there is no ideal solution to this problem.  A
  semantically ideal solution would have involved placing all source code,
  including the SIMD and Java source code, under src/ (or perhaps placing
  C library source code under lib/ and C test program source code under
  test/), all header files under include/, and all documentation under
  doc/.  However:
  
  - To me it makes more sense to have separate top-level directories for
    each language, since the SIMD extensions and the Java API are
    technically optional features.  src/ now contains only the code that
    is relevant to the core C API libraries and associated programs.
  - I didn't want to bury the java/ and simd/ directories or add a level
    of depth to them, since both directories already contain source code
    that is 3-4 levels deep.
  - I would prefer not to separate the header files from the C source
    code, because:
    1. It would be disruptive.  libjpeg and libjpeg-turbo have
       historically placed C source code and headers in the same
       directory, and people who are familiar with both projects (self
       included) are used to looking for the headers in the same directory
       as the C source code.
    2. In terms of how the headers are used internally in libjpeg-turbo,
       the distinction between public and private headers is a bit fuzzy.
  - It didn't make sense to separate the test source code from the library
    source code, since there is not a clear distinction in some cases.
    (For instance, the IJG image I/O functions are used by cjpeg and djpeg
    as well as by the TurboJPEG API.)
  
  This solution is minimally disruptive, since it keeps all C source code
  and headers together and keeps java/ and simd/ as top-level directories.
  It is a bit awkward, because java/ and simd/ technically contain source
  code, even though they are not under src/.  However, other solutions
  would have been more awkward for different reasons.
  
  Closes #226
  

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• simd/arm/jquanti-neon.c

• /*
   * jquanti-neon.c - sample data conversion and quantization (Arm Neon)
   *
   * Copyright (C) 2020-2021, Arm Limited.  All Rights Reserved.
   * Copyright (C) 2024, D. R. Commander.  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.
   */
  
  #define JPEG_INTERNALS
  #include "../../src/jinclude.h"
  #include "../../src/jpeglib.h"
  #include "../../src/jsimd.h"
  #include "../../src/jdct.h"
  #include "../../src/jsimddct.h"
  #include "../jsimd.h"
  
  #include <arm_neon.h>
  
  
  /* After downsampling, the resulting sample values are in the range [0, 255],
   * but the Discrete Cosine Transform (DCT) operates on values centered around
   * 0.
   *
   * To prepare sample values for the DCT, load samples into a DCT workspace,
   * subtracting CENTERJSAMPLE (128).  The samples, now in the range [-128, 127],
   * are also widened from 8- to 16-bit.
   *
   * The equivalent scalar C function convsamp() can be found in jcdctmgr.c.
   */
  
  void jsimd_convsamp_neon(JSAMPARRAY sample_data, JDIMENSION start_col,
                           DCTELEM *workspace)
  {
    uint8x8_t samp_row0 = vld1_u8(sample_data[0] + start_col);
    uint8x8_t samp_row1 = vld1_u8(sample_data[1] + start_col);
    uint8x8_t samp_row2 = vld1_u8(sample_data[2] + start_col);
    uint8x8_t samp_row3 = vld1_u8(sample_data[3] + start_col);
    uint8x8_t samp_row4 = vld1_u8(sample_data[4] + start_col);
    uint8x8_t samp_row5 = vld1_u8(sample_data[5] + start_col);
    uint8x8_t samp_row6 = vld1_u8(sample_data[6] + start_col);
    uint8x8_t samp_row7 = vld1_u8(sample_data[7] + start_col);
  
    int16x8_t row0 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row0, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row1 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row1, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row2 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row2, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row3 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row3, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row4 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row4, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row5 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row5, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row6 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row6, vdup_n_u8(CENTERJSAMPLE)));
    int16x8_t row7 =
      vreinterpretq_s16_u16(vsubl_u8(samp_row7, vdup_n_u8(CENTERJSAMPLE)));
  
    vst1q_s16(workspace + 0 * DCTSIZE, row0);
    vst1q_s16(workspace + 1 * DCTSIZE, row1);
    vst1q_s16(workspace + 2 * DCTSIZE, row2);
    vst1q_s16(workspace + 3 * DCTSIZE, row3);
    vst1q_s16(workspace + 4 * DCTSIZE, row4);
    vst1q_s16(workspace + 5 * DCTSIZE, row5);
    vst1q_s16(workspace + 6 * DCTSIZE, row6);
    vst1q_s16(workspace + 7 * DCTSIZE, row7);
  }
  
  
  /* After the DCT, the resulting array of coefficient values needs to be divided
   * by an array of quantization values.
   *
   * To avoid a slow division operation, the DCT coefficients are multiplied by
   * the (scaled) reciprocals of the quantization values and then right-shifted.
   *
   * The equivalent scalar C function quantize() can be found in jcdctmgr.c.
   */
  
  void jsimd_quantize_neon(JCOEFPTR coef_block, DCTELEM *divisors,
                           DCTELEM *workspace)
  {
    JCOEFPTR out_ptr = coef_block;
    UDCTELEM *recip_ptr = (UDCTELEM *)divisors;
    UDCTELEM *corr_ptr = (UDCTELEM *)divisors + DCTSIZE2;
    DCTELEM *shift_ptr = divisors + 3 * DCTSIZE2;
    int i;
  
  #if defined(__clang__) && (defined(__aarch64__) || defined(_M_ARM64))
  #pragma unroll
  #endif
    for (i = 0; i < DCTSIZE; i += DCTSIZE / 2) {
      /* Load DCT coefficients. */
      int16x8_t row0 = vld1q_s16(workspace + (i + 0) * DCTSIZE);
      int16x8_t row1 = vld1q_s16(workspace + (i + 1) * DCTSIZE);
      int16x8_t row2 = vld1q_s16(workspace + (i + 2) * DCTSIZE);
      int16x8_t row3 = vld1q_s16(workspace + (i + 3) * DCTSIZE);
      /* Load reciprocals of quantization values. */
      uint16x8_t recip0 = vld1q_u16(recip_ptr + (i + 0) * DCTSIZE);
      uint16x8_t recip1 = vld1q_u16(recip_ptr + (i + 1) * DCTSIZE);
      uint16x8_t recip2 = vld1q_u16(recip_ptr + (i + 2) * DCTSIZE);
      uint16x8_t recip3 = vld1q_u16(recip_ptr + (i + 3) * DCTSIZE);
      uint16x8_t corr0 = vld1q_u16(corr_ptr + (i + 0) * DCTSIZE);
      uint16x8_t corr1 = vld1q_u16(corr_ptr + (i + 1) * DCTSIZE);
      uint16x8_t corr2 = vld1q_u16(corr_ptr + (i + 2) * DCTSIZE);
      uint16x8_t corr3 = vld1q_u16(corr_ptr + (i + 3) * DCTSIZE);
      int16x8_t shift0 = vld1q_s16(shift_ptr + (i + 0) * DCTSIZE);
      int16x8_t shift1 = vld1q_s16(shift_ptr + (i + 1) * DCTSIZE);
      int16x8_t shift2 = vld1q_s16(shift_ptr + (i + 2) * DCTSIZE);
      int16x8_t shift3 = vld1q_s16(shift_ptr + (i + 3) * DCTSIZE);
  
      /* Extract sign from coefficients. */
      int16x8_t sign_row0 = vshrq_n_s16(row0, 15);
      int16x8_t sign_row1 = vshrq_n_s16(row1, 15);
      int16x8_t sign_row2 = vshrq_n_s16(row2, 15);
      int16x8_t sign_row3 = vshrq_n_s16(row3, 15);
      /* Get absolute value of DCT coefficients. */
      uint16x8_t abs_row0 = vreinterpretq_u16_s16(vabsq_s16(row0));
      uint16x8_t abs_row1 = vreinterpretq_u16_s16(vabsq_s16(row1));
      uint16x8_t abs_row2 = vreinterpretq_u16_s16(vabsq_s16(row2));
      uint16x8_t abs_row3 = vreinterpretq_u16_s16(vabsq_s16(row3));
      /* Add correction. */
      abs_row0 = vaddq_u16(abs_row0, corr0);
      abs_row1 = vaddq_u16(abs_row1, corr1);
      abs_row2 = vaddq_u16(abs_row2, corr2);
      abs_row3 = vaddq_u16(abs_row3, corr3);
  
      /* Multiply DCT coefficients by quantization reciprocals. */
      int32x4_t row0_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row0),
                                                         vget_low_u16(recip0)));
      int32x4_t row0_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row0),
                                                         vget_high_u16(recip0)));
      int32x4_t row1_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row1),
                                                         vget_low_u16(recip1)));
      int32x4_t row1_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row1),
                                                         vget_high_u16(recip1)));
      int32x4_t row2_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row2),
                                                         vget_low_u16(recip2)));
      int32x4_t row2_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row2),
                                                         vget_high_u16(recip2)));
      int32x4_t row3_l = vreinterpretq_s32_u32(vmull_u16(vget_low_u16(abs_row3),
                                                         vget_low_u16(recip3)));
      int32x4_t row3_h = vreinterpretq_s32_u32(vmull_u16(vget_high_u16(abs_row3),
                                                         vget_high_u16(recip3)));
      /* Narrow back to 16-bit. */
      row0 = vcombine_s16(vshrn_n_s32(row0_l, 16), vshrn_n_s32(row0_h, 16));
      row1 = vcombine_s16(vshrn_n_s32(row1_l, 16), vshrn_n_s32(row1_h, 16));
      row2 = vcombine_s16(vshrn_n_s32(row2_l, 16), vshrn_n_s32(row2_h, 16));
      row3 = vcombine_s16(vshrn_n_s32(row3_l, 16), vshrn_n_s32(row3_h, 16));
  
      /* Since VSHR only supports an immediate as its second argument, negate the
       * shift value and shift left.
       */
      row0 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row0),
                                             vnegq_s16(shift0)));
      row1 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row1),
                                             vnegq_s16(shift1)));
      row2 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row2),
                                             vnegq_s16(shift2)));
      row3 = vreinterpretq_s16_u16(vshlq_u16(vreinterpretq_u16_s16(row3),
                                             vnegq_s16(shift3)));
  
      /* Restore sign to original product. */
      row0 = veorq_s16(row0, sign_row0);
      row0 = vsubq_s16(row0, sign_row0);
      row1 = veorq_s16(row1, sign_row1);
      row1 = vsubq_s16(row1, sign_row1);
      row2 = veorq_s16(row2, sign_row2);
      row2 = vsubq_s16(row2, sign_row2);
      row3 = veorq_s16(row3, sign_row3);
      row3 = vsubq_s16(row3, sign_row3);
  
      /* Store quantized coefficients to memory. */
      vst1q_s16(out_ptr + (i + 0) * DCTSIZE, row0);
      vst1q_s16(out_ptr + (i + 1) * DCTSIZE, row1);
      vst1q_s16(out_ptr + (i + 2) * DCTSIZE, row2);
      vst1q_s16(out_ptr + (i + 3) * DCTSIZE, row3);
    }
  }
  

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