kc3-lang/libpng/arm/arm_init.c

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• Hash : b8ca9108
  Author :
  Date : 2022-10-12T12:42:09
  

  arm: Add a compile-time assertion about PNG_ARM_NEON_CHECK_SUPPORTED
  
  Following up on the previous commit by Martin Storsjö:
  
  If the availability of ARM Neon is not only known at compile time,
  but also expected by the compiler's target architecture, there should
  be no further need for a run-time check. In fact, such a check would
  be counter-productive.
  

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• arm/arm_init.c

• 
  /* arm_init.c - NEON optimised filter functions
   *
   * Copyright (c) 2018-2022 Cosmin Truta
   * Copyright (c) 2014,2016 Glenn Randers-Pehrson
   * Written by Mans Rullgard, 2011.
   *
   * This code is released under the libpng license.
   * For conditions of distribution and use, see the disclaimer
   * and license in png.h
   */
  
  /* This module requires POSIX 1003.1 functions. */
  #define _POSIX_SOURCE 1
  
  #include "../pngpriv.h"
  
  #ifdef PNG_READ_SUPPORTED
  
  #if PNG_ARM_NEON_OPT > 0
  #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
  /* WARNING: it is strongly recommended that you do not build libpng with
   * run-time checks for CPU features if at all possible.  In the case of the ARM
   * NEON instructions there is no processor-specific way of detecting the
   * presence of the required support, therefore run-time detection is extremely
   * OS specific.
   *
   * You may set the macro PNG_ARM_NEON_FILE to the file name of file containing
   * a fragment of C source code which defines the png_have_neon function.  There
   * are a number of implementations in contrib/arm-neon, but the only one that
   * has partial support is contrib/arm-neon/linux.c - a generic Linux
   * implementation which reads /proc/cpufino.
   */
  #include <signal.h> /* for sig_atomic_t */
  
  #ifndef PNG_ARM_NEON_FILE
  #  if defined(__aarch64__) || defined(_M_ARM64)
       /* ARM Neon is expected to be unconditionally available on ARM64. */
  #    error "PNG_ARM_NEON_CHECK_SUPPORTED must not be defined on ARM64"
  #  elif defined(__ARM_NEON__) || defined(__ARM_NEON)
       /* ARM Neon is expected to be available on the target CPU architecture. */
  #    error "PNG_ARM_NEON_CHECK_SUPPORTED must not be defined on this CPU arch"
  #  elif defined(__linux__)
  #    define PNG_ARM_NEON_FILE "contrib/arm-neon/linux.c"
  #  else
  #    error "No support for run-time ARM Neon checking; use compile-time options"
  #  endif
  #endif
  
  static int png_have_neon(png_structp png_ptr);
  #ifdef PNG_ARM_NEON_FILE
  #  include PNG_ARM_NEON_FILE
  #endif
  #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
  
  #ifndef PNG_ALIGNED_MEMORY_SUPPORTED
  #  error "ALIGNED_MEMORY is required; set: -DPNG_ALIGNED_MEMORY_SUPPORTED"
  #endif
  
  void
  png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
  {
     /* The switch statement is compiled in for ARM_NEON_API, the call to
      * png_have_neon is compiled in for ARM_NEON_CHECK.  If both are defined
      * the check is only performed if the API has not set the NEON option on
      * or off explicitly.  In this case the check controls what happens.
      *
      * If the CHECK is not compiled in and the option is UNSET the behavior prior
      * to 1.6.7 was to use the NEON code - this was a bug caused by having the
      * wrong order of the 'ON' and 'default' cases.  UNSET now defaults to OFF,
      * as documented in png.h
      */
     png_debug(1, "in png_init_filter_functions_neon");
  #ifdef PNG_ARM_NEON_API_SUPPORTED
     switch ((pp->options >> PNG_ARM_NEON) & 3)
     {
        case PNG_OPTION_UNSET:
           /* Allow the run-time check to execute if it has been enabled -
            * thus both API and CHECK can be turned on.  If it isn't supported
            * this case will fall through to the 'default' below, which just
            * returns.
            */
  #endif /* PNG_ARM_NEON_API_SUPPORTED */
  #ifdef PNG_ARM_NEON_CHECK_SUPPORTED
           {
              static volatile sig_atomic_t no_neon = -1; /* not checked */
  
              if (no_neon < 0)
                 no_neon = !png_have_neon(pp);
  
              if (no_neon)
                 return;
           }
  #ifdef PNG_ARM_NEON_API_SUPPORTED
           break;
  #endif
  #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
  
  #ifdef PNG_ARM_NEON_API_SUPPORTED
        default: /* OFF or INVALID */
           return;
  
        case PNG_OPTION_ON:
           /* Option turned on */
           break;
     }
  #endif
  
     /* IMPORTANT: any new external functions used here must be declared using
      * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
      * 'prefix' option to configure works:
      *
      *    ./configure --with-libpng-prefix=foobar_
      *
      * Verify you have got this right by running the above command, doing a build
      * and examining pngprefix.h; it must contain a #define for every external
      * function you add.  (Notice that this happens automatically for the
      * initialization function.)
      */
     pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
  
     if (bpp == 3)
     {
        pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
        pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
        pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
           png_read_filter_row_paeth3_neon;
     }
  
     else if (bpp == 4)
     {
        pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
        pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
        pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
            png_read_filter_row_paeth4_neon;
     }
  }
  #endif /* PNG_ARM_NEON_OPT > 0 */
  #endif /* READ */
  

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