kc3-lang/libjpeg-turbo/src/jpeg_nbits.h

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• Hash : 98c45838
  Author :
  Date : 2025-08-21T11:22:51
  

  Fix issues with Windows Arm64EC builds
  
  Arm64EC basically wraps native Arm64 functions with an emulated
  Windows/x64 ABI, which can improve performance for Windows/x64
  applications running under the x64 emulator on Windows/Arm.  When
  building for Arm64EC, the compiler defines _M_X64 and _M_ARM64EC but not
  _M_ARM64.
  

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• src/jpeg_nbits.h

• /*
   * Copyright (C) 2014, 2021, 2024-2025, D. R. Commander.
   * Copyright (C) 2014, Olle Liljenzin.
   * Copyright (C) 2020, Arm Limited.
   *
   * For conditions of distribution and use, see the accompanying README.ijg
   * file.
   */
  
  /*
   * NOTE: If USE_CLZ_INTRINSIC is defined, then clz/bsr instructions will be
   * used for bit counting rather than the lookup table.  This will reduce the
   * memory footprint by 64k, which is important for some mobile applications
   * that create many isolated instances of libjpeg-turbo (web browsers, for
   * instance.)  This may improve performance on some mobile platforms as well.
   * This feature is enabled by default only on Arm processors, because some x86
   * chips have a slow implementation of bsr, and the use of clz/bsr cannot be
   * shown to have a significant performance impact even on the x86 chips that
   * have a fast implementation of it.  When building for Armv6, you can
   * explicitly disable the use of clz/bsr by adding -mthumb to the compiler
   * flags (this defines __thumb__).
   */
  
  /* NOTE: Both GCC and Clang define __GNUC__ */
  #if (defined(__GNUC__) && (defined(__arm__) || defined(__aarch64__))) || \
      defined(_M_ARM) || defined(_M_ARM64) || defined(_M_ARM64EC)
  #if !defined(__thumb__) || defined(__thumb2__)
  #define USE_CLZ_INTRINSIC
  #endif
  #endif
  
  #ifdef USE_CLZ_INTRINSIC
  #if defined(_MSC_VER) && !defined(__clang__)
  #define JPEG_NBITS_NONZERO(x)  (32 - _CountLeadingZeros(x))
  #else
  #define JPEG_NBITS_NONZERO(x)  (32 - __builtin_clz(x))
  #endif
  #define JPEG_NBITS(x)          (x ? JPEG_NBITS_NONZERO(x) : 0)
  #else
  extern const unsigned char jpeg_nbits_table[65536];
  #define JPEG_NBITS(x)          (jpeg_nbits_table[x])
  #define JPEG_NBITS_NONZERO(x)  JPEG_NBITS(x)
  #endif
  

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