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Diffstat (limited to 'src/3rdparty/libjpeg/src/jpeg_nbits.h')
-rw-r--r-- | src/3rdparty/libjpeg/src/jpeg_nbits.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/src/3rdparty/libjpeg/src/jpeg_nbits.h b/src/3rdparty/libjpeg/src/jpeg_nbits.h new file mode 100644 index 0000000000..6481a1228d --- /dev/null +++ b/src/3rdparty/libjpeg/src/jpeg_nbits.h @@ -0,0 +1,43 @@ +/* + * Copyright (C) 2014, 2021, 2024, 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) +#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 |