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VP8LoadNewBytes: use __builtin_bswap32 if available

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mostly to balance the use of bswap64, some gcc platforms are already
interpreting the default case the same

Change-Id: Icf860f55b3f16bea349a7d721e6d6abeeb4e5cf3
This commit is contained in:
James Zern 2014-06-24 21:13:42 -07:00
parent b8811dac12
commit 1da3d46138
1 changed files with 11 additions and 5 deletions
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16
src/utils/bit_reader_inl.h
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@ -41,6 +41,12 @@ typedef uint8_t lbit_t;
#define __BIG_ENDIAN__
#endif
// gcc 4.3 has builtin functions for swap32/swap64
#if defined(__GNUC__) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
#define HAVE_BUILTIN_BSWAP
#endif
extern const uint8_t kVP8Log2Range[128];
extern const range_t kVP8NewRange[128];
@ -77,9 +83,7 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
br->buf_ += BITS >> 3;
#if !defined(__BIG_ENDIAN__)
#if (BITS > 32)
// gcc 4.3 has builtin functions for swap32/swap64
#if defined(__GNUC__) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
#if defined(HAVE_BUILTIN_BSWAP)
bits = (bit_t)__builtin_bswap64(in_bits);
#elif defined(_MSC_VER)
bits = (bit_t)_byteswap_uint64(in_bits);
@ -96,7 +100,9 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
#endif
bits >>= 64 - BITS;
#elif (BITS >= 24)
#if defined(__i386__) || defined(__x86_64__)
#if defined(HAVE_BUILTIN_BSWAP)
bits = (bit_t)__builtin_bswap32(in_bits);
#elif defined(__i386__) || defined(__x86_64__)
{
lbit_t swapped_in_bits;
__asm__ volatile("bswap %k0" : "=r"(swapped_in_bits) : "0"(in_bits));
@ -114,7 +120,7 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
bits = (bit_t)(in_bits >> 8) | ((in_bits & 0xff) << 8);
#else // BITS == 8
bits = (bit_t)in_bits;
#endif
#endif // BITS > 32
#else // BIG_ENDIAN
bits = (bit_t)in_bits;
if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS);