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add support for BITS > 32

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on x86_64 desktop, it's a little faster to use BITS=56
on MacOS (/llvm) it's _much_ faster (~10%)

Change-Id: I47c66ab7488341d8d1696d9301954b86b241b36d
This commit is contained in:
skal 2013-03-16 00:06:12 +01:00 committed by James Zern
parent 9b3db89473
commit 744930dbe2
1 changed files with 36 additions and 11 deletions
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45
src/utils/bit_reader.h
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@ -59,7 +59,7 @@ extern "C" {
// The right-justify strategy tends to use less shifts and is often faster.
//------------------------------------------------------------------------------
// BITS can be either 32, 24, 16 or 8.
// BITS can be any multiple of 8 from 8 to 56 (inclusive).
// Pick values that fit natural register size.
#if !defined(WEBP_REFERENCE_IMPLEMENTATION)
@ -68,6 +68,8 @@ extern "C" {
#if defined(__i386__) || defined(_M_IX86) // x86 32bit
#define BITS 16
#elif defined(__x86_64__) || defined(_M_X64) // x86 64bit
#define BITS 56
#elif defined(__arm__) || defined(_M_ARM) // ARM
#define BITS 24
#else // reasonable default
@ -84,9 +86,15 @@ extern "C" {
//------------------------------------------------------------------------------
// Derived types and constants
#if (BITS == 32)
typedef uint64_t bit_t; // natural register type
typedef uint32_t lbit_t; // natural type for memory I/O
// bit_t = natural register type
// lbit_t = natural type for memory I/O
#if (BITS > 32)
typedef uint64_t bit_t;
typedef uint64_t lbit_t;
#elif (BITS == 32)
typedef uint64_t bit_t;
typedef uint32_t lbit_t;
#elif (BITS == 24)
typedef uint32_t bit_t;
typedef uint32_t lbit_t;
@ -148,19 +156,36 @@ static WEBP_INLINE void VP8LoadNewBytes(VP8BitReader* const br) {
lbit_t in_bits = *(lbit_t*)br->buf_;
br->buf_ += (BITS) >> 3;
#if !defined(__BIG_ENDIAN__)
#if (BITS == 32) || (BITS == 24)
#if (BITS > 32)
// gcc 4.3 has builtin functions for swap32/swap64
#if defined(__GNUC__) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3))
bits = (bit_t)__builtin_bswap64(in_bits);
#elif defined(_MSC_VER)
bits = (bit_t)_byteswap_uint64(in_bits);
#elif defined(__x86_64__)
__asm__ volatile("bswapq %0" : "=r"(bits) : "0"(in_bits));
#else // generic code for swapping 64-bit values (suggested by bdb@)
bits = (bit_t)in_bits;
bits = ((bits & 0xffffffff00000000ull) >> 32) |
((bits & 0x00000000ffffffffull) << 32);
bits = ((bits & 0xffff0000ffff0000ull) >> 16) |
((bits & 0x0000ffff0000ffffull) << 16);
bits = ((bits & 0xff00ff00ff00ff00ull) >> 8) |
((bits & 0x00ff00ff00ff00ffull) << 8);
#endif
bits >>= 64 - BITS;
#elif (BITS >= 24)
#if defined(__i386__) || defined(__x86_64__)
__asm__ volatile("bswap %k0" : "=r"(in_bits) : "0"(in_bits));
bits = (bit_t)in_bits; // 24b/32b -> 32b/64b zero-extension
#elif defined(_MSC_VER)
bits = _byteswap_ulong(in_bits);
bits = (bit_t)_byteswap_ulong(in_bits);
#else
bits = (bit_t)(in_bits >> 24) | ((in_bits >> 8) & 0xff00)
| ((in_bits << 8) & 0xff0000) | (in_bits << 24);
#endif // x86
#if (BITS == 24)
bits >>= 8;
#endif
bits >>= (32 - BITS);
#elif (BITS == 16)
// gcc will recognize a 'rorw $8, ...' here:
bits = (bit_t)(in_bits >> 8) | ((in_bits & 0xff) << 8);
@ -248,7 +273,7 @@ static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) {
}
static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) {
const bit_t split = (br->range_ >> 1);
const range_t split = (br->range_ >> 1);
const int bit = VP8BitUpdate(br, split);
VP8Shift(br);
return bit ? -v : v;