rejigger bit counting intrinsics
Fix lz4/lz4#867 Optimize software fallback routines. Delete some faulty (and dead?) MSVC big endian code.
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lib/lz4.c
91
lib/lz4.c
@ -487,75 +487,76 @@ LZ4_memcpy_using_offset(BYTE* dstPtr, const BYTE* srcPtr, BYTE* dstEnd, const si
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**************************************/
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static unsigned LZ4_NbCommonBytes (reg_t val)
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{
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assert(val != 0);
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if (LZ4_isLittleEndian()) {
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if (sizeof(val)==8) {
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# if defined(_MSC_VER) && defined(_WIN64) && !defined(LZ4_FORCE_SW_BITCOUNT)
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if (sizeof(val) == 8) {
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# if defined(_MSC_VER) && (_MSC_VER >= 1800) && defined(_M_AMD64) && !defined(LZ4_FORCE_SW_BITCOUNT)
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/* x64 CPUS without BMI support interpret `TZCNT` as `REP BSF` */
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return (unsigned)_tzcnt_u64(val) >> 3;
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# elif defined(_MSC_VER) && defined(_WIN64) && !defined(LZ4_FORCE_SW_BITCOUNT)
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unsigned long r = 0;
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_BitScanForward64( &r, (U64)val );
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return (int)(r>>3);
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# elif (defined(__clang__) || (defined(__GNUC__) && (__GNUC__>=3))) && !defined(LZ4_FORCE_SW_BITCOUNT)
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_BitScanForward64(&r, (U64)val);
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return (unsigned)r >> 3;
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# elif (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
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((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
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!defined(LZ4_FORCE_SW_BITCOUNT)
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return (unsigned)__builtin_ctzll((U64)val) >> 3;
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# else
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static const int DeBruijnBytePos[64] = { 0, 0, 0, 0, 0, 1, 1, 2,
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0, 3, 1, 3, 1, 4, 2, 7,
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0, 2, 3, 6, 1, 5, 3, 5,
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1, 3, 4, 4, 2, 5, 6, 7,
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7, 0, 1, 2, 3, 3, 4, 6,
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2, 6, 5, 5, 3, 4, 5, 6,
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7, 1, 2, 4, 6, 4, 4, 5,
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7, 2, 6, 5, 7, 6, 7, 7 };
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return DeBruijnBytePos[((U64)((val & -(long long)val) * 0x0218A392CDABBD3FULL)) >> 58];
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const U64 m = 0x0101010101010101ULL;
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val ^= val - 1;
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return (unsigned)(((U64)((val & (m - 1)) * m)) >> 56);
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# endif
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} else /* 32 bits */ {
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# if defined(_MSC_VER) && !defined(LZ4_FORCE_SW_BITCOUNT)
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unsigned long r;
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_BitScanForward( &r, (U32)val );
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return (int)(r>>3);
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# elif (defined(__clang__) || (defined(__GNUC__) && (__GNUC__>=3))) && !defined(LZ4_FORCE_SW_BITCOUNT)
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_BitScanForward(&r, (U32)val);
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return (unsigned)r >> 3;
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# elif (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
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((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
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!defined(LZ4_FORCE_SW_BITCOUNT)
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return (unsigned)__builtin_ctz((U32)val) >> 3;
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# else
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static const int DeBruijnBytePos[32] = { 0, 0, 3, 0, 3, 1, 3, 0,
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3, 2, 2, 1, 3, 2, 0, 1,
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3, 3, 1, 2, 2, 2, 2, 0,
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3, 1, 2, 0, 1, 0, 1, 1 };
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return DeBruijnBytePos[((U32)((val & -(S32)val) * 0x077CB531U)) >> 27];
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const U32 m = 0x01010101;
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return (unsigned)((((val - 1) ^ val) & (m - 1)) * m) >> 24;
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# endif
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}
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} else /* Big Endian CPU */ {
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if (sizeof(val)==8) { /* 64-bits */
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# if defined(_MSC_VER) && defined(_WIN64) && !defined(LZ4_FORCE_SW_BITCOUNT)
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unsigned long r = 0;
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_BitScanReverse64( &r, val );
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return (unsigned)(r>>3);
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# elif (defined(__clang__) || (defined(__GNUC__) && (__GNUC__>=3))) && !defined(LZ4_FORCE_SW_BITCOUNT)
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if (sizeof(val)==8) {
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# if (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
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((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
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!defined(LZ4_FORCE_SW_BITCOUNT)
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return (unsigned)__builtin_clzll((U64)val) >> 3;
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# else
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static const U32 by32 = sizeof(val)*4; /* 32 on 64 bits (goal), 16 on 32 bits.
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Just to avoid some static analyzer complaining about shift by 32 on 32-bits target.
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Note that this code path is never triggered in 32-bits mode. */
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unsigned r;
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if (!(val>>by32)) { r=4; } else { r=0; val>>=by32; }
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if (!(val>>16)) { r+=2; val>>=8; } else { val>>=24; }
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r += (!val);
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return r;
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static const unsigned char ctz7_tab[128] = {
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7, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0,
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};
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const U64 mask = 0x0101010101010101ULL;
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val = (((val >> 8) - mask) | val) & mask;
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return ctz7_tab[((U64)(val * 0x0080402010080402ULL)) >> 57];
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# endif
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} else /* 32 bits */ {
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# if defined(_MSC_VER) && !defined(LZ4_FORCE_SW_BITCOUNT)
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unsigned long r = 0;
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_BitScanReverse( &r, (unsigned long)val );
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return (unsigned)(r>>3);
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# elif (defined(__clang__) || (defined(__GNUC__) && (__GNUC__>=3))) && !defined(LZ4_FORCE_SW_BITCOUNT)
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# if (defined(__clang__) || (defined(__GNUC__) && ((__GNUC__ > 3) || \
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((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))) && \
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!defined(LZ4_FORCE_SW_BITCOUNT)
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return (unsigned)__builtin_clz((U32)val) >> 3;
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# else
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unsigned r;
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if (!(val>>16)) { r=2; val>>=8; } else { r=0; val>>=24; }
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r += (!val);
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return r;
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val >>= 8;
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val = ((((val + 0x00FFFF00) | 0x00FFFFFF) + val) |
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(val + 0x00FF0000)) >> 24;
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return (unsigned)val ^ 3;
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# endif
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}
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}
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}
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#define STEPSIZE sizeof(reg_t)
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LZ4_FORCE_INLINE
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unsigned LZ4_count(const BYTE* pIn, const BYTE* pMatch, const BYTE* pInLimit)
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