245 lines
9.0 KiB
C
245 lines
9.0 KiB
C
/*
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* Copyright (c) Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under both the BSD-style license (found in the
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* LICENSE file in the root directory of this source tree) and the GPLv2 (found
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* in the COPYING file in the root directory of this source tree).
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* You may select, at your option, one of the above-listed licenses.
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*/
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#ifndef ZSTD_BITS_H
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#define ZSTD_BITS_H
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#include "mem.h"
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MEM_STATIC unsigned ZSTD_highbit32_fallback(U32 val) {
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static const U32 DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29,
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11, 14, 16, 18, 22, 25, 3, 30,
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8, 12, 20, 28, 15, 17, 24, 7,
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19, 27, 23, 6, 26, 5, 4, 31 };
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val |= val >> 1;
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val |= val >> 2;
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val |= val >> 4;
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val |= val >> 8;
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val |= val >> 16;
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return DeBruijnClz[(val * 0x07C4ACDDU) >> 27];
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}
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MEM_STATIC unsigned ZSTD_highbit32(U32 val) /* compress, dictBuilder, decodeCorpus */
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{
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assert(val != 0);
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{
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# if defined(_MSC_VER) /* Visual */
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# if STATIC_BMI2 == 1
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return _lzcnt_u32(val)^31;
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# else
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if (val != 0) {
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unsigned long r;
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_BitScanReverse(&r, val);
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return (unsigned)r;
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# endif
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# elif defined(__GNUC__) && (__GNUC__ >= 3) /* GCC Intrinsic */
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return (unsigned)__builtin_clz (val) ^ 31;
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# elif defined(__ICCARM__) /* IAR Intrinsic */
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return 31 - __CLZ(val);
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# else /* Software version */
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return ZSTD_highbit32_fallback(val);
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# endif
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}
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}
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MEM_STATIC unsigned ZSTD_countTrailingZeros32_fallback(U32 val)
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{
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static const int DeBruijnBytePos[32] = { 0, 1, 28, 2, 29, 14, 24, 3,
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30, 22, 20, 15, 25, 17, 4, 8,
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31, 27, 13, 23, 21, 19, 16, 7,
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26, 12, 18, 6, 11, 5, 10, 9 };
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return DeBruijnBytePos[((U32)((val & -(S32)val) * 0x077CB531U)) >> 27];
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}
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MEM_STATIC unsigned ZSTD_countTrailingZeros32(U32 val)
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{
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assert(val != 0);
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# if defined(_MSC_VER)
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if (val != 0) {
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unsigned long r;
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_BitScanForward(&r, val);
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return (unsigned)r;
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# elif defined(__GNUC__) && (__GNUC__ >= 3)
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return (unsigned)__builtin_ctz(val);
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# elif defined(__ICCARM__) /* IAR Intrinsic */
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return __CTZ(val);
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# else
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return ZSTD_countTrailingZeros32_fallback(val);
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# endif
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}
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MEM_STATIC unsigned ZSTD_countTrailingZeros64_fallback(U64 val)
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{
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static const int DeBruijnBytePos[64] = { 0, 1, 2, 7, 3, 13, 8, 19,
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4, 25, 14, 28, 9, 34, 20, 56,
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5, 17, 26, 54, 15, 41, 29, 43,
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10, 31, 38, 35, 21, 45, 49, 57,
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63, 6, 12, 18, 24, 27, 33, 55,
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16, 53, 40, 42, 30, 37, 44, 48,
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62, 11, 23, 32, 52, 39, 36, 47,
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61, 22, 51, 46, 60, 50, 59, 58 };
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return DeBruijnBytePos[((U64)((val & -(long long)val) * 0x0218A392CDABBD3FULL)) >> 58];
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}
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MEM_STATIC unsigned ZSTD_countTrailingZeros64(U64 val)
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{
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assert(val != 0);
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# if defined(_MSC_VER) && defined(_WIN64)
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# if STATIC_BMI2
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return _tzcnt_u64(val);
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# else
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if (val != 0) {
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unsigned long r;
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_BitScanForward64(&r, val);
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return (unsigned)r;
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# endif
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# elif defined(__GNUC__) && (__GNUC__ >= 4)
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if (MEM_32bits()) {
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U32 mostSignificantWord = (U32)(val >> 32);
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U32 leastSignificantWord = (U32)val;
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if (leastSignificantWord == 0) {
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return 32 + (unsigned)__builtin_ctz(mostSignificantWord);
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} else {
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return (unsigned)__builtin_ctz(leastSignificantWord);
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}
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} else {
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return (unsigned)__builtin_ctzll(val);
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}
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# else
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return ZSTD_countTrailingZeros64_fallback(val);
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# endif
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}
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MEM_STATIC unsigned ZSTD_NbCommonBytes_fallback(size_t val)
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{
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if (MEM_isLittleEndian()) {
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if (MEM_64bits()) {
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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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} else { /* 32 bits */
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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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}
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} else { /* Big Endian CPU */
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unsigned r;
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if (MEM_64bits()) {
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const unsigned n32 = sizeof(size_t)*4; /* calculate this way due to compiler complaining in 32-bits mode */
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if (!(val>>n32)) { r=4; } else { r=0; val>>=n32; }
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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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} else { /* 32 bits */
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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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}
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}
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}
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MEM_STATIC unsigned ZSTD_NbCommonBytes(size_t val)
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{
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if (MEM_isLittleEndian()) {
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if (MEM_64bits()) {
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# if defined(_MSC_VER) && defined(_WIN64)
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# if STATIC_BMI2
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return _tzcnt_u64(val) >> 3;
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# else
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if (val != 0) {
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unsigned long r;
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_BitScanForward64(&r, (U64)val);
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return (unsigned)(r >> 3);
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# endif
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# elif defined(__GNUC__) && (__GNUC__ >= 4)
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return (unsigned)(__builtin_ctzll((U64)val) >> 3);
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# else
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return ZSTD_NbCommonBytes_fallback(val);
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# endif
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} else { /* 32 bits */
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# if defined(_MSC_VER)
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if (val != 0) {
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unsigned long r;
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_BitScanForward(&r, (U32)val);
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return (unsigned)(r >> 3);
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# elif defined(__GNUC__) && (__GNUC__ >= 3)
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return (unsigned)(__builtin_ctz((U32)val) >> 3);
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# else
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return ZSTD_NbCommonBytes_fallback(val);
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# endif
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}
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} else { /* Big Endian CPU */
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if (MEM_64bits()) {
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# if defined(_MSC_VER) && defined(_WIN64)
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# if STATIC_BMI2
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return _lzcnt_u64(val) >> 3;
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# else
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if (val != 0) {
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unsigned long r;
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_BitScanReverse64(&r, (U64)val);
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return (unsigned)(r >> 3);
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# endif
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# elif defined(__GNUC__) && (__GNUC__ >= 4)
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return (unsigned)(__builtin_clzll(val) >> 3);
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# else
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return ZSTD_NbCommonBytes_fallback(val);
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# endif
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} else { /* 32 bits */
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# if defined(_MSC_VER)
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if (val != 0) {
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unsigned long r;
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_BitScanReverse(&r, (unsigned long)val);
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return (unsigned)(r >> 3);
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} else {
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/* Should not reach this code path */
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__assume(0);
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}
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# elif defined(__GNUC__) && (__GNUC__ >= 3)
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return (unsigned)(__builtin_clz((U32)val) >> 3);
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# else
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return ZSTD_NbCommonBytes_fallback(val);
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# endif
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} }
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}
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#endif /* ZSTD_BITS_H */
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