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-rw-r--r--port/port_posix_sse.cc133
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diff --git a/port/port_posix_sse.cc b/port/port_posix_sse.cc
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--- a/port/port_posix_sse.cc
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-// Copyright 2016 The LevelDB Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file. See the AUTHORS file for names of contributors.
-//
-// A portable implementation of crc32c, optimized to handle
-// four bytes at a time.
-//
-// In a separate source file to allow this accelerated CRC32C function to be
-// compiled with the appropriate compiler flags to enable x86 SSE 4.2
-// instructions.
-
-#include <stdint.h>
-#include <string.h>
-#include "port/port.h"
-
-#if defined(LEVELDB_PLATFORM_POSIX_SSE)
-
-#if defined(_MSC_VER)
-#include <intrin.h>
-#elif defined(__GNUC__) && defined(__SSE4_2__)
-#include <nmmintrin.h>
-#include <cpuid.h>
-#endif
-
-#endif // defined(LEVELDB_PLATFORM_POSIX_SSE)
-
-namespace leveldb {
-namespace port {
-
-#if defined(LEVELDB_PLATFORM_POSIX_SSE)
-
-// Used to fetch a naturally-aligned 32-bit word in little endian byte-order
-static inline uint32_t LE_LOAD32(const uint8_t *p) {
- // SSE is x86 only, so ensured that |p| is always little-endian.
- uint32_t word;
- memcpy(&word, p, sizeof(word));
- return word;
-}
-
-#if defined(_M_X64) || defined(__x86_64__) // LE_LOAD64 is only used on x64.
-
-// Used to fetch a naturally-aligned 64-bit word in little endian byte-order
-static inline uint64_t LE_LOAD64(const uint8_t *p) {
- uint64_t dword;
- memcpy(&dword, p, sizeof(dword));
- return dword;
-}
-
-#endif // defined(_M_X64) || defined(__x86_64__)
-
-static inline bool HaveSSE42() {
-#if defined(_MSC_VER)
- int cpu_info[4];
- __cpuid(cpu_info, 1);
- return (cpu_info[2] & (1 << 20)) != 0;
-#elif defined(__GNUC__)
- unsigned int eax, ebx, ecx, edx;
- __get_cpuid(1, &eax, &ebx, &ecx, &edx);
- return (ecx & (1 << 20)) != 0;
-#else
- return false;
-#endif
-}
-
-#endif // defined(LEVELDB_PLATFORM_POSIX_SSE)
-
-// For further improvements see Intel publication at:
-// http://download.intel.com/design/intarch/papers/323405.pdf
-uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size) {
-#if !defined(LEVELDB_PLATFORM_POSIX_SSE)
- return 0;
-#else
- static bool have = HaveSSE42();
- if (!have) {
- return 0;
- }
-
- const uint8_t *p = reinterpret_cast<const uint8_t *>(buf);
- const uint8_t *e = p + size;
- uint32_t l = crc ^ 0xffffffffu;
-
-#define STEP1 do { \
- l = _mm_crc32_u8(l, *p++); \
-} while (0)
-#define STEP4 do { \
- l = _mm_crc32_u32(l, LE_LOAD32(p)); \
- p += 4; \
-} while (0)
-#define STEP8 do { \
- l = _mm_crc32_u64(l, LE_LOAD64(p)); \
- p += 8; \
-} while (0)
-
- if (size > 16) {
- // Point x at first 8-byte aligned byte in string. This must be inside the
- // string, due to the size check above.
- const uintptr_t pval = reinterpret_cast<uintptr_t>(p);
- const uint8_t* x = reinterpret_cast<const uint8_t*>(((pval + 7) >> 3) << 3);
- // Process bytes until p is 8-byte aligned.
- while (p != x) {
- STEP1;
- }
-
- // _mm_crc32_u64 is only available on x64.
-#if defined(_M_X64) || defined(__x86_64__)
- // Process 8 bytes at a time
- while ((e-p) >= 8) {
- STEP8;
- }
- // Process 4 bytes at a time
- if ((e-p) >= 4) {
- STEP4;
- }
-#else // !(defined(_M_X64) || defined(__x86_64__))
- // Process 4 bytes at a time
- while ((e-p) >= 4) {
- STEP4;
- }
-#endif // defined(_M_X64) || defined(__x86_64__)
- }
- // Process the last few bytes
- while (p != e) {
- STEP1;
- }
-#undef STEP8
-#undef STEP4
-#undef STEP1
- return l ^ 0xffffffffu;
-#endif // defined(LEVELDB_PLATFORM_POSIX_SSE)
-}
-
-} // namespace port
-} // namespace leveldb