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Implement support for Intel crc32 instruction (SSE 4.2)
This change authored by vadimskipin and submitted via:
google/leveldb#309
Changes made to support iOS builds and other architectures
without support for SSE 4.2.
db_bench reports original crc32 speed at:
crc32c : 3.610 micros/op; 1082.0 MB/s (4K per op)
with this change performance has increased to:
crc32c : 0.843 micros/op; 4633.6 MB/s (4K per op)
-------------
Created by MOE: https://github.com/google/moe
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,125 @@ | ||
| // 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 { | ||
|
|
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| #if defined(LEVELDB_PLATFORM_POSIX_SSE) | ||
|
|
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| // 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; | ||
| } | ||
|
|
||
| // 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; | ||
| } | ||
|
|
||
| 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) | ||
|
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| // 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; | ||
| } | ||
|
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||
| 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) { | ||
| // Process unaligned bytes | ||
| for (unsigned int i = reinterpret_cast<uintptr_t>(p) % 8; i; --i) { | ||
| 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 |
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