Replace SSE-optimized CRC32C in POSIX port with external library.

Maintaining a hardware-accelerated CRC32C implementation tailored for
all modern platforms deserves a repository of its own. We extracted the
implementation here into https://github.com/google/crc32c and improved
it in that repository. This CL removes the SSE-optimized implementation
from this codebase, and adds the ability to use the google/crc32c
library, if it is present on the system.

The benchmarks below show the performance impact of the change. In
summary, open source builds that use the google/crc32c library can
expect a 3x improvement in CRC32C throughput, whereas builds that do not
use the library will see a 50% drop in CRC32C throughput. This
translates in much smaller changes in overall leveldb performance.

Baseline, MacBookPro13,3 with Core i7 6920HQ:
LevelDB:    version 1.20
Keys:       16 bytes each
Values:     100 bytes each (50 bytes after compression)
Entries:    1000000
RawSize:    110.6 MB (estimated)
FileSize:   62.9 MB (estimated)
------------------------------------------------
fillseq      :       3.064 micros/op;   36.1 MB/s
fillsync     :      57.861 micros/op;    1.9 MB/s (1000 ops)
fillrandom   :       3.887 micros/op;   28.5 MB/s
overwrite    :       4.140 micros/op;   26.7 MB/s
readrandom   :       7.433 micros/op; (1000000 of 1000000 found)
readrandom   :       6.825 micros/op; (1000000 of 1000000 found)
readseq      :       0.244 micros/op;  453.4 MB/s
readreverse  :       0.387 micros/op;  285.8 MB/s
compact      :  449707.000 micros/op;
readrandom   :       4.196 micros/op; (1000000 of 1000000 found)
readseq      :       0.228 micros/op;  485.8 MB/s
readreverse  :       0.320 micros/op;  345.2 MB/s
fill100K     :     562.556 micros/op;  169.6 MB/s (1000 ops)
crc32c       :       0.768 micros/op; 5085.0 MB/s (4K per op)
snappycomp   :       4.220 micros/op;  925.7 MB/s (output: 55.1%)
snappyuncomp :       0.635 micros/op; 6155.7 MB/s
acquireload  :      13.054 micros/op; (each op is 1000 loads)

New with crc32c, MacBookPro13,3 with Core i7 6920HQ:
LevelDB:    version 1.20
Keys:       16 bytes each
Values:     100 bytes each (50 bytes after compression)
Entries:    1000000
RawSize:    110.6 MB (estimated)
FileSize:   62.9 MB (estimated)
------------------------------------------------
fillseq      :       2.820 micros/op;   39.2 MB/s
fillsync     :      51.988 micros/op;    2.1 MB/s (1000 ops)
fillrandom   :       3.747 micros/op;   29.5 MB/s
overwrite    :       4.047 micros/op;   27.3 MB/s
readrandom   :       7.287 micros/op; (1000000 of 1000000 found)
readrandom   :       6.927 micros/op; (1000000 of 1000000 found)
readseq      :       0.253 micros/op;  437.5 MB/s
readreverse  :       0.411 micros/op;  269.2 MB/s
compact      :  440405.000 micros/op;
readrandom   :       4.159 micros/op; (1000000 of 1000000 found)
readseq      :       0.230 micros/op;  481.1 MB/s
readreverse  :       0.320 micros/op;  345.9 MB/s
fill100K     :     558.222 micros/op;  170.9 MB/s (1000 ops)
crc32c       :       0.214 micros/op; 18263.5 MB/s (4K per op)
snappycomp   :       4.471 micros/op;  873.7 MB/s (output: 55.1%)
snappyuncomp :       0.833 micros/op; 4688.5 MB/s
acquireload  :      13.289 micros/op; (each op is 1000 loads)

New without crc32c, MacBookPro13,3 with Core i7 6920HQ
LevelDB:    version 1.20
Keys:       16 bytes each
Values:     100 bytes each (50 bytes after compression)
Entries:    1000000
RawSize:    110.6 MB (estimated)
FileSize:   62.9 MB (estimated)
------------------------------------------------
fillseq      :       3.094 micros/op;   35.8 MB/s
fillsync     :      52.160 micros/op;    2.1 MB/s (1000 ops)
fillrandom   :       4.090 micros/op;   27.0 MB/s
overwrite    :       4.006 micros/op;   27.6 MB/s
readrandom   :       6.584 micros/op; (1000000 of 1000000 found)
readrandom   :       6.676 micros/op; (1000000 of 1000000 found)
readseq      :       0.280 micros/op;  395.2 MB/s
readreverse  :       0.391 micros/op;  283.2 MB/s
compact      :  433911.000 micros/op;
readrandom   :       4.261 micros/op; (1000000 of 1000000 found)
readseq      :       0.251 micros/op;  440.5 MB/s
readreverse  :       0.356 micros/op;  310.9 MB/s
fill100K     :     584.023 micros/op;  163.3 MB/s (1000 ops)
crc32c       :       1.384 micros/op; 2822.3 MB/s (4K per op)
snappycomp   :       4.763 micros/op;  820.1 MB/s (output: 55.1%)
snappyuncomp :       0.766 micros/op; 5098.6 MB/s
acquireload  :      12.931 micros/op; (each op is 1000 loads)

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=171667771

2 files changed, 12 insertions, 136 deletions

diff --git a/port/port_posix.h b/port/port_posix.h
index 2bc5223..2a30be3 100644
--- a/port/port_posix.h
+++ b/port/port_posix.h
@@ -39,6 +39,9 @@
 #endif
 
 #include <pthread.h>
+#if defined(HAVE_CRC32C)
+#include <crc32c/crc32c.h>
+#endif  // defined(HAVE_CRC32C)
 #ifdef HAVE_SNAPPY
 #include <snappy.h>
 #endif  // defined(HAVE_SNAPPY)
@@ -139,9 +142,15 @@ inline bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg) {
   return false;
 }
 
-uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
+inline uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size) {
+#if defined(HAVE_CRC32C)
+  return ::crc32c::Extend(crc, reinterpret_cast<const uint8_t*>(buf), size);
+#else
+  return 0;
+#endif  // defined(HAVE_CRC32C)
+}
 
-} // namespace port
-} // namespace leveldb
+}  // namespace port
+}  // namespace leveldb
 
 #endif  // STORAGE_LEVELDB_PORT_PORT_POSIX_H_
diff --git a/port/port_posix_sse.cc b/port/port_posix_sse.cc
deleted file mode 100644
index 08d9aee..0000000
--- a/port/port_posix_sse.cc
+++ /dev/null
@@ -1,133 +0,0 @@
-// 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