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

4 files changed, 29 insertions, 172 deletions

diff --git a/Makefile b/Makefile
index 4bd02a6..82dd84a 100644
--- a/Makefile
+++ b/Makefile
@@ -98,7 +98,7 @@ SHARED_MEMENVOBJECTS := $(addprefix $(SHARED_OUTDIR)/, $(MEMENV_SOURCES:.cc=.o))
 
 TESTUTIL := $(STATIC_OUTDIR)/util/testutil.o
 TESTHARNESS := $(STATIC_OUTDIR)/util/testharness.o $(TESTUTIL)
-TEST_STATIC_OBJS := $(STATIC_OUTDIR)/port/port_posix.o $(STATIC_OUTDIR)/port/port_posix_sse.o $(STATIC_OUTDIR)/util/crc32c.o $(STATIC_OUTDIR)/util/histogram.o
+TEST_STATIC_OBJS := $(STATIC_OUTDIR)/port/port_posix.o $(STATIC_OUTDIR)/util/crc32c.o $(STATIC_OUTDIR)/util/histogram.o
 
 STATIC_TESTOBJS := $(addprefix $(STATIC_OUTDIR)/, $(addsuffix .o, $(TESTS)))
 STATIC_UTILOBJS := $(addprefix $(STATIC_OUTDIR)/, $(addsuffix .o, $(UTILS)))
@@ -425,10 +425,4 @@ $(SHARED_OUTDIR)/%.o: %.cc
 	$(CXX) $(CXXFLAGS) $(SHARED_BUILD_CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
 
 $(SHARED_OUTDIR)/%.o: %.c
-	$(CC) $(CFLAGS) $(SHARED_BUILD_CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
-
-$(STATIC_OUTDIR)/port/port_posix_sse.o: port/port_posix_sse.cc
-	$(CXX) $(CXXFLAGS) $(SHARED_BUILD_CXXFLAGS) $(PLATFORM_SSEFLAGS) -c $< -o $@
-
-$(SHARED_OUTDIR)/port/port_posix_sse.o: port/port_posix_sse.cc
-	$(CXX) $(CXXFLAGS) $(SHARED_BUILD_CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) $(PLATFORM_SSEFLAGS) -c $< -o $@
+	$(CC) $(CFLAGS) $(SHARED_BUILD_CXXFLAGS) $(PLATFORM_SHARED_CFLAGS) -c $< -o $@
\ No newline at end of file
diff --git a/build_detect_platform b/build_detect_platform
index d1bb17e..b7a859f 100755
--- a/build_detect_platform
+++ b/build_detect_platform
@@ -22,6 +22,7 @@
 #
 #       -DLEVELDB_ATOMIC_PRESENT     if <atomic> is present
 #       -DLEVELDB_PLATFORM_POSIX=1   for Posix-based platforms
+#       -DHAVE_CRC32C=1              if the CRC32C library is present
 #       -DHAVE_SNAPPY=1              if the Snappy library is present
 #
 
@@ -63,7 +64,6 @@ PLATFORM_SHARED_EXT="so"
 PLATFORM_SHARED_LDFLAGS="-shared -Wl,-soname -Wl,"
 PLATFORM_SHARED_CFLAGS="-fPIC -fvisibility=hidden"
 PLATFORM_SHARED_VERSIONED=true
-PLATFORM_SSEFLAGS=
 
 MEMCMP_FLAG=
 if [ "$CXX" = "g++" ]; then
@@ -78,7 +78,6 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG -lpthread -DOS_LINUX -DCYGWIN"
         PLATFORM_LDFLAGS="-lpthread"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     Darwin)
         PLATFORM=OS_MACOSX
@@ -87,56 +86,48 @@ case "$TARGET_OS" in
         [ -z "$INSTALL_PATH" ] && INSTALL_PATH=`pwd`
         PLATFORM_SHARED_LDFLAGS="-dynamiclib -install_name $INSTALL_PATH/"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     Linux)
         PLATFORM=OS_LINUX
         COMMON_FLAGS="$MEMCMP_FLAG -pthread -DOS_LINUX"
         PLATFORM_LDFLAGS="-pthread"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     SunOS)
         PLATFORM=OS_SOLARIS
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_SOLARIS"
         PLATFORM_LIBS="-lpthread -lrt"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     FreeBSD)
         PLATFORM=OS_FREEBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_FREEBSD"
         PLATFORM_LIBS="-lpthread"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     NetBSD)
         PLATFORM=OS_NETBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_NETBSD"
         PLATFORM_LIBS="-lpthread -lgcc_s"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     OpenBSD)
         PLATFORM=OS_OPENBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_OPENBSD"
         PLATFORM_LDFLAGS="-pthread"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     DragonFly)
         PLATFORM=OS_DRAGONFLYBSD
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_DRAGONFLYBSD"
         PLATFORM_LIBS="-lpthread"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         ;;
     OS_ANDROID_CROSSCOMPILE)
         PLATFORM=OS_ANDROID
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_ANDROID -DLEVELDB_PLATFORM_POSIX=1"
         PLATFORM_LDFLAGS=""  # All pthread features are in the Android C library
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         CROSS_COMPILE=true
         ;;
     HP-UX)
@@ -144,7 +135,6 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG -D_REENTRANT -DOS_HPUX"
         PLATFORM_LDFLAGS="-pthread"
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         # man ld: +h internal_name
         PLATFORM_SHARED_LDFLAGS="-shared -Wl,+h -Wl,"
         ;;
@@ -153,7 +143,6 @@ case "$TARGET_OS" in
         COMMON_FLAGS="$MEMCMP_FLAG"
         [ -z "$INSTALL_PATH" ] && INSTALL_PATH=`pwd`
         PORT_FILE=port/port_posix.cc
-        PORT_SSE_FILE=port/port_posix_sse.cc
         PLATFORM_SHARED_EXT=
         PLATFORM_SHARED_LDFLAGS=
         PLATFORM_SHARED_CFLAGS=
@@ -180,7 +169,7 @@ set +f # re-enable globbing
 
 # The sources consist of the portable files, plus the platform-specific port
 # file.
-echo "SOURCES=$PORTABLE_FILES $PORT_FILE $PORT_SSE_FILE" >> $OUTPUT
+echo "SOURCES=$PORTABLE_FILES $PORT_FILE" >> $OUTPUT
 echo "MEMENV_SOURCES=helpers/memenv/memenv.cc" >> $OUTPUT
 
 if [ "$CROSS_COMPILE" = "true" ]; then
@@ -202,8 +191,20 @@ EOF
         COMMON_FLAGS="$COMMON_FLAGS -DLEVELDB_PLATFORM_POSIX=1"
     fi
 
+    # Test whether CRC32C library is installed
+    # https://github.com/google/crc32c
+    $CXX $CXXFLAGS -x c++ - -o $CXXOUTPUT 2>/dev/null  <<EOF
+      #include <crc32c/crc32c.h>
+      int main() {}
+EOF
+    if [ "$?" = 0 ]; then
+        COMMON_FLAGS="$COMMON_FLAGS -DHAVE_CRC32C=1"
+        PLATFORM_LIBS="$PLATFORM_LIBS -lcrc32c"
+    fi
+
+
     # Test whether Snappy library is installed
-    # http://code.google.com/p/snappy/
+    # https://github.com/google/snappy
     $CXX $CXXFLAGS -x c++ - -o $CXXOUTPUT 2>/dev/null  <<EOF
       #include <snappy.h>
       int main() {}
@@ -223,22 +224,9 @@ EOF
 
     rm -f $CXXOUTPUT 2>/dev/null
 
-    # Test if gcc SSE 4.2 is supported
-    $CXX $CXXFLAGS -x c++ - -o $CXXOUTPUT -msse4.2 2>/dev/null  <<EOF
-      int main() {}
-EOF
-    if [ "$?" = 0 ]; then
-        PLATFORM_SSEFLAGS="-msse4.2"
-    fi
-
     rm -f $CXXOUTPUT 2>/dev/null
 fi
 
-# Use the SSE 4.2 CRC32C intrinsics iff runtime checks indicate compiler supports them.
-if [ -n "$PLATFORM_SSEFLAGS" ]; then
-    PLATFORM_SSEFLAGS="$PLATFORM_SSEFLAGS -DLEVELDB_PLATFORM_POSIX_SSE"
-fi
-
 PLATFORM_CCFLAGS="$PLATFORM_CCFLAGS $COMMON_FLAGS"
 PLATFORM_CXXFLAGS="$PLATFORM_CXXFLAGS $COMMON_FLAGS"
 
@@ -249,7 +237,6 @@ echo "PLATFORM_LDFLAGS=$PLATFORM_LDFLAGS" >> $OUTPUT
 echo "PLATFORM_LIBS=$PLATFORM_LIBS" >> $OUTPUT
 echo "PLATFORM_CCFLAGS=$PLATFORM_CCFLAGS" >> $OUTPUT
 echo "PLATFORM_CXXFLAGS=$PLATFORM_CXXFLAGS" >> $OUTPUT
-echo "PLATFORM_SSEFLAGS=$PLATFORM_SSEFLAGS" >> $OUTPUT
 echo "PLATFORM_SHARED_CFLAGS=$PLATFORM_SHARED_CFLAGS" >> $OUTPUT
 echo "PLATFORM_SHARED_EXT=$PLATFORM_SHARED_EXT" >> $OUTPUT
 echo "PLATFORM_SHARED_LDFLAGS=$PLATFORM_SHARED_LDFLAGS" >> $OUTPUT
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