bench.cc

#include <string>
#include <algorithm>
#include <chrono>
#include <iostream>

#include "crc-32.hh"

std::chrono::duration<unsigned long long, std::micro>
constexpr operator""_us(unsigned long long x)
{
  return std::chrono::duration<unsigned long long, std::micro>{x};
}

int main()
{

  std::chrono::high_resolution_clock clock;

  for (int i_run=0; i_run<16; ++i_run) {

    std::string input((5<<20) + 15, 0);
    {
      char _ = 0;
      for (char& x : input)
        x = ++_;
    }

    if (i_run&1) {
      auto start = clock.now();
      auto crc = crc32c_sse(input);
      auto dur = clock.now() - start;
      std::cout << std::hex << crc << std::dec
                << " in " << (dur/1_us) << "us by sse, "
                << (double(input.size()) / (dur/1_us))
                << "MB/s\n";
    } else {
      auto start = clock.now();
      auto crc = crc32c_generic(input);
      auto dur = clock.now() - start;
      std::cout << std::hex << crc << std::dec
                << " in " << (dur/1_us) << "us by sw, "
                << (double(input.size()) / (dur/1_us))
                << "MB/s\n";
    }

  };

  return 0;
}

crc32.cc

#include <cstddef>

#ifdef __SSE4_2__

#include <cpuid.h>
#include <smmintrin.h>

bool has_sse42()
{
  unsigned int eax, ebx, ecx, edx;
  __cpuid(1, eax, ebx, ecx, edx);
  return ecx & (1<<20);
}

void sse_update_crc32c_8(uint32_t& acc, const char* first, const char* last)
{
  for (; first!=last; ++first)
    acc = _mm_crc32_u8(acc, *first);
}

void sse_update_crc32c_64(uint32_t& acc, const char* first, const char* last)
{
  for (; first!=last; first+=8)
    acc = _mm_crc32_u64(acc, *reinterpret_cast<const uint64_t*>(first));
}

template <size_t align, class T>
T* align_ceil(T* ptr)
{
  constexpr size_t add = align-1;
  constexpr size_t mask = ~add;
  return (T*)((uintptr_t(ptr)+add) & mask);
}

template <size_t align, class T>
T* align_floor(T* ptr)
{
  constexpr size_t mask = ~(align-1);
  return (T*)(uintptr_t(ptr) & mask);
}

#endif /* __SSE4_2__ */

#ifdef __SSE4_2__

uint32_t crc32c_sse(const std::string& str)
{
  const char* first = &*str.begin();
  const char* last = &*str.end();

  const char* aligned_begin = align_ceil<8>(first);
  const char* aligned_end = align_floor<8>(last);

  uint32_t acc = 0xFFFFFFFF;
  sse_update_crc32c_8(acc, first, aligned_begin);
  sse_update_crc32c_64(acc, aligned_begin, aligned_end);
  sse_update_crc32c_8(acc, aligned_end, last);
  return ~acc;
}

#endif // __SSE4_2__

uint32_t crc32c_generic(const std::string& str)
{
  static uint32_t crc_32_tab[] = {
    0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4,
    0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb,
    0x8ad958cf, 0x78b2dbcc, 0x6be22838, 0x9989ab3b,
    0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24,
    0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b,
    0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384,
    0x9a879fa0, 0x68ec1ca3, 0x7bbcef57, 0x89d76c54,
    0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b,
    0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
    0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
    0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5,
    0x6dfe410e, 0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa,
    0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45,
    0xf779deae, 0x05125dad, 0x1642ae59, 0xe4292d5a,
    0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
    0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595,
    0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48,
    0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
    0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687,
    0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
    0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927,
    0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38,
    0xdbfc821c, 0x2997011f, 0x3ac7f2eb, 0xc8ac71e8,
    0x1c661503, 0xee0d9600, 0xfd5d65f4, 0x0f36e6f7,
    0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096,
    0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789,
    0xeb1fcbad, 0x197448ae, 0x0a24bb5a, 0xf84f3859,
    0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46,
    0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9,
    0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
    0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36,
    0x3cdb9bdd, 0xceb018de, 0xdde0eb2a, 0x2f8b6829,
    0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c,
    0x456cac67, 0xb7072f64, 0xa457dc90, 0x563c5f93,
    0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043,
    0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
    0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3,
    0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc,
    0x1871a4d8, 0xea1a27db, 0xf94ad42f, 0x0b21572c,
    0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
    0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652,
    0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d,
    0x2892ed69, 0xdaf96e6a, 0xc9a99d9e, 0x3bc21e9d,
    0xef087a76, 0x1d63f975, 0x0e330a81, 0xfc588982,
    0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
    0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622,
    0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2,
    0xff56bd19, 0x0d3d3e1a, 0x1e6dcdee, 0xec064eed,
    0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530,
    0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
    0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff,
    0x8ecee914, 0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0,
    0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f,
    0x144976b4, 0xe622f5b7, 0xf5720643, 0x07198540,
    0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90,
    0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f,
    0xe330a81a, 0x115b2b19, 0x020bd8ed, 0xf0605bee,
    0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1,
    0x69e9f0d5, 0x9b8273d6, 0x88d28022, 0x7ab90321,
    0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
    0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81,
    0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e,
    0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
    0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351
  };

  uint32_t crc = 0xFFFFFFFF;

  for (uint8_t ch : str)
    crc = crc_32_tab[(crc^ch) & 0xff] ^ (crc>>8);

  return ~crc;
}

uint32_t crc32c(const std::string& str)
{
#ifdef __SSE4_2__

  static decltype(&crc32c_generic) compute = has_sse42() ? crc32c_sse : crc32c_generic;

  return compute(str);

#else
  return crc32c_generic(str);
#endif // __SSE4_2__
}