rocksdb/util/crc32c_arm64.cc

//  Copyright (c) 2018, Arm Limited and affiliates. All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).

#include "util/crc32c_arm64.h"

#if defined(__linux__) && defined(HAVE_ARM64_CRC)

#include <asm/hwcap.h>
#include <sys/auxv.h>
#ifndef HWCAP_CRC32
#define HWCAP_CRC32 (1 << 7)
#endif
uint32_t crc32c_runtime_check(void) {
  uint64_t auxv = getauxval(AT_HWCAP);
  return (auxv & HWCAP_CRC32) != 0;
}

uint32_t crc32c_arm64(uint32_t crc, unsigned char const *data,
                             unsigned len) {
  const uint8_t *buf8;
  const uint64_t *buf64 = (uint64_t *)data;
  int length = (int)len;
  crc ^= 0xffffffff;

#ifdef HAVE_ARM64_CRYPTO
  /* Crc32c Parallel computation
   *   Algorithm comes from Intel whitepaper:
   *   crc-iscsi-polynomial-crc32-instruction-paper
   *
   * Input data is divided into three equal-sized blocks
   *   Three parallel blocks (crc0, crc1, crc2) for 1024 Bytes
   *   One Block: 42(BLK_LENGTH) * 8(step length: crc32c_u64) bytes
   */
  #define BLK_LENGTH 42
  while (length >= 1024) {
    uint64_t t0, t1;
    uint32_t crc0 = 0, crc1 = 0, crc2 = 0;

    /* Parallel Param:
     *   k0 = CRC32(x ^ (42 * 8 * 8 * 2 - 1));
     *   k1 = CRC32(x ^ (42 * 8 * 8 - 1));
     */
    uint32_t k0 = 0xe417f38a, k1 = 0x8f158014;

    /* First 8 bytei for better pipelining */
    crc0 = crc32c_u64(crc, *buf64++);

    /* 3 blocks crc32c parallel computation
     *
     * 42 * 8 * 3 = 1008 (bytes)
     */
    for (int i = 0; i < BLK_LENGTH; i++, buf64++) {
      crc0 = crc32c_u64(crc0, *buf64);
      crc1 = crc32c_u64(crc1, *(buf64 + BLK_LENGTH));
      crc2 = crc32c_u64(crc2, *(buf64 + (BLK_LENGTH * 2)));
    }
    buf64 += (BLK_LENGTH * 2);

    /* Last 8 bytes */
    crc = crc32c_u64(crc2, *buf64++);

    t0 = (uint64_t)vmull_p64(crc0, k0);
    t1 = (uint64_t)vmull_p64(crc1, k1);

    /* Merge (crc0, crc1, crc2) -> crc */
    crc1 = crc32c_u64(0, t1);
    crc ^= crc1;
    crc0 = crc32c_u64(0, t0);
    crc ^= crc0;

    length -= 1024;
  }
#endif
  buf8 = (const uint8_t *)buf64;
  while (length >= 8) {
    crc = crc32c_u64(crc, *(const uint64_t*)buf8);
    buf8 += 8;
    length -= 8;
  }

  /* The following is more efficient than the straight loop */
  if (length >= 4) {
    crc = crc32c_u32(crc, *(const uint32_t*)buf8);
    buf8 += 4;
    length -= 4;
  }

  if (length >= 2) {
    crc = crc32c_u16(crc, *(const uint16_t*)buf8);
    buf8 += 2;
    length -= 2;
  }

  if (length >= 1)
    crc = crc32c_u8(crc, *buf8);

  crc ^= 0xffffffff;
  return crc;
}

#endif