src/port/pg_crc32c_sse42.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pg_crc32c_sse42.c
   4  *        Compute CRC-32C checksum using Intel SSE 4.2 instructions.
   5  *
   6  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/port/pg_crc32c_sse42.c
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #include "c.h"
  16
  17 #include <nmmintrin.h>
  18
  19 #include "port/pg_crc32c.h"
  20
  21 pg_attribute_no_sanitize_alignment()
  22 pg_crc32c
  23 pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len)
  24 {
  25         const unsigned char *p = data;
  26         const unsigned char *pend = p + len;
  27
  28         /*
  29          * Process eight bytes of data at a time.
  30          *
  31          * NB: We do unaligned accesses here. The Intel architecture allows that,
  32          * and performance testing didn't show any performance gain from aligning
  33          * the begin address.
  34          */
  35 #ifdef __x86_64__
  36         while (p + 8 <= pend)
  37         {
  38                 crc = (uint32) _mm_crc32_u64(crc, *((const uint64 *) p));
  39                 p += 8;
  40         }
  41
  42         /* Process remaining full four bytes if any */
  43         if (p + 4 <= pend)
  44         {
  45                 crc = _mm_crc32_u32(crc, *((const unsigned int *) p));
  46                 p += 4;
  47         }
  48 #else
  49
  50         /*
  51          * Process four bytes at a time. (The eight byte instruction is not
  52          * available on the 32-bit x86 architecture).
  53          */
  54         while (p + 4 <= pend)
  55         {
  56                 crc = _mm_crc32_u32(crc, *((const unsigned int *) p));
  57                 p += 4;
  58         }
  59 #endif                                                  /* __x86_64__ */
  60
  61         /* Process any remaining bytes one at a time. */
  62         while (p < pend)
  63         {
  64                 crc = _mm_crc32_u8(crc, *p);
  65                 p++;
  66         }
  67
  68         return crc;
  69 }