TLA  Line data    Source code

       1                 : /*-------------------------------------------------------------------------
       2                 :  *
       3                 :  * pg_crc32c_sse42_choose.c
       4                 :  *    Choose between Intel SSE 4.2 and software CRC-32C implementation.
       5                 :  *
       6                 :  * On first call, checks if the CPU we're running on supports Intel SSE
       7                 :  * 4.2. If it does, use the special SSE instructions for CRC-32C
       8                 :  * computation. Otherwise, fall back to the pure software implementation
       9                 :  * (slicing-by-8).
      10                 :  *
      11                 :  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
      12                 :  * Portions Copyright (c) 1994, Regents of the University of California
      13                 :  *
      14                 :  *
      15                 :  * IDENTIFICATION
      16                 :  *    src/port/pg_crc32c_sse42_choose.c
      17                 :  *
      18                 :  *-------------------------------------------------------------------------
      19                 :  */
      20                 : 
      21                 : #include "c.h"
      22                 : 
      23                 : #ifdef HAVE__GET_CPUID
      24                 : #include <cpuid.h>
      25                 : #endif
      26                 : 
      27                 : #ifdef HAVE__CPUID
      28                 : #include <intrin.h>
      29                 : #endif
      30                 : 
      31                 : #include "port/pg_crc32c.h"
      32                 : 
      33                 : static bool
      34 CBC        1419 : pg_crc32c_sse42_available(void)
      35                 : {
      36            1419 :     unsigned int exx[4] = {0, 0, 0, 0};
      37                 : 
      38                 : #if defined(HAVE__GET_CPUID)
      39            1419 :     __get_cpuid(1, &exx[0], &exx[1], &exx[2], &exx[3]);
      40                 : #elif defined(HAVE__CPUID)
      41                 :     __cpuid(exx, 1);
      42                 : #else
      43                 : #error cpuid instruction not available
      44                 : #endif
      45                 : 
      46            1419 :     return (exx[2] & (1 << 20)) != 0; /* SSE 4.2 */
      47                 : }
      48                 : 
      49                 : /*
      50                 :  * This gets called on the first call. It replaces the function pointer
      51                 :  * so that subsequent calls are routed directly to the chosen implementation.
      52                 :  */
      53                 : static pg_crc32c
      54            1419 : pg_comp_crc32c_choose(pg_crc32c crc, const void *data, size_t len)
      55                 : {
      56            1419 :     if (pg_crc32c_sse42_available())
      57            1419 :         pg_comp_crc32c = pg_comp_crc32c_sse42;
      58                 :     else
      59 UBC           0 :         pg_comp_crc32c = pg_comp_crc32c_sb8;
      60                 : 
      61 CBC        1419 :     return pg_comp_crc32c(crc, data, len);
      62                 : }
      63                 : 
      64                 : pg_crc32c   (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len) = pg_comp_crc32c_choose;