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) 1996-2024, 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        2418 : pg_crc32c_sse42_available(void)
      35             : {
      36        2418 :     unsigned int exx[4] = {0, 0, 0, 0};
      37             : 
      38             : #if defined(HAVE__GET_CPUID)
      39        2418 :     __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        2418 :     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        2418 : pg_comp_crc32c_choose(pg_crc32c crc, const void *data, size_t len)
      55             : {
      56        2418 :     if (pg_crc32c_sse42_available())
      57        2418 :         pg_comp_crc32c = pg_comp_crc32c_sse42;
      58             :     else
      59           0 :         pg_comp_crc32c = pg_comp_crc32c_sb8;
      60             : 
      61        2418 :     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;