| /*------------------------------------------------------------------------- |
| * |
| * pg_crc32c_choose.c |
| * Choose which CRC-32C implementation to use, at runtime. |
| * |
| * Try to the special CRC instructions introduced in Intel SSE 4.2, |
| * if available on the platform we're running on, but fall back to the |
| * slicing-by-8 implementation otherwise. |
| * |
| * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group |
| * Portions Copyright (c) 1994, Regents of the University of California |
| * |
| * |
| * IDENTIFICATION |
| * src/port/pg_crc32c_choose.c |
| * |
| *------------------------------------------------------------------------- |
| */ |
| |
| #include "c.h" |
| |
| #ifdef HAVE__GET_CPUID |
| #include <cpuid.h> |
| #endif |
| |
| #ifdef HAVE__CPUID |
| #include <intrin.h> |
| #endif |
| |
| #include "port/pg_crc32c.h" |
| |
| static bool |
| pg_crc32c_sse42_available(void) |
| { |
| unsigned int exx[4] = {0, 0, 0, 0}; |
| |
| #if defined(HAVE__GET_CPUID) |
| __get_cpuid(1, &exx[0], &exx[1], &exx[2], &exx[3]); |
| #elif defined(HAVE__CPUID) |
| __cpuid(exx, 1); |
| #else |
| #error cpuid instruction not available |
| #endif |
| |
| return (exx[2] & (1 << 20)) != 0; /* SSE 4.2 */ |
| } |
| |
| /* |
| * This gets called on the first call. It replaces the function pointer |
| * so that subsequent calls are routed directly to the chosen implementation. |
| */ |
| static pg_crc32c |
| pg_comp_crc32c_choose(pg_crc32c crc, const void *data, size_t len) |
| { |
| if (pg_crc32c_sse42_available()) |
| pg_comp_crc32c = pg_comp_crc32c_sse42; |
| else |
| pg_comp_crc32c = pg_comp_crc32c_sb8; |
| |
| return pg_comp_crc32c(crc, data, len); |
| } |
| |
| pg_crc32c (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len) = pg_comp_crc32c_choose; |