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Use ARMv8 CRC instructions where available.

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ARMv8 introduced special CPU instructions for calculating CRC-32C. Use
them, when available, for speed.

Like with the similar Intel CRC instructions, several factors affect
whether the instructions can be used. The compiler intrinsics for them must
be supported by the compiler, and the instructions must be supported by the
target architecture. If the compilation target architecture does not
support the instructions, but adding "-march=armv8-a+crc" makes them
available, then we compile the code with a runtime check to determine if
the host we're running on supports them or not.

For the runtime check, use glibc getauxval() function. Unfortunately,
that's not very portable, but I couldn't find any more portable way to do
it. If getauxval() is not available, the CRC instructions will still be
used if the target architecture supports them without any additional
compiler flags, but the runtime check will not be available.

Original patch by Yuqi Gu, heavily modified by me. Reviewed by Andres
Freund, Thomas Munro.

Discussion: https://www.postgresql.org/message-id/HE1PR0801MB1323D171938EABC04FFE7FA9E3110%40HE1PR0801MB1323.eurprd08.prod.outlook.com
This commit is contained in:
Heikki Linnakangas
2018-04-04 12:22:45 +03:00
parent 638a199fa9
commit f044d71e33
11 changed files with 456 additions and 41 deletions
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9
src/include/pg_config.h.in
View File

@@ -239,6 +239,9 @@
/* Define to 1 if you have the `getaddrinfo' function. */
#undef HAVE_GETADDRINFO
/* Define to 1 if you have the `getauxval' function. */
#undef HAVE_GETAUXVAL
/* Define to 1 if you have the `gethostbyname_r' function. */
#undef HAVE_GETHOSTBYNAME_R
@@ -842,6 +845,12 @@
/* Define to 1 if your <sys/time.h> declares `struct tm'. */
#undef TM_IN_SYS_TIME
/* Define to 1 to use ARMv8 CRC Extension. */
#undef USE_ARMV8_CRC32C
/* Define to 1 to use ARMv8 CRC Extension with a runtime check. */
#undef USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK
/* Define to 1 to build with assertion checks. (--enable-cassert) */
#undef USE_ASSERT_CHECKING

26
src/include/port/pg_crc32c.h
View File

@@ -42,26 +42,42 @@ typedef uint32 pg_crc32c;
#define EQ_CRC32C(c1, c2) ((c1) == (c2))
#if defined(USE_SSE42_CRC32C)
/* Use SSE4.2 instructions. */
/* Use Intel SSE4.2 instructions. */
#define COMP_CRC32C(crc, data, len) \
((crc) = pg_comp_crc32c_sse42((crc), (data), (len)))
#define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len);
#elif defined(USE_SSE42_CRC32C_WITH_RUNTIME_CHECK)
#elif defined(USE_ARMV8_CRC32C)
/* Use ARMv8 CRC Extension instructions. */
#define COMP_CRC32C(crc, data, len) \
((crc) = pg_comp_crc32c_armv8((crc), (data), (len)))
#define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
extern pg_crc32c pg_comp_crc32c_armv8(pg_crc32c crc, const void *data, size_t len);
#elif defined(USE_SSE42_CRC32C_WITH_RUNTIME_CHECK) || defined(USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK)
/*
* Use SSE4.2 instructions, but perform a runtime check first to check that
* they are available.
* Use Intel SSE 4.2 or ARMv8 instructions, but perform a runtime check first
* to check that they are available.
*/
#define COMP_CRC32C(crc, data, len) \
((crc) = pg_comp_crc32c((crc), (data), (len)))
#define FIN_CRC32C(crc) ((crc) ^= 0xFFFFFFFF)
extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len);
extern pg_crc32c pg_comp_crc32c_sb8(pg_crc32c crc, const void *data, size_t len);
extern pg_crc32c (*pg_comp_crc32c) (pg_crc32c crc, const void *data, size_t len);
#ifdef USE_SSE42_CRC32C_WITH_RUNTIME_CHECK
extern pg_crc32c pg_comp_crc32c_sse42(pg_crc32c crc, const void *data, size_t len);
#endif
#ifdef USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK
extern pg_crc32c pg_comp_crc32c_armv8(pg_crc32c crc, const void *data, size_t len);
#endif
#else
/*
* Use slicing-by-8 algorithm.