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Use Intel SSE 4.2 CRC instructions where available.

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Modern x86 and x86-64 processors with SSE 4.2 support have special
instructions, crc32b and crc32q, for calculating CRC-32C. They greatly
speed up CRC calculation.

Whether the instructions can be used or not depends on the compiler and the
target architecture. If generation of SSE 4.2 instructions is allowed for
the target (-msse4.2 flag on gcc and clang), use them. If they are not
allowed by default, but the compiler supports the -msse4.2 flag to enable
them, compile just the CRC-32C function with -msse4.2 flag, and check at
runtime whether the processor we're running on supports it. If it doesn't,
fall back to the slicing-by-8 algorithm. (With the common defaults on
current operating systems, the runtime-check variant is what you get in
practice.)

Abhijit Menon-Sen, heavily modified by me, reviewed by Andres Freund.
This commit is contained in:
Heikki Linnakangas
2015-04-14 17:05:03 +03:00
parent 4f700bcd20
commit 3dc2d62d04
11 changed files with 534 additions and 5 deletions
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27
config/c-compiler.m4
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@ -473,3 +473,30 @@ AC_DEFUN([PGAC_HAVE_GCC__ATOMIC_INT64_CAS],
if test x"$pgac_cv_gcc_atomic_int64_cas" = x"yes"; then
AC_DEFINE(HAVE_GCC__ATOMIC_INT64_CAS, 1, [Define to 1 if you have __atomic_compare_exchange_n(int64 *, int *, int64).])
fi])# PGAC_HAVE_GCC__ATOMIC_INT64_CAS
# PGAC_SSE42_CRC32_INTRINSICS
# -----------------------
# Check if the compiler supports _mm_crc32_u8 and _mm_crc32_u64 intrinsics.
# An optional compiler flag can be passed as argument (e.g. -msse4.2). If the
# intrinsics are supported, sets pgac_sse42_crc32_intrinsics, and CFLAGS_SSE42.
AC_DEFUN([PGAC_SSE42_CRC32_INTRINSICS],
[define([Ac_cachevar], [AS_TR_SH([pgac_cv_sse42_crc32_intrinsics_$1])])dnl
AC_CACHE_CHECK([for _mm_crc32_u8 and _mm_crc32_u64 with CFLAGS=$1], [Ac_cachevar],
[pgac_save_CFLAGS=$CFLAGS
CFLAGS="$pgac_save_CFLAGS $1"
ac_save_c_werror_flag=$ac_c_werror_flag
ac_c_werror_flag=yes
AC_TRY_LINK([#include <nmmintrin.h>],
[unsigned int crc = 0;
crc = _mm_crc32_u8(crc, 0);
crc = (unsigned int) _mm_crc32_u64(crc, 0);],
[Ac_cachevar=yes],
[Ac_cachevar=no])
ac_c_werror_flag=$ac_save_c_werror_flag
CFLAGS="$pgac_save_CFLAGS"])
if test x"$Ac_cachevar" = x"yes"; then
CFLAGS_SSE42="$1"
pgac_sse42_crc32_intrinsics=yes
fi
undefine([Ac_cachevar])dnl
])# PGAC_SSE42_CRC32_INTRINSICS