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Improve our method for probing the availability of ARM CRC instructions.

Browse Source 
Instead of depending on glibc's getauxval() function, just try to execute
the CRC code, and trap SIGILL if that happens.

Thomas Munro

Discussion: https://postgr.es/m/HE1PR0801MB1323D171938EABC04FFE7FA9E3110@HE1PR0801MB1323.eurprd08.prod.outlook.com
pull/32/head
Tom Lane 7 years ago
parent 40f52b16dd
commit 1c72ec6f49
4 changed files with 29 additions and 73 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 45
      configure
  2. 21
      configure.in
  3. 3
      src/include/pg_config.h.in
  4. 33
      src/port/pg_crc32c_armv8_choose.c

45
configure vendored
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@ -17344,46 +17344,6 @@ fi
fi
# In order to detect at runtime, if the ARM CRC Extension is available,
# we will do "getauxval(AT_HWCAP) & HWCAP_CRC32". Check if we have
# everything we need for that.
for ac_func in getauxval
do :
ac_fn_c_check_func "$LINENO" "getauxval" "ac_cv_func_getauxval"
if test "x$ac_cv_func_getauxval" = xyes; then :
cat >>confdefs.h <<_ACEOF
#define HAVE_GETAUXVAL 1
_ACEOF
fi
done
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <sys/auxv.h>
#include <asm/hwcap.h>
int
main ()
{
#ifndef AT_HWCAP
#error AT_HWCAP not defined
#endif
#ifndef HWCAP_CRC32
#error HWCAP_CRC32 not defined
#endif
;
return 0;
}
_ACEOF
if ac_fn_c_try_compile "$LINENO"; then :
HAVE_HWCAP_CRC32=1
fi
rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
# Select CRC-32C implementation.
#
# If we are targeting a processor that has Intel SSE 4.2 instructions, we can
@ -17414,9 +17374,8 @@ if test x"$USE_SLICING_BY_8_CRC32C" = x"" && test x"$USE_SSE42_CRC32C" = x"" &&
if test x"$pgac_armv8_crc32c_intrinsics" = x"yes" && test x"$CFLAGS_ARMV8_CRC32C" = x""; then
USE_ARMV8_CRC32C=1
else
# ARM CRC Extension, with runtime check? The getauxval() function and
# HWCAP_CRC32 are needed for the runtime check.
if test x"$pgac_armv8_crc32c_intrinsics" = x"yes" && test x"$ac_cv_func_getauxval" = x"yes" && test x"$HAVE_HWCAP_CRC32" = x"1"; then
# ARM CRC Extension, with runtime check?
if test x"$pgac_armv8_crc32c_intrinsics" = x"yes"; then
USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK=1
else
# fall back to slicing-by-8 algorithm, which doesn't require any

21
configure.in
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@ -2014,22 +2014,6 @@ if test x"$pgac_armv8_crc32c_intrinsics" != x"yes"; then
fi
AC_SUBST(CFLAGS_ARMV8_CRC32C)
# In order to detect at runtime, if the ARM CRC Extension is available,
# we will do "getauxval(AT_HWCAP) & HWCAP_CRC32". Check if we have
# everything we need for that.
AC_CHECK_FUNCS([getauxval])
AC_COMPILE_IFELSE([AC_LANG_PROGRAM([
#include <sys/auxv.h>
#include <asm/hwcap.h>
], [
#ifndef AT_HWCAP
#error AT_HWCAP not defined
#endif
#ifndef HWCAP_CRC32
#error HWCAP_CRC32 not defined
#endif
])], [HAVE_HWCAP_CRC32=1])
# Select CRC-32C implementation.
#
# If we are targeting a processor that has Intel SSE 4.2 instructions, we can
@ -2060,9 +2044,8 @@ if test x"$USE_SLICING_BY_8_CRC32C" = x"" && test x"$USE_SSE42_CRC32C" = x"" &&
if test x"$pgac_armv8_crc32c_intrinsics" = x"yes" && test x"$CFLAGS_ARMV8_CRC32C" = x""; then
USE_ARMV8_CRC32C=1
else
# ARM CRC Extension, with runtime check? The getauxval() function and
# HWCAP_CRC32 are needed for the runtime check.
if test x"$pgac_armv8_crc32c_intrinsics" = x"yes" && test x"$ac_cv_func_getauxval" = x"yes" && test x"$HAVE_HWCAP_CRC32" = x"1"; then
# ARM CRC Extension, with runtime check?
if test x"$pgac_armv8_crc32c_intrinsics" = x"yes"; then
USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK=1
else
# fall back to slicing-by-8 algorithm, which doesn't require any

3
src/include/pg_config.h.in
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@ -239,9 +239,6 @@
/* 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

33
src/port/pg_crc32c_armv8_choose.c
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@ -8,10 +8,6 @@
* computation. Otherwise, fall back to the pure software implementation
* (slicing-by-8).
*
* XXX: The glibc-specific getauxval() function, with the HWCAP_CRC32
* flag, is used to determine if the CRC Extension is available on the
* current platform. Is there a more portable way to determine that?
*
* Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
@ -24,17 +20,38 @@
#include "c.h"
#include <sys/auxv.h>
#include <asm/hwcap.h>
#include <setjmp.h>
#include "libpq/pqsignal.h"
#include "port/pg_crc32c.h"
static sigjmp_buf illegal_instruction_jump;
/*
* Probe by trying to execute pg_comp_crc32c_armv8(). If the instruction
* isn't available, we expect to get SIGILL, which we can trap.
*/
static void
illegal_instruction_handler(int signo)
{
siglongjmp(illegal_instruction_jump, 1);
}
static bool
pg_crc32c_armv8_available(void)
{
unsigned long auxv = getauxval(AT_HWCAP);
uint64 data = 42;
bool result;
pqsignal(SIGILL, illegal_instruction_handler);
if (sigsetjmp(illegal_instruction_jump, 1) == 0)
result = (pg_comp_crc32c_armv8(0, &data, sizeof(data)) == 0xdd439b0d);
else
result = false;
pqsignal(SIGILL, SIG_DFL);
return (auxv & HWCAP_CRC32) != 0;
return result;
}
/*

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