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

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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
This commit is contained in:
Tom Lane 2018-05-02 18:06:43 -04:00
parent 40f52b16dd
commit 1c72ec6f49
4 changed files with 29 additions and 73 deletions
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45
configure vendored
View File

@ -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
View File

@ -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
View File

@ -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
View File

@ -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;
return (auxv & HWCAP_CRC32) != 0;
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 result;
}
/*