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Use __sync_lock_test_and_set() for spinlocks on ARM, if available.

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Historically we've used the SWPB instruction for TAS() on ARM, but this
is deprecated and not available on ARMv6 and later.  Instead, make use
of a GCC builtin if available.  We'll still fall back to SWPB if not,
so as not to break existing ports using older GCC versions.

Eventually we might want to try using __sync_lock_test_and_set() on some
other architectures too, but for now that seems to present only risk and
not reward.

Back-patch to all supported versions, since people might want to use any
of them on more recent ARM chips.

Martin Pitt
This commit is contained in:
Tom Lane
2012-01-07 15:38:52 -05:00
parent 1fc3d18faa
commit 0a41e86584
4 changed files with 102 additions and 2 deletions
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65
configure vendored
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@ -22596,6 +22596,71 @@ fi
done
{ $as_echo "$as_me:$LINENO: checking for builtin locking functions" >&5
$as_echo_n "checking for builtin locking functions... " >&6; }
if test "${pgac_cv_gcc_int_atomics+set}" = set; then
$as_echo_n "(cached) " >&6
else
cat >conftest.$ac_ext <<_ACEOF
/* confdefs.h. */
_ACEOF
cat confdefs.h >>conftest.$ac_ext
cat >>conftest.$ac_ext <<_ACEOF
/* end confdefs.h. */
int
main ()
{
int lock = 0;
__sync_lock_test_and_set(&lock, 1);
__sync_lock_release(&lock);
;
return 0;
}
_ACEOF
rm -f conftest.$ac_objext conftest$ac_exeext
if { (ac_try="$ac_link"
case "(($ac_try" in
*\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
*) ac_try_echo=$ac_try;;
esac
eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
$as_echo "$ac_try_echo") >&5
(eval "$ac_link") 2>conftest.er1
ac_status=$?
grep -v '^ *+' conftest.er1 >conftest.err
rm -f conftest.er1
cat conftest.err >&5
$as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
(exit $ac_status); } && {
test -z "$ac_c_werror_flag" ||
test ! -s conftest.err
} && test -s conftest$ac_exeext && {
test "$cross_compiling" = yes ||
$as_test_x conftest$ac_exeext
}; then
pgac_cv_gcc_int_atomics="yes"
else
$as_echo "$as_me: failed program was:" >&5
sed 's/^/| /' conftest.$ac_ext >&5
pgac_cv_gcc_int_atomics="no"
fi
rm -rf conftest.dSYM
rm -f core conftest.err conftest.$ac_objext conftest_ipa8_conftest.oo \
conftest$ac_exeext conftest.$ac_ext
fi
{ $as_echo "$as_me:$LINENO: result: $pgac_cv_gcc_int_atomics" >&5
$as_echo "$pgac_cv_gcc_int_atomics" >&6; }
if test x"$pgac_cv_gcc_int_atomics" = x"yes"; then
cat >>confdefs.h <<\_ACEOF
#define HAVE_GCC_INT_ATOMICS 1
_ACEOF
fi
#
# Pthreads