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// Low-level functions for atomic operations: x86, x >= 3 version -*- C++ -*-
// Copyright (C) 2003-2022 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
#include <ext/atomicity.h>
namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
template<int __inst>
struct _Atomicity_lock
{
static volatile _Atomic_word _S_atomicity_lock;
};
template<int __inst>
volatile _Atomic_word _Atomicity_lock<__inst>::_S_atomicity_lock = 0;
template volatile _Atomic_word _Atomicity_lock<0>::_S_atomicity_lock;
_Atomic_word
__attribute__ ((__unused__))
__exchange_and_add(volatile _Atomic_word* __mem, int __val) throw ()
{
register _Atomic_word __result, __tmp = 1;
// Obtain the atomic exchange/add spin lock.
do
{
__asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}"
: "=m" (_Atomicity_lock<0>::_S_atomicity_lock),
"+r" (__tmp)
: "m" (_Atomicity_lock<0>::_S_atomicity_lock));
}
while (__tmp);
__result = *__mem;
*__mem += __val;
// Release spin lock.
_Atomicity_lock<0>::_S_atomicity_lock = 0;
return __result;
}
void
__attribute__ ((__unused__))
__atomic_add(volatile _Atomic_word* __mem, int __val) throw ()
{ __exchange_and_add(__mem, __val); }
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
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