1// Low-level type for atomic operations -*- C++ -*-
2
3// Copyright (C) 2004, 2005, 2006, 2007, 2009 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25#ifndef _GLIBCXX_ATOMIC_WORD_H
26#define _GLIBCXX_ATOMIC_WORD_H	1
27
28#include <bits/cxxabi_tweaks.h>
29
30typedef int _Atomic_word;
31
32namespace __gnu_cxx
33{
34  // Test the first byte of __g and ensure that no loads are hoisted across
35  // the test.
36  inline bool
37  __test_and_acquire (__cxxabiv1::__guard *__g)
38  {
39    unsigned char __c;
40    unsigned char *__p = reinterpret_cast<unsigned char *>(__g);
41    // ldN.acq is a load with an implied hoist barrier.
42    // would ld8+mask be faster than just doing an ld1?
43    __asm __volatile ("ld1.acq %0 = %1" : "=r"(__c) : "m"(*__p) : "memory");
44    return __c != 0;
45  }
46
47  // Set the first byte of __g to 1 and ensure that no stores are sunk
48  // across the store.
49  inline void
50  __set_and_release (__cxxabiv1::__guard *__g)
51  {
52    unsigned char *__p = reinterpret_cast<unsigned char *>(__g);
53    // stN.rel is a store with an implied sink barrier.
54    // could load word, set flag, and CAS it back
55    __asm __volatile ("st1.rel %0 = %1" : "=m"(*__p) : "r"(1) : "memory");
56  }
57
58  // We don't define the _BARRIER macros on ia64 because the barriers are
59  // included in the test and set, above.
60#define _GLIBCXX_GUARD_TEST_AND_ACQUIRE(G) __gnu_cxx::__test_and_acquire (G)
61#define _GLIBCXX_GUARD_SET_AND_RELEASE(G) __gnu_cxx::__set_and_release (G)
62}
63
64#endif
65