1// Low-level type for atomic operations -*- C++ -*-
2
3// Copyright (C) 2004, 2005, 2006, 2007 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 2, 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// You should have received a copy of the GNU General Public License along
17// with this library; see the file COPYING.  If not, write to the Free
18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19// USA.
20
21// As a special exception, you may use this file as part of a free software
22// library without restriction.  Specifically, if other files instantiate
23// templates or use macros or inline functions from this file, or you compile
24// this file and link it with other files to produce an executable, this
25// file does not by itself cause the resulting executable to be covered by
26// the GNU General Public License.  This exception does not however
27// invalidate any other reasons why the executable file might be covered by
28// the GNU General Public License.
29
30#ifndef _GLIBCXX_ATOMIC_WORD_H
31#define _GLIBCXX_ATOMIC_WORD_H	1
32
33#include <bits/cxxabi_tweaks.h>
34
35typedef int _Atomic_word;
36
37namespace __gnu_cxx
38{
39  // Test the first byte of __g and ensure that no loads are hoisted across
40  // the test.
41  inline bool
42  __test_and_acquire (__cxxabiv1::__guard *__g)
43  {
44    unsigned char __c;
45    unsigned char *__p = reinterpret_cast<unsigned char *>(__g);
46    // ldN.acq is a load with an implied hoist barrier.
47    // would ld8+mask be faster than just doing an ld1?
48    __asm __volatile ("ld1.acq %0 = %1" : "=r"(__c) : "m"(*__p) : "memory");
49    return __c != 0;
50  }
51
52  // Set the first byte of __g to 1 and ensure that no stores are sunk
53  // across the store.
54  inline void
55  __set_and_release (__cxxabiv1::__guard *__g)
56  {
57    unsigned char *__p = reinterpret_cast<unsigned char *>(__g);
58    // stN.rel is a store with an implied sink barrier.
59    // could load word, set flag, and CAS it back
60    __asm __volatile ("st1.rel %0 = %1" : "=m"(*__p) : "r"(1) : "memory");
61  }
62
63  // We don't define the _BARRIER macros on ia64 because the barriers are
64  // included in the test and set, above.
65#define _GLIBCXX_GUARD_TEST_AND_ACQUIRE(G) __gnu_cxx::__test_and_acquire (G)
66#define _GLIBCXX_GUARD_SET_AND_RELEASE(G) __gnu_cxx::__set_and_release (G)
67}
68
69#endif
70