atomic_word.h revision 296373
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