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       1             : // Support for atomic operations -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2004, 2005, 2006, 2008, 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             : /** @file atomicity.h
      26             :  *  This is an internal header file, included by other library headers.
      27             :  *  You should not attempt to use it directly.
      28             :  */
      29             : 
      30             : #ifndef _GLIBCXX_ATOMICITY_H
      31             : #define _GLIBCXX_ATOMICITY_H    1
      32             : 
      33             : #include <bits/c++config.h>
      34             : #include <bits/gthr.h>
      35             : #include <bits/atomic_word.h>
      36             : 
      37             : _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
      38             : 
      39             :   // Functions for portable atomic access.
      40             :   // To abstract locking primitives across all thread policies, use:
      41             :   // __exchange_and_add_dispatch
      42             :   // __atomic_add_dispatch
      43             : #ifdef _GLIBCXX_ATOMIC_BUILTINS_4
      44             :   static inline _Atomic_word 
      45      142524 :   __exchange_and_add(volatile _Atomic_word* __mem, int __val)
      46      142524 :   { return __sync_fetch_and_add(__mem, __val); }
      47             : 
      48             :   static inline void
      49      142524 :   __atomic_add(volatile _Atomic_word* __mem, int __val)
      50      142524 :   { __sync_fetch_and_add(__mem, __val); }
      51             : #else
      52             :   _Atomic_word
      53             :   __attribute__ ((__unused__))
      54             :   __exchange_and_add(volatile _Atomic_word*, int);
      55             : 
      56             :   void
      57             :   __attribute__ ((__unused__))
      58             :   __atomic_add(volatile _Atomic_word*, int);
      59             : #endif
      60             : 
      61             :   static inline _Atomic_word
      62           0 :   __exchange_and_add_single(_Atomic_word* __mem, int __val)
      63             :   {
      64           0 :     _Atomic_word __result = *__mem;
      65           0 :     *__mem += __val;
      66           0 :     return __result;
      67             :   }
      68             : 
      69             :   static inline void
      70           0 :   __atomic_add_single(_Atomic_word* __mem, int __val)
      71           0 :   { *__mem += __val; }
      72             : 
      73             :   static inline _Atomic_word
      74             :   __attribute__ ((__unused__))
      75      142524 :   __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
      76             :   {
      77             : #ifdef __GTHREADS
      78      142524 :     if (__gthread_active_p())
      79      142524 :       return __exchange_and_add(__mem, __val);
      80             :     else
      81           0 :       return __exchange_and_add_single(__mem, __val);
      82             : #else
      83             :     return __exchange_and_add_single(__mem, __val);
      84             : #endif
      85             :   }
      86             : 
      87             :   static inline void
      88             :   __attribute__ ((__unused__))
      89      142524 :   __atomic_add_dispatch(_Atomic_word* __mem, int __val)
      90             :   {
      91             : #ifdef __GTHREADS
      92      142524 :     if (__gthread_active_p())
      93      142524 :       __atomic_add(__mem, __val);
      94             :     else
      95           0 :       __atomic_add_single(__mem, __val);
      96             : #else
      97             :     __atomic_add_single(__mem, __val);
      98             : #endif
      99      142524 :   }
     100             : 
     101             : _GLIBCXX_END_NAMESPACE
     102             : 
     103             : // Even if the CPU doesn't need a memory barrier, we need to ensure
     104             : // that the compiler doesn't reorder memory accesses across the
     105             : // barriers.
     106             : #ifndef _GLIBCXX_READ_MEM_BARRIER
     107             : #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
     108             : #endif
     109             : #ifndef _GLIBCXX_WRITE_MEM_BARRIER
     110             : #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
     111             : #endif
     112             : 
     113             : #endif