libstdc++-v3/config/cpu/i386/atomicity.h

   1 // Low-level functions for atomic operations: x86, x >= 3 version  -*- C++ -*-
   2
   3 // Copyright (C) 2003 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  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_ATOMICITY_H
  31 #define _GLIBCXX_ATOMICITY_H    1
  32
  33 typedef int _Atomic_word;
  34
  35 template<int __inst>
  36   struct __Atomicity_lock
  37   {
  38     static volatile _Atomic_word _S_atomicity_lock;
  39   };
  40
  41 template<int __inst>
  42 volatile _Atomic_word __Atomicity_lock<__inst>::_S_atomicity_lock = 0;
  43
  44 template volatile _Atomic_word __Atomicity_lock<0>::_S_atomicity_lock;
  45
  46 static inline _Atomic_word
  47 __attribute__ ((__unused__))
  48 __exchange_and_add(volatile _Atomic_word* __mem, int __val)
  49 {
  50   register _Atomic_word __result, __tmp = 1;
  51
  52   /* obtain the atomic exchange/add spin lock */
  53   do {
  54     __asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}"
  55                           : "+m" (__Atomicity_lock<0>::_S_atomicity_lock),
  56                             "+r" (__tmp));
  57   } while (__tmp);
  58
  59   __result = *__mem;
  60   *__mem += __val;
  61
  62   /* release spin lock */
  63   __Atomicity_lock<0>::_S_atomicity_lock = 0;
  64
  65   return __result;
  66 }
  67
  68 static inline void
  69 __attribute__ ((__unused__))
  70 __atomic_add(volatile _Atomic_word* __mem, int __val)
  71 {
  72   __exchange_and_add(__mem, __val);
  73 }
  74
  75 #endif /* atomicity.h */