ceph/src/boost/libs/smart_ptr/include/boost/smart_ptr/detail/atomic_count_gcc_x86.hpp

   1 #ifndef BOOST_SMART_PTR_DETAIL_ATOMIC_COUNT_GCC_X86_HPP_INCLUDED
   2 #define BOOST_SMART_PTR_DETAIL_ATOMIC_COUNT_GCC_X86_HPP_INCLUDED
   3
   4 //
   5 //  boost/detail/atomic_count_gcc_x86.hpp
   6 //
   7 //  atomic_count for g++ on 486+/AMD64
   8 //
   9 //  Copyright 2007 Peter Dimov
  10 //
  11 //  Distributed under the Boost Software License, Version 1.0. (See
  12 //  accompanying file LICENSE_1_0.txt or copy at
  13 //  http://www.boost.org/LICENSE_1_0.txt)
  14 //
  15
  16 namespace boost
  17 {
  18
  19 namespace detail
  20 {
  21
  22 class atomic_count
  23 {
  24 public:
  25
  26     explicit atomic_count( long v ) : value_( static_cast< int >( v ) ) {}
  27
  28     long operator++()
  29     {
  30         return atomic_exchange_and_add( &value_, +1 ) + 1;
  31     }
  32
  33     long operator--()
  34     {
  35         return atomic_exchange_and_add( &value_, -1 ) - 1;
  36     }
  37
  38     operator long() const
  39     {
  40         return atomic_exchange_and_add( &value_, 0 );
  41     }
  42
  43 private:
  44
  45     atomic_count(atomic_count const &);
  46     atomic_count & operator=(atomic_count const &);
  47
  48     mutable int value_;
  49
  50 private:
  51
  52     static int atomic_exchange_and_add( int * pw, int dv )
  53     {
  54         // int r = *pw;
  55         // *pw += dv;
  56         // return r;
  57
  58         int r;
  59
  60         __asm__ __volatile__
  61         (
  62             "lock\n\t"
  63             "xadd %1, %0":
  64             "+m"( *pw ), "=r"( r ): // outputs (%0, %1)
  65             "1"( dv ): // inputs (%2 == %1)
  66             "memory", "cc" // clobbers
  67         );
  68
  69         return r;
  70     }
  71 };
  72
  73 } // namespace detail
  74
  75 } // namespace boost
  76
  77 #endif // #ifndef BOOST_SMART_PTR_DETAIL_ATOMIC_COUNT_GCC_X86_HPP_INCLUDED