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 
atomic_count(long v)26     explicit atomic_count( long v ) : value_( static_cast< int >( v ) ) {}
27 
operator ++()28     long operator++()
29     {
30         return atomic_exchange_and_add( &value_, +1 ) + 1;
31     }
32 
operator --()33     long operator--()
34     {
35         return atomic_exchange_and_add( &value_, -1 ) - 1;
36     }
37 
operator long() const38     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 
atomic_exchange_and_add(int * pw,int dv)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
78