From 5b57eff9b880698022432c1916cf6c852844734a Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@pdimov.com>
Date: Tue, 8 May 2007 20:14:38 +0000
Subject: [PATCH] atomic_count_gcc_x86 added since _sync doesn't work on i386

[SVN r37637]
---
 include/boost/detail/atomic_count.hpp         | 14 ++++
 include/boost/detail/atomic_count_gcc_x86.hpp | 84 +++++++++++++++++++
 2 files changed, 98 insertions(+)
 create mode 100644 include/boost/detail/atomic_count_gcc_x86.hpp

diff --git a/include/boost/detail/atomic_count.hpp b/include/boost/detail/atomic_count.hpp
index 823b929..804fd1a 100644
--- a/include/boost/detail/atomic_count.hpp
+++ b/include/boost/detail/atomic_count.hpp
@@ -90,16 +90,30 @@ typedef long atomic_count;
 }
 
 #elif defined(BOOST_AC_USE_PTHREADS)
+
 #  include <boost/detail/atomic_count_pthreads.hpp>
+
+#elif defined( __GNUC__ ) && ( defined( __i386__ ) || defined( __x86_64__ ) )
+
+# include <boost/detail/atomic_count_gcc_x86.hpp>
+
 #elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
+
 #  include <boost/detail/atomic_count_win32.hpp>
+
 #elif defined( __GNUC__ ) && ( __GNUC__ * 100 + __GNUC_MINOR__ >= 401 )
+
 #  include <boost/detail/atomic_count_sync.hpp>
+
 #elif defined(__GLIBCPP__) || defined(__GLIBCXX__)
+
 #  include <boost/detail/atomic_count_gcc.hpp>
+
 #elif defined(BOOST_HAS_PTHREADS)
+
 #  define BOOST_AC_USE_PTHREADS
 #  include <boost/detail/atomic_count_pthreads.hpp>
+
 #else
 
 // Use #define BOOST_DISABLE_THREADS to avoid the error
diff --git a/include/boost/detail/atomic_count_gcc_x86.hpp b/include/boost/detail/atomic_count_gcc_x86.hpp
new file mode 100644
index 0000000..1312e8c
--- /dev/null
+++ b/include/boost/detail/atomic_count_gcc_x86.hpp
@@ -0,0 +1,84 @@
+#ifndef BOOST_DETAIL_ATOMIC_COUNT_GCC_X86_HPP_INCLUDED
+#define BOOST_DETAIL_ATOMIC_COUNT_GCC_X86_HPP_INCLUDED
+
+//
+//  boost/detail/atomic_count_gcc_x86.hpp
+//
+//  atomic_count for g++ on 486+/AMD64
+//
+//  Copyright 2007 Peter Dimov
+//
+//  Distributed under the Boost Software License, Version 1.0. (See
+//  accompanying file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+
+namespace boost
+{
+
+namespace detail
+{
+
+class atomic_count
+{
+public:
+
+    explicit atomic_count( long v ) : value_( static_cast< int >( v ) ) {}
+
+    void operator++()
+    {
+        __asm__
+        (
+            "lock\n\t"
+            "incl %0":
+            "+m"( value_ ): // output (%0)
+            : // inputs
+            "cc" // clobbers
+        );
+    }
+
+    long operator--()
+    {
+        return atomic_exchange_and_add( &value_, -1 ) - 1;
+    }
+
+    operator long() const
+    {
+        return atomic_exchange_and_add( &value_, 0 );
+    }
+
+private:
+
+    atomic_count(atomic_count const &);
+    atomic_count & operator=(atomic_count const &);
+
+    mutable int value_;
+
+private:
+
+    static int atomic_exchange_and_add( int * pw, int dv )
+    {
+        // int r = *pw;
+        // *pw += dv;
+        // return r;
+
+        int r;
+
+        __asm__ __volatile__
+        (
+            "lock\n\t"
+            "xadd %1, %0":
+            "+m"( *pw ), "=r"( r ): // outputs (%0, %1)
+            "1"( dv ): // inputs (%2 == %1)
+            "memory", "cc" // clobbers
+        );
+
+        return r;
+    }
+};
+
+} // namespace detail
+
+} // namespace boost
+
+#endif // #ifndef BOOST_DETAIL_ATOMIC_COUNT_SYNC_HPP_INCLUDED