X-Git-Url: https://git.lyx.org/gitweb/?a=blobdiff_plain;f=boost%2Fboost%2Fmemory_order.hpp;h=4945af623b265a3f298d261038202235200e5079;hb=43c09d723435a5b203f2ac0c39e2086de836b386;hp=2524e8aa43c4cfeb4965e96aa01335df4580e045;hpb=c2f99181e60c3b92ddeed85a5910ac856d155810;p=lyx.git

diff --git a/boost/boost/memory_order.hpp b/boost/boost/memory_order.hpp
index 2524e8aa43..4945af623b 100755
--- a/boost/boost/memory_order.hpp
+++ b/boost/boost/memory_order.hpp
@@ -11,7 +11,7 @@
 //
 //  Defines enum boost::memory_order per the C++0x working draft
 //
-//  Copyright (c) 2008 Peter Dimov
+//  Copyright (c) 2008, 2009 Peter Dimov
 //
 //  Distributed under the Boost Software License, Version 1.0.
 //  See accompanying file LICENSE_1_0.txt or copy at
@@ -21,13 +21,31 @@
 namespace boost
 {
 
+//
+// Enum values are chosen so that code that needs to insert
+// a trailing fence for acquire semantics can use a single
+// test such as:
+//
+// if( mo & memory_order_acquire ) { ...fence... }
+//
+// For leading fences one can use:
+//
+// if( mo & memory_order_release ) { ...fence... }
+//
+// Architectures such as Alpha that need a fence on consume
+// can use:
+//
+// if( mo & ( memory_order_acquire | memory_order_consume ) ) { ...fence... }
+//
+
 enum memory_order
 {
     memory_order_relaxed = 0,
     memory_order_acquire = 1,
     memory_order_release = 2,
     memory_order_acq_rel = 3, // acquire | release
-    memory_order_seq_cst = 7  // acq_rel | 4
+    memory_order_seq_cst = 7, // acq_rel | 4
+    memory_order_consume = 8
 };
 
 } // namespace boost