volatile qualifier hurts single-threaded optimized case

[Paolo Carlini]

Sorry Benjamin,

one minor nit, unrelated to the other issue:

>Index: config/abi/pre/gnu.ver
>===================================================================
>--- config/abi/pre/gnu.ver	(revision 116581)
>+++ config/abi/pre/gnu.ver	(working copy)
>@@ -378,8 +378,8 @@
> 
>     # __gnu_cxx::__atomic_add
>     # __gnu_cxx::__exchange_and_add
>-    _ZN9__gnu_cxx12__atomic_add*;
>-    _ZN9__gnu_cxx18__exchange_and_add*;
>+    _ZN9__gnu_cxx12__atomic_addEPVii;
>+    _ZN9__gnu_cxx18__exchange_and_addEPVii;
>
are you sure that signature is always ok? I mean, in atomic_word.h for 
Sparc we have:

#ifdef __arch64__
  typedef long _Atomic_word;
#else
  typedef int _Atomic_word;
#endif

Paolo.