using atomic builtins

[Paolo Carlini]

Benjamin Kosnik wrote:

>One approach to using the atomic builtins would be to have a compile
>error/warning if these atomic builtins could not be used.
>
... and if you search a bit the mailing lists, certainly we discussed a 
bit the usefulness of adding a builtin macro providing exactly that 
info. if we cannot change the default i?86 target, that would be 
definitely very usuful. At some point, I think Richard Guenther even 
posted a patch essentially complete, then I don't know what happened...

Paolo.