[Patch] Use __GCC_HAVE_SYNC_COMPARE_AND_SWAP_*

[Paolo Carlini]

Peter Dimov wrote:

>> I see. In fact, as you may remember, I have been asking for an
>> infrastructure providing an emulation layer transparent to the users
>> for *years*...
>
> I understand, but isn't the infrastructure now almost in place? The 
> compiler support is present; is it not just the library support that 
> is missing?

I wish I could share your optimism :-) These issues are nasty, very 
nasty, given all the requirements. Please have a look to the past 
exchanges on the lists: people came to the conclusion that the only 
satisfactory and complete solution are multilibs. And that would not 
solve the statically linked case. Well, if you have a complete solution 
ready fullfilling all those requirements, just post it ;)

>> common and old Sparcs less and less common, I'm not sure the effort
>> still makes sense...
>
> Now, mid of 2007, with x86_64 becoming more and more
>
> I wish I could share your optimism. :-) Sadly, 386 is as rare as an 
> architecture can be, and 486 is as common as possible, and yet we 
> still have i386 as the default.

I know we have i386 as default, and that's why the builtin macros are 
useful. But new machines, all the machines we really care about of the 
"x86" family are 64-bits and in that case we finally have the atomic 
builtins as default.

Paolo.