Call for compiler help/advice: atomic builtins for v3

[Paolo Carlini]

Richard Guenther wrote:
> We could just provide fallback libcalls in libgcc
Indeed, this is an option. Not one I can implement myself quickly, but I 
think the idea of issuing a library call when the builtin is not 
available was actually meant to enable this kind of solution.

Can you work on it?
>  - though usually you
> would want a fallback on a higher level to avoid too much overhead.
>   
Well, we are talking about i386... But yes, that could make sense, for 
example if you want to compile once both for i386 and i686 and obtain 
decent performance everywhere. Consider, however, that currently we end 
up doing a function call anyway, no inlining, so...
> So - can't you work with some preprocessor magic and a define, if
> the builtins are available?
>   
I don't really understand this last remark of yours: is it an alternate 
solution?!? Any preprocessor magic has to rely on a new preprocessor 
builtin, in case, because there is no consistent, unequivocal way to 
know whether the builtins are available for the  actual target, we 
already explored that some time ago, in our (SUSE) gcc-development list too.

Paolo.