Andres Freund <andres@2ndquadrant.com> writes:
> On 2014-09-24 18:55:51 +0300, Heikki Linnakangas wrote:
>> There doesn't seem to be any hardware implementations of that in the patch.
>> Is there any architecture that has an instruction or compiler intrinsic for
>> that?
> You can implement it rather efficiently on ll/sc architectures. But I
> don't really think it matters. I prefer add_until (I've seen it named
> saturated add before as well) to live in the atomics code, rather than
> reimplement it in atomics employing code. I guess you see that
> differently?
I think the question is more like "what in the world happened to confining
ourselves to a small set of atomics". I doubt either that this exists
natively anywhere, or that it's so useful that we should expect platforms
to have efficient implementations.
regards, tom lane