Fixing core.atomic

[Max Haughton]

On Wednesday, 2 June 2021 at 15:30:46 UTC, Ola Fosheim Grøstad 
wrote:
> On Wednesday, 2 June 2021 at 15:19:59 UTC, Ola Fosheim Grøstad 
> wrote:
>> On Wednesday, 2 June 2021 at 15:09:54 UTC, rm wrote:
>>> inc/dec are implemented in terms of fetch_add.
>>
>> IIRC some architectures provide more efficient inc/dec atomics 
>> without fetch? I haven't looked at that in years, so I have no 
>> idea what the contemporary situation is.
>
> No, I think that was wrong, I think they usually return the 
> original value (or set a flag or whatever). But it doesn't 
> matter. We should just look at what the common contemporary 
> processors provide and look at instructions per clock cycles 
> throughput. I guess last generation ARM/Intel/AMD is sufficient?

Are they always fixed latency? No dependence on the load store 
queue state (etc.)  for example?