Atomics

[Alejandro (Alejandro Alonso)]

@Joe_Groff

It also seems to me that the proposal introduces the DoubleWord type primarily as a place to hang DoubleWord.AtomicRepresentation, and it wouldn't need to exist otherwise if you could refer to AtomicStorage64/128 independent of a type (though I could see wanting to have a portable AtomicStorageDoubleWord type to refer to the current target's double-word atomic storage type portably).

DoubleWord was introduced as a portable name, yes. Even if we had just AtomicStorageDoubleWord as the portable AtomicStorage, we'd still need a type for the AtomicValue conformance for use with Atomic. We can make the storage itself conform to AtomicValue, but Atomic<AtomicStorageDoubleWord> doesn't roll off the tongue.