This should be a suite of intrinsics. It's the same mistake as "register" storage, a layer violation, the actual mechanics bleeding through into the abstract machine and making an unholy mess.

If you had intrinsics it's obvious where the platform specific behaviour lives. Can we "just" do unaligned 32-bit stores to MMIO? Can we "just" write one bit of a hardware register? It depends on your platform and so as an intrinsic it's obvious how to reflect this, whereas for a type qualifier we have no idea what the compiler did and the ISO document of course has to be vague to be inclusive of everybody.