IIUC value objects can have any size, it's just that 'reference flattening' requires the object to fit into a machine word. But this is only due to how Java represents object references and its atomicity guarantees.

Naturally, a language that properly supports value semantics does not have any of these limitations.

I don’t understand this comment - the .NET CLR supports arbitrarily large value types. Are you referring to something like “atomic flattening of those types” instead? Because the CLR doesn’t guarantee that, and therefore supports flattening.

We've had MMX for a while now, I don't think we need to wait much longer.

I don't really see why you would need specific hardware to express a type in a programming language, though.

But if I don't care for object atomicity, can I get struct-like behaviour in Java for arbitrary large types?