Encodings for flattened heap values

Without reading the whole thing, and with modern C# in mind - would that be "auto-struct" of a Java-class, without say so explicitly?

Whenever I read about Project Valhalla, I'm always struck by how many of the usual approaches are somehow excluded due to ... the way the JVM has historically worked? Why is that even a concern when you're adding new features entirely?

The one that jumps out most in this post is that apparently it's considered impossible to write to just-allocated memory before transferring control to user code. Preserving the all-zero-means-null rule means that `T`, `Optional<T>`, `Optional<Optional<T>>`, etc. cannot just use a nop conversion when the value (at any level!) is present.

Some discussion of `cmpxchg16b` really should be in there. I know why it's not suitable but it's wrong to claim that only vector registers support wide atomics.

Structs. These are called structs. Or value types if you really insist.

Why is the header text flattened?