consolidated VM notes for primitive classes

[Peter Levart]

On 4/27/21 4:17 PM, Peter Levart wrote:
> Hi,
>
> I just noticed the following statement in the presented document:
>
> > If a primitive object is composed of a combination of scalars and 
> references to identity objects, the problem is less hopeless, though 
> still complicated. A primitive object becomes unreachable (in the 
> modified definition of the previous paragraph) if and only if at least 
> one of its component identity object references becomes unreachable.
>
> If this did see an implementation in the VM, we would essentially get 
> muti-referent Ephemeron(s) out of it. Not very easy to implement though.


Sorry, this is not correct. The rules for Ephemeron(s) are different. If 
primitive object became unreachable when all of its component identity 
object references became unreachable, then we would get Ephemeron. The 
rules in the document (at least one) are easier to implement.

Peter


>
>
> Regards, Peter
>
>
> On 4/21/21 8:51 AM, John Rose wrote:
>> Brian and I hammered out a document this week that
>> captures what we think is emerging as our shared
>> understanding of how adapt the JVM to support
>> primitive classes.
>>
>> It is still white-hot, not even off the press, but I think
>> it is worth looking it even in its unfinished state.
>>
>> https://github.com/openjdk/valhalla-docs/blob/main/site/design-notes/state-of-valhalla/03-vm-model.md 
>> <https://github.com/openjdk/valhalla-docs/blob/main/site/design-notes/state-of-valhalla/03-vm-model.md> 
>>
>>
>> That is the JVM side, only.  Most of it is already
>> prototyped in HotSpot, some is not.
>>
>> I’ll let Brian speak for the valhalla-doc repository
>> as a whole, but I wanted to get this out there for
>> tomorrow’s meeting.
>>
>> — John