RFR: 8230482: Initial support for empty inline classes

[Ioi Lam]

Hi Fred,

The changes look good to me.

1549   const int total_fields = length + num_injected + (is_value_type ? 
2 : 0);

Maybe add a comment what the "2" means?

Also, I think it will be good to add a Java reflection test to query the 
fields in
EmptyValue, to make sure zero fields are returned.

Thanks
- Ioi


On 9/4/19 9:28 AM, Frederic Parain wrote:
> Remi, Ioi,
>
> Here’s a new webrev with the new tests added:
>
> http://cr.openjdk.java.net/~fparain/emptyvalue/webrev.01/
>
> On a 64bits platform with compressed oops, the layout of
> the WithEmptyField class is:
>
> Layout of class runtime/valhalla/valuetypes/EmptyValueTest$WithEmptyField
> | offset | kind | size | alignment | signature | name |
> Instance fields:
>    0 RESERVED 12
>    12 INHERITED 4
>    16 FLATTENED 1 1 Qruntime/valhalla/valuetypes/EmptyValueTest$EmptyValue; empty
>    17 EMPTY 3
>    20 REGULAR 4 4 Ljava/lang/Object; o
>
> The inherited field at offset 12 being the int field from the super class.
>
> Thank you,
>
> Fred
>
>
>> On Sep 3, 2019, at 11:41, Ioi Lam <ioi.lam at oracle.com> wrote:
>>
>> Maybe we should also have some System.arraycopy() tests?
>>
>> Thanks
>> - Ioi
>>
>> On 9/3/19 8:29 AM, Remi Forax wrote:
>>> Hi Frederic,
>>> i think you can add a test where an empty inline object is used as field in the middle of several fields
>>> (perhaps using inheritance to be sure of the layout ?).
>>>
>>> Rémi
>>>
>>> ----- Mail original -----
>>>> De: "Frederic Parain" <frederic.parain at oracle.com>
>>>> À: "valhalla-dev" <valhalla-dev at openjdk.java.net>
>>>> Envoyé: Mardi 3 Septembre 2019 16:24:08
>>>> Objet: RFR: 8230482: Initial support for empty inline classes
>>>> Greetings,
>>>>
>>>> Please review this code that adds initial support for empty inline classes.
>>>>
>>>> CR: https://bugs.openjdk.java.net/browse/JDK-8230482
>>>> Webrev: http://cr.openjdk.java.net/~fparain/emptyvalue/webrev.00/index.html
>>>>
>>>> Thank you,
>>>>
>>>> Fred