RFR: 8330465: Stable Values and Collections (Internal) [v5]

[Per Minborg]

On Wed, 15 May 2024 16:26:57 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Switch to monomorphic StableValue and use lazy arrays
>
> src/java.base/share/classes/jdk/internal/lang/stable/StableValueImpl.java line 75:
> 
>> 73:      */
>> 74:     @Stable
>> 75:     private int state;
> 
> Can we change this to be a byte, so state and supplying fields can be packed together in 4 bytes in some layouts?

We had `byte` before but converted to `int` as the `byte` will get promoted to an `int` anyhow in the code logic. However, one idea would be to go back to using a `byte` again and also use a `byte` for the flag of computation invocation. This would reduce the footprint for these two fields from 8 bytes to 2 bytes.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18794#discussion_r1602800304