RFR: JDK-8232806: The LambdaMetaFactory eagerly initializes generated lambdas

[Brian Goetz]

The patch seems suitably minimal to me to meet the goals and not cause 
difficulty for future evolution of LMF (for which we have some plans, 
once some other VM work finishes up.)   Essentially, the 
disable-eager-initialization case disables the caching optimization for 
non-capturing lambdas, and we then just revert to the main 
lambda-capture path, which makes this fairly low risk.



On 10/28/2019 2:10 PM, Vojin Jovanovic wrote:
> Hi all,
>
> This email proposes a change to the LambdaMetaFactory that allows to disable eager initialization (with Unsafe) of generated lambdas. This is needed by the GraalVM Native Image, as initialization of lambdas during AOT compilation breaks our heap snapshotting (via initialization of interfaces with default methods that are super-types of a lambda). We have started from the original proposal that stores lambda instances in the static fields
>
>    https://github.com/graalvm/labs-openjdk-11/commit/00b9ecd85dedd0411837eee33635dd83e8b7def8
>
> and initializes them with Unsafe as an optimization
>
>     https://github.com/graalvm/labs-openjdk-11/commit/273e8590a7b57c0c10d9213ca9e0ba581e2817b8
>
> After the discussion with Brian Goetz, we have trimmed down to the following change:
>
>    https://bugs.openjdk.java.net/secure/attachment/85247/lambda-disable-initialization.diff
>
> The evolution of this change can be found at the issue:
>
>   https://bugs.openjdk.java.net/browse/JDK-8232806
>   
> Cheers,
> - Vojin