RFR: 8255883: Avoid multiple GeneratedMethodAccessor for same NativeMethod… [v5]

[Hui Shi]

On Wed, 11 Nov 2020 19:12:08 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Hui Shi has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.
>
> src/java.base/share/classes/jdk/internal/reflect/NativeConstructorAccessorImpl.java line 44:
> 
>> 42:     private DelegatingConstructorAccessorImpl parent;
>> 43:     private int numInvocations;
>> 44:     private int generated;
> 
> What is the reason for using an int? I remember there was a suggestion for three states but two states seems okay so curious why it was changed from boolean to int.
> The restoring to 0 in the event of failure should probably be a volatile-write. Might be clearer to declare it as a volatile.

@AlanBateman 

> What is the reason for using an int? I remember there was a suggestion for three states but two states seems okay so curious why it was changed from boolean to int.

shipilev suggested not to use sub-word CAS, so change compareAndSetBoolean to compareAndSetInt. Change field "generated" from boolean to int doesn't increase object size (no extra byte/boolean to fold into same word).

> The restoring to 0 in the event of failure should probably be a volatile-write. Might be clearer to declare it as a volatile.
"generated" field  is read once and CAS once in this method. It doesn't likely cached and no visibiliy order required.

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PR: https://git.openjdk.java.net/jdk/pull/1070