RFR: 8275063: Implementation of Foreign Function & Memory API (Second incubator) [v10]

[Paul Sandoz]

On Mon, 1 Nov 2021 12:05:32 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> This PR contains the API and implementation changes for JEP-419 [1]. A more detailed description of such changes, to avoid repetitions during the review process, is included as a separate comment.
>> 
>> [1] - https://openjdk.java.net/jeps/419
>
> Maurizio Cimadamore has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 17 commits:
> 
>  - Add cache for memory address var handles
>  - Merge branch 'master' into JEP-419
>  - Fix regression in VaList treatment on AArch64 (contributed by @nick-arm)
>  - Merge branch 'master' into JEP-419
>  - Fix copyright header in TestArrayCopy
>  - Fix failing microbenchmarks. Contributed by @FrauBoes (thanks!)
>  - * use `invokeWithArguments` to simplify new test
>  - Add test for liveness check with high-aririty downcalls
>    (make sure that if an exception occurs in a downcall because of liveness,
>    ref count of other resources are left intact).
>  - * Fix javadoc issue in VaList
>    * Fix bug in concurrent logic for shared scope acquire
>  - Address review comments
>  - ... and 7 more: https://git.openjdk.java.net/jdk/compare/5bb1992b...9b519343

src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/Utils.java line 111:

> 109:         class VarHandleCache {
> 110:             private static final Map<ValueLayout, VarHandle> handleMap = new ConcurrentHashMap<>();
> 111:             private static final Map<ValueLayout, VarHandle> handleMapNoAlignCheck = new ConcurrentHashMap<>();

Something to consider later if this is an issue. Since the number of `ValueLayout` instances is fixed, carrier x order = 18, we can use stable arrays with ordinals on the instances.

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PR: https://git.openjdk.java.net/jdk/pull/5907