RFR: 8286669: Replace MethodHandle specialization with ASM in mainline [v3]

[Rémi Forax]

On Mon, 16 May 2022 17:40:41 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Hi,
>> 
>> This PR brings over commits from the panama-foreign repo. These commits mostly pertain to the switch to ASM and away from MethodHandle combinators for the binding recipe specialization. But, there is one more commit which adds freeing of downcall stubs, since those changes were mostly Java as well.
>> 
>> Thanks,
>> Jorn
>> 
>> Testing: `run-test-jdk_foreign` with `-Dgenerator.sample.factor=-1` on Windows and Linux.
>
> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
> 
>   BootstrapMethodError -> ExceptionInInitializerError

src/java.base/share/classes/jdk/internal/foreign/abi/BindingSpecializer.java line 98:

> 96:     private static final String CLASS_DATA_DESC = methodType(Object.class, MethodHandles.Lookup.class, String.class, Class.class).descriptorString();
> 97:     private static final String RELEASE0_DESC = methodType(void.class).descriptorString();
> 98:     private static final String ACQUIRE0_DESC = methodType(void.class).descriptorString();

calling methodType() is quite slow because of the cache of MethodType so maybe those initialization should be done explicitly in a static block to avoid to recompute methodType(long).descriptorString() several times

src/java.base/share/classes/jdk/internal/foreign/abi/SoftReferenceCache.java line 42:

> 40: 
> 41:     private class Node {
> 42:         private SoftReference<V> ref;

this code looks like a double check locking so ref should be volatile

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PR: https://git.openjdk.java.net/jdk/pull/8685