RFR: 8356255: Add Stable Field Updaters to allow efficient lazy field evaluations

[Per Minborg]

On Mon, 5 May 2025 15:04:54 GMT, Chen Liang <liach at openjdk.org> wrote:

>> This sketch shows how "Stable Updaters" can be used to create stable computations of `@Stable` fields. Only one updater is needed per class, similar to `AtomicIntegerFieldUpdater`.
>
> src/java.base/share/classes/java/lang/reflect/Method.java line 101:
> 
>> 99: 
>> 100:     private static final ToIntFunction<Method> HASH_UPDATER =
>> 101:             StableFieldUpdater.ofIntRaw(Method.class, Unsafe.getUnsafe().objectFieldOffset(Method.class, "hash"), new ToIntFunction<Method>() {
> 
> If we are using unsafe to get field offsets, why don't we just accept arguments to locate a MethodHandle (like those arguments to MhUtils)?

Do you mean for interacting with the field or computing the hash?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25040#discussion_r2075052972