[lworld] RFR: 8321039: [lworld] Substitutability code must recognize new annotations

[Frederic Parain]

On Tue, 5 Dec 2023 19:57:56 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> An initial implementation for substitutability test and partial method handle and var handle support for null-restricted types. JDK-8317767 will provide the full library support for null-restricted types.    
> 
> This patch handles null-restricted field reference declared in a non-flat class.  The default value of that field is lazily set by VM on read access.  `Unsafe::getReference` may return null for null-restricted non-flat field.  
> 
> A new `jdk.internal.value.ValueClass` is created to provide JVM entry points for value classes until public APIs are defined.     `jdk.internal.misc.newNullRestrictedArray` method is moved as well.

test/jdk/valhalla/valuetypes/NullRestrictedTest.java line 55:

> 53:     public void lazyInitializedDefaultValue() {
> 54:         // VM lazily sets the null-restricted non-flat field to zero default
> 55:         assertTrue(new EmptyContainer() == EmptyContainer.default);

The `.default` syntax is translated to `aconst_init` which is going to be removed.
May be use `ValueClass.zeroInstance(EmptyContainer.class)` instead.
Applies to all `.default` usage in this file.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/960#discussion_r1417583647