[lworld] RFR: 8320437: [lworld] Adding internal null-restricted storage API points [v5]

[Roger Riggs]

On Wed, 29 Nov 2023 18:49:49 GMT, Frederic Parain <fparain at openjdk.org> wrote:

>> Adding internal null-restricted storage API points
>
> Frederic Parain has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix EnableValhalla/EnablePrimitiveClasses flags on aarch64

The substitutably code is using a VarHandle, that bottoms out in Unsafe.getValue(o, offset, valueType).
Does the VM using a  lazy encoding of the default instance as null result in code using unsafe having to know about the VM representation? 
I'd like to think NOT, but I don't think Unsafe has enough information about the field stored at offset to do the right thing.
My second choice is that the VarHandle for the field replaces the literal null of a @NullRestricted field with the default.

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PR Comment: https://git.openjdk.org/valhalla/pull/947#issuecomment-1832843917