[lilliput-jdk17u:lilliput] RFR: 8310742: [Lilliput/JDK17] Revert JVMCI _metadata field removal

[Roman Kennke]

On Fri, 23 Jun 2023 13:41:25 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> We removed _metadata._klass field from JVMCI interfaces. This is no longer necessary since we introduced UseCompactObjectHeaders, with the caveat that JVMCI can only be used with -UCOH.
> 
> Testing:
>  - [ ] tier1 -UCOH
>  - [ ] tier1 +UCOH

JVMCI args are checked before the UCOH args, via check_vm_args_consistency(). Which means that the patch is good as it is, I think. We wouldn't turn on LW locking, GC forwarding because of +UCOH and then turn off UCOH because of JVMCI.

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PR Comment: https://git.openjdk.org/lilliput-jdk17u/pull/48#issuecomment-1604728787