RFR: 8297445: PPC64: Represent Registers as values [v2]

[Martin Doerr]

On Wed, 23 Nov 2022 12:09:15 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> The recent Register implementation uses wild pointer (including null pointer) dereferences which exhibit undefined behavior. We should migrate away from pointer-based representation of Register values as it was done for x86 ([JDK-8292153](https://bugs.openjdk.org/browse/JDK-8292153)). Problems exist when trying to build with GCC 11 ([JDK-8297426](https://bugs.openjdk.org/browse/JDK-8297426)).
>> Note: Implicit conversion from `intptr_t` to `RegisterOrConstant` is no longer supported. That's why I had to replace some `add` instructions.
>
> Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update Copyright years.

Thanks for the reviews!

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PR: https://git.openjdk.org/jdk/pull/11297