RFR: 8307423: [s390x] Represent Registers as values [v2]

[Amit Kumar]

On Fri, 5 May 2023 01:56:27 GMT, Amit Kumar <amitkumar 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 11.3.0 ([JDK-8307093](https://bugs.openjdk.org/browse/JDK-8307093)).
>> 
>> Tested `fastdebug, slowdebug, optimized, release build` , `tier1-test` on fastdebug build and build with GCC-9.5.0 as well.
>
> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   formatting & suggestions from @TheRealMDoerr

src/hotspot/cpu/s390/vmreg_s390.inline.hpp line 32:

> 30:   if (this == noreg) {
> 31:     return VMRegImpl::Bad();
> 32:   }

Although @TheRealMDoerr  you've reviewed the changes. Do you think this getting rid from this check is okay? No other arch have this & this was an Typecasting error for us, after these changes.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13805#discussion_r1185649662