RFR: 8259822: [PPC64] Support the prefixed instruction format added in POWER10 [v3]

[Kazunori Ogata]

On Thu, 21 Jan 2021 01:53:02 GMT, Corey Ashford <github.com+51754783+CoreyAshford at openjdk.org> wrote:

>> Kazunori Ogata has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Update (2nd round) based on review comments
>
> This looks good overall.  I'm looking forward to being able to utilize this capability.

@CoreyAshford Thank you for your comment.  Regarding the unused code, I agree that unused code won't be tested enough, so I removed paddi_or_addi(), pli_or_li(), and is_pli().

For the comment on predicate in loadConI32 and loadConL34, I couldn't find the reason why it caused build error.  So I added comments describing they are only for Power 10 and up but can't add predicate.  I also added comments in is_paddi() as you suggested.

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PR: https://git.openjdk.java.net/jdk/pull/2095