RFR: 8259822: [PPC64] Support the prefixed instruction format added in POWER10 [v8]

[Martin Doerr]

On Thu, 25 Mar 2021 06:16:53 GMT, Kazunori Ogata <ogatak at openjdk.org> wrote:

>> The POWER10 processor, which implements Power ISA 3.1 [1], supports new instruction formats where an instruction takes two 32bit words.  The first word is called prefix, and the instructions with prefix are called prefixed instructions.  With more bits in opcode and operand fields, POWER10 supports larger immediate value in an operand, as well as many new instructions.
>> 
>> This is the first changes to handle prefixed instructions, and this adds support of prefixed addi (= paddi) instruction as an example of prefix usage.  paddi accepts 34bit immediate value, while original addi accepts 16bit value.
>> 
>> [1] https://ibm.ent.box.com/s/hhjfw0x0lrbtyzmiaffnbxh2fuo0fog0
>
> Kazunori Ogata has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Clean up compute_padding() and fix grammatical errors

Looks good to me, now. Is the latest version substantially tested? We need to rely on IBMs testing because nobody else has Power10.

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Marked as reviewed by mdoerr (Reviewer).

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