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

[Kazunori Ogata]

On Thu, 21 Jan 2021 00:58:14 GMT, Corey Ashford <github.com+51754783+CoreyAshford 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
>
> src/hotspot/cpu/ppc/ppc.ad line 5845:
> 
>> 5843:   size(12);
>> 5844:   ins_encode %{
>> 5845:     // TODO: PPC port $archOpcode(ppc64Opcode_paddi);
> 
> I'm not clear of the meaning of this and the other TODOs.
> 
> ppc640opcode_paddi doesn't seem to be defined anywhere.

This comment was simply copied from old code that was deleted in JDK-8253029.  I removed the commend in this patch, too.

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