RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v27]

[Martin Doerr]

On Wed, 26 Feb 2025 17:12:38 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

>> src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 702:
>> 
>>> 700:     __ lvx(vHigh, temp1, data);
>>> 701: #ifdef VM_LITTLE_ENDIAN
>>> 702:     __ xxspltib(vTmp12->to_vsr(), 31);
>> 
>> Is this instruction available on Power8? Shouldn't we use `vspltisb`?
>
> Need to check that. with vspltisb, we cannot broadcast more than value of 15. Hence I used this instruction instead.

I think we could use `vspltisb(vTmp12, -1)`. This would flip all bits which is also fine. `vec_perm` only looks at 5 bits per Byte.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1972073234