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

[Martin Doerr]

On Wed, 26 Feb 2025 12:21:39 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

>> JBS Issue : [JDK-8216437](https://bugs.openjdk.org/browse/JDK-8216437)
>> 
>> Currently acceleration code for GHASH is missing for PPC64. 
>> 
>> The current implementation utlilises SIMD instructions on Power and uses Karatsuba multiplication for obtaining the final result.
>
> Suchismith Roy has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - change pattern for Linux, fix for AIX
>  - change pattern for Linux, fix for AIX

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`?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1971985131