RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v28]

[Martin Doerr]

On Thu, 27 Feb 2025 13:40:51 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 one additional commit since the last revision:
> 
>   use vsplitsb

src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 562:

> 560:                               VectorRegister vReducedLow, VectorRegister vTmp8, VectorRegister vTmp9,
> 561:                               VectorRegister vCombinedResult, VectorRegister vSwappedH) {
> 562:     assert(masm != nullptr, "MacroAssembler pointer is null");

I think this assertion is not really beneficial. Who would pass nullptr?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1976042069