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 561:

> 559:                               VectorRegister vLowProduct, VectorRegister vMidProduct, VectorRegister vHighProduct,
> 560:                               VectorRegister vReducedLow, VectorRegister vTmp8, VectorRegister vTmp9,
> 561:                               VectorRegister vCombinedResult, VectorRegister vSwappedH) {

I'd adjust the indentation.

src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 574:

> 572:     masm->vsldoi(vLowProduct, vLowProduct, vLowProduct, 8);           // Swap
> 573:     masm->vxor(vLowProduct, vLowProduct, vReducedLow);                // Reduction using constant
> 574:     masm->vsldoi(vCombinedResult, vLowProduct, vLowProduct, 8);       // Swap

The part between the vpsumd instructions looks too complicated. Isn't it equivalent to the following?

    masm->vsldoi(vTmp8, vLowProduct, vHighProduct, 8);
    masm->vsldoi(vTmp9, vReducedLow, vReducedLow, 8);
    masm->vxor(vTmp8, vTmp8, vMidProduct);
    masm->vxor(vCombinedResult, vTmp8, vTmp9);

src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 699:

> 697: 
> 698:     __ bind(L_initialize_unaligned_loop);
> 699:     __ li(temp1,0);

Missing whitespace.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1975696315
PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1975694548
PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1975696864