RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v6]

[Andrew Haley]

On Wed, 15 Jan 2025 20:37:44 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> Suchismith Roy has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   restore
>
> src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 681:
> 
>> 679:   __ sldi(temp1, temp1, 56);
>> 680:   __ vxor(vZero, vZero, vZero);
>> 681:   // Load the vector from memory into vConstC2
> 
> This comment is not correct. It's not loaded from memory.

Thanks for confirming that. So the low-order-bits of the reduction polynomial are in the high byte of `temp1` at this point, and the rest of `temp1` is zero, confirming that the polynomial (z^7+z^2+z+1) is in bit-reversed order:


+  __ li(temp1, 0xc2);
+  __ sldi(temp1, temp1, 56);

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1918283067