RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v4]

[Suchismith Roy]

On Fri, 20 Dec 2024 17:19:03 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> Suchismith Roy has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  -  clearing bits
>>  -  clearing bits
>
> src/hotspot/cpu/ppc/stubGenerator_ppc.cpp line 713:
> 
>> 711:   __ vxor(vTmp1, vTmp1, vTmp1);
>> 712:   __ vxor(vZero, vZero, vZero);
>> 713:   __ mtctr(blocks);
> 
> Can `blocks` be 0?
> `blocks` is an int. The higher half of the register may possibly contain garbage and should be cleared. (Can be combined with 0 check if needed.)

(https://github.com/openjdk/jdk/blob/a641932427cbe8453130593355372837d70a098f/src/java.base/share/classes/com/sun/crypto/provider/GHASH.java#L281) In the java code, the 0 check is handled.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1907562020