RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v26]

[Martin Doerr]

On Fri, 21 Feb 2025 17:15:34 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

>> Please understand my question correctly. I didn't propose to remove all `ver_perm`. The idea is to do the same job in the loop with one `vec_perm`.
>
> Hi @TheRealMDoerr  Maybe my answer was not clear. I am not proposing to remove them. I am unable to decipher how to  reduce the 3 instructions to one, as I feel the below 2 lines are required , as per the algorithm.
>  __ vec_perm(vTmp4, vHigh, vHigh, loadOrder);
>  __ vec_perm(vTmp5, vLow, vLow, loadOrder);

The purpose of the 3 `vec_perm` instructions is to extract 16 Bytes from two 16 Byte values loaded into vector registers. This can be done by 1 `vec_perm` instruction. But I think AIX should get fixed first before we figure out how to determine the vPerm value for that (probably lvsl + vxor before the loop).

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PR Review Comment: https://git.openjdk.org/jdk/pull/20235#discussion_r1966095694