RFR: 8333382: [s390x] Enhance popcnt Instruction to use Z15 facilities [v4]

[Amit Kumar]

On Mon, 10 Jun 2024 16:14:38 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Okay I'm fine with your suggestion. But I only hope that nobody directly uses `z_popcnt` instruction. Otherwise this solution is not gonna prevent the bug you described. Maybe I should put a comment in `assembler_s390.hpp` file as well, to have a look at the helper method present in `macroAssembler_s390.hpp` file instead of using it vanilla.
>
> There's no need to hope, make `z_popcnt` protected.

done; please have a look at new commits;

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PR Review Comment: https://git.openjdk.org/jdk/pull/19509#discussion_r1634378072