RFR: 8358032: Use crypto pmull for CRC32/CRC32C intrinsics on Ampere CPU [v2]

[Liming Liu]

On Wed, 4 Jun 2025 08:27:10 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Liming Liu has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Make it be a diagnostic flag
>
> src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 4335:
> 
>> 4333:     assert_different_registers(crc, buf, len, tmp0, tmp1, tmp2);
>> 4334: 
>> 4335:     subs(tmp0, len, CryptoPmullForCRC32LowLimit);
> 
> Would it make sense to have another alignment sanity check here? It would be both helpful to make sure nobody later breaks your assumption, and could also be helpful for the reader to see the `128` alignment immediately.

I think the alignment does not effect the correctness here, but it should be >= 256. So I added the corresponding assertion above.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25609#discussion_r2128003307