RFR: 8358032: Use crypto pmull for CRC32(C) on Ampere CPU and improve for short inputs [v4]

[Liming Liu]

On Mon, 23 Jun 2025 05:50:57 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Liming Liu has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add the message for the assertions
>
> src/hotspot/cpu/aarch64/vm_version_aarch64.cpp line 126:
> 
>> 124:     warning("CryptoPmullForCRC32LowLimit must be a multiple of 128");
>> 125:     CryptoPmullForCRC32LowLimit = align_down(CryptoPmullForCRC32LowLimit, 128);
>> 126:   }
> 
> Can you describe somewhere why it has to be a multiple of `128`? Imagine someone comes across this later, and wonders if that is just some strange implementation limitation or something more fundamental, or something very subtle.

For example, if the flag is 266 which is 128x2+10, then for 266 bytes of inputs, the code path is the same as if the flag is 256.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25609#discussion_r2163034891