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

[Liming Liu]

On Mon, 23 Jun 2025 05:54:32 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> src/hotspot/cpu/aarch64/globals_aarch64.hpp line 92:
>> 
>>> 90:   product(bool, UseCryptoPmullForCRC32, false,                          \
>>> 91:           "Use Crypto PMULL instructions for CRC32 computation")        \
>>> 92:   product(uint, CryptoPmullForCRC32LowLimit, 256, DIAGNOSTIC,           \
>> 
>> Can you please add a test that uses this flag, and sets it to some selected values, and maybe even a random value?
>
> Is there already an IR test that checks for the presence of the crypto pmull? That could be good to ensure it occurs as expected and only when expected :)

Hi @eme64, what's your opinion? Personally, I think the two tests are enough for internal testing. This patch does not introduce the presence of crypto pmull. It just improves the existed instrinsics on Ampere CPU and enables it by default for Ampere, so the two tests already cover this patch.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25609#discussion_r2189280162