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 :)

There are test/hotspot/jtreg/compiler/intrinsics/zip/TestCRC32.java and TestCRC32C.java. It covers various lengths for the input, and test the intrinsics with the default values of the flag. It does not cover different values of the flag, which I think could be covered by VM_OPTIONS. I feel that it is not suitable to add the flag in the @run tag, since it is aarch64 specific while the test is generic.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25609#discussion_r2163029715