[jdk21u-dev] RFR: 8328264: AArch64: remove UseNeon condition in CRC32 intrinsic

[Goetz Lindenmaier]

On Mon, 10 Mar 2025 16:06:15 GMT, Dmitry Chuyko <dchuyko at openjdk.org> wrote:

> This is a clean backport of a tiny enhancement in one of aarch64 crc32 implementations. Similar to JDK 23 -UseNeon makes no sense in update releases either https://github.com/openjdk/jdk/pull/18294#issuecomment-1997727704
> 
> Benchmarking results for jdk21u on Graviton 2, `-XX:-UseCRC32 -XX:-UseCryptoPmullForCRC32`:
> 
> 
> Benchmark                  (count)   Mode  Cnt      Score    Error   Units
> TestCRC32.testCRC32Update       64  thrpt    4  15263.125 ± 20.681  ops/ms
> TestCRC32.testCRC32Update      128  thrpt    4   7746.327 ±  7.583  ops/ms
> TestCRC32.testCRC32Update      256  thrpt    4   3904.416 ±  3.398  ops/ms
> TestCRC32.testCRC32Update      512  thrpt    4   1959.262 ±  1.617  ops/ms
> TestCRC32.testCRC32Update     2048  thrpt    4    489.607 ±  0.286  ops/ms
> TestCRC32.testCRC32Update    16384  thrpt    4     61.355 ±  0.991  ops/ms
> TestCRC32.testCRC32Update    65536  thrpt    4     15.318 ±  0.270  ops/ms
> -->
> TestCRC32.testCRC32Update       64  thrpt    4  18649.642 ± 40.169  ops/ms
> TestCRC32.testCRC32Update      128  thrpt    4  11265.168 ± 13.246  ops/ms
> TestCRC32.testCRC32Update      256  thrpt    4   6188.989 ±  4.609  ops/ms
> TestCRC32.testCRC32Update      512  thrpt    4   3254.121 ±  3.669  ops/ms
> TestCRC32.testCRC32Update     2048  thrpt    4    846.038 ±  0.861  ops/ms
> TestCRC32.testCRC32Update    16384  thrpt    4    107.056 ±  0.116  ops/ms
> TestCRC32.testCRC32Update    65536  thrpt    4     26.780 ±  0.041  ops/ms
> 
> 
> JDK-8329749 is an optional follow-up for this backport.
> 
> Testing: tier1,2 on linux-aarch64.

Hi @dchuyko 
wouldn't it be better suitable for an LTS release to toggle the default of that flag? 
Best regards, Geotz.

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PR Comment: https://git.openjdk.org/jdk21u-dev/pull/1462#issuecomment-2721637942