RFR: 8310837: Use ByteArrayLittleEndian in java.util.zip

[Glavo]

On Sat, 24 Jun 2023 05:24:24 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Using `ByteArrayLittleEndian` is simpler and faster.
>> 
>> `make test TEST="micro:java.util.zip.ZipFileOpen"`:
>> 
>> 
>>   Benchmark                     (size)  Mode  Cnt      Score      Error  Units
>> - ZipFileOpen.openCloseZipFile     512  avgt   15  39052.832 ±  107.496  ns/op
>> + ZipFileOpen.openCloseZipFile     512  avgt   15  36275.539 ±  663.193  ns/op
>> - ZipFileOpen.openCloseZipFile    1024  avgt   15  77106.494 ± 4159.300  ns/op
>> + ZipFileOpen.openCloseZipFile    1024  avgt   15  71955.013 ± 2296.050  ns/op
>
> @LanceAndersen This one is going to require checking that startup isn't impacted.

@AlanBateman @jaikiran Sorry, I thought about its possible impact on startup time, but I don't know which tests can be used to test JVM startup time. Can you tell me some relevant tests?

In fact, I now have a branch(https://github.com/openjdk/jdk/commit/30289cc48c36bd7a59d6c707118d74383bf5f378) that rewrites `ByteArray` and `ByteArrayLittleEndian` to avoid using `VarHandle` because I hope to be able to use them more inside the JDK later.

I tested its performance with the `-Xint` option on and it is indeed faster than `VarHandle` in interpreter mode. But I think I'm missing some benchmark results of the impact on startup time to justify its necessity.

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PR Comment: https://git.openjdk.org/jdk/pull/14632#issuecomment-1605281589