RFR: 8333833: UUID toString removes the use of ByteArrayLittleEndian [v3]

[Shaojin Wen]

On Sat, 8 Jun 2024 23:30:38 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> After PR #16245, C2 optimizes stores into primitive arrays by combining values ​​into larger stores. In the UUID.toString method, ByteArrayLittleEndian can be removed, making the code more elegant and faster.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   change method name, putHex -> putHex4, and fix comments

> > You are right, ByteArray and ByteArrayLittleEndian have good performance after removing Unsafe. This is similar to the previous version of java.io.Bits
> 
> Do you have evidence that `VarHandle` affects startup time? If there is good evidence to support this, I would go ahead and rewrite #14636.

@cl4es has fixed startup regression issues, such as this https://github.com/openjdk/jdk/pull/15836

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PR Comment: https://git.openjdk.org/jdk/pull/19610#issuecomment-2156332130