RFR: 8336831: Optimize StringConcatHelper.simpleConcat [v2]

[Chen Liang]

On Fri, 19 Jul 2024 19:18:43 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> Currently simpleConcat is implemented using mix and prepend, but in this simple scenario, it can be implemented in a simpler way and can improve performance.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   share newArray

As annoying and risky as this first appeared, this patch is actually in quite good shape: The usage of `getBytes` is similar to those in StringUTF16, and there's no reason to further complicate this by splitting the handling into StringLatin1 and StringUTF16. 👍 

Another question for you: can you check out the original form over here too? https://github.com/openjdk/jdk/commit/781fb29580b08fa659019a2da09488ee4711c017#diff-f8131d8a48caf7cfc908417fad241393c2ef55408172e9a28dcaa14b1d73e1fbL1968-L1981

`simpleConcat` is required to create new String objects and `String.concat` can just return the argument/original when one part is not empty. Is there any value to extract a common `doConcat` handling both non-empty strings, called by both methods after handling the empty cases?

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PR Comment: https://git.openjdk.org/jdk/pull/20253#issuecomment-2240077201