RFR: 8336831: Optimize StringConcatHelper.simpleConcat [v3]

[Chen Liang]

On Fri, 19 Jul 2024 21:33:09 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:
> 
>   extract a common doConcat handling both non-empty strings

This patch looks ideal to me; but other reviewers may have different opinions on this review. I am ready to answer their questions for you.

I will approve your patch once you fixed the null and empty check in `String.concat` and the builds look good. Don't change your patch too often, as that means previous build results will be invalid.

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PR Comment: https://git.openjdk.org/jdk/pull/20253#issuecomment-2240220709