RFR: 8336831: Optimize StringConcatHelper.simpleConcat [v2]

[Shaojin Wen]

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

I have changed it to a shared newArray, including out of bounds checking, The performance improvement is still the same as before.


-Benchmark                             (intValue)  Mode  Cnt  Score   Error  Units (master)
-StringConcat.concatMethodConstString        4711  avgt   15  5.437 ? 0.073  ns/op

+Benchmark                             (intValue)  Mode  Cnt  Score   Error  Units (38a6f5602f0f1f4a9eec4b7f0ac1b5c4e661f667)
+StringConcat.concatMethodConstString        4711  avgt   15  5.027 ? 0.080  ns/op +8.15%

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PR Comment: https://git.openjdk.org/jdk/pull/20253#issuecomment-2239974521