RFR: 8336831: Optimize StringConcatHelper.simpleConcat [v5]

[Brett Okken]

On Fri, 19 Jul 2024 21:42:09 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 two additional commits since the last revision:
> 
>  - Update src/java.base/share/classes/java/lang/String.java
>    
>    Co-authored-by: Chen Liang <liach at openjdk.org>
>  - add comments

src/java.base/share/classes/java/lang/StringConcatHelper.java line 387:

> 385:         byte[] buf = newArray(newLength);
> 386:         s1.getBytes(buf, 0, coder);
> 387:         s2.getBytes(buf, s1.length(), coder);

Does s1 length need to be shifted by coder for dstBegin?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20253#discussion_r1685431381