RFR: 8371164: ArrayList.addAll() optimizations [v2]

[Johannes Döbler]

On Tue, 4 Nov 2025 18:43:08 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> The comment is a good idea, but splitting out the duplication may make maintenance even worse by separating the duplicate sections.  What do you think?
>> 
>> Also, I'll benchmark with the split to get the impact data.  Not sure I can meaningfully validate an impact to inlining.
>
> I think peeling off and outlining distinct paths in a larger method to separate, simpler methods usually reduces distracting noise and improves readability, but I guess that's subjective territory.

> cl4es: Consider simplifying this to reduce code duplication:

or even simpler?


Object[] a = c.getClass() == ArrayList.class ? ((ArrayList<?>)c).elementData : a.toArray();
int newNum = a.length;
...



> jengebr: Interestingly, this hurt the fast-path about 5%, but the control case about 35%.

what is the control case, LinkedList.addAll() ?

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PR Review Comment: https://git.openjdk.org/jdk/pull/28116#discussion_r2491853221