RFR: 8347555: [REDO] C2: implement optimization for series of Add of unique value [v7]

[Kangcheng Xu]

On Thu, 9 Oct 2025 12:45:05 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> @eme64 Thank you for reviewing! Those are very valid suggestion, especially on naming as this PR evolves. I've done the following:
>> 
>> - updated naming (mostly with "serial addition" to "collapsable addition (into multiplication)")
>> - updated comments
>> - moved test file
>> - merged in master
>> 
>> Please enjoy your time off!
>> 
>> Once GHA passes, @rwestrel could you please give this a quick review if you have some time? Thank you very much!
>
> @tabjy The code now looks good to me. I ran some internal testing, should take about 24h.

Many thanks to @eme64 and @rwestrel for reviewing. It was really educational!

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PR Comment: https://git.openjdk.org/jdk/pull/23506#issuecomment-3390319046