RFR: 8362394: C2: Repeated stacked string concatenation fails with "Hit MemLimit" and other resourcing errors [v4]

[Daniel Skantz]

On Mon, 11 Aug 2025 10:30:42 GMT, Galder Zamarreño <galder at openjdk.org> wrote:

>> Daniel Skantz has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   compare order
>
> test/hotspot/jtreg/compiler/stringopts/TestStackedConcatsMany.java line 28:
> 
>> 26:  * @bug 8357105
>> 27:  * @summary Test that repeated stacked string concatenations do not
>> 28:  *          consume too many compilation resources.
> 
> Is there a reasonable way to enhance the test to validate excessive resources? I'm not sure if the following example would work, but I'm wondering if there is something that can be measured deterministically. E.g. before with the given test there would be ~N IR nodes produced but now it would be a max of ~M, assuming that M is deterministically smaller than N.

What do you think, @galderz ? Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/26685#discussion_r2290189725