RFR: 8320750: Allow a testcase to run with multiple -Xlog [v2]

[Leo Korinth]

On Wed, 7 Feb 2024 20:37:15 GMT, Leo Korinth <lkorinth at openjdk.org> wrote:

>> Running a testcase with muliple -Xlog crashes JTREG test cases. This is because `Collector.toMap` is not given a merge strategy.
>> 
>> When the same argument is passed multiple times, I have added a merge strategy to use the latter value. This is similar to how it is implemented for `vm.opt.*` in JTREG.
>> 
>> If the flag tested is `-Xlog`, replace the value part with a dummy value "NONEMPTY_TEST_SENTINEL". This is because in the case of multiple `-Xlog` all values are used, and JTREG does not give a satisfactory way to represent them. This dummy value should make it hard to try to `@require` on specific values by mistake.
>> 
>> Tested with:
>> 
>>  @requires vm.opt.x.Xlog == "NONEMPTY_TEST_SENTINEL"
>>  @requires vm.opt.x.Xlog == "NONEMPTY_TEST_SENTINELXXX"
>>  @requires vm.opt.x.Xms == "3g"
>> 
>> and
>> 
>> JAVA_OPTIONS=-Xms3g -Xms4g
>> JAVA_OPTIONS=-Xms4g -Xms3g
>> JAVA_OPTIONS=-Xlog:gc* -Xlog:gc*
>> ``` 
>> 
>> Running tier1
>
> Leo Korinth has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Added test, reworked code structure after suggestions from Stefan and Johan

I have changed the code after suggestions from Stefan and Johan. I have added a test. I have verified that the test runs in tier1. I am awaiting tier 1-3 to finish.

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PR Comment: https://git.openjdk.org/jdk/pull/16824#issuecomment-1932828416