RFR: 8311588: C2: RepeatCompilation compiler directive does not choose stress seed randomly

[Christian Hagedorn]

The compiler directive `RepeatCompilation` can be used to repeat compilations of specific methods, for example for `Test::test()`:

-XX:CompileCommand=RepeatCompilation,Test::test,1000

When using this compiler directive in combination with `StressIGVN/CCP/GCM/LCM`, C2 only sets the stress seed once to a random value. Afterward, it keeps the seed for all repeated compilations. This should be changed to always select a random seed with each repetition (i.e. get the same behavior as the flag `RepeatCompilation`).

Thanks,
Christian

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Commit messages:
 - 8311588: C2: RepeatCompilation compiler directive does not choose stress seed randomly

Changes: https://git.openjdk.org/jdk/pull/14786/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14786&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311588
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/14786.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14786/head:pull/14786

PR: https://git.openjdk.org/jdk/pull/14786