RFR: 8256535: C2: randomize CCP processing order for stress testing

[Roberto Castañeda Lozano]

On Wed, 16 Dec 2020 07:58:50 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

>> Add `StressCCP` option to randomize the selection of the node to be examined in each CCP iteration.
>
> Looks good. Before integration, please make sure to run this through testing with `-XX:RepeatCompilation` to make sure it does not trigger any bugs right away.

Tested on hs-tier1-3 with `-XX:+StressCCP -XX:+LogCompilation -XX:RepeatCompilation=20` as requested by @TobiHartmann. All 76 failures have been traced to test code not handling `LogCompilation`, `RepeatCompilation` (for example [JDK-8258682](https://bugs.openjdk.java.net/browse/JDK-8258682)), or both. No failure could be attributed to `StressCCP` itself. Requesting integration.

-------------

PR: https://git.openjdk.java.net/jdk/pull/1765