RFR: 8331117: [PPC64] secondary_super_cache does not scale well

[Martin Doerr]

PPC64 implementation of [JDK-8180450](https://bugs.openjdk.org/browse/JDK-8180450). Please review!
I noticed that `r_array_length` is sometimes 0 and I don't see code for that on x86. Any idea?
How can we verify it? By comparing the performance using the micro benchmarks?

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Commit messages:
 - 8331117: [PPC64] secondary_super_cache does not scale well

Changes: https://git.openjdk.org/jdk/pull/19368/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19368&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331117
  Stats: 408 lines in 5 files changed: 408 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/19368.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19368/head:pull/19368

PR: https://git.openjdk.org/jdk/pull/19368