RFR: 8271118: C2: StressGCM should have higher priority than frequency-based policy [v2]

[Yi Yang]

> I think StressGCM should have higher priority than frequency-based policy, otherwise StressGCM has no chance to choose because the frequency-based policy would choose block first if appropriately.

Yi Yang has updated the pull request incrementally with one additional commit since the last revision:

  is_cheaper_block

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4865/files
  - new: https://git.openjdk.java.net/jdk/pull/4865/files/a16a6584..299d4b95

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4865&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4865&range=00-01

  Stats: 49 lines in 2 files changed: 38 ins; 10 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4865.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4865/head:pull/4865

PR: https://git.openjdk.java.net/jdk/pull/4865