RFR: 8263252: Improve fold_compares c2 optimizations

[Rahul Raghavan]

8263252: Improve fold_compares c2 optimizations

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Commit messages:
 - Improve fold_compares c2 optimizations

Changes: https://git.openjdk.java.net/jdk/pull/4035/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4035&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263252
  Stats: 224 lines in 2 files changed: 161 ins; 23 del; 40 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4035.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4035/head:pull/4035

PR: https://git.openjdk.java.net/jdk/pull/4035