[jdk18u] RFR: 8280123: C2: Infinite loop in CMoveINode::Ideal during IGVN

[Tobias Hartmann]

Backport of [JDK-8280123](https://bugs.openjdk.java.net/browse/JDK-8280123). Applies cleanly. Fix request is pending.

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Commit messages:
 - 8280123: C2: Infinite loop in CMoveINode::Ideal during IGVN

Changes: https://git.openjdk.java.net/jdk18u/pull/18/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=18&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280123
  Stats: 93 lines in 2 files changed: 72 ins; 4 del; 17 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/18.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/18/head:pull/18

PR: https://git.openjdk.java.net/jdk18u/pull/18