[jdk17u] RFR: 8271340: Crash PhaseIdealLoop::clone_outer_loop

[Tobias Hartmann]

Backport of [JDK-8271340](https://bugs.openjdk.java.net/browse/JDK-8271340). Applies cleanly. Approval is pending.

Thanks,
Tobias

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

Commit messages:
 - 8271340: Crash PhaseIdealLoop::clone_outer_loop

Changes: https://git.openjdk.java.net/jdk17u/pull/99/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=99&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271340
  Stats: 183 lines in 4 files changed: 140 ins; 41 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/99.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/99/head:pull/99

PR: https://git.openjdk.java.net/jdk17u/pull/99