[jdk21u-dev] RFR: 8326638: Crash in PhaseIdealLoop::remix_address_expressions due to unexpected Region instead of Loop

[Andrew Lu]

I backport this for parity with 21.0.3-oracle.

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Commit messages:
 - Backport 9f0e7da64e21237322e55ca4f0e3639fa5d1c4ed

Changes: https://git.openjdk.org/jdk21u-dev/pull/317/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=317&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8326638
  Stats: 60 lines in 2 files changed: 57 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/317.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/317/head:pull/317

PR: https://git.openjdk.org/jdk21u-dev/pull/317