[jdk19u] RFR: 8291775: C2: assert(r != __null && r->is_Region()) failed: this phi must have a region

[Tobias Hartmann]

Backport of [JDK-8291775](https://bugs.openjdk.java.net/browse/JDK-8291775). Applies cleanly. Approval is pending.

Thanks,
Tobias

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Commit messages:
 - 8291775: C2: assert(r != __null && r->is_Region()) failed: this phi must have a region

Changes: https://git.openjdk.org/jdk19u/pull/33/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19u&pr=33&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291775
  Stats: 8 lines in 2 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk19u/pull/33.diff
  Fetch: git fetch https://git.openjdk.org/jdk19u pull/33/head:pull/33

PR: https://git.openjdk.org/jdk19u/pull/33