[jdk18u] RFR: 8282592: C2: assert(false) failed: graph should be schedulable

[Tobias Hartmann]

Backport of [JDK-8282592](https://bugs.openjdk.java.net/browse/JDK-8282592). Applies cleanly. Approval is pending.

Thanks,
Tobias

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

Commit messages:
 - 8282592: C2: assert(false) failed: graph should be schedulable

Changes: https://git.openjdk.java.net/jdk18u/pull/80/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=80&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282592
  Stats: 86 lines in 3 files changed: 86 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/80.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/80/head:pull/80

PR: https://git.openjdk.java.net/jdk18u/pull/80