[jdk20] RFR: JDK-8294902: Undefined Behavior in C2 regalloc with null references

[Andrew Haley]

JDK-8294902: Undefined Behavior in C2 regalloc with null references

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Commit messages:
 - JDK-8294902: Undefined Behavior in C2 regalloc with null references

Changes: https://git.openjdk.org/jdk20/pull/26/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk20&pr=26&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294902
  Stats: 64 lines in 7 files changed: 28 ins; 1 del; 35 mod
  Patch: https://git.openjdk.org/jdk20/pull/26.diff
  Fetch: git fetch https://git.openjdk.org/jdk20 pull/26/head:pull/26

PR: https://git.openjdk.org/jdk20/pull/26