[jdk18u] RFR: 8282590: C2: assert(addp->is_AddP() && addp->outcnt() > 0) failed: Don't process dead nodes

[Tobias Hartmann]

Backport of [JDK-8282590](https://bugs.openjdk.java.net/browse/JDK-8282590). Applies cleanly. Approval is pending.

Thanks,
Tobias

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Commit messages:
 - 8282590: C2: assert(addp->is_AddP() && addp->outcnt() > 0) failed: Don't process dead nodes

Changes: https://git.openjdk.java.net/jdk18u/pull/59/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk18u&pr=59&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282590
  Stats: 39 lines in 3 files changed: 30 ins; 4 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk18u/pull/59.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk18u pull/59/head:pull/59

PR: https://git.openjdk.java.net/jdk18u/pull/59