[jdk17u-dev] RFR: 8287432: C2: assert(tn->in(0) != __null) failed: must have live top node

[Goetz Lindenmaier]

I backport this for parity with 17.0.5-oracle.

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Commit messages:
 - Backport 78d371266ae8a629db8176ced4d48e9521702cce

Changes: https://git.openjdk.org/jdk17u-dev/pull/515/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=515&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8287432
  Stats: 56 lines in 2 files changed: 55 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/515.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/515/head:pull/515

PR: https://git.openjdk.org/jdk17u-dev/pull/515