[jdk17u-dev] RFR: 8288180: C2: VectorPhase must ensure that SafePointNode memory input is a MergeMemNode

[Goetz Lindenmaier]

I backport this for parity with 17.0.17-oracle.

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Commit messages:
 - Backport 6f2223faa170a800f76a54a6637c160eadab6232

Changes: https://git.openjdk.org/jdk17u-dev/pull/3897/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3897&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288180
  Stats: 21 lines in 2 files changed: 21 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3897.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3897/head:pull/3897

PR: https://git.openjdk.org/jdk17u-dev/pull/3897