[jdk18u] RFR: 8279622: C2: miscompilation of map pattern as a vector reduction

[Tobias Hartmann]

Backport of [JDK-8279622](https://bugs.openjdk.java.net/browse/JDK-8279622). Applies cleanly. Approval is pending.

Thanks,
Tobias

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Commit messages:
 - 8279622: C2: miscompilation of map pattern as a vector reduction

Changes: https://git.openjdk.org/jdk18u/pull/157/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk18u&pr=157&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8279622
  Stats: 95 lines in 5 files changed: 95 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk18u/pull/157.diff
  Fetch: git fetch https://git.openjdk.org/jdk18u pull/157/head:pull/157

PR: https://git.openjdk.org/jdk18u/pull/157