[jdk17u-dev] RFR: 8283408: Fix a C2 crash when filling arrays with unsafe

[Martin Doerr]

Clean backport of [JDK-8283408](https://bugs.openjdk.java.net/browse/JDK-8283408)

-------------

Commit messages:
 - Backport a6740c010b7d37f991c8547be6ea72b198e9094f

Changes: https://git.openjdk.java.net/jdk17u-dev/pull/306/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u-dev&pr=306&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283408
  Stats: 75 lines in 2 files changed: 72 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk17u-dev/pull/306.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u-dev pull/306/head:pull/306

PR: https://git.openjdk.java.net/jdk17u-dev/pull/306