[jdk21u-dev] RFR: 8316594: C2 SuperWord: wrong result with hand unrolled loops

[Goetz Lindenmaier]

I backport this for parity with 21.0.3-oracle.

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Commit messages:
 - Backport 3630af26e6f05237195e53b98603adf404e90a1a

Changes: https://git.openjdk.org/jdk21u-dev/pull/110/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=110&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316594
  Stats: 112 lines in 3 files changed: 104 ins; 5 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/110.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/110/head:pull/110

PR: https://git.openjdk.org/jdk21u-dev/pull/110