[jdk21u-dev] RFR: 8333647: C2 SuperWord: some additional PopulateIndex tests

[Goetz Lindenmaier]

I backport this for parity with 21.0.7-oracle

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Commit messages:
 - Backport 487c4771818999749bfd507ab85777795bba0832

Changes: https://git.openjdk.org/jdk21u-dev/pull/1281/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1281&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8333647
  Stats: 99 lines in 2 files changed: 99 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1281.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1281/head:pull/1281

PR: https://git.openjdk.org/jdk21u-dev/pull/1281