[jdk21u-dev] RFR: 8342498: Add test for Allocation elimination after use as alignment reference by SuperWord

[Goetz Lindenmaier]

I backport this for parity with 21.0.7-oracle

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Commit messages:
 - Backport f62fc4844125cc20a91dc2be39ba05a2d3aca8cf

Changes: https://git.openjdk.org/jdk21u-dev/pull/1325/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1325&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342498
  Stats: 183 lines in 1 file changed: 183 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1325.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1325/head:pull/1325

PR: https://git.openjdk.org/jdk21u-dev/pull/1325