[jdk17u-dev] RFR: 8290082: [PPC64] ZGC C2 load barrier stub needs to preserve vector registers

[Martin Doerr]

Backport of JDK-8290082.

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Depends on: https://git.openjdk.org/jdk17u-dev/pull/536

Commit messages:
 - Backport 393dc7ade716485f4452d0185caf9e630e4c6139

Changes: https://git.openjdk.org/jdk17u-dev/pull/547/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=547&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290082
  Stats: 121 lines in 5 files changed: 41 ins; 6 del; 74 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/547.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev pull/547/head:pull/547

PR: https://git.openjdk.org/jdk17u-dev/pull/547