RFR: 8299327: Allow super late barrier expansion of store barriers in C2

[Erik Österlund]

ZGC uses super late barrier expansion for load barriers in C2. Generational ZGC needs to do the same thing but for store barriers.

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Commit messages:
 - 8299327: Allow super late barrier expansion of store barriers in C2

Changes: https://git.openjdk.org/jdk/pull/11779/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11779&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299327
  Stats: 23 lines in 8 files changed: 16 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/11779.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11779/head:pull/11779

PR: https://git.openjdk.org/jdk/pull/11779