RFR: 8299327: Allow super late barrier expansion of store barriers in C2 [v2]

[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.

Erik Österlund has updated the pull request incrementally with one additional commit since the last revision:

  Roberto feedback

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11779/files
  - new: https://git.openjdk.org/jdk/pull/11779/files/de45ec52..eefe09f4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11779&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11779&range=00-01

  Stats: 12 lines in 8 files changed: 1 ins; 2 del; 9 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