RFR: 8327647: Occasional SIGSEGV in markWord::displaced_mark_helper() for SPECjvm2008 sunflow [v3]

[Matias Saavedra Silva]

> A misplaced memory barrier causes a very intermittent crash on on some aarch64 systems. This patch adds an appropriate LoadLoad barrier after a constant pool cache field entry is loaded. Verified with tier 1-5 tests.

Matias Saavedra Silva has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:

 - Reverted change on arm32
 - Merge branch 'master' into membar_8327647
 - Moved membar inside load_field_entry
 - Corrected comments
 - Merge branch 'master' into membar_8327647
 - Removed unneeded push/pop
 - Merge branch 'master' into membar_8327647
 - Replace use of r0 with noreg
 - Added membars after load_field_entry() calls
 - 8327647: Occasional SIGSEGV in markWord::displaced_mark_helper() for SPECjvm2008 sunflow

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18477/files
  - new: https://git.openjdk.org/jdk/pull/18477/files/4f976405..f612f947

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18477&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18477&range=01-02

  Stats: 20681 lines in 356 files changed: 8945 ins; 10674 del; 1062 mod
  Patch: https://git.openjdk.org/jdk/pull/18477.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18477/head:pull/18477

PR: https://git.openjdk.org/jdk/pull/18477