RFR: 8256011: Shenandoah: Don't resurrect finalizably reachable objects [v3]

[Roman Kennke]

> In the weak-LRB we currently return referents when it is 'marked', that is when it's either reachable strongly or through a finalizable object. This means a finalizable object can be resurrected by Reference.get(), which is wrong. Only truly strongly reachable objects should be returned by Reference.get() during weak-reference-processing. 
> 
> Testing: hotspot_gc_shenandoah, tier1 & tier2 with -XX:+UseShenandoahGC

Roman Kennke 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 five additional commits since the last revision:

 - Ensure correct strength and width of LRB runtime calls
 - Merge branch 'master' into JDK-8256011
 - Merge branch 'master' into JDK-8256011
 - Simplify condition, don't resurrect finalizably reachable objects even on phantom access
 - 8256011: Shenandoah: Don't resurrect finalizably reachable objects

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1109/files
  - new: https://git.openjdk.java.net/jdk/pull/1109/files/189be782..8d979eea

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1109&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1109&range=01-02

  Stats: 47771 lines in 313 files changed: 26190 ins; 14261 del; 7320 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1109.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1109/head:pull/1109

PR: https://git.openjdk.java.net/jdk/pull/1109