[aarch64-port-dev ] RFR: 2020-06-04, Bulk integration of Shenandoah 8u to aarch64-port/jdk8u-shenandoah

[Aleksey Shipilev]

https://cr.openjdk.java.net/~shade/shenandoah/merges/aarch64-port-8u-20200604/webrev.01/

This is another integration of Shenandoah 8u from our shenandoah/jdk8 staging repository. It was
generated by plain pull from shenandoah/jdk8/hotspot repository and automatic merge.

The webrev is not very large, and mostly contains file moves and associated build changes. IMO, the
only thing that deserves explanation is the addition in src/share/vm/runtime/os.hpp:
  https://mail.openjdk.java.net/pipermail/shenandoah-dev/2020-June/012413.html

We would negotiate the push order w.r.t. upstream sync with Andrew Hughes.

Changes:
  Shenandoah: move parallelCleaning.* to shenandoah/
  Shenandoah: fix formats in ShenandoahStringSymbolTableUnlinkTask
  [backport] 8245812: Shenandoah: compute root phase parallelism
  [backport] 8245814: Shenandoah: reconsider format specifiers for stats
  [backport] 8245463: Shenandoah: refine ShenandoahPhaseTimings constructor arguments
  [backport] 8245754: Shenandoah: ditch ShenandoahAlwaysPreTouch
  [backport] 8245461: Shenandoah: refine mode name()-s
  [backport] 8245726: Shenandoah: lift/cleanup ShenandoahHeuristics names and properties
  [backport] 8245825: Shenandoah: Remove diagnostic flag ShenandoahConcurrentScanCodeRoots
  Shenandoah: move barrier sets to their proper locations
  Shenandoah: Fix build failure with +JFR -PCH
  Shenandoah: fix runtime linking failure due to non-compiled shenandoahBarrierSetC1
  [backport] 8246162: Shenandoah: full GC does not mark code roots when class unloading is off
  [backport] 8245757: Shenandoah: AlwaysPreTouch should not disable heap resizing or uncommits
   Merge

Testing: hotspot_gc_shenandoah {fastdebug,release}; it was also tested in sh/jdk8 with a few nightlies

-- 
Thanks,
-Aleksey