hg: shenandoah/jdk: Cherry-pick: 8214055: GC/C2 abstraction for phaseX

[roman at kennke.org]

Changeset: c10b425a953c
Author:    rkennke
Date:      2018-11-22 09:22 +0100
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/c10b425a953c

Cherry-pick: 8214055: GC/C2 abstraction for phaseX

! src/hotspot/share/gc/shared/c2/barrierSetC2.hpp
! src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp
! src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.hpp
! src/hotspot/share/opto/phaseX.cpp