hg: shenandoah/jdk9/hotspot: Further optimize root marking. Don't null check, and don't update refs when not needed.

[roman at kennke.org]

Changeset: 6a4c52ad30b7
Author:    rkennke
Date:      2015-10-28 21:00 +0100
URL:       http://hg.openjdk.java.net/shenandoah/jdk9/hotspot/rev/6a4c52ad30b7

Further optimize root marking. Don't null check, and don't update refs when not needed.

! src/share/vm/gc/shenandoah/shenandoahBarrierSet.inline.hpp
! src/share/vm/gc/shenandoah/shenandoahConcurrentMark.cpp