hg: shenandoah/jdk11: Implement ShenandoahBarrierSetC2::step_over_gc_barrier() to fix lock elimination bug with Shenandoah

[rkennke at redhat.com]

Changeset: f5c9d4ff794a
Author:    rkennke
Date:      2019-05-03 16:42 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk11/rev/f5c9d4ff794a

Implement ShenandoahBarrierSetC2::step_over_gc_barrier() to fix lock elimination bug with Shenandoah

! src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp