hg: shenandoah/jdk8u/hotspot: Cherry-pick fix for "8175887: C1 value numbering handling of Unsafe.get*Volatile is incorrect".

[ashipile at redhat.com]

Changeset: 218d94d4a52d
Author:    shade
Date:      2017-04-24 10:12 +0200
URL:       http://hg.openjdk.java.net/shenandoah/jdk8u/hotspot/rev/218d94d4a52d

Cherry-pick fix for "8175887: C1 value numbering handling of Unsafe.get*Volatile is incorrect".

! src/share/vm/c1/c1_ValueMap.hpp
+ test/compiler/c1/UnsafeVolatileGuardTest.java
+ test/compiler/c1/VolatileGuardTest.java