move reachabilityFence to ObjectUtils

platform/testFramework/src/com/intellij/testFramework/fixtures/impl/CodeInsightTestFixtureImpl.java

@@ -1460,8 +1460,7 @@ public class CodeInsightTestFixtureImpl extends BaseFixture implements CodeInsig
       Document document = getDocument(getFile());
       data.checkLineMarkers(DaemonCodeAnalyzerImpl.getLineMarkers(document, getProject()), document.getText());
     }
-    //noinspection ResultOfMethodCallIgnored
-    hardRefToFileElement.hashCode(); // use it so gc won't collect it
+    ObjectUtils.reachabilityFence(hardRefToFileElement);
     return elapsed;
   }
 

platform/util/src/com/intellij/util/ObjectUtils.java

@@ -37,6 +37,13 @@ public class ObjectUtils {
   public static Object sentinel(@NotNull String name) {
     return new Sentinel(name);
   }
+
+  /**
+   * They promise in http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-February/051312.html that
+   * the object reference won't be removed by JIT and GC-ed until this call.
+  */
+  public static void reachabilityFence(@SuppressWarnings("unused") Object o) {}
+
   private static class Sentinel {
     private final String myName;
 

platform/util/src/com/intellij/util/ref/GCUtil.java

@@ -16,6 +16,7 @@
 package com.intellij.util.ref;
 
 import com.intellij.diagnostic.ThreadDumper;
+import com.intellij.util.ObjectUtils;
 import org.jetbrains.annotations.TestOnly;
 
 import java.beans.Introspector;
@@ -40,7 +41,7 @@ public class GCUtil {
     //long started = System.nanoTime();
     ReferenceQueue<Object> q = new ReferenceQueue<>();
     SoftReference<Object> ref = new SoftReference<>(new Object(), q);
-    reachabilityFence(ref.get());
+    ObjectUtils.reachabilityFence(ref.get());
 
     System.gc();
 
@@ -52,7 +53,7 @@ public class GCUtil {
 
     // using ref is important as to loop to finish with several iterations: long runs of the method (~80 run of PsiModificationTrackerTest)
     // discovered 'ref' being collected and loop iterated 100 times taking a lot of time
-    reachabilityFence(ref.get());
+    ObjectUtils.reachabilityFence(ref.get());
 
     //System.out.println("Done gc'ing refs:" + ((System.nanoTime() - started) / 1000000));
   }
@@ -102,10 +103,6 @@ public class GCUtil {
     return until.getAsBoolean();
   }
 
-  // They promise in http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-February/051312.html that
-  // the object reference won't be removed by JIT and GC-ed until this call
-  private static void reachabilityFence(@SuppressWarnings("unused") Object o) {}
-
   /**
    * Using java beans (e.g. Groovy does it) results in all referenced class infos being cached in ThreadGroupContext. A valid fix
    * would be to hold BeanInfo objects on soft references, but that should be done in JDK. So let's clear this cache manually for now,