JDWP: update ReferenceType.InstancesTest

Updates debuggee of test ReferenceType.InstancesTest to make sure
unreachable objects cannot be kept alive by a DEX register in the
stack frame used by the test.

Indeed the last 'new' in a loop can be stored in a DEX register which is
not overwritten after that instruction. To avoid that situation, we move
the allocation of such objects into a separate method.

Bug: 36921933
Test: art/tools/run-jdwp-tests.sh --mode=host --variant=X64
Change-Id: I723a83430121a02470fa8bdcc9af77ec358d4929

1 files changed, 18 insertions, 11 deletions

diff --git a/jdwp/src/test/java/org/apache/harmony/jpda/tests/jdwp/ReferenceType/InstancesDebuggee.java b/jdwp/src/test/java/org/apache/harmony/jpda/tests/jdwp/ReferenceType/InstancesDebuggee.java
index b165f26..f59adf7 100644
--- a/jdwp/src/test/java/org/apache/harmony/jpda/tests/jdwp/ReferenceType/InstancesDebuggee.java
+++ b/jdwp/src/test/java/org/apache/harmony/jpda/tests/jdwp/ReferenceType/InstancesDebuggee.java
@@ -39,23 +39,30 @@ public class InstancesDebuggee extends SyncDebuggee {
 
 	@Override
 	public void run() {
-		//Objects reachable for garbage collection purpose
-		
+		// Objects reachable for garbage collection purpose.
 		ArrayList<MockClass> reachableObjs = new ArrayList<MockClass>();
-        
-		for(int i = 0; i < reachableObjNum; i++) {
-			reachableObjs.add(new MockClass(true));
-		}
-       
-		//Objects unreachable
-		for(int i = 0; i < unreachableObjNum; i++) {
-			new MockClass(false);
-		}
+		allocateReachableObjects(reachableObjs);
+
+		// Objects unreachable.
+		allocateUnreachableObjects();
+
 		synchronizer.sendMessage(JPDADebuggeeSynchronizer.SGNL_READY);
         logWriter.println("--> Debuggee: InstancesDebuggee...");
         synchronizer.receiveMessage(JPDADebuggeeSynchronizer.SGNL_CONTINUE);
 	}
 
+	private static void allocateReachableObjects(ArrayList<MockClass> reachableObjs) {
+	    for (int i = 0; i < reachableObjNum; i++) {
+            reachableObjs.add(new MockClass(true));
+        }
+	}
+
+	private static void allocateUnreachableObjects() {
+        for (int i = 0; i < unreachableObjNum; i++) {
+            new MockClass(false);
+        }
+	}
+
 	public static void main(String[] args) {
 		runDebuggee(InstancesDebuggee.class);
 	}