--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/gov/nasa/jpf/jvm/bytecode/GetHelper.java	Fri Jan 23 10:14:01 2015 -0800
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2014, United States Government, as represented by the
+ * Administrator of the National Aeronautics and Space Administration.
+ * All rights reserved.
+ *
+ * The Java Pathfinder core (jpf-core) platform is licensed under the
+ * Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ * 
+ *        http://www.apache.org/licenses/LICENSE-2.0. 
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and 
+ * limitations under the License.
+ */
+
+package gov.nasa.jpf.jvm.bytecode;
+
+import gov.nasa.jpf.vm.Instruction;
+import gov.nasa.jpf.vm.MethodInfo;
+
+/**
+ * helper class to factor out common GET code
+ * 
+ * <2do> This is going to be moved into a Java 8 interface with default methods
+ */
+public class GetHelper {
+
+  /**
+   * do a little bytecode pattern analysis on the fly, to find out if a
+   * GETFIELD or GETSTATIC is just part of a "..synchronized (obj) {..} .."
+   * pattern, which usually translates into the following pattern:
+   *   ...
+   *   getfield / getstatic
+   *   dup
+   *   [astore]
+   *   monitorenter
+   *   ...
+   *
+   * If it does, there is no need to break the transition since the object
+   * reference is not used for anything that can cause violations between
+   * the get and the monitorenter.
+   *
+   * <2do> We might want to extend this in the future to also cover sync on
+   * local vars, like "Object o = myField; synchronized(o){..}..", but then
+   * the check becomes more expensive since we get interspersed aload/astore
+   * insns, and some of the locals could be used outside the sync block. Not
+   * sure if it buys much on the bottom line
+   *   
+   * <2do> this relies on javac code patterns. The dup/astore could
+   * lead to subsequent use of the object reference w/o corresponding get/putfield
+   * insns (if it's not a volatile), but this access would be either a call
+   * or a get/putfield on a share object, i.e. would be checked separately 
+   */
+  protected static boolean isMonitorEnterPrologue(MethodInfo mi, int insnIndex){
+    Instruction[] code = mi.getInstructions();
+    int off = insnIndex+1;
+
+    if (off < code.length-3) {
+      // we don't reach out further than 3 instructions
+      if (code[off] instanceof DUP) {
+        off++;
+
+        if (code[off] instanceof ASTORE) {
+          off++;
+        }
+
+        if (code[off] instanceof MONITORENTER) {
+          return true;
+        }
+      }
+    }
+    
+    return false; // if in doubt, we assume it is not part of a monitorenter code pattern
+  }
+}