--- a/graal/com.oracle.graal.truffle/src/com/oracle/graal/truffle/substitutions/CompilerDirectivesSubstitutions.java	Thu Aug 08 19:28:42 2013 +0200
+++ b/graal/com.oracle.graal.truffle/src/com/oracle/graal/truffle/substitutions/CompilerDirectivesSubstitutions.java	Thu Aug 08 19:35:32 2013 +0200
@@ -42,6 +42,11 @@
     }
 
     @MethodSubstitution
+    public static boolean inInterpreter() {
+        return false;
+    }
+
+    @MethodSubstitution
     public static void interpreterOnly(@SuppressWarnings("unused") Runnable runnable) {
     }
 

--- a/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/CompilerDirectives.java	Thu Aug 08 19:28:42 2013 +0200
+++ b/graal/com.oracle.truffle.api/src/com/oracle/truffle/api/CompilerDirectives.java	Thu Aug 08 19:35:32 2013 +0200
@@ -45,6 +45,15 @@
     }
 
     /**
+     * Returns a boolean value indicating whether the method is executed in the interpreter.
+     * 
+     * @return {@code true} when executed in the interpreter, {@code false} in compiled code.
+     */
+    public static boolean inInterpreter() {
+        return true;
+    }
+
+    /**
      * Directive for the compiler that the given runnable should only be executed in the interpreter
      * and ignored in the compiled code.
      *