--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/com.oracle.jvmci.debug/src/com/oracle/jvmci/debug/DebugHistogram.java	Tue May 26 23:21:15 2015 +0200
@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.oracle.jvmci.debug;
+
+import java.util.*;
+
+/**
+ * Facility for recording value frequencies.
+ */
+public interface DebugHistogram {
+
+    /**
+     * Gets the name specified when this objected was {@linkplain Debug#createHistogram(String)
+     * created}.
+     */
+    String getName();
+
+    /**
+     * Increments the count for a given value.
+     */
+    void add(Object value);
+
+    void add(Object value, long count);
+
+    /**
+     * A value and a frequency. The ordering imposed by {@link #compareTo(CountedValue)} places
+     * values with higher frequencies first.
+     */
+    public class CountedValue implements Comparable<CountedValue> {
+
+        private long count;
+        private final Object value;
+
+        public CountedValue(long count, Object value) {
+            this.count = count;
+            this.value = value;
+        }
+
+        public int compareTo(CountedValue o) {
+            if (count < o.count) {
+                return 1;
+            } else if (count > o.count) {
+                return -1;
+            }
+            return 0;
+        }
+
+        @Override
+        public String toString() {
+            return count + " -> " + value;
+        }
+
+        public void inc() {
+            count++;
+        }
+
+        public void add(long n) {
+            count += n;
+        }
+
+        public long getCount() {
+            return count;
+        }
+
+        public Object getValue() {
+            return value;
+        }
+    }
+
+    /**
+     * Gets a list of the counted values, sorted in descending order of frequency.
+     */
+    List<CountedValue> getValues();
+
+    /**
+     * Interface for a service that can render a visualization of a histogram.
+     */
+    public interface Printer {
+
+        void print(DebugHistogram histogram);
+    }
+}