--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/truffle/com.oracle.truffle.api/src/com/oracle/truffle/api/profiles/ValueProfile.java	Wed Dec 16 16:38:13 2015 +0100
@@ -0,0 +1,334 @@
+/*
+ * Copyright (c) 2014, 2015, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.truffle.api.profiles;
+
+import java.util.Objects;
+
+import com.oracle.truffle.api.CompilerDirectives;
+import com.oracle.truffle.api.CompilerDirectives.CompilationFinal;
+import com.oracle.truffle.api.Truffle;
+
+/**
+ * <p>
+ * Specialized value profile to capture certain properties of <code>Object</code> runtime values.
+ * Value profiles require a runtime check in their initialized state to verify their profiled
+ * assumption. Value profiles are limited to capture monomorphic profiles only. This means that if
+ * two or more identities or classes are profiles within a single profile then the profile has no
+ * effect and no overhead after compilation. There are specialized versions of this profile with
+ * less interpreter footprint for {@link ConditionProfile boolean}, {@link ByteValueProfile byte},
+ * {@link IntValueProfile int}, {@link LongValueProfile long}, {@link FloatValueProfile float} and
+ * {@link DoubleValueProfile double} values.
+ * </p>
+ *
+ * <p>
+ * <b> Usage example: </b>
+ *
+ * <pre>
+ * class SampleNode extends Node {
+ *
+ * final ValueProfile profile = ValueProfile.create{Identity,Class}Profile();
+ *
+ *     Object execute(Object input) {
+ *         Object profiledValue = profile.profile(input);
+ *         // compiler may know now more about profiledValue
+ *         return profieldValue;
+ *     }
+ * }
+ * </pre>
+ * <p>
+ *
+ *
+ * {@inheritDoc}
+ *
+ * @see #createIdentityProfile()
+ * @see #createClassProfile()
+ */
+public abstract class ValueProfile extends Profile {
+
+    ValueProfile() {
+    }
+
+    public abstract <T> T profile(T value);
+
+    /**
+     * <p>
+     * Returns a value profile that profiles the exact class of a value. It will check the class of
+     * the profiled value and provide additional information to the compiler if only non-null values
+     * of exactly one concrete Java class are passed as a parameter to the
+     * {@link ValueProfile#profile} method. This can be beneficial if subsequent code can take
+     * advantage of knowing the concrete class of the value. The profile will degrade to the generic
+     * case if a null value or if at least two instances of two different Java classes are
+     * registered.
+     * </p>
+     *
+     * <p>
+     * <b>Compilation notes:</b> Value profiles require a runtime check in their initialized state
+     * to verify their profiled class. If two classes have been seen on a single profile instance
+     * then this profile will transition to a generic state with no overhead.
+     * </P>
+     *
+     * @see ValueProfile usage example
+     */
+    public static ValueProfile createClassProfile() {
+        if (Truffle.getRuntime().isProfilingEnabled()) {
+            return ExactClass.create();
+        } else {
+            return Disabled.INSTANCE;
+        }
+    }
+
+    /**
+     * <p>
+     * Returns a value profile that profiles the object identity of a value. A single instance can
+     * only profile one particular instance.
+     * </p>
+     *
+     * <p>
+     * <b>Compilation notes:</b> Identity profiles require a runtime check to verify their profiled
+     * object identity. If two identities have been seen on a single profile instance then this
+     * profile will transition to a generic state with no overhead.
+     * </p>
+     */
+    public static ValueProfile createIdentityProfile() {
+        if (Truffle.getRuntime().isProfilingEnabled()) {
+            return Identity.create();
+        } else {
+            return Disabled.INSTANCE;
+        }
+    }
+
+    /**
+     * <p>
+     * Returns a value profile that profiles the object equality of a value. A single instance can
+     * only profile one set of equal values.
+     * </p>
+     *
+     * <p>
+     * <b>Compilation notes:</b> Equality profiles inline the body of the equal method of the first
+     * profiled value in order to verify its assumption. Please take care that you do this only for
+     * equals implementations that your guest language actually has control over otherwise your
+     * compiled code might contain recursions or too much code. If two non equal objects have been
+     * seen on a single profile instance then this profile will transition to a generic state with
+     * no overhead.
+     * </p>
+     */
+    public static ValueProfile createEqualityProfile() {
+        if (Truffle.getRuntime().isProfilingEnabled()) {
+            return Equality.create();
+        } else {
+            return Disabled.INSTANCE;
+        }
+    }
+
+    static final class Disabled extends ValueProfile {
+
+        static final ValueProfile INSTANCE = new Disabled();
+
+        @Override
+        protected Object clone() {
+            return INSTANCE;
+        }
+
+        @Override
+        public <T> T profile(T value) {
+            return value;
+        }
+
+        @Override
+        public String toString() {
+            return toStringDisabled(ValueProfile.class);
+        }
+
+    }
+
+    static final class Equality extends ValueProfile {
+
+        private static final Object GENERIC = new Object();
+
+        @CompilationFinal protected Object cachedValue = null;
+
+        Equality() {
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public <T> T profile(T newValue) {
+            // Field needs to be cached in local variable for thread safety and startup speed.
+            Object cached = this.cachedValue;
+            if (cached != GENERIC) {
+                if (cached != null && cached.equals(newValue)) {
+                    return (T) cached;
+                } else {
+                    CompilerDirectives.transferToInterpreterAndInvalidate();
+                    if (cached == null && newValue != null) {
+                        cachedValue = newValue;
+                    } else {
+                        cachedValue = GENERIC;
+                    }
+                }
+            }
+            return newValue;
+        }
+
+        public boolean isGeneric() {
+            return getCachedValue() == GENERIC;
+        }
+
+        public boolean isUninitialized() {
+            return getCachedValue() == null;
+        }
+
+        public Object getCachedValue() {
+            return cachedValue;
+        }
+
+        @Override
+        public String toString() {
+            return toString(ValueProfile.class, isUninitialized(), isGeneric(), //
+                            String.format("value == %s@%x", cachedValue != null ? cachedValue.getClass().getSimpleName() : "null", Objects.hash(cachedValue)));
+        }
+
+        /* Needed for lazy class loading. */
+        static ValueProfile create() {
+            return new Equality();
+        }
+
+    }
+
+    static final class Identity extends ValueProfile {
+
+        private static final Object UNINITIALIZED = new Object();
+        private static final Object GENERIC = new Object();
+
+        @CompilationFinal protected Object cachedValue = UNINITIALIZED;
+
+        Identity() {
+        }
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public <T> T profile(T newValue) {
+            // Field needs to be cached in local variable for thread safety and startup speed.
+            Object cached = this.cachedValue;
+            if (cached != GENERIC) {
+                if (cached == newValue) {
+                    return (T) cached;
+                } else {
+                    CompilerDirectives.transferToInterpreterAndInvalidate();
+                    if (cachedValue == UNINITIALIZED) {
+                        cachedValue = newValue;
+                    } else {
+                        cachedValue = GENERIC;
+                    }
+                }
+            }
+            return newValue;
+        }
+
+        public boolean isGeneric() {
+            return getCachedValue() == GENERIC;
+        }
+
+        public boolean isUninitialized() {
+            return getCachedValue() == UNINITIALIZED;
+        }
+
+        public Object getCachedValue() {
+            return cachedValue;
+        }
+
+        @Override
+        public String toString() {
+            return toString(ValueProfile.class, isUninitialized(), isGeneric(), //
+                            String.format("value == %s@%x", cachedValue != null ? cachedValue.getClass().getSimpleName() : "null", Objects.hash(cachedValue)));
+        }
+
+        /* Needed for lazy class loading. */
+        static ValueProfile create() {
+            return new Identity();
+        }
+
+    }
+
+    static final class ExactClass extends ValueProfile {
+
+        @CompilationFinal protected Class<?> cachedClass;
+
+        ExactClass() {
+        }
+
+        public static ValueProfile create() {
+            return new ExactClass();
+        }
+
+        @SuppressWarnings("unchecked")
+        @Override
+        public <T> T profile(T value) {
+            // Field needs to be cached in local variable for thread safety and startup speed.
+            Class<?> clazz = cachedClass;
+            if (clazz != Object.class) {
+                if (clazz != null && value != null && clazz == value.getClass()) {
+                    /*
+                     * The cast is really only for the compiler relevant. It does not perform any
+                     * useful action in the interpreter and only takes time.
+                     */
+                    if (CompilerDirectives.inInterpreter()) {
+                        return value;
+                    } else {
+                        return (T) clazz.cast(value);
+                    }
+                } else {
+                    CompilerDirectives.transferToInterpreterAndInvalidate();
+                    if (clazz == null && value != null) {
+                        cachedClass = value.getClass();
+                    } else {
+                        cachedClass = Object.class;
+                    }
+                }
+            }
+            return value;
+        }
+
+        boolean isGeneric() {
+            return cachedClass == Object.class;
+        }
+
+        boolean isUninitialized() {
+            return cachedClass == null;
+        }
+
+        Class<?> getCachedClass() {
+            return cachedClass;
+        }
+
+        @Override
+        public String toString() {
+            return toString(ValueProfile.class, cachedClass == null, cachedClass == Object.class, //
+                            String.format("value.getClass() == %s.class", cachedClass != null ? cachedClass.getSimpleName() : "null"));
+        }
+
+    }
+
+}