gt:             if (v != null) {
context: /*
   * 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.graal.options;
  
  import java.io.*;
  import java.util.*;
  import java.util.Map.Entry;
  
  /**
   * An option value.
   */
  public class OptionValue<T> {
  
      /**
       * Temporarily changes the value for an option. The {@linkplain OptionValue#getValue() value} of
       * {@code option} is set to {@code value} until {@link OverrideScope#close()} is called on the
       * object returned by this method.
       * <p>
       * Since the returned object is {@link AutoCloseable} the try-with-resource construct can be
       * used:
       *
       * <pre>
       * try (OverrideScope s = OptionValue.override(myOption, myValue) {
       *     // code that depends on myOption == myValue
       * }
       * </pre>
       */
      public static OverrideScope override(OptionValue<?> option, Object value) {
          OverrideScope current = overrideScopes.get();
          if (current == null) {
              if (!value.equals(option.getValue())) {
                  return new SingleOverrideScope(option, value);
              }
              Map<OptionValue<?>, Object> overrides = Collections.emptyMap();
              return new MultipleOverridesScope(current, overrides);
          }
          return new MultipleOverridesScope(current, option, value);
      }
  
      /**
       * Temporarily changes the values for a set of options. The {@linkplain OptionValue#getValue()
       * value} of each {@code option} in {@code overrides} is set to the corresponding {@code value}
       * in {@code overrides} until {@link OverrideScope#close()} is called on the object returned by
       * this method.
       * <p>
       * Since the returned object is {@link AutoCloseable} the try-with-resource construct can be
       * used:
       *
       * <pre>
       * Map&lt;OptionValue, Object&gt; overrides = new HashMap&lt;&gt;();
       * overrides.put(myOption1, myValue1);
       * overrides.put(myOption2, myValue2);
       * try (OverrideScope s = OptionValue.override(overrides) {
       *     // code that depends on myOption == myValue
       * }
       * </pre>
       */
      public static OverrideScope override(Map<OptionValue<?>, Object> overrides) {
          OverrideScope current = overrideScopes.get();
          if (current == null && overrides.size() == 1) {
              Entry<OptionValue<?>, Object> single = overrides.entrySet().iterator().next();
              OptionValue<?> option = single.getKey();
              Object overrideValue = single.getValue();
              if (!overrideValue.equals(option.getValue())) {
                  return new SingleOverrideScope(option, overrideValue);
              }
          }
          return new MultipleOverridesScope(current, overrides);
      }
  
      /**
       * Temporarily changes the values for a set of options. The {@linkplain OptionValue#getValue()
       * value} of each {@code option} in {@code overrides} is set to the corresponding {@code value}
       * in {@code overrides} until {@link OverrideScope#close()} is called on the object returned by
       * this method.
       * <p>
       * Since the returned object is {@link AutoCloseable} the try-with-resource construct can be
       * used:
       *
       * <pre>
       * try (OverrideScope s = OptionValue.override(myOption1, myValue1, myOption2, myValue2) {
       *     // code that depends on myOption == myValue
       * }
       * </pre>
       *
       * @param overrides overrides in the form {@code [option1, override1, option2, override2, ...]}
       */
      public static OverrideScope override(Object... overrides) {
          OverrideScope current = overrideScopes.get();
          if (current == null && overrides.length == 2) {
              OptionValue<?> option = (OptionValue<?>) overrides[0];
              Object overrideValue = overrides[1];
              if (!overrideValue.equals(option.getValue())) {
                  return new SingleOverrideScope(option, overrideValue);
              }
          }
          Map<OptionValue<?>, Object> map = Collections.emptyMap();
          for (int i = 0; i < overrides.length; i += 2) {
              OptionValue<?> option = (OptionValue<?>) overrides[i];
              Object overrideValue = overrides[i + 1];
              if (!overrideValue.equals(option.getValue())) {
                  if (map.isEmpty()) {
                      map = new HashMap<>();
                  }
                  map.put(option, overrideValue);
              }
          }
          return new MultipleOverridesScope(current, map);
      }
  
      private static final ThreadLocal<OverrideScope> overrideScopes = new ThreadLocal<>();
  
      /**
       * The raw option value.
       */
      protected T value;
  
      private OptionDescriptor descriptor;
  
      private long reads;
      private OptionValue<?> next;
      private static OptionValue<?> head;
  
      private static final boolean ShowReadsHistogram = Boolean.getBoolean("graal.showOptionValueReadsHistogram");
  
      private static void addToHistogram(OptionValue<?> option) {
          if (ShowReadsHistogram) {
              synchronized (OptionValue.class) {
                  option.next = head;
                  head = option;
              }
          }
      }
  
      public OptionValue(T value) {
          this.value = value;
          addToHistogram(this);
      }
  
      private static final Object UNINITIALIZED = "UNINITIALIZED";
  
      /**
       * Creates an uninitialized option value for a subclass that initializes itself
       * {@link #initialValue() lazily}.
       */
      @SuppressWarnings("unchecked")
      protected OptionValue() {
          this.value = (T) UNINITIALIZED;
          addToHistogram(this);
      }
  
      /**
       * Lazy initialization of value.
       */
      protected T initialValue() {
          throw new InternalError("Uninitialized option value must override initialValue()");
      }
  
      /**
       * Sets the descriptor for this option.
       */
      public void setDescriptor(OptionDescriptor descriptor) {
          this.descriptor = descriptor;
      }
  
      /**
       * Gets the name of this option. The name for an option value with a null
       * {@linkplain #setDescriptor(OptionDescriptor) descriptor} is the value of
       * {@link Object#toString()}.
       */
      public String getName() {
          return descriptor == null ? super.toString() : (descriptor.getDeclaringClass().getName() + "." + descriptor.getName());
      }
  
      @Override
      public String toString() {
          return getName() + "=" + getValue();
      }
  
      /**
       * Gets the value of this option.
       */
      public T getValue() {
          if (ShowReadsHistogram) {
              reads++;
          }
          if (!(this instanceof StableOptionValue)) {
              OverrideScope overrideScope = overrideScopes.get();
              if (overrideScope != null) {
                  T override = overrideScope.getOverride(this);
                  if (override != null) {
                      return override;
                  }
              }
          }
          if (value == UNINITIALIZED) {
              value = initialValue();
          }
          return value;
      }
  
      /**
       * Gets the values of this option including overridden values.
       *
       * @param c the collection to which the values are added. If null, one is allocated.
       * @return the collection to which the values were added in order from most overridden to
       *         current value
       */
      @SuppressWarnings("unchecked")
      public Collection<T> getValues(Collection<T> c) {
          Collection<T> values = c == null ? new ArrayList<>() : c;
          if (!(this instanceof StableOptionValue)) {
              OverrideScope overrideScope = overrideScopes.get();
              if (overrideScope != null) {
                  overrideScope.getOverrides(this, (Collection<Object>) values);
              }
          }
          values.add(value);
          return values;
      }
  
      /**
       * Sets the value of this option.
       */
      @SuppressWarnings("unchecked")
      public void setValue(Object v) {
          this.value = (T) v;
      }
  
      /**
       * An object whose {@link #close()} method reverts the option value overriding initiated by
       * {@link OptionValue#override(OptionValue, Object)} or {@link OptionValue#override(Map)}.
       */
      public abstract static class OverrideScope implements AutoCloseable {
          abstract void addToInherited(Map<OptionValue<?>, Object> inherited);
  
          abstract <T> T getOverride(OptionValue<T> option);
  
          abstract void getOverrides(OptionValue<?> option, Collection<Object> c);
  
          public abstract void close();
      }
  
      static class SingleOverrideScope extends OverrideScope {
  
          private final OptionValue<?> option;
          private final Object value;
  
          public SingleOverrideScope(OptionValue<?> option, Object value) {
              if (option instanceof StableOptionValue) {
                  throw new IllegalArgumentException("Cannot override stable option " + option);
              }
              this.option = option;
              this.value = value;
              overrideScopes.set(this);
          }
  
          @Override
          void addToInherited(Map<OptionValue<?>, Object> inherited) {
              inherited.put(option, value);
          }
  
          @SuppressWarnings("unchecked")
          @Override
          <T> T getOverride(OptionValue<T> key) {
              if (key == this.option) {
                  return (T) value;
              }
              return null;
          }
  
          @Override
          void getOverrides(OptionValue<?> key, Collection<Object> c) {
              if (key == this.option) {
                  c.add(value);
              }
          }
  
          @Override
          public void close() {
              overrideScopes.set(null);
          }
      }
  
      static class MultipleOverridesScope extends OverrideScope {
          final OverrideScope parent;
          final Map<OptionValue<?>, Object> overrides;
  
          public MultipleOverridesScope(OverrideScope parent, OptionValue<?> option, Object value) {
              this.parent = parent;
              this.overrides = new HashMap<>();
              if (parent != null) {
                  parent.addToInherited(overrides);
              }
              if (option instanceof StableOptionValue) {
                  throw new IllegalArgumentException("Cannot override stable option " + option);
              }
              if (!value.equals(option.getValue())) {
                  this.overrides.put(option, value);
              }
              if (!overrides.isEmpty()) {
                  overrideScopes.set(this);
              }
          }
  
          MultipleOverridesScope(OverrideScope parent, Map<OptionValue<?>, Object> overrides) {
              this.parent = parent;
              if (overrides.isEmpty() && parent == null) {
                  this.overrides = Collections.emptyMap();
                  return;
              }
              this.overrides = new HashMap<>();
              if (parent != null) {
                  parent.addToInherited(this.overrides);
              }
              for (Map.Entry<OptionValue<?>, Object> e : overrides.entrySet()) {
                  OptionValue<?> option = e.getKey();
                  if (option instanceof StableOptionValue) {
                      throw new IllegalArgumentException("Cannot override stable option " + option);
                  }
                  if (!e.getValue().equals(option.getValue())) {
                      this.overrides.put(option, e.getValue());
                  }
              }
              if (!this.overrides.isEmpty()) {
                  overrideScopes.set(this);
              }
          }
  
          @Override
          void addToInherited(Map<OptionValue<?>, Object> inherited) {
              if (parent != null) {
                  parent.addToInherited(inherited);
              }
              inherited.putAll(overrides);
          }
  
          @SuppressWarnings("unchecked")
          @Override
          <T> T getOverride(OptionValue<T> option) {
              return (T) overrides.get(option);
          }
  
          @Override
          void getOverrides(OptionValue<?> option, Collection<Object> c) {
              Object v = overrides.get(option);
  