/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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 org.apache.commons.nabla.forward.instructions;

 import org.apache.commons.nabla.DifferentiationException;

 import org.apache.commons.nabla.forward.analysis.InstructionsTransformer;

 import org.apache.commons.nabla.forward.analysis.MethodDifferentiator;

 import org.objectweb.asm.Opcodes;

 import org.objectweb.asm.tree.AbstractInsnNode;

 import org.objectweb.asm.tree.InsnList;

 import org.objectweb.asm.tree.InsnNode;

 /** Differentiation transformer for DRETURN instructions.

  * <p>DRETURN instructions are replaced by ARETURN instructions

  * as a reference to a {@link

  * org.apache.commons.math3.analysis.differentiation.DerivativeStructure}

  * instance uses only one stack slot instead of two.</p>

  * @version $Id$

  */

 public class DReturnTransformer implements InstructionsTransformer {

     /** Indicator for top stack element conversion. */

     private final boolean stack0Converted;

     /** Simple constructor.

      * @param stack0Converted if true, the top level stack element has already been converted

      */

     public DReturnTransformer(final boolean stack0Converted) {

         this.stack0Converted = stack0Converted;

     }

     /** {@inheritDoc} */

     public InsnList getReplacement(final AbstractInsnNode insn,

                                    final MethodDifferentiator methodDifferentiator)

         throws DifferentiationException {

         final InsnList list = new InsnList();

         if (!stack0Converted) {

             // add conversion for top level stack element

             list.add(methodDifferentiator.doubleToDerivativeStructureConversion());

         }

         // add the return instruction for a reference type

         list.add(new InsnNode(Opcodes.ARETURN));

         return list;

     }

 }