001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.generic;
019
020/** 
021 * Super class for JSR - Jump to subroutine
022 *
023 * @version $Id: JsrInstruction.java 1749603 2016-06-21 20:50:19Z ggregory $
024 */
025public abstract class JsrInstruction extends BranchInstruction implements UnconditionalBranch,
026        TypedInstruction, StackProducer {
027
028    JsrInstruction(final short opcode, final InstructionHandle target) {
029        super(opcode, target);
030    }
031
032
033    /**
034     * Empty constructor needed for the Class.newInstance() statement in
035     * Instruction.readInstruction(). Not to be used otherwise.
036     */
037    JsrInstruction() {
038    }
039
040
041    /** @return return address type
042     */
043    @Override
044    public Type getType( final ConstantPoolGen cp ) {
045        return new ReturnaddressType(physicalSuccessor());
046    }
047
048
049    /**
050     * Returns an InstructionHandle to the physical successor
051     * of this JsrInstruction. <B>For this method to work,
052     * this JsrInstruction object must not be shared between
053     * multiple InstructionHandle objects!</B>
054     * Formally, there must not be InstructionHandle objects
055     * i, j where i != j and i.getInstruction() == this ==
056     * j.getInstruction().
057     * @return an InstructionHandle to the "next" instruction that
058     * will be executed when RETurned from a subroutine.
059     */
060    public InstructionHandle physicalSuccessor() {
061        InstructionHandle ih = super.getTarget();
062        // Rewind!
063        while (ih.getPrev() != null) {
064            ih = ih.getPrev();
065        }
066        // Find the handle for "this" JsrInstruction object.
067        while (ih.getInstruction() != this) {
068            ih = ih.getNext();
069        }
070        final InstructionHandle toThis = ih;
071        while (ih != null) {
072            ih = ih.getNext();
073            if ((ih != null) && (ih.getInstruction() == this)) {
074                throw new RuntimeException("physicalSuccessor() called on a shared JsrInstruction.");
075            }
076        }
077        // Return the physical successor        
078        return toThis.getNext();
079    }
080}