/***
* bytecode-analysis: a prototype-library based on ASM 4 that
* computes definitions/uses of each instruction
* Copyright (c) 2014 University of Sao Paulo
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
package br.usp.each.saeg.bytecode.analysis.graph;
import java.util.Arrays;
import java.util.List;
import br.usp.each.saeg.bytecode.analysis.BytecodeInstruction;
import br.usp.each.saeg.bytecode.analysis.BytecodeInstructionType;
public class BasicBlockGraphNodeJoiner extends GraphNodeVisitor {
private GraphNode root;
public void start(final GraphNode root) {
this.root = root;
}
/**
* Groups sequential instructions of the given graph in single nodes
*
* @param graph the graph to be simplified
*/
@Override
public void visit(final GraphNode node) {
GraphNode[] children = node.getChildren();
while (children.length == 1) {
final GraphNode child = children[0];
if (child == root)
return;
if (child.getParents().length == 1) {
List<GraphNode> nodeException = Arrays.asList(node.getExceptionChildren());
List<GraphNode> childException = Arrays.asList(child.getExceptionChildren());
if (!nodeException.containsAll(childException)
|| !childException.containsAll(nodeException)) {
return;
}
BytecodeInstruction instruction = node.instructions.get(node.instructions.size() - 1);
if (instruction.getType() == BytecodeInstructionType.GOTO) {
return;
}
child.removeExceptionChildren(childException);
children = child.getChildren();
node.removeChild(child);
node.addChildren(children);
child.removeChildren(children);
node.instructions.addAll(child.instructions);
}
else {
return; // return otherwise.
}
}
}
}