/***
* 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.defuse;
import java.util.Set;
import br.usp.each.saeg.bytecode.analysis.BytecodeInstruction;
import br.usp.each.saeg.bytecode.analysis.graph.GraphNode;
import br.usp.each.saeg.bytecode.analysis.graph.GraphNodeVisitor;
import br.usp.each.saeg.bytecode.analysis.graph.PreOrderTraversalStrategy;
public class LonelyDefinitionsRemover extends GraphNodeVisitor {
private Set<VariableRef> uses;
@Override
public void start(final GraphNode root) {
final VariablesCollector variables = new VariablesCollector();
new PreOrderTraversalStrategy(variables).traverse(root);
uses = variables.getUsesVariableRefs();
}
@Override
public void visit(final GraphNode node) {
for (final BytecodeInstruction insn : node.instructions) {
if (insn.frame != null && insn.frame.def != null) {
VariableRef def = null;
if (uses.contains(insn.frame.def)) {
def = insn.frame.def;
}
if (def == null && insn.frame.uses.isEmpty()) {
insn.frame = null;
} else {
insn.frame = new DefUseFrame(def, insn.frame.uses);
}
}
}
}
}