/*
* Copyright 2003-2011 JetBrains s.r.o.
*
* Licensed 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 jetbrains.mps.lang.dataFlow.framework.analyzers;
import jetbrains.mps.lang.dataFlow.framework.instructions.WriteInstruction;
import jetbrains.mps.lang.dataFlow.framework.instructions.Instruction;
import jetbrains.mps.lang.dataFlow.framework.instructions.ReadInstruction;
import jetbrains.mps.lang.dataFlow.framework.DataFlowAnalyzer;
import jetbrains.mps.lang.dataFlow.framework.Program;
import jetbrains.mps.lang.dataFlow.framework.ProgramState;
import jetbrains.mps.lang.dataFlow.framework.AnalysisDirection;
import java.util.Set;
import java.util.HashSet;
import java.util.List;
public class ReachingReadsAnalyzer implements DataFlowAnalyzer<Set<ReadInstruction>> {
@Override
public Set<ReadInstruction> initial(Program p) {
return new HashSet<ReadInstruction>();
}
@Override
public Set<ReadInstruction> merge(Program p, List<Set<ReadInstruction>> input) {
Set<ReadInstruction> result = new HashSet<ReadInstruction>();
for (Set<ReadInstruction> i : input) {
result.addAll(i);
}
return result;
}
@Override
public Set<ReadInstruction> fun(Set<ReadInstruction> input, ProgramState s) {
Instruction instruction = s.getInstruction();
Set<ReadInstruction> result = input;
if (instruction instanceof WriteInstruction) {
WriteInstruction write = (WriteInstruction) instruction;
for (ReadInstruction item : new HashSet<ReadInstruction>(result)) {
Object variable = write.getVariable();
if (variable != null && variable.equals(item.getVariable())) {
result.remove(item);
}
}
}
if (instruction instanceof ReadInstruction) {
result.add((ReadInstruction) instruction);
}
return result;
}
@Override
public AnalysisDirection getDirection() {
return AnalysisDirection.BACKWARD;
}
}