/*
* 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.IfJumpInstruction;
import jetbrains.mps.lang.dataFlow.framework.instructions.JumpInstruction;
import jetbrains.mps.lang.dataFlow.framework.instructions.WriteInstruction;
import jetbrains.mps.lang.dataFlow.framework.instructions.Instruction;
import jetbrains.mps.lang.dataFlow.framework.*;
import java.util.Set;
import java.util.HashSet;
import java.util.List;
public class MayBeInitializedVariablesAnalyzer implements DataFlowAnalyzer<VarSet> {
private Set<Instruction> myExclusions;
public MayBeInitializedVariablesAnalyzer(Instruction... exclusions) {
myExclusions = new HashSet<Instruction>(exclusions.length);
for (Instruction exclusion : exclusions) {
myExclusions.add(exclusion);
}
}
@Override
public VarSet initial(Program p) {
return new VarSet(p, false);
}
@Override
public VarSet merge(Program p, List<VarSet> input) {
if (input.isEmpty()) {
return initial(p);
}
VarSet result = new VarSet(p, false);
for (VarSet anInput : input) {
result.addAll(anInput);
}
return result;
}
@Override
public VarSet fun(VarSet input, ProgramState s) {
Instruction instruction = s.getInstruction();
VarSet result = input;
if (s.isStart()) {
result.clear();
}
if (instruction instanceof WriteInstruction && !myExclusions.contains(instruction)) {
WriteInstruction write = (WriteInstruction) instruction;
result.add(write.getVariableIndex());
}
if (instruction instanceof JumpInstruction || instruction instanceof IfJumpInstruction) {
final int to;
if (instruction instanceof JumpInstruction) {
to = ((JumpInstruction) instruction).getJumpTo();
} else {
to = ((IfJumpInstruction) instruction).getJumpTo();
}
final int current = s.getInstruction().getIndex();
if (to < current) { //jumping backwards
final Program program = instruction.getProgram();
for (Object var : program.getVariables()) {
final List<Instruction> instructions = program.getInstructionsFor(var);
if (!instructions.isEmpty()) {
if (to < instructions.get(0).getIndex()) { //declaration is inside the loop
result.remove(var);
} else { //declaration is before the loop
result.add(var);
}
}
}
}
}
return result;
}
@Override
public AnalysisDirection getDirection() {
return AnalysisDirection.FORWARD;
}
}