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1
19
20 package edu.umd.cs.findbugs.ba.npe2;
21
22 import java.util.BitSet  ;
23 import java.util.HashMap ;
24 import java.util.Map ;
25
26 import org.apache.bcel.Constants;
27 import org.apache.bcel.classfile.Method;
28 import org.apache.bcel.generic.InstructionHandle;
29
30 import edu.umd.cs.findbugs.ba.BasicBlock;
31 import edu.umd.cs.findbugs.ba.CFGBuilderException;
32 import edu.umd.cs.findbugs.ba.ClassContext;
33 import edu.umd.cs.findbugs.ba.CompactLocationNumbering;
34 import edu.umd.cs.findbugs.ba.Dataflow;
35 import edu.umd.cs.findbugs.ba.DataflowAnalysisException;
36 import edu.umd.cs.findbugs.ba.DataflowTestDriver;
37 import edu.umd.cs.findbugs.ba.DepthFirstSearch;
38 import edu.umd.cs.findbugs.ba.Edge;
39 import edu.umd.cs.findbugs.ba.EdgeTypes;
40 import edu.umd.cs.findbugs.ba.ForwardDataflowAnalysis;
41 import edu.umd.cs.findbugs.ba.Location;
42 import edu.umd.cs.findbugs.ba.npe.WillBeDereferencedInfo;
43 import edu.umd.cs.findbugs.ba.vna.ValueNumber;
44 import edu.umd.cs.findbugs.ba.vna.ValueNumberDataflow;
45 import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;
46
47
53 public class DefinitelyNullSetAnalysis extends ForwardDataflowAnalysis<DefinitelyNullSet> {
54 private ValueNumberDataflow vnaDataflow;
55 private CompactLocationNumbering compactLocationNumbering;
56 private Map <BasicBlock, Condition> conditionMap;
57
58 private static final BitSet IFNULL_OPCODE_SET = new BitSet ();
59 private static final BitSet IFACMP_OPCODE_SET = new BitSet ();
60 private static final BitSet REFCMP_OPCODE_SET = new BitSet ();
61 static {
62 IFNULL_OPCODE_SET.set(Constants.IFNULL);
63 IFNULL_OPCODE_SET.set(Constants.IFNONNULL);
64
65 IFACMP_OPCODE_SET.set(Constants.IF_ACMPEQ);
66 IFACMP_OPCODE_SET.set(Constants.IF_ACMPNE);
67
68 REFCMP_OPCODE_SET.or(IFNULL_OPCODE_SET);
69 REFCMP_OPCODE_SET.or(IFACMP_OPCODE_SET);
70 }
71
72
79 public DefinitelyNullSetAnalysis(
80 DepthFirstSearch dfs,
81 ValueNumberDataflow vnaDataflow,
82 CompactLocationNumbering compactLocationNumbering) {
83 super(dfs);
84 this.vnaDataflow = vnaDataflow;
85 this.compactLocationNumbering = compactLocationNumbering;
86 this.conditionMap = new HashMap <BasicBlock, Condition>();
87 }
88
89
92 @Override
93 public boolean isFactValid(DefinitelyNullSet fact) {
94 return fact.isValid();
95 }
96
97
100 @Override
101 public void transferInstruction(InstructionHandle handle, BasicBlock basicBlock, DefinitelyNullSet fact) throws DataflowAnalysisException {
102 Location location = new Location(handle, basicBlock);
103 ValueNumberFrame vnaFrame = vnaDataflow.getFactAfterLocation(location);
104
105 if (!vnaFrame.isValid()) {
106 fact.setTop();
107 return;
108 }
109
110
114 short opcode = handle.getInstruction().getOpcode();
115
116 if (opcode == Constants.ACONST_NULL) {
117 setTOS(vnaFrame, location, fact, NullnessValue.definitelyNullValue());
118 } else if (opcode == Constants.LDC || opcode == Constants.NEW) {
119 setTOS(vnaFrame, location, fact, NullnessValue.definitelyNotNullValue());
120 }
121
122
124 if (handle == basicBlock.getLastInstruction() && REFCMP_OPCODE_SET.get(opcode)) {
126 Condition condition = getCondition(basicBlock);
127 if (condition != null) {
128 condition.refresh(vnaDataflow.getFactAtLocation(location), fact);
130 }
131 }
132 }
133
134
142 private Condition getCondition(BasicBlock basicBlock)
143 throws DataflowAnalysisException {
144 Condition condition = conditionMap.get(basicBlock);
145 if (condition == null) {
146 Location location = new Location(basicBlock.getLastInstruction(), basicBlock);
147 short opcode = basicBlock.getLastInstruction().getInstruction().getOpcode();
148 if (IFNULL_OPCODE_SET.get(opcode)) {
149 condition = new IfNullCondition(location);
150 } else if (IFACMP_OPCODE_SET.get(opcode)) {
151 return null;
153 } else {
154 return null;
155 }
156 conditionMap.put(basicBlock, condition);
157 }
158 return condition;
159 }
160
161
164 @Override
165 public void edgeTransfer(Edge edge, DefinitelyNullSet fact) throws DataflowAnalysisException {
166 if (!fact.isValid()) {
167 return;
168 }
169
170 if (edge.getSource().isEmpty()) {
171 return;
172 }
173
174 Condition condition = getCondition(edge.getSource());
175 if (condition == null) {
176 return;
177 }
178
179 Decision decision = condition.getDecision(edge);
180 if (!decision.isFeasible()) {
181 fact.setTop();
185 return;
186 }
187
188 System.out.println("Setting " + condition.getValueNumber() + " to " + decision.getNullnessValue() + " on edge " + edge);
189
190 changeNullnessOfValue(
191 condition.getValueNumber(),
192 condition.getLocation(),
193 fact,
194 decision.getNullnessValue());
195 }
196
197
206 private void setTOS(ValueNumberFrame vnaFrame, Location location, DefinitelyNullSet fact, NullnessValue nullnessValue)
207 throws DataflowAnalysisException {
208 ValueNumber valueNumber = vnaFrame.getTopValue();
209 changeNullnessOfValue(valueNumber, location, fact, nullnessValue);
210 }
211
212
221 private void changeNullnessOfValue(ValueNumber valueNumber, Location location, DefinitelyNullSet fact, NullnessValue nullnessValue) throws DataflowAnalysisException {
222
229 fact.setNullnessValue(valueNumber, nullnessValue);
230
231 if (fact.getNulllessValue(valueNumber) != nullnessValue) {
232 throw new IllegalStateException ();
233 }
234
235 }
237
238
241 public void copy(DefinitelyNullSet source, DefinitelyNullSet dest) {
242 dest.makeSameAs(source);
243 }
244
245
248 public DefinitelyNullSet createFact() {
249 return new DefinitelyNullSet(vnaDataflow.getAnalysis().getNumValuesAllocated());
251 }
252
253
256 public void initEntryFact(DefinitelyNullSet result) throws DataflowAnalysisException {
257 result.clear();
259 }
260
261
264 public void initResultFact(DefinitelyNullSet result) {
265 result.setTop();
266 }
267
268
271 public void makeFactTop(DefinitelyNullSet fact) {
272 fact.setTop();
273 }
274 public boolean isTop(DefinitelyNullSet fact) {
275 return fact.isTop();
276 }
277
280 public void meetInto(DefinitelyNullSet fact, Edge edge, DefinitelyNullSet result) throws DataflowAnalysisException {
281
283 result.mergeWith(fact);
284 }
285
286
289 public boolean same(DefinitelyNullSet fact1, DefinitelyNullSet fact2) {
290 return fact1.equals(fact2);
291 }
292
293 public static void main(String [] args) throws Exception {
294 if (args.length != 1) {
295 System.err.println("Usage: " + DefinitelyNullSetAnalysis.class.getName() + " <classfile>");
296 System.exit(1);
297 }
298
299 DataflowTestDriver<DefinitelyNullSet, DefinitelyNullSetAnalysis> driver =
300 new DataflowTestDriver<DefinitelyNullSet, DefinitelyNullSetAnalysis>() {
301
304 @Override
305 public Dataflow<DefinitelyNullSet, DefinitelyNullSetAnalysis> createDataflow(ClassContext classContext, Method method) throws CFGBuilderException, DataflowAnalysisException {
306 return classContext.getDefinitelyNullSetDataflow(method);
307 }
308 };
309
310 driver.execute(args[0]);
311 }
312 }
313 |
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