Fix for bug reported by Ravi Chandran on the mailing list (10/01/2010). Properly add edges from method entry in the PDG

git-svn-id: https://wala.svn.sourceforge.net/svnroot/wala/trunk@3965 f5eafffb-2e1d-0410-98e4-8ec43c5233c4

com.ibm.wala.core.testdata/src/slice/TestCD5.java

@@ -0,0 +1,33 @@
+/*******************************************************************************
+ * Copyright (c) 2006 IBM Corporation.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+package slice;
+
+public class TestCD5 {
+
+  /**
+   * 
+   * @param args
+   */
+  public static void main(String[] args) {
+    int i = 0;
+    while (someBool()) {
+      ++i;
+      if (i >= 3) {
+        return;
+      }
+    }
+  }
+
+
+  public static boolean someBool() {
+    return false;
+  }
+}

com.ibm.wala.core.tests/src/com/ibm/wala/core/tests/slicer/SlicerTest.java

@@ -38,6 +38,7 @@ import com.ibm.wala.ipa.callgraph.impl.Util;
 import com.ibm.wala.ipa.cha.ClassHierarchy;
 import com.ibm.wala.ipa.cha.ClassHierarchyException;
 import com.ibm.wala.ipa.cha.IClassHierarchy;
+import com.ibm.wala.ipa.slicer.MethodEntryStatement;
 import com.ibm.wala.ipa.slicer.NormalStatement;
 import com.ibm.wala.ipa.slicer.SDG;
 import com.ibm.wala.ipa.slicer.Slicer;
@@ -371,6 +372,30 @@ public class SlicerTest {
     dumpSlice(slice);
     Assert.assertEquals(1, countConditionals(slice));
   }
+  
+  @Test
+  public void testTestCD5() throws ClassHierarchyException, IllegalArgumentException, CancelException, IOException {
+    AnalysisScope scope = findOrCreateAnalysisScope();
+
+    IClassHierarchy cha = findOrCreateCHA(scope);
+    Iterable<Entrypoint> entrypoints = com.ibm.wala.ipa.callgraph.impl.Util.makeMainEntrypoints(scope, cha,
+        TestConstants.SLICE_TESTCD5);
+    AnalysisOptions options = CallGraphTestUtil.makeAnalysisOptions(scope, entrypoints);
+
+    CallGraphBuilder builder = Util.makeZeroOneCFABuilder(options, new AnalysisCache(), cha, scope);
+    CallGraph cg = builder.makeCallGraph(options, null);
+
+    CGNode main = findMainMethod(cg);
+
+    Statement s = new MethodEntryStatement(main);
+    System.err.println("Statement: " + s);
+
+    // compute a no-data slice
+    Collection<Statement> slice = Slicer.computeForwardSlice(s, cg, builder.getPointerAnalysis(), DataDependenceOptions.NONE,
+        ControlDependenceOptions.FULL);
+    dumpSlice(slice);
+    Assert.assertTrue(slice.size() > 1);
+  }
 
   @Test
   public void testTestId() throws ClassHierarchyException, IllegalArgumentException, CancelException, IOException {

com.ibm.wala.core.tests/src/com/ibm/wala/core/tests/util/TestConstants.java

@@ -109,6 +109,8 @@ public interface TestConstants {
 
   public final static String SLICE_TESTCD4 = "Lslice/TestCD4";
 
+  public final static String SLICE_TESTCD5 = "Lslice/TestCD5";
+
   public final static String SLICE_TESTID = "Lslice/TestId";
 
   public final static String SLICE_TESTARRAYS = "Lslice/TestArrays";

com.ibm.wala.core/src/com/ibm/wala/ipa/slicer/PDG.java

@@ -295,15 +295,27 @@ public class PDG implements NumberedGraph<Statement> {
 
     // the CDG does not represent control dependences from the entry node.
     // add these manually
+    // We add control dependences to all instructions in all basic blocks B that _must_ execute.  
+    // A basic block is in B iff (1) it is the entry or (2) it is the sole successor of a block
+    // in B
     Statement methodEntry = new MethodEntryStatement(node);
-    for (Iterator<? extends ISSABasicBlock> it = cdg.iterator(); it.hasNext();) {
-      ISSABasicBlock bb = it.next();
-      if (cdg.getPredNodeCount(bb) == 0) {
-        // this is control dependent on the method entry.
-        for (SSAInstruction st : bb) {
-          Statement dest = ssaInstruction2Statement(st, ir, instructionIndices);
-          delegate.addEdge(methodEntry, dest);
+    ISSABasicBlock curBB = controlFlowGraph.entry();
+    Set<ISSABasicBlock> handledBlocks = HashSetFactory.make(2);
+    handledBlocks.add(curBB);
+    while (curBB != null) {
+      for (SSAInstruction st : curBB) {
+        Statement dest = ssaInstruction2Statement(st, ir, instructionIndices);
+        delegate.addEdge(methodEntry, dest);
+      }
+      if (controlFlowGraph.getSuccNodeCount(curBB) == 1) {
+        ISSABasicBlock succBlock = controlFlowGraph.getSuccNodes(curBB).next();
+        if (handledBlocks.add(succBlock)) {
+          curBB = succBlock;
+        } else {
+          curBB = null;
         }
+      } else {
+        curBB = null;
       }
     }
     // add CD from method entry to all callee parameter assignments