public static Set<ValueNumber> checkNonNullParams(
      Location location,
      ValueNumberFrame vnaFrame,
      ConstantPoolGen constantPool,
      @CheckForNull Method method,
      @CheckForNull IsNullValueFrame invFrame)
      throws DataflowAnalysisException {

    if (invFrame != null && !invFrame.isValid()) {
      return Collections.emptySet();
    }
    INullnessAnnotationDatabase database =
        AnalysisContext.currentAnalysisContext().getNullnessAnnotationDatabase();

    InvokeInstruction inv = (InvokeInstruction) location.getHandle().getInstruction();
    XMethod called = XFactory.createXMethod(inv, constantPool);
    SignatureParser sigParser = new SignatureParser(called.getSignature());
    int numParams = sigParser.getNumParameters();

    Set<ValueNumber> result = new HashSet<ValueNumber>();
    Iterator<String> parameterIterator = sigParser.parameterSignatureIterator();
    for (int i = 0; i < numParams; i++) {
      String parameterSignature = parameterIterator.next();
      char firstChar = parameterSignature.charAt(0);
      if (firstChar != 'L' && firstChar != '[') {
        continue;
      }
      int offset = sigParser.getSlotsFromTopOfStackForParameter(i);
      if (invFrame != null) {
        int slot = invFrame.getStackLocation(offset);
        if (!reportDereference(invFrame, slot)) {
          continue;
        }
      }
      if (database.parameterMustBeNonNull(called, i)) {
        int catchSizeNPE =
            Util.getSizeOfSurroundingTryBlock(
                method, "java/lang/NullPointerException", location.getHandle().getPosition());
        int catchSizeNFE =
            Util.getSizeOfSurroundingTryBlock(
                method, "java/lang/NumberFormatException", location.getHandle().getPosition());
        if (catchSizeNPE == Integer.MAX_VALUE
            && (!"java.lang.Integer".equals(called.getClassName())
                || catchSizeNFE == Integer.MAX_VALUE)) {
          // Get the corresponding value number
          ValueNumber vn = vnaFrame.getArgument(inv, constantPool, i, sigParser);
          result.add(vn);
        }
      }
    }
    return result;
  }
  public static Set<ValueNumber> checkUnconditionalDerefDatabase(
      Location location,
      ValueNumberFrame vnaFrame,
      ConstantPoolGen constantPool,
      @CheckForNull IsNullValueFrame invFrame,
      TypeDataflow typeDataflow)
      throws DataflowAnalysisException {
    if (invFrame != null && !invFrame.isValid()) {
      return Collections.emptySet();
    }

    InvokeInstruction inv = (InvokeInstruction) location.getHandle().getInstruction();

    SignatureParser sigParser = new SignatureParser(inv.getSignature(constantPool));
    int numParams = sigParser.getNumParameters();
    if (numParams == 0 || !sigParser.hasReferenceParameters()) {
      return Collections.emptySet();
    }
    ParameterNullnessPropertyDatabase database =
        AnalysisContext.currentAnalysisContext().getUnconditionalDerefParamDatabase();
    if (database == null) {
      if (DEBUG_CHECK_CALLS) {
        System.out.println("no database!");
      }
      return Collections.emptySet();
    }

    TypeFrame typeFrame = typeDataflow.getFactAtLocation(location);
    if (!typeFrame.isValid()) {
      if (DEBUG_CHECK_CALLS) {
        System.out.println("invalid type frame!");
      }
      return Collections.emptySet();
    }

    try {
      Set<XMethod> targetSet = Hierarchy2.resolveMethodCallTargets(inv, typeFrame, constantPool);

      if (targetSet.isEmpty()) {
        return Collections.emptySet();
      }

      if (DEBUG_CHECK_CALLS) {
        System.out.println("target set size: " + targetSet.size());
      }
      // Compute the intersection of all properties
      ParameterProperty derefParamSet = null;
      for (XMethod target : targetSet) {
        if (target.isStub()) {
          continue;
        }
        if (DEBUG_CHECK_CALLS) {
          System.out.print("Checking: " + target + ": ");
        }

        ParameterProperty targetDerefParamSet = database.getProperty(target.getMethodDescriptor());
        if (targetDerefParamSet == null) {
          // Hmm...no information for this target.
          // assume it doesn't dereference anything
          if (DEBUG_CHECK_CALLS) {
            System.out.println("==> no information, assume no guaranteed dereferences");
          }
          return Collections.emptySet();
        }

        if (DEBUG_CHECK_CALLS) {
          System.out.println("==> " + targetDerefParamSet);
        }
        if (derefParamSet == null) {
          derefParamSet = new ParameterProperty();
          derefParamSet.copyFrom(targetDerefParamSet);
        } else {
          derefParamSet.intersectWith(targetDerefParamSet);
        }
      }

      if (derefParamSet == null || derefParamSet.isEmpty()) {
        if (DEBUG) {
          System.out.println("** Nothing");
        }
        return Collections.emptySet();
      }
      if (DEBUG_CHECK_CALLS) {
        System.out.println(
            "** Summary of call @ " + location.getHandle().getPosition() + ": " + derefParamSet);
      }

      HashSet<ValueNumber> requiredToBeNonnull = new HashSet<ValueNumber>();
      for (int i = 0; i < numParams; i++) {
        if (!derefParamSet.hasProperty(i)) {
          continue;
        }
        int argSlot = vnaFrame.getStackLocation(sigParser.getSlotsFromTopOfStackForParameter(i));
        if (invFrame != null && !reportDereference(invFrame, argSlot)) {
          continue;
        }
        if (DEBUG_CHECK_CALLS) {
          System.out.println(
              "  dereference @ " + location.getHandle().getPosition() + " of parameter " + i);
        }

        requiredToBeNonnull.add(vnaFrame.getValue(argSlot));
      }
      return requiredToBeNonnull;

    } catch (ClassNotFoundException e) {
      AnalysisContext.reportMissingClass(e);
    }
    return Collections.emptySet();
  }
  private void analyzeMethod(ClassContext classContext, Method method)
      throws CFGBuilderException, DataflowAnalysisException {
    if (isSynthetic(method) || !prescreen(classContext, method)) return;
    XMethod xmethod = XFactory.createXMethod(classContext.getJavaClass(), method);
    if (xmethod.isSynthetic()) return;

    BugAccumulator accumulator = new BugAccumulator(bugReporter);

    CFG cfg = classContext.getCFG(method);
    TypeDataflow typeDataflow = classContext.getTypeDataflow(method);
    ValueNumberDataflow vnDataflow = classContext.getValueNumberDataflow(method);

    ConstantPoolGen cpg = classContext.getConstantPoolGen();
    MethodGen methodGen = classContext.getMethodGen(method);
    if (methodGen == null) return;
    String fullMethodName = methodGen.getClassName() + "." + methodGen.getName();

    String sourceFile = classContext.getJavaClass().getSourceFileName();
    if (DEBUG) {
      System.out.println("\n" + fullMethodName);
    }

    // Process each instruction
    for (Iterator<Location> iter = cfg.locationIterator(); iter.hasNext(); ) {
      Location location = iter.next();
      InstructionHandle handle = location.getHandle();
      Instruction ins = handle.getInstruction();

      // Only consider invoke instructions
      if (!(ins instanceof InvokeInstruction)) continue;

      InvokeInstruction inv = (InvokeInstruction) ins;

      XMethod invokedMethod = XFactory.createXMethod(inv, cpg);

      String invokedMethodName = invokedMethod.getName();
      String argSignature = invokedMethod.getSignature();
      argSignature = argSignature.substring(0, argSignature.indexOf(')') + 1);
      String call = invokedMethodName + argSignature;
      SignatureParser sigParser = new SignatureParser(inv.getSignature(cpg));

      Collection<Info> collection = callMap.get(call);
      if (!callMap.containsKey(call)) continue;
      for (Info info : collection) {
        Subtypes2 subtypes2 = AnalysisContext.currentAnalysisContext().getSubtypes2();
        if (DEBUG)
          System.out.println(
              "at "
                  + handle.getPosition()
                  + " Checking call to "
                  + info.interfaceForCall
                  + " : "
                  + invokedMethod);
        try {
          if (!subtypes2.isSubtype(invokedMethod.getClassDescriptor(), info.interfaceForCall))
            continue;
        } catch (ClassNotFoundException e) {
          if (info.interfaceForCall.getClassName().equals("java/util/Collection")
              && invokedMethod.getClassName().equals("com.google.common.collect.Multiset")) {
            assert true;
            // we know this is OK without needing to find definition of Multiset
          } else {
            AnalysisContext.reportMissingClass(e);
            continue;
          }
        }

        boolean allMethod;

        int typeArgument;
        if (info.typeIndex >= 0) {
          allMethod = false;
          typeArgument = info.typeIndex;
        } else {
          allMethod = true;
          typeArgument = -(1 + info.typeIndex);
        }
        int pos = info.argumentIndex;

        int lhsPos;
        if (inv instanceof INVOKESTATIC) lhsPos = sigParser.getSlotsFromTopOfStackForParameter(0);
        else lhsPos = sigParser.getTotalArgumentSize();

        int stackPos = sigParser.getSlotsFromTopOfStackForParameter(pos);

        TypeFrame frame = typeDataflow.getFactAtLocation(location);
        if (!frame.isValid()) {
          // This basic block is probably dead
          continue;
        }

        Type operandType = frame.getStackValue(stackPos);
        if (operandType.equals(TopType.instance())) {
          // unreachable
          continue;
        }

        if (operandType.equals(NullType.instance())) {
          // ignore
          continue;
        }

        ValueNumberFrame vnFrame = vnDataflow.getFactAtLocation(location);

        if (!vnFrame.isValid()) {
          AnalysisContext.logError("Invalid value number frame in " + xmethod);
          continue;
        }

        ValueNumber objectVN = vnFrame.getStackValue(lhsPos);
        ValueNumber argVN = vnFrame.getStackValue(stackPos);

        if (objectVN.equals(argVN)) {
          String bugPattern = "DMI_COLLECTIONS_SHOULD_NOT_CONTAIN_THEMSELVES";
          int priority = HIGH_PRIORITY;
          if (invokedMethodName.equals("removeAll")) {
            bugPattern = "DMI_USING_REMOVEALL_TO_CLEAR_COLLECTION";
            priority = NORMAL_PRIORITY;
          } else if (invokedMethodName.endsWith("All")) {
            bugPattern = "DMI_VACUOUS_SELF_COLLECTION_CALL";
            priority = NORMAL_PRIORITY;
          }
          if (invokedMethodName.startsWith("contains")) {
            InstructionHandle next = handle.getNext();
            if (next != null) {
              Instruction nextIns = next.getInstruction();

              if (nextIns instanceof InvokeInstruction) {
                XMethod nextMethod = XFactory.createXMethod((InvokeInstruction) nextIns, cpg);
                if (nextMethod.getName().equals("assertFalse")) continue;
              }
            }
          }
          accumulator.accumulateBug(
              new BugInstance(this, bugPattern, priority)
                  .addClassAndMethod(methodGen, sourceFile)
                  .addCalledMethod(methodGen, (InvokeInstruction) ins)
                  .addOptionalAnnotation(
                      ValueNumberSourceInfo.findAnnotationFromValueNumber(
                          method, location, objectVN, vnFrame, "INVOKED_ON")),
              SourceLineAnnotation.fromVisitedInstruction(
                  classContext, methodGen, sourceFile, handle));
        }

        // Only consider generic...
        Type objectType = frame.getStackValue(lhsPos);
        if (!(objectType instanceof GenericObjectType)) continue;

        GenericObjectType operand = (GenericObjectType) objectType;

        int expectedTypeParameters = 1;
        String simpleName = info.interfaceForCall.getSimpleName();
        if (simpleName.toLowerCase().endsWith("map") || simpleName.equals("Hashtable"))
          expectedTypeParameters = 2;
        else if (simpleName.equals("Table")) expectedTypeParameters = 3;

        // ... containers
        if (!operand.hasParameters()) continue;
        if (operand.getNumParameters() != expectedTypeParameters) continue;
        ClassDescriptor operandClass = DescriptorFactory.getClassDescriptor(operand);
        if (!isGenericCollection(operandClass)) continue;

        if (expectedTypeParameters == 2
            && Subtypes2.instanceOf(operandClass, Map.class)
            && !TypeFrameModelingVisitor.isStraightGenericMap(operandClass)) continue;
        Type expectedType;
        if (allMethod) expectedType = operand;
        else expectedType = operand.getParameterAt(typeArgument);
        Type actualType = frame.getStackValue(stackPos);
        Type equalsType = actualType;
        if (allMethod) {
          if (!(actualType instanceof GenericObjectType)) {
            continue;
          }
          equalsType = ((GenericObjectType) actualType).getParameterAt(typeArgument);
        }

        IncompatibleTypes matchResult = compareTypes(expectedType, actualType, allMethod);

        boolean parmIsObject = expectedType.getSignature().equals("Ljava/lang/Object;");
        boolean selfOperation = !allMethod && operand.equals(actualType) && !parmIsObject;
        if (!allMethod && !parmIsObject && actualType instanceof GenericObjectType) {

          GenericObjectType p2 = (GenericObjectType) actualType;
          List<? extends ReferenceType> parameters = p2.getParameters();
          if (parameters != null && parameters.equals(operand.getParameters()))
            selfOperation = true;
        }

        if (!selfOperation
            && (matchResult == IncompatibleTypes.SEEMS_OK
                || matchResult.getPriority() == Priorities.IGNORE_PRIORITY)) continue;

        if (invokedMethodName.startsWith("contains") || invokedMethodName.equals("remove")) {
          InstructionHandle next = handle.getNext();
          if (next != null) {
            Instruction nextIns = next.getInstruction();

            if (nextIns instanceof InvokeInstruction) {
              XMethod nextMethod = XFactory.createXMethod((InvokeInstruction) nextIns, cpg);
              if (nextMethod.getName().equals("assertFalse")) continue;
            }
          }
        } else if (invokedMethodName.equals("get") || invokedMethodName.equals("remove")) {
          InstructionHandle next = handle.getNext();
          if (next != null) {
            Instruction nextIns = next.getInstruction();

            if (nextIns instanceof InvokeInstruction) {
              XMethod nextMethod = XFactory.createXMethod((InvokeInstruction) nextIns, cpg);
              if (nextMethod.getName().equals("assertNull")) continue;
            }
          }
        }
        boolean noisy = false;
        if (invokedMethodName.equals("get")) {
          UnconditionalValueDerefDataflow unconditionalValueDerefDataflow =
              classContext.getUnconditionalValueDerefDataflow(method);

          UnconditionalValueDerefSet unconditionalDeref =
              unconditionalValueDerefDataflow.getFactAtLocation(location);
          ValueNumberFrame vnAfter = vnDataflow.getFactAfterLocation(location);
          ValueNumber top = vnAfter.getTopValue();
          noisy =
              unconditionalDeref.getValueNumbersThatAreUnconditionallyDereferenced().contains(top);
        }
        // Prepare bug report
        SourceLineAnnotation sourceLineAnnotation =
            SourceLineAnnotation.fromVisitedInstruction(
                classContext, methodGen, sourceFile, handle);

        // Report a bug that mentions each of the failed arguments in
        // matches

        if (expectedType instanceof GenericObjectType)
          expectedType = ((GenericObjectType) expectedType).getUpperBound();

        int priority = matchResult.getPriority();
        if (!operandClass.getClassName().startsWith("java/util")
            && priority == Priorities.HIGH_PRIORITY)
          priority = Math.max(priority, Priorities.NORMAL_PRIORITY);
        if (TestCaseDetector.likelyTestCase(xmethod))
          priority = Math.max(priority, Priorities.NORMAL_PRIORITY);
        else if (selfOperation) priority = Priorities.HIGH_PRIORITY;
        ClassDescriptor expectedClassDescriptor =
            DescriptorFactory.createClassOrObjectDescriptorFromSignature(
                expectedType.getSignature());
        ClassDescriptor actualClassDescriptor =
            DescriptorFactory.createClassOrObjectDescriptorFromSignature(equalsType.getSignature());
        ClassSummary classSummary = AnalysisContext.currentAnalysisContext().getClassSummary();
        Set<XMethod> targets = null;
        try {
          targets =
              Hierarchy2.resolveVirtualMethodCallTargets(
                  actualClassDescriptor, "equals", "(Ljava/lang/Object;)Z", false, false);
          boolean allOk = targets.size() > 0;
          for (XMethod m2 : targets)
            if (!classSummary.mightBeEqualTo(m2.getClassDescriptor(), expectedClassDescriptor))
              allOk = false;
          if (allOk) priority += 2;
        } catch (ClassNotFoundException e) {
          AnalysisContext.reportMissingClass(e);
        }
        String bugPattern = "GC_UNRELATED_TYPES";

        BugInstance bug =
            new BugInstance(this, bugPattern, priority)
                .addClassAndMethod(methodGen, sourceFile)
                .addFoundAndExpectedType(actualType, expectedType)
                .addCalledMethod(methodGen, (InvokeInstruction) ins)
                .addOptionalAnnotation(
                    ValueNumberSourceInfo.findAnnotationFromValueNumber(
                        method, location, objectVN, vnFrame, "INVOKED_ON"))
                .addOptionalAnnotation(
                    ValueNumberSourceInfo.findAnnotationFromValueNumber(
                        method, location, argVN, vnFrame, "ARGUMENT"))
                .addEqualsMethodUsed(targets);
        if (noisy) {
          WarningPropertySet<WarningProperty> propertySet =
              new WarningPropertySet<WarningProperty>();

          propertySet.addProperty(GeneralWarningProperty.NOISY_BUG);
          propertySet.decorateBugInstance(bug);
        }
        accumulator.accumulateBug(bug, sourceLineAnnotation);
      }
    }
    accumulator.reportAccumulatedBugs();
  }