livenessanalyzer.java

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        for (int offset = 0; offset < codeLength; offset++)
        {
            if (partialEvaluator.isTraced(offset))
            {
                // Loop over all variables.
                for (int variableIndex = 0; variableIndex < variablesSize; variableIndex++)
                {
                    // Is the variable alive and a category 2 type?
                    if (isAliveBefore(offset, variableIndex))
                    {
                        Value value = partialEvaluator.getVariablesBefore(offset).getValue(variableIndex);
                        if (value != null && value.isCategory2())
                        {
                            // Mark it as such.
                            setCategory2(offset, variableIndex, true);

                            // Mark the next variable as well.
                            setAliveBefore(offset, variableIndex + 1, true);
                            setCategory2(  offset, variableIndex + 1, true);
                        }
                    }

                    // Is the variable alive and a category 2 type?
                    if (isAliveAfter(offset, variableIndex))
                    {
                        Value value = partialEvaluator.getVariablesAfter(offset).getValue(variableIndex);
                        if (value != null && value.isCategory2())
                        {
                            // Mark it as such.
                            setCategory2(offset, variableIndex, true);

                            // Mark the next variable as well.
                            setAliveAfter(offset, variableIndex + 1, true);
                            setCategory2( offset, variableIndex + 1, true);
                        }
                    }
                }
            }
        }

        if (DEBUG)
        {
            // Loop over all instructions.
            for (int offset = 0; offset < codeLength; offset++)
            {
                if (partialEvaluator.isTraced(offset))
                {
                    long aliveBefore = isAliveBefore[offset];
                    long aliveAfter  = isAliveAfter[offset];
                    long category2   = isCategory2[offset];

                    // Print out the liveness of all variables before the instruction.
                    for (int variableIndex = 0; variableIndex < variablesSize; variableIndex++)
                    {
                        long variableMask = (1L << variableIndex);
                        System.out.print((aliveBefore & variableMask) != 0L ? ((category2  & variableMask) == 0L ? 'x' : '*') :
                                                                              '.');
                    }

                    // Print out the instruction itself.
                    System.out.println(" "+ InstructionFactory.create(codeAttribute.code, offset).toString(offset));

                    // Print out the liveness of all variables after the instruction.
                    for (int variableIndex = 0; variableIndex < variablesSize; variableIndex++)
                    {
                        long variableMask = (1L << variableIndex);
                        System.out.print((aliveAfter & variableMask) == 0L ? '.' :
                                         (category2  & variableMask) == 0L ? 'x' :
                                                                             '=');
                    }

                    System.out.println();
                }
            }
        }
    }


    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}


    public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
    {
        int variableIndex = variableInstruction.variableIndex;
        if (variableIndex < MAX_VARIABLES_SIZE)
        {
            long livenessMask = 1L << variableIndex;

            // Is it a load instruction or a store instruction?
            if (variableInstruction.isLoad())
            {
                // Start marking the variable before the load instruction.
                alive |= livenessMask;
            }
            else if (variableInstruction.opcode != InstructionConstants.OP_IINC)
            {
                // Stop marking the variable before the store instruction.
                alive &= ~livenessMask;

                // But do mark the variable right after the store instruction.
                isAliveAfter[offset] |= livenessMask;
            }
        }
    }


    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
    {
        // Special case: variable 0 ('this') in an initializer has to be alive
        // as long as it hasn't been initialized.
         if (offset == partialEvaluator.superInitializationOffset())
        {
            alive |= 1L;
        }
    }


    // Implementations for ExceptionInfoVisitor.

    public void visitExceptionInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, ExceptionInfo exceptionInfo)
    {
        // Are any variables alive at the start of the handler?
        long alive = isAliveBefore[exceptionInfo.u2handlerPC];
        if (alive != 0L)
        {
            // Set the same liveness flags for the entire try block.
            int startOffset = exceptionInfo.u2startPC;
            int endOffset   = exceptionInfo.u2endPC;

            for (int offset = startOffset; offset < endOffset; offset++)
            {
                if (partialEvaluator.isTraced(offset))
                {
                    isAliveBefore[offset] |= alive;
                    isAliveAfter[offset]  |= alive;
                }
            }
        }
    }


    // Small utility methods.

    /**
     * Initializes the global arrays.
     */
    private void initializeArrays(CodeAttribute codeAttribute)
    {
        int codeLength = codeAttribute.u4codeLength;

        // Create new arrays for storing information at each instruction offset.
        if (isAliveBefore.length < codeLength)
        {
            isAliveBefore = new long[codeLength];
            isAliveAfter  = new long[codeLength];
            isCategory2   = new long[codeLength];
        }
        else
        {
            for (int index = 0; index < codeLength; index++)
            {
                isAliveBefore[index] = 0L;
                isAliveAfter[index]  = 0L;
                isCategory2[index]   = 0L;
            }
        }
    }


    private long combinedLiveness(InstructionOffsetValue instructionOffsetValue)
    {
        long alive = 0L;

        int count = instructionOffsetValue.instructionOffsetCount();
        for (int index = 0; index < count; index++)
        {
            alive |= isAliveBefore[instructionOffsetValue.instructionOffset(index)];
        }

        return alive;
    }


    /**
     * Returns the minimum offset from the given instruction offsets.
     */
    private int minOffset(Value instructionOffsets)
    {
        return minOffset(instructionOffsets, Integer.MAX_VALUE);
    }


    /**
     * Returns the minimum offset from the given instruction offsets.
     */
    private int minOffset(Value instructionOffsets, int minOffset)
    {
        if (instructionOffsets != null)
        {
            InstructionOffsetValue instructionOffsetValue =
                instructionOffsets.instructionOffsetValue();

            int count = instructionOffsetValue.instructionOffsetCount();
            for (int index = 0; index < count; index++)
            {
                int offset = instructionOffsetValue.instructionOffset(index);
                if (minOffset > offset)
                {
                    minOffset = offset;
                }
            }
        }

        return minOffset;
    }


    /**
     * Returns the maximum offset from the given instruction offsets.
     */
    private int maxOffset(Value instructionOffsets)
    {
        return maxOffset(instructionOffsets, Integer.MIN_VALUE);
    }


    /**
     * Returns the maximum offset from the given instruction offsets.
     */
    private int maxOffset(Value instructionOffsets, int maxOffset)
    {
        if (instructionOffsets != null)
        {
            InstructionOffsetValue instructionOffsetValue =
                instructionOffsets.instructionOffsetValue();

            int count = instructionOffsetValue.instructionOffsetCount();
            for (int index = 0; index < count; index++)
            {
                int offset = instructionOffsetValue.instructionOffset(index);
                if (maxOffset < offset)
                {
                    maxOffset = offset;
                }
            }
        }

        return maxOffset;
    }
}