private BitSet findPreviouslyDeadBlocks() throws DataflowAnalysisException, CFGBuilderException {
        BitSet deadBlocks = new BitSet();
        ValueNumberDataflow vnaDataflow = classContext.getValueNumberDataflow(method);
        for (Iterator<BasicBlock> i = vnaDataflow.getCFG().blockIterator(); i.hasNext();) {
            BasicBlock block = i.next();
            ValueNumberFrame vnaFrame = vnaDataflow.getStartFact(block);
            if (vnaFrame.isTop()) {
                deadBlocks.set(block.getLabel());
            }
        }

        return deadBlocks;
    }
private BitSet findPreviouslyDeadBlocks ( ) throws DataflowAnalysisException , CFGBuilderException { BitSet deadBlocks = new BitSet ( ) ; ValueNumberDataflow vnaDataflow = classContext . getValueNumberDataflow ( method ) ; for ( Iterator < BasicBlock > i = vnaDataflow . getCFG ( ) . blockIterator ( ) ; i . hasNext ( ) ; ) { BasicBlock block = i . next ( ) ; ValueNumberFrame vnaFrame = vnaDataflow . getStartFact ( block ) ; if ( vnaFrame . isTop ( ) ) { deadBlocks . set ( block . getLabel ( ) ) ; } } return deadBlocks ; }
Find set of blocks which were known to be dead before doing the null
pointer analysis.

@return set of previously dead blocks, indexed by block id
@throws CFGBuilderException
@throws DataflowAnalysisException