docs: 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;
      }