code: private int processBinOp(int seen) {
          if (binaryOps.get(seen) && (stack.getStackDepth() >= 2)) {
              OpcodeStack.Item item = stack.getStackItem(1);
              return item.getRegisterNumber();
          }
          return -1;
      }
docs: looks for instructions that are binary operators, and if it is saves the left hand side register (if it exists) in the userValue.
  
  @param seen
  the opcode of the currently parsed instruction
  @return the lhs register number if it exists or -1