/// <summary>
        /// Checks whether there is a definition from the beginning to the use node
        /// </summary>
        /// <param name="fdef"></param>
        /// <param name="otherDefinedOffsets"></param>
        /// <returns></returns>
        private bool HasDefinitionFromRootToUseNode(DUCoverStore dcs, FieldDefUseStore fuse, HashSet <int> otherDefinedOffsets)
        {
            DEFUSE_FEASIBILITY_TYPE feasibilityVal;

            if (this.feasibilityDicCache.TryGetValue(fuse, out feasibilityVal))
            {
                if (feasibilityVal == DEFUSE_FEASIBILITY_TYPE.USE_FEASIBLE)
                {
                    return(false);
                }
                else
                {
                    return(true);
                }
            }

            InstructionGraph    ig  = dcs.GetInstructionGraph(fuse.Method);
            DepthFirstTraversal dft = new DepthFirstTraversal(ig);
            InstructionVertex   iv  = ig.GetVertex(fuse.Offset);
            var result = dft.HasDefClearPathFromBeginning(iv, otherDefinedOffsets);

            if (result)
            {
                this.feasibilityDicCache[fuse] = DEFUSE_FEASIBILITY_TYPE.USE_FEASIBLE;
            }
            else
            {
                this.feasibilityDicCache[fuse] = DEFUSE_FEASIBILITY_TYPE.USE_INFEASIBLE;
            }

            return(!result);
        }