X-Propagation Woes: Masking Bugs at RTL and Unnecessary Debug at the Netlist

This paper presents a complete and practical methodology to comprehensively solve the X problem in RTL design. It begins by reviewing common sources of Xs, and describes how they cause functional bugs as well as unwarranted debug that prolong verification cycles. Solving the X problem helps minimize simulation and synthesis iterations and enables various design analyses (e.g. power analysis), normally performed on netlists, to begin sooner.