I recently encountered a testcase that confirmed the old saying: "garbage in, garbage out".
The customer was running a gate-gate verification using an incorrect Liberty library (source for .db) and that caused a difference to be missed. Here are the details:
------ ------ A --|A | C --|A | B --|B Z|-- Z B --|B Z|-- Z C --|C | A --|C | ------ ------
Note the swapped connections for pins A and C. The problem was that the cell was incorrectly described as:
----------- |A | |B---buf---Z| |C | -----------
i.e. A and C had no effect on output Z. Hence the 2 designs are equivalent, based on that incorrect, incomplete library.Some lessons:
Again, remember: "garbage in, garbage out"* on Sourcelink, search for "library qualification" under Conformal for details on how to run it. It should be the first solution search returns
** we do have an AE-ware script to do strict equivalence checking, where any changes to the connections and/or cell names get flagged