Formal Verification might fail for Stratix V when using Cadence Encounter Conformal software

Description

If you attempt to use the Cadence Encounter Conformal software for formal verification of altddio_out.v, altlvds_tx.v, altlvds_rx.v, lvds_tx.v, lvds_rx.v, flvds_tx.v, flvds_rx.v, altmult_add.v, altmult_accum.v, or altpll.v, formal verification fails with the error:

Error RTL 18.3: Function call does not refer to function definition.