CPPR / CRPR
Beginner
Taking back a safety margin that was counted twice, on the stretch of clock wiring that two memory cells share.
Novice
Common path pessimism removal (also called clock reconvergence pessimism removal). When a timing check assumes the launching clock is slow and the capturing clock fast, the stretch of clock network the two share can’t be both at once. CPPR gives back that impossible difference.
Expert
Under OCV derating, the shared clock segment is treated as late for launch and early for capture in the same check. CPPR adds the late-minus-early delay of that segment back to slack. Trees that give critical flip-flop pairs a long shared path therefore gain slack.
Explained in Clock tree synthesis (Design Flow).
See also: On-chip variation (OCV), Propagated clock.