Retiming
Beginner
Moving the chip’s small memories a little earlier or later along a path, so the work between them is shared out more evenly.
Novice
Moving flip-flops forward or backward through the logic so each stage between them has a similar amount of work, without changing what the circuit outputs on each clock tick.
Expert
A transformation formalized by Leiserson and Saxe that moves registers across logic to minimize the clock period or the register count while keeping cycle-by-cycle input/output behavior. Flip-flops no longer match the RTL one-to-one, so equivalence checking needs guidance or slower sequential methods.
Explained in Logic synthesis (Design Flow).
See also: Logical equivalence checking (LEC).