Tco Constraints

For the history, cliques were around because they worked very nicely into how the fitter worked. Around the time of Apex, a completely new fitting algorithm was implemented that cliques did tie into so nicely, and so they were disabled. (The algorithm was much, much better, consistently giving better results in shorter compile times, so the trade-off was well worth it.)

In fact, you might want to look at your fitter settings and see if there's some way to enable a different fitter(it's been many years, so I don't remember this).

Since then, LogicLock regions have been introduced, including auto-sized/floating regions, which are essentially a clique with more granularity as to how big it is. That being said, most of the time if a designer takes their critical paths or hierarchy and throws them into a floating LLR, the results are equal or worse. The reason is that the fitter is already aware of what's critical and doing a very good job at optimizing it, so just drawing a rectangle around it actually limits the fitter's effectiveness and the choices it can make, but doesn't really provide it any info.

The times I do see LogicLocking help performance is when the user does it more like a floorplanning tool, i.e. they put an LLR on one edge for the PCI core, which connects to the another LLR which is the ingress hierarchy, etc. If the LogicLocking provides high-level layout information to the fitter, than it can help performance. (Not all the time, and I don't see huge gains, but it can help.)