Useful skew

Useful skew. Three flip-flops, A then B then C, with logic on each hop. The path A to B is failing setup. B is the shared flip-flop, and intentionally skewing its clock trades slack between the neighbouring paths.

• Delaying B's clock gives the data more time to arrive at B, so setup A to B improves. But the same later clock launches B to C later (hurting its setup) and shifts B's own capture edge (hurting hold A to B).
• All four checks positive - slide the skew into the window where setup and hold on both paths are met at once.

Borrowing time this way is useful skew. Find the window, then Submit design.