Understanding the Interaction:
IR Drop -> Setup Violation: Voltage drop (IR drop) at a cell reduces its effective supply voltage, making it slower. This increased cell delay can directly cause or worsen a setup violation.
Setup Fix -> IR Drop: Some setup fixes, like upsizing cells or swapping to lower Vt, increase the current draw (both peak and average) of those cells. This can worsen IR drop in the local region if the power grid is already marginal.
Correlate: Check if the cells in the failing setup paths are also located in regions with high IR drop. This helps determine if IR drop is a primary contributor to the setup violation.