Hello all!

I am woking on a multi bit adder. This requires a hierarchial approach and I have declared the Vdd and Gnd  pins as Local in my basic single-bit adder, the buiding blocks of my circuit. I know that the convention says that It should be declared as a global variable esp when we use a modular approach. But I have already started my layout and want to know if I can from this point onwards declare the Vdd and Gnd as global, the lower heirarchy Vdd and Gnd pins being local. Will this cause errors on simulations?
HOw does a local Vdd differ from a GLobal Vdd, ultimately the routing is anyways going to be performed using the layout tools which connects all the Vdd pins in the circuit right?

thanks all!
Ramus