If I were you I'd try to get a flat SPICE netlist (if the design
is in schematic form), grep the cellName (presuming it's one
master used widely) to a file and
wc -l
But that's not the specific method you seem to want.
Depending on CAD platform you might find hierarchy
browsers for layout or schematic which can filter and
count instances-of-master.
You might be able to get similar counting out of a layout
by getting the flat, "extracted" view netlisted in text form.