Would the crew or FMC have not already worked out the optimum approach speed for their weight / configuration? If so would they have this minimum approach speed handy?
In the Airbus (All FBW Airbus), minimum speed is constantly updated and presented to the pilots on the PFD (Primary Flight Display, or the FMS (MCDU PERF Page)
With each change of configuration (Flaps) the information is again updated and displayed in Various forms in the same places. Clean = Green Dot, Slats = "S" speed, and Flaps = "F" speed, which are Minimum speeds for those configurations.
During approach, we have the same indications, plus Vapp (which may include a wind correction [GS Mini]) and Vls (The lowest selectable speed [albeit this one is commonly misunderstood by many pilots])
All these speeds are computed by the FMS (actually by the FAC's) and presented to the pilots for immediate reference.
I recall that the Boeing FMS performs very similarly.
I hope this sheds some light on it for you.