DRV8300: How to measure phase current of PM motor using 2 legs shunt resistor

Hello.

I have designed 3 phase inverter to drive PM motor, I'm trying to measure phase current of motor by using 2 legs shunt resistor.

I have question that how I can calculate phase current of motor , because shunt resistor only can measure when low mosfet was conducted. What if haft bridge A and B conduct at hight side, bridge C conduct at low side (vector abc = (110))? the current will not flow to any shunt resistor. so how I can deal with that case? the same with vector abc = (101), current will flow through high side of a and c and return via shunt resistor of b phase, so we only know Ib and Ib = Ia+Ic, but dont know exactly Ia, Ic.