Purpose of Diodes D1 and D2 in H-Bridge P-Channel MOSFET Gate Drive Circuit?

While reading through a paper, I came across the attached diagram. Everything looks as expected except for diodes D1 and D2. Why are they there, what function do they serve? Normally I would expect pull-up resistors such as R3 and R4 without the diodes.
It appears that it'll only matter if the gate is high (MOSFET is off) and the supply voltage dips low, the diode will prevent the gate voltage from also dipping low along with the MOSFET source. Why would you want this, instead of letting the gate voltage follow the source voltage? Is it needed if there's enough capacitance in the gate that noise in the source voltage might cause the gate to not follow closely enough, and the MOSFET opens? What if the source voltage dips lower than the VGS limit of the MOSFET?

The supply voltage is shown as +24 volts. When H1 or H2 is high, Q5 or Q6 is turned on, grounding the gate of MOSFET Q3 or Q4, making the gate-source voltage Vgs = -24V. The IRF9540 MOSFET Vgs_maximum rating is +-20V, so this circuit is likely to cause gate-to-source shorts in Q3 or Q4.