The floating-point unit uses the regular hardware exception mechanism in MicroBlaze. When enabled, exceptions are thrown for all the IEEE standard conditions: underflow, overflow, divide-by-zero, and illegal operation, as well as for the MicroBlaze specific exception: denormalized operand error.
A floating-point exception inhibits the write to the destination register (Rd). This allows a floating-point exception handler to operate on the uncorrupted register file.