Proper test for acc to fp conversion
For the moment the only Kulisch accumulator test consists in accumulating random floats between -1 and 1 in an accumulator and checking at each loop step than the back conversion still gives the nearest float comparing it with mpfr exact accumulation.
However there is little chance to explore all corner cases by this method.
So something like checking the multiplication of a significand full of 0, full of one and in between by all possible exponent pairs, with or without adding low bit bias should be performed to test the fp_acc_round operator.