 effect on the
     result, perhaps test for r==u and do nothing in that case, rather than
     currently it looks like an <code>MPN_COPY_INCR</code> will be done to
     reduce prec+1 limbs to prec.
<li> <code>mpf_div_ui</code>: Instead of padding with low zeros, call
     <code>mpn_divrem_1</code> asking for fractional quotient limbs.
<li> <code>mpf_div_ui</code>: Eliminate <code>TMP_ALLOC</code>.  When r!=u
     there's no overlap and the division can be called on those operands.
     When r==u and is pr