es.  Try using fp operations, and also try using karatsuba
     for just three "<code>mulx</code>"s.
<li> UltraSPARC/32: Rewrite <code>mpn_lshift</code>, <code>mpn_rshift</code>.
     Will give 2 cycles/limb.  Trivial modifications of mpn/sparc64 should do.
<li> UltraSPARC/32: Write special mpn_Xmul_1 loops for s2 &lt; 2^16.
<li> UltraSPARC/32: Use <code>mulx</code> for <code>umul_ppmm</code> if
     possible (see commented out code in longlong.h).  This is unlikely to
     save more than a couple of cycles