e this (per
     commented out code).  <code>count_trailing_zeros</code> could use it too.
<li> PA64: Improve <code>mpn_addmul_1</code>, <code>mpn_submul_1</code>, and
     <code>mpn_mul_1</code>.  The current code runs at 11 cycles/limb.  It
     should be possible to saturate the cache, which will happen at 8
     cycles/limb (7.5 for mpn_mul_1).  Write special loops for s2 &lt; 2^32;
     it should be possible to make them run at about 5 cycles/limb.
<li> PPC601: See which of the power or powerpc32 code 