Why can't CSE recognize const_int's in HIGH LO_SUM pair?

[law@redhat.com]

  In message < 200109241702.f8OH2K3T028166@hiauly1.hia.nrc.ca >you write:
  > It fixes the fail of 20000731-1.c at -O1.  The one clear advantage to
  > this approach that I can see is that constants expressed in the above
  > form are recognized during jump expansion.
Yes.  

Another approach is to allow all constants in compare/branch insns initially,
then use define_splits and friends to lower to the actual capabilities of
the chip later.

jeff