Re-run of loop pass

[Jeffrey A Law]

  In message < 13865.9178.455954.70561@ongaonga.elec.canterbury.ac.nz >you write:
  > I've noticed that this can generate poorer code when unrolling loops
  > or using the bct optimisation if a BIV is eliminated on the first
  > pass.
  > 
  > On the second pass, loop_iterations is often unable to determine the
  > iteration count for loops with limits that should be able to be
  > determined at compile time.  Loop unrolling or the bct optimisation
  > then makes a dog's breakfast of things.
We've generally gotten better code.

You should investigate why the second loop pass is unable to determine
loop iteration counts.

jeff