Some Haifa scheduler bugs

[Jeffrey A Law]

  > I think you won't get the right return value. You want to return the
  > last insn in a SCHED_GROUP or a note that was placed after it.
  > I had my reasons to use two loops ;)
You're right.  Seems to me that the return value for move_insn should
always be the return value from the first call to reemit_notes.  Correct?

In which case it's pretty simple to record the return value from
the first call to reemit_notes.

And I don't doubt you had good reasons to use two loops; I just want
to make absolutely sure I understand the problem.  Handling of notes
and SCHED_GROUP_P insns have both been particularly difficult areas
of the scheduler to implement correctly.

  > The whole affair with SCHED_GROUP_P is extremely messy.
Agreed.

  > How about using extra data structures that describe which insns
  > to schedule together, which notes to put before them, and the
  > dependencies between them.
I'm all for it.

  > scheduled together with an insn might make the code clearer. I think it
  > would fit in better with the fact that Haifa schedules forward. I didn't
  > try it, though; maybe there are problems with that approach, too.
Well, haifa does both forward and backward analysis -- so it might
just move the problematical code elsewhere in the scheduler.

jeff