alpha haifa regression

[Jeffrey A Law]

  In message < 199709292023.NAA04543@cygnus.com >you write:
  > I think the correct fix here is to set the MEM_IN_STRUCT_P bit on the
  > MEM rtx created by SETUP_INCOMING_VARARGS.  This should make the sched
  > blockage insn unnecessary.
  > 
  > The MEM_IN_STRUCT_P bit should be set because these are not scalar stores.
You're probably right.  However the blockage will still be needed.

If you set MEM_IN_STRUCT_P, then the alias code will assume that
the flushback can't alias scalars.  This loses when you extract
scalars off a varargs list.

If you don't set MEM_IN_STRUCT_P, then the alias code will assume
that the flushback can't alias structs.  THis loses when you
extract structs off a varargs list.

Basically you can't win.  The way we do flushbacks creates an
aliasing situation that's going to cause problems somewhere.

Thus the easiest solution is a blockage insn.


jeff