Re: [PATCH] Fix PR37053: Move tweaks of commutative precedence to target hook

[Paolo Bonzini]

Peter Bergner wrote:
> On Sat, 2009-06-27 at 13:07 +0200, Paolo Bonzini wrote:
> > I wonder how much of the performance can be kept on Power6 if you just 
> > attack PR28690 within md_reorg.  The only problem would be if the index 
> > was allocated in r0.
>
> What exactly did you have in mind here?

Look into each MEM looking for PLUSes with the operands in the wrong 
order.  Or:

static bool
is_pointer_object (rtx x)
{
  if (REG_P (x))
    return REG_POINTER (x);
  if (MEM_P (x))
    return MEM_POINTER (x);
  return false;
}

/* We are inside a MEM, find PLUSes were the index comes first and
   invert the base and index.  DATA points to the mem within which
   *PX lies, which is used to validate the address.  */

static int
find_plus_and_frob_them (rtx *px, void *data)
{
  if (GET_CODE (x) == PLUS
      && OBJECT_P (XEXP (x, 1))
      && OBJECT_P (XEXP (x, 0))
      && is_pointer_object (XEXP (x, 1))
      && !is_pointer_object (XEXP (x, 0))
    {
      rtx mem = data;
      rtx t = XEXP (x, 0);
      XEXP (x, 0) = XEXP (x, 1);
      XEXP (x, 1) = t;
      gcc_assert (!swap_commutative_operands_p (XEXP (x, 0),
                                                XEXP (x, 1));
      if (!strict_memory_address_p (GET_MODE (mem), XEXP (mem, 0)))
        {
          /* Too bad, probably XEXP (x, 0) is r0 and cannot be made into
             an index.  Undo.  */
          XEXP (x, 1) = XEXP (x, 0);
          XEXP (x, 0) = t;
        }
    }
  return 0;
}

/* Look for memory operands and apply find_plus_and_frob_them to their
   addresses.  */
static int
find_mems_and_frob_them (rtx *px, void *data)
{
  if (GET_CODE (*px) == MEM)
    {
      for_each_rtx (&XEXP (*px, 0), find_plus_and_frob_them, *px);
      return -1;
    }
  return 0;
}

and then in a machine-dependent reorg pass (which rs6000 currently does 
not have):

FOR_EACH_BB (bb)
  FOR_BB_INSNS (bb, insn)
    if (INSN_P (insn))
      for_each_rtx (&PATTERN (insn), find_mems_and_frob_them, NULL);