RE: Is there a GIMPLE equivalent of UNSPEC?

["Unruh, Erwin" <Erwin dot Unruh at fujitsu-siemens dot com>]

OK, here are the details:

first, I have a PDImode pointer and do not want to have general arithmetic on that. So I invented a special RTL instruction to align a pointer. Within the va_arg sometimes I need to align the pointer. In 3.3.2 the code snippet in EXPAND_BUILTIN_VA_ARG looked like

  tree t = ... // address of next parameter
  /* If the value is more aligned than a word, align the pointer.  */
  if (align > PARM_BOUNDARY)
    {
      rtx r;
      r = expand_expr (t, addr_rtx, Pmode, EXPAND_NORMAL);
      r = private_align_pmode (r, align / BITS_PER_UNIT);
      t = make_tree (TREE_TYPE (ovf), r);
      t = build (MODIFY_EXPR, TREE_TYPE (ovf), ovf, t);
      TREE_SIDE_EFFECTS (t) = 1;
      expand_expr (t, const0_rtx, VOIDmode, EXPAND_NORMAL);

      t = save_expr (ovf);
    }

Second, when passing a pointer (Pmode) via va_arg, I need a special instruction to retrieve its value. In 3.3.2 I used

  rtx addr_rtx = ... // address of parameter
  rtx value_rtx = gen_reg_rtx (Pmode);
  rtx r = gen_rtx_MEM (Pmode, addr_rtx);
  set_mem_alias_set (r, get_varargs_alias_set ());
  emit_insn (gen_private_va_arg_pdi (value_rtx, r));
  addr_rtx = gen_reg_rtx (Pmode);
  r = gen_rtx_ADDRESSOF (Pmode, value_rtx, REGNO (value_rtx), 0);
  emit_move_insn (addr_rtx, r);
  // addr_rtx can now be used as a normal pointer to a Pmode entity

In both cases using an RTL unspec was a convenient way to go. All optimizing phases knew how to handle that.

If I do not find a simple way to represent those constructs in GIMPLE, I have to think about other ways to handle the underlying problem.

	Erwin


Erwin Unruh, Fujitsu Siemens Computers, C/C++ compiler group

-----Original Message-----
From: Steven Bosscher [mailto:stevenb@suse.de] 
Sent: Thursday, November 17, 2005 1:22 PM
To: Unruh, Erwin
Cc: GCC mailing list
Subject: Re: Is there a GIMPLE equivalent of UNSPEC?

On Nov 17, 2005 01:11 PM, "Unruh, Erwin"
<Erwin.Unruh@fujitsu-siemens.com> wrote:
> is there some
> equivalent.

No, there isn't.? You are not being very specific about the problem you are trying to solve.? You'll have to tell more before anyone can give you a more helpful answer.
?
Gr.
Steven
?
?