Re: Gary Thomas: Re: Code generation bug in GCC-2.8.0

[Gary Thomas <g dot thomas at opengroup dot org>]

David Edelsohn wrote:
> 
>         Some more discussion about the SVR4 PPC inlining problem which has
> not been cc'ed to the egcs mailinglist follows.  I am not enough of an
> expert about this aspect of GCC and the SVR4 port to assess whether it is
> correct.  It is a lot simpler and less intrusive than the original patch,
> and limited to rs6000 SVR4 port.
> 
> David
> 

Indeed this patch is much more refined and fixes the problem.
Thanks to Richard Kenner for distilling it.

> ------- Forwarded Message
> 
> Date: Mon, 09 Feb 1998 15:37:54 +0100 (MET)
> Organization: The Open Group / Research Institute
> Sender: gdt@gr.opengroup.org
> From: Gary Thomas <g.thomas@opengroup.org>
> To: (Richard Kenner) <kenner@vlsi1.ultra.nyu.edu>
> Subject: Re:  Code generation bug in GCC-2.8.0
> Cc: meissner@cygnus.com, dje@watson.ibm.com
> 
> On 09-Feb-98 Richard Kenner wrote:
> > Since varargs functions don't get inlined, I'm confused how this came up,
> > but any, the simplest fix is:
> >
> > Mon Feb  9 07:57:14 1998  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
> >
> >       * rs6000.c (setup_incoming_varargs): Always set rs6000_sysv_varargs_p.
> >
> > *** config/rs6000/rs6000.c.old        Thu Dec 25 13:07:01 1997
> > --- config/rs6000/rs6000.c    Mon Feb  9 08:52:36 1998
> > *************** setup_incoming_varargs (cum, mode, type,
> > *** 1487,1495 ****
> >            cum->words, cum->fregno, cum->nargs_prototype, cum->prototype,
> > GET_MODE_NAME (mode), no_rtl);
> >
> > !   if ((DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_SOLARIS) && !no_rtl)
> >       {
> >         rs6000_sysv_varargs_p = 1;
> > !       save_area = plus_constant (frame_pointer_rtx, RS6000_VARARGS_OFFSET);
> >       }
> >
> >     if (cum->words < 8)
> > --- 1487,1498 ----
> >            cum->words, cum->fregno, cum->nargs_prototype, cum->prototype,
> > GET_MODE_NAME (mode), no_rtl);
> >
> > !   if (DEFAULT_ABI == ABI_V4 || DEFAULT_ABI == ABI_SOLARIS)
> >       {
> >         rs6000_sysv_varargs_p = 1;
> > !       if (! no_rtl)
> > !     save_area = plus_constant (frame_pointer_rtx, RS6000_VARARGS_OFFSET);
> >       }
> > +   else
> > +     rs6000_sysv_varargs_p = 0;
> >
> >     if (cum->words < 8)
> 
> I don't see how this can fix the problem sice this function is only executed
> when the function is being declared, not when the code is being generated.
> The routine in question (the user routine with varargs) only has it's code
> output at the end of processing the entire file, long after the declaration
> was processed (and indeed many others potentially processed in between).
> 
> I actually observed that it executed the assignment on line 1492 when the
> declaration came along, but since this is a "static" variable whose scope
> is the current function declaration, it is incorrect whe the code is output.
> The purpose of the save/restore procedures is to preserve this type of
> information with the function definition so that it can be made available
> when the code is finally generated.  Perhaps there are better ways to do
> this (I could think of some), but I was just trying to reuse/mimick the
> way Mike had addressed the problem originally for nested functions.
> 
> >>>>> Richard Kenner writes at Mon, 9 Feb 98 10:15:08 EST:
> 
> Nope.  It's called when you go back to a previously-inlined function.
> Indeed, it's called for *precisely* this sort of thing.
> 
> ------- End of Forwarded Message

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