Hi,
On Mon, 3 Sep 2018, H.J. Lu wrote:
> > % ./gcc/cc1plus -quiet -O -g -fno-omit-frame-pointer -fno-var-tracking x.cc
> > % ./gcc/cc1plus -quiet -O -g -fno-omit-frame-pointer -fvar-tracking x.cc
>
> It is because of
>
> gcc_assert ((SUPPORTS_STACK_ALIGNMENT
> && (elim == hard_frame_pointer_rtx <<<<<<<<<<<<
So, what's the testcase testing then? Before the patch it doesn't ICE,
after the patch it doesn't ICE. What should I look out for so I can see
that what the testcase is producing without the patch is wrong?
> > I get the feeling this needs to be fixed somewhere else, namely
> > eliminate_regs. Basically if the frame pointer isn't needed, then why is
> > hard_frame_pointer_rtx even somewhere in the final RTL? The elimination
> > you do explicitely in your new routines should have been done as part of
> > general register elimination. Why isn't it?
>
> hard frame pointer isn't referenced directly in the final RTL. It is arg
> pointer in debug info, which is eliminated by hard frame pointer in
> based_loc_desc.
You talking about this, right:
/* We only use "frame base" when we're sure we're talking about the
post-prologue local stack frame. We do this by *not* running
register elimination until this point, and recognizing the special
argument pointer and soft frame pointer rtx's. */
if (reg == arg_pointer_rtx || reg == frame_pointer_rtx)
{
rtx elim = (ira_use_lra_p
? lra_eliminate_regs (reg, VOIDmode, NULL_RTX)
: eliminate_regs (reg, VOIDmode, NULL_RTX));
if (elim != reg)
{
...
So, why would eliminate_regs return hard_frame_pointer_rtx if no frame
pointer is desired?
Ciao,
Michael.
