On Mon, Jan 29, 2018 at 04:26:50PM -0600, Segher Boessenkool wrote:
> > The code actually meant pointer comparison, the question is what is
> > different on powerpc* that you end up with a different REG.
> > >From what I can see, function.c uses crtl->args.internal_arg_pointer
> > directly rather than a REG with the same REGNO.
> > Where does it become something different and why?
>
> There is a lot of code that copies any RTX that isn't obviously unique.
> Here we have a PLUS of some things, which always needs copying, can
> never be shared.
Yes, PLUS needs to be unshared.
So it ought to be handled by the PLUS handling code.
|| (GET_CODE (XEXP (incoming, 0)) == PLUS
&& XEXP (XEXP (incoming, 0), 0)
== crtl->args.internal_arg_pointer
&& CONST_INT_P (XEXP (XEXP (incoming, 0), 1)))))
Here we are talking about MEMs on the PARM_DECL DECL_RTLs, those are not
instantiated as normal IL in the RTL stream is.
I'm not saying the var-tracking.c change is wrong, but I'd like to see
analysis on what is going on.
Is the patch for -fsplit-stack where rs6000_internal_arg_pointer
returns a PLUS of some pseudo and some offset?
In that case I wonder how does the patch with rtx_equal_p actually work,
because function.c then uses plus_constant on this result, and if there are
2 non-zero offsets added, the result is a PLUS with a single offset based
on that pseudo. That would mean var-tracking.c would need special code to
handle crtl->args.internal_arg_pointer that is a PLUS, and handle it
differently from crtl->args.internal_arg_pointer that is a pseudo REG.
Jakub
