On Tue, Nov 5, 2024 at 12:19 PM Jakub Jelinek <ja...@redhat.com> wrote:
>
> On Tue, Nov 05, 2024 at 12:00:24PM +0100, Uros Bizjak wrote:
> > On Tue, Nov 5, 2024 at 11:43 AM Andreas Schwab <sch...@linux-m68k.org>
> > wrote:
> > >
> > > On Nov 05 2024, Uros Bizjak wrote:
> > >
> > > > But what is the non-deprecated way to communicate the fact that SP
> > > > changes, and possibly clobbers stack in the asm to the compiler?
> > >
> > > Since an asm statement is not allowed to change SP there is no need for
> > > that.
> >
> > asm volatile ("pushfq; popfq %0" : "=r"(x));
> >
> > doesn't change SP at any sequence point, doesn't clobber the function
> > frame, but the function using it shouldn't create redzone. How to
> > communicate this to the compiler?
>
> One possibility would be make __attribute__((target ("no-red-zone")))
> working (I think currently the option isn't TargetSave or isn't listed
> somewhere, so it doesn't work).
This won't work if we have a macro that is used in several functions.
We will have to manually add the above attribute to all functions that
inline the macro with redzone clobbering asm.
> And the other one is IMHO making it explicit that it clobbers the red zone,
> so "redzone" or "red-zone" clobber (or some other word, but can't be easily
> stack-below-sp because we have hppa with stack growing in the wrong
> direction).
We would have to define a memory clobber that would correspond to
redzone and attach it to the asm parallel RTX, perhaps:
(clobber (mem:BLK (reg:DI sp)))
that would ultimately clear "crtl->is_leaf" when detected.
Uros.
