Re: [PATCH] [RFC] PR target/52813 and target/11807

[Christophe Lyon <christophe dot lyon at linaro dot org>]

On Mon, 17 Dec 2018 at 12:47, Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Dimitar Dimitrov <dimitar@dinux.eu> writes:
> > On Sun, Dec 16 2018 at 14:36:26 EET Bernd Edlinger wrote:
> >> Hi,
> >>
> >> if I understood that right, then clobbering sp is and has always been
> >> ignored.
>
> PR77904 was about the clobber not being ignored, so the behaviour
> hasn't been consistent.
>
> I'm also not sure it was always ignored in recent sources.  The clobber
> does get added to the associated rtl insn, and it'd be surprising if
> that never had an effect.
>
> >> If that is right, then I would much prefer a warning, that says exactly
> >> that, because that would also help to understand why removing that clobber
> >> statement is safe even for old gcc versions.
>
> If the asm does leave sp with a different value, then it's never been safe,
> regardless of the gcc version.  That's why an error seems more appropriate.
>
> > Thank you. Looks like general consensus is to have a warning. See attached
> > patch that switches the error to a warning.
>
> I don't think there's a good reason to treat this differently from the
> preexisting PIC register error.  If the argument for making it a warning
> rather than an error is that the asm might happen to work by accident,
> then the same is true for the PIC register.
>

If we leave the error, maybe a more explanatory message would be helpful?
(along the lines of what I posted earlier in this thread, which may be
too verbose)

Christophe

> Thanks,
> Richard