Re: [uml-devel] arch/um/sys-i386/setjmp.S: useless #ifdef _REGPARM's?

Adrian Bunk
2006-08-22T16:07:42Z

On Mon, Aug 21, 2006 at 10:20:12PM -0400, Jeff Dike wrote:
> On Mon, Aug 21, 2006 at 11:56:41PM +0200, Adrian Bunk wrote:
> > arch/um/sys-i386/setjmp.S contains two #ifdef _REGPARM's.
> >
> > Even if regparm was used in i386 uml (which isn't currently done (why?)),
> > I don't see _REGPARM being defined anywhere.
>
> setjmp.S was stolen from klibc, and I'd just as soon leave it alone and
> not try to customize it for UML. That file will disappear if/when klibc
> is in mainline, and I can just pull it in from usr.

Ah, klibc defines _REGPARM if required.

> In general, there's no reason that regparam can't be used for UML. However,
> in the past (I don't know if it's still a problem) gcc miscompiled regparam
> code in the presence of -pg.

I didn't find a corresponding open bug in the gcc Bugzilla.

Can someone verify whether it's still present, and if yes, open a gcc
bug?

> As for why it's not, I don't see any occurences of regparam in include/linux
> or include/asm-i386 either.

It's set globally in arch/i386/Makefile:
cflags-$(CONFIG_REGPARM) += -mregparm=3

That's not pulled by UML, but if there are no outstanding problems with
regparm, we could both enable it uncomditionally on i386 and enable it
on UML/i386.

> > Is this a bug waiting for happening when regparm will be used on uml or
> > do I miss anything?
>
> Probably not.
>
> Jeff

cu
Adrian

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