Re: remove the last set_fs() in common code, and remove it for x86 and powerpc v3

[Christophe Leroy]

Le 10/09/2020 à 10:04, David Laight a écrit :
> From: Linus Torvalds
> > Sent: 09 September 2020 22:34
> > On Wed, Sep 9, 2020 at 11:42 AM Segher Boessenkool
> > <segher@xxxxxxxxxxxxxxxxxxx> wrote:
> > > It will not work like this in GCC, no.  The LLVM people know about that.
> > > I do not know why they insist on pushing this, being incompatible and
> > > everything.
> >
> > Umm. Since they'd be the ones supporting this, *gcc* would be the
> > incompatible one, not clang.
>
> I had an 'interesting' idea.
>
> Can you use a local asm register variable as an input and output to
> an 'asm volatile goto' statement?
>
> Well you can - but is it guaranteed to work :-)

With gcc at least it should work according to 
https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html

They even explicitely tell: "The only supported use for this feature is 
to specify registers for input and output operands when calling Extended 
asm "

Christophe