Re: [RFC] LKMM: Add volatile_if()

Segher Boessenkool
2021-06-07T18:27:54Z

On Mon, Jun 07, 2021 at 08:27:12AM -0700, Paul E. McKenney wrote:
> > > > > The barrier() thing can work - all we need to do is to simply make it
> > > > > impossible for gcc to validly create anything but a conditional
> > > > > branch.

> > > What would you suggest as a way of instructing the compiler to emit the
> > > conditional branch that we are looking for?
> >
> > You write it in the assembler code.
> >
> > Yes, it sucks. But it is the only way to get a branch if you really
> > want one. Now, you do not really need one here anyway, so there may be
> > some other way to satisfy the actual requirements.
>
> Hmmm... What do you see Peter asking for that is different than what
> I am asking for? ;-)

I don't know what you are referring to, sorry?

I know what you asked for: literally some way to tell the compiler to
emit a conditional branch. If that is what you want, the only way to
make sure that is what you get is by writing exactly that in assembler.

Segher