Re: PROPOSAL: Extend inline asm syntax with size spec

Segher Boessenkool
2018-11-30T09:45:20Z

On Thu, Nov 29, 2018 at 08:46:34PM +0900, Masahiro Yamada wrote:
> On Wed, Oct 10, 2018 at 1:14 AM Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
> >
> > On Mon, Oct 08, 2018 at 11:07:46AM +0200, Richard Biener wrote:
> > > On Mon, 8 Oct 2018, Segher Boessenkool wrote:
> > > > On Sun, Oct 07, 2018 at 03:53:26PM +0000, Michael Matz wrote:
> > > > > On Sun, 7 Oct 2018, Segher Boessenkool wrote:
> > > > > > On Sun, Oct 07, 2018 at 11:18:06AM +0200, Borislav Petkov wrote:
> > > > > > > Now, Richard suggested doing something like:
> > > > > > >
> > > > > > > 1) inline asm ("...")
> > > > > >
> > > > > > What would the semantics of this be?
> > > > >
> > > > > The size of the inline asm wouldn't be counted towards the inliner size
> > > > > limits (or be counted as "1").
> > > >
> > > > That sounds like a good option.
> > >
> > > Yes, I also like it for simplicity. It also avoids the requirement
> > > of translating the number (in bytes?) given by the user to
> > > "number of GIMPLE instructions" as needed by the inliner.
> >
> > This patch implements this, for C only so far. And the syntax is
> > "asm inline", which is more in line with other syntax.
> >
> > How does this look?
>
>
> Thank you very much for your work.
>
>
> https://gcc.gnu.org/ml/gcc-patches/2018-10/msg01932.html
>
> How is the progress of this in GCC ML?

Latest patch was pinged a few times:
https://gcc.gnu.org/ml/gcc-patches/2018-11/msg01569.html .

I'll ping it again. Will fix the subject as well if I remember to, sigh.

> I am really hoping the issue will be solved by compiler
> instead of the in-kernel workaround.

This will only be fixed from GCC 9 on, if the compiler adopts it. The
kernel wants to support ancient GCC, so it will need to have a workaround
for older GCC versions anyway.

Segher