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Re: PROPOSAL: Extend inline asm syntax with size spec
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Masahiro Yamada <yamada dot masahiro at socionext dot com>
- Cc: Nadav Amit <namit at vmware dot com>, Ingo Molnar <mingo at redhat dot com>, "H. Peter Anvin" <hpa at zytor dot com>, rguenther at suse dot de, matz at suse dot de, Borislav Petkov <bp at alien8 dot de>, gcc at gcc dot gnu dot org, Linux Kernel Mailing List <linux-kernel at vger dot kernel dot org>, X86 ML <x86 at kernel dot org>, Sam Ravnborg <sam at ravnborg dot org>, Alok Kataria <akataria at vmware dot com>, Christopher Li <sparse at chrisli dot org>, Greg Kroah-Hartman <gregkh at linuxfoundation dot org>, Jan Beulich <JBeulich at suse dot com>, Josh Poimboeuf <jpoimboe at redhat dot com>, Juergen Gross <jgross at suse dot com>, Kate Stewart <kstewart at linuxfoundation dot org>, Kees Cook <keescook at chromium dot org>, linux-sparse at vger dot kernel dot org, "Peter Zijlstra (Intel)" <peterz at infradead dot org>, Philippe Ombredanne <pombredanne at nexb dot com>, Thomas Gleixner <tglx at linutronix dot de>, virtualization at lists dot linux-foundation dot org, Linus Torvalds <torvalds at linux-foundation dot org>, Chris Zankel <chris at zankel dot net>, Max Filippov <jcmvbkbc at gmail dot com>, linux-xtensa at linux-xtensa dot org
- Date: Thu, 29 Nov 2018 06:25:02 -0600
- Subject: Re: PROPOSAL: Extend inline asm syntax with size spec
- References: <20181003213100.189959-1-namit@vmware.com> <20181007091805.GA30687@zn.tnic> <20181007132228.GJ29268@gate.crashing.org> <alpine.LSU.2.21.1810071534220.7867@wotan.suse.de> <20181008073128.GL29268@gate.crashing.org> <alpine.LSU.2.20.1810081105350.16707@zhemvz.fhfr.qr> <20181009145330.GT29268@gate.crashing.org> <CAK7LNARmrdtyE7JRAdJH_zbfvD_cej+TGLh+5KfT20o538KUcA@mail.gmail.com>
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