Re: clang asm-goto support (Was Re: [PATCH v2] x86/retpoline: Add clang support)

From: Thomas Gleixner
Date: Wed Feb 14 2018 - 05:44:30 EST

On Wed, 14 Feb 2018, Peter Zijlstra wrote:
> On Wed, Feb 14, 2018 at 08:41:43AM +0000, Chandler Carruth wrote:
> > Marina, Kees:
> >
> > I think the combination of LKML and the LLVM developer's list is probably
> > too large a set of folks to have a (somewhat) lengthy exploration of
> > options and how to go about this and find a good path forward.
> As one of the original authors of the jump-label implementation I'm
> saying there are no options. We're not going to do a second parallel
> implementation. If you want to build the kernel, you get to implement
> asm-goto, teh end.

Amen to that.

As x86 maintainer I'm really interested and willing to support llvm/clang
for x86 and the kernel in general, but asm-goto is not longer negotiable.

asm-goto is in the kernel since Oct 2010 and the relevant llvm/clang bug
#9295 is open since Feb 2011. All clang/llvm folks came up with in those 7
years is occasional handwaving about better solutions.

We really try to support old tools and tools which lack features for quite
a long time, but that's not a free pass for eternity.

That said, I'm not willing to wait another 7 years and I'm going to pull
the plug on compilers w/o asm-goto support soon whether llvm/clang gets
their act together or not.

Hint: GCC is not the only major compiler which supports asm-goto.