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

["Yatsina, Marina" <marina.yatsina@intel.com>]

I believe we do have the infrastructure in llvm to implement a working patch.
The "asm goto" was introduced as a solution to a problem (optimizing tracepoints/ nop patching).
When we started the discussion in llvm about adding this feature, questions arose if we can design a better solution for this problem than "asm goto".

You can find a more about the discussion in the llvm community here:
http://lists.llvm.org/pipermail/llvm-dev/2017-April/111748.html

* This is the middle of the thread, and there are more messages later on.

Thanks,
Marina

-----Original Message-----
From: Greg Kroah-Hartman [mailto:gregkh@linux-foundation.org] 
Sent: Wednesday, February 14, 2018 11:53
To: Chandler Carruth <chandlerc@google.com>
Cc: Yatsina, Marina <marina.yatsina@intel.com>; Kees Cook <keescook@google.com>; David Woodhouse <dwmw2@infradead.org>; Kreitzer, David L <david.l.kreitzer@intel.com>; Grischenko, Andrei L <andrei.l.grischenko@intel.com>; rnk@google.com; LLVM Developers <llvm-dev@lists.llvm.org>; ehsan@mozilla.com; Tayree, Coby <coby.tayree@intel.com>; Matthias Braun <matze@braunis.de>; Dean Michael Berris <dean.berris@gmail.com>; James Y Knight <jyknight@google.com>; Guenter Roeck <linux@roeck-us.net>; X86 ML <x86@kernel.org>; LKML <linux-kernel@vger.kernel.org>; Alan Cox <gnomes@lxorguk.ukuu.org.uk>; Rik van Riel <riel@redhat.com>; Andi Kleen <ak@linux.intel.com>; Josh Poimboeuf <jpoimboe@redhat.com>; Tom Lendacky <thomas.lendacky@amd.com>; Peter Zijlstra <peterz@infradead.org>; Linus Torvalds <torvalds@linux-foundation.org>; Jiri Kosina <jikos@kernel.org>; Andy Lutomirski <luto@amacapital.net>; Hansen, Dave <dave.hansen@intel.com>; Tim Chen <tim.c.chen@linux.intel.com>; Paul Turner <pjt@google.com>; Stephen Hines <srhines@google.com>; Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: clang asm-goto support (Was Re: [PATCH v2] x86/retpoline: Add clang support)

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.

Why is there any need to discuss "options" here?  What is preventing the implementation of "asm goto" in llvm?  Is it the lack of a working patch, or something else?

thanks,

greg k-h
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