When I started the original thread last year I was in favor of adding "asm
goto" and didn't understand why it wasn't done by that time.
The feedback I got is that this feature (optimizing tracepoints) is very useful
and that we do want it in llvm, but perhaps there's a cleaner way of
implementing than "asm goto". An alternative suggestion arose as well.
I'm sure you can provide a lot of background for the decisions of why "asm
goto" was chosen and which other alternatives were considered, as you were the
one to implement this. This may shed a lot of light on the alternative
suggestions that arose in my thread in the llvm community.
I think that including GCC folks in the "small team" discussion Chandler
suggested might be a very good idea, so if you have some contacts, please send
them to Chandler.
Anyway, I think we should consider the alternatives and not take "asm goto" as
a given, even though this is the implementation of this feature for the past 7
years and it works well.
I'm not saying linux kernel needs to rush and adopt an alternative solution
ASAP, but we cannot ignore that it exists and may (or may not) be the direction
of the future (for both gcc and llvm).
From: Peter Zijlstra [mailto:pet...@infradead.org]
Sent: Wednesday, February 14, 2018 11:09
To: Yatsina, Marina <marina.yats...@intel.com>
Cc: Kees Cook <keesc...@google.com>; David Woodhouse <dw...@infradead.org>;
Chandler Carruth <chandl...@google.com>; Kreitzer, David L
<david.l.kreit...@intel.com>; Grischenko, Andrei L
<andrei.l.grische...@intel.com>; r...@google.com; LLVM Developers
<llvm-...@lists.llvm.org>; eh...@mozilla.com; Tayree, Coby
<coby.tay...@intel.com>; Matthias Braun <ma...@braunis.de>; Dean Michael Berris
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Subject: Re: clang asm-goto support (Was Re: [PATCH v2] x86/retpoline: Add
On Wed, Feb 14, 2018 at 08:33:39AM +0000, Yatsina, Marina wrote:
> I hope this will give this issue a push forward and we will find a
> solution that will not prevent llvm from compiling linux kernel.
That solution is asm-goto. We (linux kernel) are not going to support something
like it. It's going to be asm-goto or bust. The feature is over 7 years old by
now, deal with it.
If you ever get to the point where it makes sense to build a kernel with LLVM,
then you can bike-shed with the GCC team on new features, until then tough luck.
Intel Israel (74) Limited
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