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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Tue, 15 Sep 2020 14:59:19 -0700
Message-ID: <CAKwvOdnctit9cQ9Na8kO5TXbZh-3ZV5x1=GLHhRVdBUK23HjnA@mail.gmail.com>
Subject: Re: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e
To:     Arvind Sankar <nivedita@alum.mit.edu>
Cc:     Borislav Petkov <bp@alien8.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Rong Chen <rong.a.chen@intel.com>,
        kernel test robot <lkp@intel.com>,
        "Li, Philip" <philip.li@intel.com>, x86-ml <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        Marco Elver <elver@google.com>
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On Tue, Sep 15, 2020 at 2:50 PM Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> On Tue, Sep 15, 2020 at 10:49:12PM +0200, Borislav Petkov wrote:
> >
> > (Btw, clang doesn't need to add that "xor %eax,%eax" - panic() should not be
> >  returning, ever. :-))
> >
>
> I think this is because panic() is varargs, and clang doesn't support
> gcc's -mskip-rax-setup. The normal ABI requires the caller to set RAX to
> the number of arguments in vector registers.
>
> https://patchwork.ozlabs.org/project/gcc/patch/20141218131150.GA32638@intel.com/

Thanks for the report.  Filed
https://bugs.llvm.org/show_bug.cgi?id=47538.  Do you have an account
there Arvind so that I can CC you on them?

Yikes, it looks like gcc 5.0 supports that.  We'd better get to
implementing that lest someone try to remove the cc-option on it soon.
-- 
Thanks,
~Nick Desaulniers