From: Matthias Kaehlcke <mka@chromium.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
James Y Knight <jyknight@google.com>,
Chandler Carruth <chandlerc@google.com>,
Stephen Hines <srhines@google.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kees Cook <keescook@google.com>,
Guenter Roeck <groeck@chromium.org>,
Greg Hackmann <ghackmann@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [GIT PULL] x86/build changes for v4.17
Date: Wed, 4 Apr 2018 13:58:48 -0700 [thread overview]
Message-ID: <20180404205848.GG87376@google.com> (raw)
In-Reply-To: <CAK8P3a1VFWYBymd3AeG1DwW++tCGsP9+vw6t8XSGHby2jmQPqA@mail.gmail.com>
El Wed, Apr 04, 2018 at 10:33:19PM +0200 Arnd Bergmann ha dit:
> On Wed, Apr 4, 2018 at 9:17 PM, Matthias Kaehlcke <mka@chromium.org> wrote:
> > El Wed, Apr 04, 2018 at 11:30:07AM +0200 Peter Zijlstra ha dit:
> >
> >> On Tue, Apr 03, 2018 at 11:06:58AM -0700, Matthias Kaehlcke wrote:
> >>
> >> > Yes, Chrome OS R67 (currently dev, soon beta) will ship a kernel built
> >> > with Clang for multiple x86 Chromebooks.
> >>
> >> But there are still _known_ miscompilations....
> >
> > Our compiler team is looking into this (missing option
> > -fno-delete-null-pointer-checks)
>
> Do you know if anyone is looking into __builtin_constant_p()
> optimization as well? We have a lot of uses of this gcc feature
> in the kernel, and if I remember correctly, clang implements
> this by basically always returning false for the cases we
> are interested in.
>
> In most cases, this is used to implement a fast-path for a helper
> function, so not doing it the same way as gcc just results in
> slower execution, but I assume we also have code that behaves
> differently on clang compared to gcc because of this.
I think I didn't come (knowingly) across that one yet. Could you point
me to an instance that could be used as an example in a bug report?
next prev parent reply other threads:[~2018-04-04 20:58 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 9:50 [GIT PULL] x86/build changes for v4.17 Ingo Molnar
2018-04-02 21:44 ` Linus Torvalds
2018-04-02 22:38 ` Matthias Kaehlcke
2018-04-03 1:26 ` Matthias Kaehlcke
2018-04-03 8:59 ` Peter Zijlstra
2018-04-03 9:51 ` Ingo Molnar
2018-04-03 12:09 ` Peter Zijlstra
2018-04-03 18:06 ` Matthias Kaehlcke
2018-04-03 21:58 ` Nick Desaulniers
2018-04-04 9:19 ` Peter Zijlstra
2018-04-04 9:38 ` Greg KH
2018-04-04 16:49 ` Nick Desaulniers
2018-04-04 17:13 ` Linus Torvalds
2018-04-04 17:46 ` Nick Desaulniers
2018-04-04 23:10 ` Nick Desaulniers
2018-04-04 16:53 ` Nick Desaulniers
2018-04-04 16:59 ` Greg KH
2018-04-04 19:26 ` James Y Knight
2018-04-04 19:42 ` Linus Torvalds
2018-04-04 22:21 ` James Y Knight
2018-04-04 22:29 ` Linus Torvalds
2018-04-05 7:08 ` Peter Zijlstra
2018-04-05 16:21 ` James Y Knight
2018-04-04 19:32 ` Josh Poimboeuf
2018-06-07 19:23 ` Nick Desaulniers
2018-06-07 20:11 ` Greg KH
2018-04-04 9:30 ` Peter Zijlstra
2018-04-04 19:17 ` Matthias Kaehlcke
2018-04-04 20:33 ` Arnd Bergmann
2018-04-04 20:58 ` Matthias Kaehlcke [this message]
2018-04-04 21:11 ` Arnd Bergmann
2018-04-04 21:46 ` Matthias Kaehlcke
2018-04-04 21:59 ` Linus Torvalds
2018-04-04 22:17 ` Matthias Kaehlcke
2018-04-04 22:39 ` Linus Torvalds
2018-04-04 23:31 ` Matthias Kaehlcke
2018-04-05 0:05 ` Linus Torvalds
2018-04-05 0:20 ` Kees Cook
2018-04-05 7:24 ` Peter Zijlstra
2018-04-05 8:04 ` Ingo Molnar
2018-04-05 8:24 ` Peter Zijlstra
2018-04-05 16:43 ` Linus Torvalds
2018-04-05 7:20 ` Peter Zijlstra
2018-04-05 17:46 ` James Y Knight
2018-04-05 18:06 ` Linus Torvalds
2018-04-05 20:51 ` James Y Knight
2018-04-05 21:13 ` Linus Torvalds
2018-04-05 22:51 ` James Y Knight
2018-04-06 2:02 ` Linus Torvalds
2018-04-05 17:47 ` James Y Knight
2018-04-04 23:04 ` Nick Desaulniers
2018-04-03 17:36 ` Linus Torvalds
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