lkml.org 
[lkml]   [2018]   [Apr]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [GIT PULL] x86/build changes for v4.17
    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?

    \
     
     \ /
      Last update: 2018-04-04 22:59    [W:2.281 / U:0.100 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site