Re: lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)

[Nick Desaulniers]

On Thu, Jun 15, 2023 at 3:52 PM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
>
> On Thu, Jun 15, 2023 at 7:22 AM Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> >
> > On Thu, Jun 15, 2023 at 02:32:02PM +0800, kernel test robot wrote:
> > > Hi Alexander,
> > >
> > > FYI, the error/warning still remains.
> > >
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > head:   b6dad5178ceaf23f369c3711062ce1f2afc33644
> > > commit: dc34d5036692c614eef23c1130ee42a201c316bf lib: test_bitmap: add compile-time optimization/evaluations assertions
> > > date:   12 months ago
> > > config: arm64-randconfig-r025-20230615 (https://download.01.org/0day-ci/archive/20230615/202306151433.QKcn7ZNn-lkp@xxxxxxxxx/config)
>
> ^ randconfig
>
> > > compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
> > > reproduce (this is a W=1 build):
> > >         mkdir -p ~/bin
> > >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # install arm64 cross compiling tool for clang build
> > >         # apt-get install binutils-aarch64-linux-gnu
> > >         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dc34d5036692c614eef23c1130ee42a201c316bf
> > >         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > >         git fetch --no-tags linus master
> > >         git checkout dc34d5036692c614eef23c1130ee42a201c316bf
> > >         # save the config file
> > >         mkdir build_dir && cp config build_dir/.config
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash lib/
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202306151433.QKcn7ZNn-lkp@xxxxxxxxx/
> > >
> > > All errors (new ones prefixed by >>):
> >
> > >    888                /*
> > >    889                 * Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }`.
> > >    890                 * Clang on s390 optimizes bitops at compile-time as intended, but at
> > >    891                 * the same time stops treating @bitmap and @bitopvar as compile-time
> > >    892                 * constants after regular test_bit() is executed, thus triggering the
> > >    893                 * build bugs below. So, call const_test_bit() there directly until
> > >    894                 * the compiler is fixed.
> > >    895                 */
> > >    896                bitmap_clear(bitmap, 0, BITS_PER_LONG);
> > >    897        #if defined(__s390__) && defined(__clang__)
> > >    898                if (!const_test_bit(7, bitmap))
> > >    899        #else
> > >    900                if (!test_bit(7, bitmap))
> > >    901        #endif
> >
> > Hmm... Reveals the bug in clang/arm64?
>
> Seems related to the config.  ARCH=arm64 defconfig +
> CONFIG_TEST_BITMAP=y doesn't trigger this for me, but the randconfig
> does.  We'll bisect the config, and update the thread tracking this:
> https://github.com/ClangBuiltLinux/linux/issues/1874

KASAN and GCOV together seem to be tickling this.

>
> >
> > >    919                res = !test_bit(18, &bitopvar);
> > >  > 920                BUILD_BUG_ON(!__builtin_constant_p(res));
> > >    921                BUILD_BUG_ON(!res);
> >
> >
> > --
> > With Best Regards,
> > Andy Shevchenko
> >
> >
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



-- 
Thanks,
~Nick Desaulniers