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 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

>
> >    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