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

[kernel test robot]

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)
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 >>):

>> lib/test_bitmap.c:920:2: error: call to '__compiletime_assert_239' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
           BUILD_BUG_ON(!__builtin_constant_p(res));
           ^
   include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
           BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
           ^
   include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
   #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
                                       ^
   include/linux/compiler_types.h:352:2: note: expanded from macro 'compiletime_assert'
           _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
           ^
   include/linux/compiler_types.h:340:2: note: expanded from macro '_compiletime_assert'
           __compiletime_assert(condition, msg, prefix, suffix)
           ^
   include/linux/compiler_types.h:333:4: note: expanded from macro '__compiletime_assert'
                           prefix ## suffix();                             \
                           ^
   <scratch space>:185:1: note: expanded from here
   __compiletime_assert_239
   ^
   1 error generated.


vim +920 lib/test_bitmap.c

   871	
   872	static void __init test_bitmap_const_eval(void)
   873	{
   874		DECLARE_BITMAP(bitmap, BITS_PER_LONG);
   875		unsigned long initvar = BIT(2);
   876		unsigned long bitopvar = 0;
   877		unsigned long var = 0;
   878		int res;
   879	
   880		/*
   881		 * Compilers must be able to optimize all of those to compile-time
   882		 * constants on any supported optimization level (-O2, -Os) and any
   883		 * architecture. Otherwise, trigger a build bug.
   884		 * The whole function gets optimized out then, there's nothing to do
   885		 * in runtime.
   886		 */
   887	
   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
   902			bitmap_set(bitmap, 5, 2);
   903	
   904		/* Equals to `unsigned long bitopvar = BIT(20)` */
   905		__change_bit(31, &bitopvar);
   906		bitmap_shift_right(&bitopvar, &bitopvar, 11, BITS_PER_LONG);
   907	
   908		/* Equals to `unsigned long var = BIT(25)` */
   909		var |= BIT(25);
   910		if (var & BIT(0))
   911			var ^= GENMASK(9, 6);
   912	
   913		/* __const_hweight<32|64>(GENMASK(6, 5)) == 2 */
   914		res = bitmap_weight(bitmap, 20);
   915		BUILD_BUG_ON(!__builtin_constant_p(res));
   916		BUILD_BUG_ON(res != 2);
   917	
   918		/* !(BIT(31) & BIT(18)) == 1 */
   919		res = !test_bit(18, &bitopvar);
 > 920		BUILD_BUG_ON(!__builtin_constant_p(res));
   921		BUILD_BUG_ON(!res);
   922	
   923		/* BIT(2) & GENMASK(14, 8) == 0 */
   924		res = initvar & GENMASK(14, 8);
   925		BUILD_BUG_ON(!__builtin_constant_p(res));
   926		BUILD_BUG_ON(res);
   927	
   928		/* ~BIT(25) */
   929		BUILD_BUG_ON(!__builtin_constant_p(~var));
   930		BUILD_BUG_ON(~var != ~BIT(25));
   931	}
   932	

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