[tip:x86/asm 3/7] lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)

[tip:x86/asm 3/7] lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm
head:   9628d19e91f1ef9e7b1321e74a88bfa646d2a8d3
commit: 01ba23bf1b3f9a4035faedc2aa450e251bcc2c7c [3/7] x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm()
config: x86_64-buildonly-randconfig-003-20250316 (https://download.01.org/0day-ci/archive/20250316/202503161004.ZmMcxxeB-lkp@intel.com/config)
compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
rustc: rustc 1.78.0 (9b00956e5 2024-04-29)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250316/202503161004.ZmMcxxeB-lkp@intel.com/reproduce)

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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202503161004.ZmMcxxeB-lkp@intel.com/

All errors (new ones prefixed by >>):

>> lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
    1269 |         BUILD_BUG_ON(!__builtin_constant_p(res));
         |         ^
   include/linux/build_bug.h:50:2: note: expanded from macro 'BUILD_BUG_ON'
      50 |         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'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^
   include/linux/compiler_types.h:542:2: note: expanded from macro 'compiletime_assert'
     542 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
         |         ^
   include/linux/compiler_types.h:530:2: note: expanded from macro '_compiletime_assert'
     530 |         __compiletime_assert(condition, msg, prefix, suffix)
         |         ^
   include/linux/compiler_types.h:523:4: note: expanded from macro '__compiletime_assert'
     523 |                         prefix ## suffix();                             \
         |                         ^
   <scratch space>:20:1: note: expanded from here
      20 | __compiletime_assert_279
         | ^
   1 error generated.


vim +1269 lib/test_bitmap.c

291f93ca339f5b5 Barry Song        2021-08-06  1227  
2356d198d2b4dde Yury Norov        2023-07-17  1228  /*
2356d198d2b4dde Yury Norov        2023-07-17  1229   * FIXME: Clang breaks compile-time evaluations when KASAN and GCOV are enabled.
2356d198d2b4dde Yury Norov        2023-07-17  1230   * To workaround it, GCOV is force-disabled in Makefile for this configuration.
2356d198d2b4dde Yury Norov        2023-07-17  1231   */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1232  static void __init test_bitmap_const_eval(void)
dc34d5036692c61 Alexander Lobakin 2022-06-24  1233  {
dc34d5036692c61 Alexander Lobakin 2022-06-24  1234  	DECLARE_BITMAP(bitmap, BITS_PER_LONG);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1235  	unsigned long initvar = BIT(2);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1236  	unsigned long bitopvar = 0;
dc34d5036692c61 Alexander Lobakin 2022-06-24  1237  	unsigned long var = 0;
dc34d5036692c61 Alexander Lobakin 2022-06-24  1238  	int res;
dc34d5036692c61 Alexander Lobakin 2022-06-24  1239  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1240  	/*
dc34d5036692c61 Alexander Lobakin 2022-06-24  1241  	 * Compilers must be able to optimize all of those to compile-time
dc34d5036692c61 Alexander Lobakin 2022-06-24  1242  	 * constants on any supported optimization level (-O2, -Os) and any
dc34d5036692c61 Alexander Lobakin 2022-06-24  1243  	 * architecture. Otherwise, trigger a build bug.
dc34d5036692c61 Alexander Lobakin 2022-06-24  1244  	 * The whole function gets optimized out then, there's nothing to do
dc34d5036692c61 Alexander Lobakin 2022-06-24  1245  	 * in runtime.
dc34d5036692c61 Alexander Lobakin 2022-06-24  1246  	 */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1247  
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1248  	/* Equals to `unsigned long bitmap[1] = { GENMASK(6, 5), }` */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1249  	bitmap_clear(bitmap, 0, BITS_PER_LONG);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1250  	if (!test_bit(7, bitmap))
dc34d5036692c61 Alexander Lobakin 2022-06-24  1251  		bitmap_set(bitmap, 5, 2);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1252  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1253  	/* Equals to `unsigned long bitopvar = BIT(20)` */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1254  	__change_bit(31, &bitopvar);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1255  	bitmap_shift_right(&bitopvar, &bitopvar, 11, BITS_PER_LONG);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1256  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1257  	/* Equals to `unsigned long var = BIT(25)` */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1258  	var |= BIT(25);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1259  	if (var & BIT(0))
dc34d5036692c61 Alexander Lobakin 2022-06-24  1260  		var ^= GENMASK(9, 6);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1261  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1262  	/* __const_hweight<32|64>(GENMASK(6, 5)) == 2 */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1263  	res = bitmap_weight(bitmap, 20);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1264  	BUILD_BUG_ON(!__builtin_constant_p(res));
dc34d5036692c61 Alexander Lobakin 2022-06-24  1265  	BUILD_BUG_ON(res != 2);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1266  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1267  	/* !(BIT(31) & BIT(18)) == 1 */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1268  	res = !test_bit(18, &bitopvar);
dc34d5036692c61 Alexander Lobakin 2022-06-24 @1269  	BUILD_BUG_ON(!__builtin_constant_p(res));
dc34d5036692c61 Alexander Lobakin 2022-06-24  1270  	BUILD_BUG_ON(!res);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1271  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1272  	/* BIT(2) & GENMASK(14, 8) == 0 */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1273  	res = initvar & GENMASK(14, 8);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1274  	BUILD_BUG_ON(!__builtin_constant_p(res));
dc34d5036692c61 Alexander Lobakin 2022-06-24  1275  	BUILD_BUG_ON(res);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1276  
dc34d5036692c61 Alexander Lobakin 2022-06-24  1277  	/* ~BIT(25) */
dc34d5036692c61 Alexander Lobakin 2022-06-24  1278  	BUILD_BUG_ON(!__builtin_constant_p(~var));
dc34d5036692c61 Alexander Lobakin 2022-06-24  1279  	BUILD_BUG_ON(~var != ~BIT(25));
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1280  
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1281  	/* ~BIT(25) | BIT(25) == ~0UL */
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1282  	bitmap_complement(&var, &var, BITS_PER_LONG);
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1283  	__assign_bit(25, &var, true);
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1284  
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1285  	/* !(~(~0UL)) == 1 */
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1286  	res = bitmap_full(&var, BITS_PER_LONG);
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1287  	BUILD_BUG_ON(!__builtin_constant_p(res));
7adaf37f7f104a7 Alexander Lobakin 2024-03-27  1288  	BUILD_BUG_ON(!res);
dc34d5036692c61 Alexander Lobakin 2022-06-24  1289  }
dc34d5036692c61 Alexander Lobakin 2022-06-24  1290  

:::::: The code at line 1269 was first introduced by commit
:::::: dc34d5036692c614eef23c1130ee42a201c316bf lib: test_bitmap: add compile-time optimization/evaluations assertions

:::::: TO: Alexander Lobakin <alexandr.lobakin@intel.com>
:::::: CC: Yury Norov <yury.norov@gmail.com>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [tip:x86/asm 3/7] lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)

[Uros Bizjak]

On Sun, Mar 16, 2025 at 3:52 AM kernel test robot <lkp@intel.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm
> head:   9628d19e91f1ef9e7b1321e74a88bfa646d2a8d3
> commit: 01ba23bf1b3f9a4035faedc2aa450e251bcc2c7c [3/7] x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm()
> config: x86_64-buildonly-randconfig-003-20250316 (https://download.01.org/0day-ci/archive/20250316/202503161004.ZmMcxxeB-lkp@intel.com/config)
> compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
> rustc: rustc 1.78.0 (9b00956e5 2024-04-29)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250316/202503161004.ZmMcxxeB-lkp@intel.com/reproduce)
>
> 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@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202503161004.ZmMcxxeB-lkp@intel.com/
>
> All errors (new ones prefixed by >>):
>
> >> lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
>     1269 |         BUILD_BUG_ON(!__builtin_constant_p(res));

I fail to see how the referred patch can cause an error in:

/* !(BIT(31) & BIT(18)) == 1 */
res = !test_bit(18, &bitopvar);
BUILD_BUG_ON(!__builtin_constant_p(res));
BUILD_BUG_ON(!res);

Otherwise, the patch fixes a correctness issue, so there is nothing to
do with the patch anyway.

Uros.

Re: [tip:x86/asm 3/7] lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)

[Alexander Lobakin]

From: Uros Bizjak <ubizjak@gmail.com>
Date: Sun, 16 Mar 2025 09:28:51 +0100

> On Sun, Mar 16, 2025 at 3:52 AM kernel test robot <lkp@intel.com> wrote:
>>
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/asm
>> head:   9628d19e91f1ef9e7b1321e74a88bfa646d2a8d3
>> commit: 01ba23bf1b3f9a4035faedc2aa450e251bcc2c7c [3/7] x86/hweight: Use ASM_CALL_CONSTRAINT in inline asm()
>> config: x86_64-buildonly-randconfig-003-20250316 (https://download.01.org/0day-ci/archive/20250316/202503161004.ZmMcxxeB-lkp@intel.com/config)
>> compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
>> rustc: rustc 1.78.0 (9b00956e5 2024-04-29)
>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250316/202503161004.ZmMcxxeB-lkp@intel.com/reproduce)
>>
>> 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@intel.com>
>> | Closes: https://lore.kernel.org/oe-kbuild-all/202503161004.ZmMcxxeB-lkp@intel.com/
>>
>> All errors (new ones prefixed by >>):
>>
>>>> lib/test_bitmap.c:1269:2: error: call to '__compiletime_assert_279' declared with 'error' attribute: BUILD_BUG_ON failed: !__builtin_constant_p(res)
>>     1269 |         BUILD_BUG_ON(!__builtin_constant_p(res));
> 
> I fail to see how the referred patch can cause an error in:
> 
> /* !(BIT(31) & BIT(18)) == 1 */
> res = !test_bit(18, &bitopvar);
> BUILD_BUG_ON(!__builtin_constant_p(res));
> BUILD_BUG_ON(!res);

Kbuild bot sometimes fails on randconfigs and random commits blaming
these commits even though they're unrelated.
Esp this function, I dunno why, but time to time on different arches
(um is the winner here) it fails to expand obvious stuff. This for sure
depends on debug stuff configuration, let's say in the attached config I
see KASAN enabled, but not always and it's unclear how to catch and
reproduce stuff (and then how to fix) reliably.

Re Clang and KASAN, there's this in lib/Makefile:

obj-$(CONFIG_TEST_BITMAP) += test_bitmap.o
ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_KASAN),yy)
# FIXME: Clang breaks test_bitmap_const_eval when KASAN and GCOV are enabled
GCOV_PROFILE_test_bitmap.o := n
endif

This was added a while ago not by me as I'm no instrumentation expert
and have no idea about those GCOV_PROFILE etc. Does 19.1.7 want more
than that to evaluate obvious things?

> 
> Otherwise, the patch fixes a correctness issue, so there is nothing to
> do with the patch anyway.
> 
> Uros.

Thanks,
Olek