linux-kernel - Re: [PATCH] log2: make is_power_of_2() integer constant expression when possible

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Message-ID: <87o96qn9oa.fsf@intel.com>
Date:   Mon, 04 Mar 2019 13:47:17 +0200
From:   Jani Nikula <jani.nikula@...el.com>
To:     kbuild test robot <lkp@...el.com>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chris Wilson <chris@...is-wilson.co.uk>
Subject: Re: [PATCH] log2: make is_power_of_2() integer constant expression when possible

On Mon, 04 Mar 2019, kbuild test robot <lkp@...el.com> wrote:
> Hi Jani,
>
> I love your patch! Perhaps something to improve:
>
> [auto build test WARNING on linus/master]
> [also build test WARNING on v5.0 next-20190301]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url:    https://github.com/0day-ci/linux/commits/Jani-Nikula/log2-make-is_power_of_2-integer-constant-expression-when-possible/20190304-153529
> config: microblaze-mmu_defconfig (attached as .config)
> compiler: microblaze-linux-gcc (GCC) 8.2.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         GCC_VERSION=8.2.0 make.cross ARCH=microblaze 
>
> All warnings (new ones prefixed by >>):
>
>>> arch/microblaze/mm/pgtable.c:185: warning: "is_power_of_2" redefined
>     #define is_power_of_2(x) ((x) != 0 && (((x) & ((x) - 1)) == 0))

Oh wow, a copy of is_power_of_2() introduced 10 years ago, apparently
unused since its introduction.


BR,
Jani.


>     
>    In file included from include/linux/kernel.h:12,
>                     from arch/microblaze/mm/pgtable.c:30:
>    include/linux/log2.h:56: note: this is the location of the previous definition
>     #define is_power_of_2(n) \
>     
>
> vim +/is_power_of_2 +185 arch/microblaze/mm/pgtable.c
>
> 15902bf6 Michal Simek 2009-05-26  183  
> 15902bf6 Michal Simek 2009-05-26  184  /* is x a power of 2? */
> 15902bf6 Michal Simek 2009-05-26 @185  #define is_power_of_2(x)	((x) != 0 && (((x) & ((x) - 1)) == 0))
> 15902bf6 Michal Simek 2009-05-26  186  
>
> :::::: The code at line 185 was first introduced by commit
> :::::: 15902bf63c8332946e5a1f48a72e3ae22874b11b microblaze_mmu_v2: Page table - ioremap - pgtable.c/h, section update
>
> :::::: TO: Michal Simek <monstr@...str.eu>
> :::::: CC: Michal Simek <monstr@...str.eu>
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

-- 
Jani Nikula, Intel Open Source Graphics Center