linux-kernel - Re: [PATCH 2/2] lib/string.c: Optimize memchr()

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Date:   Thu, 21 Jul 2022 13:06:33 +0800
From:   kernel test robot <lkp@...el.com>
To:     Yu-Jen Chang <arthurchang09@...il.com>, andy@...nel.org,
        akinobu.mita@...il.com
Cc:     kbuild-all@...ts.01.org, jserv@...s.ncku.edu.tw,
        linux-kernel@...r.kernel.org,
        Yu-Jen Chang <arthurchang09@...il.com>
Subject: Re: [PATCH 2/2] lib/string.c: Optimize memchr()

Hi Yu-Jen,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.19-rc7 next-20220720]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Yu-Jen-Chang/Optimize-memchr/20220710-223118
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git b1c428b6c3684ee8ddf4137d68b3e8d51d2a700f
config: arc-buildonly-randconfig-r005-20220719 (https://download.01.org/0day-ci/archive/20220721/202207211216.wsqhuMcj-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/307ee542c2bd8378b2225910f3f9b982df7a7669
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Yu-Jen-Chang/Optimize-memchr/20220710-223118
        git checkout 307ee542c2bd8378b2225910f3f9b982df7a7669
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@...el.com>

All errors (new ones prefixed by >>):

>> lib/string.c:902:7: error: conflicting types for 'memchr'; have 'void *(const void *, int,  long unsigned int)'
     902 | void *memchr(const void *p, int c, unsigned long length)
         |       ^~~~~~
   In file included from lib/string.c:19:
   include/linux/string.h:162:15: note: previous declaration of 'memchr' with type 'void *(const void *, int,  __kernel_size_t)' {aka 'void *(const void *, int,  unsigned int)'}
     162 | extern void * memchr(const void *,int,__kernel_size_t);
         |               ^~~~~~


vim +902 lib/string.c

   891	
   892	#ifndef __HAVE_ARCH_MEMCHR
   893	/**
   894	 * memchr - Find a character in an area of memory.
   895	 * @p: The memory area
   896	 * @c: The byte to search for
   897	 * @length: The size of the area.
   898	 *
   899	 * returns the address of the first occurrence of @c, or %NULL
   900	 * if @c is not found
   901	 */
 > 902	void *memchr(const void *p, int c, unsigned long length)
   903	{
   904		u64 mask, val;
   905		const void *end = p + length;
   906	
   907		c &= 0xff;
   908		if (p <= end - 8) {
   909			mask = c;
   910			MEMCHR_MASK_GEN(mask);
   911	
   912			for (; p <= end - 8; p += 8) {
   913				val = *(u64 *)p ^ mask;
   914				if ((val + 0xfefefefefefefeffu) &
   915				    (~val & 0x8080808080808080u))
   916					break;
   917			}
   918		}
   919	
   920		for (; p < end; p++)
   921			if (*(unsigned char *)p == c)
   922				return (void *)p;
   923	
   924		return NULL;
   925	}
   926	EXPORT_SYMBOL(memchr);
   927	#endif
   928	

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