linux-kernel - arch/arm/lib/xor-neon.c:30:2: warning: This code requires at least version 4.6 of GCC

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Message-ID: <202201291408.Pkylyt75-lkp@intel.com>
Date:   Sat, 29 Jan 2022 15:02:58 +0800
From:   kernel test robot <lkp@...el.com>
To:     "Justin M. Forbes" <jforbes@...oraproject.org>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org,
        "Jason A. Donenfeld" <zx2c4@...nel.org>
Subject: arch/arm/lib/xor-neon.c:30:2: warning: This code requires at least
 version 4.6 of GCC

Hi Justin,

First bad commit (maybe != root cause):

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   169387e2aa291a4e3cb856053730fe99d6cec06f
commit: e56e18985596617ae426ed5997fb2e737cffb58b lib/crypto: add prompts back to crypto libraries
date:   11 days ago
config: arm-randconfig-r004-20220128 (https://download.01.org/0day-ci/archive/20220129/202201291408.Pkylyt75-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 33b45ee44b1f32ffdbc995e6fec806271b4b3ba4)
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
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e56e18985596617ae426ed5997fb2e737cffb58b
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout e56e18985596617ae426ed5997fb2e737cffb58b
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash

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

All warnings (new ones prefixed by >>):

>> arch/arm/lib/xor-neon.c:30:2: warning: This code requires at least version 4.6 of GCC [-W#warnings]
   #warning This code requires at least version 4.6 of GCC
    ^
   1 warning generated.

Kconfig warnings: (for reference only)
   WARNING: unmet direct dependencies detected for TEGRA20_APB_DMA
   Depends on DMADEVICES && (ARCH_TEGRA || COMPILE_TEST
   Selected by
   - SOC_TEGRA_FUSE && ARCH_TEGRA && ARCH_TEGRA_2x_SOC


vim +30 arch/arm/lib/xor-neon.c

01956597cbc46d Ard Biesheuvel 2013-05-17  16  
01956597cbc46d Ard Biesheuvel 2013-05-17  17  /*
01956597cbc46d Ard Biesheuvel 2013-05-17  18   * Pull in the reference implementations while instructing GCC (through
01956597cbc46d Ard Biesheuvel 2013-05-17  19   * -ftree-vectorize) to attempt to exploit implicit parallelism and emit
01956597cbc46d Ard Biesheuvel 2013-05-17  20   * NEON instructions.
01956597cbc46d Ard Biesheuvel 2013-05-17  21   */
01956597cbc46d Ard Biesheuvel 2013-05-17  22  #if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
01956597cbc46d Ard Biesheuvel 2013-05-17  23  #pragma GCC optimize "tree-vectorize"
01956597cbc46d Ard Biesheuvel 2013-05-17  24  #else
01956597cbc46d Ard Biesheuvel 2013-05-17  25  /*
01956597cbc46d Ard Biesheuvel 2013-05-17  26   * While older versions of GCC do not generate incorrect code, they fail to
01956597cbc46d Ard Biesheuvel 2013-05-17  27   * recognize the parallel nature of these functions, and emit plain ARM code,
01956597cbc46d Ard Biesheuvel 2013-05-17  28   * which is known to be slower than the optimized ARM code in asm-arm/xor.h.
01956597cbc46d Ard Biesheuvel 2013-05-17  29   */
01956597cbc46d Ard Biesheuvel 2013-05-17 @30  #warning This code requires at least version 4.6 of GCC
01956597cbc46d Ard Biesheuvel 2013-05-17  31  #endif
01956597cbc46d Ard Biesheuvel 2013-05-17  32  

:::::: The code at line 30 was first introduced by commit
:::::: 01956597cbc46df072f20f90a40eebe356200c38 ARM: crypto: add NEON accelerated XOR implementation

:::::: TO: Ard Biesheuvel <ard.biesheuvel@...aro.org>
:::::: CC: Ard Biesheuvel <ard.biesheuvel@...aro.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org