# git rev-parse -q --verify 7d42223a874f7426b58792166fce20f78581b5c4^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/mirror/linux-kbuild.git for-next
# git rev-parse -q --verify 7d42223a874f7426b58792166fce20f78581b5c4^{commit}
7d42223a874f7426b58792166fce20f78581b5c4
# git checkout -q -f -B kisskb 7d42223a874f7426b58792166fce20f78581b5c4
# git clean -qxdf
# < git log -1
# commit 7d42223a874f7426b58792166fce20f78581b5c4
# Author: Masahiro Yamada <masahiroy@kernel.org>
# Date:   Wed Apr 8 03:43:36 2020 +0900
# 
#     kbuild: support LLVM=1 to switch the default tools to Clang/LLVM
#     
#     As Documentation/kbuild/llvm.rst implies, building the kernel with a
#     full set of LLVM tools gets very verbose and unwieldy.
#     
#     Provide a single switch LLVM=1 to use Clang and LLVM tools instead
#     of GCC and Binutils. You can pass it from the command line or as an
#     environment variable.
#     
#     Please note LLVM=1 does not turn on the integrated assembler. You need
#     to pass LLVM_IA=1 to use it. When the upstream kernel is ready for the
#     integrated assembler, I think we can make it default.
#     
#     We discussed what we need, and we agreed to go with a simple boolean
#     flag that switches both target and host tools:
#     
#       https://lkml.org/lkml/2020/3/28/494
#       https://lkml.org/lkml/2020/4/3/43
#     
#     Some items discussed, but not adopted:
#     
#     - LLVM_DIR
#     
#       When multiple versions of LLVM are installed, I just thought supporting
#       LLVM_DIR=/path/to/my/llvm/bin/ might be useful.
#     
#       CC      = $(LLVM_DIR)clang
#       LD      = $(LLVM_DIR)ld.lld
#         ...
#     
#       However, we can handle this by modifying PATH. So, we decided to not do
#       this.
#     
#     - LLVM_SUFFIX
#     
#       Some distributions (e.g. Debian) package specific versions of LLVM with
#       naming conventions that use the version as a suffix.
#     
#       CC      = clang$(LLVM_SUFFIX)
#       LD      = ld.lld(LLVM_SUFFIX)
#         ...
#     
#       will allow a user to pass LLVM_SUFFIX=-11 to use clang-11 etc.,
#       but the suffixed versions in /usr/bin/ are symlinks to binaries in
#       /usr/lib/llvm-#/bin/, so this can also be handled by PATH.
#     
#     Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
#     Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
#     Tested-by: Nathan Chancellor <natechancellor@gmail.com> # build
#     Tested-by: Nick Desaulniers <ndesaulniers@google.com>
#     Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-ld --version
# < git log --format=%s --max-count=1 7d42223a874f7426b58792166fce20f78581b5c4
# < make -s -j 10 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  defconfig
# < make -s -j 10 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  help
# make -s -j 10 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  olddefconfig
# make -s -j 10 ARCH=s390 O=/kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/s390-linux/bin/s390-linux-  
/kisskb/src/kernel/futex.c: In function 'do_futex':
/kisskb/src/kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized]
   return oldval == cmparg;
                 ^
/kisskb/src/kernel/futex.c:1652:6: note: 'oldval' was declared here
  int oldval, ret;
      ^
/kisskb/src/fs/btrfs/backref.c: In function 'is_shared_data_backref':
/kisskb/src/fs/btrfs/backref.c:394:9: warning: missing braces around initializer [-Wmissing-braces]
  struct prelim_ref target = {0};
         ^
/kisskb/src/fs/btrfs/backref.c:394:9: warning: (near initialization for 'target.rbnode') [-Wmissing-braces]
Completed OK
# rm -rf /kisskb/build/kbuild_s390-defconfig_s390x-gcc4.9
# Build took: 0:07:26.166096