[PATCH] kbuild: remove AS variable

Masahiro Yamada

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Mar 24, 2020, 12:15:38 PM3/24/20

to linux-...@vger.kernel.org, David S . Miller, net...@vger.kernel.org, linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek, clang-bu...@googlegroups.com

As commit 5ef872636ca7 ("kbuild: get rid of misleading $(AS) from
documents") noted, we rarely use $(AS) in the kernel build.

Now that the only/last user of $(AS) in drivers/net/wan/Makefile was
converted to $(CC), $(AS) is no longer used in the build process.

You can still pass in AS=clang, which is just a switch to turn on
the LLVM integrated assembler.

Signed-off-by: Masahiro Yamada <masa...@kernel.org>
---

Makefile | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 16d8271192d1..339e8c51a10b 100644
--- a/Makefile
+++ b/Makefile
@@ -405,7 +405,6 @@ KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)

# Make variables (CC, etc...)
-AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E
@@ -472,7 +471,7 @@ KBUILD_LDFLAGS :=
GCC_PLUGINS_CFLAGS :=
CLANG_FLAGS :=

-export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
+export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF PAHOLE LEX YACC AWK INSTALLKERNEL
export PERL PYTHON PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
--
2.17.1

Masahiro Yamada

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Mar 24, 2020, 12:16:08 PM3/24/20

to linux-...@vger.kernel.org, David S . Miller, net...@vger.kernel.org, linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek, clang-bu...@googlegroups.com

Nick Desaulniers

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Mar 24, 2020, 3:39:02 PM3/24/20

to Masahiro Yamada, Linux Kbuild mailing list, David S . Miller, Network Development, LKML, Michal Marek, clang-built-linux

On Tue, Mar 24, 2020 at 9:16 AM Masahiro Yamada <masa...@kernel.org> wrote:
>
> As commit 5ef872636ca7 ("kbuild: get rid of misleading $(AS) from
> documents") noted, we rarely use $(AS) in the kernel build.
>
> Now that the only/last user of $(AS) in drivers/net/wan/Makefile was
> converted to $(CC), $(AS) is no longer used in the build process.

TIL that we don't actually invoke the assembler at all for out of line
assembly files, but rather use the compiler as the "driver".
scripts/Makefile.build:
329 quiet_cmd_as_o_S = AS $(quiet_modtag) $@
330 cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<

Though I am personally conflicted, as
commit 055efab3120b ("kbuild: drop support for cc-ldoption")
since we do the opposite for the linker (we do not use the compiler as
the driver for the linker using -Wl,-foo flags). I wish we were
consistent in this regard (and not using the compiler as the driver),
but that is a yak-shave+bikeshed (I typed out yakshed without
thinking; maybe a new entry for Linux kernel urban dictionary or The
Jargon File) for another day.

$ grep -nR --include="Makefile" '(AS)' .
Turned up only this change and the above referenced wan driver.

Reviewed-by: Nick Desaulniers <ndesau...@google.com>
Tested-by: Nick Desaulniers <ndesau...@google.com>

--
Thanks,
~Nick Desaulniers

Nathan Chancellor

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Mar 24, 2020, 3:43:39 PM3/24/20

to Masahiro Yamada, linux-...@vger.kernel.org, David S . Miller, net...@vger.kernel.org, linux-...@vger.kernel.org, Michal Marek, clang-bu...@googlegroups.com

On Wed, Mar 25, 2020 at 01:15:39AM +0900, Masahiro Yamada wrote:
> As commit 5ef872636ca7 ("kbuild: get rid of misleading $(AS) from
> documents") noted, we rarely use $(AS) in the kernel build.
>
> Now that the only/last user of $(AS) in drivers/net/wan/Makefile was
> converted to $(CC), $(AS) is no longer used in the build process.
>
> You can still pass in AS=clang, which is just a switch to turn on
> the LLVM integrated assembler.
>
> Signed-off-by: Masahiro Yamada <masa...@kernel.org>

Reviewed-by: Nathan Chancellor <natecha...@gmail.com>

Nick Desaulniers

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Mar 24, 2020, 3:43:58 PM3/24/20

to Masahiro Yamada, Linux Kbuild mailing list, David S . Miller, Network Development, LKML, Michal Marek, clang-built-linux

Just noting that this got rolled up into a 3 patch series:
https://lore.kernel.org/lkml/CAKwvOdkjiyyt8Ju2j2O4cm1s...@mail.gmail.com/T/#u

> --
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--
Thanks,
~Nick Desaulniers

Nick Desaulniers

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Mar 24, 2020, 3:59:06 PM3/24/20

to Masahiro Yamada, Linux Kbuild mailing list, David S . Miller, Network Development, LKML, Michal Marek, clang-built-linux

On Tue, Mar 24, 2020 at 12:38 PM Nick Desaulniers
<ndesau...@google.com> wrote:
> consistent in this regard (and not using the compiler as the driver),

Ah, the preprocessor; we need to preprocess the .S files, .s files are
fine (though we have .lds.S files that are not `-x
assembler-with-cpp`)

--
Thanks,
~Nick Desaulniers

kbuild test robot

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Mar 25, 2020, 6:00:24 PM3/25/20

to Masahiro Yamada, kbuil...@lists.01.org, clang-bu...@googlegroups.com, linux-...@vger.kernel.org, David S . Miller, net...@vger.kernel.org, linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek

Hi Masahiro,

I love your patch! Yet something to improve:

[auto build test ERROR on kbuild/for-next]
[also build test ERROR on net-next/master net/master linus/master v5.6-rc7 next-20200325]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url: https://github.com/0day-ci/linux/commits/Masahiro-Yamada/net-wan-wanxl-use-CC68K-instead-of-AS68K-for-rebuilding-firmware/20200326-034145
base: https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git for-next
config: powerpc-defconfig (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 2093fdd429d52348e08969180ac6b1e705fc4ff6)
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
COMPILER=clang make.cross ARCH=powerpc

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <l...@intel.com>

All errors (new ones prefixed by >>):

>> /bin/sh: 0: Illegal option --
6 real 3 user 2 sys 107.14% cpu make distclean
--
>> /bin/sh: 0: Illegal option --
4 real 4 user 1 sys 114.93% cpu make olddefconfig
--
>> /bin/sh: 0: Illegal option --
/usr/bin/ld: scripts/dtc/dtc-parser.tab.o:(.bss+0x10): multiple definition of `yylloc'; scripts/dtc/dtc-lexer.lex.o:(.bss+0x58): first defined here
clang-11: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [scripts/Makefile.host:116: scripts/dtc/dtc] Error 1
make[2]: Target '__build' not remade because of errors.
make[1]: *** [Makefile:1270: scripts_dtc] Error 2
make[1]: Target 'prepare' not remade because of errors.
make: *** [Makefile:180: sub-make] Error 2
17 real 6 user 11 sys 102.46% cpu make prepare

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

.config.gz

Masahiro Yamada

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Mar 26, 2020, 1:58:03 AM3/26/20

to linux-...@vger.kernel.org, clang-bu...@googlegroups.com, Geert Uytterhoeven, Masahiro Yamada, Michal Marek, linux-...@vger.kernel.org

As commit 5ef872636ca7 ("kbuild: get rid of misleading $(AS) from

documents") noted, we rarely use $(AS) directly in the kernel build.

Now that the only/last user of $(AS) in drivers/net/wan/Makefile was
converted to $(CC), $(AS) is no longer used in the build process.

You can still pass in AS=clang, which is just a switch to turn on
the LLVM integrated assembler.

Signed-off-by: Masahiro Yamada <masa...@kernel.org>

Reviewed-by: Nick Desaulniers <ndesau...@google.com>
Tested-by: Nick Desaulniers <ndesau...@google.com>

Reviewed-by: Nathan Chancellor <natecha...@gmail.com>
---

Changes in v2:
- Fix breakage of CC=clang build

Makefile | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Makefile b/Makefile

index fcec84681e4e..2e12fa1cc8f3 100644

--- a/Makefile
+++ b/Makefile
@@ -405,7 +405,6 @@ KBUILD_HOSTLDFLAGS := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
KBUILD_HOSTLDLIBS := $(HOST_LFS_LIBS) $(HOSTLDLIBS)

# Make variables (CC, etc...)
-AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
CC = $(CROSS_COMPILE)gcc
CPP = $(CC) -E

@@ -535,7 +534,7 @@ endif
ifneq ($(GCC_TOOLCHAIN),)
CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN)
endif
-ifeq ($(shell $(AS) --version 2>&1 | head -n 1 | grep clang),)
+ifeq ($(if $(AS),$(shell $(AS) --version 2>&1 | head -n 1 | grep clang)),)
CLANG_FLAGS += -no-integrated-as
endif
CLANG_FLAGS += -Werror=unknown-warning-option
--
2.17.1

Masahiro Yamada

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Mar 26, 2020, 2:14:55 AM3/26/20

to Nick Desaulniers, Linux Kbuild mailing list, David S . Miller, Network Development, LKML, Michal Marek, clang-built-linux

Hi Nick,

Right, there is no '*.s' source file in the kernel tree.

If we want to de-couple $(AS), we must the compilation
before the assemble stage ( $(CC) -S ), but
doing so does not buy us.

So, $(CC) always works as the front-end
for compiling both .c and .S files.

You can see the internal database by
'make --print-data-base'.

I see the following for *.S -> *.o rule.

# default
COMPILE.S = $(CC) $(ASFLAGS) $(CPPFLAGS) $(TARGET_MACH) -c

So, using $(CC) is the right thing.

Even if we keep AS, we cannot do like AS=llvm-as
since llvm-as is a different kind of tool
that processes LLVM assembly (.ll) .

--
Best Regards
Masahiro Yamada

kbuild test robot

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Mar 26, 2020, 7:36:04 AM3/26/20

to Masahiro Yamada, kbuil...@lists.01.org, clang-bu...@googlegroups.com, linux-kbuild@vger.kernel.org, David S . Miller, net...@vger.kernel.org, linux-...@vger.kernel.org, Masahiro Yamada, Michal Marek

Hi Masahiro,

I love your patch! Yet something to improve:

[auto build test ERROR on kbuild/for-next]

[also build test ERROR on v5.6-rc7 next-20200326]
[cannot apply to sparc-next/master ipvs/master]

[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url: https://github.com/0day-ci/linux/commits/Masahiro-Yamada/kbuild-remove-AS-variable/20200326-034016
base: https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git for-next
config: x86_64-randconfig-d002-20200326 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 4b428e8f18c7006f69b3d4ef0fdf091d998d0941)

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

COMPILER=clang make.cross ARCH=x86_64

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <l...@intel.com>

All errors (new ones prefixed by >>):

>> /bin/bash: --: invalid option
Usage: /bin/bash [GNU long option] [option] ...
/bin/bash [GNU long option] [option] script-file ...
GNU long options:
--debug
--debugger
--dump-po-strings
--dump-strings
--help
--init-file
--login
--noediting
--noprofile
--norc
--posix
--pretty-print
--rcfile
--restricted
--verbose
--version
Shell options:
-ilrsD or -c command or -O shopt_option (invocation only)
-abefhkmnptuvxBCHP or -o option
make[1]: *** [Makefile:1697: drivers] Error 2
make[1]: Target '_all' not remade because of errors.