linux-kernel - Re: [PATCH] kbuild: check CONFIG_AS_IS_LLVM instead of LLVM

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Date:   Tue, 10 Aug 2021 09:05:58 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:SIFIVE DRIVERS" <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH] kbuild: check CONFIG_AS_IS_LLVM instead of LLVM_IAS

On Fri, Aug 6, 2021 at 3:46 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On 8/5/2021 8:01 AM, Masahiro Yamada wrote:
> > LLVM_IAS is the user interface to set the -(no-)integrated-as flag,
> > and it should be used only for that purpose.
> >
> > LLVM_IAS is checked in some places to determine the assembler type,
> > but it is not precise.
> >
> >   $ make CC=gcc LLVM_IAS=1
> >
> > ... will use the GNU assembler since LLVM_IAS=1 is effective only when
> > $(CC) is clang.
> >
> > Of course, the combination of CC=gcc and LLVM_IAS=1 does not make
> > sense, but the build system can be more robust against such insane
> > input.
> >
> > Commit ba64beb17493a ("kbuild: check the minimum assembler version in
> > Kconfig") introduced CONFIG_AS_IS_GNU/LLVM, which is more precise
> > because Kconfig checks the version string from the assembler in use.
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
>
> Reviewed-by: Nathan Chancellor <nathan@...nel.org>





Applied to linux-kbuild.




> > ---
> >
> >   Makefile            | 2 +-
> >   arch/riscv/Makefile | 2 +-
> >   2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 4ab151060931..8b56c9692c3c 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -844,7 +844,7 @@ else
> >   DEBUG_CFLAGS        += -g
> >   endif
> >
> > -ifneq ($(LLVM_IAS),1)
> > +ifndef CONFIG_AS_IS_LLVM
> >   KBUILD_AFLAGS       += -Wa,-gdwarf-2
> >   endif
> >
> > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> > index bc74afdbf31e..dcfbd2a87d41 100644
> > --- a/arch/riscv/Makefile
> > +++ b/arch/riscv/Makefile
> > @@ -41,7 +41,7 @@ endif
> >   ifeq ($(CONFIG_LD_IS_LLD),y)
> >       KBUILD_CFLAGS += -mno-relax
> >       KBUILD_AFLAGS += -mno-relax
> > -ifneq ($(LLVM_IAS),1)
> > +ifndef CONFIG_AS_IS_LLVM
> >       KBUILD_CFLAGS += -Wa,-mno-relax
> >       KBUILD_AFLAGS += -Wa,-mno-relax
> >   endif
> >



-- 
Best Regards
Masahiro Yamada