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From:   Sedat Dilek <sedat.dilek@gmail.com>
Date:   Fri, 10 Apr 2020 08:38:05 +0200
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Subject: Re: [PATCH] ARM: do not assemble iwmmxt.S with LLVM toolchain
To:     Jian Cai <caij2003@gmail.com>
Cc:     Nick Desaulniers <ndesaulniers@google.com>, manojgupta@google.com,
        Peter.Smith@arm.com, stefan@agner.ch, samitolvanen@google.com,
        ilie.halip@gmail.com, jiancai@google.com,
        Russell King <linux@armlinux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
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        Andrew Morton <akpm@linux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Doug Anderson <armlinux@m.disordat.com>,
        Benjamin Gaignard <benjamin.gaignard@linaro.org>,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
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        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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On Fri, Apr 10, 2020 at 1:28 AM Jian Cai <caij2003@gmail.com> wrote:
>
> iwmmxt.S contains XScale instructions LLVM ARM backend does not support.
> Skip this file if LLVM integrated assemmbler or LLD is used to build ARM
> kernel.
>
> Signed-off-by: Jian Cai <caij2003@gmail.com>
> ---
>  arch/arm/Kconfig | 2 +-
>  init/Kconfig     | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 66a04f6f4775..39de8fc64a73 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -804,7 +804,7 @@ source "arch/arm/mm/Kconfig"
>
>  config IWMMXT
>         bool "Enable iWMMXt support"
> -       depends on CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_PJ4 || CPU=
_PJ4B
> +       depends on !AS_IS_CLANG && !LD_IS_LLD && (CPU_XSCALE || CPU_XSC3 =
|| CPU_MOHAWK || CPU_PJ4 || CPU_PJ4B)
>         default y if PXA27x || PXA3xx || ARCH_MMP || CPU_PJ4 || CPU_PJ4B
>         help
>           Enable support for iWMMXt context switching at run time if
> diff --git a/init/Kconfig b/init/Kconfig
> index 1c12059e0f7e..b0ab3271e900 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -19,6 +19,12 @@ config GCC_VERSION
>  config CC_IS_CLANG
>         def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
>
> +config AS_IS_CLANG
> +       def_bool $(success,$(AS) --version | head -n 1 | grep -q clang)
> +
> +config LD_IS_LLD
> +       def_bool $(success,$(LD) --version | head -n 1 | grep -q LLD)
> +
>  config CLANG_VERSION
>         int
>         default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
> --
> 2.26.0.110.g2183baf09c-goog

Yesterday, when looking trough commits in Linus tree, I saw:

"init/kconfig: Add LD_VERSION Kconfig"

Nick had a patchset to distinguish LINKER via Kconfig (I cannot find
it right now).

So we should do all this the way CC_IS_XXX CC_VERSION handling is done.

I just want to point to [2] where we can rework (simplify) this
handling for CC and LD handling in a further step.
In one of Peter Z. tree someone started to do so (I was inspired by that).

Unfortunately, the hunk from [1] is IMHO a bit mis-placed and CC and
LD handling should stay together:

CC_IS_XXX where XXX is GCC or CLANG
CC_VERSION where CC is GCC or CLANG

LD_IS_XXX where XXX is BFD or GOLD or LLD
LD_VERSION

Just my =E2=82=AC0,02.

Regards,
- Sedat -

[1] https://git.kernel.org/linus/9553d16fa671b9621c5e2847d08bd90d3be3349c
[2] https://github.com/ClangBuiltLinux/linux/issues/941