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From: Nick Desaulniers <ndesaulniers@google.com>
To: Nathan Chancellor <nathan@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	 Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	linux-mips@vger.kernel.org,  linux-kernel@vger.kernel.org,
	llvm@lists.linux.dev
Subject: Re: [PATCH 2/2] MIPS: Loongson64: Wrap -mno-branch-likely with cc-option
Date: Mon, 24 Jan 2022 12:40:58 -0800	[thread overview]
Message-ID: <CAKwvOdmTBUcre5+=kopcyAv3q=55=Z5O65QHmvy3Ra2JqgLNHw@mail.gmail.com> (raw)
In-Reply-To: <20220120214001.1879469-2-nathan@kernel.org>

On Thu, Jan 20, 2022 at 1:40 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> This flag is not supported by clang, which results in a warning:
>
>   clang-14: warning: argument unused during compilation: '-mno-branch-likely' [-Wunused-command-line-argument]
>
> This breaks cc-option, which adds -Werror to make this warning fatal and
> catch flags that are not supported. Wrap the flag in cc-option so that
> it does not cause cc-option to fail, which can cause randconfigs to be
> really noisy.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

We should convert more of these tests to Kconfig checks that run once
per configuration, rather than multiple times for a build. IIRC Linus
mentioned this somewhere...yeah, the -Wimplicit-fallthrough patches.
See
dee2b702bcf06 ("kconfig: Add support for -Wimplicit-fallthrough")

I wonder if we can check ARCH or SUBARCH in Kconfig to limit invoking
the tool under test for certain arch specific command line flags?

I'll take this patch over such a larger change, but I think towards
the goal of speeding up already configured builds, we eventually want
to be migrating cc-option and ld-option checks to Kconfig.

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

> ---
>  arch/mips/loongson64/Platform | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform
> index 981d3abc150e..acf9edc9b15d 100644
> --- a/arch/mips/loongson64/Platform
> +++ b/arch/mips/loongson64/Platform
> @@ -26,5 +26,6 @@ cflags-y += $(call cc-option,-mno-loongson-mmi)
>  # Loongson Machines' Support
>  #
>
> -cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 -mno-branch-likely
> +cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64
> +cflags-$(CONFIG_MACH_LOONGSON64) += $(call cc-option,-mno-branch-likely)
>  load-$(CONFIG_CPU_LOONGSON64) += 0xffffffff80200000
> --
> 2.34.1
>
>


-- 
Thanks,
~Nick Desaulniers

  reply	other threads:[~2022-01-24 20:41 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-20 21:40 [PATCH 1/2] MIPS: Loongson64: Clean up use of cc-ifversion Nathan Chancellor
2022-01-20 21:40 ` [PATCH 2/2] MIPS: Loongson64: Wrap -mno-branch-likely with cc-option Nathan Chancellor
2022-01-24 20:40   ` Nick Desaulniers [this message]
2022-01-24 22:37     ` Nathan Chancellor
2022-01-24 22:49       ` Nick Desaulniers
2022-01-24 23:09         ` Nathan Chancellor
2022-01-24 20:31 ` [PATCH 1/2] MIPS: Loongson64: Clean up use of cc-ifversion Nick Desaulniers
2022-01-25  0:03   ` Jiaxun Yang
2022-01-25  1:25     ` Nathan Chancellor
2022-01-25 21:19       ` Jiaxun Yang

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