linux-kernel - Re: [PATCH v2 2/2] MIPS: Loongson{2ef,64}: Wrap -mno-branch-likely with cc-option

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Message-ID: <20220207173609.GC16822@alpha.franken.de>
Date:   Mon, 7 Feb 2022 18:36:09 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH v2 2/2] MIPS: Loongson{2ef,64}: Wrap -mno-branch-likely
 with cc-option

On Tue, Jan 25, 2022 at 03:19:25PM -0700, Nathan Chancellor 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 this flag in cc-option so that it does not cause cc-option to fail,
> which can cause randconfigs to be really noisy, due to warnings not
> getting disabled that should be.
> 
> Additionally, move the cc-option check to Kconfig so that the check is
> done at configuration time, rather than build time, as builds with no
> configuration change will be quicker because the cc-option call will not
> need to happen in those instances.
> 
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
> ---
> 
> v1 -> v2: https://lore.kernel.org/r/20220120214001.1879469-2-nathan@kernel.org/
> 
> * Move cc-option call to Kconfig (Nick).
> * Also apply to loongson2ef, even though this will not currently build
>   with clang.
> 
>  arch/mips/Kconfig              | 4 ++++
>  arch/mips/loongson2ef/Platform | 3 ++-
>  arch/mips/loongson64/Platform  | 3 ++-
>  3 files changed, 8 insertions(+), 2 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]