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Date:   Thu, 25 Feb 2021 12:03:48 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Arnd Bergmann <arnd@arndb.de>, Miguel Ojeda <ojeda@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Marco Elver <elver@google.com>,
        Sami Tolvanen <samitolvanen@google.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Randy Dunlap <rdunlap@infradead.org>,
        clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*
Message-ID: <202102251203.03762F77@keescook>
References: <20210225164513.3667778-1-arnd@kernel.org>
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On Thu, Feb 25, 2021 at 05:45:09PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
> definitions of the three HAVE_BUILTIN_BSWAP macros, which requires falling
> back to the open-coded version and hoping that the compiler detects it.
> 
> Since all versions of clang support the __builtin_bswap interfaces,
> add back the flags and have the headers pick these up automatically.
> 
> This results in a 4% improvement of compilation speed for arm defconfig.
> 
> Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Cc: stable@vger.kernel.org
Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook