From: Nathan Chancellor <nathan@kernel.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Arnd Bergmann <arnd@arndb.de>, Miguel Ojeda <ojeda@kernel.org>,
Kees Cook <keescook@chromium.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*
Date: Thu, 25 Feb 2021 12:29:41 -0700 [thread overview]
Message-ID: <20210225192941.GA2026@MSI.localdomain> (raw)
In-Reply-To: <20210225164513.3667778-1-arnd@kernel.org>
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>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
> include/linux/compiler-clang.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index 6478bff6fcc2..bbfa9ff6a2ec 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -33,6 +33,16 @@
> #define __no_sanitize_thread
> #endif
>
> +/*
> + * sparse (__CHECKER__) pretends to be gcc, but can't do constant
> + * folding in __builtin_bswap*() (yet), so don't set these for it.
> + */
> +#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
> +#define __HAVE_BUILTIN_BSWAP32__
> +#define __HAVE_BUILTIN_BSWAP64__
> +#define __HAVE_BUILTIN_BSWAP16__
> +#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
> +
> #if __has_feature(undefined_behavior_sanitizer)
> /* GCC does not have __SANITIZE_UNDEFINED__ */
> #define __no_sanitize_undefined \
> --
> 2.29.2
>
next prev parent reply other threads:[~2021-02-25 19:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 16:45 [PATCH] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP* Arnd Bergmann
2021-02-25 19:29 ` Nathan Chancellor [this message]
2021-02-25 20:03 ` Kees Cook
2021-02-25 20:06 ` Andrew Morton
2021-02-25 20:14 ` Kees Cook
2021-02-25 20:18 ` Nathan Chancellor
2021-02-26 3:58 ` Miguel Ojeda
2021-02-26 3:34 ` Miguel Ojeda
2021-02-25 21:01 ` Nick Desaulniers
2021-02-26 7:47 ` Luc Van Oostenryck
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