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Date:   Wed, 18 Oct 2023 17:27:54 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Alexander Lobakin <aleksander.lobakin@intel.com>
Cc:     Yury Norov <yury.norov@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Alexander Potapenko <glider@google.com>,
        Eric Dumazet <edumazet@google.com>,
        David Ahern <dsahern@kernel.org>,
        Przemek Kitszel <przemyslaw.kitszel@intel.com>,
        Simon Horman <simon.horman@corigine.com>,
        netdev@vger.kernel.org, linux-btrfs@vger.kernel.org,
        dm-devel@redhat.com, ntfs3@lists.linux.dev,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 04/13] linkmode: convert
 linkmode_{test,set,clear,mod}_bit() to macros
Message-ID: <20231018172754.3eec4885@kernel.org>
In-Reply-To: <20231016165247.14212-5-aleksander.lobakin@intel.com>
References: <20231016165247.14212-1-aleksander.lobakin@intel.com>
        <20231016165247.14212-5-aleksander.lobakin@intel.com>
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On Mon, 16 Oct 2023 18:52:38 +0200 Alexander Lobakin wrote:
> Since commit b03fc1173c0c ("bitops: let optimize out non-atomic bitops
> on compile-time constants"), the non-atomic bitops are macros which can
> be expanded by the compilers into compile-time expressions, which will
> result in better optimized object code. Unfortunately, turned out that
> passing `volatile` to those macros discards any possibility of
> optimization, as the compilers then don't even try to look whether
> the passed bitmap is known at compilation time. In addition to that,
> the mentioned linkmode helpers are marked with `inline`, not
> `__always_inline`, meaning that it's not guaranteed some compiler won't
> uninline them for no reason, which will also effectively prevent them
> from being optimized (it's a well-known thing the compilers sometimes
> uninline `2 + 2`).
> Convert linkmode_*_bit() from inlines to macros. Their calling
> convention are 1:1 with the corresponding bitops, so that it's not even
> needed to enumerate and map the arguments, only the names. No changes in
> vmlinux' object code (compiled by LLVM for x86_64) whatsoever, but that
> doesn't necessarily means the change is meaningless.

Acked-by: Jakub Kicinski <kuba@kernel.org>

This one can go in with the rest, it's trivial enough.