Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <CAHk-=wiWwDYxNhnStS0e+p-NTFAQSHvab=2-8LwxunCVuY5-2A@mail.gmail.com>
 <20220725161141.GA1306881@roeck-us.net> <CAHk-=whtGUwJwHUSNsXd4g7cok=n0Zwje7nACp8skh1fa2NtJA@mail.gmail.com>
 <CAHk-=wgGrewyOqT7Cm-eHKp5W+8rJ=aL8iNtsbhRfc0YD2gbeA@mail.gmail.com> <Yt7+pPyEmYYH8D1K@yury-laptop>
In-Reply-To: <Yt7+pPyEmYYH8D1K@yury-laptop>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 25 Jul 2022 13:40:58 -0700
Message-ID: <CAHk-=wg6k1oxtEF3M7_icZ_62Je4R0VUaA69jo4xrOTxF_mMoQ@mail.gmail.com>
Subject: Re: Linux 5.19-rc8
To:     Yury Norov <yury.norov@gmail.com>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Dennis Zhou <dennis@kernel.org>,
        Russell King - ARM Linux <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Jul 25, 2022 at 1:35 PM Yury Norov <yury.norov@gmail.com> wrote:
>
> Here we have 2 ugly options - having pairs of almost identical
> functions, or passing dummy variables. I decided that copy-pasting is
> worse than abusing branch predictor.

The thing is, we have solutions for this - just use a single inline
function, and make it *see* the constant.

That way the compiler can DTRT, either generating two copies (with the
constant elided) or depending on the branch predictor.

That's particularly true in a case like this, when there is only *one*
case for the normal situation (ie little-endian). Because let's face
it, big-endian is completely dead and legacy model.

              Linus