linux-kernel - Re: Linux 5.19-rc8

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Message-ID: <CAHk-=wg6k1oxtEF3M7_icZ_62Je4R0VUaA69jo4xrOTxF_mMoQ@mail.gmail.com>
Date:   Mon, 25 Jul 2022 13:40:58 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Dennis Zhou <dennis@...nel.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Linux 5.19-rc8

On Mon, Jul 25, 2022 at 1:35 PM Yury Norov <yury.norov@...il.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