linux-kernel - Re: x86 copy performance regression

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Message-ID: <CAHk-=wh16fVwO2yZ4Fx0kyRHsNDhGddzNxfQQz2+x08=CPvk_Q@mail.gmail.com>
Date:   Fri, 26 May 2023 10:40:39 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: x86 copy performance regression

On Fri, May 26, 2023 at 10:25 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> arch/x86/lib/copy_user_64.S:34:2: error: invalid instruction mnemonic
> 'alternative'

Ok, that's just odd. For me, assembler mnemonics - very much including
macros - are case-insensitive.

It's actually documented that way, with the example given is for a
macro that is declared as "sum" and then used as "SUM":

   https://sourceware.org/binutils/docs/as/Macro.html

And if you want to use macros as pseudo-instructions, that's what you
want, since typically assembler instructions are not case sensitive.

But yeah, your build environment is clearly different, and yes, we
declare the macro with all caps, and other places use it that way too.

Clang?

              Linus