linux-kernel - Re: [PATCH 1/1] x86: Change mov $0, %reg with xor %reg, %reg

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Message-ID: <Yuvrd2yWLnyxOVLU@zn.tnic>
Date:   Thu, 4 Aug 2022 17:53:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Kanna Scarlet <knscarlet@...weeb.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Bill Metzenthen <billm@...bpc.org.au>,
        Brijesh Singh <brijesh.singh@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Michael Roth <michael.roth@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ammar Faizi <ammarfaizi2@...weeb.org>,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] x86: Change mov $0, %reg with xor %reg, %reg

On Thu, Aug 04, 2022 at 03:26:55PM +0000, Kanna Scarlet wrote:
> Change mov $0, %reg with xor %reg, %reg because xor %reg, %reg is
> smaller so it is good to save space

Bonus points if you find out what other advantage

XOR reg,reg

has when it comes to clearing integer registers.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette