linux-kernel - Re: [PATCH v3 11/11] x86: support i386 with Clang

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Message-ID: <87zh7qy4i4.fsf@nanos.tec.linutronix.de>
Date:   Thu, 23 Jul 2020 11:17:39 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        David Woodhouse <dwmw2@...radead.org>,
        Dmitry Golovin <dima@...ovin.in>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v3 11/11] x86: support i386 with Clang

Thomas Gleixner <tglx@...utronix.de> writes:
> Nick Desaulniers <ndesaulniers@...gle.com> writes:
>
> I'm glad I looked myself at this.
>
>> We also don't want to swap the use of "=q" with "=r". For 64b, it
>> doesn't matter. For 32b, it's possible that a 32b register without a 8b
>> lower alias (i.e. ESI, EDI, EBP) is selected which the assembler will
>> then reject.
>
> The above is really garbage.
>
> We don't want? It's simply not possible to do so, because ...
>
> 64b,32b,8b. For heavens sake is it too much asked to write a changelog
> with understandable wording instead of ambiguous abbreviations?
>
> There is no maximum character limit for changelogs.

Gah. Hit send too fast.

>> With this, Clang can finally build an i386 defconfig.

With what? I can't find anything which explains the solution at the
conceptual level. Sigh.

Thanks,

        tglx