linux-kernel - Re: [PATCH] x86/vdso: include generic _

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Message-ID: <20190318230331.GW6058@hirez.programming.kicks-ass.net>
Date:   Tue, 19 Mar 2019 00:03:31 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Manoj Gupta <manojgupta@...omium.org>,
        Tiancong Wang <tcwang@...omium.org>,
        Stephen Hines <srhines@...gle.com>,
        clang-built-linux@...glegroups.com,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH] x86/vdso: include generic __lshrdi3 in 32-bit vDSO

On Mon, Mar 18, 2019 at 01:44:35PM -0700, Matthias Kaehlcke wrote:
> You have a point, enabling -Oz (aggressive optimization for size)
> doesn't seem a good choice for the entire kernel.

Note that in this instance, -Os actually generates _smaller_ code than
-Oz, now that's mostly because of stupid register shuffling, but still.

> I'll send a patch to change it (back) to -Os.

Thanks!