linux-kernel - Re: [PATCH] bitfield: Use __ffs64(x) to fix missing _

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Message-ID: <20171009073434.0110d4fb@cakuba.netronome.com>
Date:   Mon, 9 Oct 2017 07:34:34 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kbuild test robot <fengguang.wu@...el.com>,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bitfield: Use __ffs64(x) to fix missing __ffsdi2()

On Mon,  9 Oct 2017 10:40:49 +0200, Geert Uytterhoeven wrote:
> On most architectures[*], gcc turns __builtin_ffsll() into a call to
> __ffsdi2(), which is not provided by any architecture, leading to
> failures like:
> 
>     rcar-gen3-cpg.c:(.text+0x289): undefined reference to `__ffsdi2'
> 
> To fix this, use __ffs64() instead, which is available on all
> architectures.
> 
> [*] Known exceptions are some 64-bit architectures like amd64, arm64,
>     ia64, powerpc64, and tilegx.
> 
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Fixes: 3e9b3112ec74f192 ("add basic register-field manipulation macros")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

Acked-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

Thanks!