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Date:   Sat, 21 Nov 2020 21:23:10 +0100
From:   Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org, christophe.leroy@csgroup.eu,
        Jakub Jelinek <jakub@redhat.com>, rdunlap@infradead.org
Subject: Re: [PATCH] ilog2: Improve ilog2 for constant arguments
Message-ID: <20201121202310.lx2iqqebal3fmmmo@ltop.local>
References: <20201120125154.GB3040@hirez.programming.kicks-ass.net>
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On Fri, Nov 20, 2020 at 01:51:54PM +0100, Peter Zijlstra wrote:
> 
> Other option would be to change the const_ilog2 macro, though as the
> description says it is meant to be used also in C constant expressions,
> and while GCC will fold it to constant with constant argument even in
> those, perhaps it is better to avoid using extensions in that case.

Just for info, the description is outdated and Sparse is just fine with
__builtin_clzll() and friends in constant expressions (since Feb 2017)
 
-- Luc