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Date: Thu, 21 Dec 2017 15:11:30 +0100 From: Peter Zijlstra <peterz@...radead.org> To: David Laight <David.Laight@...LAB.COM> Cc: 'Crt Mori' <cmo@...exis.com>, Jonathan Cameron <jic23@...nel.org>, Ingo Molnar <mingo@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, Rusty Russell <rusty@...tcorp.com.au>, Ian Abbott <abbotti@....co.uk>, Larry Finger <Larry.Finger@...inger.net>, Niklas Soderlund <niklas.soderlund+renesas@...natech.se>, Thomas Gleixner <tglx@...utronix.de>, Krzysztof Kozlowski <krzk@...nel.org>, Masahiro Yamada <yamada.masahiro@...ionext.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>, Joe Perches <joe@...ches.com> Subject: Re: [PATCH v10 1/3] lib: Add strongly typed 64bit int_sqrt On Thu, Dec 21, 2017 at 01:56:55PM +0000, David Laight wrote: > > This part above looks like FLS > It also does the rest of the required shifts. Still, fls() + shift is way faster on hardware that has an fls instruction. Writing out that binary search doesn't make sense.
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