linux-kernel - Re: [PATCH] powerpc: sysdev: cpm1: Optimise gpio bit calculation

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Message-ID: <20170310130222.GG31469@gate.crashing.org>
Date:   Fri, 10 Mar 2017 07:02:22 -0600
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Scott Wood <oss@...error.net>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: sysdev: cpm1: Optimise gpio bit calculation

On Fri, Mar 10, 2017 at 07:41:33PM +1100, Michael Ellerman wrote:
> Well yeah, it saves one instruction, but is it worth it? Are these gpio
> routines in some hot path I don't know about?

If there was a GCC PR for this we probably would make GCC optimise
this; there are many similar things that are optimised already, just
not this one.


Segher