linux-kernel - Re: [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code

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Message-ID: <538C2694.1090308@ladisch.de>
Date:	Mon, 02 Jun 2014 09:24:04 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>
CC:	Paul Gortmaker <paul.gortmaker@...driver.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch: ia64: kernel: palinfo.c:  Optimization of the Code

Rickard Strandqvist wrote:
> From what I know, AND is faster then modulo.

Which is why the compiler does this optimization automatically,
if it can prove that it is correct.

> -		if (i != 0 && (i%64) == 0)
> +		if (i != 0 && (i&63) == 0)

Did you prove that i cannot be negative?


Regards,
Clemens
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