From: Clemens Ladisch <clemens@ladisch.de>
To: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code
Date: Mon, 02 Jun 2014 07:24:04 +0000 [thread overview]
Message-ID: <538C2694.1090308@ladisch.de> (raw)
In-Reply-To: <1401659019-17586-1-git-send-email-rickard_strandqvist@spectrumdigital.se>
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
WARNING: multiple messages have this Message-ID (diff)
From: Clemens Ladisch <clemens@ladisch.de>
To: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>,
Tony Luck <tony.luck@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code
Date: Mon, 02 Jun 2014 09:24:04 +0200 [thread overview]
Message-ID: <538C2694.1090308@ladisch.de> (raw)
In-Reply-To: <1401659019-17586-1-git-send-email-rickard_strandqvist@spectrumdigital.se>
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
next prev parent reply other threads:[~2014-06-02 7:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-01 21:43 [PATCH] arch: ia64: kernel: palinfo.c: Optimization of the Code Rickard Strandqvist
2014-06-01 21:43 ` Rickard Strandqvist
2014-06-02 7:24 ` Clemens Ladisch [this message]
2014-06-02 7:24 ` Clemens Ladisch
2014-06-02 17:59 ` Rickard Strandqvist
2014-06-02 17:59 ` Rickard Strandqvist
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