From: "H. Peter Anvin" <hpa@zytor.com>
To: Roland Dreier <rdreier@cisco.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
joerg.roedel@amd.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] introduce lower_32_bits() macro
Date: Fri, 25 Jul 2008 17:39:21 -0400 [thread overview]
Message-ID: <488A4809.8080703@zytor.com> (raw)
In-Reply-To: <ada63qtvg57.fsf@cisco.com>
Roland Dreier wrote:
> > There's some readability benefit. Sometimes it is hard to understand
> > why some random open-coded cast was used. But I seem to recall that
> > there was another reason why we decided we needed this. I forget, and
> > so apparently did the changelog author ;)
>
> The guy who added the macro explained it in a comment ;)
>
> * A basic shift-right of a 64- or 32-bit quantity. Use this to suppress
> * the "right shift count >= width of type" warning when that quantity is
> * 32-bits.
That was for upper_32_bits() -- and can also be done with an internal
(u64) cast; it would be interesting to find out if that would generate
better code.
-hpa
next prev parent reply other threads:[~2008-07-25 21:40 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-25 15:12 [PATCH] introduce lower_32_bits() macro Joerg Roedel
2008-07-25 16:06 ` H. Peter Anvin
2008-07-25 20:47 ` Andrew Morton
2008-07-25 20:54 ` Roland Dreier
2008-07-25 21:39 ` H. Peter Anvin [this message]
2008-07-25 20:54 ` H. Peter Anvin
2008-07-28 10:59 ` Joerg Roedel
2008-07-28 12:07 ` Joerg Roedel
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