From: Tim Walberg <twalberg@comcast.net>
To: Michal Nazarewicz <mina86@tlen.pl>
Cc: ratheesh k <ratheesh.ksz@gmail.com>, linux-c-programming@vger.kernel.org
Subject: Re: union to get parts of integer
Date: Mon, 20 Dec 2010 09:30:08 -0600 [thread overview]
Message-ID: <20101220153008.GH16355@comcast.net> (raw)
In-Reply-To: <87aak0tsf3.fsf@erwin.mina86.com>
It's likely that either the union or direct pointer expressions yield
more efficient code, as they can probably be compiled to direct byte-width
load/store instructions, rather than shifts and logical ands... However,
if the code's not in a critical path for performance, it probably won't
matter. And on some architectures, there may not be byte-width operations,
I guess...
On 12/20/2010 15:44 +0100, Michal Nazarewicz wrote:
>>
>> ((char *)&i)[0].
>>
>> However, are you sure that you need this? Don't you need "(i & 255)",
>> "((i >> 8) & 255)", etc. instead?
>>
>> --
>> Best regards, _ _
>> .o. | Liege of Serenly Enlightened Majesty of o' \,=./ `o
>> ..o | Computer Science, Michal "mina86" Nazarewicz (o o)
>> ooo +--<mina86-tlen.pl>--<jid:mina86-jabber.org>--ooO--(_)--Ooo--
End of included message
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next prev parent reply other threads:[~2010-12-20 15:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-20 10:40 union to get parts of integer ratheesh k
2010-12-20 12:03 ` Reza Hoorfar
2010-12-20 14:44 ` Michal Nazarewicz
2010-12-20 15:30 ` Tim Walberg [this message]
2010-12-20 15:40 ` Michal Nazarewicz
2010-12-21 16:22 ` Glynn Clements
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