From: "Dave Korn" <dave.korn@artimi.com>
To: <gdb@sourceware.org>
Subject: RE: (len % 1) != 0
Date: Tue, 19 Feb 2008 18:35:00 -0000 [thread overview]
Message-ID: <008001c87325$6db805e0$2e08a8c0@CAM.ARTIMI.COM> (raw)
In-Reply-To: <18363.7810.91075.314867@gargle.gargle.HOWL>
On 19 February 2008 18:23, Paul Koning wrote:
>>>>>> "Dave" == Dave Korn <dave.korn@artimi.com> writes:
>
> Dave> On 19 February 2008 16:30, Sheng-Liang Song wrote:
> >> or
> >>
> >> (len & 1) != 0 <=> (len % 2) != 0
> >>
>
> Dave> That would have the advantage of not requiring a divide
> Dave> operation :)
>
> It shouldn't matter -- the optimizer will do the right thing, as I
> recall.
NB len == signed int.
Yes, it can simplify it to a bunch of shifts and sign extends and masks
without using an explicit divide, but it's not as good as a simple AND
operation. (Maybe VRP in 4.x could handle that by knowing that the result of
strlen has to be >= 0, but 3.x series won't do it).
cheers,
DaveK
--
Can't think of a witty .sigline today....
next prev parent reply other threads:[~2008-02-19 18:30 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-17 5:57 Bin Chen
2008-02-17 14:13 ` Eli Zaretskii
2008-02-17 14:41 ` Bin Chen
2008-02-17 15:26 ` Daniel Jacobowitz
2008-02-19 16:32 ` Sheng-Liang Song
2008-02-19 18:25 ` Dave Korn
2008-02-19 18:30 ` David Daney
[not found] ` <18363.7810.91075.314867@gargle.gargle.HOWL>
2008-02-19 18:35 ` Dave Korn [this message]
2008-02-19 18:47 ` David Daney
2008-02-19 18:49 ` Daniel Jacobowitz
2008-02-19 19:08 ` Dave Korn
2008-02-19 21:41 ` Andreas Schwab
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