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From: "Dave Korn" <dave.korn@artimi.com>
To: <gdb@sourceware.org>
References: <5800c1cc0802162157g3ac31acas4ae95585b9b2e263@mail.gmail.com><E1JQkG0-0005DD-0k@fencepost.gnu.org><5800c1cc0802170641g68ab2e5fte724cd076412333@mail.gmail.com><20080217152625.GA4810@caradoc.them.org><47BB03ED.5060708@baymicrosystems.com><007f01c87324$00f45a90$2e08a8c0@CAM.ARTIMI.COM> <18363.7810.91075.314867@gargle.gargle.HOWL>
Subject: RE: (len % 1) != 0
Date: Tue, 19 Feb 2008 18:35:00 -0000
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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....