Re: Why is complex lea slow?

From	Andrew Reilly <areilly---@bigpond.net.au>
Newsgroups	comp.arch
Subject	Re: Why is complex lea slow?
Date	2011-05-19 00:11 +0000
Message-ID	<93j5i9FoosU1@mid.individual.net> (permalink)
References	<9ceb0829-013e-4ee4-8ab3-9378ae59fe37@glegroupsg2000goo.googlegroups.com> <eo9ca8-fmg.ln1@ntp6.tmsw.no> <4DD3C8CA.70909@SPAM.comp-arch.net>

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On Wed, 18 May 2011 06:25:30 -0700, Andy \"Krazy\" Glew wrote:

> What machines make dynamic shifts slower than, say, a shift by 29?
> 
> Why?

Some ARM versions are one cycle slower for dynamic than immediate 
shifts.  I can't say why: always assumed it was a pipeline issue, 
register read vs instruction constant...

[Note that shifting isn't a special instruction in the traditional ARM 
instruction set, it's something that you can do to the second argument of 
any ALU operation.]

Cheers,

-- 
Andrew

Thread

Re: Why is complex lea slow? "Paul A. Clayton" <paaronclayton@gmail.com> - 2011-05-17 12:58 -0700
  Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-18 09:40 +0200
    Re: Why is complex lea slow? "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-05-18 06:25 -0700
      Re: Why is complex lea slow? "Andy \"Krazy\" Glew" <andy@SPAM.comp-arch.net> - 2011-05-18 06:39 -0700
      Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-18 20:49 +0200
      Re: Why is complex lea slow? Andrew Reilly <areilly---@bigpond.net.au> - 2011-05-19 00:11 +0000
    Re: Why is complex lea slow? MitchAlsup <MitchAlsup@aol.com> - 2011-05-24 13:44 -0700
      Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-25 08:43 +0200
        Re: Why is complex lea slow? MitchAlsup <MitchAlsup@aol.com> - 2011-05-25 08:31 -0700
      Re: Why is complex lea slow? timcaffrey@aol.com (Tim McCaffrey) - 2011-05-25 14:53 +0000
        Re: Why is complex lea slow? MitchAlsup <MitchAlsup@aol.com> - 2011-05-25 08:31 -0700
          Re: Why is complex lea slow? timcaffrey@aol.com (Tim McCaffrey) - 2011-05-26 19:45 +0000
            Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-26 20:01 +0000
              Re: Why is complex lea slow? nmm1@cam.ac.uk - 2011-05-26 20:29 +0100
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-26 20:14 +0000
                Re: Why is complex lea slow? nmm1@cam.ac.uk - 2011-05-26 21:04 +0100
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-26 20:55 +0000
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-26 20:57 +0000
                Re: Why is complex lea slow? nmm1@cam.ac.uk - 2011-05-26 21:30 +0100
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-26 22:57 +0100
                Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-27 07:42 +0200
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-27 06:11 +0000
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-27 07:18 +0100
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-27 06:33 +0000
                Re: Why is complex lea slow? Michael S <already5chosen@yahoo.com> - 2011-05-27 03:24 -0700
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-27 22:24 +0100
                Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-28 13:51 +0200
                Re: Why is complex lea slow? Quadibloc <jsavard@ecn.ab.ca> - 2011-05-27 17:42 -0700
                Re: Why is complex lea slow? Quadibloc <jsavard@ecn.ab.ca> - 2011-05-27 17:40 -0700
                Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-27 08:55 +0200
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-27 07:42 +0000
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-27 09:24 +0100
                Re: Why is complex lea slow? nmm1@cam.ac.uk - 2011-05-27 08:55 +0100
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-27 10:20 +0100
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-27 08:53 +0000
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-27 10:23 +0100
                Re: Why is complex lea slow? kenney@cix.compulink.co.uk - 2011-05-27 23:47 -0500
                Re: Why is complex lea slow? Quadibloc <jsavard@ecn.ab.ca> - 2011-05-27 17:44 -0700
                Re: Why is complex lea slow? Bill Findlay <yaldnif.w@blueyonder.co.uk> - 2011-05-28 02:12 +0100
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-28 02:57 +0000
                Re: Why is complex lea slow? Tom Gardner <spamjunk@blueyonder.co.uk> - 2011-05-28 09:27 +0100
                Algol hardware representations, was: Why is complex lea slow? Bill Findlay <yaldnif.w@blueyonder.co.uk> - 2011-05-28 15:26 +0100
                Re: Why is complex lea slow? Quadibloc <jsavard@ecn.ab.ca> - 2011-05-28 08:57 -0700
                Re: Why is complex lea slow? Chris Gray <cg@GraySage.com> - 2011-05-27 14:14 -0600
                Re: Why is complex lea slow? timcaffrey@aol.com (Tim McCaffrey) - 2011-05-26 23:26 +0000
                Re: Why is complex lea slow? Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2011-05-26 21:41 -0600
              Re: Why is complex lea slow? Terje Mathisen <"terje.mathisen at tmsw.no"> - 2011-05-27 07:37 +0200
                Re: Why is complex lea slow? kym@kymhorsell.com - 2011-05-27 06:16 +0000
                Re: Why is complex lea slow? Quadibloc <jsavard@ecn.ab.ca> - 2011-05-27 17:52 -0700
  Re: Why is complex lea slow? Piotr Wyderski <peter.pan@neverland.mil> - 2011-05-19 17:13 +0200

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